csswg-drafts/css-text-decor-4/Overview.html at 7d6bab922cce3c47fc1bfe572383cb1f128fa1c1 · w3c/csswg-drafts · GitHub

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<!doctype html>
<html lang="en">
  <head>

    <meta content="text/html; charset=utf-8" http-equiv="Content-Type">


    <title>CSS Text Decoration Module Level 4</title>


    <link href="../default.css" rel="stylesheet" type="text/css">


    <link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">


    <link href="https://www.w3.org/StyleSheets/TR/w3c-unofficial" rel="stylesheet" type="text/css">


  </head>


  <body class="h-entry">

    <div class="head">

      <p data-fill-with="logo"><a class="logo" href="http://www.w3.org/">
    <img alt="W3C" height="48" src="https://www.w3.org/Icons/w3c_home" width="72">
</a>
</p>

      <h1 class="p-name no-ref" id="title">CSS Text Decoration Module Level 4</h1>

      <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Unofficial Proposal Draft,
    <time class="dt-updated" datetime="2015-01-07">7 January 2015</time></span></h2>

      <div data-fill-with="spec-metadata">
        <dl>
          <dt>This version:</dt>
          <dd><a class="u-url" href="http://dev.w3.org/csswg/css-text-decor-4/">http://dev.w3.org/csswg/css-text-decor-4/</a></dd>
          <dt>Latest version:</dt>
          <dd><a href="http://www.w3.org/TR/css-text-decor-4/">http://www.w3.org/TR/css-text-decor-4/</a></dd>
          <dt>Feedback:</dt>
          <dd><span><a href="mailto:www-style@w3.org?subject=%5Bcss-text-decor%5D%20feedback">www-style@w3.org</a> with subject line “<kbd>[css-text-decor] <var>… message topic …</var></kbd>” (<a href="http://lists.w3.org/Archives/Public/www-style/" rel="discussion">archives</a>)</span></dd>
          <dt>Issue Tracking:</dt>
          <dd><a href="#issues-index">Inline In Spec</a></dd>
          <dd><span><a href="http://www.w3.org/Style/CSS/Tracker/products/10">http://www.w3.org/Style/CSS/Tracker/products/10</a></span></dd>
          <dt class="editor">Editors:</dt>
          <dd class="editor">
            <div class="p-author h-card vcard"><a class="p-name fn u-url url" href="http://fantasai.inkedblade.net/contact">fantasai</a> (<span class="p-org org">Invited Expert</span>)</div>
          </dd>
          <dd class="editor">
            <div class="p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:kojiishi@gluesoft.co.jp">Koji Ishii</a> (<span class="p-org org">Invited Expert</span>)</div>
          </dd>
        </dl>
      </div>

      <div data-fill-with="warning"></div>

      <p class="copyright" data-fill-with="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>

      <hr title="Separator for header">
</div>


    <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>

    <div class="p-summary" data-fill-with="abstract">
      <p>This module contains the features of CSS relating to text decoration, such as underlines, text shadows, and emphasis marks.</p>

<a href="http://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.</div>


    <h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>

    <div data-fill-with="status"></div>

    <div data-fill-with="at-risk"></div>


    <h2 class="no-num no-toc no-ref heading settled" id="contents"><span class="content">Table of Contents</span></h2>

    <div data-fill-with="table-of-contents" role="navigation">
      <ul class="toc" role="directory">
        <li><a href="#intro"><span class="secno">1</span> <span class="content">Things To Include Here</span></a></li>
        <li><a href="#temp"><span class="secno">2</span> <span class="content">Rescued L3 Brainstorming: Ignore For Now</span></a>
          <ul class="toc">
            <li><a href="#text-emphasis-skip"><span class="secno">2.1</span> <span class="content">
Emphasis Mark Skip: the <span class="property" data-link-type="propdesc" title="text-emphasis-skip">text-emphasis-skip</span> property</span></a></li>
          </ul>
        </li>
        <li><a href="#conformance"><span class="secno"></span> <span class="content">
Conformance</span></a>
          <ul class="toc">
            <li><a href="#conventions"><span class="secno"></span> <span class="content">
Document conventions</span></a></li>
            <li><a href="#conformance-classes"><span class="secno"></span> <span class="content">
Conformance classes</span></a></li>
            <li><a href="#partial"><span class="secno"></span> <span class="content">
Partial implementations</span></a></li>
            <li><a href="#experimental"><span class="secno"></span> <span class="content">
Experimental implementations</span></a></li>
            <li><a href="#testing"><span class="secno"></span> <span class="content">
Non-experimental implementations</span></a></li>
          </ul>
        </li>
        <li><a href="#references"><span class="secno"></span> <span class="content">References</span></a>
          <ul class="toc">
            <li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a></li>
          </ul>
        </li>
        <li><a href="#index"><span class="secno"></span> <span class="content">Index</span></a></li>
        <li><a href="#property-index"><span class="secno"></span> <span class="content">Property Index</span></a></li>
        <li><a href="#issues-index"><span class="secno"></span> <span class="content">Issues Index</span></a></li>
      </ul></div>

    <main>


      <p class="issue" id="issue-54832a4b"><a class="self-link" href="#issue-54832a4b"></a>This is just a place to keep ideas at the moment.
It has no status at W3C and has not yet been discussed by the CSSWG.</p>


      <h2 class="heading settled" data-level="1" id="intro"><span class="secno">1. </span><span class="content">Things To Include Here</span><a class="self-link" href="#intro"></a></h2>


      <p>In addition to all of the features in Level 3, a completed initial draft of this module will include:</p>


      <ul>

        <li>text-shadow with spread
		</li>
        <li>fill/stroke on text
		</li>
        <li>a text-decoration-offset property
		</li>
        <li>a text-line-width property
	</li>
      </ul>


      <h2 class="heading settled" data-level="2" id="temp"><span class="secno">2. </span><span class="content">Rescued L3 Brainstorming: Ignore For Now</span><a class="self-link" href="#temp"></a></h2>


      <h3 class="heading settled" data-level="2.1" id="text-emphasis-skip"><span class="secno">2.1. </span><span class="content">
Emphasis Mark Skip: the <a class="property" data-link-type="propdesc" href="#propdef-text-emphasis-skip">text-emphasis-skip</a> property</span><a class="self-link" href="#text-emphasis-skip"></a></h3>


      <p class="issue" id="issue-064596ad"><a class="self-link" href="#issue-064596ad"></a>This section is under brainstorming.
	It’s also not yet clear if this property is needed quite yet, despite differences in desired behavior among publications.

	</p>
      <table class="propdef">

        <tbody>

          <tr>

            <th>Name:</th>


            <td><dfn class="css" data-dfn-type="property" data-export="" id="propdef-text-emphasis-skip">text-emphasis-skip<a class="self-link" href="#propdef-text-emphasis-skip"></a></dfn></td>


          </tr>


          <tr>

            <th>Value:</th>


            <td>spaces ||
				punctuation ||
				symbols ||
				narrow
			</td>


          </tr>


          <tr>

            <th>Initial:</th>


            <td>spaces
		</td>
          </tr>


          <tr>

            <th>Applies to:</th>


            <td>all elements</td>


          </tr>


          <tr>

            <th>Inherited:</th>


            <td>yes</td>


          </tr>


          <tr>

            <th>Percentages:</th>


            <td>N/A</td>


          </tr>


          <tr>

            <th>Media:</th>


            <td>visual</td>


          </tr>


          <tr>

            <th>Computed value:</th>


            <td>as specified</td>


          </tr>


        </tbody>


      </table>


      <p>This property describes for which characters marks are drawn.
	The values have following meanings:</p>


      <dl for="text-emphasis-skip" type="value">

        <dt><dfn data-dfn-type="dfn" data-noexport="" id="spaces">spaces<a class="self-link" href="#spaces"></a></dfn>
		</dt>
        <dd>
			Skip <a href="http://www.w3.org/TR/css-text/#word-separator">Word separators</a> or characters
			belonging to the Unicode separator category (Z*).
			(But note that emphasis marks <em>are</em> drawn for a space
			 that combines with any combining characters.)

		</dd>
        <dt><dfn data-dfn-type="dfn" data-noexport="" id="punctuation">punctuation<a class="self-link" href="#punctuation"></a></dfn>
		</dt>
        <dd>
			Skip punctuation.
			Punctuation in this definition includes characters belonging to
			the Unicode Pc, Pd, Ps, Pe, Pi, or Pf categories.
			It also includes characters where the Unicode category is Po and
			the Sentence_Break property <a data-biblio-type="normative" data-link-type="biblio" href="#biblio-uax29" title="UAX29">[UAX29]</a> of the Unicode database
			<a data-biblio-type="normative" data-link-type="biblio" href="#biblio-uax44" title="UAX44">[UAX44]</a> is ATerm, Close, SContinue, or STerm.

		</dd>
        <dt><dfn data-dfn-type="dfn" data-noexport="" id="symbols">symbols<a class="self-link" href="#symbols"></a></dfn>
		</dt>
        <dd>Skip symbols.
			Symbols in this definition includes characters belonging to
			the Unicode S* category.
			It also includes the Unicode Po category
			that are not defined as <span class="css">punctuation</span> above.

		</dd>
        <dt><dfn data-dfn-type="dfn" data-noexport="" id="narrow">narrow<a class="self-link" href="#narrow"></a></dfn>
		</dt>
        <dd>Skip characters where the East_Asian_Width property <a data-biblio-type="normative" data-link-type="biblio" href="#biblio-uax11" title="UAX11">[UAX11]</a>
			of the Unicode database <a data-biblio-type="normative" data-link-type="biblio" href="#biblio-uax44" title="UAX44">[UAX44]</a> is not F (Fullwidth) or W (Wide).
	</dd>
      </dl>


      <p>Characters belonging to the Unicode classes for control codes
	and unassigned characters (Cc, Cf, Cn) are skipped
	regardless of the value of this property.</p>


      <p class="issue" id="issue-509ba68a"><a class="self-link" href="#issue-509ba68a"></a>This syntax requires UA to implement drawing marks for spaces.
	Is there any use case for doing so?
	If not, should we modify the syntax not to allow drawing marks for spaces?

</p>

</main>

    <h2 class="no-ref no-num heading settled" id="conformance"><span class="content">
Conformance</span><a class="self-link" href="#conformance"></a></h2>


    <h3 class="no-ref heading settled" id="conventions"><span class="content">
Document conventions</span><a class="self-link" href="#conventions"></a></h3>


    <p>Conformance requirements are expressed with a combination of
    descriptive assertions and RFC 2119 terminology. The key words "MUST",
    "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
    "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this
    document are to be interpreted as described in RFC 2119.
    However, for readability, these words do not appear in all uppercase
    letters in this specification.

    </p>
    <p>All of the text of this specification is normative except sections
    explicitly marked as non-normative, examples, and notes. <a data-biblio-type="normative" data-link-type="biblio" href="#biblio-rfc2119" title="RFC2119">[RFC2119]</a></p>


    <p>Examples in this specification are introduced with the words "for example"
    or are set apart from the normative text with <code>class="example"</code>,
    like this:

    </p>
    <div class="example">

      <p>This is an example of an informative example.</p>


    </div>


    <p>Informative notes begin with the word "Note" and are set apart from the
    normative text with <code>class="note"</code>, like this:

    </p>
    <p class="note" role="note">Note, this is an informative note.</p>


    <p>Advisements are normative sections styled to evoke special attention and are
    set apart from other normative text with <code>&lt;strong class="advisement"></code>, like
    this:

    <strong class="advisement">
        UAs MUST provide an accessible alternative.
    </strong>

</p>
    <h3 class="no-ref heading settled" id="conformance-classes"><span class="content">
Conformance classes</span><a class="self-link" href="#conformance-classes"></a></h3>


    <p>Conformance to this specification
    is defined for three conformance classes:
    </p>
    <dl>

      <dt>style sheet
            </dt>
      <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
            style sheet</a>.
        </dd>
      <dt>renderer
            </dt>
      <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
            that interprets the semantics of a style sheet and renders
            documents that use them.
        </dd>
      <dt>authoring tool
            </dt>
      <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
            that writes a style sheet.
    </dd>
    </dl>


    <p>A style sheet is conformant to this specification
    if all of its statements that use syntax defined in this module are valid
    according to the generic CSS grammar and the individual grammars of each
    feature defined in this module.

    </p>
    <p>A renderer is conformant to this specification
    if, in addition to interpreting the style sheet as defined by the
    appropriate specifications, it supports all the features defined
    by this specification by parsing them correctly
    and rendering the document accordingly. However, the inability of a
    UA to correctly render a document due to limitations of the device
    does not make the UA non-conformant. (For example, a UA is not
    required to render color on a monochrome monitor.)

    </p>
    <p>An authoring tool is conformant to this specification
    if it writes style sheets that are syntactically correct according to the
    generic CSS grammar and the individual grammars of each feature in
    this module, and meet all other conformance requirements of style sheets
    as described in this module.

</p>
    <h3 class="no-ref heading settled" id="partial"><span class="content">
Partial implementations</span><a class="self-link" href="#partial"></a></h3>


    <p>So that authors can exploit the forward-compatible parsing rules to
    assign fallback values, CSS renderers <strong>must</strong>
    treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore
    as appropriate</a>) any at-rules, properties, property values, keywords,
    and other syntactic constructs for which they have no usable level of
    support. In particular, user agents <strong>must not</strong> selectively
    ignore unsupported component values and honor supported values in a single
    multi-value property declaration: if any value is considered invalid
    (as unsupported values must be), CSS requires that the entire declaration
    be ignored.</p>


    <h3 class="no-ref heading settled" id="experimental"><span class="content">
Experimental implementations</span><a class="self-link" href="#experimental"></a></h3>


    <p>To avoid clashes with future CSS features, the CSS2.1 specification
    reserves a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
    syntax</a> for proprietary and experimental extensions to CSS.

    </p>
    <p>Prior to a specification reaching the Candidate Recommendation stage
    in the W3C process, all implementations of a CSS feature are considered
    experimental. The CSS Working Group recommends that implementations
    use a vendor-prefixed syntax for such features, including those in
    W3C Working Drafts. This avoids incompatibilities with future changes
    in the draft.
    </p>


    <h3 class="no-ref heading settled" id="testing"><span class="content">
Non-experimental implementations</span><a class="self-link" href="#testing"></a></h3>


    <p>Once a specification reaches the Candidate Recommendation stage,
    non-experimental implementations are possible, and implementors should
    release an unprefixed implementation of any CR-level feature they
    can demonstrate to be correctly implemented according to spec.

    </p>
    <p>To establish and maintain the interoperability of CSS across
    implementations, the CSS Working Group requests that non-experimental
    CSS renderers submit an implementation report (and, if necessary, the
    testcases used for that implementation report) to the W3C before
    releasing an unprefixed implementation of any CSS features. Testcases
    submitted to W3C are subject to review and correction by the CSS
    Working Group.

    </p>
    <p>Further information on submitting testcases and implementation reports
    can be found from on the CSS Working Group’s website at
    <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
    Questions should be directed to the
    <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
    mailing list.


</p>
    <h2 class="no-num heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
    <h3 class="no-num heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
    <dl>
      <dt id="biblio-uax11" title="UAX11"><a class="self-link" href="#biblio-uax11"></a>[UAX11]</dt>
      <dd>Asmus Freytag. <a href="http://www.unicode.org/unicode/reports/tr11/tr11-8.html">East Asian Width</a>. 23 March 2001. Unicode Standard Annex #11. URL: <a href="http://www.unicode.org/unicode/reports/tr11/tr11-8.html">http://www.unicode.org/unicode/reports/tr11/tr11-8.html</a></dd>
      <dt id="biblio-uax29" title="UAX29"><a class="self-link" href="#biblio-uax29"></a>[UAX29]</dt>
      <dd>Mark Davis. <a href="http://www.unicode.org/unicode/reports/tr29/tr29-9.html">Text Boundaries</a>. 25 March 2005. Unicode Standard Annex #29. URL: <a href="http://www.unicode.org/unicode/reports/tr29/tr29-9.html">http://www.unicode.org/unicode/reports/tr29/tr29-9.html</a></dd>
      <dt id="biblio-uax44" title="UAX44"><a class="self-link" href="#biblio-uax44"></a>[UAX44]</dt>
      <dd>Mark Davis; Ken Whistler. <a href="http://www.unicode.org/reports/tr44/">Unicode Character Database</a>. 25 September 2013. URL: <a href="http://www.unicode.org/reports/tr44/">http://www.unicode.org/reports/tr44/</a></dd>
      <dt id="biblio-rfc2119" title="rfc2119"><a class="self-link" href="#biblio-rfc2119"></a>[rfc2119]</dt>
      <dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a></dd>
    </dl>
    <h2 class="no-num heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
    <ul class="indexlist">
      <li>narrow, <a href="#narrow" title="section 2.1">2.1</a></li>
      <li>punctuation, <a href="#punctuation" title="section 2.1">2.1</a></li>
      <li>spaces, <a href="#spaces" title="section 2.1">2.1</a></li>
      <li>symbols, <a href="#symbols" title="section 2.1">2.1</a></li>
      <li>text-emphasis-skip, <a href="#propdef-text-emphasis-skip" title="section 2.1">2.1</a></li>
    </ul>
    <h2 class="no-num heading settled" id="property-index"><span class="content">Property Index</span><a class="self-link" href="#property-index"></a></h2>
    <table class="proptable data">
      <thead>
        <tr>
          <th scope="col">Name</th>
          <th scope="col">Value</th>
          <th scope="col">Initial</th>
          <th scope="col">Applies to</th>
          <th scope="col">Inh.</th>
          <th scope="col">%ages</th>
          <th scope="col">Media</th>
          <th scope="col">Computed value</th>
        </tr>
      </thead>
      <tbody>
        <tr>
          <th scope="row"><a class="css" data-link-type="property" href="#propdef-text-emphasis-skip">text-emphasis-skip</a></th>
          <td>spaces ||
				punctuation ||
				symbols ||
				narrow</td>
          <td>spaces</td>
          <td>all elements</td>
          <td>yes</td>
          <td>N/A</td>
          <td>visual</td>
          <td>as specified</td>
        </tr>
      </tbody>
    </table>
    <h2 class="no-num heading settled" id="issues-index"><span class="content">Issues Index</span><a class="self-link" href="#issues-index"></a></h2>
    <div style="counter-reset:issue">
      <div class="issue">This is just a place to keep ideas at the moment.
It has no status at W3C and has not yet been discussed by the CSSWG.<a href="#issue-54832a4b"> ↵ </a></div>
      <div class="issue">This section is under brainstorming.
	It’s also not yet clear if this property is needed quite yet, despite differences in desired behavior among publications.

	<a href="#issue-064596ad"> ↵ </a></div>
      <div class="issue">This syntax requires UA to implement drawing marks for spaces.
	Is there any use case for doing so?
	If not, should we modify the syntax not to allow drawing marks for spaces?

<a href="#issue-509ba68a"> ↵ </a></div>
    </div></body>
</html>