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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en-US">
<head>
<title>CSSOM</title>
<style type="text/css">
pre.idl { border:solid thin; background:#eee; color:#000; padding:0.5em }
pre.idl :link, pre.idl :visited { color:inherit; background:transparent }
dfn { font-weight:bold; font-style:normal }
.example { margin-left:1em; padding-left:1em; border-left:double; color:#222; background:#fcfcfc }
.example table code { color:inherit }
td, th { padding:.1em }
.note { margin-left:2em; color:green; font-style:italic; font-weight:bold }
p.note::before { content:"Note: " }
.XXX { padding:.5em; border:solid red }
p.XXX::before { content:"Issue: " }
dl.switch { padding-left:2em }
dl.switch > dt { text-indent:-1.5em }
dl.switch > dt:before { content:'\21AA'; padding:0 0.5em 0 0; display:inline-block; width:1em; text-align:right; line-height:0.5em }
m em.ct { text-transform:lowercase; font-variant:small-caps; font-style:normal }
code { color:orangered }
code :link, code :visited { color:inherit }
</style>
<link rel="stylesheet" href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS]">
</head>
<body class="draft">
<div class="head">
<h1 id="cssom">CSSOM</h1>
<h2 class="no-num no-toc" id="">[LONGSTATUS] [DATE: 3 August 2002]</h2>
<dl>
<dt>This Version:</dt>
<dd><a href="[VERSION]/">http://www.w3.org/TR/[YEAR]/ED-cssom-[CDATE]/</a></dd>
<dt>Latest Version:</dt>
<dd><a href="http://www.w3.org/TR/cssom/">http://www.w3.org/TR/cssom/</a></dd>
<dt>Latest Editor's draft:</dt>
<dd><a href="http://dev.w3.org/csswg/cssom/">http://dev.w3.org/csswg/cssom/</a></dd>
<dt>Previous Version:</dt>
<dd><a href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/">http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/</a></dd>
<dt>Editor:</dt>
<dd><a href="http://annevankesteren.nl/">Anne van Kesteren</a>
(<a href="http://www.opera.com/">Opera Software ASA</a>)
<<a href="mailto:annevk@opera.com">annevk@opera.com</a>></dd>
</dl>
</div>
<h2 class="no-num no-toc" id="abstract">Abstract</h2>
<p>CSSOM defines APIs (including generic parsing and serialization rules)
for Media Queries, Selectors, and of course CSS itself.</p>
<h2 class="no-num no-toc" id="sotd">Status of this Document</h2>
<p class="XXX">The plan is that this document provides the successor to
DOM Level 2 Style.</p>
<!--status-->
<h2 class="no-num no-toc" id="toc">Table of Contents</h2>
<!--toc-->
<h2 id="introduction">Introduction</h2>
<p class="XXX">...</p>
<h3 id="history">History</h3>
<p>Several interfaces from DOM Level 2 Style
<a href="http://www.w3.org/mid/Pine.LNX.4.05.10310302134070.1173-100000@lanalana.inria.fr" title="[CSSOM] CSSValue and related interfaces (message from the CSS WG)">have
been obsoleted</a> because they were thought to be too awkward for
frequent use. This specification no longer contains those features.
<code>DOMImplementationCSS</code> and <code>CSSCharsetRule</code> have
been removed as well as they were not deemed necessary.</p>
<h2 id="infrastructure">Common Infrastructure</h2>
<h3 id="terminology">Terminology</h3>
<p class="XXX">
<dfn>resolve a URL</dfn>,
<dfn>case-sensitive</dfn>,
<dfn>converted to ASCII lowercase</dfn>,
<dfn>ASCII case-insensitive</dfn>,
<dfn>URL</dfn>,
<dfn>Content-Type metadata</dfn>,
<dfn>supported styling language</dfn>,
<dfn><code>xml-stylesheet</code> processing instruction</dfn>,
<dfn>fetch</dfn>, ...
</p>
<p>When this specification talks about object <code><var title="">A</var></code>
where <code><var title="">A</var></code> is actually an interface, it generally means
an object implementing interface <code><var title="">A</var></code>.</p>
<p>The term <dfn id="whitespace">whitespace</dfn> is used as defined in
CSS. <!--XXX <a href="#ref-css">[CSS]</a>--></p>
<h3 id="conformance">Conformance Requirements</h3>
<p>Everything in this specification is normative except for diagrams,
examples, notes and sections marked non-normative.</p>
<p>The key words <em class="ct">must</em>, <em class="ct">must not</em>,
<em class="ct">required</em>, <em class="ct">shall</em>, <em class="ct">shall
not</em>, <em class="ct">should</em>, <em class="ct">should not</em>,
<em class="ct">recommended</em>, <em class="ct">may</em>, and
<em class="ct">optional</em> in the normative parts of this document are to be
interpreted as described in RFC 2119
<a href="#ref-rfc2119">[RFC2119]</a>.</p>
<!-- XXX
<p>The following conformance classes are defined (and considered) by this
specification:</p>
<dl>
<dt><dfn id="conforming-implementation">conforming implementation</dfn></dt>
<dd>A user agent that implements all interfaces described in this
specification and follows all <em class="ct">must</em>-,
<em class="ct">required</em>- and <em class="ct">shall</em>-level of criteria
in this specification.</dd>
<dt><dfn id="conforming-document">conforming document</dfn></dt>
<dd>A document that follows all <em class="ct">must</em>-,
<em class="ct">required</em>- and <em class="ct">shall</em>-level of criteria
in this specification that apply to document authors.</dd>
<dt><dfn id="conforming-authoring-tool">conforming authoring tool</dfn></dt>
<dd>One that produces conforming documents.</dd>
</dl>
-->
<h3>Common Serializing Idioms</h3>
<p>To <dfn>serialize a character</dfn> means to create a string of
"<code>\</code>" (U+005C), followed by the character.</p>
<p>To <dfn>serialize a character as code point</dfn> means to create a
string of "<code>\</code>" (U+005C), followed by the Unicode code point as
the smallest possible number of hexadecimal digits in the range 0-9 a-f
(U+0030 to U+0039 and U+0061 to U+0066) to represent the code point in
base 16, followed by a space (U+0020).</p>
<p>To <dfn>serialize an identifier</dfn> means to create a string represented
by the concatenation of, for each character of the identifier:</p>
<ul>
<li>If the character is in the range U+0000 to U+001F, the character
<span title="serialize a character as code point">escaped as code point</span>.</li>
<li>If the character is the first character and is in the range 0-9
(U+0030 to U+0039), the character
<span title="serialize a character as code point">escaped as code point</span>.</li>
<li>If the character is the second character and is in the range 0-9
(U+0030 to U+0039) and the first character is a "<code>-</code>"
(U+002D), the character
<span title="serialize a character as code point">escaped as code point</span>.</li>
<li>If the character is the second character and is "<code>-</code>"
(U+002D) and the first character is "<code>-</code>" too, the
<span title="serialize a character">escaped</span> character.</li>
<li>If the character is not handled by one of the above rules and is
greater than or equal to U+0080, is "<code>-</code>" (U+002D) or
"<code>_</code>" (U+005F), or is in one of the ranges 0-9 (U+0030 to
U+0039), A-Z (U+0041 to U+005A), or a-z (U+0061 to U+007A), the character
itself.</li>
<li>Otherwise, the <span title="serialize a character">escaped</span>
character.</li>
</ul>
<p>To <dfn>serialize a string</dfn> means to create a string represented
by '<code>"</code>' (U+0022), followed by the result of applying the rules
below to each character of the given string, followed by
'<code>"</code>' (U+0022):</p>
<ul>
<li>If the character is in the range U+0000 to U+001F, the character
<span title="serialize a character as code point">escaped as code point</span>.</li>
<li>If the character is '<code>"</code>' (U+0022) or '<code>\</code>'
(U+005C), the <span title="serialize a character">escaped</span> character.</li>
<li>Otherwise, the character itself.</li>
</ul>
<p class="note">"<code>'</code>" (U+0027) is not escaped because strings
are always serialized with '<code>"</code>' (U+0022).</p>
<p>To <dfn>serialize a URL</dfn> means to create a string represented by
"<code title="">url(</code>", followed by the
<span title="serialize a string">string escaped</span> value of the given
string, followed by "<code>)</code>".</p>
<p>To <dfn>serialize a comma-separated list</dfn> concatenate all items of
the list in list order while separating them by "<code>,</code>" (U+002C),
followed by a space (U+0020).</p>
<p>To <dfn>serialize a whitespace-separated list</dfn> concatenate all
items of the list in list order while separating them a space (U+0020).</p>
<h2>Media Queries</h2>
<p>Media queries are defined by the Media Queries specification. This
section defines various concepts around media queries, including their API
and serialization form.</p>
<!-- XXX ref -->
<h3>Parsing Media Queries</h3>
<p>To
<dfn id="parse-a-list-of-media-queries">parse a list of media queries</dfn>
for a given string <var title="">s</var> into a list of media queries is defined in
the Media Queries specification. Return the list of one or more media
queries that the algorithm defined there gives.</p> <!-- XXX ref -->
<p class="note">A media query that ends up being "ignored" will turn
into "<code title="">not all</code>".</p>
<p>To
<dfn id="parse-a-media-query">parse a media query</dfn> for a given string
<var title="">s</var> means to follow the
<span>parse a list of media queries</span> steps and return null if more
than one media query is returned or a media query if a
single media query is returned.</p>
<p class="note">Again, a media query that ends up being "ignored" will
turn into "<code title="">not all</code>".</p>
<h3>Serializing Media Queries</h3>
<p>To
<dfn id="serialize-a-list-of-media-queries">serialize a list of media queries</dfn>
run these steps:</p>
<ol>
<li><p>If the list of media queries is empty return the empty string and
terminate these steps.</p></li>
<li><p><span title="serialize a media query">Serialize</span> each
media query in the list of media queries, sort them in lexicographical
order, and then
<span title="serialize a comma-separated list">serialize</span> the
list.</p></li>
</ol>
<p>To
<dfn id="serialize-a-media-query">serialize a media query</dfn> let
<var title="">s</var> be the empty string, run the steps below, and
finally return <var title="">s</var>:</p>
<ol>
<li><p>If the media query is negated append "<code>not</code>", followed
by a space (U+0020), to <var title="">s</var>.</p></li>
<li><p>Let <var title="">type</var> be the media type of the media query,
<span title="serialize an identifier">escaped</span> and
<span>converted to ASCII lowercase</span>.</p></li>
<li><p>If the media query does not contain media features append
<var title="">type</var>, to <var title="">s</var>,
then return <var title="">s</var> and terminate this algorithm.</p></li>
<li><p>If <var title="">type</var> is not "<code>all</code>" or if the
media query is negated append <var title="">type</var>, followed by a
space (U+0020), followed by "<code>and</code>", followed by a space
(U+0020), to <var title="">s</var>.</p></li>
<li><p>Sort the media features in lexicographical order.</p></li>
<li>
<p>Then, for each media feature:</p>
<ol>
<li>Append a "<code>(</code>" (U+0028), followed by the media feature
name, <span>converted to ASCII lowercase</span>, to
<var title="">s</var>.</p></li>
<li><p>If a value is given append a "<code>:</code>" (U+003A), followed
by a space (U+0020), followed by the
<span title="serialize a media feature value">serialized media feature value</span>,
to <var title="">s</var>.</p>
<li><p>Append a "<code>)</code>" (U+0029) to
<var title="">s</var>.</p></li>
<li><p>If this is not the last media feature append a space (U+0020),
followed by "<code>and</code>", followed by a space (U+0020), to
<var title="">s</var>.</p></li>
</ol>
</li>
</ol>
<div class="example">
<p>Here are some examples of input (first column) and output (second
column):</p>
<table>
<thead>
<tr><th>Input<th>Output
<tbody>
<tr>
<td><code>not screen and (min-WIDTH:5px) AND (max-width:40px )</code>
<td><code>not screen and (max-width: 40px) and (min-width: 5px)</code>
<tr>
<td><code>all and (color) and (color)</code>
<td><code>(color)</code>
</table>
</div>
<h4>Serializing Media Feature Values</h4>
<p class="XXX">This should probably be done in terms of mapping it to
serializing CSS values as media features are defined in terms of CSS
values after all.</p>
<p>To <dfn id="serialize-a-media-feature-value">serialize a media feature value</dfn>
named <var title="">v</var> locate <var title="">v</var> in the first
column of the table below and use the serialization format described in
the second column:</p>
<table>
<tr>
<th>Media Feature
<th>Serialization
<tr>
<td><code title="">width</code>
<td>...
<tr>
<td><code title="">height</code>
<td>...
<tr>
<td><code title="">device-width</code>
<td>...
<tr>
<td><code title="">device-height</code>
<td>...
<tr>
<td><code title="">orientation</code>
<td>
<p>If the value is `<code title="">portrait</code>`: "<code title="">portrait</code>".</p>
<p>If the value is `<code title="">landscape</code>`: "<code title="">landscape</code>".</p>
<tr>
<td><code title="">aspect-ratio</code>
<td>...
<tr>
<td><code title="">device-aspect-ratio</code>
<td>...
<tr>
<td><code title="">color</code>
<td>...
<tr>
<td><code title="">color-index</code>
<td>...
<tr>
<td><code title="">monochrome</code>
<td>...
<tr>
<td><code title="">resolution</code>
<td>...
<tr>
<td><code title="">scan</code>
<td>
<p>If the value is `<code title="">progressive</code>`: "<code title="">progressive</code>".</p>
<p>If the value is `<code title="">interlace</code>`: "<code title="">interlace</code>".</p>
<tr>
<td><code title="">grid</code>
<td>...
</table>
<p>Other specifications can extend this table and vendor-prefixed media
features can have custom serialization formats as well.</p>
<h3>Comparing Media Queries</h3>
<p>To
<dfn id="compare-lists-of-media-queries">compare lists of media queries</dfn>
<var title="">l1</var> and <var title="">l2</var> means to
<span title="serialize a list of media queries">serialize</span> them both
and return true if they are a <span>case-sensitive</span> match and false
if they are not.</p>
<p>To
<dfn id="compare-media-queries">compare media queries</dfn>
<var title="">m1</var> and <var title="">m2</var> means to
<span title="serialize a media query">serialize</span> them both and
return true if they are a <span>case-sensitive</span> match and false if
they are not.</p>
<h3>The <code title="">MediaList</code> Interface</h3>
<p>An object that implements the <code>MediaList</code> interface has an
associated <dfn>collection of media queries</dfn>.</p>
<!-- http://dev.w3.org/2006/webapi/WebIDL/#idl-indexed-properties -->
<pre class="idl">interface <dfn>MediaList</dfn> {
stringifier attribute DOMString <span title="dom-MediaList-mediaText">mediaText</span>;
readonly attribute unsigned long <span title="dom-MediaList-length">length</span>;
getter DOMString <span title="dom-MediaList-item">item</span>(unsigned long <var title="">index</var>);
void <span title="dom-MediaList-appendMedium">appendMedium</span>(DOMString <var title="">medium</var>);
void <span title="dom-MediaList-deleteMedium">deleteMedium</span>(DOMString <var title="">medium</var>);
};</pre>
<p>The
<dfn id="dom-medialist-mediatext" title="dom-MediaList-mediaText"><code>mediaText</code></dfn>
attribute, on getting, <em class="ct">must</em> return a
<span title="serialize a list of media queries">serialization</span> of
the <span>collection of media queries</span>.</p>
<p>On setting the <code title="dom-MediaList-mediaText">mediaText</code>
attribute these steps <em class="ct">must</em> be run:</p>
<ol>
<li><p>Empty the <span>collection of media queries</span>.</p></li>
<li><p>If the given value is the empty string terminate these
steps.</p></li>
<li><p>Append all the media queries as a result of
<span title="parse a list of media queries">parsing</span> the given
value to the <span>collection of media queries</span>.</p></li>
</ol>
<p>The
<dfn id="dom-medialist-length" title="dom-MediaList-length"><code>length</code></dfn>
attribute <em class="ct">must</em> return the number of media queries in
the <span>collection of media queries</span>.</p>
<p>The
<dfn id="dom-medialist-item" title="dom-MediaList-item"><code>item(<var title="">index</var>)</code></dfn>
method <em class="ct">must</em> return the media query in the
<span>collection of media queries</span> given by
<var title="">index</var>, or null, if <var title="">index</var> is
greater than or equal to the number of media queries in the
<span>collection of media queries</span>.</p>
<!-- XXX need consistency here WebIDL? list of media queries? -->
<p>The
<dfn id="dom-medialist-appendmedium" title="dom-MediaList-appendmedium"><code>appendMedium(<var title="">medium</var>)</code></dfn>
method <em class="ct">must</em> run these steps:</p>
<ol>
<li><p>Let <var title="">m</var> be the result of
<span title="parse a media query">parsing</span> the given
value.</p></li>
<li><p>If <var title="">m</var> is null terminate these steps.</p></li>
<li><p>If <span title="compare media queries">comparing</span>
<var title="">m</var> with any of the media queries in the
<span>collection of media queries</span> returns true terminate these
steps.</p></li>
<li><p>Append <var title="">m</var> to the
<span>collection of media queries</span>.</p></li>
</ol>
<p>The
<dfn id="dom-medialist-deletemedium" title="dom-MediaList-deletemedium"><code>deleteMedium(<var title="">medium</var>)</code></dfn>
method <em class="ct">must</em> run these steps:</p>
<ol>
<li><p>Let <var title="">m</var> be the result of
<span title="parse a media query">parsing</span> the given
value.</p></li>
<li><p>If <var title="">m</var> is null terminate these steps.</p></li>
<li><p>Remove any media query from the
<span>collection of media queries</span> for which
<span title="compare media queries">comparing</span> the media query with
<var title="">m</var> returns true.</p></li>
</ol>
<h3>Creating a <code title="">MediaList</code> Object</h3>
<p>To
<dfn id="create-a-medialist-object">create a <code>MediaList</code> object</dfn>
from <var title="">s</var> run these steps:</p>
<ol>
<li><p>Create a new <code>MediaList</code> object.</p></li>
<li><p>Set its <span title="dom-MediaList-mediaText">mediaText</span>
attribute to <var title="">s</var>.</p></li>
<li><p>Return the newly created <code>MediaList</code> object.</p></li>
</ol>
<h2>Selectors</h2>
<p>Selectors are defined in the Selectors specification. This section
mainly defines how to serialize them.</p> <!-- XXX ref -->
<!-- XXX ref universal selector etc? some are in <span> some not -->
<h3>Parsing Selectors</h3>
<p>To
<dfn id="parse-a-group-of-selectors">parse a group of selectors</dfn>
means to parse the value using the <code title="">selectors_group</code>
production defined in the Selectors specification and return either a
group of selectors if parsing did not fail or null if parsing did
fail.</p> <!-- XXX ref -->
<h3>Serializing Selectors</h3>
<!-- http://dump.testsuite.org/2009/cssom/serializing-selectors.htm -->
<p>To
<dfn id="serialize-a-group-of-selectors">serialize a group of selectors</dfn>
<span title="serialize a selector">serialize</span> each selector in the
group of selectors and then
<span title="serialize a comma-separated list">serialize</span> the
group.</p>
<p>To <dfn id="serialize-a-selector">serialize a selector</dfn> let
<var title="">s</var> be the empty string, run the steps below for each
part of the chain of the selector, and finally return
<var title="">s</var>:</p>
<ol>
<li><p>If there is only one <span>simple selector</span> in the
<span>sequence of simple selectors</span> which is a
<span>universal selector</span>, append the result of
<span title="serialize a simple selector">serializing</span> the
<span>universal selector</span> to <var title="">s</var>.</p></li>
<li><p>Otherwise, for each <span>simple selector</span> in the
<span>sequence of simple selectors</span> that is not a
universal selector of which the <span>namespace prefix</span> maps to
the null namespace (not in a namespace) or of which the
<span>namespace prefix</span> maps to a namespace that is not the
<span>default namespace</span>
<span title="serialize a simple selector">serialize</span> the
<span>simple selector</span> and append the result to
<var title="">s</var>.</p></li>
<li><p>If this is not the last part of the chain of the selector append a
space (U+0020), followed by the combinator
"<code>></code>",
"<code>+</code>", or
"<code>~</code>"
as appropriate, followed by another space (U+0020) if the combinator was
not whitespace, to <var title="">s</var>.</p></li>
<li><p>If this is the last part of the chain of the selector and there is
a pseudo-element, append "<code>::</code>" followed by the name of the
pseudo-class, to <var title="">s</var>.</p></li>
</ol>
<p>To
<dfn id="serialize-a-simple-selector">serialize a simple selector</dfn>
let <var title="">s</var> be the empty string, run the steps below, and
finally return <var title="">s</var>:</p>
<dl class="switch">
<dt>type selector</dt>
<dt>universal selector</dt>
<dd>
<ol>
<li><p>If the <span>namespace prefix</span> maps to a namespace that is
not the <span>default namespace</span> and is not the
null namespace (not in a namespace) append the
<span title="serialize an identifier">escaped</span>
<span>namespace prefix</span>, followed by a "<code>|</code>" (U+007C)
to <var title="">s</var>.</p></li>
<li><p>If the <span>namespace prefix</span> maps to a namespace that is
the null namespace (not in a namespace) append
"<code>|</code>" (U+007C) to <var title="">s</var>.</p></li>
<!-- This includes |* -->
<li><p>If this is a type selector append the
<span title="serialize an identifier">escaped</span> element name to
<var title="">s</var>.</p>
<li><p>If this is a universal selector append "<code>*</code> (U+002A)
to <var title="">s</var>.</p></li>
</ol>
</dd>
<dt>attribute selector</dt>
<dd>
<ol>
<li><p>Append "<code>[</code>" (U+005B) to
<var title="">s</var>.</p></li>
<li><p>If the <span>namespace prefix</span> maps to a namespace that is
not the null namespace (not in a namespace) append the
<span title="serialize an identifier">escaped</span>
<span>namespace prefix</span>, followed by a "<code>|</code>" (U+007C)
to <var title="">s</var>.</p></li>
<li><p>If the <span>namespace prefix</span> maps to a namespace that is
the null namespace (not in a namespace) append
"<code>|</code>" (U+007C) to <var title="">s</var>.</p></li>
<!-- This includes |* -->
<li><p>Append the <span title="serialize an identifier">escaped</span>
attribute name to <var title="">s</var>.</p></li>
<li><p>If there is an attribute value specified, append
"<code>=</code>",
"<code>~=</code>",
"<code>|=</code>",
"<code>^=</code>",
"<code>$=</code>", or
"<code>*=</code>"
as appropriate (depending on the type of attribute selector), followed
by the <span title="serialize a string">string escaped</span>
attribute value, to <var title="">s</var>.</p></li>
<li><p>Append "<code>]</code>" (U+005D) to
<var title="">s</vaR>.</p></li>
</ol>
</dd>
<dt>class selector</dt>
<dd><p>Append a "<code>.</code>" (U+002E), followed by the
<span title="serialize an identifier">escaped</span> class name to
<var title="">s</var>.</p></dd>
<dt>ID selector</dt>
<dd><p>Append a "<code>#</code>" (U+0023), followed by the
<span title="serialize an identifier">escaped</span> ID to
<var title="">s</var>.</p></dd>
<dt>pseudo-class</dt>
<dd>
<p>If the pseudo-class does not accept arguments append
"<code>:</code>" (U+003A), followed by the name of the pseudo-class, to
<var title="">s</var>.</p>
<p>Otherwise, append "<code>:</code>" (U+003A), followed by the name of
the pseudo-class, followed by "<code>(</code>" (U+0028), followed by the
value of the pseudo-class argument determined as per below, followed by
"<code>)</code>" (U+0029), to <var title="">s</var>.</p>
<dl class="switch">
<dt><code title="">:lang()</code></dt>
<dd><p>The <span title="serialize an identifier">escaped</span>
value.</p></dd>
<dt><code title="">:nth-child()</code></dt>
<dt><code title="">:nth-last-child()</code></dt>
<dt><code title="">:nth-of-type()</code></dt>
<dt><code title="">:nth-last-of-type()</code></dt>
<dd>
<ol>
<li><p>If the value is odd let the value be
"<code title="">2n+1</code>".</p></li>
<li><p>If the value is even let the value be
"<code title="">2n</code>".</p></li>
<li><p>If <var title="">a</var> is zero let the value be
<var title="">b</var>
<span title="serialize a CSS component value">serialized</span> as <integer>.</p></li>
<li><p>If <var title="">a</var> is one or minus one and
<var title="">b</var> is zero let the value be
"<code title="">n</code>" (U+006E).</p></li>
<li><p>If <var title="">a</var> is one or minus one let the value be
"<code title="">n</code>" (U+006E), followed by
"<code>+</code>" (U+002B) if <var title="">b</var> is positive,
followed by <var title="">b</var>
<span title="serialize a CSS component value">serialized</span> as <integer>.</p></li>
<li><p>If <var title="">b</var> is zero let the value be
<var title="">a</var>
<span title="serialize a CSS component value">serialized</span> as <integer>,
followed by "<code title="">n</code>" (U+006E).</p></li>
<li><p>Otherwise let the value be
<var title="">a</var>
<span title="serialize a CSS component value">serialized</span> as <integer>,
followed by "<code title="">n</code>" (U+006E), followed by
"<code>+</code>" (U+002B) if <var title="">b</var> is positive,
followed by <var title="">b</var>
<span title="serialize a CSS component value">serialized</span> as <integer>.</p></li>
</ol>
</dd>
<dt><code title="">:not()</code></dt>
<dd><p>The result of serializing the value using the rules for
<span title="serialize a group of selectors">serializing a group of selectors</span>.</p></dd>
</dl>
</dd>
</dl>
<h2>CSS</h2>
<h3>Style Sheet</h3>
<!-- XXX
element inserted into the DOM, style sheet created, element removed from
the DOM, what happens to StyleSheet?
-->
<p>A <dfn id="style-sheet">style sheet</dfn> is an abstract concept that
represents a style sheet as defined by the CSS specification. In the DOM a
<span>style sheet</span> is a <code>CSSStyleSheet</code> object. A
<span>style sheet</span> has a number of associated properties:</p>
<dl>
<dt><dfn id="style-sheet-type">style sheet type</dfn></dt>
<dd><p>The literal string "<code>text/css</code>".</p></dd>
<dt><dfn id="style-sheet-location">style sheet location</dfn></dt>
<dd><p>The <span>URL</span> of the <span>style sheet</span> or null if
the <span>style sheet</span> was embedded.</p></dd>
<dt><dfn id="style-sheet-parent">style sheet parent</dfn></dt>
<dd><p>The <span>style sheet</span> that is the parent of the
<span>style sheet</span>.</p></dd>
<dt><dfn id="style-sheet-owner-node">style sheet owner node</dfn></dt>
<dd><p>The DOM node associated with the <span>style sheet</span> or
null if there is no associated DOM node.</p></dd>
<dt><dfn id="style-sheet-owner-css-rule">style sheet owner CSS rule</dfn></dt>
<dd><p>The <span>CSS rule</span> in the <span>style sheet parent</span>
that caused the inclusion of the <span>style sheet</span> or null if
there is no such <span>CSS rule</span>.</p></dd>
<dt><dfn id="style-sheet-media">style sheet media</dfn></dt>
<dd>
<p>The <code>MediaList</code> object associated with the
<span>style sheet</span>.</p>
<p>If this property is set to a string run the
<span>create a <code>MediaList</code> object</span> steps for that
string and associate the returned object with the
<span>style sheet</span>.</p>
</dd>
<dt><dfn id="style-sheet-title">style sheet title</dfn></dt>
<dd>
<p>The title of the <span>style sheet</span>. It is said to be empty
if the title is the empty string.</p>
<div class="example">
<p>In these examples the <span>style sheet title</span> ends up being
empty:</p>
<pre><style title=""> body { background:papayawhip } </style></pre>
<pre><style> body { background:orange } </style></pre>
</div>
</dd>
<dt><dfn id="style-sheet-alternate-flag">style sheet alternate flag</dfn></dt>
<dd>
<p>Either true or false. False by default.</p>
<div class="example">
<p>The following <span title="style sheet">style sheets</span> have
their <span>style sheet alternate flag</span> set:</p>
<pre><code><?xml-stylesheet alternate="yes" title="x" href="data:text/css,…"?></code></pre>
<pre><code><link rel="alternate stylesheet" title="x" href="data:text/css,…"></code></pre>
</div>
</dd>
<dt><dfn id="style-sheet-disabled-flag">style sheet disabled flag</dfn></dt>
<dd>
<p>Either true or false. False by default.</p>
<p class="note">Even when false it does not necessarily mean that the
<span>style sheet</span> is actually rendered.</p>
</dd>
<dt><dfn id="style-sheet-css-rules">style sheet CSS rules</dfn></dt>
<dd><p>The <span title="CSS rule">CSS rules</span> associated with the
<span>style sheet</span>.</p></dd>
</dl>
<p>When you are to <span>create a style sheet</span> the above properties,
with the exception of <span>style sheet type</span> and
<span>style sheet CSS rules</span>, are to be set to
their proper values.</p>
<!-- same-origin restrictions -->
<h4>The <code title="">StyleSheet</code> Interface</h4>
<p>The <code>StyleSheet</code> interface represents a base interface that
has no meaning on its own.</p>
<pre class="idl">interface <dfn id="stylesheet">StyleSheet</dfn> {
readonly attribute DOMString <span title="dom-StyleSheet-type">type</span>;
readonly attribute DOMString <span title="dom-StyleSheet-href">href</span>;
readonly attribute Node <span title="dom-StyleSheet-ownerNode">ownerNode</span>;
readonly attribute <span>StyleSheet</span> <span title="dom-StyleSheet-parentStyleSheet">parentStyleSheet</span>;
readonly attribute DOMString <span title="dom-StyleSheet-title">title</span>;
[PutForwards=<span title="dom-MediaList-mediaText">mediaText</span>] readonly attribute <span>MediaList</span> <span title="dom-StyleSheet-media">media</span>;
attribute boolean <span title="dom-StyleSheet-disabled">disabled</span>;
};</pre>
<p>The
<dfn id="dom-stylesheet-type" title="dom-StyleSheet-type"><code>type</code></dfn>
attribute <em class="ct">must</em> return the
<span>style sheet type</span>.</p>
<p>The
<dfn id="dom-stylesheet-href" title="dom-StyleSheet-href"><code>href</code></dfn>
attribute <em class="ct">must</em> return the
<span>style sheet location</span>.</p>
<p>The
<dfn id="dom-stylesheet-ownernode" title="dom-StyleSheet-ownerNode"><code>ownerNode</code></dfn>
attribute <em class="ct">must</em> return the
<span>style sheet owner node</span>.</p>
<p>The
<dfn id="dom-stylesheet-parentstylesheet" title="dom-StyleSheet-parentStyleSheet"><code>parentStyleSheet</code></dfn>
attribute <em class="ct">must</em> return the
<span>style sheet parent</span>.</p>
<p>The
<dfn id="dom-stylesheet-title" title="dom-StyleSheet-title"><code>title</code></dfn>
attribute <em class="ct">must</em> return the
<span>style sheet title</span>.</p>
<p>The
<dfn id="dom-stylesheet-media" title="dom-StyleSheet-media"><code>media</code></dfn>
attribute <em class="ct">must</em> return the
<span>style sheet media</span>.</p>
<p>The
<dfn id="dom-stylesheet-disabled" title="dom-StyleSheet-disabled"><code>disabled</code></dfn>
attribute <em class="ct">must</em>, on getting, return the
<span>style sheet disabled flag</span>. On setting, it
<em class="ct">must</em> set the <span>style sheet disabled flag</span> to
the given value.</p>
<h4>The <code title="">CSSStyleSheet</code> Interface</h4>
<p>The <code>CSSStyleSheet</code> interface represents a
<span>style sheet</span>.</p>
<!--
IE exposes:
owningElement, pages, id, type, href, disabled, cssText, readOnly, title,
parentStyleSheet, imports, rules, media
-->
<pre class="idl">interface <dfn>CSSStyleSheet</dfn> : <span>StyleSheet</span> {
readonly attribute <span>CSSRule</span> <span title="dom-CSSStyleSheet-ownerRule">ownerRule</span>;
readonly attribute <span>CSSRuleList</span> <span title="dom-CSSStyleSheet-cssRules">cssRules</span>;
unsigned long <span title="dom-CSSStyleSheet-insertRule">insertRule</span>(DOMString <var title="">rule</var>, unsigned long <var title="">index</var>);
void <span title="dom-CSSStyleSheet-deleteRule">deleteRule</span>(unsigned long <var title="">index</var>);
};</pre>
<p>The
<dfn id="dom-cssstylesheet-ownerrule" title="dom-CSSStyleSheet-ownerRule"><code>ownerRule</code></dfn>
attribute <em class="ct">must</em> return the
<span>style sheet owner CSS rule</span>.</p>
<p>The
<dfn id="dom-cssstylesheet-cssrules" title="dom-CSSStyleSheet-cssRules"><code>cssRules</code></dfn>
attribute <em class="ct">must</em> return a <code>CSSRuleList</code>
object representing the <span>style sheet CSS rules</span>.</p>
<p class="note">CSS rules that were dropped during parsing can not be
found using APIs described by this specification.</p>
<p>The
<dfn id="dom-cssstylesheet-insertrule" title="dom-CSSStyleSheet-insertRule"><code>insertRule(<var title="">rule</var>, <var title="">index</var>)</code></dfn>
method <em class="ct">must</em> <span>insert a CSS rule</span>
<var title="">rule</var> the in CSS rule list returned by
<code title="dom-CSSStyleSheet-cssRules">cssRules</code> at
<var title="">index</var>.</p>
<p>The
<dfn id="dom-cssstylesheet-deleterule" title="dom-CSSStyleSheet-deleteRule"><code>deleteRule(<var title="">index</var>)</code></dfn>
method <em class="ct">must</em> <span>remove a CSS rule</span> from the
CSS rule list returned by
<code title="dom-CSSStyleSheet-cssRules">cssRules</code> at
<var title="">index</var>.</p>
<h3>Style Sheet Collections</h3>
<p>Below various new concepts are defined that are associated with each
<code>Document</code> object.</p>
<p>Each <code>Document</code> has an associated list of zero or more
<span title="style sheet">style sheets</span>, named the
<dfn id="document-style-sheets">document style sheets</dfn>. This is
an ordered list that contains all
<span title="style sheet">style sheets</span> associated with the
<code>Document</code>, in <span>tree order</span>, with
<span title="style sheet">style sheets</span> created from HTTP
<code title="http-link">Link</code> headers first, if any, in header
order.</p>
<p>To <dfn id="create-a-style-sheet">create a style sheet</dfn>, run these
steps:</p>
<ol>
<li><p>Create a new <span>style sheet</span> object and set its
properties as specified.</p></li>
<li><p>Then run the <span>add a style sheet</span> steps for the newly
created <span>style sheet</span>.</p></li>
</ol>
<p>To <dfn id="add-a-style-sheet">add a style sheet</dfn>, run these
steps:</p>
<ol>
<li><p>Add the <span>style sheet</span> to the list of
<span>document style sheets</span> at the appropriate location. The
remainder of these steps deal with the
<span>style sheet disabled flag</span>.</p></li>
<li><p>If the <span>style sheet disabled flag</span> is true terminate
these steps.</p></li>
<li><p>If the <span>style sheet title</span> is non-empty, the
<span>style sheet alternate flag</span> is false, and
<span>preferred style sheet set name</span> is the empty string
<span>change the preferred style sheet set name</span> to the
<span>style sheet title</span>.</p></li>
<li>
<p>If any of the following is true set the
<span>style sheet disabled flag</span> to false and terminate these
steps:</p>
<ul>
<li><p>The <span>style sheet title</span> is empty.</p></li>
<li><p>The <span>last style sheet set name</span> is null and the
<span>style sheet title</span> is a <span>case-sensitive</span> match
for the <span>preferred style sheet set name</span>.</p></li>
<li><p>The <span>style sheet title</span> is a
<span>case-sensitive</span> match for the
<span>last style sheet set name</span>.</p></li>
</ul>
</li>
<li><p>Set the <span>style sheet disabled flag</span> to true.</p></li>
</ol>
<p>A <dfn id="persistent-style-sheet">persistent style sheet</dfn> is a
<span>style sheet</span> from the <span>document style sheets</span>
whose <span>style sheet title</span> is the empty string and whose
<span>style sheet alternate flag</span> is false.</p>
<p>A <dfn id="style-sheet-set">style sheet set</dfn> is an ordered
collection of one or more <span title="style sheet">style sheets</span>
from the <span>document style sheets</span> which have an identical
<span>style sheet title</span> that is not the empty string.</p>