E84D updated font-feature-settings syntax · w3c/csswg-drafts@19c3530 · GitHub
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John Daggett
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updated font-feature-settings syntax
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‎css3-fonts/Fonts.html‎

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<h1>CSS Fonts Module Level 3</h1>
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<h2 class="no-num no-toc" id=editors>Editor's Draft 3 March 2011</h2>
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<h2 class="no-num no-toc" id=editors>Editor's Draft 4 March 2011</h2>
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<dl id=authors>
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<dt>This version:
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<dd><a
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href="http://dev.w3.org/csswg/css3-fonts/">http://dev.w3.org/csswg/css3-fonts/</a>
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<!-- <dd><a href="http://www.w3.org/TR/2011/ED-css3-fonts-20110303">http://www.w3.org/TR/2011/ED-css3-fonts-20110303</a> -->
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<!-- <dd><a href="http://www.w3.org/TR/2011/ED-css3-fonts-20110304">http://www.w3.org/TR/2011/ED-css3-fonts-20110304</a> -->
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<dt>Latest version:
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<tr>
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<td>Value:
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<td>normal | &lt;string&gt;
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<td>normal | [&lt;featuretag&gt;]+
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<tr>
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FBC8 <td>Initial:
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<td>as specified
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</table>
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<!-- ...they are not well-suited for use in a general use property. -->
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<p>This property provides low-level control over font features. It is
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intended as a way of providing access to font features that are not widely
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used but are needed for a particular use case. A value of ‘<code
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class=property>normal</code>’ means that no change in rendering occurs
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due to this property while a string value defines a specific set of font
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settings to be used when rendering. A null string is equivalent to
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specifying a value of ‘<code class=property>normal</code>’. This
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property only affects font rendering, its value does not affect font
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selection.
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<p>The string used is specific to the type of font used. For OpenType
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fonts, the value of ‘<code class=css>&lt;string&gt;</code>’ is a
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comma-separated list of &lt;feature-name&gt;=&lt;integer&gt; paired
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values, where ‘<code class=css>&lt;feature-name&gt;</code>’ is the
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case-sensitive name of an OpenType feature defined in <a
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<p>This property provides low-level control over OpenType font features. It
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is intended as a way of providing access to font features that are not
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widely used but are needed for a particular use case. A value of ‘<code
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class=property>normal</code>’ means that no change in glyph selection or
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positioning occurs due to this property.
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<p>
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<pre>/* enable small caps and use second swash alternate */
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font-feature-settings: smcp swsh(2);</pre>
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<p>Feature tags are used with the following syntax:
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<pre
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class=prod><dfn id=ltfeaturetaggt><var>&lt;featuretag&gt;</var></dfn> = [ot-]ident[( &lt;integer&gt; | on | off )]?</pre>
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<p>The identifier indicates a case-sensitive OpenType feature tag. For it
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to match an OpenType feature contained in a font, it must follow the
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syntax rules for tags. OpenType feature tags that are not valid CSS
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class=property>ot-</code>’. In this case the ‘<code
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class=property>ot-</code>’ prefex is removed and the remaining portion
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of the identifier is used to lookup the feature tag in the font. Feature
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tags need only match a feature tag defined in the font, they are not
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limited to explicitly registered OpenType features. Fonts defining custom
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feature tags should follow the <a
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href="http://www.microsoft.com/typography/otspec/featuretags.htm">tag name
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rules</a> defined in the OpenType specification <a
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href="#OPENTYPE-FEATURES"
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rel=biblioentry>[OPENTYPE-FEATURES]<!--{{!OPENTYPE-FEATURES}}--></a> and
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‘<code class=css>&lt;integer&gt;</code>’ is 0 or a positive integer.
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For OpenType features that are boolean in nature, a value of 0 disables
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the feature and a non-zero value enables the feature. Value pairs that
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refer to non-existent features or use values not appropriate for the
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feature are ignored. Whitespace within the string is ignored.
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rel=biblioentry>[OPENTYPE-FEATURES]<!--{{!OPENTYPE-FEATURES}}--></a>.
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Feature tags not present in the font are ignored; a user agent must not
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attempt to synthesize fallback behavior based on these feature tags.
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<p>If present, a value in parentheses indicates an index used for glyph
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selection. An &lt;integer&gt; value must be 0 or greater. A value of 0
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indicates that the feature is disabled. For boolean features, a value of 1
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enables the feature. For non-boolean features, a value of 1 or greater
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enables the feature and indicates the feature selection index. A value of
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‘<code class=property>on</code>’ is synonymous with 1 and ‘<code
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class=property>off</code>’ is synonymous with 0. If the value in
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parentheses is omitted, a value of 1 is assumed.
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<pre>
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font-feature-settings: dlig(1); /* dlig=1 enable discretionary ligatures */
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font-feature-settings: smcp(on); /* smcp=1 enable small caps */
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font-feature-settings: ot-c2sc; /* c2sc=1 enable caps to small caps */
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font-feature-settings: liga(off); /* liga=0 no common ligatures */
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font-feature-settings: tnum hist; /* tnum=1, hist=1 enabled tabular numbers and historical forms */
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font-feature-settings: 3piX(1); /* invalid syntax, feature tag not identifier */
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font-feature-settings: ot-3piX; /* 3piX=1 (this feature not defined) */
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font-feature-settings: PKRN; /* PKRN=1 enable custom feature */
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</pre>
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<p>Authors should generally use ‘<code class=property><a
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href="#propdef-font-variant">font-variant</a></code>’ and its related
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subproperties whenever possible and only use this property for special
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cases where its use is the only way of accessing a particular infrequently
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used font feature.</p>
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<!--
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used font feature.
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Substitute epigraphy example below.
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Scholars studying Greek coin inscriptions often come across many
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different variations for individual Greek letters found on ancient
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coinage. Using a font containing character variants found in these
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inscriptions, an author can describe precisely the appearance of
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the underlying Greek text without using Unicode private-user codepoints.
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-->
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<p>Although specifically defined for OpenType feature tags, feature tags
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for other modern font formats that support font features may be added in
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the future.
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<div class=example>
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<p>The Japanese text below will be rendered with half-width kana
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characters:</p>
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<pre lang=ja>
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body { font-feature-settings: "hwid=1"; /* Half-width OpenType feature */ }
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body { font-feature-settings: hwid; /* Half-width OpenType feature */ }
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&lt;p>毎日<a href="http://images.google.com/images?q=%E3%82%AB%E3%83%AC%E3%83%BC" style="text-decoration: none;">カレー</a>食べてるのに、飽きない&lt;/p>
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</pre>
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<li>Revised font matching algorithm
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<li>Added font-weight-synthetic, font-style-synthetic properties
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<li>Added specific requirements and guidelines for dealing with OpenType
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names
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<li>Added font-weight-synthetic, font-style-synthetic properties</li>
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<!-- Added specific requirements and guidelines for dealing with OpenType names -->
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</ul>
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<h2 class=no-num id=acknowledgments>Acknowledgments</h2>
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<li><var>&lt;feature-index&gt;</var>, <a href="#ltfeature-indexgt"
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title="&lt;feature-index&gt;"><strong>6.9</strong></a>
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<li><var>&lt;featuretag&gt;</var>, <a href="#ltfeaturetaggt"
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title="&lt;featuretag&gt;"><strong>6.12</strong></a>
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<li><var>&lt;feature-value-list&gt;</var>, <a
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href="#ltfeature-value-listgt"
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title="&lt;feature-value-list&gt;"><strong>6.9</strong></a>
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<td><a class=property
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href="#propdef-font-feature-settings">font-feature-settings</a>
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<td>normal | &lt;string&gt;
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<td>normal | [&lt;featuretag&gt;]+
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<td>normal
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<td>normal | inherit | [ &lt;contextual-alt-values&gt; ||
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stylistic(&lt;feature-value-name&gt;) || historical-forms ||
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styleset(&lt;;feature-value-name&gt; [, &lt;feature-value-name&gt;]*)
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|| character-variant(&lt;feature-value-name&gt;
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styleset(&lt;feature-value-name&gt; [, &lt;feature-value-name&gt;]*) ||
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character-variant(&lt;feature-value-name&gt;
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[,&lt;feature-value-name&gt;]*) || swash(&lt;feature-value-name&gt;) ||
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contextual-swash(&lt;feature-value-name&gt;) ||
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ornament(&lt;feature-value-name&gt;) ||
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to do:
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- rework intro to font features
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- describe how font-variant values do *not* apply for system-wide fallback
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- rework syntax of font-feature-settings
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- define on/off as aliases for 1/0 when numeric selectors are used for font-feature-settings
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- wording for superscript/subscript handling
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- wordi 5B77 ng of OpenType family name handling
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- font-stretch matching
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- handling combining sequences in the font matching algorithm
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- fix-up fi ligature example
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done:
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* add character-variant
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-->

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