Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
This CSS3 module defines properties for text manipulation and specifies their processing model. It covers line breaking, justification and alignment, white space handling, text decoration and text transformation.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This CSS module has been produced as a combined effort of the W3C Internationalization Activity, and the Style Activity and is maintained by the CSS Working Group. It also includes contributions made by participants in the XSL Working Group (members only).
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
Feedback on this draft should be posted to the (archived) public mailing list www-style@w3.org (see instructions) with [css3-text] in the subject line. You are strongly encouraged to complain if you see something stupid in this draft. The editors will do their best to respond to all feedback.
The following features are at risk and may be cut from the spec during its CR period if there are no (correct) implementations:
tab-size
’ property
start end
’ and ‘<string>
’ values of ‘text-align
’
hanging-punctuation
’ property
word-spacing
’
text-decoration-skip
’ property /
‘ink
’ value
text-decoration-line
’ property
text-decoration-color
’ property
text-decoration-style
’ property
text-decoration
’ property
text-decoration-skip
’ property
text-underline-position
’ property
text-shadow
’ property
[document here]
This draft describes features that are specific to certain scripts. There is an ongoing discussion about where these features belong: in existing CSS properties, in new CSS properties, or perhaps in other specifications.
This module replaces and extends the text-level features defined in [CSS21] chapter 16.
This specification follows the CSS property definition conventions from [CSS21]. Value types not defined in this specification are defined in CSS Level 2 Revision 1 [CSS21]. Other CSS modules may expand the definitions of these value types: for example [CSS3COLOR], when combined with this module, expands the definition of the <color> value type as used in this specification.
In addition to the property-specific values listed in their definitions, all properties defined in this specification also accept the inherit keyword as their property value. For readability it has not been repeated explicitly.
A grapheme cluster is what a language user considers to be a character or a basic unit of the script. The term is described in detail in the Unicode Technical Report: Text Boundaries [UAX29]. This specification uses the extended grapheme cluster definition in [UAX29] (not the legacy grapheme cluster definition). The UA may further tailor the definition as allowed by Unicode. Within this specification, the ambiguous term character is used as a friendlier synonym for grapheme cluster. See Characters and Properties for how to determine the Unicode properties of a character.
A letter for the purpose of this specification is a character belonging to one of the Letter or Number general categories in Unicode. [UAX44]
The rendering characteristics of a character divided by an element boundary is undefined: it may be rendered as belonging to either side of the boundary, or as some approximation of belonging to both. Authors are forewarned that dividing grapheme clusters by element boundaries may give inconsistent or undesired results.
text-transform
’ propertyName: | text-transform |
---|---|
Value: | none | [ [ capitalize | uppercase | lowercase ] || full-width || full-size-kana ] |
Initial: | none |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property transforms text for styling purposes. Values have the following meanings:
none
’
capitalize
’
uppercase
’
lowercase
’
full-width
’
full-size-kana
’
The case mapping rules for the character repertoire specified by the Unicode Standard can be found on the Unicode Consortium Web site [UNICODE]. The UA must use the full case mappings for Unicode characters, including any conditional casing rules, as defined in Default Case Algorithm section. If (and only if) the content language of the element is, according to the rules of the document language, known, then any appropriate language-specific rules must be applied as well. These minimally include, but are not limited to, the language-specific rules in Unicode's SpecialCasing.txt.
For example, in Turkish there are two “i”s, one with a dot—“İ” and “i”— and one without—“I” and “ı”. Thus the usual case mappings between “I” and “i” are replaced with a different set of mappings to their respective undotted/dotted counterparts, which do not exist in English. This mapping must only take effect if the language is known to be Turkish or Azeri; in other languages, the usual mapping of “I” and “i” is required. This rule is thus conditionally defined in Unicode's SpecialCasing.txt file.
The definition of "word" used for ‘capitalize
’ is UA-dependent; [UAX29] is suggested (but not
required) for determining such word boundaries. Authors should not expect
‘capitalize
’ to follow
language-specific titlecasing conventions (such as skipping articles in
English).
The definition of fullwidth and halfwidth forms can be found on the Unicode consortium web site at [UAX11]. The mapping to fullwidth form is defined by taking code points with the <wide> or the <narrow> tag in their Decomposition_Mapping in [UAX44]. For the <narrow> tag, the mapping is from the code point to the decomposition (minus <narrow> tag), and for the <wide> tag, the mapping is from the decomposition (minus the <wide> tag) back to the original code point.
The mappings for small Kana to normal Kana are defined in Small Kana Mappings.
When multiple values are specified and therefore multiple transformations need to be applied, they are applied in the following order:
capitalize
’, ‘uppercase
’, and ‘lowercase
’
full-width
’
full-size-kana
’
Text transformation happens after white
space processing, which means that ‘full-width
’ transforms only preserved U+0020 spaces
to U+3000.
The following example converts the ASCII characters in abbreviations in Japanese to their fullwidth variants so that they lay out and line break like ideographs:
abbr:lang(ja) { text-transform: full-width; }
CSS may introduce the ability to create custom mapping
tables for less common text transforms, such as by an ‘@text-transform
’
rule similar to ‘@counter-style
’ from
[CSS3LIST], and
this mechanism may be used to replace ‘full-size-kana
’.
The source text of a document often contains formatting that is not relevant to the final rendering: for example, breaking the source into segments (lines) for ease of editing or adding white space characters such as tabs and spaces to indent the source code. CSS white space processing allows the author to control interpretation of such formatting: to preserve or collapse it away when rendering the document. Note that white space processing in CSS interprets white space characters only for rendering: it has no effect on the underlying document data.
CSS does not define document segmentation rules. Segments could be separated by a particular newline seqence (such as a line feed or CRLF pair), or delimited by some other mechanism, such as the SGML RECORD-START and RECORD-END tokens. For CSS processing, each document-defined segment break, CRLF sequence (U+000D U+000A), carriage return (U+000D), and line feed (U+000A) in the text is treated as a segment break, which is then interpreted for rendering as defined below.
Note that the document parser may have not only normalized segment breaks, but also collapsed other space characters or otherwise processed white space according to markup rules. Because CSS processing occurs after the parsing stage, it is not possible to restore these characters for styling. Therefore, some of the behavior specified below can be affected by these limitations and may be user agent dependent.
Note that anonymous inlines consisting entirely of collapsible white space are removed from the rendering tree. See [CSS21] section 9.2.2.1
Control characters (Unicode class Cc) other than tab (U+0009), line feed (U+000A), and carriage return (U+000D) are ignored for the purpose of rendering.
text-space-collapse
’ propertyName: | text-space-collapse |
---|---|
Value: | collapse | preserve | preserve-breaks |
Initial: | collapse |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property declares whether and how white space inside the element is collapsed. Values have the following meanings, which must be interpreted according to the white space processing rules:
collapse
’
preserve
’
preserve-breaks
’
See White Space Processing Rules
for details on how white space collapses. An informative summary of
‘collapse
’ is presented below:
tab-size
’ propertyName: | tab-size |
---|---|
Value: | <integer> | <length> |
Initial: | 8 |
Applies to: | block containers |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property determines the measure of the tab character (U+0009) when rendered. Integers represent the measure in space characters (U+0020). Negative integers are not allowed.
White space processing affects only spaces (U+0020), tabs (U+0009), and segment breaks.
For each inline (including anonymous inlines) within an inline formatting context, white space characters are handled as follows, ignoring bidi formatting characters as if they were not there:
If ‘text-space-collapse
’ is set to
‘collapse
’ or ‘preserve-breaks
’, white space characters are
considered collapsible and are processed by
performing the following steps:
If ‘text-space-collapse
’ is set to
‘preserve
’, any sequence of spaces is
treated as a sequence of non-breaking spaces. However, a line breaking
opportunity exists at the end of the sequence.
Then, the entire block is rendered. Inlines are laid out, taking bidi
reordering into account, and wrapping as specified by the ‘text-wrap
’
property.
As each line is laid out,
tab-size
’ property.
text-wrap
’ set to ‘normal
’ or ‘avoid
’ the UA may visually collapse their
character advance widths.
White space that was not removed during the white space processing steps is called preserved white space.
Consider the following markup fragment, taking special note of spaces (with varied backgrounds and borders for emphasis and identification):
<ltr>A <rtl> B </rtl> C</ltr>
where the <ltr>
element represents a left-to-right
embedding and the <rtl>
element represents a
right-to-left embedding. If the ‘text-space-collapse
’ property is set to
‘collapse
’, the above processing model
would result in the following:
This would leave two spaces, one after the A in the left-to-right embedding level, and one after the B in the right-to-left embedding level. This is then ordered according to the Unicode bidirectional algorithm, with the end result being:
A BC
Note that there are two spaces between A and B, and none between B and C. This is best avoided by putting spaces outside the element instead of just inside the opening and closing tags and, where practical, by relying on implicit bidirectionality instead of explicit embedding levels.
When ‘text-space-collapse
’ is ‘preserve-breaks
’, segment breaks are not collapsible and are transformed into a
preserved line feed (U+000A).
When segment breaks are collapsible, they are either transformed into a space (U+0020) or removed depending on the context before and after the break.
Note that the white space processing rules have already removed any tabs and spaces after the segment break before these checks take place.
Comments on how well this would work in practice would be very much appreciated, particularly from people who work with Thai and similar scripts.
white-space
’ propertyName: | white-space |
---|---|
Value: | normal | pre | nowrap | pre-wrap | pre-line |
Initial: | not defined for shorthand properties |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | see individual properties |
The ‘white-space
’ property is a shorthand for
the ‘text-space-collapse
’ and ‘text-wrap
’
properties. Not all combinations are represented. Values have the
following meanings:
normal
’
text-space-collapse
’ to ‘collapse
’ and ‘text-wrap
’ to ‘normal
’
pre
’
text-space-collapse
’ to ‘preserve
’ and ‘text-wrap
’ to ‘none
’
nowrap
’
text-space-collapse
’ to ‘collapse
’ and ‘text-wrap
’ to ‘none
’
pre-wrap
’
text-space-collapse
’ to ‘preserve
’ and ‘text-wrap
’ to ‘normal
’
pre-line
’
text-space-collapse
’ to ‘preserve-breaks
’ and ‘text-wrap
’ to
‘normal
’
The following informative table summarizes the behavior of various
‘white-space
’ values:
New Lines | Spaces and Tabs | Text Wrapping | |
---|---|---|---|
normal | Collapse | Collapse | Wrap |
pre | Preserve | Preserve | No wrap |
nowrap | Collapse | Collapse | No wrap |
pre-wrap | Preserve | Preserve | Wrap |
pre-line | Preserve | Collapse | Wrap |
In most writing systems, in the absence of hyphenation a line break occurs only at word boundaries. Many writing systems use spaces or punctuation to explicitly separate words, and line break opportunities can be identified by these characters. Scripts such as Thai, Lao, and Khmer, however, do not use spaces or punctuation to separate words. Although the zero width space (U+200B) can be used as an explicit word delimiter in these scripts, this practice is not common. As a result, a lexical resource is needed to correctly identify break points in such texts.
In several other writing systems, (including Chinese, Japanese, Yi, and sometimes also Korean) a line break opportunity is based on character boundaries, not word boundaries. In these systems a line can break anywhere except between certain character combinations. Additionally the level of strictness in these restrictions can vary with the typesetting style.
CSS does not fully define where line breaking opportunities occur, however some controls are provided to distinguish common variations. For breaking opportunities created by characters that disappear at the line break (i.e. spaces), properties on the element containing that character control the line breaking at that opportunity. For breaking opportunities defined by the boundary between two characters, the properties on the element containing the boundary control breaking. For break opportunities given by the first or last character of a box, the break occurs immediately before/after the box rather than breaking the box.
Further information on line breaking conventions can be found in [JLREQ] and [JIS4051] for Japanese, [ZHMARK] for Chinese, and in [UAX14] for all scripts in Unicode.
Any guidance for appropriate references here would be much appreciated.
Floated and absolutely-positioned elements do not introduce a line breaking opportunity. The line breaking behavior of a replaced element is equivalent to that of the Object Replacement Character (U+FFFC).
line-break
’ propertyName: | line-break |
---|---|
Value: | auto | loose | normal | strict |
Initial: | auto |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property specifies the strictness of line-breaking rules applied within an element: particularly how line-breaking interacts with punctuation. Values have the following meanings:
auto
’
loose
’
normal
’
strict
’
CSS distinguishes between three levels of strictness in the rules for implicit line breaking. The precise set of rules in effect for each level is up to the UA and should follow language conventions. However, this specification does recommend that:
strict
’ line breaking and allowed in ‘normal
’ and ‘loose
’:
normal
’ and ‘strict
’ line breaking and allowed in ‘loose
’:
In CSS3 no distinction is made among the levels of strictness in non-CJK text: only CJK codepoints are affected, unless the text is marked as Chinese or Japanese, in which case some additional common codepoints are affected. However a future level of CSS may add behaviors affecting non-CJK text.
Support for this property is optional. It is recommended for UAs that wish to support CJK typography and strongly recommended for UAs in the Japanese market.
The CSSWG recognizes that in a future edition of the specification finer control over line breaking may be necessary to satisfy high-end publishing requirements.
word-break
’ propertyName: | word-break |
---|---|
Value: | normal | keep-all | break-all |
Initial: | normal |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property specifies line break opportunities within words. Values have the following meanings:
normal
’
break-all
’
keep-all
’
normal
’. This option is
mostly used where the presence of word separator characters still creates
line-breaking opportunities, as in Korean.
Here's a mixed-script sample text:
这是一些汉字, and some Latin, و کمی نوشتنن عربی, and some complex LTR.
The break-points are determined as follows (indicated by ‘·’):
word-break: normal
’
这·是·一·些·汉·字,·and·some·Latin,·و·کمی·نوشتنن·عربی·and·some·complex·LTR.
word-break: break-all
’
这·是·一·些·汉·字·a·n·d·s·o·m·e·L·a·t·i·n,·و·ﮐ·ﻤ·ﻰ·ﻧ·ﻮ·ﺷ·ﺘ·ﻦ·ﻋ·ﺮ·ﺑ·ﻰ,·a·n·d·s·o·m·e·c·o·m·p·l·e·x·L·T·R.
word-break: keep-all
’
这是一些汉字,·and·some·Latin,·و·کمی·نوشتنن·عربی,·and·some·complex·LTR.
When shaping scripts such as Arabic are allowed to break within words
due to ‘break-all
’, the characters must
still be shaped as if the word were not broken.
Hyphenation allows the controlled splitting of words to improve the layout of paragraphs. CSS Text Level 3 does not define the exact rules for hyphenation, however UAs are strongly encouraged to optimize their line-breaking implementation to choose good break points and appropriate hyphenation points.
Hyphenation is controlled with the ‘hyphens
’ property.
Hyphenation opportunities are not considered when calculating
‘min-content
’ intrinsic sizes.
hyphens
’
propertyName: | hyphens |
Value: | none | manual | auto |
---|---|
Initial: | manual |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property controls whether hyphenation is allowed to create more break opportunities within a line of text. Values have the following meanings:
none
’
manual
’
In Unicode, U+00AD is a conditional "soft hyphen" and U+2010 is an explicit hyphen. Unicode Standard Annex #14 describes the role of soft hyphens in Unicode line breaking. [UAX14] In HTML, ­ represents the soft hyphen character which suggests a hyphenation opportunity.
ex­ample
auto
’
Correct automatic hyphenation requires a hyphenation resource
appropriate to the language of the text being broken. The UA is therefore
only required to automatically hyphenate text for which the author has
declared a language (e.g. via HTML lang
or XML
xml:lang
) and for which it has an appropriate hyphenation
resource.
When shaping scripts such as Arabic are allowed to break within words due to hyphenation, the characters must still be shaped as if the word were not broken.
For example, if the word “نوشتنن” were hyphenated, it would appear as “ﻧﻮﺷ-ﺘﻦ” not as “ﻧﻮﺵ-ﺗﻦ”.
Text wrapping is controlled by the ‘text-wrap
’ and ‘overflow-wrap
’ properties:
text-wrap
’ propertyName: | text-wrap |
---|---|
Value: | normal | none | avoid |
Initial: | normal |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property specifies the mode for text wrapping. Possible values:
normal
’
none
’
avoid
’
normal
’.
Regardless of the ‘text-wrap
’ value, lines always break at
forced breaks: for all values, line-breaking behavior defined for the BK,
CR, LF, CM NL, and SG line breaking classes in [UAX14] must be honored.
When ‘text-wrap
’ is set to ‘normal
’ or ‘avoid
’, UAs that allow breaks at punctuation
other than spaces should prioritize breakpoints. For example, if breaks
after slashes have a lower priority than spaces, the sequence "check /etc"
will never break between the ‘/
’ and
the ‘e
’. The UA may use the width
of the containing block, the text's language, and other factors in
assigning priorities. As long as care is taken to avoid such awkward
breaks, allowing breaks at appropriate punctuation other than spaces is
recommended, as it results in more even-looking margins, particularly in
narrow measures.
Using ‘text-wrap: avoid
’, the
priority of breakpoints can be set to reflect the intended grouping of
text.
Given the rules
footer { text-wrap: avoid; /* inherits to all descendants */ }
and the following markup:
<footer> <venue>27th Internationalization and Unicode Conference</venue> • <date>April 7, 2005</date> • <place>Berlin, Germany</place> </footer>
In a narrow window the footer could be broken as
27th Internationalization and Unicode Conference • April 7, 2005 • Berlin, Germany
or in a narrower window as
27th Internationalization and Unicode Conference • April 7, 2005 • Berlin, Germany
but not as
27th Internationalization and Unicode Conference • April 7, 2005 • Berlin, Germany
overflow-wrap
’ propertyName: | overflow-wrap |
---|---|
Value: | normal | break-word |
Initial: | normal |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property specifies whether the UA may break within a word to
prevent overflow when an otherwise-unbreakable string is too long to fit
within the line box. It only has an effect when ‘text-wrap
’ is
either ‘normal
’ or ‘avoid
’. Possible values:
normal
’
word-break:
keep-all
’ may be relaxed to match ‘word-break: normal
’ and the various hyphenation
limit properties may be ignored if there are no otherwise-acceptable
break points in the line.
break-word
’
Break opportunities not part of ‘overflow-wrap:
normal
’ line breaking are not considered when calculating
‘min-content
’ intrinsic sizes.
For legacy reasons, UAs may also accept ‘word-wrap
’ as an alternate name for the
‘overflow-wrap
’ property. However this
syntax non-conforming in author style sheets.
text-align
’ propertyName: | text-align |
---|---|
Value: | [ [ start | end | left | right | center ] || <string> ] | justify | match-parent | start end |
Initial: | start |
Applies to: | block containers |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value, except for ‘match-parent ’ (see prose)
|
This property describes how inline contents of a block are aligned along the inline axis if the contents do not completely fill the line box. Values have the following meanings:
start
’
end
’
left
’
left
’
aligns to the edge of the line box that would be the start edge for
left-to-right text.)
right
’
right
’
aligns to the edge of the line box that would be the end edge for
left-to-right text.)
center
’
justify
’
text-justify
’ property.
<string>
’
match-parent
’
inherit
’ except that an inherited
‘start
’ or ‘end
’ keyword is calculated against its
parent's ‘direction
’ value and
results in a computed value of either ‘left
’ or ‘right
’.
start end
’
start
’ alignment of the
first line and any line immediately after a forced line break; and
‘end
’ alignment of any remaining lines
not affected by ‘text-align-last
’.
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-level boxes within each line box align with respect to the start
and end sides of the line box: alignment is not with respect to the viewport or
containing block.
In the case of ‘justify
’, the UA
may stretch or shrink any inline boxes by adjusting their text in addition to shifting
their positions. (See also ‘text-justify
’, ‘letter-spacing
’, and ‘word-spacing
’.) If an element's white
space is set to be collapsible, then the UA is not
required to adjust its text for the purpose of justification and may
instead treat the text as having no expansion opportunities. If the UA
chooses to adjust the text, then it must ensure that tab stops continue to
line up as required by the white space
processing rules.
When multiple cells in a column have an alignment character specified, the alignment character of each such cell in the column is centered along a single column-parallel axis and the rest of the text in the column shifted accordingly. (Note that the strings do not have to be the same for each cell, although they usually are.)
TD { text-align: "." center }will cause the column of dollar figures in the following HTML table:
<TABLE> <COL width="40"> <TR> <TH>Long distance calls <TR> <TD> $1.30 <TR> <TD> $2.50 <TR> <TD> $10.80 <TR> <TD> $111.01 <TR> <TD> $85. <TR> <TD> N/A <TR> <TD> $.05 <TR> <TD> $.06 </TABLE>
to align along the decimal point. The table might be rendered as follows:
+---------------------+ | Long distance calls | +---------------------+ | $11.30 | | $22.50 | | $0.80 | | $200567.01 | | $85. | | N/A | | $.05 | | $.06 | +---------------------+
A keyword value may be specified in conjunction with the <string>
value; if it is not given, it defaults to ‘right
’. This value is used:
left
’, the rightmost column for ‘right
’ and ‘center
’, the startmost column for ‘start
’, the endmost column for ‘end
’.
center
’, the UA may center the aligned contents
using its extremes, center the alignment axis itself (insofar as
possible), or optically center the aligned contents some other way (such
as by taking a weighted average of the extent of the cells' contents to
either side of the axis).
Right alignment is used by default for character-based alignment because numbering systems are almost all left-to-right even in right-to-left writing systems, and the primary use case of character-based alignment is for numerical alignment.
If the alignment character appears more than once in the text, the first instance is used for alignment. If the alignment character does not appear in a cell at all, the string is aligned as if the alignment character had been inserted at the end of its contents.
Character-based alignment occurs before table cell width computation so that auto width computations can leave enough space for alignment. Whether column-spanning cells participate in the alignment prior to or after width computation is undefined. If width constraints on the cell contents prevent full alignment throughout the column, the resulting alignment is undefined.
text-align-last
’ propertyName: | text-align-last |
---|---|
Value: | auto | start | end | left | right | center | justify |
Initial: | auto |
Applies to: | block containers |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property describes how the last line of a block or a line right
before a forced line break is aligned. If a line is also the first line of
the block or the first line after a forced line break, then, unless
‘text-align
’ assigns an explicit first line
alignment (via ‘start end
’), ‘text-align-last
’ takes precedence over
‘text-align
’.
If ‘auto
’ is specified, content on
the affected line is aligned per ‘text-align
’ unless ‘text-align
’ is
set to ‘justify
’. In this case, content
is justified if ‘text-justify
’ is ‘distribute
’ and start-aligned otherwise. All other
values have the same meanings as in ‘text-align
’.
text-justify
’ propertyName: | text-justify |
---|---|
Value: | auto | none | inter-word | inter-ideograph | inter-cluster | distribute | kashida |
Initial: | auto |
Applies to: | block containers and, optionally, inline elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property selects the justification method used when a line's
alignment is set to ‘justify
’ (see
‘text-align
’), primarily by controlling
which scripts' characters are adjusted together or separately. The
property applies to block containers, but the UA may (but is not required
to) also support it on inline elements. It takes the following values:
auto
’
One possible algorithm is to determine the behavior based
on the language of the paragraph: the UA can then choose appropriate
value for the language, like ‘inter-ideograph
’ for CJK, or ‘inter-word
’ for English. Another possibility is
to use a justification method that is a universal compromise for all
scripts, e.g. the ‘inter-cluster
’
method with block scripts raised to first priority.
none
’
inter-word
’
inter-ideograph
’
inter-cluster
’
distribute
’
kashida
’
When justifying text, the user agent takes the remaining space between
the ends of a line's contents and the edges of its line box, and
distributes that space throughout its contents so that the contents
exactly fill the line box. If the ‘letter-spacing
’ and ‘word-spacing
’
property values allow it, the user agent may also distribute negative
space, putting more content on the line than would otherwise fit under
normal spacing conditions. The exact justification algorithm is
UA-dependent; however, CSS provides some general guidelines which should
be followed when any justification method other than ‘auto
’ is specified.
CSS defines expansion opportunities as points where the justification algorithm may alter spacing within the text. These expansion opportunities fall into priority levels as defined by the justification method. Within a line, expansion and compression should primarily target the first-priority expansion opportunities; lower priority expansion opportunities are adjusted at a lower priority as needed.
Expansion and compression limits are given by the letter-spacing and word-spacing properties. How any remaining space
is distributed once all expansion opportunities reach their limits is up
to the UA. If the inline contents of a line cannot be stretched to the
full width of the line box, then they must be aligned as specified by the
‘text-align-last
’ property. (If ‘text-align-last
’ is ‘justify
’, then they must be aligned as for
‘center
’ if ‘text-justify
’
is ‘distribute
’ and as ‘start
’ otherwise.)
The expansion opportunity priorities for values of ‘text-justify
’
are given in the table below. Since justification behavior varies by
writing system, expansion opportunities are organized by script categories. An expansion opportunity
exists between two letters at a priority level when at least one of
them belongs to a script category at that level and the other does not
belong to a higher priority level. All scripts in the same priority level
must be treated exactly the same. Word separators (spaces) and other
symbols and punctuation are treated specially, see below.
‘inter-word ’
| ‘inter-ideograph ’
| ‘distribute ’
| ‘inter-cluster ’
| ‘kashida ’
| ‘auto ’
| |
---|---|---|---|---|---|---|
block | 2 | 1 | 1 | 2 | 3 | 1* |
clustered | 2 | 2 | 1 | 1 | 3 | 1* |
cursive | 2 | 2 | 2 | 2 | 1 | 2* |
discrete | 2 | 2 | 1 | 2 | 3 | 2* |
connected | never | never | never | never | never | never |
spaces | 1 | 1 | 1 | 1 | 2 | 1* |
symbols | 2 | 1 | 1 | 1 | 3 | * |
* The ‘auto
’
column defined above is informative; it suggests a prioritization that
presents a universal compromise among justification methods.
The spaces
category represents expansion opportunities at word separators. (See ‘word-spacing
’.) Except when ‘text-justify
’
is ‘distribute
’, the UA may treat
spaces differently than other expansion points in the same priority, but
must not change their priority with respect to expansion points in other
priority levels. For example, in Japanese ‘inter-ideograph
’ justification (which treats CJK
characters at a higher priority than Latin characters), word spaces
traditionally have a higher priority than inter-CJK spacing, and the UA
may split the 1st-priority level to implement that. However the UA is not
allowed to drop spaces to the same priority as Latin characters.
The symbols
category represents the expansion opportunities existing at or between any
pair of characters from the Unicode Symbols (S*) and Punctuation (P*)
classes. The default justification priority of these points is given
above. However, there may be additional rules controlling their
justification behavior due to typographic tradition. Therefore, the UA may
reassign specific characters or introduce additional levels of
prioritization to handle expansion opportunities involving symbols and
punctuation. For example, there are traditionally no expansion
opportunities between consecutive EM DASH U+2014, HORIZONTAL BAR U+2015,
HORIZONTAL ELLIPSIS U+2026, or TWO DOT LEADER U+2025 characters [JLREQ]; thus a UA might
assign these characters to the "never" prioritization level. As another
example, certain fullwidth punctuation characters are considered to
contain an expansion opportunity (see ‘text-spacing
’). The UA might therefore assign
these characters to a higher prioritization level than the opportunities
between ideographic characters.
For justification of cursive scripts, words may be expanded through kashida elongation or other cursive expansion processes. Kashida may be applied in discrete units or continuously, and the prioritization of kashida points is UA-dependent: for example, the UA may apply more at the end of the line. The UA should not apply kashida to fonts for which it is inappropriate. It may instead rely on other justification methods that lengthen or shorten Arabic segments (e.g. by substituting in swash forms or optional ligatures). Because elongation rules depend on the typeface style, the UA should rely on on the font whenever possible rather than inserting kashida based on a font-independent ruleset. The UA should limit elongation so that, e.g. in multi-script lines a short stretch of Arabic will not be forced to soak up too much of the extra space by itself. If the UA does not support cursive elongation, then, as with connected scripts, no expansion points exist between characters of these scripts.
The UA may enable or break optional ligatures or use other font features such as alternate glyphs or glyph compression to help justify the text under any method. This behavior is not controlled by this level of CSS.
Add example of using ‘text-justify
’ with the TeX algorithm.
3.8 Line Adjustment in [JLREQ] gives an example of a set of
rules for how a text formatter can justify Japanese text. It describes
rules for cases where the ‘text-justify
’ property is ‘inter-ideograph
’ and the ‘text-spacing
’ property does not specify
‘no-compress
’.
It produces an effect similar to cases where the computed value of
‘text-spacing
’ property does not
specify ‘trim-end
’ or ‘space-end
’. If the UA wants to prohibit this
behavior, rule b. of 3.8.3 should be omitted.
Note that the rules described in the document specifically target Japanese. Therefore they may produce non-optimal results when used to justify other languages such as English. To make the rules more applicable to other scripts, the UA could, for instance, omit the rule to compress half-width spaces (rule a. of 3.8.3).
CSS offers control over text spacing via the ‘word-spacing
’
and ‘letter-spacing
’ properties. While in CSS1
and CSS2 these could only be ‘normal
’
(justifiable) or a fixed length, CSS3 can indicate range constraints to
control flexibility in justification. In addition the ‘word-spacing
’
property can now be specified in percentages, making it possible to, for
example, double or eliminate word spacing.
In the following example, word spacing is halved, but may expand up to its full amount if needed for text justification.
p { word-spacing: -50% 0%; }
The <spacing-limit> value type, which
represents optimum, minimum, and maximum spacing in ‘word-spacing
’
and ‘letter-spacing
’, is defined as
<spacing-limit> = [ normal | <length> | <percentage>]{1,3}
If three values are specified, they represent the optimum, minimum, and maximum in that order. If only two values are specified, then the first represents both the optimum and the minimum, and the second represents the maximum. If just one value is specified, then it represents the optimum, minimum, and maximum. The values are interpreted as defined below:
normal
’
<length>
’
<percentage>
’
word-spacing
’. Negative values are not
allowed.
In the absence of justification the optimum spacing is be used. The text
justification process may alter the spacing from its optimum (see the ‘text-justify
’ property, above) but must
not violate the minimum spacing limit and should also avoid exceeding the
maximum.
The minimum is treated as a hard constraint: if the maximum is less than the minimum, then the used it is set to the minimum. Likewise for the optimum. Similarly if the maximum is less than the optimum, then the used optimum is set to the used maximum.
Normal spacing: Although ‘normal
’ spacing is UA-defined, the normal minimum
and maximum must be defined relative to the optimum so that the minimum
and maximum limits increase and decrease with changes to the optimum
spacing. These limits may also vary according to some measure of the
amount of text on a line (e.g. block width divided by font size), as
larger measures can accommodate tighter spacing constraints. Normal
optimum/minimum/maximum spacing may also vary based on the value of the ‘text-justify
’ property, the element's
language, and other factors. Normal spacing between a pair of connected or cursive characters is always zero.
word-spacing
’ propertyName: | word-spacing |
---|---|
Value: | <spacing-limit> |
Initial: | normal |
Applies to: | all elements |
Inherited: | yes |
Percentages: | refers to width of the affected glyph |
Media: | visual |
Computed value: | as specified, except with <length> values computed to absolute lengths |
This property specifies the minimum, maximum, and optimal spacing between “words”.
Additional spacing is applied to each word-separator character left in the text after the white space processing rules have been applied, and should be applied half on each side of the character.
The following example will make all the spaces between words in Arabic be rendered as zero-width, and double the width of each space in English:
:lang(ar) { word-spacing: -100%; } :lang(en) { word-spacing: 100%; }
The following example will add half the the width of the “0” glyph to word spacing character [CSS3VAL]:
p { word-spacing: 0.5ch; }
Word-separator characters include the space (U+0020), the no-break space (U+00A0), the Ethiopic word space (U+1361), the Aegean word separators (U+10100,U+10101), the Ugaritic word divider (U+1039F), and the Tibetan tsek (U+0F0B, U+0F0C). If there are no word-separator characters, or if the word-separating character has a zero advance width (such as the zero width space U+200B) then the user agent must not create an additional spacing between words. General punctuation and fixed-width spaces (such as U+3000 and U+2000 through U+200A) are not considered word-separator characters.
letter-spacing
’ propertyName: | letter-spacing |
---|---|
Value: | <spacing-limit> |
Initial: | normal |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified, except with <length> values computed to absolute lengths |
This property specifies the minimum, maximum, and optimal spacing
between characters. Letter-spacing is applied in addition to any
word-spacing. ‘normal
’ optimum
letter-spacing is typically zero.
Letter-spacing must not be applied at the beginning or at the end of a line. At element boundaries, the total letter spacing between two characters is given by and rendered within the innermost element that contains the boundary.
For the purpose of letter-spacing, each consecutive run of atomic inlines (such as image and/or inline blocks) is treated as a single character.
For example, given the markup
<P>a<LS>b<Z>cd</Z><Y>ef</Y></LS>g</P>
and the style sheet
LS { letter-spacing: 1em; } Z { letter-spacing: 0.3em; } Y { letter-spacing: 0.4em; }
the spacing would be
a[0]b[1em]c[0.3em]d[1em]e[0.4em]f[0]g
UAs may apply letter-spacing to cursive scripts. In this case, UAs should extend the space between disjoint characters as specified above and extend the visible connection between cursively connected characters by the same amount (rather than leaving a gap). The UA may use glyph substitution or other font capabilities to spread out the letters. If the UA cannot expand a cursive script without breaking the cursive connections, it should not apply letter-spacing between characters of that script at all.
Letter-spacing ignores zero-width characters (such as those from the
Unicode Cf category). For example, ‘letter-spacing
’ applied to
A&zwsp;B
is identical to AB
.
When the resulting space between two characters is not the same as the default space, user agents should not use optional ligatures.
Edge effects control the indentation of lines with respect to other
lines in the block (‘text-indent
’) and how content is aligned
to the start and end edges of a line (‘hanging-punctuation
’).
text-indent
’ propertyName: | text-indent |
---|---|
Value: | [ <length> | <percentage> ] && [ hanging || each-line ]? |
Initial: | 0 |
Applies to: | block containers |
Inherited: | yes |
Percentages: | refers to width of containing block |
Media: | visual |
Computed value: | the percentage as specified or the absolute length, plus any keywords as specified |
This property specifies the indentation applied to lines of inline
content in a block. The indent is treated as a margin applied to the start
edge of the line box. Unless otherwise specified via the ‘each-line
’ and/or ‘hanging
’ keywords, only lines that are the first
formatted line of an element are affected. For example, the first line
of an anonymous block box is only affected if it is the first child of its
parent element.
Values have the following meanings:
<length>
’
<percentage>
’
each-line
’
hanging
’
If ‘text-align
’ is ‘start
’ and ‘text-indent
’
is ‘5em
’ in left-to-right text with no
floats present, then first line of text will start 5em into the block:
Since CSS1 it has been possible to indent the first line of a block element using the 'text-indent' property.
Note that since the ‘text-indent
’ property inherits, when
specified on a block element, it will affect descendant inline-block
elements. For this reason, it is often wise to specify ‘text-indent: 0
’ on elements that are specified
‘display: inline-block
’.
hanging-punctuation
’ propertyName: | hanging-punctuation |
---|---|
Value: | none | [ first || [ force-end | allow-end ] || last ] |
Initial: | none |
Applies to: | inline elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property determines whether a punctuation mark, if one is present, may be placed outside the line box (or in the indent) at the start or at the end of a line of text.
Note that if there is not sufficient padding on the block container, hanging punctuation can trigger overflow.
Values have the following meanings:
none
’
first
’
last
’
force-end
’
allow-end
’
When a punctuation mark hangs, it is not considered when measuring the line's contents for fit, alignment, or justification. Depending on the line's alignment, this can push the mark outside the line box. At most one punctuation character may hang outside each edge of the line.
A hanging punctuation mark is still enclosed inside its inline box and participates in text justification: its character advance width is just not measured when determining how much content fits on the line, how much the line's contents need to be expanded or compressed for justification, or how to position the content within the line box for text alignment.
Non-zero start and end borders or padding on an inline box are not allowed to hang. This can prevent a hangable punctuation mark from hanging: for example, a period at the end of an inline box with end padding cannot hang outside the end edge of a line.
Stops and commas allowed to hang include:
U+002C | , | COMMA |
U+002E | . | FULL STOP |
U+060C | ، | ARABIC COMMA |
U+06D4 | ۔ | ARABIC FULL STOP |
U+3001 | 、 | IDEOGRAPHIC COMMA |
U+3002 | 。 | IDEOGRAPHIC FULL STOP |
U+FF0C | , | FULLWIDTH COMMA |
U+FF0E | . | FULLWIDTH FULL STOP |
U+FE50 | ﹐ | SMALL COMMA |
U+FE51 | ﹑ | SMALL IDEOGRAPHIC COMMA |
U+FE52 | ﹒ | SMALL FULL STOP |
U+FF61 | 。 | HALFWIDTH IDEOGRAPHIC FULL STOP |
U+FF64 | 、 | HALFWIDTH IDEOGRAPHIC COMMA |
The UA may include other characters as appropriate.
The CSS Working Group would appreciate if UAs including other characters would inform the working group of such additions.
Support for this property is optional. It is recommended for UAs that wish to support CJK typography, particularly those in the Japanese market.
The ‘allow-end
’ and ‘force-end
’ are two variations of hanging
punctuation used in East Asia.
p {
hanging-punctuation: allow-end;
}
p {
hanging-punctuation: force-end;
}
The punctuation at the end of the first line for ‘allow-end
’ does not hang, because it fits without
hanging. However, if ‘force-end
’ is
used, it is forced to hang. The justification measures the line without
the hanging punctuation. Therefore the line is expanded.
The following properties describe line decorations that are added to the content of an element. When specified on or propagated to an inline box, such decoration affects all the boxes generated by that element, and is further propagated to any in-flow block-level boxes that split the inline (see CSS2.1 section 9.2.1.1) When specified on or propagated to a ruby box, the decorations are further propagated only to the ruby base. When specified on or propagated to a a block container that establishes an inline formatting context, the decorations are propagated to an anonymous inline element that wraps all the in-flow inline-level children of the block container. For all other elements, the decorations are propagated to any in-flow children.
Note that text decorations are not propagated to any out-of-flow descendants, nor to the contents of atomic inline-level descendants such as inline blocks and inline tables.
By default underlines, overlines, and line-throughs are applied only to
text (including white space, letter spacing, and word spacing): margins,
borders, and padding are skipped. Elements containing no text, such as
images, are likewise not decorated. The ‘text-decoration-skip
’ property can be used
to modify this behavior, for example allowing inline replaced elements to
be underlined or requiring that white space be skipped.
In determining the position and thickness of text decoration lines, user agents may consider the font sizes and dominant baselines of descendants, but for a given element's decoration must use the same position and thickness throughout each line box. The color and line style of decorations must remain the same on all decorations applied by a given element, even if descendant elements have different color or line style values.
The following figure shows the averaging for underline:
In the three fragments of underlined text, the underline is drawn consecutively lower and thicker as the ratio of large text to small text increases.
Relatively positioning a descendant moves all text decorations affecting
it along with the descendant's text; it does not affect calculation of the
decoration's initial position on that line. The ‘visibility
’ property, filters, and other
graphical transformations likewise affect text decorations as part of the
text they're drawn on, even if the decorations were specified on an
ancestor element. Does this include ‘text-shadow
’?
What about text-fill etc.?
In the following style sheet and document fragment:
blockquote { text-decoration: underline; color: blue; }
em { display: block; }
cite { color: fuchsia; }
<blockquote>
<p>
<span>
Help, help!
<em> I am under a hat! </em>
<cite> —GwieF </cite>
</span>
</p>
</blockquote>
...the underlining for the blockquote element is propagated to an
anonymous inline element that surrounds the span element, causing the
text "Help, help!" to be blue, with the blue underlining from the
anonymous inline underneath it, the color being taken from the blockquote
element. The <em>text</em>
in the em block is
also underlined, as it is in an in-flow block to which the underline is
propagated. The final line of text is fuchsia, but the underline
underneath it is still the blue underline from the anonymous inline
element.
This diagram shows the boxes involved in the example above. The rounded aqua line represents the anonymous inline element wrapping the inline contents of the paragraph element, the rounded blue line represents the span element, and the orange lines represent the blocks.
text-decoration-line
’ propertyName: | text-decoration-line |
---|---|
Value: | none | [ underline || overline || line-through ] |
Initial: | none |
Applies to: | all elements |
Inherited: | no (but see prose) |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
Specifies what line decorations, if any, are added to the element. Values have the following meanings:
none
’
underline
’
overline
’
line-through
’
text-decoration-color
’ propertyName: | text-decoration-color |
---|---|
Value: | <color> |
Initial: | currentColor |
Applies to: | all elements |
Inherited: | no |
Percentages: | N/A |
Media: | visual |
Computed value: | the computed color |
This property specifies the color of text decoration (underlines
overlines, and line-throughs) set on the element with ‘text-decoration-line
’.
text-decoration-style
’ propertyName: | text-decoration-style |
---|---|
Value: | solid | double | dotted | dashed | wavy |
Initial: | solid |
Applies to: | all elements |
Inherited: | no |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property specifies the style of the line(s) drawn for text
decoration specified on the element. Values have the same meaning as for
the border-style
properties [CSS3BG]. ‘wavy
’ indicates a wavy line.
text-decoration
’ propertyName: | text-decoration |
---|---|
Value: | <text-decoration-line> || <text-decoration-style> || <text-decoration-color> || blink |
Initial: | none |
Applies to: | all elements |
Inherited: | no |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property is a shorthand for setting ‘text-decoration-line
’, ‘text-decoration-color
’, and ‘text-decoration-style
’ in one declaration.
Omitted values are set to their initial values. A ‘text-decoration
’ declaration that omits
both the ‘text-decoration-color
’ and ‘text-decoration-style
’ values is
backwards-compatible with CSS Levels 1 and 2.
If the ‘blink
’ keyword is specified
the text blinks (alternates between visible and invisible). Conforming
user agents may simply not blink the text. Note that not blinking the text
is one technique to satisfy checkpoint
3.3 of WAI-UAAG.
The following example underlines unvisited links with a solid blue underline in CSS1 and CSS2 UAs and a navy dotted underline in CSS3 UAs.
:link {
color: blue;
text-decoration: underline;
text-decoration: navy dotted underline; /* Ignored in CSS1/CSS2 UAs */
}
text-decoration-skip
’ propertyName: | text-decoration-skip |
---|---|
Value: | none | [ objects || spaces || ink || edges ] |
Initial: | objects |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property specifies what parts of the element's content any text decoration affecting the element must skip over. It controls all text decoration lines drawn by the element and also any text decoration lines drawn by its ancestors. Values have the following meanings:
none
’
objects
’
spaces
’
ink
’
edges
’
Do we need a value that doesn't skip margins and padding?
Note that this property inherits and that descendant elements can have a different setting.
text-underline-position
’ propertyName: | text-underline-position |
---|---|
Value: | auto | alphabetic | [ below || [ left | right ] ] |
Initial: | auto |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property sets the position of an underline specified on the same element: it does not affect underlines specified by ancestor elements. Values have the following meanings:
auto
’
It is suggested that the underline position be ‘alphabetic
’ unless it crosses either subscripted
(or otherwise lowered) text, or it affects characters from Asian scripts
such as Han or Tibetan, for which an alphabetic underline is too high:
in such cases, aligning to the em box edge as described for ‘below left
’ is more appropriate.
alphabetic
’
‘text-underline-position:
alphabetic
’
below
’
vertical-align
’
values given as lengths, percentages, ‘top
’, or ‘bottom
’ when making this adjustment. (Note that
images that are not affected by the underline per ‘text-decoration-skip
’ will not affect the
position of the underline.)
‘text-underline-position:
below
’
Because ‘text-underline-position
’ inherits, and
is not reset by the ‘text-decoration
’ shorthand, the
following example switches the document to use ‘below
’ underlining, which can be more
appropriate for writing systems with long, complicated descenders. It
is also often useful for mathematical or chemical texts that use many
subscripts.
:root { text-underline-position: below; }
left
’
below
’, on the left edge of the text.
right
’
below
’, except it is aligned to the
right edge of the text. If this causes the underline to be drawn on the
"over" side of the text, then an overline also switches sides and is
drawn on the "under" side.
If ‘below
’ is specified alone,
‘left
’ is also implied. If ‘left
’ or ‘right
’
is specified alone, ‘below
’ is also
implied.
| |
‘left ’
| ‘right ’
|
In vertical typographic modes, the ‘text-underline-position
’ values
‘left
’ and ‘right
’ allow placing the underline on either side
of the text. (In horizontal typographic modes, both values are treated as
‘below
’.)
The following example styles modern Chinese, Japanese, and Korean texts with the appropriate underline positions in both horizontal and vertical text:
:lang(ja), :lang(ko) { text-underline-position: below right; } :lang(zh) { text-underline-position: below left; }
In some cases (such as in OpenType) the font format can offer
information about the appropriate position of an underline. Typically
this information gives the position of an ‘alphabetic
’ underline; in some cases (especially
in CJK fonts), it gives the position of a ‘below
left
’ underline. (In this case, the font's underline metrics
typically touch the bottom edge of the em box). The UA is encouraged to
use information (such as the underline thickness, or appropriate
alphabetic alignment) from the font wherever appropriate.
East Asian documents traditionally use small symbols next to each glyph to emphasize a run of text. For example:
Accent emphasis (shown in blue for clarity) applied to Japanese text
text-emphasis-style
’ propertyName: | text-emphasis-style |
---|---|
Value: | none | [ [ filled | open ] || [ dot | circle | double-circle | triangle | sesame ] ] | <string> |
Initial: | none |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | ‘none ’, a pair of keywords
representing the shape and fill, or a string
|
This property applies emphasis marks to the element's text. Values have the following meanings:
none
’
filled
’
open
’
dot
’
•
’, and the open dot is U+25E6 ‘◦
’.
circle
’
●
’, and the open circle is
U+25CB ‘○
’.
double-circle
’
◉
’, and the open double-circle
is U+25CE ‘◎
’.
triangle
’
▲
’, and the open triangle is U+25B3
‘△
’.
sesame
’
﹅
’, and the open sesame is U+FE46
‘﹆
’.
<string>
’
If a shape keyword is specified but neither of ‘filled
’ nor ‘open
’ is specified, ‘filled
’ is assumed. If only ‘filled
’ or ‘open
’ is specified, the shape keyword computes to
‘circle
’ in horizontal writing mode and
‘sesame
’ in vertical writing mode.
The marks should be drawn using the element's font settings with its size scaled down to 50%. However, not all fonts have all these glyphs, and some fonts use inappropriate sizes for emphasis marks in these code points. The UA may opt to use a font known to be good for emphasis marks, or the marks may instead be synthesized by the UA. Marks must remain upright in vertical typographic modes: like CJK characters, they do not rotate to match the writing mode.
One example of good fonts for emphasis marks is Adobe's opensource project, Kenten Generic OpenType Font, which is specially designed for the emphasis marks.
The marks are drawn once for each character. However, emphasis marks are not drawn for characters that are:
If emphasis marks are drawn for characters for which ruby is drawn in the same position as the emphasis mark, the ruby should be stacked between the emphasis marks and the base text. In this case, the position of the emphasis marks for a given element should be determined as if all characters have ruby boxes of the same height as the highest ruby box in the element. If the UA is not capable of drawing ruby and emphasis marks on the same side, the UA may hide ruby and draw only emphasis marks.
Emphasis marks applied to 4 characters, and ruby to 2 of them
A future level of CSS may define controls to specify what to do when emphasis marks and ruby text coincide.
text-emphasis-color
’ propertyName: | text-emphasis-color |
---|---|
Value: | <color> |
Initial: | currentcolor |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property specifies the foreground color of the emphasis marks.
text-emphasis
’ propertyName: | text-emphasis |
---|---|
Value: | ‘<text-emphasis-style> ’
|| ‘<text-emphasis-color> ’
|
Initial: | see individual properties |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | see individual properties |
This property is a shorthand for setting ‘text-emphasis-style
’ and ‘text-emphasis-color
’ in one declaration.
Omitted values are set to their initial values.
Note that ‘text-emphasis-position
’ is not reset in
this shorthand. This is because typically the shape and color vary, but
the position is consistent for a particular language throughout the
document. Therefore the position should inherit independently.
text-emphasis-position
’ propertyName: | text-emphasis-position |
---|---|
Value: | [ above | below ] && [ right | left ] |
Initial: | above right |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | as specified |
This property describes where emphasis marks are drawn at. The values have following meanings:
above
’
below
’
right
’
left
’
Emphasis marks are drawn exactly as if each character was assigned the
mark as its ruby annotation text with the ruby position given by ‘text-emphasis-position
’ and the ruby
alignment as centered.
The effect of emphasis marks on the line height is the same as for ruby text.
Note, the preferred position of emphasis marks depends on the language.
In Japanese for example, the preferred position is ‘above right
’. In Chinese, on the other hand, the
preferred position is ‘below right
’.
The informative table below summarizes the preferred emphasis mark
positions for Chinese and Japanese:
Language | Preferred mark position | Illustration | ||
---|---|---|---|---|
Horizontal | Vertical | |||
Japanese | above | right | | |
Chinese | below | right | |
text-shadow
’ propertyName: | text-shadow |
---|---|
Value: | none | [ <length>{2,3} && <color>? ]# |
Initial: | none |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | a color plus three absolute <length>s |
This property accepts a comma-separated list of shadow effects to be
applied to the text of the element. Values are interpreted as for ‘box-shadow
’. [CSS3BG] The shadow is applied to
all of the element's text as well as any text decorations it specifies.
The shadow effects are applied front-to-back: the first shadow is on top. The shadows may thus overlay each other, but they never overlay the text itself. The shadow must be painted at a stack level between the element's border and/or background, if present, and the elements text and text decoration. UAs should avoid painting text shadows over text in adjacent elements belonging to the same stack level and stacking context. (This may mean that the exact stack level of the shadows depends on whether the element has a border or background: the exact stacking behavior of text shadows is thus UA-defined.)
Unlike ‘box-shadow
’, text
shadows are not clipped to the shadowed shape and may show through if the
text is partially-transparent. Like ‘box-shadow
’, text shadows do not influence
layout, and do not trigger scrolling or increase the size of the
scrollable area.
The painting order of shadows defined here is the opposite of that defined in the 1998 CSS2 Recommendation.
The ‘text-shadow
’ property applies to both the
::first-line
and ::first-letter
pseudo-elements.
Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.
All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. [RFC2119]
Examples in this specification are introduced with the words “for
example” or are set apart from the normative text with
class="example"
, like this:
This is an example of an informative example.
Informative notes begin with the word “Note” and are set apart from
the normative text with class="note"
, like this:
Note, this is an informative note.
Conformance to CSS Text Level 3 is defined for three conformance classes:
A style sheet is conformant to CSS Text Level 3 if all of its declarations that use properties defined in this module have values that are valid according to the generic CSS grammar and the individual grammars of each property as given in this module.
A renderer is conformant to CSS Text Level 3 if, in addition to interpreting the style sheet as defined by the appropriate specifications, it supports all the features defined by CSS Text Level 3 by parsing them correctly and rendering the document accordingly. However, the inability of a UA to correctly render a document due to limitations of the device does not make the UA non-conformant. (For example, a UA is not required to render color on a monochrome monitor.)
An authoring tool is conformant to CSS Text Level 3 if it writes style sheets that are syntactically correct according to the generic CSS grammar and the individual grammars of each feature in this module, and meet all other conformance requirements of style sheets as described in this module.
So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid (and ignore as appropriate) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support. In particular, user agents must not selectively ignore unsupported component values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored.
To avoid clashes with future CSS features, the CSS2.1 specification reserves a prefixed syntax for proprietary and experimental extensions to CSS.
Prior to a specification reaching the Candidate Recommendation stage in the W3C process, all implementations of a CSS feature are considered experimental. The CSS Working Group recommends that implementations use a vendor-prefixed syntax for such features, including those in W3C Working Drafts. This avoids incompatibilities with future changes in the draft.
Once a specification reaches the Candidate Recommendation stage, non-experimental implementations are possible, and implementors should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec.
To establish and maintain the interoperability of CSS across implementations, the CSS Working Group requests that non-experimental CSS renderers submit an implementation report (and, if necessary, the testcases used for that implementation report) to the W3C before releasing an unprefixed implementation of any CSS features. Testcases submitted to W3C are subject to review and correction by the CSS Working Group.
Further information on submitting testcases and implementation reports can be found from on the CSS Working Group's website at http://www.w3.org/Style/CSS/Test/. Questions should be directed to the public-css-testsuite@w3.org mailing list.
For this specification to be advanced to Proposed Recommendation, there must be at least two independent, interoperable implementations of each feature. Each feature may be implemented by a different set of products, there is no requirement that all features be implemented by a single product. For the purposes of this criterion, we define the following terms:
The specification will remain Candidate Recommendation for at least six months.
This specification would not have been possible without the help from: Ayman Aldahleh, Bert Bos, Tantek Çelik, Stephen Deach, John Daggett, Martin Dürst, Laurie Anna Edlund, Ben Errez, Yaniv Feinberg, Arye Gittelman, Ian Hickson, Martin Heijdra, Richard Ishida, Masayasu Ishikawa, Michael Jochimsen, Eric LeVine, Ambrose Li, Håkon Wium Lie, Chris Lilley, Ken Lunde, Nat McCully, Shinyu Murakami, Paul Nelson, Chris Pratley, Marcin Sawicki, Arnold Schrijver, Rahul Sonnad, Michel Suignard, Takao Suzuki, Frank Tang, Chris Thrasher, Etan Wexler, Chris Wilson, Masafumi Yabe and Steve Zilles.
A number of less-stable features have been deferred to Level 4:
discard
’, ‘trim-inner
’, ‘consume-before
’, and ‘consume-after
’ values of ‘text-space-collapse
’
hyphenate-character
’,
‘hyphenate-limit-zone
’,
‘hyphenate-limit-word
’,
‘hyphenate-limit-lines
’, and
‘hyphenate-limit-last
’ properties
hyphenate
’ value of ‘overflow-wrap
’
text-spacing
’ property
no/replace-underline/overline/line-through
’ values
of ‘text-decoration-line
’
text-emphasis-skip
’
property
text-shadow
’
Other major changes include:
text-align
’ to
only allow the ‘start end
’
combination, since no use cases were presented for any others.
<string> justify
’).
Allow reordering of ‘text-align
’ values.
letter-spacing
’ and change its definition
for ‘word-spacing
’ to be relative to the
affected character.
last
’ value of
‘hanging-punctuation
’
below
’, ‘left
’, and ‘right
’ to be specified on their own for ‘text-underline-position
’.
Significant details updated:
text-justify
’ table for ‘distribute
’
letter-spacing
’ and ‘word-spacing
’
definitions
text-underline-position: auto
’
text-transform: fullwidth
’
This appendix is informative, and is to help UA developers to implement default stylesheet, but UA developers are free to ignore or change.
/* make list items align together */
li { text-align: match-parent; }
/* disable inheritance of text-emphasis marks to ruby text:
emphasis marks should only apply to base text */
rt { text-emphasis: none; }
:root:lang(zh), [lang|=zh] {
/* default emphasis mark position is 'below right' for Chinese */
text-emphasis-position: below right;
}
:root:lang(zh), [lang|=zh] {
/* default underline position is 'below left' for Japanese and Korean */
text-underline-position: below right;
}
If you find any issues, recommendations to add, or corrections, please send the information to www-style@w3.org with [css3-text] in the subject line.
This appendix is informative (non-normative).
Typographic behavior varies somewhat by language, but varies drastically by writing system. This appendix categorizes some common scripts in Unicode 6.0 according to their justification and spacing behavior. Category descriptions are descriptive, not prescriptive; the determining factor is the prioritization of expansion opportunities.
UAs should treat unrecognized scripts as discrete.
This listing should ideally be exhaustive wrt Unicode. Please send suggestions and corrections to the CSS Working Group.
Guidelines for classification consider letter-spacing and justification:
A | I | U | E | O | |||||
---|---|---|---|---|---|---|---|---|---|
small | normal | small | normal | small | normal | small | normal | small | normal |
ぁ U+3041 | あ U+3042 | ぃ U+3043 | い U+3044 | ぅ U+3045 | う U+3046 | ぇ U+3047 | え U+3048 | ぉ U+3049 | お U+304A |
ゕ U+3095 | か U+304B | ゖ U+3096 | け U+3051 | ||||||
っ U+3063 | つ U+3064 | ||||||||
ゃ U+3083 | や U+3084 | ゅ U+3085 | ゆ U+3086 | ょ U+3087 | よ U+3088 | ||||
ゎ U+308E | わ U+308F | ||||||||
ァ U+30A1 | ア U+30A2 | ィ U+30A3 | イ U+30A4 | ゥ U+30A5 | ウ U+30A6 | ェ U+30A7 | エ U+30A8 | ォ U+30A9 | オ U+30AA |
ヵ U+30F5 | カ U+30AB | ㇰ U+31F0 | ク U+30AF | ヶ U+30F6 | ケ U+30B1 | ||||
ㇱ U+31F1 | シ U+30B7 | ㇲ U+31F2 | ス U+30B9 | ||||||
ッ U+30C3 | ツ U+30C4 | ㇳ U+31F3 | ト U+30C8 | ||||||
ㇴ U+31F4 | ヌ U+30CC | ||||||||
ㇵ U+31F5 | ハ U+30CF | ㇶ U+31F6 | ヒ U+30D2 | ㇷ U+31F7 | フ U+30D5 | ㇸ U+31F8 | ヘ U+30D8 | ㇹ U+31F9 | ホ U+30DB |
ㇺ U+31FA | ム U+30E0 | ||||||||
ャ U+30E3 | ヤ U+30E4 | ュ U+30E5 | ユ U+30E6 | ョ U+30E7 | ヨ U+30E8 | ||||
ㇻ U+31FB | ラ U+30E9 | ㇼ U+31FC | リ U+30EA | ㇽ U+31FD | ル U+30EB | ㇾ U+31FE | レ U+30EC | ㇿ U+31FF | ロ U+30ED |
ヮ U+30EE | ワ U+30EF | ||||||||
ァ U+FF67 | ア U+FF71 | ィ U+FF68 | イ U+FF72 | ゥ U+FF69 | ウ U+FF73 | ェ U+FF6A | エ U+FF74 | ォ U+FF6B | オ U+FF75 |
ッ U+FF6F | ツ U+FF82 | ||||||||
ャ U+FF6C | ヤ U+FF94 | ュ U+FF6D | ユ U+FF95 | ョ U+FF6E | ヨ U+FF96 |
The following list defines the order of text operations. (Implementations are not bound to this order as long as the resulting layout is the same.)
Property | Values | Initial | Applies to | Inh. | Percentages | Media |
---|---|---|---|---|---|---|
hanging-punctuation | none | [ first || [ force-end | allow-end ] || last ] | none | inline elements | yes | N/A | visual |
hyphens | none | manual | auto | manual | all elements | yes | N/A | visual |
letter-spacing | <spacing-limit> | normal | all elements | yes | N/A | visual |
line-break | auto | loose | normal | strict | auto | all elements | yes | N/A | visual |
overflow-wrap | normal | break-word | normal | all elements | yes | N/A | visual |
tab-size | <integer> | <length> | 8 | block containers | yes | N/A | visual |
text-align | [ [ start | end | left | right | center ] || <string> ] | justify | match-parent | start end | start | block containers | yes | N/A | visual |
text-align-last | auto | start | end | left | right | center | justify | auto | block containers | yes | N/A | visual |
text-decoration | <text-decoration-line> || <text-decoration-style> || <text-decoration-color> || blink | none | all elements | no | N/A | visual |
text-decoration-color | <color> | currentColor | all elements | no | N/A | visual |
text-decoration-line | none | [ underline || overline || line-through ] | none | all elements | no (but see prose) | N/A | visual |
text-decoration-skip | none | [ objects || spaces || ink || edges ] | objects | all elements | yes | N/A | visual |
text-decoration-style | solid | double | dotted | dashed | wavy | solid | all elements | no | N/A | visual |
text-emphasis | ‘<text-emphasis-style>’ || ‘<text-emphasis-color>’ | see individual properties | all elements | yes | N/A | visual |
text-emphasis-color | <color> | currentcolor | all elements | yes | N/A | visual |
text-emphasis-position | [ above | below ] && [ right | left ] | above right | all elements | yes | N/A | visual |
text-emphasis-style | none | [ [ filled | open ] || [ dot | circle | double-circle | triangle | sesame ] ] | <string> | none | all elements | yes | N/A | visual |
text-indent | [ <length> | <percentage> ] && [ hanging || each-line ]? | 0 | block containers | yes | refers to width of containing block | visual |
text-justify | auto | none | inter-word | inter-ideograph | inter-cluster | distribute | kashida | auto | block containers and, optionally, inline elements | yes | N/A | visual |
text-shadow | none | [ <length>{2,3} && <color>? ]# | none | all elements | yes | N/A | visual |
text-space-collapse | collapse | preserve | preserve-breaks | collapse | all elements | yes | N/A | visual |
text-transform | none | [ [ capitalize | uppercase | lowercase ] || full-width || full-size-kana ] | none | all elements | yes | N/A | visual |
text-underline-position | auto | alphabetic | [ below || [ left | right ] ] | auto | all elements | yes | N/A | visual |
text-wrap | normal | none | avoid | normal | all elements | yes | N/A | visual |
white-space | normal | pre | nowrap | pre-wrap | pre-line | not defined for shorthand properties | all elements | yes | N/A | visual |
word-break | normal | keep-all | break-all | normal | all elements | yes | N/A | visual |
word-spacing | <spacing-limit> | normal | all elements | yes | refers to width of the affected glyph | visual |