W3C

CSS3 module: text

W3C Working Draft 24 October 2002

This version:
http://www.w3.org/TR/2002/WD-css3-text-20021024
Latest version:
http://www.w3.org/TR/css3-text
Previous version:
http://www.w3.org/TR/2002/WD-css3-text-20020515
Editor:
Michel Suignard (Microsoft)
Contributors:
Original CSS2 authors, and
Bert Bos (W3C)
Tantek Çelik (Microsoft)
Chris Lilley (W3C)
Martin Sawicki (Microsoft, former editor)
Michel Suignard (Microsoft)
Chris Wilson (Microsoft)
Steve Zilles (Adobe)

Abstract

This document presents a set of text formatting properties for CSS3. Many of these properties already existed in CSS 2 [CSS2]. Many of the new properties have been added to address basic requirements in international text layout, particularly for East Asian and bidirectional text.

Status of This Document

This document is a working draft of the CSS working group which is part of the Style activity. It contains a proposal for features to be included in CSS level 3.

This is the last call for comments, before the working group will decide if the draft is ready for Candidate Recommendation. The deadline for comments is 27 November 2002.

Feedback is very much welcome. Comments can be sent directly to the editor, but the mailing list www-style@w3.org (see instructions) is also open and is preferred for discussion of this and other drafts in the Style area. The mailing list is archived.

This document has been produced as a combined effort of the W3C Internationalization Activity, and the Style Activity. It also includes extensive contribution made by members of the XSL Working Group (members only). Finally, some of the proposal surfaced first in the Scalable Vector Graphics (SVG) 1.0 Specification [SVG1.0]. The text has been duplicated in this document to reflect which properties and specification should eventually be referenced in CSS itself.

This working draft may be updated, replaced or rendered obsolete by other W3C documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". Its publication does not imply endorsement by the W3C membership or the CSS Working Group (members only).

Patent disclosures relevant to CSS may be found on the Working Group's public patent disclosure page.

To find the latest version of this working draft, please follow the "Latest version" link above, or visit the list of W3C Technical Reports.

Contents


1. Dependencies on other modules

This CSS3 module depends on the following other CSS3 modules:

It has non-normative (informative) references to the following other CSS3 modules:

2. Introduction

In both CSS1 and CSS2, text formatting has been limited to simple effects like for example: text decoration, text alignment and character spacing. However, International typography contains types of formatting that could not be achieved without using special workarounds or graphics.

Along with already existing text related properties, this document presents a number of new CSS properties to represent such formatting. For example, the features this proposal covers include two of the most important features for East Asian typography: vertical text and layout grid.

There is a number of illustrations in this document for which the following legend is used:

Symbolic wide-cell glyph representation - wide-cell glyph (e.g. Han) which is the n-th character in the text run,
Symbolic narrow-cell glyph representation - narrow-cell glyph (e.g. Roman) which is the n-th glyph in the text run,
Symbolic connected glyph representation - connected glyph (e.g. Arabic) which is the n-th glyph in the text run.

Many typographical properties in East Asian typography depends on the fact that a character is typically rendered as either a wide or narrow character. All characters described by the Unicode Standard [UNICODE] can be categorized by a width property. This is covered by the Unicode Standard Annex [UAX-11].

The orientation which the above symbols assume in the diagrams corresponds to the orientation that the glyphs they represent are intended to assume when rendered in the UA (user agent). Spacing between these characters in the diagrams is usually symbolic, unless intentionally changed to make a point.

Furthermore, all properties, in addition to the noted values, take 'initial' and 'inherit'. These values are not repeated in each of the property value enumeration.

This module uses extensively the 'before', 'after', 'start' and 'end' notation to specify the four edges of a box relative to its text advance direction, independently of its absolute positioning in terms of 'top', 'bottom', 'left' and 'right' (corresponding respectively to the 'before', 'after', 'start' and 'end' positions in a typical Western text layout). This notation is also used extensively in [XSL1.0] for the same purpose.

Finally, in this document, requirements are expressed using the key words "MUST", "MUST NOT", "REQUIRED", "SHALL" and "SHALL NOT". Recommendations are expressed using the key words "SHOULD", "SHOULD NOT" and "RECOMMENDED". "MAY" and "OPTIONAL" are used to indicate optional features or behavior. These keywords are used in accordance with [RFC2119]. For legibility these keywords are used in lowercase form.


3. Text layout

3.1. Text layout introduction

This section describes the text layout features supported by CSS, which includes support for various international writing directions, such as left-to-right (e.g., Roman scripts), right-to-left (e.g., Hebrew or Arabic), bidirectional (e.g., mixing Roman with Arabic) and vertical (e.g., Asian scripts).

The 'writing-mode' property determines an inline progression and a block (line to line) progression. For example, Roman scripts are typically written left to right and top to bottom. The glyph orientation determines the orientation of the rendered visual shape of characters relative to the inline progression.

Within a line, the adjustment to the current text position is based on the current glyph orientation relative to the inline progression, the metrics of the glyph just rendered, kerning tables in the font and the current values of various attributes and properties, such as the spacing properties.

Bi-directionality introduces another level of complexity in text layout, as in many combinations of 'writing-mode' and glyph orientation values the proper directionality of text will be determined by an algorithm. The Unicode standard ([UNICODE], section 3.12) defines such an algorithm consisting of an implicit part based on character properties, as well as explicit controls for embeddings and overrides. It is also possible to override the inherent directionality of the content characters by using of combination of the 'writing-mode' and 'unicode-bidi' properties.

CSS3 relies on this algorithm to achieve proper text bidirectional rendering. However reordering of characters only occurs for specific values of the glyph orientation properties. See their description for the exact conditions.

CSS2 specified the 'direction' property which is a subset of the 'writing-mode' property as it only determines an inline progression. The 'direction' property may still be used when no block progression change is desired.

The HTML 4.01 specification ([HTML401], section 8.2) defines bi-directionality behavior for HTML elements. Conforming HTML user agents may therefore ignore the 'direction' and 'unicode-bidi' properties in author and user style sheets. The style sheet rules that would achieve the bidi behavior specified in HTML 4.01 are given in the sample style sheet. The HTML 4.01 specification also contains more information on bidirectionality issues. Note that HTML 4.01 does not cover the more general case described by the 'writing-mode' property.

3.2. Setting the inline and block progressions: the 'writing-mode' and 'direction' properties

The 'writing-mode' property specifies whether the inline progression shall be left-to-right, right-to-left, or top-to-bottom. (Note that even when the inline progression is left-to-right or right-to-left, some or all of the content within a given element might advance in the opposite direction because of the Unicode [UNICODE] bidirectional algorithm or because of explicit text advance overrides due to this property or 'direction' and 'unicode-bidi'. This property also changes the 'direction' property for the element. For more on bidirectional text, see the section about Embedding and override.

Name: writing-mode
Value: lr-tb | rl-tb | tb-rl | tb-lr | bt-rl | bt-lr | lr | rl | tb
Initial: lr-tb
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)
lr-tb | lr
Sets the inline progression to left-to-right, and the block progression to top-to-bottom as is common in most Roman-based documents. For most characters, the current text position is advanced from left to right after each glyph is rendered. The 'direction' property is set to 'ltr'.
rl-tb | rl
Sets the inline progression to right-to-left, and the block progression to top-to-bottom as is common in Arabic or Hebrew scripts. The direction property is set to 'rtl'.
tb-rl | tb
Sets the inline progression to top-to-bottom, and the block progression to right-to-left as is common in Asian scripts. The baseline alignment may be different in this context. Typically, the dominant baseline runs through the center of the upright glyphs. The direction property is set to 'ltr'.
tb-lr
Sets the inline progression to top-to-bottom, and the block progression to left-to-right as is common in Mongolian script. This type of vertical layout also occurs in Latin based documents, particularly in table column or row labels. The baseline alignment may be different in this context. Typically, the dominant baseline runs through the center of the upright glyphs. The direction property is set to 'ltr'.
bt-rl
Sets the inline progression to bottom-to-top, and the block progression to right-to-left. This value only exists to cover the case of the direction property value 'rtl' applied to an element where the current writing-mode property value is 'tb-rl' or 'tb'. The direction property is set to 'rtl'.
bt-lr
Sets the inline progression to bottom-to-top, and the block progression to left-to-right. This value only exists to cover the case of the direction property value 'rtl' applied to an element where the current writing-mode property value is 'tb-lr'. The direction property is set to 'rtl'.

The combination of inline progression and block progression set by the writing-mode property is also referred as a flow orientation. In such contexts, the values: lr-tb, lr, rl-tb and rl correspond to horizontal flow orientations, and the others (tb-rl, tb, tb-lr, bt-rl, bt-lr) correspond to vertical flow orientations.

For horizontal flow orientations, the top and bottom margins can be collapsed. For vertical flow orientations, the left and right margin can be collapsed. See Collapsing margins in the CSS3 Box module [forthcoming] for the details of collapsing margins.

This property also specifies the direction of table column layout, the direction of the overflow when determined by the inline progression (such as the 'start' and 'end' value of the 'text-align' property), the initial alignment of text and the position of an incomplete last line in a block in case of 'text-align: justify'.

For the 'writing-mode' property to have any effect on inline-level elements, one or both of the following conditions must be met:

An inline-level element that has a different writing-mode value than its parent becomes an inline-block element.

Here is a diagram of a horizontal flow (writing-mode: lr-tb):

Figure showing how a block with

Here is a diagram for a vertical flow used in East Asia (writing-mode: tb-rl) :

Figure showing how a block with

And finally, here is a diagram for another flow used for Uyghur and Mongolian (writing-mode: tb-lr):

Figure showing how a block with

In East Asian documents, it is often preferred to display certain Latin-based strings, such as numerals in a year, always in a horizontal layout flow regardless of the flow mode of the line of text these strings appear in, as in:

Layout of Tate Naka Yoko, showing a group of glyphs appearing
horizontally in a vertical column of text Example of Tate Naka Yoko, showing the
year 1996 appearing horizontally in a column of vertical text

Horizontal in vertical (a.k.a "Tate-chu-yoko")

This effect is known as "Tate chu yoko". In order to achieve it in an XHTML context, the Latin string should be enclosed within a span element with an horizontal flow orientation, as in:

.hinv {writing-mode: lr-tb; display: inline-block;}
<span class="hinv">1996</span>

This is an application of changing the flow of an inline element as described earlier. Line breaking is normally disabled for such runs of text. This can be accomplished using the CSS 'white-space: nowrap' property setting.

Name: direction
Value: ltr | rtl
Initial: ltr
Applies to: all elements and generated content, but see prose
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

Values for this property have the following meanings:

ltr
Left-to-right direction.
rtl
Right-to-left direction.

This property specifies the inline progression and the direction of embeddings and overrides (see 'unicode-bidi') for the Unicode bidirectional algorithm. The block progression is not affected by this property. The values 'ltr' and 'rtl' have to be interpreted 'relatively' to the line direction. In addition, it specifies the direction of table column layout, the direction of the overflow when determined by the inline progression (such as the 'start' and 'end' value of the 'text-align' property), the initial alignment of text and the position of an incomplete last line in a block in case of 'text-align: justify'. For the 'direction' property to have any effect on inline-level elements, the 'unicode-bidi' property's value must be 'embed' or 'bidi-override' and the glyph orientation of the characters within the element must be 'auto' or 90/-90 degree in vertical layout or 0/180 degree in horizontal layout.

Note. The 'writing-mode' and 'direction' properties, when specified for table column elements, are not inherited by cells in the column since columns don't exist in the document tree. Thus, CSS cannot easily capture the "dir" attribute inheritance rules described in [[HTML4.01], section 11.3.2.

Note. The 'writing-mode' and 'direction' properties interact with each other. As such, 'writing-mode' resets the 'direction' value. Similarly, modifying 'direction' after 'writing-mode' changes effectively the 'writing-mode' value to the opposite inline progression. For example, 'direction:rtl' applied to an element with 'writing-mode:lr-tb' effectively makes 'writing-mode:rl-tb'. This is one of the main reason why the mixed usage of these two properties is discouraged or at least they should be used with great caution.

3.3. Glyph orientation within a text run: the 'glyph-orientation-vertical' and 'glyph-orientation-horizontal' properties

In some cases, it is required to alter the orientation of a sequence of characters relative to the inline progression. The requirement is particularly applicable to vertical layouts of East Asian documents, where sometimes half-width Roman text is to be displayed horizontally and other times vertically.

Two properties control the glyph orientation relative to the inline progression. 'glyph-orientation-vertical' controls glyph orientation when the inline progression is vertical. 'glyph-orientation-horizontal' controls glyph orientation when the inline progression is horizontal. It is necessary to distinguish between vertical and horizontal for the following reasons:

Name: glyph-orientation-vertical
Value: <angle> | auto
Initial: auto
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value:

specified value (except for initial and inherit)

<angle>
The user agent may round the value of the angle to the values of glyph rotation supported by the user agent. Conforming user agents may only support the following values: 0deg, 90deg, 180deg and 270deg, other values can also be supported..
A value of "0deg" indicates that all glyphs are oriented with the bottom of the glyphs toward the inline progression, resulting in glyphs which are stacked vertically on top of each other. A value of "90deg" indicates a rotation of 90 degrees clockwise from the "0deg" orientation. For characters which have this property set to 90 or 270 degree, reordering is first applied according to the Unicode Bidi algorithm and then the resulting glyphs are rotated according to the <angle> value. The rotation specified by this value is applied to the glyph representations of all assigned Unicode character codes.
auto
The glyph orientation relative to the inline progression is determined automatically based on the Unicode character code of the rendered character.

Full-width ideographic and full-width Roman glyphs (excluding ideographic punctuation) are oriented as if an <angle> of "0deg" had been specified for top to bottom inline progression and "180deg" for bottom to top inline progression (resulting in glyphs which are stacked vertically on top of each other).

Ideographic punctuation and other ideographic characters having alternate horizontal and vertical glyph shapes shall use the vertical shape of the glyph.

Text which is not full-width will be set as if an <angle> of "90deg" had been specified; thus, half-width Roman text will be rotated 90 degree clockwise versus full-width ideographic and full-width Roman text.

Hebrew and Arabic text are also rotated 90 degree clockwise. The visual order of this text is determined by the bidirectional algorithm applied prior to the rotation.

Note. A value of auto will generally produce the expected results in common uses of mixing Japanese with European characters; however, the exact algorithms are based on complex interactions between many factors, including font design, and thus different algorithms might be employed in different processing environments. For precise control, specify explicit <angle> values.

This property specifies the orientation of glyphs relative to the inline and block progressions determined by the 'writing-mode' property. This property is applied only to text written in a vertical writing-mode. Conforming user agents may do the following in increasing levels of supports:

  1. support only the 90deg value,
  2. support the 0deg, 90deg, 180deg and 270deg values,
  3. support all values above and any number of additional values.

The value of this property affects both the alignment and height of the glyph area generated for the affected glyphs. If a glyph is oriented so that the normal orientation of the glyph is parallel to the dominant-baseline, then the vertical alignment-point of the rotated glyph is aligned with the alignment-baseline appropriate to that glyph. The baseline to which the rotated glyph is aligned is the vertical baseline identified by the "alignment-baseline" for the script to which the glyph belongs. The height of the glyph area is determined from the height font characteristic for the glyph.

The horizontal alignment points, baselines and heights (computed as glyph advance width) are used if the normal orientation of the glyph is perpendicular to the dominant-baseline.

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 characters with half-width Roman characters when 'glyph-orientation-vertical' for the Roman characters is either auto or "90deg". The diagram on the right show the result of mixing full-width ideographic characters with half-width Roman characters when Roman characters are specified to have a 'glyph-orientation-vertical' of "0deg".

Layout of mixed glyphs in vertical-ideographic mode.
Wide-cell glyphs are upright, Non-wide-cell glyphs are rotated by 90
degrees. Example of mixed Japanese and English in vertical-ideographic layout.
Japanese glyphs are upright, English rotated. Layout of mixed glyphs in
vertical mode. All glyphs are upright. Example of mixed Japanese and English in
vertical layout. All glyphs are upright.

The bidi algorithm and the 'glyph-orientation-vertical' property have the following interaction:

  1. The bidi algorithm is applied separately to each contiguous text range having the same glyph-orientation-vertical value. In other words a change in the property value resets the bidi algorithm.
  2. When the glyph-orientation-vertical value is 270 degree, all mirroring symbols after all due bidi processing are mirrored before being rotated 270 degree clockwise. This is done to achieve the desired rendering result, which is to have the mirroring characters pointing 'inward' the text they are enclosing.
Name: glyph-orientation-horizontal
Value: <angle>
Initial: 0deg
Applies to: all inline-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: <angle>
<angle>
The user agent may round the value of the angle to the values of glyph rotation supported by the user agent. A value of "0deg" indicates that all glyphs are oriented with the right edge of the glyphs toward the inline progression, resulting in glyphs which are positioned side by side. A value of "90deg" indicates an orientation of 90 degrees clockwise from the "0" orientation. For characters which have this property set to 0 or 180 degree, reordering is first applied according to the Unicode Bidi algorithm and then the resulting glyphs are rotated clockwise according to the <angle> value.

This property specifies the orientation of glyphs relative to the inline progression determined by the 'writing-mode' property. This property is applied only to text written in a horizontal writing-mode. Conforming user agents may do the following in increasing levels of supports:

  1. support only the 0deg value,
  2. support the 0deg, 90deg, 180deg and 270deg values,
  3. support all values above and any number of additional values.

The value of this property affects both the alignment and width of the glyph area generated for the affected glyphs. If a glyph is oriented so that the normal orientation of the glyph is parallel to the dominant-baseline, then the vertical alignment-point of the rotated glyph is aligned with the alignment-baseline appropriate to that glyph. The baseline to which the rotated glyph is aligned is the horizontal baseline identified by the "alignment-baseline" for the script to which the glyph belongs. The width of the glyph area is determined from the vertical width font characteristic for the glyph.

The horizontal alignment points, baselines and widths are used if the normal orientation of the glyph is perpendicular to the dominant-baseline.

3.4. Embedding and override: the 'unicode-bidi' property

Name: unicode-bidi
Value: normal | embed | bidi-override
Initial: normal
Applies to: all elements and generated content, but see prose
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified (except for initial and inherit)

This property allows further control of the Unicode bidirectional algorithm by allowing new embedding levels or direction overrides. Values for this property have the following meanings:

normal
The element does not open an additional level of embedding with respect to the bidirectional algorithm. For inline-level elements, implicit reordering works across element boundaries.
embed
If the element is inline-level, this value opens an additional level of embedding with respect to the bidirectional algorithm. The direction of this embedding level is given by the 'direction' property. Inside the element, reordering is done implicitly. This corresponds to adding a LRE (U+202A; for 'direction: ltr') or RLE (U+202B; for 'direction: rtl') at the start of the element and a PDF (U+202C) at the end of the element.
bidi-override
If the element is inline-level or a block-level element that contains only continuous stretches of inline elements, this creates an override. This means that inside the element, reordering is strictly in sequence according to the 'direction' property; the implicit part of the bidirectional algorithm is ignored. This corresponds to adding a LRO (U+202D; for 'direction: ltr') or RLO (U+202E; for 'direction: rtl') at the start of the element and a PDF (U+202C) at the end of the element.

The final order of characters in each block-level element is the same as if the bidi control codes had been added as described above, mark-up had been stripped, and the resulting character sequence had been passed to an implementation of the Unicode bidirectional algorithm for plain text that produced the same line-breaks as the styled text. In this process, non-textual entities such as images are treated as neutral characters, unless their 'unicode-bidi' property has a value other than 'normal', in which case they are treated as strong characters in the 'direction' specified for the element.

Note. In order to be able to flow inline boxes in a uniform direction (either entirely left-to-right or entirely right-to-left), more inline boxes (including anonymous inline boxes) may have to be created, and some inline boxes may have to be split up and reordered before flowing.

Because the Unicode algorithm has a limit of 61 levels of embedding, care should be taken not to use 'unicode-bidi' with a value other than 'normal' unless appropriate. In particular, a value of 'inherit' should be used with extreme caution. However, for elements that are, in general, intended to be displayed as blocks, a setting of 'unicode-bidi: embed' is preferred to keep the element together in case display is changed to inline (see example below).

The following example shows an XML document with bidirectional text. It illustrates an important design principle: DTD designers should take bidi into account both in the language proper (elements and attributes) and in any accompanying style sheets. The style sheets should be designed so that bidi rules are separate from other style rules. The bidi rules should not be overridden by other style sheets so that the document language's or DTD's bidi behavior is preserved.

Example(s):

In this example, lowercase letters in element contents stand for inherently left-to-right characters and uppercase letters represent inherently right-to-left characters:

<hebrew>
  <par>HEBREW1 HEBREW2 english3 HEBREW4 HEBREW5</par>
  <par>HEBREW6 <emph>HEBREW7</emph> HEBREW8</par>
</hebrew>
<english>
  <par>english9 english10 english11 HEBREW12 HEBREW13</par>
  <par>english14 english15 english16</par>
  <par>english17 <he-quo>HEBREW18 english19 HEBREW20</he-quo></par>
</english>

Since this is XML, the style sheet is responsible for setting the writing direction. This is the style sheet:

/* Rules for bidi */
hebrew, he-quo  {direction: rtl; unicode-bidi: embed}
english         {direction: ltr; unicode-bidi: embed}

/* Rules for presentation */
hebrew, english, par  {display: block}
emph                  {font-weight: bold}

The hebrew element is a block with a right-to-left base direction, the english element is a block with a left-to-right base direction. The par elements are blocks that inherit the base direction from their parents. Thus, the first two par elements are read starting at the top right, the final three are read starting at the top left. Please note that hebrew and english are chosen as element names for explicitness only; in general, element names should convey structure without reference to language.

The emph element is inline-level, and since its value for 'unicode-bidi' is 'normal' (the initial value), it has no effect on the ordering of the text. The he-quo element, on the other hand, creates an embedding.

The formatting of this text might look like this if the line length is long:

               5WERBEH 4WERBEH english3 2WERBEH 1WERBEH

                                8WERBEH 7WERBEH 6WERBEH

english9 english10 english11 13WERBEH 12WERBEH

english14 english15 english16

english17 20WERBEH english19 18WERBEH

Note that the he-quo embedding causes HEBREW18 to be to the right of english19.

If lines have to be broken, it might be more like this:

       2WERBEH 1WERBEH
  -EH 4WERBEH english3
                 5WERB

   -EH 7WERBEH 6WERBEH
                 8WERB

english9 english10 en-
glish11 12WERBEH
13WERBEH

english14 english15
english16

english17 18WERBEH
20WERBEH english19

Because HEBREW18 must be read before english19, it is on the line above english19. Just breaking the long line from the earlier formatting would not have worked. Note also that the first syllable from english19 might have fit on the previous line, but hyphenation of left-to-right words in a right-to-left context, and vice versa, is usually suppressed to avoid having to display a hyphen in the middle of a line.

3.5. Script character classification: the 'text-script' property

In text layout, many of the behaviors are related to a character classification based on scripts. For example, line breaking or text justification behaviors depend on the 'dominant' script of the textual content of an element. Furthermore, baseline alignment may be processed based on the same dominant script. That dominant script can be heuristically determined by finding the first character (after reordering) that has an unambiguous script identifier in an element. It can also be explicitly specified by using the 'text-script' property.

Name: text-script
Value: auto | none | <script>
Initial: auto
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: none or <script> (explicit or determined in the case of 'auto')

Values have the following meanings:

auto
Use the first character descendant, after any reordering due to character direction and bi-directionality, which has an unambiguous script identifier to determine the dominant script of the element's content. This determines the computed script value. Each textual component of the element may however behave in typographical related behaviors as dictated by its script identifier. In the absence of any textual components with a clear script identifier (or no textual content at all), the computed value is 'Latin'.
none
Indicates the script is unknown or is not significant to the proper formatting of this element.
<script>
A script definition in conformance with [ISO15924]. All textual components of the element must behave in typography related behaviors as dictated by this script value, not the inherent script value of these textual components.

Note 1. The Unicode technical report [UTR-24]: Script Names specifies script allocations for the whole character repertoire covered by the Unicode Standard [UNICODE].

Note 2. Setting an explicit script property value on an element reclassifies all its textual content to the given script. For example setting the script to a script belonging to the CJK group (Chinese, Japanese, Korean) makes the content behave as a CJK content for line-breaking rules. And setting an Arabic text to Latin would prevent the context to be affected by the Kashida justification effect. Typically, this property should be set to an explicit script value only when the textual content is script ambiguous and a specific behavior is sought.


4. Text alignment and justification

4.1. Text alignment: the 'text-align' property

Name: text-align
Value: start | end | left | right | center | justify | <string>
Initial: start
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property describes how inline content of a block is aligned. Values have the following meanings:

start
The text is aligned on the start of the inline progression.
end
The text is aligned on the end of the inline progression.
left, right
In horizontal inline progression, the text is aligned on the left or right respectively. In vertical inline progression, the alignment is UA dependent. Because these two values are not related to the current inline progression, the values 'start' and 'end' are typically preferred.
center
The text is center aligned.
justify
The text is justified. The justification algorithm can be further refined by using the 'text-justify' property. Although conforming CSS2 user agents could interpret the value 'justify' as 'start',  conforming CSS3 user agents may not, unless a profile specifies otherwise.
<string>
Specifies a string on which cells in a table column will align (see the section on horizontal alignment in a column for details and an example). This value applies only to table cells. If set on other elements, it will be treated as 'start'.

A block of text is a stack of line boxes. In the case of 'start', 'end', 'left', 'right' and 'center', this property specifies how the inline boxes within each line box align with respect to the line box's start and end sides; alignment is not with respect to the viewport. In the case of 'justify', the UA may stretch the inline boxes in addition to adjusting their positions. (See also 'letter-spacing' and 'word-spacing'.)

Example(s):

In this example, note that since 'text-align' is inherited, all block-level elements inside the div element with 'class=important' will have their inline content centered.

div.important { text-align: center }

Note. The property initial value has changed between CSS2 and CSS3 from being UA dependent in CSS2 to be related to the current text advance direction in CSS3 (through the usage of the 'start' value).

4.2. Justification: the 'text-justify' property

Name: text-justify
Value: auto | inter-word | inter-ideograph | distribute | newspaper | inter-cluster | kashida
Initial: auto
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property selects the type of justify alignment. It affects the text layout only if 'text-align' is set to 'justify'. That way, UA's that do not support this property will still render the text as fully justified, which most of the time is at least partially correct. Typically the text-justify property does not affect the last line, unless the last line itself is justified. Most of the text-justify values affects writing systems in very specific ways. These writing systems (or group of) are:

The text-justification behavior of textual components is guided by the script classification of the characters. The 'text-script' property allows to modify the behavior of these components.

Depending on the text-justify value, spacing may be altered between words or letters.

The possible values for the text-justify property are:

auto
The UA determines the justification algorithm to follow, based on a balance between performance and adequate presentation quality. Inter-word expansion is typically used for all scripts that use space as word delimiter. However, if the kashida-space property has a non zero value it is recommended to use kashida elongation for Arabic text.
inter-word
Selects the simplest and fastest full justification behavior, which spreads the text evenly across the line by increasing the width of the space between words only. The concept of a word is script dependent, the exact algorithm is determined by the user agent. At minimum, justification is expected to occur at each white space boundary. No expansion or compression occurs within the words, i.e. no additional letter spacing is created. No kashida effect takes place.

The diagram below illustrates this mode, by showing how the characters are laid out in the last two lines of an element:

Diagram showing glyph distribution in inter-word justification

Mixed glyph layout in the last two lines in an inter-word justified element

For example a viewer could render an 'inter-word' justified paragraph in the following way:

Example of inter-word justification applied to mixed Japanese
and English text

Inter-word justification applied to mixed text

newspaper
Selects the justification behavior in which both inter-word and inter-letter spacing can be expanded or reduced to spread the text across the whole line. Also, text distribution on any given line may depend on the layout or the contents of the previous or the following several lines. This is the significantly slower and more sophisticated type of the full justify behavior preferred in newspaper and magazines, as it is especially useful for narrow columns. For example, typically, compression is tried first. If unsuccessful, expansion occurs: inter-word spaces are expanded up to a threshold, and finally inter-letter expansion is performed. This is applied to all scripts groups except Devanagari and other South Asian writing systems using baseline connectors. The threshold value may be related to the column width (in number of characters). The exact layout algorithm is determined by the user agent. Further explanation about multi-column layout can be found in the CSS3 Multi-layout module.

The diagram below illustrates this mode:

Diagram showing character distribution in newspaper
justification

Mixed character layout in the last two lines of a newspaper justified element

Note. In CSS3 a value of 'letter-spacing: 0' no longer inhibits spacing-out of words for justification. The letter-spacing value is just an entry to the letter-spacing process that occurs prior to the possible justification process. Justification may alter the initial spacing between letters, especially with the 'text-justify: newspaper' value.

inter-ideograph
In this mode, letter-spacing modification only occurs for the CJK group. Others only use inter-word expansion. No kashida effect takes place. This is the preferred justification in the context of the Japanese writing system, but not Latin nor Korean.

The diagram below illustrates this mode:

Diagram showing glyph distribution in inter-ideograph
justification

Mixed glyph layout in the last two lines in an inter-ideograph justified element

Below is an example of how this mode would work:

Example of inter-ideograph justification applied to mixed
Japanese and English text

Inter-ideograph justification applied to mixed text

distribute
Like 'newspaper' it allows letter spacing modification for most script groups (except Hindi), but unlike newspaper, it does not prioritize between word spacing and letter spacing, i.e. the space character gets the same letter spacing modification as others. And by consequence there are no variations between narrow and wide columns. This value is best used in East Asian context.

The diagram below illustrates this mode:

Diagram showing character distribution in distribute
justification

Mixed character layout in the last two lines of a distribute justified element

For example a viewer could render a 'distribute' justified paragraph in the following way:

Example of distribute justification applied to mixed Japanese
and English text

Distribute justification applied to mixed text

inter-cluster
Plays the same role as inter-ideograph but for South Eastern Asian scripts. That is letter spacing only occurs for clusters belonging to those scripts. A cluster is defined as a group of characters formatted as a single unit.
kashida
Plays the same role as inter-ideograph but for Arabic through the Kashida effect. That is, no letter spacing occurs for other scripts.

The following table describes the expansion/compression strategy for the combination of each script groups and the text-justify property value for each relevant text-justify property value:

text-justify property value
Script groups auto* inter-word newspaper inter-ideograph distribute inter-cluster kashida
Latin word-spacing only* word-spacing only prioritization between word-spacing and letter-spacing word-spacing only word-spacing and letter-spacing word-spacing only word-spacing only
CJK no extra spacing* no extra spacing letter-spacing letter-spacing letter-spacing no extra spacing no extra spacing
Devanagari* word-spacing* word-spacing word-spacing word-spacing word-spacing word-spacing word-spacing
Arabic kashida and word-spacing* word-spacing kashida and word-spacing word-spacing kashida and word-spacing word-spacing kashida and word-spacing
SE Asian clusters inter-cluster spacing* inter-cluster spacing inter-cluster spacing no extra spacing inter-cluster spacing inter-cluster spacing no extra spacing

Interaction between text-justify values and script groups

*The values shown for the auto column are only a recommendation. The UAs might implement a different strategy.

*The Devanagari entry represents as well other scripts and writing systems used in India that use baseline connectors like Bengali and Gurmukhi.

4.3. Last line alignment: the 'text-align-last' property'

Name: text-align-last
Value: auto | start | end | center | justify | size
Initial: auto
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property describes how the last line of the inline content of a block is aligned. This also applies to the only line of a block if it contains a single line, the line preceding a <br> element in a XHTML context, or a hard line break in other languages, and to last lines of anonymous blocks. Typically the last line is aligned like the other lines of the block element, this is set by the 'text-align' property. However, in some situations like when the 'text-align' property is set to 'justify', the last line may be aligned differently.

Values have the following meanings:

auto
The last line will be aligned like the other lines, that is determined by the value of the 'text-align' property. However, if the 'text-align' property is set to the value 'justify', the last line will be aligned to the start of the inline progression.
start, end and center
Start, end and center text respectively.
justify
The last line will be justified like the other lines, using the justification type set by the 'text-justify' property. Note however that if there is no expansion opportunity in the last line, the line might not appear justified.
size
The line content is scaled to fit on the line. All the fonts on the line must be scaled by the same factor. Typically this value is used for single line element. Finally, this value, unlike the others, may change (i.e. decrease) the number of lines in a block element.

The following XHTML example shows the usage of the alignment properties in a case where all lines are justified in a distributed justification. This is commonly found in East Asian typography:

p.distributealllines
 { text-align: justify;
   text-justify: distribute;
   text-align-last: justify }

4.4. Minimum and maximum font size: the 'min-font-size' and 'max-font-size' property

Name: min-font-size
Value: <font-size> | auto
Initial: auto
Applies to: all elements and generated content
Inherited: yes
Percentages: element's computed 'font-size'
Media: visual
Computed value: <font-size>

If 'text-align-last' is 'size', the fonts of the last line of an element are not allowed to become smaller than the smaller of 'font-size' and 'min-font-size'. 'auto' means that the user agent determine the minimum readable font-size for the media. For example, a value is 9px is recommended for Latin scripts.

Name: max-font-size
Value: <font-size> | auto
Initial: auto
Applies to: all elements and generated content
Inherited: yes
Percentages: element's computed 'font-size'
Media: visual
Computed value: <font-size>

If 'text-align-last' is 'size', the fonts of the last line of an element are not allowed to become larger than the larger of 'font-size' and 'max-font-size'. 'auto' means that there is no limit.

4.5. Additional compression: The 'text-justify-trim' property

Name: text-justify-trim
Value: none | punctuation | punctuation-and-kana
Initial: punctuation
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This sets the individual font blank space compression permissions for the text justification algorithm, when 'text-justify' is anything other than 'inter-word'. This special type of space compression occurs on the font level, i.e. the blank space within the character area itself may be reduced without affecting the appearance of the glyph. This applies to wide-cell glyphs only. Possible values:

none
No wide-cell font space compression is allowed.

Diagram of glyph layout with no compression

Glyph layout with no compression

punctuation
Space can be taken away only from wide-cell punctuation glyphs.

Diagram of glyph layout with punctuation compression

Glyph layout with punctuation compression

punct-and-kana
Space compression is allowed on wide-cell punctuation and wide-cell Kana glyphs.

Diagram of character layout with punct-and-kana compression

Character layout with punctuation and Kana compression

4.6. Kashida effect: the 'text-kashida-space' property'

Name: text-kashida-space
Value: <percentage>
Initial: 0%
Applies to: block-level elements
Inherited: yes
Percentages: as described
Media: visual
Computed value: <percentage>

Kashida is a typographic effect used in Arabic writing systems that allows character elongation at some carefully chosen points in Arabic. Each elongation can be accomplished using a number of kashida glyphs, a single graphic or character elongation on each side of the kashida point. (The UA may use either mechanism based on font or system capability). The text-kashida-space property expresses the ratio of the kashida expansion size to the white space expansion size, 0% means no kashida expansion, 100% means kashida expansion only . This property can be used with any justification style where kashida expansion is used (currently text-justify: auto, kashida, distribute and newspaper).

In the diagram below showing two identical paragraphs of Arabic text, the blue line in the second line (not justified) shows the length that is used for kashida and divided among the elongation opportunities in the first line (justified), as indicated by the red underlines:

Example of kashida applied to Arabic text

Kashida applied to Arabic text

In that example no expansion occurs between the word themselves, indicating that the text-kashida-space property is set to 100%.


5. Indentation: the 'text-indent' property

Name: text-indent
Value: <length> | <percentage>
Initial: 0
Applies to: block-level elements
Inherited: yes
Percentages: refers to width of containing block
Media: visual
Computed value: <length>

This property specifies the indentation of the first line of text in a block. More precisely, it specifies the indentation of the first box that flows into the block's first line box. The box is indented with respect to the starting edge of the line box. User agents should render this indentation as blank space. When the 'text-align' property is not set to align the text at the starting edge, this property only specifies a minimum indentation.

Values have the following meanings:

<length>
The indentation is a fixed length.
<percentage>
The indentation is a percentage of the containing block width.

The value of 'text-indent' may be negative, but there may be implementation-specific limits.

Note:

Note: Since the 'text-indent' property inherits, when specified on a block element, it will affect descendent inline-block elements. For this reason, it is often wise to specify 'text-indent: 0' on elements that are specified 'display: inline-block'.

Example(s):

The following example causes a '3em' text indent.

  p { text-indent: 3em }

6. Line breaking

6.1. Types of line breaking

In documents written in Latin-based languages, where runs of characters make up words and words are separated by spaces or hyphens, line breaking is relatively simple. In the most general case, (assuming no hyphenation dictionary is available to the UA), a line break can occur only at whitespace characters or hyphens, including U+00AD SOFT HYPHEN.

In ideographic typography, however, where what appears as a single glyph can represent an entire word and no spaces nor any other word separating characters are needed, a line breaking opportunity is not as obvious as a space. It can occur after or before many other characters. Certain line breaking restrictions still apply, but they are not as strict as they are in Latin typography.

Thai is another interesting example with its own special line breaking rules. Since Thai words are made up of runs of characters, it resembles Latin in that respect. But the lack of spaces as word delimiters, or in fact any consistent word delimiters, makes it similar to CJK. Thai, like Latin in the absence of a hyphenating dictionary, never breaks inside of words. In fact, a knowledge of the vocabulary is necessary to be able to correctly break a line of Thai text. Finally, the Unicode character: U+200B ZERO WIDTH SPACE can be inserted in such scripts to specify an explicit line breaking opportunity.

A number of levels of line-breaking "strictness" can be used in Japanese typography. These levels add or remove line breaking restrictions. The model presented in this specification distinguishes between two most commonly used line breaking levels for Japanese text, using the 'line-break' property.

In ideographic typography, it is also possible, though not always preferred, to allow line breaks to occur inside of quoted Latin and Hangul (Korean) words without following the line breaking rules of those particular scripts. The model proposed in this document gives the author control over that behavior through the 'word-break-CJK' property.

In addition, hyphenation is controlled by 'word-break-inside'. All these properties are also available through the 'word-break' short hand property.

Finally, there is an additional property 'wrap-option' which may influence line-breaking, especially the property value 'wrap-option: emergency' which provides for emergency word-breaking for long words.

Line breaking is also covered by the Unicode Standard Annex [UAX-14], available from the Unicode Web site. It contains a detailed recommendation and corresponding data for each Unicode character.

6.2. Line breaking: the 'line-break' property

Name: line-break
Value: normal | strict
Initial: normal
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property selects the set of line breaking rules to be used for text. The values described below are especially useful to CJK authors, but the property itself is open to other, not yet specified settings for non-CJK authors as well. (This is an area for future expansion.)

normal
Selects the normal line breaking mode for CJK. While the UA is free to define its own line breaking restrictions for the 'normal' mode, it is recommended that breaks between small katakana and hiragana characters be allowed. That is the preference in modern Japanese typography, and is especially desirable for narrow columns. Japanese katakana words tend to be long, and it is preferable to allow line breaks to occur among such characters than to have excessive expansion due to justification.
strict
Selects a more restrictive line breaking mode for CJK text. While the UA is free to define its own line breaking restrictions for the 'strict' mode, it is recommended that the restrictions specified by the JIS X-4051 [JIS-X-4051] be followed. That implies that in this mode, small katakana and hiragana characters are not allowed to start a line.

In Japanese, a set of line breaking restrictions is referred to as "Kinsoku". JIS X-4051 [JIS-X-4051] is a popular source of reference for this behavior using the strict set of rules. This architecture involves character classification into line breaking behavior classes. Those classes are then analyzed in a two dimensional behavior table where each row-column position represents a pair action to be taken at the occurrence of these classes. For example, given a closing character class and an opening character class, the intersection in that table of these two classes (the first character belonging to the opening class and the second belonging to the closing class) will indicate no line breaking opportunity. The rules described by JIS X-4051 have been superseded by the Unicode Technical Report #14 mentioned earlier.

Note that both values, 'normal' and 'strict' imply that a set of line-breaking restrictions is in use. In fact, there appears to be no valid line breaking mode in CJK in which line breaks can appear just anywhere among ideographs.

6.3. Word breaking: the 'word-break-CJK', 'word-break-inside' properties and the shorthand 'word-break' property

Name: word-break-CJK
Value: normal | break-all | keep-all
Initial: normal
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property controls line-breaking behavior inside of words from a CJK point of view. Possible values:

normal
Keeps non-CJK scripts together (according to their own rules), while Hangul and CJK (including the Korean Hanja characters) break everywhere or according to the rules of the 'line-break' mode. Note however that the behavior of non-CJK scripts can be superseded by using the value 'emergency' in the 'wrap-option' property, or the value 'hyphenate' in the 'word-break-inside' property.
break-all
Same as 'normal' for CJK and Hangul, but non-CJK scripts can break anywhere. This option is used mostly in a context where the text is predominantly using CJK characters with few non-CJK excerpts and it is desired that the text be better distributed on each line. The UAs may however limit the break everywhere behavior for script using clusters like Thai.
keep-all
Same as 'normal' for all non-CJK scripts. CJK and Hangul are kept together. This option should only be used in the context of CJK used in small clusters like in the Korean writing system.

The following example shows a paragraph style where all non-CJK scripts can break anywhere.

p.anywordbreaks { word-break: break-all }
Name: word-break-inside
Value: normal | hyphenate
Initial: normal
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property controls the hyphenation behavior inside of words. Possible values:

normal
A word should always stay in a single line. Note however that this can be superseded by using the value 'break-all' in the 'word-break-CJK' property, or the value 'emergency' in the 'wrap-option' property. Moreover, explicit hyphenation characters (hyphen, soft hyphen, etc...) still create line breaking opportunities.
hyphenate
Words can be broken at an appropriate hyphenation point. It requires that the user agent have an hyphenation dictionary for the language of the text being broken. Setting this value activates the hyphenation engine in the user agent.
Name: word-break
Value: <'word-break-CJK'> || <'word-break-inside'>
Initial: see individual properties
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: see individual properties

The 'word-break' property is a shorthand property for setting 'word-break-CJK', and 'word-break-inside', at the same place in the style sheet.

All word-break related properties are first reset to their initial values (all 'normal'). Then, those properties that are given explicit values in the 'word-break' shorthand are set to those values.


7. Text Wrapping, White-space Control and Text Overflow

The following section describes text wrapping, white-space handling and text overflow. Text wrapping and white-space handling are interrelated through the CSS2 'white-space' property combining these two effects together. Text wrapping and text overflow both deal with situation where the text reaches the flow after-edge of its containing box.

CSS3 clearly separates these three effects in different sets of property while keeping the 'white-space' property for compatibility reason.

7.1. Text wrapping: the 'wrap-option' property

Name: wrap-option
Value: wrap | hard-wrap | soft-wrap | emergency
Initial: wrap
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property controls whether or not text wraps when it reaches the flow edge of its containing block box. Several value descriptions use the term preserved line feed characters (U+000A). A preserved line-feed character (either from the source content or from occurrence of "\A" in generated content) is maintained for presentation purpose and may therefore influence text wrapping. The preserved status of line-feed characters is determined by the 'linefeed-treatment' property. The 'wrap-option' possible values are:

wrap
The text is wrapped at the best line-breaking opportunity (if required) within the available block inline progression dimension (block width in horizontal text flow). The best line-breaking opportunity is determined in priority by the existence of preserved line-feed characters (U+000A), or by the line-breaking algorithm controlled by the 'line-break' and word-break' properties.
hard-wrap
The text is only wrapped where explicitly specified by preserved line feed characters (U+000A). In the case when lines are longer than the available block width, the overflow will be treated in accordance with the 'overflow' property specified in the element.
soft-wrap
The text is wrapped exactly at the block width and where explicitly specified by preserved line feed characters (U+000A). No line-breaking algorithm is invoked.
emergency
The text is wrapped like for the 'wrap' case, except that the line-breaking algorithm will allow as a last resort option a text wrap after the last character which can fit before the ending-edge of the line, independently of 'line-break' and word-break' properties. For example, this deals with the situation of very long words constrained in a fixed-width container with no scrolling allowed.

7.2. White-space control: the 'linefeed-treatment', 'white-space-treatment', 'all-space-treatment' properties and the 'white-space' shorthand property

White-space processing in the context of CSS is the mechanism by which all white-space characters are interpreted for rendering purpose. The white-space set is determined by the XML [XML1.0] specification as being a combination of one or more space characters (Unicode value U+0020), carriage returns (U+000D), line feeds (U+000A), or tabs (U+0009).

Note: [HTML401] also defines the form feed character (U+000C) as a white space character, but that character is not part of any XHTML versions as they are all based on XML.

The amount of white space processing that can be achieved by a user agent that supports CSS is directly related to the CSS processing model, especially the document parsing and validation. After parsing and possible validation, the document tree may contain text nodes that contain unprocessed white space characters, or the document tree may already have been processed in a way that white space characters have been collapsed and partially removed (white space normalization).

In that respect, the CSS properties related to white space processing can only be effective if the CSS processor has access to the white space characters that were originally encoded in the document. However, end-of-line characters are typically handled (like by XML processors) in such a way that any arbitrary combination of end-of-line characters is replaced by a single line feed character (U+000A).

Note: XML Schema, through its 'whiteSpace' facet can constrain exactly the type of white space characters still available to a rendering process like CSS for elements containing string datatype. In addition, some XML languages like [XHTML1.0] may have their own white-space processing rules when parsing and validating documents with white-space characters. Therefore, some of the behaviors described below may be affected by these limitations and may be user agent dependent in these contexts.

In addition, line feed characters can be inserted in generated content by using the '\A' string. The behavior of these inserted line feed characters is identical to original line feed characters part of the source document and is controlled by the same set of properties.

The initial white-space processing, similar to [XHTMLMOD] is as follows:

Note: These rendering rules make no assumption about the storage model of these white-space character sequences. It is outside the scope of CSS to determine the character code values accessible through programming interface such as DOM. These rules do not apply to elements that have an explicit white-space rendering behavior (like the pre element in XHTML).

Note: In determining how to convert a LINE FEED character a user agent should consider the following cases, whereby the script of characters on either side of the LINE FEED determines the choice of the replacement. Characters of COMMON script (such as punctuation) are treated as the same as the script on the other side:

  1. If the characters preceding and following the LINE FEED character belong to a script in which the SPACE character is used as a word separator, the LINE FEED character should be converted into a SPACE character. Examples of such scripts are Latin, Greek, and Cyrillic.

  2. If the characters preceding and following the LINE FEED character belong to an ideographic-based script or writing system in which there is no word separator, the LINE FEED should be converted into no character. Examples of such scripts or writing systems are Chinese, Japanese.

  3. If the characters preceding and following the LINE FEED character belong to a non ideographic-based script in which there is no word separator, the LINE FEED should be converted into a ZERO WIDTH SPACE character (&#x200B;) or no character. Examples of such scripts are Thai, Khmer.

  4. If none of the conditions in (1) through (3) are true, the LINE FEED character should be converted into a SPACE character.

The Unicode [UNICODE] technical report TR#24 (Script Names) [UTR-24] provides an assignment of script names to all characters.

When white-space characters are collapsed for rendering purpose, the style applied to the collapsed set is the one that would be applied to first white-space character of the set.

The following properties: 'linefeed-treatment', 'white-space-treatment' and 'all-space-treatment' allow precise control of that behavior. The 'linefeed-treatment' determines the rendering of the line feed characters. The 'white-space-treatment' determines the rendering of white space character (except line feed). And the 'all-space-treatment' property determines the treatment of consecutive white-space characters after consideration of the two prior properties. The 'white-space' property is a shorthand property for these three properties as well as the 'wrap-option' property.

Name: linefeed-treatment
Value: auto | ignore | preserve | treat-as-space | treat-as-zero-width-space | ignore-if-after-linefeed
Initial: auto
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property specifies the treatment of linefeeds (U+000A characters). Values have the following meanings:

auto
Linefeed characters are transformed for rendering purpose into one of the following characters: a space character, a zero width space character (U+200B), or no character (i.e. not rendered). The choice of the resulting character is conditioned by the script property of the characters preceding and following the line feed character in the same line flow elements part of the same block element. The result of the transformation can be treated by subsequent CSS processing (including white space collapsing).
ignore
Linefeed characters are ignored. i.e. they are transformed for rendering purpose into no character.
preserve
Linefeed characters indicate an end of line of boundary.
treat-as-space
Linefeed characters are transformed for rendering purpose into a space character (U+0020). The result of the transformation can be treated by subsequent CSS processing (including white space collapsing).
treat-as-zero-width-space
Linefeed characters are transformed for rendering purpose into a zero width space character (U+200B). The result of the transformation can be treated by subsequent CSS processing (including white space collapsing).
ignore-if-after-linefeed
Specifies that any linefeed characters that immediately follows a linefeed character, shall be discarded. This allows multiple consecutive linefeed characters to be collapsed into a single linefeed.

Note: The Unicode Standard [UNICODE] recommends that the zero width space is considered a valid line-break point and that if two characters with a zero width space in between are placed on the same line they are placed with no space between them; and that if they are placed on two lines no additional glyph area, such as for a hyphen, is created at the line-break.

Name: white-space-treatment
Value: ignore | preserve | ignore-if-before-linefeed | ignore-if-after-linefeed |
ignore-if-surrounding-linefeed
Initial: ignore-if-surrounding-linefeed
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property specifies the treatment of space (U+0020) and other white-space characters except for linefeeds (U+000A), since their treatment is determine by the linefeed-treatment property. White-space characters, when rendered as an advance width, use the width of the space character (U+0020). Values have the following meanings:

ignore
White space characters, except for linefeeds, are ignored. i.e. they are transformed for rendering purpose into no character.
preserve
All white space characters are rendered as intended (advance width). The treatment of linefeeds is not determined by this property.
ignore-if-before-linefeed
Specifies that any white space characters, except for linefeeds, that immediately precedes a linefeed character, shall be discarded. This action shall take place regardless of the setting of the linefeed-treatment property.
ignore-if-after-linefeed
Specifies that any white space characters, except for linefeeds, that immediately follows a linefeed character, shall be discarded. This action shall take place regardless of the setting of the linefeed-treatment property.
ignore-if-surrounding-linefeed
Specifies that any white space characters, except for linefeeds, that immediately precedes or follows a linefeed character, shall be discarded. This action shall take place regardless of the setting of the linefeed-treatment property.
Name: all-space-treatment
Value: preserve | collapse
Initial: collapse
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

The "all-space-treatment" property specifies the treatment of all consecutive white-space characters (with no exception for linefeed characters, unlike the "white-space-treatment" property). Values have the following meanings:

preserve
All white-space characters are rendered as intended. The tab character (U+0009) is rendered as the smallest non-zero number of spaces necessary to line characters up along tab stops that are every 8 characters.
collapse
Specifies that a character is not rendered if:
Name: white-space
Value: normal | pre | nowrap | pre-wrap | pre-lines
Initial: not defined for shorthand properties
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: see individual properties

This property declares how 'white-space' inside the element is handled. Setting a value on the 'white-space' property set the respective values on 'wrap-option', 'linefeed-treatment', 'white-space-treatment' and 'all-space-treatment'. Although, strictly speaking, the property has no initial value, it is equivalent to 'normal'. The definition of the property values are established by referring to the individual white-space properties set as follows:

white-space: wrap-option: linefeed-treatment: white-space-treatment: all-space-treatment:
normal wrap auto ignore-if-surrounding-linefeed collapse
pre hard-wrap preserve preserve preserve
nowrap hard-wrap auto ignore-if-surrounding-linefeed collapse
pre-wrap wrap preserve preserve preserve
pre-lineswrappreserveignore-if-surrounding-linefeed collapse

Example(s):

The following examples show what white-space behavior is expected from the PRE and P elements, and the "nowrap" attribute in HTML, and in generated content.

pre        { white-space: pre }
p          { white-space: normal }
td[nowrap] { white-space: nowrap }
:before, :after {white-space: pre-lines }

In addition, the effect of an HTML PRE element with the non-standard "wrap" attribute is demonstrated by the following example:

pre[wrap]  {white-space: pre-wrap }

7.3. Text overflow: the 'text-overflow-mode', 'text-overflow-ellipsis' properties and the shorthand 'text-overflow' property

Text overflow deals with the situation where some textual content is clipped when it overflows the element's box in its text advance direction as determined by the writing-mode property value. This situation may only occur when the 'overflow' property has the values: hidden, scroll and auto (in the latter case only when the UA behavior results in content scrolling).

Text overflow allows the author to introduce a visual hint at the two ending boundaries of the text flow within the element box (after and end). The hint is typically an ellipsis character "...", although the actual character representation may vary. An image may also be substituted. Setting a non empty string (or an uri for an image) for either text flow boundary enables the presentation of the hint. If both hints should appear, only the 'after' hint is rendered. Initially, only the end of line hint is shown (correspond to the right of any over flown lines for left to right inline progression).

The text-overflow is divided in properties: 'text-overflow-mode' that controls the presentation of hint characters, 'text-overflow-ellipsis' that controls the values of the hint characters presented at the box boundaries and a shorthand property: 'text-overflow'.

Name: text-overflow-mode
Value: clip | ellipsis | ellipsis-word
Initial: clip
Applies to: all block-level elements
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)
clip
clip text as appropriate for the text content. Glyphs representation of the text may be only partially rendered.
ellipsis
an ellipsis string is inserted at each box boundaries where a text overflow occurs. The values of these ellipsis strings is determined by the 'text-overflow-ellipsis' property. The insertions take place at the boundary of the last full glyph representation of a line of text.
ellipsis-word
similar to 'ellipsis', but the insertions take place at the boundary of the last full glyph representation of a word within the line of text.

The hint characters only replace textual information. If the clipping occurs on a replaced element, standard clipping occurs.

Although the property is not inherited, overflowing children blocks that are either statically or relatively positioned and do not have a specified width or height will be hinted as specified by their parent text-overflow-mode property value. Consider the following example:

<div class="citation">
<p class="sentence"><span class="nowrap">I didn't like the play,</span> but then I saw
it under adverse conditions - the curtain was up.
<div class="attributed-to">_Groucho_Marx_</div>
</p>
</div>

Here is the style sheet controlling the overflow situations:

div.citation      { width:100px; border: thin solid red; overflow: hidden;
                    text-overflow-mode:ellipsis;font-size:14px }
span.nowrap       { white-space : nowrap; }
div.attributed-to { position: relative;left:8px }

This will result in the content of the span to be partially visible and the ellipsis will be shown, the inner div which is relatively positioned will only show a partial ellipsis as it is offset by few pixels: Image
of ellipsis in text overflow

Other children blocks, like absolute positioned blocks, or blocks with specified width or height won't show hinting. For example, setting the p element of the previous figure with the following style:

p.sentence { width :100px; margin-top : 50px; margin-left : 50px; }

will result on no ellipsis shown for its content (because it has a specified width and furthermore the text wrapping occurs in the 'hidden' overflow area of its parent element). This would be shown like this: Image of a child block element without ellipsis

In other words, the text-overflow-mode only affects the textual content of a block element which participate in its own inline flow.

Name: text-overflow-ellipsis
Value: [<ellipsis-end> | <uri> [, <ellipsis-after> | <uri>]?]
Initial: "..."
Applies to: all block-level elements
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)
<ellipsis-end>
controls the value of the hint characters presented after the text flow within each line of an element box. It takes as value a text string. An empty string disables the hint. The initial value is '...'. In a horizontal text flow ('writing-mode' = 'lr-tb), the hint string would appear on each line of the element box where the text overflows on the right.
<ellipsis-after>
controls the value of the hint character presented after the text flow within an element box. It takes as value a text string. An empty string disables the hints. The initial value is empty. In a horizontal left-to-right text flow, the hint string would appear on the right side of the last line. If <ellipsis-after> is non empty and would appear at the same location than <ellipsis-end>, only <ellipsis-after> is shown. The <ellipsis-after> may only appear if there is content which is clipped because of the block-progression dimension of the block, not because the last line cannot fit.
uri
And URI can replace any of the string value and set an image to be used as the hint indication. Being specified is equivalent to a non empty string for the respective ellipsis.

The font-size used for the ellipsis characters is the element font-size.

Name: text-overflow
Value: <'text-overflow-mode'> || <'text-overflow-ellipsis'>
Initial: not defined for shorthand properties
Applies to: all block-level elements
Inherited: no
Percentages: N/A
Media: visual
Computed value: see individual properties

This property is the shorthand for 'text-overflow-mode' and 'text-overflow-ellipsis'.


8. Text spacing

8.1. Letter spacing: the 'letter-spacing' property

Name: letter-spacing
Value: normal | <length>
Initial: normal
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: <length> or 'normal'

This property specifies spacing behavior between text characters. Values have the following meanings:

normal
The spacing is the normal spacing for the current font. It is typically zero-length. However, this value allows the user agent to alter the space between characters in order to justify text.
<length>
This value indicates inter-character space in addition to the default space between characters. The value is added to the advance width of each spacing character (as opposed to combining character) or group of characters that are clustered in single grapheme unit (like in Thai, Khmer, etc.), including the last character of the element. Characters which are joined together by effect of applying a cursive font to them, or by standard typography rules (Arabic script, Northern Indian scripts like Devanagari) have the valued added to the normal advance width of each spacing characters. Combining characters (not spacing) do not get any letter-spacing effect, only the combination of the base character and its combining characters does.
For justification purposes, user agents should minimize effect on letter-spacing as much as possible (priority to word-spacing expansion/compression as opposed to character-spacing expansion/compression).
Values may be negative, but there may be implementation-specific limits. The justification algorithm may further modify the inter-character spacing, but only in text where there is no other opportunities to distribute the extra spacing (such as single word on a line, ideographic text).

Because of the visual disruptive effect of modifying letter-spacing on writing systems which use joined characters, like for example Arabic, the usage of this property is discouraged in those cases.

There are cases like Japanese or Chinese writing systems where justification will change all letter-spacing effects as there is no other opportunity in the line to expand or compress the character content in order to fit the line span.

Character spacing algorithms are user agent-dependent. For example, the spacing will not occur necessarily between all characters, but instead between each glyph that constitutes either a letter or a cluster unit. Furthermore this property should not be used for scripts and/or fonts that link characters together (cursive fonts for Roman scripts, all Arabic cases, Indic scripts with headline like Devanagari, etc...). Character spacing may also be influenced by justification (see the 'text-align' property).

Example(s):

In this example, the space between characters in blockquote elements is increased by '0.1em'.

blockquote { letter-spacing: 0.1em }

In the following example, the user agent is requested not to alter inter-character space:

blockquote { letter-spacing: 0cm }   /* Same as '0' */

When the resultant space between two characters is not the same as the default space, user agents should not use ligatures.

8.2. Word spacing: the 'word-spacing' property

Name: word-spacing
Value: normal | none | <length>
Initial: normal
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: <length>, 'normal' or 'none'

This property specifies spacing behavior between words. Values have the following meanings:

normal
The normal inter-word space, as defined by the current font and/or the user agent. If the inter-word boundary is delimited by one or several white-space characters, they should be visible. If there are no characters, the user agent doesn't have to create an additional character advance width.
none
There is no inter-word space. All white-space characters are treated like zero-length characters.
<length>
This value indicates inter-word space in addition to the default space between words. Values may be negative, but there may be implementation-specific limits.

Word spacing algorithms are user agent-dependent. Determining word boundary is typically done by detecting white space characters. There are however many scripts and writing systems that do not separate their words by any character (like Japanese, Chinese, Thai, etc...), detecting word boundaries in these cases require dictionary based algorithms that may not be supported by all user agents. Word spacing is also influenced by justification (see the 'text-align' property).

Example(s):

In this example, the word-spacing between each word in H1 elements is increased by '1em'.

h1 { word-spacing: 1em }

8.3. Punctuation trimming: the 'punctuation-trim' property

Name: punctuation-trim
Value: none | start
Initial: none
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property determines whether or not a full-width punctuation mark character should be trimmed if it appears at the beginning of a line, so that its "ink" lines up with the first glyph in the line above and below. In some scenarios, it may be preferable for the author not to allow leading punctuation marks to be trimmed, for example when it is more important that the glyphs tend to line up vertically. In other scenarios such an effect is desirable, for example when it is more important for the author that as much text as possible fits on a single line.

Possible values:

none
Leading punctuation is not trimmed.

Diagram of glyph layout without leading punctuation compressionExample of
Japanese text without leading punctuation compression

Glyph layout with no leading punctuation compression

start
Leading punctuation is trimmed.

Diagram of glyph layout with leading punctuation compressionExample of
Japanese text with leading punctuation compression

Glyph layout with leading punctuation compression

(Note that this property may in the future be expanded to cover other punctuation behaviors for other types of punctuation as well, not just wide-cell.)

8.4. Adding space: the 'text-autospace' property

Name: text-autospace
Value: none | [ideograph-numeric || ideograph-alpha || ideograph-space || ideograph-parenthesis]
Initial: none
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

When a run of non-ideographic or numeric characters appears inside of ideographic text, a certain amount of space is often preferred on both sides of the non-ideographic text to separate it from the surrounding ideographic glyphs. This property controls the creation of that space when rendering the text. That added width does not correspond to the insertion of additional space characters, but instead to the width increment of existing glyphs.

(A commonly used algorithm for determining this behavior is specified in JIS X-4051 [JIS-X-4051].)

This property is additive with the 'word-spacing' and 'letter-spacing' [CSS2] properties, that is, the amount of spacing contributed by the 'letter-spacing' setting (if any) is added to the spacing created by 'text-autospace'. The same applies to 'word-spacing'.

Possible values:

none
No extra space is created.
ideograph-numeric
Creates extra spacing between runs of ideographic text and numeric glyphs.
ideograph-alpha
Creates extra spacing between runs of ideographic text and non-ideographic text, such as Latin-based, Cyrillic, Greek, Arabic or Hebrew.
ideograph-space
Extends the width of the space character while surrounded by ideographs.
ideograph-parenthesis
Creates extra spacing between normal (non wide) parenthesis and ideographs.
span.autospace { text-autospace:none; }
<span class="autospace">[ideographs]1997[ideographs]</span>

would appear as:

Diagram of glyph layout without autospace

Example of Japanese text
mixed with a number without autospace

Mixed glyph layout when autospace is disabled

while changing the style to the following:

span.autospace { text-autospace:ideograph-numeric; }

would make the same text appear more like:

Diagram of glyph layout with autospace

Example of Japanese text
mixed with a number without autospace

Mixed glyph layout when autospace is enabled

8.5. Text kerning: the 'kerning-mode' and 'kerning-pair-threshold' property

Name: kerning-mode
Value: none | [pair || contextual]
Initial: none
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property controls all kerning effects. Some kerning effects are based on information located explicitly on fonts (pair-kerning). Others are based on context and typical ink placement within characters and don't rely on font information. Pair kerning is used mainly for Latin, Greek and Cyrillic scripts, while contextual kerning is more common in East Asian context. A typical example of pair kerning is the pair 'Wa'. A good example of contextual kerning is the pair '[[' (when using the wide width variant). Possible values:

none
no kerning is enabled
pair
enables pair kerning
contextual
enables contextual kerning
Name: kerning-pair-threshold
Value: auto | <length>
Initial: auto
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: <length> or 'auto'

This property controls the font size threshold, above which pair kerning would be active (if enabled).  Possible values:

auto
The user agent determines the font-size threshold above which the kerning takes place.
<length>
<font-size> threshold.

 


9. Text decoration

9.1. Introduction

Until CSS2, the only text decorations available were available through the 'text-decoration' property exposing itself various effects underline, overline, line-through, etc... and the text-shadows property. However the text-decoration property has some limitations stemming from its syntax, which allows for multiple 'text-decoration' formatting effects to be specified at the same time but it precludes finer control over each of those formatting effects. More specifically, it offers no way to control the color or line style of the underline, overline or line-through.

CSS3 extends the model by introducing new properties allowing additional controls over those formatting effects. CSS3 also makes turning these formatting effects on or off possible without affecting any other 'text-decoration' settings.

Furthermore, to reflect the usage of underline in East Asian vertical writing, a new control is offered on the underline positioning, this allows the underline to appear before (on the right in vertical text flow) or after (on the left in vertical text flow) the formatted text. The property is called 'text-underline-position'.

The 'text-decoration' property itself is now a shorthand property for all these new properties, but it only takes its own set of values which affects all the other text decoration properties.

These properties describe decorations that are added to the text of an element. If they are specified for a block-level element, it affects the root inline box (the anonymous inline box which wraps all the inline children of an element).

If they are specified for (or affects) an inline-level element, it affects all boxes generated by the element. If an element is empty or is a replaced element (e.g., the IMG element in XHTML), user agents must ignore these properties. Text content also excludes white space characters that are collapsed during the white space processing.

All these text decoration properties are not inherited, but descendant boxes should be formatted with the same decoration (e.g., they should all be underlined). The color of decorations should remain the same even if descendant elements have different 'color' values.

Finally, user agents may chose either to average thickness and positions of the 'line' text-decorations based on the children text size and baselines, or to ignore the text of children. The following figure shows the averaging for underline:

image of underline averaging

On these 3 segments of underline text, the underline bar is drawn lower and thicker as the ratio of large text increase for the each consecutive underlined text segment.

Note: Typically the underline superscript text segments are averaged, while the subscript segments are not.

9.2. Text decoration style: the 'text-underline-style', 'text-line-through-style' and 'text-overline-style' properties

Names: text-underline-style, text-line-through-style, text-overline-style
Value: none | solid | double | dotted | thick | dashed | dot-dash | dot-dot-dash | wave
Initial: none
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

These properties specifies the line style for underline, line-through and overline text decoration. Possible values:

none
no line
solid
solid line
double
double line
dotted
dotted line
thick
single line using a greater line width.
dashed
dashed line style.
dot-dash
line style consisting of a dot-and-dash pattern.
dot-dot-dash
line style consisting of two-dots-and-a-dash pattern.
wave
wavy line

The following figure shows the appearance of these various line styles.

All the line styles

The line styles

9.3. Text decoration color: the 'text-underline-color', 'text-line-through-color' and 'text-overline-color' properties

Names: text-underline-color, text-line-through-color, text-overline-color
Value: auto | <color>
Initial: auto
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

These property specifies the line color for the underline, line-through and overline text decorations. Possible values:

auto
The color of the underline is determined by the 'color' property. 
<color>
Specifies a color value.

9.4. Text decoration mode: the 'text-underline-mode', 'text-line-through-mode' and 'text-overline-mode' properties

Name: text-underline-mode, text-line-through-modetext-overline-mode
Value: continuous | words
Initial: continuous
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

These properties set the mode for the underline, line-through and overline text decorations, determining whether the text decoration affects the white-space characters or not. Possible values:

continuous
this value means that the line is continuous.
words
this means that only non-whitespace text will be lined.

9.5. Other text decoration simple properties: 'text-underline-position' and 'text-blink'

Name: text-underline-position
Value: auto-pos | before-edge | after-baseline | after-edge
Initial: auto-pos
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property sets the position of the underline when set through the 'text-underline-style' property. It can appear either 'before' (above in an horizontal flow) or after (below in an horizontal flow) the run of text in relation to its baseline orientation. This property is typically used in vertical writing context where it may be desired to have the underline appear 'before' the run of text. This results in having the underline appearing on the right side of the vertical writing column. Possible values:

auto-pos
In horizontal inline progression, the underline if set will appear after the text alphabetic baseline. In vertical inline progression, if the language is set to Japanese, the underline if set will appear before the text edge (EM box edge).
before-edge
the underline if set will appear before the edge of the EM box.
after-baseline
the underline if set will appear after the alphabetic baseline. In this case the underline may cross some descenders.
after-edge
the underline if set will appear after the edge of the EM box. In this case the underline does not cross the descenders. This is sometimes called 'accounting' underline.
Name: text-blink
Value: none | blink
Initial: none
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property specifies the blink mode. Possible values:

none
no blink
blink
blink
Conforming CSS2 user agents are not required to support this value.

9.6. Text decoration shorthand properties: 'text-underline', 'text-line-through', 'text-overline' and 'text-decoration'

The 'text-underline' property is the shorthand for 'text-underline-style', 'text-underline-color', 'text-underline-mode' and 'text-underline-position'.

Name: text-underline
Value: <'text-underline-style'> || <'text-underline-color'> || <'text-underline-mode'> || <'text-underline-position'>
Initial: not defined for shorthand properties
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

The 'line-through' property is the shorthand for 'text-line-through-style', 'text-line-through-color' and 'text-line-through-mode'.

Name: text-line-through
Value: <'text-line-through-style'> || <'text-line-through-color'> || <'text-line-through-mode'>
Initial: not defined for shorthand properties
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: see individual properties

This 'text-overline' property is the shorthand for 'text-overline-style', 'text-overline-color' and 'text-overline-mode'.

Name: text-overline
Value: <'text-overline-style'> || <'text-overline-color'> || <'text-overline-mode'>
Initial: not defined for shorthand properties
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: see individual properties

The 'text-decoration' property is a shorthand that takes its own set of values.

Name: text-decoration
Value: none | [ underline || overline || line-through || blink]
Initial: see individual properties
Applies to: all elements and generated content
Inherited: no (see prose)
Percentages: N/A
Media: visual
Computed value: see individual properties

The 'text-decoration' shorthand sets the properties 'text-underline-style', 'text-underline-color', 'text-underline-mode', 'text-underline-position', 'text-line-through-style', 'text-line-through-color', 'text-line-through-mode', 'text-overline-style', 'text-overline-color', 'text-overline-mode' and 'text-blink' to their default values, and then the values of the shorthand change these defaults as follows:

none
All the sub-properties maintain their defaults.
underline
'text-underline-style' is 'solid' rather than 'none'.
overline
'text-overline-style' is 'solid' rather than 'none'.
line-through
'text-line-through-style' is 'solid' rather than 'none'.
blink
'text-blink' is 'blink' rather than 'none'.

Conforming user agents are not required to support the 'blink' value.

Although the property has no explicit initial value, it is equivalent to the value 'none.

Example(s):

In the following example for XHTML, the text content of all a elements acting as hyperlinks will be underlined and blinking:

a[href] { text-decoration: underline blink }

9.7. Text shadows: the 'text-shadow' property

Name: text-shadow
Value: none | [<color> || <length> <length> <length>? ,]* [<color> || <length> <length> <length>?]
Initial: none
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified values (except for initial and inherit)

This property accepts a comma-separated list of shadow effects to be applied to the text of the element. The shadow effects are applied in the order specified and may thus overlay each other, but they will never overlay the text itself. Shadow effects do not alter the size of a box, but may extend beyond its boundaries. The stack level of the shadow effects is the same as for the element itself.

Each shadow effect must specify a shadow offset and may optionally specify a blur radius and a shadow color.

A shadow offset is specified with two <length> values that indicate the distance from the text. The first length value specifies the horizontal distance to the right of the text. A negative horizontal length value places the shadow to the left of the text. The second length value specifies the vertical distance below the text. A negative vertical length value places the shadow above the text.

A blur radius may optionally be specified after the shadow offset. The blur radius is a length value that indicates the boundaries of the blur effect. The exact algorithm for computing the blur effect is not specified. User agents may only implement only part of this property by ignoring blur effects. Such user agents should consider declarations that specify the optional third parameter to be parser errors, as described in the Syntax module [link TBD].

A color value may optionally be specified before or after the length values of the shadow effect. The color value will be used as the basis for the shadow effect. If no color is specified, the value of the 'color' property will be used instead.

Text shadows may be used with the ::first-letter and ::first-line pseudo-elements.

Example(s):

The example below will set a text shadow to the right and below the element's text. Since no color has been specified, the shadow will have the same color as the element itself, and since no blur radius is specified, the text shadow will not be blurred:

h1 { text-shadow: 0.2em 0.2em }

The next example will place a shadow to the right and below the element's text. The shadow will have a 5px blur radius and will be red.

h2 { text-shadow: 3px 3px 5px red }

The next example specifies a list of shadow effects. The first shadow will be to the right and below the element's text and will be red with no blurring. The second shadow will overlay the first shadow effect, and it will be yellow, blurred, and placed to the left and below the text. The third shadow effect will be placed to the right and above the text. Since no shadow color is specified for the third shadow effect, the value of the element's 'color' property will be used:

h2 { text-shadow: 3px 3px red, yellow -3px 3px 2px, 3px -3px }

Example(s):

Consider this example:

span.glow {
    background: white;
    color: white;
    text-shadow: black 0px 0px 5px;
}

Here, the 'background' and 'color' properties have the same value and the 'text-shadow' property is used to create a "solar eclipse" effect:

Solar eclipse effect

Note. This property is not defined in CSS1. Some shadow effects (such as the one in the last example) may render text invisible in UAs that only support CSS1.


10. Document grid

10.1. What is document grid?

It is very common for the glyphs in documents written in East Asian languages, such as Chinese or Japanese, to be laid out on the page according to a specified one- or two-dimensional grid. The concept of grid can also be used in other, non-ideographic contexts such as Braille or monospaced layout.

The diagram below represents a fragment of horizontal text on a page with mixed wide-cell and narrow-cell glyphs that a Japanese user intended to be laid out on a grid which resulted in 9 glyphs per line (gray grid lines shown for clarity):

Example of strict (genko) grid applied to mixed Japanese and
English in horizontal layout.

'Genko' grid applied to mixed text

The grid behavior can be set on the line progression, on the block progression or both. The grid on the block progression is determined by the following properties:

The block progression grid is not described in this section as it can be simply achieved by using the appropriate line related properties mentioned above and described in the CSS3 Line module.

The grid on the line progression is obtained by altering the character advance width (or line progression) of inline elements.  There are several modes:

Two properties control this advance width modification: 'line-grid-mode' enables it and 'line-grid-progression' determines its value. The shorthand 'line-grid' allows to set both together.

10.2 Line grid mode: the 'line-grid-mode' property

Name: line-grid-mode
Value: none | ideograph | all
Initial: none
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

Specifies the line grid behavior. Each line grid mode value entails a different set of rules for rendering inline contents. Possible values:

none

No line grid. Standard text alignments apply to the block element.

ideograph
This mode applies in the following ways to the various categories of character:

Mixed glyph layout in strict grid

Mixed glyph layout in strict grid

Object layout in strict grid. Large rectangular object is
centered horizontally within 2 grid spaces

Object layout in strict grid

The ideograph mode disables all special text justification and glyph width adjustment normally applied to the contents of the block element.

If a line break opportunity cannot be found in a text run going over the line boundary, then that text run will be pushed down to the next line and the last part of the previous line will be left blank.

Here is an example of mixed text in ideograph grid mode:

Example of strict grid applied to mixed Japanese and English
text in horizontal layout

Strict grid applied to mixed text

all
This type of grid can be used to achieve mono-spaced layout. The layout rules are simple: all non-connected glyphs are treated as equal, that is every glyph is centered within a single grid space by default. Runs of connected glyphs are treated as strips the same way as in 'ideograph' grid. Justification or any other character-width changing behaviors are disabled for the block element.

Layout in fixed grid mode. All glyphs equally spread out.

Mixed glyph layout in fixed grid

For example:

Example of fixed grid mode in mixed Japanese and English text in
horizontal layout

Fixed grid applied to mixed text

The 'letter-spacing' property does not apply to characters in a grid but does apply for all characters not in the grid (i.e. all characters for 'line-grid-mode: none', non-ideographs for 'line-grid-mode: ideograph' and all non-connected glyphs for 'line-grid-mode: all').

10.3 Line grid progression: the 'line-grid-progression' property

Name: line-grid-progression
Value: text-height | line-height | <length>
Initial: normal
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: <length>

This property affects the line progression of characters subject to the fixed advance width as determined by the 'line-grid-mode' property.

Possible values:

text-height
The computed value of the block element text-height is used.
line-height
The computed value of the block element line-height is used.
<length>
Inline progression dimension of the line grid's unit space.
div.section1 { line-grid-progression: .5in }

would make each glyph in a horizontally laid out part of a document rendered within 0.5 inch of horizontal space:

Example of a line-grid-char setting applied to mixed Japanese
and English text in horizontal layout

Enlarged character grid applied to mixed text in horizontal layout

If the section's layout flow is vertical, then 0.5in becomes the vertical distance between consecutive characters in a column:

Example of a line-grid-char setting applied to mixed Japanese
and English text in vertical-ideographic layout

Enlarged character grid applied to mixed text in vertical-ideographic layout

10.4 Line grid: the 'line-grid' shorthand property

Name: line-grid
Value: <'line-grid-mode'> || <'line-grid-progression'> 
Initial: not defined for shorthand properties
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: see individual properties

The 'line-grid' property is a shorthand property for setting 'line-grid-mode', 'line-grid-progression'. The following is an example of setting the grid in both progression:

div.grid { line-height:20pt;
           text-height: max-size;
           line-stacking-strategy: grid-height;
           line-grid: ideograph line-height; }

This set for the div element a grid with 20pt inline and block progression dimensions. All ideographs will be set in cells sized in multiple of 20pt in both direction.


11. Miscellaneous text formatting

11.1. Capitalization: the 'text-transform' property

Name: text-transform
Value: capitalize | uppercase | lowercase | none
Initial: none
Applies to: all elements and generated content
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property controls capitalization effects of an element's text. Values have the following meanings:

capitalize
Puts the first character of each word in uppercase.
uppercase
Puts all characters of each word in uppercase.
lowercase
Puts all characters of each word in lowercase.
none
No capitalization effects.

Although limited, the case mapping process has some language dependencies. Some well known examples are Turkish and Greek. See HTML [HTML40] for ways to find the language of an HTML element. XML, and consequently [XHTML1.0], uses an attribute called xml:lang and there may be other language-specific language-specific methods to determine the language.

The case mapping rules for the character repertoire specified by the Unicode Standard 3.0 can be found on the Unicode Consortium web site: http://www.unicode.org.

Conforming user agents must support case mapping rules according to the Unicode Standard 3.0 for all characters specified by that standard. Note that the conformance rule is more stringent than the ones specified in lower levels of CSS.

Example:

In this example, all text in an h1 element is transformed to uppercase text.

h1 { text-transform: uppercase }

11.2. Hanging punctuation: the 'hanging-punctuation' property

Name: hanging-punctuation
Value: none | start | end | both
Initial: none
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property determines whether a punctuation mark, if one is present, may be placed outside the content area in the padding or margin area, at the start or at the end of a full line of text. Allowing a punctuation to 'hang' at the end of a line is is a common practice in East Asian typography. It is the responsibility of the style writer to create meaningful padding and margin areas to allow effective rendering of the punctuation. It should also be noted that compression may occur in the line, including compression of the punctuation characters independently of this effect.

Possible values:

none
Punctuation is not allowed to be placed outside the content area.
start
A leading punctuation, if present, may overhang at the start of the content area. It is placed in the padding or margin area.
end
An ending punctuation, if present, may overhang at the end of the content area. It is placed in the padding or margin area.
both
A punctuation, if present, may overhang at either the start or the end of the content area.

Here is an example where overhanging is not allowed:

Example of Japanese text with hanging punctuation disabled

No hanging punctuation allowed (the punctuation and the character preceding it shown in blue for clarity)

In the following example overhanging is allowed at the end of the content area.

Example of Japanese text with hanging punctuation enabled

Hanging punctuation appearing in the end of line padding area (the punctuation and the character preceding it shown in blue for clarity)

Note: User agents should follow the convention of the scripts for trimming either only the first lines or all lines. For example, in Roman text, only a punctuation appearing at the starting point of the first line may be placed outside the content area. It would look improper in other lines. The following figure shows an example of correct usage.

Example of leading punctuation in Roman typography

11.3. Combining text: the 'text-combine' property'

Name: text-combine
Value: none | letters | lines
Initial: none
Applies to: all elements and generated content
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value (except for initial and inherit)

This property controls the creation of composite characters (a.k.a. "kumimoji") or lines (a.k.a. "warichu").

Possible values:

none
No composite characters are created.
letters
Combines glyphs to fit within the space of a single wide-cell glyph, by reducing them in size and stacking them next to and/or on top of each other. This effect is commonly used in Asian typography.

No more than 5 glyphs can be combined at a time. If more than five are included inside of the element with this property setting, only the first five are combined. The rest is rendered as regular text. If the text to be combined results in a single glyph, no special combination effect occurs. The following texts shows the arrangement for 2, 3, 4 and 5 characters:

Diagram of two-character kumimoji

Diagram of three-character kumimoji

Diagram of four-character kumimoji

Diagram of five-character kumimoji

The valid "Kumimoji" arrangements

The following mark-up:

span.kumimoji { text-combine: letters }

could make the following 4 characters appear as one (shown in blue for clarity):

Example of four-character kumimoji in Japanese

"Kumimoji" applied to four characters

lines
Combines the glyphs so they fit into two lines of equal length and height, whose combined height is equal to or slightly greater than the height of the line they appear in. The combined lines appear inline with the surrounding text. The Japanese Standard [JIS-X-4051] describes recommended guidelines for this feature.  A summary of these guidelines is provided here:
  1. This combination is restricted to two lines.
  2. The combination should be preceded and followed by bracket or parenthesis characters
  3. The combination may be broken across several lines, each line box representing its own logical subset of the combination.

The following figure shows a typical usage for this feature.

Diagram of character layout in warichu

Glyph layout in "Warichu"

The following mark-up:

span.warichu { text-combine: lines }
    

would make the enclosed text look like the following (shown in blue for clarity):

Example of warichu in Japanese

"Warichu" applied to 10 characters

12. Properties index

In addition to the specified values, all properties take the

Property Values Initial Applies to Inh. Percentages Media
all-space-treatment preserve | collapse collapse all elements and generated content yes N/A visual
direction ltr | rtl ltr all elements and generated content, but see prose yes N/A visual
glyph-orientation-horizontal <angle> 0deg all inline-level elements yes N/A visual
glyph-orientation-vertical <angle> | auto auto all elements and generated content yes N/A visual
hanging-punctuation none | start | end | both none block-level elements yes N/A visual
kerning-mode none | [pair || contextual] none all elements and generated content yes N/A visual
kerning-pair-threshold auto | <length> auto all elements and generated content yes N/A visual
line-grid <'line-grid-mode'> || <'line-grid-progression'> not defined for shorthand properties block-level elements yes N/A visual
line-grid-mode none | ideograph | allnone block-level elements yes N/Avisual
line-grid-progression text-height | line-height | <length>normalblock-level elements yes N/Avisual
letter-spacing normal | <length> normal all elements and generated content yes N/A visual
line-break normal | strict normal all elements and generated content yes N/A visual
linefeed-treatment auto | ignore | preserve | treat-as-space | treat-as-zero-width-space | ignore-if-after-linefeedtreat-as-space all elements and generated content yes N/A visual
max-font-size <font-size> | auto auto all elements and generated content yes element's computed 'font-size' visual
min-font-size <font-size> | auto auto all elements and generated content yes element's computed 'font-size' visual
punctuation-trim none | start none block-level elements yes N/A visual
text-script auto | none | <script> auto all elements and generated content yes N/A visual
text-align start | end | left | right | center | justify | <string> start block-level elements yes N/A visual
text-align-last auto | start | end | center | justify | size auto block-level elements yes N/A visual
text-autospace none | [ideograph-numeric || ideograph-alpha || ideograph-space || ideograph-parenthesis] none all elements and generated content yes N/A visual
text-blink none | blinknoneall elements and generated content noN/Avisual
text-combine none | letters | lines none all elements and generated content no N/A visual
text-decoration none | [ underline || overline || line-through || blink] not defined for shorthand propertiesall elements and generated content no (see prose) N/A visual
text-indent <length> | <percentage> 0 block-level elements yes refers to width of containing block visual
text-justify auto | inter-word | inter-ideograph | distribute | newspaper | inter-cluster | kashida auto block-level elements yes N/A visual
text-justify-trim none | punctuation | punctuation-and-kana punctuation block-level elements yes N/A visual
text-kashida-space <percentage> 0% block-level elements yes as described visual
text-line-through <'text-line-through-style'> || <'text-line-through-color'> || <'text-line-through-mode'> not defined for shorthand properties all elements and generated content no N/A visual
text-line-through-color auto | <color> auto all elements and generated content no N/A visual
text-line-through-mode continuous | words continuous all elements and generated content no N/A visual
text-line-through-style none | solid | double | dotted | thick | dashed | dot-dash | dot-dot-dash | wave none all elements and generated content no N/A visual
text-overflow <'text-overflow-mode'> || <'text-overflow-ellipsis'> not defined for shorthand properties all block-level elements no N/A visual
text-overflow-ellipsis [<ellipsis-end> | <uri> [, <ellipsis-after> | <uri>]?] "..." all block-level elements no N/A visual
text-overflow-mode clip | ellipsis | ellipsis-word clip all block-level elements no N/A visual
text-overline <'text-overline-style'> || <'text-overline-color'> || <'text-overline-mode'> not defined for shorthand properties all elements and generated content no N/A visual
text-overline-color auto | <color> auto all elements and generated content no N/A visual
text-overline-mode continuous | words continuous all elements and generated content no N/A visual
text-overline-style none | solid | double | dotted | thick | dashed | dot-dash | dot-dot-dash | wave none all elements and generated content no N/A visual
text-shadow none | [<color> || <length> <length> <length>? ,]* [<color> || <length> <length> <length>?] none all elements and generated content no (see prose) N/A visual
text-transform capitalize | uppercase | lowercase | none none all elements and generated content yes N/A visual
text-underline <'text-underline-style'> || <'text-underline-color'> || <'text-underline-mode'> || <'text-underline-position'> not defined for shorthand properties all elements and generated content no N/A visual
text-underline-color auto | <color> auto all elements and generated content no N/A visual
text-underline-mode continuous | words continuous all elements and generated content no N/A visual
text-underline-position auto-pos | before-edge | after-baseline | after-edge auto-pos all elements and generated content no N/A visual
text-underline-style none | solid | double | dotted | thick | dashed | dot-dash | dot-dot-dash | wave none all elements and generated content no N/A visual
unicode-bidi normal | embed | bidi-override normal all elements and generated content, but see prose no N/A visual
white-space normal | pre | nowrap | pre-wrap | pre-linesnot defined for shorthand properties all elements and generated content yes N/A visual
white-space-treatment ignore | preserve | ignore-if-before-linefeed | ignore-if-after-linefeed | ignore-if-surrounding-linefeed ignore-if-surrounding-linefeed all elements and generated content yes N/A visual
word-break <'word-break-CJK'> || <'word-break-inside'> see individual properties all elements and generated content yes N/A visual
word-break-CJK normal | break-all | keep-all normal all elements and generated content yes N/A visual
word-break-inside normal | hyphenate normal all elements and generated content yes N/A visual
word-spacing normal | none | <length> normal all elements and generated content yes N/A visual
wrap-option wrap | hard-wrap | soft-wrap | emergency wrap all elements and generated content yes N/A visual
writing-mode lr-tb | rl-tb | tb-rl | tb-lr | bt-rl | bt-lr | lr | rl | tb lr-tb all elements and generated content yes N/A visual

The following properties are defined in other specifications:

14. Profiles

There are 3 modules defined by this chapter:

CSS1 text model:

CSS2 text model:

CSS3 text model:

The CSS1 text module is made of the following properties/values:

Name Values Initial Applies to Inherited Percentages Media groups
'letter-spacing' normal | <length> normal all elements yes N/A N/A
'text-align' left | right | center | justify start block-level elements yes N/A N/A
'text-decoration' none | [ underline || overline || line-through || blink ] none all elements no (see prose) N/A N/A
'text-indent' <length> | <percentage> | inherit 0 block-level elements yes refers to width of containing block N/A
'text-transform' capitalize | uppercase | lowercase | none | inherit none all elements yes N/A N/A
'word-spacing' normal | <length> normal all elements yes N/A N/A
'white-space' normal | pre | nowrap normal all elements yes N/A N/A

Concerning the 'text-align' property, a conforming CSS1 user agent my interpret the value 'justify' as 'left' or 'right', depending on whether the element's current text direction is left-to-right or riht-to-left respectively.

The following table describes the CSS2 text module. Because all properties have added the 'inherit' value and have a media type, all CSS1 properties have been specified below as well. The properties added are: 'direction', 'text-shadow' and 'unicode-bidi'. In addition, the 'text-align' has a new value: <string>. Concerning the 'text-align' property, a conforming CSS1 user agent my interpret the value 'justify' as 'left' or 'right', depending on whether the element's current text direction is left-to-right or riht-to-left respectively. Properties that applies to all elements also applies to generated content.

.Name Values Initial Applies to Inherited Percentages Media groups
'direction' ltr | rtl | inherit ltr all elements and generated content, but see prose yes N/A visual
'letter-spacing' normal | <length> | inherit normal all elements and generated content yes N/A visual
'text-align' left | right | center | justify | <string> | inherit start block-level elements yes N/A visual
'text-decoration' none | [ underline || overline || line-through || blink] | inherit none all elements and generated content no (see prose) N/A visual
'text-indent' <length> | <percentage> | inherit 0 block-level elements yes refers to width of containing block visual
'text-shadow' none | [<color> || <length> <length> <length>? ,]* [<color> || <length> <length> <length>?] | inherit none all elements and generated content no (see prose) N/A visual
'text-transform' capitalize | uppercase | lowercase | none | inherit none all elements and generated content yes N/A visual
'unicode-bidi' normal | embed | bidi-override | inherit normal all elements and generated content, but see prose no N/A visual
'white-space' normal | pre | nowrap | inherit normal block-level elements yes N/A visual
'word-spacing' normal | <length> | inherit normal all elements and generated content N/A visual

The CSS3 module adds the following properties:

It also modifies the following properties as described:


15. Glossary

Hangul
Subset of the Korean writing system.
Hanja
Subset of the Korean writing system that utilizes ideographic characters borrowed or adapted from the Chinese writing system. Also see Kanji.
Hiragana
Japanese syllabic script, or character of that script. Rounded and cursive in appearance. Subset of the Japanese writing system, used together with kanji and katakana. In recent times, mostly used to write Japanese words when kanji are not available or appropriate, and word endings and particles. Also see Katakana.
Ideograph
A character that is used to represent an idea, word, or word component, in contrast to a character from an alphabetic or syllabic script. The most well-known ideographic script is used (with some variation) in East Asia (China, Japan, Korea,...).
Kana
Collective term for hiragana and katakana.
Kanji
Japanese term for ideographs; ideographs used in Japanese. Subset of the Japanese writing system, used together with hiragana and katakana. Also see Hanja.
Kashida
Arabic elongation character.
Katakana
Subset of the Japanese writing system consisting of phonetic characters used to represent Roman words. Also see Hiragana.
Kinsoku
Japanese term for a set (or sets) of line breaking restrictions.
Kumimoji
Composite character consisting of up to 5 characters that are reduced in size and combined to fit within the space of a single character.
Logograph, Logogram
Character in the Chinese (or East Asian in general) writing system that represents an entire word.
Ruby
A run of text that appears in the vicinity of another run of text and serves as an annotation or a pronunciation guide for that text.
Tate chu yoko
Run of horizontal text inside of a column of vertical text; frequently used in East Asian documents for displaying certain numbers, such as years.
Warichu
A run of text of reduced font size that appears inside of a line of text as two lines of equal height and length


Appendix A: Vertical Layout Effect on CSS Properties

In general, the existing [CSS2] properties that imply directionality or position are absolute, i.e. "left" means "left" and "top" means "top" regardless of the writing mode of the page. The purpose of this appendix however is to list the exceptions to that rule and clarify ambiguities. If a property does not appear in this list, it is intended to be interpreted as absolute, i.e. it does not rotate when the layout mode changes.

CSS Property Effect in vertical layout
'clear' 'float' and 'clear' property values interpretation is absolute in horizontal flow and logical in vertical flow (left is start, right is end)
'direction' relative (logical), i.e. ltr implies top-to-bottom character progression in vertical layout
'display' relative (logical), i.e. the values that are directional (table-) are relative to the element orientation as specified by the writing mode.
'float' [see the note about 'clear']
'line-height' relative (logical), i.e. this controls the "height" of a line if horizontal, or the "width", if vertical. In other words, this controls the size of the line in the dimension perpendicular to the baseline.
'quotes' relative (logical), the concept of open-quotes and close-quotes is already used in CSS. Note that the quote glyph may vary depending on the glyph-orientation.
'text-align' 'left' and 'right' are physical in horizontal inline progression and UA dependent in vertical inline progression. 'start' and 'end' are always relative.
'text-decoration' relative (logical), i.e. underline and overline are parallel to the baseline. Underline appears on the left side of a vertical column and overline appears on the right
'unicode-bidi' relative (logical), i.e. it affects glyph progression regardless of layout
'vertical-align' relative (logical), top and bottom values maps to before and after-edge values in baseline alignment properties

Acknowledgments

This specification would not have been possible without the help from:

Ayman Aldahleh, Stephen Deach, Martin Dürst, Laurie Anna Edlund, Ben Errez, Yaniv Feinberg, Arye Gittelman, Richard Ishida, Koji Ishii, Masayasu Ishikawa, Michael Jochimsen, Eric LeVine, Chris Pratley, Rahul Sonnad, Frank Tang, Chris Thrasher, Masafumi Yabe.


References

Normative references

Other references

[CSS2]
Bert Bos; Hċkon Wium Lie; Chris Lilley; Ian Jacobs. Cascading Style Sheets, level 2. 1998. W3C Recommendation. URL: http://www.w3.org/TR/REC-CSS2
[CSS3-background]
Tim Boland; Bert Bos. CSS3 module: backgrounds. 19 February 2002. W3C working draft. (Work in progress.) URL: http://www.w3.org/TR/2002/WD-css3-background-20020219
[CSS3-color]
Tantek Çelik; Chris Lilley. CSS3 module: color. 5 March 2001. W3C working draft. (Work in progress.) URL: http://www.w3.org/TR/2001/WD-css3-color-20010305
[CSS3-fonts]
Michel Suignard; Chris Lilley. CSS3 module: fonts. 31 July 2001. W3C working draft. (Work in progress.) URL: http://www.w3.org/TR/2001/WD-css3-fonts-20010731
[HTML40]
Raggett, D.; Le Hors, A.; Jacobs, I.. HTML 4.0 Specification (revised). Apr 1998. W3C Recommendation. URL: http://www.w3.org/TR/1998/REC-html40-19980424
[HTML401]
Raggett, D.; Le Hors, A.; Jacobs, I.. HTML 4.01 Specification. Dec 1999. W3C Recommendation. URL: http://www.w3.org/TR/1999/REC-html401-19991224
[ISO15924]
Code for the representation of names of scripts. International Organization for Standardization.. 1998. ISO 15924:1998. Draft International Standard
[JIS-X-4051]
Line composition rules for Japanese documents. Japanese Standards Association. 1995. JIS X 4051-1995. In Japanese
[RFC2119]
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. Internet RFC 2119. URL: http://www.ietf.org/rfc/rfc2119.txt
[SVG1.0]
Various. Scalable Vector Graphics (SVG) 1.0 Specification. Sep 2001. W3C Recommendation. URL: http://www.w3.org/TR/2001/REC-SVG-20010904
[UAX-11]
Asmus Freytag. East Asian Width. 15 March 2002. Unicode Standard Annex #11. URL: http://www.unicode.org/unicode/reports/tr11/tr11-10
[UAX-14]
Asmus Freytag. Line Breaking Properties. 15 March 2002. Unicode Standard Annex #14. URL: http://www.unicode.org/unicode/reports/tr14/tr14-12
[UNICODE]
The Unicode Consortium. Book version: The Unicode Standard: Version 3.0. Addison Wesley Longman. 2000. ISBN 0-201-61633-5. Online version: The Unicode Standard: Version 3.2.0, URL:
http://www.unicode.org/unicode/standard/versions/enumeratedversions.html#Unicode_3_2_0
For more information, consult the Unicode Consortium's home page at http://www.unicode.org/
[UTR-24]
Mark Davis. Script Names. 1st April 2002. Unicode Technical Report #24. URL: http://www.unicode.org/unicode/reports/tr24/tr24-4.html
[XHTML1.0]
Steven Pemberton; et al. XHTML 1.0: The Extensible HyperText Markup Language. Jan 2000. W3C Recommendation. URL: http://www.w3.org/TR/2000/REC-xhtml1-20000126
[XHTMLMOD]
Adams, Robert; Altheim, Murray; et al. Modularization of XHTML. Apr 2001. W3C Recommendation. URL: http://www.w3.org/TR/2001/REC-xhtml-modularization-20010410
[XML1.0]
Tim Bray; Jean Paoli; C. M. Sperberg-McQueen; Eve Maler. Extensible Markup Language (XML) 1.0 (Second Edition). Oct 2000. W3C Recommendation. URL: http://www.w3.org/TR/2000/REC-xml-20001006
[XSL1.0]
Adler, Sharon; Berglund, Anders; et al. Extensible Stylesheet Language (XSL) Version 1.0. Oct 2001. W3C Recommendation. URL: http://www.w3.org/TR/2001/REC-xsl-20011015