csswg-drafts/css3-ui/Overview.html at a8b17fac2e62816e994f3f63b7b9076820e6781d · w3c/csswg-drafts · GitHub

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">

<html>
 <head><meta content="text/html; charset=utf-8" http-equiv=Content-Type>
  <meta content="text/css" http-equiv=Content-Style-Type>
  <meta content=en http-equiv=Content-Language>
  <meta content="Tantek &Ccedil;elik" lang=tr name=author>

  <title>CSS Basic User Interface Module Level 3 (CSS3 UI)</title>
  <link href="../default.css" rel=stylesheet title=Default type="text/css">

  <style type="text/css">
.subtoc ul,.subtoc ol { list-style-type: none }
ol.objectives { list-style: decimal }
ol.issues { list-style: decimal }
.html4ss { font-size:90%}
h1 {font-size:200%; clear:both}
h2 {font-size:170%; clear:both}
h3 {font-size:150%; clear:both}
h4 {font-size:130%}
h5 {font-size:120%}
h6 {font-size:110%}
h1+h2 {page-break-before: avoid}
h2 {page-break-before: always}
dd p:first-child { margin-top:0 }

</style>
  <link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel=stylesheet
  type="text/css">
  <!-- toggle to W3C-WD for TR publication, W3C-ED for editing -->

 <body>
  <div class=head> <a href="http://www.w3.org/"><img alt=W3C height=48
   src="http://www.w3.org/Icons/w3c_home" width=72> </a>
   <h1>CSS Basic User Interface Module Level 3 (CSS3 UI)</h1>

   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 18 January
    2012</h2>

   <dl>
    <dt>This version:</dt>
    <!-- TR "This version". Update "WD" below as needed to CR/PR/REC -->
    <!-- <dd><a href="http://www.w3.org/TR/2012/WD-css3-ui-20120118/">
    http://www.w3.org/TR/2012/WD-css3-ui-20120118/</a>
  </dd> -->
    <!-- editor's draft "This version" -->

    <dd><a href="http://dev.w3.org/csswg/css3-ui/">
     http://dev.w3.org/csswg/css3-ui/</a>

    <dt>Latest version:

    <dd><a
     href="http://www.w3.org/TR/css3-ui/">http://www.w3.org/TR/css3-ui/</a>

    <dt>Editor's draft:

    <dd><a
     href="http://dev.w3.org/csswg/css3-ui/">http://dev.w3.org/csswg/css3-ui/</a>

    <dt>Previous version:

    <dd><a href="http://www.w3.org/TR/2012/WD-css3-ui-20120117/"
     rel=previous>http://www.w3.org/TR/2012/WD-css3-ui-20120117/</a>

    <dt>Issues list:

    <dd><a
     href="http://wiki.csswg.org/spec/css3-ui">http://wiki.csswg.org/spec/css3-ui</a>

    <dt>Discussion:

    <dd><a
     href="mailto:www-style@w3.org?subject=%5Bcss3-ui%5D%20feedback">www-style@w3.org</a>
     with subject line &ldquo;<kbd>[css3-ui] <var>&hellip; message topic
     &hellip;</var></kbd>&rdquo; (<a
     href="http://lists.w3.org/Archives/Public/www-style/">archives</a>)

    <dt>Editor:

    <dd class="h-card vcard"> <a class="p-name fn u-url url"
     href="http://tantek.com" lang=tr rel=author> Tantek &Ccedil;elik</a> (<a
     class="company h-org org" href="http://www.mozilla.org/">Mozilla
     Foundation</a>, and before at <a
     href="http://www.microsoft.com/">Microsoft Corporation</a>) &lt;<a
     class="u-email email"
     href="mailto:tantek@cs.stanford.edu">tantek@cs.stanford.edu</a>&gt;
   </dl>
   <!--begin-copyright-->
   <p class=copyright><a
    rel=license>Copyright</a> &copy; 2012 <a
    href="http://www.w3.org/"><acronym
    title="World Wide Web Consortium">W3C</acronym></a><sup>&reg;</sup> (<a
    href="http://www.csail.mit.edu/"><acronym
    title="Massachusetts Institute of Technology">MIT</acronym></a>, <a
    href="http://www.ercim.eu/"><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>
   <!--end-copyright-->
  </div>

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

  <p>This section is <em>informative</em>.

  <p>CSS (Cascading Style Sheets) is a language for describing the rendering
   of HTML and XML documents on screen, on paper, in speech, etc. It uses
   various selectors, properties and values to style basic user interface
   elements in a document. This specification describes those user interface
   related selectors, properties and values that are proposed for CSS
   level&nbsp;3 to style HTML and XML (including XHTML and XForms). It
   includes and extends user interface related features from the selectors,
   properties and values of CSS level&nbsp;2 revision 1 and Selectors
   specifications.

  <h2 class="no-num no-toc" id=status style="page-break-before:auto">Status
   of this document</h2>
  <!--begin-status-->

  <p>This is a public copy of the editors' draft. It is provided for
   discussion only and may change at any moment. Its publication here does
   not imply endorsement of its contents by W3C. Don't cite this document
   other than as work in progress.

  <p>The (<a
   href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
   mailing list <a
   href="mailto:www-style@w3.org?Subject=%5Bcss3-ui%5D%20PUT%20SUBJECT%20HERE">
   www-style@w3.org</a> (see <a
   href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
   discussion of this specification. When sending e-mail, please put the text
   &#8220;css3-ui&#8221; in the subject, preferably like this:
   &#8220;[<!---->css3-ui<!---->] <em>&hellip;summary of
   comment&hellip;</em>&#8221;

  <p>This document was produced by the <a href="/Style/CSS/members">CSS
   Working Group</a> (part of the <a href="/Style/">Style Activity</a>).

  <p>This document was produced by a group operating under the <a
   href="/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent
   Policy</a>. W3C maintains a <a href="/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="/Consortium/Patent-Policy-20040205/#def-essential">Essential
   Claim(s)</a> must disclose the information in accordance with <a
   href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the
   W3C Patent Policy</a>.</p>
  <!--end-status-->

  <p>This specification is a <strong>Last Call Working Draft</strong>,
   although it was previously a Candidate Recommendation. It has been
   returned to Last Call Working Draft because this draft removes features
   that were not implemented sufficiently to advance to Proposed
   Recommendation, and had not been previously listed as at risk, as <a
   href="http://www.w3.org/2005/10/Process-20051014/tr.html#cfi">required</a>
   by the W3C Process. This draft also adds a couple of new properties and
   values. See <a href="#changes">Appendix C. Changes</a> for further
   details. <!-- This specification may advance directly to Proposed
Recommendation following the last call, depending on comments and
implementation reports. -->
   All persons are encouraged to review this document and send comments to
   the <a href="http://lists.w3.org/Archives/Public/www-style/">www-style
   mailing list</a> as described above. The <strong>deadline for
   comments</strong> is four weeks after the date of publication in the
   header or 14 February 2012, whichever is sooner.

  <h3 class="no-num no-toc" id=crec>Candidate Recommendation Exit Criteria</h3>

  <p>For this specification to enter the Proposed Recommendation stage, the
   following conditions shall be met:

  <ol>
   <li>
    <p>There must be at least two interoperable implementations for every
     feature. For the purposes of this criterion, we define the following
     terms:</p>

    <dl>
     <dt>feature

     <dd>
      <p> A section or subsection of the specification.</p>

     <dt>interoperable

     <dd>
      <p>passing the respective test cases in the test suite, or, if the
       implementation is not a web browser, equivalent tests. Every relevant
       test in the test suite should have an equivalent test created if such
       a user agent (UA) is to be used to claim interoperability. In addition
       if such a UA is to be used to claim interoperability, then there must
       one or more additional UAs which can also pass those equivalent tests
       in the same way for the purpose of interoperability. The equivalent
       tests must be made publicly available for the purposes of peer review.</p>

     <dt>implementation

     <dd>
      <p>a user agent which:</p>

      <ol class=inline>
       <li>implements the feature.

       <li>is available (i.e. publicly downloadable or available through some
        other public point of sale mechanism). This is the "show me"
        requirement.

       <li>is shipping (i.e. development, private or unofficial versions are
        insufficient).

       <li>is not experimental (i.e. is intended for a wide audience and
        could be used on a daily basis).
      </ol>
    </dl>

   <li>
    <p>A minimum of six months of the CR period must have elapsed. This is to
     ensure that enough time is given for any remaining major errors to be
     caught.

   <li>
    <p>The CR period will be extended if implementations are slow to appear.

   <li>
    <p>Features that are <em>at risk</em> (see the below list) will be
     dropped (thus reducing the list of "all" features mentioned above) if
     two or more interoperable implementations of those features are not
     found by the end of the CR period, or if sufficient and adequate tests
     (by judgment of the Working Group) have not been produced for those
     features by the end of the CR period.
  </ol>

  <p>A <a href="/Style/CSS/Test/">test suite</a> and a <a
   href="/Style/css3-updates/css3-ui-implementations">report on
   implementations</a> will be provided before the document becomes a
   Proposed Recommendation.

  <h3 class="no-num no-toc" id=atrisk>Features at risk</h3>

  <p>The Working Group has identified the following features as at risk of
   being removed from CSS Basic User Interface Module Level 3 when exiting
   CR. Implementors are urged to implement these features, if they wish to
   see these features remain in this specification. All other features are
   either defined in a normative reference (e.g. CSS 2.1 <a href="#CSS21"
   rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> or Selectors <a
   href="#SELECT" rel=biblioentry>[SELECT]<!--{{!SELECT}}--></a>) or are
   believed to have two or more implementations, and thus will not be dropped
   without returning to last call.

  <ul><!--
 At risk due to only one implementation, or obsolete dependency:
 XForms is defunct on the web.
 <li>XForms needs:	:default :valid :invalid :in-range :out-of-range :required :optional :read-only :read-write ::value ::choices ::repeat-item ::repeat-index</li>

 <li>box-sizing: padding-box - only FF supports in prefixed version</li>

 <li>ime-mode: new - not sure about IE5+ vs FF3+ interop
 </li>

 <li>nav-index, nav-up, nav-down, nav-right, nav-left, properties
 		implemented for sure only by Opera, http://www.opera.com/docs/specs/presto22/#css
 		possibly obsolete: Tasman v1 internal implementation
 		possibly current: MSTV Tasman
 		required (depended on) by non-web DVB-HTML, ATSC standards
 		 - unknown if any DVB-HTML or ATSC simulators
 </li>

 Not at risk:
 <li>CSS2.1:  		:hover :active :focus</li>
 <li>Selectors:		:enabled :disabled :checked</li>
 <li>:indeterminate implemented by FF3.6, IE9, Opera 10.6, Saf3</li>

 <li>box-sizing implemented by IE5/Mac, Opera
 		-moz-box-sizing implemented by Mozilla
 </li>
 <li>outline, outline-width, outline-color, outline-style all in CSS 2.1</li>
 <li>outline-offset property
 		implemented by Safari 1.2
 </li>
 <li>cursor property:
 		CSS2.1: auto | default | help | pointer | wait | crosshair | text |
e-resize | n-resize | ne-resize | nw-resize | s-resize | se-resize | sw-resize | w-resize
		IE5/Mac implements: none | progress | cell
		IE6/Windows implements: <uri> | progress | not-allowed | no-drop | vertical-text | all-scroll | col-resize | row-resize | move |
		Mozilla implements: progress | cell(as -moz-cell) | alias(as -moz-alias) | copy(as -moz-copy) | context-menu(as -moz-context-menu) |
		freedesktop.org copied all the cursors from the CSS3-UI LC Working Draft
			by FredrikHoeglund - 14 Oct 2003
			http://freedesktop.org/Standards/cursor-spec
 </li>
 <li>'cursor' property values: ew-resize | ns-resize | nesw-resize | nwse-resize
    implemented by Firefox and Safari
 </li>
 <li>'resize' property
    implemented by Firefox 4 and Safari
 </li>
 -->

   <li>::value ::choices ::repeat-item ::repeat-index pseudo-elements

   <li>&lsquo;<a href="#box-sizing0"><code
    class=property>box-sizing</code></a>&rsquo; property value: padding-box

   <li>&lsquo;<a href="#content"><code
    class=property>content</code></a>&rsquo; property value: icon

   <li>&lsquo;<a href="#icon"><code class=property>icon</code></a>&rsquo;
    property

   <li>&lsquo;<a href="#ime-mode"><code
    class=property>ime-mode</code></a>&rsquo; property

   <li>&lsquo;<a href="#nav-index0"><code
    class=property>nav-index</code></a>&rsquo;, &lsquo;<a
    href="#nav-up"><code class=property>nav-up</code></a>&rsquo;, &lsquo;<a
    href="#nav-down"><code class=property>nav-down</code></a>&rsquo;,
    &lsquo;<a href="#nav-right"><code
    class=property>nav-right</code></a>&rsquo;, &lsquo;<a
    href="#nav-left"><code class=property>nav-left</code></a>&rsquo;
    properties

   <li>&lsquo;<a href="#text-overflow0"><code
    class=property>text-overflow</code></a>&rsquo; property value:
    &lt;string&gt;

   <li>&lsquo;<a href="#text-overflow0"><code
    class=property>text-overflow</code></a>&rsquo; property 2-value syntax
    and definition.
  </ul>

  <h2 class="no-num no-toc" id=summary>Overview</h2>

  <p>This section is <em>informative</em>.

  <p>This document is one of the "modules" for the upcoming CSS3
   specification. It not only describes the user interface related properties
   and values that already exist in <a
   href="http://www.w3.org/TR/REC-CSS1">CSS1</a> <a href="#CSS1"
   rel=biblioentry>[CSS1]<!--{{CSS1}}--></a> and <a
   href="http://www.w3.org/TR/CSS21">CSS2.1</a> <a href="#CSS21"
   rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>, but introduces new
   properties and values for CSS3 as well. The Working Group doesn't expect
   that all implementations of CSS3 will implement all properties or values.
   Instead, there will probably be a small number of variants of CSS3,
   so-called "profiles".

  <p>This document is the result of the merging of relevant parts of the
   following Recommendations and Working Drafts, and the addition of some new
   features.

  <ul>
   <li>Cascading Style Sheets, level 2, revision 1 <a href="#CSS21"
    rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>

   <li><a href="http://www.w3.org/TR/2000/WD-css3-userint-20000216">User
    Interface for CSS3 (16 February 2000)</a> <a href="#CSSUI"
    rel=biblioentry>[CSSUI]<!--{{CSSUI}}--></a>
  </ul>

  <p>This specification contains:

  <ul>
   <li>Pseudo-classes and pseudo-elements to style user interface states and
    element fragments respectively.

   <li>Additions to the user interface features in <a
    href="http://www.w3.org/TR/CSS21">CSS2.1</a>.

   <li>Directional focus navigation properties.

   <li>A mechanism to allow the styling of elements as icons for
    accessibility.
  </ul>

  <h2 class="no-num no-toc" id=contents>Table of contents</h2>
  <!--begin-toc-->

  <ul class=toc>
   <li><a href="#intro"><span class=secno>1. </span>Introduction</a>
    <ul class=toc>
     <li><a href="#purpose"><span class=secno>1.1. </span>Purpose</a>
    </ul>

   <li><a href="#conformance"><span class=secno>2. </span>Conformance</a>
    <ul class=toc>
     <li><a href="#definitions"><span class=secno>2.1. </span>Definitions</a>


     <li><a href="#classes-of-products"><span class=secno>2.2. </span>Classes
      of products</a>

     <li><a href="#extensions"><span class=secno>2.3. </span>Extensions</a>
    </ul>

   <li><a href="#dependencies-on-other-modules"><span class=secno>3.
    </span>Dependencies on other modules</a>

   <li><a href="#user-interface-selectors"><span class=secno>4. </span>User
    Interface Selectors</a>
    <ul class=toc>
     <li><a href="#pseudo-classes"><span class=secno>4.1. </span>User
      interface states: pseudo-classes</a>
      <ul class=toc>
       <li><a href="#active"><span class=secno>4.1.1. </span>:active
        details</a>

       <li><a href="#indeterminate"><span class=secno>4.1.2. </span> The
        indeterminate-value pseudo-class &lsquo;<code
        class=css>:indeterminate</code>&rsquo;</a>

       <li><a href="#pseudo-default"><span class=secno>4.1.3.
        </span>:default</a>

       <li><a href="#pseudo-validity"><span class=secno>4.1.4.
        </span><span>:valid</span> and <span>:invalid</span></a>

       <li><a href="#pseudo-range"><span class=secno>4.1.5.
        </span><span>:in-range</span> and <span>:out-of-range</span></a>

       <li><a href="#pseudo-required-value"><span class=secno>4.1.6.
        </span><span>:required</span> and <span>:optional</span></a>

       <li><a href="#pseudo-ro-rw"><span class=secno>4.1.7.
        </span><span>:read-only</span> and <span>:read-write</span></a>
      </ul>

     <li><a href="#pseudo-elements"><span class=secno>4.2. </span>User
      interface element fragments: pseudo-elements</a>
      <ul class=toc>
       <li><a href="#pseudo-value"><span class=secno>4.2.1.
        </span>::value</a>

       <li><a href="#pseudo-choices"><span class=secno>4.2.2.
        </span>::choices</a>

       <li><a href="#pseudo-repeat-item"><span class=secno>4.2.3.
        </span>::repeat-item</a>

       <li><a href="#pseudo-repeat-index"><span class=secno>4.2.4.
        </span>::repeat-index</a>
      </ul>
    </ul>

   <li><a href="#element-icons"><span class=secno>5. </span>Element icons</a>

    <ul class=toc>
     <li><a href="#content-property-addition"><span class=secno>5.1.
      </span><span class=property>&lsquo;<code
      class=property>content</code>&rsquo;</span> property addition</a>

     <li><a href="#icon-property"><span class=secno>5.2. </span><span
      class=property>&lsquo;<code class=property>icon</code>&rsquo;</span>
      property</a>
    </ul>

   <li><a href="#box-model-addition"><span class=secno>6. </span>Box Model
    addition</a>
    <ul class=toc>
     <li><a href="#box-sizing"><span class=secno>6.1. </span><span
      class=property>&lsquo;<code
      class=property>box-sizing</code>&rsquo;</span> property</a>
    </ul>

   <li><a href="#outline-properties"><span class=secno>7. </span>Outline
    properties</a>
    <ul class=toc>
     <li><a href="#outline"><span class=secno>7.1. </span><span
      class=property>&lsquo;<code class=property>outline</code>&rsquo;</span>
      property</a>

     <li><a href="#outline-width"><span class=secno>7.2. </span><span
      class=property>&lsquo;<code
      class=property>outline-width</code>&rsquo;</span> property</a>

     <li><a href="#outline-style"><span class=secno>7.3. </span><span
      class=property>&lsquo;<code
      class=property>outline-style</code>&rsquo;</span> property</a>

     <li><a href="#outline-color"><span class=secno>7.4. </span><span
      class=property>&lsquo;<code
      class=property>outline-color</code>&rsquo;</span> property</a>

     <li><a href="#outline-offset"><span class=secno>7.5. </span><span
      class=property>&lsquo;<code
      class=property>outline-offset</code>&rsquo;</span> property</a>
    </ul>

   <li><a href="#resizing-amp-overflow"><span class=secno>8. </span>Resizing
    &amp; Overflow</a>
    <ul class=toc>
     <li><a href="#resize"><span class=secno>8.1. </span><span
      class=property>&lsquo;<code class=property>resize</code>&rsquo;</span>
      property</a>

     <li><a href="#text-overflow"><span class=secno>8.2. </span> Overflow
      Ellipsis: the &lsquo;<code class=property>text-overflow</code>&rsquo;
      property</a>
    </ul>

   <li><a href="#pointing-devices-and-keyboards"><span class=secno>9.
    </span>Pointing Devices and Keyboards</a>
    <ul class=toc>
     <li><a href="#pointer-interaction"><span class=secno>9.1. </span>Pointer
      interaction</a>
      <ul class=toc>
       <li><a href="#cursor"><span class=secno>9.1.1. </span><span
        class=property>&lsquo;<code
        class=property>cursor</code>&rsquo;</span> property</a>
      </ul>

     <li><a href="#keyboard"><span class=secno>9.2. </span>Keyboard
      control</a>
      <ul class=toc>
       <li><a href="#nav-index"><span class=secno>9.2.1. </span>Sequential
        navigation order: the <span class=property>&lsquo;<code
        class=property>nav-index</code>&rsquo;</span> property</a>

       <li><a href="#nav-dir"><span class=secno>9.2.2. </span>Directional
        focus navigation: the <span class=property>&lsquo;<code
        class=property>nav-up</code>&rsquo;</span>, <span
        class=property>&lsquo;<code
        class=property>nav-right</code>&rsquo;</span>, <span
        class=property>&lsquo;<code
        class=property>nav-down</code>&rsquo;</span>, <span
        class=property>&lsquo;<code
        class=property>nav-left</code>&rsquo;</span> properties</a>

       <li><a href="#input-method-editor"><span class=secno>9.2.3.
        </span>Input method editor: the <span class=property>&lsquo;<code
        class=property>ime-mode</code>&rsquo;</span> property</a>
      </ul>
    </ul>

   <li class=no-num><a href="#acknowledgments">Appendix A.
    Acknowledgments</a>

   <li class=no-num><a href="#references">Appendix B. Bibiliography</a>

   <li class=no-num><a href="#changes">Appendix C. Changes</a>
    <ul class=toc>
     <li class=no-num><a href="#changes-list">List of substantial changes</a>

    </ul>

   <li class=no-num><a
    href="#appendix-d.-default-style-sheet-addition">Appendix D. Default
    style sheet additions for HTML</a>

   <li class=no-num><a href="#appendix-e-test-suite">Appendix E: Test
    Suite</a>

   <li class=no-num><a href="#index">Index</a>

   <li class=no-num><a href="#property-index">Property index</a>
  </ul>
  <!--end-toc-->

  <hr>

  <h2 id=intro><span class=secno>1. </span>Introduction</h2>

  <p> CSS3 is a set of modules, divided up and profiled in order to simplify
   the specification, and to allow implementors the flexibility of supporting
   the particular modules appropriate for their implementations.

  <p> This module describes selectors and CSS properties which enable authors
   to style user interface related states, element fragments, properties and
   values.

  <p><a href="http://www.w3.org/TR/REC-CSS1#anchor-pseudo-classes">Section
   2.1 of CSS1</a> <a href="#CSS1" rel=biblioentry>[CSS1]<!--{{CSS1}}--></a>
   and <a href="http://www.w3.org/TR/CSS2/ui.html">Chapter 18 of CSS2</a> <a
   href="#CSS2" rel=biblioentry>[CSS2]<!--{{CSS2}}--></a> introduced several
   user interface related pseudo-classes, properties and values. <a
   href="http://www.w3.org/TR/css3-selectors/#UIstates">Section 6.6.4 of
   Selectors</a> <a href="#SELECT"
   rel=biblioentry>[SELECT]<!--{{!SELECT}}--></a> also describes several
   additional user interface related pseudo-classes (and one pseudo-element).


  <p> This Working Draft extends them to provide the ability, through CSS, to
   style elements based upon additional user interface states, to style
   fragments of user interface elements, and to alter the dynamic
   presentation of elements in ways previously only available through
   specific HTML4/XHTML1 elements and attributes.

  <h3 id=purpose><span class=secno>1.1. </span>Purpose</h3>

  <p>The purpose of this specification is to achieve the following
   objectives:

  <ul>
   <li>Extend the user interface features in CSS2.1.

   <li>Provide additional CSS mechanisms to augment or replace other dynamic
    presentation related features in HTML4/XHTML1.

   <li>Introduce directional navigation properties to assist in the
    construction of user interfaces which make use of a directional
    navigation model.

   <li>Introduce properties and values to specify icon presentations for
    elements to enhance accessibility.
  </ul>

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

  <h3 id=definitions><span class=secno>2.1. </span>Definitions</h3>

  <p>The key words <span class=index-def id=must title=MUST>"MUST"</span>,
   <span class=index-def id=must-not title="MUST NOT">"MUST NOT"</span>,
   <span class=index-def id=required title=REQUIRED>"REQUIRED"</span>, <span
   class=index-def id=shall title=SHALL>"SHALL"</span>, <span class=index-def
   id=shall-not title="SHALL NOT">"SHALL NOT"</span>, <span class=index-def
   id=should title=SHOULD>"SHOULD"</span>, <span class=index-def
   id=should-not title="SHOULD NOT">"SHOULD NOT"</span>, <span
   class=index-def id=recommended title=RECOMMENDED>"RECOMMENDED"</span>,
   <span class=index-def id=may title=MAY>"MAY"</span>, and <span
   class=index-def id=optional title=OPTIONAL>"OPTIONAL"</span> in this
   document are to be interpreted as described in RFC&nbsp;2119 (see <a
   href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>).
   However, for readability, these words do not typically appear in all
   uppercase letters in this specification.

  <p>Additional key words, e.g. "User agent (UA)", are <a
   href="http://www.w3.org/TR/CSS21/conform.html#defs">defined by CSS 2.1</a>
   (<a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>, section
   3.1).

  <h3 id=classes-of-products><span class=secno>2.2. </span>Classes of
   products</h3>

  <p>The following classes of products (many of which overlap) should
   consider implementing this specification:

  <ul>
   <li>Web browsers

   <li>User agents that implement one or more of the following types of
    content: HTML (<a href="#HTML401"
    rel=biblioentry>[HTML401]<!--{{HTML401}}--></a>, <a href="#HTML5"
    rel=biblioentry>[HTML5]<!--{{HTML5}}--></a>), XHTML (<a href="#XHTML10"
    rel=biblioentry>[XHTML10]<!--{{XHTML10}}--></a>, <a href="#XHTML11"
    rel=biblioentry>[XHTML11]<!--{{XHTML11}}--></a>), XForms (e.g. <a
    href="#XFORMS11" rel=biblioentry>[XFORMS11]<!--{{XFORMS11}}--></a>), SVG
    (e.g. <a href="#SVG10" rel=biblioentry>[SVG10]<!--{{SVG10}}--></a>, <a
    href="#SVG11" rel=biblioentry>[SVG11]<!--{{SVG11}}--></a>) or other
    content languages that contain forms controls or are intended for user
    interaction

   <li>User agents that implement one or more levels or modules of CSS (e.g.
    <a href="#CSS1" rel=biblioentry>[CSS1]<!--{{CSS1}}--></a>, <a
    href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>)
  </ul>

  <h3 id=extensions><span class=secno>2.3. </span>Extensions</h3>

  <p>This specification does not define any explicit extension mechanisms. If
   an implementation needs to extend the functionality of this specification,
   it must follow any/all guidelines and requirements of extensions as
   defined in CSS2.1, e.g. <a
   href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">Vendor-specific
   extensions</a> (<a href="#CSS21"
   rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>, section 4.1.2.1).

  <h2 id=dependencies-on-other-modules><span class=secno>3.
   </span>Dependencies on other modules</h2>

  <p> This CSS3 module depends on the following other specifications.

  <ul>
   <li><a href="#SELECT" rel=biblioentry>[SELECT]<!--{{!SELECT}}--></a>

   <li><a href="#CSS3COLOR"
    rel=biblioentry>[CSS3COLOR]<!--{{!CSS3COLOR}}--></a>

   <li><a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
  </ul>
  <!--
<p>It has non-normative (informative) references to the following
other specifications:</p>
<ul>
</ul>
-->

  <p> The following work is related to the CSS Basic User Interface Module
   Level 3 (CSS3 Basic UI).

  <ul>
   <li><a href="#HTML401" rel=biblioentry>[HTML401]<!--{{HTML401}}--></a>

   <li><a href="#HTML5" rel=biblioentry>[HTML5]<!--{{HTML5}}--></a>

   <li><a href="#UAAG10" rel=biblioentry>[UAAG10]<!--{{UAAG10}}--></a>

   <li><a href="#XML10" rel=biblioentry>[XML10]<!--{{XML10}}--></a>

   <li><a href="#XHTML10" rel=biblioentry>[XHTML10]<!--{{XHTML10}}--></a>

   <li><a href="#XHTML11" rel=biblioentry>[XHTML11]<!--{{XHTML11}}--></a>

   <li><a href="#XFORMS11" rel=biblioentry>[XFORMS11]<!--{{XFORMS11}}--></a>
  </ul>

  <p>This specification does not define what is a form element.

  <h2 id=user-interface-selectors><span class=secno>4. </span>User Interface
   Selectors</h2>

  <h3 id=pseudo-classes><span class=secno>4.1. </span>User interface states:
   pseudo-classes</h3>

  <p>The Selectors specification <a
   href="http://www.w3.org/TR/css3-selectors/#UIstates">defines several user
   interface selectors</a> (<a href="#SELECT"
   rel=biblioentry>[SELECT]<!--{{!SELECT}}--></a>, sections 6.6.1 and 6.6.4)
   which represent user interface states:

  <ul>
   <li id=psuedo-hover><a
    href="http://www.w3.org/TR/css3-selectors/#useraction-pseudos">:hover</a>

   <li id=pseudo-active><a
    href="http://www.w3.org/TR/css3-selectors/#useraction-pseudos">:active</a>

   <li id=pseudo-focus><a
    href="http://www.w3.org/TR/css3-selectors/#useraction-pseudos">:focus</a>

   <li id=pseudo-enabled><a
    href="http://www.w3.org/TR/css3-selectors/#enableddisabled">:enabled</a>

   <li id=pseudo-disabled><a
    href="http://www.w3.org/TR/css3-selectors/#enableddisabled">:disabled</a>

   <li id=pseudo-checked><a
    href="http://www.w3.org/TR/css3-selectors/#checked">:checked</a>

   <li id=pseudo-indeterminate><a
    href="http://www.w3.org/TR/css3-selectors/#indeterminate">:indeterminate</a>
  </ul>

  <p>These pseudo-classes as defined by <a href="#SELECT"
   rel=biblioentry>[SELECT]<!--{{!SELECT}}--></a> are included in this
   specification by reference.

  <p>CSS 2.1 <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
   specifies additional details for some of the selectors mentioned, above
   and beyond Selectors.

  <h4 id=active><span class=secno>4.1.1. </span>:active details</h4>

  <p>In addition, on systems with more than one mouse button, :active is
   clarified to apply only to the primary or primary activation button
   (typically the "left" mouse button), and any aliases thereof.

  <h4 id=indeterminate><span class=secno>4.1.2. </span> The
   indeterminate-value pseudo-class &lsquo;<code
   class=css>:indeterminate</code>&rsquo;</h4>

  <p>The <code>:indeterminate</code> pseudo-class applies to UI elements
   whose value is in an indeterminate state. For example, radio and checkbox
   elements can be toggled between checked and unchecked states, but are
   sometimes in an indeterminate state, neither checked nor unchecked.
   Similarly a progress meter can be in an indeterminate state when the
   percent completion is unknown.

  <p>Like the <code>:checked</code> pseudo-class, <code>:indeterminate</code>
   applies to all media. Components of a radio-group initialized with no
   pre-selected choice, for example, would be <code>:indeterminate</code>
   even in a static display.

  <h4 class="no-num no-toc" id=new-user-interface-state-pseudo-classes>New
   user interface state pseudo-classes</h4>

  <p>In addition to the above-mentioned pseudo-classes, this specification
   introduces several new pseudo-classes to define additional user interface
   states.

  <ul>
   <li>:default

   <li>:valid

   <li>:invalid

   <li>:in-range

   <li>:out-of-range

   <li>:required

   <li>:optional

   <li>:read-only

   <li>:read-write
  </ul>

  <p>Specifically, these new states (except for :default) are provided as a
   way to style elements which are in the respective states as defined by
   XForms <a href="#XFORMS11"
   rel=biblioentry>[XFORMS11]<!--{{XFORMS11}}--></a>.

  <h4 id=pseudo-default><span class=secno>4.1.3. </span>:default</h4>

  <p>The :default selector applies to the one or more UI elements that are
   the default among a set of similar elements. This selector typically
   applies to context menu items, buttons, and select lists/menus.

  <p> One example is the default submit button among a set of buttons.
   Another example is the default option from a popup menu. Multiple elements
   in a select-many group could have multiple :default elements, like a
   selection of pizza toppings for example.

  <h4 id=pseudo-validity><span class=secno>4.1.4. </span><span
   id=pseudo-valid>:valid</span> and <span id=pseudo-invalid>:invalid</span></h4>

  <p>An element is :valid or :invalid when it is, respectively, valid or
   invalid with respect to data validity semantics defined by a different
   specification (e.g. <a href="#XFORMS11"
   rel=biblioentry>[XFORMS11]<!--{{XFORMS11}}--></a>). An element which lacks
   data validity semantics is neither :valid nor :invalid. This is different
   from an element which otherwise has no constraints. Such an element would
   always be :valid.

  <h4 id=pseudo-range><span class=secno>4.1.5. </span><span
   id=pseudo-in-range>:in-range</span> and <span
   id=pseudo-out-of-range>:out-of-range</span></h4>

  <p> The :in-range and :out-of-range pseudo-classes apply only to elements
   that have range limitations. An element is :in-range or :out-of-range when
   the value that the element is bound to is in range or out of range of the
   presentation (e.g. visual or spoken representation) of the element
   respectively. An element that lacks data range limits or is not a form
   control is neither :in-range nor :out-of-range. E.g. a slider element with
   a value of 11 presented as a slider control that only represents the
   values from 1-10 is :out-of-range. Another example is a menu element with
   a value of "E" that happens to be presented as a popup menu that only has
   choices "A", "B" and "C".

  <h4 id=pseudo-required-value><span class=secno>4.1.6. </span><span
   id=pseudo-required>:required</span> and <span
   id=pseudo-optional>:optional</span></h4>

  <p>A form element is :required or :optional if a value for it is,
   respectively, required or optional before the form it belongs to is
   submitted. Elements that are not form elements are neither required nor
   optional.

  <h4 id=pseudo-ro-rw><span class=secno>4.1.7. </span><span
   id=pseudo-read-only>:read-only</span> and <span
   id=pseudo-read-write>:read-write</span></h4>

  <p>An element whose contents are not user-alterable is :read-only. However,
   elements whose contents are user-alterable (such as text input fields) are
   considered to be in a :read-write state. In typical documents, most
   elements are :read-only. However it may be possible (e.g. in the context
   of an editor) for any element to become :read-write.

  <h3 id=pseudo-elements><span class=secno>4.2. </span>User interface element
   fragments: pseudo-elements</h3>

  <p> In addition to the above-mentioned pseudo-element, this specification
   introduces four new pseudo-elements to provide access to additional user
   interface element fragments.

  <ul>
   <li>::value

   <li>::choices

   <li>::repeat-item

   <li>::repeat-index
  </ul>

  <p>Specifically, these new pseudo-elements are provided as a way to style
   user interface fragments as defined by XForms <a href="#XFORMS11"
   rel=biblioentry>[XFORMS11]<!--{{XFORMS11}}--></a>.

  <p class=note> Note: The ::value, ::choices, ::repeat-item, and
   ::repeat-index pseudo-elements are all at risk.

  <h4 id=pseudo-value><span class=secno>4.2.1. </span>::value</h4>

  <p>A form element may contain both a label for its data value, and the data
   value itself. For such elements, the ::value pseudo-element selects the
   representation of just the data value itself, in order to style its
   appearance.

  <div class=example>
   <p style="display:none">Example(s):</p>

   <h4 class="no-num no-toc" id=fictional-markup-and-illustration>fictional
    markup and illustration</h4>

   <p> Here is an example which illustrates the ::value of a text input field
    with fictional markup which is then styled with CSS.</p>

   <h5 class="no-num no-toc"
    id=sample-xforms-fragment-with-fictional-ma>sample XForms fragment with
    fictional markup:</h5>

   <pre><code>
&lt;input&gt;
  &lt;label&gt;Zip code&lt;label&gt;
  <em>&lt;input::value/&gt;</em>
&lt;/input&gt;
</code></pre>

   <h5 class="no-num no-toc" id=sample-css>sample CSS:</h5>

   <pre><code class=css>
input { border:dashed }
label { border:dotted }
input::value { border:solid }
</code></pre>

   <h5 class="no-num no-toc" id=an-htmlcss-approximation-of-this-example>an
    HTML+CSS approximation of this example</h5>

   <p> <span style="border:dashed;display:inline-block;padding:10px"> <label
    style="border:dotted;display:inline-block;padding:2px;margin:0;font-size:1em">Zip
    code</label> <input
    style="border:solid;display:inline-block;padding:2px;margin:0;font-size:1em"
    type=text value=94117> </span></p>

   <p>Spacing (in the form of padding) has been added to the above
    approximation to separate the borders and make the individual
    (pseudo-)elements easier to distinguish.</p>
  </div>

  <p>The ::value pseudo-element is similar to an inline-level element, but
   with certain restrictions. The following properties apply to
   <code>::value</code> pseudo-element: font properties, color property,
   background properties, &lsquo;<code
   class=property>word-spacing</code>&rsquo;, &lsquo;<code
   class=property>letter-spacing</code>&rsquo;, &lsquo;<code
   class=property>text-decoration</code>&rsquo;, &lsquo;<code
   class=property>vertical-align</code>&rsquo;, &lsquo;<code
   class=property>text-transform</code>&rsquo;, &lsquo;<code
   class=property>line-height</code>&rsquo;. UAs may apply other properties
   as well.

  <h4 id=pseudo-choices><span class=secno>4.2.2. </span>::choices</h4>

  <p>Similarly, a form element which represents a list of options may contain
   both a label for the list, and the list of choices itself. For such
   elements, the ::choices pseudo-element selects the representation of just
   the list of choices themselves, in order to style their appearance.

  <p>A list of radio buttons can also be selected with the ::choices
   pseudo-element, and the currently chosen radio button can be selected with
   the ::value pseudo-element.

  <h4 id=pseudo-repeat-item><span class=secno>4.2.3. </span>::repeat-item</h4>

  <p> The ::repeat-item pseudo-element represents a single item from a
   repeating sequence. It is generated as a parent to all the elements in a
   single repeating item. Each ::repeat-item is associated with a particular
   instance data node, and is affected by the model item properties (e.g.
   &lsquo;<code class=css><code>relevant</code></code>&rsquo;) found there,
   as the related style properties will cascade to the child elements.

  <h4 id=pseudo-repeat-index><span class=secno>4.2.4. </span>::repeat-index</h4>

  <p> The ::repeat-index pseudo-element represents the current item of a
   repeating sequence. It takes the place of the ::repeat-item as a parent of
   all the elements in the index repeating item.

  <div class=note>
   <p> <em><strong>Note.</strong> Any style declarations that an author wants
    to apply to all repeat items, including the index, must be done so by
    using both ::repeat-item and ::repeat-index selectors. Styles that are
    only applied to ::repeat-item will not automatically be applied to the
    respective ::repeat-index. </em></p>
  </div>

  <div class=example>
   <p style="display:none">Example(s):</p>

   <h4 class="no-num no-toc"
    id=repeat-item-and-repeat-index-fictional-m>::repeat-item and
    ::repeat-index fictional markup</h4>

   <p> Here is an example that illustrates both ::repeat-item and
    ::repeat-index, since they are often both available and used at the same
    time. Assume appropriate namespace declarations were made in a header
    somewhere preceding the code in the example.</p>