Scalable Vector Graphics (SVG) 2

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’
structural elements — ‘defs’, ‘g’, ‘svg’, ‘symbol’, ‘use’

a, altGlyphDef, clipPath, color-profile, cursor, filter, font, font-face, foreignObject, image, marker, mask, script, style, switch, text, view

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
document event attributes — ‘onunload’, ‘onabort’, ‘onerror’, ‘onresize’, ‘onscroll’, ‘onzoom’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
‘viewBox’
‘preserveAspectRatio’
‘zoomAndPan’
‘x’
‘y’
‘width’
‘height’
‘version’
‘baseProfile’
‘playbackOrder’
‘timelineBegin’

DOM Interfaces:

SVGSVGElement

Attribute definitions:

Name Value Lacuna value Animatable version <number> (none) no

Name	Value	Lacuna value	Animatable
version	<number>	(none)	no

Indicates the SVG language version to which this document fragment conforms.

In SVG 1.0 [SVG10], this attribute was fixed to the value '1.0'. For SVG 1.1, the attribute should have the value '1.1'.

What are we doing with the ‘version’ attribute? It's not clear whether it is useful to keep.

Name Value Lacuna value Animatable baseProfile <anything> none no

Name	Value	Lacuna value	Animatable
baseProfile	<anything>	none	no

Describes the minimum SVG language profile that the author believes is necessary to correctly render the content. The attribute does not specify any processing restrictions; It can be considered metadata. For example, the value of the attribute could be used by an authoring tool to warn the user when they are modifying the document beyond the scope of the specified base profile. Each SVG profile should define the text that is appropriate for this attribute.

It's unlikely SVG 2 will have profiles as 1.0 and 1.1 did. Do we keep the attribute in case others wish to profile SVG? (Or should we be discouraging that?)

Name Value Lacuna value Animatable x, y <length> 0 yes

Name	Value	Lacuna value	Animatable
x, y	<length>	0	yes

The ‘x’ and ‘y’ attributes specify the top-left corner of the rectangular region into which an embedded ‘svg’ element is placed. On an outermost svg element, these attributes have no effect.

Name Value Lacuna value Animatable width, height <length> | <percentage> 100% yes

Name	Value	Lacuna value	Animatable
width, height	<length> \| <percentage>	100%	yes

For outermost svg elements, the ‘width’ and ‘height’ attributes specify the intrinsice size of the SVG document fragment. For embedded ‘svg’ elements, they specify the size of the rectangular region into which the ‘svg’ element is placed.

A negative value is an error (see Error processing). A value of zero disables rendering of the element.

When zero is used on an outer ‘svg’ element, does this disable rendering too? Or does it just affect the intrinsic size?

Name Value Lacuna value Animatable preserveAspectRatio defer? <align> [ meet | slice ]? xMidYMid meet yes

Name	Value	Lacuna value	Animatable
preserveAspectRatio	defer? <align> [ meet \| slice ]?	xMidYMid meet	yes

Specifies the fitting behavior when the aspect ratio of the ‘svg’ element does not match the aspect ratio of the rectangle it is placed in. See the definition of ‘preserveAspectRatio’ for details.

Name Value Lacuna value Animatable zoomAndPan disable | magnify magnify no

Name	Value	Lacuna value	Animatable
zoomAndPan	disable \| magnify	magnify	no

Specifies whether the user agent should supply a means to zoom and pan the SVG content. See the definition of ‘zoomAndPan’ for details.

Name Value Lacuna value Animatable playbackOrder forwardOnly | all all no

Name	Value	Lacuna value	Animatable
playbackOrder	forwardOnly \| all	all	no

This attribute may be harmonized and/or replaced with the work done as part of the Web Animation specification.

Indicates whether it is possible to seek backwards in the document. In earlier versions of SVG there was no need to put restrictions on the direction of seeking but with the newly introduced facilities for long-running documents (e.g. the ‘discard’ element) there is sometimes a need to restrict this.

If ‘playbackOrder’ is set to 'forwardOnly', the content will probably contain ‘discard’ elements or scripts that destroy resources, thus seeking back in the document's timeline may result in missing content. If ‘playbackOrder’ is 'forwardOnly', the content should not provide a way, through hyperlinking or script, of seeking backwards in the timeline. Similarly the UA should disable any controls it may provide in the user interface for seeking backwards. Content with playbackOrder="forwardOnly" that provides a mechanism for seeking backwards in time may result in undefined behavior or a document that is in error.

Can't we define this so that there is no undefined behavior?

Attribute values have the following meanings:

'forwardOnly': This file is intended to be played only in the forward direction, sequentially, therefore seeking backwards should not be allowed.
'all': Indicates that the document is authored appropriately for seeking in both directions.

Name Value Lacuna value Animatable timelineBegin onLoad | onStart onLoad no

Name	Value	Lacuna value	Animatable
timelineBegin	onLoad \| onStart	onLoad	no

This attribute may be harmonized and/or replaced with the work done as part of the Web Animation specification.

Controls the initialization of the timeline for the document.

The ‘svg’ element controls the document timeline, which is the timeline of the ‘svg’ element's time container. For progressively loaded animations, the author would typically set this attribute to 'onStart', thus allowing the timeline to begin as the document loads, rather than waiting until the complete document is loaded.

Attribute values have the following meanings:

'onLoad': The document's timeline starts the moment the load event for the rootmost ‘svg’ element is triggered.
'onStart': The document's timeline starts at the moment the rootmost ‘svg’ element's start-tag as defined in XML 1.0 ([XML10], section 3.1) is fully parsed and processed.
What about when the SVG document fragment is within an XHTML document? Is there a single timeline for the whole document, and if so, does it start at the parse time for the first <svg> start tag? What about when using the HTML parser?

If an SVG document is likely to be referenced as a component of another document, the author will often want to include a ‘viewBox’ attribute on the outermost svg element of the referenced document. This attribute provides a convenient way to design SVG documents to scale-to-fit into an arbitrary viewport.

This paragraph feels out of place just after the list of attributes specific to ‘svg’.

5.2. Grouping: the ‘g’ element

5.2.1. Overview

The ‘g’ element is a container element for grouping together related graphics elements.

Grouping constructs, when used in conjunction with the ‘desc’ and ‘title’ elements, provide information about document structure and semantics. Documents that are rich in structure may be rendered graphically, as speech, or as braille, and thus promote accessibility.

That generously structured content with ‘title’ and ‘desc’ is more accessible isn't necessarily true. It also seems like a stretch to claim that documents "rich in structure" can be rendered as speech or braille, without specific references to how that can be achieved. More fundamental uses of grouping that should be mentioned are (a) for specifying common styling of inherited properties, and (b) for selecting elements to apply a group effect like filters and group opacity.

A group of elements, as well as individual objects, can be given a name using the ‘id’ attribute. Named groups are needed for several purposes such as animation and re-usable objects.

An example:

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="1.1" width="5cm" height="5cm">
  <desc>Two groups, each of two rectangles</desc>
  <g id="group1" fill="red">
    <rect x="1cm" y="1cm" width="1cm" height="1cm"/>
    <rect x="3cm" y="1cm" width="1cm" height="1cm"/>
  </g>
  <g id="group2" fill="blue">
    <rect x="1cm" y="3cm" width="1cm" height="1cm"/>
    <rect x="3cm" y="3cm" width="1cm" height="1cm"/>
  </g>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x=".01cm" y=".01cm" width="4.98cm" height="4.98cm"
        fill="none" stroke="blue" stroke-width=".02cm"/>
</svg>

A ‘g’ element can contain other ‘g’ elements nested within it, to an arbitrary depth. Thus, the following is possible:

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="1.1" width="4in" height="3in">
  <desc>Groups can nest</desc>
  <g>
     <g>
       <g>
       </g>
     </g>
   </g>
</svg>

This is not a particularly useful example.

SVG 2 Requirement:	Have unknown elements treated as ‘g’ for the purpose of rendering.
Resolution:	Accept having unknown elements treated as ‘g’ for the purpose of rendering.
Purpose:	To allow fallbacks without the use of ‘switch’, and to align with the behavior of unknown elements in HTML.
Owner:	Nobody (no action)

Any element that is not contained within a ‘g’ is treated (at least conceptually) as if it were in its own group.

It is unclear what this sentence actually means. Does it mean that all operations that apply to groups (such as group opacity, filter effects, etc.) can apply to single elements too? If so, then it should say that.

5.2.2. The ‘g’ element

‘g’

Categories:

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’
structural elements — ‘defs’, ‘g’, ‘svg’, ‘symbol’, ‘use’

a, altGlyphDef, clipPath, color-profile, cursor, filter, font, font-face, foreignObject, image, marker, mask, script, style, switch, text, view

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’

DOM Interfaces:

SVGGElement

5.3. Defining content for reuse, and the ‘defs’ element

5.3.1. Overview

SVG allows graphical objects to be defined for later reuse. To do this, it makes extensive use of IRI references [RFC3987] to these other objects. For example, to fill a rectangle with a linear gradient, you first define a ‘linearGradient’ element and give it an ID, as in:

<linearGradient id="MyGradient">...</linearGradient>

You then reference the linear gradient as the value of the ‘fill’ property for the rectangle, as in:

<rect style="fill:url(#MyGradient)"/>

Some types of element, such as gradients, will not by themselves produce a graphical result. They can therefore be placed anywhere convenient. However, sometimes it is desired to define a graphical object and prevent it from being directly rendered. it is only there to be referenced elsewhere. To do this, and to allow convenient grouping defined content, SVG provides the ‘defs’ element.

It is recommended that, wherever possible, referenced elements be defined inside of a ‘defs’ element. Among the elements that are always referenced: ‘altGlyphDef’, ‘clipPath’, ‘cursor’, ‘filter’, ‘linearGradient’, ‘marker’, ‘mask’, ‘pattern’, ‘radialGradient’ and ‘symbol’. Defining these elements inside of a ‘defs’ element promotes understandability of the SVG content and thus promotes accessibility.

Again this claim about accessibility is dubious.

We should have a term for definition elements (since we now have a corresponding IDL interface) and reference it here.

5.3.2. The ‘defs’ element

‘defs’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’
structural elements — ‘defs’, ‘g’, ‘svg’, ‘symbol’, ‘use’

a, altGlyphDef, clipPath, color-profile, cursor, filter, font, font-face, foreignObject, image, marker, mask, script, style, switch, text, view

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’

DOM Interfaces:

SVGDefsElement

The ‘defs’ element is a container element for referenced elements. For understandability and accessibility reasons, it is recommended that, whenever possible, referenced elements be defined inside of a ‘defs’.

The content model for ‘defs’ is the same as for the ‘g’ element; thus, any element that can be a child of a ‘g’ can also be a child of a ‘defs’, and vice versa.

Elements that are descendants of a ‘defs’ are not rendered directly; they are prevented from becoming part of the rendering tree just as if the ‘defs’ element were a ‘g’ element and the ‘display’ property were set to none. Note, however, that the descendants of a ‘defs’ are always present in the source tree and thus can always be referenced by other elements; thus, the value of the ‘display’ property on the ‘defs’ element or any of its descendants does not prevent those elements from being referenced by other elements.

To provide some SVG user agents with an opportunity to implement efficient implementations in streaming environments, creators of SVG content are encouraged to place all elements which are targets of local IRI references within a ‘defs’ element which is a direct child of one of the ancestors of the referencing element. For example:

Is this really about efficiency of implementations? If anything, it looks like it is ensuring progressively rendered documents don't make forward references that would otherwise cause an incorrect rendering before the referenced element is loaded.

<?xml version="1.0" standalone="no"?>
<svg width="8cm" height="3cm"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Local URI references within ancestor's 'defs' element.</desc>
  <defs>
    <linearGradient id="Gradient01">
      <stop offset="20%" stop-color="#39F" />
      <stop offset="90%" stop-color="#F3F" />
    </linearGradient>
  </defs>
  <rect x="1cm" y="1cm" width="6cm" height="1cm" 
        fill="url(#Gradient01)"  />

  <!-- Show outline of canvas using 'rect' element -->
  <rect x=".01cm" y=".01cm" width="7.98cm" height="2.98cm"
        fill="none" stroke="blue" stroke-width=".02cm" />

</svg>

In the document above, the linear gradient is defined within a ‘defs’ element which is the direct child of the ‘svg’ element, which in turn is an ancestor of the ‘rect’ element which references the linear gradient. Thus, the above document conforms to the guideline.

5.4. The ‘discard’ element

Would this element be better as part of the Animation chapter? It also needs to be a member of the element categories that other animation elements are, and an IDL interface needs to be written for it.

SVG 2 Requirement:	Have the ‘discard’ element to declaratively discard elements from the document tree.
Resolution:	SVG 2 will support the discard element.
Purpose:	To conserve memory while displaying long-running documents.
Owner:	Cyril (ACTION-3319)

‘discard’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’

Attributes:

conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
‘begin’
‘href’

DOM Interfaces:

Need to define SVGDiscardElement DOM interface for ‘discard’ element.

The ‘discard’ element allows authors to specify the time at which particular elements are to be discarded, thereby reducing the resources required by an SVG user agent. This is particularly useful to help SVG viewers conserve memory while displaying long-running documents. This element will not be processed by static SVG viewers.

The ‘discard’ element may occur wherever the ‘animate’ element may.

Attribute definitions:

Name Value Lacuna value Animatable href <iri> (none) no

Name	Value	Lacuna value	Animatable
href	<iri>	(none)	no

An IRI reference that identifies the target element to discard. See the definition of ‘href’ on animation elements for details on identifying a target element.

Note that if the target element is not part of the current SVG document fragment then whether the target element will be removed or not is defined by the host language.

If the ‘href’ attribute is not provided, then the target element will be the immediate parent element of the discard element.

Name Value Lacuna value Animatable begin <begin-value-list> 0s no

Name	Value	Lacuna value	Animatable
begin	<begin-value-list>	0s	no

Indicates when the target element will be discarded. See the definition of ‘begin’ on animation elements for details.

The ‘discard’ element has an implicit simple duration of "indefinite". As soon as the element's active duration starts, the SVG user agent discards the element identified by the ‘href’ attribute ([SMIL], section 5.4.5). The removal operation acts as if removeChild were called on the parent of the target element with the target element as parameter. [DOM4] The SVG user agent must remove the target node as well as all of its attributes and descendants.

After removal of the target element, the ‘discard’ element is no longer useful. It must also be discarded following the target element removal. If the ‘href’ attribute has an invalid IRI reference (the target element did not exist, for example), the ‘discard’ element itself must still be removed following activation.

Seeking backwards in the timeline ([SMIL], section 5.4.5) must not re-insert the discarded elements. Discarded elements are intended to be completely removed from memory. So, authors are encouraged to set the ‘playbackOrder’ attribute to "forwardOnly" when using the ‘discard’ element.

The ‘discard’ element itself can be discarded prior to its activation, in which case it will never trigger the removal of its own target element. SVG user agents must allow the ‘discard’ element to be the target of another ‘discard’ element.

The following example demonstrates a simple usage of the ‘discard’ element. The list below describes relevant behavior in the document timeline of this example:

At time = 0:: When the document timeline starts, the blue ellipse starts to move down the page.
At time = 1 second:: The red rectangle starts moving up the page.
At time = 2 seconds:: The ‘animateTransform’ on the ‘ellipse’ ends. The ‘ellipse’ and its children are also discarded, as it is the target element of a ‘discard’ with begin="2". The green ‘polygon’ starts to move across the page.
At time = 3 seconds:: The animation on the red rectangle ends. The rectangle and its children are discarded as it is the target of a ‘discard’ element with begin="3".
At time = 4 seconds:: The animation on the green triangle ends. The green ‘polygon’ and its children are discarded as it is the target of a ‘discard’ element with begin="4".

<svg xmlns="http://www.w3.org/2000/svg" width="352" height="240" playbackOrder="forwardOnly">
    
  <ellipse cx="98.5" cy="17.5" rx="20.5" ry="17.5" fill="blue" stroke="black" 
           transform="translate(9 252) translate(3 -296)">
    <animateTransform attributeName="transform" begin="0s" dur="2s" fill="remove"
                      calcMode="linear" type="translate" additive="sum"
                      from="0 0" to="-18 305"/>
    <discard begin="2s"/>
  </ellipse>
  
  <rect x="182" y="-39" width="39" height="30" fill="red" stroke="black"
        transform="translate(30 301)">
    <animateTransform attributeName="transform" begin="1s" dur="2s" fill="remove"
                      calcMode="linear" type="translate" additive="sum"
                      from="0 0" to="-26 -304"/>
    <discard begin="3s"/>
  </rect>
  
  <polygon points="-66,83.5814 -43,123.419 -89,123.419" fill="green" stroke="black" 
           transform="matrix(1 0 0 1.1798 0 -18.6096)">
    <animateTransform attributeName="transform" begin="2s" dur="2s"
                      fill="remove" calcMode="linear" type="translate" additive="sum"
                      from="0 0" to="460 63.5699"/>
    <discard begin="4s"/>
  </polygon>
</svg>

5.5. The ‘desc’ and ‘title’ elements

‘desc’

Categories:

Descriptive element

Content model:

Any elements or character data.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
style attributes — ‘class’, ‘style’
‘lang’

DOM Interfaces:

SVGDescElement

‘title’

Categories:

Descriptive element

Content model:

Any elements or character data.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
style attributes — ‘class’, ‘style’
‘lang’

DOM Interfaces:

SVGTitleElement

The attribute ‘lang’ added to allow internationalization of the ‘desc’ and ‘title’ elements.

Adding 'lang' resolved at Rigi Kaltbad face-to-face. Removed text that limited number of 'desc' and 'title' elements.

Is there any updated wording from SVG Tiny 1.2 that we should be using wrt tooltips?

Each container element or graphics element in an SVG drawing can supply one or more ‘desc’ and/or one or more ‘title’ description strings where the description is text-only. When the current SVG document fragment is rendered as SVG on visual media, ‘desc’ and ‘title’ elements are not rendered as part of the graphics. User agents may, however, for example, display the ‘title’ element as a tooltip, as the pointing device moves over particular elements. Alternate presentations are possible, both visual and aural, which display the ‘desc’ and ‘title’ elements but do not display ‘path’ elements or other graphics elements. This is readily achieved by using a different (perhaps user) style sheet. For deep hierarchies, and for following ‘use’ element references, it is sometimes desirable to allow the user to control how deep they drill down into descriptive text.

I don't think it is easy to use a style sheet to cause an element's ‘title’ to be rendered in place of its graphics.

More than one ‘desc’ or ‘title’ may be present with different ‘lang’ attributes. The text displayed will be the text from the element where the ‘lang’ attribute best matches the language set by the user agent. If no match exists, the text from the first element is used (to allow default text to be given for legacy renderers). If multiple equally valid matches exist, the first match is used.

'lang' should be defined here (rather than pointing to the glyph definition).

The following is an example. In typical operation, the SVG user agent would not render the ‘desc’ and ‘title’ elements but would render the remaining contents of the ‘g’ element.

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="1.1" width="4in" height="3in">
  <g>
    <title>Company sales by region</title>
    <title lang="fr">Chiffre d'affaires par région</title>
    <desc>Bar chart which shows company sales by region.</desc>
    <desc lang="fr">Graphique illustrant les ventes par région.</desc>
    <!-- Bar chart defined as vector data -->
  </g>
</svg>

Description and title elements can contain marked-up text from other namespaces. Here is an example:

<?xml version="1.0" standalone="yes"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="1.1" width="4in" height="3in">
  <desc xmlns:mydoc="http://example.org/mydoc">
    <mydoc:title>This is an example SVG file</mydoc:title>
    <mydoc:para>The global description uses markup from the 
      <mydoc:emph>mydoc</mydoc:emph> namespace.</mydoc:para>
  </desc>
  <g>
    <!-- the picture goes here -->
  </g>
</svg>

We should say what purpose including other-namespaced markup in ‘title’ and ‘desc’ has. If it is just that these are basically metadata extension points for other profiles or uses of SVG, then we should say that.

Authors should always provide a ‘title’ child element to the outermost svg element within a stand-alone SVG document. The ‘title’ child element to an ‘svg’ element serves the purposes of identifying the content of the given SVG document fragment. Since users often consult documents out of context, authors should provide context-rich titles. Thus, instead of a title such as "Introduction", which doesn't provide much contextual background, authors should supply a title such as "Introduction to Medieval Bee-Keeping" instead. For reasons of accessibility, user agents should always make the content of the ‘title’ child element to the outermost svg element available to users. The mechanism for doing so depends on the user agent (e.g., as a caption, spoken).

We have this sentence here about tooltips which is stronger than the earlier note that some implementations do this. We should look at how HTML describes the ‘title’ attribute and whether a tooltip is required, suggested, etc., and follow that.

Once we have said how ARIA attributes can be used in SVG, we might want to define ‘title’ and ‘desc’ in a manner consistent with them, so that it is clear what it means for example for an element to have both a ‘desc’ element child and an ‘aria-describedby’ attribute.

5.6. The ‘symbol’ element

‘symbol’

Categories:

Graphics element, graphics referencing element, structural element

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’
structural elements — ‘defs’, ‘g’, ‘svg’, ‘symbol’, ‘use’

a, altGlyphDef, clipPath, color-profile, cursor, filter, font, font-face, foreignObject, image, marker, mask, script, style, switch, text, view

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
‘preserveAspectRatio’
‘viewBox’

DOM Interfaces:

SVGSymbolElement

The ‘symbol’ element is used to define graphical template objects which can be instantiated by a ‘use’ element.

The use of ‘symbol’ elements for graphics that are used multiple times in the same document adds structure and semantics. Documents that are rich in structure may be rendered graphically, as speech, or as braille, and thus promote accessibility.

Again this mention of accessibility through the use of structure (this time with ‘symbol’ elements). We should include an example here or in the Accessibility appendix that shows how this is the case and what the actual effects of structuring content with ‘symbol’ are.

The key distinctions between a ‘symbol’ and a ‘g’ are:

A ‘symbol’ element itself is not rendered. Only instances of a ‘symbol’ element (i.e., a reference to a ‘symbol’ by a ‘use’ element) are rendered.
A ‘symbol’ element has attributes ‘viewBox’ and ‘preserveAspectRatio’ which allow a ‘symbol’ to scale-to-fit within a rectangular viewport defined by the referencing ‘use’ element.

Closely related to the ‘symbol’ element are the ‘marker’ and ‘pattern’ elements.

‘symbol’ elements are never rendered directly; their only usage is as something that can be referenced using the ‘use’ element. The ‘display’ property does not apply to the ‘symbol’ element; thus, ‘symbol’ elements are not directly rendered even if the ‘display’ property is set to a value other than none, and ‘symbol’ elements are available for referencing even when the ‘display’ property on the ‘symbol’ element or any of its ancestors is set to none.

5.7. The ‘use’ element

SVG 2 Requirement:	Allow ‘use’ to reference an external document's root element by omitting the fragment.
Resolution:	We will relax referencing requirements to particular elements to allow dropping fragments to mean referencing root element, where it makes sense, such as with use, in SVG 2.
Purpose:	To avoid requiring authors to modify the referenced document to add an ID to the root element.
Owner:	Cameron (ACTION-3417)

‘use’

Categories:

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

clipPath, marker, mask

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘x’
‘y’
‘width’
‘height’
‘xlink:href’

DOM Interfaces:

SVGUseElement

Any ‘svg’, ‘symbol’, ‘g’, graphics element or other ‘use’ is potentially a template object that can be re-used (i.e., "instanced") in the SVG document via a ‘use’ element. The ‘use’ element references another element and indicates that the graphical contents of that element is included/drawn at that given point in the document.

‘use’ is described as referencing template objects, but the parameters of the template are limited – just different inherited property values.

The ‘use’ element can reference an entire SVG document by specifying an ‘xlink:href’ value without a fragment. Such references are taken to be referring to the root element of the referenced document.

This allows an entire SVG document to be referenced without having to ensure that it has an ID on its root element.

The ‘use’ element has optional attributes ‘x’, ‘y’, ‘width’ and ‘height’ which are used to map the graphical contents of the referenced element onto a rectangular region within the current coordinate system.

The effect of a ‘use’ element is as if the contents of the referenced element were deeply cloned into a separate non-exposed DOM tree which had the ‘use’ element as its parent and all of the ‘use’ element's ancestors as its higher-level ancestors. Because the cloned DOM tree is non-exposed, the SVG Document Object Model (DOM) only contains the ‘use’ element and its attributes. The SVG DOM does not show the referenced element's contents as children of ‘use’ element.

We should define the behavior of ‘use’ in terms of Web Components.

For user agents that support Styling with CSS, the conceptual deep cloning of the referenced element into a non-exposed DOM tree also copies any property values resulting from the CSS cascade ([CSS21], chapter 6) on the referenced element and its contents. CSS2 selectors can be applied to the original (i.e., referenced) elements because they are part of the formal document structure. CSS2 selectors cannot be applied to the (conceptually) cloned DOM tree because its contents are not part of the formal document structure.

We should be requiring CSS styling in SVG 2. Also, hopefully, how styles can apply or not to elements in the shadow tree (and how event handling works, below) should be specified by how we define ‘use’ to work in terms of Web Components.

Property inheritance, however, works as if the referenced element had been textually included as a deeply cloned child of the ‘use’ element. The referenced element inherits properties from the ‘use’ element and the ‘use’ element's ancestors. An instance of a referenced element does not inherit properties from the referenced element's original parents.

If event attributes are assigned to referenced elements, then the actual target for the event will be the SVGElementInstance object within the "instance tree" corresponding to the given referenced element.

Once we define ‘use’ in terms of Web Components, will we drop instance trees?

The event handling for the non-exposed tree works as if the referenced element had been textually included as a deeply cloned child of the ‘use’ element, except that events are dispatched to the SVGElementInstance objects. The event's target and currentTarget attributes are set to the SVGElementInstance that corresponds to the target and current target elements in the referenced subtree. An event propagates through the exposed and non-exposed portions of the tree in the same manner as it would in the regular document tree: first going from the root element to the ‘use’ element and then through non-exposed tree elements in the capture phase, followed by the target phase at the target of the event, then bubbling back through non-exposed tree to the use element and then back through regular tree to the root element in bubbling phase.

An element and all its corresponding SVGElementInstance objects share an event listener list. The currentTarget attribute of the event can be used to determine through which object an event listener was invoked.

The behavior of the ‘visibility’ property conforms to this model of property inheritance. Thus, specifying 'visibility:hidden' on a ‘use’ element does not guarantee that the referenced content will not be rendered. If the ‘use’ element specifies 'visibility:hidden' and the element it references specifies 'visibility:hidden' or 'visibility:inherit', then that one element will be hidden. However, if the referenced element instead specifies 'visibility:visible', then that element will be visible even if the ‘use’ element specifies 'visibility:hidden'.

Why is ‘visibility’ called out specially? It might be better just to include an example that shows this.

Animations on a referenced element will cause the instances to also be animated.

A ‘use’ element has the same visual effect as if the ‘use’ element were replaced by the following generated content:

Except that the replaced content shouldn't affect how styles are matched.

If the ‘use’ element references a ‘symbol’ element:

In the generated content, the ‘use’ will be replaced by ‘g’, where all attributes from the ‘use’ element except for ‘x’, ‘y’, ‘width’, ‘height’ and ‘xlink:href’ are transferred to the generated ‘g’ element. An additional transformation translate(x,y) is appended to the end (i.e., right-side) of the ‘transform’ property on the generated ‘g’, where x and y represent the values of the ‘x’ and ‘y’ attributes on the ‘use’ element. The referenced ‘symbol’ and its contents are deep-cloned into the generated tree, with the exception that the ‘symbol’ is replaced by an ‘svg’. This generated ‘svg’ will always have explicit values for attributes ‘width’ and ‘height’. If attributes ‘width’ and/or ‘height’ are provided on the ‘use’ element, then these attributes will be transferred to the generated ‘svg’. If attributes ‘width’ and/or ‘height’ are not specified, the generated ‘svg’ element will use values of '100%' for these attributes.
If the ‘use’ element references an ‘svg’ element:

In the generated content, the ‘use’ will be replaced by ‘g’, where all attributes from the ‘use’ element except for ‘x’, ‘y’, ‘width’, ‘height’ and ‘xlink:href’ are transferred to the generated ‘g’ element. An additional transformation translate(x,y) is appended to the end (i.e., right-side) of the ‘transform’ property on the generated ‘g’, where x and y represent the values of the ‘x’ and ‘y’ attributes on the ‘use’ element. The referenced ‘svg’ and its contents are deep-cloned into the generated tree. If attributes ‘width’ and/or ‘height’ are provided on the ‘use’ element, then these values will override the corresponding attributes on the ‘svg’ in the generated tree.
Otherwise:

In the generated content, the ‘use’ will be replaced by ‘g’, where all attributes from the ‘use’ element except for ‘x’, ‘y’, ‘width’, ‘height’ and ‘xlink:href’ are transferred to the generated ‘g’ element. An additional transformation translate(x,y) is appended to the end (i.e., right-side) of the ‘transform’ property on the generated ‘g’, where x and y represent the values of the ‘x’ and ‘y’ attributes on the ‘use’ element. The referenced object and its contents are deep-cloned into the generated tree.

For user agents that support Styling with CSS, the generated ‘g’ element carries along with it the "cascaded" property values on the ‘use’ element which result from the CSS cascade ([CSS21], chapter 6). Additionally, the copy (deep clone) of the referenced resource carries along with it the "cascaded" property values resulting from the CSS cascade on the original (i.e., referenced) elements. Thus, the result of various CSS selectors in combination with the ‘class’ and ‘style’ attributes are, in effect, replaced by the functional equivalent of a ‘style’ attribute in the generated content which conveys the "cascaded" property values.

Example Use01 below has a simple ‘use’ on a ‘rect’.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 100 30" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <desc>Example Use01 - Simple case of 'use' on a 'rect'</desc>
  <defs>
    <rect id="MyRect" width="60" height="10"/>
  </defs>
  <rect x=".1" y=".1" width="99.8" height="29.8"
        fill="none" stroke="blue" stroke-width=".2" />
  <use x="20" y="10" xlink:href="#MyRect" />
</svg>

Example Use01

View this example as SVG (SVG-enabled browsers only)

The visual effect would be equivalent to the following document:

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 100 30"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example Use01-GeneratedContent - Simple case of 'use' on a 'rect'</desc>
  <!-- 'defs' section left out -->

  <rect x=".1" y=".1" width="99.8" height="29.8"
        fill="none" stroke="blue" stroke-width=".2" />

  <!-- Start of generated content. Replaces 'use' -->
  <g transform="translate(20,10)">
    <rect width="60" height="10"/>
  </g>
  <!-- End of generated content -->

</svg>

View this example as SVG (SVG-enabled browsers only)

Example Use02 below has a ‘use’ on a ‘symbol’.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 100 30" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <desc>Example Use02 - 'use' on a 'symbol'</desc>
  <defs>
    <symbol id="MySymbol" viewBox="0 0 20 20">
      <desc>MySymbol - four rectangles in a grid</desc>
      <rect x="1" y="1" width="8" height="8"/>
      <rect x="11" y="1" width="8" height="8"/>
      <rect x="1" y="11" width="8" height="8"/>
      <rect x="11" y="11" width="8" height="8"/>
    </symbol>
  </defs>
  <rect x=".1" y=".1" width="99.8" height="29.8"
        fill="none" stroke="blue" stroke-width=".2" />
  <use x="45" y="10" width="10" height="10" 
       xlink:href="#MySymbol" />
</svg>

Example Use02

View this example as SVG (SVG-enabled browsers only)

The visual effect would be equivalent to the following document:

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 100 30"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example Use02-GeneratedContent - 'use' on a 'symbol'</desc>

  <!-- 'defs' section left out -->

  <rect x=".1" y=".1" width="99.8" height="29.8"
        fill="none" stroke="blue" stroke-width=".2" />

  <!-- Start of generated content. Replaces 'use' -->
  <g transform="translate(45, 10)" >
    <!-- Start of referenced 'symbol'. 'symbol' replaced by 'svg',
         with x,y,width,height=0,0,100%,100% -->
    <svg width="10" height="10" 
         viewBox="0 0 20 20">
      <rect x="1" y="1" width="8" height="8"/>
      <rect x="11" y="1" width="8" height="8"/>
      <rect x="1" y="11" width="8" height="8"/>
      <rect x="11" y="11" width="8" height="8"/>
    </svg>
    <!-- End of referenced symbol -->
  </g>
  <!-- End of generated content -->

</svg>

View this example as SVG (SVG-enabled browsers only)

Example Use03 illustrates what happens when a ‘use’ has a ‘transform’ property.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 100 30" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <desc>Example Use03 - 'use' with a 'transform' attribute</desc>
  <defs>
    <rect id="MyRect" x="0" y="0" width="60" height="10"/>
  </defs>
  <rect x=".1" y=".1" width="99.8" height="29.8"
        fill="none" stroke="blue" stroke-width=".2" />
  <use xlink:href="#MyRect"
       transform="translate(20,2.5) rotate(10)" />
</svg>

Example Use03

View this example as SVG (SVG-enabled browsers only)

The visual effect would be equivalent to the following document:

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 100 30"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example Use03-GeneratedContent - 'use' with a 'transform' attribute</desc>

  <!-- 'defs' section left out -->

  <rect x=".1" y=".1" width="99.8" height="29.8"
        fill="none" stroke="blue" stroke-width=".2" />

  <!-- Start of generated content. Replaces 'use' -->
  <g transform="translate(20,2.5) rotate(10)">
    <rect x="0" y="0" width="60" height="10"/>
  </g>
  <!-- End of generated content -->

</svg>

View this example as SVG (SVG-enabled browsers only)

Example Use04 illustrates a ‘use’ element with various methods of applying CSS styling.

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="3cm" viewBox="0 0 1200 300" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <desc>Example Use04 - 'use' with CSS styling</desc>
  <defs style=" /* rule 9 */ stroke-miterlimit: 10" >
    <path id="MyPath" d="M300 50 L900 50 L900 250 L300 250"
                     class="MyPathClass"
                     style=" /* rule 10 */ stroke-dasharray:300,100" />
  </defs>
  <style type="text/css">
    <![CDATA[
      /* rule 1 */ #MyUse { fill: blue }
      /* rule 2 */ #MyPath { stroke: red }
      /* rule 3 */ use { fill-opacity: .5 }
      /* rule 4 */ path { stroke-opacity: .5 }
      /* rule 5 */ .MyUseClass { stroke-linecap: round }
      /* rule 6 */ .MyPathClass { stroke-linejoin: bevel }
      /* rule 7 */ use > path { shape-rendering: optimizeQuality }
      /* rule 8 */ g > path { visibility: hidden }
    ]]>
  </style>

  <rect x="0" y="0" width="1200" height="300"
         style="fill:none; stroke:blue; stroke-width:3"/>
  <g style=" /* rule 11 */ stroke-width:40">
    <use id="MyUse" xlink:href="#MyPath" 
         class="MyUseClass"
         style="/* rule 12 */ stroke-dashoffset:50" />
  </g>
</svg>

Example Use04

View this example as SVG (SVG-enabled browsers only)

The visual effect would be equivalent to the following document. Observe that some of the style rules above apply to the generated content (i.e., rules 1-6, 10-12), whereas others do not (i.e., rules 7-9). The rules which do not affect the generated content are:

Rules 7 and 8: CSS selectors only apply to the formal document tree, not on the generated tree; thus, these selectors will not yield a match.
Rule 9: The generated tree only inherits from the ancestors of the ‘use’ element and does not inherit from the ancestors of the referenced element; thus, this rule does not affect the generated content.

In the generated content below, the selectors that yield a match have been transferred into inline ‘style’ attributes for illustrative purposes.

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="3cm" viewBox="0 0 1200 300"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example Use04-GeneratedContent - 'use' with a 'transform' attribute</desc>

  <!-- 'style' and 'defs' sections left out -->

  <rect x="0" y="0" width="1200" height="300"
         style="fill:none; stroke:blue; stroke-width:3"/>
  <g style="/* rule 11 */ stroke-width:40">

    <!-- Start of generated content. Replaces 'use' -->
    <g style="/* rule 1 */ fill:blue;
                 /* rule 3 */ fill-opacity:.5;
                 /* rule 5 */ stroke-linecap:round;
                 /* rule 12 */ stroke-dashoffset:50" >
      <path d="M300 50 L900 50 L900 250 L300 250"
            style="/* rule 2 */ stroke:red; 
                   /* rule 4 */ stroke-opacity:.5; 
                   /* rule 6 */ stroke-linejoin: bevel; 
                   /* rule 10 */ stroke-dasharray:300,100" />
    </g> 
    <!-- End of generated content -->

  </g>
</svg>

View this example as SVG (SVG-enabled browsers only)

When a ‘use’ references another element which is another ‘use’ or whose content contains a ‘use’ element, then the deep cloning approach described above is recursive. However, a set of references that directly or indirectly reference a element to create a circular dependency is an error, as described in References and the ‘defs’ element.

Attribute definitions:

Name Value Lacuna value Animatable x, y <length> 0 yes width, height <length> (see prose) yes

Name	Value	Lacuna value	Animatable
x, y	<length>	0	yes
width, height	<length>	(see prose)	yes

The ‘x’, ‘y’, ‘width’ and ‘height’ attributes specify the positioning of the referenced element. The ‘width’ and ‘height’ attributes have different lacuna values depending on the type of the referenced element:

‘svg’: The lacuna values are the ‘width’ and ‘height’ values from the referenced ‘svg’ element.
anything else: The lacuna values are '100%'.

A negative value for ‘width’ or ‘height’ is an error (see Error processing). If ‘width’ or ‘height’ is zero then rendering of the ‘use’ element is disabled.

Name Value Lacuna value Animatable href <iri> (none) yes

Name	Value	Lacuna value	Animatable
href	<iri>	(none)	yes

An IRI reference to the element/fragment within an SVG document to be cloned for rendering.

5.8. The ‘image’ element

‘image’

Categories:

Graphics element, graphics referencing element

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

clipPath, marker, mask

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
presentation attributes —
‘preserveAspectRatio’
‘x’
‘y’
‘width’
‘height’
‘xlink:href’

DOM Interfaces:

SVGImageElement

The ‘image’ element indicates that the contents of a complete file are to be rendered into a given rectangle within the current user coordinate system. The ‘image’ element can refer to raster image files such as PNG or JPEG or to files with MIME type of "image/svg+xml". Conforming SVG viewers need to support at least PNG, JPEG and SVG format files.

The result of processing an ‘image’ is always a four-channel RGBA result. When an ‘image’ element references a raster image file such as PNG or JPEG files which only has three channels (RGB), then the effect is as if the object were converted into a 4-channel RGBA image with the alpha channel uniformly set to 1. For a single-channel raster image, the effect is as if the object were converted into a 4-channel RGBA image, where the single channel from the referenced object is used to compute the three color channels and the alpha channel is uniformly set to 1.

An ‘image’ element establishes a new viewport for the referenced file as described in Establishing a new viewport. The bounds for the new viewport are defined by attributes ‘x’, ‘y’, ‘width’ and ‘height’. The placement and scaling of the referenced image are controlled by the ‘preserveAspectRatio’ attribute on the ‘image’ element.

When an ‘image’ element references an SVG image, the ‘clip’ and ‘overflow’ properties on the root element in the referenced SVG image are ignored (in the same manner as the ‘x’, ‘y’, ‘width’ and ‘height’ attributes are ignored). Unless the value of ‘preserveAspectRatio’ on the ‘image’ element starts with 'defer', the ‘preserveAspectRatio’ attribute on the root element in the referenced SVG image is also ignored (see ‘preserveAspectRatio’ for details). Instead, the ‘preserveAspectRatio’ attribute on the referencing ‘image’ element defines how the SVG image content is fitted into the viewport and the ‘clip’ and ‘overflow’ properties on the ‘image’ element define how the SVG image content is clipped (or not) relative to the viewport.

Why does it make sense to override ‘clip’ but not ‘clip-path’?

The value of the ‘viewBox’ attribute to use when evaluating the ‘preserveAspectRatio’ attribute is defined by the referenced content. For content that clearly identifies a viewBox (e.g. an SVG file with the ‘viewBox’ attribute on the outermost svg element) that value should be used. For most raster content (PNG, JPEG) the bounds of the image should be used (i.e. the ‘image’ element has an implicit ‘viewBox’ of '0 0 raster-image-width raster-image-height'). Where no value is readily available (e.g. an SVG file with no ‘viewBox’ attribute on the outermost svg element) the ‘preserveAspectRatio’ attribute is ignored, and only the translation due to the ‘x’ & ‘y’ attributes of the viewport is used to display the content.

We should say how the use of an #xywh media fragment interacts with the the above.

For example, if the image element referenced a PNG or JPEG and preserveAspectRatio="xMinYMin meet", then the aspect ratio of the raster would be preserved (which means that the scale factor from image's coordinates to current user space coordinates would be the same for both X and Y), the raster would be sized as large as possible while ensuring that the entire raster fits within the viewport, and the top/left of the raster would be aligned with the top/left of the viewport as defined by the attributes ‘x’, ‘y’, ‘width’ and ‘height’ on the ‘image’ element. If the value of ‘preserveAspectRatio’ was 'none' then aspect ratio of the image would not be preserved. The image would be fitted such that the top/left corner of the raster exactly aligns with coordinate (‘x’, ‘y’) and the bottom/right corner of the raster exactly aligns with coordinate (‘x’+‘width’, ‘y’+‘height’).

The resource referenced by the ‘image’ element represents a separate document which generates its own parse tree and document object model (if the resource is XML). Thus, there is no inheritance of properties into the image.

Unlike ‘use’, the ‘image’ element cannot reference elements within an SVG file.

SVG 2 Requirement:	Support auto-sized images.
Resolution:	We will allow auto-sized images in SVG 2.
Purpose:	To allow raster images to use their own size without the need to set width and height.
Owner:	Cameron (ACTION-3340)

SVG 2 Requirement:	Support selecting part of an ‘image’ for display.
Resolution:	We will have a method for ‘image’ to select a part of an image to display, maybe by allowing ‘viewBox’ on it.
Purpose:	To allow selection of part of an image without requiring the author to manually slice the image.
Owner:	Nobody

SVG 2 Requirement:	Support the ‘object-fit’ and ‘object-position’ properties from css3-images.
Resolution:	SVG 2 will depend on CSS3 Image Values and CSS4 Image Values.
Purpose:	To align with the CSS way of specifying image fitting that ‘preserveAspectRatio’ provides.
Owner:	Cameron or Erik (no action)

Attribute definitions:

Name Value Lacuna value Animatable x, y <length> 0 yes width, height <length> | auto 0 yes

Name	Value	Lacuna value	Animatable
x, y	<length>	0	yes
width, height	<length> \| auto	0	yes

The ‘x’, ‘y’, ‘width’ and ‘height’ attributes specify the rectangular region into which the referenced image is placed.

A negative value for ‘width’ or ‘height’ is invalid (see Error processing). A value of zero for either attribute disables rendering of the element.

The 'auto' value for ‘width’ and ‘height’ is used to size the ‘image’ element automatically based on the intrinsic size or aspect ratio of the referenced image. If the intrinsic aspect ratio of the referenced image is unknown, it is assumed to be 2:1. If the intrinsic size of the referenced image is unknown, it is assumed to be 300×150, just as is required for CSS replaced elements. If 'auto' is specified for just one of ‘width’ or ‘height’, then the other is determined based on the intrinsic aspect ratio. The automatically determined ‘width’ and ‘height’ values are interpreted as user units, and are reflected in the x and y IDL attributes as SVG_LENGTHTYPE_NUMBER values.

Name Value Lacuna value Animatable xlink:href <iri> (none) yes

Name	Value	Lacuna value	Animatable
xlink:href	<iri>	(none)	yes

An IRI reference identifying the image to render.

Name Value Lacuna value Animatable preserveAspectRatio defer? <align> [ meet | slice ]? xMidYMid meet yes

Name	Value	Lacuna value	Animatable
preserveAspectRatio	defer? <align> [ meet \| slice ]?	xMidYMid meet	yes

Specifies the fitting behavior when the aspect ratio of the referenced image does not match the aspect ratio of the rectangle it is placed in. See the definition of ‘preserveAspectRatio’ for details.

An example:

<?xml version="1.0" standalone="no"?>
<svg width="4in" height="3in" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <desc>This graphic links to an external image
  </desc>
  <image x="200" y="200" width="100px" height="100px"
         xlink:href="myimage.png">
    <title>My image</title>
  </image>
</svg>

5.9. Conditional processing

5.9.1. Conditional processing overview

SVG contains a ‘switch’ element along with attributes ‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’ to provide an ability to specify alternate viewing depending on the capabilities of a given user agent or the user's language.

Attributes ‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’ act as tests and return either true or false results. The ‘switch’ renders the first of its children for which all of these attributes test true. If the given attribute is not specified, then a true value is assumed.

It sounds strange to talk about attributes "returning" a value.

Similar to the ‘display’ property, conditional processing attributes only affect the direct rendering of elements and do not prevent elements from being successfully referenced by other elements (such as via a ‘use’).

In consequence:

‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’ attributes affect ‘a’, ‘altGlyph’, ‘foreignObject’, ‘textPath’, ‘tref’, and ‘tspan’ elements.
‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’ attributes will have no effect on the ‘clipPath’, ‘filter’, ‘marker’, ‘mask’, ‘pattern’ and ‘symbol’ elements or on gradient elements.
‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’ attributes do not apply to the ‘defs’, and ‘cursor’ elements because they are not part of the rendering tree.
‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’ attributes affect ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, and ‘set’ elements. If the conditional statement on these animation elements fails, the animation will never be triggered.

5.9.2. The ‘switch’ element

‘switch’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’

a, clipPath, foreignObject, g, image, marker, mask, svg, switch, text, use

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’

DOM Interfaces:

SVGSwitchElement

The ‘switch’ element evaluates the ‘requiredFeatures’, ‘requiredExtensions’ and ‘systemLanguage’ attributes on its direct child elements in order, and then processes and renders the first child for which these attributes evaluate to true. All others will be bypassed and therefore not rendered. If the child element is a container element such as a ‘g’, then the entire subtree is either processed/rendered or bypassed/not rendered.

Note that the values of properties ‘display’ and ‘visibility’ have no effect on ‘switch’ element processing. In particular, setting ‘display’ to none on a child of a ‘switch’ element has no effect on true/false testing associated with ‘switch’ element processing.

For more information and an example, see Embedding foreign object types.

5.9.3. The ‘requiredFeatures’ attribute

Name Value Lacuna value Animatable requiredFeatures list-of-features (none) no

Name	Value	Lacuna value	Animatable
requiredFeatures	list-of-features	(none)	no

Need a grammar for list-of-features.

The value is a list of feature strings, with the individual values separated by white space. Determines whether all of the named features are supported by the user agent. Only feature strings defined in the Feature String appendix are allowed. If all of the given features are supported, then the attribute evaluates to true; otherwise, the current element and its children are skipped and thus will not be rendered.

If the attribute is not present, then its implicit return value is "true". If a null string or empty string value is given to attribute ‘requiredFeatures’, the attribute returns "false".

‘requiredFeatures’ is often used in conjunction with the ‘switch’ element. If the ‘requiredFeatures’ is used in other situations, then it represents a simple switch on the given element whether to render the element or not.

5.9.4. The ‘requiredExtensions’ attribute

The ‘requiredExtensions’ attribute defines a list of required language extensions. Language extensions are capabilities within a user agent that go beyond the feature set defined in this specification. Each extension is identified by an IRI reference.

Name Value Lacuna value Animatable requiredExtensions list-of-extensions (none) no: The value is a list of IRI references which identify the required extensions, with the individual values separated by white space. Determines whether all of the named extensions are supported by the user agent. If all of the given extensions are supported, then the attribute evaluates to true; otherwise, the current element and its children are skipped and thus will not be rendered.

Name	Value	Lacuna value	Animatable
requiredExtensions	list-of-extensions	(none)	no

If a given IRI reference contains white space within itself, that white space must be escaped.

If the attribute is not present, then its implicit return value is "true". If a null string or empty string value is given to attribute ‘requiredExtensions’, the attribute returns "false".

‘requiredExtensions’ is often used in conjunction with the ‘switch’ element. If the ‘requiredExtensions’ is used in other situations, then it represents a simple switch on the given element whether to render the element or not.

The IRI names for the extension should include versioning information, such as "http://example.org/SVGExtensionXYZ/1.0", so that script writers can distinguish between different versions of a given extension.

5.9.5. The ‘systemLanguage’ attribute

The attribute value is a comma-separated list of language names as defined in BCP 47 [BCP47].

Evaluates to "true" if one of the languages indicated by user preferences exactly equals one of the languages given in the value of this parameter, or if one of the languages indicated by user preferences exactly equals a prefix of one of the languages given in the value of this parameter such that the first tag character following the prefix is "-".

Evaluates to "false" otherwise.

Note: This use of a prefix matching rule does not imply that language tags are assigned to languages in such a way that it is always true that if a user understands a language with a certain tag, then this user will also understand all languages with tags for which this tag is a prefix.

The prefix rule simply allows the use of prefix tags if this is the case.

Implementation note: When making the choice of linguistic preference available to the user, implementers should take into account the fact that users are not familiar with the details of language matching as described above, and should provide appropriate guidance. As an example, users may assume that on selecting "en-gb", they will be served any kind of English document if British English is not available. The user interface for setting user preferences should guide the user to add "en" to get the best matching behavior.

Multiple languages MAY be listed for content that is intended for multiple audiences. For example, content that is presented simultaneously in the original Maori and English versions, would call for:

<text systemLanguage="mi, en"><!-- content goes here --></text>

However, just because multiple languages are present within the object on which the ‘systemLanguage’ test attribute is placed, this does not mean that it is intended for multiple linguistic audiences. An example would be a beginner's language primer, such as "A First Lesson in Latin," which is clearly intended to be used by an English-literate audience. In this case, the ‘systemLanguage’ test attribute should only include "en".

Authoring note: Authors should realize that if several alternative language objects are enclosed in a ‘switch’, and none of them matches, this may lead to situations where no content is displayed. It is thus recommended to include a "catch-all" choice at the end of such a ‘switch’ which is acceptable in all cases.

For the ‘systemLanguage’ attribute: Animatable: no.

If the attribute is not present, then its implicit return value is "true". If a null string or empty string value is given to attribute ‘systemLanguage’, the attribute returns "false".

‘systemLanguage’ is often used in conjunction with the ‘switch’ element. If the ‘systemLanguage’ is used in other situations, then it represents a simple switch on the given element whether to render the element or not.

Should have an attribute definition table in this section.

5.9.6. Applicability of test attributes

The following list describes the applicability of the test attributes to the elements that do not directly produce rendering.

This was already mentioned in the "Conditional processing overview" section. We should just describe this once.

the test attributes do not effect the ‘mask’, ‘clipPath’, ‘linearGradient’, ‘radialGradient’ and ‘pattern’ elements. The test attributes on a referenced element do not affect the rendering of the referencing element.
the test attributes do not effect the ‘defs’, and ‘cursor’ elements as they are not part of the rendering tree.
an animation element (‘animate’, ‘animateMotion’, ‘animateTransform’, ‘animateColor’ and ‘set’) will never be triggered if it has a test attribute that evaluates to false.

5.10. Common attributes

5.10.1. Attributes common to all elements: ‘id’ and ‘xml:base’

The ‘id’ and ‘xml:base’ attributes are available on all SVG elements:

Name Value Lacuna value Animatable id name (none) no

Name	Value	Lacuna value	Animatable
id	name	(none)	no

Need a grammar for name.

Standard XML attribute for assigning a unique name to an element. Refer to the Extensible Markup Language (XML) 1.0 Recommendation [XML10].

Name Value Lacuna value Animatable xml:base <iri> (none) no

Name	Value	Lacuna value	Animatable
xml:base	<iri>	(none)	no

Specifies a base IRI other than the base IRI of the document or external entity. Refer to the XML Base specification [XML-BASE].

Are we happy to keep promoting the use of ‘xml:base’? Is it a use case worth trying to include a more HTML-like syntax for – the ‘base’ element? We anyway need to define somewhere what effect the HTML ‘base’ element has on any SVG document fragments.

5.10.2. The ‘xml:lang’ and ‘xml:space’ attributes

Elements that might contain character data content have attributes ‘xml:lang’ and ‘xml:space’.

SVG 2 Requirement:	Deprecate the use of ‘xml:space’ to affect text layout and use the ‘white-space’ property instead.
Resolution:	We drop xml:space from SVG 2 and remove the relating tests from the SVG 1.1. test suite.
Purpose:	To align with CSS.
Owner:	Chris (ACTION-3004 and ACTION-3005, done)

Should we be moving ‘lang’ instead of ‘xlink:lang’?

Name Value Lacuna value Animatable xml:lang languageID (none) no

Name	Value	Lacuna value	Animatable
xml:lang	languageID	(none)	no

Need a grammar for languageID.

Standard XML attribute to specify the language (e.g., English) used in the contents and attribute values of particular elements. Refer to the Extensible Markup Language (XML) 1.0 Recommendation [XML10].

Name Value Lacuna value Animatable xml:space default | preserve default no

Name	Value	Lacuna value	Animatable
xml:space	default \| preserve	default	no

Deprecated XML attribute to specify whether white space is preserved in character data. The only possible values are 'default' and 'preserve'. Refer to the Extensible Markup Language (XML) 1.0 Recommendation [XML10] and to the discussion white space handling in SVG.

New content should use the ‘white-space’ property instead.

5.11. WAI-ARIA attributes

5.11.1. Role attribute

Rendered SVG elements may have an ARIA role attribute specified. The attribute, if specified, must have a value that is a set of space-separated tokens representing the various WAI-ARIA roles that the element belongs to. These tokens are role values defined in Definition of Roles ([ARIA], section 5.4).

The WAI-ARIA role that an SVG element has assigned to it is the first non-abstract role found in the list of values generated when the role attribute is split on spaces.

Name Value Lacuna value Animatable role white-space space separated tokens having values defined in Definition of Roles ([ARIA], section 5.4) default no: The role value is a set of white-space separated machine-extractable semantic information used to define the purpose of the element.

Name	Value	Lacuna value	Animatable
role	white-space space separated tokens having values defined in Definition of Roles ([ARIA], section 5.4)	default	no

5.11.2. State and property attributes (all aria- attributes)

Every renderable SVG element may have WAI-ARIA state and property attributes specified. These attributes are defined by ARIA in Definitions of States and Properties (all aria-* attributes) ([ARIA], section 6.6).

These attributes, if specified, must have a value that is the WAI-ARIA value type in the "Value" field of the definition for the state or property, mapped to the appropriate SVG value type according to Mapping WAI-ARIA Value types to langauges using the SVG mapping ([ARIA], section 10.2).

WAI-ARIA State and Property attributes can be used on any element. They are not always meaningful, however, and in such cases user agents might not perform any processing aside from including them in the DOM. Unlike some other host languages, SVG is not considered to have strong native host language semantics in terms of the user interface, consequently state and property attributes are processed according to the ARIA and ARIA User Agent Implementation Guide specifications. [ARIA] [ARIAIMPL]

5.12. DOM interfaces

5.12.1. Interface Document

The DOM Core specification defines a Document interface, which this specification extends.

In the case where an SVG document is embedded by reference, such as when an HTML document has an ‘object’ element whose ‘href’ attribute references an SVG document (i.e., a document whose MIME type is "image/svg+xml" and whose root element is thus an ‘svg’ element), there will exist two distinct DOM hierarchies. The first DOM hierarchy will be for the referencing document (e.g., an XHTML document). The second DOM hierarchy will be for the referenced SVG document.

HTML defines title, referrer and domain. We should remove them and file a bug on HTML to ensure that title does the right thing for SVG documents.

For historical reasons, Window objects must also have a writable, configurable, non-enumerable property named SVGDocument whose value is the Document interface object.

partial interface Document {
  readonly attribute DOMString title;
  readonly attribute DOMString referrer;
  readonly attribute DOMString domain;
  readonly attribute SVGSVGElement rootElement;
};

Attributes:

title (readonly DOMString): The title of a document as specified by the ‘title’ sub-element of the ‘svg’ root element (i.e., <svg><title>Here is the title</title>...</svg>)
referrer (readonly DOMString): Returns the URI of the page that linked to this page. The value is an empty string if the user navigated to the page directly (not through a link, but, for example, via a bookmark).
domain (readonly DOMString): The domain name of the server that served the document, or a null string if the server cannot be identified by a domain name.
rootElement (readonly SVGSVGElement): The root ‘svg’ in the document hierarchy.

5.12.2. Interface SVGSVGElement

A key interface definition is the SVGSVGElement interface, which is the interface that corresponds to the ‘svg’ element. This interface contains various miscellaneous commonly-used utility methods, such as matrix operations and the ability to control the time of redraw on visual rendering devices.

SVGSVGElement implements ViewCSS and DocumentCSS to provide access to the computed values of properties and the override style sheet as described in DOM Level 2 Style [DOM2STYLE].

Does it make sense for SVGSVGElement to implement ViewCSS and DocumentCSS? Shouldn't the former be on Window and the latter on Document or SVGDocument?

interface SVGSVGElement : SVGGraphicsElement {

  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
  readonly attribute SVGAnimatedLength width;
  readonly attribute SVGAnimatedLength height;
  readonly attribute SVGRect viewport;
  readonly attribute float pixelUnitToMillimeterX;
  readonly attribute float pixelUnitToMillimeterY;
  readonly attribute float screenPixelToMillimeterX;
  readonly attribute float screenPixelToMillimeterY;
  readonly attribute boolean useCurrentView;
  readonly attribute SVGViewSpec currentView;
           attribute float currentScale;
  readonly attribute SVGPoint currentTranslate;

  unsigned long suspendRedraw(unsigned long maxWaitMilliseconds);
  void unsuspendRedraw(unsigned long suspendHandleID);
  void unsuspendRedrawAll();
  void forceRedraw();
  void pauseAnimations();
  void unpauseAnimations();
  boolean animationsPaused();
  float getCurrentTime();
  void setCurrentTime(float seconds);
  NodeList getIntersectionList(SVGRect rect, SVGElement referenceElement);
  NodeList getEnclosureList(SVGRect rect, SVGElement referenceElement);
  boolean checkIntersection(SVGElement element, SVGRect rect);
  boolean checkEnclosure(SVGElement element, SVGRect rect);
  void deselectAll();
  SVGNumber createSVGNumber();
  SVGLength createSVGLength();
  SVGAngle createSVGAngle();
  SVGPoint createSVGPoint();
  SVGMatrix createSVGMatrix();
  SVGRect createSVGRect();
  SVGTransform createSVGTransform();
  SVGTransform createSVGTransformFromMatrix(SVGMatrix matrix);
  Element getElementById(DOMString elementId);
};

SVGSVGElement implements ViewCSS;
SVGSVGElement implements DocumentCSS;
SVGSVGElement implements SVGFitToViewBox;
SVGSVGElement implements SVGZoomAndPan;

Attributes:

x (readonly SVGAnimatedLength)

Corresponds to attribute ‘x’ on the given ‘svg’ element.

y (readonly SVGAnimatedLength)

Corresponds to attribute ‘y’ on the given ‘svg’ element.

width (readonly SVGAnimatedLength)

Corresponds to attribute ‘width’ on the given ‘svg’ element.

height (readonly SVGAnimatedLength)

Corresponds to attribute ‘height’ on the given ‘svg’ element.

viewport (readonly SVGRect)

The position and size of the viewport (implicit or explicit) that corresponds to this ‘svg’ element. When the user agent is actually rendering the content, then the position and size values represent the actual values when rendering. The position and size values are unitless values in the coordinate system of the parent element. If no parent element exists (i.e., ‘svg’ element represents the root of the document tree), if this SVG document is embedded as part of another document (e.g., via the HTML ‘object’ element), then the position and size are unitless values in the coordinate system of the parent document. (If the parent uses CSS or XSL layout, then unitless values represent pixel units for the current CSS or XSL viewport, as described in the CSS2 specification.) If the parent element does not have a coordinate system, then the user agent should provide reasonable default values for this attribute.

The SVGRect object is read only.

pixelUnitToMillimeterX (readonly float)

Size of a pixel units (as defined by CSS2) along the x-axis of the viewport, which represents a unit somewhere in the range of 70dpi to 120dpi, and, on systems that support this, might actually match the characteristics of the target medium. On systems where it is impossible to know the size of a pixel, a suitable default pixel size is provided.

Should this and the next three IDL attributes be removed? Are they implemented?

pixelUnitToMillimeterY (readonly float)

Corresponding size of a pixel unit along the y-axis of the viewport.

screenPixelToMillimeterX (readonly float)

User interface (UI) events in DOM Level 2 indicate the screen positions at which the given UI event occurred. When the user agent actually knows the physical size of a "screen unit", this attribute will express that information; otherwise, user agents will provide a suitable default value such as .28mm.

screenPixelToMillimeterY (readonly float)

Corresponding size of a screen pixel along the y-axis of the viewport.

useCurrentView (readonly boolean)

The initial view (i.e., before magnification and panning) of the current innermost SVG document fragment can be either the "standard" view (i.e., based on attributes on the ‘svg’ element such as ‘viewBox’) or to a "custom" view (i.e., a hyperlink into a particular ‘view’ or other element - see Linking into SVG content: IRI fragments and SVG views). If the initial view is the "standard" view, then this attribute is false. If the initial view is a "custom" view, then this attribute is true.

currentView (readonly SVGViewSpec)

The definition of the initial view (i.e., before magnification and panning) of the current innermost SVG document fragment. The meaning depends on the situation:

If the initial view was a "standard" view, then:
- the values for viewBox, preserveAspectRatio and zoomAndPan within currentView will match the values for the corresponding DOM attributes that are on SVGSVGElement directly
- the values for transform and viewTarget within currentView will be null
If the initial view was a link into a ‘view’ element, then:
- the values for viewBox, preserveAspectRatio and zoomAndPan within currentView will correspond to the corresponding attributes for the given ‘view’ element
- the values for transform and viewTarget within currentView will be null
If the initial view was a link into another element (i.e., other than a ‘view’), then:
- the values for viewBox, preserveAspectRatio and zoomAndPan within currentView will match the values for the corresponding DOM attributes that are on SVGSVGElement directly for the closest ancestor ‘svg’ element
- the values for transform within currentView will be null
- the viewTarget within currentView will represent the target of the link
If the initial view was a link into the SVG document fragment using an SVG view specification fragment identifier (i.e., #svgView(...)), then:
- the values for viewBox, preserveAspectRatio, zoomAndPan, transform and viewTarget within currentView will correspond to the values from the SVG view specification fragment identifier

The object itself and its contents are both read only.

currentScale (float)

On an outermost svg element, this attribute indicates the current scale factor relative to the initial view to take into account user magnification and panning operations, as described under Magnification and panning. DOM attributes currentScale and currentTranslate are equivalent to the 2x3 matrix [a b c d e f] = [currentScale 0 0 currentScale currentTranslate.x currentTranslate.y]. If "magnification" is enabled (i.e., zoomAndPan="magnify"), then the effect is as if an extra transformation were placed at the outermost level on the SVG document fragment (i.e., outside the outermost svg element).

When accessed on an ‘svg’ element that is not an outermost svg element, it is undefined what behavior this attribute has.

currentTranslate (readonly SVGPoint)

On an outermost svg element, the corresponding translation factor that takes into account user "magnification".

When accessed on an ‘svg’ element that is not an outermost svg element, it is undefined what behavior this attribute has.

Operations:

unsigned long suspendRedraw(unsigned long maxWaitMilliseconds)

This method is deprecated, and is only kept due to compatibility with legacy content. Calling this method has no effect on redrawing.

Parameters

unsigned long maxWaitMilliseconds

This parameter is ignored.

Returns

The returned value is always 1.

void unsuspendRedraw(unsigned long suspendHandleID)

This method is deprecated, and is only kept due to compatibility with legacy content. Calling this method has no effect on redrawing.

Parameters

unsigned long suspendHandleID

This parameter is ignored.

void unsuspendRedrawAll()

This method is deprecated, and is only kept due to compatibility with legacy content. Calling this method has no effect on redrawing.

void forceRedraw()

In rendering environments supporting interactivity, forces the user agent to immediately redraw all regions of the viewport that require updating.

Should this method be neutered as suspendRedraw and friends have been? Do implementations actually support painting in the middle of a running script by calling this method?

void pauseAnimations()

Suspends (i.e., pauses) all currently running animations that are defined within the SVG document fragment corresponding to this ‘svg’ element, causing the animation clock corresponding to this document fragment to stand still until it is unpaused.

void unpauseAnimations()

Unsuspends (i.e., unpauses) currently running animations that are defined within the SVG document fragment, causing the animation clock to continue from the time at which it was suspended.

boolean animationsPaused()

Returns true if this SVG document fragment is in a paused state.

Returns: Boolean indicating whether this SVG document fragment is in a paused state.

float getCurrentTime()

Returns the current time in seconds relative to the start time for the current SVG document fragment. If getCurrentTime is called before the document timeline has begun (for example, by script running in a ‘script’ element before the document's SVGLoad event is dispatched), then 0 is returned.

Returns: The current time in seconds, or 0 if the document timeline has not yet begun.

void setCurrentTime(float seconds)

Adjusts the clock for this SVG document fragment, establishing a new current time. If setCurrentTime is called before the document timeline has begun (for example, by script running in a ‘script’ element before the document's SVGLoad event is dispatched), then the value of seconds in the last invocation of the method gives the time that the document will seek to once the document timeline has begun.

Parameters

float seconds

The new current time in seconds relative to the start time for the current SVG document fragment.

NodeList getIntersectionList(SVGRect rect, SVGElement referenceElement)

Returns the list of graphics elements whose rendered content intersects the supplied rectangle. Each candidate graphics element is to be considered a match only if the same graphics element can be a target of pointer events as defined in ‘pointer-events’ processing.

Parameters

SVGRect rect

The test rectangle. The values are in the initial coordinate system for the current ‘svg’ element.
SVGElement referenceElement

If not null, then any intersected element that doesn't have the referenceElement as ancestor must not be included in the returned NodeList.

Returns

A list of Elements whose content intersects the supplied rectangle. This NodeList must be implemented identically to the NodeList interface as defined in DOM4 ([DOM4], section 8.1) with the exception that the interface is not live.

NodeList getEnclosureList(SVGRect rect, SVGElement referenceElement)

Returns the list of graphics elements whose rendered content is entirely contained within the supplied rectangle. Each candidate graphics element is to be considered a match only if the same graphics element can be a target of pointer events as defined in ‘pointer-events’ processing.

Parameters

SVGRect rect

The test rectangle. The values are in the initial coordinate system for the current ‘svg’ element.
SVGElement referenceElement

If not null, then any intersected element that doesn't have the referenceElement as ancestor must not be included in the returned NodeList.

Returns

A list of Elements whose content is enclosed by the supplied rectangle. This NodeList must be implemented identically to the NodeList interface as defined in DOM4 ([DOM4], section 8.1) with the exception that the interface is not live.

boolean checkIntersection(SVGElement element, SVGRect rect)

Returns true if the rendered content of the given element intersects the supplied rectangle. Each candidate graphics element is to be considered a match only if the same graphics element can be a target of pointer events as defined in ‘pointer-events’ processing.

Parameters

SVGElement element

The element on which to perform the given test.
SVGRect rect

The test rectangle. The values are in the initial coordinate system for the current ‘svg’ element.

Returns

True or false, depending on whether the given element intersects the supplied rectangle.

boolean checkEnclosure(SVGElement element, SVGRect rect)

Returns true if the rendered content of the given element is entirely contained within the supplied rectangle. Each candidate graphics element is to be considered a match only if the same graphics element can be a target of pointer events as defined in ‘pointer-events’ processing.

Parameters

SVGElement element

The element on which to perform the given test.
SVGRect rect

The test rectangle. The values are in the initial coordinate system for the current ‘svg’ element.

Returns

True or false, depending on whether the given element is enclosed by the supplied rectangle.

void deselectAll()

Unselects any selected objects, including any selections of text strings and type-in bars.

What is a type-in bar? Do we need deselectAll given we have DOM Selection?

SVGNumber createSVGNumber()

Creates an SVGNumber object outside of any document trees. The object is initialized to a value of zero.

Returns: An SVGNumber object.

SVGLength createSVGLength()

Creates an SVGLength object outside of any document trees. The object is initialized to the value of 0 user units.

Returns: An SVGLength object.

SVGAngle createSVGAngle()

Creates an SVGAngle object outside of any document trees. The object is initialized to the value 0 degrees (unitless).

Returns: An SVGAngle object.

SVGPoint createSVGPoint()

Creates an SVGPoint object outside of any document trees. The object is initialized to the point (0,0) in the user coordinate system.

Returns: An SVGPoint object.

SVGMatrix createSVGMatrix()

Creates an SVGMatrix object outside of any document trees. The object is initialized to the identity matrix.

Returns: An SVGMatrix object.

SVGRect createSVGRect()

Creates an SVGRect object outside of any document trees. The object is initialized such that all values are set to 0 user units.

Returns: An SVGRect object.

SVGTransform createSVGTransform()

Creates an SVGTransform object outside of any document trees. The object is initialized to an identity matrix transform (SVG_TRANSFORM_MATRIX).

Returns: An SVGTransform object.

SVGTransform createSVGTransformFromMatrix(SVGMatrix matrix)

Creates an SVGTransform object outside of any document trees. The object is initialized to the given matrix transform (i.e., SVG_TRANSFORM_MATRIX). The values from the parameter matrix are copied, the matrix parameter is not adopted as SVGTransform::matrix.

Parameters

SVGMatrix matrix

The transform matrix.

Returns

An SVGTransform object.

Element getElementById(DOMString elementId)

Searches this SVG document fragment (i.e., the search is restricted to a subset of the document tree) for an Element whose id is given by elementId. If an Element is found, that Element is returned. If no such element exists, returns null. Behavior is not defined if more than one element has this id.

Do we need this? If so, can we define it in terms of calling Document.getElementById and checking whether the returned element is within the subtree?

Parameters

DOMString elementId

The unique id value for an element.

Returns

The matching element.

5.12.3. Interface SVGGElement

The SVGSVGElement interface corresponds to the ‘g’ element.

interface SVGGElement : SVGGraphicsElement {
};

5.12.4. Interface SVGDefsElement

The SVGDefsElement interface corresponds to the ‘defs’ element.

interface SVGDefsElement : SVGGraphicsElement {
};

5.12.5. Interface SVGDescElement

The SVGDescElement interface corresponds to the ‘desc’ element.

interface SVGDescElement : SVGElement {
};

5.12.6. Interface SVGTitleElement

The SVGTitleElement interface corresponds to the ‘title’ element.

interface SVGTitleElement : SVGElement {
};

5.12.7. Interface SVGSymbolElement

The SVGSymbolElement interface corresponds to the ‘symbol’ element.

interface SVGSymbolElement : SVGElement {
};

SVGSymbolElement implements SVGFitToViewBox;

5.12.8. Interface SVGUseElement

The SVGUseElement interface corresponds to the ‘use’ element.

interface SVGUseElement : SVGGraphicsElement {
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
  readonly attribute SVGAnimatedLength width;
  readonly attribute SVGAnimatedLength height;
  readonly attribute SVGElementInstance instanceRoot;
  readonly attribute SVGElementInstance animatedInstanceRoot;
};

SVGUseElement implements SVGURIReference;

Attributes:

x (readonly SVGAnimatedLength): Corresponds to attribute ‘x’ on the given ‘use’ element.
y (readonly SVGAnimatedLength): Corresponds to attribute ‘y’ on the given ‘use’ element.
width (readonly SVGAnimatedLength): Corresponds to attribute ‘width’ on the given ‘use’ element.
height (readonly SVGAnimatedLength): Corresponds to attribute ‘height’ on the given ‘use’ element.
instanceRoot (readonly SVGElementInstance): The root of the "instance tree". See description of SVGElementInstance for a discussion on the instance tree.
animatedInstanceRoot (readonly SVGElementInstance): If the ‘xlink:href’ attribute is being animated, contains the current animated root of the "instance tree". If the ‘xlink:href’ attribute is not currently being animated, contains the same value as instanceRoot. See description of SVGElementInstance for a discussion on the instance tree.

5.12.9. Interface SVGElementInstance

For each ‘use’ element, the SVG DOM maintains a shadow tree (the "instance tree") of objects of type SVGElementInstance. An SVGElementInstance represents a single node in the instance tree. The root object in the instance tree is pointed to by the instanceRoot attribute on the SVGUseElement object for the corresponding ‘use’ element.

If the ‘use’ element references a simple graphics element such as a ‘rect’, then there is only a single SVGElementInstance object, and the correspondingElement attribute on this SVGElementInstance object is the SVGRectElement that corresponds to the referenced ‘rect’ element.

If the ‘use’ element references a ‘g’ which contains two ‘rect’ elements, then the instance tree contains three SVGElementInstance objects, a root SVGElementInstance object whose correspondingElement is the SVGGElement object for the ‘g’, and then two child SVGElementInstance objects, each of which has its correspondingElement that is an SVGRectElement object.

If the referenced object is itself a ‘use’, or if there are ‘use’ subelements within the referenced object, the instance tree will contain recursive expansion of the indirect references to form a complete tree. For example, if a ‘use’ element references a ‘g’, and the ‘g’ itself contains a ‘use’, and that ‘use’ references a ‘rect’, then the instance tree for the original (outermost) ‘use’ will consist of a hierarchy of SVGElementInstance objects, as follows:

SVGElementInstance #1 (parentNode=null, firstChild=#2, correspondingElement is the 'g')
  SVGElementInstance #2 (parentNode=#1, firstChild=#3, correspondingElement is the other 'use')
    SVGElementInstance #3 (parentNode=#2, firstChild=null, correspondingElement is the 'rect')

interface SVGElementInstance : EventTarget {
  readonly attribute SVGElement correspondingElement;
  readonly attribute SVGUseElement correspondingUseElement;
  readonly attribute SVGElementInstance parentNode;
  readonly attribute SVGElementInstanceList childNodes;
  readonly attribute SVGElementInstance firstChild;
  readonly attribute SVGElementInstance lastChild;
  readonly attribute SVGElementInstance previousSibling;
  readonly attribute SVGElementInstance nextSibling;
};

Attributes:

correspondingElement (readonly SVGElement): The corresponding element to which this object is an instance. For example, if a ‘use’ element references a ‘rect’ element, then an SVGElementInstance is created, with its correspondingElement being the SVGRectElement object for the ‘rect’ element.
correspondingUseElement (readonly SVGUseElement): The corresponding ‘use’ element to which this SVGElementInstance object belongs. When ‘use’ elements are nested (e.g., a ‘use’ references another ‘use’ which references a graphics element such as a ‘rect’), then the correspondingUseElement is the outermost ‘use’ (i.e., the one which indirectly references the ‘rect’, not the one with the direct reference).
parentNode (readonly SVGElementInstance): The parent of this SVGElementInstance within the instance tree. All SVGElementInstance objects have a parent except the SVGElementInstance which corresponds to the element which was directly referenced by the ‘use’ element, in which case parentNode is null.
childNodes (readonly SVGElementInstanceList): An SVGElementInstanceList that contains all children of this SVGElementInstance within the instance tree. If there are no children, this is an SVGElementInstanceList containing no entries (i.e., an empty list).
firstChild (readonly SVGElementInstance): The first child of this SVGElementInstance within the instance tree. If there is no such SVGElementInstance, this returns null.
lastChild (readonly SVGElementInstance): The last child of this SVGElementInstance within the instance tree. If there is no such SVGElementInstance, this returns null.
previousSibling (readonly SVGElementInstance): The SVGElementInstance immediately preceding this SVGElementInstance. If there is no such SVGElementInstance, this returns null.
nextSibling (readonly SVGElementInstance): The SVGElementInstance immediately following this SVGElementInstance. If there is no such SVGElementInstance, this returns null.

5.12.10. Interface SVGElementInstanceList

The SVGElementInstanceList interface provides the abstraction of an ordered collection of SVGElementInstance objects, without defining or constraining how this collection is implemented.

interface SVGElementInstanceList {

  readonly attribute unsigned long length;

  SVGElementInstance item(unsigned long index);
};

Attributes:

length (readonly unsigned long): The number of SVGElementInstance objects in the list. The range of valid child indices is 0 to length-1 inclusive.

Operations:

SVGElementInstance item(unsigned long index)

Returns the indexth item in the collection. If index is greater than or equal to the number of nodes in the list, this returns null.

Parameters

unsigned long index

Index into the collection.

Returns

The SVGElementInstance object at the indexth position in the SVGElementInstanceList, or null if that is not a valid index.

5.12.11. Interface SVGImageElement

The SVGImageElement interface corresponds to the ‘image’ element.

interface SVGImageElement : SVGGraphicsElement {
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
  readonly attribute SVGAnimatedLength width;
  readonly attribute SVGAnimatedLength height;
  readonly attribute SVGAnimatedPreserveAspectRatio preserveAspectRatio;
};

SVGImageElement implements SVGURIReference;

Attributes:

x (readonly SVGAnimatedLength): Corresponds to attribute ‘x’ on the given ‘image’ element.
y (readonly SVGAnimatedLength): Corresponds to attribute ‘y’ on the given ‘image’ element.
width (readonly SVGAnimatedLength): Corresponds to attribute ‘width’ on the given ‘image’ element.
height (readonly SVGAnimatedLength): Corresponds to attribute ‘height’ on the given ‘image’ element.
preserveAspectRatio (readonly SVGAnimatedPreserveAspectRatio): Corresponds to attribute ‘preserveAspectRatio’ on the given ‘image’ element.

5.12.12. Interface SVGSwitchElement

The SVGSwitchElement interface corresponds to the ‘switch’ element.

interface SVGSwitchElement : SVGGraphicsElement {
};

5.12.13. Interface GetSVGDocument

This interface provides access to an SVG document embedded by reference in another DOM-based language. The expectation is that the interface is implemented on DOM objects that allow such SVG document references, such as the DOM Element object that corresponds to an HTML ‘object’ element. Such DOM objects are often also required to implement the EmbeddingElement defined in the Window specification [WINDOW].

This interface is deprecated and may be dropped from future versions of the SVG specification. Authors are suggested to use the contentDocument attribute on the EmbeddingElement interface to obtain a referenced SVG document, if that interface is available.

interface GetSVGDocument {
  SVGDocument getSVGDocument();
};

Operations:

SVGDocument getSVGDocument()

This method must return the Document object embedded content in an embedding element, or null if there is no document.

Note that this is equivalent to fetching the value of the EmbeddingElement::contentDocument attribute of the embedding element, if the EmbeddingElement interface is also implemented. The author is advised to check that the document element of the returned Document is indeed an ‘svg’ element instead of assuming that that will always be the case.

Returns: The Document object for the referenced document, or null if there is no document.

Chapter 6: Styling

6.1. SVG's styling properties

SVG uses styling properties to describe many of its document parameters. Styling properties define how the graphics elements in the SVG content are to be rendered. SVG uses styling properties for the following:

Parameters which are clearly visual in nature and thus lend themselves to styling. Examples include all attributes that define how an object is "painted," such as fill and stroke colors, linewidths and dash styles.
Parameters having to do with text styling such as font family and size.
Parameters which impact the way that graphical elements are rendered, such as specifying clipping paths, masks, arrowheads, markers and filter effects.

SVG shares many of its styling properties with CSS [CSS21] and XSL [XSL]. Except for any additional SVG-specific rules explicitly mentioned in this specification, the normative definition of properties that are shared with CSS and XSL is the definition of the property from the CSS 2.1 specification [CSS21].

The following properties are shared between CSS 2.1 and SVG. Most of these properties are also defined in XSL:

This list needs to be updated. We should list all the properties we normative require support for, and which specification they are defined in.

Font properties:
- ‘font’
- ‘font-family’
- ‘font-size’
- ‘font-size-adjust’
- ‘font-stretch’
- ‘font-style’
- ‘font-variant’
- ‘font-weight’
Text properties:
- ‘direction’
- ‘letter-spacing’
- ‘text-decoration’
- ‘unicode-bidi’
- ‘word-spacing’
Other properties for visual media:
- ‘clip’, only applicable to outermost svg element.
- ‘color’, used to provide a potential indirect value (currentColor) for the ‘fill’, ‘stroke’, ‘stop-color’, ‘flood-color’ and ‘lighting-color’ properties. (The SVG properties which support color allow a color specification which is extended from CSS 2.1 to accommodate color definitions in arbitrary color spaces. See Color profile descriptions.)
- ‘cursor’
- ‘display’
- ‘overflow’, only applicable to elements which establish a new viewport.
- ‘visibility’

The following SVG properties are not defined in CSS 2.1. The complete normative definitions for these properties are found in this specification:

Clipping, Masking and Compositing properties:
- ‘clip-path’
- ‘clip-rule’
- ‘mask’
- ‘opacity’
Filter Effects properties:
- ‘enable-background’
- ‘filter’
- ‘flood-color’
- ‘flood-opacity’
- ‘lighting-color’
Gradient properties:
- ‘stop-color’
- ‘stop-opacity’
Interactivity properties:
- ‘pointer-events’
Color and Painting properties:
- ‘color-interpolation’
- ‘color-rendering’
- ‘fill’
- ‘fill-opacity’
- ‘fill-rule’
- ‘image-rendering’
- ‘marker’
- ‘marker-end’
- ‘marker-mid’
- ‘marker-start’
- ‘shape-rendering’
- ‘stroke’
- ‘stroke-dasharray’
- ‘stroke-dashoffset’
- ‘stroke-linecap’
- ‘stroke-linejoin’
- ‘stroke-miterlimit’
- ‘stroke-opacity’
- ‘stroke-width’
- ‘text-rendering’
Text properties:
- ‘alignment-baseline’
- ‘baseline-shift’
- ‘dominant-baseline’
- ‘glyph-orientation-horizontal’
- ‘glyph-orientation-vertical’
- ‘text-anchor’
- ‘writing-mode’

A table that lists and summarizes the styling properties can be found in the Property Index.

6.2. Usage scenarios for styling

Does this section add anything?

SVG has many usage scenarios, each with different needs. Here are three common usage scenarios:

SVG content used as an exchange format (style sheet language-independent):

In some usage scenarios, reliable interoperability of SVG content across software tools is the main goal. Since support for a particular style sheet language is not guaranteed across all implementations, it is a requirement that SVG content can be fully specified without the use of a style sheet language.
SVG content generated as the output from XSLT:

XSLT offers the ability to take a stream of arbitrary XML content as input, apply potentially complex transformations, and then generate SVG content as output [XSLT]. XSLT can be used to transform XML data extracted from databases into an SVG graphical representation of that data. It is a requirement that fully specified SVG content can be generated from XSLT.
SVG content styled with CSS:

CSS is a widely implemented declarative language for assigning styling properties to XML content, including SVG [CSS21]. It represents a combination of features, simplicity and compactness that makes it very suitable for many applications of SVG. It is a requirement that CSS styling can be applied to SVG content.

6.3. Alternative ways to specify styling properties

Styling properties can be assigned to SVG elements in the following two ways:

Presentation attributes

Styling properties can be assigned using SVG's presentation attributes. For each styling property defined in this specification, there is a corresponding XML presentation attribute available on all relevant SVG elements. Detailed information on the presentation attributes can be found in Specifying properties using the presentation attributes.

The presentation attributes are style sheet language independent and thus are applicable to usage scenario 1 above (i.e., tool interoperability). Because it is straightforward to assign values to XML attributes from XSLT, the presentation attributes are well-suited to usage scenario 2 above (i.e., SVG generation from XSLT). (See Styling with XSL below.)

Conforming SVG Interpreters and Conforming SVG Viewers are required to support SVG's presentation attributes.
CSS Stylesheets

To support usage scenario 3 above, SVG content can be styled with CSS. For more information, see Styling with CSS.

Conforming SVG Interpreters and Conforming SVG Viewers that support CSS styling of generic (i.e., text-based) XML content are required to also support CSS styling of SVG content.

6.4. Specifying properties using the presentation attributes

For each styling property defined in this specification (see Property Index), there is a corresponding XML attribute (the presentation attribute) with the same name that is available on all relevant SVG elements. For example, SVG has a ‘fill’ property that defines how to paint the interior of a shape. There is a corresponding presentation attribute with the same name (i.e., ‘fill’) that can be used to specify a value for the ‘fill’ property on a given element.

We should state that for each property defined in this specification, plus for each in a list here for properties in other specifications, there exists a presentation attribute.

Do we plan to grow a presentation attribute for each new CSS property that we support?

The following example shows how the ‘fill’ and ‘stroke’ properties can be specified on a ‘rect’ using the ‘fill’ and ‘stroke’ presentation attributes. The rectangle will be filled with red and outlined with blue:

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
     width="10cm" height="5cm" viewBox="0 0 1000 500">
  <rect x="200" y="100" width="600" height="300" 
        fill="red" stroke="blue" stroke-width="3"/>
</svg>

The presentation attributes offer the following advantages:

Broad support. All versions of Conforming SVG Interpreters and Conforming SVG Viewers are required to support the presentation attributes.
Simplicity. Styling properties can be attached to elements by simply providing a value for the presentation attribute on the proper elements.
Restyling. SVG content that uses the presentation attributes is highly compatible with downstream processing using XSLT [XSLT] [XSLT2] or supplemental styling by adding CSS style rules to override some of the presentation attributes.
Convenient generation using XSLT. In some cases, XSLT can be used to generate fully styled SVG content. The presentation attributes are compatible with convenient generation of SVG from XSLT.

In some situations, SVG content that uses the presentation attributes has potential limitations versus SVG content that is styled with a style sheet language such as CSS (see Styling with CSS). In other situations, such as when an XSLT style sheet generates SVG content from semantically rich XML source files, the limitations below may not apply. Depending on the situation, some of the following potential limitations may or may not apply to the presentation attributes:

Styling attached to content. The presentation attributes are attached directly to particular elements, thereby diminishing potential advantages that comes from abstracting styling from content, such as the ability to restyle documents for different uses and environments.
Flattened data model. In and of themselves, the presentation attributes do not offer the higher level abstractions that you get with a styling system, such as the ability to define named collections of properties which are applied to particular categories of elements. The result is that, in many cases, important higher level semantic information can be lost, potentially making document reuse and restyling more difficult.
Potential increase in file size. Many types of graphics use similar styling properties across multiple elements. For example, a company organization chart might assign one collection of styling properties to the boxes around temporary workers (e.g., dashed outlines, red fill), and a different collection of styling properties to permanent workers (e.g., solid outlines, blue fill). Styling systems such as CSS allow collections of properties to be defined once in a file. With the styling attributes, it might be necessary to specify presentation attributes on each different element.
Potential difficulty when embedded into a CSS-styled parent document. When SVG content is embedded in other XML, and the desire is to style all aspects of the compound document with CSS, use of the presentation attributes might introduce complexity and difficulty. In this case, it is sometimes easier if the SVG content does not use the presentation attributes and instead is styled using CSS facilities.

For user agents that support CSS, the presentation attributes must be translated to corresponding CSS style rules according to rules described in Precedence of non-CSS presentational hints ([CSS21], section 6.4.4), with the additional clarification that the presentation attributes are conceptually inserted into a new author style sheet which is the first in the author style sheet collection. The presentation attributes thus will participate in the CSS 2.1 cascade as if they were replaced by corresponding CSS style rules placed at the start of the author style sheet with a specificity of zero. In general, this means that the presentation attributes have lower priority than other CSS style rules specified in author style sheets or ‘style’ attributes.

User agents that do not support CSS must ignore any CSS style rules defined in CSS style sheets and ‘style’ attributes. In this case, the CSS cascade does not apply. (Inheritance of properties, however, does apply. See Property inheritance.)

An !important declaration ([CSS21], section 6.4.2) within a presentation attribute definition is an invalid value.

Animation of presentation attributes is equivalent to animating the corresponding property. Thus, the same effect occurs from animating the presentation attribute with attributeType="XML" as occurs with animating the corresponding property with attributeType="CSS" (see ‘attributeType’).

6.5. Styling with XSL

How much do we really need to mention XSLT? Probably the only thing worth mentioning is that <?xml-stylesheet?> can be used in an XML serialized SVG document (not that we require support for this, though).

XSL style sheets [XSLT] [XSLT2] define how to transform XML content into something else, usually other XML. When XSLT is used in conjunction with SVG, sometimes SVG content will serve as both input and output for XSL style sheets. Other times, XSL style sheets will take non-SVG content as input and generate SVG content as output.

The following example uses an external XSL style sheet to transform SVG content into modified SVG content (see Referencing external style sheets). The style sheet sets the ‘fill’ and ‘stroke’ properties on all rectangles to red and blue, respectively:

mystyle.xsl
<?xml version="1.0" standalone="no"?>
<xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:svg="http://www.w3.org/2000/svg">
  <xsl:output
    method="xml"
    encoding="utf-8">
  <!-- Add version to topmost 'svg' element -->
  <xsl:template match="/svg:svg">
    <xsl:copy>
      <xsl:copy-of select="@*"/>
      <xsl:attribute name="version">1.1</xsl:attribute>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>
  <!-- Add styling to all 'rect' elements -->
  <xsl:template match="svg:rect">
    <xsl:copy>
      <xsl:copy-of select="@*"/>
      <xsl:attribute name="fill">red</xsl:attribute>
      <xsl:attribute name="stroke">blue</xsl:attribute>
      <xsl:attribute name="stroke-width">3</xsl:attribute>
    </xsl:copy>
  </xsl:template>
</xsl:stylesheet>

SVG file to be transformed by mystyle.xsl
<?xml version="1.0" standalone="no"?>
<?xml-stylesheet href="mystyle.xsl" type="application/xml"?>
<svg xmlns="http://www.w3.org/2000/svg"
     width="10cm" height="5cm">
  <rect x="2cm" y="1cm" width="6cm" height="3cm"/>
</svg>

SVG content after applying mystyle.xsl
<?xml version="1.0" encoding="utf-8"?>
<svg xmlns="http://www.w3.org/2000/svg"
     width="10cm" height="5cm" version="1.1">
  <rect x="2cm" y="1cm" width="6cm" height="3cm" fill="red" stroke="blue" stroke-width="3"/>
</svg>

6.6. Styling with CSS

SVG implementations that support CSS are required to support the following:

External CSS style sheets referenced from the current document (see Referencing external style sheets)
Internal CSS style sheets (i.e., style sheets embedded within the current document, such as within an SVG ‘style’ element)
Inline style (i.e., CSS property declarations within a ‘style’ attribute on a particular SVG element)

The following example shows the use of an external CSS style sheet to set the ‘fill’ and ‘stroke’ properties on all rectangles to red and blue, respectively:

mystyle.css
rect {
  fill: red;
  stroke: blue;
  stroke-width: 3
}

SVG file referencing mystyle.css
<?xml version="1.0" standalone="no"?>
<?xml-stylesheet href="mystyle.css" type="text/css"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
     width="10cm" height="5cm" viewBox="0 0 1000 500">
  <rect x="200" y="100" width="600" height="300"/>
</svg>

View this example as SVG (SVG-enabled browsers only)

CSS style sheets can be embedded within SVG content inside of a ‘style’ element. The following example uses an internal CSS style sheet to achieve the same result as the previous example:

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
     width="10cm" height="5cm" viewBox="0 0 1000 500">
  <defs>
    <style type="text/css"><![CDATA[
      rect {
        fill: red;
        stroke: blue;
        stroke-width: 3
      }
    ]]></style>
  </defs>
  <rect x="200" y="100" width="600" height="300"/>
</svg>

View this example as SVG (SVG-enabled browsers only)

Note how the CSS style sheet is placed within a CDATA construct (i.e., <![CDATA[ ... ]]>). Placing internal CSS style sheets within CDATA blocks is sometimes necessary since CSS style sheets can include characters, such as ">", which conflict with XML parsers. Even if a given style sheet does not use characters that conflict with XML parsing, it is highly recommended that internal style sheets be placed inside CDATA blocks.

Implementations that support CSS are also required to support CSS inline style. Similar to the ‘style’ attribute in HTML, CSS inline style can be declared within a ‘style’ attribute in SVG by specifying a semicolon-separated list of property declarations, where each property declaration has the form "name: value". Note that property declarations inside the ‘style’ attribute must follow CSS style rules, see The 'style' attribute.

The following example shows how the ‘fill’ and ‘stroke’ properties can be specified on a ‘rect’ using the ‘style’ attribute. Just like the previous example, the rectangle will be filled with red and outlined with blue:

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
     width="10cm" height="5cm" viewBox="0 0 1000 500">
  <rect x="200" y="100" width="600" height="300" 
        style="fill: red; stroke: blue; stroke-width: 3"/>
</svg>

View this example as SVG (SVG-enabled browsers only)

In an SVG user agent that supports CSS style sheets, the following facilities from CSS 2.1 must be supported:

CSS 2.1 selectors within style sheets ([CSS21], chapter 5). Because SVG is intended to be used as one component in a multiple namespace XML application and CSS 2.1 is not namespace aware, type selectors will only match against the local part of the element's qualified name.
External CSS style sheets [XML-SS], CSS style sheets within ‘style’ elements and CSS declaration blocks ([CSS21], section 4.1.7) within ‘style’ attributes attached to specific SVG elements.
CSS 2.1 rules for assigning property values, cascading and inheritance ([CSS21], chapter 6).
@media, @import and @charset rules within style sheets ([CSS21], sections 7.2.1, 6.3 and 4.4).
@font-face rules within style sheets ([CSS3FONTS], section 4.1).
CSS 2.1's dynamic pseudo-classes :hover, :active and :focus and pseudo-classes :first-child, :visited, :link and :lang ([CSS21], section 5.11). The remaining CSS2 pseudo-classes, including those having to do with generated content ([CSS21], chapter 12), are not part of the SVG language definition. An SVG element gains focus when it is selected. See Text selection.
For the purposes of aural media, SVG represents a CSS-stylable XML grammar. In user agents that support aural style sheets, CSS aural style properties can be applied as defined in CSS2 ([CSS21], chapter 19). (See Aural style sheets.)
CSS style sheets defined within a ‘style’ element can be immediate character data content of the ‘style’ element or can be embedded within a CDATA section ([XML10], section 2.7).

SVG defines an @color-profile at-rule ([CSS21], section 4.1.5) for defining color profiles so that ICC color profiles can be applied to CSS-styled SVG content.

Note the following about relative URIs and external CSS style sheets: The CSS 2.1 specification says ([CSS21], section 4.3.4) that relative URIs (as defined in Uniform Resource Identifiers (URI): Generic Syntax [RFC3986]) within style sheets are resolved such that the base URI is that of the style sheet, not that of the referencing document.

6.7. Case sensitivity of property names and values

Property declarations via presentation attributes are expressed in XML [XML10], which is case-sensitive. CSS property declarations specified either in CSS style sheets or in a ‘style’ attribute, on the other hand, are generally case-insensitive with some exceptions ([CSS21], section 4.1.3).

Because presentation attributes are expressed as XML attributes, their names are case-sensitive and must be given exactly as they are defined. When using a presentation attribute to specify a value for the ‘fill’ property, the presentation attribute must be be specified as fill="…" and not fill="…" or Fill="…". Keyword values, such as italic in font-style="italic", are also case-sensitive and must be specified using the exact case used in the specification which defines the given keyword. For example, the keyword sRGB must have lowercase "s" and uppercase "RGB".

Property declarations within CSS style sheets or in a ‘style’ attribute must only conform to CSS rules, which are generally more lenient with regard to case sensitivity. However, to promote consistency across the different ways for expressing styling properties, it is strongly recommended that authors use the exact property names (usually, lowercase letters and hyphens) as defined in the relevant specification and express all keywords using the same case as is required by presentation attributes and not take advantage of CSS's ability to ignore case.

SVG 2 Requirement:	Consider relaxing case sensitivity of presentation attribute values.
Resolution:	We will make property values case insensitivity.
Purpose:	To align presentation attribute syntax parsing with parsing of the corresponding CSS property.
Owner:	Cameron (ACTION-3276)

6.8. Facilities from CSS and XSL used by SVG

SVG shares various relevant properties and approaches common to CSS and XSL, plus the semantics of many of the processing rules.

SVG shares the following facilities with CSS and XSL:

Shared properties. Many of SVG's properties are shared between CSS 2.1, XSL and SVG. (See list of shared properties).
Syntax rules. (The normative references are CSS2 syntax and basic data types and The grammar of CSS 2.1; in [CSS21], chapter 4 and appendix D.)
Allowable data types. (The normative reference is CSS 2.1 syntax and basic data types ([CSS21], chapter 4), with the exception that SVG length and angle values without a unit identifier. See Units.)
Inheritance rules.
The color keywords from CSS 2.1 that correspond to the colors used by objects in the user's environment. (The normative reference is CSS 2.1 system colors; in [CSS21], section 18.2.)
For implementations that support CSS styling of SVG content, then that styling must be compatible with various other rules in CSS. (See Styling with CSS.)

6.9. Referencing external style sheets

External style sheets are referenced using the mechanism documented in Associating Style Sheets with XML documents Version 1.0 [XML-SS].

We should suggest @import as a means for referencing external CSS style sheets that will also work in an HTML5 document.

Where is it defined that an HTML ‘link’ element can cause a style sheet to be loaded and applied to SVG content? Should we allow (an SVG or HTML namespace) ‘link’ element in an SVG document fragment?

6.10. The ‘style’ element

SVG 2 Requirement:	Add HTML5 ‘style’ element attributes to SVG's ‘style’ element.
Resolution:	SVG 2 ‘style’ element shall be aligned with the HTML5 ‘style’ element.
Purpose:	To not surprise authors with different behavior for the ‘style’ element in HTML and SVG content.
Owner:	Cameron (ACTION-3277)

The ‘style’ element allows style sheets to be embedded directly within SVG content. SVG's ‘style’ element has the same attributes as the corresponding element in HTML (see HTML's ‘style’ element).

‘style’

Categories:

None

Content model:

Any elements or character data.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
‘type’
‘media’
‘title’

DOM Interfaces:

SVGStyleElement

Attribute definitions:

Name Value Lacuna value Animatable type content-type text/css no: This attribute specifies the style sheet language of the element's contents. The style sheet language is specified as a content type (e.g., "text/css"), as per MIME Part Two: Media Types [RFC2046]. If the attribute is not specified, then the style sheet language is assumed to be CSS.
Name Value Lacuna value Animatable media media (none) no: This attribute specifies the intended destination medium for style information. It may be a single media descriptor or a comma-separated list. The default value for this attribute is "all". The set of recognized media-descriptors are the list of media types recognized by CSS 2.1 ([CSS21], section 7.3).
Name Value Lacuna value Animatable title advisory-title (none) no: (For compatibility with HTML 4 [HTML4].) This attribute specifies an advisory title for the ‘style’ element.

Name	Value	Lacuna value	Animatable
type	content-type	text/css	no

Name	Value	Lacuna value	Animatable
media	media	(none)	no

Name	Value	Lacuna value	Animatable
title	advisory-title	(none)	no

The syntax of style data depends on the style sheet language.

Some style sheet languages might allow a wider variety of rules in the ‘style’ element than in the ‘style’. For example, with CSS, rules can be declared within a ‘style’ element that cannot be declared within a ‘style’ attribute.

An example showing the ‘style’ element is provided above (see example).

6.11. The ‘class’ attribute

Attribute definitions:

class = list: This attribute assigns a class name or set of class names to an element. Any number of elements may be assigned the same class name or names. Multiple class names must be separated by white space characters.
Animatable: yes.

The ‘class’ attribute assigns one or more class names to an element. The element may be said to belong to these classes. A class name may be shared by several element instances. The ‘class’ attribute has several roles:

As a style sheet selector (when an author wishes to assign style information to a set of elements).
For general purpose processing by user agents.

In the following example, the ‘text’ element is used in conjunction with the ‘class’ attribute to markup document messages. Messages appear in both English and French versions.

<!-- English messages -->
<text class="info" lang="en">Variable declared twice</text>
<text class="warning" lang="en">Undeclared variable</text>
<text class="error" lang="en">Bad syntax for variable name</text>
<!-- French messages -->
<text class="info" lang="fr">Variable déclarée deux fois</text>
<text class="warning" lang="fr">Variable indéfinie</text>
<text class="error" lang="fr">Erreur de syntaxe pour variable</text>

In an SVG user agent that supports CSS styling, the following CSS style rules would tell visual user agents to display informational messages in green, warning messages in yellow, and error messages in red:

text.info    { color: green }
text.warning { color: yellow }
text.error   { color: red }

6.12. The ‘style’ attribute

The ‘style’ attribute allows per-element style rules to be specified directly on a given element. When CSS styling is used, CSS inline style is specified by including semicolon-separated property declarations of the form "name : value" within the ‘style’ attribute. Property declarations must follow CSS style rules thus CSS defined properties (e.g. 'font-size') when having a <length> value must include a unit (for non-zero values). See SVG's styling properties for a list of CSS defined properties.

Attribute definitions:

style = style: This attribute specifies style information for the current element. The style attribute specifies style information for a single element. The style sheet language of inline style rules is CSS.
Animatable: no.

The style attribute may be used to apply a particular style to an individual SVG element. If the style will be reused for several elements, authors should use the ‘style’ element to regroup that information. For optimal flexibility, authors should define styles in external style sheets.

An example showing the ‘style’ attribute is provided above (see example).

6.13. Property inheritance

Whether or not the user agent supports CSS, property inheritance in SVG follows the property inheritance rules defined in the CSS 2.1 specification. The normative definition for property inheritance is the Inheritance section of the CSS 2.1 specification ([CSS21], section 6.2).

The definition of each property indicates whether the property can inherit the value of its parent.

In SVG, as in CSS 2.1, most elements inherit computed values ([CSS21], section 6.1.2). For cases where something other than computed values are inherited, the property definition will describe the inheritance rules. For specified values ([CSS21], section 6.1.1) which are expressed in user units, in pixels (e.g., 20px) or in absolute values, the computed value equals the specified value. For specified values which use certain relative units (i.e., em, ex and percentages), the computed value will have the same units as the value to which it is relative. Thus, if the parent element has a ‘font-size’ of 10pt and the current element has a ‘font-size’ of 120%, then the computed value for ‘font-size’ on the current element will be 12pt. In cases where the referenced value for relative units is not expressed in any of the standard SVG units (i.e., CSS units or user units), such as when a percentage is used relative to the current viewport or an object bounding box, then the computed value will be in user units.

Note that SVG has some facilities wherein a property which is specified on an ancestor element might effect its descendant element, even if the descendant element has a different assigned value for that property. For example, if a ‘clip-path’ property is specified on an ancestor element, and the current element has a ‘clip-path’ of none, the ancestor's clipping path still applies to the current element because the semantics of SVG state that the clipping path used on a given element is the intersection of all clipping paths specified on itself and all ancestor elements. The key concept is that property assignment (with possible property inheritance) happens first. After properties values have been assigned to the various elements, then the user agent applies the semantics of each assigned property, which might result in the property assignment of an ancestor element affecting the rendering of its descendants.

6.14. The scope/range of styles

The following define the scope/range of style sheets:

Stand-alone SVG document: There is one parse tree. Style sheets defined anywhere within the SVG document (in style elements or style attributes, or in external style sheets linked with the style sheet processing instruction) apply across the entire SVG document.
Stand-alone SVG document embedded in an HTML or XML document with the ‘img’, ‘object’ (HTML) or ‘image’ (SVG) elements: There are two completely separate parse trees; one for the referencing document (perhaps HTML or XHTML), and one for the SVG document. Style sheets defined anywhere within the referencing document (in style elements or style attributes, or in external style sheets linked with the style sheet processing instruction) apply across the entire referencing document but have no effect on the referenced SVG document. Style sheets defined anywhere within the referenced SVG document (in style elements or style attributes, or in external style sheets linked with the style sheet processing instruction) apply across the entire SVG document, but do not affect the referencing document (perhaps HTML or XHTML). To get the same styling across both the [X]HTML document and the SVG document, link them both to the same style sheet.
Stand-alone SVG content textually included in an XML document: There is a single parse tree, using multiple namespaces; one or more subtrees are in the SVG namespace. Style sheets defined anywhere within the XML document (in style elements or style attributes, or in external style sheets linked with the style sheet processing instruction) apply across the entire document, including those parts of it in the SVG namespace. To get different styling for the SVG part, use the ‘style’ attribute, or put an ‘id’ on the ‘svg’ element and use contextual CSS selectors, or use XSL selectors.

As part of unifying HTML's and SVG's ‘style’ element, we should allow and mention scoped style sheets here.

6.15. User agent style sheet

The user agent shall maintain a user agent style sheet ([CSS21], section 6.4) for elements in the SVG namespace for visual media ([CSS21], section 7.3.1). The user agent style sheet below is expressed using CSS syntax; however, user agents are required to support the behavior that corresponds to this default style sheet even if CSS style sheets are not supported in the user agent:

svg, symbol, image, marker, pattern, foreignObject { overflow: hidden }
svg { width:attr(width); height:attr(height) }

This needs to be reviewed. It should at least use @namespace to cause the rules to match only SVG elements. attr(width) won't do the right thing if the ‘width’ attribute does not use a unit. And what about when the attributes are being animated? Presumably attr() doesn't look at animated values.

The first line of the above user agent style sheet will cause the initial clipping path to be established at the bounds of the initial viewport. Furthermore, it will cause new clipping paths to be established at the bounds of the listed elements, all of which are elements that establish a new viewport. (Refer to the description of SVG's use of the ‘overflow’ property for more information.)

The second line of the above user agent style sheet will cause the ‘width’ and ‘height’ attributes on the ‘svg’ element to be used as the default values for the 'width' and 'height' properties during layout ([CSS21], chapter 9).

6.16. Aural style sheets

For the purposes of aural media, SVG represents a stylable XML grammar. In user agents that support CSS aural style sheets, aural style properties ([CSS21], chapter 19) can be applied as defined in CSS 2.1.

Aural style properties can be applied to any SVG element that can contain character data content, including ‘desc’ ‘title’ ‘tspan’, ‘tref’, ‘altGlyph’ and ‘textPath’. On user agents that support aural style sheets, the following CSS 2.1 properties can be applied:

The above list misses ‘a’, which can be within a ‘text’ element. Is there a conformance class in CSS we can link to for "user agents that support aural style sheets"? Are aural properties still relevant?

Aural property	Definition in [CSS21]
‘azimuth’	Section A.8
‘cue’	Section A.6
‘cue-after’	Section A.6
‘cue-before’	Section A.6
‘elevation’	Section A.8
‘pause’	Section A.5
‘pause-after’	Section A.5
‘pause-before’	Section A.5
‘pitch’	Section A.9
‘pitch-range’	Section A.9
‘play-during’	Section A.7
‘richness’	Section A.9
‘speak’	Section A.4
‘speak-header’	Section A.11.1
‘speak-numeral’	Section A.10
‘speak-punctuation’	Section A.10
‘speech-rate’	Section A.9
‘stress’	Section A.9
‘voice-family’	Section A.9
‘volume’	Section A.3

For user agents that support aural style sheets and also support DOM Level 2 Core, the user agent is required to support the DOM interfaces defined in Document Object Model CSS ([DOM2STYLE], chapter 2) that correspond to aural properties. (See Relationship with DOM2 CSS object model.)

6.17. DOM interfaces

6.17.1. Interface SVGStyleElement

The SVGStyleElement interface corresponds to the ‘style’ element.

interface SVGStyleElement : SVGElement {
  attribute DOMString type;
  attribute DOMString media;
  attribute DOMString title;
};

Attributes:

type (DOMString): Corresponds to attribute ‘type’ on the given element.
media (DOMString): Corresponds to attribute ‘media’ on the given element.
title (DOMString): Corresponds to attribute ‘title’ on the given element.

Chapter 7: Coordinate Systems, Transformations and Units

7.1. Introduction

For all media, the SVG canvas describes "the space where the SVG content is rendered." The canvas is infinite for each dimension of the space, but rendering occurs relative to a finite rectangular region of the canvas. This finite rectangular region is called the SVG viewport. For visual media ([CSS21], section 7.3.1) the SVG viewport is the viewing area where the user sees the SVG content.

The size of the SVG viewport (i.e., its width and height) is determined by a negotiation process (see Establishing the size of the initial viewport) between the SVG document fragment and its parent (real or implicit). Once that negotiation process is completed, the SVG user agent is provided the following information:

a number (usually an integer) that represents the width in "pixels" of the viewport
a number (usually an integer) that represents the height in "pixels" of the viewport
(highly desirable but not required) a real number value that indicates the size in real world units, such as millimeters, of a "pixel" (i.e., a px unit as defined in CSS 2.1 ([CSS21], section 4.3.2)

Why are real world units relevant? Shouldn't we just be relying on CSS' fixed ratio of mm to px units?

Using the above information, the SVG user agent determines the viewport, an initial viewport coordinate system and an initial user coordinate system such that the two coordinates systems are identical. Both coordinates systems are established such that the origin matches the origin of the viewport (for the root viewport, the viewport origin is at the top/left corner), and one unit in the initial coordinate system equals one "pixel" in the viewport. (See Initial coordinate system.) The viewport coordinate system is also called viewport space and the user coordinate system is also called user space.

Lengths in SVG can be specified as:

(if no unit identifier is provided) values in user space — for example, "15"
(if a unit identifier is provided) a length expressed as an absolute or relative unit measure — for example, "15mm" or "5em"

The supported length unit identifiers are: em, ex, px, pt, pc, cm, mm, in, and percentages.

A new user space (i.e., a new current coordinate system) can be established at any place within an SVG document fragment by specifying transformations in the form of transformation matrices or simple transformation operations such as rotation, skewing, scaling and translation. Establishing new user spaces via coordinate system transformations are fundamental operations to 2D graphics and represent the usual method of controlling the size, position, rotation and skew of graphic objects.

New viewports also can be established. By establishing a new viewport, you can redefine the meaning of percentages units and provide a new reference rectangle for "fitting" a graphic into a particular rectangular area. ("Fit" means that a given graphic is transformed in such a way that its bounding box in user space aligns exactly with the edges of a given viewport.)

7.2. The initial viewport

Do we need to port over some more up-to-date definitions of sizing from SVG Tiny 1.2?

The SVG user agent negotiates with its parent user agent to determine the viewport into which the SVG user agent can render the document. In some circumstances, SVG content will be embedded (by reference or inline) within a containing document. This containing document might include attributes, properties and/or other parameters (explicit or implicit) which specify or provide hints about the dimensions of the viewport for the SVG content. SVG content itself optionally can provide information about the appropriate viewport region for the content via the ‘width’ and ‘height’ XML attributes on the outermost svg element. The negotiation process uses any information provided by the containing document and the SVG content itself to choose the viewport location and size.

Talking about a "parent user agent" really makes this sound like we have a separate plugin SVG implementation communicating with a browser hosting the plugin. These days, it's going to be the same user agent.

The ‘width’ attribute on the outermost svg element establishes the viewport's width, unless the following conditions are met:

the SVG content is a separately stored resource that is embedded by reference (such as the ‘object’ element in XHTML [XHTML]), or the SVG content is embedded inline within a containing document;
and the referencing element or containing document is styled using CSS [CSS21] or XSL [XSL];
and there are CSS-compatible positioning properties ([CSS21], section 9.3) specified on the referencing element (e.g., the ‘object’ element) or on the containing document's outermost svg element that are sufficient to establish the width of the viewport.

Under these conditions, the positioning properties establish the viewport's width.

Similarly, if there are positioning properties specified on the referencing element or on the outermost svg element that are sufficient to establish the height of the viewport, then these positioning properties establish the viewport's height; otherwise, the ‘height’ attribute on the outermost svg element establishes the viewport's height.

If the ‘width’ or ‘height’ attributes on the outermost svg element are in user units (i.e., no unit identifier has been provided), then the value is assumed to be equivalent to the same number of "px" units (see Units).

In the following example, an SVG graphic is embedded inline within a parent XML document which is formatted using CSS layout rules. Since CSS positioning properties are not provided on the outermost svg element, the width="100px" and height="200px" attributes determine the size of the initial viewport:

<?xml version="1.0" standalone="yes"?>
<parent xmlns="http://some.url">
   
   <!-- SVG graphic -->
   <svg xmlns='http://www.w3.org/2000/svg'
      width="100px" height="200px" version="1.1">
      <path d="M100,100 Q200,400,300,100"/>
      <!-- rest of SVG graphic would go here -->
   </svg>   
   
</parent>

The initial clipping path for the SVG document fragment is established according to the rules described in The initial clipping path.

7.3. The initial coordinate system

For the outermost svg element, the SVG user agent determines an initial viewport coordinate system and an initial user coordinate system such that the two coordinates systems are identical. The origin of both coordinate systems is at the origin of the viewport, and one unit in the initial coordinate system equals one "pixel" (i.e., a px unit as defined in CSS 2.1 ([CSS21], section 4.3.2) in the viewport. In most cases, such as stand-alone SVG documents or SVG document fragments embedded (by reference or inline) within XML parent documents where the parent's layout is determined by CSS [CSS21] or XSL [XSL], the initial viewport coordinate system (and therefore the initial user coordinate system) has its origin at the top/left of the viewport, with the positive x-axis pointing towards the right, the positive y-axis pointing down, and text rendered with an "upright" orientation, which means glyphs are oriented such that Roman characters and full-size ideographic characters for Asian scripts have the top edge of the corresponding glyphs oriented upwards and the right edge of the corresponding glyphs oriented to the right.

If the SVG implementation is part of a user agent which supports styling XML documents using CSS 2.1 compatible px units, then the SVG user agent should get its initial value for the size of a px unit in real world units to match the value used for other XML styling operations; otherwise, if the user agent can determine the size of a px unit from its environment, it should use that value; otherwise, it should choose an appropriate size for one px unit. In all cases, the size of a px must be in conformance with the rules described in CSS 2.1 ([CSS21], section 4.3.2).

Example InitialCoords below shows that the initial coordinate system has the origin at the top/left with the x-axis pointing to the right and the y-axis pointing down. The initial user coordinate system has one user unit equal to the parent (implicit or explicit) user agent's "pixel".

<?xml version="1.0" standalone="no"?>
<svg width="300px" height="100px" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <desc>Example InitialCoords - SVG's initial coordinate system</desc>

  <g fill="none" stroke="black" stroke-width="3" >
    <line x1="0" y1="1.5" x2="300" y2="1.5" />
    <line x1="1.5" y1="0" x2="1.5" y2="100" />
  </g>
  <g fill="red" stroke="none" >
    <rect x="0" y="0" width="3" height="3" />
    <rect x="297" y="0" width="3" height="3" />
    <rect x="0" y="97" width="3" height="3" />
  </g>
  <g font-size="14" font-family="Verdana" >
    <text x="10" y="20">(0,0)</text>
    <text x="240" y="20">(300,0)</text>
    <text x="10" y="90">(0,100)</text>
  </g>
</svg>

Example InitialCoords

View this example as SVG (SVG-enabled browsers only)

7.4. Coordinate system transformations

A new user space (i.e., a new current coordinate system) can be established by specifying transformations in the form of a ‘transform’ property on a container element or graphics element or a ‘viewBox’ attribute on an ‘svg’, ‘symbol’, ‘marker’, ‘pattern’ and the ‘view’ element. The ‘transform’ property and ‘viewBox’ attribute transform user space coordinates and lengths on sibling attributes on the given element (see effect of the ‘transform’ attribute on sibling attributes and effect of the ‘viewBox’ attribute on sibling attributes) and all of its descendants. Transformations can be nested, in which case the effect of the transformations are cumulative.

The section "effect of the transform attribute on sibling attributes" has been removed since we now reference the ‘transform’ property, but we probably should still include a similar section on how the property affects attributes on the element.

Example OrigCoordSys below shows a document without transformations. The text string is specified in the initial coordinate system.

<?xml version="1.0" standalone="no"?>
<svg width="400px" height="150px"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example OrigCoordSys - Simple transformations: original picture</desc>
  <g fill="none" stroke="black" stroke-width="3" >
    <!-- Draw the axes of the original coordinate system -->
    <line x1="0" y1="1.5" x2="400" y2="1.5" />
    <line x1="1.5" y1="0" x2="1.5" y2="150" />
  </g>
  <g>
    <text x="30" y="30" font-size="20" font-family="Verdana" >
      ABC (orig coord system)
    </text>
  </g>
</svg>

Example OrigCoordSys

View this example as SVG (SVG-enabled browsers only)

Example NewCoordSys establishes a new user coordinate system by specifying transform="translate(50,50)" on the third ‘g’ element below. The new user coordinate system has its origin at location (50,50) in the original coordinate system. The result of this transformation is that the coordinate (30,30) in the new user coordinate system gets mapped to coordinate (80,80) in the original coordinate system (i.e., the coordinates have been translated by 50 units in X and 50 units in Y).

<?xml version="1.0" standalone="no"?>
<svg width="400px" height="150px"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example NewCoordSys - New user coordinate system</desc>
  <g fill="none" stroke="black" stroke-width="3" >
    <!-- Draw the axes of the original coordinate system -->
    <line x1="0" y1="1.5" x2="400" y2="1.5" />
    <line x1="1.5" y1="0" x2="1.5" y2="150" />
  </g>
  <g>
    <text x="30" y="30" font-size="20" font-family="Verdana" >
      ABC (orig coord system)
    </text>
  </g>
  <!-- Establish a new coordinate system, which is
       shifted (i.e., translated) from the initial coordinate
       system by 50 user units along each axis. -->
  <g transform="translate(50,50)">
    <g fill="none" stroke="red" stroke-width="3" >
      <!-- Draw lines of length 50 user units along 
           the axes of the new coordinate system -->
      <line x1="0" y1="0" x2="50" y2="0" stroke="red" />
      <line x1="0" y1="0" x2="0" y2="50" />
    </g>
    <text x="30" y="30" font-size="20" font-family="Verdana" >
      ABC (translated coord system)
    </text>
  </g>
</svg>

Example NewCoordSys

View this example as SVG (SVG-enabled browsers only)

Example RotateScale illustrates simple rotate and scale transformations. The example defines two new coordinate systems:

one which is the result of a translation by 50 units in X and 30 units in Y, followed by a rotation of 30 degrees
another which is the result of a translation by 200 units in X and 40 units in Y, followed by a scale transformation of 1.5.

<?xml version="1.0" standalone="no"?>
<svg width="400px" height="120px" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <desc>Example RotateScale - Rotate and scale transforms</desc>
  <g fill="none" stroke="black" stroke-width="3" >
    <!-- Draw the axes of the original coordinate system -->
    <line x1="0" y1="1.5" x2="400" y2="1.5" />
    <line x1="1.5" y1="0" x2="1.5" y2="120" />
  </g>
  <!-- Establish a new coordinate system whose origin is at (50,30)
       in the initial coord. system and which is rotated by 30 degrees. -->
  <g transform="translate(50,30)">
    <g transform="rotate(30)">
      <g fill="none" stroke="red" stroke-width="3" >
        <line x1="0" y1="0" x2="50" y2="0" />
        <line x1="0" y1="0" x2="0" y2="50" />
      </g>
      <text x="0" y="0" font-size="20" font-family="Verdana" fill="blue" >
        ABC (rotate)
      </text>
    </g>
  </g>
  <!-- Establish a new coordinate system whose origin is at (200,40)
       in the initial coord. system and which is scaled by 1.5. -->
  <g transform="translate(200,40)">
    <g transform="scale(1.5)">
      <g fill="none" stroke="red" stroke-width="3" >
        <line x1="0" y1="0" x2="50" y2="0" />
        <line x1="0" y1="0" x2="0" y2="50" />
      </g>
      <text x="0" y="0" font-size="20" font-family="Verdana" fill="blue" >
        ABC (scale)
      </text>
    </g>
  </g>
</svg>

Example RotateScale

View this example as SVG (SVG-enabled browsers only)

Example Skew defines two coordinate systems which are skewed relative to the origin coordinate system.

<?xml version="1.0" standalone="no"?>
<svg width="400px" height="120px" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <desc>Example Skew - Show effects of skewX and skewY</desc>
  <g fill="none" stroke="black" stroke-width="3" >
    <!-- Draw the axes of the original coordinate system -->
    <line x1="0" y1="1.5" x2="400" y2="1.5" />
    <line x1="1.5" y1="0" x2="1.5" y2="120" />
  </g>
  <!-- Establish a new coordinate system whose origin is at (30,30)
       in the initial coord. system and which is skewed in X by 30 degrees. -->
  <g transform="translate(30,30)">
    <g transform="skewX(30)">
      <g fill="none" stroke="red" stroke-width="3" >
        <line x1="0" y1="0" x2="50" y2="0" />
        <line x1="0" y1="0" x2="0" y2="50" />
      </g>
      <text x="0" y="0" font-size="20" font-family="Verdana" fill="blue" >
        ABC (skewX)
      </text>
    </g>
  </g>
  <!-- Establish a new coordinate system whose origin is at (200,30)
       in the initial coord. system and which is skewed in Y by 30 degrees. -->
  <g transform="translate(200,30)">
    <g transform="skewY(30)">
      <g fill="none" stroke="red" stroke-width="3" >
        <line x1="0" y1="0" x2="50" y2="0" />
        <line x1="0" y1="0" x2="0" y2="50" />
      </g>
      <text x="0" y="0" font-size="20" font-family="Verdana" fill="blue" >
        ABC (skewY)
      </text>
    </g>
  </g>
</svg>

Example Skew

View this example as SVG (SVG-enabled browsers only)

7.5. Nested transformations

Transformations can be nested to any level. The effect of nested transformations is to post-multiply (i.e., concatenate) the subsequent transformation matrices onto previously defined transformations:
3-by-3 matrix concatenation

For each given element, the accumulation of all transformations that have been defined on the given element and all of its ancestors up to and including the element that established the current viewport (usually, the ‘svg’ element which is the most immediate ancestor to the given element) is called the current transformation matrix or CTM. The CTM thus represents the mapping of current user coordinates to viewport coordinates:
current transformation matrix: CTM

Example Nested illustrates nested transformations.

<?xml version="1.0" standalone="no"?>
<svg width="400px" height="150px" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <desc>Example Nested - Nested transformations</desc>
  <g fill="none" stroke="black" stroke-width="3" >
    <!-- Draw the axes of the original coordinate system -->
    <line x1="0" y1="1.5" x2="400" y2="1.5" />
    <line x1="1.5" y1="0" x2="1.5" y2="150" />
  </g>
  <!-- First, a translate -->
  <g transform="translate(50,90)">
    <g fill="none" stroke="red" stroke-width="3" >
      <line x1="0" y1="0" x2="50" y2="0" />
      <line x1="0" y1="0" x2="0" y2="50" />
    </g>
    <text x="0" y="0" font-size="16" font-family="Verdana" >
      ....Translate(1)
    </text>
    <!-- Second, a rotate -->
    <g transform="rotate(-45)">
      <g fill="none" stroke="green" stroke-width="3" >
        <line x1="0" y1="0" x2="50" y2="0" />
        <line x1="0" y1="0" x2="0" y2="50" />
      </g>
      <text x="0" y="0" font-size="16" font-family="Verdana" >
        ....Rotate(2)
      </text>
      <!-- Third, another translate -->
      <g transform="translate(130,160)">
        <g fill="none" stroke="blue" stroke-width="3" >
          <line x1="0" y1="0" x2="50" y2="0" />
          <line x1="0" y1="0" x2="0" y2="50" />
        </g>
        <text x="0" y="0" font-size="16" font-family="Verdana" >
          ....Translate(3)
        </text>
      </g>
    </g>
  </g>
</svg>

Example Nested

View this example as SVG (SVG-enabled browsers only)

In the example above, the CTM within the third nested transformation (i.e., the transform="translate(130,160)") consists of the concatenation of the three transformations, as follows:
Matrix concatenation

7.6. The ‘transform’ property

Name:	transform
Animatable:	yes

Do we need this blue box, and if so, should we expand it to include all of the property definition information? Some sections (such as for ‘color’) do not have the blue box. Others, like the one for ‘white-space’, have all the information from the CSS specification it comes from. Regardless, I think we don't need to mention whether the property is animatable since all properties are animatable.

The term <transform-list> used by this specification is equivalent to a list of <transform-functions>, the value of the ‘transform’ property.

See the CSS3 Transforms spec for the description of the ‘transform’ property and the value of <transform-functions> [CSS3TRANSFORMS].

7.7. The ‘viewBox’ attribute

It is often desirable to specify that a given set of graphics stretch to fit a particular container element. The ‘viewBox’ attribute provides this capability.

All elements that establish a new viewport (see elements that establish viewports), plus the ‘marker’, ‘pattern’ and ‘view’ elements have attribute ‘viewBox’. The value of the ‘viewBox’ attribute is a list of four numbers <min-x>, <min-y>, <width> and <height>, separated by whitespace and/or a comma, which specify a rectangle in user space which should be mapped to the bounds of the viewport established by the given element, taking into account attribute ‘preserveAspectRatio’. If specified, an additional transformation is applied to all descendants of the given element to achieve the specified effect.

A negative value for <width> or <height> is an error (see Error processing). A value of zero disables rendering of the element.

Example ViewBox illustrates the use of the ‘viewBox’ attribute on the outermost svg element to specify that the SVG content should stretch to fit bounds of the viewport.

<?xml version="1.0" standalone="no"?>
<svg width="300px" height="200px" version="1.1"
     viewBox="0 0 1500 1000" preserveAspectRatio="none"
     xmlns="http://www.w3.org/2000/svg">
  <desc>Example ViewBox - uses the viewBox 
   attribute to automatically create an initial user coordinate
   system which causes the graphic to scale to fit into the
   viewport no matter what size the viewport is.</desc>
  <!-- This rectangle goes from (0,0) to (1500,1000) in user space.
       Because of the viewBox attribute above,
       the rectangle will end up filling the entire area
       reserved for the SVG content. -->
  <rect x="0" y="0" width="1500" height="1000" 
        fill="yellow" stroke="blue" stroke-width="12"  />
  <!-- A large, red triangle -->
  <path fill="red"  d="M 750,100 L 250,900 L 1250,900 z"/>
  <!-- A text string that spans most of the viewport -->
  <text x="100" y="600" font-size="200" font-family="Verdana" >
    Stretch to fit
  </text>
</svg>

Example ViewBox
Rendered into viewport with width=300px, height=200px		Rendered into viewport with width=150px, height=200px

View this example as SVG (SVG-enabled browsers only)

The effect of the ‘viewBox’ attribute is that the user agent automatically supplies the appropriate transformation matrix to map the specified rectangle in user space to the bounds of a designated region (often, the viewport). To achieve the effect of the example on the left, with viewport dimensions of 300 by 200 pixels, the user agent needs to automatically insert a transformation which scales both X and Y by 0.2. The effect is equivalent to having a viewport of size 300px by 200px and the following supplemental transformation in the document, as follows:

<?xml version="1.0" standalone="no"?>
<svg width="300px" height="200px" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <g transform="scale(0.2)">
    <!-- Rest of document goes here -->
  </g>
</svg>

To achieve the effect of the example on the right, with viewport dimensions of 150 by 200 pixels, the user agent needs to automatically insert a transformation which scales X by 0.1 and Y by 0.2. The effect is equivalent to having a viewport of size 150px by 200px and the following supplemental transformation in the document, as follows:

<?xml version="1.0" standalone="no"?>
<svg width="150px" height="200px" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <g transform="scale(0.1 0.2)">
    <!-- Rest of document goes here -->
  </g>
</svg>

(Note: in some cases the user agent will need to supply a translate transformation in addition to a scale transformation. For example, on an outermost svg element, a translate transformation will be needed if the ‘viewBox’ attributes specifies values other than zero for <min-x> or <min-y>.)

Unlike the ‘transform’ property (see effect of the ‘transform’ attribute on sibling attributes), the automatic transformation that is created due to a ‘viewBox’ does not affect the ‘x’, ‘y’, ‘width’ and ‘height’ attributes (or in the case of the ‘marker’ element, the ‘markerWidth’ and ‘markerHeight’ attributes) on the element with the ‘viewBox’ attribute. Thus, in the example above which shows an ‘svg’ element which has attributes ‘width’, ‘height’ and ‘viewBox’, the ‘width’ and ‘height’ attributes represent values in the coordinate system that exists before the ‘viewBox’ transformation is applied. On the other hand, like the ‘transform’ property, it does establish a new coordinate system for all other attributes and for descendant elements.

Link to the "effect of the 'transform' attribute on sibling attributes" in the above paragraph needs to be update.

For the ‘viewBox’ attribute:

Animatable: yes.

7.8. The ‘preserveAspectRatio’ attribute

In some cases, typically when using the ‘viewBox’ attribute, it is desirable that the graphics stretch to fit non-uniformly to take up the entire viewport. In other cases, it is desirable that uniform scaling be used for the purposes of preserving the aspect ratio of the graphics.

Attribute preserveAspectRatio="[defer] <align> [<meetOrSlice>]", which is available for all elements that establish a new viewport (see elements that establish viewports), plus the ‘image’, ‘marker’, ‘pattern’ and ‘view’ elements, indicates whether or not to force uniform scaling.

For elements that establish a new viewport (see elements that establish viewports), plus the ‘marker’, ‘pattern’ and ‘view’ elements, ‘preserveAspectRatio’ only applies when a value has been provided for ‘viewBox’ on the same element. For these elements, if attribute ‘viewBox’ is not provided, then ‘preserveAspectRatio’ is ignored.

For ‘image’ elements, ‘preserveAspectRatio’ indicates how referenced images should be fitted with respect to the reference rectangle and whether the aspect ratio of the referenced image should be preserved with respect to the current user coordinate system.

If the value of ‘preserveAspectRatio’ on an ‘image’ element starts with 'defer' then the value of the ‘preserveAspectRatio’ attribute on the referenced content if present should be used. If the referenced content lacks a value for ‘preserveAspectRatio’ then the ‘preserveAspectRatio’ attribute should be processed as normal (ignoring 'defer'). For ‘preserveAspectRatio’ on all other elements the 'defer' portion of the attribute is ignored.

The <align> parameter indicates whether to force uniform scaling and, if so, the alignment method to use in case the aspect ratio of the ‘viewBox’ doesn't match the aspect ratio of the viewport. The <align> parameter must be one of the following strings:

none - Do not force uniform scaling. Scale the graphic content of the given element non-uniformly if necessary such that the element's bounding box exactly matches the viewport rectangle.
(Note: if <align> is none, then the optional <meetOrSlice> value is ignored.)
xMinYMin - Force uniform scaling.
Align the <min-x> of the element's ‘viewBox’ with the smallest X value of the viewport.
Align the <min-y> of the element's ‘viewBox’ with the smallest Y value of the viewport.
xMidYMin - Force uniform scaling.
Align the midpoint X value of the element's ‘viewBox’ with the midpoint X value of the viewport.
Align the <min-y> of the element's ‘viewBox’ with the smallest Y value of the viewport.
xMaxYMin - Force uniform scaling.
Align the <min-x>+<width> of the element's ‘viewBox’ with the maximum X value of the viewport.
Align the <min-y> of the element's ‘viewBox’ with the smallest Y value of the viewport.
xMinYMid - Force uniform scaling.
Align the <min-x> of the element's ‘viewBox’ with the smallest X value of the viewport.
Align the midpoint Y value of the element's ‘viewBox’ with the midpoint Y value of the viewport.
xMidYMid (the default) - Force uniform scaling.
Align the midpoint X value of the element's ‘viewBox’ with the midpoint X value of the viewport.
Align the midpoint Y value of the element's ‘viewBox’ with the midpoint Y value of the viewport.
xMaxYMid - Force uniform scaling.
Align the <min-x>+<width> of the element's ‘viewBox’ with the maximum X value of the viewport.
Align the midpoint Y value of the element's ‘viewBox’ with the midpoint Y value of the viewport.
xMinYMax - Force uniform scaling.
Align the <min-x> of the element's ‘viewBox’ with the smallest X value of the viewport.
Align the <min-y>+<height> of the element's ‘viewBox’ with the maximum Y value of the viewport.
xMidYMax - Force uniform scaling.
Align the midpoint X value of the element's ‘viewBox’ with the midpoint X value of the viewport.
Align the <min-y>+<height> of the element's ‘viewBox’ with the maximum Y value of the viewport.
xMaxYMax - Force uniform scaling.
Align the <min-x>+<width> of the element's ‘viewBox’ with the maximum X value of the viewport.
Align the <min-y>+<height> of the element's ‘viewBox’ with the maximum Y value of the viewport.

The <meetOrSlice> parameter is optional and, if provided, is separated from the <align> value by one or more spaces and then must be one of the following strings:

meet (the default) - Scale the graphic such that:
- aspect ratio is preserved
- the entire ‘viewBox’ is visible within the viewport
- the ‘viewBox’ is scaled up as much as possible, while still meeting the other criteria
In this case, if the aspect ratio of the graphic does not match the viewport, some of the viewport will extend beyond the bounds of the ‘viewBox’ (i.e., the area into which the ‘viewBox’ will draw will be smaller than the viewport).
slice - Scale the graphic such that:
- aspect ratio is preserved
- the entire viewport is covered by the ‘viewBox’
- the ‘viewBox’ is scaled down as much as possible, while still meeting the other criteria
In this case, if the aspect ratio of the ‘viewBox’ does not match the viewport, some of the ‘viewBox’ will extend beyond the bounds of the viewport (i.e., the area into which the ‘viewBox’ will draw is larger than the viewport).

Example PreserveAspectRatio illustrates the various options on ‘preserveAspectRatio’. To save space, XML entities have been defined for the three repeated graphic objects, the rectangle with the smile inside and the outlines of the two rectangles which have the same dimensions as the target viewports. The example creates several new viewports by including ‘svg’ sub-elements embedded inside the outermost svg element (see Establishing a new viewport).

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg [
<!ENTITY Smile "
<rect x='.5' y='.5' width='29' height='39' fill='black' stroke='red'/>
<g transform='translate(0, 5)'>
<circle cx='15' cy='15' r='10' fill='yellow'/>
<circle cx='12' cy='12' r='1.5' fill='black'/>
<circle cx='17' cy='12' r='1.5' fill='black'/>
<path d='M 10 19 A 8 8 0 0 0 20 19' stroke='black' stroke-width='2'/>
</g>
">
<!ENTITY Viewport1 "<rect x='.5' y='.5' width='49' height='29'
fill='none' stroke='blue'/>">
<!ENTITY Viewport2 "<rect x='.5' y='.5' width='29' height='59'
fill='none' stroke='blue'/>">
]>

<svg width="450px" height="300px" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <desc>Example PreserveAspectRatio - illustrates preserveAspectRatio attribute</desc>
  <rect x="1" y="1" width="448" height="298"
        fill="none" stroke="blue"/>
  <g font-size="9">
    <text x="10" y="30">SVG to fit</text>
    <g transform="translate(20,40)">&Smile;</g>
    <text x="10" y="110">Viewport 1</text>
    <g transform="translate(10,120)">&Viewport1;</g>
    <text x="10" y="180">Viewport 2</text>
    <g transform="translate(20,190)">&Viewport2;</g>

    <g id="meet-group-1" transform="translate(100, 60)">
      <text x="0" y="-30">--------------- meet ---------------</text>
      <g><text y="-10">xMin*</text>&Viewport1;
        <svg preserveAspectRatio="xMinYMin meet" viewBox="0 0 30 40"
             width="50" height="30">&Smile;</svg></g>
      <g transform="translate(70,0)"><text y="-10">xMid*</text>&Viewport1;
        <svg preserveAspectRatio="xMidYMid meet" viewBox="0 0 30 40"
             width="50" height="30">&Smile;</svg></g>
      <g transform="translate(0,70)"><text y="-10">xMax*</text>&Viewport1;
        <svg preserveAspectRatio="xMaxYMax meet" viewBox="0 0 30 40"
             width="50" height="30">&Smile;</svg></g>
    </g>

    <g id="meet-group-2" transform="translate(250, 60)">
      <text x="0" y="-30">---------- meet ----------</text>
      <g><text y="-10">*YMin</text>&Viewport2;
        <svg preserveAspectRatio="xMinYMin meet" viewBox="0 0 30 40"
             width="30" height="60">&Smile;</svg></g>
      <g transform="translate(50, 0)"><text y="-10">*YMid</text>&Viewport2;
        <svg preserveAspectRatio="xMidYMid meet" viewBox="0 0 30 40"
             width="30" height="60">&Smile;</svg></g>
      <g transform="translate(100, 0)"><text y="-10">*YMax</text>&Viewport2;
        <svg preserveAspectRatio="xMaxYMax meet" viewBox="0 0 30 40"
             width="30" height="60">&Smile;</svg></g>
    </g>

    <g id="slice-group-1" transform="translate(100, 220)">
      <text x="0" y="-30">---------- slice ----------</text>
      <g><text y="-10">xMin*</text>&Viewport2;
        <svg preserveAspectRatio="xMinYMin slice" viewBox="0 0 30 40"
             width="30" height="60">&Smile;</svg></g>
      <g transform="translate(50,0)"><text y="-10">xMid*</text>&Viewport2;
        <svg preserveAspectRatio="xMidYMid slice" viewBox="0 0 30 40"
             width="30" height="60">&Smile;</svg></g>
      <g transform="translate(100,0)"><text y="-10">xMax*</text>&Viewport2;
        <svg preserveAspectRatio="xMaxYMax slice" viewBox="0 0 30 40"
             width="30" height="60">&Smile;</svg></g>
    </g>

    <g id="slice-group-2" transform="translate(250, 220)">
      <text x="0" y="-30">--------------- slice ---------------</text>
      <g><text y="-10">*YMin</text>&Viewport1;
        <svg preserveAspectRatio="xMinYMin slice" viewBox="0 0 30 40"
             width="50" height="30">&Smile;</svg></g>
      <g transform="translate(70,0)"><text y="-10">*YMid</text>&Viewport1;
        <svg preserveAspectRatio="xMidYMid slice" viewBox="0 0 30 40"
             width="50" height="30">&Smile;</svg></g>
      <g transform="translate(140,0)"><text y="-10">*YMax</text>&Viewport1;
        <svg preserveAspectRatio="xMaxYMax slice" viewBox="0 0 30 40"
             width="50" height="30">&Smile;</svg></g>
    </g>   
  </g>
</svg>

Example PreserveAspectRatio

View this example as SVG (SVG-enabled browsers only)

This example should stop using DTD entities and use ‘use’ instead.

For the ‘preserveAspectRatio’ attribute:

Animatable: yes.

7.9. Establishing a new viewport

At any point in an SVG drawing, you can establish a new viewport into which all contained graphics is drawn by including an ‘svg’ element inside SVG content. By establishing a new viewport, you also implicitly establish a new viewport coordinate system, a new user coordinate system, and, potentially, a new clipping path (see the definition of the ‘overflow’ property). Additionally, there is a new meaning for percentage units defined to be relative to the current viewport since a new viewport has been established (see Units).

The bounds of the new viewport are defined by the ‘x’, ‘y’, ‘width’ and ‘height’ attributes on the element establishing the new viewport, such as an ‘svg’ element. Both the new viewport coordinate system and the new user coordinate system have their origins at (‘x’, ‘y’), where ‘x’ and ‘y’ represent the value of the corresponding attributes on the element establishing the viewport. The orientation of the new viewport coordinate system and the new user coordinate system correspond to the orientation of the current user coordinate system for the element establishing the viewport. A single unit in the new viewport coordinate system and the new user coordinate system are the same size as a single unit in the current user coordinate system for the element establishing the viewport.

Here is an example:

<?xml version="1.0" standalone="no"?>
<svg width="4in" height="3in" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <desc>This SVG drawing embeds another one,
    thus establishing a new viewport
  </desc>
  <!-- The following statement establishing a new viewport
       and renders SVG drawing B into that viewport -->
  <svg x="25%" y="25%" width="50%" height="50%">
     <!-- drawing B goes here -->
  </svg>
</svg>

For an extensive example of creating new viewports, see Example PreserveAspectRatio.

The following elements establish new viewports:

The ‘svg’ element
A ‘symbol’ element define new viewports whenever they are instanced by a ‘use’ element.
An ‘image’ element that references an SVG file will result in the establishment of a temporary new viewport since the referenced resource by definition will have an ‘svg’ element.
A ‘foreignObject’ element creates a new viewport for rendering the content that is within the element.

Whether a new viewport also establishes a new additional clipping path is determined by the value of the ‘overflow’ property on the element that establishes the new viewport. If a clipping path is created to correspond to the new viewport, the clipping path's geometry is determined by the value of the ‘clip’ property. Also, see Clip to viewport vs. clip to ‘viewBox’.

7.10. Units

All coordinates and lengths in SVG can be specified with or without a unit identifier.

This is misleading – path data for example takes values that look like coordinates and lengths yet does not allow units.

When a coordinate or length value is a number without a unit identifier (e.g., "25"), then the given coordinate or length is assumed to be in user units (i.e., a value in the current user coordinate system). For example:

<text font-size="50">Text size is 50 user units</text>

Alternatively, a coordinate or length value can be expressed as a number followed by a unit identifier (e.g., "25cm" or "15em"). (Note that CSS defined properties used in a CSS style sheet or the ‘style’ attribute require units for non-zero lengths, see SVG's styling properties.) The list of unit identifiers in SVG matches the list of unit identifiers in CSS: em, ex, px, pt, pc, cm, mm and in. The <length> type can also have a percentage unit identifier. The following describes how the various unit identifiers are processed:

As in CSS, the em and ex unit identifiers are relative to the current font's font-size and x-height, respectively.
One px unit is defined to be equal to one user unit. Thus, a length of "5px" is the same as a length of "5".

Note that at initialization, a user unit in the the initial coordinate system is equivalenced to the parent environment's notion of a px unit. Thus, in the the initial coordinate system, because the user coordinate system aligns exactly with the parent's coordinate system, and because often the parent's coordinate system aligns with the device pixel grid, "5px" might actually map to 5 devices pixels. However, if there are any coordinate system transformation due to the use of ‘transform’ or ‘viewBox’ attributes, because "5px" maps to 5 user units and because the coordinate system transformations have resulted in a revised user coordinate system, "5px" likely will not map to 5 device pixels. As a result, in most circumstances, "px" units will not map to the device pixel grid.
The other absolute unit identifiers from CSS (i.e., pt, pc, cm, mm, in) are all defined as an appropriate multiple of one px unit (which, according to the previous item, is defined to be equal to one user unit), based on what the SVG user agent determines is the size of a px unit (possibly passed from the parent processor or environment at initialization time). For example, suppose that the user agent can determine from its environment that "1px" corresponds to "0.2822222mm" (i.e., 90dpi). Then, for all processing of SVG content:
- "1pt" equals "1.25px" (and therefore 1.25 user units)
- "1pc" equals "15px" (and therefore 15 user units)
- "1mm" would be "3.543307px" (3.543307 user units)
- "1cm" equals "35.43307px" (and therefore 35.43307 user units)
- "1in" equals "90px" (and therefore 90 user units)

Note that use of px units or any other absolute unit identifiers can cause inconsistent visual results on different viewing environments since the size of "1px" may map to a different number of user units on different systems; thus, absolute units identifiers are only recommended for the ‘width’ and the ‘height’ on outermost svg elements and situations where the content contains no transformations and it is desirable to specify values relative to the device pixel grid or to a particular real world unit size.

That's wrong. 1px always corresponds to one user unit, and the "absolute" units must be interpreted as CSS says to, i.e. as fixed multiples of the CSS px, and not anything to do with the display's resolution. The recommendation to use the absolute units (apart from px) only for ‘width’ and ‘height’ on root ‘svg’ is a good one, however. Defining the size of a document in mm and then using mm units for shapes within it is going to give counterintuitive results, since they'll be converted to user units to resolve against the view box.

For percentage values that are defined to be relative to the size of viewport:

For any x-coordinate value or width value expressed as a percentage of the viewport, the value to use is the specified percentage of the actual-width in user units for the nearest containing viewport, where actual-width is the width dimension of the viewport element within the user coordinate system for the viewport element.
For any y-coordinate value or height value expressed as a percentage of the viewport, the value to use is the specified percentage of the actual-height in user units for the nearest containing viewport, where actual-height is the height dimension of the viewport element within the user coordinate system for the viewport element.
For any other length value expressed as a percentage of the viewport, the percentage is calculated as the specified percentage of sqrt((actual-width)**2 + (actual-height)**2)/sqrt(2).

Example Units below illustrates some of the processing rules for different types of units.

<?xml version="1.0" standalone="no"?>
<svg width="400px" height="200px" viewBox="0 0 4000 2000"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example Units</title>
  <desc>Illustrates various units options</desc>

  <!-- Frame the picture -->
  <rect x="5" y="5" width="3990" height="1990" 
        fill="none" stroke="blue" stroke-width="10"/>

  <g fill="blue" stroke="red" font-family="Verdana" font-size="150">
    <!-- Absolute unit specifiers -->
    <g transform="translate(400,0)">
      <text x="-50" y="300" fill="black" stroke="none">Abs. units:</text>
      <rect x="0" y="400" width="4in" height="2in" stroke-width=".4in"/>
      <rect x="0" y="750" width="384" height="192" stroke-width="38.4"/>
      <g transform="scale(2)">
        <rect x="0" y="600" width="4in" height="2in" stroke-width=".4in"/>
      </g>
    </g>

    <!-- Relative unit specifiers -->
    <g transform="translate(1600,0)">
      <text x="-50" y="300" fill="black" stroke="none">Rel. units:</text>
      <rect x="0" y="400" width="2.5em" height="1.25em" stroke-width=".25em"/>
      <rect x="0" y="750" width="375" height="187.5" stroke-width="37.5"/>
      <g transform="scale(2)">
        <rect x="0" y="600" width="2.5em" height="1.25em" stroke-width=".25em"/>
      </g>
    </g>

    <!-- Percentages -->
    <g transform="translate(2800,0)">
      <text x="-50" y="300" fill="black" stroke="none">Percentages:</text>
      <rect x="0" y="400" width="10%" height="10%" stroke-width="1%"/>
      <rect x="0" y="750" width="400" height="200" stroke-width="31.62"/>
      <g transform="scale(2)">
        <rect x="0" y="600" width="10%" height="10%" stroke-width="1%"/>
      </g>
    </g>
  </g>
</svg>

Example Units

View this example as SVG (SVG-enabled browsers only)

The three rectangles on the left demonstrate the use of one of the absolute unit identifiers, the "in" unit (inch). The reference image above was generated on a 96dpi system (i.e., 1 inch = 96 pixels). Therefore, the topmost rectangle, which is specified in inches, is exactly the same size as the middle rectangle, which is specified in user units such that there are 96 user units for each corresponding inch in the topmost rectangle. (Note: on systems with different screen resolutions, the top and middle rectangles will likely be rendered at different sizes.) The bottom rectangle of the group illustrates what happens when values specified in inches are scaled.

The example needs to be changed in light of the issue above about absolute units.

The three rectangles in the middle demonstrate the use of one of the relative unit identifiers, the "em" unit. Because the ‘font-size’ property has been set to 150 on the outermost ‘g’ element, each "em" unit is equal to 150 user units. The topmost rectangle, which is specified in "em" units, is exactly the same size as the middle rectangle, which is specified in user units such that there are 150 user units for each corresponding "em" unit in the topmost rectangle. The bottom rectangle of the group illustrates what happens when values specified in "em" units are scaled.

The three rectangles on the right demonstrate the use of percentages. Note that the width and height of the viewport in the user coordinate system for the viewport element (in this case, the outermost svg element) are 4000 and 2000, respectively, because processing the ‘viewBox’ attribute results in a transformed user coordinate system. The topmost rectangle, which is specified in percentage units, is exactly the same size as the middle rectangle, which is specified in equivalent user units. In particular, note that the ‘stroke-width’ property in the middle rectangle is set to 1% of the sqrt((actual-width)**2 + (actual-height)**2) / sqrt(2), which in this case is .01*sqrt(4000*4000+2000*2000)/sqrt(2), or 31.62. The bottom rectangle of the group illustrates what happens when values specified in percentage units are scaled.

7.11. Object bounding box units

The following elements offer the option of expressing coordinate values and lengths as fractions (and, in some cases, percentages) of the bounding box, by setting a specified attribute to 'objectBoundingBox' on the given element:

Need a line for ‘meshGradient’.

Element	Attribute	Effect
‘linearGradient’	‘gradientUnits’	Indicates that the attributes which specify the gradient vector (‘x1’, ‘y1’, ‘x2’, ‘y2’) represent fractions or percentages of the bounding box of the element to which the gradient is applied.
‘radialGradient’	‘gradientUnits’	Indicates that the attributes which specify the center (‘cx’, ‘cy’), the radius (‘r’) and focus (‘fx’, ‘fy’) represent fractions or percentages of the bounding box of the element to which the gradient is applied.
‘pattern’	‘patternUnits’	Indicates that the attributes which define how to tile the pattern (‘x’, ‘y’, ‘width’, ‘height’) are established using the bounding box of the element to which the pattern is applied.
‘pattern’	‘patternContentUnits’	Indicates that the user coordinate system for the contents of the pattern is established using the bounding box of the element to which the pattern is applied.
‘clipPath’	‘clipPathUnits’	Indicates that the user coordinate system for the contents of the ‘clipPath’ element is established using the bounding box of the element to which the clipping path is applied.
‘mask’	‘maskUnits’	Indicates that the attributes which define the masking region (‘x’, ‘y’, ‘width’, ‘height’) is established using the bounding box of the element to which the mask is applied.
‘mask’	‘maskContentUnits’	Indicates that the user coordinate system for the contents of the ‘mask’ element are established using the bounding box of the element to which the mask is applied.
‘filter’	‘filterUnits’	Indicates that the attributes which define the filter effects region (‘x’, ‘y’, ‘width’, ‘height’) represent fractions or percentages of the bounding box of the element to which the filter is applied.
‘filter’	‘primitiveUnits’	Indicates that the various length values within the filter primitives represent fractions or percentages of the bounding box of the element to which the filter is applied.

In the discussion that follows, the term applicable element is the element to which the given effect applies. For gradients and patterns, the applicable element is the graphics element which has its ‘fill’ or ‘stroke’ property referencing the given gradient or pattern. (See Inheritance of Painting Properties. For special rules concerning text elements, see the discussion of object bounding box units and text elements.) For clipping paths, masks and filters, the applicable element can be either a container element or a graphics element.

When keyword objectBoundingBox is used, then the effect is as if a supplemental transformation matrix were inserted into the list of nested transformation matrices to create a new user coordinate system.

First, the (minx,miny) and (maxx,maxy) coordinates are determined for the applicable element and all of its descendants. The values minx, miny, maxx and maxy are determined by computing the maximum extent of the shape of the element in X and Y with respect to the user coordinate system for the applicable element. The bounding box is the tightest fitting rectangle aligned with the axes of the applicable element's user coordinate system that entirely encloses the applicable element and its descendants. The bounding box is computed exclusive of any values for clipping, masking, filter effects, opacity and stroke-width. For curved shapes, the bounding box encloses all portions of the shape, not just end points. For ‘text’ elements, for the purposes of the bounding box calculation, each glyph is treated as a separate graphics element. The calculations assume that all glyphs occupy the full glyph cell. For example, for horizontal text, the calculations assume that each glyph extends vertically to the full ascent and descent values for the font.

Then, coordinate (0,0) in the new user coordinate system is mapped to the (minx,miny) corner of the tight bounding box within the user coordinate system of the applicable element and coordinate (1,1) in the new user coordinate system is mapped to the (maxx,maxy) corner of the tight bounding box of the applicable element. In most situations, the following transformation matrix produces the correct effect:

[ (maxx-minx) 0 0 (maxy-miny) minx miny ]

When percentages are used with attributes that define the gradient vector, the pattern tile, the filter region or the masking region, a percentage represents the same value as the corresponding decimal value (e.g., 50% means the same as 0.5). If percentages are used within the content of a ‘pattern’, ‘clipPath’, ‘mask’ or ‘filter’ element, these values are treated according to the processing rules for percentages as defined in Units.

Any numeric value can be specified for values expressed as a fraction or percentage of object bounding box units. In particular, fractions less are zero or greater than one and percentages less than 0% or greater than 100% can be specified.

Keyword objectBoundingBox should not be used when the geometry of the applicable element has no width or no height, such as the case of a horizontal or vertical line, even when the line has actual thickness when viewed due to having a non-zero stroke width since stroke width is ignored for bounding box calculations. When the geometry of the applicable element has no width or height and objectBoundingBox is specified, then the given effect (e.g., a gradient or a filter) will be ignored.

7.12. Intrinsic sizing properties of the viewport of SVG content

SVG needs to specify how to calculate some intrinsic sizing properties to enable inclusion within other languages. The intrinsic width and height of the viewport of SVG content must be determined from the ‘width’ and ‘height’ attributes. If either of these are not specified, a value of '100%' must be assumed. Note: the ‘width’ and ‘height’ attributes are not the same as the CSS width and height properties. Specifically, percentage values do not provide an intrinsic width or height, and do not indicate a percentage of the containing block. Rather, once the viewport is established, they indicate the portion of the viewport that is actually covered by image data.

The intrinsic aspect ratio of the viewport of SVG content is necessary for example, when including SVG from an ‘object’ element in HTML styled with CSS. It is possible (indeed, common) for an SVG graphic to have an intrinsic aspect ratio but not to have an intrinsic width or height. The intrinsic aspect ratio must be calculated based upon the following rules:

The aspect ratio is calculated by dividing a width by a height.
If the ‘width’ and ‘height’ of the rootmost ‘svg’ element are both specified with unit identifiers (in, mm, cm, pt, pc, px, em, ex) or in user units, then the aspect ratio is calculated from the ‘width’ and ‘height’ attributes after resolving both values to user units.
If either/both of the ‘width’ and ‘height’ of the rootmost ‘svg’ element are in percentage units (or omitted), the aspect ratio is calculated from the width and height values of the ‘viewBox’ specified for the current SVG document fragment. If the ‘viewBox’ is not correctly specified, or set to 'none', the intrinsic aspect ratio cannot be calculated and is considered unspecified.

Examples:

Example: Intrinsic Aspect Ratio 1

<svg xmlns="http://www.w3.org/2000/svg" version="1.2" baseProfile="tiny"
     width="10cm" height="5cm">
  ...
</svg>

In this example the intrinsic aspect ratio of the viewport is 2:1. The intrinsic width is 10cm and the intrinsic height is 5cm.

Example: Intrinsic Aspect Ratio 2

<svg xmlns="http://www.w3.org/2000/svg" version="1.2" baseProfile="tiny"
     width="100%" height="50%" viewBox="0 0 200 200">
  ...
</svg>

In this example the intrinsic aspect ratio of the rootmost viewport is 1:1. An aspect ratio calculation in this case allows embedding in an object within a containing block that is only constrained in one direction.

Example: Intrinsic Aspect Ratio 3

<svg xmlns="http://www.w3.org/2000/svg" version="1.2" baseProfile="tiny"
     width="10cm" viewBox="0 0 200 200">
  ...
</svg>

In this case the intrinsic aspect ratio is 1:1.

Example: Intrinsic Aspect Ratio 4

<svg xmlns="http://www.w3.org/2000/svg" version="1.2" baseProfile="tiny"
     width="75%" height="10cm" viewBox="0 0 200 200">
  ...
</svg>

In this example, the intrinsic aspect ratio is 1:1.

7.13. Geographic coordinate systems

In order to allow interoperability between SVG content generators and user agents dealing with maps encoded in SVG, the use of a common metadata definition for describing the coordinate system used to generate SVG documents is encouraged.

Such metadata must be added under the ‘metadata’ element of the topmost ‘svg’ element describing the map, consisting of an RDF description of the Coordinate Reference System definition used to generate the SVG map [RDF-PRIMER]. Note that the presence of this metadata does not affect the rendering of the SVG in any way; it merely provides added semantic value for applications that make use of combined maps.

The definition must be conformant to the XML grammar described in GML 3.2.1, an OpenGIS Standard for encoding common CRS data types in XML [GML]. In order to correctly map the 2-dimensional data used by SVG, the CRS must be of subtype ProjectedCRS or Geographic2dCRS. The first axis of the described CRS maps the SVG x-axis and the second axis maps the SVG y-axis.

The main purpose of such metadata is to indicate to the user agent that two or more SVG documents can be overlayed or merged into a single document. Obviously, if two maps reference the same Coordinate Reference System definition and have the same SVG ‘transform’ property value then they can be overlayed without reprojecting the data. If the maps reference different Coordinate Reference Systems and/or have different SVG ‘transform’ property values, then a specialized cartographic user agent may choose to transform the coordinate data to overlay the data. However, typical SVG user agents are not required to perform these types of transformations, or even recognize the metadata. It is described in this specification so that the connection between geographic coordinate systems and the SVG coordinate system is clear.

7.14. The ‘svg:transform’ attribute

Do we need this section? Should we instead have a guide on how other specifications should re-use specific attributes or elements?

Attribute definition:

svg:transform = "<transform>" | "none"

<transform>: Specifies the affine transformation that has been applied to the map data. The syntax is identical to that described in The ‘transform’ property section.
none: Specifies that no supplemental affine transformation has been applied to the map data. Using this value has the same meaning as specifying the identity matrix, which in turn is just the same as not specifying the ‘svg:transform’ the attribute at all.

Animatable: no.

This attribute describes an optional additional affine transformation that may have been applied during this mapping. This attribute may be added to the OpenGIS ‘CoordinateReferenceSystem’ element. Note that, unlike the ‘transform’ property, it does not indicate that a transformation is to be applied to the data within the file. Instead, it simply describes the transformation that was already applied to the data when being encoded in SVG.

There are three typical uses for the ‘svg:transform’ global attribute. These are described below and used in the examples.

Most ProjectedCRS have the north direction represented by positive values of the second axis and conversely SVG has a y-down coordinate system. That's why, in order to follow the usual way to represent a map with the north at its top, it is recommended for that kind of ProjectedCRS to use the ‘svg:transform’ global attribute with a 'scale(1, -1)' value as in the third example below.
Most Geographic2dCRS have the latitude as their first axis rather than the longitude, which means that the south-north axis would be represented by the x-axis in SVG instead of the usual y-axis. That's why, in order to follow the usual way to represent a map with the north at its top, it is recommended for that kind of Geographic2dCRS to use the ‘svg:transform’ global attribute with a 'rotate(-90)' value as in the first example (while also adding the 'scale(1, -1)' as for ProjectedCRS).
In addition, when converting for profiles which place restrictions on precision of real number values, it may be useful to add an additional scaling factor to retain good precision for a specific area. When generating an SVG document from WGS84 geographic coordinates (EPGS 4326), we recommend the use of an additional 100 times scaling factor corresponding to an ‘svg:transform’ global attribute with a 'rotate(-90) scale(100)' value (shown in the second example). Different scaling values may be required depending on the particular CRS.

Below is a simple example of the coordinate metadata, which describes the coordinate system used by the document via a URI.

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
     width="100" height="100" viewBox="0 0 1000 1000">

  <desc>An example that references coordinate data.</desc>

  <metadata>
    <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
             xmlns:crs="http://www.ogc.org/crs"
             xmlns:svg="http://www.w3.org/2000/svg">
      <rdf:Description rdf:about="">
        <!-- The Coordinate Reference System is described
             through a URI. -->
        <crs:CoordinateReferenceSystem
            svg:transform="rotate(-90)"
            rdf:resource="http://www.example.org/srs/epsg.xml#4326"/>
      </rdf:Description>
    </rdf:RDF>
  </metadata>

  <!-- The actual map content -->
</svg>

The second example uses a well-known identifier to describe the coordinate system. Note that the coordinates used in the document have had the supplied transform applied.

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
     width="100" height="100" viewBox="0 0 1000 1000">

  <desc>Example using a well known coordinate system.</desc>

  <metadata>
    <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
             xmlns:crs="http://www.ogc.org/crs"
             xmlns:svg="http://www.w3.org/2000/svg">
      <rdf:Description rdf:about="">
        <!-- In case of a well-known Coordinate Reference System
             an 'Identifier' is enough to describe the CRS -->
        <crs:CoordinateReferenceSystem svg:transform="rotate(-90) scale(100, 100)">
          <crs:Identifier>
            <crs:code>4326</crs:code>
            <crs:codeSpace>EPSG</crs:codeSpace>
            <crs:edition>5.2</crs:edition>
          </crs:Identifier>
        </crs:CoordinateReferenceSystem>
      </rdf:Description>
    </rdf:RDF>
  </metadata>

  <!-- The actual map content -->
</svg>

The third example defines the coordinate system completely within the SVG document.

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
     width="100" height="100" viewBox="0 0 1000 1000">

  <desc>Coordinate metadata defined within the SVG document</desc>

  <metadata>
    <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
             xmlns:crs="http://www.ogc.org/crs"
             xmlns:svg="http://www.w3.org/2000/svg">
      <rdf:Description rdf:about="">
        <!-- For other CRS it should be entirely defined -->
        <crs:CoordinateReferenceSystem svg:transform="scale(1,-1)">
          <crs:NameSet>
            <crs:name>Mercator projection of WGS84</crs:name>
          </crs:NameSet>
          <crs:ProjectedCRS>
            <!-- The actual definition of the CRS -->
            <crs:CartesianCoordinateSystem>
              <crs:dimension>2</crs:dimension>
              <crs:CoordinateAxis>
                <crs:axisDirection>north</crs:axisDirection>
                <crs:AngularUnit>
                  <crs:Identifier>
                    <crs:code>9108</crs:code>
                    <crs:codeSpace>EPSG</crs:codeSpace>
                    <crs:edition>5.2</crs:edition>
                  </crs:Identifier>
                </crs:AngularUnit>
              </crs:CoordinateAxis>
              <crs:CoordinateAxis>
                <crs:axisDirection>east</crs:axisDirection>
                <crs:AngularUnit>
                  <crs:Identifier>
                    <crs:code>9108</crs:code>
                    <crs:codeSpace>EPSG</crs:codeSpace>
                    <crs:edition>5.2</crs:edition>
                  </crs:Identifier>
                </crs:AngularUnit>
              </crs:CoordinateAxis>
            </crs:CartesianCoordinateSystem>
            <crs:CoordinateReferenceSystem>
              <!-- the reference system of that projected system is
                         WGS84 which is EPSG 4326 in EPSG codeSpace -->
              <crs:NameSet>
                <crs:name>WGS 84</crs:name>
              </crs:NameSet>
              <crs:Identifier>
                <crs:code>4326</crs:code>
                <crs:codeSpace>EPSG</crs:codeSpace>
                <crs:edition>5.2</crs:edition>
              </crs:Identifier>
            </crs:CoordinateReferenceSystem>
            <crs:CoordinateTransformationDefinition>
              <crs:sourceDimensions>2</crs:sourceDimensions>
              <crs:targetDimensions>2</crs:targetDimensions>
              <crs:ParameterizedTransformation>
                <crs:TransformationMethod>
                  <!-- the projection is a Mercator projection which is
                        EPSG 9805 in EPSG codeSpace -->
                  <crs:NameSet>
                    <crs:name>Mercator</crs:name>
                  </crs:NameSet>
                  <crs:Identifier>
                    <crs:code>9805</crs:code>
                    <crs:codeSpace>EPSG</crs:codeSpace>
                    <crs:edition>5.2</crs:edition>
                  </crs:Identifier>
                  <crs:description>Mercator (2SP)</crs:description>
                </crs:TransformationMethod>
                <crs:Parameter>
                  <crs:NameSet>
                    <crs:name>Latitude of 1st standart parallel</crs:name>
                  </crs:NameSet>
                  <crs:Identifier>
                    <crs:code>8823</crs:code>
                    <crs:codeSpace>EPSG</crs:codeSpace>
                    <crs:edition>5.2</crs:edition>
                  </crs:Identifier>
                  <crs:value>0</crs:value>
                </crs:Parameter>
                <crs:Parameter>
                  <crs:NameSet>
                    <crs:name>Longitude of natural origin</crs:name>
                  </crs:NameSet>
                  <crs:Identifier>
                    <crs:code>8802</crs:code>
                    <crs:codeSpace>EPSG</crs:codeSpace>
                    <crs:edition>5.2</crs:edition>
                  </crs:Identifier>
                  <crs:value>0</crs:value>
                </crs:Parameter>
                <crs:Parameter>
                  <crs:NameSet>
                    <crs:name>False Easting</crs:name>
                  </crs:NameSet>
                  <crs:Identifier>
                    <crs:code>8806</crs:code>         
                    <crs:codeSpace>EPSG</crs:codeSpace>
                    <crs:edition>5.2</crs:edition>
                  </crs:Identifier>
                  <crs:value>0</crs:value>
                </crs:Parameter>
                <crs:Parameter>
                  <crs:NameSet>
                    <crs:name>False Northing</crs:name>
                  </crs:NameSet>
                  <crs:Identifier>
                    <crs:code>8807</crs:code>
                    <crs:codeSpace>EPSG</crs:codeSpace>
                    <crs:edition>5.2</crs:edition>
                  </crs:Identifier>
                  <crs:value>0</crs:value>
                </crs:Parameter>
              </crs:ParameterizedTransformation>
            </crs:CoordinateTransformationDefinition>
          </crs:ProjectedCRS>
        </crs:CoordinateReferenceSystem>
      </rdf:Description>
    </rdf:RDF>
  </metadata>

  <!-- the actual map content -->
</svg>

7.15. DOM interfaces

7.15.1. Interface SVGPoint

Many of the SVG DOM interfaces refer to objects of class SVGPoint. An SVGPoint is an (x, y) coordinate pair. When used in matrix operations, an SVGPoint is treated as a vector of the form:

[x]
[y]
[1]

If an SVGPoint object is designated as read only, then attempting to assign to one of its attributes will result in an exception being thrown.

[Constructor,
 Constructor(float x, float y)]
interface SVGPoint {

  attribute float x;
  attribute float y;

  SVGPoint matrixTransform(SVGMatrix matrix);
};

Constructors:

SVGPoint(): Creates a new SVGPoint object with its x and y attributes set to 0.
SVGPoint(float x, float y): Creates a new SVGPoint object with its x and y attributes set to x and y, respectively.

Attributes:

x (float)

The x coordinate.

Exceptions on setting

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised if the SVGPoint object is read only.

y (float)

The y coordinate.

Exceptions on setting

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised if the SVGPoint object is read only.

Operations:

SVGPoint matrixTransform(SVGMatrix matrix)

Applies a 2x3 matrix transformation on this SVGPoint object and returns a new, transformed SVGPoint object:

newpoint = matrix * thispoint

Parameters

SVGMatrix matrix

The matrix which is to be applied to this SVGPoint object.

Returns

A new SVGPoint object.

7.15.2. Interface SVGPointList

This interface defines a list of SVGPoint objects.

SVGPointList has the same attributes and methods as other SVGxxxList interfaces. Implementers may consider using a single base class to implement the various SVGxxxList interfaces.

The supported property indices of an SVGPointList object is all non-negative integers less than the length of the list.

interface SVGPointList {

  readonly attribute unsigned long length;
  readonly attribute unsigned long numberOfItems;

  void clear();
  SVGPoint initialize(SVGPoint newItem);
  getter SVGPoint getItem(unsigned long index):
  SVGPoint insertItemBefore(SVGPoint newItem, unsigned long index);
  SVGPoint replaceItem(SVGPoint newItem, unsigned long index);
  SVGPoint removeItem(unsigned long index);
  SVGPoint appendItem(SVGPoint newItem);
  setter void (unsigned long index, SVGPoint newItem);
};

Attributes:

length (readonly unsigned long): The number of items in the list.
numberOfItems (readonly unsigned long): The number of items in the list.

Operations:

void clear()

Clears all existing current items from the list, with the result being an empty list.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

SVGPoint initialize(SVGPoint newItem)

Parameters

SVGPoint newItem

The item which should become the only member of the list.

Returns

The item being inserted into the list.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

SVGPoint getItem(unsigned long index)

Returns the specified item from the list. The returned item is the item itself and not a copy. Any changes made to the item are immediately reflected in the list.

Parameters

unsigned long index

The index of the item from the list which is to be returned. The first item is number 0.

Returns

The selected item.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGPoint insertItemBefore(SVGPoint newItem, unsigned long index)

Parameters

SVGPoint newItem

The item which is to be inserted into the list.
unsigned long index

The index of the item before which the new item is to be inserted. The first item is number 0. If the index is equal to 0, then the new item is inserted at the front of the list. If the index is greater than or equal to numberOfItems, then the new item is appended to the end of the list.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

SVGPoint replaceItem(SVGPoint newItem, unsigned long index)

Parameters

SVGPoint newItem

The item which is to be inserted into the list.
unsigned long index

The index of the item which is to be replaced. The first item is number 0.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.
DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGPoint removeItem(unsigned long index)

Removes an existing item from the list.

Parameters

unsigned long index

The index of the item which is to be removed. The first item is number 0.

Returns

The removed item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.
DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGPoint appendItem(SVGPoint newItem)

Parameters

SVGPoint newItem

The item which is to be inserted. The first item is number 0.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

setter void (unsigned long index, SVGPoint newItem)

Replaces the item at index index with newItem.

7.15.3. Interface SVGMatrix

Many of SVG's graphics operations utilize 2x3 matrices of the form:

[a c e]
[b d f]

which, when expanded into a 3x3 matrix for the purposes of matrix arithmetic, become:

[a c e]
[b d f]
[0 0 1]

[Constructor,
 Constructor(float a, float b, float c, float d, float e, float f)]
interface SVGMatrix {

  attribute float a;
  attribute float b;
  attribute float c;
  attribute float d;
  attribute float e;
  attribute float f;

  SVGMatrix multiply(SVGMatrix secondMatrix);
  SVGMatrix inverse();
  SVGMatrix translate(float x, float y);
  SVGMatrix scale(float scaleFactor);
  SVGMatrix scaleNonUniform(float scaleFactorX, float scaleFactorY);
  SVGMatrix rotate(float angle);
  SVGMatrix rotateFromVector(float x, float y);
  SVGMatrix flipX();
  SVGMatrix flipY();
  SVGMatrix skewX(float angle);
  SVGMatrix skewY(float angle);
};

Constructors:

SVGMatrix(): Creates a new SVGMatrix object whose a, b, c, d, e and f attributes are all set to 0.
SVGMatrix(float a, float b, float c, float d, float e, float f): Creates a new SVGMatrix object whose a, b, c, d, e and f attributes are set to the values of the respective argument passed to the constructor.

Attributes:

a (float): The a component of the matrix.
b (float): The b component of the matrix.
c (float): The c component of the matrix.
d (float): The d component of the matrix.
e (float): The e component of the matrix.
f (float): The f component of the matrix.

Operations:

SVGMatrix multiply(SVGMatrix secondMatrix)

Performs matrix multiplication. This matrix is post-multiplied by another matrix, returning the resulting new matrix.

Parameters

SVGMatrix secondMatrix

The matrix which is post-multiplied to this matrix.

Returns

The resulting matrix.

SVGMatrix inverse()

Returns the inverse matrix.

Returns

The inverse matrix.

Exceptions

InvalidStateError: Raised if this matrix is not invertible.

SVGMatrix translate(float x, float y)

Post-multiplies a translation transformation on the current matrix and returns the resulting matrix.

Parameters

float x

The distance to translate along the x-axis.
float y

The distance to translate along the y-axis.

Returns

The resulting matrix.

SVGMatrix scale(float scaleFactor)

Post-multiplies a uniform scale transformation on the current matrix and returns the resulting matrix.

Parameters

float scaleFactor

Scale factor in both X and Y.

Returns

The resulting matrix.

SVGMatrix scaleNonUniform(float scaleFactorX, float scaleFactorY)

Post-multiplies a non-uniform scale transformation on the current matrix and returns the resulting matrix.

Parameters

float scaleFactorX

Scale factor in X.
float scaleFactorY

Scale factor in Y.

Returns

The resulting matrix.

SVGMatrix rotate(float angle)

Post-multiplies a rotation transformation on the current matrix and returns the resulting matrix.

Parameters

float angle

Rotation angle.

Returns

The resulting matrix.

SVGMatrix rotateFromVector(float x, float y)

Post-multiplies a rotation transformation on the current matrix and returns the resulting matrix. The rotation angle is determined by taking (+/-) atan(y/x). The direction of the vector (x, y) determines whether the positive or negative angle value is used.

Parameters

float x

The X coordinate of the vector (x,y). Must not be zero.
float y

The Y coordinate of the vector (x,y). Must not be zero.

Returns

The resulting matrix.

Exceptions

InvalidAccessError: Raised if one of the parameters has an invalid value.

SVGMatrix flipX()

Post-multiplies the transformation [-1 0 0 1 0 0] and returns the resulting matrix.

Returns: The resulting matrix.

SVGMatrix flipY()

Post-multiplies the transformation [1 0 0 -1 0 0] and returns the resulting matrix.

Returns: The resulting matrix.

SVGMatrix skewX(float angle)

Post-multiplies a skewX transformation on the current matrix and returns the resulting matrix.

Parameters

float angle

Skew angle.

Returns

The resulting matrix.

Exceptions

InvalidAccessError: Raised when (angle + 90) mod 180 = 0.

SVGMatrix skewY(float angle)

Post-multiplies a skewY transformation on the current matrix and returns the resulting matrix.

Parameters

float angle

Skew angle.

Returns

The resulting matrix.

Exceptions

InvalidAccessError: Raised when (angle + 90) mod 180 = 0.

7.15.4. Interface SVGTransform

SVGTransform is the interface for one of the component transformations within an SVGTransformList; thus, an SVGTransform object corresponds to a single component (e.g., 'scale(…)' or 'matrix(…)') within a ‘transform’ attribute specification.

[Constructor,
 Constructor(SVGMatrix matrix),
 Constructor(DOMString value)]
interface SVGTransform {

  // Transform Types
  const unsigned short SVG_TRANSFORM_UNKNOWN = 0;
  const unsigned short SVG_TRANSFORM_MATRIX = 1;
  const unsigned short SVG_TRANSFORM_TRANSLATE = 2;
  const unsigned short SVG_TRANSFORM_SCALE = 3;
  const unsigned short SVG_TRANSFORM_ROTATE = 4;
  const unsigned short SVG_TRANSFORM_SKEWX = 5;
  const unsigned short SVG_TRANSFORM_SKEWY = 6;

  readonly attribute unsigned short type;
  readonly attribute SVGMatrix matrix;
  readonly attribute float angle;

  void setMatrix(SVGMatrix matrix);
  void setTranslate(float tx, float ty);
  void setScale(float sx, float sy);
  void setRotate(float angle, float cx, float cy);
  void setSkewX(float angle);
  void setSkewY(float angle);
};

Constructors:

SVGTransform(): Creates a new SVGTransform object whose type attribute is set to SVG_TRANSFORM_MATRIX and whose matrix attribute is set to an SVGMatrix object that represents the identity matrix.
SVGTransform(SVGMatrix matrix): Creates a new SVGTransform object whose type attribute is set to SVG_TRANSFORM_MATRIX and whose matrix attribute is set to an SVGMatrix object whose attributes are all initialized to be the same as the corresponding attributes in matrix.
SVGTransform(DOMString value): Creates a new SVGTransform object whose type and matrix attributes are set to values determined by parsing value as a <transform-function>.

If value could not be parsed as a <transform-function>, then a SyntaxError is thrown.

The CSS Transforms specification does not have a grammar for <transform-function> yet.

Constants in group “Transform Types”:

SVG_TRANSFORM_UNKNOWN (unsigned short): The unit type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_TRANSFORM_MATRIX (unsigned short): A 'matrix(…)' transformation.
SVG_TRANSFORM_TRANSLATE (unsigned short): A 'translate(…)' transformation.
SVG_TRANSFORM_SCALE (unsigned short): A 'scale(…)' transformation.
SVG_TRANSFORM_ROTATE (unsigned short): A 'rotate(…)' transformation.
SVG_TRANSFORM_SKEWX (unsigned short): A 'skewX(…)' transformation.
SVG_TRANSFORM_SKEWY (unsigned short): A 'skewY(…)' transformation.

Attributes:

type (readonly unsigned short)

The type of the value as specified by one of the SVG_TRANSFORM_* constants defined on this interface.

matrix (readonly SVGMatrix)

The matrix that represents this transformation. The matrix object is live, meaning that any changes made to the SVGTransform object are immediately reflected in the matrix object and vice versa. In case the matrix object is changed directly (i.e., without using the methods on the SVGTransform interface itself) then the type of the SVGTransform changes to SVG_TRANSFORM_MATRIX.

For SVG_TRANSFORM_MATRIX, the matrix contains the a, b, c, d, e, f values supplied by the user.
For SVG_TRANSFORM_TRANSLATE, e and f represent the translation amounts (a=1, b=0, c=0 and d=1).
For SVG_TRANSFORM_SCALE, a and d represent the scale amounts (b=0, c=0, e=0 and f=0).
For SVG_TRANSFORM_SKEWX and SVG_TRANSFORM_SKEWY, a, b, c and d represent the matrix which will result in the given skew (e=0 and f=0).
For SVG_TRANSFORM_ROTATE, a, b, c, d, e and f together represent the matrix which will result in the given rotation. When the rotation is around the center point (0, 0), e and f will be zero.

angle (readonly float)

A convenience attribute for SVG_TRANSFORM_ROTATE, SVG_TRANSFORM_SKEWX and SVG_TRANSFORM_SKEWY. It holds the angle that was specified.

For SVG_TRANSFORM_MATRIX, SVG_TRANSFORM_TRANSLATE and SVG_TRANSFORM_SCALE, angle will be zero.

Operations:

void setMatrix(SVGMatrix matrix)

Sets the transform type to SVG_TRANSFORM_MATRIX, with parameter matrix defining the new transformation. The values from the parameter matrix are copied, the matrix parameter does not replace SVGTransform::matrix.

Parameters

SVGMatrix matrix

The new matrix for the transformation.

void setTranslate(float tx, float ty)

Sets the transform type to SVG_TRANSFORM_TRANSLATE, with parameters tx and ty defining the translation amounts.

Parameters

float tx

The translation amount in X.
float ty

The translation amount in Y.

void setScale(float sx, float sy)

Sets the transform type to SVG_TRANSFORM_SCALE, with parameters sx and sy defining the scale amounts.

Parameters

float sx

The scale amount in X.
float sy

The scale amount in Y.

void setRotate(float angle, float cx, float cy)

Sets the transform type to SVG_TRANSFORM_ROTATE, with parameter angle defining the rotation angle and parameters cx and cy defining the optional center of rotation.

Parameters

float angle

The rotation angle.
float cx

The x coordinate of center of rotation.
float cy

The y coordinate of center of rotation.

void setSkewX(float angle)

Sets the transform type to SVG_TRANSFORM_SKEWX, with parameter angle defining the amount of skew.

Parameters

float angle

The skew angle.

void setSkewY(float angle)

Sets the transform type to SVG_TRANSFORM_SKEWY, with parameter angle defining the amount of skew.

Parameters

float angle

The skew angle.

7.15.5. Interface SVGTransformList

This section needs to be updated to describe how it reflects the value of the ‘transform’ property, or just defer to css3-tranforms if everything is defined there.

This interface defines a list of SVGTransform objects.

The SVGTransformList and SVGTransform interfaces correspond to the various attributes which specify a set of transformations, such as the ‘transform’ property which is available for many of SVG's elements.

SVGTransformList has the same attributes and methods as other SVGxxxList interfaces. Implementers may consider using a single base class to implement the various SVGxxxList interfaces.

The supported property indices of an SVGTransformList object is all non-negative integers less than the length of the list.

An SVGTransformList object can be designated as read only, which means that attempts to modify the object will result in an exception being thrown, as described below.

interface SVGTransformList {

  readonly attribute unsigned long length;
  readonly attribute unsigned long numberOfItems;

  void clear();
  SVGTransform initialize(SVGTransform newItem);
  getter SVGTransform getItem(unsigned long index);
  SVGTransform insertItemBefore(SVGTransform newItem, unsigned long index);
  SVGTransform replaceItem(SVGTransform newItem, unsigned long index);
  SVGTransform removeItem(unsigned long index);
  SVGTransform appendItem(SVGTransform newItem);
  SVGTransform createSVGTransformFromMatrix(SVGMatrix matrix);
  SVGTransform? consolidate();
  setter void (unsigned long index, SVGTransform newItem);
};

Attributes:

length (readonly unsigned long): The number of items in the list.
numberOfItems (readonly unsigned long): The number of items in the list.

Operations:

void clear()

Clears all existing current items from the list, with the result being an empty list.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list is read only.

SVGTransform initialize(SVGTransform newItem)

Parameters

SVGTransform newItem

The item which should become the only member of the list.

Returns

The item being inserted into the list.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list is read only.

SVGTransform getItem(unsigned long index)

Returns the specified item from the list. The returned item is the item itself and not a copy. Any changes made to the item are immediately reflected in the list.

Parameters

unsigned long index

The index of the item from the list which is to be returned. The first item is number 0.

Returns

The selected item.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGTransform insertItemBefore(SVGTransform newItem, unsigned long index)

Parameters

SVGTransform newItem

The item which is to be inserted into the list.
unsigned long index

The index of the item before which the new item is to be inserted. The first item is number 0. If the index is equal to 0, then the new item is inserted at the front of the list. If the index is greater than or equal to numberOfItems, then the new item is appended to the end of the list.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list is read only.

SVGTransform replaceItem(SVGTransform newItem, unsigned long index)

Parameters

SVGTransform newItem

The item which is to be inserted into the list.
unsigned long index

The index of the item which is to be replaced. The first item is number 0.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list is read only.
DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGTransform removeItem(unsigned long index)

Removes an existing item from the list.

Parameters

unsigned long index

The index of the item which is to be removed. The first item is number 0.

Returns

The removed item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list is read only.
DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGTransform appendItem(SVGTransform newItem)

Parameters

SVGTransform newItem

The item which is to be inserted. The first item is number 0.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list is read only.

SVGTransform createSVGTransformFromMatrix(SVGMatrix matrix)

Creates an SVGTransform object which is initialized to transform of type SVG_TRANSFORM_MATRIX and whose values are the given matrix. The values from the parameter matrix are copied, the matrix parameter is not adopted as SVGTransform::matrix.

Parameters

SVGMatrix matrix

The matrix which defines the transformation.

Returns

The returned SVGTransform object.

SVGTransform consolidate()

Consolidates the list of separate SVGTransform objects by multiplying the equivalent transformation matrices together to result in a list consisting of a single SVGTransform object of type SVG_TRANSFORM_MATRIX. The consolidation operation creates new SVGTransform object as the first and only item in the list. The returned item is the item itself and not a copy. Any changes made to the item are immediately reflected in the list.

Returns

The resulting SVGTransform object which becomes single item in the list. If the list was empty, then a value of null is returned.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list is read only.

setter void (unsigned long index, SVGTransform newItem)

Replaces the item at index index with newItem. If the list is read only, then a NoModificationAllowedError is thrown.

7.15.6. Interface SVGAnimatedTransformList

Used for the various attributes which specify a set of transformations, such as the ‘transform’ property which is available for many of SVG's elements, and which can be animated.

interface SVGAnimatedTransformList {
  readonly attribute SVGTransformList baseVal;
  readonly attribute SVGTransformList animVal;
};

Attributes:

baseVal (readonly SVGTransformList): The base value of the given attribute before applying any animations.
animVal (readonly SVGTransformList): A read only SVGTransformList representing the current animated value of the given attribute. If the given attribute is not currently being animated, then the SVGTransformList will have the same contents as baseVal. The object referenced by animVal will always be distinct from the one referenced by baseVal, even when the attribute is not animated.

7.15.7. Interface SVGPreserveAspectRatio

The SVGPreserveAspectRatio interface corresponds to the ‘preserveAspectRatio’ attribute, which is available for some of SVG's elements.

An SVGPreserveAspectRatio object can be designated as read only, which means that attempts to modify the object will result in an exception being thrown, as described below.

interface SVGPreserveAspectRatio {

  // Alignment Types
  const unsigned short SVG_PRESERVEASPECTRATIO_UNKNOWN = 0;
  const unsigned short SVG_PRESERVEASPECTRATIO_NONE = 1;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMINYMIN = 2;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMIDYMIN = 3;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMAXYMIN = 4;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMINYMID = 5;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMIDYMID = 6;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMAXYMID = 7;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMINYMAX = 8;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMIDYMAX = 9;
  const unsigned short SVG_PRESERVEASPECTRATIO_XMAXYMAX = 10;

  // Meet-or-slice Types
  const unsigned short SVG_MEETORSLICE_UNKNOWN = 0;
  const unsigned short SVG_MEETORSLICE_MEET = 1;
  const unsigned short SVG_MEETORSLICE_SLICE = 2;

  attribute unsigned short align;
  attribute unsigned short meetOrSlice;
};

Constants in group “Alignment Types”:

SVG_PRESERVEASPECTRATIO_UNKNOWN (unsigned short): The enumeration was set to a value that is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_PRESERVEASPECTRATIO_NONE (unsigned short): Corresponds to value 'none' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMINYMIN (unsigned short): Corresponds to value 'xMinYMin' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMIDYMIN (unsigned short): Corresponds to value 'xMidYMin' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMAXYMIN (unsigned short): Corresponds to value 'xMaxYMin' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMINYMID (unsigned short): Corresponds to value 'XMinYMid' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMIDYMID (unsigned short): Corresponds to value 'xMidYMid' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMAXYMID (unsigned short): Corresponds to value 'xMaxYMid' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMINYMAX (unsigned short): Corresponds to value 'xMinYMax' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMIDYMAX (unsigned short): Corresponds to value 'xMidYMax' for attribute ‘preserveAspectRatio’.
SVG_PRESERVEASPECTRATIO_XMAXYMAX (unsigned short): Corresponds to value 'xMaxYMax' for attribute ‘preserveAspectRatio’.

Constants in group “Meet-or-slice Types”:

SVG_MEETORSLICE_UNKNOWN (unsigned short): The enumeration was set to a value that is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_MEETORSLICE_MEET (unsigned short): Corresponds to value 'meet' for attribute ‘preserveAspectRatio’.
SVG_MEETORSLICE_SLICE (unsigned short): Corresponds to value 'slice' for attribute ‘preserveAspectRatio’.

Attributes:

align (unsigned short)

The type of the alignment value as specified by one of the SVG_PRESERVEASPECTRATIO_* constants defined on this interface.

Exceptions on setting

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the object is read only.

meetOrSlice (unsigned short)

The type of the meet-or-slice value as specified by one of the SVG_MEETORSLICE_* constants defined on this interface.

Exceptions on setting

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the object is read only.

7.15.8. Interface SVGAnimatedPreserveAspectRatio

Used for attributes of type SVGPreserveAspectRatio which can be animated.

interface SVGAnimatedPreserveAspectRatio {
  readonly attribute SVGPreserveAspectRatio baseVal;
  readonly attribute SVGPreserveAspectRatio animVal;
};

Attributes:

baseVal (readonly SVGPreserveAspectRatio): The base value of the given attribute before applying any animations.
animVal (readonly SVGPreserveAspectRatio): A read only SVGPreserveAspectRatio representing the current animated value of the given attribute. If the given attribute is not currently being animated, then the SVGPreserveAspectRatio will have the same contents as baseVal. The object referenced by animVal will always be distinct from the one referenced by baseVal, even when the attribute is not animated.

Chapter 8: Paths

8.1. Introduction

Paths represent the outline of a shape which can be filled, stroked, used as a clipping path, or any combination of the three. (See Filling, Stroking and Paint Servers and Clipping, Masking and Compositing.)

Also they can be used by ‘mpath’ and ‘textPath’.

A path is described using the concept of a current point. In an analogy with drawing on paper, the current point can be thought of as the location of the pen. The position of the pen can be changed, and the outline of a shape (open or closed) can be traced by dragging the pen in either straight lines or curves.

Paths represent the geometry of the outline of an object, defined in terms of moveto (set a new current point), lineto (draw a straight line), curveto (draw a curve using a cubic Bézier), arc (elliptical or circular arc) and closepath (close the current shape by drawing a line to the last moveto) elements. Compound paths (i.e., a path with multiple subpaths) are possible to allow effects such as "donut holes" in objects.

This chapter describes the syntax, behavior and DOM interfaces for SVG paths. Various implementation notes for SVG paths can be found in ‘path’ element implementation notes and Elliptical arc implementation notes.

A path is defined in SVG using the ‘path’ element.

The basic shapes are all described in terms of what their equivalent path is, which is what their shape is as a path. (The equivalent path of a ‘path’ element is simply the path itself.)

8.2. The ‘path’ element

‘path’

Categories:

Graphics element, markable element, shape element

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

clipPath, marker, mask

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
‘d’
‘pathLength’

DOM Interfaces:

SVGPathElement

Attribute definitions:

d = "path data": The definition of the outline of a shape. See Path data.
Animatable: yes. Path data animation is only possible when each path data specification within an animation specification has exactly the same list of path data commands as the ‘d’ attribute. If an animation is specified and the list of path data commands is not the same, then the animation specification is in error (see Error Processing). The animation engine interpolates each parameter to each path data command separately based on the attributes to the given animation element. Flags and booleans are interpolated as fractions between zero and one, with any non-zero value considered to be a value of one/true.
pathLength = "<number>": The author's computation of the total length of the path, in user units. This value is used to calibrate the user agent's own distance-along-a-path calculations with that of the author. The user agent will scale all distance-along-a-path computations by the ratio of ‘pathLength’ to the user agent's own computed value for total path length. ‘pathLength’ potentially affects calculations for text on a path, motion animation and various stroke operations.
A negative value is an error (see Error processing).
Animatable: yes.

8.3. Path data

SVG 2 Requirement:	Include smooth path between points functionality.
Resolution:	We will add a Catmull Rom syntax to the path syntax with a tension parameter to control the whole curve (not per-point control).
Purpose:	Provide an easy way to graph data, etc.
Owner:	Doug (ACTION-3085)

SVG 2 Requirement:	Support turtle-graphics-like current rotation in path syntax.
Resolution:	We will add a path rotation command.
Purpose:	Make path rotations easier to animate and pie charts easier to draw.
Owner:	Cameron (ACTION-3125)

8.3.1. General information about path data

A path is defined by including a ‘path’ element which contains a d="(path data)" attribute, where the ‘d’ attribute contains the moveto, line, curve (both cubic and quadratic Béziers), arc and closepath instructions.

Example triangle01 specifies a path in the shape of a triangle. (The M indicates a moveto, the Ls indicate linetos, and the z indicates a closepath).

<?xml version="1.0" standalone="no"?>
<svg width="4cm" height="4cm" viewBox="0 0 400 400"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example triangle01- simple example of a 'path'</title>
  <desc>A path that draws a triangle</desc>
  <rect x="1" y="1" width="398" height="398"
        fill="none" stroke="blue" />
  <path d="M 100 100 L 300 100 L 200 300 z"
        fill="red" stroke="blue" stroke-width="3" />
</svg>

Example triangle01

View this example as SVG (SVG-enabled browsers only)

Path data can contain newline characters and thus can be broken up into multiple lines to improve readability. Because of line length limitations with certain related tools, it is recommended that SVG generators split long path data strings across multiple lines, with each line not exceeding 255 characters. Also note that newline characters are only allowed at certain places within path data.

The path data is defined to allow newline characters, but it should be noted that newlines inside attributes in markup will be normalized to space characters while parsing. If you wanted to, you could write

<path d="M 100,100&#10;L 200,150"/>

but it's not likely that you'd want to.

Are there tools that have line limits nowadays? Do we still need to recommend generators to split up path data at 255 characters?

The sentence about newline characters being allowed only at certain places makes it sound like these places are different from where white space more generally is allowed, but that's not the case.

The syntax of path data is concise in order to allow for minimal file size and efficient downloads, since many SVG files will be dominated by their path data. Some of the ways that SVG attempts to minimize the size of path data are as follows:

All instructions are expressed as one character (e.g., a moveto is expressed as an M).
Superfluous white space and separators such as commas can be eliminated (e.g., "M 100 100 L 200 200" contains unnecessary spaces and could be expressed more compactly as "M100 100L200 200").
The command letter can be eliminated on subsequent commands if the same command is used multiple times in a row (e.g., you can drop the second "L" in "M 100 200 L 200 100 L -100 -200" and use "M 100 200 L 200 100 -100 -200" instead).
Relative versions of all commands are available (uppercase means absolute coordinates, lowercase means relative coordinates).
Alternate forms of lineto are available to optimize the special cases of horizontal and vertical lines (absolute and relative).
Alternate forms of curve are available to optimize the special cases where some of the control points on the current segment can be determined automatically from the control points on the previous segment.

The path data syntax is a prefix notation (i.e., commands followed by parameters). The only allowable decimal point is a Unicode U+0046 FULL STOP (".") character (also referred to in Unicode as PERIOD, dot and decimal point) and no other delimiter characters are allowed [UNICODE]. (For example, the following is an invalid numeric value in a path data stream: "13,000.56". Instead, say: "13000.56".)

For the relative versions of the commands, all coordinate values are relative to the current point at the start of the command.

In the tables below, the following notation is used:

(): grouping of parameters
+: 1 or more of the given parameter(s) is required

The following sections list the commands.

8.3.2. The "moveto" commands

The "moveto" commands (M or m) establish a new current point. The effect is as if the "pen" were lifted and moved to a new location. A path data segment (if there is one) must begin with a "moveto" command. Subsequent "moveto" commands (i.e., when the "moveto" is not the first command) represent the start of a new subpath:

Command	Name	Parameters	Description
M (absolute) m (relative)	moveto	(x y)+	Start a new sub-path at the given (x,y) coordinate. M (uppercase) indicates that absolute coordinates will follow; m (lowercase) indicates that relative coordinates will follow. If a moveto is followed by multiple pairs of coordinates, the subsequent pairs are treated as implicit lineto commands. Hence, implicit lineto commands will be relative if the moveto is relative, and absolute if the moveto is absolute. If a relative moveto (m) appears as the first element of the path, then it is treated as a pair of absolute coordinates. In this case, subsequent pairs of coordinates are treated as relative even though the initial moveto is interpreted as an absolute moveto.

8.3.3. The "closepath" command

The "closepath" (Z or z) ends the current subpath and causes an automatic straight line to be drawn from the current point to the initial point of the current subpath. If a "closepath" is followed immediately by a "moveto", then the "moveto" identifies the start point of the next subpath. If a "closepath" is followed immediately by any other command, then the next subpath starts at the same initial point as the current subpath.

When a subpath ends in a "closepath," it differs in behavior from what happens when "manually" closing a subpath via a "lineto" command in how ‘stroke-linejoin’ and ‘stroke-linecap’ are implemented. With "closepath", the end of the final segment of the subpath is "joined" with the start of the initial segment of the subpath using the current value of ‘stroke-linejoin’. If you instead "manually" close the subpath via a "lineto" command, the start of the first segment and the end of the last segment are not joined but instead are each capped using the current value of ‘stroke-linecap’. At the end of the command, the new current point is set to the initial point of the current subpath.

Command	Name	Parameters	Description
Z or z	closepath	(none)	Close the current subpath by drawing a straight line from the current point to current subpath's initial point. Since the Z and z commands take no parameters, they have an identical effect.

8.3.4. The "lineto" commands

The various "lineto" commands draw straight lines from the current point to a new point:

Command	Name	Parameters	Description
L (absolute) l (relative)	lineto	(x y)+	Draw a line from the current point to the given (x,y) coordinate which becomes the new current point. L (uppercase) indicates that absolute coordinates will follow; l (lowercase) indicates that relative coordinates will follow. A number of coordinates pairs may be specified to draw a polyline. At the end of the command, the new current point is set to the final set of coordinates provided.
H (absolute) h (relative)	horizontal lineto	x+	Draws a horizontal line from the current point (cpx, cpy) to (x, cpy). H (uppercase) indicates that absolute coordinates will follow; h (lowercase) indicates that relative coordinates will follow. Multiple x values can be provided (although usually this doesn't make sense). At the end of the command, the new current point becomes (x, cpy) for the final value of x.
V (absolute) v (relative)	vertical lineto	y+	Draws a vertical line from the current point (cpx, cpy) to (cpx, y). V (uppercase) indicates that absolute coordinates will follow; v (lowercase) indicates that relative coordinates will follow. Multiple y values can be provided (although usually this doesn't make sense). At the end of the command, the new current point becomes (cpx, y) for the final value of y.

8.3.5. The curve commands

These three groups of commands draw curves:

Cubic Bézier commands (C, c, S and s). A cubic Bézier segment is defined by a start point, an end point, and two control points.
Quadratic Bézier commands (Q, q, T and t). A quadratic Bézier segment is defined by a start point, an end point, and one control point.
Elliptical arc commands (A and a). An elliptical arc segment draws a segment of an ellipse.

8.3.6. The cubic Bézier curve commands

The cubic Bézier commands are as follows:

Command	Name	Parameters	Description
C (absolute) c (relative)	curveto	(x1 y1 x2 y2 x y)+	Draws a cubic Bézier curve from the current point to (x,y) using (x1,y1) as the control point at the beginning of the curve and (x2,y2) as the control point at the end of the curve. C (uppercase) indicates that absolute coordinates will follow; c (lowercase) indicates that relative coordinates will follow. Multiple sets of coordinates may be specified to draw a polybézier. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybézier.
S (absolute) s (relative)	shorthand/smooth curveto	(x2 y2 x y)+	Draws a cubic Bézier curve from the current point to (x,y). The first control point is assumed to be the reflection of the second control point on the previous command relative to the current point. (If there is no previous command or if the previous command was not an C, c, S or s, assume the first control point is coincident with the current point.) (x2,y2) is the second control point (i.e., the control point at the end of the curve). S (uppercase) indicates that absolute coordinates will follow; s (lowercase) indicates that relative coordinates will follow. Multiple sets of coordinates may be specified to draw a polybézier. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybézier.

Example cubic01 shows some simple uses of cubic Bézier commands within a path. The example uses an internal CSS style sheet to assign styling properties. Note that the control point for the "S" command is computed automatically as the reflection of the control point for the previous "C" command relative to the start point of the "S" command.

<?xml version="1.0" standalone="no"?>
<svg width="5cm" height="4cm" viewBox="0 0 500 400"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example cubic01- cubic Bézier commands in path data</title>
  <desc>Picture showing a simple example of path data
        using both a "C" and an "S" command,
        along with annotations showing the control points
        and end points</desc>
  <style type="text/css"><![CDATA[
    .Border { fill:none; stroke:blue; stroke-width:1 }
    .Connect { fill:none; stroke:#888888; stroke-width:2 }
    .SamplePath { fill:none; stroke:red; stroke-width:5 }
    .EndPoint { fill:none; stroke:#888888; stroke-width:2 }
    .CtlPoint { fill:#888888; stroke:none }
    .AutoCtlPoint { fill:none; stroke:blue; stroke-width:4 }
    .Label { font-size:22; font-family:Verdana }
  ]]></style>

  <rect class="Border" x="1" y="1" width="498" height="398" />

  <polyline class="Connect" points="100,200 100,100" />
  <polyline class="Connect" points="250,100 250,200" />
  <polyline class="Connect" points="250,200 250,300" />
  <polyline class="Connect" points="400,300 400,200" />
  <path class="SamplePath" d="M100,200 C100,100 250,100 250,200
                                       S400,300 400,200" />
  <circle class="EndPoint" cx="100" cy="200" r="10" />
  <circle class="EndPoint" cx="250" cy="200" r="10" />
  <circle class="EndPoint" cx="400" cy="200" r="10" />
  <circle class="CtlPoint" cx="100" cy="100" r="10" />
  <circle class="CtlPoint" cx="250" cy="100" r="10" />
  <circle class="CtlPoint" cx="400" cy="300" r="10" />
  <circle class="AutoCtlPoint" cx="250" cy="300" r="9" />
  <text class="Label" x="25" y="70">M100,200 C100,100 250,100 250,200</text>
  <text class="Label" x="325" y="350"
        style="text-anchor:middle">S400,300 400,200</text>
</svg>

Example cubic01

View this example as SVG (SVG-enabled browsers only)

The following picture shows some how cubic Bézier curves change their shape depending on the position of the control points. The first five examples illustrate a single cubic Bézier path segment. The example at the lower right shows a "C" command followed by an "S" command.

Example cubic02 - cubic Bézier commands in path data

View this example as SVG (SVG-enabled browsers only)

8.3.7. The quadratic Bézier curve commands

The quadratic Bézier commands are as follows:

Command	Name	Parameters	Description
Q (absolute) q (relative)	quadratic Bézier curveto	(x1 y1 x y)+	Draws a quadratic Bézier curve from the current point to (x,y) using (x1,y1) as the control point. Q (uppercase) indicates that absolute coordinates will follow; q (lowercase) indicates that relative coordinates will follow. Multiple sets of coordinates may be specified to draw a polybézier. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybézier.
T (absolute) t (relative)	Shorthand/smooth quadratic Bézier curveto	(x y)+	Draws a quadratic Bézier curve from the current point to (x,y). The control point is assumed to be the reflection of the control point on the previous command relative to the current point. (If there is no previous command or if the previous command was not a Q, q, T or t, assume the control point is coincident with the current point.) T (uppercase) indicates that absolute coordinates will follow; t (lowercase) indicates that relative coordinates will follow. At the end of the command, the new current point becomes the final (x,y) coordinate pair used in the polybézier.

Example quad01 shows some simple uses of quadratic Bézier commands within a path. Note that the control point for the "T" command is computed automatically as the reflection of the control point for the previous "Q" command relative to the start point of the "T" command.

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="6cm" viewBox="0 0 1200 600"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example quad01 - quadratic Bézier commands in path data</title>
  <desc>Picture showing a "Q" a "T" command,
        along with annotations showing the control points
        and end points</desc>
  <rect x="1" y="1" width="1198" height="598"
        fill="none" stroke="blue" stroke-width="1" />

  <path d="M200,300 Q400,50 600,300 T1000,300"
        fill="none" stroke="red" stroke-width="5"  />
  <!-- End points -->
  <g fill="black" >
    <circle cx="200" cy="300" r="10"/>
    <circle cx="600" cy="300" r="10"/>
    <circle cx="1000" cy="300" r="10"/>
  </g>
  <!-- Control points and lines from end points to control points -->
  <g fill="#888888" >
    <circle cx="400" cy="50" r="10"/>
    <circle cx="800" cy="550" r="10"/>
  </g>
  <path d="M200,300 L400,50 L600,300 
           L800,550 L1000,300"
        fill="none" stroke="#888888" stroke-width="2" />
</svg>

Example quad01

View this example as SVG (SVG-enabled browsers only)

8.3.8. The elliptical arc curve commands

SVG 2 Requirement:	Make it simpler to draw arcs in SVG path syntax.
Resolution:	Make arcs in paths easier.
Purpose:	To make it easier for authors to write path data with arcs by hand.
Owner:	Cameron (ACTION-3151)

The elliptical arc commands are as follows:

Command	Name	Parameters	Description
A (absolute) a (relative)	elliptical arc	(rx ry x-axis-rotation large-arc-flag sweep-flag x y)+	Draws an elliptical arc from the current point to (x, y). The size and orientation of the ellipse are defined by two radii (rx, ry) and an x-axis-rotation, which indicates how the ellipse as a whole is rotated relative to the current coordinate system. The center (cx, cy) of the ellipse is calculated automatically to satisfy the constraints imposed by the other parameters. large-arc-flag and sweep-flag contribute to the automatic calculations and help determine how the arc is drawn.

Example arcs01 shows some simple uses of arc commands within a path.

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="5.25cm" viewBox="0 0 1200 400"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example arcs01 - arc commands in path data</title>
  <desc>Picture of a pie chart with two pie wedges and
        a picture of a line with arc blips</desc>
  <rect x="1" y="1" width="1198" height="398"
        fill="none" stroke="blue" stroke-width="1" />

  <path d="M300,200 h-150 a150,150 0 1,0 150,-150 z"
        fill="red" stroke="blue" stroke-width="5" />
  <path d="M275,175 v-150 a150,150 0 0,0 -150,150 z"
        fill="yellow" stroke="blue" stroke-width="5" />

  <path d="M600,350 l 50,-25 
           a25,25 -30 0,1 50,-25 l 50,-25 
           a25,50 -30 0,1 50,-25 l 50,-25 
           a25,75 -30 0,1 50,-25 l 50,-25 
           a25,100 -30 0,1 50,-25 l 50,-25"
        fill="none" stroke="red" stroke-width="5"  />
</svg>

Example arcs01

View this example as SVG (SVG-enabled browsers only)

The elliptical arc command draws a section of an ellipse which meets the following constraints:

the arc starts at the current point
the arc ends at point (x, y)
the ellipse has the two radii (rx, ry)
the x-axis of the ellipse is rotated by x-axis-rotation relative to the x-axis of the current coordinate system.

For most situations, there are actually four different arcs (two different ellipses, each with two different arc sweeps) that satisfy these constraints. large-arc-flag and sweep-flag indicate which one of the four arcs are drawn, as follows:

Of the four candidate arc sweeps, two will represent an arc sweep of greater than or equal to 180 degrees (the "large-arc"), and two will represent an arc sweep of less than or equal to 180 degrees (the "small-arc"). If large-arc-flag is '1', then one of the two larger arc sweeps will be chosen; otherwise, if large-arc-flag is '0', one of the smaller arc sweeps will be chosen,
If sweep-flag is '1', then the arc will be drawn in a "positive-angle" direction (i.e., the ellipse formula x=cx+rx*cos(theta) and y=cy+ry*sin(theta) is evaluated such that theta starts at an angle corresponding to the current point and increases positively until the arc reaches (x,y)). A value of 0 causes the arc to be drawn in a "negative-angle" direction (i.e., theta starts at an angle value corresponding to the current point and decreases until the arc reaches (x,y)).

The following illustrates the four combinations of large-arc-flag and sweep-flag and the four different arcs that will be drawn based on the values of these flags. For each case, the following path data command was used:

<path d="M 125,75 a100,50 0 ?,? 100,50"
      style="fill:none; stroke:red; stroke-width:6"/>

where "?,?" is replaced by "0,0" "0,1" "1,0" and "1,1" to generate the four possible cases.

Illustration of flags in arc commands

View this example as SVG (SVG-enabled browsers only)

Refer to Elliptical arc implementation notes for detailed implementation notes for the path data elliptical arc commands.

8.3.9. The grammar for path data

The following notation is used in the Backus-Naur Form (BNF) description of the grammar for path data:

*: 0 or more
+: 1 or more
?: 0 or 1
(): grouping
|: separates alternatives
double quotes surround literals

The following is the BNF for SVG paths.

svg-path:
    wsp* moveto-drawto-command-groups? wsp*
moveto-drawto-command-groups:
    moveto-drawto-command-group
    | moveto-drawto-command-group wsp* moveto-drawto-command-groups
moveto-drawto-command-group:
    moveto wsp* drawto-commands?
drawto-commands:
    drawto-command
    | drawto-command wsp* drawto-commands
drawto-command:
    closepath
    | lineto
    | horizontal-lineto
    | vertical-lineto
    | curveto
    | smooth-curveto
    | quadratic-bezier-curveto
    | smooth-quadratic-bezier-curveto
    | elliptical-arc
moveto:
    ( "M" | "m" ) wsp* moveto-argument-sequence
moveto-argument-sequence:
    coordinate-pair
    | coordinate-pair comma-wsp? lineto-argument-sequence
closepath:
    ("Z" | "z")
lineto:
    ( "L" | "l" ) wsp* lineto-argument-sequence
lineto-argument-sequence:
    coordinate-pair
    | coordinate-pair comma-wsp? lineto-argument-sequence
horizontal-lineto:
    ( "H" | "h" ) wsp* horizontal-lineto-argument-sequence
horizontal-lineto-argument-sequence:
    coordinate
    | coordinate comma-wsp? horizontal-lineto-argument-sequence
vertical-lineto:
    ( "V" | "v" ) wsp* vertical-lineto-argument-sequence
vertical-lineto-argument-sequence:
    coordinate
    | coordinate comma-wsp? vertical-lineto-argument-sequence
curveto:
    ( "C" | "c" ) wsp* curveto-argument-sequence
curveto-argument-sequence:
    curveto-argument
    | curveto-argument comma-wsp? curveto-argument-sequence
curveto-argument:
    coordinate-pair comma-wsp? coordinate-pair comma-wsp? coordinate-pair
smooth-curveto:
    ( "S" | "s" ) wsp* smooth-curveto-argument-sequence
smooth-curveto-argument-sequence:
    smooth-curveto-argument
    | smooth-curveto-argument comma-wsp? smooth-curveto-argument-sequence
smooth-curveto-argument:
    coordinate-pair comma-wsp? coordinate-pair
quadratic-bezier-curveto:
    ( "Q" | "q" ) wsp* quadratic-bezier-curveto-argument-sequence
quadratic-bezier-curveto-argument-sequence:
    quadratic-bezier-curveto-argument
    | quadratic-bezier-curveto-argument comma-wsp? 
        quadratic-bezier-curveto-argument-sequence
quadratic-bezier-curveto-argument:
    coordinate-pair comma-wsp? coordinate-pair
smooth-quadratic-bezier-curveto:
    ( "T" | "t" ) wsp* smooth-quadratic-bezier-curveto-argument-sequence
smooth-quadratic-bezier-curveto-argument-sequence:
    coordinate-pair
    | coordinate-pair comma-wsp? smooth-quadratic-bezier-curveto-argument-sequence
elliptical-arc:
    ( "A" | "a" ) wsp* elliptical-arc-argument-sequence
elliptical-arc-argument-sequence:
    elliptical-arc-argument
    | elliptical-arc-argument comma-wsp? elliptical-arc-argument-sequence
elliptical-arc-argument:
    number comma-wsp? number comma-wsp? 
        number comma-wsp flag comma-wsp? flag comma-wsp? coordinate-pair
coordinate-pair:
    coordinate comma-wsp? coordinate
coordinate:
    number
nonnegative-number:
    integer-constant
    | floating-point-constant
number:
    sign? integer-constant
    | sign? floating-point-constant
flag:
    "0" | "1"
comma-wsp:
    (wsp+ comma? wsp*) | (comma wsp*)
comma:
    ","
integer-constant:
    digit-sequence
floating-point-constant:
    fractional-constant exponent?
    | digit-sequence exponent
fractional-constant:
    digit-sequence? "." digit-sequence
    | digit-sequence "."
exponent:
    ( "e" | "E" ) sign? digit-sequence
sign:
    "+" | "-"
digit-sequence:
    digit
    | digit digit-sequence
digit:
    "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
wsp:
    (#x20 | #x9 | #xD | #xA)

The processing of the BNF must consume as much of a given BNF production as possible, stopping at the point when a character is encountered which no longer satisfies the production. Thus, in the string "M 100-200", the first coordinate for the "moveto" consumes the characters "100" and stops upon encountering the minus sign because the minus sign cannot follow a digit in the production of a "coordinate". The result is that the first coordinate will be "100" and the second coordinate will be "-200".

Similarly, for the string "M 0.6.5", the first coordinate of the "moveto" consumes the characters "0.6" and stops upon encountering the second decimal point because the production of a "coordinate" only allows one decimal point. The result is that the first coordinate will be "0.6" and the second coordinate will be ".5".

Note that the BNF allows the path ‘d’ attribute to be empty. This is not an error, instead it disables rendering of the path.

8.4. Distance along a path

Various operations, including text on a path and motion animation and various stroke operations, require that the user agent compute the distance along the geometry of a graphics element, such as a ‘path’.

Exact mathematics exist for computing distance along a path, but the formulas are highly complex and require substantial computation. It is recommended that authoring products and user agents employ algorithms that produce as precise results as possible; however, to accommodate implementation differences and to help distance calculations produce results that approximate author intent, the ‘pathLength’ attribute can be used to provide the author's computation of the total length of the path so that the user agent can scale distance-along-a-path computations by the ratio of ‘pathLength’ to the user agent's own computed value for total path length.

A "moveto" operation within a ‘path’ element is defined to have zero length. Only the various "lineto", "curveto" and "arcto" commands contribute to path length calculations.

8.5. DOM interfaces

8.5.1. Interface SVGPathSeg

The SVGPathSeg interface is a base interface that corresponds to a single command within a path data specification.

interface SVGPathSeg {

  // Path Segment Types
  const unsigned short PATHSEG_UNKNOWN = 0;
  const unsigned short PATHSEG_CLOSEPATH = 1;
  const unsigned short PATHSEG_MOVETO_ABS = 2;
  const unsigned short PATHSEG_MOVETO_REL = 3;
  const unsigned short PATHSEG_LINETO_ABS = 4;
  const unsigned short PATHSEG_LINETO_REL = 5;
  const unsigned short PATHSEG_CURVETO_CUBIC_ABS = 6;
  const unsigned short PATHSEG_CURVETO_CUBIC_REL = 7;
  const unsigned short PATHSEG_CURVETO_QUADRATIC_ABS = 8;
  const unsigned short PATHSEG_CURVETO_QUADRATIC_REL = 9;
  const unsigned short PATHSEG_ARC_ABS = 10;
  const unsigned short PATHSEG_ARC_REL = 11;
  const unsigned short PATHSEG_LINETO_HORIZONTAL_ABS = 12;
  const unsigned short PATHSEG_LINETO_HORIZONTAL_REL = 13;
  const unsigned short PATHSEG_LINETO_VERTICAL_ABS = 14;
  const unsigned short PATHSEG_LINETO_VERTICAL_REL = 15;
  const unsigned short PATHSEG_CURVETO_CUBIC_SMOOTH_ABS = 16;
  const unsigned short PATHSEG_CURVETO_CUBIC_SMOOTH_REL = 17;
  const unsigned short PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS = 18;
  const unsigned short PATHSEG_CURVETO_QUADRATIC_SMOOTH_REL = 19;

  readonly attribute unsigned short pathSegType;
  readonly attribute DOMString pathSegTypeAsLetter;
};

Constants in group “Path Segment Types”:

PATHSEG_UNKNOWN (unsigned short): The unit type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
PATHSEG_CLOSEPATH (unsigned short): Corresponds to a "closepath" (z) path data command.
PATHSEG_MOVETO_ABS (unsigned short): Corresponds to a "absolute moveto" (M) path data command.
PATHSEG_MOVETO_REL (unsigned short): Corresponds to a "relative moveto" (m) path data command.
PATHSEG_LINETO_ABS (unsigned short): Corresponds to a "absolute lineto" (L) path data command.
PATHSEG_LINETO_REL (unsigned short): Corresponds to a "relative lineto" (l) path data command.
PATHSEG_CURVETO_CUBIC_ABS (unsigned short): Corresponds to a "absolute cubic Bézier curveto" (C) path data command.
PATHSEG_CURVETO_CUBIC_REL (unsigned short): Corresponds to a "relative cubic Bézier curveto" (c) path data command.
PATHSEG_CURVETO_QUADRATIC_ABS (unsigned short): Corresponds to a "absolute quadratic Bézier curveto" (Q) path data command.
PATHSEG_CURVETO_QUADRATIC_REL (unsigned short): Corresponds to a "relative quadratic Bézier curveto" (q) path data command.
PATHSEG_ARC_ABS (unsigned short): Corresponds to a "absolute arcto" (A) path data command.
PATHSEG_ARC_REL (unsigned short): Corresponds to a "relative arcto" (a) path data command.
PATHSEG_LINETO_HORIZONTAL_ABS (unsigned short): Corresponds to a "absolute horizontal lineto" (H) path data command.
PATHSEG_LINETO_HORIZONTAL_REL (unsigned short): Corresponds to a "relative horizontal lineto" (h) path data command.
PATHSEG_LINETO_VERTICAL_ABS (unsigned short): Corresponds to a "absolute vertical lineto" (V) path data command.
PATHSEG_LINETO_VERTICAL_REL (unsigned short): Corresponds to a "relative vertical lineto" (v) path data command.
PATHSEG_CURVETO_CUBIC_SMOOTH_ABS (unsigned short): Corresponds to a "absolute smooth cubic curveto" (S) path data command.
PATHSEG_CURVETO_CUBIC_SMOOTH_REL (unsigned short): Corresponds to a "relative smooth cubic curveto" (s) path data command.
PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS (unsigned short): Corresponds to a "absolute smooth quadratic curveto" (T) path data command.
PATHSEG_CURVETO_QUADRATIC_SMOOTH_REL (unsigned short): Corresponds to a "relative smooth quadratic curveto" (t) path data command.

Attributes:

pathSegType (readonly unsigned short): The type of the path segment as specified by one of the constants defined on this interface.
pathSegTypeAsLetter (readonly DOMString): The type of the path segment, specified by the corresponding one character command name.

8.5.2. Interface SVGPathSegClosePath

The SVGPathSegClosePath interface corresponds to a "closepath" (z) path data command.

interface SVGPathSegClosePath : SVGPathSeg {
};

8.5.3. Interface SVGPathSegMovetoAbs

The SVGPathSegMovetoAbs interface corresponds to an "absolute moveto" (M) path data command.

interface SVGPathSegMovetoAbs : SVGPathSeg {
  attribute float x;
  attribute float y;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.
y (float): The absolute Y coordinate for the end point of this path segment.

8.5.4. Interface SVGPathSegMovetoRel

The SVGPathSegMovetoRel interface corresponds to a "relative moveto" (m) path data command.

interface SVGPathSegMovetoRel : SVGPathSeg {
  attribute float x;
  attribute float y;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.
y (float): The relative Y coordinate for the end point of this path segment.

8.5.5. Interface SVGPathSegLinetoAbs

The SVGPathSegLinetoAbs interface corresponds to an "absolute lineto" (L) path data command.

interface SVGPathSegLinetoAbs : SVGPathSeg {
  attribute float x;
  attribute float y;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.
y (float): The absolute Y coordinate for the end point of this path segment.

8.5.6. Interface SVGPathSegLinetoRel

The SVGPathSegLinetoRel interface corresponds to a "relative lineto" (l) path data command.

interface SVGPathSegLinetoRel : SVGPathSeg {
  attribute float x;
  attribute float y;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.
y (float): The relative Y coordinate for the end point of this path segment.

8.5.7. Interface SVGPathSegCurvetoCubicAbs

The SVGPathSegCurvetoCubicAbs interface corresponds to an "absolute cubic Bézier curveto" (C) path data command.

interface SVGPathSegCurvetoCubicAbs : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float x1;
  attribute float y1;
  attribute float x2;
  attribute float y2;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.
y (float): The absolute Y coordinate for the end point of this path segment.
x1 (float): The absolute X coordinate for the first control point.
y1 (float): The absolute Y coordinate for the first control point.
x2 (float): The absolute X coordinate for the second control point.
y2 (float): The absolute Y coordinate for the second control point.

8.5.8. Interface SVGPathSegCurvetoCubicRel

The SVGPathSegCurvetoCubicRel interface corresponds to a "relative cubic Bézier curveto" (c) path data command.

interface SVGPathSegCurvetoCubicRel : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float x1;
  attribute float y1;
  attribute float x2;
  attribute float y2;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.
y (float): The relative Y coordinate for the end point of this path segment.
x1 (float): The relative X coordinate for the first control point.
y1 (float): The relative Y coordinate for the first control point.
x2 (float): The relative X coordinate for the second control point.
y2 (float): The relative Y coordinate for the second control point.

8.5.9. Interface SVGPathSegCurvetoQuadraticAbs

The SVGPathSegCurvetoQuadraticAbs interface corresponds to an "absolute quadratic Bézier curveto" (Q) path data command.

interface SVGPathSegCurvetoQuadraticAbs : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float x1;
  attribute float y1;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.
y (float): The absolute Y coordinate for the end point of this path segment.
x1 (float): The absolute X coordinate for the first control point.
y1 (float): The absolute Y coordinate for the first control point.

8.5.10. Interface SVGPathSegCurvetoQuadraticRel

The SVGPathSegCurvetoQuadraticRel interface corresponds to a "relative quadratic Bézier curveto" (q) path data command.

interface SVGPathSegCurvetoQuadraticRel : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float x1;
  attribute float y1;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.
y (float): The relative Y coordinate for the end point of this path segment.
x1 (float): The relative X coordinate for the first control point.
y1 (float): The relative Y coordinate for the first control point.

8.5.11. Interface SVGPathSegArcAbs

The SVGPathSegArcAbs interface corresponds to an "absolute arcto" (A) path data command.

interface SVGPathSegArcAbs : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float r1;
  attribute float r2;
  attribute float angle;
  attribute boolean largeArcFlag;
  attribute boolean sweepFlag;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.
y (float): The absolute Y coordinate for the end point of this path segment.
r1 (float): The x-axis radius for the ellipse (i.e., r1).
r2 (float): The y-axis radius for the ellipse (i.e., r2).
angle (float): The rotation angle in degrees for the ellipse's x-axis relative to the x-axis of the user coordinate system.
largeArcFlag (boolean): The value of the large-arc-flag parameter.
sweepFlag (boolean): The value of the sweep-flag parameter.

8.5.12. Interface SVGPathSegArcRel

The SVGPathSegArcRel interface corresponds to a "relative arcto" (a) path data command.

interface SVGPathSegArcRel : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float r1;
  attribute float r2;
  attribute float angle;
  attribute boolean largeArcFlag;
  attribute boolean sweepFlag;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.
y (float): The relative Y coordinate for the end point of this path segment.
r1 (float): The x-axis radius for the ellipse (i.e., r1).
r2 (float): The y-axis radius for the ellipse (i.e., r2).
angle (float): The rotation angle in degrees for the ellipse's x-axis relative to the x-axis of the user coordinate system.
largeArcFlag (boolean): The value of the large-arc-flag parameter.
sweepFlag (boolean): The value of the sweep-flag parameter.

8.5.13. Interface SVGPathSegLinetoHorizontalAbs

The SVGPathSegLinetoHorizontalAbs interface corresponds to an "absolute horizontal lineto" (H) path data command.

interface SVGPathSegLinetoHorizontalAbs : SVGPathSeg {
  attribute float x;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.

8.5.14. Interface SVGPathSegLinetoHorizontalRel

The SVGPathSegLinetoHorizontalRel interface corresponds to a "relative horizontal lineto" (h) path data command.

interface SVGPathSegLinetoHorizontalRel : SVGPathSeg {
  attribute float x;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.

8.5.15. Interface SVGPathSegLinetoVerticalAbs

The SVGPathSegLinetoVerticalAbs interface corresponds to an "absolute vertical lineto" (V) path data command.

interface SVGPathSegLinetoVerticalAbs : SVGPathSeg {
  attribute float y;
};

Attributes:

y (float): The absolute Y coordinate for the end point of this path segment.

8.5.16. Interface SVGPathSegLinetoVerticalRel

The SVGPathSegLinetoVerticalRel interface corresponds to a "relative vertical lineto" (v) path data command.

interface SVGPathSegLinetoVerticalRel : SVGPathSeg {
  attribute float y;
};

Attributes:

y (float): The relative Y coordinate for the end point of this path segment.

8.5.17. Interface SVGPathSegCurvetoCubicSmoothAbs

The SVGPathSegCurvetoCubicSmoothAbs interface corresponds to an "absolute smooth cubic curveto" (S) path data command.

interface SVGPathSegCurvetoCubicSmoothAbs : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float x2;
  attribute float y2;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.
y (float): The absolute Y coordinate for the end point of this path segment.
x2 (float): The absolute X coordinate for the second control point.
y2 (float): The absolute Y coordinate for the second control point.

8.5.18. Interface SVGPathSegCurvetoCubicSmoothRel

The SVGPathSegCurvetoCubicSmoothRel interface corresponds to a "relative smooth cubic curveto" (s) path data command.

interface SVGPathSegCurvetoCubicSmoothRel : SVGPathSeg {
  attribute float x;
  attribute float y;
  attribute float x2;
  attribute float y2;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.
y (float): The relative Y coordinate for the end point of this path segment.
x2 (float): The relative X coordinate for the second control point.
y2 (float): The relative Y coordinate for the second control point.

8.5.19. Interface SVGPathSegCurvetoQuadraticSmoothAbs

The SVGPathSegCurvetoQuadraticSmoothAbs interface corresponds to an "absolute smooth cubic curveto" (T) path data command.

interface SVGPathSegCurvetoQuadraticSmoothAbs : SVGPathSeg {
  attribute float x;
  attribute float y;
};

Attributes:

x (float): The absolute X coordinate for the end point of this path segment.
y (float): The absolute Y coordinate for the end point of this path segment.

8.5.20. Interface SVGPathSegCurvetoQuadraticSmoothRel

The SVGPathSegCurvetoQuadraticSmoothRel interface corresponds to a "relative smooth cubic curveto" (t) path data command.

interface SVGPathSegCurvetoQuadraticSmoothRel : SVGPathSeg {
  attribute float x;
  attribute float y;
};

Attributes:

x (float): The relative X coordinate for the end point of this path segment.
y (float): The relative Y coordinate for the end point of this path segment.

8.5.21. Interface SVGPathSegList

This interface defines a list of SVGPathSeg objects.

SVGPathSegList has the same attributes and methods as other SVGxxxList interfaces. Implementers may consider using a single base class to implement the various SVGxxxList interfaces.

The supported property indices of an SVGPathSegList object is all non-negative integers less than the length of the list.

interface SVGPathSegList {

  readonly attribute unsigned long length;
  readonly attribute unsigned long numberOfItems;

  void clear();
  SVGPathSeg initialize(SVGPathSeg newItem);
  getter SVGPathSeg getItem(unsigned long index);
  SVGPathSeg insertItemBefore(SVGPathSeg newItem, unsigned long index);
  SVGPathSeg replaceItem(SVGPathSeg newItem, unsigned long index);
  SVGPathSeg removeItem(unsigned long index);
  SVGPathSeg appendItem(SVGPathSeg newItem);
  setter void (unsigned long index, SVGPathSeg newItem);
};

Attributes:

length (readonly unsigned long): The number of items in the list.
numberOfItems (readonly unsigned long): The number of items in the list.

Operations:

void clear()

Clears all existing current items from the list, with the result being an empty list.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

SVGPathSeg initialize(SVGPathSeg newItem)

Parameters

SVGPathSeg newItem

The item which should become the only member of the list.

Returns

The item being inserted into the list.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

SVGPathSeg getItem(unsigned long index)

Returns the specified item from the list. The returned item is the item itself and not a copy. Any changes made to the item are immediately reflected in the list.

Parameters

unsigned long index

The index of the item from the list which is to be returned. The first item is number 0.

Returns

The selected item.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGPathSeg insertItemBefore(SVGPathSeg newItem, unsigned long index)

Parameters

SVGPathSeg newItem

The item which is to be inserted into the list.
unsigned long index

The index of the item before which the new item is to be inserted. The first item is number 0. If the index is equal to 0, then the new item is inserted at the front of the list. If the index is greater than or equal to numberOfItems, then the new item is appended to the end of the list.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

SVGPathSeg replaceItem(SVGPathSeg newItem, unsigned long index)

Parameters

SVGPathSeg newItem

The item which is to be inserted into the list.
unsigned long index

The index of the item which is to be replaced. The first item is number 0.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.
DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGPathSeg removeItem(unsigned long index)

Removes an existing item from the list.

Parameters

unsigned long index

The index of the item which is to be removed. The first item is number 0.

Returns

The removed item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.
DOMException, code INDEX_SIZE_ERR: Raised if the index number is greater than or equal to numberOfItems.

SVGPathSeg appendItem(SVGPathSeg newItem)

Parameters

SVGPathSeg newItem

The item which is to be inserted. The first item is number 0.

Returns

The inserted item.

Exceptions

DOMException, code NO_MODIFICATION_ALLOWED_ERR: Raised when the list cannot be modified.

setter void (unsigned long index, SVGPathSeg newItem)

Replaces the item at index index with newItem.

8.5.22. Interface SVGAnimatedPathData

The SVGAnimatedPathData interface supports elements which have a ‘d’ attribute which holds SVG path data, and supports the ability to animate that attribute.

The SVGAnimatedPathData interface provides two lists to access and modify the base (i.e., static) contents of the ‘d’ attribute:

DOM attribute pathSegList provides access to the static/base contents of the ‘d’ attribute in a form which matches one-for-one with SVG's syntax.
DOM attribute normalizedPathSegList provides normalized access to the static/base contents of the ‘d’ attribute where all path data commands are expressed in terms of the following subset of SVGPathSeg types: SVG_PATHSEG_MOVETO_ABS (M), SVG_PATHSEG_LINETO_ABS (L), SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and SVG_PATHSEG_CLOSEPATH (z).

and two lists to access the current animated values of the ‘d’ attribute:

DOM attribute animatedPathSegList provides access to the current animated contents of the ‘d’ attribute in a form which matches one-for-one with SVG's syntax.
DOM attribute animatedNormalizedPathSegList provides normalized access to the current animated contents of the ‘d’ attribute where all path data commands are expressed in terms of the following subset of SVGPathSeg types: SVG_PATHSEG_MOVETO_ABS (M), SVG_PATHSEG_LINETO_ABS (L), SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and SVG_PATHSEG_CLOSEPATH (z).

Each of the two lists are always kept synchronized. Modifications to one list will immediately cause the corresponding list to be modified. Modifications to normalizedPathSegList might cause entries in pathSegList to be broken into a set of normalized path segments.

Additionally, the ‘d’ attribute on the ‘path’ element accessed via the XML DOM (e.g., using the getAttribute() method call) will reflect any changes made to pathSegList or normalizedPathSegList.

interface SVGAnimatedPathData {
  readonly attribute SVGPathSegList pathSegList;
  readonly attribute SVGPathSegList normalizedPathSegList;
  readonly attribute SVGPathSegList animatedPathSegList;
  readonly attribute SVGPathSegList animatedNormalizedPathSegList;
};

Attributes:

pathSegList (readonly SVGPathSegList): Provides access to the base (i.e., static) contents of the ‘d’ attribute in a form which matches one-for-one with SVG's syntax. Thus, if the ‘d’ attribute has an "absolute moveto (M)" and an "absolute arcto (A)" command, then pathSegList will have two entries: a SVG_PATHSEG_MOVETO_ABS and a SVG_PATHSEG_ARC_ABS.
normalizedPathSegList (readonly SVGPathSegList): Provides access to the base (i.e., static) contents of the ‘d’ attribute in a form where all path data commands are expressed in terms of the following subset of SVGPathSeg types: SVG_PATHSEG_MOVETO_ABS (M), SVG_PATHSEG_LINETO_ABS (L), SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and SVG_PATHSEG_CLOSEPATH (z). Thus, if the ‘d’ attribute has an "absolute moveto (M)" and an "absolute arcto (A)" command, then pathSegList will have one SVG_PATHSEG_MOVETO_ABS entry followed by a series of SVG_PATHSEG_LINETO_ABS entries which approximate the arc. This alternate representation is available to provide a simpler interface to developers who would benefit from a more limited set of commands.

The only valid SVGPathSeg types are SVG_PATHSEG_MOVETO_ABS (M), SVG_PATHSEG_LINETO_ABS (L), SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and SVG_PATHSEG_CLOSEPATH (z).
animatedPathSegList (readonly SVGPathSegList): Provides access to the current animated contents of the ‘d’ attribute in a form which matches one-for-one with SVG's syntax. If the given attribute or property is being animated, contains the current animated value of the attribute or property, and both the object itself and its contents are read only. If the given attribute or property is not currently being animated, contains the same value as pathSegList.
animatedNormalizedPathSegList (readonly SVGPathSegList): Provides access to the current animated contents of the ‘d’ attribute in a form where all path data commands are expressed in terms of the following subset of SVGPathSeg types: SVG_PATHSEG_MOVETO_ABS (M), SVG_PATHSEG_LINETO_ABS (L), SVG_PATHSEG_CURVETO_CUBIC_ABS (C) and SVG_PATHSEG_CLOSEPATH (z). If the given attribute or property is being animated, contains the current animated value of the attribute or property, and both the object itself and its contents are read only. If the given attribute or property is not currently being animated, contains the same value as normalizedPathSegList.

8.5.23. Interface SVGPathElement

The SVGPathElement interface corresponds to the ‘path’ element.

interface SVGPathElement : SVGGeometryElement {

  readonly attribute SVGAnimatedNumber pathLength;

  float getTotalLength();
  SVGPoint getPointAtLength(float distance);
  unsigned long getPathSegAtLength(float distance);
  SVGPathSegClosePath createSVGPathSegClosePath();
  SVGPathSegMovetoAbs createSVGPathSegMovetoAbs(float x, float y);
  SVGPathSegMovetoRel createSVGPathSegMovetoRel(float x, float y);
  SVGPathSegLinetoAbs createSVGPathSegLinetoAbs(float x, float y);
  SVGPathSegLinetoRel createSVGPathSegLinetoRel(float x, float y);
  SVGPathSegCurvetoCubicAbs createSVGPathSegCurvetoCubicAbs(float x, float y, float x1, float y1, float x2, float y2);
  SVGPathSegCurvetoCubicRel createSVGPathSegCurvetoCubicRel(float x, float y, float x1, float y1, float x2, float y2);
  SVGPathSegCurvetoQuadraticAbs createSVGPathSegCurvetoQuadraticAbs(float x, float y, float x1, float y1);
  SVGPathSegCurvetoQuadraticRel createSVGPathSegCurvetoQuadraticRel(float x, float y, float x1, float y1);
  SVGPathSegArcAbs createSVGPathSegArcAbs(float x, float y, float r1, float r2, float angle, boolean largeArcFlag, boolean sweepFlag);
  SVGPathSegArcRel createSVGPathSegArcRel(float x, float y, float r1, float r2, float angle, boolean largeArcFlag, boolean sweepFlag);
  SVGPathSegLinetoHorizontalAbs createSVGPathSegLinetoHorizontalAbs(float x);
  SVGPathSegLinetoHorizontalRel createSVGPathSegLinetoHorizontalRel(float x);
  SVGPathSegLinetoVerticalAbs createSVGPathSegLinetoVerticalAbs(float y);
  SVGPathSegLinetoVerticalRel createSVGPathSegLinetoVerticalRel(float y);
  SVGPathSegCurvetoCubicSmoothAbs createSVGPathSegCurvetoCubicSmoothAbs(float x, float y, float x2, float y2);
  SVGPathSegCurvetoCubicSmoothRel createSVGPathSegCurvetoCubicSmoothRel(float x, float y, float x2, float y2);
  SVGPathSegCurvetoQuadraticSmoothAbs createSVGPathSegCurvetoQuadraticSmoothAbs(float x, float y);
  SVGPathSegCurvetoQuadraticSmoothRel createSVGPathSegCurvetoQuadraticSmoothRel(float x, float y);
};

SVGPathElement implements SVGAnimatedPathData;
SVGPathElement implements SVGMarkableElement;

Attributes:

pathLength (readonly SVGAnimatedNumber): Corresponds to attribute pathLength on the given ‘path’ element.

Operations:

float getTotalLength()

Returns the user agent's computed value for the total length of the path using the user agent's distance-along-a-path algorithm, as a distance in the current user coordinate system.

Returns: The total length of the path.

SVGPoint getPointAtLength(float distance)

Returns the (x,y) coordinate in user space which is distance units along the path, utilizing the user agent's distance-along-a-path algorithm.

Parameters

float distance

The distance along the path, relative to the start of the path, as a distance in the current user coordinate system.

Returns

The returned point in user space.

unsigned long getPathSegAtLength(float distance)

Returns the index into pathSegList which is distance units along the path, utilizing the user agent's distance-along-a-path algorithm.

Parameters

float distance

The distance along the path, relative to the start of the path, as a distance in the current user coordinate system.

Returns

The index of the path segment, where the first path segment is number 0.

SVGPathSegClosePath createSVGPathSegClosePath()

Returns a stand-alone, parentless SVGPathSegClosePath object.

Returns: A stand-alone, parentless SVGPathSegClosePath object.

SVGPathSegMovetoAbs createSVGPathSegMovetoAbs(float x, float y)

Returns a stand-alone, parentless SVGPathSegMovetoAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.
float y

The absolute Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegMovetoAbs object.

SVGPathSegMovetoRel createSVGPathSegMovetoRel(float x, float y)

Returns a stand-alone, parentless SVGPathSegMovetoRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.
float y

The relative Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegMovetoRel object.

SVGPathSegLinetoAbs createSVGPathSegLinetoAbs(float x, float y)

Returns a stand-alone, parentless SVGPathSegLinetoAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.
float y

The absolute Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegLinetoAbs object.

SVGPathSegLinetoRel createSVGPathSegLinetoRel(float x, float y)

Returns a stand-alone, parentless SVGPathSegLinetoRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.
float y

The relative Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegLinetoRel object.

SVGPathSegCurvetoCubicAbs createSVGPathSegCurvetoCubicAbs(float x, float y, float x1, float y1, float x2, float y2)

Returns a stand-alone, parentless SVGPathSegCurvetoCubicAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.
float y

The absolute Y coordinate for the end point of this path segment.
float x1

The absolute X coordinate for the first control point.
float y1

The absolute Y coordinate for the first control point.
float x2

The absolute X coordinate for the second control point.
float y2

The absolute Y coordinate for the second control point.

Returns

A stand-alone, parentless SVGPathSegCurvetoCubicAbs object.

SVGPathSegCurvetoCubicRel createSVGPathSegCurvetoCubicRel(float x, float y, float x1, float y1, float x2, float y2)

Returns a stand-alone, parentless SVGPathSegCurvetoCubicRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.
float y

The relative Y coordinate for the end point of this path segment.
float x1

The relative X coordinate for the first control point.
float y1

The relative Y coordinate for the first control point.
float x2

The relative X coordinate for the second control point.
float y2

The relative Y coordinate for the second control point.

Returns

A stand-alone, parentless SVGPathSegCurvetoCubicRel object.

SVGPathSegCurvetoQuadraticAbs createSVGPathSegCurvetoQuadraticAbs(float x, float y, float x1, float y1)

Returns a stand-alone, parentless SVGPathSegCurvetoQuadraticAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.
float y

The absolute Y coordinate for the end point of this path segment.
float x1

The absolute X coordinate for the first control point.
float y1

The absolute Y coordinate for the first control point.

Returns

A stand-alone, parentless SVGPathSegCurvetoQuadraticAbs object.

SVGPathSegCurvetoQuadraticRel createSVGPathSegCurvetoQuadraticRel(float x, float y, float x1, float y1)

Returns a stand-alone, parentless SVGPathSegCurvetoQuadraticRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.
float y

The relative Y coordinate for the end point of this path segment.
float x1

The relative X coordinate for the first control point.
float y1

The relative Y coordinate for the first control point.

Returns

A stand-alone, parentless SVGPathSegCurvetoQuadraticRel object.

SVGPathSegArcAbs createSVGPathSegArcAbs(float x, float y, float r1, float r2, float angle, boolean largeArcFlag, boolean sweepFlag)

Returns a stand-alone, parentless SVGPathSegArcAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.
float y

The absolute Y coordinate for the end point of this path segment.
float r1

The x-axis radius for the ellipse (i.e., r1).
float r2

The y-axis radius for the ellipse (i.e., r2).
float angle

The rotation angle in degrees for the ellipse's x-axis relative to the x-axis of the user coordinate system.
boolean largeArcFlag

The value of the large-arc-flag parameter.
boolean sweepFlag

The value of the large-arc-flag parameter.

Returns

A stand-alone, parentless SVGPathSegArcAbs object.

SVGPathSegArcRel createSVGPathSegArcRel(float x, float y, float r1, float r2, float angle, boolean largeArcFlag, boolean sweepFlag)

Returns a stand-alone, parentless SVGPathSegArcRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.
float y

The relative Y coordinate for the end point of this path segment.
float r1

The x-axis radius for the ellipse (i.e., r1).
float r2

The y-axis radius for the ellipse (i.e., r2).
float angle

The rotation angle in degrees for the ellipse's x-axis relative to the x-axis of the user coordinate system.
boolean largeArcFlag

The value of the large-arc-flag parameter.
boolean sweepFlag

The value of the large-arc-flag parameter.

Returns

A stand-alone, parentless SVGPathSegArcRel object.

SVGPathSegLinetoHorizontalAbs createSVGPathSegLinetoHorizontalAbs(float x)

Returns a stand-alone, parentless SVGPathSegLinetoHorizontalAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegLinetoHorizontalAbs object.

SVGPathSegLinetoHorizontalRel createSVGPathSegLinetoHorizontalRel(float x)

Returns a stand-alone, parentless SVGPathSegLinetoHorizontalRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegLinetoHorizontalRel object.

SVGPathSegLinetoVerticalAbs createSVGPathSegLinetoVerticalAbs(float y)

Returns a stand-alone, parentless SVGPathSegLinetoVerticalAbs object.

Parameters

float y

The absolute Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegLinetoVerticalAbs object.

SVGPathSegLinetoVerticalRel createSVGPathSegLinetoVerticalRel(float y)

Returns a stand-alone, parentless SVGPathSegLinetoVerticalRel object.

Parameters

float y

The relative Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegLinetoVerticalRel object.

SVGPathSegCurvetoCubicSmoothAbs createSVGPathSegCurvetoCubicSmoothAbs(float x, float y, float x2, float y2)

Returns a stand-alone, parentless SVGPathSegCurvetoCubicSmoothAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.
float y

The absolute Y coordinate for the end point of this path segment.
float x2

The absolute X coordinate for the second control point.
float y2

The absolute Y coordinate for the second control point.

Returns

A stand-alone, parentless SVGPathSegCurvetoCubicSmoothAbs object.

SVGPathSegCurvetoCubicSmoothRel createSVGPathSegCurvetoCubicSmoothRel(float x, float y, float x2, float y2)

Returns a stand-alone, parentless SVGPathSegCurvetoCubicSmoothRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.
float y

The relative Y coordinate for the end point of this path segment.
float x2

The relative X coordinate for the second control point.
float y2

The relative Y coordinate for the second control point.

Returns

A stand-alone, parentless SVGPathSegCurvetoCubicSmoothRel object.

SVGPathSegCurvetoQuadraticSmoothAbs createSVGPathSegCurvetoQuadraticSmoothAbs(float x, float y)

Returns a stand-alone, parentless SVGPathSegCurvetoQuadraticSmoothAbs object.

Parameters

float x

The absolute X coordinate for the end point of this path segment.
float y

The absolute Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegCurvetoQuadraticSmoothAbs object.

SVGPathSegCurvetoQuadraticSmoothRel createSVGPathSegCurvetoQuadraticSmoothRel(float x, float y)

Returns a stand-alone, parentless SVGPathSegCurvetoQuadraticSmoothRel object.

Parameters

float x

The relative X coordinate for the end point of this path segment.
float y

The relative Y coordinate for the end point of this path segment.

Returns

A stand-alone, parentless SVGPathSegCurvetoQuadraticSmoothRel object.

Chapter 10: Text

SVG 2 Requirement:	Support text in shapes.
Resolution:	SVG 2 will require automatic text wrapping compatible with CSS.
Purpose:	Text in flow charts, etc.
Owner:	Tav (no action)

SVG 2 Requirement:	Have a way to specify flip-invariant text.
Resolution:	SVG 2 will have a way to specify flip-invariant text.
Purpose:	To keep text readable if an image is rotated.
Owner:	Doug (no action)

10.1. Introduction

Text that is to be rendered as part of an SVG document fragment is specified using the ‘text’ element. The characters to be drawn are expressed as XML character data ([XML10], section 2.4) inside the ‘text’ element.

SVG's ‘text’ elements are rendered like other graphics elements. Thus, coordinate system transformations, painting, clipping and masking features apply to ‘text’ elements in the same way as they apply to shapes such as paths and rectangles.

Each ‘text’ element causes a single string of text to be rendered. SVG performs no automatic line breaking or word wrapping. To achieve the effect of multiple lines of text, use one of the following methods:

The author or authoring package needs to pre-compute the line breaks and use multiple ‘text’ elements (one for each line of text).
The author or authoring package needs to pre-compute the line breaks and use a single ‘text’ element with one or more ‘tspan’ child elements with appropriate values for attributes ‘x’, ‘y’, ‘dx’ and ‘dy’ to set new start positions for those characters which start new lines. (This approach allows user text selection across multiple lines of text -- see Text selection and clipboard operations.)
Express the text to be rendered in another XML namespace such as XHTML [XHTML] embedded inline within a ‘foreignObject’ element. (Note: the exact semantics of this approach are not completely defined at this time.)

The text strings within ‘text’ elements can be rendered in a straight line or rendered along the outline of a ‘path’ element. SVG supports the following international text processing features for both straight line text and text on a path:

horizontal and vertical orientation of text
left-to-right or bidirectional text (i.e., languages which intermix right-to-left and left-to-right text, such as Arabic and Hebrew)
when SVG fonts are used, automatic selection of the correct glyph corresponding to the current form for Arabic and Han text

(The layout rules for straight line text are described in Text layout. The layout rules for text on a path are described in Text on a path layout rules.)

Because SVG text is packaged as XML character data:

Text data in SVG content is readily accessible to the visually impaired (see Accessibility Support)
In many viewing scenarios, the user will be able to search for and select text strings and copy selected text strings to the system clipboard (see Text selection and clipboard operations)
XML-compatible Web search engines will find text strings in SVG content with no additional effort over what they need to do to find text strings in other XML documents

Multi-language SVG content is possible by substituting different text strings based on the user's preferred language.

For accessibility reasons, it is recommended that text which is included in a document have appropriate semantic markup to indicate its function. See SVG accessibility guidelines for more information.

10.2. Characters and their corresponding glyphs

In XML [XML10], textual content is defined in terms of a sequence of XML characters, where each character is defined by a particular Unicode code point [UNICODE]. Fonts, on the other hand, consist of a collection of glyphs and other associated information, such as font tables. A glyph is a presentable form of one or more characters (or a part of a character in some cases). Each glyph consists of some sort of identifier (in some cases a string, in other cases a number) along with drawing instructions for rendering that particular glyph.

In many cases, there is a one-to-one mapping of Unicode characters (i.e., Unicode code points) to glyphs in a font. For example, it is common for a font designed for Latin languages (where the term Latin is used for European languages such as English with alphabets similar to and/or derivative to the Latin language) to contain a single glyph for each of the standard ASCII characters (i.e., A-to-Z, a-to-z, 0-to-9, plus the various punctuation characters found in ASCII). Thus, in most situations, the string "XML", which consists of three Unicode characters, would be rendered by the three glyphs corresponding to "X", "M" and "L", respectively.

In various other cases, however, there is not a strict one-to-one mapping of Unicode characters to glyphs. Some of the circumstances when the mapping is not one-to-one:

Ligatures - For best looking typesetting, it is often desirable that particular sequences of characters are rendered as a single glyph. An example is the word "office". Many fonts will define an "ffi" ligature. When the word "office" is rendered, sometimes the user agent will render the glyph for the "ffi" ligature instead of rendering distinct glyphs (i.e., "f", "f" and "i") for each of the three characters. Thus, for ligatures, multiple Unicode characters map to a single glyph. (Note that for proper rendering of some languages, ligatures are required for certain character combinations.)
Composite characters - In various situations, commonly used adornments such as diacritical marks will be stored once in a font as a particular glyph and then composed with one or more other glyphs to result in the desired character. For example, it is possible that a font engine might render the é character by first rendering the glyph for e and then rendering the glyph for ´ (the accent mark) such that the accent mark will appear over the e. In this situation, a single Unicode character maps to multiple glyphs.
Glyph substitution - Some typography systems examine the nature of the textual content and utilize different glyphs in different circumstances. For example, in Arabic, the same Unicode character might render as any of four different glyphs, depending on such factors as whether the character appears at the start, the end or the middle of a sequence of cursively joined characters. Different glyphs might be used for a punctuation character depending on inline-progression-direction (e.g., horizontal vs. vertical). In these situations, a single Unicode character might map to one of several alternative glyphs.
In some languages, particular sequences of characters will be converted into multiple glyphs such that parts of a particular character are in one glyph and the remainder of that character is in another glyph.
Alternative glyph specification - SVG contains a facility for the author to explicitly specify that a particular sequence of Unicode characters is to be rendered using a particular glyph. (See Alternate glyphs.) When this facility is used, multiple Unicode characters map to a single glyph.

In many situations, the algorithms for mapping from characters to glyphs are system-dependent, resulting in the possibility that the rendering of text might be (usually slightly) different when viewed in different user environments. If the author of SVG content requires precise selection of fonts and glyphs, then the recommendation is that the necessary fonts (potentially subsetted to include only the glyphs needed for the given document) be available either as SVG fonts embedded within the SVG content or as downloadable fonts ([CSS3FONTS], section 1) posted at the same Web location as the SVG content.

Throughout this chapter, the term character shall be equivalent to the definition of a character in XML [XML10].

10.3. Fonts, font tables and baselines

SVG 2 Requirement:	Support text aligned to different baselines.
Resolution:	SVG 2 will support glyphs being aligned to different baselines, perhaps by using existing or improved CSS properties.
Purpose:	To allow glyphs in horizontal text to have different vertical alignments for stylistic effects.
Owner:	Chris (no action)

A font consists of a collection of glyphs together with the information (the font tables) necessary to use those glyphs to present characters on some medium. The combination of the collection of glyphs and the font tables is called the font data. The font tables include the information necessary to map characters to glyphs, to determine the size of glyph areas and to position the glyph area. Each font table consists of one or more font characteristics, such as the font-weight and font-style.

The geometric font characteristics are expressed in a coordinate system based on the EM box. (The EM is a relative measure of the height of the glyphs in the font.) The box 1 EM high and 1 EM wide is called the design space. This space is given a geometric coordinates by sub-dividing the EM into a number of units per em.

Note: Units per em is a font characteristic. A typical value for units per em is 1000 or 2048.

The coordinate space of the EM box is called the design space coordinate system. For scalable fonts, the curves and lines that are used to draw a glyph are represented using this coordinate system.

Note: Most often, the (0,0) point in this coordinate system is positioned on the left edge of the EM box, but not at the bottom left corner. The Y coordinate of the bottom of a roman capital letter is usually zero. And the descenders on lowercase roman letters have negative coordinate values.

SVG assumes that the font tables will provide at least three font characteristics: an ascent, a descent and a set of baseline-tables. The ascent is the distance to the top of the EM box from the (0,0) point of the font; the descent is the distance to the bottom of the EM box from the (0.0) point of the font. The baseline-table is explained below.

Note: Within an OpenType font, for horizontal writing-modes, the ascent and descent are given by the sTypoAscender and sTypoDescender entries in the OS/2 table. For vertical writing-modes, the descent (the distance, in this case from the (0,0) point to the left edge of the glyph) is normally zero because the (0,0) point is on the left edge. The ascent for vertical writing-modes is either 1 em or is specified by the ideographic top baseline value in the OpenType Base table for vertical writing-modes.

In horizontal writing-modes, the glyphs of a given script are positioned so that a particular point on each glyph, the alignment-point, is aligned with the alignment-points of the other glyphs in that script. The glyphs of different scripts, for example, Western, Northern Indic and Far-Eastern scripts, are typically aligned at different points on the glyph. For example, Western glyphs are aligned on the bottoms of the capital letters, northern indic glyphs are aligned at the top of a horizontal stroke near the top of the glyphs and far-eastern glyphs are aligned either at the bottom or center of the glyph. Within a script and within a line of text having a single font-size, the sequence of alignment-points defines, in the inline- progression-direction, a geometric line called a baseline. Western and most other alphabetic and syllabic glyphs are aligned to an "alphabetic" baseline, the northern indic glyphs are aligned to a "hanging" baseline and the far-eastern glyphs are aligned to an "ideographic" baseline.

A baseline-table specifies the position of one or more baselines in the design space coordinate system. The function of the baseline table is to facilitate the alignment of different scripts with respect to each other when they are mixed on the same text line. Because the desired relative alignments may depend on which script is dominant in a line (or block), there may be a different baseline table for each script. In addition, different alignment positions are needed for horizontal and vertical writing modes. Therefore, the font may have a set of baseline tables: typically, one or more for horizontal writing-modes and zero or more for vertical writing-modes.

Note: Some fonts may not have values for the baseline tables. Heuristics are suggested for approximating the baseline tables when a given font does not supply baseline tables.

SVG further assumes that for each glyph in the font data for a font, there are two width values, two alignment-baselines and two alignment-points, one each for horizontal writing-modes and the other for vertical writing-modes. (Even though it is specified as a width, for vertical writing-modes the width is used in the vertical direction.) The script to which a glyph belongs determines an alignment-baseline to which the glyph is to be aligned. The inline-progression-direction position of the alignment-point is on the start-edge of the glyph.

Properties related to baselines are described below under Baseline alignment properties.

In addition to the font characteristics required above, a font may also supply substitution and positioning tables that can be used by a formatter to re-order, combine and position a sequence of glyphs to make one or more composite glyphs. The combination may be as simple as a ligature, or as complex as an indic syllable which combines, usually with some re-ordering, multiple consonants and vowel glyphs.

10.4. The ‘text’ element

SVG 2 Requirement:	Have a DOM method to convert a ‘text’ element to outline path data.
Resolution:	We will add a DOM method to convert a ‘text’ element to outline path data, possibly moving the functionality to the FXTF.
Purpose:	To allow manipualtion of text as a path.
Owner:	Cameron (ACTION-3076)

The ‘text’ element defines a graphics element consisting of text. The XML character data within the ‘text’ element, along with relevant attributes and properties and character-to-glyph mapping tables within the font itself, define the glyphs to be rendered. (See Characters and their corresponding glyphs.) The attributes and properties on the ‘text’ element indicate such things as the writing direction, font specification and painting attributes which describe how exactly to render the characters. Subsequent sections of this chapter describe the relevant text-specific attributes and properties, particular text layout and bidirectionality.

Since ‘text’ elements are rendered using the same rendering methods as other graphics elements, all of the same coordinate system transformations, painting, clipping and masking features that apply to shapes such as paths and rectangles also apply to ‘text’ elements.

It is possible to apply a gradient, pattern, clipping path, mask or filter to text. When one of these facilities is applied to text and keyword 'objectBoundingBox' is used (see Object bounding box units) to specify a graphical effect relative to the "object bounding box", then the object bounding box units are computed relative to the entire ‘text’ element in all cases, even when different effects are applied to different ‘tspan’ elements within the same ‘text’ element.

The ‘text’ element renders its first glyph (after bidirectionality reordering) at the initial current text position, which is established by the ‘x’ and ‘y’ attributes on the ‘text’ element (with possible adjustments due to the value of the ‘text-anchor’ property, the presence of a ‘textPath’ element containing the first character, and/or an ‘x’, ‘y’, ‘dx’ or ‘dy’ attributes on a ‘tspan’, ‘tref’ or ‘altGlyph’ element which contains the first character). After the glyph(s) corresponding to the given character is(are) rendered, the current text position is updated for the next character. In the simplest case, the new current text position is the previous current text position plus the glyphs' advance value (horizontal or vertical). See text layout for a description of glyph placement and glyph advance.

‘text’

Categories:

Graphics element, text content element

Content model:

Any number of the following elements or character data, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
text content child elements — ‘tspan’, ‘tref’, ‘textPath’, ‘altGlyph’

a, clipPath, marker, mask

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
‘lengthAdjust’
‘x’
‘y’
‘dx’
‘dy’
‘rotate’
‘textLength’
‘width’

DOM Interfaces:

SVGTextElement

Attribute definitions:

x = "<list-of-coordinates>": If a single <length> is provided, then the value represents the new absolute X coordinate for the current text position for rendering the glyphs that correspond to the first character within this element or any of its descendants.
If a comma- or space-separated list of n <length>s is provided, then the values represent new absolute X coordinates for the current text position for rendering the glyphs corresponding to each of the first n characters within this element or any of its descendants.
For additional processing rules, refer to the description of the ‘x’ attribute on the ‘tspan’ element.
If the attribute is not specified, the effect is as if a value of "0" were specified.
Animatable: yes.
y = "<list-of-coordinates>": The corresponding list of absolute Y coordinates for the glyphs corresponding to the characters within this element. The processing rules for the ‘y’ attribute parallel the processing rules for the ‘x’ attribute.
If the attribute is not specified, the effect is as if a value of "0" were specified.
Animatable: yes.
dx = "<list-of-lengths>": Shifts in the current text position along the x-axis for the characters within this element or any of its descendants.
Refer to the description of the ‘dx’ attribute on the ‘tspan’ element.
If the attribute is not specified on this element or any of its descendants, no supplemental shifts along the x-axis will occur.
Animatable: yes.
dy = "<list-of-lengths>": Shifts in the current text position along the y-axis for the characters within this element or any of its descendants.
Refer to the description of the ‘dy’ attribute on the ‘tspan’ element.
If the attribute is not specified on this element or any of its descendants, no supplemental shifts along the y-axis will occur.
Animatable: yes.
rotate = "<list-of-numbers>": The supplemental rotation about the current text position that will be applied to all of the glyphs corresponding to each character within this element.
Refer to the description of the ‘rotate’ attribute on the ‘tspan’ element.
If the attribute is not specified on this element or any of its descendants, no supplemental rotations will occur.
Animatable: yes (non-additive).
textLength = "<length>": The author's computation of the total sum of all of the advance values that correspond to character data within this element, including the advance value on the glyph (horizontal or vertical), the effect of properties ‘letter-spacing’ and ‘word-spacing’ and adjustments due to attributes ‘dx’ and ‘dy’ on ‘tspan’ elements. This value is used to calibrate the user agent's own calculations with that of the author.
The purpose of this attribute is to allow the author to achieve exact alignment, in visual rendering order after any bidirectional reordering, for the first and last rendered glyphs that correspond to this element; thus, for the last rendered character (in visual rendering order after any bidirectional reordering), any supplemental inter-character spacing beyond normal glyph advances are ignored (in most cases) when the user agent determines the appropriate amount to expand/compress the text string to fit within a length of ‘textLength’.
A negative value is an error (see Error processing).
If the attribute is not specified, the effect is as if the author's computation exactly matched the value calculated by the user agent; thus, no advance adjustments are made.
Animatable: yes.
lengthAdjust = "spacing|spacingAndGlyphs": Indicates the type of adjustments which the user agent shall make to make the rendered length of the text match the value specified on the ‘textLength’ attribute.
'spacing' indicates that only the advance values are adjusted. The glyphs themselves are not stretched or compressed.
'spacingAndGlyphs' indicates that the advance values are adjusted and the glyphs themselves stretched or compressed in one axis (i.e., a direction parallel to the inline-progression-direction).
The user agent is required to achieve correct start and end positions for the text strings, but the locations of intermediate glyphs are not predictable because user agents might employ advanced algorithms to stretch or compress text strings in order to balance correct start and end positioning with optimal typography.
Note that, for a text string that contains n characters, the adjustments to the advance values often occur only for n−1 characters (see description of attribute ‘textLength’), whereas stretching or compressing of the glyphs will be applied to all n characters.
If the attribute is not specified, the effect is as a value of 'spacing' were specified.
Animatable: yes.

width = "<length>": Indicates the maximum length that the text is allowed to have before being subject to ‘text-overflow’ handling. Whenever the sum of advances (including properties ‘letter-spacing’ and ‘word-spacing’ and adjustments due to attributes ‘dx’ and ‘dy’ on ‘tspan’ elements) computed by the user agent exceeds the given width the ‘text’ element is subject to ‘text-overflow’ processing.
The given width does not affect SVG DOM methods for measuring text, but does affect the boundingbox of the element.

The lacuna value for ‘width’ is as if the attribute wasn't specified.
Animatable: yes.

Example text01 below contains the text string "Hello, out there" which will be rendered onto the canvas using the Verdana font family with the glyphs filled with the color blue.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 1000 300"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example text01 - 'Hello, out there' in blue</desc>

  <text x="250" y="150" 
        font-family="Verdana" font-size="55" fill="blue" >
    Hello, out there
  </text>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example test01

View this example as SVG (SVG-enabled browsers only)

10.5. The ‘tspan’ element

SVG 2 Requirement:	Allow transforms on ‘tspan’.
Resolution:	SVG 2 will allow transforms on ‘tspan’.
Purpose:	Align with other elements such as ‘a’ which already allow transforms.
Owner:	Cameron (no action)

Within a ‘text’ element, text and font properties and the current text position can be adjusted with absolute or relative coordinate values by including a ‘tspan’ element.

‘tspan’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements or character data, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

a, altGlyph, animate, animateColor, set, tref, tspan

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
‘x’
‘y’
‘dx’
‘dy’
‘rotate’
‘textLength’
‘lengthAdjust’

DOM Interfaces:

SVGTSpanElement

Attribute definitions:

x = "<list-of-coordinates>": If a single <length> is provided, then the value represents the new absolute X coordinate for the current text position for rendering the glyphs that correspond to the first character within this element or any of its descendants.
If a comma- or space-separated list of n <length>s is provided, then the values represent new absolute X coordinates for the current text position for rendering the glyphs corresponding to each of the first n characters within this element or any of its descendants.
If more <length>s are provided than characters, then the extra <length>s will have no effect on glyph positioning.
If more characters exist than <length>s, then for each of these extra characters: (a) if an ancestor ‘text’ or ‘tspan’ element specifies an absolute X coordinate for the given character via an ‘x’ attribute, then that absolute X coordinate is used as the starting X coordinate for that character (nearest ancestor has precedence), else (b) the starting X coordinate for rendering the glyphs corresponding to the given character is the X coordinate of the resulting current text position from the most recently rendered glyph for the current ‘text’ element.
If the attribute is not specified: (a) if an ancestor ‘text’ or ‘tspan’ element specifies an absolute X coordinate for a given character via an ‘x’ attribute, then that absolute X coordinate is used (nearest ancestor has precedence), else (b) the starting X coordinate for rendering the glyphs corresponding to a given character is the X coordinate of the resulting current text position from the most recently rendered glyph for the current ‘text’ element.
Animatable: yes.
y = "<list-of-coordinates>": The corresponding list of absolute Y coordinates for the glyphs corresponding to the characters within this element. The processing rules for the ‘y’ attribute parallel the processing rules for the ‘x’ attribute.
Animatable: yes.
dx = "<list-of-lengths>": If a single <length> is provided, this value represents the new relative X coordinate for the current text position for rendering the glyphs corresponding to the first character within this element or any of its descendants. The current text position is shifted along the x-axis of the current user coordinate system by <length> before the first character's glyphs are rendered.
If a comma- or space-separated list of n <length>s is provided, then the values represent incremental shifts along the x-axis for the current text position before rendering the glyphs corresponding to the first n characters within this element or any of its descendants. Thus, before the glyphs are rendered corresponding to each character, the current text position resulting from drawing the glyphs for the previous character within the current ‘text’ element is shifted along the X axis of the current user coordinate system by <length>.
If more <length>s are provided than characters, then any extra <length>s will have no effect on glyph positioning.
If more characters exist than <length>s, then for each of these extra characters: (a) if an ancestor ‘text’ or ‘tspan’ element specifies a relative X coordinate for the given character via a ‘dx’ attribute, then the current text position is shifted along the x-axis of the current user coordinate system by that amount (nearest ancestor has precedence), else (b) no extra shift along the x-axis occurs.
If the attribute is not specified: (a) if an ancestor ‘text’ or ‘tspan’ element specifies a relative X coordinate for a given character via a ‘dx’ attribute, then the current text position is shifted along the x-axis of the current user coordinate system by that amount (nearest ancestor has precedence), else (b) no extra shift along the x-axis occurs.
Animatable: yes.
dy = "<list-of-lengths>": The corresponding list of relative Y coordinates for the characters within the ‘tspan’ element. The processing rules for the ‘dy’ attribute parallel the processing rules for the ‘dx’ attribute.
Animatable: yes.
rotate = "<list-of-numbers>": The supplemental rotation about the current text position that will be applied to all of the glyphs corresponding to each character within this element.
If a comma- or space-separated list of <number>s is provided, then the first <number> represents the supplemental rotation for the glyphs corresponding to the first character within this element or any of its descendants, the second <number> represents the supplemental rotation for the glyphs that correspond to the second character, and so on.
If more <number>s are provided than there are characters, then the extra <number>s will be ignored.
If more characters are provided than <number>s, then for each of these extra characters the rotation value specified by the last number must be used.
If the attribute is not specified and if an ancestor ‘text’ or ‘tspan’ element specifies a supplemental rotation for a given character via a ‘rotate’ attribute, then the given supplemental rotation is applied to the given character (nearest ancestor has precedence). If there are more characters than <number>s specified in the ancestor's ‘rotate’ attribute, then for each of these extra characters the rotation value specified by the last number must be used.
This supplemental rotation has no impact on the rules by which current text position is modified as glyphs get rendered and is supplemental to any rotation due to text on a path and to ‘glyph-orientation-horizontal’ or ‘glyph-orientation-vertical’.
Animatable: yes (non-additive).
textLength = "<length>": The author's computation of the total sum of all of the advance values that correspond to character data within this element, including the advance value on the glyph (horizontal or vertical), the effect of properties ‘letter-spacing’ and ‘word-spacing’ and adjustments due to attributes ‘dx’ and ‘dy’ on this ‘tspan’ element or any descendants. This value is used to calibrate the user agent's own calculations with that of the author.
The purpose of this attribute is to allow the author to achieve exact alignment, in visual rendering order after any bidirectional reordering, for the first and last rendered glyphs that correspond to this element; thus, for the last rendered character (in visual rendering order after any bidirectional reordering), any supplemental inter-character spacing beyond normal glyph advances are ignored (in most cases) when the user agent determines the appropriate amount to expand/compress the text string to fit within a length of ‘textLength’.
If attribute ‘textLength’ is specified on a given element and also specified on an ancestor, the adjustments on all character data within this element are controlled by the value of ‘textLength’ on this element exclusively, with the possible side-effect that the adjustment ratio for the contents of this element might be different than the adjustment ratio used for other content that shares the same ancestor. The user agent must assume that the total advance values for the other content within that ancestor is the difference between the advance value on that ancestor and the advance value for this element.
A negative value is an error (see Error processing).
If the attribute is not specified anywhere within a ‘text’ element, the effect is as if the author's computation exactly matched the value calculated by the user agent; thus, no advance adjustments are made.
Animatable: yes.

The ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ on the ‘tspan’ element are useful in high-end typography scenarios where individual glyphs require exact placement. These attributes are useful for minor positioning adjustments between characters or for major positioning adjustments, such as moving the current text position to a new location to achieve the visual effect of a new line of text. Multi-line ‘text’ elements are possible by defining different ‘tspan’ elements for each line of text, with attributes ‘x’, ‘y’, ‘dx’ and/or ‘dy’ defining the position of each ‘tspan’. (An advantage of such an approach is that users will be able to perform multi-line text selection.)

In situations where micro-level positioning adjustment are necessary for advanced typographic control, the SVG content designer needs to ensure that the necessary font will be available for all viewers of the document (e.g., package up the necessary font data in the form of an SVG font or an alternative WebFont format which is stored at the same Web site as the SVG content) and that the viewing software will process the font in the expected way (the capabilities, characteristics and font layout mechanisms vary greatly from system to system). If the SVG content contains ‘x’, ‘y’, ‘dx’ or ‘dy’ attribute values which are meant to correspond to a particular font processed by a particular set of viewing software and either of these requirements is not met, then the text might display with poor quality.

The following additional rules apply to attributes ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ when they contain a list of numbers:

When a single XML character maps to a single glyph - In this case, the i-th value for the ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ attributes is applied to the glyph that corresponds to the i-th character.
When a single XML character maps to multiple glyphs (e.g., when an accent glyph is placed on top of a base glyph) - In this case, the i-th value for the ‘x’, ‘y’, ‘dx’ and ‘dy’ values are applied (i.e., the current text position is adjusted) before rendering the first glyph. The rotation transformation corresponding to the i-th ‘rotate’ value is applied to the glyphs and to the inter-glyph advance values corresponding to this character on a group basis (i.e., the rotation value creates a temporary new rotated coordinate system, and the glyphs orresponding to the character are rendered into this rotated coordinate system).
When multiple XML characters map to a single glyph (e.g., when a ligature is used) - Suppose that the i-th and (i+1)-th XML characters map to a single glyph. In this case, the i-th value for the ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ attributes all apply when rendering the glyph. The (i+1)-th values, however, for ‘x’, ‘y’ and ‘rotate’ are ignored (exception: the final ‘rotate’ value in the list would still apply to subsequent characters), whereas the ‘dx’ and ‘dy’ are applied to the subsequent XML character (i.e., the (i+2)-th character), if one exists, by translating the current text position by the given amounts before rendering the first glyph associated with that character.
When there is a many-to-many mapping of characters to glyphs (e.g., when three characters map to two glyphs, such as when the first glyph expresses the first character and half of the second character, and the second glyph expresses the other half of the second character plus the third character) - Suppose that the i-th, (i+1)-th and (i+2)-th XML characters map to two glyphs. In this case, the i-th value for the ‘x’, ‘y’, ‘dx’ and ‘dy’ values are applied (i.e., the current text position is adjusted) before rendering the first glyph. The rotation transformation corresponding to the i-th ‘rotate’ value is applied to both the two glyphs and the glyph advance values for the first glyph on a group basis (i.e., the rotation value creates a temporary new rotated coordinate system, and the two glyphs are rendered into the temporary rotated coordinate system). The (i+1)-th and (i+2)-th values, however, for the ‘x’, ‘y’ and ‘rotate’ attributes are not applied (exception: the final ‘rotate’ value in the list would still apply to subsequent characters), whereas the (i+1)-th and (i+2)-th values for the ‘dx’ and ‘dy’ attributes are applied to the subsequent XML character (i.e., the (i+3)-th character), if one exists, by translating the current text position by the given amounts before rendering the first glyph associated with that character.
Relationship to bidirectionality - As described below in the discussion on bidirectionality, text is laid out in a two-step process, where any bidirectional text is first re-ordered into a left-to-right string, and then text layout occurs with the re-ordered text string. Whenever the character data within a ‘tspan’ element is re-ordered, the corresponding elements within the ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ are also re-ordered to maintain the correspondence. For example, suppose that you have the following ‘tspan’ element:
```
<tspan dx="11 12 13 14 15 0 21 22 23 0 31 32 33 34 35 36">Latin and Hebrew</tspan>
```
and that the word "Hebrew" will be drawn right-to-left. First, the character data and the corresponding values in the ‘dx’ list will be reordered, such that the text string will be "Latin and werbeH" and the list of values for the ‘dx’ attribute will be "11 12 13 14 15 0 21 22 23 0 36 35 34 33 32 31". After this re-ordering, the glyphs corresponding to the characters will be positioned using standard left-to-right layout rules.

The following examples show basic use of the ‘tspan’ element.

Example tspan01 uses a ‘tspan’ element to indicate that the word "not" is to use a bold font and have red fill.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 1000 300"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example tspan01 - using tspan to change visual attributes</desc>

  <g font-family="Verdana" font-size="45" >
    <text x="200" y="150" fill="blue" >
      You are
        <tspan font-weight="bold" fill="red" >not</tspan>
      a banana.
    </text>
  </g>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example tspan01

Example tspan02 uses the ‘dx’ and ‘dy’ attributes on the ‘tspan’ element to adjust the current text position horizontally and vertically for particular text strings within a ‘text’ element.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 1000 300"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example tspan02 - using tspan's dx and dy attributes 
        for incremental positioning adjustments</desc>

  <g font-family="Verdana" font-size="45" >
    <text x="200" y="150" fill="blue" >
      But you
        <tspan dx="2em" dy="-50" font-weight="bold" fill="red" >
          are
        </tspan>
        <tspan dy="100">
           a peach!
        </tspan>
    </text>
  </g>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example tspan02

View this example as SVG (SVG-enabled browsers only)

Example tspan03 uses the ‘x’ and ‘y’ attributes on the ‘tspan’ element to establish a new absolute current text position for each glyph to be rendered. The example shows two lines of text within a single ‘text’ element. Because both lines of text are within the same ‘text’ element, the user will be able to select through both lines of text and copy the text to the system clipboard in user agents that support text selection and clipboard operations.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 1000 300"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example tspan03 - using tspan's x and y attributes 
        for multiline text and precise glyph positioning</desc>

  <g font-family="Verdana" font-size="45" >
    <text fill="rgb(255,164,0)" >
      <tspan x="300 350 400 450 500 550 600 650" y="100">
        Cute and
      </tspan>
      <tspan x="375 425 475 525 575" y="200">
         fuzzy
      </tspan>
    </text>
  </g>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example tspan03

View this example as SVG (SVG-enabled browsers only)

Example tspan04 uses the ‘rotate’ attribute on the ‘tspan’ element to rotate the glyphs to be rendered. This example shows a single text string in a ‘tspan’ element that contains more characters than the number of values specified in the ‘rotate’ attribute. In this case the last value specified in the ‘rotate’ attribute of the ‘tspan’ must be applied to the remaining characters in the string.

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 1000 300"
  xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>
    Example tspan04 - The number of rotate values is less than the number of
    characters in the string.
  </desc>
  <text font-family="Verdana" font-size="55" fill="blue" >
    <tspan x="250" y="150" rotate="-30,0,30">
      Hello, out there
    </tspan>
  </text>
  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
  fill="none" stroke="blue" stroke-width="2" />
</svg>

Example tspan04

View this example as SVG (SVG-enabled browsers only)

Example tspan05 specifies the ‘rotate’ attribute on the ‘text’ element and on all but one of the child ‘tspan’ elements to rotate the glyphs to be rendered. The example demonstrates the propagation of the ‘rotate’ attribute.

<?xml version="1.0" standalone="no"?>
<svg width="100%" height="100%" viewBox="0 0 500 120"
  xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>
    Example tspan05 - propagation of rotation values to nested tspan elements.
  </desc>
  <text id="parent" font-family="Arial, sans-serif" font-size="32" fill="red" x="40" y="40"
    rotate="5,15,25,35,45,55">
    Not

    <tspan id="child1" rotate="-10,-20,-30,-40" fill="orange">
      all characters

      <tspan id="child2" rotate="70,60,50,40,30,20,10" fill="yellow">
        in
        
        <tspan id="child3">
          the
        </tspan>
      </tspan>

      <tspan id="child4" fill="orange" x="40" y="90">
        text
      </tspan>

      have a
    </tspan>

    <tspan id="child5" rotate="-10" fill="blue">
      specified
    </tspan>

    rotation
  </text>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="498" height="118" fill="none"
        stroke="blue" stroke-width="2" />
</svg>

Example tspan05

View this example as SVG (SVG-enabled browsers only)

Rotation of red text inside the ‘text’ element:

The ‘rotate’ value will rotate the characters in the text "Not " by 5, 15, 25 and 35 degrees respectively.
A ‘rotate’ value is applied to the space that follows the text "Not", to the space in between the text in the "child1" and "child5" ‘tspan’ elements, and to the space before the text "rotation".
The next current ‘rotate’ value specified is 45 followed by 55. The current ‘rotate’ value in the ‘text’ element is incremented as subsequent characters in the text of the child ‘tspan’ elements are processed.
The next immediate ‘tspan’ element specifies rotate values for the text, hence the current ‘rotate’ value will change to the next value in the list (but is not used) as each character is processed until the last value of 55 degrees is reached.
The last ‘rotate’ value of 55 degrees will be applied to all the characters in the text "rotation".

Rotation of the orange text inside the "child1" ‘tspan’element:

The ‘rotate’ value will rotate the first 4 characters in the text "all characters " by -10, -20, -30 and -40 respectively.
The last ‘rotate’ value of -40 becomes the current ‘rotate’ value and will be applied to all subsequent characters in the ‘tspan’ element and to any child ‘tspan’ elements that do not specify ‘rotate’ values.
The "child4" ‘tspan’ element does not specify any ‘rotate’ values and thus uses the current ‘rotate’ of its ancestor ("child1" ‘tspan’ element). All the characters in the text "text" specified within the "child4" ‘tspan’ element will be rotated by -40 degrees.
The last ‘rotate’ value of -40 degrees will be applied to all the characters in the text "have a".
A ‘rotate’ value is applied to the space in between the text in the "child2" and "child4" ‘tspan’ elements, and to the space before the text "have a".

Rotation of the yellow text inside the "child2" ‘tspan’element:

The ‘rotate’ value will rotate the characters in the (yellow) text "in " by 70, 60, and 50 degrees respectively.
A ‘rotate’ value is applied to the space that follows the text "in".
There are more ‘rotate’ values specified than characters, thus the additional ‘rotate’ values will be applied to the "child3" ‘tspan’ element which does not specified any ‘rotate’ values.
The characters in the text "the" specified within the "child3" ‘tspan’ element will be rotated 40, 30 and 20 degrees respectively.

Rotation of the blue text inside the "child5" ‘tspan’ element:

The ‘rotate’ value will rotate all the characters in text "specified" by -10 degrees.
Only one ‘rotate’ value is specified and is thus applied to all characters in the ‘tspan’ element.

The following diagram illustrates how the rotation values propagate to ‘tspan’ elements nested withing a ‘text’ element:

Image that shows propagation of rotation values

10.6. The ‘tref’ element

SVG 2 Requirement:	Allow ‘tref’ to point to non-SVG elements.
Resolution:	We agree to remove the restriction of ‘tref’ pointing to only an SVG document fragment.
Purpose:	To allow easier text substitution.
Owner:	Cameron (ACTION-3130)

The textual content for a ‘text’ can be either character data directly embedded within the ‘text’ element or the character data content of a referenced element, where the referencing is specified with a ‘tref’ element.

‘tref’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

animate, animateColor, set

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘x’
‘y’
‘dx’
‘dy’
‘rotate’
‘textLength’
‘lengthAdjust’
‘xlink:href’

DOM Interfaces:

SVGTRefElement

Attribute definitions:

xlink:href = "<iri>": An IRI reference to an element whose character data content shall be used as character data for this ‘tref’ element.
Animatable: yes.

All character data within the referenced element, including character data enclosed within additional markup, will be rendered.

The ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ attributes have the same meanings as for the ‘tspan’ element. The attributes are applied as if the ‘tref’ element was replaced by a ‘tspan’ with the referenced character data (stripped of all supplemental markup) embedded within the hypothetical ‘tspan’ element.

Example tref01 shows how to use character data from a different element as the character data for a given ‘tspan’ element. The first ‘text’ element (with id="ReferencedText") will not draw because it is part of a ‘defs’ element. The second ‘text’ element draws the string "Inline character data". The third ‘text’ element draws the string "Reference character data" because it includes a ‘tref’ element which is a reference to element "ReferencedText", and that element's character data is "Referenced character data".

<?xml version="1.0" standalone="no"?>
<svg width="10cm" height="3cm" viewBox="0 0 1000 300" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <text id="ReferencedText">
      Referenced character data
    </text>
  </defs>
  <desc>Example tref01 - inline vs reference text content</desc>

  <text x="100" y="100" font-size="45" fill="blue" >
    Inline character data
  </text>
  <text x="100" y="200" font-size="45" fill="red" >
    <tref xlink:href="#ReferencedText"/>
  </text>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example tref01

10.7. Text layout

SVG 2 Requirement:	Include text layout improvements from SVG Tiny 1.2.
Resolution:	SVG 2 will include the improved text from SVG Tiny 1.2 on characters and glyphs, text layout, text selection, text search.
Purpose:	To include clearer descriptions of text layout; no functional change.
Owner:	Chris (ACTION-3236)

SVG 2 Requirement:	Align with CSS for text layout functionality.
Resolution:	SVG 2 Will use CSS3 definitions for text layout (white space, bidi, etc.) that is not specific to SVG.
Purpose:	To facilitate shared specification and implementation of text layout in HTML and SVG.
Owner:	Cameron and Chris (ACTION-3004, ACTION-3005)

This section describes the text layout features supported by SVG, which includes support for various international writing directions, such as left-to-right (e.g., Latin scripts) and bidirectional (e.g., Hebrew or Arabic) and vertical (e.g., Asian scripts). The descriptions in this section assume straight line text (i.e., text that is either strictly horizontal or vertical with respect to the current user coordinate system). Subsequent sections describe the supplemental layout rules for text on a path.

SVG does not provide for automatic line breaks or word wrapping, which makes internationalized text layout for SVG relatively simpler than it is for languages which support formatting of multi-line text blocks.

For each ‘text’ element, the SVG user agent determines the current reference orientation. For standard horizontal or vertical text (i.e., no text-on-a-path), the reference orientation is the vector pointing towards negative infinity in Y within the current user coordinate system. (Note: in the initial coordinate system, the reference orientation is up.) For text on a path, the reference orientation is reset with each character.

Based on the reference orientation and the value for property ‘writing-mode’, the SVG user agent determines the current inline-progression-direction. For left-to-right text, the inline-progression-direction points 90 degrees clockwise from the reference orientation vector. For right-to-left text, the inline progression points 90 degrees counter-clockwise from the reference orientation vector. For top-to-bottom text, the inline-progression-direction points 180 degrees from the reference orientation vector.

Based on the reference orientation and the value for property ‘writing-mode’, the SVG user agent determines the current block-progression-direction. For left-to-right and right-to-left text, the block-progression-direction points 180 degrees from the reference orientation vector because the only available horizontal ‘writing-mode’s are lr-tb and rl-tb. For top-to-bottom text, the block-progression-direction always points 90 degrees counter-clockwise from the reference orientation vector because the only available top-to-bottom ‘writing-mode’ is tb-rl.

The shift direction is the direction towards which the baseline table moves due to positive values for property ‘baseline-shift’. The shift direction is such that a positive value shifts the baseline table towards the topmost entry in the parent's baseline table.

In processing a given ‘text’ element, the SVG user agent keeps track of the current text position. The initial current text position is established by the ‘x’ and ‘y’ attributes on the ‘text’ element.

The current text position is adjusted after each glyph to establish a new current text position at which the next glyph shall be rendered. The adjustment to the current text position is based on the current inline-progression-direction, glyph-specific advance values corresponding to the glyph orientation of the glyph just rendered, kerning tables in the font and the current values of various attributes and properties, such as the spacing properties and any ‘x’, ‘y’, ‘dx’ and ‘dy’ attributes on ‘text’, ‘tspan’, ‘tref’ or ‘altGlyph’ elements. If a glyph does not provide explicit advance values corresponding to the current glyph orientation, then an appropriate approximation should be used. For vertical text, a suggested approximation is the sum of the ascent and descent values for the glyph. Another suggested approximation for an advance value for both horizontal and vertical text is the size of an em (see units-per-em).

For each glyph to be rendered, the SVG user agent determines an appropriate alignment-point on the glyph which will be placed exactly at the current text position. The alignment-point is determined based on glyph cell metrics in the glyph itself, the current inline-progression-direction and the glyph orientation relative to the inline-progression-direction. For most uses of Latin text (i.e., writing-mode:lr, text-anchor:start and alignment-baseline:baseline) the alignment-point in the glyph will be the intersection of left edge of the glyph cell (or some other glyph-specific x-axis coordinate indicating a left-side origin point) with the Latin baseline of the glyph. For many cases with top-to-bottom vertical text layout, the reference point will be either a glyph-specific origin point based on the set of vertical baselines for the font or the intersection of the center of the glyph with its top line (see top baseline; in [CSS3LINEBOX], section 4.2). If a glyph does not provide explicit origin points corresponding to the current glyph orientation, then an appropriate approximation should be used, such as the intersection of the left edge of the glyph with the appropriate horizontal baseline for the glyph or intersection of the top edge of the glyph with the appropriate vertical baseline. If baseline tables are not available, user agents should establish baseline tables that reflect common practice.

Adjustments to the current text position are either absolute position adjustments or relative position adjustments. An absolute position adjustment occurs in the following circumstances:

At the start of a ‘text’ element
At the start of each ‘textPath’ element
For each character within a ‘text’, ‘tspan’, ‘tref’ and ‘altGlyph’ element which has an ‘x’ or ‘y’ attribute value assigned to it explicitly

All other position adjustments to the current text position are relative position adjustments.

Each absolute position adjustment defines a new text chunk. Absolute position adjustments impact text layout in the following ways:

Ligatures only occur when a set of characters which might map to a ligature are all in the same text chunk.
Each text chunk represents a separate block of text for alignment due to ‘text-anchor’ property values.
Reordering of characters due to bidirectionality only occurs within a text chunk. Reordering does not happen across text chunks.

The following additional rules apply to ligature formation:

As defined in CSS 2.1, ([CSS21], section 16.4), when the resultant space between two characters is not the same as the default space, user agents should not use ligatures; thus, if there is a non-default value for ‘letter-spacing’, the user agent should not use ligatures.
Ligature formation should not be enabled for the glyphs corresponding to characters within different DOM text nodes; thus, characters separated by markup should not use ligatures.
As mentioned above, ligature formation should not be enabled for the glyphs corresponding to characters within different text chunks.

10.7.1. Setting the inline-progression-direction

The ‘writing-mode’ property specifies whether the initial inline-progression-direction for a ‘text’ element shall be left-to-right, right-to-left, or top-to-bottom. The ‘writing-mode’ property applies only to ‘text’ elements; the property is ignored for ‘tspan’, ‘tref’, ‘altGlyph’ and ‘textPath’ sub-elements. (Note that the inline-progression-direction can change within a ‘text’ element due to the Unicode bidirectional algorithm and properties ‘direction’ and ‘unicode-bidi’. For more on bidirectional text, see Relationship with bidirectionality.)

‘writing-mode’

Value:	lr-tb \| rl-tb \| tb-rl \| lr \| rl \| tb
Initial:	lr-tb
Applies to:	‘text’ elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	no

lr-tb | lr: Sets the initial inline-progression-direction to left-to-right, as is common in most Latin-based documents. For most characters, the current text position is advanced from left to right after each glyph is rendered. (When the character data includes characters which are subject to the Unicode bidirectional algorithm, the text advance rules are more complex. See Relationship with bidirectionality).
rl-tb | rl: Sets the initial inline-progression-direction to right-to-left, as is common in Arabic or Hebrew scripts. (See Relationship with bidirectionality.)
tb-rl | tb: Sets the initial inline-progression-direction to top-to-bottom, as is common in some Asian scripts, such as Chinese and Japanese. Though hardly as frequent as horizontal, this type of vertical layout also occurs in Latin based documents, particularly in table column or row labels. In most cases, the vertical baselines running through the middle of each glyph are aligned.

10.7.2. Glyph orientation within a text run

In some cases, it is required to alter the orientation of a sequence of characters relative to the inline-progression-direction. The requirement is particularly applicable to vertical layouts of East Asian documents, where sometimes narrow-cell Latin text is to be displayed horizontally and other times vertically.

Two properties control the glyph orientation relative to the reference orientation for each of the two possible inline-progression-directions. ‘glyph-orientation-vertical’ controls glyph orientation when the inline-progression-direction is vertical. ‘glyph-orientation-horizontal’ controls glyph orientation when the inline-progression-direction is horizontal.

‘glyph-orientation-vertical’

Value:	auto \| <angle> \| <number>
Initial:	auto
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	no

auto

Fullwidth ideographic and fullwidth Latin text will be set with a glyph-orientation of 0-degrees.

Ideographic punctuation and other ideographic characters having alternate horizontal and vertical forms will use the vertical form of the glyph.
Text which is not fullwidth will be set with a glyph-orientation of 90-degrees.

This reorientation rule applies only to the first-level non-ideographic text. All further embedding of writing-modes or bidi processing will be based on the first-level rotation.
NOTE:
- This is equivalent to having set the non-ideographic text string horizontally honoring the bidi-rule, then rotating the resultant sequence of inline-areas (one area for each change of glyph direction) 90-degrees clockwise.
  
  It should be noted that text set in this "rotated" manner may contain ligatures or other glyph combining and reordering common to the language and script. (This "rotated" presentation form does not disable auto-ligature formation or similar context-driven variations.)
- The determination of which characters should be auto-rotated may vary across user agents. The determination is based on a complex interaction between country, language, script, character properties, font, and character context. It is suggested that one consult the Unicode TR 11 and the various JIS or other national standards.

<angle>

<number>

The glyph orientation angle. A value specified as a <number> is interpreted as an angle in degrees. The value of the angle is restricted to 0, 90, 180, and 270 degrees. The user agent shall round the value of the angle to the closest of the permitted values.
A value of 0deg indicates that all glyphs are set with the top of the glyphs oriented towards the reference orientation. A value of 90deg indicates an orientation of 90 degrees clockwise from the reference orientation.

This property is applied only to text written in a vertical ‘writing-mode’.

The glyph orientation affects the amount that the current text position advances as each glyph is rendered. When the inline-progression-direction is vertical and the ‘glyph-orientation-vertical’ results in an orientation angle that is a multiple of 180 degrees, then the current text position is incremented according to the vertical metrics of the glyph. Otherwise, if the ‘glyph-orientation-vertical’ results in an orientation angle that is not a multiple of 180 degrees, then the current text position is incremented according to the horizontal metrics of the glyph.

The text layout diagrams in this section use the following symbols:

	wide-cell glyph (e.g. Han) which is the n-th glyph in the text run
	narrow-cell glyph (e.g. Latin) which is the n-th glyph in the text run

The orientation which the above symbols assume in the diagrams corresponds to the orientation that the Unicode characters they represent are intended to assume when rendered in the user agent. Spacing between the glyphs in the diagrams is usually symbolic, unless intentionally changed to make a point.

The diagrams below illustrate different uses of ‘glyph-orientation-vertical’. The diagram on the left shows the result of the mixing of full-width ideographic glyphs with narrow-cell Latin glyphs when ‘glyph-orientation-vertical’ for the Latin characters is either auto or 90. The diagram on the right show the result of mixing full-width ideographic glyphs with narrow-cell Latin glyphs when Latin glyphs are specified to have a ‘glyph-orientation-vertical’ of 0.

‘glyph-orientation-horizontal’

Value:	<angle> \| <number>
Initial:	0deg
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	no

<angle>
<number>: The glyph orientation angle. A value specified as a <number> is interpreted as an angle in degrees. The value of the angle is restricted to 0, 90, 180, and 270 degrees. The user agent shall round the value of the angle to the closest of the permitted values.
A value of 0deg indicates that all glyphs are set with the top of the glyphs oriented towards the reference orientation. A value of 90deg indicates an orientation of 90 degrees clockwise from the reference orientation.

This property is applied only to text written in a horizontal ‘writing-mode’.

The glyph orientation affects the amount that the current text position advances as each glyph is rendered. When the reference orientation direction is horizontal and the ‘glyph-orientation-horizontal’ results in an orientation angle that is a multiple of 180 degrees, then the current text position is incremented according to the horizontal metrics of the glyph. Otherwise, if the ‘glyph-orientation-horizontal’ results in an orientation angle that is not a multiple of 180 degrees, then the current text position is incremented according to the vertical metrics of the glyph.

10.7.3. Relationship with bidirectionality

The characters in certain scripts are written from right to left. In some documents, in particular those written with the Arabic or Hebrew script, and in some mixed-language contexts, text in a single line may appear with mixed directionality. This phenomenon is called bidirectionality, or "bidi" for short.

The Unicode standard ([UNICODE], specifically [UAX9]) defines a complex algorithm for determining the proper directionality of text. The algorithm consists of an implicit part based on character properties, as well as explicit controls for embeddings and overrides. The SVG user agent applies this bidirectional algorithm when determining the layout of characters within a text content block element.

The ‘direction’ and ‘unicode-bidi’ properties allow authors to override the inherent directionality of the content characters and thus explicitly control how the elements and attributes of a document language map to this algorithm. These two properties are applicable to all characters whose glyphs are perpendicular to the inline-progression-direction.

In many cases, the bidirectional algorithm from Unicode [UNICODE] produces the desired result automatically, and in such cases the author does not need to use these properties. For other cases, such as when using right-to-left languages, it may be sufficient to add the ‘direction’ property to the rootmost ‘svg’ element, and allow that direction to inherit to all text elements, as in the following example (which may be used as a template):

<svg xmlns="http://www.w3.org/2000/svg"
     width="100%" height="100%" viewBox="0 0 400 400"
     direction="rtl" xml:lang="fa">

  <title direction="ltr" xml:lang="en">Right-to-left Text</title>
  <desc direction="ltr" xml:lang="en">
    A simple example for using the 'direction' property in documents
    that predominantly use right-to-left languages.
  </desc>

  <text x="200" y="200" font-size="20">داستان SVG 1.1 SE طولا ني است.</text>

</svg>

Example

View this example as SVG (SVG-enabled browsers only)

Below is another example, where where implicit bidi reordering is not sufficient:

<?xml version="1.0" encoding="utf-8"?>
<svg xmlns="http://www.w3.org/2000/svg"
     width="100%" height="100%" viewBox="0 0 400 400"
     direction="rtl" xml:lang="he">

  <title direction="ltr" xml:lang="en">Right-to-left Text</title>
  <desc direction="ltr" xml:lang="en">
    An example for using the 'direction' and 'unicode-bidi' properties
    in documents that predominantly use right-to-left languages.
  </desc>

  <text x="200" y="200" font-size="20"> כתובת 
	MAC:&#x200F;
    	<tspan direction="ltr" unicode-bidi="embed">00-24-AF-2A-55-FC</tspan> 
	</text>

</svg>

Example

View this example as SVG (SVG-enabled browsers only)

Within text content elements, the alignment of text with regards to the ‘text-anchor’ property is determined by the value of the ‘direction’ property. For example, given a ‘text’ element with a ‘text-anchor’ value of "end", for a ‘direction’ value of "ltr", the text will extend to the left of the position of the ‘text’ element's ‘x’ attribute value, while for ‘direction’ value of "rtl", the text will extend to the right of the position of the ‘text’ element's ‘x’ attribute value.

A more complete discussion of bidirectionality can be found in the Text direction section of CSS 2.1 ([CSS21], section 9.10).

The processing model for bidirectional text is as follows. The user agent processes the characters which are provided in logical order (i.e., the order the characters appear in the original document, either via direct inclusion or via indirect reference due a ‘tref’ element). The user agent determines the set of independent blocks within each of which it should apply the Unicode bidirectional algorithm. Each text chunk represents an independent block of text. Additionally, any change in glyph orientation due to processing of properties ‘glyph-orientation-horizontal’ or ‘glyph-orientation-vertical’ will subdivide the independent blocks of text further. After processing the Unicode bidirectional algorithm and properties ‘direction’ and ‘unicode-bidi’ on each of the independent text blocks, the user agent will have a potentially re-ordered list of characters which are now in left-to-right rendering order. Simultaneous with re-ordering of the characters, the dx, dy and rotate attributes on the ‘tspan’ and ‘tref’ elements are also re-ordered to maintain the original correspondence between characters and attribute values. While kerning or ligature processing might be font-specific, the preferred model is that kerning and ligature processing occurs between combinations of characters or glyphs after the characters have been re-ordered.

‘direction’

Value:	ltr \| rtl
Initial:	ltr
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	no

This property specifies the base writing direction of text and the direction of embeddings and overrides (see ‘unicode-bidi’) for the Unicode bidirectional algorithm. For the ‘direction’ property to have any effect on an element that does not by itself establish a new text chunk (such as a ‘tspan’ element without absolute position adjustments due to ‘x’ or ‘y’ attributes), the ‘unicode-bidi’ property's value must be embed or bidi-override.

Except for any additional information provided in this specification, the normative definition of the ‘direction’ property is in CSS 2.1 ([CSS21], section 9.10).

The ‘direction’ property applies only to glyphs oriented perpendicular to the inline-progression-direction, which includes the usual case of horizontally-oriented Latin or Arabic text and the case of narrow-cell Latin or Arabic characters rotated 90 degrees clockwise relative to a top-to-bottom inline-progression-direction.

‘unicode-bidi’

Value:	normal \| embed \| bidi-override
Initial:	normal
Applies to:	text content elements
Inherited:	no
Percentages:	N/A
Media:	visual
Animatable:	no

Except for any additional information provided in this specification, the normative definition of the ‘unicode-bidi’ property is in CSS 2.1 ([CSS21], section 9.10).

10.8. Text rendering order

The glyphs associated with the characters within a ‘text’ element are rendered in the logical order of the characters in the original document, independent of any re-ordering necessary to implement bidirectionality. Thus, for text that goes right-to-left visually, the glyphs associated with the rightmost character are rendered before the glyphs associated with the other characters.

Additionally, each distinct glyph is rendered in its entirety (i.e., it is filled and stroked as specified by the ‘fill’ and ‘stroke’ properties) before the next glyph gets rendered.

10.8.1. Text overflow processing

SVG 2 Requirement:	Add ‘`text-overflow`’ functionality.
Resolution:	We will add text-overflow in SVG 2.
Purpose:	To align with CSS, allow indicating that not all text is shown.
Owner:	Erik (ACTION-3003)

New in SVG 2. Added to allow user agents to handle text strings that overflow a predefined width in a more useful way. Aligns SVG and HTML/CSS text processing.

See the CSS3 UI specification for the definition of 'text-overflow'. [CSS3UI]

SVG uses the ‘text-overflow’ property to control how text content block elements render when the text overflows a specified ‘width’.

When applied to a text content block element setting ‘text-overflow’ to ellipsis then if the text that is to be rendered overflows the specified ‘width’ an ellipsis is rendered such that it fits within the given width. For the purposes of rendering the ellipsis is treated as if it replaced the characters at the point where it is inserted. The text positioning attributes (‘x’, ‘y’, ‘dx’, ‘dy’, ‘rotate’) apply to the ellipsis as if it was one character in the logical document order mapping to one glyph. In SVG ‘text-overflow’ has an effect if there is a validly specified ‘width’ attribute, regardless of the computed value of the ‘overflow’ property on the text content block element.

Any other value for ‘text-overflow’ is treated as if it wasn't specified.

SVG could allow the keyword 'clip' to work too. It's already possible to do clipping with clip-path, but it's unconditional, where this would theoretically only clip if the text overflowed. It's mostly a convenient shorthand.

Note that the effect of ‘text-overflow’ is purely visual, the ellipsis itself does not become part of the DOM. For all the DOM methods it's as if ‘text-overflow’ wasn't applied, and as if ‘width’ didn't constrain the text.

The following example shows the use of ‘text-overflow’. The top line shows text as it would normally be rendered, without any width restriction. The middle line shows text with text-overflow=clip specified, and the bottom line shows text with text-overflow=ellipsis.

<svg xmlns="http://www.w3.org/2000/svg"
     width="180" height="120" viewBox="0 0 180 120">
  <style>
    text { font: 16px sans-serif; }
    rect { fill: none; stroke: black; vector-effect: non-scaling-stroke; stroke-width: 1; }
  </style>

  <g>
    <rect x="19.5" y="16.5" width="100" height="20"/>
    <text x="20" y="2em" width="100">SVG is awesome</text>
  </g>

  <g transform="translate(0,30)">
    <rect x="19.5" y="16.5" width="100" height="20"/>
    <text x="20" y="2em" width="100" text-overflow="clip">SVG is awesome</text>
  </g>

  <g transform="translate(0,60)">
    <rect x="19.5" y="16.5" width="100" height="20"/>
    <text x="20" y="2em" width="100" text-overflow="ellipsis">SVG is awesome</text>
  </g>
</svg>

Image showing the use of the text-overflow property.

The ‘text-overflow’ property used on text elements, the bottom line showing text with an ellipsis applied.

10.9. Alignment properties

10.9.1. Text alignment properties

The ‘text-anchor’ property is used to align (start-, middle- or end-alignment) a string of text relative to a given point.

The ‘text-anchor’ property is applied to each individual text chunk within a given ‘text’ element. Each text chunk has an initial current text position, which represents the point in the user coordinate system resulting from (depending on context) application of the ‘x’ and ‘y’ attributes on the ‘text’ element, any ‘x’ or ‘y’ attribute values on a ‘tspan’, ‘tref’ or ‘altGlyph’ element assigned explicitly to the first rendered character in a text chunk, or determination of the initial current text position for a ‘textPath’ element.

Name:	text-anchor
Value:	start \| middle \| end
Initial:	start
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

Values have the following meanings:

start: The rendered characters are aligned such that the start of the resulting rendered text is at the initial current text position. For an element with a ‘direction’ property value of "ltr" (typical for most European languages), the left side of the text is rendered at the initial text position. For an element with a ‘direction’ property value of "rtl" (typical for Arabic and Hebrew), the right side of the text is rendered at the initial text position. For an element with a vertical primary text direction (often typical for Asian text), the top side of the text is rendered at the initial text position.
middle: The rendered characters are aligned such that the geometric middle of the resulting rendered text is at the initial current text position.
end: The rendered characters are aligned such that the end of the resulting rendered text is at the initial current text position. For an element with a ‘direction’ property value of "ltr" (typical for most European languages), the right side of the text is rendered at the initial text position. For an element with a ‘direction’ property value of "rtl" (typical for Arabic and Hebrew), the left side of the text is rendered at the initial text position. For an element with a vertical primary text direction (often typical for Asian text), the bottom of the text is rendered at the initial text position.

10.9.2. Baseline alignment properties

SVG 2 Requirement:	Align with CSS for baseline alignment functionality.
Resolution:	SVG 2 will deprecate ‘baseline-shift’ and use ‘vertical-align’ instead.
Purpose:	To align with CSS.
Owner:	Cameron (ACTION-3281)

An overview of baseline alignment and baseline tables can be found above in Fonts, font tables and baselines.

One of the characteristics of international text is that there are different baselines (different alignment points) for glyphs in different scripts. For example, in horizontal writing, ideographic scripts, such as Han Ideographs, Katakana, Hiragana, and Hangul, alignment occurs with a baseline near the bottoms of the glyphs; alphabetic based scripts, such as Latin, Cyrillic, Hebrew, Arabic, align a point that is the bottom of most glyphs, but some glyphs descend below the baseline; and Indic based scripts are aligned at a point that is near the top of the glyphs.

When different scripts are mixed on a line of text, an adjustment must be made to ensure that the glyphs in the different scripts are aligned correctly with one another. OpenType [OPENTYPE] fonts have a Baseline table (BASE) [OPENTYPE-BASETABLE] that specifies the offsets of the alternative baselines from the current baseline.

SVG uses a similar baseline table model that assumes one script (at one font-size) is the "dominant run" during processing of a ‘text’ element; that is, all other baselines are defined in relation to this dominant run. The baseline of the script with the dominant run is called the dominant baseline. So, for example, if the dominant baseline is the alphabetic baseline, there will be offsets in the baseline table for the alternate baselines, such as the ideographic baseline and the Indic baseline. There will also be an offset for the math baseline which is used for some math fonts. Note that there are separate baseline tables for horizontal and vertical writing-modes. The offsets in these tables may be different for horizontal and vertical writing.

The baseline table established at the start of processing of a ‘text’ element is called the dominant baseline table.

Because the value of the ‘font-family’ property is a list of fonts, to insure a consistent choice of baseline table we define the nominal font in a font list as the first font in the list for which a glyph is available. This is the first font that could contain a glyph for each character encountered. (For this definition, glyph data is assumed to be present if a font substitution is made or if the font is synthesized.) This definition insures a content independent determination of the font and baseline table that is to be used.

The value of the ‘font-size’ property on the ‘text’ element establishes the dominant baseline table font size.

The model assumes that each glyph has a 'alignment-baseline' value which specifies the baseline with which the glyph is to be aligned. (The 'alignment-baseline' is called the "Baseline Tag" in the OpenType baseline table description.) The initial value of the ‘alignment-baseline’ property uses the baseline identifier associated with the given glyph. Alternate values for ‘alignment-baseline’ can be useful for glyphs such as a "*" which are ambiguous with respect to script membership.

The model assumes that the font from which the glyph is drawn also has a baseline table, the font baseline table. This baseline table has offsets in units-per-em from the (0,0) point to each of the baselines the font knows about. In particular, it has the offset from the glyph's (0,0) point to the baseline identified by the 'alignment-baseline'.

The offset values in the baseline table are in "design units" which means fractional units of the EM. Thus, the current ‘font-size’ is used to determine the actual offset from the dominant baseline to the alternate baselines.

The glyph is aligned so that its baseline identified by its 'alignment-baseline' is aligned with the baseline with the same name from the dominant baseline table.

The offset from the dominant baseline of the parent to the baseline identified by the 'alignment-baseline' is computed using the dominant baseline table and dominant baseline table font size. The font baseline table and font size applicable to the glyph are used to compute the offset from the identified baseline to the (0,0) point of the glyph. This second offset is subtracted from the first offset to get the position of the (0,0) point in the shift direction. Both offsets are computed by multiplying the baseline value from the baseline table times the appropriate font size value.

If the 'alignment-baseline' identifies the dominant baseline, then the first offset is zero and the glyph is aligned with the dominant baseline; otherwise, the glyph is aligned with the chosen alternate baseline.

The baseline-identifiers below are used in this specification. Some of these are determined by baseline-tables contained in a font as described in XSL ([XSL], section 7.9.1). Others are computed from other font characteristics as described below.

alphabetic: This identifies the baseline used by most alphabetic and syllabic scripts. These include, but are not limited to, many Western, Southern Indic, Southeast Asian (non-ideographic) scripts.
ideographic: This identifies the baseline used by ideographic scripts. For historical reasons, this baseline is at the bottom of the ideographic EM box and not in the center of the ideographic EM box. See the "central" baseline. The ideographic scripts include Chinese, Japanese, Korean, and Vietnamese Chu Nom.
hanging: This identifies the baseline used by certain Indic scripts. These scripts include Devanagari, Gurmukhi and Bengali.
mathematical: This identifies the baseline used by mathematical symbols.
central: This identifies a computed baseline that is at the center of the EM box. This baseline lies halfway between the text-before-edge and text-after-edge baselines.

NOTE:
For ideographic fonts, this baseline is often used to align the glyphs; it is an alternative to the ideographic baseline.
middle: This identifies a baseline that is offset from the alphabetic baseline in the shift-direction by 1/2 the value of the x-height font characteristic. The position of this baseline may be obtained from the font data or, for fonts that have a font characteristic for "x-height", it may be computed using 1/2 the "x-height". Lacking either of these pieces of information, the position of this baseline may be approximated by the "central" baseline.
text-before-edge: This identifies the before-edge of the EM box. The position of this baseline may be specified in the baseline-table or it may be calculated.

NOTE:
The position of this baseline is normally around or at the top of the ascenders, but it may not encompass all accents that can appear above a glyph. For these fonts the value of the "ascent" font characteristic is used. For ideographic fonts, the position of this baseline is normally 1 EM in the shift-direction from the "ideographic" baseline. However, some ideographic fonts have a reduced width in the inline-progression-direction to allow tighter setting. When such a font, designed only for vertical writing-modes, is used in a horizontal writing-mode, the "text-before-edge" baseline may be less than 1 EM from the text-after-edge.
text-after-edge: This identifies the after-edge of the EM box. The position of this baseline may be specified in the baseline-table or it may be calculated.

NOTE:
For fonts with descenders, the position of this baseline is normally around or at the bottom of the descenders. For these fonts the value of the "descent" font characteristic is used. For ideographic fonts, the position of this baseline is normally at the "ideographic" baseline.

There are, in addition, two computed baselines that are only defined for line areas. Since SVG does not support the notion of computations based on line areas, the two computed baselines are mapped as follows:

before-edge: For SVG, this is equivalent to text-before-edge.
after-edge: For SVG, this is equivalent to text-after-edge.

There are also four baselines that are defined only for horizontal writing-modes.

top: This baseline is the same as the "before-edge" baseline in a horizontal writing-mode and is undefined in a vertical writing mode.
text-top: This baseline is the same as the "text-before-edge" baseline in a horizontal writing-mode and is undefined in a vertical writing mode.
bottom: This baseline is the same as the "after-edge" baseline in a horizontal writing-mode and is undefined in a vertical writing mode.
text-bottom: This baseline is the same as the "text-after-edge" baseline in a horizontal writing-mode and is undefined in a vertical writing mode.

The baseline-alignment properties follow.

‘dominant-baseline’

Value:	auto \| use-script \| no-change \| reset-size \| ideographic \| alphabetic \| hanging \| mathematical \| central \| middle \| text-after-edge \| text-before-edge
Initial:	auto
Applies to:	text content elements
Inherited:	no
Percentages:	N/A
Media:	visual
Animatable:	yes

The "dominant-baseline" property is used to determine or re-determine a scaled-baseline-table. A scaled-baseline-table is a compound value with three components: a baseline-identifier for the dominant-baseline, a baseline-table and a baseline-table font-size. Some values of the property re-determine all three values; other only re-establish the baseline-table font-size. When the initial value, auto, would give an undesired result, this property can be used to explicitly set the desire scaled-baseline-table.

Values for the property have the following meaning:

auto

If this property occurs on a ‘text’ element, then the computed value depends on the value of the ‘writing-mode’ property. If the 'writing-mode' is horizontal, then the value of the dominant-baseline component is 'alphabetic', else if the 'writing-mode' is vertical, then the value of the dominant-baseline component is 'central'.

If this property occurs on a ‘tspan’, ‘tref’, ‘altGlyph’ or ‘textPath’ element, then the dominant-baseline and the baseline-table components remain the same as those of the parent text content element. If the computed ‘baseline-shift’ value actually shifts the baseline, then the baseline-table font-size component is set to the value of the ‘font-size’ property on the element on which the ‘dominant-baseline’ property occurs, otherwise the baseline-table font-size remains the same as that of the element. If there is no parent text content element, the scaled-baseline-table value is constructed as above for ‘text’ elements.

use-script

The dominant-baseline and the baseline-table components are set by determining the predominant script of the character data content. The ‘writing-mode’, whether horizontal or vertical, is used to select the appropriate set of baseline-tables and the dominant baseline is used to select the baseline-table that corresponds to that baseline. The baseline-table font-size component is set to the value of the ‘font-size’ property on the element on which the ‘dominant-baseline’ property occurs.

no-change

The dominant-baseline, the baseline-table, and the baseline-table font-size remain the same as that of the parent text content element.

reset-size

The dominant-baseline and the baseline-table remain the same, but the baseline-table font-size is changed to the value of the ‘font-size’ property on this element. This re-scales the baseline-table for the current ‘font-size’.

ideographic

The baseline-identifier for the dominant-baseline is set to be 'ideographic', the derived baseline-table is constructed using the 'ideographic' baseline-table in the nominal font, and the baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

alphabetic

The baseline-identifier for the dominant-baseline is set to be 'alphabetic', the derived baseline-table is constructed using the 'alphabetic' baseline-table in the nominal font, and the baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

hanging

The baseline-identifier for the dominant-baseline is set to be 'hanging', the derived baseline-table is constructed using the 'hanging' baseline-table in the nominal font, and the baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

mathematical

The baseline-identifier for the dominant-baseline is set to be 'mathematical', the derived baseline-table is constructed using the 'mathematical' baseline-table in the nominal font, and the baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

central

The baseline-identifier for the dominant-baseline is set to be 'central'. The derived baseline-table is constructed from the defined baselines in a baseline-table in the nominal font. That font baseline-table is chosen using the following priority order of baseline-table names: 'ideographic', 'alphabetic', 'hanging', 'mathematical'. The baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

middle

The baseline-identifier for the dominant-baseline is set to be 'middle'. The derived baseline-table is constructed from the defined baselines in a baseline-table in the nominal font. That font baseline -table is chosen using the following priority order of baseline-table names: 'alphabetic', 'ideographic', 'hanging', 'mathematical'. The baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

text-after-edge

The baseline-identifier for the dominant-baseline is set to be 'text-after-edge'. The derived baseline-table is constructed from the defined baselines in a baseline-table in the nominal font. The choice of which font baseline-table to use from the baseline-tables in the nominal font is implementation defined. The baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

NOTE: using the following priority order of baseline-table names: 'alphabetic', 'ideographic', 'hanging', 'mathematical' is probably a reasonable strategy for determining which font baseline-table to use.

text-before-edge

The baseline-identifier for the dominant-baseline is set to be 'text-before-edge'. The derived baseline-table is constructed from the defined baselines in a baseline-table in the nominal font. The choice of which baseline-table to use from the baseline-tables in the nominal font is implementation defined. The baseline-table font-size is changed to the value of the ‘font-size’ property on this element.

NOTE: Using the following priority order of baseline-table names: 'alphabetic', 'ideographic', 'hanging', 'mathematical' is probably a reasonable strategy for determining which font baseline-table to use.

If there is no baseline table in the nominal font or if the baseline table lacks an entry for the desired baseline, then the user agent may use heuristics to determine the position of the desired baseline.

‘alignment-baseline’

Value:	auto \| baseline \| before-edge \| text-before-edge \| middle \| central \| after-edge \| text-after-edge \| ideographic \| alphabetic \| hanging \| mathematical
Initial:	auto
Applies to:	‘tspan’, ‘tref’, ‘altGlyph’, ‘textPath’ elements
Inherited:	no
Percentages:	N/A
Media:	visual
Animatable:	yes

This property specifies how an object is aligned with respect to its parent. This property specifies which baseline of this element is to be aligned with the corresponding baseline of the parent. For example, this allows alphabetic baselines in Roman text to stay aligned across font size changes. It defaults to the baseline with the same name as the computed value of the alignment-baseline property. That is, the position of "ideographic" alignment-point in the block-progression-direction is the position of the "ideographic" baseline in the baseline-table of the object being aligned.

Values have the following meanings:

auto: The value is the dominant-baseline of the script to which the character belongs - i.e., use the dominant-baseline of the parent.
baseline: The alignment-point of the object being aligned is aligned with the dominant-baseline of the parent text content element.
before-edge: The alignment-point of the object being aligned is aligned with the "before-edge" baseline of the parent text content element.
text-before-edge: The alignment-point of the object being aligned is aligned with the "text-before-edge" baseline of the parent text content element.
middle: The alignment-point of the object being aligned is aligned with the "middle" baseline of the parent text content element.
central: The alignment-point of the object being aligned is aligned with the "central" baseline of the parent text content element.
after-edge: The alignment-point of the object being aligned is aligned with the "after-edge" baseline of the parent text content element.
text-after-edge: The alignment-point of the object being aligned is aligned with the "text-after-edge" baseline of the parent text content element.
ideographic: The alignment-point of the object being aligned is aligned with the "ideographic" baseline of the parent text content element.
alphabetic: The alignment-point of the object being aligned is aligned with the "alphabetic" baseline of the parent text content element.
hanging: The alignment-point of the object being aligned is aligned with the "hanging" baseline of the parent text content element.
mathematical: The alignment-point of the object being aligned is aligned with the "mathematical" baseline of the parent text content element.

‘baseline-shift’

Value:	baseline \| sub \| super \| <percentage> \| <length>
Initial:	baseline
Applies to:	‘tspan’, ‘tref’, ‘altGlyph’, ‘textPath’ elements
Inherited:	no
Percentages:	refers to the "line-height" of the ‘text’ element, which in the case of SVG is defined to be equal to the ‘`font-size`’
Media:	visual
Animatable:	yes

The ‘baseline-shift’ property allows repositioning of the dominant-baseline relative to the dominant-baseline of the parent text content element. The shifted object might be a sub- or superscript. Within the shifted object, the whole baseline-table is offset; not just a single baseline. The amount of the shift is determined from information from the parent text content element, the sub- or superscript offset from the nominal font of the parent text content element, percent of the "line-height" of the parent text content element or an absolute value.

In SVG, the ‘baseline-shift’ property represents a supplemental adjustment to the baseline tables. The ‘baseline-shift’ property shifts the baseline tables for each glyph to temporary new positions, for example to lift the glyph into superscript or subscript position, but it does not effect the current text position. When the current text position is adjusted after rendering a glyph to take into account glyph advance values, the adjustment happens as if there were no baseline shift.

‘baseline-shift’ properties can nest. Each nested ‘baseline-shift’ is added to previous baseline shift values.

Values for the property have the following meaning:

baseline: There is no baseline shift; the dominant-baseline remains in its original position.
sub: The dominant-baseline is shifted to the default position for subscripts. The offset to this position is determined using the font data for the nominal font. Because in most fonts the subscript position is normally given relative to the "alphabetic" baseline, the user agent may compute the effective position for subscripts for superscripts when some other baseline is dominant. The suggested computation is to subtract the difference between the position of the dominant baseline and the position of the "alphabetic" baseline from the position of the subscript. The resulting offset is determined by multiplying the effective subscript position by the dominant baseline-table font-size. If there is no applicable font data the user agent may use heuristics to determine the offset.
super: The dominant-baseline is shifted to the default position for superscripts. The offset to this position is determined using the font data for the nominal font. Because in most fonts the superscript position is normally given relative to the "alphabetic" baseline, the user agent may compute the effective position for superscripts when some other baseline is dominant. The suggested computation is to subtract the difference between the position of the dominant baseline and the position of the "alphabetic" baseline from the position of the superscript. The resulting offset is determined by multiplying the effective superscript position by the dominant baseline-table font-size. If there is no applicable font data the user agent may use heuristics to determine the offset.
<percentage>: The computed value of the property is this percentage multiplied by the computed "line-height" of the ‘text’ element. The dominant-baseline is shifted in the shift direction (positive value) or opposite to the shift direction (negative value) of the parent text content element by the computed value. A value of "0%" is equivalent to "baseline".
<length>: The dominant-baseline is shifted in the shift direction (positive value) or opposite to the shift direction (negative value) of the parent text content element by the <length> value. A value of "0cm" is equivalent to "baseline".

10.10. Font selection properties

SVG uses the following font specification properties. Except for any additional information provided in this specification, the normative definition of these properties is in CSS 2.1 ([CSS21], chapter 15). Any SVG-specific notes about these properties are contained in the descriptions below.

‘font-family’

Value:	[[ <family-name> \| <generic-family> ],]* [<family-name> \| <generic-family>]
Initial:	depends on user agent
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes

This property indicates which font family is to be used to render the text, specified as a prioritized list of font family names and/or generic family names. Unless the family name corresponds to a CSS IDENT, it must be quoted. Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 15.3).

‘font-style’

Value:	normal \| italic \| oblique
Initial:	normal
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes

This property specifies whether the text is to be rendered using a normal, italic or oblique face. Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 15.4).

‘font-variant’

Value:	normal \| small-caps
Initial:	normal
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes

This property indicates whether the text is to be rendered using the normal glyphs for lowercase characters or using small-caps glyphs for lowercase characters. Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 15.5).

‘font-weight’

Value:	normal \| bold \| bolder \| lighter \| 100 \| 200 \| 300 \| 400 \| 500 \| 600 \| 700 \| 800 \| 900
Initial:	normal
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes

This property refers to the boldness or lightness of the glyphs used to render the text, relative to other fonts in the same font family. Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 15.6).

‘font-stretch’

Value:	normal \| wider \| narrower \| ultra-condensed \| extra-condensed \| condensed \| semi-condensed \| semi-expanded \| expanded \| extra-expanded \| ultra-expanded
Initial:	normal
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes

This property indicates the desired amount of condensing or expansion in the glyphs used to render the text. Except for any additional information provided in this specification, the normative definition of the property is in CSS3 Fonts ([CSS3FONTS], section 3.3).

‘font-size’

Value:	<absolute-size> \| <relative-size> \| <length> \| <percentage>
Initial:	medium
Applies to:	text content elements
Inherited:	yes, the computed value is inherited
Percentages:	refer to parent element's font size
Media:	visual
Animatable:	yes

This property refers to the size of the font from baseline to baseline when multiple lines of text are set solid in a multiline layout environment. For SVG, if a <length> is provided without a unit identifier (e.g., an unqualified number such as 128), the SVG user agent processes the <length> as a height value in the current user coordinate system.

If a <length> is provided with one of the unit identifiers (e.g., 12pt or 10%), then the SVG user agent converts the <length> into a corresponding value in the current user coordinate system by applying the rules described in Units.

Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 15.7).

‘font-size-adjust’

Value:	<number> \| none
Initial:	none
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes (non-additive)

This property allows authors to specify an aspect value for an element that will preserve the x-height of the first choice font in a substitute font. Except for any additional information provided in this specification, the normative definition of the property is in CSS3 Fonts ([CSS3FONTS], section 3.6).

‘font’

Value:	[ [ <'font-style'> \|\| <'font-variant'> \|\| <'font-weight'> ]? <'font-size'> [ / <'line-height'> ]? <'font-family'> ] \| caption \| icon \| menu \| message-box \| small-caption \| status-bar
Initial:	see individual properties
Applies to:	text content elements
Inherited:	yes
Percentages:	allowed on 'font-size' and 'line-height' (Note: for the purposes of processing the ‘`font`’ property in SVG, 'line-height' is assumed to be equal the value for property ‘`font-size`’)
Media:	visual
Animatable:	yes (non-additive)

Shorthand property for setting ‘font-style’, ‘font-variant’, ‘font-weight’, ‘font-size’, ‘line-height’ and ‘font-family’. The ‘line-height’ property has no effect on text layout in SVG. For the purposes of the ‘font’ property, ‘line-height’ is assumed to be equal to the value of the ‘font-size’ property. Conforming SVG Viewers are not required to support the various system font options (caption, icon, menu, message-box, small-caption and status-bar) and can use a system font or one of the generic fonts instead.

Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 15.8).

10.11. Spacing properties

Two properties affect the space between characters and words:

‘letter-spacing’ indicates an amount of space that is to be added between text characters.
‘word-spacing’ indicates the spacing behavior between words.

Note that the ‘kerning’ property from SVG 1.1 has been removed in favor of using ‘letter-spacing’ to add or remove spacing between glyphs and the ‘font-kerning’ property to disable kerning based on information from the font.

We need to require ‘font-kerning’.

‘letter-spacing’

Value:	normal \| <length>
Initial:	normal
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes

This property specifies spacing behavior between text characters.

For SVG, if a <length> is provided without a unit identifier (e.g., an unqualified number such as 128), the SVG user agent processes the <length> as a width value in the current user coordinate system.

If a <length> is provided with one of the unit identifiers (e.g., .25em or 1%), then the SVG user agent converts the <length> into a corresponding value in the current user coordinate system by applying the rules described in Units.

Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 16.4).

‘word-spacing’

Value:	normal \| <length>
Initial:	normal
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Animatable:	yes

This property specifies spacing behavior between words. For SVG, if a <length> is provided without a unit identifier (e.g., an unqualified number such as 128), the SVG user agent processes the <length> as a width value in the current user coordinate system.

Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 16.4).

10.12. Text decoration

‘text-decoration’

Value:	none \| [ underline \|\| overline \|\| line-through \|\| blink ]
Initial:	none
Applies to:	text content elements
Inherited:	no (see prose)
Percentages:	N/A
Media:	visual
Animatable:	yes

This property describes decorations that are added to the text of an element. Conforming SVG Viewers are not required to support the blink value.

Except for any additional information provided in this specification, the normative definition of the property is in CSS 2.1 ([CSS21], section 16.3.1).

The CSS 2.1 specification defines the behavior of the ‘text-decoration’ property using the terminology "block-level elements" and "inline elements". For the purposes of the ‘text-decoration’ property and SVG, a ‘text’ element represents a block-level element and any of the potential children of a ‘text’ element (e.g., a ‘tspan’) represent inline elements.

Also, the CSS 2.1 definition of ‘text-decoration’ specifies that the "color of the decorations" remain the same on descendant elements. Since SVG offers a painting model consisting of the ability to apply various types of paint (see Painting: Filling, Stroking and Marker Symbols) to both the interior (i.e., the "fill") and the outline (i.e., the "stroke") of text, for SVG the ‘text-decoration’ property is defined such that, for an element which has a specified value for the ‘text-decoration’ property, all decorations on its content and that of its descendants are rendered using the same fill and stroke properties as are present on the given element. If the ‘text-decoration’ property is specified on a descendant, then that overrides the ancestor.

Because SVG allows text to be both filled and stroked, drawing order matters in some circumstances with text decorations. Text decoration drawing order should be as follows:

All text decorations except line-through should be drawn before the text is filled and stroked; thus, the text is rendered on top of these decorations.
Line-through should be drawn after the text is filled and stroked; thus, the line-through is rendered on top of the text.

Example textdecoration01 provides examples for ‘text-decoration’. The first line of text has no value for ‘text-decoration’, so the initial value of text-decoration:none is used. The second line shows text-decoration:line-through. The third line shows text-decoration:underline. The fourth line illustrates the rule whereby decorations are rendered using the same fill and stroke properties as are present on the element for which the ‘text-decoration’ is specified. Since ‘text-decoration’ is specified on the ‘text’ element, all text within the ‘text’ element has its underline rendered with the same fill and stroke properties as exist on the ‘text’ element (i.e., blue fill, red stroke), even though the various words have different fill and stroke property values. However, the word "different" explicitly specifies a value for ‘text-decoration’; thus, its underline is rendered using the fill and stroke properties as the ‘tspan’ element that surrounds the word "different" (i.e., yellow fill, darkgreen stroke):

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="4cm" viewBox="0 0 1200 400"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example textdecoration01 - behavior of 'text-decoration' property</desc>
  <rect x="1" y="1" width="1198" height="398" fill="none" stroke="blue" stroke-width="2" />
  <g font-size="60" fill="blue" stroke="red" stroke-width="1" >
    <text x="100" y="75">Normal text</text>
    <text x="100" y="165" text-decoration="line-through" >Text with line-through</text>
    <text x="100" y="255" text-decoration="underline" >Underlined text</text>
    <text x="100" y="345" text-decoration="underline" >
      <tspan>One </tspan>
      <tspan fill="yellow" stroke="purple" >word </tspan>
      <tspan fill="yellow" stroke="black" >has </tspan>
      <tspan fill="yellow" stroke="darkgreen" text-decoration="underline" >different </tspan>
      <tspan fill="yellow" stroke="blue" >underlining</tspan>
    </text>
  </g>
</svg>

Example textdecoration01

View this example as SVG (SVG-enabled browsers only)

10.13. Text on a path

In addition to text drawn in a straight line, SVG also includes the ability to place text along the shape of a ‘path’ element. To specify that a block of text is to be rendered along the shape of a ‘path’, include the given text within a ‘textPath’ element which includes an ‘xlink:href’ attribute with an IRI reference to a ‘path’ element, or a ‘d’ attribute that specifies the path data directly.

10.13.1. The ‘textPath’ element

‘textPath’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements or character data, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

a, altGlyph, animate, animateColor, clipPath, marker, mask, set, tref, tspan

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘lengthAdjust’
‘textLength’
‘d’
‘xlink:href’
‘startOffset’
‘method’
‘spacing’

DOM Interfaces:

SVGTextPathElement

SVG 2 Requirement:	Have a more precise explanation of text path stretch methods.
Resolution:	We will clarify method="stretch" on >'textPath' elements.
Purpose:	Improve interoperability of the feature.
Owner:	Cameron (no action)

Attribute definitions:

startOffset = "<length>": An offset from the start of the path for the initial current text position, calculated using the user agent's distance along the path algorithm.
If a <length> other than a percentage is given, then the ‘startOffset’ represents a distance along the path measured in the current user coordinate system.
If a percentage is given, then the ‘startOffset’ represents a percentage distance along the entire path. Thus, startOffset="0%" indicates the start point of the path and startOffset="100%" indicates the end point of the path.

If the attribute is not specified, the effect is as if a value of "0" were specified.
Animatable: yes.
method = "align | stretch": Indicates the method by which text should be rendered along the path.
A value of align indicates that the glyphs should be rendered using simple 2x3 transformations such that there is no stretching/warping of the glyphs. Typically, supplemental rotation, scaling and translation transformations are done for each glyph to be rendered. As a result, with align, fonts where the glyphs are designed to be connected (e.g., cursive fonts), the connections may not align properly when text is rendered along a path.
A value of stretch indicates that the glyph outlines will be converted into paths, and then all end points and control points will be adjusted to be along the perpendicular vectors from the path, thereby stretching and possibly warping the glyphs. With this approach, connected glyphs, such as in cursive scripts, will maintain their connections.
If the attribute is not specified, the effect is as if a value of align were specified.
Animatable: yes.
spacing = "auto | exact": Indicates how the user agent should determine the spacing between glyphs that are to be rendered along a path.
A value of exact indicates that the glyphs should be rendered exactly according to the spacing rules as specified in Text on a path layout rules.
A value of auto indicates that the user agent should use text-on-a-path layout algorithms to adjust the spacing between glyphs in order to achieve visually appealing results.
If the attribute is not specified, the effect is as if a value of exact were specified.
Animatable: yes.
d = "path data": The definition of the path onto which the glyphs will be rendered. The handling of erroneous path data follows the behavior specified in the ‘path’ element implementation notes.
If both the ‘d’ attribute and ‘xlink:href’ attributes are specified, it is as if the ‘xlink:href’ attribute were not specified for the purposes of rendering. In the SVGTextPathElement interface both values will still be reflected. Furthermore, if a value for ‘xlink:href’ is specified in markup and path data is subsequently specified via the pathSegList member of the SVGTextPathElement, then this is equivalent to specifying the ‘d’ attribute—the ‘xlink:href’ will be disregarded for rendering and the path specified in the pathSegList will be used instead.
Animatable: yes.
xlink:href = "<iri>": An IRI reference to the ‘path’ element onto which the glyphs will be rendered. If <iri> is an invalid reference (e.g., no such element exists, or the referenced element is not a ‘path’), then the ‘textPath’ element is in error and its entire contents shall not be rendered by the user agent.
Animatable: yes.

The path data coordinates within the referenced ‘path’ element are assumed to be in the same coordinate system as the current ‘text’ element, not in the coordinate system where the ‘path’ element is defined. The ‘transform’ attribute on the referenced ‘path’ element represents a supplemental transformation relative to the current user coordinate system for the current ‘text’ element, including any adjustments to the current user coordinate system due to a possible ‘transform’ property on the current ‘text’ element. For example, the following fragment of SVG content:

<svg xmlns="http://www.w3.org/2000/svg" 
     xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1">
  <g transform="translate(25,25)">
    <defs>
      <path id="path1" transform="scale(2)" d="..." fill="none" stroke="red"/>
    </defs>
  </g>
  <text transform="rotate(45)">
    <textPath xlink:href="#path1">Text along path1</textPath>
  </text>
</svg>

should have the same effect as the following:

<svg xmlns="http://www.w3.org/2000/svg" 
     xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1">
  <g transform="rotate(45)">
    <defs>
      <path id="path1" transform="scale(2)" d="..." fill="none" stroke="red"/>
    </defs>
    <text>
      <textPath xlink:href="#path1">Text along path1</textPath>
    </text>
  </g>
</svg>

Note that the transform="translate(25,25)" has no effect on the ‘textPath’ element, whereas the transform="rotate(45)" applies to both the ‘text’ and the use of the ‘path’ element as the referenced shape for text on a path.

Example toap01 provides a simple example of text on a path:

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="3.6cm" viewBox="0 0 1000 300" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>
  <desc>Example toap01 - simple text on a path</desc>

  <use xlink:href="#MyPath" fill="none" stroke="red"  />
  <text font-family="Verdana" font-size="42.5" fill="blue" >
    <textPath xlink:href="#MyPath">
      We go up, then we go down, then up again
    </textPath>
  </text>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example toap01

Example toap02 shows how ‘tspan’ elements can be included within ‘textPath’ elements to adjust styling attributes and adjust the current text position before rendering a particular glyph. The first occurrence of the word "up" is filled with the color red. Attribute ‘dy’ is used to lift the word "up" from the baseline.

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="3.6cm" viewBox="0 0 1000 300" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>
  <desc>Example toap02 - tspan within textPath</desc>

  <use xlink:href="#MyPath" fill="none" stroke="red"  />
  <text font-family="Verdana" font-size="42.5" fill="blue" >
    <textPath xlink:href="#MyPath">
      We go 
      <tspan dy="-30" fill="red" >
        up
      </tspan>
      <tspan dy="30">
        ,
      </tspan>
      then we go down, then up again
    </textPath>
  </text>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example toap02

View this example as SVG (SVG-enabled browsers only)

Example toap03 demonstrates the use of the ‘startOffset’ attribute on the ‘textPath’ element to specify the start position of the text string as a particular position along the path. Notice that glyphs that fall off the end of the path are not rendered (see text on a path layout rules).

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="3.6cm" viewBox="0 0 1000 300" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>
  <desc>Example toap03 - text on a path with startOffset attribute</desc>

  <use xlink:href="#MyPath" fill="none" stroke="red"  />
  <text font-family="Verdana" font-size="42.5" fill="blue" >
    <textPath xlink:href="#MyPath" startOffset="80%">
      We go up, then we go down, then up again
    </textPath>
  </text>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example toap03

View this example as SVG (SVG-enabled browsers only)

10.13.2. Text on a path layout rules

Conceptually, for text on a path the target path is stretched out into either a horizontal or vertical straight line segment. For horizontal text layout flows, the path is stretched out into a hypothetical horizontal line segment such that the start of the path is mapped to the left of the line segment. For vertical text layout flows, the path is stretched out into a hypothetical vertical line segment such that the start of the path is mapped to the top of the line segment. The standard text layout rules are applied to the hypothetical straight line segment and the result is mapped back onto the target path. Vertical and bidirectional text layout rules also apply to text on a path.

The reference orientation is determined individually for each glyph that is rendered along the path. For horizontal text layout flows, the reference orientation for a given glyph is the vector that starts at the intersection point on the path to which the glyph is attached and which points in the direction 90 degrees counter-clockwise from the angle of the curve at the intersection point. For vertical text layout flows, the reference orientation for a given glyph is the vector that starts at the intersection point on the path to which the glyph is attached and which points in the direction 180 degrees from the angle of the curve at the intersection point.

Example toap04 will be used to illustrate the particular layout rules for text on a path that supplement the basic text layout rules for straight line horizontal or vertical text.

<?xml version="1.0" standalone="no"?>
<svg width="12cm" height="3.6cm" viewBox="0 0 1000 300" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <path id="MyPath"
          d="M 100 125 
             C 150 125 250 175 300 175
             C 350 175 450 125 500 125
             C 550 125 650 175 700 175
             C 750 175 850 125 900 125" />
  </defs>
  <desc>Example toap04 - text on a path layout rules</desc>

  <use xlink:href="#MyPath" fill="none" stroke="red"  />
  <text font-family="Verdana" font-size="60" fill="blue" letter-spacing="2" >
    <textPath xlink:href="#MyPath">
      Choose shame or get war 
    </textPath>
  </text>

  <!-- Show outline of canvas using 'rect' element -->
  <rect x="1" y="1" width="998" height="298"
        fill="none" stroke="blue" stroke-width="2" />
</svg>

Example toap04

View this example as SVG (SVG-enabled browsers only)

The following picture does an initial zoom in on the first glyph in the ‘text’ element.

The small dot above shows the point at which the glyph is attached to the path. The box around the glyph shows the glyph is rotated such that its horizontal axis is parallel to the tangent of the curve at the point at which the glyph is attached to the path. The box also shows the glyph's charwidth (i.e., the amount which the current text position advances horizontally when the glyph is drawn using horizontal text layout).

The next picture zooms in further to demonstrate the detailed layout rules.

For left-to-right horizontal text layout along a path (i.e., when the glyph orientation is perpendicular to the inline-progression-direction), the layout rules are as follows:

Determine the startpoint-on-the-path for the first glyph using attribute ‘startOffset’ and property ‘text-anchor’. For text-anchor:start, startpoint-on-the-path is the point on the path which represents the point on the path which is ‘startOffset’ distance along the path from the start of the path, calculated using the user agent's distance along the path algorithm. For text-anchor:middle, startpoint-on-the-path is the point on the path which represents the point on the path which is [ ‘startOffset’ minus half of the total advance values for all of the glyphs in the ‘textPath’ element ] distance along the path from the start of the path, calculated using the user agent's distance along the path algorithm. For text-anchor:end, startpoint-on-the-path is the point on the path which represents the point on the path which is [ ‘startOffset’ minus the total advance values for all of the glyphs in the ‘textPath’ element ]. Before rendering the first glyph, the horizontal component of the startpoint-on-the-path is adjusted to take into account various horizontal alignment text properties and attributes, such as a ‘dx’ attribute value on a ‘tspan’ element. (In the picture above, the startpoint-on-the-path is the leftmost dot on the path.)
Determine the glyph's charwidth (i.e., the amount which the current text position advances horizontally when the glyph is drawn using horizontal text layout). (In the picture above, the charwidth is the distance between the two dots at the side of the box.)
Determine the point on the curve which is charwidth distance along the path from the startpoint-on-the-path for this glyph, calculated using the user agent's distance along the path algorithm. This point is the endpoint-on-the-path for the glyph. (In the picture above, the endpoint-on-the-path for the glyph is the rightmost dot on the path.)
Determine the midpoint-on-the-path, which is the point on the path which is "halfway" (user agents can choose either a distance calculation or a parametric calculation) between the startpoint-on-the-path and the endpoint-on-the-path. (In the picture above, the midpoint-on-the-path is shown as a white dot.)
Determine the glyph-midline, which is the vertical line in the glyph's coordinate system that goes through the glyph's x-axis midpoint. (In the picture above, the glyph-midline is shown as a dashed line.)
Position the glyph such that the glyph-midline passes through the midpoint-on-the-path and is perpendicular to the line through the startpoint-on-the-path and the endpoint-on-the-path.
Align the glyph vertically relative to the midpoint-on-the-path based on property ‘alignment-baseline’ and any specified values for attribute ‘dy’ on a ‘tspan’ element. In the example above, the ‘alignment-baseline’ property is unspecified, so the initial value of alignment-baseline:baseline will be used. There are no ‘tspan’ elements; thus, the baseline of the glyph is aligned to the midpoint-on-the-path.
For each subsequent glyph, set a new startpoint-on-the-path as the previous endpoint-on-the-path, but with appropriate adjustments taking into account horizontal kerning tables in the font and current values of various attributes and properties, including spacing properties and ‘tspan’ elements with values provided for attributes ‘dx’ and ‘dy’. All adjustments are calculated as distance adjustments along the path, calculated using the user agent's distance along the path algorithm.
Glyphs whose midpoint-on-the-path are off either end of the path are not rendered.
Continue rendering glyphs until there are no more glyphs.

Comparable rules are used for top-to-bottom vertical text layout along a path (i.e., when the glyph orientation is parallel with the inline-progression-direction), the layout rules are as follows:

Determine the startpoint-on-the-path using the same method as for horizontal text layout along a path, except that before rendering the first glyph, the horizontal component of the startpoint-on-the-path is adjusted to take into account various vertical alignment text properties and attributes, such as a ‘dy’ attribute value on a ‘tspan’ element.
Determine the glyph's charheight (i.e., the amount which the current text position advances vertically when the glyph is drawn using vertical text layout).
Determine the point on the curve which is charheight distance along the path from the startpoint-on-the-path for this glyph, calculated using the user agent's distance along the path algorithm. This point is the endpoint-on-the-path for the glyph.
Determine the midpoint-on-the-path, which is the point on the path which is "halfway" (user agents can choose either a distance calculation or a parametric calculation) between the startpoint-on-the-path and the endpoint-on-the-path.
Determine the glyph-midline, which is the horizontal line in the glyph's coordinate system that goes through the glyph's y-axis midpoint.
Position the glyph such that the glyph-midline passes through the midpoint-on-the-path and is perpendicular to the line through the startpoint-on-the-path and the endpoint-on-the-path.
Align the glyph horizontally (where horizontal is relative to the glyph's coordinate system) relative to the midpoint-on-the-path based on property ‘alignment-baseline’ and any specified values for attribute ‘dx’ on a ‘tspan’ element.
For each subsequent glyph, set a new startpoint-on-the-path as the previous endpoint-on-the-path, but with appropriate adjustments taking into account vertical kerning tables in the font and current values of various attributes and properties, including spacing properties and ‘tspan’ elements with values provided for attributes ‘dx’ and ‘dy’. All adjustments are calculated as distance adjustments along the path, calculated using the user agent's distance along the path algorithm.
Glyphs whose midpoint-on-the-path are off either end of the path are not rendered.
Continue rendering glyphs until there are no more glyphs.

In the calculations above, if either the startpoint-on-the-path or the endpoint-on-the-path is off the end of the path, then extend the path beyond its end points with a straight line that is parallel to the tangent at the path at its end point so that the midpoint-on-the-path can still be calculated.

When the inline-progression-direction is horizontal, then any ‘x’ attributes on ‘text’, ‘tspan’, ‘tref’ or ‘altGlyph’ elements represent new absolute offsets along the path, thus providing explicit new values for startpoint-on-the-path. Any ‘y’ attributes on ‘text’, ‘tspan’, ‘tref’ or ‘altGlyph’ elements are ignored. When the inline-progression-direction is vertical, then any ‘y’ attributes on ‘text’, ‘tspan’, ‘tref’ or ‘altGlyph’ elements represent new absolute offsets along the path, thus providing explicit new values for startpoint-on-the-path. Any ‘x’ attributes on ‘text’, ‘tspan’, ‘tref’ or ‘altGlyph’ elements are ignored.

10.14. Alternate glyphs

There are situations such as ligatures, special-purpose fonts (e.g., a font for music symbols) or alternate glyphs for Asian text strings where it is required that a different set of glyphs is used than the glyph(s) which normally corresponds to the given character data.

10.14.1. The ‘altGlyph’ element

The ‘altGlyph’ element provides control over the glyphs used to render particular character data.

‘altGlyph’

Categories:

Content model:

Any elements or character data.

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
graphical event attributes — ‘onfocusin’, ‘onfocusout’, ‘onactivate’, ‘onclick’, ‘onmousedown’, ‘onmouseup’, ‘onmouseover’, ‘onmousemove’, ‘onmouseout’, ‘onload’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘x’
‘y’
‘dx’
‘dy’
‘glyphRef’
‘format’
‘rotate’
‘xlink:href’

DOM Interfaces:

SVGAltGlyphElement

Attribute definitions:

xlink:href = "<iri>": An IRI reference either to a ‘glyph’ element in an SVG document fragment or to an ‘altGlyphDef’ element.

If the reference is to a ‘glyph’ element and that glyph is available, then that glyph is rendered instead of the character(s) that are inside of the ‘altGlyph’ element.

If the reference is to an ‘altGlyphDef’ element, then if an appropriate set of alternate glyphs is located from processing the ‘altGlyphDef’ element, then those alternate glyphs are rendered instead of the character(s) that are inside of the ‘altGlyph’ element.

Animatable: no.
glyphRef = "<string>": The glyph identifier, the format of which is dependent on the ‘format’ of the given font. (Same meaning as the ‘glyphRef’ attribute on the ‘glyphRef’ element.)
Animatable: no.
format = "<string>": The format of the given font. If the font is in one of the formats listed in CSS2, such as TrueDoc™ Portable Font Resource or Embedded OpenType, then the <string> must contain the corresponding font format string, such as truedoc-pfr or embedded-opentype. (This attribute has the same meaning as the ‘format’ attribute on the ‘glyphRef’ element.) This refers to CSS 2; it needs to be reviewed against the formats described by CSS3 Fonts.
Animatable: no.
x = "<list-of-coordinates>": The <length> values are processed in the same manner as the ‘x’ attribute on the ‘tspan’ element, with the following exception: If the referenced alternate glyphs are rendered instead of the Unicode characters inside the ‘altGlyph’ element, then any absolute X coordinates specified via an ‘x’ attribute on this element or any ancestor ‘text’ or ‘tspan’ elements for Unicode characters 2 through n within the ‘altGlyph’ element are ignored. Any absolute X coordinate specified via an ‘x’ attribute on this element or any ancestor ‘text’ or ‘tspan’ elements for the first Unicode character within the ‘altGlyph’ element sets a new absolute X coordinate for the current text position before rendering the first alternate glyph.
Animatable: yes.
y = "<list-of-coordinates>": The corresponding absolute Y coordinates for rendering the ‘altGlyph’ element.
Animatable: yes.
dx = "<list-of-lengths>": The <length> values are processed in the same manner as the ‘dx’ attribute on the ‘tspan’ element, with the following exception: If the referenced alternate glyphs are rendered instead of the Unicode characters inside the ‘altGlyph’ element, then any relative X coordinates specified via an ‘dx’ attribute on this element or any ancestor ‘text’ or ‘tspan’ elements for Unicode characters 2 through n within the ‘altGlyph’ element are ignored. Any relative X coordinate specified via an ‘dx’ attribute on this element or any ancestor ‘text’ or ‘tspan’ elements for the first Unicode character within the ‘altGlyph’ element sets a new relative X coordinate for the current text position before rendering the first alternate glyph.
Animatable: yes.
dy = "<list-of-lengths>": The corresponding relative Y coordinates for rendering the ‘altGlyph’ element.
Animatable: yes.
rotate = "<list-of-numbers>": The <number> values are processed in the same manner as the ‘rotate’ attribute on the ‘tspan’ element, with the following exception: If the referenced alternate glyphs are rendered instead of the Unicode characters inside the ‘altGlyph’ element, then any supplemental rotation values specified via an ‘rotate’ attribute on this element or any ancestor ‘text’ or ‘tspan’ elements for Unicode characters 2 through n within the ‘altGlyph’ element are ignored. Supplemental rotation values specified via an ‘rotate’ attribute on this element or any ancestor ‘text’ or ‘tspan’ elements for the first Unicode character within the ‘altGlyph’ element sets a new supplemental rotation angle before rendering the alternate glyphs.
Animatable: yes (non-additive).

If the references to alternate glyphs do not result in successful identification of alternate glyphs to use, then the character(s) that are inside of the ‘altGlyph’ element are rendered as if the ‘altGlyph’ element were a ‘tspan’ element instead.

An ‘altGlyph’ element either references a ‘glyph’ element or an ‘altGlyphDef’ element via its ‘xlink:href’ attribute or identifies a glyph by means of font selection properties, a glyph identifier and a font format. If the ‘xlink:href’ attribute is specified, it takes precedence, and the other glyph identification attributes and properties are ignored.

10.14.2. The ‘altGlyphDef’, ‘altGlyphItem’ and ‘glyphRef’ elements

The ‘altGlyphDef’ element defines a set of possible glyph substitutions.

‘altGlyphDef’

Categories:

None

Content model:

Either:

one or more ‘glyphRef’ elements, or
one or more ‘altGlyphItem’ elements.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’

DOM Interfaces:

SVGAltGlyphDefElement

An ‘altGlyphDef’ can contain either of the following:

In the simplest case, an ‘altGlyphDef’ contains one or more ‘glyphRef’ elements. Each ‘glyphRef’ element references a single glyph within a particular font. If all of the referenced glyphs are available, then these glyphs are rendered instead of the character(s) inside of the referencing ‘altGlyph’ element. If any of the referenced glyphs are unavailable, then the character(s) that are inside of the ‘altGlyph’ element are rendered as if there were not an ‘altGlyph’ element surrounding those characters.
In the more complex case, an ‘altGlyphDef’ contains one or more ‘altGlyphItem’ elements. Each ‘altGlyphItem’ represents a candidate set of substitute glyphs. Each ‘altGlyphItem’ contains one or more ‘glyphRef’ elements. Each ‘glyphRef’ element references a single glyph within a particular font. The first ‘altGlyphItem’ in which all referenced glyphs are available is chosen. The glyphs referenced from this ‘altGlyphItem’ are rendered instead of the character(s) that are inside of the referencing ‘altGlyph’ element. If none of the ‘altGlyphItem’ elements result in a successful match (i.e., none of the ‘altGlyphItem’ elements has all of its referenced glyphs available), then the character(s) that are inside of the ‘altGlyph’ element are rendered as if there were not an ‘altGlyph’ element surrounding those characters.

The ‘altGlyphItem’ element defines a candidate set of possible glyph substitutions. The first ‘altGlyphItem’ element whose referenced glyphs are all available is chosen. Its glyphs are rendered instead of the character(s) that are inside of the referencing ‘altGlyph’ element.

‘altGlyphItem’

Categories:

None

Content model:

One or more ‘glyphRef’ elements.

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’

DOM Interfaces:

SVGAltGlyphItemElement

The ‘glyphRef’ element defines a possible glyph to use.

‘glyphRef’

Categories:

None

Content model:

Empty.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
style attributes — ‘class’, ‘style’
presentation attributes —
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘x’
‘y’
‘dx’
‘dy’
‘glyphRef’
‘format’
‘xlink:href’

DOM Interfaces:

SVGGlyphRefElement

Attribute definitions:

xlink:href = "<iri>": An IRI reference to a ‘glyph’ element in an SVG document fragment. The referenced ‘glyph’ is rendered as an alternate glyph.
Animatable: no.
glyphRef = "<string>": The glyph identifier, the format of which is dependent on the ‘format’ of the given font.
Animatable: no.
format = "<string>": The format of the given font. If the font is in one of the formats listed in CSS2, such as TrueDoc™ Portable Font Resource or Embedded OpenType, then the <string> must contain the corresponding font format string, such as truedoc-pfr or embedded-opentype. This refers to CSS 2; it needs to be reviewed against the formats described by CSS3 Fonts.
Animatable: no.
x = "<number>": This value represents the new absolute X coordinate within the font's coordinate system for this glyph.
The font coordinate system is based on the em square model described in the Fonts chapter of CSS2. CSS3 Fonts doesn't talk about the em square much.
If the attribute is not specified, for the first ‘glyphRef’ child element, the effect is as if the attribute were set to "0", whereas for subsequent ‘glyphRef’ child elements, the effect is as if the attribute were set to the end X coordinate from the previous ‘glyphRef’ element.
Animatable: no.
y = "<number>": The corresponding new absolute Y coordinate within the font's coordinate system for this glyph.
Animatable: no.
dx = "<number>": This value represents the relative X coordinate within the font's coordinate system for this glyph. The glyph is thus shifted by <number> units along the positive X axis within the font's coordinate system supplemental to the absolute X coordinate established by the ‘x’ attribute (either due to an explicit ‘x’ attribute or due to default value processing for the ‘x’ attribute).
The font coordinate system is based on the em square model described in the Fonts chapter of CSS2. CSS3 Fonts doesn't talk about the em square much.
If the attribute is not specified, the effect is as if the attribute were set to "0".
Animatable: no.
dy = "<number>": The corresponding number of units within the font's coordinate system to shift the glyph along the positive Y axis relative to the absolute Y coordinate established by the ‘y’ attribute.
Animatable: no.

A ‘glyphRef’ either references a ‘glyph’ element in an SVG document fragment via its ‘xlink:href’ attribute or identifies a glyph by means of font selection properties, a glyph identifier and a font format. If insufficient attributes and properties have been specified to identify a glyph, then the ‘glyphRef’ is processed in the same manner as when a glyph reference is fully specified, but the given glyph is not available. If the ‘xlink:href’ attribute is specified, it takes precedence, and the other glyph identification attributes and properties are ignored.

10.15. White space handling

New in SVG 2. Added ‘white-space’ to allow a more useful way to control whitespace handling. Aligns SVG and HTML/CSS text processing. ‘xml:space’ deprecated in new content, retained for backwards compatibility.

10.15.1. SVG 2 Preferred white space handling

Rendering of white space in SVG 2 is controlled by the ‘white-space’ property. This specifies two things:

whether and how white space inside the element is collapsed
whether lines may wrap at unforced soft wrap opportunities

Name:	white-space
Value:	normal \| pre \| nowrap \| pre-wrap \| pre-line
Initial:	not defined for shorthand properties
Applies to:	text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	see individual properties
Animatable:	yes

Values and their meanings are defined in [CSS3 Text].

10.15.2. Legacy whitespace handling

For compatibility, SVG 2 also supports the XML attribute ‘xml:space’ to specify the handling of white space characters within a given ‘text’ element's character data. New content should not use ‘xml:space’ but instead, use the ‘white-space’ property.

Note that any child element of a ‘text’ element may also have an ‘xml:space’ attribute which will apply to that child element's text content. The SVG user agent has special processing rules associated with this attribute as described below. These are behaviors that occur subsequent to XML parsing [XML10] and any construction of a DOM.

‘xml:space’ is an inheritable attribute which can have one of two values:

'default': (The initial/default value for ‘xml:space’.) When xml:space="default", the SVG user agent will do the following using a copy of the original character data content. First, it will remove all newline characters. Then it will convert all tab characters into space characters. Then, it will strip off all leading and trailing space characters. Then, all contiguous space characters will be consolidated.
'preserve': When xml:space="preserve", the SVG user agent will do the following using a copy of the original character data content. It will convert all newline and tab characters into space characters. Then, it will draw all space characters, including leading, trailing and multiple contiguous space characters. Thus, when drawn with xml:space="preserve", the string "a b" (three spaces between "a" and "b") will produce a larger separation between "a" and "b" than "a b" (one space between "a" and "b").

The following example illustrates that line indentation can be important when using xml:space="default". The fragment below show two pairs of similar ‘text’ elements, with both ‘text’ elements using xml:space="default". For these examples, there is no extra white space at the end of any of the lines (i.e., the line break occurs immediately after the last visible character).

[01]  <text xml:space='default'>
[02]    WS example
[03]    indented lines
[04]  </text>
[05]  <text xml:space='preserve'>WS example indented lines</text>
[06]
[07]  <text xml:space='default'>
[08]WS example
[09]non-indented lines
[10]  </text>
[11]  <text xml:space='preserve'>WS examplenon-indented lines</text>

The first pair of ‘text’ elements above show the effect of indented character data. The attribute xml:space="default" in the first ‘text’ element instructs the user agent to:

convert all tabs (if any) to space characters,
strip out all line breaks (i.e., strip out the line breaks at the end of lines [01], [02] and [03]),
strip out all leading space characters (i.e., strip out space characters before "WS example" on line [02]),
strip out all trailing space characters (i.e., strip out space characters before "</text>" on line [04]),
consolidate all intermediate space characters (i.e., the space characters before "indented lines" on line [03]) into a single space character.

The second pair of ‘text’ elements above show the effect of non-indented character data. The attribute xml:space="default" in the third ‘text’ element instructs the user agent to:

convert all tabs (if any) to space characters,
strip out all line breaks (i.e., strip out the line breaks at the end of lines [07], [08] and [09]),
strip out all leading space characters (there are no leading space characters in this example),
strip out all trailing space characters (i.e., strip out space characters before "</text>" on line [10]),
consolidate all intermediate space characters into a single space character (in this example, there are no intermediate space characters).

Note that XML parsers are required to convert the standard representations for a newline indicator (e.g., the literal two-character sequence "#xD#xA" or the stand-alone literals #xD or #xA) into the single character #xA before passing character data to the application. Thus, each newline in SVG will be represented by the single character #xA, no matter what representation for newlines might have been used in the original resource. (See XML end-of-line handling.)

Any features in the SVG language or the SVG DOM that are based on character position number, such as the ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ attributes on the ‘text’, ‘tspan’, ‘tref’ and ‘altGlyph’ elements, are based on character position after applying the white space handling rules described here. In particular, if xml:space="default", it is often the case that white space characters are removed as part of processing. Character position numbers index into the text string after the white space characters have been removed per the rules in this section.

Note that a glyph corresponding to a whitespace character should only be displayed as a visible but blank space, even if the glyph itself happens to be non-blank. See display of unsupported characters [UNICODE].

The ‘xml:space’ attribute is:

Animatable: no.

10.15.3. Duplicate whitespace directives

Older, SVG 1.1 content will use ‘xml:space’. New content, and older content that is being reworked, will use ‘white-space’ and remove any existing ‘xml:space’. However, user agents may come across content which uses both methods on the same element. If the ‘white-space’ property is set on any element, then the value of ‘xml:space’ is ignored.

10.16. Text selection and clipboard operations

Conforming SVG viewers on systems which have the capacity for text selection (e.g., systems which are equipped with a pointer device such as a mouse) and which have system clipboards for copy/paste operations are required to support:

user selection of text strings in SVG content
the ability to copy selected text strings to the system clipboard

A text selection operation starts when all of the following occur:

the user positions the pointing device over a glyph that has been rendered as part of a ‘text’ element, initiates a select operation (e.g., pressing the standard system mouse button for select operations) and then moves the pointing device while continuing the select operation (e.g., continuing to press the standard system mouse button for select operations)
no other visible graphics element has been painted above the glyph at the point at which the pointing device was clicked
no links or events have been assigned to the ‘text’, ‘tspan’ or ‘textPath’ element(s) (or their ancestors) associated with the given glyph.

As the text selection operation proceeds (e.g., the user continues to press the given mouse button), all associated events with other graphics elements are ignored (i.e., the text selection operation is modal) and the SVG user agent shall dynamically indicate which characters are selected by an appropriate highlighting technique, such as redrawing the selected glyphs with inverse colors. As the pointer is moved during the text selection process, the end glyph for the text selection operation is the glyph within the same ‘text’ element whose glyph cell is closest to the pointer. All characters within the ‘text’ element whose position within the ‘text’ element is between the start of selection and end of selection shall be highlighted, regardless of position on the canvas and regardless of any graphics elements that might be above the end of selection point.

Once the text selection operation ends (e.g., the user releases the given mouse button), the selected text will stay highlighted until an event occurs which cancels text selection, such as a pointer device activation event (e.g., pressing a mouse button).

Detailed rules for determining which characters to highlight during a text selection operation are provided in Text selection implementation notes.

For systems which have system clipboards, the SVG user agent is required to provide a user interface for initiating a copy of the currently selected text to the system clipboard. It is sufficient for the SVG user agent to post the selected text string in the system's appropriate clipboard format for plain text, but it is preferable if the SVG user agent also posts a rich text alternative which captures the various font properties associated with the given text string.

For bidirectional text, the user agent must support text selection in logical order, which will result in discontinuous highlighting of glyphs due to the bidirectional reordering of characters. User agents can provide an alternative ability to select bidirectional text in visual rendering order (i.e., after bidirectional text layout algorithms have been applied), with the result that selected character data might be discontinuous logically. In this case, if the user requests that bidirectional text be copied to the clipboard, then the user agent is required to make appropriate adjustments to copy only the visually selected characters to the clipboard.

When feasible, it is recommended that generators of SVG attempt to order their text strings to facilitate properly ordered text selection within SVG viewing applications such as Web browsers.

10.17. DOM interfaces

10.17.1. Interface SVGTextContentElement

The SVGTextContentElement is inherited by various text-related interfaces, such as SVGTextElement, SVGTSpanElement, SVGTRefElement, SVGAltGlyphElement and SVGTextPathElement.

For the methods on this interface that refer to an index to a character or a number of characters, these references are to be interpreted as an index to a UTF-16 code unit or a number of UTF-16 code units, respectively. This is for consistency with DOM Level 2 Core, where methods on the CharacterData interface use UTF-16 code units as indexes and counts within the character data. Thus for example, if the text content of a ‘text’ element is a single non-BMP character, such as U+10000, then invoking getNumberOfChars on that element will return 2 since there are two UTF-16 code units (the surrogate pair) used to represent that one character.

interface SVGTextContentElement : SVGGraphicsElement {

  // lengthAdjust Types
  const unsigned short LENGTHADJUST_UNKNOWN = 0;
  const unsigned short LENGTHADJUST_SPACING = 1;
  const unsigned short LENGTHADJUST_SPACINGANDGLYPHS = 2;

  readonly attribute SVGAnimatedLength textLength;
  readonly attribute SVGAnimatedEnumeration lengthAdjust;

  long getNumberOfChars();
  float getComputedTextLength();
  float getSubStringLength(unsigned long charnum, unsigned long nchars);
  SVGPoint getStartPositionOfChar(unsigned long charnum);
  SVGPoint getEndPositionOfChar(unsigned long charnum);
  SVGRect getExtentOfChar(unsigned long charnum);
  float getRotationOfChar(unsigned long charnum);
  long getCharNumAtPosition(SVGPoint point);
  void selectSubString(unsigned long charnum, unsigned long nchars);
};

Constants in group “lengthAdjust Types”:

LENGTHADJUST_UNKNOWN (unsigned short): The enumeration was set to a value that is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
LENGTHADJUST_SPACING (unsigned short): Corresponds to value 'spacing'.
LENGTHADJUST_SPACINGANDGLYPHS (unsigned short): Corresponds to value 'spacingAndGlyphs'.

Attributes:

textLength (readonly SVGAnimatedLength): Corresponds to attribute ‘textLength’ on the given element.
lengthAdjust (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘lengthAdjust’ on the given element. The value must be one of the length adjust constants defined on this interface.

Operations:

long getNumberOfChars()

Returns the total number of characters available for rendering within the current element, which includes referenced characters from ‘tref’ reference, regardless of whether they will be rendered. Effectively, this is equivalent to the length of the Node::textContent attribute from DOM4 ([DOM4], section 5.3), if that attribute also expanded ‘tref’ elements.

Returns: Total number of characters.

float getComputedTextLength()

The total sum of all of the advance values from rendering all of the characters within this element, including the advance value on the glyphs (horizontal or vertical), the effect of properties ‘letter-spacing’ and ‘word-spacing’ and adjustments due to attributes ‘dx’ and ‘dy’ on ‘tspan’ elements. For non-rendering environments, the user agent shall make reasonable assumptions about glyph metrics.

Returns: The text advance distance.

float getSubStringLength(unsigned long charnum, unsigned long nchars)

The total sum of all of the advance values from rendering the specified substring of the characters, including the advance value on the glyphs (horizontal or vertical), the effect of properties ‘letter-spacing’ and ‘word-spacing’ and adjustments due to attributes ‘dx’ and ‘dy’ on ‘tspan’ elements. For non-rendering environments, the user agent shall make reasonable assumptions about glyph metrics. If multiple consecutive characters are rendered inseparably (e.g., as a single glyph or a sequence of glyphs, or because the range encompasses half of a surrogate pair), and nchars is greater than 0 then the measured range shall be expanded so that each of the inseparable characters are included.

Parameters

unsigned long charnum

The index of the first character in the substring, where the first character has an index of 0.
unsigned long nchars

The number of characters in the substring. If nchars specifies more characters than are available, then the substring will consist of all characters starting with charnum until the end of the list of characters.

Returns

The text advance distance.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if charnum or nchars is negative or if charnum is greater than or equal to the number of characters at this node.

SVGPoint getStartPositionOfChar(unsigned long charnum)

Returns the current text position before rendering the character in the user coordinate system for rendering the glyph(s) that correspond to the specified character. The current text position has already taken into account the effects of any inter-character adjustments due to properties ‘letter-spacing’ and ‘word-spacing’ and adjustments due to attributes ‘x’, ‘y’, ‘dx’ and ‘dy’. If multiple consecutive characters are rendered inseparably (e.g., as a single glyph or a sequence of glyphs), then each of the inseparable characters will return the start position for the first glyph.

Parameters

unsigned long charnum

The index of the character, where the first character has an index of 0.

Returns

The character's start position.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if the charnum is negative or if charnum is greater than or equal to the number of characters at this node.

SVGPoint getEndPositionOfChar(unsigned long charnum)

Returns the current text position after rendering the character in the user coordinate system for rendering the glyph(s) that correspond to the specified character. This current text position does not take into account the effects of any inter-character adjustments to prepare for the next character, such as properties ‘letter-spacing’ and ‘word-spacing’ and adjustments due to attributes ‘x’, ‘y’, ‘dx’ and ‘dy’. If multiple consecutive characters are rendered inseparably (e.g., as a single glyph or a sequence of glyphs), then each of the inseparable characters will return the end position for the last glyph.

Parameters

unsigned long charnum

The index of the character, where the first character has an index of 0.

Returns

The character's end position.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if the charnum is negative or if charnum is greater than or equal to the number of characters at this node.

SVGRect getExtentOfChar(unsigned long charnum)

Returns a tightest rectangle which defines the minimum and maximum X and Y values in the user coordinate system for rendering the glyph(s) that correspond to the specified character. The calculations assume that all glyphs occupy the full standard glyph cell for the font. If multiple consecutive characters are rendered inseparably (e.g., as a single glyph or a sequence of glyphs), then each of the inseparable characters will return the same extent.

Parameters

unsigned long charnum

The index of the character, where the first character has an index of 0.

Returns

The rectangle which encloses all of the rendered glyph(s).

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if the charnum is negative or if charnum is greater than or equal to the number of characters at this node.

float getRotationOfChar(unsigned long charnum)

Returns the rotation value relative to the current user coordinate system used to render the glyph(s) corresponding to the specified character. If multiple glyph(s) are used to render the given character and the glyphs each have different rotations (e.g., due to text-on-a-path), the user agent shall return an average value (e.g., the rotation angle at the midpoint along the path for all glyphs used to render this character). The rotation value represents the rotation that is supplemental to any rotation due to properties ‘glyph-orientation-horizontal’ and ‘glyph-orientation-vertical’; thus, any glyph rotations due to these properties are not included into the returned rotation value. If multiple consecutive characters are rendered inseparably (e.g., as a single glyph or a sequence of glyphs), then each of the inseparable characters will return the same rotation value.

Parameters

unsigned long charnum

The index of the character, where the first character has an index of 0.

Returns

The rotation angle.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if the charnum is negative or if charnum is greater than or equal to the number of characters at this node.

long getCharNumAtPosition(SVGPoint point)

Returns the index of the character whose corresponding glyph cell bounding box contains the specified point. The calculations assume that all glyphs occupy the full standard glyph cell for the font. If no such character exists, a value of -1 is returned. If multiple such characters exist, the character within the element whose glyphs were rendered last (i.e., take into account any reordering such as for bidirectional text) is used. If multiple consecutive characters are rendered inseparably (e.g., as a single glyph or a sequence of glyphs), then the user agent shall allocate an equal percentage of the text advance amount to each of the contributing characters in determining which of the characters is chosen.

Parameters

SVGPoint point

A point in user space.

Returns

The index of the character which is at the given point, where the first character has an index of 0.

void selectSubString(unsigned long charnum, unsigned long nchars)

Causes the specified substring to be selected just as if the user selected the substring interactively.

Parameters

unsigned long charnum

The index of the start character which is at the given point, where the first character has an index of 0.
unsigned long nchars

The number of characters in the substring. If nchars specifies more characters than are available, then the substring will consist of all characters starting with charnum until the end of the list of characters.

Exceptions

DOMException, code INDEX_SIZE_ERR: Raised if charnum or nchars is negative or if charnum is greater than or equal to the number of characters at this node.

10.17.2. Interface SVGTextPositioningElement

The SVGTextPositioningElement interface is inherited by text-related interfaces: SVGTextElement, SVGTSpanElement, SVGTRefElement and SVGAltGlyphElement.

interface SVGTextPositioningElement : SVGTextContentElement {
  readonly attribute SVGAnimatedLengthList x;
  readonly attribute SVGAnimatedLengthList y;
  readonly attribute SVGAnimatedLengthList dx;
  readonly attribute SVGAnimatedLengthList dy;
  readonly attribute SVGAnimatedNumberList rotate;
};

Attributes:

x (readonly SVGAnimatedLengthList): Corresponds to attribute ‘x’ on the given element.
y (readonly SVGAnimatedLengthList): Corresponds to attribute ‘y’ on the given element.
dx (readonly SVGAnimatedLengthList): Corresponds to attribute ‘dx’ on the given element.
dy (readonly SVGAnimatedLengthList): Corresponds to attribute ‘dy’ on the given element.
rotate (readonly SVGAnimatedNumberList): Corresponds to attribute ‘rotate’ on the given element.

10.17.3. Interface SVGTextElement

The SVGTextElement interface corresponds to the ‘text’ element.

interface SVGTextElement : SVGTextPositioningElement {
};

10.17.4. Interface SVGTSpanElement

The SVGTSpanElement interface corresponds to the ‘tspan’ element.

interface SVGTSpanElement : SVGTextPositioningElement {
};

10.17.5. Interface SVGTRefElement

The SVGTRefElement interface corresponds to the ‘tref’ element.

interface SVGTRefElement : SVGTextPositioningElement {
};

SVGTRefElement implements SVGURIReference;

10.17.6. Interface SVGTextPathElement

The SVGTextPathElement interface corresponds to the ‘textPath’ element.

interface SVGTextPathElement : SVGTextContentElement {

  // textPath Method Types
  const unsigned short TEXTPATH_METHODTYPE_UNKNOWN = 0;
  const unsigned short TEXTPATH_METHODTYPE_ALIGN = 1;
  const unsigned short TEXTPATH_METHODTYPE_STRETCH = 2;

  // textPath Spacing Types
  const unsigned short TEXTPATH_SPACINGTYPE_UNKNOWN = 0;
  const unsigned short TEXTPATH_SPACINGTYPE_AUTO = 1;
  const unsigned short TEXTPATH_SPACINGTYPE_EXACT = 2;

  readonly attribute SVGAnimatedLength startOffset;
  readonly attribute SVGAnimatedEnumeration method;
  readonly attribute SVGAnimatedEnumeration spacing;
};

SVGTextPathElement implements SVGURIReference;
SVGTextPathElement implements SVGAnimatedPathData;

Constants in group “textPath Method Types”:

TEXTPATH_METHODTYPE_UNKNOWN (unsigned short): The enumeration was set to a value that is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
TEXTPATH_METHODTYPE_ALIGN (unsigned short): Corresponds to value 'align'.
TEXTPATH_METHODTYPE_STRETCH (unsigned short): Corresponds to value 'stretch'.

Constants in group “textPath Spacing Types”:

TEXTPATH_SPACINGTYPE_UNKNOWN (unsigned short): The enumeration was set to a value that is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
TEXTPATH_SPACINGTYPE_AUTO (unsigned short): Corresponds to value 'auto'.
TEXTPATH_SPACINGTYPE_EXACT (unsigned short): Corresponds to value 'exact'.

Attributes:

startOffset (readonly SVGAnimatedLength): Corresponds to attribute ‘startOffset’ on the given ‘textPath’ element.
method (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘method’ on the given ‘textPath’ element.
spacing (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘spacing’ on the given ‘textPath’ element.

10.17.7. Interface SVGAltGlyphElement

The SVGAltGlyphElement interface corresponds to the ‘altGlyph’ element.

interface SVGAltGlyphElement : SVGTextPositioningElement {
  attribute DOMString glyphRef;
  attribute DOMString format;
};

SVGAltGlyphElement implements SVGURIReference;

Attributes:

glyphRef (DOMString): Corresponds to attribute ‘glyphRef’ on the given element.
format (DOMString): Corresponds to attribute ‘format’ on the given element.

10.17.8. Interface SVGAltGlyphDefElement

The SVGAltGlyphDefElement interface corresponds to the ‘altGlyphDef’ element.

interface SVGAltGlyphDefElement : SVGElement {
};

10.17.9. Interface SVGAltGlyphItemElement

The SVGAltGlyphItemElement interface corresponds to the ‘altGlyphItem’ element.

interface SVGAltGlyphItemElement : SVGElement {
};

10.17.10. Interface SVGGlyphRefElement

The SVGGlyphRefElement interface corresponds to the ‘glyphRef’ element.

interface SVGGlyphRefElement : SVGElement {
  attribute DOMString glyphRef;
  attribute DOMString format;
  attribute float x;
  attribute float y;
  attribute float dx;
  attribute float dy;
};

SVGGlyphRefElement implements SVGURIReference;

Attributes:

glyphRef (DOMString): Corresponds to attribute ‘glyphRef’ on the given element.
format (DOMString): Corresponds to attribute ‘format’ on the given element.
x (float): Corresponds to attribute ‘x’ on the given element.
y (float): Corresponds to attribute ‘y’ on the given element.
dx (float): Corresponds to attribute ‘dx’ on the given element.
dy (float): Corresponds to attribute ‘dy’ on the given element.

Chapter 11: Painting: Filling, Stroking and Marker Symbols

11.1. Introduction

Graphical elements that define a shape – ‘path’ elements, basic shapes and text content elements – are rendered by being filled, which is painting the interior of the object, and stroked, which is painting along the outline of the object. Filling and stroking are both painting operations. SVG 2 supports a number of different paints that the fill and stroke of a graphical element can be painted with:

a single color
a gradient (linear, radial or mesh)
a pattern (vector or raster, possibly tiled)
other images as specified using CSS Image Value syntax [CSS3IMAGES]

The paint to use for filling and stroking an element is specified using the ‘fill’ and ‘stroke’ properties. The following section describes the different values that can be used for these properties.

Other properties, such as ‘fill-opacity’ and ‘stroke-width’, also have an effect on the way fill and stroke paint is applied to the canvas. The Fill properties and Stroke properties sections below describe these properties.

Certain elements – ‘path’, ‘polyline’, ‘polygon’ and ‘line’ elements – can also have marker symbols drawn at their vertices or at other positions along the path that they describe. The Markers section below describes how markers can be defined and used.

11.2. Specifying paint

SVG 2 Requirement:	Add new paint values for referencing current fill paint, stroke paint, etc.
Resolution:	We will add new paint values currentFillPaint, currentStrokePaint etc. to SVG 2
Purpose:	Among other things, to provide an easy way to match marker color to stroke color.
Owner:	Chris (ACTION-3094)

Properties ‘fill’ and ‘stroke’ take on a value of type <paint>:

<paint> =

Values have the following meaning:

none: Indicates that no paint is applied.
<color>: A solid color as defined in CSS Color Module Level 3. [CSS3COLOR] All forms of <color> defined by that specification are valid for use as a <paint> value. This includes the basic color keywords, RGB & RGBA color values, the transparent value, HSL & HSLA color values, the extended color keywords, the currentColor value, and the CSS2 UI colors. Note that when currentColor is used, it refers to the current animated value of the ‘color’ property.
<gradient>: A CSS gradient value as defined in CSS Image Values and Replaced Content Module Level 3. Percentage values are resolved against the bounding box of the element to which the gradient is applied.
<color>? <icccolor>: An ICC color [ICC42] with an optional sRGB fallback color if the ICC color cannot be used. The user agent searches the color profile description database for a color profile description entry whose name descriptor matches the <author-ident> part of the <icccolor> and uses the last matching entry that is found. If no match is found, then the sRGB fallback color is used instead, if provided; otherwise the document is in error (see Error processing). The comma and/or whitespace separated list of <number>s within the <icccolor> is a set of ICC-profile-specific color values. (In most cases, the <number>s will be in the range 0 to 1.) Note that color interpolation occurs in an RGB color space even if an ICC-based color specification is provided (see ‘color-interpolation’). For more on ICC-based colors, refer to Color profile descriptions.
[ <funciri> | child | <child-selector> ] [ none | <color> | [ <color>? <icccolor> ] ]?: A reference to a paint server element with an optional fallback color or none. The <funciri>, child keyword, or <child-selector> is used to identify a ‘solidColor’ element, gradient element or ‘pattern’ element, which defines the paint to use. The child keyword in this instance matches the last child paint server element of the element where the paint value is specified. If the reference is not valid (e.g., it points to an element that does not exist, no element was matched, or the element is not a valid paint server), then the fallback value is used, if provided; otherwise, the document is in error (see Error processing).
context-fill
context-stroke: The same paint as the computed value of the ‘fill’ or ‘stroke’ property, respectively, of the context element. If there is no context element, then no paint is applied. If the referenced paint is a gradient or a pattern, then the coordinate space to use and the object used for any 'objectBoundingBox'-relative values are the same as those of the context element.

11.3. Fill properties

11.3.1. Specifying fill paint: the ‘fill’ property

Name:	fill
Value:	<paint>
Initial:	black
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified, but with <color> values computed and <funciri> values made absolute
Animatable:	yes

The ‘fill’ property paints the interior of the given graphical element. The area to be painted consists of any areas inside the outline of the shape. To determine the inside of the shape, all subpaths are considered, and the interior is determined according to the rules associated with the current value of the ‘fill-rule’ property. The zero-width geometric outline of a shape is included in the area to be painted.

The fill operation fills open subpaths by performing the fill operation as if an additional "closepath" command were added to the path to connect the last point of the subpath with the first point of the subpath. Thus, fill operations apply to both open subpaths within ‘path’ elements (i.e., subpaths without a closepath command) and ‘polyline’ elements.

11.3.2. Winding rule: the ‘fill-rule’ property

Name:	fill-rule
Value:	nonzero \| evenodd
Initial:	nonzero
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

The ‘fill-rule’ property indicates the algorithm (or winding rule) which is to be used to determine what parts of the canvas are included inside the shape. For a simple, non-intersecting path, it is intuitively clear what region lies "inside"; however, for a more complex path, such as a path that intersects itself or where one subpath encloses another, the interpretation of "inside" is not so obvious.

The ‘fill-rule’ property provides two options for how the inside of a shape is determined:

nonzero: This rule determines the "insideness" of a point on the canvas by drawing a ray from that point to infinity in any direction and then examining the places where a segment of the shape crosses the ray. Starting with a count of zero, add one each time a path segment crosses the ray from left to right and subtract one each time a path segment crosses the ray from right to left. After counting the crossings, if the result is zero then the point is outside the path. Otherwise, it is inside. The following drawing illustrates the nonzero rule:

The effect of a nonzero fill rule on paths with self-intersections and enclosed subpaths.
evenodd: This rule determines the "insideness" of a point on the canvas by drawing a ray from that point to infinity in any direction and counting the number of path segments from the given shape that the ray crosses. If this number is odd, the point is inside; if even, the point is outside. The following drawing illustrates the evenodd rule:

The effect of an evenodd fill rule on paths with self-intersections and enclosed subpaths.

The above descriptions do not specify what to do if a path segment coincides with or is tangent to the ray. Since any ray will do, one may simply choose a different ray that does not have such problem intersections.

11.3.3. Fill paint opacity: the ‘fill-opacity’ property

Name:	fill-opacity
Value:	<number>
Initial:	1
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified, but clamped to the range [0, 1]
Animatable:	yes

‘fill-opacity’ specifies the opacity of the painting operation used to paint the interior the current object. (See Painting shapes and text.) A value of 0 means fully transparent, and a value of 1 means fully opaque.

See also the ‘opacity’ property, which specifies group opacity.

11.4. Stroke properties

SVG 2 Requirement:	Support non-scaling stroke.
Resolutions:	SVG 2 will include non-scaling stroke. SVG 2 will have the ‘vector-effect’ property.
Purpose:	To support strokes whose width does not change when zooming a page, as common for example in maps.
Owner:	Chris or Erik (no action)
Note:	Note that this could be part of more generic non-scaling features.

The following are the properties which affect how an element is stroked.

In all cases, all stroking properties which are affected by directionality, such as those having to do with dash patterns, must be rendered such that the stroke operation starts at the same point at which the graphics element starts. In particular, for ‘path’ elements, the start of the path is the first point of the initial "moveto" command.

For stroking properties such as dash patterns whose computations are dependent on progress along the outline of the graphics element, distance calculations are required to utilize the SVG user agent's standard Distance along a path algorithms.

When stroking is performed using a complex paint server, such as a gradient or a pattern, the stroke operation must be identical to the result that would have occurred if the geometric shape defined by the geometry of the current graphics element and its associated stroking properties were converted to an equivalent ‘path’ element and then filled using the given paint server.

11.4.1. Specifying stroke paint: the ‘stroke’ property

Name:	stroke
Value:	<paint>
Initial:	none
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified, but with <color> values computed and <funciri> values made absolute
Animatable:	yes

The ‘stroke’ property paints along the outline of the given graphical element.

A subpath (see Paths) consisting of a single moveto shall not be stroked. Any zero length subpath shall not be stroked if the ‘stroke-linecap’ property has a value of butt but shall be stroked if the ‘stroke-linecap’ property has a value of round or square, producing respectively a circle or a square centered at the given point. Examples of zero length subpaths include 'M 10,10 L 10,10', 'M 20,20 h 0', 'M 30,30 z' and 'M 40,40 c 0,0 0,0 0,0'.

SVG 2 Requirement:	Include a way to specify stroke position.
Resolution:	SVG 2 shall include a way to specify stroke position.
Purpose:	To allow a stroke to be inside or outside the path.
Owner:	Cameron (ACTION-3162)
Note:	See proposal page.

SVG 2 Requirement:	Allow more author control over positions of dashes.
Resolution:	SVG 2 shall allow more author control over positions of dashes.
Purpose:	To allow things like aligning dashes at rectangle corners or along paths, needed for mapping.
Owner:	Cameron (ACTION-3163)
Note:	See proposal page.

11.4.2. Stroke paint opacity: the ‘stroke-opacity’ property

Name:	stroke-opacity
Value:	<number>
Initial:	1
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified, but clamped to the range [0, 1]
Animatable:	yes

The ‘stroke-opacity’ property specifies the opacity of the painting operation used to stroke the current object. (See Painting shapes and text.) As with ‘fill-opacity’, a value of 0 means fully transparent, and a value of 1 means fully opaque.

See also the ‘opacity’ property, which specifies group opacity.

11.4.3. Stroke width: the ‘stroke-width’ property

Name:	stroke-width
Value:	<percentage> \| <length>
Initial:	1
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	refer to the size of the current viewport (see Units)
Media:	visual
Computed value:	as specified
Animatable:	yes

This property specifies the width of the stroke on the current object. A zero value causes no stroke to be painted. A negative value is invalid.

11.4.4. Drawing caps at the ends of strokes: the ‘stroke-linecap’ property

Name:	stroke-linecap
Value:	butt \| round \| square
Initial:	butt
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

‘stroke-linecap’ specifies the shape to be used at the end of open subpaths when they are stroked. The possible values are:

butt: This value indicates that the stroke for each subpath does not extend beyond its two endpoints. A zero length subpath will therefore not have any stroke.
round: This value indicates that at each end of each subpath, the shape representing the stroke will be extended by a half circle with a radius equal to the stroke width. If a subpath has zero length, then the resulting effect is that the stroke for that subpath consists solely of a full circle centered at the subpath's point.
square: This value indicates that at the end of each subpath, the shape representing the stroke will be extended by a rectangle with the same width as the stroke width and whose length is half of the stroke width. If a subpath has zero length, then the resulting effect is that the stroke for that subpath consists solely of a square with side length equal to the stroke width, centered at the subpath's point, and oriented such that two of its sides are parallel to the effective tangent at that subpath's point. See ‘path’ element implementation notes for details on how to determine the tangent at a zero-length subpath.

Image showing three paths, each with a different line cap.

The three types of line caps.

See the definition of the cap shape below for a more precise description of the shape a line cap will have.

11.4.5. Controlling line joins: the ‘stroke-linejoin’ and ‘stroke-miterlimit’ properties

Name:	stroke-linejoin
Value:	miter \| round \| bevel \| arcs
Initial:	miter
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

‘stroke-linejoin’ specifies the shape to be used at the corners of paths or basic shapes when they are stroked. For further details see the path implementation notes.

miter: This value indicates that a sharp corner is to be used to join path segments. The corner is formed by extending the outer edges of the stroke at the tangents of the path segments until they intersect.
round: This value indicates that a round corner is to be used to join path segments. The corner is a circular sector centered on the join point.
bevel: This value indicates that a bevelled corner is to be used to join path segments. The bevel shape is a triangle that fills the area between the two stroked segments.
arcs: This value indicates that an arcs corner is to be used to join path segments. The arcs shape is formed by extending the outer edges of the stroke at the join point with arcs that have the same curvature as the outer edges at the join point.

Is there a better name than arcs for this property value? I (Tav) prefer talon (as in bird claw). The term arc has other uses in SVG and in graphics in general. The term talon would be unique as well as fit in with the existing property value names for line-join.

How does the miter limit apply? (It's hard to get really long joins.) Do you fall back to miter or bevel? (Probably miter as it is more in the style.)

The arcs value is new in SVG 2. It was added to provide a better looking join when the path segments at the join are curved.

Adding new line join was approved at Rigi Kaltbad group meeting.

Image showing four paths, each with a different line join.

The four types of line joins.

Name:	stroke-miterlimit
Value:	<number>
Initial:	4
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

When two line segments meet at a sharp angle and miter joins have been specified for ‘stroke-linejoin’, it is possible for the miter to extend far beyond the thickness of the line stroking the path. The ‘stroke-miterlimit’ imposes a limit on the ratio of the miter length to the ‘stroke-width’. When the limit is exceeded, the join is converted from a miter to a bevel.

How should this apply to arcs line-joins?

<number>: The limit on the ratio of the miter length to the ‘stroke-width’. The value of <miterlimit> must be a <number> greater than or equal to 1. Any other value is an error (see Error processing).

The ratio of miter length (distance between the outer tip and the inner corner of the miter) to ‘stroke-width’ is directly related to the angle θ between the segments in user space by the formula:

\frac{miterLength}{‘stroke-width’} = \frac{1}{\sin \frac{θ}{2}}

miterLength / stroke-width = 1 / sin(theta / 2)

For example, a miter limit of 1.414 converts miters to bevels for theta less than 90 degrees, a limit of 4.0 converts them for theta less than approximately 29 degrees, and a limit of 10.0 converts them for theta less than approximately 11.5 degrees.

See the definition of the line join shape below for a more precise description of the shape a line join will have.

11.4.6. Dashing strokes: the ‘stroke-dasharray’ and ‘stroke-dashoffset’ properties

Name:	stroke-dasharray
Value:	none \| <dasharray>
Initial:	none
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	refer to the size of the current viewport (see Units)
Media:	visual
Computed value:	as specified
Animatable:	yes (non-additive)

where:

<dasharray> = [ <length> | <percentage> ]#*

The ‘stroke-dasharray’ property controls the pattern of dashes and gaps used to form the shape of a path's stroke.

none

Indicates that no dashing is used.

<dasharray>

Specifies a dashing pattern to use. A <dasharray> is a list of comma and/or white space separated lengths and percentages. Each value specifies a length along the path for which the stroke is to be painted (a dash) and not painted (a gap). Every second value in the list beginning with the first one specifies the length of a dash, and every other value specifies the length of a gap between the dashes. If the list has an odd number of values, then it is repeated to yield an even number of values. (Thus, the rendering behavior of stroke-dasharray: 5,3,2 is equivalent to stroke-dasharray: 5,3,2,5,3,2.)

The resulting even-length dashing pattern is repeated along each subpath. The dashing pattern is reset and begins again at the start of each subpath.

If any value in the list is negative, the <dasharray> value is invalid. If all of the values in the list are zero, then the stroke is rendered as if a value of none were specified.

A dashed stroke. The dashing pattern is 20,10. The red line shows the actual path that is stroked.

Name:	stroke-dashoffset
Value:	<length> \| <percentage>
Initial:	0
Applies to:	shapes and text content elements
Inherited:	yes
Percentages:	refer to the size of the current viewport (see Units)
Media:	visual
Computed value:	as specified
Animatable:	yes

The ‘stroke-dashoffset’ property specifies the distance into the repeated dash pattern to start the stroke dashing at the beginning of the path. If the value is negative, then the effect is the same as dash offset d:

d = s - |‘stroke-dashoffset’| mod s

d = s - (abs(stroke-dashoffset) mod s)

where s is the sum of the dash array values.

Image showing a thick, dashed stroke with a non-zero dash offset.

A dashed stroke with a non-zero dash offset. The dashing pattern is 20,10 and the dash offset is 15. The red line shows the actual path that is stroked.

See the definition of dash positions below for a more precise description of positions along a path that dashes will be placed.

11.4.7. Computing the shape of the stroke

SVG 2 Requirement:	Specify stroke dashing more precisely.
Resolution:	SVG 2 shall specify stroke dashing more precisely.
Purpose:	To define dash starting point on basic shapes and path segments.
Owner:	Cameron (no action)

Something in this section needs to reference ‘pathLength’ so that dash lengths are in the author's path length space.

The following algorithm describes what the shape of a ‘path’ or basic shape's stroke is, taking into account the stroking properties above:

This should include text elements too, but should we keep stroke dashing on text?

Let shape be an empty shape.
Let path be the equivalent path of the element.
For each subpath of path:
1. Let positions be the dash positions for the subpath.
2. For each pair <start, end> in positions:
  1. Let dash be the shape that includes, for all distances between start and end along the subpath, all points that lie on the line perpendicular to the subpath at that distance and which are within distance ‘stroke-width’ of the point on the subpath at that position.
  2. Set dash to be the union of dash and the starting cap shape for the subpath at position start.
  3. Set dash to be the union of dash and the ending cap shape for the subpath at position end.
  4. Let index and last be the indexes of the path segments in the subpath at distance start and end along the subpath.
    It does not matter whether any zero length segments are included when choosing index and last.
  5. While index < last:
    1. Set dash to be the union of dash and the line join shape for the subpath at segment index index.
    2. Set index to index + 1.
  6. Set shape to be the union of shape and stroke.
Return shape.

The dash positions for a given subpath of the equivalent path of a ‘path’ or basic shape is a sequence of pairs of values, which represent the starting and ending distance along the subpath for each of the dashes that form the subpath's stroke. It is determined as follows:

Let pathlength be the length of the subpath.
Let dashes be the list of values of ‘stroke-dasharray’ on the element, converted to user units, repeated if necessary so that it has an even number of elements; if the property has the value none, then the list has a single value 0.
Let count be the number of values in dashes.
Let sum be the sum of the values in dashes.
If sum = 0, then return a sequence with the single pair <0, pathlength>.
Let positions be an empty sequence.
Let offset be the value of the ‘stroke-dashoffset’ property on the element.
If offset is negative, then set offset to sum − abs(offset).
Set offset to offset mod sum.
Let index be the smallest integer such that sum(dashes_i, 0 ≤ i ≤ index) ≥ offset.
Let dashlength be min(sum(dashes_i, 0 ≤ i ≤ index) − offset, pathlength).
If index mod 2 = 0, then append to positions the pair <0, dashlength>.
Let position be dashlength.
While position < pathlength:
1. Set index to (index + 1) mod count.
2. Let dashlength be min(dashes_index, pathlength − position).
3. If index mod 2 = 0, then append to positions the pair <position, position + dashlength>.
4. Set position to position + dashlength.
Return positions.

The starting and ending cap shapes at a given position along a subpath are determined as follows:

If ‘stroke-linecap’ is butt, then return an empty shape.
Otherwise, if ‘stroke-linecap’ is round, then:
1. If this is a starting cap, then return a semicircle of radius ‘stroke-width’ positioned such that:
  - Its straight edge is parallel to the line perpendicular to the subpath at distance position along it.
  - The midpoint of its straight edge is at the point that is along the subpath at distance position.
  - The direction from the midpoint of its arc to the midpoint of its straight edge is the same as the direction of the subpath at distance position along it.
2. Otherwise, this is an ending cap. Return a semicircle of radius ‘stroke-width’ positioned such that:
  - Its straight edge is parallel to the line perpendicular to the subpath at distance position along it.
  - The midpoint of its straight edge is at the point that is along the subpath at distance position.
  - The direction from the midpoint of its straight edge to the midpoint of its arc is the same as the direction of the subpath at distance position along it.
Otherwise, ‘stroke-linecap’ is square:
1. If this is a starting cap, then return a rectangle with side lengths ‘stroke-width’ and ‘stroke-width’ / 2 positioned such that:
  - Its longer edges, A and B, are parallel to the line perpendicular to the subpath at distance position along it.
  - The midpoint of A is at start.
  - The direction from the midpoint of B to the midpoint of A is the same as the direction of the subpath at distance position along it.
2. Otherwise, this is an ending cap. Return a rectangle with side lengths ‘stroke-width’ and ‘stroke-width’ / 2 positioned such that:
  - Its longer edges, A and B, are parallel to the line perpendicular to the subpath at distance position along it.
  - The midpoint of A is at end.
  - The direction from the midpoint of A to the midpoint of B is the same as the direction of the subpath at distance position along it.

Image showing how to construct the three types of line caps

The three different ‘stroke-linecap’ values used on paths with a single, non-zero length subpath. The white line is the path itself and the thick gray area is the stroke. On the top row, the green lines indicate the perpendicular to the tangent at the path endpoints and the pink areas are the caps. The bottom row shows the stroke without the perpendicular and cap highlighting.

The line join shape for a given segment of a subpath is determined as follows:

Let P be the point at the end of the segment.
Let A be the line parallel to the tangent at the end of the segment.
Let B be the line parallel to the tangent at the start of the following segment.
If A and B are the same line, then return an empty shape.
Let A_left and A_right be lines parallel to A at a distance of ‘stroke-width’ / 2 to the left and to the right of A, respectively.
Let B_left and B_right be lines parallel to B at a distance of ‘stroke-width’ / 2 to the left and to the right of B, respectively.
Let P₁, P₂ and P₃ be points determined as follows:
1. If the acute angle between A and B is on the right of these lines, considering the direction of the subpath, then P₁ and P₂ are the points on A_left and B_left closest to P, and P₃ is the intersection of A_left and B_left.
2. Otherwise, P₁ and P₂ are the points on A_right and B_right closest to P, and P₃ is the intersection of A_right and B_right.
Let bevel be the triangle formed from the three points P, P₁ and P₂.
If ‘stroke-linejoin’ is round, then return the union of bevel and a circular sector of radius ‘stroke-width’, centered on P, and which has P₁ and P₂ as the two endpoints of the arc.
If ‘stroke-linejoin’ is arcs, then find the circles that are tangent to the stroke edges at P₁ and P₂ with the same curvature as the edges at those points (see below). If both curvatures are zero fall through to miter. Extend the stroke edges using these circles (or a line, in the case of zero curvature). If the two circles (or circle and line) intersect, return the area inside the region defined by the lines that connect P with P₁ and P₂ and the arcs defined by the circles (or arc and line) between the closest intersection point to P, and P₁ and P₂. If the two circles (or circle and line) do not intersect, fall through to miter. Note that the curvatures are calculated in user-space before any transforms are applied.
Let θ be the angle between A and B.
If ‘stroke-linejoin’ is miter and 1 / sin(θ / 2) ≤ ‘stroke-miterlimit’, then return the union of bevel and the triangle formed from the three points P₁, P₂ and P₃.
Return bevel.

Image showing the lines and points computed to construct a round line join.

Construction of a round line join shape, shown in pink. The white line is the original path, which has two segments that come to a point, and the gray region is the stroke.

Image showing the lines and points computed to construct an arcs line join.

Construction of an arcs line join shape, shown in pink. The white line is the original path, which has two segments that come to a point, and the gray region is the stroke. The dashed lines show circles that are tangent to and have the curvature of the segments at the join. The olive-green circles (concentric with the dashed circles) define the join shape.

11.4.8. Computing the circles for the arcs 'stroke-linejoin'

The arcs ‘stroke-linejoin’ requires finding circles that are both tangent to and have the same curvatures as the outer stroke edges at the ends of path segments. To find one of these circles, first calculate the curvature κ of the path segment at its end (see below). Next, find the radius of a circle corresponding to this curvature: r = 1/κ. Increase or decrease the radius by one half of the stroke width to account for the stroke: r_c = r ± ½ stroke-width. The center of the circle will be on a line normal to the path end a distance of r_c away from the outer stroke edge at the end.

For a line: the curvature is infinite. Extend the outer stroke edge by a line.

For an elliptical arc:

Need to do. This isn't as trivial as it first looks since we have to deal with rx != ry and an arbitrary rotation.

For a quadratic Bézier:

κ (0) = \frac{1}{2} \frac{(P_{1} - P_{0}) \times (P_{2} - P_{1})}{| P_{1} - P_{0} |^{3}}

$$\kappa(0) = {2\over3}{(P_1-P_0)\times((P_0-P_1)+(P_2-P_1))\over|P_1-P_0|^3}$$

κ (1) = \frac{1}{2} \frac{(P_{2} - P_{1}) \times (P_{0} - P_{1})}{| P_{2} - P_{1} |^{3}}

$$\kappa(0) = {2\over3}{(P_1-P_0)\times((P_0-P_1)+(P_2-P_1))\over|P_1-P_0|^3}$$

Where κ(0) and κ(1) are the signed curvatures at the start and end of the path segment respectively, and the P's are the three points that define the quadratic Bézier.

For a cubic Bézier:

κ (0) = \frac{2}{3} \frac{(P_{1} - P_{0}) \times (P_{2} - P_{1})}{| P_{1} - P_{0} |^{3}}

$$\kappa(0) = {2\over3}{(P_1-P_0)\times((P_0-P_1)+(P_2-P_1))\over|P_1-P_0|^3}$$

κ (1) = \frac{2}{3} \frac{(P_{3} - P_{2}) \times (P_{1} - P_{2})}{| P_{3} - P_{2} |^{3}}

$$\kappa(1) = {2\over3}{(P_3-P_2)\times((P_1-P_2)+(P_3-P_2))\over|P_3-P_2|^3}$$

Where κ(0) and κ(1) are the signed curvatures at the start and end of the path segment respectively, and the P's are the four points that define the cubic Bézier. Note, if P₀ and P₁, or P₂ and P₃ are degenerate, the curvature will be infinite and a line should be used in constructing the join.

11.5. Controlling visibility: the effect of the ‘display’ and ‘visibility’ properties

See the CSS 2.1 specification for the definitions of ‘display’ and ‘visibility’. [CSS21]

SVG uses two properties to control the visibility of container elements, graphics elements and text content elements: ‘display’ and ‘visibility’.

When applied to certain container elements, graphics elements or text content elements, setting ‘display’ to none results in the element not becoming part of the rendering tree. Such elements and all of their descendants (regardless of their own ‘display’ property value):

are not rendered
are not sensitive to pointer events
do not contribute to bounding box calculations
do not contribute to masks or clipping paths, when descendants of a ‘mask’ or ‘clipPath’ element
are not considered when performing text layout

Elements that have any other ‘display’ value than none behave normally with respect to all of the above.

The ‘display’ property only applies to the following SVG elements: ‘svg’, ‘g’, ‘switch’, ‘a’, ‘foreignObject’, graphics elements and text content elements. Note that ‘display’ is not an inherited property.

The ‘display’ property affects the direct processing of a given element, but it does not prevent it from being referenced by other elements. For example, setting display: none on a ‘path’ element will prevent that element from getting rendered directly onto the canvas, but the ‘path’ element can still be referenced by a ‘textPath’ element; furthermore, its geometry will be used in text-on-a-path processing even if the ‘path’ has display: none.

When applied to a graphics element or text content element, setting ‘visibility’ to hidden or collapse results in the element not being painted. It is, however, still part of the rendering tree, is sensitive to pointer events (depending on the value of ‘pointer-events’), contributes to bounding box calculations and clipping paths, and does affect text layout.

The ‘visibility’ property only applies to graphics elements and text content elements. Note that since ‘visibility’ is an inherited property, although it has no effect on a container element itself, its inherited value can affect descendant elements.

11.6. Non-scaling stroke

Sometimes it is of interest to let the outline of an object keep its original width no matter which transforms are applied to it. For example, in a map with a 2px wide line representing roads it is of interest to keep the roads 2px wide even when the user zooms into the map. To achieve this, SVG Tiny 1.2 introduces the 'vector-effect' property. Future versions of the SVG language will allow for more powerful vector effects through this property but this version restricts it to being able to specify the non-scaling stroke behavior.

Name:	vector-effect
Value:	non-scaling-stroke \| none
Initial:	none
Applies to:	graphics elements
Inherited:	no
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

none: Specifies that no vector effect shall be applied, i.e. the default rendering behaviour from SVG 1.1 is used which is to first fill the geometry of a shape with a specified paint, then stroke the outline with a specified paint.
non-scaling-stroke: Modifies the way an object is stroked. Normally stroking involves calculating stroke outline of the shape's path in current user space and filling that outline with the stroke paint (color or gradient). With the non-scaling-stroke vector effect, stroke outline shall be calculated in the "host" coordinate space instead of user coordinate space. More precisely: a user agent establishes a host coordinate space which in SVG Tiny 1.2 is always the same as "screen coordinate space". The stroke outline is calculated in the following manner: first, the shape's path is transformed into the host coordinate space. Stroke outline is calculated in the host coordinate space. The resulting outline is transformed back to the user coordinate system. (Stroke outline is always filled with stroke paint in the current user space). The resulting visual effect of this modification is that stroke width is not dependant on the transformations of the element (including non-uniform scaling and shear transformations) and zoom level.

Note: Future versions of SVG may allow ways to control the host coordinate system.

Below is an example of the non-scaling-stroke 'vector-effect'.

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.2" baseProfile="tiny"
     width="6cm" height="4cm" viewBox="0 0 600 400" 
     viewport-fill="rgb(255,150,200)">

  <desc>Example non-scaling stroke</desc>
  <rect x="1" y="1" width="598" height="398" fill="none" stroke="black"/>
  
  <g transform="scale(9,1)">
    <line stroke="black" stroke-width="5" x1="10" y1="50" x2="10" y2="350"/>
    <line vector-effect="non-scaling-stroke" stroke="black" stroke-width="5" 
        x1="32" y1="50" x2="32" y2="350"/>
    <line vector-effect="none" stroke="black" stroke-width="5" 
        x1="55" y1="50" x2="55" y2="350"/>
  </g>

</svg>

11.7. Markers

SVG 2 Requirement:	Improve markers.
Resolution:	We will improve markers for SVG 2.
Purpose:	To solve the common problems authors have with SVG markers.
Owner:	Cameron (ACTION-3286)

A marker is a graphical object that is painted at particular positions along a ‘path’, ‘line’, ‘polyline’ or ‘polygon’ element, together known as the markable elements. There are four ways markers can be placed on these elements:

The ‘marker-start’ and ‘marker-end’ properties can be used to place markers at the first and last vertex, and the ‘marker-mid’ property can be used to place markers at every other vertex (aside from the first and last). The ‘marker-start’ and ‘marker-end’ can be used for example to add arrowheads to paths. Markers placed using these properties are known as vertex markers.
The ‘marker-segment’ property can be used to place markers at the center of every path segment. These markers are known as segment markers.
The ‘marker-pattern’ property can be used to define a regular repeating pattern of markers to place along the length of the path. Markers placed with ‘marker-pattern’ are known as repeating markers.
A child ‘marker’ element with a ‘position’ attribute can be used to place a marker at a particular location along the path. Such markers are known as positioned markers.

There are probably better terms to use than "vertex" and "segment" markers. At least, "vertex" would go more naturally with "edge", but we should use more natural sounding names.

The graphics for a marker are defined by a ‘marker’ element. The ‘marker-start’, ‘marker-end’, ‘marker-mid’, ‘marker-segment’ and ‘marker-pattern’ properties, together known as the marker properties, reference ‘marker’ elements.

Markers can be animated, and as with ‘use’ elements, the animated effects will show on all current uses of the markers within the document.

Markers on a given element are painted in the following order, from bottom to top:

any marker specified by ‘marker-start’
alternating ‘marker-mid’ and ‘marker-segment’ markers, in order of their position along the path
any repeating markers, in order of their position along the path
any positioned markers, in document order of the ‘marker’ element children

11.7.1. The ‘marker’ element

‘marker’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’
structural elements — ‘defs’, ‘g’, ‘svg’, ‘symbol’, ‘use’

a, altGlyphDef, clipPath, color-profile, cursor, filter, font, font-face, foreignObject, image, marker, mask, script, style, switch, text, view

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’
‘viewBox’
‘preserveAspectRatio’
‘refX’
‘refY’
‘markerUnits’
‘markerWidth’
‘markerHeight’
‘orient’
‘position’
‘href’

DOM Interfaces:

SVGMarkerElement

The ‘marker’ element defines the graphics that are to be used for drawing markers on a markable element.

Attribute definitions:

Name Value Lacuna value Animatable markerUnits strokeWidth | userSpaceOnUse strokeWidth yes

The ‘markerUnits’ attribute defines the coordinate system for attributes ‘markerWidth’, ‘markerHeight’ and the contents of the ‘marker’. Values have the following meanings:

strokeWidth: ‘markerWidth’, ‘markerHeight’ and the contents of the ‘marker’ represent values in a coordinate system which has a single unit equal the size in user units of the current stroke width (see the ‘stroke-width’ property) in place for the graphic object referencing the marker.
userSpaceOnUse: ‘markerWidth’, ‘markerHeight’ and the contents of the ‘marker’ represent values in the current user coordinate system in place for the graphic object referencing the marker (i.e., the user coordinate system for the element referencing the ‘marker’ element via a marker property).

Name Value Lacuna value Animatable markerWidth, markerHeight <length> 3 yes

The ‘markerWidth’ and ‘markerHeight’ attributes represent the size of the viewport into which the marker is to be fitted according to the ‘viewBox’ and ‘preserveAspectRatio’ attributes. A value of zero for either attribute results in nothing being rendered for the marker. A negative value for either attribute is an error (see Error processing).

Name Value Lacuna value Animatable refX, refY <length> 0 yes

The ‘refX’ and ‘refY’ attributes define the reference point of the marker which is to be placed exactly at the marker's position on the markable element. They are interpreted as being in the coordinate system of the marker contents, after application of the ‘viewBox’ and ‘preserveAspectRatio’ attributes.

Name Value Lacuna value Animatable orient auto | <angle> | <number> 0 yes (non-additive)

The ‘orient’ attribute indicates how the marker is rotated when it is placed at its position on the markable element. Values have the following meaning:

'auto'

A value of 'auto' indicates that the marker is oriented such that its positive x-axis is pointing in the direction of the path at the point it is placed.

If the marker is a segment marker, then the direction the marker is oriented is, if considering the incoming and outgoing directions as unit vectors, in the direction of the sum of these two vectors. If this sum is zero, then the marker is oriented in the incoming direction.

If the marker is on the first or last vertex of a closed subpath, then the incoming direction taken from the final path segment and the outgoing direction is taken from:

the first path segment of the following subpath, if the following subpath does not begin with a 'moveto' command, and
the first path segment of the current subpath, if the following subpath does begin with a 'moveto' command or if there is no following subpath.

<angle>

<number>

An <angle> value represents the angle the marker's positive x-axis makes with the positive x-axis in the user space of the markable element, and a <number> value with no unit represents an angle in degrees. For example, if a value of '0' is given, then the marker will be drawn such that its x-axis will align with the x-axis of the user space of the graphic object referencing the marker. A value of '90deg' will result in the marker being drawn with its positive x-axis in the direction of the positive y-axis of the markable element's user space.

The orientation occurs after the marker has been fitted into its viewport. See the Details on how markers are rendered section below for an illustrative example.

Name Value Lacuna value Animatable position <length> | <percentage> as if not specified yes

If the ‘marker’ element is a child of a markable element, then the presence of a ‘position’ attribute indicates that the marker is a positioned marker and that it will be painted at the specified distance along the path. If the value is negative or greater than the length of the path, then no marker will be painted. If this attribute is specified on a ‘marker’ that is not a child of a markable element, then it has no effect beyond being exposed in the DOM.

Should a negative or greater than path length value be an "in error" / "unsupported" value?

Name Value Lacuna value Animatable href <iri> as if not specified yes

When a ‘marker’ element is being used as a positioned marker, the ‘href’ attribute indicates that the ‘marker’ referenced by the attribute is to be used as the definition of the marker. The graphical content of the referencing ‘marker’ element and any of its attributes that affect marker processing are ignored. Authors must not place any child graphical content in the referencing ‘marker’ or specify the ‘viewBox’, ‘preserveAspectRatio’, ‘refX’, ‘refY’, ‘markerUnits’, ‘markerWidth’, ‘markerHeight’ or ‘orient’ attributes on it.

We should say something about referencing ‘marker’ elements that have an ‘href’ with the marker properties. I suspect we should just allow this. Whether we want to allow the full element-referencing thing that you can do with gradients, with selective overriding of attributes, I'm not sure.

The contents of the ‘marker’ are relative to a new coordinate system. The ‘markerUnits’ attribute determines an initial scale factor for transforming the graphics in the marker into the user coordinate system for the referencing element. An additional set of transformations might occur if there is a ‘viewBox’ attribute, in which case the coordinate system for the contents of the ‘marker’ will be transformed due to the processing of attributes ‘viewBox’ and ‘preserveAspectRatio’. If there is no ‘viewBox’ attribute, then the assumed default value for the the ‘viewBox’ attribute has the origin of the viewBox coincident with the origin of the viewport and the width/height of the viewBox the same as the width/height of the viewport.

The user agent style sheet sets the ‘overflow’ property for ‘marker’ elements to hidden, which causes a rectangular clipping path to be created at the bounds of marker's viewport. Unless the ‘overflow’ property is overridden, any graphics within the marker which goes outside of the marker's viewport will be clipped.

Properties inherit into the ‘marker’ element from its ancestors; properties do not inherit from the element referencing the ‘marker’ element. Note however that by using the context-stroke value for the ‘fill’ or ‘stroke’ on elements in its definition, a single marker can be designed to match the style of the element referencing the marker.

‘marker’ elements are only rendered directly when they are used as children of a markable element and have a ‘position’ attribute specified. This causes the marker to be painted as a positioned marker. All other ‘marker’ elements are not rendered directly and must be referenced by one of the marker properties to be rendered. The ‘display’ property does not apply to the ‘marker’ element; thus, ‘marker’ elements are not directly rendered even if the ‘display’ property is set to a value other than none, and ‘marker’ elements are available for referencing even when the ‘display’ property on the ‘marker’ element or any of its ancestors is set to none. ‘marker’ elements that are used as positioned markers can simultaneously be referenced by the marker properties to be used as segment markers and repeating markers.

Event attributes and event listeners attached to the contents of a ‘marker’ element are not processed; only the rendering aspects of ‘marker’ elements are processed.

Make interaction work on positioned markers.

The following example shows the use of positioned markers to place symbols at particular distances along a path.

<svg xmlns="http://www.w3.org/2000/svg"
     width="600" height="200" viewBox="0 0 600 200">

   <defs>
     <marker id="Square" markerWidth="10" markerHeight="10"
             refX="5" refY="5" orient="auto">
       <path d="M 5,1 L 9,5 5,9 1,5 z" fill="#6a9100"/>
     </marker>
     <marker id="Circle" markerWidth="10" markerHeight="10"
             refX="5" refY="5" orient="auto">
       <circle cx="5" cy="5" r="2" fill="dodgerblue"/>
     </marker>
   </defs>

   <path d="M 100,50 C 100,250 500,-50 300,150"
         fill="none" stroke="deeppink" stroke-width="3">
     <marker href="#Square" position="0"/>
     <marker href="#Square" position="100%"/>
     <marker href="#Circle" position="50px"/>
     <marker href="#Circle" position="calc(100% - 50px)"/>
     <marker refX="5" refY="5" position="50%">
       <!-- the cross -->
       <path d="M 3,3 L 7,7 M 3,7 L 7,3"
             fill="none" stroke="black" stroke-width="2"/>
     </marker>
   </path>
</svg>

Image showing the use of positioned markers.

Child ‘marker’ elements are used to position two square and two circular markers. The cross marker is defined inline and does not need an ID.

11.7.2. Referencing ‘marker’ elements

A number of marker properties allow specifying a ‘marker’ using a <marker-ref> value.

<marker-ref> =

none |
<funciri> |
child |
<child-selector>

Values have the following meaning

<funciri>: Indicates that the ‘marker’ element referenced by the <funciri> value will be used. If the IRI reference is not valid (e.g., it points to an object that is undefined or the object is not a ‘marker’ element), then the marker reference is also not valid.
child: Indicates that the last child ‘marker’ element of the element where the property is specified will be used. If there is no such element, then the reference is not valid.
<child-selector>: Indicates that the first matching descendent ‘marker’ specified by the <child-selector>, applied in the context of the element where the property is specified, will be used. If no element matches any of the selectors contained in the <child-selector>, or the first match is not a ‘marker’, then the reference is not valid.

11.7.3. Vertex markers: the ‘marker-start’, ‘marker-mid’ and ‘marker-end’ properties

Name:	marker-start, marker-mid, marker-end
Value:	none \| <marker-ref>
Initial:	none
Applies to:	markable elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified, but with <funciri> values (that are part of a <marker-ref>) made absolute
Animatable:	yes

The ‘marker-start’ and ‘marker-end’ properties are used to specify the marker that will be drawn at the first and last vertices of the given markable element, respectively. ‘marker-mid’ is used to specify the marker that will be drawn at all other vertices (i.e., every vertex except the first and last). Possible values for ‘marker-start’, ‘marker-mid’ and ‘marker-end’ are:

none: Indicates that no marker symbol will be drawn at the given vertex or vertices.
<marker-ref>: Indicates that the ‘marker’ element referenced by the <marker-ref> value will be drawn at the given vertex or vertices. If the reference is not valid, then no marker will be drawn at the given vertex or vertices.

For ‘polygon’ elements, the last vertex is the same as the first vertex, and for ‘path’ elements that end with a closed subpath, the last vertex is the same as the first vertex of that final subpath. In this case, if the value of ‘marker-end’ is not none, then it is possible that two markers will be rendered on that final vertex.

Note that ‘marker-start’ and ‘marker-end’ refer to the first and last vertex of the entire path, not each subpath.

The following example shows a triangular marker symbol used as a vertex marker to form an arrowhead at the end of two paths.

<svg xmlns="http://www.w3.org/2000/svg"
     width="275" height="200" viewBox="0 0 275 200">
  <defs>
    <marker id="Triangle" viewBox="0 0 10 10" refX="1" refY="5" 
            markerUnits="strokeWidth" markerWidth="4" markerHeight="3"
            orient="auto">
      <path d="M 0 0 L 10 5 L 0 10 z" fill="context-stroke"/>
    </marker>
  </defs>

  <g fill="none" stroke-width="10" marker-end="url(#Triangle)">
    <path stroke="crimson" d="M 100,75 C 125,50 150,50 175,75"/>
    <path stroke="olivedrab" d="M 175,125 C 150,150 125,150 100,125"/>
  </g>
</svg>

Image showing the use of an automatically oriented marker.

The triangle is placed at the end of the path and oriented automatically so that it points in the right direction. The use of context-stroke ensures the fill of the triangle matches the stroke of each ‘path’.

11.7.4. Segment markers: the ‘marker-segment’ property

Name:	marker-segment
Value:	none \| <marker-ref>
Initial:	none
Applies to:	markable elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified, but with <funciri> values (that are part of a <marker-ref>) made absolute
Animatable:	yes

New in SVG 2. Added to allow automatically placing marker symbols on path edges, as is common in for example line graphs.

The ‘marker-segment’ property is used to specify the marker that will be drawn at the center of each length path segment. Possible values are:

none: Indicates that no marker symbol will be drawn at the given vertex or vertices.
<marker-ref>: Indicates that the ‘marker’ element referenced by the <marker-ref> value will be drawn at the center of each path segment. If the reference is not valid, then no marker will be drawn at the path segment centers.

The following example shows the use of both vertex markers and segment markers to construct a line graph.

<svg xmlns="http://www.w3.org/2000/svg" width="400" height="200">

  <marker id="Circle" markerWidth="8" markerHeight="8" refX="4" refY="4"
          markerUnits="userSpaceOnUse">
    <circle cx="4" cy="4" r="3" fill="deeppink"/>
  </marker>

  <marker id="Cross" markerWidth="10" markerHeight="10" refX="0" refY="0"
          viewBox="-5 -5 10 10" markerUnits="userSpaceOnUse"
          fill="none">
    <path d="M -4,-4 L 4,4 M -4,4 L 4,-4" stroke="white" stroke-width="4"/>
    <path d="M -4,-4 L 4,4 M -4,4 L 4,-4" stroke="black" stroke-width="2"/>
  </marker>

  <!-- grid lines -->
  <path stroke="#888" d="M 40,20 360,20 M 40,40 360,40 M 40,60 360,60
                         M 40,80 360,80 M 40,100 360,100 M 40,120 360,120
                         M 40,140 360,140 M 40,160 360,160 M 40,180 360,180"/>

  <!-- the graph line -->
  <polyline points="50,100 100,20 150,50 200,130 250,80 300,170 350,100"
            fill="none" stroke="deeppink" stroke-width="2"
            marker="url(#Circle)" marker-segment="url(#Cross)"/>
</svg>

Image showing the use of segment markers.

Segment markers are used to place crosses at the center of each line segment in the line graph.

11.7.5. Repeating markers: the ‘marker-pattern’ property

Name:	marker-pattern
Value:	[ none \| <length> \| <percentage> \| <marker-ref> ]+
Initial:	none
Applies to:	markable elements
Inherited:	yes
Percentages:	refer to the length of the path
Media:	visual
Computed value:	as specified, but with <funciri> values (that are part of a <marker-ref>) made absolute
Animatable:	yes

New in SVG 2. Added to allow markers to be placed along a path at positions unrelated to the segments used to form the path.

The ‘marker-pattern’ property is used to specify a pattern of markers and gaps to be repeated along the length of the markable element. Values have the following meanings:

none: Indicates that no marker will be painted at the current position along the path.
<length>
<percentage>: Indicates the length of a gap in the repeated pattern of markers.
<marker-ref>: A reference to a ‘marker’ that will be placed at the current position along the path. If the reference is not valid, then no marker will be drawn at the current position.

If a value other than none is given, and the sum of the <length>s and <percentage>s is not positive, then it is an invalid value.

Unlike vertex markers, the orientation of an orient="auto" repeating marker that happens to lie on a vertex does not take into account the incoming and outgoing directions. Instead, it is simply oriented such that its positive x-axis is aligned with the direction of the path at its position.

The following example shows the use of the ‘marker-pattern’ property to specify a repeating pattern of two different markers spaced along a path.

<svg xmlns="http://www.w3.org/2000/svg" width="600" height="200">

  <marker id="DoubleDash" markerWidth="8" markerHeight="12" refX="0" refY="0"
          viewBox="-4 -6 8 12" markerUnits="userSpaceOnUse" orient="auto">
    <rect x="-3" y="-5" width="2" height="10"/>
    <rect x="1" y="-5" width="2" height="10"/>
  </marker>
  <marker id="SingleDash" markerWidth="4" markerHeight="12" refX="0" refY="0"
          viewBox="-2 -6 4 12" markerUnits="userSpaceOnUse" orient="auto">
    <rect x="-1" y="-5" width="2" height="10"/>
  </marker>

  <path d="M 50,100 S 100,132 150,86 200,173 250,76 300,81
                      350,136 400,87 450,166 500,87 550,96"
        stroke="deeppink" stroke-width="2" fill="none"
        marker-pattern="40 url(#DoubleDash) 40 url(#SingleDash)"/>
</svg>

Image showing the use of repeating markers.

Markers specified with the ‘marker-pattern’ property are placed along the path at fixed distances, not relative to the path vertices.

11.7.6. Marker shorthand: the ‘marker’ property

Name:	marker
Value:	[ none \| <marker-ref> ]{1,4} [ / <‘marker-pattern’> ]? \| <marker-ref>{0,4} [ <length> \| <percentage> ] [ <length> \| <percentage> \| <marker-ref> ]*
Initial:	not defined for shorthand properties
Applies to:	markable elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	see individual properties
Animatable:	yes

The ‘marker’ property sets values for the ‘marker-start’, ‘marker-mid’, ‘marker-end’, ‘marker-segment’ and ‘marker-pattern’ properties. Values for have the following meanings:

none | <marker-ref>: Sets ‘marker-start’, ‘marker-mid’ and ‘marker-end’ to the specified value, and sets ‘marker-segment’ and ‘marker-pattern’ to none.
[ none | <marker-ref> ]{2}: Sets ‘marker-start’ and ‘marker-end’ to the two values specified, and sets ‘marker-mid’, ‘marker-segment’ and ‘marker-pattern’ to none.
[ none | <marker-ref> ]{3}: Sets ‘marker-start’, ‘marker-mid’ and ‘marker-end’ to the three values specified, and sets ‘marker-segment’ and ‘marker-pattern’ to none.
[ none | <marker-ref> ]{4}: Sets ‘marker-start’, ‘marker-segment’, ‘marker-mid’ and ‘marker-end’ to the four <marker-ref> values specified, and sets ‘marker-pattern’ to none.
[ none | <marker-ref> ]{1,4} / <‘marker-pattern’>: Sets ‘marker-start’, ‘marker-segment’, ‘marker-mid’ and ‘marker-end’ to the four <marker-ref> values specified before the slash, and sets ‘marker-pattern’ to the value after the slash.
anything else: Sets ‘marker-start’, ‘marker-segment’, ‘marker-mid’ and ‘marker-end’ to none, and sets ‘marker-pattern’ to the specified value.

11.7.7. Knocking out the stroke: the ‘marker-knockout-left’ and ‘marker-knockout-right’ properties

The marker knockout properties are still under heavy development and are subject to change. Feedback on how authors might prefer to specify marker knockout shapes is welcome.

Name:	marker-knockout-left, marker-knockout-right
Value:	<knockout-offset> \| <knockout-shape> [ at <knockout-offset> ]?
Initial:	0
Applies to:	‘marker’
Inherited:	no
Percentages:	see prose
Media:	visual
Computed value:	as specified
Animatable:	yes

where:

<knockout-offset> =

[ <length> | <percentage> ]

<knockout-shape> =

[ <length> | <percentage> ] inverted? circle |

[ <length> | <percentage> ]{2} inverted? ellipse |

[ <length> | <percentage> ]{1,2} inverted? [ rectangle | triangle ]

New in SVG 2. Added to allow authors to specify parts of a stroke that should be clipped away when a marker is placed on a path. This helps with arrowheads, where the stroke must not be visible behind the pointy end, and with hollow markers as seen in metro maps, where the center of a marker is transparent and the stroke should not show through.

When specified on a ‘marker’ element, the ‘marker-knockout-left’ and ‘marker-knockout-right’ properties together specify a shape to clip away when when painting the stroke of an element that uses the marker. ‘marker-knockout-left’ specifies the left side of the shape and ‘marker-knockout-right’ the right side. These two sides are joined together with straight lines.

The <knockout-offset> part of the value, if specified, is the offset from the marker position, outwards, along the tangent, that the knockout shape side is placed at. This is the knockout shape side position. If it is omitted, then the offset is assumed to be zero. The value can be negative. Percentage values refer to the width of the marker contents viewport.

The <knockout-shape> part of the value, if specified, is the left or right side of the knockout shape. Values have the following meanings:

[ <length> | <percentage> ]{2} inverted? ellipse

The knockout shape side is an arc. The lengths or percentages specified are the x-radius and y-radius of the ellipse from which the arc is taken. A length is interpreted as being in the marker contents coordinate system. If the first value is a percentage, then it refers to the width of the marker contents viewport, and if the second value is a percentage then it refers to the height of the marker contents viewport.

If the inverted keyword is not specified, then the arc is constructed by placing the center of the ellipse at the knockout shape side position. First we consider only the 180° arc of the ellipse which points in the direction of the start of the start of the path, if this is the left knockout shape side, or the end of the path if this is the right knockout shape side. If the y-radius is less than or equal to half of the stroke width of the path the marker is on, then this 180° arc is the final knockout shape side. Otherwise, we intersect the arc with the two lines that are offset, by half of the stroke width, from the tangent to the marker orientation. The resulting arc with its start and end points on these two lines is the final knockout shape side.

If the inverted keyword is specified, then the arc is constructed by placing the center of the ellipse at a distance of two times its x-radius along the tangent to the marker orientation, in the direction of the start of the path if this is the left knockout shape side, or the end of the path if this is the right knockout shape side. We consider only the 180° arc of the ellipse that is pointing in the opposite direction. If the y-radius is less or equal to half of the stroke width of the path the marker is on, then this 180° arc is the final knockout shape side. Otherwise, we intersect the arc with the two lines that are offset, by half of the stroke width, from the tangent to the marker orientation. The resulting arc with its side and end points on these two lines is the final knockout shape side.

[ <length> | <percentage> ] inverted? circle

The knockout shape side is an arc. The shape is computed in the same way as the ellipse shape, but with both radii of the ellipse being the specified length or percentage, and with a percentage referring to the size of the marker contents viewport.

[ <length> | <percentage> ]{1,2} inverted? rectangle

The knockout shape side comprises one or two rectangles. These rectangles are aligned such that their top and bottom edges are parallel to the tangent to the marker orientation. The length or percentage is a width and the second, if specified, is a height. Percentage values here refer to the width and height of the marker contents viewport, respectively.

If the inverted keyword is not specified, then the knockout shape side is a single rectangle. The width of the rectangle is the specified width value. The height of the rectangle is the maximum of the stroke width of the path on which the marker exists and the specified height value, if it is specified. If it is not specified, then the height of the rectangle is just the stroke width. The rectangle is posisioned such that the center of its right hand edge is positioned at the knockout shape side position and the extent of its width is in the direction of the start of the path, if this is the left knockout shape side, or the end of the path if this is the right knockout shape side.

If the inverted keyword is specified, then the knockout shape side comprises two rectangles. If the specified height is greater than or equal to the stroke width, then the height of these rectangles is zero; otherwise, their heights are half of the difference between the stroke width and the specified height. The top edge of one of the rectangles is half of the stroke width away from the marker orientation tangent line, with its bottom edge closer to the tangent line. The other rectangle has its bottom edge half of the stroke width away from the tangent line and its top edge closer to the tangent line. The right edges of the rectangles are aligned with each other and also with the line perpendicular to the marker orientation tangent line. The extent of the widths of the rectangles is in the direction of the start of the path, if this is the left knockout shape side, or the end of the path if this is the right knockout shape side.

[ <length> | <percentage> ]{1,2} inverted? rectangle

[ <length> | <percentage> ]{1,2} inverted? triangle

...

A diagram showing the construction of these shapes would be helpful.

Need to define how the two shape sides are joined together. It's taking the top and bottom points from both shapes, drawing vertical lines to the edge of the stroke shape, then drawing two horizontal lines to join them together.

The two knockout shape sides must not intersect, although they may touch. If they do intersect, then no knockout is performed for that marker when painting the stroke.

For example, using 8px inverted triangle at -4px for ‘marker-knockout-left’ and 8px triangle for ‘marker-knockout-right’ is allowed, as the two straight lines that form the left shape side do not intersect with either of the two straight lines that form the right shape side. However, using 8px triangle at -4px for both properties would obviously cause an intersection, and so would not be allowed.

Image showing various marker knockout shapes.

An illustration of the use of inverted and non-inverted circle, rectangle and triangle knockout shapes, at both 0px and 10px offsets. The value beneath each pink stroke is used for both ‘marker-knockout-left’ and ‘marker-knockout-right’. (The marker itself here has no content and does not render anything.)

While this is nice for straight line segments, if the path is curved at the marker position then it might be preferable to have the knockout shapes aligned with the tangent at the knockout shape side position, rather than with the marker orientation. Especially if the knockout is being used as a fancy dash pattern. Then we would likely want to join the left and right sides of the shape with a curved shape (along the stroke) and not just a rectangle. If we allow this, then computing that shape is going to be hard, and will mean that determining whether the left and right sides of the knockout shape intersect, and determining what the intersections of all of the knockout shapes on a path are, is also going to be hard. Perhaps that can be handled by extending dashing line caps with these shapes rather than here? Regardless of whether it is handled by marker knockouts or new line caps, it's going to be non-trivial to compute the right shapes.

Another thing to note is that knockouts here are like setting up a clipping path to remove parts of the stroke when it's painted. That means that if the stroke intersects itself over the knockout areas, it's going to be knocked out of all bits of the stroke that go through those areas. That may or may not be fine depending on your use cases.

11.7.8. Details on how markers are rendered

Markers are drawn after the given object is filled and stroked.

For each marker that is drawn, a temporary new user coordinate system is established so that the marker will be positioned and sized correctly, as follows:

The axes of the temporary new user coordinate system are aligned according to the ‘orient’ attribute on the ‘marker’ element and the slope of the curve at the given vertex. (Note: if there is a discontinuity at a vertex, the slope is the average of the slopes of the two segments of the curve that join at the given vertex. If a slope cannot be determined, the slope is assumed to be zero.)
A temporary new coordinate system is established by attribute ‘markerUnits’. If ‘markerUnits’ equals 'strokeWidth', then the temporary new user coordinate system is the result of scaling the current user coordinate system by the current value of property ‘stroke-width’. If ‘markerUnits’ equals 'userSpaceOnUse', then no extra scale transformation is applied.
An additional set of transformations might occur if the ‘marker’ element includes a ‘viewBox’ attribute, in which case additional transformations are set up to produce the necessary result due to attributes ‘viewBox’ and ‘preserveAspectRatio’.
If the ‘overflow’ property on the ‘marker’ element indicates that the marker needs to be clipped to its viewport, then an implicit clipping path is established at the bounds of the viewport.

The rendering effect of a marker is as if the contents of the referenced ‘marker’ element were deeply cloned into a separate non-exposed DOM tree for each instance of the marker. Because the cloned DOM tree is non-exposed, the SVG DOM does not show the cloned instance of the marker.

For user agents that support Styling with CSS, the conceptual deep cloning of the referenced ‘marker’ element into a non-exposed DOM tree also copies any property values resulting from the CSS cascade ([CSS21], chapter 6) and property inheritance on the referenced element and its contents. CSS 2.1 selectors can be applied to the original (i.e., referenced) elements because they are part of the formal document structure. CSS 2.1 selectors cannot be applied to the (conceptually) cloned DOM tree because its contents are not part of the formal document structure.

For illustrative purposes, we'll repeat the marker example shown earlier:

<?xml version="1.0" standalone="no"?>
<svg width="4in" height="2in" 
     viewBox="0 0 4000 2000" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <defs>
    <marker id="Triangle"
      viewBox="0 0 10 10" refX="0" refY="5" 
      markerUnits="strokeWidth"
      markerWidth="4" markerHeight="3"
      orient="auto">
      <path d="M 0 0 L 10 5 L 0 10 z" />
    </marker>
  </defs>
  <rect x="10" y="10" width="3980" height="1980"
       fill="none" stroke="blue" stroke-width="10" />
  <desc>Placing an arrowhead at the end of a path.
  </desc>
  <path d="M 1000 750 L 2000 750 L 2500 1250"
        fill="none" stroke="black" stroke-width="100" 
        marker-end="url(#Triangle)"  />
</svg>

The rendering effect of the above file will be visually identical to the following:

<?xml version="1.0" standalone="no"?>
<svg width="4in" height="2in" 
     viewBox="0 0 4000 2000" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <desc>File which produces the same effect
      as the marker example file, but without
      using markers.
  </desc>
  <rect x="10" y="10" width="3980" height="1980"
       fill="none" stroke="blue" stroke-width="10" />
  <!-- The path draws as before, but without the marker properties -->
  <path d="M 1000 750 L 2000 750 L 2500 1250"
        fill="none" stroke="black" stroke-width="100"  />
  <!-- The following logic simulates drawing a marker 
       at final vertex of the path. -->
  <!-- First off, move the origin of the user coordinate system
       so that the origin is now aligned with the end point of the path. -->
  <g transform="translate(2500,1250)" >
    <!-- Rotate the coordinate system 45 degrees because
         the marker specified orient="auto" and the final segment
         of the path is going in the direction of 45 degrees. -->
    <g transform="rotate(45)" >
      <!-- Scale the coordinate system to match the coordinate system
           indicated by the 'markerUnits' attributes, which in this case has
           a value of 'strokeWidth'. Therefore, scale the coordinate system
           by the current value of the 'stroke-width' property, which is 100. -->
      <g transform="scale(100)" >
        <!-- Translate the coordinate system by 
             (-refX*viewBoxToMarkerUnitsScaleX, -refY*viewBoxToMarkerUnitsScaleY)
             in order that (refX,refY) within the marker will align with the vertex.
             In this case, we use the default value for preserveAspectRatio
             ('xMidYMid meet'), which means find a uniform scale factor
             (i.e., viewBoxToMarkerUnitsScaleX=viewBoxToMarkerUnitsScaleY)
             such that the viewBox fits entirely within the viewport ('meet') and 
             is center-aligned ('xMidYMid'). In this case, the uniform scale factor
             is markerHeight/viewBoxHeight=3/10=.3. Therefore, translate by
             (-refX*.3,-refY*.3)=(0*.3,-5*.3)=(0,-1.5). -->
        <g transform="translate(0,-1.5)" >
          <!-- There is an implicit clipping path because the user agent style
               sheet says that the 'overflow' property for markers has the value
               'hidden'. To achieve this, create a clipping path at the bounds
               of the viewport. Note that in this case the viewport extends
               0.5 units to the left and right of the viewBox due to 
               a uniform scale factor, different ratios for markerWidth/viewBoxWidth
               and markerHeight/viewBoxHeight, and 'xMidYMid' alignment -->
          <clipPath id="cp1" >
            <rect x="-0.5" y="0" width="4" height="3" />
          </clipPath>
          <g clip-path="url(#cp1)" >
            <!-- Scale the coordinate system by the uniform scale factor
                 markerHeight/viewBoxHeight=3/10=.3 to set the coordinate
                 system to viewBox units. -->
            <g transform="scale(.3)" >
              <!-- This 'g' element carries all property values that result from
                   cascading and inheritance of properties on the original 'marker' element.
                   In this example, neither fill nor stroke was specified on the 'marker'
                   element or any ancestors of the 'marker', so the initial values of
                   "black" and "none" are used, respectively. -->
             <g fill="black" stroke="none" >
                <!-- Expand out the contents of the 'marker' element. -->
                <path d="M 0 0 L 10 5 L 0 10 z" />
              </g>
            </g>
          </g>
        </g>
      </g>
    </g>
  </g>
</svg>

11.8. Controlling paint operation order: the ‘paint-order’ property

SVG 2 Requirement:	Support control of the order of filling, stroke and painting markers on shapes.
Resolution:	SVG 2 will adopt the ‘paint-order’ property proposal, though possibly with a different name.
Purpose:	To address the common desire to paint strokes below fills without having to duplicate an element.
Owner:	Cameron (ACTION-3285)

Name:	paint-order
Value:	normal \| [ fill \|\| stroke \|\| markers ]
Initial:	normal
Applies to:	graphics elements and text content elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

New in SVG 2. Added primarily to allow painting the stroke of text below its fill without needing to duplicate the ‘text’ element.

The ‘paint-order’ property controls the order that the three paint operations that shapes and text are rendered with: their fill, their stroke and any markers they might have.

Is there a better name than ‘paint-order’?

When the value of this property is normal, the element is painted with the standard order of painting operations: the fill is painted first, then its stroke and finally its markers.

When any of the other keywords are used, the order of the paint operations for painting the element is as given, from left to right. If any of the three keywords are omitted, they are painted last, in the order they would be painted with paint-order: normal.

This mean that, for example, paint-order: stroke has the same rendering behavior as paint-order: stroke fill markers.

This does not affect interaction, but once the marker children proposal is added to the spec, it will be possible for ‘marker’ elements to receive mouse events or not depending on the value of ‘paint-order’.

The Rendering chapter will need some changes to accommodate ‘paint-order’, and should probably gain a more precise description of exactly how an SVG fragment is rendered.

Should there be a way of addressing the individual types of markers – vertex & segment, repeating, positioned – given they are currently specified to render in that order?

The following example shows how the ‘paint-order’ property can be used to render stroked text in a more aesthetically pleasing manner.

<svg xmlns="http://www.w3.org/2000/svg"
     width="600" height="150" viewBox="0 0 600 150">

  <style>
    text {
      font: 80px bold sans-serif; stroke-linejoin: round;
      text-anchor: middle; fill: peachpuff; stroke: crimson;
    }
  </style>

  <text x="150" y="100" stroke-width="6px">pizazz</text>
  <text x="450" y="100" stroke-width="12px" paint-order="stroke">pizazz</text>
</svg>

Image showing the effect of paint-order.

Text painted with its stroke below the fill.

11.9. Color space for interpolation: the ‘color-interpolation’ property

Name:	color-interpolation
Value:	auto \| sRGB \| linearRGB
Initial:	sRGB
Applies to:	container elements, graphics elements, gradient elements, ‘animate’ and ‘animateColor’
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

The SVG user agent performs color interpolations and compositing at various points as it processes SVG content. The ‘color-interpolation’ property controls which color space is used for the following graphics operations:

interpolating between gradient stops,
interpolating color when performing color animations with either ‘animate’ or ‘animateColor’,
and alpha compositing of graphics elements into the current background.

For filter effects, the ‘color-interpolation-filters’ property controls which color space is used. [FILTERS]

The ‘color-interpolation’ property chooses between color operations occurring in the sRGB color space or in a (light energy linear) linearized RGB color space. Having chosen the appropriate color space, component-wise linear interpolation is used. Possible values for ‘color-interpolation’ are:

auto: Indicates that the user agent can choose either the sRGB or linearRGB spaces for color interpolation. This option indicates that the author doesn't require that color interpolation occur in a particular color space.
sRGB: Indicates that color interpolation occurs in the sRGB color space.
linearRGB: Indicates that color interpolation occurs in the linearized RGB color space as described below.

The conversion formulas between the sRGB color space (i.e., nonlinear with 2.2 gamma curve) and the linearized RGB color space (i.e., color values expressed as sRGB tristimulus values without a gamma curve) can be found in the sRGB specification [SRGB]. For illustrative purposes, the following formula shows the conversion from sRGB to linearized RGB, where C_srgb is one of the three sRGB color components, C_linear is the corresponding linearized RGB color component, and all color values are between 0 and 1:

C_{linear} = {\begin{cases} \frac{C_{srgb}}{12.92} & if C_{srgb} \leq 0.04045 \\ {(\frac{C_{srgb} + 0.055}{1.055})}^{2.4} & if C_{srgb} > 0.04045 \end{cases}

if C_srgb <= 0.04045
  C_linear = C_srgb / 12.92
else if c_srgb > 0.04045
  C_linear = ((C_srgb + 0.055) / 1.055) ^ 2.4

Out-of-range color values, if supported by the user agent, also are converted using the above formulas. (See Clamping values which are restricted to a particular range.)

When a child element is blended into a background, the value of the ‘color-interpolation’ property on the child determines the type of blending, not the value of the ‘color-interpolation’ on the parent. For gradients which make use of the ‘xlink:href’ attribute to reference another gradient, the gradient uses the ‘color-interpolation’ property value from the gradient element which is directly referenced by the ‘fill’ or ‘stroke’ property. When animating colors, color interpolation is performed according to the value of the ‘color-interpolation’ property on the element being animated.

11.10. Rendering hints

11.10.1. The ‘color-rendering’ property

Name:	color-rendering
Value:	auto \| optimizeSpeed \| optimizeQuality
Initial:	auto
Applies to:	container elements, graphics elements, gradient elements, ‘animate’ and ‘animateColor’
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

The creator of SVG content might want to provide a hint to the implementation about how to make speed vs. quality tradeoffs as it performs color interpolation and compositing. The ‘color-rendering’ property provides a hint to the SVG user agent about how to optimize its color interpolation and compositing operations. Possible values are:

auto: Indicates that the user agent shall make appropriate tradeoffs to balance speed and quality, but quality shall be given more importance than speed.
optimizeSpeed: Indicates that the user agent shall emphasize rendering speed over quality. For RGB display devices, this option will sometimes cause the user agent to perform color interpolation and compositing in the device RGB color space.
optimizeQuality: Indicates that the user agent shall emphasize quality over rendering speed.

‘color-rendering’ takes precedence over ‘color-interpolation-filters’. For example, assume color-rendering: optimizeSpeed and color-interpolation-filters: linearRGB. In this case, the SVG user agent should perform color operations in a way that optimizes performance, which might mean sacrificing the color interpolation precision as specified by color-interpolation-filters: linearRGB.

11.10.2. The ‘shape-rendering’ property

Name:	shape-rendering
Value:	auto \| optimizeSpeed \| crispEdges \| geometricPrecision
Initial:	auto
Applies to:	shapes
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

The creator of SVG content might want to provide a hint to the implementation about what tradeoffs to make as it renders vector graphics elements such as ‘path’ elements and basic shapes such as circles and rectangles. The ‘shape-rendering’ property provides these hints. Possible values are:

auto: Indicates that the user agent shall make appropriate tradeoffs to balance speed, crisp edges and geometric precision, but with geometric precision given more importance than speed and crisp edges.
optimizeSpeed: Indicates that the user agent shall emphasize rendering speed over geometric precision and crisp edges. This option will sometimes cause the user agent to turn off shape anti-aliasing.
crispEdges: Indicates that the user agent shall attempt to emphasize the contrast between clean edges of artwork over rendering speed and geometric precision. To achieve crisp edges, the user agent might turn off anti-aliasing for all lines and curves or possibly just for straight lines which are close to vertical or horizontal. Also, the user agent might adjust line positions and line widths to align edges with device pixels.
geometricPrecision: Indicates that the user agent shall emphasize geometric precision over speed and crisp edges.

11.10.3. The ‘text-rendering’ property

Name:	text-rendering
Value:	auto \| optimizeSpeed \| optimizeLegibility \| geometricPrecision
Initial:	auto
Applies to:	‘text’
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

The creator of SVG content might want to provide a hint to the implementation about what tradeoffs to make as it renders text. The ‘text-rendering’ property provides these hints. Possible values are:

auto: Indicates that the user agent shall make appropriate tradeoffs to balance speed, legibility and geometric precision, but with legibility given more importance than speed and geometric precision.
optimizeSpeed: Indicates that the user agent shall emphasize rendering speed over legibility and geometric precision. This option will sometimes cause the user agent to turn off text anti-aliasing.
optimizeLegibility: Indicates that the user agent shall emphasize legibility over rendering speed and geometric precision. The user agent will often choose whether to apply anti-aliasing techniques, built-in font hinting or both to produce the most legible text.
geometricPrecision: Indicates that the user agent shall emphasize geometric precision over legibility and rendering speed. This option will usually cause the user agent to suspend the use of hinting so that glyph outlines are drawn with comparable geometric precision to the rendering of path data.

11.10.4. The ‘image-rendering’ property

Name:	image-rendering
Value:	auto \| optimizeQuality \| optimizeSpeed
Initial:	auto
Applies to:	shapes
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

The creator of SVG content might want to provide a hint to the implementation about how to make speed vs. quality tradeoffs as it performs image processing. The ‘image-rendering’ property provides a hint to the SVG user agent about how to optimize its image rendering. Possible values are:

auto: Indicates that the user agent shall make appropriate tradeoffs to balance speed and quality, but quality shall be given more importance than speed. The user agent shall employ a resampling algorithm at least as good as nearest neighbor resampling, but bilinear resampling is strongly preferred. For Conforming High-Quality SVG Viewers, the user agent shall employ a resampling algorithm at least as good as bilinear resampling.
optimizeQuality: Indicates that the user agent shall emphasize quality over rendering speed. The user agent shall employ a resampling algorithm at least as good as bilinear resampling.
optimizeSpeed: Indicates that the user agent shall emphasize rendering speed over quality. The user agent should use a resampling algorithm which achieves the goal of fast rendering, with the requirement that the resampling algorithm shall be at least as good as nearest neighbor resampling. If performance goals can be achieved with higher quality algorithms, then the user agent should use the higher quality algorithms instead of nearest neighbor resampling.

In all cases, resampling must be done in a truecolor (e.g., 24-bit) color space even if the original data and/or the target device is indexed color.

11.10.5. The ‘buffered-rendering’ property

SVG 2 Requirement:	Support a hint to indicate that an element's rendering should be cached.
Resolution:	SVG 2 will add ‘buffered-rendering’, as implementor feedback indicates that it is needed.
Purpose:	For caching rendered results for faster display.
Owner:	Erik (no action)

The creator of SVG content might want to provide a hint to the implementation about how often an element is modified to make speed vs. memory tradeoffs as it performs rendering. The ‘buffered-rendering’ property provides a hint to the SVG user agent about how to buffer the rendering of elements:

Name:	buffered-rendering
Value:	auto \| dynamic \| static
Initial:	auto
Applies to:	container elements and graphics elements
Inherited:	no
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

auto: Indicates that the user agent is expected to use a reasonable compromise between speed of update and resource allocation.
dynamic: Indicates that the element is expected to be modified often.
static: Indicates that the element is not expected to be modified often. This suggests that user agent may be able to allocate resources, such as an offscreen buffer, that would allow increased performance in redraw. It does not mean that the element will never change. If an element is modified when the value is 'static', then redraw might have reduced performance.

11.11. Inheritance of painting properties

The values of any of the painting properties defined in this chapter can be inherited from a given object's parent. Painting, however, is always done on each graphics element individually, never at the container element (e.g., a ‘g’) level. Thus, for the following SVG, even though the gradient fill is specified on the ‘g’, the gradient is simply inherited through the ‘g’ element down into each rectangle, each of which is rendered such that its interior is painted with the gradient.

Any painting properties defined in terms of the object's bounding box use the bounding box of the graphics element to which the operation applies. Note that text elements are defined such that any painting operations defined in terms of the object's bounding box use the bounding box of the entire ‘text’ element. (See the discussion of object bounding box units and text elements.)

The following example shows how painting properties are inherited from a ‘g’ element to its child ‘rect’ elements.

<svg xmlns="http://www.w3.org/2000/svg"
     width="350" height="100" viewBox="0 0 350 100">
  <defs>
    <linearGradient id="OrangeYellow" gradientUnits="objectBoundingBox">
      <stop offset="0%" stop-color="#F60"/>
      <stop offset="100%" stop-color="#FF6"/>
    </linearGradient>
  </defs>
  <g stroke="black" stroke-width="2px" fill="url(#OrangeYellow)">
    <rect x="50" y="25" width="100" height="50"/>
    <rect x="200" y="25" width="100" height="50"/>
  </g>
</svg>

Image demonstrating the inheritance of painting properties.

Both rectangles are filled with the same orange-to-yellow gradient.

11.12. DOM interfaces

11.12.1. Interface SVGPaint

interface SVGPaint : SVGColor { 

  // Paint Types
  const unsigned short SVG_PAINTTYPE_UNKNOWN = 0;
  const unsigned short SVG_PAINTTYPE_RGBCOLOR = 1;
  const unsigned short SVG_PAINTTYPE_RGBCOLOR_ICCCOLOR = 2;
  const unsigned short SVG_PAINTTYPE_NONE = 101;
  const unsigned short SVG_PAINTTYPE_CURRENTCOLOR = 102;
  const unsigned short SVG_PAINTTYPE_URI_NONE = 103;
  const unsigned short SVG_PAINTTYPE_URI_CURRENTCOLOR = 104;
  const unsigned short SVG_PAINTTYPE_URI_RGBCOLOR = 105;
  const unsigned short SVG_PAINTTYPE_URI_RGBCOLOR_ICCCOLOR = 106;
  const unsigned short SVG_PAINTTYPE_URI = 107;

  readonly attribute unsigned short paintType;
  readonly attribute DOMString uri;

  void setUri(DOMString uri);
  void setPaint(unsigned short paintType, DOMString uri, DOMString rgbColor, DOMString iccColor);
};

There are some missing definitions of SVGPaint members here. The interface might be going away, however.

11.12.2. Interface SVGMarkerInstance

The SVGMarkerInstance interface is used to represent an instance of a marker that is on a markable element. An SVGMarkerInstance can represent any kind of marker, including positioned markers.

What should we do about liveness? If it is live, we could have it know what index it is for, and always return information about the marker at that index (and return null for the element if that index is no longer valid).

interface SVGMarkerInstance {
  readonly attribute SVGMarkerElement element;
  readonly attribute float position;
  readonly attribute SVGPoint point;
  readonly attribute float angle;
};

Attributes:

element (readonly SVGMarkerElement): The ‘marker’ element that defines the marker. If the marker is a vertex marker, segment marker or repeating marker, then this will be the ‘marker’ element that the relevant marker property referenced. If the marker is a positioned marker, then this will be the child ‘marker’ element of the markable element.
position (readonly float): The distance along the equivalent path of the markable element that the marker is positioned at.
point (readonly SVGPoint): The point, in the user space of the markable element, that the marker is positioned at. The SVGPoint object is read only.
angle (readonly float): The orientation of the marker relative to a vector pointing in the direction of the positive y-axis of the markable element's user space.

11.12.3. Interface SVGMarkerList

The SVGMarkerList interface is used to expose the list of markers that are painted on a given markable element. This list includes all vertex markers, segment markers, repeating markers and positioned markers. The list of SVGMarkerInstance objects is maintained in the order that the markers are painted (see Markers).

The supported property indices of an SVGPathSegList object is all non-negative integers less than the length of the list.

interface SVGMarkerList {
  readonly attribute unsigned long length;
  getter SVGMarkerInstance? item(unsigned long index);
};

Attributes:

length (readonly unsigned long): The number of markers on this element.

Operations:

SVGMarkerInstance? item(unsigned long index)

Gets the SVGMarkerInstance at the given position in the list of markers on this element.

Parameters

unsigned long index

The index of the SVGMarkerInstance to return.

Returns

Returns the SVGMarkerInstance at position index in the list of markers on this element, or null if index is out of range.

11.12.4. Interface SVGMarkableElement

The SVGMarkableElement interface is implemented on all markable elements, and provides access to the markers that are placed on the element's path.

[NoInterfaceObject]
interface SVGMarkableElement {
  readonly attribute SVGMarkerList markers;

  long getMarkerIndexFromPoint(SVGPoint point);
};

Attributes:

markers (readonly SVGMarkerList): The list of markers on this element.

Operations:

long getMarkerIndexFromPoint(SVGPoint point)

Returns the index into the SVGMarkerList of the marker that is at the specified point. Normal hit testing rules apply; the value of the ‘pointer-events’ property on the elements that comprise the markers, as well as its value on this element, is honored, and the top-most marker is selected when there are multiple markers whose content is at the given point.

Parameters

SVGPoint point

The point to check for intersection with the markers on this element. The SVGPoint is interpreted as a point in the user space of this element.

Returns

The index into this element's SVGMarkerList of the marker at the given point, or -1 if there is no such marker.

11.12.5. Interface SVGMarkerElement

The SVGMarkerElement interface corresponds to the ‘marker’ element.

interface SVGMarkerElement : SVGElement {

  // Marker Unit Types
  const unsigned short SVG_MARKERUNITS_UNKNOWN = 0;
  const unsigned short SVG_MARKERUNITS_USERSPACEONUSE = 1;
  const unsigned short SVG_MARKERUNITS_STROKEWIDTH = 2;

  // Marker Orientation Types
  const unsigned short SVG_MARKER_ORIENT_UNKNOWN = 0;
  const unsigned short SVG_MARKER_ORIENT_AUTO = 1;
  const unsigned short SVG_MARKER_ORIENT_ANGLE = 2;

  readonly attribute SVGAnimatedLength refX;
  readonly attribute SVGAnimatedLength refY;
  readonly attribute SVGAnimatedEnumeration markerUnits;
  readonly attribute SVGAnimatedLength markerWidth;
  readonly attribute SVGAnimatedLength markerHeight;
  readonly attribute SVGAnimatedEnumeration orientType;
  readonly attribute SVGAnimatedAngle orientAngle;

  void setOrientToAuto();
  void setOrientToAngle(SVGAngle angle);
};

SVGMarkerElement implements SVGFitToViewBox;

Constants in group “Marker Unit Types”:

SVG_MARKERUNITS_UNKNOWN (unsigned short): The marker unit type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_MARKERUNITS_USERSPACEONUSE (unsigned short): The value of attribute ‘markerUnits’ is 'userSpaceOnUse'.
SVG_MARKERUNITS_STROKEWIDTH (unsigned short): The value of attribute ‘markerUnits’ is 'strokeWidth'.

Constants in group “Marker Orientation Types”:

SVG_MARKER_ORIENT_UNKNOWN (unsigned short): The marker orientation is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_MARKER_ORIENT_AUTO (unsigned short): Attribute ‘orient’ has value 'auto'.
SVG_MARKER_ORIENT_ANGLE (unsigned short): Attribute ‘orient’ has an angle value.

Attributes:

refX (readonly SVGAnimatedLength): Corresponds to attribute ‘refX’ on the given ‘marker’ element.
refY (readonly SVGAnimatedLength): Corresponds to attribute ‘refY’ on the given ‘marker’ element.
markerUnits (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘markerUnits’ on the given ‘marker’ element. One of the Marker Unit Types defined on this interface.
markerWidth (readonly SVGAnimatedLength): Corresponds to attribute ‘markerWidth’ on the given ‘marker’ element.
markerHeight (readonly SVGAnimatedLength): Corresponds to attribute ‘markerHeight’ on the given ‘marker’ element.
orientType (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘orient’ on the given ‘marker’ element. One of the Marker Orientation Types defined on this interface.
orientAngle (readonly SVGAnimatedAngle): Corresponds to attribute ‘orient’ on the given ‘marker’ element. If markerUnits is SVG_MARKER_ORIENT_ANGLE, the angle value for attribute ‘orient’; otherwise, it will be set to zero.

Operations:

void setOrientToAuto()

Sets the value of attribute ‘orient’ to 'auto'.

void setOrientToAngle(SVGAngle angle)

Sets the value of attribute ‘orient’ to the given angle.

Parameters

SVGAngle angle

The angle value to use for attribute ‘orient’.

Chapter 13: Paint Servers: Solid Colors, Gradients, and Patterns

13.1. Introduction

This section covers Paint Servers, a method which allows the ‘fill’ or ‘stroke’ of an object to be defined by a resource found elsewhere. It allows resources to be reused throughout a document. See the section Painting: Filling and Stroking for a general discussion of filling and stroking objects.

SVG defines three types of paint servers:

Solid colors,
Gradients,
Patterns.

SVG1.1 refers to "built-in" paint servers. Is there any other kind?

SVG 2 Requirement:	Support hatching.
Resolution:	SVG 2 should support hatching without the artifacts that patterns currently impose.
Purpose:	To allow the kinds of patterns required for mapping, engraving, etc. where continuous lines are required.
Owner:	Tav (no action)

SVG 2 Requirement:	Arbitrary fills for shapes.
Resolution:	SVG 2 shall support filling and stroking from arbitrary elements.
Purpose:	To allow for example videos or images to be used as a fill source.
Owner:	Alex? (no action)

It seems that all paint servers (except perhaps, mesh gradients, when rendered directly) inherit from their ancestors and do not inherit from the element referencing the paint server. Rather than repeating this for each type of paint server, can the text be moved into the introduction section for paint servers?

Three types of paint servers. From left to right: A solid color ("MyLightPurple"). A linear gradient. A pattern.

Paint servers are used by including an IRI reference in a ‘fill’ or ‘stroke’ property (i.e. fill="#MyLightPurple").

13.2. Solid colors

Solid Colors are new in SVG 2 (ported from SVG 1.2 Tiny).

SVG 2 Requirement:	Support named colors.
Resolution:	Will add ‘solidColor’ element to SVG 2.
Purpose:	To provide an easy mechanism for creating named colors and palettes. Also useful for animation.
Owner:	Tav (no action)

The 'solidColor' element is a paint server that provides a single color with opacity. It can be referenced any place a single color can be used. The 'solidColor' element allows a palette to be defined and used consistently throughout a document. It is also useful as away of animating a palette colors. (See the chapter Color for a more general discussion of color in SVG.)

Properties inherit into the ‘solidColor’ element from its ancestors; properties do not inherit from the element referencing the ‘solidColor’ element.

‘solidColor’ elements are never rendered directly; their only usage is as something that can be referenced using the ‘fill’ and ‘stroke’ properties. The ‘display’ property does not apply to the ‘solidColor’ element; thus, ‘solidColor’ elements are not directly rendered even if the ‘display’ property is set to a value other than none, and ‘solidColor’ elements are available for referencing even when the ‘display’ property on the ‘solidColor’ element or any of its ancestors is set to none.

Solid colors are defined by a ‘solidColor’ element.

‘solidColor’

Categories:

Paint server element

Content model:

Any number of the following elements, in any order:

paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

animate, animateColor, set

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’

DOM Interfaces:

SVGSolidColorElement

13.2.1. Properties

‘solid-color’

The ‘solid-color’ property specifies the color of the ‘solidColor’. The keyword currentColor and ICC colors can be specified in the same manner as within a <paint> specification for the ‘fill’ and ‘stroke’ properties.

Value: currentColor | <color> <icccolor>
Initial: black
Applies to: ‘solid-color’ elements
Inherited: no
Percentages: N/A
Media: visual
Animatable: yes

‘solid-opacity’

The ‘solid-opacity’ property defines the opacity of the ‘solidColor’.

Value: <opacity-value>
Initial: 1
Applies to: ‘solid-color’ elements
Inherited: no
Percentages: N/A
Media: visual
Animatable: yes

<opacity-value>: The opacity of the 'solidColor'. Any values outside the range 0.0 (fully transparent) to 1.0 (fully opaque) must be clamped to this range. The value of 'solid-opacity' is independent of the opacity used to render the paint via ‘fill’ or ‘stroke’.

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="2.0"
     viewBox="0 0 300 100" >

  <title>Example solidColor</title>
  <desc>Fill objects using a solidColor paint server.</desc>

  <defs>
    <solidColor id="MyLightPurple" solid-color="#a080ff" solid-opacity="0.5"/>
  </defs>

  <!-- The shapes are filled using a solidColor paint server -->
  <circle fill="url(#MyLightPurple)" cx="50" cy="50" r="40"/>
  <rect   fill="url(#MyLightPurple)" x="110" y="10" width="80" height="80"/>
  <path   fill="url(#MyLightPurple)" d="m 250 10 l 40 80 -80 0 z"/>
</svg>

Example solidcolor.svg

View this example as SVG (SVG-enabled browsers only)

13.3. Gradients

Gradients consist of smooth color transitions between points on a drawing surface. SVG provides for three types of gradients:

linear gradients,
radial gradients,
mesh gradients.

Once a gradient is defined, a graphics element can be filled or stroked with the gradient by setting the ‘fill’ or ‘stroke’ properties to reference the gradient.

Color transitions for linear and radial gradients are defined by a series of color stops along a gradient vector. A gradient normal defines how the colors in a vector are painted to the surface. For a linear gradient, the normal corresponds to lines with the same color. It is perpendicular to the vector in an untransformed gradient. When a graphics element references a gradient, conceptually the graphics element should take a copy of the gradient vector and gradient normal and treat it as part of its own geometry. Any transformations applied to the graphics element geometry also apply to the copied gradient vector and gradient normal. Any gradient transforms that are specified on the reference gradient are applied before any graphics element transformations are applied to the gradient.

Image of linear and radial gradients with vectors and normals indicated.

Linear and radial gradients with the gradient vector and gradient normal indicated. The vector consists of three stops shown by small circles.

Would it be better to just refer to the normal as the line where color is constant. In this case, it would be a circle for an untransformed radial gradient.

Alternative figure:

Linear and radial gradients with the gradient vector indicated. The vector consists of three stops shown by small circles. One gradient normal is shown for each gradient.

Color transitions for mesh gradients are defined by an array of color stops. The mapping of colors to the drawing surface in this case is done by geometric data located in the stops. This is discussed in detail in the mesh gradients section.

13.3.1. Linear gradients

Linear gradients are defined by a ‘linearGradient’ element.

‘linearGradient’

Categories:

Gradient element, paint server element

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

animate, animateTransform, set, stop

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘x1’
‘y1’
‘x2’
‘y2’
‘gradientUnits’
‘gradientTransform’
‘spreadMethod’
‘xlink:href’

DOM Interfaces:

SVGLinearGradientElement

13.3.1.1. Attributes

gradientUnits

Defines the coordinate system for attributes ‘x1’, ‘y1’, ‘x2’ and ‘y2’.

Value: userSpaceOnUse | objectBoundingBox
lacuna value: objectBoundingBox
Animatable: yes

userSpaceOnUse

If gradientUnits="userSpaceOnUse", ‘x1’, ‘y1’, ‘x2’, and ‘y2’ represent values in the coordinate system that results from taking the current user coordinate system in place at the time when the gradient element is referenced (i.e., the user coordinate system for the element referencing the gradient element via a ‘fill’ or ‘stroke’ property) and then applying the transform specified by attribute ‘gradientTransform’. Percentages represent values relative to the current viewport.

objectBoundingBox

If gradientUnits="objectBoundingBox", the user coordinate system for attributes ‘x1’, ‘y1’, ‘x2’ and ‘y2’ is established using the bounding box of the element to which the gradient is applied (see Object bounding box units) and then applying the transform specified by attribute ‘gradientTransform’. Percentages represent values relative to the bounding box for the object.

When gradientUnits="objectBoundingBox" and ‘gradientTransform’ is the identity matrix, the normal of the linear gradient is perpendicular to the gradient vector in object bounding box space (i.e., the abstract coordinate system where (0,0) is at the top/left of the object bounding box and (1,1) is at the bottom/right of the object bounding box). When the object's bounding box is not square, the gradient normal which is initially perpendicular to the gradient vector within object bounding box space may render non-perpendicular relative to the gradient vector in user space. If the gradient vector is parallel to one of the axes of the bounding box, the gradient normal will remain perpendicular. This transformation is due to application of the non-uniform scaling transformation from bounding box space to user space.

gradientTransform

Contains the definition of an optional additional transformation from the gradient coordinate system onto the target coordinate system (i.e., 'userSpaceOnUse' or 'objectBoundingBox'). This allows for things such as skewing the gradient. This additional transformation matrix is post-multiplied to (i.e., inserted to the right of) any previously defined transformations, including the implicit transformation necessary to convert from object bounding box units to user space.

Value: <transform-list>
lacuna value: identity transform
Animatable: yes

x1

‘x1’, ‘y1’, ‘x2’ and ‘y2’ define a gradient vector for the linear gradient. This gradient vector provides starting and ending points onto which the gradient stops are mapped. The values of ‘x1’, ‘y1’, ‘x2’ and ‘y2’ can be either numbers or percentages.

Value: <length>
lacuna value: 0%
Animatable: yes

y1

See ‘x1’.

Value: <length>
lacuna value: 0%
Animatable: yes

x2

See ‘x1’.

Value: <length>
lacuna value: 100%
Animatable: yes

y2

See ‘x1’.

Value: <length>
lacuna value: 100%
Animatable: yes

SVG 1.1 2nd edition has lacuna value="0%".

spreadMethod

Indicates what happens if the gradient starts or ends inside the bounds of the target rectangle.

Value: pad | reflect | repeat
lacuna value: pad
Animatable: yes

pad: Use the terminal colors of the gradient to fill the remainder of the target region.
reflect: Reflect the gradient pattern start-to-end, end-to-start, start-to-end, etc. continuously until the target rectangle is filled.
repeat: Repeat the gradient pattern start-to-end, start-to-end, start-to-end, etc. continuously until the target region is filled.

Image of the three possible values for 'spreadMethod'.

Illustration of the three possible values for spreadMethod, from left to right: pad, reflect, repeat. The gradient vector spans from 40% to 60% of the bounding box width.

xlink:href

An IRI reference to a different ‘linearGradient’ or ‘radialGradient’ element within the current SVG document fragment. Any ‘linearGradient’ attributes which are defined on the referenced element which are not defined on this element are inherited by this element. If this element has no defined gradient stops, and the referenced element does (possibly due to its own ‘xlink:href’ attribute), then this element inherits the gradient stop from the referenced element. Inheritance can be indirect to an arbitrary level; thus, if the referenced element inherits attribute or gradient stops due to its own ‘xlink:href’ attribute, then the current element can inherit those attributes or gradient stops.

Value: <iri>
lacuna value: empty
Animatable: yes

13.3.1.2. Notes on linear gradients

If ‘x1’ = ‘x2’ and ‘y1’ = ‘y2’, then the area to be painted will be painted as a single color using the color and opacity of the last gradient stop.

Properties inherit into the ‘linearGradient’ element from its ancestors; properties do not inherit from the element referencing the ‘linearGradient’ element.

‘linearGradient’ elements are never rendered directly; their only usage is as something that can be referenced using the ‘fill’ and ‘stroke’ properties. The ‘display’ property does not apply to the ‘linearGradient’ element; thus, ‘linearGradient’ elements are not directly rendered even if the ‘display’ property is set to a value other than none, and ‘linearGradient’ elements are available for referencing even when the ‘display’ property on the ‘linearGradient’ element or any of its ancestors is set to none.

Example lingrad01 shows how to fill a rectangle by referencing a linear gradient paint server.

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="1.1"
     viewBox="0 0 300 200" >

  <title>Example lingrag01</title>
  <desc>Fill a rectangle using a linear-gradient paint server.</desc>

  <defs>
    <linearGradient id="MyGradient">
      <stop offset="5%" stop-color="#A8F" />
      <stop offset="95%" stop-color="#FDC" />
    </linearGradient>
  </defs>

  <!-- The rectangle is filled using a linear-gradient paint server -->
  <rect fill="url(#MyGradient)"
	stroke="black"
	stroke-width="2"
	x="25" y="25" width="250" height="150"/>
</svg>

Example lingrad01

View this example as SVG (SVG-enabled browsers only)

13.3.2. Radial gradients

Radial gradients are defined by a ‘radialGradient’ element.

‘radialGradient’

Categories:

Gradient element, paint server element

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

animate, animateTransform, set, stop

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘cx’
‘cy’
‘r’
‘fx’
‘fy’
‘fr’
‘gradientUnits’
‘gradientTransform’
‘spreadMethod’
‘xlink:href’

DOM Interfaces:

SVGRadialGradientElement

13.3.2.1. Attributes

gradientUnits = "userSpaceOnUse | objectBoundingBox"

Defines the coordinate system for attributes ‘cx’, ‘cy’, ‘r’, ‘fx’, ‘fy’, and ‘fr’.

lacuna value: objectBoundingBox
Animatable: yes

userSpaceOnUse

If gradientUnits="userSpaceOnUse", ‘cx’, ‘cy’, ‘r’, ‘fx’, ‘fy’, and ‘fr’ represent values in the coordinate system that results from taking the current user coordinate system in place at the time when the gradient element is referenced (i.e., the user coordinate system for the element referencing the gradient element via a ‘fill’ or ‘stroke’ property) and then applying the transform specified by attribute ‘gradientTransform’. Percentages represent values relative to the current viewport.

objectBoundingBox

If gradientUnits="objectBoundingBox", the user coordinate system for attributes ‘cx’, ‘cy’, ‘r’, ‘fx’, ‘fr’, and ‘fr’ is established using the bounding box of the element to which the gradient is applied (see Object bounding box units) and then applying the transform specified by attribute ‘gradientTransform’. Percentages represent values relative to the bounding box for the object.

When gradientUnits="objectBoundingBox" and ‘gradientTransform’ is the identity matrix, then the rings of the radial gradient are circular with respect to the object bounding box space (i.e., the abstract coordinate system where (0,0) is at the top/left of the object bounding box and (1,1) is at the bottom/right of the object bounding box). When the object's bounding box is not square, the rings that are conceptually circular within object bounding box space will render as elliptical due to application of the non-uniform scaling transformation from bounding box space to user space.

gradientTransform = "<transform-list>"

lacuna value: identity transform
Animatable: yes

cx = "<length>"

‘cx’, ‘cy’ and ‘r’ define the end circle for the radial gradient. The gradient will be drawn such that the 100% gradient stop is mapped to the perimeter of this end circle.

lacuna value: 50%
Animatable: yes

cy = "<length>"

See ‘cx’.

lacuna value: 50%
Animatable: yes

r = "<length>"

See ‘cx’.

A negative value is an error (see Error processing).

lacuna value: 50%
Animatable: yes

fx = "<length>"

‘fx’, ‘fy’, and ‘fr’ define the start circle for the radial gradient. The gradient will be drawn such that the 0% gradient stop is mapped to the perimeter of this start circle.

lacuna value: see below
Animatable: yes

If attribute ‘fx’ is not specified, ‘fx’ will coincide with the presentational value of ‘cx’ for the element whether the value for 'cx' was inherited or not. If the element references an element that specifies a value for 'fx', then the value of 'fx' is inherited from the referenced element.

Diagram of various radial gradient attributes.

This diagram shows how the geometric attributes are defined for the case where ‘fr’ is 50% of ‘r’. The small circle marks the center of the outermost circle (‘cx’,‘cy’), while the cross marks the center of the innermost circle (‘fx’,‘fy’). The dashed lines show two gradient vectors. Vectors connect corresponding points on the inner and outer most circles. The region outside the outer circle is painted with the the last ‘stop-color’ while the region inside the inner circle is painted with the first ‘stop-color’.

fy = "<length>"

See ‘fx’.

lacuna value: see below
Animatable: yes

If attribute ‘fy’ is not specified, ‘fy’ will coincide with the presentational value of ‘cy’ for the element whether the value for 'cy' was inherited or not. If the element references an element that specifies a value for 'fy', then the value of 'fy' is inherited from the referenced element.

fr = "<length>"

New in SVG 2. Added to align with Canvas.

‘fr’ is the radius of the focal circle. See ‘fx’.

A negative value is an error (see Error processing).

lacuna value: 0%, see below
Animatable: yes

If the attribute is not specified, the effect is as if a value of '0%' were specified. If the element references an element that specifies a value for 'fr', then the value of 'fr' is inherited from the referenced element.

SVG 2 Requirement:	Allow specifying focal circle radius in radial gradients.
Resolution:	Add an ‘fr’ attribute to ‘radialGradient’> for SVG 2.
Purpose:	To align with Canvas. The zero-offset stop would be along the circle defined by the ‘fx’, ‘fy’ and ‘fr’ attributes.
Owner:	Erik (ACTION-3098)

spreadMethod = "pad | reflect | repeat"

Indicates what happens if the gradient starts or ends inside the bounds of the object(s) being painted by the gradient. Has the same values and meanings as the ‘spreadMethod’ attribute on ‘linearGradient’ element.

lacuna value: pad
Animatable: yes

xlink:href = "<iri>"

An IRI reference to a different ‘linearGradient’ or ‘radialGradient’ element within the current SVG document fragment. Any ‘radialGradient’ attributes which are defined on the referenced element which are not defined on this element are inherited by this element. If this element has no defined gradient stops, and the referenced element does (possibly due to its own ‘xlink:href’ attribute), then this element inherits the gradient stop from the referenced element. Inheritance can be indirect to an arbitrary level; thus, if the referenced element inherits attribute or gradient stops due to its own ‘xlink:href’ attribute, then the current element can inherit those attributes or gradient stops.

lacuna value: empty
Animatable: yes

SVG 2 Requirement:	Clarify radial gradients with focal point on the circle.
Resolution:	When the focal point is on the circle edge, with repeat, then the distance between the first and last stop for the repeating colors is 0 and the paint should generate a color that is the average of all the gradient stops.
Purpose:	To improve interoperability of radial gradients.
Owner:	Erik (ACTION-3097)
Note:	SVG 1.1 does not define what to do when the focal point is on the circle edge, with 'repeat'. The distance between the first and last stop for the repeating colors is 0. It was resolved that the paint should generate a color that is the weighted average (by offset) of all the gradient stops.

13.3.2.2. Notes on radial gradients

Changed in SVG 2. SVG 1.1 required that the focal point, if outside the end circle, be moved to be on the end circle. The change was made to align with Canvas.

Allowing the focal point to lie outside the end circle was resolved at the Rigi Kaltbad working group meeting.

If the start circle defined by ‘fx’, ‘fy’ and ‘fr’ lies outside the end circle defined by ‘cx’, ‘cy’, and ‘r’, effectively a cone is created, touched by the two circles. Areas outside the cone stay untouched by the gradient (transparent black).

If the start circle fully overlaps with the end circle, no gradient is drawn. The area stays untouched (transparent black).

Image of a radial gradient with the focal (start circle) outside
the start circle.

A radial gradient with the focal (start) circle outside the start circle. The focal circle is the larger circle on the left. The gradient has spreadMethod="reflect".

Image of two radial gradients, one with the focus just inside the circumference
and one with the focus on the circumference.

Two radial gradients with spreadMethod="repeat". On the left, the focal point is just inside the right side of the circle defined by by ‘cx’, ‘cy’, and ‘r’. On the right, the focal point is on the circle. In this case, the area painted to the right of the circumference has a fill equal to the weighted average of the colors in the gradient vector.

The treatment of the area to the right of the gradient in the right-hand side of the above figure is different from that of Canvas where the area would be transparent black. The difference is to maintain compatibility with SVG 1.1.

The color space for the weighted average is the same as in which the gradient is interpolated. See Rigi Kaltbad working group meeting.

Properties inherit into the ‘radialGradient’ element from its ancestors; properties do not inherit from the element referencing the ‘radialGradient’ element.

‘radialGradient’ elements are never rendered directly; their only usage is as something that can be referenced using the ‘fill’ and ‘stroke’ properties. The ‘display’ property does not apply to the ‘radialGradient’ element; thus, ‘radialGradient’ elements are not directly rendered even if the ‘display’ property is set to a value other than none, and ‘radialGradient’ elements are available for referencing even when the ‘display’ property on the ‘radialGradient’ element or any of its ancestors is set to none.

Example radgrad01 shows how to fill a rectangle by referencing a radial gradient paint server.

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="1.1"
     viewBox="0 0 300 200" >
  <title>Example radgrad01</title>
  <desc>Fill a rectangle by referencing a radial gradient paint server.</desc>

  <defs>
    <radialGradient id="MyGradient"
		    gradientUnits="userSpaceOnUse"
		    cx="150" cy="100"
		    r="100">
      <stop offset="0%"   stop-color="#A8F" />
      <stop offset="50%"  stop-color="#FDC" />
      <stop offset="100%" stop-color="#A8F" />
    </radialGradient>
  </defs>

  <!-- The rectangle is filled using a radial gradient paint server -->
  <rect fill="url(#MyGradient)"
	stroke="black"
	stroke-width="2"
	x="25" y="25" width="250" height="150"/>
</svg>

Example radgrad01

View this example as SVG (SVG-enabled browsers only)

13.3.3. Mesh gradients

New in SVG 2. Added to allow shadings along curved lines. This is needed, for example, in creating life-like drawings.

The mesh gradients in SVG are based on an array of Coons Patches. A Coons Patch is a shading defined by colors place at the corners of an area enclosed by four Bézier curves.

A single Coons-Mesh patch.

A Coons Patch is equivalent to a bi-cubic Ferguson patch where the distance between a cubic Bézier end point and its nearest control point is one-third the length of the corresponding Ferguson tangent line.

The corner colors are mapped to the patch area with a two step process. First the colors are placed at the corners of a unit square the area inside the square is colored using a bilinear interpolation. Second, the points inside the square are mapped to points inside the patch using the following formula (u, and v are the coordinates inside the unit square):

S = S_C + S_D − S_B, where
S_C(u,v) = (1−v)×C₁(u) + v×C₂(u),
S_D(u,v) = (1−u)×D₁(v) + u×D₂(v), and
S_B(u,v) = (1−v)×[(1-u)×C₁(0) + u×C₁(1)]
             +  v×[(1−u)×C₂(0) + u×C₂(1)].

MathML gets stripped out by build script.

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <msup><mi>S</mi></msup><mo>=</mo><mi>S</mi><msub>C</msub><mo>+</mo><mi>S</mi><msub>D</msub>
  </mrow>
</math>

Come up with better explanation of the mapping with diagram. The subtraction term in the above formula ensures that the boundary conditions are met.

One method of rendering a patch is to "divide and conquer." Check if the four corner colors of the patch are the same within a specified tolerance. If so, paint the patch with the average color using the normal path filling routine. If not, divide the patch into four smaller patches and repeat the color tolerance check. Repeat the process as many times as necessary.

Another way to render a patch is to first divide the patch vertically or horizontally into a series of smaller patches that are each less than one pixel high or wide. Then each resulting patch can be rendered as a path.

For a mesh, the individual patches are placed in an array. There are two reasons for using an array. The first is that an array of meshes is a natural result for most content creation processes (start with a path and then subdivide its area into rows and columns of patches). The second is that the data can be compacted by sharing sides and corners. The array structure is conceptual only. The actual mesh can be distorted in any way possible. The mesh gradient syntax is designed so that it is easy to simulate other types of gradients such as conical gradients or triangle meshes as shown in the examples below.

The structure of a mesh gradient is as follows:

<meshGradient x="100" y="100">
  <meshRow>
    <meshPatch>
      <stop .../>
        Up to four stops in first patch. See details below.
    </meshPatch>
    <meshPatch>
      Any number of meshPatches in row.
    </meshPatch>
  </meshRow>
  <meshRow>
    Any number of meshRows, each with the same number of meshPatches as in the first row.
  </meshRow>
</meshGradient>

SVG 2 Requirement:	Support photorealistic gradients.
Resolution:	Mesh gradients are accepted by the WG for SVG 2.
Purpose:	To allow more complex gradients such as those found in nature.
Owner:	Tav (ACTION-3121)

Resolution: Rename stop-path to 'd' or 'path' (Coons patch syntax).

Seattle 2011 F2F day 3

Resolution: We will allow just C/c/L/l in mesh path data. We will leave out tensor control points. We will not allow multiple colors at mesh intersections, just use zero size patches instead.

Boston 2011 F2F

Mesh gradients are defined by a ‘meshGradient’ element.

‘meshGradient’

Categories:

Gradient element, paint server element

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

animate, animateTransform, meshRow, set

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘x’
‘y’
‘gradientUnits’
‘gradientTransform’
‘xlink:href’

DOM Interfaces:

SVGMeshGradientElement

TODO: Define ‘x’, ‘y’, ‘gradientUnits’ ‘gradientTransform’ and ‘href’ attributes.

Mesh rows are defined by a ‘meshRow’ element.

‘meshRow’

Categories:

None

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

meshPatch

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’

DOM Interfaces:

SVGMeshRowElement

Mesh patches are defined by a ‘meshPatch’ element.

‘meshPatch’

Categories:

None

Content model:

Any number of descriptive elements and from one to four ‘stop’ elements, in any order.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’

DOM Interfaces:

SVGMeshPatchElement

13.3.4. Gradient stops

The vector (linear and radial gradients) or array (mesh gradients) of colors to use in a gradient is defined by the ‘stop’ elements that are child elements to a ‘linearGradient’, ‘radialGradient’, or ‘meshPatch’ element.

In SVG 1.1, the above read: "The ramp of colors..." but "ramp" is used nowhere else in this section.

‘stop’

Categories:

None

Content model:

Any number of the following elements, in any order:

paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

animate, animateColor, set

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’
‘offset’
‘path’

DOM Interfaces:

SVGStopElement

13.3.4.1. Attributes

offset

Indicates were the gradient stop is placed. For linear gradients, the ‘offset’ attribute represents a location along the gradient vector. For radial gradients, it represents a fractional distance from the edge of the innermost/smallest circle to the edge of the outermost/largest circle. This attribute does not apply to mesh gradients.

Value: <number> | <percentage>
lacuna value: see notes below
Animatable: yes

<number>: A number usually ranging from 0 to 1.
<percentage>: A percentage usually ranging from 0% to 100%.

path

Gives the path for one side of a mesh gradient patch. This attribute applies only to mesh gradients.

Value: mesh path data
lacuna value: see notes below
Animatable: yes

A description of mesh path data.

13.3.4.2. Properties

‘stop-color’

The ‘stop-color’ property indicates what color to use at that gradient stop. The keyword currentColor and ICC colors can be specified in the same manner as within a <paint> specification for the ‘fill’ and ‘stroke’ properties.

Value: currentColor | <color> <icccolor>
Initial: black
Applies to: ‘stop’ elements
Inherited: no
Percentages: N/A
Media: visual
Animatable: yes

‘stop-opacity’

The ‘stop-opacity’ property defines the opacity of a given gradient stop.

Value: <opacity-value>
Initial: 1
Applies to: ‘stop’ elements
Inherited: no
Percentages: N/A
Media: visual
Animatable: yes

<opacity-value>: The opacity of the 'stopColor'. Any values outside the range 0.0 (fully transparent) to 1.0 (fully opaque) must be clamped to this range. The value of 'stop-opacity' is independent of the opacity used to render the paint via ‘fill’ or ‘stroke’.

13.3.4.3. Notes on gradient stops

Gradient offset values less than 0 (or less than 0%) are rounded up to 0%. Gradient offset values greater than 1 (or greater than 100%) are rounded down to 100%.
It is necessary that at least two stops defined to have a gradient effect. If no stops are defined, then painting shall occur as if 'none' were specified as the paint style. If one stop is defined, then paint with the solid color fill using the color defined for that gradient stop.
Each gradient offset value is required to be equal to or greater than the previous gradient stop's offset value. If a given gradient stop's offset value is not equal to or greater than all previous offset values, then the offset value is adjusted to be equal to the largest of all previous offset values.
If two gradient stops have the same offset value, then the latter gradient stop controls the color value at the overlap point. In particular:
```
<stop offset="0" stop-color="white"/>
<stop offset=".2" stop-color="red"/>
<stop offset=".2" stop-color="blue"/>
<stop offset="1" stop-color="black"/>
```
will have approximately the same effect as:
```
<stop offset="0" stop-color="white"/>
<stop offset=".1999999999" stop-color="red"/>
<stop offset=".2" stop-color="blue"/>
<stop offset="1" stop-color="black"/>
```
which is a gradient that goes smoothly from white to red, then abruptly shifts from red to blue, and then goes smoothly from blue to black.

13.4. Patterns

A pattern is used to ‘fill’ or ‘stroke’ an object using a pre-defined graphic object which can be replicated ("tiled") at fixed intervals in x and y to cover the areas to be painted. Patterns are defined using a ‘pattern’ element and then referenced by properties ‘fill’ and ‘stroke’ on a given graphics element to indicate that the given element shall be filled or stroked with the pattern.

Attributes ‘x’, ‘y’, ‘width’, ‘height’ and ‘patternUnits’ define a reference rectangle somewhere on the infinite canvas. The reference rectangle has its top/left at (x, y) and its bottom/right at (x + width, y + height). The tiling theoretically extends a series of such rectangles to infinity in X and Y (positive and negative), with rectangles starting at (x + m*width, y + n* height) for each possible integer value for m and n.

‘pattern’

Categories:

Container element, paint server element

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’
structural elements — ‘defs’, ‘g’, ‘svg’, ‘symbol’, ‘use’

a, altGlyphDef, clipPath, color-profile, cursor, filter, font, font-face, foreignObject, image, marker, mask, script, style, switch, text, view

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
presentation attributes —
style attributes — ‘class’, ‘style’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘viewBox’
‘preserveAspectRatio’
‘x’
‘y’
‘width’
‘height’
‘patternUnits’
‘patternContentUnits’
‘patternTransform’
‘xlink:href’

DOM Interfaces:

SVGPatternElement

13.4.1. Attributes

patternUnits

Defines the coordinate system for attributes ‘x’, ‘y’, ‘width’ and ‘height’.

Value: userSpaceOnUse | objectBoundingBox
lacuna value: objectBoundingBox
Animatable: yes

userSpaceOnUse: If patternUnits="userSpaceOnUse", ‘x’, ‘y’, ‘width’ and ‘height’ represent values in the coordinate system that results from taking the current user coordinate system in place at the time when the ‘pattern’ element is referenced (i.e., the user coordinate system for the element referencing the ‘pattern’ element via a ‘fill’ or ‘stroke’ property) and then applying the transform specified by attribute ‘patternTransform’. Percentages represent values relative to the current viewport.
objectBoundingBox: If patternUnits="objectBoundingBox", the user coordinate system for attributes ‘x’, ‘y’, ‘width’ and ‘height’ is established using the bounding box of the element to which the pattern is applied (see Object bounding box units) and then applying the transform specified by attribute ‘patternTransform’. Percentages represent values relative to the bounding box for the object.

patternContentUnits

Defines the coordinate system for the contents of the ‘pattern’. Note that this attribute has no effect if attribute ‘viewBox’ is specified.

Value: userSpaceOnUse | objectBoundingBox
lacuna value: userSpaceOnUse
Animatable: yes

userSpaceOnUse: If patternContentUnits="userSpaceOnUse", the user coordinate system for the contents of the ‘pattern’ element is the coordinate system that results from taking the current user coordinate system in place at the time when the ‘pattern’ element is referenced (i.e., the user coordinate system for the element referencing the ‘pattern’ element via a ‘fill’ or ‘stroke’ property) and then applying the transform specified by attribute ‘patternTransform’.
objectBoundingBox: If patternContentUnits="objectBoundingBox", the user coordinate system for the contents of the ‘pattern’ element is established using the bounding box of the element to which the pattern is applied (see Object bounding box units) and then applying the transform specified by attribute ‘patternTransform’.

patternTransform

Contains the definition of an optional additional transformation from the pattern coordinate system onto the target coordinate system (i.e., 'userSpaceOnUse' or 'objectBoundingBox'). This allows for things such as skewing the pattern tiles. This additional transformation matrix is post-multiplied to (i.e., inserted to the right of) any previously defined transformations, including the implicit transformation necessary to convert from object bounding box units to user space.

Value: <transform-list>
lacuna value: identity transform
Animatable: yes

x

‘x’, ‘y’, ‘width’ and ‘height’ indicate how the pattern tiles are placed and spaced. These attributes represent coordinates and values in the coordinate space specified by the combination of attributes ‘patternUnits’ and ‘patternTransform’.

Value: <length>
lacuna value: 0
Animatable: yes

y

See ‘x’.

Value: <length>
lacuna value: 0
Animatable: yes

width

See ‘x’.

Value: <length>
lacuna value: 0
Animatable: yes

A negative value is an error (see Error processing). A value of zero disables rendering of the element (i.e., no paint is applied).

height

See ‘x’.

Value: <length>
lacuna value: 0
Animatable: yes

A negative value is an error (see Error processing). A value of zero disables rendering of the element (i.e., no paint is applied).

xlink:href

An IRI reference to a different ‘pattern’ element within the current SVG document fragment. Any attributes which are defined on the referenced element which are not defined on this element are inherited by this element. If this element has no children, and the referenced element does (possibly due to its own ‘xlink:href’ attribute), then this element inherits the children from the referenced element. Inheritance can be indirect to an arbitrary level; thus, if the referenced element inherits attributes or children due to its own ‘xlink:href’ attribute, then the current element can inherit those attributes or children.

Value: <iri>
lacuna value: empty
Animatable: yes

preserveAspectRatio

See ‘preserveAspectRatio’.

Value: [defer] <align> [<meetOrSlice>]
lacuna value: xMidYMid meet
Animatable: yes

13.4.2. Notes on patterns

SVG's user agent style sheet sets the ‘overflow’ property for ‘pattern’ elements to hidden, which causes a rectangular clipping path to be created at the bounds of the pattern tile. Unless the ‘overflow’ property is overridden, any graphics within the pattern which goes outside of the pattern rectangle will be clipped. Note that if the ‘overflow’ property is set to visible the rendering behavior for the pattern is undefined. Example pattern01 below shows the effect of clipping to the pattern tile.

The contents of the ‘pattern’ are relative to a new coordinate system. If there is a ‘viewBox’ attribute, then the new coordinate system is fitted into the region defined by the ‘x’, ‘y’, ‘width’, ‘height’ and ‘patternUnits’ attributes on the ‘pattern’ element using the standard rules for ‘viewBox’ and ‘preserveAspectRatio’. If there is no ‘viewBox’ attribute, then the new coordinate system has its origin at (x, y), where x is established by the ‘x’ attribute on the ‘pattern’ element, and y is established by the ‘y’ attribute on the ‘pattern’ element. Thus, in the following example:

<pattern x="10" y="10" width="20" height="20">
  <rect x="5" y="5" width="10" height="10"/>
</pattern>

the rectangle has its top/left located 5 units to the right and 5 units down from the origin of the pattern tile.

The ‘viewBox’ attribute introduces a supplemental transformation which is applied on top of any transformations necessary to create a new pattern coordinate system due to attributes ‘x’, ‘y’, ‘width’, ‘height’ and ‘patternUnits’.

Properties inherit into the ‘pattern’ element from its ancestors; properties do not inherit from the element referencing the ‘pattern’ element.

‘pattern’ elements are never rendered directly; their only usage is as something that can be referenced using the ‘fill’ and ‘stroke’ properties. The ‘display’ property does not apply to the ‘pattern’ element; thus, ‘pattern’ elements are not directly rendered even if the ‘display’ property is set to a value other than none, and ‘pattern’ elements are available for referencing even when the ‘display’ property on the ‘pattern’ element or any of its ancestors is set to none.

Event attributes and event listeners attached to the contents of a ‘pattern’ element are not processed; only the rendering aspects of ‘pattern’ elements are processed.

Example pattern01 shows how to fill a rectangle by referencing a pattern paint server. Note how the blue stroke of each triangle has been slightly clipped at the top and the left. This is due to SVG's user agent style sheet setting the ‘overflow’ property for ‘pattern’ elements to hidden, which causes the pattern to be clipped to the bounds of the pattern tile.

<?xml version="1.0" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg"
     version="1.1"
     viewBox="0 0 300 200" >

  <title>Example pattern01</title>
  <desc>Fill an ellipse using a pattern paint server.</desc>

  <defs>
    <pattern id="TrianglePattern"
	     patternUnits="userSpaceOnUse"
             x="0" y="0" width="50" height="50"
             viewBox="0 0 10 10" >
      <path d="M 0 0 L 7 0 L 3.5 7 z"
	    fill="plum"
	    stroke="blue" />
    </pattern> 
  </defs>

  <!-- The ellipse is filled using a triangle pattern paint server -->
  <ellipse fill="url(#TrianglePattern)"
	   stroke="black"
	   stroke-width="2"
           cx="150" cy="100" rx="125" ry="75" />
</svg>

Example pattern01

View this example as SVG (SVG-enabled browsers only)

13.5. DOM interfaces

13.5.1. Interface SVGSolidColorElement

IDL needs to be added for SVGSolidColorElement.

13.5.2. Interface SVGGradientElement

The SVGGradientElement interface is a base interface used by SVGLinearGradientElement and SVGRadialGradientElement.

interface SVGGradientElement : SVGElement {

  // Spread Method Types
  const unsigned short SVG_SPREADMETHOD_UNKNOWN = 0;
  const unsigned short SVG_SPREADMETHOD_PAD = 1;
  const unsigned short SVG_SPREADMETHOD_REFLECT = 2;
  const unsigned short SVG_SPREADMETHOD_REPEAT = 3;

  readonly attribute SVGAnimatedEnumeration gradientUnits;
  readonly attribute SVGAnimatedTransformList gradientTransform;
  readonly attribute SVGAnimatedEnumeration spreadMethod;
};

SVGGradientElement implements SVGURIReference;
SVGGradientElement implements SVGUnitTypes;

Constants in group “Spread Method Types”:

SVG_SPREADMETHOD_UNKNOWN (unsigned short): The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_SPREADMETHOD_PAD (unsigned short): Corresponds to value 'pad'.
SVG_SPREADMETHOD_REFLECT (unsigned short): Corresponds to value 'reflect'.
SVG_SPREADMETHOD_REPEAT (unsigned short): Corresponds to value 'repeat'.

Attributes:

gradientUnits (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘gradientUnits’ on the given element. Takes one of the constants defined in SVGUnitTypes.
gradientTransform (readonly SVGAnimatedTransformList): Corresponds to attribute ‘gradientTransform’ on the given element.
spreadMethod (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘spreadMethod’ on the given element. One of the Spread Method Types defined on this interface.

13.5.3. Interface SVGLinearGradientElement

The SVGLinearGradientElement interface corresponds to the ‘linearGradient’ element.

interface SVGLinearGradientElement : SVGGradientElement {
  readonly attribute SVGAnimatedLength x1;
  readonly attribute SVGAnimatedLength y1;
  readonly attribute SVGAnimatedLength x2;
  readonly attribute SVGAnimatedLength y2;
};

Attributes:

x1 (readonly SVGAnimatedLength): Corresponds to attribute ‘x1’ on the given ‘linearGradient’ element.
y1 (readonly SVGAnimatedLength): Corresponds to attribute ‘y1’ on the given ‘linearGradient’ element.
x2 (readonly SVGAnimatedLength): Corresponds to attribute ‘x2’ on the given ‘linearGradient’ element.
y2 (readonly SVGAnimatedLength): Corresponds to attribute ‘y2’ on the given ‘linearGradient’ element.

13.5.4. Interface SVGRadialGradientElement

The SVGRadialGradientElement interface corresponds to the ‘radialGradient’ element.

interface SVGRadialGradientElement : SVGGradientElement {
  readonly attribute SVGAnimatedLength cx;
  readonly attribute SVGAnimatedLength cy;
  readonly attribute SVGAnimatedLength r;
  readonly attribute SVGAnimatedLength fx;
  readonly attribute SVGAnimatedLength fy;
  readonly attribute SVGAnimatedLength fr;
};

Attributes:

cx (readonly SVGAnimatedLength): Corresponds to attribute ‘cx’ on the given ‘radialGradient’ element.
cy (readonly SVGAnimatedLength): Corresponds to attribute ‘cy’ on the given ‘radialGradient’ element.
r (readonly SVGAnimatedLength): Corresponds to attribute ‘r’ on the given ‘radialGradient’ element.
fx (readonly SVGAnimatedLength): Corresponds to attribute ‘fx’ on the given ‘radialGradient’ element.
fy (readonly SVGAnimatedLength): Corresponds to attribute ‘fy’ on the given ‘radialGradient’ element.
fr (readonly SVGAnimatedLength): Corresponds to attribute ‘fr’ on the given ‘radialGradient’ element.

13.5.5. Interface SVGMeshGradientElement

The SVGMeshGradientElement interface corresponds to the ‘meshGradient’ element.

interface SVGMeshGradientElement : SVGGradientElement {
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
};

Attributes:

x (readonly SVGAnimatedLength): Corresponds to attribute ‘x’ on the given ‘meshGradient’ element.
y (readonly SVGAnimatedLength): Corresponds to attribute ‘y’ on the given ‘meshGradient’ element.

13.5.6. Interface SVGMeshRowElement

interface SVGMeshRowElement : SVGElement {
};

13.5.7. Interface SVGMeshPatchElement

interface SVGMeshPatchElement : SVGElement {
};

13.5.8. Interface SVGStopElement

The SVGStopElement interface corresponds to the ‘stop’ element.

interface SVGStopElement : SVGElement {
  readonly attribute SVGAnimatedNumber offset;
};

Attributes:

offset (readonly SVGAnimatedNumber): Corresponds to attribute ‘offset’ on the given ‘stop’ element.

13.5.9. Interface SVGPatternElement

The SVGPatternElement interface corresponds to the ‘pattern’ element.

interface SVGPatternElement : SVGElement {
  readonly attribute SVGAnimatedEnumeration patternUnits;
  readonly attribute SVGAnimatedEnumeration patternContentUnits;
  readonly attribute SVGAnimatedTransformList patternTransform;
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
  readonly attribute SVGAnimatedLength width;
  readonly attribute SVGAnimatedLength height;
};

SVGPatternElement implements SVGFitToViewBox;
SVGPatternElement implements SVGURIReference;
SVGPatternElement implements SVGUnitTypes;

Attributes:

patternUnits (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘patternUnits’ on the given ‘pattern’ element. Takes one of the constants defined in SVGUnitTypes.
patternContentUnits (readonly SVGAnimatedEnumeration): Corresponds to attribute ‘patternContentUnits’ on the given ‘pattern’ element. Takes one of the constants defined in SVGUnitTypes.
patternTransform (readonly SVGAnimatedTransformList): Corresponds to attribute ‘patternTransform’ on the given ‘pattern’ element.
x (readonly SVGAnimatedLength): Corresponds to attribute ‘x’ on the given ‘pattern’ element.
y (readonly SVGAnimatedLength): Corresponds to attribute ‘y’ on the given ‘pattern’ element.
width (readonly SVGAnimatedLength): Corresponds to attribute ‘width’ on the given ‘pattern’ element.
height (readonly SVGAnimatedLength): Corresponds to attribute ‘height’ on the given ‘pattern’ element.

Chapter 16: Interactivity

16.1. Introduction

SVG content can be interactive (i.e., responsive to user-initiated events) by utilizing the following features in the SVG language:

User-initiated actions such as button presses on the pointing device (e.g., a mouse) can cause animations or scripts to execute.
The user can initiate hyperlinks to new Web pages (see Links out of SVG content: the ‘a’ element) by actions such as mouse clicks when the pointing device is positioned over particular graphics elements.
In many cases, depending on the value of the ‘zoomAndPan’ attribute on the ‘svg’ element and on the characteristics of the user agent, users are able to zoom into and pan around SVG content.
User movements of the pointing device can cause changes to the cursor that shows the current position of the pointing device.

This chapter describes:

information about events, including under which circumstances events are triggered
how to indicate whether a given document can be zoomed and panned
how to specify which cursors to use

Related information can be found in other chapters:

hyperlinks are discussed in Links
scripting and event attributes are discussed in Scripting
SVG's relationship to DOM2 events is discussed in Relationship with DOM2 event model
animation is discussed in Animation

16.2. Complete list of supported events

SVG 2 Requirement:	Support anchor change events.
Resolution:	SVG 2 will consider adding HTML document wide events (including hashchange) apply to SVG documents where they make sense.
Purpose:	To allow authors to use the same set of event listener attributes on a root SVG element that they can on an HTML body or root element.
Owner:	Cameron (ACTION-3278)

SVG 2 Requirement:	Have event listener attributes on an appropriate interface.
Resolution:	SVG 2 will move all events listener attributes to Element, in accordance with the similar move in HTML.
Purpose:	To align with HTML.
Owner:	Cameron (ACTION-3283)

SVG 2 Requirement:	Introduce evt as an alias to event in event handlers.
Resolution:	We decide to resolve ISSUE-2176 by introducing evt as an alias to event in event handlers.
Purpose:	To align with HTML.
Owner:	Cameron (ACTION-3093)

SVG 2 Requirement:	Support drag & drop functionality.
Resolution:	SVG 2 may require drag & drop functionality, and we'll investigate HTML5's functionality for that.
Purpose:	To allow easier drag & drop in SVG, and to align with HTML.
Owner:	Erik (ACTION-3328)

The following aspects of SVG are affected by events:

Using SVG Document Object Model (DOM), a script can register DOM 2 event listeners ([DOM2EVENTS], section 1.3) so that script can be invoked when a given event occurs.
SVG includes event attributes on selected elements which define script that can be executed when a given event occurs in association with the given element.
SVG's animation elements can be defined to begin or end based on events.

The following table lists all of the events which are recognized and supported in SVG. The Event name in the first column is the name to use within SVG's animation elements to define the events which can start or end animations. The DOM2 name in the second column is the name to use when defining DOM 2 event listeners ([DOM2EVENTS], section 1.3). The Event attribute name in the fourth column contains the corresponding name of the event attributes that can be attached to elements in the SVG language.

Requirements in the table on whether an event of a given type bubbles or is cancelable apply only to events that are created and dispatched by the user agent. Events of those types created from script using the createEvent method on the Document interface can be made to bubble or be cancelable with the initEvent method.

Having all these SVG-specific duplicates of standard DOM events isn't ideal. How much can we remove? SVGLoad in particular, and how it is currently required to fire for every element.

Event name and description	DOM2 name	DOM2 category	Event attribute name
focusin Occurs when an element receives focus, such as when a ‘text’ becomes selected.	DOMFocusIn	UIEvent	onfocusin
focusout Occurs when an element loses focus, such as when a ‘text’ becomes unselected.	DOMFocusOut	UIEvent	onfocusout
activate Occurs when an element is activated, for instance, through a mouse click or a keypress. A numerical argument is provided to give an indication of the type of activation that occurs: 1 for a simple activation (e.g. a simple click or Enter), 2 for hyperactivation (for instance a double click or Shift Enter).	DOMActivate	UIEvent	onactivate
click Occurs when the pointing device button is clicked over an element. A click is defined as a mousedown and mouseup over the same screen location. The sequence of these events is: `mousedown`, `mouseup`, `click`. If multiple clicks occur at the same screen location, the sequence repeats with the `detail` attribute incrementing with each repetition.	(same)	MouseEvent	onclick
mousedown Occurs when the pointing device button is pressed over an element.	(same)	MouseEvent	onmousedown
mouseup Occurs when the pointing device button is released over an element.	(same)	MouseEvent	onmouseup
mouseover Occurs when the pointing device is moved onto an element.	(same)	MouseEvent	onmouseover
mousemove Occurs when the pointing device is moved while it is over an element.	(same)	MouseEvent	onmousemove
mouseout Occurs when the pointing device is moved away from an element.	(same)	MouseEvent	onmouseout
DOMSubtreeModified This is a general event for notification of all changes to the document. It can be used instead of the more specific events listed below. (The normative definition of this event is the description in the DOM2 specification.)	(same)	MutationEvent	none
DOMNodeInserted Fired when a node has been added as a child of another node. (The normative definition of this event is the description in the DOM2 specification.)	(same)	MutationEvent	none
DOMNodeRemoved Fired when a node is being removed from another node. (The normative definition of this event is the description in the DOM2 specification.)	(same)	MutationEvent	none
DOMNodeRemovedFromDocument Fired when a node is being removed from a document, either through direct removal of the Node or removal of a subtree in which it is contained. (The normative definition of this event is the description in the DOM2 specification.)	(same)	MutationEvent	none
DOMNodeInsertedIntoDocument Fired when a node is being inserted into a document, either through direct insertion of the Node or insertion of a subtree in which it is contained. (The normative definition of this event is the description in the DOM2 specification.)	(same)	MutationEvent	none
DOMAttrModified Fired after an attribute has been modified on a node. (The normative definition of this event is the description in the DOM2 specification.)	(same)	MutationEvent	none
DOMCharacterDataModified Fired after CharacterData within a node has been modified but the node itself has not been inserted or deleted. (The normative definition of this event is the description in the DOM2 specification.)	(same)	MutationEvent	none
SVGLoad The event is triggered at the point at which the user agent has fully parsed the element and its descendants and is ready to act appropriately upon that element, such as being ready to render the element to the target device. Referenced external resources that are required must be loaded, parsed and ready to render before the event is triggered. Optional external resources are not required to be ready for the event to be triggered. Now that ‘externalResourcesRequired’ has been removed, we need to have better wording for when SVGLoad is dispatched. SVGLoad events do not bubble and are not cancelable.	(same)	none	onload
SVGUnload Only applicable to outermost svg elements. The unload event occurs when the DOM implementation removes a document from a window or frame. SVGUnload events do not bubble and are not cancelable.	(same)	none	onunload
SVGAbort The abort event occurs when page loading is stopped before an element has been allowed to load completely. SVGAbort events bubble but are not cancelable.	(same)	none	onabort
SVGError The error event occurs when an element does not load properly or when an error occurs during script execution. SVGError events bubble but are not cancelable.	(same)	none	onerror
SVGResize Occurs when a document view is being resized. This event is only applicable to outermost svg elements and is dispatched after the resize operation has taken place. The target of the event is the ‘svg’ element. SVGResize events bubble but are not cancelable.	(same)	none	onresize
SVGScroll Occurs when a document view is being shifted along the X or Y or both axis, either through a direct user interaction or any change on the currentTranslate property available on SVGSVGElement interface. This event is only applicable to outermost svg elements and is dispatched after the shift modification has taken place. The target of the event is the ‘svg’ element. SVGScroll events bubble but are not cancelable.	(same)	none	onscroll
SVGZoom Occurs when the zoom level of a document view is being changed, either through a direct user interaction or any change to the currentScale property available on SVGSVGElement interface. This event is only applicable to outermost svg elements and is dispatched after the zoom level modification has taken place. The target of the event is the ‘svg’ element. SVGZoom events bubble but are not cancelable.	none	none	onzoom
beginEvent Occurs when an animation element begins. For details, see the description of Interface TimeEvent in the SMIL Animation specification.	none	none	onbegin
endEvent Occurs when an animation element ends. For details, see the description of Interface TimeEvent in the SMIL Animation specification.	none	none	onend
repeatEvent Occurs when an animation element repeats. It is raised each time the element repeats, after the first iteration. For details, see the description of Interface TimeEvent in the SMIL Animation specification.	none	none	onrepeat

As in DOM 2 Key events ([DOM2EVENTS], section 1.6.3), the SVG specification does not provide a key event set. An event set designed for use with keyboard input devices will be included in a later version of the DOM and SVG specifications.

Details on the parameters passed to event listeners for the event types from DOM2 can be found in the DOM2 specification. For other event types, the parameters passed to event listeners are described elsewhere in this specification.

Event listener attributes can be specified on some elements to listen to a given event. The script in such attributes is run only in response to "bubbling" and "at target" phase events dispatched to the element.

Likewise, event-value timing specifiers used in animation element ‘begin’ and ‘end’ attributes are resolved to concrete times only in response to "bubbling" and "at target" phase events dispatched to the relevant element.

16.3. User interface events

On user agents which support interactivity, it is common for authors to define SVG documents such that they are responsive to user interface events. Among the set of possible user events are pointer events, keyboard events, and document events.

In response to user interface (UI) events, the author might start an animation, perform a hyperlink to another Web page, highlight part of the document (e.g., change the color of the graphics elements which are under the pointer), initiate a "roll-over" (e.g., cause some previously hidden graphics elements to appear near the pointer) or launch a script which communicates with a remote database.

16.4. Pointer events

User interface events that occur because of user actions performed on a pointer device are called pointer events.

Many systems support pointer devices such as a mouse or trackball. On systems which use a mouse, pointer events consist of actions such as mouse movements and mouse clicks. On systems with a different pointer device, the pointing device often emulates the behavior of the mouse by providing a mechanism for equivalent user actions, such as a button to press which is equivalent to a mouse click.

For each pointer event, the SVG user agent determines the target element of a given pointer event. The target element is the topmost graphics element whose relevant graphical content is under the pointer at the time of the event. (See property ‘pointer-events’ for a description of how to determine whether an element's relevant graphical content is under the pointer, and thus in which circumstances that graphic element can be the target element for a pointer event.) When an element is not displayed (i.e., when the ‘display’ property on that element or one of its ancestors has a value of none), that element cannot be the target of pointer events.

If a target element for the pointer event exists, then the event is dispatched to that element according to the normal event flow ([DOM2EVENTS], section 1.2). Note, however, that if the target element is in a ‘use’ element shadow tree, that the event flow will include SVGElementInstance objects. See The ‘use’ element for details.

If a target element for the pointer event does not exist, then the event is ignored.

16.5. Hit-testing and processing order for user interface events

There are two distinct aspects of pointer-device interaction with an element or area:

hit-testing, to determine if a pointer event (such as a mouse movement or mouse click) occurred within the interaction area of an element, and the subsequent DOM event flow;
functional processing of actions associated with any relevant element.

16.5.1. Hit-testing

Determining whether a pointer event results in a positive hit-test depends upon the position of the pointer, the size and shape of the graphics element, and the computed value of the ‘pointer-events’ property on the element. The definition of the ‘pointer-events’ property below describes the exact region that is sensitive to pointer events for a given type of graphics element.

Note that the ‘svg’ element is not a graphics element, and in a Conforming SVG Stand-Alone File a rootmost ‘svg’ element will never be the target of pointer events, though events can bubble to this element. If a pointer event does not result in a positive hit-test on a graphics element, then it should evoke any user-agent-specific window behavior, such as a presenting a context menu or controls to allow zooming and panning of an SVG document fragment.

This specification does not define the behavior of pointer events on the rootmost ‘svg’ element for SVG images which are embedded by reference or inclusion within another document, e.g., whether the rootmost ‘svg’ element embedded in an HTML document intercepts mouse click events; future specifications may define this behavior, but for the purpose of this specification, the behavior is implementation-specific.

16.5.2. Event processing

An element which is the target of a user interface event may have particular interaction behaviors, depending upon the type of element and whether it has explicit associated interactions, such as scripted event listeners, CSS pseudo-classes matches, or declarative animations with event-based timing. The algorithm and order for processing user interface events for a given target element, after dispatching the DOM event, is as follows:

If an event handler registered on this element invokes the preventDefault() DOM method, then no further processing for this element is performed, and the event follows the event flow processing as described in DOM Level 2 Events [DOM2EVENTS] (or its successor);
If the element has an associated title or description, such as a ‘title’ element or an ‘xlink:title’ attribute, and the user agent supports the display of such information (e.g. via a tooltip or status-bar message), that information should be displayed, as appropriate to the type of pointer event;
If the element matches any relevant dynamic pseudo-class selectors appropriate to the type of pointer event, such as :hover, :active, or :focus as described in [CSS21], section 5.11, then the relevant class properties are applied;
If the element and the event type are associated with the activation or cancelation of declarative animation though the use of event-value timing specifiers, any corresponding instance times must be resolved, and any conseqential actions of this instance time resolution (such as immediately starting or stopping the animation) must be performed;
If the element is a hyperlink (e.g., it is a descendant element of an ‘a’ element), and the pointer event is of a type that activates that hyperlink (e.g. via a mouse click), and if the hyperlink traversal changes the context of the content (e.g. opens a different document, or moves the pointer away from this element by moving to another part of the same document), then no further processing for this element is performed;
If the element is a text content element, and the event type is one which the user agent recognizes as part of a text-selection operation (e.g., a mouse click and drag, or a double-click), then the text selection algorithm is performed;
If the event type is one which the user agent associates with the evocation of special user-interface controls (e.g., a right-click or command-click evoking a context menu), the user agent should evoke such user-agent-specific behavior, such as presenting a context menu or controls to allow zooming and panning of an SVG document fragment.

16.6. The ‘pointer-events’ property

In different circumstances, authors may want to control under what conditions particular graphic elements can become the target of pointer events. For example, the author might want a given element to receive pointer events only when the pointer is over the stroked perimeter of a given shape. In other cases, the author might want a given element to ignore pointer events under all circumstances so that graphical elements underneath the given element will become the target of pointer events.

The effects of masking and clipping differ with respect to pointer events. A clip path is a geometric boundary, and a given point is clearly either inside or outside that boundary; thus, pointer events must be captured normally over the rendered areas of a clipped element, but must not be captured over the clipped areas, as described in the definition of clipping paths. By contrast, a mask is not a binary transition, but a pixel operation, and different behavior for fully transparent and almost-but-not-fully-transparent may be confusingly arbitrary; as a consequence, for elements with a mask applied, pointer events must still be captured even in areas where the mask goes to zero opacity. If an author wishes to achieve an effect where the transparent parts of a mask allow pointer events to pass to an element below, a combination of masking and clipping may be used.

The ‘filter’ property has no effect on pointer events processing, and must in this context be treated as if the ‘filter’ wasn't specified.

For example, suppose a circle with a ‘stroke’ of red (i.e., the outline is solid red) and a ‘fill’ of none (i.e., the interior is not painted) is rendered directly on top of a rectangle with a ‘fill’ of blue. The author might want the circle to be the target of pointer events only when the pointer is over the perimeter of the circle. When the pointer is over the interior of the circle, the author might want the underlying rectangle to be the target element of pointer events.

The ‘pointer-events’ property specifies under what circumstances a given graphics element can be the target element for a pointer event. It affects the circumstances under which the following are processed:

user interface events such as mouse clicks
dynamic pseudo-classes (i.e., :hover, :active and :focus; [CSS21], section 5.11)
hyperlinks (see Links out of SVG content: the ‘a’ element)

Name:	pointer-events
Value:	visiblePainted \| visibleFill \| visibleStroke \| visible \| painted \| fill \| stroke \| all \| none
Initial:	visiblePainted
Applies to:	graphics elements and text content child elements
Inherited:	yes
Percentages:	N/A
Media:	visual
Computed value:	as specified
Animatable:	yes

visiblePainted: The given element can be the target element for pointer events when the ‘visibility’ property is set to visible and when the pointer is over a "painted" area. The pointer is over a painted area if it is over the interior (i.e., fill) of the element and the ‘fill’ property has an actual value other than none or it is over the perimeter (i.e., stroke) of the element and the ‘stroke’ property is set to a value other than none.
visibleFill: The given element can be the target element for pointer events when the ‘visibility’ property is set to visible and when the pointer is over the interior (i.e., fill) of the element. The value of the ‘fill’ property does not affect event processing.
visibleStroke: The given element can be the target element for pointer events when the ‘visibility’ property is set to visible and when the pointer is over the perimeter (i.e., stroke) of the element. The value of the ‘stroke’ property does not affect event processing.
visible: The given element can be the target element for pointer events when the ‘visibility’ property is set to visible and the pointer is over either the interior (i.e., fill) or the perimeter (i.e., stroke) of the element. The values of the ‘fill’ and ‘stroke’ do not affect event processing.
painted: The given element can be the target element for pointer events when the pointer is over a "painted" area. The pointer is over a painted area if it is over the interior (i.e., fill) of the element and the ‘fill’ property has an actual value other than none or it is over the perimeter (i.e., stroke) of the element and the ‘stroke’ property has an actual value other than none. The value of the ‘visibility’ property does not effect event processing.
fill: The given element can be the target element for pointer events when the pointer is over the interior (i.e., fill) of the element. The values of the ‘fill’ and ‘visibility’ properties do not affect event processing.
stroke: The given element can be the target element for pointer events when the pointer is over the perimeter (i.e., stroke) of the element. The values of the ‘stroke’ and ‘visibility’ properties do not affect event processing.
all: The given element can be the target element for pointer events whenever the pointer is over either the interior (i.e., fill) or the perimeter (i.e., stroke) of the element. The values of the ‘fill’, ‘stroke’ and ‘visibility’ properties do not affect event processing.
none: The given element does not receive pointer events.

For text elements, hit-testing is performed on a character cell basis:

The value visiblePainted means that the text string can receive events anywhere within the character cell if either the ‘fill’ property is set to a value other than none or the ‘stroke’ property is set to a value other than none, with the additional requirement that the ‘visibility’ property is set to visible.
The values visibleFill, visibleStroke and visible are equivalent and indicate that the text string can receive events anywhere within the character cell if the ‘visibility’ property is set to visible. The values of the ‘fill’ and ‘stroke’ properties do not affect event processing.
The value painted means that the text string can receive events anywhere within the character cell if either the ‘fill’ property is set to a value other than none or the ‘stroke’ property is set to a value other than none. The value of the ‘visibility’ property does not affect event processing.
The values fill, stroke and all are equivalent and indicate that the text string can receive events anywhere within the character cell. The values of the ‘fill’, ‘stroke’ and ‘visibility’ properties do not affect event processing.
The value none indicates that the given text does not receive pointer events.

For raster images, hit-testing is either performed on a whole-image basis (i.e., the rectangular area for the image is one of the determinants for whether the image receives the event) or on a per-pixel basis (i.e., the alpha values for pixels under the pointer help determine whether the image receives the event):

The value visiblePainted means that the raster image can receive events anywhere within the bounds of the image if any pixel from the raster image which is under the pointer is not fully transparent, with the additional requirement that the ‘visibility’ property is set to visible.
The values visibleFill, visibleStroke and visible are equivalent and indicate that the image can receive events anywhere within the rectangular area for the image if the ‘visibility’ property is set to visible.
The value painted means that the raster image can receive events anywhere within the bounds of the image if any pixel from the raster image which is under the pointer is not fully transparent. The value of the ‘visibility’ property does not affect event processing.
The values fill, stroke and all are equivalent and indicate that the image can receive events anywhere within the rectangular area for the image. The value of the ‘visibility’ property does not affect event processing.
The value none indicates that the image does not receive pointer events.

Note that for raster images, the values of properties ‘opacity’, ‘fill-opacity’, ‘stroke-opacity’, ‘fill’ and ‘stroke’ do not affect event processing.

16.7. Magnification and panning

SVG 2 Requirement:	Support level of detail control.
Resolution:	We will support Level of Detail control in SVG 2.
Purpose:	Control visibility of elements based on zoom level (useful, for example, in mapping).
Owner:	Doug (no action)
Note:	See Tiling and Layering Module for SVG 1.2 Tiny.

Magnification represents a complete, uniform transformation on an SVG document fragment, where the magnify operation scales all graphical elements by the same amount. A magnify operation has the effect of a supplemental scale and translate transformation placed at the outermost level on the SVG document fragment (i.e., outside the outermost svg element).

Panning represents a translation (i.e., a shift) transformation on an SVG document fragment in response to a user interface action.

SVG user agents that operate in interaction-capable user environments are required to support the ability to magnify and pan.

The outermost svg element in an SVG document fragment has attribute ‘zoomAndPan’, which takes the possible values of disable and magnify, with the default being magnify.

If disable, the user agent shall disable any magnification and panning controls and not allow the user to magnify or pan on the given document fragment.

If magnify, in environments that support user interactivity, the user agent shall provide controls to allow the user to perform a "magnify" operation on the document fragment.

If a ‘zoomAndPan’ attribute is assigned to an inner ‘svg’ element, the ‘zoomAndPan’ setting on the inner ‘svg’ element will have no effect on the SVG user agent.

Animatable: no.

16.8. Cursors

Some interactive display environments provide the ability to modify the appearance of the pointer, which is also known as the cursor. Three types of cursors are available:

Standard built-in cursors
Platform-specific custom cursors
Platform-independent custom cursors

The ‘cursor’ property is used to specify which cursor to use. The ‘cursor’ property can be used to reference standard built-in cursors by specifying a keyword such as crosshair or a custom cursor. Custom cursors are referenced via a <FuncIRI> and can point to either an external resource such as a platform-specific cursor file or to a ‘cursor’ element, which can be used to define a platform-independent cursor.

16.8.1. The effect of the ‘cursor’ property

See the CSS Basic User Interface Module Level 3 specification for the definition of ‘cursor’. [CSS3UI]

SVG uses the ‘cursor’ property to specify the type of cursor to be displayed for the pointing device when it is over a region of an element that is sensitive to pointer events, according to the value of the ‘pointer-events’ property. SVG extends the definition of ‘cursor’ from the CSS Basic User Interface Module Level 3 specification as follows:

All <uri> values in the definition of the property are instead parsed as <funciri> values.
The SVG implementation must support an <funciri> value being an IRI reference to an SVG ‘cursor’ element. If the <x> and <y> values are given for a <funciri> that refers to a ‘cursor’, they override its ‘x’ and ‘y’ attributes.

16.8.2. The ‘cursor’ element

The ‘cursor’ element can be used to define a platform-independent custom cursor. A recommended approach for defining a platform-independent custom cursor is to create a PNG image [PNG] and define a ‘cursor’ element that references the PNG image and identifies the exact position within the image which is the pointer position (i.e., the hot spot).

The PNG format is recommended because it supports the ability to define a transparency mask via an alpha channel. If a different image format is used, this format should support the definition of a transparency mask (two options: provide an explicit alpha channel or use a particular pixel color to indicate transparency). If the transparency mask can be determined, the mask defines the shape of the cursor; otherwise, the cursor is an opaque rectangle. Typically, the other pixel information (e.g., the R, G and B channels) defines the colors for those parts of the cursor which are not masked out. Note that cursors usually contain at least two colors so that the cursor can be visible over most backgrounds.

‘cursor’

Categories:

None

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’

Attributes:

aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘x’
‘y’
‘xlink:href’

DOM Interfaces:

SVGCursorElement

Attribute definitions:

x = "<length>": The x-coordinate of the position in the cursor's coordinate system which represents the precise position that is being pointed to.
If the attribute is not specified, the effect is as if a value of '0' were specified.
Animatable: yes.
y = "<length>": The y-coordinate of the position in the cursor's coordinate system which represents the precise position that is being pointed to.
If the attribute is not specified, the effect is as if a value of '0' were specified.
Animatable: yes.
xlink:href = "<FuncIRI>": A Functional IRI reference to the file or element which provides the image of the cursor.
Animatable: yes.

SVG user agents are required to support PNG format images as targets of the ‘xlink:href’ attribute.

Add an example.

16.9. DOM interfaces

16.9.1. Interface SVGCursorElement

The SVGCursorElement interface corresponds to the ‘cursor’ element.

interface SVGCursorElement : SVGElement {
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
};

SVGCursorElement implements SVGURIReference;

Attributes:

x (readonly SVGAnimatedLength): Corresponds to attribute ‘x’ on the given ‘cursor’ element.
y (readonly SVGAnimatedLength): Corresponds to attribute ‘y’ on the given ‘cursor’ element.

Chapter 19: Animation

SVG 2 Requirements:	Support for non-negative speed on time containers Support path-based animations of pairs of attributes Define all explicitly undefined parts of the SVG 1.1 spec (wrt to to-animations) Support motion animation of a specified speed Apply the changes from SVG Tiny 1.2 Animations chapter
Resolutions:	We will solve animation reversing in SVG 2. We will have support for non-negative speed="" on time containers (if we decide to include time containers) in SVG 2. We will support path-based animation of pairs of attributes. We will allow `<animateTransform type="matrix">` in SVG 2. We will support motion animation of a specified speed in SVG 2. SVG 2 will apply the changes from SVG 1.2 Tiny to the SVG animation section.
Purpose:	General improvements to the animation features of SVG 2.
Owner:	Brian (no action)
Note:	These will be addressed in the separate Web Animations specification, which SVG 2 will eventually reference.

19.1. Introduction

Because the Web is a dynamic medium, SVG supports the ability to change vector graphics over time. SVG content can be animated in the following ways:

Using CSS Animations [CSSANIMATIONS]. A CSS module that describes a way for authors to animate the values of CSS properties over time, using keyframes. The behavior of these keyframe animations can be controlled by specifying their duration, number of repeats, and repeating behavior.
Using CSS Transitions [CSS3TRANSITIONS]. A CSS module that allows changes to values of CSS properties to occur smoothly over a specified duration.
Using SVG's animation elements. SVG document fragments can describe time-based modifications to the document's elements. Using the various animation elements, you can define motion paths, fade-in or fade-out effects, and objects that grow, shrink, spin or change color.
Using the SVG DOM. The SVG DOM is defined based on the DOM4 specification [DOM4]. Every attribute and style sheet setting is accessible to scripting, and SVG offers a set of additional DOM interfaces to support efficient animation via scripting. As a result, virtually any kind of animation can be achieved. The timer facilities in scripting languages such as ECMAScript can be used to start up and control the animations [ECMA-262]. (See example below.)
SVG has been designed to allow SMIL [SMIL] to use animated or static SVG content as media components.

19.2. Animation elements

19.2.1. Overview

SVG's animation elements were developed in collaboration with the W3C Synchronized Multimedia (SYMM) Working Group, developers of the Synchronized Multimedia Integration Language (SMIL) 3.0 Specification [SMIL].

The SYMM Working Group, in collaboration with the SVG Working Group, has authored the SMIL Animation specification [SMILANIM], which represents a general-purpose XML animation feature set. SVG incorporates the animation features defined in the SMIL Animation specification and provides some SVG-specific extensions.

For an introduction to the approach and features available in any language that supports SMIL Animation, see SMIL Animation overview and SMIL Animation animation model ([SMILANIM], sections 2 and 3). For the list of animation features which go beyond SMIL Animation, see SVG extensions to SMIL Animation.

19.2.2. Relationship to SMIL Animation

SVG is a host language in terms of SMIL Animation and therefore introduces additional constraints and features as permitted by that specification. Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for SVG's animation elements and attributes is the SMIL Animation specification [SMILANIM].

SVG supports the following four animation elements which are defined in the SMIL Animation specification:

‘animate’	allows scalar attributes and properties to be assigned different values over time
‘set’	a convenient shorthand for ‘animate’, which is useful for assigning animation values to non-numeric attributes and properties, such as the ‘`visibility`’ property
‘animateMotion’	moves an element along a motion path
‘animateColor’	modifies the color value of particular attributes or properties over time

Although SVG defines ‘animateColor’, its use is deprecated in favor of simply using the ‘animate’ element to target properties that can take color values.

Additionally, SVG includes the following compatible extensions to SMIL Animation:

‘animateTransform’	modifies one of SVG's transformation attributes over time, such as the ‘`transform`’ attribute
‘path’ attribute	SVG allows any feature from SVG's path data syntax to be specified in a ‘path’ attribute to the ‘animateMotion’ element (SMIL Animation only allows a subset of SVG's path data syntax within a ‘path’ attribute)
‘mpath’ element	SVG allows an ‘animateMotion’ element to contain a child ‘mpath’ element which references an SVG ‘path’ element as the definition of the motion path
‘keyPoints’ attribute	SVG adds a ‘keyPoints’ attribute to the ‘animateMotion’ to provide precise control of the velocity of motion path animations
‘rotate’ attribute	SVG adds a ‘rotate’ attribute to the ‘animateMotion’ to control whether an object is automatically rotated so that its x-axis points in the same direction (or opposite direction) as the directional tangent vector of the motion path

The description of ‘animateTransform’ above should reference the ‘transform’ property.

For compatibility with other aspects of the language, SVG uses IRI references via an ‘xlink:href’ attribute to identify the elements which are to be targets of the animations, as allowed in SMIL 3.0.

SMIL Animation requires that the host language define the meaning for document begin and the document end. Since an ‘svg’ is sometimes the root of the XML document tree and other times can be a component of a parent XML grammar, the document begin for a given SVG document fragment is defined to be the exact time at which the ‘svg’ element's SVGLoad event is triggered. The document end of an SVG document fragment is the point at which the document fragment has been released and is no longer being processed by the user agent. However, nested ‘svg’ elements within an SVG document do not constitute document fragments in this sense, and do not define a separate document begin; all times within the nested SVG fragment are relative to the document time defined for the root ‘svg’ element.

For SVG, the term presentation time indicates the position in the timeline relative to the document begin of a given document fragment.

SVG defines more constrained error processing than is defined in the SMIL Animation specification [SMILANIM]. SMIL Animation defines error processing behavior where the document continues to run in certain error situations, whereas all animations within an SVG document fragment will stop in the event of any error within the document (see Error processing).

19.2.3. Animation elements example

Example anim01 below demonstrates each of SVG's five animation elements.

<?xml version="1.0" standalone="no"?>
<svg width="8cm" height="3cm"  viewBox="0 0 800 300"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <desc>Example anim01 - demonstrate animation elements</desc>
  <rect x="1" y="1" width="798" height="298" 
        fill="none" stroke="blue" stroke-width="2" />
  <!-- The following illustrates the use of the 'animate' element
        to animate a rectangles x, y, and width attributes so that
        the rectangle grows to ultimately fill the viewport. -->
  <rect id="RectElement" x="300" y="100" width="300" height="100"
        fill="rgb(255,255,0)"  >
    <animate attributeName="x" attributeType="XML"
             begin="0s" dur="9s" fill="freeze" from="300" to="0" />
    <animate attributeName="y" attributeType="XML"
             begin="0s" dur="9s" fill="freeze" from="100" to="0" />
    <animate attributeName="width" attributeType="XML"
             begin="0s" dur="9s" fill="freeze" from="300" to="800" />
    <animate attributeName="height" attributeType="XML"
             begin="0s" dur="9s" fill="freeze" from="100" to="300" />
  </rect>
  <!-- Set up a new user coordinate system so that
        the text string's origin is at (0,0), allowing
        rotation and scale relative to the new origin -->
  <g transform="translate(100,100)" >
    <!-- The following illustrates the use of the 'set', 'animateMotion',
         'animate' and 'animateTransform' elements. The 'text' element 
         below starts off hidden (i.e., invisible). At 3 seconds, it:
           * becomes visible
           * continuously moves diagonally across the viewport
           * changes color from blue to dark red
           * rotates from -30 to zero degrees
           * scales by a factor of three. -->
    <text id="TextElement" x="0" y="0"
          font-family="Verdana" font-size="35.27" visibility="hidden"  > 
      It's alive!
      <set attributeName="visibility" attributeType="CSS" to="visible"
           begin="3s" dur="6s" fill="freeze" />
      <animateMotion path="M 0 0 L 100 100" 
           begin="3s" dur="6s" fill="freeze" />
      <animate attributeName="fill" attributeType="CSS"
           from="rgb(0,0,255)" to="rgb(128,0,0)"
           begin="3s" dur="6s" fill="freeze" />
      <animateTransform attributeName="transform" attributeType="XML"
           type="rotate" from="-30" to="0"
           begin="3s" dur="6s" fill="freeze" />
      <animateTransform attributeName="transform" attributeType="XML"
           type="scale" from="1" to="3" additive="sum"
           begin="3s" dur="6s" fill="freeze" />
    </text>
  </g>
</svg>

Example anim01
At zero seconds		At three seconds
At six seconds		At nine seconds

View this example as SVG (SVG-enabled browsers only)

The sections below describe the various animation attributes and elements.

19.2.4. Attributes to identify the target element for an animation

The following attribute is common to all animation elements and identifies the target element for the animation.

Attribute definitions:

xlink:href = "<iri>"

An IRI reference to the element which is the target of this animation and which therefore will be modified over time.

The target element must be part of the current SVG document fragment.

<iri> must point to exactly one target element which is capable of being the target of the given animation. If <iri> points to multiple target elements, if the given target element is not capable of being a target of the given animation, or if the given target element is not part of the current SVG document fragment, then the document is in error (see Error processing).

If the ‘xlink:href’ attribute is not provided, then the target element will be the immediate parent element of the current animation element.

Refer to the descriptions of the individual animation elements for any restrictions on what types of elements can be targets of particular types of animations.

Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: Specifying the animation target ([SMILANIM], section 3.1).

19.2.5. Attributes to identify the target attribute or property for an animation

The following attributes are the animation attribute target attributes, which identify the target attribute or property for the given target element whose value changes over time.

Attribute definitions:

attributeName = "<attributeName>"

Specifies the name of the target attribute. An XMLNS prefix may be used to indicate the XML namespace for the attribute. The prefix will be interpreted in the scope of the current (i.e., the referencing) animation element.

attributeType = "CSS | XML | auto"

Specifies the namespace in which the target attribute and its associated values are defined. The attribute value is one of the following (values are case-sensitive):

CSS: This specifies that the value of ‘attributeName’ is the name of a CSS property defined as animatable in this specification.
XML: This specifies that the value of ‘attributeName’ is the name of an XML attribute defined in the default XML namespace for the target element. If the value for ‘attributeName’ has an XMLNS prefix, the implementation must use the associated namespace as defined in the scope of the target element. The attribute must be defined as animatable in this specification.
auto: The implementation should match the ‘attributeName’ to an attribute for the target element. The implementation must first search through the list of CSS properties for a matching property name, and if none is found, search the default XML namespace for the element.

The default value is 'auto'.

19.2.6. Animation with namespaces

Example animns01 below shows a namespace prefix being resolved to a namespace name in the scope of the referencing element, and that namespace name being used (regardless of the prefix which happens to be used in the target scope) to identify the attribute being animated.

<?xml version="1.0" encoding="UTF-8"?>
<svg version="1.1" xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink">
  <title>Demonstration of the resolution of namespaces for animation</title>
  <!-- at the point of definition, the QName a:href resolves to the namespace
       name "http://www.w3.org/1999/xlink" and the local name "href" -->
  <g xmlns:a="http://www.w3.org/1999/xlink">
    <animate attributeName="a:href" xlink:href="#foo" dur="2s" to="two.png" fill="freeze"/>
  </g>
  <!-- at the point of use, the namespace name "http://www.w3.org/1999/xlink"
       happens to be bound to the namespace prefix 'b' while the prefix
       'xlink' is bound to a different namespace name -->
  <g xmlns:b="http://www.w3.org/1999/xlink" xmlns:xlink="http://example.net/bar">
    <image xml:id="foo" b:href="one.png" x="35" y="50" width="410" height="160"/>
  </g>
</svg>

View this example as SVG (SVG-enabled browsers only)

19.2.7. Paced animation and complex types

Paced animations assume a notion of distance between the various animation values defined by the ‘to’, ‘from’, ‘by’ and ‘values’ attributes. Distance is defined only for scalar types (such as <length>), colors and the subset of transformation types that are supported by ‘animateTransform’. In the list of distance functions below, V_a and V_b represent the two values the distance between which is being calculated.

Since paced animation is intended to produce an animation with an even pace of change, it does not make sense to define distance functions for all data types. Distance can be usefully defined for types whose values are n-dimensional vectors (including scalars, which are 1-dimensional vectors). For example, a <length> value is a scalar value, and a <color> value is a 3-dimensional vector. Thus attributes of these types can have paced animation applied to them. On the other hand, a <list-of-length> (as used by ‘stroke-dasharray’) is a list of scalars (1-dimensional vectors), and <list-of-points> (as used by the ‘points’ attribute on a ‘polygon’) is a list of 2-dimensional vectors. Therefore, these types do not have a distance function defined and cannot have paced animation applied to them.

The distance functions for types that support paced animation are as follows:

<integer>, <length> and <number>

distance(V_a, V_b) = |V_a − V_b|

Examples: animating the ‘x’ attribute on a ‘rect’, or the ‘stroke-width’ property on a ‘circle’.

<color>

distance(V_a, V_b) = sqrt((V_a.red − V_b.red)² + (V_a.green − V_b.green)² + (V_a.blue − V_b.blue)²), where:

V_i.red is the red component of the V_i color value,

V_i.green is the green component of the V_i color value, and

V_i.blue is the blue component of the V_i color value.

Each of the color component values is usually in the range [0, 1], where 0 represents none of that color component, and 1 represents the maximum amount of that color component, in the sRGB gamut [SRGB]. Since <color> values may specify colors outside of the sRGB gamut, these component values may lie outside the range [0, 1].

Example: animating the ‘fill’ property on an ‘ellipse’.

Transform definitions of type 'translate'

distance(V_a, V_b) = sqrt((V_a.tx − V_b.tx)² + (V_a.ty − V_b.ty)²), where:

V_i.tx is the x component of the V_i translation transform value, and

V_i.ty is the y component of the V_i translation transform value.

Example (for all transform definition types): animating the ‘transform’ attribute on a ‘g’ using ‘animateTransform’.

Transform definitions of type 'scale'

distance(V_a, V_b) = sqrt((V_a.sx − V_b.sx)² + (V_a.sy − V_b.sy)²), where:

V_i.sx is the x component of the V_i scale transform value, and

V_i.sy is the y component of the V_i scale transform value.

Note that, as when specifying scale transformations in a <transform-list>, if the y component of the scale is omitted it is implicitly equal to the x component.

Transform definitions of type 'rotate', 'skewX' and 'skewY'

distance(V_a, V_b) = sqrt((V_a.angle − V_b.angle)²), where:

V_i.angle is the angle component of the V_i rotation or skew transform value.

Since the distance function for rotations is not in terms of the rotation center point components, a paced animation that changes the rotation center point may not appear to have a paced movement when the animation is applied.

Distance functions for all other data types are not defined. If calcMode="paced" is used on an animation of an attribute or property whose type is not one of those listed above, the animation effect is undefined. SVG user agents may choose to perform the animation as if calcMode="linear", but this is not required. Authors are recommended not to specify paced animation on types not listed above.

19.2.8. Attributes to control the timing of the animation

The following attributes are the animation timing attributes. They are common to all animation elements and control the timing of the animation, including what causes the animation to start and end, whether the animation runs repeatedly, and whether to retain the end state the animation once the animation ends.

In the syntax specifications that follow, optional white space is indicated as "S", defined as follows:

S ::= (#x20 | #x9 | #xD | #xA)*

Attribute definitions:

begin = "begin-value-list"

Defines when the element should begin (i.e. become active).

The attribute value is a semicolon separated list of values.

begin-value-list ::= begin-value (S? ";" S? begin-value-list )?

A semicolon separated list of begin values. The interpretation of a list of begin times is detailed in SMIL Animation's section on "Evaluation of begin and end time lists".

Describes the element begin.

offset-value ::= ( S? "+" | "-" S? )? ( Clock-value )

For SMIL Animation, this describes the element begin as an offset from an implicit syncbase. For SVG, the implicit syncbase begin is defined to be relative to the document begin. Negative begin times are entirely valid and easy to compute, as long as there is a resolved document begin time.

syncbase-value ::= ( Id-value "." ( "begin" | "end" ) ) ( S? ("+"|"-") S? Clock-value )?

Describes a syncbase and an optional offset from that syncbase. The element begin is defined relative to the begin or active end of another animation. A syncbase consists of an ID reference to another animation element followed by either begin or end to identify whether to synchronize with the beginning or active end of the referenced animation element.

event-value ::= ( Id-value "." )? ( event-ref ) ( S? ("+"|"-") S? Clock-value )?

Describes an event and an optional offset that determine the element begin. The animation begin is defined relative to the time that the event is raised. The list of event-symbols available for a given event-base element is the list of event attributes available for the given element as defined in the Interactivity chapter, with the one difference that the leading 'on' is removed from the event name (i.e., the animation event name is 'click', not 'onclick'). A list of all events supported by SVG can be found in Complete list of supported events. Details of event-based timing are described in SMIL Animation: Unifying Event-based and Scheduled Timing.

repeat-value ::= ( Id-value "." )? "repeat(" integer ")" ( S? ("+"|"-") S? Clock-value )?

Describes a qualified repeat event. The element begin is defined relative to the time that the repeat event is raised with the specified iteration value.

accessKey-value ::= "accessKey(" character ")" ( S? ("+"|"-") S? Clock-value )?

Describes an accessKey that determines the element begin. The element begin is defined relative to the time that the accessKey character is input by the user.

wallclock-sync-value ::= "wallclock(" wallclock-value ")"

Describes the element begin as a real-world clock time. The wallclock time syntax is based upon syntax defined in Representation of dates and times [ISO8601].

"indefinite"

The begin of the animation will be determined by a "beginElement()" method call or a hyperlink targeted to the element.

The animation DOM methods are described in DOM interfaces.

Hyperlink-based timing is described in SMIL Animation: Hyperlinks and timing.

dur = Clock-value | "media" | "indefinite"

Specifies the simple duration.

The attribute value can be one of the following:

Clock-value: Specifies the length of the simple duration in presentation time. Value must be greater than 0.
"media": Specifies the simple duration as the intrinsic media duration. This is only valid for elements that define media.
(For SVG's animation elements, if 'media' is specified, the attribute will be ignored.)
"indefinite": Specifies the simple duration as indefinite.

If the animation does not have a ‘dur’ attribute, the simple duration is indefinite. Note that interpolation will not work if the simple duration is indefinite (although this may still be useful for ‘set’ elements). Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'dur' attribute ([SMILANIM], section 3.2.1).

end = "end-value-list"

Defines an end value for the animation that can constrain the active duration. The attribute value is a semicolon separated list of values.

end-value-list ::= end-value (S? ";" S? end-value-list )?: A semicolon separated list of end values. The interpretation of a list of end times is detailed below.

end-value ::= ( offset-value | syncbase-value | event-value | repeat-value | accessKey-value | wallclock-sync-value | "indefinite" ): Describes the active end of the animation.

A value of 'indefinite' specifies that the end of the animation will be determined by an endElement method call (the animation DOM methods are described in DOM interfaces).

min = Clock-value | "media"

Specifies the minimum value of the active duration.

The attribute value can be either of the following:

Clock-value

Specifies the length of the minimum value of the active duration, measured in local time.

Value must be greater than 0.

"media"

Specifies the minimum value of the active duration as the intrinsic media duration. This is only valid for elements that define media. (For SVG's animation elements, if 'media' is specified, the attribute will be ignored.)

The default value for ‘min’ is '0'. This does not constrain the active duration at all.

max = Clock-value | "media"

Specifies the maximum value of the active duration.

The attribute value can be either of the following:

Clock-value

Specifies the length of the maximum value of the active duration, measured in local time.

Value must be greater than 0.

"media"

Specifies the maximum value of the active duration as the intrinsic media duration. This is only valid for elements that define media. (For SVG's animation elements, if 'media' is specified, the attribute will be ignored.)

There is no default value for ‘max’. This does not constrain the active duration at all.

restart = "always" | "whenNotActive" | "never"

always: The animation can be restarted at any time.
This is the default value.
whenNotActive: The animation can only be restarted when it is not active (i.e. after the active end). Attempts to restart the animation during its active duration are ignored.
never: The element cannot be restarted for the remainder of the current simple duration of the parent time container. (In the case of SVG, since the parent time container is the SVG document fragment, then the animation cannot be restarted for the remainder of the document duration.)

repeatCount = numeric value | "indefinite"

Specifies the number of iterations of the animation function. It can have the following attribute values:

numeric value: This is a (base 10) "floating point" numeric value that specifies the number of iterations. It can include partial iterations expressed as fraction values. A fractional value describes a portion of the simple duration. Values must be greater than 0.
"indefinite": The animation is defined to repeat indefinitely (i.e. until the document ends).

Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'repeatCount' attribute ([SMILANIM], section 3.3.1).

repeatDur = Clock-value | "indefinite"

Specifies the total duration for repeat. It can have the following attribute values:

Clock-value: Specifies the duration in presentation time to repeat the animation function f(t).
"indefinite": The animation is defined to repeat indefinitely (i.e. until the document ends).

fill = "freeze" | "remove"

This attribute can have the following values:

freeze

The animation effect F(t) is defined to freeze the effect value at the last value of the active duration. The animation effect is "frozen" for the remainder of the document duration (or until the animation is restarted - see SMIL Animation: Restarting animation).

remove

The animation effect is removed (no longer applied) when the active duration of the animation is over. After the active end of the animation, the animation no longer affects the target (unless the animation is restarted - see SMIL Animation: Restarting animation).

This is the default value.

The SMIL Animation specification [SMILANIM] defines the detailed processing rules associated with the above attributes. Except for any SVG-specific rules explicitly mentioned in this specification, the SMIL Animation specification is the normative definition of the processing rules for the above attributes.

19.2.8.1. Clock values

Clock values have the same syntax as in SMIL Animation specification [SMILANIM]. The grammar for clock values is repeated here:

Clock-val         ::= Full-clock-val | Partial-clock-val 
                      | Timecount-val
Full-clock-val    ::= Hours ":" Minutes ":" Seconds ("." Fraction)?
Partial-clock-val ::= Minutes ":" Seconds ("." Fraction)?
Timecount-val     ::= Timecount ("." Fraction)? (Metric)?
Metric            ::= "h" | "min" | "s" | "ms"
Hours             ::= DIGIT+; any positive number
Minutes           ::= 2DIGIT; range from 00 to 59
Seconds           ::= 2DIGIT; range from 00 to 59
Fraction          ::= DIGIT+
Timecount         ::= DIGIT+
2DIGIT            ::= DIGIT DIGIT
DIGIT             ::= [0-9]

For Timecount values, the default metric suffix is "s" (for seconds). No embedded white space is allowed in clock values, although leading and trailing white space characters will be ignored.

Clock values describe presentation time.

The following are examples of legal clock values:

Full clock values: 02:30:03 = 2 hours, 30 minutes and 3 seconds
50:00:10.25 = 50 hours, 10 seconds and 250 milliseconds
Partial clock value: 02:33 = 2 minutes and 33 seconds
00:10.5 = 10.5 seconds = 10 seconds and 500 milliseconds
Timecount values:
3.2h    = 3.2 hours = 3 hours and 12 minutes
45min   = 45 minutes
30s     = 30 seconds
5ms     = 5 milliseconds
12.467 = 12 seconds and 467 milliseconds

Fractional values are just (base 10) floating point definitions of seconds. Thus:

00.5s = 500 milliseconds
00:00.005 = 5 milliseconds

19.2.9. Attributes that define animation values over time

The following attributes are the animation value attributes. They are common to elements ‘animate’, ‘animateColor’, ‘animateMotion’ and ‘animateTransform’. These attributes define the values that are assigned to the target attribute or property over time. The attributes below provide control over the relative timing of keyframes and the interpolation method between discrete values.

Attribute definitions:

calcMode = "discrete | linear | paced | spline"

Specifies the interpolation mode for the animation. This can take any of the following values. The default mode is 'linear', however if the attribute does not support linear interpolation (e.g. for strings), the ‘calcMode’ attribute is ignored and discrete interpolation is used.

discrete: This specifies that the animation function will jump from one value to the next without any interpolation.
linear: Simple linear interpolation between values is used to calculate the animation function. Except for ‘animateMotion’, this is the default ‘calcMode’.
paced: Defines interpolation to produce an even pace of change across the animation. This is only supported for the data types for which there is an appropriate distance function defined, which includes only scalar numeric types plus the types listed in Paced animation and complex types. If 'paced' is specified, any ‘keyTimes’ or ‘keySplines’ will be ignored. For ‘animateMotion’, this is the default ‘calcMode’. Authors are discouraged from using paced animation on types that do not have a distance function defined, due to its unpredictable behavior in some user agents.
spline: Interpolates from one value in the ‘values’ list to the next according to a time function defined by a cubic Bézier spline. The points of the spline are defined in the ‘keyTimes’ attribute, and the control points for each interval are defined in the ‘keySplines’ attribute.

values = "<list>"

A semicolon-separated list of one or more values. Vector-valued attributes are supported using the vector syntax of the ‘attributeType’ domain. Per the SMIL specification, leading and trailing white space, and white space before and after semicolon separators, is allowed and will be ignored. Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'values' attribute ([SMILANIM], section 3.2.2).

keyTimes = "<list>"

A semicolon-separated list of time values used to control the pacing of the animation. Each time in the list corresponds to a value in the ‘values’ attribute list, and defines when the value is used in the animation function. Each time value in the ‘keyTimes’ list is specified as a floating point value between 0 and 1 (inclusive), representing a proportional offset into the simple duration of the animation element.

For animations specified with a ‘values’ list, the ‘keyTimes’ attribute if specified must have exactly as many values as there are in the ‘values’ attribute. For from/to/by animations, the ‘keyTimes’ attribute if specified must have two values.

Each successive time value must be greater than or equal to the preceding time value.

The ‘keyTimes’ list semantics depends upon the interpolation mode:

For linear and spline animation, the first time value in the list must be 0, and the last time value in the list must be 1. The key time associated with each value defines when the value is set; values are interpolated between the key times.
For discrete animation, the first time value in the list must be 0. The time associated with each value defines when the value is set; the animation function uses that value until the next time defined in ‘keyTimes’.

If the interpolation mode is 'paced', the ‘keyTimes’ attribute is ignored.

If there are any errors in the ‘keyTimes’ specification (bad values, too many or too few values), the document fragment is in error (see error processing).

If the simple duration is indefinite, any ‘keyTimes’ specification will be ignored.

Because paced animation interpolation is unspecified for some value types, authors are encouraged to use 'linear' animation interpolation with calculated ‘keyTimes’ to achieve particular interpolation behavior for these types.

keySplines = "<list>"

A set of Bézier control points associated with the ‘keyTimes’ list, defining a cubic Bézier function that controls interval pacing. The attribute value is a semicolon-separated list of control point descriptions. Each control point description is a set of four values: x1 y1 x2 y2, describing the Bézier control points for one time segment. Note: SMIL allows these values to be separated either by commas with optional whitespace, or by whitespace alone. The ‘keyTimes’ values that define the associated segment are the Bézier "anchor points", and the ‘keySplines’ values are the control points. Thus, there must be one fewer sets of control points than there are ‘keyTimes’.

The values must all be in the range 0 to 1.

This attribute is ignored unless the ‘calcMode’ is set to 'spline'.

If there are any errors in the ‘keySplines’ specification (bad values, too many or too few values), the document fragment is in error (see error processing).

Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'keySplines' attribute ([SMILANIM], section 3.2.3).

from = "<value>"

Specifies the starting value of the animation.
Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'from' attribute ([SMILANIM], section 3.2.2).

to = "<value>"

Specifies the ending value of the animation.
Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'to' attribute ([SMILANIM], section 3.2.2).

by = "<value>"

Specifies a relative offset value for the animation.
Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'by' attribute ([SMILANIM], section 3.2.2).

The animation values specified in the animation element must be legal values for the specified attribute. Leading and trailing white space, and white space before and after semicolon separators, will be ignored.

All values specified must be legal values for the specified attribute (as defined in the associated namespace). If any values are not legal, the document fragment is in error (see error processing).

If a list of values is used, the animation will apply the values in order over the course of the animation. If a list of ‘values’ is specified, any ‘from’, ‘to’ and ‘by’ attribute values are ignored.

The processing rules for the variants of from/by/to animations are described in Animation function values with the following exception.

In order to provide behavior that is intuitive and consistent between discrete animations with an explicitly specified ‘from’ attribute (e.g. "from-to animation") and those where the underlying value is used (e.g. "to animation"), the behavior of discrete to-animation in SVG deviates from the definition in SMIL Animation. As with a discrete from-to animation, a discrete to animation will set the underlying value for the first half of the simple duration (or, if a ‘keyTimes’ list is provided, until the simple duration specified by the second value in the ‘keyTimes’ list) and the ‘to’ value for the remainder of the simple duration.

The following figure illustrates the interpretation of the ‘keySplines’ attribute. Each diagram illustrates the effect of ‘keySplines’ settings for a single interval (i.e. between the associated pairs of values in the ‘keyTimes’ and ‘values’ lists.). The horizontal axis can be thought of as the input value for the unit progress of interpolation within the interval - i.e. the pace with which interpolation proceeds along the given interval. The vertical axis is the resulting value for the unit progress, yielded by the function that the ‘keySplines’ attribute defines. Another way of describing this is that the horizontal axis is the input unit time for the interval, and the vertical axis is the output unit time. See also the section Timing and real-world clock times.

Examples of keySplines
keySplines="0 0 1 1" (the default)	keySplines=".5 0 .5 1"
keySplines="0 .75 .25 1"	keySplines="1 0 .25 .25"

To illustrate the calculations, consider the simple example:

<animate dur="4s" values="10; 20" keyTimes="0; 1"
     calcMode="spline" keySplines={as in table} />

Using the ‘keySplines’ values for each of the four cases above, the approximate interpolated values as the animation proceeds are:

keySplines values
Value of ‘keySplines’	Initial value	After 1s	After 2s	After 3s	Final value
0 0 1 1	10.0	12.5	15.0	17.5	20.0
.5 0 .5 1	10.0	11.0	15.0	19.0	20.0
0 .75 .25 1	10.0	18.0	19.3	19.8	20.0
1 0 .25 .25	10.0	10.1	10.6	16.9	20.0

For a formal definition of Bézier spline calculation, see [FOLEY-VANDAM], pp. 488-491.

19.2.10. Attributes that control whether animations are additive

It is frequently useful to define animation as an offset or delta to an attribute's value, rather than as absolute values.

A simple "grow" animation can increase the width of an object by 10 pixels:

<rect width="20px" ...>
  <animate attributeName="width" from="0px" to="10px" dur="10s"
           additive="sum"/>
</rect>

It is frequently useful for repeated animations to build upon the previous results, accumulating with each iteration.

The following example causes the rectangle to continue to grow with each repeat of the animation:

<rect width="20px" ...>
  <animate attributeName="width" from="0px" to="10px" dur="10s"
           additive="sum" accumulate="sum" repeatCount="5"/>
</rect>

At the end of the first repetition, the rectangle has a width of 30 pixels. At the end of the second repetition, the rectangle has a width of 40 pixels. At the end of the fifth repetition, the rectangle has a width of 70 pixels.

For more information about additive animations, see SMIL Animation: Additive animation. For more information on cumulative animations, see SMIL Animation: Controlling behavior of repeating animation - Cumulative animation.

The following attributes are the animation addition attributes, which are common to elements ‘animate’, ‘animateColor’, ‘animateMotion’ and ‘animateTransform’.

Attribute definitions:

additive = "replace | sum"

Controls whether or not the animation is additive.

sum: Specifies that the animation will add to the underlying value of the attribute and other lower priority animations.
replace: Specifies that the animation will override the underlying value of the attribute and other lower priority animations. This is the default, however the behavior is also affected by the animation value attributes ‘by’ and ‘to’, as described in SMIL Animation: How from, to and by attributes affect additive behavior.

accumulate = "none | sum"

Controls whether or not the animation is cumulative.

sum: Specifies that each repeat iteration after the first builds upon the last value of the previous iteration.
none: Specifies that repeat iterations are not cumulative. This is the default.

This attribute is ignored if the target attribute value does not support addition, or if the animation element does not repeat.

Cumulative animation is not defined for "to animation".

This attribute will be ignored if the animation function is specified with only the ‘to’ attribute.

Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this attribute is the SMIL Animation specification. In particular, see SMIL Animation: 'accumulate' attribute ([SMILANIM], section 3.3.1).

19.2.11. Inheritance

SVG allows both attributes and properties to be animated. If a given attribute or property is inheritable by descendants, then animations on a parent element such as a ‘g’ element has the effect of propagating the attribute or property animation values to descendant elements as the animation proceeds; thus, descendant elements can inherit animated attributes and properties from their ancestors.

19.2.12. The ‘animate’ element

The ‘animate’ element is used to animate a single attribute or property over time.

This example makes a rectangle repeatedly fade away over 5 seconds:

<rect>
  <animate attributeType="CSS" attributeName="opacity" 
         from="1" to="0" dur="5s" repeatCount="indefinite" />
</rect>

Except for any SVG-specific rules explicitly mentioned in this specification, the normative definition for this element is the SMIL Animation specification. In particular, see SMIL Animation: 'animate' element ([SMILANIM], section 4.1).

‘animate’

Categories:

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’

Attributes:

conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
animation event attributes — ‘onbegin’, ‘onend’, ‘onrepeat’, ‘onload’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
animation attribute target attributes — ‘attributeType’, ‘attributeName’
animation timing attributes — ‘begin’, ‘dur’, ‘end’, ‘min’, ‘max’, ‘restart’, ‘repeatCount’, ‘repeatDur’, ‘fill’
animation value attributes — ‘calcMode’, ‘values’, ‘keyTimes’, ‘keySplines’, ‘from’, ‘to’, ‘by’
animation addition attributes — ‘additive’, ‘accumulate’
presentation attributes —

DOM Interfaces:

SVGAnimateElement

The ‘color-interpolation’ property applies to color interpolations that result from animations using the ‘animate’ element.

For a list of attributes and properties that can be animated using the ‘animate’ element, see Elements, attributes and properties that can be animated.

19.2.13. The ‘set’ element

The ‘set’ element provides a simple means of just setting the value of an attribute for a specified duration. It supports all attribute types, including those that cannot reasonably be interpolated, such as string and boolean values. The ‘set’ element is non-additive. The additive and accumulate attributes are not allowed, and will be ignored if specified.

‘set’

Categories:

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’

Attributes:

conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
animation event attributes — ‘onbegin’, ‘onend’, ‘onrepeat’, ‘onload’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
animation attribute target attributes — ‘attributeType’, ‘attributeName’
animation timing attributes — ‘begin’, ‘dur’, ‘end’, ‘min’, ‘max’, ‘restart’, ‘repeatCount’, ‘repeatDur’, ‘fill’
‘to’

DOM Interfaces:

SVGSetElement

Attribute definitions:

to = "<value>": Specifies the value for the attribute during the duration of the ‘set’ element. The argument value must match the attribute type.

For a list of attributes and properties that can be animated using the ‘set’ element, see Elements, attributes and properties that can be animated.

19.2.14. The ‘animateMotion’ element

The ‘animateMotion’ element causes a referenced element to move along a motion path.

‘animateMotion’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of descriptive elements and at most one ‘mpath’ element, in any order.

Attributes:

conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
animation event attributes — ‘onbegin’, ‘onend’, ‘onrepeat’, ‘onload’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
animation timing attributes — ‘begin’, ‘dur’, ‘end’, ‘min’, ‘max’, ‘restart’, ‘repeatCount’, ‘repeatDur’, ‘fill’
animation value attributes — ‘calcMode’, ‘values’, ‘keyTimes’, ‘keySplines’, ‘from’, ‘to’, ‘by’
animation addition attributes — ‘additive’, ‘accumulate’
‘path’
‘keyPoints’
‘rotate’
‘origin’

DOM Interfaces:

SVGAnimateMotionElement

Attribute definitions:

calcMode = "discrete | linear | paced | spline"

Specifies the interpolation mode for the animation. Refer to general description of the ‘calcMode’ attribute above. The only difference is that the default value for the ‘calcMode’ for ‘animateMotion’ is 'paced'. See SMIL Animation: 'calcMode' attribute for 'animateMotion'.

path = "<path-data>"

The motion path, expressed in the same format and interpreted the same way as the ‘d’ attribute on the ‘path’ element. The effect of a motion path animation is to add a supplemental transformation matrix onto the CTM for the referenced object which causes a translation along the x- and y-axes of the current user coordinate system by the computed X and Y values computed over time.

keyPoints = "<list-of-numbers>"

‘keyPoints’ takes a semicolon-separated list of floating point values between 0 and 1 and indicates how far along the motion path the object shall move at the moment in time specified by corresponding ‘keyTimes’ value. Distance calculations use the user agent's distance along the path algorithm. Each progress value in the list corresponds to a value in the ‘keyTimes’ attribute list.

If a list of ‘keyPoints’ is specified, there must be exactly as many values in the ‘keyPoints’ list as in the ‘keyTimes’ list.

If there are any errors in the ‘keyPoints’ specification (bad values, too many or too few values), then the document is in error (see Error processing).

rotate = "<number> | auto | auto-reverse"

The ‘rotate’ attribute post-multiplies a supplemental transformation matrix onto the CTM of the target element to apply a rotation transformation about the origin of the current user coordinate system. The rotation transformation is applied after the supplemental translation transformation that is computed due to the ‘path’ attribute.

auto: Indicates that the object is rotated over time by the angle of the direction (i.e., directional tangent vector) of the motion path.
auto-reverse: Indicates that the object is rotated over time by the angle of the direction (i.e., directional tangent vector) of the motion path plus 180 degrees.
<number>: Indicates that the target element has a constant rotation transformation applied to it, where the rotation angle is the specified number of degrees.

The default value is '0'.

origin = "default"

The ‘origin’ attribute is defined in the SMIL Animation specification ([SMILANIM], section 4.3). It has no effect in SVG.

‘mpath’

Categories:

None

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘xlink:href’

DOM Interfaces:

SVGMPathElement

Attribute definitions:

xlink:href = "<iri>": An IRI reference to the ‘path’ element which defines the motion path.
Animatable: no.

For ‘animateMotion’, the specified values for ‘from’, ‘by’, ‘to’ and ‘values’ consists of x, y coordinate pairs, with a single comma and/or white space separating the x coordinate from the y coordinate. For example, from="33,15" specifies an x coordinate value of 33 and a y coordinate value of 15.

If provided, the ‘values’ attribute must consists of a list of x, y coordinate pairs. Coordinate values are separated by at least one white space character or a comma. Additional white space around the separator is allowed. For example, values="10,20;30,20;30,40" or values="10mm,20mm;30mm,20mm;30mm,40mm". Each coordinate represents a length. Attributes ‘from’, ‘by’, ‘to’ and ‘values’ specify a shape on the current canvas which represents the motion path.

Two options are available which allow definition of a motion path using any of SVG's path data commands:

the ‘path’ attribute defines a motion path directly on ‘animateMotion’ element using any of SVG's path data commands.
the ‘mpath’ sub-element provides the ability to reference an external ‘path’ element as the definition of the motion path.

Note that SVG's path data commands can only contain values in user space, whereas ‘from’, ‘by’, ‘to’ and ‘values’ can specify coordinates in user space or using unit identifiers. See Units.

The various (x,y) points of the shape provide a supplemental transformation matrix onto the CTM for the referenced object which causes a translation along the x- and y-axes of the current user coordinate system by the (x,y) values of the shape computed over time. Thus, the referenced object is translated over time by the offset of the motion path relative to the origin of the current user coordinate system. The supplemental transformation is applied on top of any transformations due to the target element's ‘transform’ property or any animations on that attribute due to ‘animateTransform’ elements on the target element.

The ‘additive’ and ‘accumulate’ attributes apply to ‘animateMotion’ elements. Multiple ‘animateMotion’ elements all simultaneously referencing the same target element can be additive with respect to each other; however, the transformations which result from the ‘animateMotion’ elements are always supplemental to any transformations due to the target element's ‘transform’ property or any ‘animateTransform’ elements.

The default calculation mode (‘calcMode’) for ‘animateMotion’ is "paced". This will produce constant velocity motion along the specified path. Note that while animateMotion elements can be additive, it is important to observe that the addition of two or more "paced" (constant velocity) animations might not result in a combined motion animation with constant velocity.

When a path is combined with "discrete", "linear" or "spline" ‘calcMode’ settings, and if attribute ‘keyPoints’ is not provided, the number of values is defined to be the number of points defined by the path, unless there are "move to" commands within the path. A "move to" command within the path (i.e. other than at the beginning of the path description) A "move to" command does not count as an additional point when dividing up the duration, or when associating ‘keyTimes’, ‘keySplines’ and ‘keyPoints’ values. When a path is combined with a "paced" ‘calcMode’ setting, all "move to" commands are considered to have 0 length (i.e. they always happen instantaneously), and is not considered in computing the pacing.

For more flexibility in controlling the velocity along the motion path, the ‘keyPoints’ attribute provides the ability to specify the progress along the motion path for each of the ‘keyTimes’ specified values. If specified, ‘keyPoints’ causes ‘keyTimes’ to apply to the values in ‘keyPoints’ rather than the points specified in the ‘values’ attribute array or the points on the ‘path’ attribute.

The override rules for ‘animateMotion’ are as follows. Regarding the definition of the motion path, the ‘mpath’ element overrides the the ‘path’ attribute, which overrides ‘values’, which overrides ‘from’, ‘by’ and ‘to’. Regarding determining the points which correspond to the ‘keyTimes’ attributes, the ‘keyPoints’ attribute overrides ‘path’, which overrides ‘values’, which overrides ‘from’, ‘by’ and ‘to’.

At any time t within a motion path animation of duration dur, the computed coordinate (x,y) along the motion path is determined by finding the point (x,y) which is t/dur distance along the motion path using the user agent's distance along the path algorithm.

The following example demonstrates the supplemental transformation matrices that are computed during a motion path animation.

Example animMotion01 shows a triangle moving along a motion path.

<?xml version="1.0" standalone="no"?>
<svg width="5cm" height="3cm"  viewBox="0 0 500 300"
     xmlns="http://www.w3.org/2000/svg" version="1.1"
     xmlns:xlink="http://www.w3.org/1999/xlink" >
  <desc>Example animMotion01 - demonstrate motion animation computations</desc>
  <rect x="1" y="1" width="498" height="298"
        fill="none" stroke="blue" stroke-width="2" />
  <!-- Draw the outline of the motion path in blue, along
          with three small circles at the start, middle and end. -->
  <path id="path1" d="M100,250 C 100,50 400,50 400,250"
        fill="none" stroke="blue" stroke-width="7.06"  />
  <circle cx="100" cy="250" r="17.64" fill="blue"  />
  <circle cx="250" cy="100" r="17.64" fill="blue"  />
  <circle cx="400" cy="250" r="17.64" fill="blue"  />
  <!-- Here is a triangle which will be moved about the motion path.
       It is defined with an upright orientation with the base of
       the triangle centered horizontally just above the origin. -->
  <path d="M-25,-12.5 L25,-12.5 L 0,-87.5 z"
        fill="yellow" stroke="red" stroke-width="7.06"  >
    <!-- Define the motion path animation -->
    <animateMotion dur="6s" repeatCount="indefinite" rotate="auto" >
       <mpath xlink:href="#path1"/>
    </animateMotion>
  </path>
</svg>

Example animMotion01
At zero seconds	At three seconds	At six seconds

The following table shows the supplemental transformation matrices that are applied to achieve the effect of the motion path animation.

Example animMotion01 time slices
	After 0s	After 3s	After 6s
Supplemental transform due to movement along motion path	translate(100,250)	translate(250,100)	translate(400,250)
Supplemental transform due to rotate="auto"	rotate(-90)	rotate(0)	rotate(90)

For a list of elements that can be animated using the ‘animateMotion’ element, see Elements, attributes and properties that can be animated.

19.2.15. The ‘animateColor’ element

The ‘animateColor’ element specifies a color transformation over time.

‘animateColor’

Categories:

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’

Attributes:

conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
animation event attributes — ‘onbegin’, ‘onend’, ‘onrepeat’, ‘onload’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
animation attribute target attributes — ‘attributeType’, ‘attributeName’
animation timing attributes — ‘begin’, ‘dur’, ‘end’, ‘min’, ‘max’, ‘restart’, ‘repeatCount’, ‘repeatDur’, ‘fill’
animation value attributes — ‘calcMode’, ‘values’, ‘keyTimes’, ‘keySplines’, ‘from’, ‘to’, ‘by’
animation addition attributes — ‘additive’, ‘accumulate’
presentation attributes —
aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-controls’, ‘aria-describedby’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’

DOM Interfaces:

SVGAnimateColorElement

The ‘from’, ‘by’ and ‘to’ attributes take color values, where each color value is expressed using the following syntax (the same syntax as used in SVG's properties that can take color values):

<color> <icccolor>?

The ‘values’ attribute for the ‘animateColor’ element consists of a semicolon-separated list of color values, with each color value expressed in the above syntax.

Out of range color values can be provided, but user agent processing will be implementation dependent. User agents should clamp color values to allow color range values as late as possible, but note that system differences might preclude consistent behavior across different systems.

The ‘color-interpolation’ property applies to color interpolations that result from ‘animateColor’ animations.

The use of ‘animateColor’ is deprecated, since all of its functionality can be achieved simply by using ‘animate’ to target properties that can take color values. The ‘animateColor’ element may be dropped from a future version of the SVG specification.

For a list of attributes and properties that can be animated using the ‘animateColor’ element, see Elements, attributes and properties that can be animated.

19.2.16. The ‘animateTransform’ element

The ‘animateTransform’ element animates a transformation attribute on a target element, thereby allowing animations to control translation, scaling, rotation and/or skewing.

This section should talk about the ‘transform’ property.

‘animateTransform’

Categories:

View this example as SVG (SVG-enabled browsers only)

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’

Attributes:

conditional processing attributes — ‘requiredFeatures’, ‘requiredExtensions’, ‘systemLanguage’
core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
animation event attributes — ‘onbegin’, ‘onend’, ‘onrepeat’, ‘onload’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
animation attribute target attributes — ‘attributeType’, ‘attributeName’
animation timing attributes — ‘begin’, ‘dur’, ‘end’, ‘min’, ‘max’, ‘restart’, ‘repeatCount’, ‘repeatDur’, ‘fill’
animation value attributes — ‘calcMode’, ‘values’, ‘keyTimes’, ‘keySplines’, ‘from’, ‘to’, ‘by’
animation addition attributes — ‘additive’, ‘accumulate’
‘type’

DOM Interfaces:

SVGAnimateTransformElement

Attribute definitions:

type = "translate | scale | rotate | skewX | skewY": Indicates the type of transformation which is to have its values change over time. If the attribute is not specified, then the effect is as if a value of 'translate' were specified.

The ‘from’, ‘by’ and ‘to’ attributes take a value expressed using the same syntax that is available for the given transformation type:

For a type="translate", each individual value is expressed as <tx> [,<ty>].
For a type="scale", each individual value is expressed as <sx> [,<sy>].
For a type="rotate", each individual value is expressed as <rotate-angle> [<cx> <cy>].
For a type="skewX" and type="skewY", each individual value is expressed as <skew-angle>.

(See The ‘transform’ property.)

The ‘values’ attribute for the ‘animateTransform’ element consists of a semicolon-separated list of values, where each individual value is expressed as described above for ‘from’, ‘by’ and ‘to’.

The animation effect for ‘animateTransform’ is post-multiplied to the underlying value for additive ‘animateTransform’ animations (see below) instead of added to the underlying value, due to the specific behavior of ‘animateTransform’.

From-to, from-by and by animations are defined in SMIL to be equivalent to a corresponding values animation. See the Animation function values section of SMIL Animation ([SMILANIM], section 3.2.2). However, to animations are a mixture of additive and non-additive behavior, as described in the How from, to and by attributes affect additive behavior section of SMIL Animation ([SMILANIM], section 3.3.6). To animations provide specific functionality to get a smooth change from the underlying value to the ‘to’ attribute value, which conflicts mathematically with the requirement for additive transform animations to be post-multiplied. As a consequence, in SVG 1.1 the behavior of to animations for ‘animateTransform’ is undefined. Authors are suggested to use from-to, from-by, by or values animations to achieve any desired transform animation.

If ‘calcMode’ has the value 'paced', then the "distance" for the transformation is calculated as further described in Paced animations and complex types.

When an animation is active, the effect of non-additive ‘animateTransform’ (i.e., additive="replace") is to replace the given attribute's value with the transformation defined by the ‘animateTransform’. The effect of additive (i.e., additive="sum") is to post-multiply the transformation matrix corresponding to the transformation defined by this ‘animateTransform’.

To illustrate:

<rect transform="skewX(30)"...>
  <animateTransform attributeName="transform" attributeType="XML"
                    type="rotate" from="0" to="90" dur="5s"
                    additive="replace" fill="freeze"/>
  <animateTransform attributeName="transform" attributeType="XML"
                    type="scale" from="1" to="2" dur="5s"
                    additive="replace" fill="freeze"/>
</rect>

In the code snippet above, because the both animations have additive="replace", the first animation overrides the transformation on the rectangle itself and the second animation overrides the transformation from the first animation; therefore, at time 5 seconds, the visual result of the above two animations would be equivalent to the following static rectangle:

<rect transform="scale(2)" ... />

<rect transform="skewX(30)"...>
  <animateTransform attributeName="transform" attributeType="XML"
                    type="rotate" from="0" to="90" dur="5s" 
                    additive="sum" fill="freeze"/>
  <animateTransform attributeName="transform" attributeType="XML"
                    type="scale" from="1" to="2" dur="5s"
                    additive="sum" fill="freeze"/>
</rect>

In this code snippet, because the both animations have additive="sum", the first animation post-multiplies its transformation to any transformations on the rectangle itself and the second animation post-multiplies its transformation to any transformation from the first animation; therefore, at time 5 seconds, the visual result of the above two animations would be equivalent to the following static rectangle:

<rect transform="skewX(30) rotate(90) scale(2)" ... />

The zero value used when performing a by animation with type="scale" is indeed 0. Thus, performing the following animation causes the rectangle to be invisible at time 0s (since the animated transform list value is 'scale(0)'), and be scaled back to its original size at time 5s (since the animated transform list value is 'scale(1)'):

<rect width="100" height="100">
  <animateTransform attributeName="transform" attributeType="XML"
                    type="scale" by="1" dur="5s" fill="freeze"/>
</rect>

When a transform animation has accumulate='sum', the accumulation that occurs for each completed repetition of the animation is computed on the values specified in the ‘animateTransform’ element's animation value attributes (i.e., ‘values’, ‘from’, ‘to’ and ‘by’) and not on the transformation matrix that these values represent.

For example, in the following code snippet, 3 is added to the scale value at the start of each repetition:

<rect width="100" height="100">
  <animateTransform attributeName="transform" attributeType="XML"
                    type="scale" from="2" to="3" repeatCount="3" dur="4s"
                    fill="freeze"/>
</rect>

The following graph and table shows the animated ‘transform’ value on the ‘rect’ over the course of the animation:

The scale value animates from 2 to 12 with discontinuities at 4s and 8s.

Time	Value
0s	scale(2)
1s	scale(2.25)
2s	scale(2.5)
3s	scale(2.75)
4s	scale(5)
5s	scale(5.25)
6s	scale(5.5)
7s	scale(5.75)
8s	scale(8)
9s	scale(8.25)
10s	scale(8.5)
11s	scale(8.75)
12s	scale(9)

Transform item types that can have multiple values – 'translate', 'scale' and 'rotate' – are treated as vectors and accumulation is performed with vector addition. Optional values that are omitted are taken to have their usual implied value: 1 for the <sy> component of a 'scale' and 0 for the <tx> component of a 'translate' and the <cx cy> components of a 'rotate'.

For example, consider the following code snippet, which has a cumulative transform animation of type 'rotate':

<rect width="100" height="100">
  <animateTransform attributeName="transform" attributeType="XML"
                    type="rotate" from="0 30 40" to="10 30 40"
                    repeatCount="2" dur="1s" fill="freeze"/>
</rect>

At time 1 second, the animated value of ‘transform’ on the ‘rect’ will jump from 'rotate(10 30 40)' to 'rotate(10 60 80)', because the effect of the accumulation is to take the value at the end of the first repetition, '10 30 40', and add to it the value at simple duration t = 0s, which is '0 30 40'.

For a list of attributes and properties that can be animated using the ‘animateTransform’ element, see Elements, attributes and properties that can be animated.

19.2.17. Elements, attributes and properties that can be animated

The following lists all of the elements which can be animated by an ‘animateMotion’ element:

‘svg’
‘g’
‘defs’
‘use’
‘image’
‘switch’
‘path’
‘rect’
‘circle’
‘ellipse’
‘line’
‘polyline’
‘polygon’
‘text’
‘clipPath’
‘mask’
‘a’
‘foreignObject’

Each attribute or property within this specification indicates whether or not it can be animated by SVG's animation elements. Animatable attributes and properties are designated as follows:

Animatable: yes.

whereas attributes and properties that cannot be animated are designated:

Animatable: no.

Some properties are defined as being animatable but only for non-additive animations:

Animatable: yes (non-additive).

SVG has a defined set of basic data types for its various supported attributes and properties. For those attributes and properties that can be animated, the following table indicates which animation elements can be used to animate each of the basic data types. If a given attribute or property can take values of keywords (which are not additive) or numeric values (which are additive), then additive animations are possible if the subsequent animation uses a numeric value even if the base animation uses a keyword value; however, if the subsequent animation uses a keyword value, additive animation is not possible.

Animatable data types
Data type	Additive?	‘animate’	‘set’	‘animateColor’	‘animateTransform’	Notes
<angle>	yes	yes	yes	no	no
<color>	yes	yes	yes	yes	no	Only additive if each value can be converted to an RGB color.
<frequency>	no	no	no	no	no
<integer>	yes	yes	yes	no	no
<length>	yes	yes	yes	no	no
<list-of-`T`s>	no	yes	yes	no	no
<number>	yes	yes	yes	no	no
<paint>	yes	yes	yes	yes	no	Only additive if each value can be converted to an RGB color.
<percentage>	yes	yes	yes	no	no
<time>	no	no	no	no	no
<iri>	no	yes	yes	no	no
All other data types used in animatable attributes and properties	no	yes	yes	no	no

Any deviation from the above table or other special note about the animation capabilities of a particular attribute or property is included in the section of the specification where the given attribute or property is defined.

19.3. Animation using the SVG DOM

Example dom01 shows a simple animation using the DOM.

<?xml version="1.0" standalone="no"?>
<svg width="4cm" height="2cm" viewBox="0 0 400 200"
     xmlns="http://www.w3.org/2000/svg"
     onload="StartAnimation(evt)" version="1.1">
  <script type="application/ecmascript"><![CDATA[
    var timevalue = 0;
    var timer_increment = 50;
    var max_time = 5000;
    var text_element;
    function StartAnimation(evt) {
      text_element = evt.target.ownerDocument.getElementById("TextElement");
      ShowAndGrowElement();
    }
    function ShowAndGrowElement() {
      timevalue = timevalue + timer_increment;
      if (timevalue > max_time)
        return;
      // Scale the text string gradually until it is 20 times larger
      scalefactor = (timevalue * 20.) / max_time;
      text_element.setAttribute("transform", "scale(" + scalefactor + ")");
      // Make the string more opaque
      opacityfactor = timevalue / max_time;
      text_element.setAttribute("opacity", opacityfactor);
      // Call ShowAndGrowElement again <timer_increment> milliseconds later.
      setTimeout("ShowAndGrowElement()", timer_increment)
    }
    window.ShowAndGrowElement = ShowAndGrowElement
  ]]></script>
  <rect x="1" y="1" width="398" height="198"
        fill="none" stroke="blue" stroke-width="2"/>
  <g transform="translate(50,150)" fill="red" font-size="7">
    <text id="TextElement">SVG</text>
  </g>
</svg>

Example dom01
At zero seconds	At 2.5 seconds	At five seconds

The above SVG file contains a single graphics element, a text string that says "SVG". The animation loops for 5 seconds. The text string starts out small and transparent and grows to be large and opaque. Here is an explanation of how this example works:

The onload="StartAnimation(evt)" attribute indicates that, once the document has been fully loaded and processed, invoke ECMAScript function StartAnimation.
The ‘script’ element defines the ECMAScript which makes the animation happen. The StartAnimation() function is only called once to give a value to global variable text_element and to make the initial call to ShowAndGrowElement(). ShowAndGrowElement() is called every 50 milliseconds and resets the ‘transform’ and ‘style’ attributes on the text element to new values each time it is called. At the end of ShowAndGrowElement, the function tells the ECMAScript engine to call itself again after 50 more milliseconds.
The ‘g’ element shifts the coordinate system so that the origin is shifted toward the lower-left of the viewing area. It also defines the fill color and font-size to use when drawing the text string.
The ‘text’ element contains the text string and is the element whose attributes get changed during the animation.

If scripts are modifying the same attributes or properties that are being animated by SVG's animation elements, the scripts modify the base value for the animation. If a base value is modified while an animation element is animating the corresponding attribute or property, the animations are required to adjust dynamically to the new base value.

If a script is modifying a property on the override style sheet at the same time that an animation element is animating that property, the result is implementation-dependent; thus, it is recommended that this be avoided.

19.4. DOM interfaces

Below are the DOM interfaces for the elements defined in this chapter. In addition, TimeEvent, which is from SMIL Animation, is included here for easy reference.

19.4.1. Interface TimeEvent

The TimeEvent interface, defined in SMIL Animation: Supported interfaces, provides specific contextual information associated with Time events.

The different types of events that can occur are:

beginEvent

This event is raised when the element local timeline begins to play. It will be raised each time the element begins the active duration (i.e. when it restarts, but not when it repeats). It may be raised both in the course of normal (i.e. scheduled or interactive) timeline play, as well as in the case that the element was begun with the beginElement or beginElementAt methods. Note that if an element is restarted while it is currently playing, the element will raise an end event and another begin event, as the element restarts.

Bubbles: No
Cancelable: No
Context Info: None

endEvent

This event is raised at the active end of the element. Note that this event is not raised at the simple end of each repeat. This event may be raised both in the course of normal (i.e. scheduled or interactive) timeline play, as well as in the case that the element was ended with the endElement or endElementAt methods. Note that if an element is restarted while it is currently playing, the element will raise an end event and another begin event, as the element restarts.

Bubbles: No
Cancelable: No
Context Info: None

repeatEvent

This event is raised when an element local timeline repeats. It will be raised each time the element repeats, after the first iteration.
The event provides a numerical indication of which repeat iteration is beginning. The value is a 0-based integer, but the repeat event is not raised for the first iteration and so the observed values of the detail attribute will be >= 1.

Bubbles: No
Cancelable: No
Context Info: detail (current iteration)

interface TimeEvent : Event {

  readonly attribute AbstractView view;
  readonly attribute long detail;

  void initTimeEvent(DOMString typeArg, AbstractView viewArg, long detailArg);
};

Attributes:

view (readonly AbstractView): The view attribute identifies the AbstractView [DOM2VIEWS] from which the event was generated.
detail (readonly long): Specifies some detail information about the Event, depending on the type of the event. For this event type, indicates the repeat number for the animation.

Operations:

void initTimeEvent(DOMString typeArg, AbstractView viewArg, long detailArg)

The initTimeEvent method is used to initialize the value of a TimeEvent created with document.createEvent(). This method may only be called before the TimeEvent has been dispatched via the dispatchEvent method, though it may be called multiple times during that phase if necessary. If called multiple times, the final invocation takes precedence.

Parameters

DOMString typeArg

Specifies the event type.
AbstractView viewArg

Specifies the Event's AbstractView.
long detailArg

Specifies the Event's detail.

19.4.2. Interface SVGAnimationElement

The SVGAnimationElement interface is the base interface for all of the animation element interfaces: SVGAnimateElement, SVGSetElement, SVGAnimateColorElement, SVGAnimateMotionElement and SVGAnimateTransformElement.

Unlike other SVG DOM interfaces, the SVG DOM does not specify convenience DOM properties corresponding to the various language attributes on SVG's animation elements. Specification of these convenience properties in a way that will be compatible with future versions of SMIL Animation is expected in a future version of SVG. The current method for accessing and modifying the attributes on the animation elements is to use the standard getAttribute, setAttribute, getAttributeNS and setAttributeNS defined in DOM4 [DOM4].

SMIL Animation supports several methods for controlling the behavior of animation: beginElement(), beginElementAt(), endElement() and endElementAt(). These methods are used to begin and end the active duration of an element. Authors can (but are not required to) declare the timing to respond to the DOM using the following syntax:

<animate begin="indefinite" end="indefinite" .../>

If a DOM method call is made to begin or end the element (using beginElement(), beginElementAt(), endElement() or endElementAt()), each method call creates a single instance time (in the appropriate instance times list). These times are then interpreted as part of the semantics of lists of times, as described in Evaluation of begin and end time lists.

The instance time associated with a beginElement() or endElement() call is the current presentation time at the time of the DOM method call.
The instance time associated with a beginElementAt() or endElementAt() call is the current presentation time at the time of the DOM method call, plus or minus the specified offset.
Note that beginElement() is subject to the ‘restart’ attribute in the same manner that event-based begin timing is. Refer also to SMIL Animation: Restarting animation ([SMILANIM], section 3.3.7).

interface SVGAnimationElement : SVGElement {

  readonly attribute SVGElement targetElement;

  float getStartTime();
  float getCurrentTime();
  float getSimpleDuration();

  void beginElement();
  void beginElementAt(float offset);
  void endElement();
  void endElementAt(float offset);
};

SVGAnimationElement implements SVGTests;

Attributes:

targetElement (readonly SVGElement): The element which is being animated.

Operations:

float getStartTime()

Returns the begin time, in seconds, for this animation element's current interval, if it exists, regardless of whether the interval has begun yet. If there is no current interval, then a DOMException with code INVALID_STATE_ERR is thrown.

Returns

The start time, in seconds, of this animation element's current interval.

Exceptions

DOMException, code INVALID_STATE_ERR: The animation element does not have a current interval.

float getCurrentTime()

Returns the current time in seconds relative to time zero for the given time container.

Returns: The current time in seconds relative to time zero for the given time container.

float getSimpleDuration()

Returns the number of seconds for the simple duration for this animation. If the simple duration is undefined (e.g., the end time is indefinite), then an exception is raised.

Returns

number of seconds for the simple duration for this animation.

Exceptions

DOMException, code NOT_SUPPORTED_ERR: The simple duration is not determined on the given element.

void beginElement()

Creates a begin instance time for the current time. The new instance time is added to the begin instance times list. The behavior of this method is equivalent to beginElementAt(0).

void beginElementAt(float offset)

Creates a begin instance time for the current time plus the specified offset. The new instance time is added to the begin instance times list.

Parameters

float offset

The offset from the current document time, in seconds, at which to begin the element.

void endElement()

Creates an end instance time for the current time. The new instance time is added to the end instance times list. The behavior of this method is equivalent to endElementAt(0).

void endElementAt(float offset)

Creates a end instance time for the current time plus the specified offset. The new instance time is added to the end instance times list.

Parameters

float offset

The offset from the current document time, in seconds, at which to end the element.

19.4.3. Interface SVGAnimateElement

The SVGAnimateElement interface corresponds to the ‘animate’ element.

Object-oriented access to the attributes of the ‘animate’ element via the SVG DOM is not available.

interface SVGAnimateElement : SVGAnimationElement {
};

19.4.4. Interface SVGSetElement

The SVGSetElement interface corresponds to the ‘set’ element.

Object-oriented access to the attributes of the ‘set’ element via the SVG DOM is not available.

interface SVGSetElement : SVGAnimationElement {
};

19.4.5. Interface SVGAnimateMotionElement

The SVGAnimateMotionElement interface corresponds to the ‘animateMotion’ element.

Object-oriented access to the attributes of the ‘animateMotion’ element via the SVG DOM is not available.

interface SVGAnimateMotionElement : SVGAnimationElement {
};

19.4.6. Interface SVGMPathElement

The SVGMPathElement interface corresponds to the ‘mpath’ element.

interface SVGMPathElement : SVGElement {
};

SVGMPathElement implements SVGURIReference;

19.4.7. Interface SVGAnimateColorElement

The SVGAnimateColorElement interface corresponds to the ‘animateColor’ element.

Object-oriented access to the attributes of the ‘animateColor’ element via the SVG DOM is not available.

interface SVGAnimateColorElement : SVGAnimationElement {
};

19.4.8. Interface SVGAnimateTransformElement

The SVGAnimateTransformElement interface corresponds to the ‘animateTransform’ element.

Object-oriented access to the attributes of the ‘animateTransform’ element via the SVG DOM is not available.

interface SVGAnimateTransformElement : SVGAnimationElement {
};

Chapter 20: Fonts

SVG 2 Requirement:	Include explicit support for Web Open Font Format (WOFF).
Resolution:	We will mandate WOFF support in SVG 2.
Purpose:	To allow access to full OpenType features for internationalisation and advanced typography.
Owner:	Chris (no action)

SVG 2 Requirement:	Mandate support for SVG Tiny fonts.
Resolution:	SVG 2 will mandate support for SVG Tiny fonts support, and SVG Full fonts will be specified in a separate module.
Purpose:	Backwards compatibility for deployed content.
Owner:	Erik (ACTION-3126), Chris (✓ ACTION-3127)
Note:	The "separate module" is now being worked on in the SVG Glyphs for OpenType community group.

SVG 2 Requirement:	Reference CSS3 Fonts.
Resolution:	SVG 2 will depend on CSS3 Fonts.
Purpose:	Alignment with CSS 2.1 and CSS3 for Web font functionality, and to provide access to advanced typographic features of fonts.
Owner:	Chris (ACTION-3123)

20.1. Introduction

Reliable delivery of fonts is a requirement for SVG. Designers need to create SVG content with arbitrary fonts and know that the same graphical result will appear when the content is viewed by all end users, even when end users do not have the necessary fonts installed on their computers. This parallels the print world, where the designer uses a given font when authoring a drawing for print, and the graphical content appears exactly the same in the printed version as it appeared on the designer's authoring system.

SVG utilizes the WebFonts facility defined in ([CSS3 Fonts]) as a key mechanism for reliable delivery of font data to end users. In a common scenario, SVG authoring applications generate compressed, subsetted WebFonts for all text elements used by a given SVG document fragment.

One disadvantage to the WebFont facility in the past was that specifications did not require support of particular font formats. The result was that different implementations supported different Web font formats, thereby making it difficult for Web site creators to post a single Web site using WebFonts that worked across all user agents.

SVG 2 mandates support for Web Open Font Format [WOFF], which is now supported in most user agents. Besides enabling compressed, subsetted WebFonts with accompanying metadata for clear licensing, WOFF also benefits from OpenType multilingual features and support for advanced typography. Thus, content authors can author CSS to request discretionary ligatures, swash forms, old-style figures etc. while also ensuring that a font is provided which supports those features.

In SVG 1.1, to provide a common font format for SVG that is guaranteed to be supported by all conforming SVG viewers, SVG provideed a facility to define fonts in SVG. This facility was called SVG fonts. For backwards compatibility, SVG 2 requires support for a subset of SVG Fonts, SVG Tiny Fonts, which has been widely deployed especially for mobile content.

20.2. Describing a font

20.2.1. Overview of font descriptions

A font description provides the bridge between an author's font specification and the font data, which is the data needed to format text and to render the abstract glyphs to which the characters map — the actual scalable outlines or bitmaps. Fonts are referenced by properties, such as the ‘font-family’ property.

Each specified font description is added to the font database and so that it can be used to select the relevant font data. The font description contains descriptors such as the location of the font data on the Web, and characterizations of that font data. The font descriptors are also needed to match the font properties to particular font data. The level of detail of a font description can vary from just the name of the font up to a list of glyph widths.

For more about font descriptions, refer to CSS Fonts Module Level 3. [CSS3FONTS]

20.2.2. Alternative ways for providing a font description

Font descriptions can be specified in either of the following ways:

a ‘font-face’ element
an @font-face rule ([CSS3FONTS], section 4.1) within a CSS style sheet (only applicable for user agents which support using CSS to style the SVG content)

20.2.3. The ‘font-face’ element

The ‘font-face’ element corresponds directly to the @font-face facility in CSS3 Fonts ([CSS3FONTS], section 4.1). It can be used to describe the characteristics of any font, SVG font or otherwise.

When used to describe the characteristics of an SVG font contained within the same document, it is recommended that the ‘font-face’ element be a child of the ‘font’ element it is describing so that the ‘font’ element can be self-contained and fully-described. In this case, any ‘font-face-src’ elements within the ‘font-face’ element are ignored as it is assumed that the ‘font-face’ element is describing the characteristics of its parent ‘font’ element.

‘font-face’

Categories:

None

Content model:

Any number of descriptive elements and at most one ‘font-face-src’ element, in any order.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
‘font-family’
‘font-style’
‘font-variant’
‘font-weight’
‘font-stretch’
‘font-size’
‘unicode-range’
‘units-per-em’
‘panose-1’
‘stemv’
‘stemh’
‘slope’
‘cap-height’
‘x-height’
‘accent-height’
‘ascent’
‘descent’
‘widths’
‘bbox’
‘ideographic’
‘alphabetic’
‘mathematical’
‘hanging’
‘v-ideographic’
‘v-alphabetic’
‘v-mathematical’
‘v-hanging’
‘underline-position’
‘underline-thickness’
‘strikethrough-position’
‘strikethrough-thickness’
‘overline-position’
‘overline-thickness’

DOM Interfaces:

SVGFontFaceElement

Attribute definitions:

font-family = "<string>"

Same syntax and semantics as the ‘font-family’ descriptor within an @font-face rule.
Animatable: no.

Same syntax and semantics as the ‘font-style’ descriptor within an @font-face rule. The style of a font. Takes on the same values as the ‘font-style’ property, except that a comma-separated list is permitted.
If the attribute is not specified, the effect is as if a value of 'all' were specified.
Animatable: no.

font-variant = "[normal | small-caps] [,[normal | small-caps]]*"

Same syntax and semantics as the ‘font-variant’ descriptor within an @font-face rule. Indication of whether this face is the small-caps variant of a font. Takes on the same values as the ‘font-variant’ property, except that a comma-separated list is permitted.
If the attribute is not specified, the effect is as if a value of 'normal' were specified.
Animatable: no.

font-weight = "all | [normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900] [, [normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900]]*"

Same syntax and semantics as the ‘font-weight’ descriptor within an @font-face rule.
The weight of a face relative to others in the same font family. Takes on the same values as the ‘font-weight’ property with three exceptions:

relative keywords (bolder, lighter) are not permitted
a comma-separated list of values is permitted, for fonts that contain multiple weights
an additional keyword, 'all', is permitted, which means that the font will match for all possible weights; either because it contains multiple weights, or because that face only has a single weight.

If the attribute is not specified, the effect is as if a value of 'all' were specified.
Animatable: no.

Same syntax and semantics as the ‘font-stretch’ descriptor within an @font-face rule. Indication of the condensed or expanded nature of the face relative to others in the same font family. Takes on the same values as the ‘font-stretch’ property except that:

relative keywords (wider, narrower) are not permitted
a comma-separated list is permitted
the keyword 'all' is permitted

If the attribute is not specified, the effect is as if a value of 'normal' were specified.
Animatable: no.

font-size = "<string>"

Same syntax and semantics as the ‘font-size’ descriptor within an @font-face rule.
Animatable: no.

CSS3 Fonts does not have a font-size descriptor.

unicode-range = "<urange> [, <urange>]*"

Same syntax and semantics as the ‘unicode-range’ descriptor within an @font-face rule. The range of ISO 10646 characters [UNICODE] possibly covered by the glyphs in the font. Except for any additional information provided in this specification, the normative definition of the attribute is in CSS 2.1 ([CSS21], section 4.5).
If the attribute is not specified, the effect is as if a value of 'U+0-10FFFF' were specified.
Animatable: no.

units-per-em = "<number>"

Same syntax and semantics as the ‘units-per-em’ descriptor within an @font-face rule. The number of coordinate units on the em square, the size of the design grid on which glyphs are laid out.
This value is almost always necessary as nearly every other attribute requires the definition of a design grid.
If the attribute is not specified, the effect is as if a value of '1000' were specified.
Animatable: no.

CSS3 Fonts does not have a units-per-em descriptor.

panose-1 = "[<integer>]{10}"

Same syntax and semantics as the ‘panose-1’ descriptor within an @font-face rule. The Panose-1 number, consisting of ten decimal integers, separated by whitespace. Except for any additional information provided in this specification, the normative definition of the attribute is in CSS2.
If the attribute is not specified, the effect is as if a value of '0 0 0 0 0 0 0 0 0 0' were specified.
Animatable: no.

CSS3 Fonts does not have a panose-1 descriptor.

stemv = "<number>"

Same syntax and semantics as the ‘stemv’ descriptor within an @font-face rule.
Animatable: no.

CSS3 Fonts does not have a stemv descriptor.

stemh = "<number>"

Same syntax and semantics as the ‘stemh’ descriptor within an @font-face rule.
Animatable: no.

CSS3 Fonts does not have a stemh descriptor.

slope = "<number>"

Same syntax and semantics as the ‘slope’ descriptor within an @font-face rule. The vertical stroke angle of the font. Except for any additional information provided in this specification, the normative definition of the attribute is in CSS2.
If the attribute is not specified, the effect is as if a value of '0' were specified.
Animatable: no.

CSS3 Fonts does not have a slope descriptor.

cap-height = "<number>"

Same syntax and semantics as the ‘cap-height’ descriptor within an @font-face rule. The height of uppercase glyphs in the font within the font coordinate system.
Animatable: no.

CSS3 Fonts does not have a cap-height descriptor.

x-height = "<number>"

Same syntax and semantics as the ‘x-height’ descriptor within an @font-face rule. The height of lowercase glyphs in the font within the font coordinate system.
Animatable: no.

CSS3 Fonts does not have an x-height descriptor.

accent-height = "<number>"

The distance from the origin to the top of accent characters, measured by a distance within the font coordinate system.
If the attribute is not specified, the effect is as if the attribute were set to the value of the ‘ascent’ attribute.
Animatable: no.

ascent = "<number>"

Same syntax and semantics as the ‘ascent’ descriptor within an @font-face rule. The maximum unaccented height of the font within the font coordinate system.
If the attribute is not specified, the effect is as if the attribute were set to the difference between the ‘units-per-em’ value and the ‘vert-origin-y’ value for the corresponding font.
Animatable: no.

CSS3 Fonts does not have an ascent descriptor.

descent = "<number>"

Same syntax and semantics as the ‘descent’ descriptor within an @font-face rule. The maximum unaccented depth of the font within the font coordinate system.
If the attribute is not specified, the effect is as if the attribute were set to the ‘vert-origin-y’ value for the corresponding font.
Animatable: no.

CSS3 Fonts does not have a descent descriptor.

widths = "<string>"

Same syntax and semantics as the ‘widths’ descriptor within an @font-face rule.
Animatable: no.

CSS3 Fonts does not have a widths descriptor.

bbox = "<string>"

Same syntax and semantics as the ‘bbox’ descriptor within an @font-face rule.
Animatable: no.

CSS3 Fonts does not have a bbox descriptor.

ideographic = "<number>"

For horizontally oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve ideographic baseline alignment. The value is an offset in the font coordinate system.
Animatable: no.

alphabetic = "<number>"

Same syntax and semantics as the ‘baseline’ descriptor within an @font-face rule. For horizontally oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve alphabetic baseline alignment. The value is an offset in the font coordinate system.
Animatable: no.

CSS3 Fonts does not have a baseline descriptor.

mathematical = "<number>"

Same syntax and semantics as the ‘mathline’ descriptor within an @font-face rule. For horizontally oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve mathematical baseline alignment. The value is an offset in the font coordinate system.
Animatable: no.

CSS3 Fonts does not have a mathline descriptor.

hanging = "<number>"

For horizontally oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve hanging baseline alignment. The value is an offset in the font coordinate system.
Animatable: no.

v-ideographic = "<number>"

For vertically oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve ideographic baseline alignment. The value is an offset in the font coordinate system relative to the glyph-specific ‘vert-origin-x’ attribute.
Animatable: no.

v-alphabetic = "<number>"

For vertically oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve alphabetic baseline alignment. The value is an offset in the font coordinate system relative to the glyph-specific ‘vert-origin-x’ attribute.
Animatable: no.

v-mathematical = "<number>"

For vertically oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve mathematical baseline alignment. The value is an offset in the font coordinate system relative to the glyph-specific ‘vert-origin-x’ attribute.
Animatable: no.

v-hanging = "<number>"

For vertically oriented glyph layouts, indicates the alignment coordinate for glyphs to achieve hanging baseline alignment. The value is an offset in the font coordinate system relative to the glyph-specific ‘vert-origin-x’ attribute.
Animatable: no.

underline-position = "<number>"

The ideal position of an underline within the font coordinate system.
Animatable: no.

underline-thickness = "<number>"

The ideal thickness of an underline, expressed as a length within the font coordinate system.
Animatable: no.

strikethrough-position = "<number>"

The ideal position of a strike-through within the font coordinate system.
Animatable: no.

strikethrough-thickness = "<number>"

The ideal thickness of a strike-through, expressed as a length within the font coordinate system.
Animatable: no.

overline-position = "<number>"

The ideal position of an overline within the font coordinate system.
Animatable: no.

overline-thickness = "<number>"

The ideal thickness of an overline, expressed as a length within the font coordinate system.
Animatable: no.

The following elements and attributes correspond to the ‘src’ descriptor within an @font-face rule. Refer to the descriptions of the @font-face rule and 'src' descriptor in the CSS 2.1 specification ([CSS21], sections 4.1 and 4.3.)

20.2.4. The ‘font-face-src’ element

The ‘font-face-src’ element, together with the ‘font-face-uri’ and ‘font-face-format’ elements described in the following sections, correspond to the ‘src’ descriptor within an @font-face rule. (Refer to the descriptions of the @font-face rule and 'src' descriptor in the CSS3 Fonts specification ([CSS3FONTS], sections 4.1 and 4.3.)

A ‘font-face-src’ element contains ‘font-face-uri’ and ‘font-face-name’ elements, which are used for referencing external and local fonts, respectively.

‘font-face-src’

Categories:

None

Content model:

One or more of the following elements, in any order:

font-face-name, font-face-uri

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’

DOM Interfaces:

SVGFontFaceSrcElement

20.2.5. The ‘font-face-uri’ and ‘font-face-format’ elements

The ‘font-face-uri’ element is used within a ‘font-face-src’ element to reference a font defined inside or outside of the current SVG document.

When a ‘font-face-uri’ is referencing an SVG font, then that reference must be to an SVG ‘font’ element, therefore requiring the use of a fragment identifier [RFC3986]. The referenced ‘font’ element can be local (i.e., within the same document as the ‘font-face-uri’ element) or remote (i.e., within a different document).

‘font-face-uri’

Categories:

None

Content model:

Any number of the following elements, in any order:

font-face-format

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
xlink attributes — ‘xlink:href’, ‘xlink:show’, ‘xlink:actuate’, ‘xlink:type’, ‘xlink:role’, ‘xlink:arcrole’, ‘xlink:title’
‘xlink:href’

DOM Interfaces:

SVGFontFaceUriElement

Attribute definitions:

xlink:href = "<IRI>": The ‘xlink:href’ attribute specifies the location of the referenced font.
Animatable: no.

Child ‘font-face-format’ elements of a ‘font-face-uri’ element are used to specify the supported formats of the font referenced by that ‘font-face-uri’ element. They correspond to entries in a format(…) clause of the ‘src’ descriptor in an @font-face rule.

‘font-face-format’

Categories:

None

Content model:

Empty.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
‘string’

DOM Interfaces:

SVGFontFaceFormatElement

Attribute definitions:

string = "<anything>": The ‘string’ attribute is a hint to the user agent, and specifies a list of formats that the font referenced by the parent ‘font-face-uri’ element supports. The syntax of the attribute value is a format string as defined in CSS2, such as 'truetype'. Refer to the description of the 'src' descriptor in CSS2 for details on how the format hint is interpreted.
Animatable: no.
CSS3 Fonts does not have format strings.

20.2.6. The ‘font-face-name’ element

The ‘font-face-name’ element is used within a ‘font-face-src’ element to reference a local font by name. It corresponds to a local(…) clause in an @font-face rule ‘src’ descriptor.

‘font-face-name’

Categories:

None

Content model:

Empty.

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
‘name’

DOM Interfaces:

SVGFontFaceNameElement

Attribute definitions:

name = "<anything>": The ‘name’ attribute specifies the name of a local font. Unlike the syntax allowed between the parentheses of the local(…) clause in an @font-face rule ‘src’ descriptor, the font name specified in this attribute is not surrounded in single or double quotes. Refer to the description of the 'src' descriptor in CSS3 Fonts for details on how the font name is interpreted ([CSS3FONTS], section 4.3).
Animatable: no.

20.3. Overview of SVG fonts

An SVG font is a font defined using SVG's ‘font’ element.

The purpose of SVG fonts is to allow for delivery of glyph outlines in display-only environments. SVG fonts that accompany Web pages must be supported only in browsing and viewing situations. Graphics editing applications or file translation tools must not attempt to convert SVG fonts into system fonts. The intent is that SVG files be interchangeable between two content creators, but not the SVG fonts that might accompany these SVG files. Instead, each content creator will need to license the given font before being able to successfully edit the SVG file. The ‘font-face-name’ element indicates the name of licensed font to use for editing.

SVG fonts contain unhinted font outlines. Because of this, on many implementations there will be limitations regarding the quality and legibility of text in small font sizes. For increased quality and legibility in small font sizes, content creators may want to use an alternate font technology, such as fonts that ship with operating systems or an alternate WebFont format.

Because SVG fonts are expressed using SVG elements and attributes, in some cases the SVG font will take up more space than if the font were expressed in a different WebFont format which was especially designed for compact expression of font data. For the fastest delivery of Web pages, content creators may want to use an alternate font technology.

A key value of SVG fonts is guaranteed availability in SVG user agents. In some situations, it might be appropriate for an SVG font to be the first choice for rendering some text. In other situations, the SVG font might be an alternate, back-up font in case the first choice font (perhaps a hinted system font) is not available to a given user.

The characteristics and attributes of SVG fonts correspond closely to the font characteristics and parameters described in the CSS Fonts Modules Level 3 specification [CSS3FONTS]. In this model, various font metrics, such as advance values and baseline locations, and the glyph outlines themselves, are expressed in units that are relative to an abstract square whose height is the intended distance between lines of type in the same type size. This square is called the em square and it is the design grid on which the glyph outlines are defined. The value of the ‘units-per-em’ attribute on the ‘font-face’ element specifies how many units the em square is divided into. Common values for other font types are, for example, 250 (Intellifont), 1000 (Type 1) and 2048 (TrueType, TrueType GX and Open-Type). Unlike standard graphics in SVG, where the initial coordinate system has the y-axis pointing downward (see The initial coordinate system), the design grid for SVG fonts, along with the initial coordinate system for the glyphs, has the y-axis pointing upward for consistency with accepted industry practice for many popular font formats.

SVG fonts and their associated glyphs do not specify bounding box information. Because the glyph outlines are expressed as SVG graphics elements, the implementation has the option to render the glyphs either using standard graphics calls or by using special-purpose font rendering technology, in which case any necessary maximum bounding box and overhang calculations can be performed from analysis of the graphics elements contained within the glyph outlines.

An SVG font can be either embedded within the same document that uses the font or saved as part of an external resource.

Here is an example of how you might embed an SVG font inside of an SVG document.

<?xml version="1.0" standalone="yes"?>
<svg width="400px" height="300px" version="1.1"
  xmlns = 'http://www.w3.org/2000/svg'>
  <defs>
    <font id="Font1" horiz-adv-x="1000">
      <font-face font-family="Super Sans" font-weight="bold" font-style="normal"
          units-per-em="1000" cap-height="600" x-height="400"
          ascent="700" descent="300"
          alphabetic="0" mathematical="350" ideographic="400" hanging="500">
        <font-face-src>
          <font-face-name name="Super Sans Bold"/>
        </font-face-src>
      </font-face>
      <missing-glyph><path d="M0,0h200v200h-200z"/></missing-glyph>
      <glyph unicode="!" horiz-adv-x="300"><!-- Outline of exclam. pt. glyph --></glyph>
      <glyph unicode="@"><!-- Outline of @ glyph --></glyph>
      <!-- more glyphs -->
    </font>
  </defs>
  <text x="100" y="100" 
           style="font-family: 'Super Sans', Helvetica, sans-serif;
                  font-weight: bold; font-style: normal">Text 
    using embedded font</text>
</svg>

Here is an example of how you might use the CSS @font-face facility ([CSS3FONTS], section 4.1) to reference an SVG font which is saved in an external file. First referenced SVG font file:

<?xml version="1.0" standalone="yes"?>
<svg width="100%" height="100%" version="1.1"
 xmlns = 'http://www.w3.org/2000/svg'>
  <defs>
    <font id="Font2" horiz-adv-x="1000">
      <font-face font-family="Super Sans" font-weight="normal" font-style="italic"
          units-per-em="1000" cap-height="600" x-height="400"
          ascent="700" descent="300"
          alphabetic="0" mathematical="350" ideographic="400" hanging="500">
        <font-face-src>
          <font-face-name name="Super Sans Italic"/>
        </font-face-src>
      </font-face>
      <missing-glyph><path d="M0,0h200v200h-200z"/></missing-glyph>
      <glyph unicode="!" horiz-adv-x="300"><!-- Outline of exclam. pt. glyph --></glyph>
      <glyph unicode="@"><!-- Outline of @ glyph --></glyph>
      <!-- more glyphs -->
    </font>
  </defs>
</svg>

The SVG file which uses/references the above SVG font

<?xml version="1.0" standalone="yes"?>
<svg width="400px" height="300px" version="1.1"
 xmlns = 'http://www.w3.org/2000/svg'>  
  <defs>
    <style type="text/css">
      @font-face {
        font-family: 'Super Sans'; 
        font-weight: normal;
        font-style: italic;
        src: url("myfont.svg#Font2") format("svg")
      }
   </style>
  </defs>
  <text x="100" y="100"
           style="font-family: 'Super Sans'; font-weight:normal;
                  font-style: italic">Text using referenced font</text>
</svg>

20.4. The ‘font’ element

The ‘font’ element defines an SVG font.

‘font’

Categories:

None

Content model:

Any number of the following elements, in any order:

descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’

clipPath, font-face, glyph, hkern, marker, mask, missing-glyph, vkern

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
style attributes — ‘class’, ‘style’
presentation attributes —
‘horiz-origin-x’
‘horiz-origin-y’
‘horiz-adv-x’
‘vert-origin-x’
‘vert-origin-y’
‘vert-adv-y’

DOM Interfaces:

SVGFontElement

Attribute definitions:

horiz-origin-x = "<number>": The X-coordinate in the font coordinate system of the origin of a glyph to be used when drawing horizontally oriented text. (Note that the origin applies to all glyphs in the font.)
If the attribute is not specified, the effect is as if a value of '0' were specified.
Animatable: no.
horiz-origin-y = "<number>": The Y-coordinate in the font coordinate system of the origin of a glyph to be used when drawing horizontally oriented text. (Note that the origin applies to all glyphs in the font.)
If the attribute is not specified, the effect is as if a value of '0' were specified.
Animatable: no.
horiz-adv-x = "<number>": The default horizontal advance after rendering a glyph in horizontal orientation. Glyph widths are required to be non-negative, even if the glyph is typically rendered right-to-left, as in Hebrew and Arabic scripts.
Animatable: no.
vert-origin-x = "<number>": The default X-coordinate in the font coordinate system of the origin of a glyph to be used when drawing vertically oriented text.
If the attribute is not specified, the effect is as if the attribute were set to half of the effective value of attribute ‘horiz-adv-x’.
Animatable: no.
vert-origin-y = "<number>": The default Y-coordinate in the font coordinate system of the origin of a glyph to be used when drawing vertically oriented text.
If the attribute is not specified, the effect is as if the attribute were set to the position specified by the font's ‘ascent’ attribute.
Animatable: no.
vert-adv-y = "<number>": The default vertical advance after rendering a glyph in vertical orientation.
If the attribute is not specified, the effect is as if a value equivalent of one em were specified (see ‘units-per-em’).
Animatable: no.

Each ‘font’ element must have a ‘font-face’ child element which describes various characteristics of the font.

20.5. The ‘glyph’ element

The ‘glyph’ element defines the graphics for a given glyph. The coordinate system for the glyph is defined by the various attributes in the ‘font’ element.

The graphics that make up the ‘glyph’ can be a single path data specification within the ‘d’ attribute, arbitrary SVG as content within the ‘glyph’, or both. These two alternatives are processed differently (see below).

‘glyph’

Categories:

Content model:

Any number of the following elements, in any order:

animation elements — ‘animate’, ‘animateColor’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
descriptive elements — ‘desc’, ‘title’, ‘metadata’
paint server elements — ‘solidColor’, ‘linearGradient’, ‘radialGradient’, ‘meshGradient’, ‘pattern’
shape elements — ‘circle’, ‘ellipse’, ‘line’, ‘path’, ‘polygon’, ‘polyline’, ‘rect’
structural elements — ‘defs’, ‘g’, ‘svg’, ‘symbol’, ‘use’

a, altGlyphDef, clipPath, color-profile, cursor, filter, font, font-face, foreignObject, image, marker, mask, script, style, switch, text, view

Attributes:

core attributes — ‘id’, ‘xml:base’, ‘xml:lang’, ‘xml:space’
style attributes — ‘class’, ‘style’
presentation attributes —
‘d’
‘horiz-adv-x’
‘vert-origin-x’
‘vert-origin-y’
‘vert-adv-y’
‘unicode’
‘glyph-name’
‘orientation’
‘arabic-form’
‘lang’

DOM Interfaces:

SVGGlyphElement

Attribute definitions:

unicode = "<string>": One or more Unicode characters indicating the sequence of Unicode characters which corresponds to this glyph. If a character is provided, then this glyph corresponds to the given Unicode character. If multiple characters are provided, then this glyph corresponds to the given sequence of Unicode characters. One use of a sequence of characters is ligatures. For example, if unicode="ffl", then the given glyph will be used to render the sequence of characters "f", "f", and "l".

It is often useful to refer to characters using XML character references expressed in hexadecimal notation or decimal notation. For example, unicode="ffl" could be expressed as XML character references in hexadecimal notation as unicode="ffl" or in decimal notation as unicode="ffl".

The ‘unicode’ attribute contributes to the process for deciding which glyph(s) are used to represent which character(s). See glyph selection rules. If the ‘unicode’ attribute is not provided for a given ‘glyph’, then the only way to use this glyph is via an ‘altGlyph’ reference.
Animatable: no.
glyph-name = "<author-ident> [, <author-ident> ]* ": A name for the glyph. It is recommended that glyph names be unique within a font. The glyph names can be used in situations where Unicode character numbers do not provide sufficient information to access the correct glyph, such as when there are multiple glyphs per Unicode character. The glyph names can be referenced in kerning definitions.
Animatable: no.
d = "path data": The definition of the outline of a glyph, using the same syntax as for the ‘d’ attribute on a ‘path’ element. See Path data.
See below for a discussion of this attribute.
Animatable: no.
orientation = "h | v": Indicates that the given glyph is only to be used for a particular inline-progression-direction (i.e., horizontal or vertical). If the attribute is not specified, then the glyph can be used in all cases (i.e., both horizontal and vertical inline-progression-direction).
Animatable: no.
arabic-form = "initial | medial | terminal | isolated": For Arabic glyphs, indicates which of the four possible forms this glyph represents.
Animatable: no.
lang = "%LanguageCodes;": The attribute value is a comma-separated list of language names as defined in BCP 47 [BCP47]. The glyph can be used if the ‘xml:lang’ attribute exactly matches one of the languages given in the value of this parameter, or if the ‘xml:lang’ attribute exactly equals a prefix of one of the languages given in the value of this parameter such that the first tag character following the prefix is "-".
Animatable: no.
horiz-adv-x = "<number>": The horizontal advance after rendering the glyph in horizontal orientation. If the attribute is not specified, the effect is as if the attribute were set to the value of the font's ‘horiz-adv-x’ attribute.
Glyph widths are required to be non-negative, even if the glyph is typically rendered right-to-left, as in Hebrew and Arabic scripts.
Animatable: no.
vert-origin-x = "<number>": The X-coordinate in the font coordinate system of the origin of the glyph to be used when drawing vertically oriented text.
If the attribute is not specified, the effect is as if the attribute were set to the value of the font's ‘vert-origin-x’ attribute.
Animatable: no.
vert-origin-y = "<number>": The Y-coordinate in the font coordinate system of the origin of a glyph to be used when drawing vertically oriented text.
If the attribute is not specified, the effect is as if the attribute were set to the value of the font's ‘vert-origin-y’ attribute.
Animatable: no.
vert-adv-y = "<number>": The vertical advance after rendering a glyph in vertical orientation.
If the attribute is not specified, the effect is as if the attribute were set to the value of the font's ‘vert-adv-y’ attribute.
Animatable: no.

The graphics for the ‘glyph’ can be specified using either the ‘d’ attribute or arbitrary SVG as content within the ‘glyph’.

If the ‘d’ attribute is specified, then the path data within this attribute is processed as follows:

Any relative coordinates within the path data specification are converted into equivalent absolute coordinates
Each of these absolute coordinates is transformed from the font coordinate system into the ‘text’ element's current coordinate system such that the origin of the font coordinate system is properly positioned and rotated to align with the current text position and orientation for the glyph, and scaled so that the correct ‘font-size’ is achieved.
The resulting, transformed path specification is rendered as if it were a ‘path’ element, using the styling properties that apply to the characters which correspond to the given glyph, and ignoring any styling properties specified on the ‘font’ element or the ‘glyph’ element.

If the ‘glyph’ has child elements, then those child elements are rendered in a manner similar to how the ‘use’ element renders a referenced symbol. The rendering effect is as if the contents of the referenced ‘glyph’ element were deeply cloned into a separate non-exposed DOM tree. Because the cloned DOM tree is non-exposed, the SVG DOM does not show the cloned instance.

For user agents that support Styling with CSS, the conceptual deep cloning of the referenced ‘glyph’ element into a non-exposed DOM tree also copies any property values resulting from the CSS cascade ([CSS21], chapter 6) on the referenced ‘glyph’ and its contents, and also applies any property values on the ‘font’ element. CSS 2.1 selectors can be applied to the original (i.e., referenced) elements because they are part of the formal document structure. CSS 2.1 selectors cannot be applied to the (conceptually) cloned DOM tree because its contents are not part of the formal document structure.

Property inheritance, however, works as if the referenced ‘glyph’ had been textually included as a deeply cloned child within the document tree. The referenced ‘glyph’ inherits properties from the element that contains the characters that correspond to the ‘glyph’. The ‘glyph’ does not inherit properties from the ‘font’ element's original parents.

In the generated content, for each instance of a given ‘glyph’, a ‘g’ is created which carries with it all property values resulting from the CSS cascade on the ‘font’ element for the referenced ‘glyph’. Within this ‘g’ is another ‘g’ which carries with it all property values resulting from the CSS cascade on the ‘glyph’ element. The original contents of the ‘glyph’ element are deep-cloned within the inner ‘g’ element.

If the ‘glyph’ has both a ‘d’ attribute and child elements, the ‘d’ attribute is rendered first, and then the child elements.

In general, the ‘d’ attribute renders in the same manner as system fonts. For example, a dashed pattern will usually look the same if applied to a system font or to an SVG font which defines its glyphs using the ‘d’ attribute. Many implementations will be able to render glyphs defined with the ‘d’ attribute quickly and will be able to use a font cache for further performance gains.

Defining a glyph by including child elements within the ‘glyph’ gives greater flexibility but more complexity. Different fill and stroke techniques can be used on different parts of the glyphs. For example, the base of an "i" could be red, and the dot could be blue. This approach has an inherent complexity with units. Any properties specified on a text elements which represents a length, such as the ‘stroke-width’ property, might produce surprising results since the length value will be processed in the coordinate system of the glyph.

20.6. The ‘missing-glyph’ element

The ‘missing-glyph’ element defines the graphics to use if there is an attempt to draw a glyph from a given font and the given glyph has not been defined. The attributes on the ‘missing-glyph’ element have the same meaning as the corresponding attributes on the ‘glyph’ element.

‘missing-glyph’

Categories: