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<!DOCTYPE html public '-//W3C//DTD HTML 4.01//EN'
'http://www.w3.org/TR/html4/strict.dtd'>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>CSS Text Level 3</title>
<link rel="stylesheet" type="text/css" href="default.css">
<style type="text/css">
.data, .proptable {
margin: 1em auto;
border-collapse: collapse;
border: solid #005A9B;
}
.data caption {
width: 100%;
text-align: center;
}
.data td, .data th,
.proptable td, .proptable th {
border: thin solid;
padding: 0.2em;
text-align: center;
}
.data thead th[scope="row"],
.proptable thead th[scope="row"] {
text-align: right;
background: #A4C8E2;
color: inherit;
}
.data thead,
.proptable thead {
background: #EEEEEE;
color: inherit;
}
.data tbody th:first-child,
.proptable tbody th:first-child {
text-align: right;
background: #EEEEEE;
color: inherit;
}
.data thead,
.data tbody,
.data tfoot,
.data colgroup {
border: solid;
}
table.propdef {
table-layout: auto;
}
.propdef th {
font-style: italic;
font-weight: normal;
text-align: left;
width: 3em;
}
dt dfn code {
font-size: inherit;
}
</style>
<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; }
tt[lang="ja"] { font-family: "MS Gothic", "Osaka", monospace }
</style>
<link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-WD.css">
</head>
<body>
<div class="head">
<p><a href="http://www.w3.org/"><img height="48" width="72" alt="W3C" src="http://www.w3.org/Icons/w3c_home"></a></p>
<h1>CSS Text Level 3</h1>
<!--
<h2 class="no-num no-toc">Editor's Draft $Date$</h2>
-->
<h2 class="no-num no-toc">W3C Working Draft 5 October 2010</h2>
<dl>
<dt>This version:</dt>
<!-- <dd><a href="http://dev.w3.org/csswg/css3-text/Overview.html">$Date$ (CVS $Revision$)</a> -->
<dd><a
href="http://www.w3.org/TR/2010/WD-css3-text-20101005/">http://www.w3.org/TR/2010/WD-css3-text-20101005/</a></dd>
<dt>Latest version:</dt>
<dd><a
href="http://www.w3.org/TR/css3-text/">http://www.w3.org/TR/css3-text/</a></dd>
<dt>Previous version:</dt>
<dd><a
href="http://www.w3.org/TR/2007/WD-css3-text-20070306/">http://www.w3.org/TR/2007/WD-css3-text-20070306/</a></dd>
<dt>Editors:</dt>
<dd><a href="http://fantasai.inkedblade.net/contact">Elika J. Etemad</a> (Invited Expert)</dd>
<dd><a href="mailto:kojiishi@gluesoft.co.jp">Koji Ishii</a> (Antenna House)</dd>
<dd><a href="mailto:murakami@antenna.co.jp">Shinyu Murakami</a> (Antenna House)</dd>
</dl>
<p class="copyright"><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">
Copyright</a> © 2007 <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.org/"><acronym
title="European Research Consortium for Informatics and
Mathematics">ERCIM</acronym></a>, <a
href="http://www.keio.ac.jp/">Keio</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>
<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, text decoration and text
transformation.</p>
<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>
<p>This Text module and a separate (upcoming) Writing Modes module
replace and obsolete the <a href="http://www.w3.org/TR/2003/CR-css3-text-20030514/">May
2003 CSS3 Text Module Candidate Recommendation</a>. Since this is a
thorough overhaul of the previous CR, a <a href="#changes">list
of changes</a> has been provided.</p>
<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>
<p><strong>If you have implemented properties from the
<a href="http://www.w3.org/TR/2003/CR-css3-text-20030514/">May 2003
CSS3 Text CR</a></strong>
<em>please</em> let us know so we can take that into account as
we redraft the spec. You can post to
<a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> (public),
post to the <a href="http://lists.w3.org/Archives/Member/w3c-css-wg/">CSS WG mailing list</a>
(<a href="http://cgi.w3.org/MemberAccess/AccessRequest">Member-restricted</a>),
or <a href="http://fantasai.inkedblade.net/contact">email fantasai directly</a> (personal).</p>
<p>The following features are at risk and may be cut from the spec during
its CR period: the 'text-outline' property, the ''unrestricted'' value
of 'text-wrap'</p>
<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>
<li><a href="#conformance"><span class=secno>2. </span> Conformance</a>
<ul class=toc>
<li><a href="#partial-impl"><span class=secno>2.1. </span> Partial and
Experimental Implementations</a>
</ul>
<li><a href="#white-space-processing"><span class=secno>3. </span> White
Space Processing</a>
<ul class=toc>
<li><a href="#white-space-collapsing"><span class=secno>3.1. </span>
White Space Collapsing: the ‘<code
class=property>white-space-collapsing</code>’ property</a>
<li><a href="#white-space-rules"><span class=secno>3.2. </span> The
White Space Processing Rules</a>
<ul class=toc>
<li><a href="#egbidiwscollapse"><span class=secno>3.2.1. </span>
Example of bidirectionality with white space collapsing</a>
<li><a href="#line-break-transform"><span class=secno>3.2.2. </span>
Line Break Transformation Rules</a>
<li><a href="#white-space-summary"><span class=secno>3.2.3. </span>
Informative Summary of White Space Collapsing Effects</a>
</ul>
<li><a href="#white-space"><span class=secno>3.3. </span> White Space
and Text Wrapping Shorthand: the ‘<code
class=property>white-space</code>’ property</a>
</ul>
<li><a href="#line-breaking"><span class=secno>4. </span> Line Breaking
and Word Boundaries</a>
<ul class=toc>
<li><a href="#line-break"><span class=secno>4.1. </span> Line Breaking
Restrictions for CJK Scripts: the ‘<code
class=property>line-break</code>’ property</a>
<li><a href="#word-break"><span class=secno>4.2. </span> Line Breaking
Rules for non-CJK Scripts: the ‘<code
class=property>word-break</code>’ property</a>
</ul>
<li><a href="#wrapping"><span class=secno>5. </span> Text Wrapping</a>
<ul class=toc>
<li><a href="#text-wrap"><span class=secno>5.1. </span> Text Wrap
Settings: the ‘<code class=property>text-wrap</code>’
property</a>
<ul class=toc>
<li><a href="#example-suppress"><span class=secno>5.1.1.
</span>Example of using ‘<code class=css>text-wrap:
suppress</code>’ in presenting a footer</a>
</ul>
<li><a href="#word-wrap"><span class=secno>5.2. </span> Emergency
Wrapping: the ‘<code class=property>word-wrap</code>’
property</a>
</ul>
<li><a href="#justification"><span class=secno>6. </span> Alignment and
Justification</a>
<ul class=toc>
<li><a href="#text-align"><span class=secno>6.1. </span> Text Alignment:
the ‘<code class=property>text-align</code>’ property</a>
<li><a href="#text-align-last"><span class=secno>6.2. </span> Last Line
Alignment: the ‘<code
class=property>text-align-last</code>’ property</a>
<li><a href="#text-justify"><span class=secno>6.3. </span> Justification
Method: the ‘<code class=property>text-justify</code>’
property</a>
</ul>
<li><a href="#spacing"><span class=secno>7. </span> Spacing</a>
<ul class=toc>
<li><a href="#word-spacing"><span class=secno>7.1. </span> Word Spacing:
the ‘<code class=property>word-spacing</code>’ property</a>
<li><a href="#letter-spacing"><span class=secno>7.2. </span> Tracking:
the ‘<code class=property>letter-spacing</code>’
property</a>
<li><a href="#punctuation-trim"><span class=secno>7.3. </span> Fullwidth
Punctuation Kerning: the ‘<code
class=property>punctuation-trim</code>’ property</a>
<li><a href="#text-autospace"><span class=secno>7.4. </span> Adding
space: the ‘<code class=property>text-autospace</code>’
property</a>
</ul>
<li><a href="#decoration"><span class=secno>8. </span> Text Decoration</a>
<ul class=toc>
<li><a href="#line-decoration"><span class=secno>8.1. </span> Line
Decoration: Underline, Overline, and Strike-Through</a>
<ul class=toc>
<li><a href="#text-decoration-line"><span class=secno>8.1.1. </span>
Text Decoration Lines: the ‘<code
class=property>text-decoration-line</code>’ property</a>
<li><a href="#text-decoration-color"><span class=secno>8.1.2. </span>
Text Decoration Color: the ‘<code
class=property>text-decoration-color</code>’ property</a>
<li><a href="#text-decoration-style"><span class=secno>8.1.3. </span>
Text Decoration Style: the ‘<code
class=property>text-decoration-style</code>’ property</a>
<li><a href="#text-decoration"><span class=secno>8.1.4. </span> Text
Decoration Shorthand: the ‘<code
class=property>text-decoration</code>’ property</a>
<li><a href="#text-decoration-skip"><span class=secno>8.1.5. </span>
Text Decoration Line Continuity: the ‘<code
class=property>text-decoration-skip</code>’ property</a>
<li><a href="#text-underline-position"><span class=secno>8.1.6.
</span> Text Underline Position: the ‘<code
class=property>text-underline-position</code>’ property</a>
</ul>
<li><a href="#emphasis-marks"><span class=secno>8.2. </span> Emphasis
Marks</a>
<ul class=toc>
<li><a href="#text-emphasis-style"><span class=secno>8.2.1. </span>
Emphasis Mark Style: the ‘<code
class=property>text-emphasis-style</code>’ property</a>
<li><a href="#text-emphasis-color"><span class=secno>8.2.2. </span>
Emphasis Mark Color: the ‘<code
class=property>text-emphasis-color</code>’ property</a>
<li><a href="#text-emphasis"><span class=secno>8.2.3. </span> Emphasis
Mark Shorthand: the ‘<code
class=property>text-emphasis</code>’ property</a>
<li><a href="#text-emphasis-position"><span class=secno>8.2.4. </span>
Emphasis Mark Position: the ‘<code
class=property>text-emphasis-position</code>’ property</a>
</ul>
<li><a href="#text-shadow"><span class=secno>8.3. </span> Text Shadows:
the ‘<code class=property>text-shadow</code>’ property</a>
<li><a href="#text-outline"><span class=secno>8.4. </span> Text
Outlines: the ‘<code class=property>text-outline</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>
<li><a href="#text-overflow"><span class=secno>9.3. </span> Overflow
Ellipsis: the ‘<code class=property>text-overflow</code>’
property</a>
</ul>
<li><a href="#transforming"><span class=secno>10. </span> Transforming
Text</a>
<ul class=toc>
<li><a href="#text-transform"><span class=secno>10.1. </span>
Transforming Text: the ‘<code
class=property>text-transform</code>’ property</a>
</ul>
<li><a href="#changes"><span class=secno>11. </span> Changes from the May
2003 CSS3 Text <abbr title="Candidate Recommendation">CR</abbr></a>
<li><a href="#recent-changes"><span class=secno>12. </span> Changes from
the June 2007 CSS3 Text WD</a>
<li><a href="#acknowledgements"><span class=secno>13. </span>
Acknowledgements</a>
<li><a href="#references"><span class=secno>14. </span> References</a>
<ul class=toc>
<li><a href="#normative-ref"><span class=secno>14.1. </span> Normative
References</a>
<li><a href="#informative-ref"><span class=secno>14.2. </span>
Informative References</a>
</ul>
<li><a href="#appendix"><span class=secno>15. </span> Appendix</a>
<ul class=toc>
<li><a href="#default-stylesheet"><span class=secno>15.1. </span>
Default UA Stylesheet</a>
</ul>
</ul>
<!--end-toc-->
<h2 id="intro"><span class="secno">1.</span>
Introduction</h2>
<p>[document here]</p>
<h2 id="conformance"><span class="secno">2.</span>
Conformance</h2>
<p>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]]</p>
<p>Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with <code>class="example"</code>,
like this:
<div class="example">
<p>This is an example of an informative example.</p>
</div>
<p>Informative notes begin with the word “Note” and are set apart from the
normative text with <code>class="note"</code>, like this:
<p class="note">Note, this is an informative note.</p>
<p>Conformance to CSS Text Level 3 is defined for three classes:
<dl>
<dt><dfn title="style sheet!!as conformance class">style sheet</dfn>
<dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
style sheet</a>.
<dt><dfn>renderer</dfn></dt>
<dd>A UA that interprets the semantics of a style sheet and renders
<span>documents</span> that use them.
<dt><dfn id="authoring-tool">authoring tool</dfn></dt>
<dd>A UA that writes a style sheet.
</dl>
<p>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.
<p>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 properties 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.)
<p>An authoring tool is conformant to CSS Text
Level 3 if it writes syntactically correct style sheets, according
to the generic CSS grammar and the individual grammars of each
property in this module.
<h3 id="partial-impl"><span class="secno">2.1.</span> Partial and Experimental Implementations</h3>
<p>UAs must treat as invalid any properties or values they do not support.
Experimental implementations of a feature should support only a
vendor-prefixed syntax for the property/value.</p>
<h2 id="white-space-processing"><span class="secno">3.</span>
White Space Processing</h2>
<p>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.
<p>Segments in the document source can be separated by a carriage
return (U+000D), a linefeed (U+000A) or both (U+000D U+000A),
or by some other mechanism that identifies the beginning
and end of document segments, such as the SGML RECORD-START
and RECORD-END tokens.
If no segmentation rules are specified for the document language,
each line feed (U+000A), carriage return (U+000D) and CRLF sequence
(U+000D U+000A) in the text is considered a segment break. (This
default rule also applies to generated content.)
In CSS, each such segment break is treated as a single line feed
character (U+000A).
<p>White space processing in CSS interprets white space characters
for rendering: it has no effect on the underlying document data.
In the context of CSS, the document white space set is defined
to be any space characters (Unicode value U+0020), tab characters
(U+0009), and line feeds (U+000A).
<p class="note">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 <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>
<p>Control characters other than U+0009 (tab), U+000A (line feed),
U+0020 (space), and U+202x (bidi formatting characters) are treated
as characters to render in the same way as any normal character.
<span class="issue">Copied from CSS2.1 but this has got to be wrong.</span>
<h3 id="white-space-collapsing"><span class="secno">3.1.</span>
White Space Collapsing: the 'white-space-collapsing' property</h3>
<p class="issue">This section is still under discussion and may change in future drafts.</p>
<table class="propdef">
<tbody>
<tr>
<th>Name:</th>
<td><dfn>white-space-collapsing</dfn></td>
</tr>
<tr>
<th>Value:</th>
<td>collapse | discard | [ [preserve | preserve-breaks] && trim-inner ]</td>
</tr>
<tr>
<th>Initial:</th>
<td>collapse</td>
</tr>
<tr>
<th>Applies to:</th>
<td>all elements</td>
</tr>
<tr>
<th>Inherited:</th>
<td>yes</td>
</tr>
<tr>
<th>Percentages:</th>
<td>N/A</td>
</tr>
<tr>
<th>Media:</th>
<td>visual</td>
</tr>
<tr>
<th>Computed value:</th>
<td>specified value</td>
</tr>
</tbody>
</table>
<p class="issue">Rename to white-space-trim or white-space-adjust? white-space-collapsing has an 'ing' and is confusing with XSL</p>
<p>This property declares whether and how
<a href="#white-space-processing">white space</a> inside the element is
collapsed. Values have the following meanings, which must be interpreted
according to the <a href="#white-space-rules">white space processing
rules</a>:</p>
<dl>
<dt><dfn title="white-space-collapsing:collapse"><code>collapse</code></dfn></dt>
<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).</dd>
<dt><dfn title="white-space-collapsing:preserve"><code>preserve</code></dfn></dt>
<dd>This value prevents user agents from collapsing sequences
of white space. Segment breaks are preserved as forced line breaks.</dd>
<dt><dfn title="white-space-collapsing:preserve-breaks"><code>preserve-breaks</code></dfn></dt>
<dd>This value collapses white space as for 'collapse', but preserves
segment breaks as forced line breaks.</dd>
<dt><dfn title="white-space-collapsing:discard"><code>discard</code></dfn></dt>
<dd>This value directs user agents to "discard" all white space in the
element.
<dt><dfn title="white-space-collapsing:trim-inner"><code>trim-inner</code></dfn></dt>
<dd>This value directs UAs to discard all whitespace at the beginning of
a block up to and including the last line break before the first
non-white-space character in the block as well as to discard all white
space at the end of a block starting with the first line break after
the last non-white-space character in the block.</dd>
</dl>
<h3 id="white-space-rules"><span class="secno">3.2.</span>
The White Space Processing Rules</h3>
<p>For each inline (including anonymous inlines), white space
characters are handled as follows, ignoring bidi formatting
characters as if they were not there:</p>
<ul>
<li id="collapse"><p>If <span class="property">'white-space-collapsing'</span>
is set to 'collapse' or 'preserve-breaks', white space characters
are considered <dfn>collapsible</dfn> and are processed by
performing the following steps:</p>
<ol>
<li>All spaces and tabs immediately following a line feed character
are removed. (This has the effect of discarding all white space
at the start of a line but preserving a trailing space if one
exists at the end.)</li>
<li>If <span class="property">'white-space-collapsing'</span> is not
'preserve-breaks', line feed characters are transformed for
rendering according to the <a href="#line-break-transform">line
break transformation rules</a>.
</li>
<li>Every tab (U+0009) is converted to a space (U+0020)</li>
<li>Any space (U+0020) following another collabsible space
(U+0020)—even a space before the inline—is removed.
However, if removing this space would eliminate a line breaking
opportunity in the text, that opportunity is still considered
to exist.</li>
</ol>
</li>
<li><p>If <span class="property">'white-space-collapsing'</span> is set to
'preserve', any sequence of spaces (U+0020) unbroken by an element
boundary is treated as a sequence of non-breaking spaces. However,
a line breaking opportunity exists at the end of the sequence.</p></li>
<li><p>If <span class="property">'white-space-collapsing'</span> is set to
'discard', the first white space character in every white space
sequence is converted to a zero width non-joiner (U+200C) and
the rest of the sequence is removed.</p>
</ul>
<p>Then, the entire block is rendered. Inlines are laid out, taking bidi
reordering into account, and wrapping as specified by the
<span class="property">'text-wrap'</span> property.</p>
<p>As each line is laid out,</p>
<ol>
<li>A sequence of collapsible spaces (U+0020) at the beginning of a
line is removed.</li>
<li>Each tab (U+0009) is rendered as a horizontal shift that lines up
the start edge of the next glyph with the next tab stop.
Tab stops occur at points that are multiples of 8 times the width
of a space (U+0020) rendered in the block's font from the block's
starting content edge.</li>
<li>A sequence of collapsible spaces (U+0020) at the end of a line
is removed.</li>
<li>If spaces (U+0020) or tabs (U+0009) at the end of a line are
non-collapsible but have 'text-wrap' set to 'normal' or 'suppress'
the UA may visually collapse them.
</ol>
<div class="example">
<h4 id="egbidiwscollapse"><span class="secno">3.2.1.</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):
</p>
<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 'white-space-collapsing' property is set
to 'collapse', the above processing model would result in the
following:</p>
<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>
<li>The space before the C (<span class="egbidiwsbC"> </span>)
would collapse with the space after the B (<span
class="egbidiwsaB"> </span>).</li>
</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:</p>
<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.</p>
</div>
<h4 id="line-break-transform"><span class="secno">3.2.2.</span>
Line Break Transformation Rules</h4>
<p>When line feeds are <a href="#collapse">collapsible</a>, they are
either transformed into a space (U+0020) or removed depending on the
script context before and after the line break.</p>
<p>The script context is determined by the Unicode-given script value
[UAX24] of the first character that side of the line feed. However,
characters such as punctuation that belong to the COMMON and INHERITED
scripts are ignored in this check; the next character is examined
instead. The UA must not examine characters outside the block and may
limit its examination to as few as four characters on each side of the
line feed. If the check fails to find an acceptable script value
(i.e. it has hit the check limits), then the script context is neutral.</p>
<p class="note">Note that the white space processing rules have already
removed any tabs and spaces after the line feed before these checks
take place.</p>
<ul>
<li>If the character immediately before or immediately after the line
feed is the zero width space character (U+200B), then the line feed
is removed.
<li>Otherwise, if the script context on one side of the line feed is
Han, Yi, Hiragana, or Katakana and the context on the other side is
Han, Yi, Hiragana, Katakana, or neutral, then the line feed is removed.
<p class="issue">IE removes line feed not only between two Hiragana
but also Hiragana and fullwidth alphabets.
Firefox, Opera, and Safari does not remove line breaks even between
two Hiragana.
Should fullwidth Latin be considered in this rule?</p>
<li>Otherwise, if ''text-autospace'' property is set to add extra spaces
for the combination of the character before the line feed and after,
then the line break is removed.
<p class="issue">Any feedback on this behavior is appreciated.
Now that we have text-autospace property, it makes sense to favor it than inserting spaces.
However, we also want to preserve backward compatibility as much as possible.
That is the reason why the line feed should be removed only if text-autospace inserts spaces instead.</p></li>
<li>Otherwise, the line feed is converted to a space (U+0020).
</ul>
<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.</p>
<h4 id="white-space-summary"><span class="secno">3.2.3.</span>
Informative Summary of White Space Collapsing Effects</h4>
<ul>
<li>Consecutive white space collapses into a single space.
<li>A sequence of line breaks and other white space between
two ideographic characters collapses into nothing unless
there is a space before the first line break in the sequence.
<li>A zero width space immediately before or anywhere after
a line break causes the entire sequence of white space
beginning with the line break to collapse into a zero width
space.
</ul>
<h3 id="white-space"><span class="secno">3.3.</span>
White Space and Text Wrapping Shorthand: the 'white-space' property</h3>
<table class="propdef">
<tbody>
<tr>
<th>Name:</th>
<td><dfn>white-space</dfn></td>
</tr>
<tr>
<th>Value:</th>
<td>normal | pre | nowrap | pre-wrap | pre-line</td>
</tr>
<tr>
<th>Initial:</th>
<td>not defined for shorthand properties</td>
</tr>
<tr>
<th>Applies to:</th>
<td>all elements</td>
</tr>
<tr>
<th>Inherited:</th>
<td>yes</td>
</tr>
<tr>
<th>Percentages:</th>
<td>N/A</td>
</tr>
<tr>
<th>Media:</th>
<td>visual</td>
</tr>
<tr>
<th>Computed value:</th>
<td>see individual properties</td>
</tr>
</tbody>
</table>
<p>The 'white-space' property is a shorthand for the
<a href="#white-space-collapsing">'white-space-collapsing'</a>
and <a href="#text-wrap">'text-wrap'</a> properties.
Not all combinations are represented.
Values have the following meanings:</p>
<dl>
<dt><dfn title="white-space:normal"><code>normal</code></dfn></dt>
<dd>Sets 'white-space-collapsing' to 'collapse' and
'text-wrap' to 'normal'</dd>
<dt><dfn title="white-space:pre"><code>pre</code></dfn></dt>
<dd>Sets 'white-space-collapsing' to 'preserve' and
'text-wrap' to 'none'</dd>
<dt><dfn title="white-space:nowrap"><code>nowrap</code></dfn></dt>
<dd>Sets 'white-space-collapsing' to 'collapse' and
'text-wrap' to 'none'</dd>
<dt><dfn title="white-space:pre-wrap"><code>pre-wrap</code></dfn></dt>
<dd>Sets 'white-space-collapsing' to 'preserve' and
'text-wrap' to 'normal'</dd>
<dt><dfn title="white-space:pre-line"><code>pre-line</code></dfn></dt>
<dd>Sets 'white-space-collapsing' to 'preserve-breaks' and
'text-wrap' to 'normal'</dd>
</dl>
<p>The following informative table summarizes the behavior of various
'white-space' values:</p>
<table class="data">
<thead>
<tr>
<th></th>
<th>New Lines</th>
<th>Spaces and Tabs</th>
<th>Text Wrapping</th>
</tr>
</thead>
<tbody>
<tr>
<th>normal</th>
<td>Collapse</td>
<td>Collapse</td>
<td>Wrap</td>
</tr>
<tr>
<th>pre</th>
<td>Preserve</td>
<td>Preserve</td>
<td>No wrap</td>
</tr>
<tr>
<th>nowrap</th>
<td>Collapse</td>
<td>Collapse</td>
<td>No wrap</td>
</tr>
<tr>
<th>pre-wrap</th>
<td>Preserve</td>
<td>Preserve</td>
<td>Wrap</td>
</tr>
<tr>
<th>pre-line</th>
<td>Preserve</td>
<td>Collapse</td>
<td>Wrap</td>
</tbody>
</table>
<h2 id="line-breaking"><span class="secno">4.</span>
Line Breaking and Word Boundaries</h2>
<p>For most scripts, 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.
<p>In several other writing systems, (including Chinese, Japanese, Yi,
and sometimes also Korean) a line break opportunities are based on
syllable boundaries, not words. In these systems a line can break
anywhere <em>except</em> between certain character combinations.
Additionally the level of strictness in these restrictions can vary
with the typesetting style.</p>
<p class="issue">Specify that out-of-flow elements do not introduce line
breaking opportunities. Specify whether images introduce line breaking
opportunities. Specify that CSS3 Text does not otherwise specify line
breaking opportunities.</p>
<h3 id="line-break"><span class="secno">4.1.</span>
Line Breaking Restrictions for CJK Scripts: the 'line-break' property</h3>
<p>This property specifies line break opporunities for CJK scripts.</p>
<p>CSS distinguishes between three levels of strictness in the rules for
implicit line breaking in CJK text. The precise set of rules in effect
for the strict and loose levels is up to the UA and should follow
language conventions. However, this specification does recommend that:</p>
<ul>
<li>Following breaks be forbidden in strict line breaking and allowed in normal:
<ul>
<li>breaks before Japanese small kana
<li>breaks before the KATAKANA-HIRAGANA PROLONGED SOUND MARK (U+30FC)
<li>breaks before the hyphens (U+2010, U+2013, U+301C, U+30A0)
</ul>
<li>Following breaks be forbidden in normal and strict line breaking and allowed in newspaper:
<ul>
<li>breaks before Japanese iteration marks (U+3005, U+303B, U+309D, U+309E, U+30FD, U+30FE)
<li>breaks before the middle dots (U+003A, U+003B, U+30FB, U+FF1A, U+FF1B, U+FF65)</li>
<li>breaks before the dividing punctuation marks (U+0021, U+003F, U+203C, U+2047, U+2048, U+2049, U+FF01, U+FF1F)</li>
<li>breaks before the inseparatable characters (U+2014, U+2025, U+2026, U+3033, U+3034, U+3035)</li>
<li>breaks before the iteration marks (U+3005, U+303B, U+309D, U+309E, U+30FD, U+30FE)</li>
<li>breaks before the postfixes (U+0025, U+00A2, U+00B0, U+2030, U+2032, U+2033, U+2103, U+FF05, U+FFE0)</li>
<li>breaks after the prefixes (U+0024, U+00A3, U+00A5, U+20AC, U+2116, U+FF04, U+FFE1, U+FFE5)</li>
</ul>
</ul>
<p class="note">Information on line breaking conventions can be found in
[<a href="#JIS4051">JIS4051</a>] for Japanese,
[<a href="#ZHMARK">标点符号</a>] for Chinese, and [?] for Korean, and
in [<a href="#UAX14">UAX14</a>] for all scripts in Unicode.
<!-- The CSS Working Group notes that although UAX 14 contains a wealth of
information about line breaking conventions, a literal implementation
of its algorithm has been found to be inadequate in multiple situations. --></p>
<p class="issue">Any guidance for appropriate references here would be
much appreciated.</p>
<table class="propdef">
<tbody>
<tr>
<th>Name:</th>
<td><dfn>line-break</dfn></td>
</tr>
<tr>
<th>Value:</th>
<td>auto | newspaper | normal | strict | keep-all</td>
</tr>
<tr>
<th>Initial:</th>
<td>auto</td>
</tr>
<tr>
<th>Applies to:</th>
<td>all elements</td>
</tr>
<tr>
<th>Inherited:</th>
<td>yes</td>
</tr>
<tr>
<th>Percentages:</th>
<td>N/A</td>
</tr>
<tr>
<th>Media:</th>
<td>visual</td>
</tr>
<tr>
<th>Computed value:</th>
<td>specified value</td>
</tr>
</tbody>
</table>
<p>This property specifies what set of line breaking restrictions are in
effect within the element.
Values have the following meanings:</p>
<dl>
<dt><dfn title="line-break:auto"><code>auto</code></dfn></dt>
<dd>The UA determines the set of line-breaking restrictions to use for CJK scripts,
and it may vary the restrictions based on the length of the line; e.g.,
use a less restrictive set of line-break restrictions for short lines,
so that justifications works better without adding a lot of extra spaces.</dd>
<dt><dfn title="line-break:newspaper"><code>newspaper</code></dfn></dt>
<dd>Breaks CJK scripts using the least restrictive set of line-breaking restrictions
for short lines, such as newspapers.</dd>
<dt><dfn title="line-break:normal"><code>normal</code></dfn></dt>
<dd>Breaks CJK scripts using a normal set of line-breaking restrictions.</dd>
<dt><dfn title="line-break:strict"><code>strict</code></dfn></dt>
<dd>Breaks CJK scripts using a more restrictive set of line-breaking restrictions than 'normal'.</dd>
<dt><dfn title="line-break:keep-all"><code>keep-all</code></dfn></dt>
<dd>Sequences of CJK characters can no longer break on implied break points.
This option should only be used where the presence of white space
characters still creates line-breaking opportunities, as in Korean.</dd>
</dl>
<h3 id="word-break"><span class="secno">4.2.</span>
Line Breaking Rules for non-CJK Scripts: the 'word-break' property</h3>
<p>This property specifies line break opportunities for non-CJK scripts.</p>
<table class="propdef">
<tbody>
<tr>
<th>Name:</th>
<td><dfn>word-break</dfn></td>
</tr>
<tr>
<th>Value:</th>
<td>normal | break-all | hyphenate </td>
</tr>
<tr>
<th>Initial:</th>
<td>normal</td>
</tr>
<tr>
<th>Applies to:</th>