SVG 2 – 09 July 2015 TopContentsPreviousNextElementsAttributesProperties

# Chapter 12: Painting: Filling, Stroking and Marker Symbols

## 12.1. Introduction

### 12.1.1. Definitions

fill
The operation of painting the interior of a shape or the interior of the character glyphs in a text string.
paint
A paint represents a way of putting color values onto the canvas. A paint might consist of both color values and associated alpha values which control the blending of colors against already existing color values on the canvas. SVG supports three types of built-in paint: color, gradients and patterns.
paint server element
An element that defines a paint server. Specifically: hatch, , mesh, pattern, and .
stroke
The operation of painting the outline of a shape or the outline of character glyphs in a text string.

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 pattern (vector or raster, possibly tiled),
• a hatch,
• 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.

Some graphics elements – path elements and basic shapes – 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.

SVG 2 adds markers on shapes. Resolved at Tokyo F2F.

## 12.2. Specifying paint

SVG 2 Requirement: Add new paint values for referencing current fill paint, stroke paint, etc. We will add new paint values currentFillPaint, currentStrokePaint etc. to SVG 2 Among other things, to provide an easy way to match marker color to stroke color. Chris (ACTION-3094)
SVG 2 Addition: Allow multiple paints in fill and stroke. We will allow multiple paints in the fill and stroke properties in SVG 2. Useful for creating cross hatchings, putting a partially transparent pattern on top of a solid fill, etc. Tav (ACTION-3500)

Properties ‘fill’ and ‘stroke’ take on a comma separated list of values of type <paint>. Each paint is applied to an element in reverse order. Note, only a paint server in the last position may take an optional fallback color.

The ability to apply more than one paint to an element is new in SVG 2.

The paint order follows that of CSS backgrounds.

<rect width="100" height="100" fill="url(#MyHatch1), url(#MyHatch2), powderblue">


The type <paint> is defined as:

<paint> = [ <paint-layer> , ]* <final-paint-layer>
<paint-layer> = <paint-source>|| <position> [ / <paint-size> ]? || <repeat-style> ||
[ <shape-box> | fill | stroke | view-box ] || [ <shape-box> | fill | stroke | view-box ]
<final-paint-layer> = <paint-source> || <position> [ / <paint-size> ]? || <repeat-style> ||
[ <shape-box> | fill | stroke | view-box ] ||
[ <shape-box> | fill | stroke | view-box ] || <color>
<paint-source> = none | <image> | <url> | context-fill | context-stroke

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.
<url>
A reference to a paint server element with, if the paint server is the last paint specified, an optional fallback color or none. The <url>, child keyword, or <child-selector> is used to identify a element, gradient element, pattern element, or hatch 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 the paint server reference is the last paint specified and if the fallback color is provided); otherwise, it must be treated as if none was specified.

Changed from SVG 1.1 behavior where document is in error if paint server missing or invalid.

<rect width="100" height="100" fill="url(#MyHatch1), url(#MyHatch2) powderblue">


How should 'child' behave with allowing multiple paints?

This section needs additional examples, especially one with 'child'.

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.
context element
The context element of an element is defined as follows:
• If the element is within a marker, and is being rendered as part of that marker due to being referenced via a marker property, then the context element is the element referencing that marker.
• If the element is within a sub-tree that is instantiated with a use element, then the context element is that use element.
• Otherwise, there is no context element.

Should gradient elements also be context elements?

## 12.3. The effect of the ‘color’ property

See the CSS Color Module Level 3 specification for the definition of ‘color’. [CSS3COLOR]

The ‘color’ property is used to provide a potential indirect value, currentColor, for the ‘fill’, ‘stroke’, ‘solid-color’, ‘stop-color’, ‘flood-color’ and ‘lighting-color’ properties. The property has no other effect on SVG elements.

The following example shows how the inherited value of the ‘color’ property from an HTML document can be used to set the color of SVG text in an inline SVG fragment.

<!DOCTYPE html>
<style>
body { color: #468; font: 16px sans-serif }
svg { border: 1px solid #888; background-color: #eee }
</style>
<svg width="200" height="100">
<g fill="currentColor">
<text x="70" y="55" text-anchor="end">START</text>
<text x="130" y="55">STOP</text>
<path d="M 85,45 h 25 v -5 l 10,10 -10,10 v -5 h -25 z"/>
</g>
</svg>


The text and arrow in the SVG fragment are filled with the same color as the inherited ‘color’ property.

## 12.4. Fill properties

### 12.4.1. Specifying fill paint: the ‘fill’ property

Name: fill black shapes and text content elements yes N/A visual as specified, but with values computed and values made absolute 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.

### 12.4.2. Winding rule: the ‘fill-rule’ property

Name: fill-rule nonzero | evenodd nonzero shapes and text content elements yes N/A visual as specified 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:

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 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.

### 12.4.3. Fill paint opacity: the ‘fill-opacity’ property

Name: fill-opacity 1 shapes and text content elements yes N/A visual as specified, but clamped to the range [0, 1] 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.

## 12.5. Stroke properties

SVG 2 Requirement: Support non-scaling stroke. SVG 2 will include non-scaling stroke. SVG 2 will have the ‘vector-effect’ property. To support strokes whose width does not change when zooming a page, as common for example in maps. Chris or Erik (no action) Note that this could be part of more generic non-scaling features.

In this section, we define a number of properties that allow the author to control different aspects of a stroke, including its paint, thickness, use of dashing, and joining and capping of path segments.

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.

### 12.5.1. Specifying stroke paint: the ‘stroke’ property

Name: stroke none shapes and text content elements yes N/A visual as specified, but with values computed and values made absolute yes

The ‘stroke’ property paints along the outline of the given graphical element.

Note that when stroking a path element, any subpath consisting of a moveto but no following line drawing command will not be stroked. Any other type of zero-length subpath, such as 'M 10,10 L 10,10' or 'M 30,30 Z' will also not be stroked if the ‘stroke-linecap’ property has a value of butt. See the definition of the stroke shape below for the details of computing the stroke of a path.

SVG 2 Requirement: Include a way to specify stroke position. SVG 2 shall include a way to specify stroke position. To allow a stroke to be inside or outside the path. Cameron (ACTION-3162) See proposal page.

### 12.5.2. Stroke paint opacity: the ‘stroke-opacity’ property

Name: stroke-opacity 1 shapes and text content elements yes N/A visual as specified, but clamped to the range [0, 1] 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.

### 12.5.3. Stroke width: the ‘stroke-width’ property

Name: stroke-width | 1 shapes and text content elements yes refer to the size of the current viewport (see Units) visual absolute length or percentage 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.

### 12.5.4. Drawing caps at the ends of strokes: the ‘stroke-linecap’ property

Name: stroke-linecap butt | round | square butt shapes and text content elements yes N/A visual as specified 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.

See the definition of the cap shape below for a more precise description of the shape a line cap will have.

### 12.5.5. Controlling line joins: the ‘stroke-linejoin’ and ‘stroke-miterlimit’ properties

Name: stroke-linejoin miter | miter-clip | round | bevel | arcs miter shapes and text content elements yes N/A visual as specified 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. If the ‘stroke-miterlimit’ is exceeded, the line join falls back to bevel (see below).
miter-clip
This value is the same as miter but if the ‘stroke-miterlimit’ is exceeded, the miter is clipped at a miter length equal to the ‘stroke-miterlimit’ value multiplied by the stroke width (see below).
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.

The miter-clip and arcs values are new in SVG 2. The miter-clip value offers a more consistent presentation for a path with multiple joins as well as better behavior when a path is animated. The arcs value provides a better looking join when the path segments at the join are curved.

Adding 'arcs' line join was resolved at the Rigi Kaltbad group meeting.

Adding 'miter-clip' line join was resolved at the Sydney (2015) group meeting.

Name: stroke-miterlimit 4 shapes and text content elements yes N/A visual as specified yes

When two line segments meet at a sharp angle and a value of miter, miter-clip, or arcs has been specified for ‘stroke-linejoin’, it is possible for the join to extend far beyond the thickness of the line stroking the path. The ‘stroke-miterlimit’ imposes a limit on the extent of the line join.

<number>
The limit on the extent of a miter, miter-clip, or arcs line join as a multiple of the ‘stroke-width’ value. The value of ‘stroke-miterlimit’ must be a <number> greater than or equal to 1. Any other value is an error (see Error processing).

For the miter or the miter-clip values, given the angle θ between the segments in local coordinate system, the miter length is calculated by:

$\mathrm{miter length}=\frac{\mathrm{‘stroke-width’}}{\mathrm{sin}\frac{\theta }{2}}$
miter length = stroke-width / sin(theta / 2)

If the miter length divided by the stroke width exceeds the ‘stroke-miterlimit’ then for the value:

miter
the join is converted to a bevel;
miter-clip
the miter is clipped by a line perpendicular to the line bisecting the angle between the two path segments at a distance of the value of miter length from the intersection of the two path segments.

For the arcs value, the miter length is calculated along a circular arc that is tangent to the line bisecting the angle between the two segments at the point the two segments intersect and passes through the end point of the join. The line join is clipped, if necessary, by a line perpendicular to this arc at a miter length equal to the value of the ‘stroke-miterlimit’ value multiplied by the stroke width.

The effect of 'stroke-miterlimit' on an 'arcs' line join was resolved at Sydney (2015) group meeting.

See the definition of the line join shape below for a more precise description of the shape a line join will have.

### 12.5.6. Dashing strokes: the ‘stroke-dasharray’ and ‘stroke-dashoffset’ properties

Name: stroke-dasharray none | none shapes and text content elements yes refer to the size of the current viewport (see Units) visual absolute lengths or percentages for , or keyword specified yes (non-additive)

where:

<dasharray> = [ <length> | <percentage> | <number> ]#*

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 or percentages. Each value specifies a length along the path for which the stroke is to be painted (a dash) and not painted (a gap). The first value and every second value in the list after it 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 a solid line without any dashing.

Name: stroke-dashoffset | 0 shapes and text content elements yes refer to the size of the current viewport (see Units) visual absolute length or percentage 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:

$d=s-\left|\mathrm{‘stroke-dashoffset’}\right|mods$
d = s - (abs(stroke-dashoffset) mod s)

where s is the sum of the dash array values.

See the definition of dash positions below for a more precise description of positions along a path that dashes will be placed.

### 12.5.7. Computing the shape of the stroke

SVG 2 Requirement: Specify stroke dashing more precisely. SVG 2 shall specify stroke dashing more precisely. To define dash starting point on basic shapes and path segments. Cameron (no action)

Something in this section needs to reference so that dash lengths are in the author's path length space.

The stroke shape of an element is the shape that is filled by the ‘stroke’ property. Since text elements can be rendered in multiple chunks, each chunk has its own stroke shape. The following algorithm describes what the stroke shape of a path, basic shape or individual text chunk is, taking into account the stroking properties above:

1. Let shape be an empty shape.
2. Let path be the equivalent path of the element (or the individual chunk of a text element).
3. 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.
4. 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:

1. Let pathlength be the length of the subpath.
2. 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.
3. Let count be the number of values in dashes.
4. Let sum be the sum of the values in dashes.
5. If sum = 0, then return a sequence with the single pair <0, pathlength>.
6. Let positions be an empty sequence.
7. Let offset be the value of the ‘stroke-dashoffset’ property on the element.
8. If offset is negative, then set offset to sum − abs(offset).
9. Set offset to offset mod sum.
10. Let index be the smallest integer such that sum(dashesi, 0 ≤ iindex) ≥ offset.
11. Let dashlength be min(sum(dashesi, 0 ≤ iindex) − offset, pathlength).
12. If index mod 2 = 0, then append to positions the pair <0, dashlength>.
13. Let position be dashlength.
14. While position < pathlength:
1. Set index to (index + 1) mod count.
2. Let dashlength be min(dashesindex, pathlengthposition).
3. If index mod 2 = 0, then append to positions the pair <position, position + dashlength>.
4. Set position to position + dashlength.
15. Return positions.

The starting and ending cap shapes at a given position along a subpath are determined as follows:

1. If ‘stroke-linecap’ is butt, then return an empty shape.
2. 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.
3. 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.

The line join shape for a given segment of a subpath is determined as follows:

1. Let P be the point at the end of the segment.
2. Let A be the line parallel to the tangent at the end of the segment.
3. Let B be the line parallel to the tangent at the start of the following segment.
4. If A and B are the same line, then return an empty shape.
5. Let Aleft and Aright be lines parallel to A at a distance of ‘stroke-width’ / 2 to the left and to the right of A relative to the subpath direction, respectively.
6. Let Bleft and Bright be lines parallel to B at a distance of ‘stroke-width’ / 2 to the left and to the right of B, relative to the subpath direction, respectively.
7. Let P1, P2 and P3 be points determined as follows:
1. If the smaller 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 Aleft and Bleft closest to P, and P3 is the intersection of Aleft and Bleft.
2. Otherwise, P1 and P2 are the points on Aright and Bright closest to P, and P3 is the intersection of Aright and Bright.
8. Let bevel be the triangle formed from the three points P, P1 and P2.
9. 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.
10. 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-clip. Extend the stroke edges using these circles (or a line, in the case of zero curvature). If the two circles (or circle and line) do not intersect, fall through to miter-clip. If the two circles (or circle and line) intersect, the line join region is 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. Next calculate the miter limit as defined in the ‘stroke-miterlimit’ section. Clip any part of the line join region that extends past the miter limit. Return the resulting region. Note that the curvatures are calculated in user-space before any transforms are applied.
11. If ‘stroke-linejoin’ is miter or miter-clip then the line join region is the union of bevel and the triangle formed from the three points P1, P2 and P3.
12. Let θ be the angle between A and B. If 1 / sin(θ / 2) ≤ ‘stroke-miterlimit’, then return the line join region.
13. If ‘stroke-linejoin’ is miter-clip, then clip any part of the line join region that extends past the miter limit and return this region.
14. Return bevel.

### 12.5.8. Computing the circles for the arcs 'stroke-linejoin'

The arcsstroke-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: rc = r ± ½ stroke-width. The center of the circle will be on a line normal to the path end a distance of rc 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:

$\kappa \left(t\right)=\frac{{r}_{x}{r}_{y}}{\left({r}_{x}^{2}{\mathrm{sin}}^{2}t+{r}_{y}^{2}{\mathrm{cos}}^{2}t{\right)}^{3/2}}$
$$\kappa(t) = {{r_x r_y}\over{(r_x^2 \sin^2 t + r_y^2 \cos^2 t)^{3/2}}}$$

where:

$t=\mathrm{arctan}\left(\frac{{r}_{y}}{{r}_{x}}\mathrm{tan}\theta \right)$
$$t = \arctan ( {r_y \over r_x} \tan \theta )$$

The parameter θ at the beginning or end of an arc segment can be found by using the formulas in the Elliptical arc implementation notes. (Note, some renderers convert elliptical arcs to cubic Béziers prior to rendering so the equations here may not be needed.)

$\kappa \left(0\right)=\frac{1}{2}\frac{\left({P}_{1}-{P}_{0}\right)×\left({P}_{2}-{P}_{1}\right)}{|{P}_{1}-{P}_{0}{|}^{3}}$
$$\kappa(0) = {2\over3}{(P_1-P_0)\times((P_0-P_1)+(P_2-P_1))\over|P_1-P_0|^3}$$
$\kappa \left(1\right)=\frac{1}{2}\frac{\left({P}_{2}-{P}_{1}\right)×\left({P}_{0}-{P}_{1}\right)}{|{P}_{2}-{P}_{1}{|}^{3}}$
$$\kappa(0) = {2\over3}{(P_1-P_0)\times((P_0-P_1)+(P_2-P_1))\over|P_1-P_0|^3}$$

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:

$\kappa \left(0\right)=\frac{2}{3}\frac{\left({P}_{1}-{P}_{0}\right)×\left({P}_{2}-{P}_{1}\right)}{|{P}_{1}-{P}_{0}{|}^{3}}$
$$\kappa(0) = {2\over3}{(P_1-P_0)\times((P_0-P_1)+(P_2-P_1))\over|P_1-P_0|^3}$$
$\kappa \left(1\right)=\frac{2}{3}\frac{\left({P}_{3}-{P}_{2}\right)×\left({P}_{1}-{P}_{2}\right)}{|{P}_{3}-{P}_{2}{|}^{3}}$
$$\kappa(1) = {2\over3}{(P_3-P_2)\times((P_1-P_2)+(P_3-P_2))\over|P_3-P_2|^3}$$

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.

## 12.6. 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):

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, , 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.

## 12.7. Vector Effects

SVG 2 Requirement: SVG 2 will have constrained transformations based on SVG 1.2 Tiny. Add vector effects extension proposal to SVG 2 specification. To include non-scaling features (non-scaling part of the object, and non-scaling entire object Satoru Takagi (ACTION-3619)

Sometimes it is of interest to let the outline of an object keep its original width or to let the position of an object fix 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, or introductory notes on the graphic chart in which panning is possible.

To offer such effects regarding special coordinate transformations and graphic drawings, SVG Tiny 1.2 introduces the ‘vector-effect’ property. Although SVG Tiny 1.2 introduced only non-scaling stroke behavior, this version introduces a number of additional effects. Furthermore, since these effects can be specified in combination, they show more various effects. And, future versions of the SVG language will allow for more powerful vector effects through this property.

Name: vector-effect none | [non-scaling-stroke | non-scaling-size | non-rotation | fixed-position]+ [ viewport | screen ]? none (When values except none are set, viewport becomes the another initial value.) graphics elements no N/A visual as specified 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 local coordinate system 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 local coordinate system. 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 local coordinate system. (Stroke outline is always filled with stroke paint in the current local coordinate system). 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.
non-scaling-size
Specifies special local coordinate system toward this element and its descendant by constrained transformations with the following characteristics. The scale of the local coordinate system do not change in spite of change of CTMs from a host coordinate space. However, it does not specify the suppression of rotation and skew. Also, it does not specify the fixation of placement of local coordinate system. Since non-scaling-size suppresses scaling of local coordinate system, it also has the characteristic of non-scaling-stroke. The transformation formula and the example behavior are indicated to the following chapter.
non-rotation
Specifies special local coordinate system toward this element and its descendant by constrained transformations with the following characteristics. The rotation and skew of the local coordinate system is suppressd in spite of change of CTMs from a host coordinate space. However, it does not specify the suppression of scaling. Also, it does not specify the fixation of placement of local coordinate system. The transformation formula and the example behavior are indicated to the following chapter.
fixed-position
Specifies special local coordinate system toward this element and its descendant by constrained transformations with the following characteristics. The placement of local coordinate system is fixed in spite of change of CTMs from a host coordinate space. However, it does not specify the suppression of rotation, skew and scaling. When the element that has fixed-position effect and also has property, that property is consumed for this effect. The shift conponents e and f of matrix of property are used to transfer the origin of fixed local coordinate system. The transformation formula and the example behavior are indicated to the following chapter.

These values can be enumerated. Thereby, the effect which has these characteristics simultaneously can be specified.

The following two values assists the above-mentioned values. They show the host coordinate space of constrained transformations. Especially it has effective for the element belonging to nested viewport coordinate system such as nested contents or nested svg elements. An initial value in case it is not specified is viewport.

viewport
Specifies immediate viewport coordinate system as the host coordinate space. When that element belongs to nested viewport coordinate system, vector effects are applied toward viewport coordinate system to which that element belongs directly. That is, that vector effect is not effective for change of CTM on ancestral viewport coordinate system.
screen
It specifies the coordinate system of content which under the immediate control of user agent. So to speak, it is "scrren" which user agent has. ("screen coordinate space" in SVGT1.2) Even if that element belongs to nested viewport coordinate system, that vector effect is always effective for change of CTM of the any hierarchy. If the SVG implementation is part of a user agent which supports CSS compatible px units, it is a coordinate system on CSS pixel of rootmost content. Generally, the pixel (or dot) of a device and pixel of CSS are not always equal by influences of the zoom function which user agent itself has, and variation of dpi. (see resolution [CSS Values and Units Module Level 3]) Accordingly, this value does not specify constrained transformations toward the such a device coordinate system.

Note: Future versions of SVG may allow ways to specify the device coordinate system.

### 12.7.1. Computing the vector effects

This section shows the list of transformation formulas regarding combinations of the values for clarification of the behavior of vector effects excluding non-scaling-stroke which has clear implications.

The normal coordinate transformation formula from local coordinate system to viewport coordinate system is as follows.

The code assumes a 2D rendering context. Width CSS Transforms we get a 3D rendering context as well? How does that work on perspective or 3D transformations?
CSS Transforms Level 1 mentions about 3D rendering context and non scaling stroke with the purport that the functionality becomes no affect. Is it appropriate to extend it to all the vector effects?

$\begin{array}{l}\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\text{CTM}\cdot \left[\begin{array}{c}{x}_{\mathrm{userspace}}\\ {y}_{\mathrm{userspace}}\\ 1\end{array}\right]\\ \text{CTM}=\left[\begin{array}{ccc}{a}_{\mathrm{ctm}}& {c}_{\mathrm{ctm}}& {e}_{\mathrm{ctm}}\\ {b}_{\mathrm{ctm}}& {d}_{\mathrm{ctm}}& {f}_{\mathrm{ctm}}\\ 0& 0& 1\end{array}\right]\end{array}$
<circle vector-effect="veValue" transform="translate(xo yo)" cx="xf" cy="yf" r=".."/>


When the ‘vector-effect’ is added to an element like the above, the transformation formula for user coordinate to the device coordinate changes as follows. Here, xf and yf are user coordinate of the corresponding element and its descendant. And, xo and yo are matrix element e and f of the transform attribute which the corresponding element has. In addition, |det(CTM)| is absolute value of the determinants of CTM. When this value becomes 0 and non-scaling-size is appointed, ‘vector-effect’ becomes invalidity namely none.

$\text{det}\left(\text{CTM}\right)={a}_{\mathrm{ctm}}\cdot {d}_{\mathrm{ctm}}-{b}_{\mathrm{ctm}}\cdot {c}_{\mathrm{ctm}}$
veValue Formula
non-scaling-size
$\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\text{CTM}\cdot \left[\begin{array}{c}\text{0}\\ \text{0}\\ 1\end{array}\right]+\frac{\text{CTM}}{\sqrt{\left|\text{det}\left(\text{CTM}\right)\right|}}\cdot \left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 0\end{array}\right]\cdot \left[\begin{array}{c}{x}_{f}\\ {y}_{f}\\ 1\end{array}\right]$
non-rotation
$\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\text{CTM}\cdot \left[\begin{array}{c}\text{0}\\ \text{0}\\ 1\end{array}\right]+\sqrt{\left|\text{det}\left(\text{CTM}\right)\right|}\cdot \left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 0\end{array}\right]\cdot \left[\begin{array}{c}{x}_{f}\\ {y}_{f}\\ 1\end{array}\right]$
non-scaling-size non-rotation
$\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\text{CTM}\cdot \left[\begin{array}{c}\text{0}\\ \text{0}\\ 1\end{array}\right]+\left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 0\end{array}\right]\cdot \left[\begin{array}{c}{x}_{f}\\ {y}_{f}\\ 1\end{array}\right]$
fixed-position
$\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\left[\begin{array}{c}{x}_{o}\\ {y}_{o}\\ 1\end{array}\right]+\text{CTM}\cdot \left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 0\end{array}\right]\cdot \left[\begin{array}{c}{x}_{f}\\ {y}_{f}\\ 1\end{array}\right]$
fixed-position non-scaling-size
$\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\left[\begin{array}{c}{x}_{o}\\ {y}_{o}\\ 1\end{array}\right]+\frac{\text{CTM}}{\sqrt{\left|\text{det}\left(\text{CTM}\right)\right|}}\cdot \left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 0\end{array}\right]\cdot \left[\begin{array}{c}{x}_{f}\\ {y}_{f}\\ 1\end{array}\right]$
fixed-position non-rotation
$\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\left[\begin{array}{c}{x}_{o}\\ {y}_{o}\\ 1\end{array}\right]+\sqrt{\left|\text{det}\left(\text{CTM}\right)\right|}\cdot \left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 0\end{array}\right]\cdot \left[\begin{array}{c}{x}_{f}\\ {y}_{f}\\ 1\end{array}\right]$
fixed-position non-scaling-size non-rotation
$\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]=\left[\begin{array}{c}{x}_{o}\\ {y}_{o}\\ 1\end{array}\right]+\left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 0\end{array}\right]\cdot \left[\begin{array}{c}{x}_{f}\\ {y}_{f}\\ 1\end{array}\right]$

### 12.7.2. Computing the vector effects for nested viewport coordinate systems

Below is normal coordinate transformation formula for nested viewport coordinate systems without vector effects. xviewport(UA) and yviewport(UA) are coordinates which under the immediate control of user agent. CTMthis is CTM for the transformation matrix from local coordinate system of an target graphic to viewport coordinate system to which it belongs. CTMparent is CTM for the transformation matrix from aforementioned viewport coordinate system to viewport coordinate system of the parent of that. And, CTMroot is CTM for rootmost viewport coordinate system (UA).

$\left[\begin{array}{c}{x}_{\mathrm{viewport\left(UA\right)}}\\ {y}_{\mathrm{viewport\left(UA\right)}}\\ 1\end{array}\right]={\text{CTM}}_{\mathrm{root}}\cdot \text{...}\cdot {\text{CTM}}_{\mathrm{parent}}\cdot {\text{CTM}}_{\mathrm{this}}\cdot \left[\begin{array}{c}{x}_{\mathrm{userspace}}\\ {y}_{\mathrm{userspace}}\\ 1\end{array}\right]$

When applying seven formulas of the preceding section to nested viewport coordinate systems, the application way of those formulas changes as follows by whether viewport or screen is specified as the additional value of ‘vector-effect’.

When viewport value is specified, user agent computes coordinates combining either of seven formulas of the preceding chapter, and the following formulas.

$\begin{array}{l}\left[\begin{array}{c}{x}_{\mathrm{viewport}\left(\mathrm{UA}\right)}\\ {y}_{\mathrm{viewport}\left(\mathrm{UA}\right)}\\ 1\end{array}\right]={\text{CTM}}_{\text{root}}\cdot \text{...}\cdot {\text{CTM}}_{\text{parent}}\cdot \left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]\\ \text{CTM}={\text{CTM}}_{\text{this}}\end{array}$

When screen value is specified, user agent computes coordinates combining either of seven formulas of the preceding chapter, and the following formulas.

$\begin{array}{l}\left[\begin{array}{c}{x}_{\mathrm{viewport}\left(\mathrm{UA}\right)}\\ {y}_{\mathrm{viewport}\left(\mathrm{UA}\right)}\\ 1\end{array}\right]=\left[\begin{array}{c}{x}_{\mathrm{viewport}}\\ {y}_{\mathrm{viewport}}\\ 1\end{array}\right]\\ \text{CTM}={\text{CTM}}_{\text{root}}\cdot \text{...}\cdot {\text{CTM}}_{\text{parent}}\cdot {\text{CTM}}_{\text{this}}\end{array}$

### 12.7.3. Examples of vector effects

Below is an example of the non-scaling-strokevector-effect’.

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg"
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>

Below is an example of the nonevector-effect’ (no vector effect).

 Before changing CTM After changing CTM

Source code

<svg xmlns="http://www.w3.org/2000/svg" viewBox="-50,-50,500,500" height="500" width="500">

<rect x="-50" y="-50" width="500" height="500" stroke="orange" stroke-width="3" fill="none"></rect>

<!-- Nested local coordinate system is transformed by this transform attribute -->
<g id="base" transform="matrix(2.1169438081370817,0.3576047954311102,-0.3576047954311102,1.4700998667618626,0,0) translate(-50,-50)">
<svg viewBox="-50,-50,500,500" height="500" width="500">
<!-- Graph paper on the this svg's base local coordinate system -->
<g stroke="green" stroke-width="1" fill="none">
<circle cx="0" cy="0" r="10"></circle>
<circle cx="150" cy="150" r="7"></circle>
<path fill="green" stroke="none" d="M0,-3 L30,-3 25,-10 50,0 25,10 30,3 0,3z"></path>

<line x1="-100" y1="-100" x2="600" y2="-100" stroke-dasharray="5,5"></line>
<line x1="-100" y1="000" x2="600" y2="000"></line>
<line x1="-100" y1="100" x2="600" y2="100" stroke-dasharray="5,5"></line>
<line x1="-100" y1="200" x2="600" y2="200" stroke-dasharray="5,5"></line>
<line x1="-100" y1="300" x2="600" y2="300" stroke-dasharray="5,5"></line>
<line x1="-100" y1="400" x2="600" y2="400" stroke-dasharray="5,5"></line>
<line x1="-100" y1="500" x2="600" y2="500" stroke-dasharray="5,5"></line>

<line y1="-100" x1="-100" y2="600" x2="-100" stroke-dasharray="5,5"></line>
<line y1="-100" x1="000" y2="600" x2="000"></line>
<line y1="-100" x1="100" y2="600" x2="100" stroke-dasharray="5,5"></line>
<line y1="-100" x1="200" y2="600" x2="200" stroke-dasharray="5,5"></line>
<line y1="-100" x1="300" y2="600" x2="300" stroke-dasharray="5,5"></line>
<line y1="-100" x1="400" y2="600" x2="400" stroke-dasharray="5,5"></line>
<line y1="-100" x1="500" y2="600" x2="500" stroke-dasharray="5,5"></line>
</g>

<!-- Figure having vector effect -->
<!-- An thick red right arrow and small rectangle on this figure's nested local coordinate system origin -->
<path id="ve" vector-effect="none" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"></path>
</svg>
</g>
</svg>


Below is an example of the non-scaling-size.

 Before changing CTM After changing CTM
<path id="ve" vector-effect="non-scaling-size" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"/>

Below is an example of the non-rotation.

 Before changing CTM After changing CTM
<path id="ve" vector-effect="non-rotation" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"/>

Below is an example of the non-scaling-size non-rotation.

 Before changing CTM After changing CTM
<path id="ve" vector-effect="non-scaling-size non-rotation" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"/>

Below is an example of the fixed-position.

 Before changing CTM After changing CTM
<path id="ve" vector-effect="fixed-position" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"/>

Below is an example of the non-scaling-size fixed-position.

 Before changing CTM After changing CTM
<path id="ve" vector-effect="non-scaling-size fixed-position" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"/>

Below is an example of the non-rotation fixed-position.

 Before changing CTM After changing CTM
<path id="ve" vector-effect="non-rotation fixed-position" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"/>

Below is an example of the non-scaling-size non-rotation fixed-position.

 Before changing CTM After changing CTM
<path id="ve" vector-effect="non-scaling-size non-rotation fixed-position" stroke="red" stroke-width="3" fill="none" transform="matrix(1,0,0,1,150,150)" d="M-50,-50 L50,-50 50,-100 150,0 50,100 50,50 -50,50 -50,-50z M5 0 L0 -5  -5 0 0 5z"/>

## 12.8. Markers

SVG 2 Requirement: Improve markers. We will improve markers for SVG 2. To solve the common problems authors have with SVG markers. 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.

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.

In SVG 2, vertex markers are the only kind of markers available. Other specifications will add new types of markers.

The graphics for a marker are defined by a marker element. The ‘marker-start’, ‘marker-end’ and ‘marker-mid’ 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:

### 12.8.1. The ‘marker’ element

marker
Categories:
Container element
Content model:
Any number of the following elements, in any order:
a, clipPath, cursor, filter, foreignObject, image, marker, mask, script, style, switch, text, view
Attributes:
DOM Interfaces:

The marker element defines the graphics that are to be used for drawing markers on a markable element.

Attribute definitions:

Name Value Initial value Animatable
markerUnits strokeWidth | userSpaceOnUse strokeWidth yes

The attribute defines the coordinate system for attributes , and the contents of the marker. Values have the following meanings:

strokeWidth
, 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
, 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 Initial value Animatable
markerWidth, markerHeight <length> | <percentage> | <number> 3 yes

The and attributes represent the size of the viewport into which the marker is to be fitted according to the viewBox and 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 Initial value Animatable
refX <length> | <percentage> | <number> | left | center | right 0 yes
refY <length> | <percentage> | <number> | top | center | bottom 0 yes

New in SVG 2: geometric keywords (matches use in symbol).

We will add top/center/bottom, left/center/right keywords to refX/refY on marker/symbol. Resolved at London F2F. Values inspired by 'background-position'.

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 attributes.

Name Value Initial value Animatable
orient auto | auto-start-reverse | <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.

This needs to reference a definition for how directionality of a given start/mid/end vertex is calculated. Part of that (which should be moved somewhere more appropriate) is in the path element implementation notes. Some wording from SVG 1.1 appears to have been lost, compare with this.

Here's an example that is a bit unclear currently:  <svg> <marker id="m" orient="auto" overflow="visible"> <rect x="-1" y="-0.5" width="1" height="1" fill="green"/> </marker> <path d="M50,0C50,50 50,100 50,100" marker-end="url(#m)" stroke-width="100" stroke="red"/> </svg> 
The second control point and the endpoint coincide, should this mean that the direction of the endpoint is a) unknown [aka default to 0 degrees] or b) that you have to look at the previous segment(s)/command(s) until a direction can be established?

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.
'auto-start-reverse'

A value of 'auto-start-reverse' means the same as 'auto' except that for a marker placed by ‘marker-start’, the orientation is 180° different from the orientation as determined by 'auto'.

This allows a single arrowhead marker to be defined that can be used for both the start and end of a path, point in the right directions.

<angle>
<number>

An <angle> value represents the angle the marker's positive x-axis makes with the positive x-axis in the local coordinate system 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 local coordinate system.

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.

The contents of the marker are relative to a new coordinate system. The 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 . 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 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.

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.

### 12.8.2. Referencing ‘marker’ elements

A number of marker properties allow specifying a marker using a <marker-ref> value.

<marker-ref> =
<url> |
child |
<child-selector>

where:

<child-selector> =
select(compound selector#)

Values have the following meaning

<url>
Indicates that the marker element referenced by the <url> value will be used. If the URL 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.

### 12.8.3. Vertex markers: the ‘marker-start’, ‘marker-mid’ and ‘marker-end’ properties

Name: marker-start, marker-mid, marker-end none | none markable elements yes N/A visual as specified, but with values (that are part of a ) made absolute 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>

### 12.8.4. Marker shorthand: the ‘marker’ property

Name: marker none | not defined for shorthand properties markable elements yes N/A visual see individual properties yes

The ‘marker’ property sets values for the ‘marker-start’, ‘marker-mid’ and ‘marker-end’ properties. The value of the ‘marker’ is used directly for all three of the corresponding longhand properties.

### 12.8.5. Details on how markers are rendered

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 . If 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 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 .
• 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"
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"
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>


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

## 12.9. Controlling paint operation order: the ‘paint-order’ property

SVG 2 Requirement: Support control of the order of filling, stroke and painting markers on shapes. SVG 2 will adopt the ‘paint-order’ property proposal, though possibly with a different name. The property name is now resolved, see 15 Nov 2013 minutes. To address the common desire to paint strokes below fills without having to duplicate an element. Cameron (ACTION-3285)
Name: paint-order normal | [ fill || stroke || markers ] normal graphics elements and text content elements yes N/A visual as specified 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.

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’.

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>


## 12.10. Color space for interpolation: the ‘color-interpolation’ property

Name: color-interpolation auto | sRGB | linearRGB sRGB container elements, graphics elements, gradient elements and ‘animate’ yes N/A visual as specified 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:

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 Csrgb is one of the three sRGB color components, Clinear is the corresponding linearized RGB color component, and all color values are between 0 and 1:

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 ‘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.

## 12.11. Rendering hints

### 12.11.1. The ‘color-rendering’ property

Name: color-rendering auto | optimizeSpeed | optimizeQuality auto container elements, graphics elements, gradient elements and ‘animate’ yes N/A visual as specified 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.

### 12.11.2. The ‘shape-rendering’ property

Name: shape-rendering auto | optimizeSpeed | crispEdges | geometricPrecision auto shapes yes N/A visual as specified 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.

### 12.11.3. The ‘text-rendering’ property

Name: text-rendering auto | optimizeSpeed | optimizeLegibility | geometricPrecision auto ‘text’ yes N/A visual as specified 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.

### 12.11.4. The ‘image-rendering’ property

The CSS Image Values and Replacement Conent Module Level 4 may in the future redefine this property. In particular it should allow the choice between smoothing and keeping a pixelated look when upscaling.

Name: image-rendering auto | optimizeQuality | optimizeSpeed auto shapes yes N/A visual as specified 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. High quality SVG viewers should perform image resampling using a linear color space.

### 12.11.5. The ‘buffered-rendering’ property

SVG 2 Requirement: Support a hint to indicate that an element's rendering should be cached. SVG 2 will add ‘buffered-rendering’, as implementor feedback indicates that it is needed. For caching rendered results for faster display. 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 auto | dynamic | static auto container elements and graphics elements no N/A visual as specified 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.

## 12.12. 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>
<stop offset="0%" stop-color="#F60"/>
<stop offset="100%" stop-color="#FF6"/>
</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>

## 12.13. DOM interfaces

### 12.13.1. 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;

attribute DOMString orient;

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 othe other 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 is 'userSpaceOnUse'.
SVG_MARKERUNITS_STROKEWIDTH (unsigned short)
The value of attribute is 'strokeWidth'.
Constants in group “Marker Orientation Types”:
SVG_MARKER_ORIENT_UNKNOWN (unsigned short)
The marker orientation is 'auto-start-rotate' or is not one of the 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:
Corresponds to attribute refX on the given marker element.
Corresponds to attribute refY on the given marker element.
Corresponds to attribute on the given marker element. One of the Marker Unit Types defined on this interface.
Corresponds to attribute on the given marker element.
Corresponds to attribute on the given marker element.
Corresponds to attribute orient on the given marker element. One of the Marker Orientation Types defined on this interface. If the orient attribute is set to 'auto-start-rotate', then the value of orientType is SVG_MARKER_ORIENT_UNKNOWN.