csswg-drafts/cssom-values/Overview.html at e76de12cd354391517011884d3b56f2d54130e86 · xfq/csswg-drafts · GitHub

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<!DOCTYPE html><html lang="en-US"><head>
  <meta charset="utf-8">
  <title>CSSOM Values Module</title>
  <link href="../default.css" rel="stylesheet">
  <link href="https://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet">
 </head>
 <body class="draft">
<div class="head">

<!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="https://www.w3.org/Icons/w3c_home" width="72"></a></p>
<!--end-logo-->

 <h1>CSSOM Values Module</h1>

 <h2 class="no-num no-toc" id="w3c-doctype">Editor's Draft 8 January 2014</h2>

 <dl>

  <dt>This Version:</dt>
  <dd class="dontpublish"><a href="http://dev.w3.org/csswg/cssom-values/">http://dev.w3.org/csswg/cssom-values/</a></dd>


  <dt class="dontpublish">Participate:</dt>
  <dd class="dontpublish"><a href="mailto:www-style@w3.org?subject=%5Bcssom-values%5D%20">www-style@w3.org</a> (<a href="http://lists.w3.org/Archives/Public/www-style/">archives</a>)
  <dd class="dontpublish"><a href="https://www.w3.org/Bugs/Public/enter_bug.cgi?product=CSS&amp;component=CSSOM%20Values">File a bug</a> (<a href="https://www.w3.org/Bugs/Public/buglist.cgi?component=CSSOM%20Values&amp;product=CSS&amp;resolution=---">open bugs</a>) <script async="" src="https://w3c-test.org/resources.whatwg.org/file-bug.js"></script>
  <dd class="dontpublish"><a href="irc://irc.w3.org:6665/css">IRC: #css on W3C</a></dd>


  <dt class="dontpublish">Previous Version:</dt>

  <dt>Editors:</dt>
  <dd>Simon Pieters
  (<a href="http://www.opera.com/">Opera Software ASA</a>)
  &lt;<a href="mailto:simonp@opera.com">simonp@opera.com</a>&gt;</dd>
  <dd><a href="http://www.w3.org/wiki/User:Gadams">Glenn Adams</a>
  (<a href="http://www.cox.com/">Cox Communications, Inc.</a>)
  &lt;<a href="mailto:glenn.adams@cox.com">glenn.adams@cox.com</a>&gt;</dd>

 </dl>


<!--begin-copyright-->
<p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2014 <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>
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</div>

<hr class="top">

<h2 class="no-num no-toc" id="abstract">Abstract</h2>

<p>This CSSOM Values module defines APIs for accessing and manipulating CSS property
values using object oriented value representations. These APIs are intended to replace
the underimplemented and underutilized <code title="">CSSValue</code> and related APIs defined by
<a class="informative" href="#refsDOM2STYLE">[DOM2STYLE]</a>.</p>


<h2 class="no-num no-toc" id="sotd">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>This is the 8 January 2014 Editor's Draft of CSSOM. Please send
comments to
<a href="mailto:www-style@w3.org?subject=%5Bcssom-values%5D%20">www-style@w3.org</a>
(<a href="http://lists.w3.org/Archives/Public/www-style/">archived</a>)
with <samp>[cssom-values]</samp> at the start of the subject line.


<!-- XXX include this text upon FPWD publishing
<p>This is the 8 January 2014 First Public Working Draft of CSSOM, produced by the
<a href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part
of the <a href="http://www.w3.org/Style/">Style Activity</a>).
-->
<!--XXX remove "First Public" after initial publication -->

<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>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>

<h2 class="no-num no-toc" id="toc">Table of Contents</h2>


<!--begin-toc-->
<ul class="toc">
 <li><a href="#introduction"><span class="secno">1 </span>Introduction</a></li>
 <li><a href="#conformance"><span class="secno">2 </span>Conformance</a>
  <ul class="toc">
   <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ul></li>
 <li><a href="#css-values"><span class="secno">3 </span>CSS Values</a>
  <ul class="toc">
   <li><a href="#the-cssvalue-interface"><span class="secno">3.1 </span>The <code title="">CSSValue</code> Interface</a></li>
   <li><a href="#the-cssstyledeclaration-interface"><span class="secno">3.2 </span>The <code title="">CSSStyleDeclaration</code> Interface</a></li>
   <li><a href="#the-cssstyledeclarationvalue-interface"><span class="secno">3.3 </span>The <code title="">CSSStyleDeclarationValue</code> Interface</a></li>
   <li><a href="#the-csspropertyvalue-interface"><span class="secno">3.4 </span>The <code title="">CSSPropertyValue</code> Interface</a></li>
   <li><a href="#the-csspropertyvaluelist-interface"><span class="secno">3.5 </span>The <code title="">CSSPropertyValueList</code> Interface</a></li>
   <li><a href="#the-cssmapvalue-interface"><span class="secno">3.6 </span>The <code title="">CSSMapValue</code> Interface</a></li>
   <li><a href="#the-csscomponentvalue-interface"><span class="secno">3.7 </span>The <code title="">CSSComponentValue</code> Interface</a>
    <ul class="toc">
     <li><a href="#the-csscolorcomponentvalue-interface"><span class="secno">3.7.1 </span>The <code title="">CSSColorComponentValue</code> Interface</a></li>
     <li><a href="#the-cssidentifiercomponentvalue-interface"><span class="secno">3.7.2 </span>The <code title="">CSSIdentifierComponentValue</code> Interface</a></li>
     <li><a href="#the-csskeywordcomponentvalue-interface"><span class="secno">3.7.3 </span>The <code title="">CSSKeywordComponentValue</code> Interface</a></li>
     <li><a href="#the-csslengthcomponentvalue-interface"><span class="secno">3.7.4 </span>The <code title="">CSSLengthComponentValue</code> Interface</a></li>
     <li><a href="#the-csspercentagecomponentvalue-interface"><span class="secno">3.7.5 </span>The <code title="">CSSPercentageComponentValue</code> Interface</a></li>
     <li><a href="#the-cssstringcomponentvalue-interface"><span class="secno">3.7.6 </span>The <code title="">CSSStringComponentValue</code> Interface</a></li>
     <li><a href="#the-cssurlcomponentvalue-interface"><span class="secno">3.7.7 </span>The <code title="">CSSURLComponentValue</code> Interface</a></ul></ul></li>
 <li><a class="no-num" href="#references">References</a></li>
 <li><a class="no-num" href="#acknowledgments">Acknowledgments</a></ul>
<!--end-toc-->

<h2 id="introduction"><span class="secno">1 </span>Introduction</h2>

<p>This CSSOM Values module defines APIs for accessing and manipulating CSS property
values using object oriented value representations.</p>

<h2 id="conformance"><span class="secno">2 </span>Conformance</h2>

<p>All diagrams, examples, and notes in this specification are
non-normative, as are all sections explicitly marked non-normative.
Everything else in this specification is normative.

<p>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 RFC2119. For readability, these words do
not appear in all uppercase letters in this specification.
<a href="#refsRFC2119">[RFC2119]</a>

<p>Requirements phrased in the imperative as part of algorithms
(such as "strip any leading space characters" or "return false and
terminate these steps") are to be interpreted with the meaning of the
key word ("must", "should", "may", etc) used in introducing the
algorithm.

<p>Conformance requirements phrased as algorithms or specific steps
may be implemented in any manner, so long as the end result is
equivalent. (In particular, the algorithms defined in this
specification are intended to be easy to follow, and not intended to
be performant.)

<p>Unless otherwise stated, string comparisons are done in a
<a class="external" data-anolis-spec="dom" href="http://dom.spec.whatwg.org/#case-sensitive">case-sensitive</a> manner.

<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3>

<p>This specification relies upon the following underlying specifications:</p>

<dl>

<dt>CSSOM</dt>
<dd><p>A conforming user agent must support the CSS Object
Model. <a href="#refsCSSOM">[CSSOM]</a></p>
<p class="issue">Narrow this dependency to specific features of CSSOM.</p>
</dd>

</dl>

<h2 id="css-values"><span class="secno">3 </span>CSS Values</h2>

<h3 id="the-cssvalue-interface"><span class="secno">3.1 </span>The <code title="">CSSValue</code> Interface</h3>

<pre class="idl">interface <dfn id="cssvalue">CSSValue</dfn> {
  <span class="issue" title="">// ...</span>
};</pre>

<h3 id="the-cssstyledeclaration-interface"><span class="secno">3.2 </span>The <code title="">CSSStyleDeclaration</code> Interface</h3>

<pre class="idl">partial interface <dfn id="cssstyledeclaration">CSSStyleDeclaration</dfn> {
  readonly attribute <a href="#cssstyledeclarationvalue">CSSStyleDeclarationValue</a> <a href="#dom-cssstyledeclaration-values" title="dom-CSSStyleDeclaration-values">values</a>;
};</pre>

<p class="issue"><dfn id="dom-cssstyledeclaration-values" title="dom-CSSStyleDeclaration-values"><code>values</code></dfn>

<h3 id="the-cssstyledeclarationvalue-interface"><span class="secno">3.3 </span>The <code title="">CSSStyleDeclarationValue</code> Interface</h3>

<pre class="idl">interface <dfn id="cssstyledeclarationvalue">CSSStyleDeclarationValue</dfn> {
  // CSS Properties
<!--CSSOM-DECLARATIONVALUEIDL-->
};</pre>

<p class="issue">The rough idea is that this interface exposes the full
list of supported properties as well that each return a
<code><a href="#csspropertyvalue">CSSPropertyValue</a></code> object. That object can implement other
objects depending on the property involved. E.g. for '<code title="">width</code>'
the object would implement <code><a href="#csslengthcomponentvalue">CSSLengthComponentValue</a></code> and
<code><a href="#csspercentagecomponentvalue">CSSPercentageComponentValue</a></code>.</p>

<h3 id="the-csspropertyvalue-interface"><span class="secno">3.4 </span>The <code title="">CSSPropertyValue</code> Interface</h3>

<pre class="idl">interface <dfn id="csspropertyvalue">CSSPropertyValue</dfn> {
           attribute DOMString <a href="#dom-csspropertyvalue-csstext" title="dom-CSSPropertyValue-cssText">cssText</a>;
};</pre>

<p class="issue"><dfn id="dom-csspropertyvalue-csstext" title="dom-CSSPropertyValue-cssText"><code>cssText</code></dfn>

<!--
 what does the CSSValue represent
  "map"
  "list"
  "space-list"
  "component"

 if it is a CSSComponentValue

-->

<h3 id="the-csspropertyvaluelist-interface"><span class="secno">3.5 </span>The <code title="">CSSPropertyValueList</code> Interface</h3>

<pre class="idl">[NoInterfaceObject] interface <dfn id="csspropertyvaluelist">CSSPropertyValueList</dfn> {
  readonly attribute <a href="#cssvalue">CSSValue</a>[] <a href="#dom-csspropertyvalue-list" title="dom-CSSPropertyValue-list">list</a>;
};</pre>

<p class="issue"><dfn id="dom-csspropertyvalue-list" title="dom-CSSPropertyValue-list"><code>list</code></dfn>

<p class="issue">Ideally this attribute just returns a mutable array.</p>

<h3 id="the-cssmapvalue-interface"><span class="secno">3.6 </span>The <code title="">CSSMapValue</code> Interface</h3>

<pre class="idl">[NoInterfaceObject] interface <dfn id="cssmapvalue">CSSMapValue</dfn> {
  getter <a href="#cssvalue">CSSValue</a> (DOMString <var>name</var>);
};</pre>
<!-- see HTML5 DOMStringMap -->

<p class="issue">This seems the simplest we can get away with.</p>

<h3 id="the-csscomponentvalue-interface"><span class="secno">3.7 </span>The <code title="">CSSComponentValue</code> Interface</h3>

<pre class="idl">[NoInterfaceObject] interface <dfn id="csscomponentvalue">CSSComponentValue</dfn> {
  readonly attribute DOMString <a href="#dom-csscomponentvalue-type" title="dom-CSSComponentValue-type">type</a>;
           attribute any <a href="#dom-csscomponentvalue-value" title="dom-CSSComponentValue-value">value</a>;
};</pre>

<p class="issue"><dfn id="dom-csscomponentvalue-type" title="dom-CSSComponentValue-type"><code>type</code></dfn>
<p class="issue"><dfn id="dom-csscomponentvalue-value" title="dom-CSSComponentValue-value"><code>value</code></dfn>

<p class="issue">type returns "string", "keyword", "identifier", "color", "em", "ex", "px", "url".</p>

<h4 id="the-csscolorcomponentvalue-interface"><span class="secno">3.7.1 </span>The <code title="">CSSColorComponentValue</code> Interface</h4>

<pre class="idl">[NoInterfaceObject] interface <dfn id="csscolorcomponentvalue">CSSColorComponentValue</dfn> {
           attribute short <a href="#dom-csscolorcomponentvalue-red" title="dom-CSSColorComponentValue-red">red</a>;
           attribute short <a href="#dom-csscolorcomponentvalue-green" title="dom-CSSColorComponentValue-green">green</a>;
           attribute short <a href="#dom-csscolorcomponentvalue-blue" title="dom-CSSColorComponentValue-blue">blue</a>;
           attribute float <a href="#dom-csscolorcomponentvalue-alpha" title="dom-CSSColorComponentValue-alpha">alpha</a>;
};</pre>

<p class="issue"><dfn id="dom-csscolorcomponentvalue-red" title="dom-CSSColorComponentValue-red"><code>red</code></dfn>
<p class="issue"><dfn id="dom-csscolorcomponentvalue-green" title="dom-CSSColorComponentValue-green"><code>green</code></dfn>
<p class="issue"><dfn id="dom-csscolorcomponentvalue-blue" title="dom-CSSColorComponentValue-blue"><code>blue</code></dfn>
<p class="issue"><dfn id="dom-csscolorcomponentvalue-alpha" title="dom-CSSColorComponentValue-alpha"><code>alpha</code></dfn>

<p class="issue">We can make this more complex later. This will probably move into the CSS Color Level 4.</p>

<h4 id="the-cssidentifiercomponentvalue-interface"><span class="secno">3.7.2 </span>The <code title="">CSSIdentifierComponentValue</code> Interface</h4>

<pre class="idl">[NoInterfaceObject] interface <dfn id="cssidentifiercomponentvalue">CSSIdentifierComponentValue</dfn> {
           attribute DOMString <a href="#dom-cssstringcomponentvalue-identifier" title="dom-CSSStringComponentValue-identifier">identifier</a>;
};</pre>

<p class="issue"><dfn id="dom-cssstringcomponentvalue-identifier" title="dom-CSSStringComponentValue-identifier"><code>identifier</code></dfn>

<h4 id="the-csskeywordcomponentvalue-interface"><span class="secno">3.7.3 </span>The <code title="">CSSKeywordComponentValue</code> Interface</h4>

<pre class="idl">[NoInterfaceObject] interface <dfn id="csskeywordcomponentvalue">CSSKeywordComponentValue</dfn> {
           attribute DOMString <a href="#dom-cssstringcomponentvalue-keyword" title="dom-CSSStringComponentValue-keyword">keyword</a>;
};</pre>

<p class="issue"><dfn id="dom-cssstringcomponentvalue-keyword" title="dom-CSSStringComponentValue-keyword"><code>keyword</code></dfn>

<h4 id="the-csslengthcomponentvalue-interface"><span class="secno">3.7.4 </span>The <code title="">CSSLengthComponentValue</code> Interface</h4>

<pre class="idl">[NoInterfaceObject] interface <dfn id="csslengthcomponentvalue">CSSLengthComponentValue</dfn> {
           attribute float <a href="#dom-csslengthcomponentvalue-em" title="dom-CSSLengthComponentValue-em">em</a>;
           attribute float <a href="#dom-csslengthcomponentvalue-ex" title="dom-CSSLengthComponentValue-ex">ex</a>;
           attribute float <a href="#dom-csslengthcomponentvalue-px" title="dom-CSSLengthComponentValue-px">px</a>;
           <span class="issue" title="">// figure out what to do with absolute lengths</span>
};</pre>

<p class="issue"><dfn id="dom-csslengthcomponentvalue-em" title="dom-CSSLengthComponentValue-em"><code>em</code></dfn>
<p class="issue"><dfn id="dom-csslengthcomponentvalue-ex" title="dom-CSSLengthComponentValue-ex"><code>ex</code></dfn>
<p class="issue"><dfn id="dom-csslengthcomponentvalue-px" title="dom-CSSLengthComponentValue-px"><code>px</code></dfn>

<h4 id="the-csspercentagecomponentvalue-interface"><span class="secno">3.7.5 </span>The <code title="">CSSPercentageComponentValue</code> Interface</h4>

<pre class="idl">[NoInterfaceObject] interface <dfn id="csspercentagecomponentvalue">CSSPercentageComponentValue</dfn> {
           attribute float <a href="#dom-csspercentagecomponentvalue-percent" title="dom-CSSPercentageComponentValue-percent">percent</a>;
};</pre>

<p class="issue"><dfn id="dom-csspercentagecomponentvalue-percent" title="dom-CSSPercentageComponentValue-percent"><code>percent</code></dfn>

<h4 id="the-cssstringcomponentvalue-interface"><span class="secno">3.7.6 </span>The <code title="">CSSStringComponentValue</code> Interface</h4>

<pre class="idl">[NoInterfaceObject] interface <dfn id="cssstringcomponentvalue">CSSStringComponentValue</dfn> {
           attribute DOMString <a href="#dom-cssstringcomponentvalue-string" title="dom-CSSStringComponentValue-string">string</a>;
};</pre>

<p class="issue"><dfn id="dom-cssstringcomponentvalue-string" title="dom-CSSStringComponentValue-string"><code>string</code></dfn>

<h4 id="the-cssurlcomponentvalue-interface"><span class="secno">3.7.7 </span>The <code title="">CSSURLComponentValue</code> Interface</h4>

<pre class="idl">[NoInterfaceObject] interface <dfn id="cssurlcomponentvalue">CSSURLComponentValue</dfn> {
           attribute DOMString? <a href="#dom-cssurlcomponentvalue-url" title="dom-CSSURLComponentValue-url">url</a>;
};</pre>

<p class="issue"><dfn id="dom-cssurlcomponentvalue-url" title="dom-CSSURLComponentValue-url"><code>url</code></dfn>


<h2 class="no-num" id="references">References</h2>
<div id="anolis-references"><dl><dt id="refsCSSOM">[CSSOM]
<dd><cite><a href="http://dev.w3.org/csswg/cssom/">CSS Object Model (CSSOM)</a></cite>, Simon Pieters and Glenn Adams. W3C.

<dt id="refsDOM2STYLE">[DOM2STYLE]
<dd>(Non-normative) <cite><a href="http://www.w3.org/TR/DOM-Level-2-Style/">Document Object Model (DOM) Level 2 Style Specification</a></cite>, Chris Wilson, Philippe Le Hégaret and Vidur Apparao. W3C.

<dt id="refsRFC2119">[RFC2119]
<dd><cite><a href="http://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a></cite>, Scott Bradner. IETF.

</dl></div>


<h2 class="no-num" id="acknowledgments">Acknowledgments</h2>

<p>The editors would like to thank

Alexey Feldgendler,
Brian Kardell,
Christian Krebs,
Daniel Glazman,
David Baron,
<i>fantasai</i>,
Hallvord R. M. Steen,
Ian Hickson,
John Daggett,
Lachlan Hunt,
Morten Stenshorne,
Philip Taylor,
Robert O'Callahan,
Sjoerd Visscher,
<!--Simon Pieters,-->
Sylvain Galineau,
Tarquin Wilton-Jones, and
Zack Weinberg

for contributing to this specification.</p>

<p>Special thanks to Anne van Kesteren who authored the material upon which this work is based.</p>

<!-- XXX NOTES

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