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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang=en>
1DE3
<head profile="http://dublincore.org/documents/2008/08/04/dc-html/ ">
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
<title>CSS Text Module Level 3 (CSS3 Text)</title>
<link href="http://purl.org/dc/terms/" rel=schema.dcterms>
<link href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=dcterms.rights>
<meta content="CSS Text Module Level 3 (CSS3 Text)" name=dcterms.title>
<meta content=text name=dcterms.type>
<meta content=2013-03-06 name=dcterms.issued>
<meta content="Elika J. Etemad" name=dcterms.creator>
<meta content="Koji Ishii" name=dcterms.creator>
<meta content=W3C name=dcterms.publisher>
<meta content="http://dev.w3.org/csswg/css3-text/" name=dcterms.identifier>
<link href="#contents" rel=contents><!--<link rel=index href="#index">-->
<link href="../default.css" rel=stylesheet type="text/css">
<style type="text/css">
.egbidiwsaA,.egbidiwsbB,.egbidiwsaB,.egbidiwsbC
{ white-space:pre;font-size:80%;font-family:monospace; vertical-align:2px; margin:1px }
.egbidiwsaA { background:lime;padding:2px; }
.egbidiwsbB { border:2px solid blue }
.egbidiwsaB { background:yellow;border:2px dotted white }
.egbidiwsbC { border:2px dotted red }
.char { border: 1px dotted gray; }
.quarter { font-size: 25%; }
tt[lang="ja"] { font-family: "MS Gothic", "Osaka", monospace }
div.figure table {
margin :auto;
}
</style>
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
type="text/css">
<body>
<div class=head> <!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt=W3C height=48
src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
<h1>CSS Text Module Level 3</h1>
<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 6 March 2013</h2>
<dl>
<dt>This version:</dt>
<!--
<dd><a href="http://www.w3.org/TR/2013/WD-css3-text-20130306/">http://www.w3.org/TR/2013/WD-css3-text-20130306/</a></dd>
-->
<dd><a
href="http://dev.w3.org/csswg/css3-text/">http://dev.w3.org/csswg/css3-text/</a>
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-text/">http://www.w3.org/TR/css3-text/</a>
<dt>Latest editor's draft:
<dd><a
href="http://dev.w3.org/csswg/css3-text/">http://dev.w3.org/csswg/css3-text/</a>
<dt>Previous version:
<dd><a
href="http://www.w3.org/TR/2012/WD-css3-text-20121113/">http://www.w3.org/TR/2012/WD-css3-text-20121113/</a>
<dt>Issues List:
<dd><a
href="http://www.w3.org/Style/CSS/Tracker/products/10">http://www.w3.org/Style/CSS/Tracker/products/10</a>
<dt>Feedback:</dt>
<dd><a href="mailto:www-style@w3.org?subject=%5Bcss-text%5D%20feedback">www-style@w3.org</a>
with subject line “<kbd>[css-text]
<var>… message topic …</var></kbd>”
(<a rel="discussion" href="http://lists.w3.org/Archives/Public/www-style/">archives</a>)
<dt>Editors:
<dd><a href="http://fantasai.inkedblade.net/contact">Elika J. Etemad</a>
(Mozilla)
<dd><a href="mailto:koji.a.ishii@mail.rakuten.com">Koji Ishii</a>
(Rakuten, Inc.)
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2013 <a href="http://www.w3.org/"><abbr
title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><abbr
title="Massachusetts Institute of Technology">MIT</abbr></a>, <a
href="http://www.ercim.eu/"><abbr
title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
<a href="http://www.keio.ac.jp/">Keio</a>, <a
href="http://ev.buaa.edu.cn/">Beihang</a>), All Rights Reserved. W3C <a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
and <a
href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>
<!--end-copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id=abstract>Abstract</h2>
<p>This CSS3 module defines properties for text manipulation and specifies
their processing model. It covers line breaking, justification and
alignment, white space handling, and text transformation.
<h2 class="no-num no-toc" id=status>Status of This Document</h2>
<p><em>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 <a href="http://www.w3.org/TR/">W3C technical reports
index at http://www.w3.org/TR/.</a></em>
<p>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.
<p>This CSS module has been produced as a combined effort of the <a
href="http://www.w3.org/International/Activity">W3C Internationalization
Activity</a>, and the <a href="http://www.w3.org/Style/Activity">Style
Activity</a> and is maintained by the <a
href="http://www.w3.org/Style/CSS/members">CSS Working Group</a>. It also
includes contributions made by participants in the <a
href="http://www.w3.org/Style/XSL/Group/">XSL Working Group</a> (<a
href="http://cgi.w3.org/MemberAccess/AccessRequest">members only</a>).
<p>This document was produced by a group operating under the <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February
2004 W3C Patent Policy</a>. W3C maintains a <a
href="http://www.w3.org/2004/01/pp-impl/32061/status"
rel=disclosure>public list of any patent disclosures</a> 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 <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
6 of the W3C Patent Policy</a>.
<p><strong>Feedback on this draft should be posted to the (<a
href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
mailing list <a
href="mailto:www-style@w3.org">www-style@w3.org</a></strong> (see <a
href="http://www.w3.org/Mail/Request">instructions</a>) <strong>with
<kbd>[css3-text]</kbd> in the subject line.</strong> 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.
<p>The following features are at risk and may be cut from the spec during
its CR period if there are no (correct) implementations:
<ul>
<li>the ‘<code class=css>full-width</code>’ value of ‘<a
href="#text-transform0"><code class=property>text-transform</code></a>’
<li>the <length> values of the ‘<a href="#tab-size1"><code
class=property>tab-size</code></a>’ property
<li>the ‘<code class=css>start end</code>’ value of ‘<a
href="#text-align0"><code class=property>text-align</code></a>’
<li>the ‘<a href="#text-justify0"><code
class=property>text-justify</code></a>’ property
<li>the percentage values of ‘<a href="#word-spacing0"><code
class=property>word-spacing</code></a>’
<li>minimum and maximum limits of ‘<a href="#word-spacing0"><code
class=property>word-spacing</code></a>’ and ‘<a
href="#letter-spacing0"><code class=property>letter-spacing</code></a>’
<li>the ‘<a href="#hanging-punctuation0"><code
class=property>hanging-punctuation</code></a>’ property
</ul>
<h2 class="no-num no-toc" id=contents> Table of Contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#intro"><span class=secno>1. </span> Introduction</a>
<ul class=toc>
<li><a href="#placement"><span class=secno>1.1. </span> Module
Interactions</a>
<li><a href="#values"><span class=secno>1.2. </span> Values</a>
<li><a href="#terms"><span class=secno>1.3. </span> Terminology</a>
</ul>
<li><a href="#transforming"><span class=secno>2. </span> Transforming
Text</a>
<ul class=toc>
<li><a href="#text-transform"><span class=secno>2.1. </span>
Transforming Text: the ‘<code class=property>text-transform</code>’
property</a>
</ul>
<li><a href="#white-space"><span class=secno>3. </span> White Space and
Wrapping: the ‘<code class=property>white-space</code>’ property</a>
<li><a href="#white-space-processing"><span class=secno>4. </span> White
Space Processing Details</a>
<ul class=toc>
<li><a href="#white-space-rules"><span class=secno>4.1. </span> The
White Space Processing Rules</a>
<ul class=toc>
<li><a href="#egbidiwscollapse"><span class=secno>4.1.1. </span>
Example of bidirectionality with white space collapsing</a>
<li><a href="#line-break-transform"><span class=secno>4.1.2. </span>
Line Break Transformation Rules</a>
</ul>
<li><a href="#tab-size"><span class=secno>4.2. </span> Tab Character
Size: the ‘<code class=property>tab-size</code>’ property</a>
</ul>
<li><a href="#line-breaking"><span class=secno>5. </span> Line Breaking
and Word Boundaries</a>
<ul class=toc>
<li><a href="#line-break-details"><span class=secno>5.1. </span> Line
Breaking Details</a>
<li><a href="#line-break"><span class=secno>5.2. </span> Breaking Rules
for Punctuation: the ‘<code class=property>line-break</code>’
property</a>
<li><a href="#word-break"><span class=secno>5.3. </span> Breaking Rules
for Letters: the ‘<code class=property>word-break</code>’
property</a>
</ul>
<li><a href="#hyphenation"><span class=secno>6. </span>Hyphenation</a>
<ul class=toc>
<li><a href="#hyphens"><span class=secno>6.1. </span>Hyphenation
Control: the ‘<code class=property>hyphens</code>’ property</a>
<li><a href="#overflow-wrap"><span class=secno>6.2. </span> Overflow
Wrapping: the ‘<code class=property>word-wrap</code>’/‘<code
class=property>overflow-wrap</code>’ property</a>
</ul>
<li><a href="#justification"><span class=secno>7. </span> Alignment and
Justification</a>
<ul class=toc>
<li><a href="#text-align"><span class=secno>7.1. </span> Text Alignment:
the ‘<code class=property>text-align</code>’ property</a>
<ul class=toc>
<li><a href="#bidi-linebox"><span class=secno>7.1.1. </span>
Bidirectionality and Line Boxes</a>
</ul>
<li><a href="#text-align-last"><span class=secno>7.2. </span> Last Line
Alignment: the ‘<code class=property>text-align-last</code>’
property</a>
<li><a href="#text-justify"><span class=secno>7.3. </span> Justification
Method: the ‘<code class=property>text-justify</code>’ property</a>
</ul>
<li><a href="#spacing"><span class=secno>8. </span> Spacing</a>
<ul class=toc>
<li><a href="#word-spacing"><span class=secno>8.1. </span> Word Spacing:
the ‘<code class=property>word-spacing</code>’ property</a>
<li><a href="#letter-spacing"><span class=secno>8.2. </span> Tracking:
the ‘<code class=property>letter-spacing</code>’ property</a>
</ul>
<li><a href="#edge-effects"><span class=secno>9. </span> Edge Effects</a>
<ul class=toc>
<li><a href="#text-indent"><span class=secno>9.1. </span> First Line
Indentation: the ‘<code class=property>text-indent</code>’
property</a>
<li><a href="#hanging-punctuation"><span class=secno>9.2. </span>
Hanging Punctuation: the ‘<code
class=property>hanging-punctuation</code>’ property</a>
</ul>
<li><a href="#conformance"><span class=secno>10. </span> Conformance</a>
<ul class=toc>
<li><a href="#conventions"><span class=secno>10.1. </span> Document
Conventions</a>
<li><a href="#conformance-classes"><span class=secno>10.2. </span>
Conformance Classes</a>
<li><a href="#partial"><span class=secno>10.3. </span> Partial
Implementations</a>
<li><a href="#experimental"><span class=secno>10.4. </span> Experimental
Implementations</a>
<li><a href="#testing"><span class=secno>10.5. </span>Non-Experimental
Implementations</a>
<li><a href="#cr-exit-criteria"><span class=secno>10.6. </span> CR Exit
Criteria</a>
</ul>
<li class=no-num><a href="#acknowledgements"> Appendix A:
Acknowledgements</a>
<li class=no-num><a href="#appendix-b-references">Appendix B:
References</a>
<ul class=toc>
<li class=no-num><a href="#normative-ref">Normative references</a>
<li class=no-num><a href="#informative-ref">Informative references</a>
</ul>
<li class=no-num><a href="#changes">Appendix C: Changes</a>
<ul class=toc>
<li class=no-num><a href="#recent-changes"> Changes from the November
2012 CSS3 Text <abbr title="Working Draft">WD</abbr></a>
</ul>
<li class=no-num><a href="#default-stylesheet"> Appendix D: Default UA
Stylesheet</a>
<li class=no-num><a href="#script-groups">Appendix E: Scripts and
Spacing</a>
<li class=no-num><a
href="#appendix-f-text-processing-order-of-oper">Appendix F: Text
Processing Order of Operations</a>
<li class=no-num><a href="#appendix-g-full-property-index">Appendix G:
Full Property Index</a>
</ul>
<!--end-toc-->
<h2 id=intro><span class=secno>1. </span> Introduction</h2>
<p>[document here]
<p class=issue>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.
<p class=note> <a name=decoration></a> <a name=text-decoration></a> <a
name=line-decoration></a> <a name=text-decoration-line></a> <a
name=text-decoration-color></a> <a name=text-decoration-style></a> <a
name=text-decoration-skip></a> <a name=text-underline-position></a> <a
name=emphasis-marks></a> <a name=text-emphasis-style></a> <a
name=text-emphasis-color></a> <a name=text-emphasis></a> <a
name=text-emphasis-position></a> <a name=text-shadow></a> Text decoration
has moved to CSS Text Decoration Module Level 3 <a href="#CSS3-TEXT-DECOR"
rel=biblioentry>[CSS3-TEXT-DECOR]<!--{{CSS3-TEXT-DECOR}}--></a>.
<h3 id=placement><span class=secno>1.1. </span> Module Interactions</h3>
<p>This module replaces and extends the text-level features defined in <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> chapter 16.
<h3 id=values><span class=secno>1.2. </span> Values</h3>
<p>This specification follows the <a
href="http://www.w3.org/TR/CSS21/about.html#property-defs">CSS property
definition conventions</a> from <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Value types not defined in
this specification are defined in CSS Level 2 Revision 1 <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Other CSS
modules may expand the definitions of these value types: for example <a
href="#CSS3COLOR" rel=biblioentry>[CSS3COLOR]<!--{{CSS3COLOR}}--></a>,
when combined with this module, expands the definition of the
<color> value type as used in this specification.
<p>In addition to the property-specific values listed in their definitions,
all properties defined in this specification also accept the <a
href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">inherit</a>
keyword as their property value. For readability it has not been repeated
explicitly.
<h3 id=terms><span class=secno>1.3. </span> Terminology</h3>
<p id=grapheme-cluster>A <dfn id=grapheme-cluster0>grapheme cluster</dfn>
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 <a href="#UAX29"
rel=biblioentry>[UAX29]<!--{{!UAX29}}--></a>. This specification uses the
<em>extended grapheme cluster</em> definition in <a href="#UAX29"
rel=biblioentry>[UAX29]<!--{{!UAX29}}--></a> (not the <em>legacy grapheme
cluster</em> definition). The UA may further tailor the definition as
allowed by Unicode. Within this specification, the ambiguous term <dfn
id=character>character</dfn> is used as a friendlier synonym for <a
href="#grapheme-cluster0"><i>grapheme cluster</i></a>. See <a
href="http://dev.w3.org/csswg/css3-writing-modes/#character-properties">Characters
and Properties</a> for how to determine the Unicode properties of a
character.
<p id=letter>A <dfn id=letter0>letter</dfn> for the purpose of this
specification is a <a href="#character"><i>character</i></a> belonging to
one of the Letter or Number general categories in Unicode. <a
href="#UAX44" rel=biblioentry>[UAX44]<!--{{!UAX44}}--></a>
<p>The rendering characteristics of a <a
href="#character"><i>character</i></a> 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.
<p>The <dfn id=content-language>content language</dfn> of an element is the
(human) language the element is declared to be in, according to the rules
of the <a
href="http://www.w3.org/TR/CSS21/conform.html#doclanguage">document
language</a>. For example, the rules for determining the <a
href="#content-language"><i>content language</i></a> of an HTML element
use the <code>lang</code> attribute and are defined in <a href="#HTML5"
rel=biblioentry>[HTML5]<!--{{HTML5}}--></a>, and the rules for determining
the <a href="#content-language"><i>content language</i></a> of an XML
element use the <code>xml:lang</code> attribute and are <a
href="http://www.w3.org/TR/REC-xml/#sec-lang-tag">defined</a> in <a
href="#XML10" rel=biblioentry>[XML10]<!--{{XML10}}--></a>. Note that it is
possible for the <a href="#content-language"><i>content language</i></a>
of an element to be unknown.
<p>Other terminology and concepts used in this specification are defined in
<a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> and <a
href="#CSS3-WRITING-MODES"
rel=biblioentry>[CSS3-WRITING-MODES]<!--{{!CSS3-WRITING-MODES}}--></a>.
<h2 id=transforming><span class=secno>2. </span> Transforming Text</h2>
<h3 id=text-transform><span class=secno>2.1. </span> <a name=caps-prop></a>
Transforming Text: the ‘<a href="#text-transform0"><code
class=property>text-transform</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=text-transform0>text-transform</dfn>
<tr>
<th><a href="#values">Value</a>:
<td>none | capitalize | uppercase | lowercase | full-width
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>as specified
</table>
<p>This property transforms text for styling purposes. (It has no effect on
the underlying content.) Values have the following meanings:
<dl>
<dt><dfn id=none title="text-transform:none">‘<code
class=css>none</code>’</dfn>
<dd>No effects.
<dt><dfn id=capitalize title="text-transform:capitalize">‘<code
class=css>capitalize</code>’</dfn>
<dd>Puts the first <a href="#letter0"><i>letter</i></a> of each word in
titlecase; other characters are unaffected.
<dt><dfn id=uppercase title="text-transform:uppercase">‘<code
class=css>uppercase</code>’</dfn>
<dd>Puts all <a href="#letter0"><i>letters</i></a> in uppercase.
<dt><dfn id=lowercase title="text-transform:lowercase">‘<code
class=css>lowercase</code>’</dfn>
<dd>Puts all <a href="#letter0"><i>letters</i></a> in lowercase.
<dt><dfn id=full-width title="text-transform:full-width">‘<code
class=css>full-width</code>’</dfn>
<dd>Puts all characters in fullwidth form. If the character does not have
a corresponding fullwidth form, it is left as is. This value is typically
used to typeset Latin characters and digits like ideographic characters.
<!--
<dt><dfn title="text-transform:full-size-kana">''full-size-kana''</dfn></dt>
<dd>Converts all small Kana characters to normal Kana.
The mappings for small Kana to normal Kana are defined in
<a href="#small-kana">Small Kana Mappings</a>.</p>
<p class=note>
This value is typically used for ruby annotation text,
where due to the small type size, small Kana
is often drawn as large Kana.
This value allows such underlying text to use correct orthography
so that it is accessible and can be styled correctly
when not presented as ruby.
-->
</dl>
<p>The case mapping rules for the character repertoire specified by the
Unicode Standard can be found on the Unicode Consortium Web site <a
href="#UNICODE" rel=biblioentry>[UNICODE]<!--{{!UNICODE}}--></a>. 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 <a href="#content-language"><i>content language</i></a>
of the element is, according to the rules of the <a
href="http://www.w3.org/TR/CSS21/conform.html#doclanguage">document
language</a>, 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 <a
href="http://www.unicode.org/Public/UNIDATA/SpecialCasing.txt">SpecialCasing.txt</a>.
<div class=example>
<p>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 <a href="#content-language"><i>content language</i></a> is
Turkish (or another Turkic language that uses Turkish casing rules); in
other languages, the usual mapping of “I” and “i” is required.
This rule is thus conditionally defined in Unicode's SpecialCasing.txt
file.
</div>
<!--
<div class="example">
<p>An example where the UA may choose to include rules beyond those
in Unicode is Greek. In Greek, if the entire word is in upper case
(''text-transform: capitalize'' vs. ''text-transform: uppercase''),
accents are dropped or transformed according to language-specific rules.
http://blogs.msdn.com/b/michkap/archive/2006/08/18/706383.aspx
</div>
-->
<p>The definition of "word" used for ‘<code
class=css>capitalize</code>’ is UA-dependent; <a href="#UAX29"
rel=biblioentry>[UAX29]<!--{{!UAX29}}--></a> is suggested (but not
required) for determining such word boundaries. Authors should not expect
‘<code class=css>capitalize</code>’ to follow language-specific
titlecasing conventions (such as skipping articles in English).
<p>The definition of fullwidth and halfwidth forms can be found on the
Unicode consortium web site at <a href="#UAX11"
rel=biblioentry>[UAX11]<!--{{!UAX11}}--></a>. The mapping to fullwidth
form is defined by taking code points with the <wide> or the
<narrow> tag in their Decomposition_Mapping in <a href="#UAX44"
rel=biblioentry>[UAX44]<!--{{!UAX44}}--></a>. 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.
<p>Text transformation happens after <a href="#white-space-rules">white
space processing</a>, which means that ‘<code
class=css>full-width</code>’ transforms only preserved U+0020 spaces to
U+3000.
<div class=example>
<p>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:
<pre>abbr:lang(ja) { text-transform: full-width; }</pre>
</div>
<p class=note> A future level of CSS may introduce the ability to create
custom mapping tables for less common text transforms, such as by an
‘<code class=css>@text-transform</code>’ rule similar to ‘<code
class=css>@counter-style</code>’ from <a href="#CSS-COUNTER-STYLES-3"
rel=biblioentry>[CSS-COUNTER-STYLES-3]<!--{{CSS-COUNTER-STYLES-3}}--></a>.
<!--
This mechanism may be used to replace ''full-size-kana''. This would
require authors needing this functionality to copy out the conversion
tables, however.
-->
<h2 id=white-space><span class=secno>3. </span><a
id=white-space-collapsing></a><a id=text-wrap></a> White Space and
Wrapping: the ‘<a href="#white-space0"><code
class=property>white-space</code></a>’ property</h2>
<p>This property specifies two things:
<ul>
<li>whether and how <a href="#white-space-processing">white space</a>
inside the element is collapsed
<li>whether lines may <a href="#wrapping"><i>wrap</i></a> at unforced <a
href="#soft-wrap-opportunity"><i>soft wrap opportunities</i></a>
</ul>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=white-space0>white-space</dfn>
<tr>
<th><a href="#values">Value</a>:
<td>normal | pre | nowrap | pre-wrap | pre-line
<tr>
<th>Initial:
<td>not defined for shorthand properties
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>see individual properties
</table>
<p>Values have the following meanings, which must be interpreted according
to the <a href="#white-space-rules">White Space Processing</a> and <a
href="#line-breaking">Line Breaking</a> rules:
<dl>
<dt><dfn id=normal title="white-space:normal">‘<code
class=css>normal</code>’</dfn>
<dd>This value directs user agents to collapse sequences of white space
into a single character (or <a href="#line-break-transform">in some
cases</a>, no character). Lines may wrap at allowed <a
href="#soft-wrap-opportunity"><i>soft wrap opportunities</i></a>, as
determined by the line-breaking rules in effect, in order to minimize
overflow.
<dt><dfn id=pre title="white-space:pre">‘<code
class=css>pre</code>’</dfn>
<dd>This value prevents user agents from collapsing sequences of white
space. <a href="#segment-break"><i>Segment breaks</i></a> such as line
feeds and carriage returns are preserved as <a
href="#forced-line-break"><i>forced line breaks</i></a>. Lines only break
at <a href="#forced-line-break"><i>forced line breaks</i></a>; content
that does not fit within the block container overflows it.
<dt><dfn id=nowrap title="white-space:nowrap">‘<code
class=css>nowrap</code>’</dfn>
<dd>Like ‘<code class=css>normal</code>’, this value collapses white
space; but like ‘<code class=css>pre</code>’, it does not allow
wrapping.
<dt><dfn id=pre-wrap title="white-space:pre-wrap">‘<code
class=css>pre-wrap</code>’</dfn>
<dd>Like ‘<code class=css>pre</code>’, this value preserves white
space; but like ‘<code class=css>normal</code>’, it allows wrapping.
<dt><dfn id=pre-line title="white-space:pre-line">‘<code
class=css>pre-line</code>’</dfn>
<dd>Like ‘<code class=css>normal</code>’, this value collapses
consecutive spaces and allows wrapping, but preserves <a
href="#segment-break"><i>segment breaks</i></a> in the source as <a
href="#forced-line-break"><i>forced line breaks</i></a>.
</dl>
<p>The following informative table summarizes the behavior of various ‘<a
href="#white-space0"><code class=property>white-space</code></a>’
values:
<table class=data>
<colgroup class=header></colgroup>
<colgroup span=3></colgroup>
<thead>
<tr>
<th>
<th>New Lines
<th>Spaces and Tabs
<th>Text Wrapping
<tbody>
<tr>
<th>‘<code class=css>normal</code>’
<td>Collapse
<td>Collapse
<td>Wrap
<tr>
<th>‘<code class=css>pre</code>’
<td>Preserve
<td>Preserve
<td>No wrap
<tr>
<th>‘<code class=css>nowrap</code>’
<td>Collapse
<td>Collapse
<td>No wrap
<tr>
<th>‘<code class=css>pre-wrap</code>’
<td>Preserve
<td>Preserve
<td>Wrap
<tr>
<th>‘<code class=css>pre-line</code>’
<td>Preserve
<td>Collapse
<td>Wrap
</table>
<p>See <a href="#white-space-processing">White Space Processing Rules</a>
for details on ho
863
w white space collapses. An informative summary of
collapsing (‘<code class=css>normal</code>’ and ‘<code
class=css>nowrap</code>’) is presented below:
<ul>
<li>A sequence of segment breaks and other white space between two
Chinese, Japanese, or Yi characters collapses into nothing.
<li>A zero widt
1035D
h space before or after a white space sequence containing a
segment break causes the entire sequence of white space to collapse into
a zero width space.
<li>Otherwise, consecutive white space collapses into a single space.
</ul>
<p>See <a href="#line-breaking">Line Breaking</a> for details on wrapping
behavior.
<h2 id=white-space-processing><span class=secno>4. </span> White Space
Processing Details</h2>
<p>The source text of a document often contains formatting that is not
relevant to the final rendering: for example, <a
href="http://rhodesmill.org/brandon/2012/one-sentence-per-line/">breaking
the source into segments</a> (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.
White space processing in CSS interprets white space characters only for
rendering: it has no effect on the underlying document data.
<p>White space processing in CSS is controlled with the ‘<a
href="#white-space0"><code class=property>white-space</code></a>’
property.
<p id=segment-normalization> 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 language–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 <dfn id=segment-break>segment break</dfn>, which is then interpreted for
rendering as specified by the ‘<a href="#white-space0"><code
class=property>white-space</code></a>’ property.
<p class=note>Note that the document parser may have not only normalized
any segment breaks, but also collapsed other space characters or otherwise
processed white space according to markup rules. Because CSS processing
occurs <em>after</em> 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.
<p class=note>Note that anonymous inlines consisting entirely of <a
href="#collapsible"><i>collapsible</i></a> white space are removed from
the rendering tree. See <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{CSS21}}--></a> section <a
href="http://www.w3.org/TR/CSS21/visuren.html#anonymous">9.2.2.1</a>
<p>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.
<h3 id=white-space-rules><span class=secno>4.1. </span> The White Space
Processing Rules</h3>
<p>White space processing affects only spaces (U+0020), tabs (U+0009), and
<a href="#segment-normalization">segment breaks</a>.
<p>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:
<ul>
<li id=collapse>
<p>If ‘<a href="#white-space0"><code
class=property>white-space</code></a>’ is set to ‘<code
class=css>normal</code>’, ‘<code class=css>nowrap</code>’, or
‘<code class=css>pre-line</code>’, white space characters are
considered <dfn id=collapsible>collapsible</dfn> and are processed by
performing the following steps:
<ol>
<li>All spaces and tabs immediately preceding or following a segment
break are removed.
<li>Segment breaks are transformed for rendering according to the <a
href="#line-break-transform">line break transformation rules</a>.
<li>Every tab is converted to a space (U+0020).
<li>Any space immediately following another collapsible space —even
one outside the boundary of the inline containing the space, provided
they are within the same inline formatting context—is collapsed to
have zero advance width. (It is invisible, but retains its <a
href="#soft-wrap-opportunity"><i>soft wrap opportunity</i></a>, if
any.)
</ol>
<li>
<p>If ‘<a href="#white-space0"><code
class=property>white-space</code></a>’ is set to ‘<code
class=css>pre-wrap</code>’, any sequence of spaces is treated as a
sequence of non-breaking spaces. However, a <a
href="#soft-wrap-opportunity"><i>soft wrap opportunity</i></a> exists at
the end of the sequence.
</ul>
<p>Then, the entire block is rendered. Inlines are laid out, taking bidi
reordering into account, and <a href="#wrapping"><i>wrapping</i></a> as
specified by the ‘<a href="#white-space0"><code
class=property>white-space</code></a>’ property.
<p>As each line is laid out,
<ol>
<li>A sequence of collapsible spaces at the beginning of a line is
removed.
<li>Each tab is rendered as a horizontal shift that lines up the start
edge of the next glyph with the next tab stop. <dfn id=tab-stops>Tab
stops</dfn> occur at points that are multiples of the <a
href="#tab-size0"><i>tab size</i></a> from the block's starting content
edge. The <dfn id=tab-size0>tab size</dfn> is given by the ‘<a
href="#tab-size1"><code class=property>tab-size</code></a>’ property.
<li>A sequence of <a href="#collapsible"><i>collapsible</i></a> spaces at
the end of a line is removed.
<li>If spaces or tabs at the end of a line are non-collapsible but have
‘<code class=property>text-wrap</code>’ set to ‘<code
class=property>normal</code>’ the UA may visually collapse their
character advance widths.
</ol>
<p>White space that was not removed or collapsed during the white space
processing steps is called <dfn id=preserved>preserved</dfn> white space.
<div class=example>
<h4 id=egbidiwscollapse><span class=secno>4.1.1. </span> Example of
bidirectionality with white space collapsing</h4>
<p>Consider the following markup fragment, taking special note of spaces
(with varied backgrounds and borders for emphasis and identification):
<pre><code><ltr>A<span class=egbidiwsaA> </span><rtl><span
class=egbidiwsbB> </span>B<span
class=egbidiwsaB> </span></rtl><span
class=egbidiwsbC> </span>C</ltr></code></pre>
<p>where the <code><ltr></code> element represents a left-to-right
embedding and the <code><rtl></code> element represents a
right-to-left embedding. If the ‘<code
class=property>text-space-collapse</code>’ property is set to ‘<code
class=css>collapse</code>’, the above processing model would result in
the following:
<ul style="line-height:1.3">
<li>The space before the B (<span class=egbidiwsbB> </span>) would
collapse with the space after the A (<span class=egbidiwsaA> </span>).
<li>The space before the C (<span class=egbidiwsbC> </span>) would
collapse with the space after the B (<span class=egbidiwsaB> </span>).
</ul>
<p>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:
<pre>A<span class=egbidiwsaA> </span><span class=egbidiwsaB> </span>BC</pre>
<p>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.
</div>
<h4 id=line-break-transform><span class=secno>4.1.2. </span> Line Break
Transformation Rules</h4>
<p>When ‘<a href="#white-space0"><code
class=property>white-space</code></a>’ is ‘<code
class=css>pre</code>’, ‘<code class=css>pre-wrap</code>’, or
‘<code class=css>pre-line</code>’, <a href="#segment-break"><i>segment
breaks</i></a> are not <a href="#collapsible"><i>collapsible</i></a> and
are instead transformed into a preserved line feed (U+000A).
<p>For other values of ‘<a href="#white-space0"><code
class=property>white-space</code></a>’, <a
href="#segment-break"><i>segment breaks</i></a> are <a
href="#collapsible"><i>collapsible</i></a>, and are either transformed
into a space (U+0020) or removed depending on the context before and after
the break:
<ul>
<li>If the character immediately before or immediately after the segment
break is the zero-width space character (U+200B), then the break is
removed, leaving behind the zero-width space.
<li>Otherwise, if the East Asian Width property <a href="#UAX11"
rel=biblioentry>[UAX11]<!--{{!UAX11}}--></a> of both the character before
and after the line feed is F, W, or H (not A), and neither side is
Hangul, then the segment break is removed.
<li>Otherwise, the segment break is converted to a space (U+0020).
</ul>
<p class=note>Note that the white space processing rules have already
removed any tabs and spaces after the segment break before these checks
take place.
<p class=issue>Comments on how well this would work in practice would be
very much appreciated, particularly from people who work with Thai and
similar scripts. Note that browser implementations do not currently follow
these rules (although IE does in some cases transform the break).