drafts: css3-fonts/Overview.html@55bbedf65a90 (annotated)

css3-fonts/Overview.html@55bbedf65a90 (annotated)

css3-fonts/Overview.html

Wed, 06 Feb 2013 10:00:12 -0700

author: John Daggett <jdaggett@mozilla.com>
date: Wed, 06 Feb 2013 10:00:12 -0700
changeset 7361: 55bbedf65a90
parent 7357: e3ce550667e5
child 7362: a2d67885ffdd
permissions: -rw-r--r--

[css3-fonts] add animatable attribute to font properties

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
 "http://www.w3.org/TR/html4/strict.dtd">
 <html lang=en>
  <head><meta content="text/html;charset=utf-8" http-equiv=Content-Type>
   <title>CSS Fonts Module Level 3</title>
   <!--
       FIXME when publishing: copy the current default.css and link to
       "default.css" rather than "../default.css"
    -->
   <link href="../default.css" rel=stylesheet type="text/css">
   <link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
   <!-- I'm just experimenting here, don't get your bee in a bonnet -->
   <script src="http://use.typekit.com/xon2bky.js"
   type="text/javascript"></script>
   <script type="text/javascript">try{Typekit.load();}catch(e){}</script>
   <style type="text/css">
   body, th, td, h1, h2, h3, h4, h5, h6 {
     font-family: "myriad-pro", sans-serif !important;
   }
   body {
     padding: 2em 70px 2em 70px;
   }
   p + p, p.mtb {
     margin-top: 0.8em;
     text-indent: 0px;
   }
   #bolderlighter {
     width: 40%;
   }
   #bolderlighter th {
     text-align: center;
   }
   #fontformats td, #eventhandlers td, #fontformats th, #eventhandlers th {
     padding-right: 2em;
     text-align: left;
   }
   dd {
     margin-bottom: 1em;
   }
   #authors dd {
     margin-bottom: 0;
   }
   #fontstylematchingalg {
     list-style-type: lower-alpha;
   }
   #fontmatchingalg ul, #fontmatchingalg ol {
     margin-top: 0.8em;
   }
   #fontmatchingalg li + li {
     margin-top: 0.8em;
   }
   div.example {
     padding: 1em;
     margin-top: 1em;
   }
   div.example + div.example {
     margin-top: 2em;
   }
   div.figure {
     page-break-inside: avoid;
   }
   pre.prod { white-space: pre-wrap; margin: 1em 0 1em 2em }
   div.featex {
     width: 700px;
   }
   div.featex img {
     margin: auto;
     display: block;
   }
   span.tag {
     font-family: monospace;
     font-size: 120%;
   }
   ol ol {
     list-style-type: lower-alpha;
   }
   .idl-code {
     font-weight: bold;
     color: #c50;
   }
   </style>
   <link href="http://www.w3.org/StyleSheets/TR/W3C-WD.css" rel=stylesheet
   type="text/css">
  <body>
   <div class=head> <!--begin-logo-->
    <p><a href="http://www.w3.org/"><img alt=W3C height=48
     src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
    <h1>CSS Fonts Module Level 3</h1>
    <h2 class="no-num no-toc" id=w3c-working-draft-12-february-2013>W3C
     Working Draft 12 February 2013</h2>
    <dl id=authors>
     <dt>This version:</dt>
     <!-- <dd><a href="http://dev.w3.org/csswg/css3-fonts/">http://dev.w3.org/csswg/css3-fonts/</a> -->
     <dd><a
      href="http://www.w3.org/TR/2013/WD-css3-fonts-20130212/">http://www.w3.org/TR/2013/WD-css3-fonts-20130212/</a>
     <dt>Latest version:
     <dd><a
      href="http://www.w3.org/TR/css3-fonts/">http://www.w3.org/TR/css3-fonts/</a>
     <dt>Latest editor's draft:
     <dd><a
      href="http://dev.w3.org/csswg/css3-fonts/">http://dev.w3.org/csswg/css3-fonts/</a>
     <dt>Previous version:
     <dd><a
      href="http://www.w3.org/TR/2012/WD-css3-fonts-20121211/">http://www.w3.org/TR/2012/WD-css3-fonts-20121211/</a>
     <dt>Issues List:
     <dd><a href="http://www.w3.org/Style/CSS/Tracker/products/18">CSS3 Fonts
      issues in Tracker</a>
     <dd><a
      href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&amp;product=CSS&amp;component=Fonts&amp;bug_status=NEW&amp;bug_status=ASSIGNED&amp;bug_status=REOPENED">CSS3
      Fonts issues in Bugzilla</a>
     <dt>Discussion:
     <dd><a
      href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a>
      with subject line “<kbd>[css3-fonts] topic</kbd>”
     <dt>Editor:
     <dd><a href="mailto:jdaggett@mozilla.com">John Daggett (Mozilla)</a>
    </dl>
    <!--begin-copyright-->
    <p class=copyright><a
     href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
     rel=license>Copyright</a> © 2013 <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>
    <!--end-copyright-->
    <hr title="Separator for header">
   </div>
   <h2 class="no-num no-toc" id=abstract>Abstract</h2>
   <p>This CSS3 module describes how font properties are specified and how
    font resources are loaded dynamically. The contents of this specification
    are a consolidation of content previously divided into <a
    href="http://www.w3.org/TR/2002/WD-css3-fonts-20020802/">CSS3 Fonts</a>
    and <a href="http://www.w3.org/TR/2002/WD-css3-webfonts-20020802/">CSS3
    Web Fonts</a> modules.
   <h2 class="no-num no-toc" id=status>Status of this document</h2>
   <!--begin-status-->
   <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>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>The (<a
    href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
    mailing list <a href="mailto:www-style@w3.org">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 “css3-fonts” in the subject, preferably like this:
    “[<!---->css3-fonts<!---->] <em>…summary of comment…</em>”
   <p>This document was 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>).
   <p>This document was produced by a group operating under the <a
    href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February
 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
 of the W3C Patent Policy</a>.</p>
   <!--end-status-->
   <!--
 <h3 class="no-num no-toc" id="atrisk">Features at risk</h3>
 <p>The following features are at risk and may be removed when exiting CR:</p>
 <ul>
 </ul>
 -->
   <h2 class="no-num no-toc" id=contents>Table of contents</h2>
   <!--begin-toc-->
   <ul class=toc>
    <li><a href="#introduction"><span class=secno>1 </span>Introduction</a>
    <li><a href="#typography-background"><span class=secno>2 </span>Typography
     Background</a>
    <li><a href="#basic-font-props"><span class=secno>3 </span>Basic Font
     Properties</a>
     <ul class=toc>
      <li><a href="#font-family-prop"><span class=secno>3.1 </span>Font
       family: the font-family property</a>
       <ul class=toc>
        <li><a href="#generic-font-families"><span class=secno>3.1.1
         </span>Generic font families</a>
       </ul>
      <li><a href="#font-weight-prop"><span class=secno>3.2 </span>Font
       weight: the font-weight property</a>
      <li><a href="#font-stretch-prop"><span class=secno>3.3 </span>Font
       width: the font-stretch property</a>
      <li><a href="#font-style-prop"><span class=secno>3.4 </span>Font style:
       the font-style property</a>
      <li><a href="#font-size-prop"><span class=secno>3.5 </span>Font size:
       the font-size property</a>
      <li><a href="#font-size-adjust-prop"><span class=secno>3.6
       </span>Relative sizing: the font-size-adjust property</a>
      <li><a href="#font-prop"><span class=secno>3.7 </span>Shorthand font
       property: the font property</a>
      <li><a href="#font-synthesis-prop"><span class=secno>3.8
       </span>Controlling synthetic faces: the font-synthesis property</a>
     </ul>
    <li><a href="#font-resources"><span class=secno>4 </span>Font
     Resources</a>
     <ul class=toc>
      <li><a href="#font-face-rule"><span class=secno>4.1 </span>The
       <code>@font-face</code> rule</a>
      <li><a href="#font-family-desc"><span class=secno>4.2 </span>Font
       family: the font-family descriptor</a>
      <li><a href="#src-desc"><span class=secno>4.3 </span>Font reference: the
       src descriptor</a>
      <li><a href="#font-prop-desc"><span class=secno>4.4 </span>Font property
       descriptors: the font-style, font-weight, font-stretch descriptors</a>
      <li><a href="#unicode-range-desc"><span class=secno>4.5 </span>Character
       range: the unicode-range descriptor</a>
      <li><a href="#font-rend-desc"><span class=secno>4.6 </span>Font
       features: the font-variant and font-feature-settings descriptors</a>
      <li><a href="#font-face-loading"><span class=secno>4.7 </span>Font
       loading guidelines</a>
      <li><a href="#same-origin-restriction"><span class=secno>4.8
       </span>Same-origin restriction for fonts</a>
       <ul class=toc>
        <li><a href="#default-same-origin-restriction"><span class=secno>4.8.1
         </span>Default same-origin restriction</a>
        <li><a href="#allowing-cross-origin-font-loading"><span
         class=secno>4.8.2 </span>Allowing cross-origin font loading</a>
       </ul>
     </ul>
    <li><a href="#font-matching-algorithm"><span class=secno>5 </span>Font
     Matching Algorithm</a>
     <ul class=toc>
      <li><a href="#font-family-casing"><span class=secno>5.1 </span>Case
       sensitivity of font family names</a>
      <li><a href="#font-style-matching"><span class=secno>5.2 </span>Matching
       font styles</a>
      <li><a href="#cluster-matching"><span class=secno>5.3 </span>Cluster
       matching</a>
      <li><a href="#char-handling-issues"><span class=secno>5.4
       </span>Character handling issues</a>
      <li><a href="#font-matching-changes"><span class=secno>5.5 </span>Font
       matching changes since CSS 2.1</a>
      <li><a href="#font-matching-examples"><span class=secno>5.6 </span>Font
       matching examples</a>
     </ul>
    <li><a href="#font-rend-props"><span class=secno>6 </span>Font Feature
     Properties</a>
     <ul class=toc>
      <li><a href="#glyph-selection-positioning"><span class=secno>6.1
       </span>Glyph selection and positioning</a>
      <li><a href="#language-specific-support"><span class=secno>6.2
       </span>Language-specific display</a>
      <li><a href="#font-kerning-prop"><span class=secno>6.3 </span>Kerning:
       the font-kerning property</a>
      <li><a href="#font-variant-ligatures-prop"><span class=secno>6.4
       </span>Ligatures: the font-variant-ligatures property</a>
      <li><a href="#font-variant-position-prop"><span class=secno>6.5
       </span>Subscript and superscript forms: the font-variant-position
       property</a>
      <li><a href="#font-variant-caps-prop"><span class=secno>6.6
       </span>Capitalization: the font-variant-caps property</a>
      <li><a href="#font-variant-numeric-prop"><span class=secno>6.7
       </span>Numerical formatting: the font-variant-numeric property</a>
      <li><a href="#font-variant-alternates-prop"><span class=secno>6.8
       </span>Alternates and swashes: the font-variant-alternates property</a>
      <li><a href="#font-feature-values"><span class=secno>6.9 </span>Defining
       font specific alternates: the <code>@font-feature-values</code>
       rule</a>
      <li><a href="#font-variant-east-asian-prop"><span class=secno>6.10
       </span>East Asian text rendering: the font-variant-east-asian
       property</a>
      <li><a href="#font-variant-prop"><span class=secno>6.11 </span>Overall
       shorthand for font rendering: the font-variant property</a>
      <li><a href="#font-feature-settings-prop"><span class=secno>6.12
       </span>Low-level font feature settings control: the
       font-feature-settings property</a>
      <li><a href="#font-language-override-prop"><span class=secno>6.13
       </span>Font language override: the font-language-override property</a>
     </ul>
    <li><a href="#font-feature-resolution"><span class=secno>7 </span>Font
     Feature Resolution </a>
     <ul class=toc>
      <li><a href="#default-features"><span class=secno>7.1 </span>Default
       features</a>
      <li><a href="#feature-precedence"><span class=secno>7.2 </span>Feature
       precedence</a>
      <li><a href="#feature-precedence-examples"><span class=secno>7.3
       </span>Feature precedence examples</a>
     </ul>
    <li><a href="#object-model"><span class=secno>8 </span>Object Model</a>
     <ul class=toc>
      <li><a href="#om-fontface"><span class=secno>8.1 </span>The
       <code>CSSFontFaceRule</code> interface</a>
      <li><a href="#om-fontfeaturevalues"><span class=secno>8.2 </span>The
       <code>CSSFontFeatureValuesRule</code> interface</a>
     </ul>
    <li><a href="#font-load-events"><span class=secno>9 </span>Font Load
     Events</a>
     <ul class=toc>
      <li><a href="#document-fontloader"><span class=secno>9.1
       </span>Extension to the <code>document</code> interface</a>
      <li><a href="#fontloader-interface"><span class=secno>9.2 </span>The
       <code>FontLoader</code> Interface</a>
       <ul class=toc>
        <li><a href="#events"><span class=secno>9.2.1 </span>Events</a>
        <li><a href="#methods"><span class=secno>9.2.2 </span>Methods</a>
       </ul>
      <li><a href="#font-load-event-examples"><span class=secno>9.3
       </span>Font load event examples</a>
     </ul>
    <li class=no-num><a href="#platform-props-to-css">Appendix A: Mapping
     platform font properties to CSS properties</a>
    <li class=no-num><a href="#ch-ch-ch-changes">Changes</a>
     <ul class=toc>
      <li class=no-num><a href="#recent-changes"> Changes from the December
 CSS3 Fonts Working Draft</a>
     </ul>
    <li class=no-num><a href="#acknowledgments">Acknowledgments</a>
    <li class=no-num><a href="#conformance"> Conformance</a>
     <ul class=toc>
      <li class=no-num><a href="#conventions"> Document Conventions</a>
      <li class=no-num><a href="#conformance-classes"> Conformance Classes</a>
      <li class=no-num><a href="#partial"> Partial Implementations</a>
      <li class=no-num><a href="#experimental"> Experimental
       Implementations</a>
      <li class=no-num><a href="#testing"> Non-Experimental
       Implementations</a>
     </ul>
    <li class=no-num><a href="#references">References</a>
     <ul class=toc>
      <li class=no-num><a href="#normative-references">Normative
       References</a>
      <li class=no-num><a href="#other-references">Other References</a>
     </ul>
    <li class=no-num><a href="#index">Index</a>
    <li class=no-num><a href="#property-index">Property index</a>
   </ul>
   <!--end-toc-->
   <h2 id=introduction><span class=secno>1 </span>Introduction</h2>
   <p>A font provides a resource containing the visual representation of
    characters. At the simplest level it contains information that maps
    character codes to shapes (called glyphs) that represent these characters.
    Fonts sharing a common design style are commonly grouped into font
    families classified by a set of standard font properties. Within a family,
    the shape displayed for a given character can vary by stroke weight, slant
    or relative width, among others. An individual font face is described by a
    unique combination of these properties. For a given range of text, CSS
    font properties are used to select a font family and a specific font face
    within that family to be used when rendering that text. As a simple
    example, to use the bold form of Helvetica one could use:
   <pre>body {
     font-family: Helvetica;
     font-weight: bold;
 }</pre>
   <p>Font resources may be installed locally on the system on which a user
    agent is running or downloadable. For local font resources descriptive
    information can be obtained directly from the font resource. For
    downloadable font resources (sometimes referred to as web fonts), the
    descriptive information is included with the reference to the font
    resource.
   <p>Families of fonts typically don't contain a single face for each
    possible variation of font properties. The CSS font selection mechanism
    describes how to match a given set of CSS font properties to a single font
    face.
   <h2 id=typography-background><span class=secno>2 </span>Typography
    Background</h2>
   <p><em>This section is non-normative.</em>
   <p> Typographic traditions vary across the globe, so there is no unique way
    to classify all fonts across languages and cultures. For even common Latin
    letters, wide variations are possible:
   <div class=figure><img alt="variations in glyphs for a single character"
    src=aaaaaa.png>
    <p class=caption>One character, many glyph variations
   </div>
   <p>Differences in the anatomy of letterforms is one way to distinguish
    fonts. For Latin fonts, flourishes at the ends of a character's main
    strokes, or serifs, can distinguish a font from those without. Similar
    comparisons exist in non-Latin fonts between fonts with tapered strokes
    and those using primarily uniform strokes:
   <div class=figure><img alt="serif vs. non-serifs" src=serifvssansserif.png>
    <p class=caption>Letterforms with and without serifs
   </div>
   <div class=figure><img alt="serif vs. non-serifs for japanese"
    src=minchovsgothic.png>
    <p class=caption>Similar groupings for Japanese typefaces
   </div>
   <p>Fonts contain letterforms and the data needed to map characters to these
    letterforms. Often this may be a simple one-to-one mapping, but more
    complex mappings are also possible. The use of combining diacritic marks
    creates many variations for an underlying letterform:
   <div class=figure><img alt="diacritic marks" src=aaaaaa-diacritics.png>
    <p class=caption>Variations with diacritic marks
   </div>
   <p>A sequence of characters can be represented by a single glyph known as a
    ligature:
   <div class=figure><img alt="example of a fi ligature"
    src=final-ligature.png>
    <p class=caption>Ligature example
   </div>
   <p>Visual transformations based on textual context are often stylistic
    option in European languages. They are required to correctly render
    languages like Arabic, the lam and alef characters below <em>must</em> be
    combined when they exist in sequence:
   <div class=figure><img alt="lam alef ligature" src=lamaleflig.png>
    <p class=caption>Required Arabic ligature
   </div>
   <p>The relative complexity of these shaping transformations requires
    additional data within the font.
   <p>Sets of font faces with various stylistic variations are often grouped
    together into font families. In the simplest case a regular face is
    supplemented with bold and italic faces, but much more extensive groupings
    are possible. Variations in the thickness of letterform strokes, the <dfn
    id=weight>weight</dfn>, and the overall proportions of the letterform, the
    <dfn id=width>width</dfn>, are most common. In the example below, each
    letter uses a different font face within the Univers font family. The
    width used increases from top to bottom and the weight increases from left
    to right:
   <div class=figure><img alt="various width and weight variations within a
    single family" src=weightwidthvariations.png>
    <p class=caption>Weight and width variations within a single font family
   </div>
   <p>Creating fonts that support multiple scripts is a difficult task;
    designers need to understand the cultural traditions surrounding the use
    of type in different scripts and come up with letterforms that somehow
    share a common theme. Many languages often share a common script and each
    of these languages may have noticeable stylistic differences. For example,
    the Arabic script is shared by Persian and Urdu and Cyrillic is used with
    many languages, not just Russian.
   <p>The character map of a font defines the mapping of characters to glyphs
    for that font. If a document contains characters not supported by the
    character maps of the fonts contained in a font family list, a user agent
    may use a system font fallback procedure to locate an appropriate font
    that does. If no appropriate font can be found, some form of "missing
    glyph" character will be rendered by the user agent. Fallback can occur
    when the list of font families does not include a font that supports a
    given character.
   <p>Although the character map of a font maps a given character to a glyph
    for that character, modern font technologies such as OpenType and AAT
    (Apple Advanced Typography) provide ways of mapping a character to
    different glyphs based upon feature settings. Fonts in these formats allow
    these features to be embedded in the font itself and controlled by
    applications. Common typographic features which can be specified this way
    include ligatures, swashes, contextual alternates, proportional and
    tabular figures, and automatic fractions, to list just a few. For a visual
    overview of OpenType features, see the <a href="#OPENTYPE-FONT-GUIDE"
    rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
   <h2 id=basic-font-props><span class=secno>3 </span>Basic Font Properties</h2>
   <p>The particular font face used to render a character is determined by the
    font family and other font properties that apply to a given element. This
    structure allows settings to be varied independent of each other.</p>
   <!-- prop: font-family -->
   <h3 id=font-family-prop><span class=secno>3.1 </span>Font family: the <a
    href="#propdef-font-family">font-family</a> property</h3>
   <table class=propdef id=namefont-familyvalue-ltfamily-name-ltgen>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-family>font-family</dfn>
     <tr>
      <td>Value:
      <td>[ &lt;family-name> | &lt;generic-family> ]#
     <tr>
      <td>Initial:
      <td>depends on user agent
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property specifies a prioritized list of font family names or
    generic family names. A font family defines a set of faces that vary in
    weight, width or slope. CSS uses the combination of a family name with
    other style attributes to select an individual face. Using this selection
    mechanism, rather than selecting a face via the style name as is often
    done in design applications, allows some degree of regularity in textual
    display when fallback occurs.
   <p class=note>Designers should note that the CSS definition of font
    attributes used for selection are explicitly not intended to define a font
    taxonomy. A type designer's idea of a family may often extend to a set of
    faces that vary along axes other than just the standard axes of weight,
    width and slope. A family may extend to include both a set of serif faces
    and a set of sans-serif faces or vary along axes that are unique to that
    family. The CSS font selection mechanism merely provides a way to
    determine the “closest” substitute when substitution is necessary.
   <p>Unlike other CSS properties, component values are a comma-separated list
    indicating alternatives. A user agent iterates through the list of family
    names until it matches an available font that contains a glyph for the
    character to be rendered. This allows for differences in available fonts
    across platforms and for differences in the range of characters supported
    by individual fonts.
   <p>A font family name only specifies a name given to a set of font faces,
    it does not specify an individual face. Given the availability of the
    fonts below, Futura would match but Futura Medium would not:
   <div class=figure><img alt="family and face names"
    src=familyvsfacename.png>
    <p class=caption>Family and individual face names
   </div>
   <p>Consider the example below:
   <div class=example>
    <pre>body {
     font-family: Helvetica, Verdana, sans-serif;
 }</pre>
    <p>If Helvetica is available it will be used when rendering. If neither
     Helvetica nor Verdana is present, then the user-agent-defined sans serif
     font will be used.</p>
   </div>
   <p>There are two types of font family names:
   <dl>
    <dt>&lt;family-name&gt;
    <dd>The name of a font family of choice such as Helvetica or Verdana in
     the previous example.
    <dt>&lt;generic-family&gt;
    <dd> The following generic family keywords are defined: ‘<a
     href="#serif"><code class=property>serif</code></a>’, ‘<a
     href="#sans-serif"><code class=property>sans-serif</code></a>’, ‘<a
     href="#cursive"><code class=property>cursive</code></a>’, ‘<a
     href="#fantasy"><code class=property>fantasy</code></a>’, and ‘<a
     href="#monospace"><code class=property>monospace</code></a>’. These
     keywords can be used as a general fallback mechanism when an author's
     desired font choices are not available. As keywords, they must not be
     quoted. Authors are encouraged to append a generic font family as a last
     alternative for improved robustness.
   </dl>
   <p>Font family names must either be given quoted as <a
    href="//www.w3.org/TR/CSS21/syndata.html#strings">strings,</a> or unquoted
    as a sequence of one or more <a
    href="//www.w3.org/TR/CSS21/syndata.html#value-def-identifier">identifiers.</a>
    This means most punctuation characters and digits at the start of each
    token must be escaped in unquoted font family names.
   <p>To illustrate this, the following declarations are invalid:
   <pre>
 font-family: Red/Black, sans-serif;
 font-family: "Lucida" Grande, sans-serif;
 font-family: Ahem!, sans-serif;
 font-family: test@foo, sans-serif;
 font-family: #POUND, sans-serif;
 font-family: Hawaii 5-0, sans-serif;
 </pre>
   <p>If a sequence of identifiers is given as a font family name, the
    computed value is the name converted to a string by joining all the
    identifiers in the sequence by single spaces.
   <p>To avoid mistakes in escaping, it is recommended to quote font family
    names that contain white space, digits, or punctuation characters other
    than hyphens:
   <pre>
 body { font-family: "New Century Schoolbook", serif }
 &lt;BODY STYLE="font-family: '21st Century', fantasy">
 </pre>
   <p>Font family <em>names</em> that happen to be the same as a keyword value
    (‘<code class=property>inherit</code>’, ‘<a href="#serif"><code
    class=property>serif</code></a>’, ‘<a href="#sans-serif"><code
    class=property>sans-serif</code></a>’, ‘<a href="#monospace"><code
    class=property>monospace</code></a>’, ‘<a href="#fantasy"><code
    class=property>fantasy</code></a>’, and ‘<a href="#cursive"><code
    class=property>cursive</code></a>’) must be quoted to prevent confusion
    with the keywords with the same names. The keywords ‘<code
    class=property>initial</code>’ and ‘<code
    class=property>default</code>’ are reserved for future use and must also
    be quoted when used as font names. UAs must not consider these keywords as
    matching the ‘<code class=css>&lt;family-name&gt;</code>’ type.
   <p>The precise way a set of fonts are grouped into font families varies
    depending upon the platform font management API's. The Windows GDI API
    only allows four faces to be grouped into a family while the DirectWrite
    API and API's on OSX and other platforms support font families with a
    variety of weights, widths and slopes (see <a
    href="#platform-props-to-css">Appendix A</a> for more details).
   <p>Some font formats allow fonts to carry multiple localizations of the
    family name. User agents must recognize and correctly match all of these
    names independent of the underlying platform localization, system API used
    or document encoding:
   <div class=figure><img alt="examples of localized family names"
    src=localizedfamilynames.png>
    <p class=caption>Localized family names
   </div>
   <h4 id=generic-font-families><span class=secno>3.1.1 </span>Generic font
    families</h4>
   <p>All five generic font families are defined to exist in all CSS
    implementations (they need not necessarily map to five distinct actual
    fonts). User agents should provide reasonable default choices for the
    generic font families, which express the characteristics of each family as
    well as possible within the limits allowed by the underlying technology.
    User agents are encouraged to allow users to select alternative choices
    for the generic fonts.
   <h5 class="no-num no-toc"> <span class=index-def id=serif0 title="serif,
    definition of"><a name=serif-def><dfn id=serif>serif</dfn></a></span></h5>
   <p>Glyphs of serif fonts, as the term is used in CSS, have finishing
    strokes, flared or tapering ends, or have actual serifed endings
    (including slab serifs). Serif fonts are typically proportionately-spaced.
    They often display a greater variation between thick and thin strokes than
    fonts from the ‘<a href="#sans-serif"><code
    class=property>sans-serif</code></a>’ generic font family. CSS uses the
    term ‘<a href="#serif"><code class=property>serif</code></a>’ to apply
    to a font for any script, although other names may be more familiar for
    particular scripts, such as Mincho (Japanese), Sung, Song or Kai
    (Chinese), Batang (Korean). Any font that is so described may be used to
    represent the generic ‘<a href="#serif"><code
    class=property>serif</code></a>’ family.
   <div class=figure><img alt="sample serif fonts" src=serifexamples.png>
    <p class=caption>Sample serif fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=sans-serif0
    title="sans-serif, definition of"> <a name=sans-serif-def><dfn
    id=sans-serif>sans-serif</dfn></a></span></h5>
   <p>Glyphs in sans-serif fonts, as the term is used in CSS, have stroke
    endings that are plain -- without any flaring, cross stroke, or other
    ornamentation. Sans-serif fonts are typically proportionately-spaced. They
    often have little variation between thick and thin strokes, compared to
    fonts from the ‘<a href="#serif"><code
    class=property>serif</code></a>’ family. CSS uses the term ‘<a
    href="#sans-serif"><code class=property>sans-serif</code></a>’ to apply
    to a font for any script, although other names may be more familiar for
    particular scripts, such as Gothic (Japanese), Hei (Chinese), or Gulim
    (Korean). Any font that is so described may be used to represent the
    generic ‘<a href="#sans-serif"><code
    class=property>sans-serif</code></a>’ family.
   <div class=figure><img alt="sample sans-serif fonts"
    src=sansserifexamples.png>
    <p class=caption>Sample sans-serif fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=cursive0
    title="cursive, definition of"> <a name=cursive-def><dfn
    id=cursive>cursive</dfn></a></span></h5>
   <p>Glyphs in cursive fonts generally have either joining strokes or other
    cursive characteristics beyond those of italic typefaces. The glyphs are
    partially or completely connected, and the result looks more like
    handwritten pen or brush writing than printed letterwork. Some scripts,
    such as Arabic, are almost always cursive. CSS uses the term ‘<a
    href="#cursive"><code class=property>cursive</code></a>’ to apply to a
    font for any script, although other names such as Chancery, Brush, Swing
    and Script are also used in font names.
   <div class=figure><img alt="sample cursive fonts" src=cursiveexamples.png>
    <p class=caption>Sample cursive fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=fantasy0
    title="fantasy, definition of"> <a name=fantasy-def><dfn
    id=fantasy>fantasy</dfn></a></span></h5>
   <p>Fantasy fonts are primarily decorative fonts that contain playful
    representations of characters. These do not include Pi or Picture fonts
    which do not represent actual characters.
   <div class=figure><img alt="sample fantasy fonts" src=fantasyexamples.png>
    <p class=caption>Sample fantasy fonts
   </div>
   <h5 class="no-num no-toc"> <span class=index-def id=monospace0
    title="monospace, definition of"> <a name=monospace-def><dfn
    id=monospace>monospace</dfn></a></span></h5>
   <p>The sole criterion of a monospace font is that all glyphs have the same
    fixed width. This is often used to render samples of computer code.
   <div class=figure><img alt="sample monospace fonts"
    src=monospaceexamples.png>
    <p class=caption>Sample monospace fonts
   </div>
   <!-- prop: font-weight -->
   <h3 id=font-weight-prop><span class=secno>3.2 </span>Font weight: the <a
    href="#propdef-font-weight">font-weight</a> property</h3>
   <table class=propdef id=namefont-weightvaluenormal-bold-bolder-l>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-weight>font-weight</dfn>
     <tr>
      <td>Value:
      <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
       | 700 | 800 | 900
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>see description
     <tr>
      <td>Animatable:
      <td>as <a
       href="http://dev.w3.org/csswg/css3-transitions/#animtype-font-weight">font
       weight</a>
   </table>
   <p>The <a class=noxref href="#font-weight-prop"><span
    class=property>‘<code class=property>font-weight</code>’</span></a>
    property specifies weight of glyphs in the font, their degree of blackness
    or stroke thickness.
   <p>Values have the following meanings:
   <dl>
    <dt>100 to 900
    <dd>These values form an ordered sequence, where each number indicates a
     weight that is at least as dark as its predecessor. These roughly
     correspond to the commonly used weight names below:
   </dl>
   <ul>
    <li>100 - Thin
    <li>200 - Extra Light (Ultra Light)
    <li>300 - Light
    <li>400 - Normal
    <li>500 - Medium
    <li>600 - Semi Bold (Demi Bold)
    <li>700 - Bold
    <li>800 - Extra Bold (Ultra Bold)
    <li>900 - Black (Heavy)
   </ul>
   <dl>
    <dt><a href="#normal2"><strong>normal</strong></a>
    <dd>Same as ‘<code class=css>400</code>’.
    <dt><strong>bold</strong>
    <dd>Same as ‘<code class=css>700</code>’.
    <dt><strong>bolder</strong>
    <dd>Specifies the weight of the face bolder than the inherited value.
    <dt><strong>lighter</strong>
    <dd>Specifies the weight of the face lighter than the inherited value.
   </dl>
   <p>Font formats that use a scale other than a nine step scale should map
    their scale onto the CSS scale so that 400 roughly corresponds with a face
    that would be labeled as Regular, Book, Roman and 700 roughly matches a
    face that would be labeled as Bold. Or weights may be inferred from the
    style names, ones that correspond roughly with the scale above. The scale
    is relative, so a face with a larger weight value must never appear
    lighter. If style names are used to infer weights, care should be taken to
    handle variations in style names across locales.
   <p>Quite often there are only a few weights available for a particular font
    family. When a weight is specified for which no face exists, a face with a
    nearby weight is used. In general, bold weights map to faces with heavier
    weights and light weights map to faces with lighter weights (see the <a
    href="#font-matching-algorithm">font matching section below</a> for a
    precise definition). The examples here illustrate which face is used for
    different weights, grey indicates a face for that weight does not exist so
    a face with a nearby weight is used:
   <div class=figure><img alt="weight mappings for a family with 400, 700 and
 weights" src=optimaweights.png>
    <p class=caption>Weight mappings for a font family with 400, 700 and 900
     weight faces
   </div>
   <div class=figure><img alt="weight mappings for a family with 300, 600
    weights" src=hiraginoweights.png>
    <p class=caption>Weight mappings for a font family with 300 and 600 weight
     faces
   </div>
   <p>Although the practice is not well-loved by typographers, bold faces are
    often synthesized by user agents for faces that lack actual bold faces.
    For the purposes of style matching, these faces must be treated as if they
    exist within the family.
   <p>Values of ‘<code class=property>bolder</code>’ and ‘<code
    class=property>lighter</code>’ indicate values relative to the weight of
    the parent element. Based on the inherited weight value, the weight used
    is calculated using the chart below. Child elements inherit the calculated
    weight, not a value of ‘<code class=property>bolder</code>’ or
    ‘<code class=property>lighter</code>’.
   <table class=data id=bolderlighter summary="Bolder/lighter mappings">
    <thead>
     <tr>
      <th>Inherited value
      <th>bolder
      <th>lighter
    <tbody>
     <tr>
      <th>100
      <td>400
      <td>100
     <tr>
      <th>200
      <td>400
      <td>100
     <tr>
      <th>300
      <td>400
      <td>100
     <tr>
      <th>400
      <td>700
      <td>100
     <tr>
      <th>500
      <td>700
      <td>100
     <tr>
      <th>600
      <td>900
      <td>400
     <tr>
      <th>700
      <td>900
      <td>400
     <tr>
      <th>800
      <td>900
      <td>700
     <tr>
      <th>900
      <td>900
      <td>700
   </table>
   <p>The table above is equivalent to selecting the next relative bolder or
    lighter face, given a font family containing normal and bold faces along
    with a thin and a heavy face. Authors who desire finer control over the
    exact weight values used for a given element should use numerical values
    instead of relative weights.</p>
   <!-- prop: font-stretch -->
   <h3 id=font-stretch-prop><span class=secno>3.3 </span>Font width: the <a
    href="#propdef-font-stretch">font-stretch</a> property</h3>
   <table class=propdef id=namefont-stretchvaluenormal-ultra-conden>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-stretch>font-stretch</dfn>
     <tr>
      <td>Value:
      <td>normal | ultra-condensed | extra-condensed | condensed |
       semi-condensed | semi-expanded | expanded | extra-expanded |
       ultra-expanded
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>as <a href="#font-stretch-animation">font stretch</a>
   </table>
   <p>The <a class=noxref href="#font-stretch-prop"><span
    class=property>‘<code class=property>font-stretch</code>’</span></a>
    property selects a normal, condensed, or expanded face from a font family.
    Absolute keyword values have the following ordering, from narrowest to
    widest:
   <ul>
    <li>Ultra Condensed
    <li>Extra Condensed
    <li>Condensed
    <li>Semi Condensed
    <li>Normal
    <li>Semi Expanded
    <li>Expanded
    <li>Extra Expanded
    <li>Ultra Expanded
   </ul>
   <p>The scale is relative, so a face with a font-stretch value higher in the
    list above should never appear wider. When a face does not exist for a
    given width, normal or condensed values map to a narrower face, otherwise
    a wider face. Conversely, expanded values map to a wider face, otherwise a
    narrower face. The figure below shows how the nine font-stretch property
    settings affect font selection for font family containing a variety of
    widths, grey indicates a width for which no face exists and a different
    width is substituted:
   <div class=figure><img alt="width mappings for a family with condensed,
    normal and expanded faces" src=universwidths.png>
    <p class=caption>Width mappings for a font family with condensed, normal
     and expanded width faces
   </div>
   <p id=font-stretch-animation>Animation of font stretch: Font stretch is
    interpolated in discrete steps. The interpolation happens as though the
    ordered values are equally spaced real numbers. The interpolation result
    is rounded to the nearest value, with values exactly halfway between two
    values rounded towards the later value in the list above.</p>
   <!-- prop: font-style -->
   <h3 id=font-style-prop><span class=secno>3.4 </span>Font style: the <a
    href="#propdef-font-style">font-style</a> property</h3>
   <table class=propdef id=namefont-stylevaluenormal-italic-oblique>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-style>font-style</dfn>
     <tr>
      <td>Value:
      <td>normal | italic | oblique
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>The <a class=noxref href="#font-style-prop"><span
    class=property>‘<code class=property>font-style</code>’</span></a>
    property allows italic or oblique faces to be selected. Italic forms are
    generally cursive in nature while oblique faces are typically sloped
    versions of the regular face. Oblique faces can be simulated by
    artificially sloping the glyphs of the regular face. Compare the
    artificially sloped renderings of Palatino ‘<code
    class=property>a</code>’ and Baskerville ‘<code
    class=property>N</code>’ in grey with the actual italic versions:
   <div class=figure><img alt="artificial sloping vs. real italics"
    src=realvsfakeitalics.png>
    <p class=caption>Artificial sloping versus real italics
   </div>
   <p>A value of ‘<a href="#normal2"><code
    class=property>normal</code></a>’ selects a face that is classified as
    ‘<a href="#normal2"><code class=property>normal</code></a>’, while
    ‘<code class=property>oblique</code>’ selects a font that is labeled
    ‘<code class=property>oblique</code>’. A value of ‘<code
    class=property>italic</code>’ selects a font that is labeled ‘<code
    class=property>italic</code>’, or, if that is not available, one labeled
    ‘<code class=property>oblique</code>’. If no italic or oblique faces
    is available, an oblique face can by synthesized by rendering the normal
    face with a sloping transformation applied.
   <p>Many scripts lack the tradition of mixing a cursive form within text
    rendered with a normal face. Chinese, Japanese and Korean fonts almost
    always lack italic or oblique faces. Fonts that support a mixture of
    scripts will sometimes omit specific scripts such as Arabic from the set
    of glyphs supported in the italic face. User agents should be careful
    about making character map assumptions across faces.
   <p class=issue>For synthetic italics in vertical runs of Chinese, Japanese,
    or Korean text, is there a need to define explicitly the direction of the
    faux oblique for runs that include a mixture of ideographic and Latin
    text?</p>
   <!-- prop: font-size -->
   <h3 id=font-size-prop><span class=secno>3.5 </span>Font size: the <a
    href="#propdef-font-size">font-size</a> property</h3>
   <table class=propdef id=namefont-sizevalueltabsolute-size-ltrela>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-size>font-size</dfn>
     <tr>
      <td>Value:
      <td>&lt;absolute-size> | &lt;relative-size> | &lt;length> |
       &lt;percentage>
     <tr>
      <td>Initial:
      <td>medium
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>refer to parent element's font size
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>absolute length
     <tr>
      <td>Animatable:
      <td>as <a
       href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
   </table>
   <p>This property indicates the desired height of glyphs from the font. For
    scalable fonts, the font-size is a scale factor applied to the EM unit of
    the font. (Note that certain glyphs may bleed outside their EM box.) For
    non-scalable fonts, the font-size is converted into absolute units and
    matched against the declared font-size of the font, using the same
    absolute coordinate space for both of the matched values. Values have the
    following meanings:
   <dl>
    <dt><a name=x18><span class=index-def id=ltabsolute-sizegt
     title="&lt;absolute-size&gt;">
     <strong>&lt;absolute-size&gt;</strong></span></a>
    <dd> An <a class=value-def
     name=value-def-absolute-size>&lt;absolute-size&gt;</a> keyword refers to
     an entry in a table of font sizes computed and kept by the user agent.
     Possible values are:
     <p> [ xx-small | x-small | small | medium | large | x-large | xx-large ]</p>
    <dt><a name=x19><span class=index-def id=ltrelative-sizegt
     title="&lt;relative-size&gt;">
     <strong>&lt;relative-size&gt;</strong></span></a>
    <dd> A <a class=value-def
     name=value-def-relative-size>&lt;relative-size&gt;</a> keyword is
     interpreted relative to the table of font sizes and the font size of the
     parent element. Possible values are:
     <p> [ larger | smaller ]
     <p> For example, if the parent element has a font size of ‘<code
      class=property>medium</code>’, a value of ‘<code
      class=property>larger</code>’ will make the font size of the current
      element be ‘<code class=property>large</code>’. If the parent
      element's size is not close to a table entry, the user agent is free to
      interpolate between table entries or round off to the closest one. The
      user agent may have to extrapolate table values if the numerical value
      goes beyond the keywords.
    <dt><span class=index-inst id=ltlengthgt
     title="&lt;length&gt;">&lt;length&gt;</span>
    <dd>A length value specifies an absolute font size (that is independent of
     the user agent's font table). Negative lengths are illegal.
    <dt><span class=index-inst id=ltpercentagegt-
     title="&lt;percentage&gt;">&lt;percentage&gt; </span>
    <dd>A percentage value specifies an absolute font size relative to the
     parent element's font size. Use of percentage values, or values in
     ‘<code class=property>em</code>’s, leads to more robust and
     cascadable style sheets.
   </dl>
   <p>The following table provides user agent's guideline for the
    absolute-size scaling factor and their mapping to XHTML heading and
    absolute font-sizes. The ‘<code class=property>medium</code>’ value is
    used as the reference middle value. The user agent may fine-tune these
    values for different fonts or different types of display devices.
   <table class=data>
    <thead>
     <tr>
      <th>CSS absolute-size values
      <th>xx-small
      <th>x-small
      <th>small
      <th>medium
      <th>large
      <th>x-large
      <th>xx-large
      <th>
    <tbody>
     <tr>
      <th>scaling factor
      <td>3/5
      <td>3/4
      <td>8/9
      <td>1
      <td>6/5
      <td>3/2
      <td>2/1
      <td>3/1
     <tr>
      <th>XHTML headings
      <td>h6
      <td>
      <td>h5
      <td>h4
      <td>h3
      <td>h2
      <td>h1
      <td>
     <tr>
      <th>XHTML font sizes
      <td>1
      <td>
      <td>2
      <td>3
      <td>4
      <td>5
      <td>6
      <td>7
   </table>
   <p class=note><em><strong>Note 1.</strong> To preserve readability, an UA
    applying these guidelines should nevertheless avoid creating font-size
    resulting in less than 9 pixels per EM unit on a computer display .</em>
   <p class=note><em><strong>Note 2.</strong> In CSS1, the suggested scaling
    factor between adjacent indexes was 1.5 which user experience proved to be
    too large. In CSS2, the suggested scaling factor for computer screen
    between adjacent indexes was 1.2 which still created issues for the small
    sizes. The new scaling factor varies between each index to provide a
    better readability.</em>
   <p>The actual value of this property may differ from the computed value due
    a numerical value on ‘<a href="#propdef-font-size-adjust"><code
    class=property>font-size-adjust</code></a>’ and the unavailability of
    certain font sizes.
   <p>Child elements inherit the computed <a class=noxref
    href="#font-size-prop"> <span class=property>‘<code
    class=property>font-size</code>’</span></a> value (otherwise, the effect
    of <a class=noxref href="#font-size-adjust-prop"><span
    class=property>‘<code
    class=property>font-size-adjust</code>’</span></a> would compound).
   <div class=example>
    <p style="display:none">Example(s):
    <p>
    <pre>p { font-size: 12pt; }
 blockquote { font-size: larger }
 em { font-size: 150% }
 em { font-size: 1.5em }
 </pre>
   </div>
   <!-- prop: font-size-adjust -->
   <h3 id=font-size-adjust-prop><span class=secno>3.6 </span>Relative sizing:
    the <a href="#propdef-font-size-adjust">font-size-adjust</a> property</h3>
   <table class=propdef id=namefont-size-adjustvaluenone-auto-ltnum>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-size-adjust>font-size-adjust</dfn>
     <tr>
      <td>Value:
      <td>none | auto | &lt;number>
     <tr>
      <td>Initial:
      <td>none
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>as <a
       href="http://dev.w3.org/csswg/css3-transitions/#animtype-number">number</a>
   </table>
   <p>For any given font size, the apparent size and legibility of text varies
    across fonts. For scripts such as Latin or Cyrillic that distinguish
    between upper and lowercase letters, the relative height of lowercase
    letters compared to their uppercase counterparts is a determining factor
    of legibility. This is commonly referred to as the <a class=index-def
    href="#aspect-value" id=aspect-value0 title="aspect value"><dfn
    id=aspect-value>aspect value</dfn></a>. Precisely defined, it is equal to
    the x-height of a font divided by the font size.
   <p>In situations where font fallback occurs, fallback fonts may not share
    the same aspect ratio as the desired font family and will thus appear less
    readable. The font-size-adjust property is a way to preserve the
    readability of text when font fallback occurs. It does this by adjusting
    the font-size so that the x-height is the same regardless of the font
    used.
   <div class=example>
    <p>The style defined below defines Verdana as the desired font family, but
     if Verdana is not available Futura or Times will be used.</p>
    <pre>p {
     font-family: Verdana, Futura, Times;
 }
 &lt;p>Lorem ipsum dolor sit amet, ...&lt;/p>
 </pre>
    <p>Verdana has a relatively high aspect ratio, lowercase letters are
     relatively tall compared to uppercase letters, so at small sizes text
     appears legible. Times has a lower aspect ratio and so if fallback
     occurs, the text will be less legible at small sizes than Verdana.</p>
   </div>
   <p>How text rendered in each of these fonts compares is shown below, the
    columns show text rendered in Verdana, Futura and Times. The same
    font-size value is used across cells within each row and red lines are
    included to show the differences in x-height. In the upper half each row
    is rendered in the same font-size value. The same is true for the lower
    half but in this half the font-size-adjust property is also set so that
    the actual font size is adjusted to preserve the x-height across each row.
    Note how small text remains relatively legible across each row in the
    lower half.
   <div class=figure><img alt="text with and without font-size-adjust"
    src=fontsizeadjust.png>
    <p class=caption>Text with and without the use of font-size-adjust
   </div>
   <p>This property allows authors to specify an aspect value for an element
    that will effectively preserve the x-height of the first choice font,
    whether it is substituted or not. Values have the following meanings:
   <dl>
    <dt><strong>none</strong>
    <dd>Do not preserve the font's x-height.
    <dt><strong>auto</strong>
    <dd>Behaves just like &lt;number>, except the number used is the aspect
     value calculated by user agents for the first font in the list of fonts
     defined for the initial value of the ‘<a
     href="#descdef-font-family"><code
     class=property>font-family</code></a>’ property. Effectively this is
     the default font used when ‘<a href="#descdef-font-family"><code
     class=property>font-family</code></a>’ is not otherwise specified.
     <p>Authors can use this value to specify that font size should be
      normalized across fonts based on the x-height without the need to
      specify the aspect ratio explicitly.</p>
    <dt><span class=index-inst id=ltnumbergt
     title="&lt;number&gt;">&lt;number&gt;</span>
    <dd>Specifies the aspect value used in the calculation below to calculate
     the adjusted font size:
     <pre>c  =  ( a / a' ) s
 </pre>
     <p>where:</p>
     <pre>s  =  font-size value
 a  =  aspect value as specified by the font-size-adjust property
 a' =  aspect value of actual font
 c  =  adjusted font-size to use
 </pre>
     <p>This value applies to any font that is selected but in typical usage
      it should be based on the aspect value of the first font in the
      font-family list. If this is specified accurately, the <tt>(a/a')</tt>
      term in the formula above is effectively 1 for the first font and no
      adjustment occurs. If the value is specified inaccurately, text rendered
      using the first font in the family list will display differently in
      older user agents that don't support font-size-adjust.</p>
   </dl>
   <p>Authors can calculate the aspect value for a given font by comparing
    spans with the same content but different font-size-adjust properties. If
    the same font-size is used, the spans will match when the font-size-adjust
    value is accurate for the given font.
   <div class=example>
    <p>Two spans with borders are used to determine the aspect value of a
     font. The font-size is the same for both spans but the font-size-adjust
     property is specified only for the right span. Starting with a value of
 .5, the aspect value can be adjusted until the borders around the two
     letters line up.</p>
    <pre>p {
     font-family: Futura;
     font-size: 500px;
 }
 span {
     border: solid 1px red;
 }
 .adjust {
     font-size-adjust: 0.5;
 }
 &lt;p>&lt;span>b&lt;/span>&lt;span class="adjust">b&lt;/span>&lt;/p>
 </pre>
    <div class=figure><img alt="Futura with an aspect value of 0.5"
     src=beforefontsizeadjust.png>
     <p class=caption>Futura with an aspect value of 0.5
    </div>
    <p>The box on the right is a bit bigger than the one on the left, so the
     aspect value of this font is something less than 0.5. Adjust the value
     until the boxes align.</p>
   </div>
   <!-- prop: font -->
   <!-- jtdfix, crap, preprocessor is inserting links to descriptors rather than properties.  bert, make it stop... -->
   <!-- <a href="#font-stretch-prop" class="noxref"><span class="property">'font-stretch'</span></a> -->
   <h3 id=font-prop><span class=secno>3.7 </span>Shorthand font property: the
    <a href="#propdef-font">font</a> property</h3>
   <table class=propdef id=namefontvalue-ltlsquofont-stylersquo-ltf>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font>font</dfn>
     <tr>
      <td>Value:
      <td>[ [ &lt;‘<a href="#propdef-font-style"><code
       class=property>font-style</code></a>’> || &lt;font-variant-css21> ||
       &lt;‘<a href="#propdef-font-weight"><code
       class=property>font-weight</code></a>’> || &lt;‘<a
       href="#propdef-font-stretch"><code
       class=property>font-stretch</code></a>’> ]? &lt;‘<a
       href="#propdef-font-size"><code class=property>font-size</code></a>’>
       [ / &lt;‘<code class=property>line-height</code>’> ]? &lt;‘<a
       href="#descdef-font-family"><code
       class=property>font-family</code></a>’> ] | caption | icon | menu |
       message-box | small-caption | status-bar
     <tr>
      <td>Initial:
      <td>see individual properties
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>see individual properties
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>see individual properties
     <tr>
      <td>Animatable:
      <td>see individual properties
   </table>
   <p>The <span class=property>‘<a href="#propdef-font"><code
    class=property>font</code></a>’</span> property is, except as described
    below, a shorthand property for setting ‘<a
    href="#propdef-font-style"><code class=property>font-style</code></a>’,
    <span class=property>‘<a href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’</span>, <span
    class=property>‘<a href="#propdef-font-weight"><code
    class=property>font-weight</code></a>’</span>, <span
    class=property>‘<a href="#propdef-font-stretch"><code
    class=property>font-stretch</code></a>’</span>, <span
    class=property>‘<a href="#propdef-font-size"><code
    class=property>font-size</code></a>’</span>, ‘<code
    class=property>line-height</code>’, <span class=property>‘<a
    href="#descdef-font-family"><code
    class=property>font-family</code></a>’</span> at the same place in the
    stylesheet. Values for the <span class=property>‘<a
    href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’</span> property may also be
    included but only those supported in CSS 2.1, none of the font-variant
    values added in this specification can be used in the <span
    class=property>‘<a href="#propdef-font"><code
    class=property>font</code></a>’</span> shorthand:
   <pre
    class=prod><dfn id=ltfont-variant-css21gt><var>&lt;font-variant-css21&gt;</var></dfn> = [normal | small-caps]</pre>
   <p>The syntax of this property is based on a traditional typographical
    shorthand notation to set multiple properties related to fonts.
   <p>All font-related properties are first reset to their initial values,
    including those listed in the preceding paragraph plus <span
    class=property>‘<a href="#propdef-font-size-adjust"><code
    class=property>font-size-adjust</code></a>’</span>, <span
    class=property>‘<a href="#propdef-font-kerning"><code
    class=property>font-kerning</code></a>’</span> and all font feature
    properties. Then, those properties that are given explicit values in the
    <span class=property>‘<a href="#propdef-font"><code
    class=property>font</code></a>’</span> shorthand are set to those
    values. For a definition of allowed and initial values, see the previously
    defined properties. For reasons of backwards compatibility, it is not
    possible to set <span class=property>‘<a
    href="#propdef-font-size-adjust"><code
    class=property>font-size-adjust</code></a>’</span> to anything other
    than its initial value using the <span class=property>‘<a
    href="#propdef-font"><code class=property>font</code></a>’</span>
    shorthand property; instead, use the individual property.
   <div class=example>
    <p style="display:none">Example(s):
    <p>
    <pre>p { font: 12pt/14pt sans-serif }
 p { font: 80% sans-serif }
 p { font: x-large/110% &quot;new century schoolbook&quot;, serif }
 p { font: bold italic large Palatino, serif }
 p { font: normal small-caps 120%/120% fantasy }
 p { font: condensed oblique 12pt &quot;Helvetica Neue&quot;, serif; }
 </pre>
    <p> In the second rule, the font size percentage value (‘<code
     class=css>80%</code>’) refers to the font size of the parent element.
     In the third rule, the line height percentage (‘<code
     class=css>110%</code>’) refers to the font size of the element itself.
    <p>The first three rules do not specify the <span class=property>‘<a
     href="#propdef-font-variant"><code
     class=property>font-variant</code></a>’</span> and <span
     class=property>‘<a href="#propdef-font-weight"><code
     class=property>font-weight</code></a>’</span> explicitly, so these
     properties receive their initial values (‘<a href="#normal2"><code
     class=property>normal</code></a>’). Notice that the font family name
     "new century schoolbook", which contains spaces, is enclosed in quotes.
     The fourth rule sets the <span class=property>‘<a
     href="#propdef-font-weight"><code
     class=property>font-weight</code></a>’</span> to ‘<code
     class=property>bold</code>’, the <span class=property>‘<a
     href="#propdef-font-style"><code
     class=property>font-style</code></a>’</span> to ‘<code
     class=property>italic</code>’, and implicitly sets <span
     class=property>‘<a href="#propdef-font-variant"><code
     class=property>font-variant</code></a>’</span> to ‘<a
     href="#normal2"><code class=property>normal</code></a>’.
    <p> The fifth rule sets the <span class=property>‘<a
     href="#propdef-font-variant"><code
     class=property>font-variant</code></a>’</span> (‘<a
     href="#small-caps"><code class=property>small-caps</code></a>’), the
     <span class=property>‘<a href="#propdef-font-size"><code
     class=property>font-size</code></a>’</span> (120% of the parent's font
     size), the <span class=property>‘<code
     class=property>line-height</code>’</span> (120% of the font size) and
     the <span class=property>‘<a href="#descdef-font-family"><code
     class=property>font-family</code></a>’</span> (‘<a
     href="#fantasy"><code class=property>fantasy</code></a>’). It follows
     that the keyword ‘<a href="#normal2"><code
     class=property>normal</code></a>’ applies to the two remaining
     properties: <span class=property>‘<a href="#propdef-font-style"><code
     class=property>font-style</code></a>’</span> and <span
     class=property>‘<a href="#propdef-font-weight"><code
     class=property>font-weight</code></a>’</span>.
    <p>The sixth rule sets the <span class=property>‘<a
     href="#propdef-font-style"><code
     class=property>font-style</code></a>’</span>, <span
     class=property>‘<a href="#propdef-font-stretch"><code
     class=property>font-stretch</code></a>’</span>, <span
     class=property>‘<a href="#propdef-font-size"><code
     class=property>font-size</code></a>’</span>, and <span
     class=property>‘<a href="#descdef-font-family"><code
     class=property>font-family</code></a>’</span>, the other font
     properties being set to their initial values.
   </div>
   <p>Since the ‘<a href="#propdef-font-stretch"><code
    class=property>font-stretch</code></a>’ property was not defined in CSS
 .1, when using ‘<a href="#propdef-font-stretch"><code
    class=property>font-stretch</code></a>’ values within ‘<a
    href="#propdef-font"><code class=property>font</code></a>’ rules,
    authors should include a extra version compatible with older user agents:
   <pre>p {
   font: 80% sans-serif;   /* for older user agents */
   font: condensed 80% sans-serif;
 }</pre>
   <p>The following values refer to system fonts:
   <dl>
    <dt><strong>caption</strong>
    <dd>The font used for captioned controls (e.g., buttons, drop-downs,
     etc.).
    <dt><strong>icon</strong>
    <dd>The font used to label icons.
    <dt><strong>menu</strong>
    <dd>The font used in menus (e.g., dropdown menus and menu lists).
    <dt><strong>message-box</strong>
    <dd>The font used in dialog boxes.
    <dt><strong>small-caption</strong>
    <dd>The font used for labeling small controls.
    <dt><strong>status-bar</strong>
    <dd>The font used in window status bars.
   </dl>
   <p>System fonts may only be set as a whole; that is, the font family, size,
    weight, style, etc. are all set at the same time. These values may then be
    altered individually if desired. If no font with the indicated
    characteristics exists on a given platform, the user agent should either
    intelligently substitute (e.g., a smaller version of the ‘<code
    class=property>caption</code>’ font might be used for the ‘<code
    class=property>small-caption</code>’ font), or substitute a user agent
    default font. As for regular fonts, if, for a system font, any of the
    individual properties are not part of the operating system's available
    user preferences, those properties should be set to their initial values.
   <p>That is why this property is "almost" a shorthand property: system fonts
    can only be specified with this property, not with <span
    class=property>‘<a href="#descdef-font-family"><code
    class=property>font-family</code></a>’</span> itself, so <span
    class=property>‘<a href="#propdef-font"><code
    class=property>font</code></a>’</span> allows authors to do more than
    the sum of its subproperties. However, the individual properties such as
    <span class=property>‘<a href="#propdef-font-weight"><code
    class=property>font-weight</code></a>’</span> are still given values
    taken from the system font, which can be independently varied.
   <p>Note that the keywords used for the system fonts listed above are only
    treated as keywords when they occur in the initial position, in other
    positions the same string is treated as part of the font family name:
   <pre>  font: menu;        /* use the font settings for system menus */
   font: large menu;  /* use a font family named "menu" */</pre>
   <div class=example>
    <p style="display:none">Example(s):
    <p>
    <pre>button { font: 300 italic 1.3em/1.7em &quot;FB Armada&quot;, sans-serif }
 button p { font: menu }
 button p em { font-weight: bolder }
 </pre>
    <p>If the font used for dropdown menus on a particular system happened to
     be, for example, 9-point Charcoal, with a weight of 600, then P elements
     that were descendants of BUTTON would be displayed as if this rule were
     in effect:
    <pre>button p { font: 600 9pt Charcoal }
 </pre>
    <p>Because the <span class=property>‘<a href="#propdef-font"><code
     class=property>font</code></a>’</span> shorthand resets to its initial
     value any property not explicitly given a value, this has the same effect
     as this declaration:
    <pre>button p {
   font-style: normal;
   font-variant: normal;
   font-weight: 600;
   font-size: 9pt;
   line-height: normal;
   font-family: Charcoal
 }
 </pre>
   </div>
   <!-- prop: font-synthesis -->
   <h3 id=font-synthesis-prop><span class=secno>3.8 </span>Controlling
    synthetic faces: the <a href="#propdef-font-synthesis">font-synthesis</a>
    property</h3>
   <table class=propdef id=namefont-synthesisvaluenone-weight-style>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-synthesis>font-synthesis</dfn>
     <tr>
      <td>Value:
      <td>none | [ weight || style ]
     <tr>
      <td>Initial:
      <td>weight style
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property controls whether user agents are allowed to synthesize
    bold or oblique font faces when a font family lacks bold or italic faces.
    If ‘<a href="#weight"><code class=property>weight</code></a>’ is not
    specified, user agents must not synthesize bold faces and if ‘<code
    class=property>style</code>’ is not specified user agents must not
    synthesize italic faces. A value of ‘<code class=property>none</code>’
    disallows all synthetic faces.
   <div class=example>
    <p>The style rule below disables the use of synthetically obliqued Arabic:</p>
    <pre>*:lang(ar) { font-synthesis: none; }
 </pre>
   </div>
   <h2 id=font-resources><span class=secno>4 </span>Font Resources</h2>
   <h3 id=font-face-rule><span class=secno>4.1 </span>The
    <code>@font-face</code> rule</h3>
   <p>The <code>@font-face</code> rule allows for linking to fonts that are
    automatically activated when needed. This allows authors to select a font
    that closely matches the design goals for a given page rather than
    limiting the font choice to a set of fonts available on all platforms. A
    set of font descriptors define the location of a font resource, either
    locally or externally, along with the style characteristics of an
    individual face. Multiple <code>@font-face</code> rules can be used to
    construct font families with a variety of faces. Using CSS font matching
    rules, a user agent can selectively download only those faces that are
    needed for a given piece of text.
   <p>The general form of an <span class=index-def id=font-face
    title="@font-face"><code>@font-face</code></span> <span class=index-inst
    id=at-rule title=at-rules>at-rule</span> is:
   <pre>
 @font-face { <span class=value-inst-font-description>&lt;font-description&gt;</span> }
 </pre>
   <p>where <span class=index-def id=ltfont-descriptiongt
    title="&lt;font-description&gt;"><a
    name=value-def-font-description>&lt;font-description&gt;</a></span> has
    the form:
   <pre>
 descriptor: value;
 descriptor: value;
 [...]
 descriptor: value;
 </pre>
   <p>Each <span class=index-inst id=font-face0
    title="@font-face"><code>@font-face</code></span> rule specifies a value
    for every font descriptor, either implicitly or explicitly. Those not
    given explicit values in the rule take the initial value listed with each
    descriptor in this specification. These descriptors apply solely within
    the context of the <code>@font-face</code> rule in which they are defined,
    and do not apply to document language elements. There is no notion of
    which elements the descriptors apply to or whether the values are
    inherited by child elements. When a given descriptor occurs multiple times
    in a given <code>@font-face</code> rule, only the last specified value is
    used, all prior values for that descriptor are ignored.
   <div class=example>
    <p>To use a downloadable font called Gentium:</p>
    <pre>
 @font-face {
   font-family: Gentium;
   src: url(http://example.com/fonts/Gentium.ttf);
 }
 p { font-family: Gentium, serif; }
 </pre>
    <p>The user agent will download Gentium and use it when rendering text
     within paragraph elements. If for some reason the site serving the font
     is unavailable, the default serif font will be used.</p>
   </div>
   <p>A given set of <code>@font-face</code> rules define a set of fonts
    available to containing documents. Multiple rules can be used to define a
    family with a large set of faces. When font matching is done fonts defined
    using these rules are considered before other available fonts on a system.
   <p>Downloaded fonts are only available to documents that reference them,
    the process of activating these fonts should not make them available to
    other applications or to documents that don't directly link to the same
    font. User agent implementers might consider it convenient to use
    downloaded fonts when rendering characters in other documents for which no
    other available font exists as part of the system font fallback procedure.
    This would cause a security leak since the contents of one page would be
    able to affect other pages, something an attacker could use as an attack
    vector. These restrictions do not affect caching behavior, fonts are
    cached the same way other web resources are cached.
   <p>User agents which do not understand the <code>@font-face</code> rule
    encounter the opening curly bracket and ignore forward until the closing
    curly bracket. This at-rule conforms with the forward-compatible parsing
    requirement of CSS, parsers may ignore these rules without error. Any
    descriptors that are not recognized or implemented by a given user agent
    must be ignored. <code>@font-face</code> rules require a font-family and
    src descriptor, if either of these are missing the <code>@font-face</code>
    must be ignored.
   <p>In cases where user agents have limited platform resources or implement
    the ability to disable downloadable font resources,
    <code>@font-face</code> rules must simply be ignored; the behavior of
    individual descriptors as defined in this specification should not be
    altered.
   <h3 id=font-family-desc><span class=secno>4.2 </span>Font family: the <a
    href="#descdef-font-family">font-family</a> descriptor</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-family>font-family</dfn>
     <tr>
      <td>Value:
      <td>&lt;family-name>
     <tr>
      <td><em>Initial:</em>
      <td>N/A
   </table>
   <p>This descriptor defines the font family name that will be used in all
    CSS font family name matching, overriding font family names contained in
    the underlying font data. If the font family name is the same as a font
    family available in a given user's environment, it effectively hides the
    underlying font for documents that use the stylesheet. This permits a web
    author to freely choose font-family names without worrying about conflicts
    with font family names present in a given user's environment. Errors
    loading font data do not affect font name matching behavior. User agents
    that apply platform font aliasing rules to font family names defined via
    <code>@font-face</code> rules are considered non-conformant.
   <h3 id=src-desc><span class=secno>4.3 </span>Font reference: the <a
    href="#descdef-src">src</a> descriptor</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-src>src</dfn>
     <tr>
      <td>Value:
      <td>[ &lt;uri> [format(&lt;string>#)]? | &lt;font-face-name> ]#
     <tr>
      <td><em>Initial:</em>
      <td>N/A
   </table>
   <p>This descriptor specifies the resource containing font data. It is
    required, whether the font is downloadable or locally installed. Its value
    is a prioritized, comma-separated list of external references or locally
    installed font face names. When a font is needed the user agent iterates
    over the set of references listed, using the first one it can successfully
    activate. Fonts containing invalid data or local font faces that are not
    found are ignored and the user agent loads the next font in the list
    (platform substitutions for a given font must not be used).
   <p>As with other URIs in CSS, the URI may be partial, in which case it is
    resolved relative to the location of the style sheet containing the <span
    class=index-inst id=font-face1
    title="@font-face"><code>@font-face</code></span> rule. In the case of SVG
    fonts, the URL points to an element within a document containing SVG font
    definitions. If the element reference is omitted, a reference to the first
    defined font is implied. Similarly, font container formats that can
    contain more than one font must load one and only one of the fonts for a
    given <code>@font-face</code> rule. Fragment identifiers are used to
    indicate which font to load. If a container format lacks a defined
    fragment identifier scheme, implementations should use a simple 1-based
    indexing scheme (e.g. "font-collection#1" for the first font,
    "font-collection#2" for the second font).
   <pre>
 src: url(fonts/simple.ttf);   /* load simple.ttf relative to stylesheet location */
 src: url(/fonts/simple.ttf);  /* load simple.ttf from absolute location */
 src: url(fonts.svg#simple);   /* load SVG font with id 'simple' */
 </pre>
   <p>External references consist of a URI, followed by an optional hint
    describing the format of the font resource referenced by that URI. The
    format hint contains a comma-separated list of format strings that denote
    well-known font formats. Conformant user agents must skip downloading a
    font resource if the format hints indicate only unsupported or unknown
    font formats. If no format hints are supplied, the user agent should
    download the font resource.
   <pre>
 /* load WOFF font if possible, otherwise use OpenType font */
 @font-face {
   font-family: bodytext;
   src: url(ideal-sans-serif.woff) format("woff"),
        url(basic-sans-serif.ttf) format("opentype");
 }
 </pre>
   <p>Format strings defined by this specification:
   <table class=data id=fontformats>
    <thead>
     <tr>
      <th>String
      <th>Font Format
      <th>Common extensions
    <tbody>
     <tr>
      <th>"woff"
      <td><a href="http://www.w3.org/TR/WOFF/">WOFF (Web Open Font Format)</a>
      <td>.woff
     <tr>
      <th>"truetype"
      <td><a
       href="http://www.microsoft.com/typography/otspec/default.htm">TrueType</a>
      <td>.ttf
     <tr>
      <th>"opentype"
      <td><a
       href="http://www.microsoft.com/typography/otspec/default.htm">OpenType</a>
      <td>.ttf, .otf
     <tr>
      <th>"embedded-opentype"
      <td><a
       href="http://www.w3.org/Submission/2008/SUBM-EOT-20080305/">Embedded
       OpenType</a>
      <td>.eot
     <tr>
      <th>"svg"
      <td><a href="http://www.w3.org/TR/SVG/fonts.html">SVG Font</a>
      <td>.svg, .svgz
   </table>
   <p>Given the overlap in common usage between TrueType and OpenType, the
    format hints "truetype" and "opentype" must be considered as synonymous; a
    format hint of "opentype" does not imply that the font contains Postscript
    CFF style glyph data or that it contains OpenType layout information (see
    <a href="#platform-props-to-css">Appendix A</a> for more background on
    this).
   <p>When authors would prefer to use a locally available copy of a given
    font and download it if it's not, local() can be used. The locally
    installed <span class=index-def id=ltfont-face-namegt
    title="&lt;font-face-name&gt;"><a
    name=value-def-font-face-name>&lt;font-face-name&gt;</a></span> is a
    format-specific string that uniquely identifies a single font face within
    a larger family. The syntax for a &lt;font-face-name&gt; is a unique font
    face name enclosed by "local(" and ")".
   <pre>
 /* regular face of Gentium */
 @font-face {
   font-family: MyGentium;
   src: local(Gentium),   /* use locally available Gentium */
        url(Gentium.ttf); /* otherwise, download it */
 }
 </pre>
   <p>The name can optionally be enclosed in quotes. For OpenType and TrueType
    fonts, this string is used to match only the Postscript name or the full
    font name in the name table of locally available fonts. Which is used
    varies by platform and font, so authors should include both of these names
    to assure proper matching across platforms.
   <pre>
 /* bold face of Gentium */
 @font-face {
   font-family: MyGentium;
   src: local(Gentium Bold),   /* full font name */
        local(Gentium-Bold),   /* Postscript name */
        url(GentiumBold.ttf);  /* otherwise, download it */
   font-weight: bold;
 }
 </pre>
   <p>Just as a <code>@font-face</code> rule specifies the characteristics of
    a single font within a family, the unique name used with local() specifies
    a single font, not an entire font family. Defined in terms of OpenType
    font data, the Postscript name is found in the font's <a
    href="http://www.microsoft.com/typography/otspec/name.htm">name table</a>,
    in the name record with nameID = 6 (see <a href="#OPENTYPE"
    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> for more details). The
    Postscript name is the commonly used key for all fonts on OSX and for
    Postscript CFF fonts under Windows. The full font name (nameID = 4) is
    used as a unique key for fonts with TrueType glyphs on Windows.
   <p>For OpenType fonts with multiple localizations of the full font name,
    the US English version is used (language ID = 0x409 for Windows and
    language ID = 0 for Macintosh) or the first localization when a US English
    full font name is not available (the OpenType specification recommends
    that <a href="http://www.microsoft.com/typography/otspec/recom.htm">all
    fonts minimally include US English names</a>). User agents that also match
    other full font names, e.g. matching the Dutch name when the current
    system locale is set to Dutch, are considered non-conformant. This is done
    not to prefer English but to avoid matching inconsistencies across font
    versions and OS localizations, since font style names (e.g. "Bold") are
    frequently localized into many languages and the set of localizations
    available varies widely across platform and font version. User agents that
    match a concatenation of family name (nameID = 1) with style name (nameID
    = 2) are considered non-conformant.
   <p>This also allows for referencing faces that belong to larger families
    that cannot otherwise be referenced.
   <div class=example>
    <p>Use a local font or reference an SVG font in another document:</p>
    <pre>
 @font-face {
   font-family: Headline;
   src: local(Futura-Medium),
        url(fonts.svg#MyGeometricModern) format("svg");
 }
 </pre>
    <p>Create an alias for local Japanese fonts on different platforms:</p>
    <pre>
 @font-face {
   font-family: jpgothic;
   src: local(HiraKakuPro-W3), local(Meiryo), local(IPAPGothic);
 }
 </pre>
    <p>Reference a font face that cannot be matched within a larger family:</p>
    <pre>
 @font-face {
   font-family: Hoefler Text Ornaments;
   /* has the same font properties as Hoefler Text Regular */
   src: local(HoeflerText-Ornaments);
 }
 </pre>
    <p>Since localized fullnames should never match, a document with the
     header style rules below would always render using the default serif
     font, regardless whether a particular system locale parameter is set to
     Finnish or not:</p>
    <pre>
 @font-face {
   font-family: SectionHeader;
   src: local("Arial Lihavoitu");  /* Finnish fullname for Arial Bold, should fail */
   font-weight: bold;
 }
 h2 { font-family: SectionHeader, serif; }
 </pre>
    <p>A conformant user agent should never load the font ‘<code
     class=css>gentium.eot</code>’ in the example below, since it is
     included in the first definition of the ‘<a href="#descdef-src"><code
     class=property>src</code></a>’ descriptor which is overridden by the
     second definition in the same <code>@font-face</code> rule:</p>
    <pre>
 @font-face {
   font-family: MainText;
   src: url(gentium.eot); /* for use with older non-conformant user agents */
   src: local("Gentium"), url(gentium.ttf);  /* Overrides src definition */
 }
 </pre>
   </div>
   <h3 id=font-prop-desc><span class=secno>4.4 </span>Font property
    descriptors: the <a href="#descdef-font-style">font-style</a>, <a
    href="#descdef-font-weight">font-weight</a>, <a
    href="#descdef-font-stretch">font-stretch</a> descriptors</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-style title="font-style
       (descriptor)">font-style</dfn>
     <tr>
      <td>Value:
      <td>normal | italic | oblique
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-weight title="font-weight
       (descriptor)">font-weight</dfn>
     <tr>
      <td>Value:
      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-stretch title="font-stretch
       (descriptor)">font-stretch</dfn>
     <tr>
      <td>Value:
      <td>normal | ultra-condensed | extra-condensed | condensed |
       semi-condensed | semi-expanded | expanded | extra-expanded |
       ultra-expanded
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <p>These descriptors define the characteristics of a font face and are used
    in the process of matching styles to specific faces. For a font family
    defined with several <code>@font-face</code> rules, user agents can either
    download all faces in the family or use these descriptors to selectively
    download font faces that match actual styles used in document. The values
    for these descriptors are the same as those for the corresponding font
    properties except that relative keywords are not allowed, ‘<code
    class=property>bolder</code>’ and ‘<code
    class=property>lighter</code>’. If these descriptors are omitted,
    default values are assumed.
   <p>The value for these font face style attributes is used in place of the
    style implied by the underlying font data. This allows authors to combine
    faces in flexible combinations, even in situations where the original font
    data was arranged differently. User agents that implement synthetic
    bolding and obliqueing must only apply synthetic styling in cases where
    the font descriptors imply this is needed, rather than based on the style
    attributes implied by the font data.
   <h3 id=unicode-range-desc><span class=secno>4.5 </span>Character range: the
    <a href="#descdef-unicode-range">unicode-range</a> descriptor</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-unicode-range>unicode-range</dfn>
     <tr>
      <td>Value:
      <td>&lt;urange>#
     <tr>
      <td><em>Initial:</em>
      <td>U+0-10FFFF
   </table>
   <p>This descriptor defines the range of Unicode characters supported by a
    given font. The values of <span class=index-def id=lturangegt
    title="&lt;urange&gt;"><a name=value-def-urange>&lt;urange&gt;</a></span>
    are expressed using hexadecimal numbers prefixed by "U+" or "u+",
    corresponding to <a href="http://www.unicode.org/charts/">Unicode
    character code points</a>. The unicode-range descriptor serves as a hint
    for user agents when deciding whether or not to download a font resource.
   <p>Unicode range values are written using hexadecimal values and are ASCII
    case-insensitive. Each is prefixed by "U+" or "u+" and multiple,
    discontinuous ranges are separated by commas. Whitespace before or after
    commas is ignored. Valid character code values vary between 0 and 10FFFF
    inclusive. A single range has three basic forms:
   <ul>
    <li>a single code point (e.g. U+416)
    <li>an interval value range (e.g. U+400-4ff)
    <li>a range where trailing ‘<code class=css>?</code>’ characters imply
     ‘<code class=css>any digit value</code>’ (e.g. U+4??)
   </ul>
   <p>Ranges that do not fit any of the above three forms are considered to be
    parse errors and the descriptor is omitted. Interval ranges consisting of
    a single code point are valid. Ranges specified with ‘?’ that lack an
    initial digit (e.g. "U+???") are also valid, and are treated as if there
    was a single 0 before the question marks (thus, "U+???" = "U+0???" =
    "U+0000-0FFF"). "U+??????" is not a syntax error, even though "U+0??????"
    would be. Ranges can overlap but interval ranges that descend (e.g.
    U+400-32f) are invalid and omitted rather than treated as parse errors;
    they have no effect on other ranges in a list of ranges. Ranges are
    clipped to the domain of Unicode code points (currently 0 – 10FFFF
    inclusive); a range entirely outside the domain is omitted. Without any
    valid ranges, the descriptor is omitted. User agents may normalize the
    list of ranges into a list that is different but represents the same set
    of character code points.
   <p>The character range can be a subset of the full <a
    href="#character-map"><em>character map</em></a> of the underlying font.
    The effective unicode-range used when mapping characters to fonts is the
    intersection of the unicode range specified and the underlying <a
    href="#character-map"><em>character map</em></a> of the font. This means
    that authors do not need to define the unicode-range of a font precisely,
    broad ranges for which a sparse set of code points are defined in the font
    can be used. Code points outside of the defined unicode-range are ignored,
    regardless of whether the font contains a glyph for that code point or
    not. User agents that download fonts for characters outside the defined
    unicode-range are considered non-conformant. Likewise, user agents that
    render a character using a font resource for which the defined
    unicode-range does not include that character are also considered
    non-conformant.
   <p>Example ranges for specific languages or characters:
   <dl>
    <dt>unicode-range: U+A5;
    <dd>a single code point, the yen/yuan symbol
    <dt>unicode-range: U+0-7F;
    <dd>code range for basic ASCII characters
    <dt>unicode-range: U+590-5ff;
    <dd>code range for Hebrew characters
    <dt>unicode-range: U+A5, U+4E00-9FFF, U+30??, U+FF00-FF9F;
    <dd>code range for Japanese kanji, hiragana and katakana characters plus
     yen/yuan symbol
   </dl>
   <div class=example>
    <p>The BBC provides news services in a wide variety of languages, many
     that are not well supported across all platforms. Using an
     <code>@font-face</code> rule, the BBC could provide a font for any of
     these languages, as it already does via a manual font download.</p>
    <pre>
 @font-face {
   font-family: BBCBengali;
   src: url(fonts/BBCBengali.ttf) format("opentype");
   unicode-range: U+00-FF, U+980-9FF;
 }
 </pre>
   </div>
   <div class=example>
    <p>Technical documents often require a wide range of symbols. The STIX
     Fonts project is one project aimed at providing fonts to support a wide
     range of technical typesetting in a standardized way. The example below
     shows the use of a font that provides glyphs for many of the mathematical
     and technical symbol ranges within Unicode:</p>
    <pre>
 @font-face {
   font-family: STIXGeneral;
   src: local(STIXGeneral), url(/stixfonts/STIXGeneral.otf);
   unicode-range: U+000-49F, U+2000-27FF, U+2900-2BFF, U+1D400-1D7FF;
 }
 </pre>
   </div>
   <p>Multiple <code>@font-face</code> rules with different unicode ranges for
    the same family and style descriptor values can be used to create
    composite fonts that mix the glyphs from different fonts for different
    scripts. This can be used to combine fonts that only contain glyphs for a
    single script (e.g. Latin, Greek, Cyrillic) or it can be used by authors
    as a way of segmenting a font into fonts for commonly used characters and
    less frequently used characters. Since the user agent will only pull down
    the fonts it needs this helps reduce page bandwidth.
   <p>If the unicode ranges overlap for a set of <code>@font-face</code> rules
    with the same family and style descriptor values, the rules are ordered in
    the reverse order they were defined; the last rule defined is the first to
    be checked for a given character.
   <div class=example>
    <p>This example shows how an author can override the glyphs used for Latin
     characters in a Japanese font with glyphs from a different font. The
     first rule specifies no range so it defaults to the entire range. The
     range specified in the second rule overlaps but takes precedence because
     it is defined later.</p>
    <pre>
 @font-face {
   font-family: JapaneseWithGentium;
   src: local(MSMincho);
   /* no range specified, defaults to entire range */
 }
 @font-face {
   font-family: JapaneseWithGentium;
   src: url(../fonts/Gentium.ttf);
   unicode-range: U+0-2FF;
 }
 </pre>
   </div>
   <div class=example>
    <p>Consider a family constructed to optimize bandwidth by separating out
     Latin, Japanese and other characters into different font files:</p>
    <pre>
 /* fallback font - size: 4.5MB */
 @font-face {
   font-family: DroidSans;
   src: url(DroidSansFallback.ttf);
   /* no range specified, defaults to entire range */
 }
 /* Japanese glyphs - size: 1.2MB */
 @font-face {
   font-family: DroidSans;
   src: url(DroidSansJapanese.ttf);
   unicode-range: U+3000-9FFF, U+ff??;
 }
 /* Latin, Greek, Cyrillic along with some
    punctuation and symbols - size: 190KB */
 @font-face {
   font-family: DroidSans;
   src: url(DroidSans.ttf);
   unicode-range: U+000-5FF, U+1e00-1fff, U+2000-2300;
 }
 </pre>
    <p>For simple Latin text, only the font for Latin characters is
     downloaded:</p>
    <pre>
 body { font-family: DroidSans; }
 &lt;p>This is that&lt;/p>
 </pre>
    <p>In this case the user agent first checks the unicode-range for the font
     containing Latin characters (DroidSans.ttf). Since all the characters
     above are in the range U+0-5FF, the user agent downloads the font and
     renders the text with that font.</p>
    <p>Next, consider text that makes use of an arrow character (⇨):</p>
    <pre>
 &lt;p>This &amp;#x21e8; that&lt;p>
 </pre>
    <p>The user agent again first checks the unicode-range of the font
     containing Latin characters. Since U+2000-2300 includes the arrow code
     point (U+21E8), the user agent downloads the font. For this character
     however the Latin font does not have a matching glyph, so the effective
     unicode-range used for font matching excludes this code point. Next, the
     user agent evaluates the Japanese font. The unicode-range for the
     Japanese font, U+3000-9FFF and U+ff??, does not include U+21E8, so the
     user agent does not download the Japanese font. Next the fallback font is
     considered. The <code>@font-face</code> rule for the fallback font does
     not define unicode-range so its value defaults to the range of all
     Unicode code points. The fallback font is downloaded and used to render
     the arrow character.</p>
   </div>
   <h3 id=font-rend-desc><span class=secno>4.6 </span>Font features: the <a
    href="#descdef-font-variant">font-variant</a> and <a
    href="#descdef-font-feature-settings">font-feature-settings</a>
    descriptors</h3>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-variant title="font-variant
       (descriptor)">font-variant</dfn>
     <tr>
      <td>Value:
      <td>normal | [ &lt;common-lig-values&gt; ||
       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
       character-variant(&lt;feature-value-name&gt;#) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
       ruby ]
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <table class=descdef>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=descdef-font-feature-settings title="font-feature-settings
       (descriptor)">font-feature-settings</dfn>
     <tr>
      <td>Value:
      <td>normal | &lt;feature-tag-value&gt;#
     <tr>
      <td><em>Initial:</em>
      <td>normal
   </table>
   <p>These descriptors define settings that apply when the font defined by an
    <code>@font-face</code> rule is rendered. They do not affect font
    selection. Values are identical to those defined for the corresponding
    ‘<a href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’ and ‘<a
    href="#propdef-font-feature-settings"><code
    class=property>font-feature-settings</code></a>’ properties defined
    below except that the value ‘<code class=property>inherit</code>’ is
    omitted. When multiple font feature descriptors or properties are used,
    the cumulative effect on text rendering is described below.
   <h3 id=font-face-loading><span class=secno>4.7 </span>Font loading
    guidelines</h3>
   <p>The <code>@font-face</code> rule is designed to allow lazy loading of
    fonts, fonts are only downloaded when needed for use within a document. A
    stylesheet can include <code>@font-face</code> rules for a library of
    fonts of which only a select set are used; user agents must only download
    those fonts that are referred to within the style rules applicable to a
    given page. User agents that download all fonts defined in
    <code>@font-face</code> rules without considering whether those fonts are
    in fact used within a page are considered non-conformant. In cases where a
    font might be downloaded in character fallback cases, user agents may
    download a font if it's listed in a font list but is not actually used for
    a given text run.
   <pre>
 @font-face {
   font-family: GeometricModern;
   src: url(font.ttf);
 }
 p {
   /* font will be downloaded for pages with p elements */
   font-family: GeometricModern, sans-serif;
 }
 h2 {
   /* font may be downloaded for pages with h2 elements, even if Futura is available locally */
   font-family: Futura, GeometricModern, sans-serif;
 }
 </pre>
   <p>In cases where textual content is loaded before downloadable fonts are
    available, user agents may render text as it would be rendered if
    downloadable font resources are not available or they may render text
    transparently with fallback fonts to avoid a flash of text using a
    fallback font. In cases where the font download fails user agents must
    display text, simply leaving transparent text is considered non-conformant
    behavior. Authors are advised to use fallback fonts in their font lists
    that closely match the vertical metrics of the downloadable fonts to avoid
    large page reflows where possible.
   <h3 id=same-origin-restriction><span class=secno>4.8 </span>Same-origin
    restriction for fonts</h3>
   <h4 id=default-same-origin-restriction><span class=secno>4.8.1
    </span>Default same-origin restriction</h4>
   <!-- TPAC 2011 Resolution to require same-origin restriction for loading fonts:
   http://lists.w3.org/Archives/Public/www-style/2011Nov/0711.html
   http://www.w3.org/2011/10/31-webapps-minutes.html#item02
 -->
   <p>User agents must implement a same-origin restriction when loading fonts
    via the <code>@font-face</code> mechanism. This restriction limits the
    loading of fonts for a given document to fonts loaded from the same
    origin. Fonts can only be loaded via the same host, port, and method
    combination as the containing document, using the <a
    href="http://www.w3.org/TR/html5/browsers.html#origin">origin matching
    algorithm</a> described in the <a href="#HTML5"
    rel=biblioentry>[HTML5]<!--{{!HTML5}}--></a> specification. The origin of
    the stylesheet containing <code>@font-face</code> rules is not used when
    deciding whether a font is same origin or not, only the origin of the
    containing document is used. The restriction applies to all font types.
   <p>Given a document located at http://example.com/page.html, fonts defined
    with ‘<a href="#descdef-src"><code class=property>src</code></a>’
    definitions considered cross origin must not be loaded:
   <pre>
 /* same origin (i.e. domain, protocol, port match document) */
 src: url(fonts/simple.ttf);
 src: url(//fonts/simple.ttf);
 /* cross origin, different protocol */
 src: url(https://example.com/fonts/simple.ttf);
 /* cross origin, different domain */
 src: url(http://another.example.com/fonts/simple.ttf);
 </pre>
   <h4 id=allowing-cross-origin-font-loading><span class=secno>4.8.2
    </span>Allowing cross-origin font loading</h4>
   <p>User agents must also implement the ability to relax this restriction
    using cross-site origin controls <a href="#CORS"
    rel=biblioentry>[CORS]<!--{{!CORS}}--></a> for fonts loaded via HTTP.
    Sites can explicitly allow cross-site downloading of font data using the
    <code>Access-Control-Allow-Origin</code> HTTP header. For other protocols,
    no explicit relaxation mechanism is defined or required.
   <p>For font loads over HTTP, cross-origin requests must be made with the
    following parameter settings which are used in conjunction with the <a
    href="http://www.w3.org/TR/cors/#cross-origin-request-0"> <em>cross-origin
    request algorithm</em></a> <a href="#CORS"
    rel=biblioentry>[CORS]<!--{{!CORS}}--></a>:
   <ul>
    <li><em>request URL</em> — the URL of the font resource in the <a
     href="#descdef-src"><code>src</code></a> descriptor
    <li><em>request method</em> — GET
    <li><em>author request headers</em> — none
    <li><em>request entity body</em> — empty
    <li><em>source origin</em> — the origin of the page which linked to the
     stylesheet
    <li><em>manual redirect flag</em> — false
    <li><em>omit credentials flag</em> — true
    <li><em>force preflight flag</em> — false
   </ul>
   <h2 id=font-matching-algorithm><span class=secno>5 </span>Font Matching
    Algorithm</h2>
   <p>The algorithm below describes how fonts are associated with individual
    runs of text. For each character in the run a font family is chosen and a
    particular font face is selected containing a glyph for that character.
   <h3 id=font-family-casing><span class=secno>5.1 </span>Case sensitivity of
    font family names</h3>
   <p>As part of the font matching algorithm outlined below, user agents must
    match font family names used in style rules with actual font family names
    contained in fonts available in a given environment or defined via
    <code>@font-face</code> rules. User agents must match these names case
    insensitively, using the "Default Caseless Matching" algorithm outlined in
    the Unicode specification <a href="#UNICODE6"
    rel=biblioentry>[UNICODE6]<!--{{!UNICODE6}}--></a>. This algorithm is
    detailed in section 3.13 entitled "Default Case Algorithms". Specifically,
    the algorithm must be applied without normalizing the strings involved and
    without applying any language-specific tailorings. The case folding method
    specified by this algorithm uses the case mappings with status field
    ‘<code class=property>C</code>’ or ‘<code class=property>F</code>’
    in the CaseFolding.txt file of the Unicode Character Database.
   <p class=note> Implementors should take care to verify that a given
    caseless string comparison implementation uses this precise algorithm and
    not assume that a given platform string matching routine follows it, as
    many of these have locale-specific behavior or use some level of string
    normalization.
   <p class=note> For authors this means that font family names are matched
    case insensitively, whether or not those names exist in a platform font or
    in the <code>@font-face</code> rules contained in a stylesheet. Authors
    should take care to ensure that names use a character sequence consistent
    with the actual font family name, particularly when using combining
    characters such as diacritical marks. For example, a family name that
    contains an uppercase A (U+0041) followed by a combining ring (U+030A)
    will <strong>not</strong> match a name that looks identical but which uses
    the precomposed lowercase a-ring character (U+00E5) instead of the
    combining sequence.
   <h3 id=font-style-matching><span class=secno>5.2 </span>Matching font
    styles</h3>
   <p>The procedure for choosing fonts consists of iterating over the font
    families determined by the font-family property, selecting a font face
    with the appropriate style based on other font properties and then
    determining whether a glyph exists for a given character. This is done
    using the <dfn id=character-map>character map</dfn> of the font, data
    which maps characters to the default glyph for that character. Codepoint
    sequences consisting of a base character followed by a sequence of
    combining characters are treated slightly differently, see the section on
    <a href="#cluster-matching">cluster matching</a> below.
   <p>For this procedure, the <dfn id=default-face>default face</dfn> for a
    given font family is defined to be the face that would be selected if all
    font style properties were set to their initial value.
   <ol id=fontmatchingalg>
    <li>Using the computed font property values for a given element, the user
     agent starts with the first family name in the fontlist specified by the
     <span class=property>‘<a href="#descdef-font-family"><code
     class=property>font-family</code></a>’</span> property.
    <li>If the family name is unquoted and is a generic family name, the user
     agent looks up the appropriate font family name to be used. User agents
     may choose the generic font family to use based on the language of the
     containing element or the Unicode range of the character.
    <li>For other family names, the user agent attempts to find the family
     name among fonts defined via <code>@font-face</code> rules and then among
     available system fonts, matching names with a case-insensitive comparison
     as outlined <a href="#font-family-casing">in the section above</a>. On
     systems containing fonts with multiple localized font family names, user
     agents must match any of these names independent of the underlying system
     locale or platform API used. If a font family defined via
     <code>@font-face</code> rules contains only invalid font data, it should
     be considered as if a font was present but contained an empty <a
     href="#character-map"><em>character map</em></a>; matching a platform
     font with the same name must not occur in this case.
    <li>If a font family match occurs, the user agent assembles the set of
     font faces in that family and then narrows the set to a single face using
     other font properties in the order given below:
     <ol id=fontstylematchingalg>
      <li><span class=property>‘<a href="#propdef-font-stretch"><code
       class=property>font-stretch</code></a>’</span> is tried first. If the
       matching set contains faces with width values matching the ‘<a
       href="#propdef-font-stretch"><code
       class=property>font-stretch</code></a>’ value, faces with other width
       values are removed from the matching set. If there is no face that
       exactly matches the width value the nearest width is used instead. If
       the value of ‘<a href="#propdef-font-stretch"><code
       class=property>font-stretch</code></a>’ is ‘<a
       href="#normal2"><code class=property>normal</code></a>’ or one of the
       condensed values, narrower width values are checked first, then wider
       values. If the value of ‘<a href="#propdef-font-stretch"><code
       class=property>font-stretch</code></a>’ is one of the expanded
       values, wider values are checked first, followed by narrower values.
       Once the closest matching width has been determined by this process,
       faces with other widths are removed from the matching set.
      <li><span class=property>‘<a href="#propdef-font-style"><code
       class=property>font-style</code></a>’</span> is tried next. If the
       value of ‘<a href="#propdef-font-style"><code
       class=property>font-style</code></a>’ is ‘<code
       class=property>italic</code>’, italic faces are checked first, then
       oblique, then normal faces. If the value is ‘<code
       class=property>oblique</code>’, oblique faces are checked first, then
       italic faces and then normal faces. If the value is ‘<a
       href="#normal2"><code class=property>normal</code></a>’, normal faces
       are checked first, then oblique faces, then italic faces. Faces with
       other style values are excluded from the matching set. User agents are
       permitted to distinguish between italic and oblique faces within
       platform font families but this is not required, they may treat all
       italic or oblique faces as italic faces. However, within font families
       defined via <code>@font-face</code> rules, italic and oblique faces
       must be distinguished using the value of the ‘<a
       href="#propdef-font-style"><code
       class=property>font-style</code></a>’ descriptor.
      <li><span class=property>‘<a href="#propdef-font-weight"><code
       class=property>font-weight</code></a>’</span> is matched next, it
       will always reduce the matching set to a single font face. If
       bolder/lighter relative weights are used, the effective weight is
       calculated based on the inherited weight value, as described in the
       definition of the ‘<a href="#propdef-font-weight"><code
       class=property>font-weight</code></a>’ property. Given the desired
       weight and the weights of faces in the matching set after the steps
       above, if the desired weight is available that face matches. Otherwise,
       a weight is chosen using the rules below:
       <ul>
        <li>If the desired weight is less than 400, weights below the desired
         weight are checked in descending order followed by weights above the
         desired weight in ascending order until a match is found.
        <li>If the desired weight is greater than 500, weights above the
         desired weight are checked in ascending order followed by weights
         below the desired weight in descending order until a match is found.
        <li>If the desired weight is 400, 500 is checked first and then the
         rule for desired weights less than 400 is used.
        <li>If the desired weight is 500, 400 is checked first and then the
         rule for desired weights less than 400 is used.
       </ul>
      <li><span class=property>‘<a href="#propdef-font-size"><code
       class=property>font-size</code></a>’</span> must be matched within a
       UA-dependent margin of tolerance. (Typically, sizes for scalable fonts
       are rounded to the nearest whole pixel, while the tolerance for
       bitmapped fonts could be as large as 20%.) Further computations, e.g.,
       by ‘<code class=property>em</code>’ values in other properties, are
       based on the <span class=property>‘<a href="#propdef-font-size"><code
       class=property>font-size</code></a>’</span> value that is used, not
       the one that is specified.
     </ol>
    <li>
     <p>If no matching face exists or the matched face does not contain a
      glyph for the character to be rendered, the next family name is selected
      and the previous two steps repeated. Glyphs from other faces in the
      family are not considered. The only exception is that user agents may
      optionally substitute a synthetic version of the <a
      href="#default-face"><em>default face</em></a> if that face supports a
      given glyph (e.g. a synthetic italic version of the regular face may be
      used if the italic face doesn't support glyphs for Arabic).</p>
     <!-- resolution on the above: http://lists.w3.org/Archives/Public/www-style/2012Nov/0292.html -->
     <p>If the matched font is defined via an <code>@font-face</code> rule and
      needs to be downloaded, the font resource is downloaded. While the
      download occurs, the user agent can either wait until the font is
      downloaded or render once with substituted font metrics and render again
      once the font is downloaded.</p>
    <li>If there are no more font families to be evaluated and no matching
     face has been found, then the user agent performs a <em>system font
     fallback</em> procedure to find the best match for the character to be
     rendered. The result of this procedure may vary across user agents.
    <li>If a particular character cannot be displayed using any font, the user
     agent should indicate by some means that a character is not being
     displayed, displaying either a symbolic representation of the missing
     glyph (e.g. using a <a
     href="http://en.wikipedia.org/wiki/Last_resort_font">Last Resort
     Font</a>) or using the missing character glyph from a default font.
   </ol>
   <h3 id=cluster-matching><span class=secno>5.3 </span>Cluster matching</h3>
   <p>When text contains characters such as combining diacritics, ideally the
    base character should be rendered using the same font as the diacritic,
    this assures proper placement of the diacritic. For this reason, the font
    matching algorithm for clusters is more specialized than the general case
    of matching a single character by itself. For sequences containing
    variation selectors, which indicate the precise glyph to be used for a
    given character, user agents always attempt system font fallback to find
    the appropriate glyph before using the default glyph of the base
    character.
   <p>A font is considered to <em>support</em> a given character if (1) the
    character is contained in the font's <a
    href="#character-map"><em>character map</em></a> and (2) if required by
    the containing script, shaping information is available for that
    character. Some legacy fonts may include a given character in the <a
    href="#character-map"><em>character map</em></a> but lack the shaping
    information (e.g. <a
    href="http://www.microsoft.com/typography/otspec/ttochap1.htm">OpenType
    layout tables</a> or <a
    href="http://scripts.sil.org/cms/scripts/page.php?site_id=projects&amp;item_id=graphite_techAbout">Graphite
    tables</a>) necessary for correctly rendering text runs containing that
    character.
   <p>A sequence of codepoints containing combining diacritics or other
    modifiers is termed a grapheme cluster (see <a href="#CSS3TEXT"
    rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a> for a more complete
    description). For a given cluster containing a base character, <em>b</em>
    and a sequence of combining characters <em>c1, c2…</em>, the entire
    cluster is matched using these steps:
   <ol>
    <li>For each family in the font list, a face is chosen using the style
     selection rules defined in the previous section.
     <ol>
      <li>If all characters in the sequence <em>b + c1 + c2 …</em> are
       completely supported by the font, select this font for the sequence.
      <li>If a sequence of multiple codepoints is canonically equivalent to a
       single character and the font supports that character, select this font
       for the sequence.
     </ol>
    <li>If no font was found in the font list in step 1:
     <ol>
      <li>If <em>c1</em> is a variation selector, system fallback must be used
       to find a font that supports the full sequence of <em>b + c1</em>. If
       no font on the system supports the full sequence, match the single
       character <em>b</em> using the normal procedure for matching single
       characters and ignore the variation selector. Note: a sequence with
       more than one variation selector is treated as an encoding error and
       the trailing selectors are ignored.
      <li>Otherwise, the user agent may optionally use system font fallback to
       match a font that supports the entire cluster.
     </ol>
    <li>If no font is found in step 2, use the matching sequence from step 1
     to determine the longest sequence that is completely matched by a font in
     the font list and attempt to match the remaining combining characters
     separately using the rules for single characters.
   </ol>
   <h3 id=char-handling-issues><span class=secno>5.4 </span>Character handling
    issues</h3>
   <p>The procedure above is always performed on text runs containing Unicode
    characters, documents using legacy encodings are assumed to have been
    transcoded before matching fonts. For fonts containing <a
    href="#character-map"><em title="character map">character maps</em></a>
    for both legacy encodings and Unicode, the contents of the legacy encoding
    <a href="#character-map"><em>character map</em></a> must have no effect on
    the results of the font matching process.
   <p>The font matching process does not assume that text runs are in either
    normalized or denormalized form (see <a href="#CHARMOD-NORM"
    rel=biblioentry>[CHARMOD-NORM]<!--{{CHARMOD-NORM}}--></a> for more
    details). Layout engines often convert base character plus combining
    character sequences into precomposed characters if they exist. The font
    matching algorithm outlined here supports both ways and fonts can
    generally support either but variations can occur. Authors should always
    tailor their choice of fonts to their content, including whether that
    content contains normalized or denormalized character streams.
   <p>If a given character is a Private-Use Area Unicode codepoint and none of
    the fonts in the fontlist contain a glyph for that codepoint, user agents
    must display some form of missing glyph symbol for that character rather
    than attempting system font fallback for that codepoint. When matching the
    replacement character U+FFFD, user agents may skip the font matching
    process and immediately display some form of missing glyph symbol, they
    are not required to display the glyph from the font that would be selected
    by the font matching process.
   <p>In general, the fonts for a given family will all have the same or
    similar <a href="#character-map"><em title="character map">character
    maps</em></a>. The process outlined here is designed to handle even font
    families containing faces with widely variant <a href="#character-map"><em
    title="character map">character maps</em></a>. However, authors are
    cautioned that the use of such families can lead to unexpected results.
   <p>Optimizations of this process are allowed provided that an
    implementation behaves as if the algorithm had been followed exactly.
    Matching occurs in a well-defined order to insure that the results are as
    consistent as possible across user agents, given an identical set of
    available fonts and rendering technology.
   <h3 id=font-matching-changes><span class=secno>5.5 </span>Font matching
    changes since CSS 2.1</h3>
   <p>The algorithm above is different from CSS 2.1 in a number of key places.
    These changes were made to better reflect actual font matching behavior
    across user agent implementations.
   <p>Differences compared to the font matching algorithm in CSS 2.1:
   <ul>
    <li>The algorithm includes font-stretch matching.
    <li>All possible font-style matching scenarios are delineated.
    <li>Small-caps fonts are not matched as part of the font matching process,
     they are now handled via font features.
    <li>Unicode variation selector matching is required.
    <li>Cluster sequences are matched as a unit.
   </ul>
   <h3 id=font-matching-examples><span class=secno>5.6 </span>Font matching
    examples</h3>
   <div class=example>
    <p>It's useful to note that the CSS selector syntax may be used to create
     language-sensitive typography. For example, some Chinese and Japanese
     characters are unified to have the same Unicode code point, although the
     abstract glyphs are not the same in the two languages.
    <pre>*:lang(ja-jp) { font: 900 14pt/16pt &quot;Heisei Mincho W9&quot;, serif; }
 *:lang(zh-tw) { font: 800 14pt/16.5pt &quot;Li Sung&quot;, serif; }
 </pre>
    <p>This selects any element that has the given language - Japanese or
     Traditional Chinese - and uses the appropriate font.
   </div>
   <h2 id=font-rend-props><span class=secno>6 </span>Font Feature Properties</h2>
   <p>Modern font technologies support a variety of advanced typographic and
    language-specific font features. Using these features, a single font can
    provide glyphs for a wide range of ligatures, contextual and stylistic
    alternates, tabular and old-style figures, small capitals, automatic
    fractions, swashes, and alternates specific to a given language. To allow
    authors control over these font capabilities, the font-variant property
    has been expanded for CSS3, it now functions as a shorthand for a set of
    properties that provide control over stylistic font features.
   <h3 id=glyph-selection-positioning><span class=secno>6.1 </span>Glyph
    selection and positioning</h3>
   <p>Simple fonts used for displaying Latin text use a very basic processing
    model, fonts contain a <a href="#character-map"><em>character map</em></a>
    which maps a given character to a glyph for that character. Glyphs for
    subsequent characters are simply placed next in line along a run of text.
    Font formats such as OpenType and AAT (Apple Advanced Typography) use a
    richer processing model, the glyph for a given character can be chosen and
    positioned not just based on a single character, but also based on
    surrounding characters along with the language, script, and features
    enabled for the text. Font features may be required for specific scripts,
    or recommended as enabled by default or they may be stylistic features
    meant to be used under author control.
   <p>For a good visual overview of these features, see the <a
    href="#OPENTYPE-FONT-GUIDE"
    rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
    For a detailed description of glyph processing for OpenType fonts, see <a
    href="#WINDOWS-GLYPH-PROC"
    rel=biblioentry>[WINDOWS-GLYPH-PROC]<!--{{WINDOWS-GLYPH-PROC}}--></a>.
   <p>Stylistic font features can be classified into two broad categories,
    ones that affect the harmonization of glyph shapes with the surrounding
    context, such as kerning and ligature features, and those such as the
    small-caps, subscript/superscript and alternate features that affect shape
    selection.
   <p>The subproperties of font-variant listed below are used to control these
    stylistic font features; they do not control features that are required
    for displaying certain scripts, such as the OpenType features used when
    displaying Arabic or Indic language text. They affect glyph selection and
    positioning, they do not affect font selection as described in the font
    matching section (except in cases required for compatibility with CSS
 .1).
   <p>To assure consistent behavior across user agents, the equivalent
    OpenType property settings are listed for individual properties and must
    be considered normative. When using other font formats these should be
    used as a guideline to map CSS font feature property values to specific
    font features.
   <h3 id=language-specific-support><span class=secno>6.2
    </span>Language-specific display</h3>
   <p>OpenType also supports language-specific glyph selection and
    positioning, so that text can be displayed correctly in cases where the
    language dictates a specific display behavior. Languages often share a
    common script but the shape of certain letters may vary across those
    languages, such as the variations in certain Cyrillic letters used in
    Russian and Bulgarian text. In Latin text, it's common to render "fi" with
    an explicit fi-ligature that lacks a dot on the "i". However, in languages
    such as Turkish which uses both a dotted-i and a dotless-i, it's important
    to not use this ligature or use a specialized version that contains a dot
    over the "i". The example below shows language-specific variations based
    on stylistic traditions found in Spanish, Italian and French orthography:
   <div class=featex><img alt="language specific forms, spanish"
    src=locl-1.png></div>
   <div class=featex><img alt="language specific forms, italian"
    src=locl-2.png></div>
   <div class=featex><img alt="language specific forms, french"
    src=locl-3.png></div>
   <p>If the content language of the element is known, according to the rules
    of the <a
    href="http://www.w3.org/TR/CSS21/conform.html#doclanguage">document
    language</a>, user agents are required to infer the OpenType language
    system from the content language and use that when selecting and
    positioning glyphs using an OpenType font.
   <p>For OpenType fonts, in some cases it may be necessary to explicitly
    declare the OpenType language to be used, for example when displaying text
    in a given language that uses the typographic conventions of another
    language or when the font does not explicitly support a given language but
    supports a language that shares common typographic conventions. The ‘<a
    href="#propdef-font-language-override"><code
    class=property>font-language-override</code></a>’ property is used for
    this purpose.
   <p class=issue>Should user agents be allowed to infer the OpenType language
    or simply use only the default language system? Do we also need a
    normative definition of how the script system is inferred?</p>
   <!-- prop: font-kerning -->
   <h3 id=font-kerning-prop><span class=secno>6.3 </span>Kerning: the <a
    href="#propdef-font-kerning">font-kerning</a> property</h3>
   <table class=propdef id=namefont-kerningvalueauto-normal-noneini>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-kerning>font-kerning</dfn>
     <tr>
      <td>Value:
      <td>auto | normal | none
     <tr>
      <td>Initial:
      <td>auto
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Kerning is the contextual adjustment of inter-glyph spacing. This
    property controls metric kerning, kerning that utilizes adjustment data
    contained in the font. The value ‘<a href="#normal2"><code
    class=property>normal</code></a>’ implies that kerning is applied while
    the value ‘<code class=property>none</code>’ implies that kerning is
    not applied when rendering text. If the value is ‘<code
    class=property>auto</code>’, a user agent is free to choose whether
    kerning is enabled or not by default and to vary that default based on the
    underlying text script.
   <p>For fonts that do not include kerning data this property will have no
    visible effect. When rendering with OpenType fonts, the <a
    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>
    specification suggests that kerning be enabled by default. When kerning is
    enabled, the OpenType <span class=tag>kern</span> feature is enabled (for
    vertical text runs the <span class=tag>vkrn</span> feature is enabled).
    User agents must also support fonts that only support kerning via data
    contained in a ‘<code class=property>kern</code>’ font table, as
    detailed in the OpenType specification. Authors may prefer to disable
    kerning in situations where performance is more important that precise
    appearance. If the ‘<code class=property>letter-spacing</code>’
    property is defined, kerning adjustments are considered part of the
    default spacing, letter spacing adjustments are made after kerning has
    been applied.</p>
   <!-- prop: font-variant-ligatures -->
   <h3 id=font-variant-ligatures-prop><span class=secno>6.4 </span>Ligatures:
    the <a href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
    property</h3>
   <table class=propdef id=namefont-variant-ligaturesvaluenormal-no>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-ligatures>font-variant-ligatures</dfn>
     <tr>
      <td>Value:
      <td>normal | none | [ &lt;common-lig-values> ||
       &lt;discretionary-lig-values> || &lt;historical-lig-values> ||
       &lt;contextual-alt-values> ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Ligatures and contextual forms are ways of combining glyphs to produce
    more harmonized forms. A value of ‘<a href="#normal2"><code
    class=property>normal</code></a>’ implies that common default features
    are enabled, <a href="#font-feature-resolution">as described in detail in
    the next section</a>. For OpenType fonts, common ligatures and contextual
    forms are on by default, discretionary and historical ligatures are not. A
    value of ‘<code class=property>none</code>’ implies that all types of
    ligatures and contextual forms covered by this property are explicitly
    disabled. In situations where ligatures are not considered necessary, this
    may improve the speed of text rendering.
   <pre
    class=prod><dfn id=ltcommon-lig-values><var>&lt;common-lig-values></var></dfn>        = [ common-ligatures | no-common-ligatures ]</pre>
   <pre
    class=prod><dfn id=ltdiscretionary-lig-values><var>&lt;discretionary-lig-values></var></dfn> = [ discretionary-ligatures | no-discretionary-ligatures ]</pre>
   <pre
    class=prod><dfn id=lthistorical-lig-values><var>&lt;historical-lig-values></var></dfn>    = [ historical-ligatures | no-historical-ligatures ]</pre>
   <pre
    class=prod><dfn id=ltcontextual-alt-valuesgt><var>&lt;contextual-alt-values&gt;</var></dfn>    = [ contextual | no-contextual ]</pre>
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=common-ligatures>common-ligatures</dfn>
    <dd>Enables display of common ligatures (OpenType features: <span
     class=tag>liga, clig</span>). For OpenType fonts, common ligatures are
     enabled by default.
   </dl>
   <div class=featex><img alt="common ligature example" src=liga.png></div>
   <dl>
    <dt><dfn id=no-common-ligatures>no-common-ligatures</dfn>
    <dd>Disables display of common ligatures (OpenType features: <span
     class=tag>liga, clig</span>).
    <dt><dfn id=discretionary-ligatures>discretionary-ligatures</dfn>
    <dd>Enables display of discretionary ligatures (OpenType feature: <span
     class=tag>dlig</span>). Which ligatures are discretionary, or optional,
     is decided by the type designer so authors will need to refer to the
     documentation of a given font to understand which ligatures are
     considered discretionary.
   </dl>
   <div class=featex><img alt="discretionary ligature example" src=dlig.png></div>
   <dl>
    <dt><dfn id=no-discretionary-ligatures>no-discretionary-ligatures</dfn>
    <dd>Disables display of discretionary ligatures (OpenType feature: <span
     class=tag>dlig</span>).
    <dt><dfn id=historical-ligatures>historical-ligatures</dfn>
    <dd>Enables display of historical ligatures (OpenType feature: <span
     class=tag>hlig</span>).
   </dl>
   <div class=featex><img alt="historical ligature example" src=hlig.png></div>
   <dl>
    <dt><dfn id=no-historical-ligatures>no-historical-ligatures</dfn>
    <dd>Disables display of historical ligatures (OpenType feature: <span
     class=tag>hlig</span>).
    <dt><dfn id=contextual>contextual</dfn>
    <dd>Enables display of contextual alternates (OpenType feature: <span
     class=tag>calt</span>). Although not strictly a ligature feature, like
     ligatures this feature is commonly used to harmonize the shapes of glyphs
     with the surrounding context. For OpenType fonts, this feature is on by
     default.
   </dl>
   <div class=featex><img alt="contextual alternate example" src=calt.png></div>
   <dl>
    <dt><dfn id=no-contextual>no-contextual</dfn>
    <dd>Disables display of contextual alternates (OpenType feature: <span
     class=tag>calt</span>).
   </dl>
   <p>Required ligatures, needed for correctly rendering complex scripts, are
    not affected by the settings above, including ‘<code
    class=property>none</code>’ (OpenType feature: <span
    class=tag>rlig</span>).</p>
   <!-- prop: font-variant-position -->
   <h3 id=font-variant-position-prop><span class=secno>6.5 </span>Subscript
    and superscript forms: the <a
    href="#propdef-font-variant-position">font-variant-position</a> property</h3>
   <table class=propdef id=namefont-variant-positionvaluenormal-sub>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-position>font-variant-position</dfn>
     <tr>
      <td>Value:
      <td>normal | sub | super
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property is used to enable typographic subscript and superscript
    glyphs. These are alternate glyphs designed within the same em-box as
    default glyphs and are intended to be laid out on the same baseline as the
    default glyphs, with no resizing or repositioning of the baseline. They
    are explicitly designed to match the surrounding text and to be more
    readable without affecting the line height.
   <div class=figure><img alt="comparison between real subscript glyphs and
    synthesized ones" src=realsubscripts.png>
    <p class=caption>Subscript glyphs (top) vs. typical synthesized subscripts
     (bottom)
   </div>
   <p>The values ‘<code class=property>sub</code>’ and ‘<code
    class=property>super</code>’ imply the appropriate variant glyph is
    displayed when available in the font (OpenType features: <span
    class=tag>subs, sups</span>). A value of ‘<a href="#normal2"><code
    class=property>normal</code></a>’ implies neither of these alternate
    glyphs are substituted.
   <p>Because of the semantic nature of subscripts and superscripts, when the
    value is either ‘<code class=property>sub</code>’ or ‘<code
    class=property>super</code>’ for a given run of text and a variant glyph
    is not available for all the characters in the run, simulated glyphs are
    synthesized for all characters using reduced forms of the default glyph.
    This is done to avoid a mixture of variant glyphs and synthesized ones
    within the same run of text, since there is no guarantee that two types of
    glyphs would be aligned correctly.
   <p>In the case of OpenType fonts that lack subscript or superscript glyphs
    for a given character, user agents must use the appropriate subscript and
    superscript metrics specified in the selected font's <a
    href="http://www.microsoft.com/typography/otspec/os2.htm#subxs">OS/2
    table</a> <a href="#OPENTYPE"
    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> to calculate the size
    and offset of the synthesized substitutes.
   <p>In the past, user agents have used font-size and vertical-align to
    simulate subscripts and superscripts for the <span class=tag>sub</span>
    and <span class=tag>sup</span> elements. To allow a backwards compatible
    way of defining subscripts and superscripts, it is recommended that
    authors use conditional rules <a href="#CSS3-CONDITIONAL"
    rel=biblioentry>[CSS3-CONDITIONAL]<!--{{CSS3-CONDITIONAL}}--></a> so that
    older user agents will still render subscripts and superscripts via the
    older mechanism.
   <p>Authors should note that fonts typically only provide subscript and
    superscript glyphs for a subset of all characters supported by the font.
    While subscript and superscript glyphs are often available for Latin
    numbers, glyphs for punctuation and letter characters are less frequently
    provided. The synthetic fallback rules defined for this property assure
    that subscripts and superscripts will always appear but the appearance may
    not match author expectations if the font used does not provide the
    appropriate alternate glyph for all characters contained in a subscript or
    superscript.
   <div class=figure><img alt="alternate superscripts vs. glyphs synthesized
    using superscript metrics" src=superscript-alt-synth.png>
    <p class=caption>Superscript alternate glyph (left), synthesized
     superscript glyphs (middle), and incorrect mixture of the two (right)
   </div>
   <p>This property is not cumulative, applying it to subelements within a
    subscript or superscript won't nest the placement of a subscript or
    superscript glyph. Images contained within text runs where the value of
    this property is ‘<code class=property>sub</code>’ or ‘<code
    class=property>super</code>’ will be drawn just as they would if the
    value was ‘<a href="#normal2"><code class=property>normal</code></a>’.
    Likewise, text decorations such as underlines or emphasis marks will
    render in the same position as they would for the default glyphs, since
    this property does not affect the baseline position.
   <p>Because of these limitations, font-variant-position is not recommended
    for use in user agent stylesheets. Authors should use it in cases where
    subscripts or superscripts will only contain the narrow range of
    characters supported by the fonts specified.
   <div class=example>
    <p>A typical user agent default style for the <span class=tag>sub</span>
     element:</p>
    <pre>sub {
   vertical-align: sub;
   font-size: smaller;
   line-height: normal;
 }
 </pre>
    <p>Using font-variant-position to specify typographic subscripts in a way
     that will still show subscripts in older user agents:</p>
    <pre>@supports ( font-variant-position: sub ) {
   sub {
     vertical-align: inherit;
     font-size: 100%;
     line-height: inherit;
     font-variant-position: sub;
   }
 }
 </pre>
    <p>User agents that support the ‘<a
     href="#propdef-font-variant-position"><code
     class=property>font-variant-position</code></a>’ property will select a
     subscript variant glyph and render this without adjusting the baseline or
     font-size. Older user agents will ignore the ‘<a
     href="#propdef-font-variant-position"><code
     class=property>font-variant-position</code></a>’ property definition
     and use the standard defaults for subscripts.</p>
   </div>
   <!-- prop: font-variant-caps -->
   <h3 id=font-variant-caps-prop><span class=secno>6.6 </span>Capitalization:
    the <a href="#propdef-font-variant-caps">font-variant-caps</a> property</h3>
   <table class=propdef id=namefont-variant-capsvaluenormal-small-c>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-caps>font-variant-caps</dfn>
     <tr>
      <td>Value:
      <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
       | unicase | titling-caps
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Specifies control over capitalized forms.
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=normal>normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=small-caps>small-caps</dfn>
    <dd>Enables display of small capitals (OpenType feature: <span
     class=tag>smcp</span>). Small-caps glyphs typically use the form of
     uppercase letters but are reduced to the size of lowercase letters.
   </dl>
   <div class=featex><img alt="small-caps example" src=smcp.png></div>
   <dl>
    <dt><dfn id=all-small-caps>all-small-caps</dfn>
    <dd>Enables display of small capitals for both upper and lowercase letters
     (OpenType features: <span class=tag>c2sc, smcp</span>).
    <dt><dfn id=petite-caps>petite-caps</dfn>
    <dd>Enables display of petite capitals (OpenType feature: <span
     class=tag>pcap</span>).
    <dt><dfn id=all-petite-caps>all-petite-caps</dfn>
    <dd>Enables display of petite capitals for both upper and lowercase
     letters (OpenType features: <span class=tag>c2pc, pcap</span>).
    <dt><dfn id=unicase>unicase</dfn>
    <dd>Enables display of mixture of small capitals for uppercase letters
     with normal lowercase letters (OpenType feature: <span
     class=tag>unic</span>).
    <dt><dfn id=titling-caps>titling-caps</dfn>
    <dd>Enables display of titling capitals (OpenType feature: <span
     class=tag>titl</span>). Uppercase letter glyphs are often designed for
     use with lowercase letters. When used in all uppercase titling sequences
     they can appear too strong. Titling capitals are designed specifically
     for this situation.
   </dl>
   <p>This property allows the selection of alternate glyphs used for small or
    petite capitals or for titling. These glyphs are specifically designed to
    blend well with the surrounding normal glyphs, to maintain the weight and
    readability which suffers when text is simply resized to fit this purpose.
   <p>The availability of these glyphs is based on whether a given feature is
    defined or not in the feature list of the font. User agents can optionally
    decide this on a per-script basis but should explicitly not decide this on
    a per-character basis.
   <p>Some fonts may only support a subset or none of the features described
    for this property. For backwards compatibility with CSS 2.1, if ‘<a
    href="#small-caps"><code class=property>small-caps</code></a>’ or ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’
    is specified but small-caps glyphs are not available for a given font,
    user agents should simulate a small-caps font, for example by taking a
    normal font and replacing the glyphs for lowercase letters with scaled
    versions of the glyphs for uppercase characters (replacing the glyphs for
    both upper and lowercase letters in the case of ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’).
   <div class=figure style="padding: 0; margin: auto;"><img alt="synthetic vs.
    real small-caps" class=hires src=synthetic-vs-real-small-caps.png
    width=512px>
    <p class=caption>Synthetic vs. real small-caps
   </div>
   <p>To match the surrounding text, a font may provide alternate glyphs for
    caseless characters when these features are enabled but when a user agent
    simulates small capitals, it must not attempt to simulate alternates for
    codepoints which are considered caseless.
   <div class=figure style="padding: 0; margin: auto;"><img alt="caseless
    characters with small-caps, all-small-caps enabled" class=hires
    src=small-capitals-variations.png width=418px>
    <p class=caption>Caseless characters with small-caps, all-small-caps
     enabled
   </div>
   <p>If either ‘<a href="#petite-caps"><code
    class=property>petite-caps</code></a>’ or ‘<a
    href="#all-petite-caps"><code class=property>all-petite-caps</code></a>’
    is specified for a font that doesn't support these features, the property
    behaves as if ‘<a href="#small-caps"><code
    class=property>small-caps</code></a>’ or ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
    respectively, had been specified. If ‘<a href="#unicase"><code
    class=property>unicase</code></a>’ is specified for a font that doesn't
    support that feature, the property behaves as if ‘<a
    href="#small-caps"><code class=property>small-caps</code></a>’ was
    applied only to lowercased uppercase letters. If ‘<a
    href="#titling-caps"><code class=property>titling-caps</code></a>’ is
    specified with a font that does not support this feature, this property
    has no visible effect. When simulated small capital glyphs are used, for
    scripts that lack uppercase and lowercase letters, ‘<a
    href="#small-caps"><code class=property>small-caps</code></a>’, ‘<a
    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
    ‘<a href="#petite-caps"><code class=property>petite-caps</code></a>’,
    ‘<a href="#all-petite-caps"><code
    class=property>all-petite-caps</code></a>’ and ‘<a
    href="#unicase"><code class=property>unicase</code></a>’ have no visible
    effect.
   <p>When casing transforms are used to simulate small capitals, the casing
    transformations should match those used for the <span
    class=property>‘<code class=property>text-transform</code>’</span>
    property.
   <p>As a last resort, unscaled uppercase letter glyphs in a normal font may
    replace glyphs in a small-caps font so that the text appears in all
    uppercase letters.
   <div class=figure style="padding: 0; margin: auto;"><img alt="using
    all-small-caps in acronym-laden text" class=hires
    src=acronym-laden-text.png width=596px>
    <p class=caption>Using small capitals to improve readability in
     acronym-laden text
   </div>
   <div class=example>
    <p>Quotes rendered italicised, with small-caps on the first line:</p>
    <pre>blockquote            { font-style: italic; }
 blockquote:first-line { font-variant: small-caps; }
 &lt;blockquote><a href="http://lists.w3.org/Archives/Public/www-style/2009Dec/0036.html" style="text-decoration: none">I'll be honor-bound to slap them like a haddock.</a>&lt;/blockquote>
 </pre>
   </div>
   <!-- prop: font-variant-numeric -->
   <h3 id=font-variant-numeric-prop><span class=secno>6.7 </span>Numerical
    formatting: the <a
    href="#propdef-font-variant-numeric">font-variant-numeric</a> property</h3>
   <table class=propdef id=namefont-variant-numericvaluenormal-ltnu>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant-numeric>font-variant-numeric</dfn>
     <tr>
      <td>Value:
      <td>normal | [ &lt;numeric-figure-values&gt; ||
       &lt;numeric-spacing-values&gt; || &lt;numeric-fraction-values&gt; ||
       ordinal || slashed-zero ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Specifies control over numerical forms.
   <pre
    class=prod><dfn id=ltnumeric-figure-valuesgt><var>&lt;numeric-figure-values&gt;</var></dfn>   = [ lining-nums | oldstyle-nums ]</pre>
   <pre
    class=prod><dfn id=ltnumeric-spacing-valuesgt><var>&lt;numeric-spacing-values&gt;</var></dfn>  = [ proportional-nums | tabular-nums ]</pre>
   <pre
    class=prod><dfn id=ltnumeric-fraction-valuesgt><var>&lt;numeric-fraction-values&gt;</var></dfn> = [ diagonal-fractions | stacked-fractions ]</pre>
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=normal0>normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=lining-nums>lining-nums</dfn>
    <dd>Enables display of lining numerals (OpenType feature: <span
     class=tag>lnum</span>).
    <dt><dfn id=oldstyle-nums>oldstyle-nums</dfn>
    <dd>Enables display of old-style numerals (OpenType feature: <span
     class=tag>onum</span>).
    <dt><dfn id=proportional-nums>proportional-nums</dfn>
    <dd>Enables display of proportional numerals (OpenType feature: <span
     class=tag>pnum</span>).
    <dt><dfn id=tabular-nums>tabular-nums</dfn>
    <dd>Enables display of tabular numerals (OpenType feature: <span
     class=tag>tnum</span>).
   </dl>
   <p>The example below shows how these different properties can be combined
    to influence the rendering of tabular data with fonts that support these
    features. Within normal paragraph text, proportional numbers are used
    while tabular numbers are used so that columns of numbers line up
    properly:
   <div class=figure style="padding: 0; margin: auto;"><img alt="combining
    number styles" src=numberstyles.png>
    <p class=caption>Using number styles
   </div>
   <dl>
    <dt><dfn id=diagonal-fractions>diagonal-fractions</dfn>
    <dd>Enables display of lining diagonal fractions (OpenType feature: <span
     class=tag>frac</span>).
   </dl>
   <div class=featex><img alt="diagonal fraction example" src=frac.png></div>
   <dl>
    <dt><dfn id=stacked-fractions>stacked-fractions</dfn>
    <dd>Enables display of lining stacked fractions (OpenType feature: <span
     class=tag>afrc</span>).
   </dl>
   <div class=featex><img alt="stacked fraction example" src=afrc.png></div>
   <dl>
    <dt><dfn id=ordinal>ordinal</dfn>
    <dd>Enables display of forms used with ordinal numbers (OpenType feature:
     <span class=tag>ordn</span>).
    <dt><dfn id=slashed-zero>slashed-zero</dfn>
    <dd>Enables display of slashed zeros (OpenType feature: <span
     class=tag>zero</span>).
   </dl>
   <div class=featex><img alt="slashed zero example" src=zero.png></div>
   <div class=example id=steak-marinade>
    <p>A simple flank steak marinade recipe, rendered with automatic fractions
     and old-style numerals:</p>
    <pre>.amount { font-variant-numeric: oldstyle-nums diagonal-fractions; }
 &lt;h4>Steak marinade:&lt;/h4>
 &lt;ul>
   &lt;li>&lt;span class="amount">2&lt;/span> tbsp olive oil&lt;/li>
   &lt;li>&lt;span class="amount">1&lt;/span> tbsp lemon juice&lt;/li>
   &lt;li>&lt;span class="amount">1&lt;/span> tbsp soy sauce&lt;/li>
   &lt;li>&lt;span class="amount">1 1/2&lt;/span> tbsp dry minced onion&lt;/li>
   &lt;li>&lt;span class="amount">2 1/2&lt;/span> tsp italian seasoning&lt;/li>
   &lt;li>Salt &amp;amp; pepper&lt;/li>
 &lt;/ul>
 &lt;p>Mix the meat with the marinade and let it sit covered in the refrigerator
 for a few hours or overnight.&lt;/p>
 </pre>
   </div>
   <!-- prop: font-variant-alternates -->
   <h3 id=font-variant-alternates-prop><span class=secno>6.8 </span>Alternates
    and swashes: the <a
    href="#propdef-font-variant-alternates">font-variant-alternates</a>
    property</h3>
   <table class=propdef id=namefont-variant-alternatesvaluenormal-s>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn
       id=propdef-font-variant-alternates>font-variant-alternates</dfn>
     <tr>
      <td>Value:
      <td>normal | [ stylistic(&lt;feature-value-name&gt;) || historical-forms
       || styleset(&lt;feature-value-name&gt;#) ||
       character-variant(&lt;feature-value-name&gt;#) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>For any given character, fonts can provide a variety of alternate glyphs
    in addition to the default glyph for that character. This property
    provides control over the selection of these alternate glyphs.
   <p>In cases where multiple alternates are possible, authors define a
    <code>&lt;feature-value-name&gt;</code> using the
    <code>@font-feature-values</code> rule described below to indicate the
    specific alternate to be used. The nature of these alternates is font
    specific, so the rule defines values for a specific font family or set of
    families. When a particular value has not been defined for a given family,
    the named value is treated as if the feature had omitted from the style
    rule. If a given value is outside the range supported by a given font, the
    value is ignored. These values never apply to generic font families, nor
    to families selected as part of system font fallback. Values that behave
    this way are marked as <em>font specific</em>.
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=normal1>normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=stylisticltfeature-value-namegt
     title=stylistic>stylistic(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables display of stylistic alternates (<em>font specific</em>,
     OpenType feature: <span class=tag>salt
     &lt;feature-value-name&gt;</span>).
   </dl>
   <div class=featex><img alt="stylistic alternate example" src=salt.png></div>
   <dl>
    <dt><dfn id=historical-forms>historical-forms</dfn>
    <dd>Enables display of historical forms (OpenType feature: <span
     class=tag>hist</span>).
   </dl>
   <div class=featex><img alt="historical form example" src=hist.png></div>
   <dl>
    <dt><dfn id=stylesetltfeature-value-namegt
     title=styleset>styleset(&lt;feature-value-name&gt;#)</dfn>
    <dd>Enables display with stylistic sets (<em>font specific</em>, OpenType
     feature: <span class=tag>ss&lt;feature-index&gt;</span> OpenType
     currently defines <span class=tag>ss01</span> through <span
     class=tag>ss20</span>).
   </dl>
   <div class=featex><img alt="styleset example" src=ssnn.png></div>
   <dl>
    <dt><dfn id=character-variantltfeature-value-namegt
     title=character-variant>character-variant(&lt;feature-value-name&gt;#)</dfn>
    <dd>Enables display of specific character variants (<em>font
     specific</em>, OpenType feature: <span
     class=tag>cv&lt;feature-index&gt;</span> OpenType currently defines <span
     class=tag>cv01</span> through <span class=tag>cv99</span>).
    <dt><dfn id=swashltfeature-value-namegt
     title=swash>swash(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables display of swash glyphs (<em>font specific</em>, OpenType
     feature: <span class=tag>swsh &lt;feature-index&gt;, cswh
     &lt;feature-index&gt;</span>).
   </dl>
   <div class=featex><img alt="swash example" src=swsh.png></div>
   <dl>
    <dt><dfn id=ornamentsltfeature-value-namegt
     title=ornaments>ornaments(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables replacement of default glyphs with ornaments, if provided in
     the font (<em>font specific</em>, OpenType feature: <span class=tag>ornm
     &lt;feature-index&gt;</span>). Some fonts may offer ornament glyphs as
     alternates for a wide collection of characters; however, displaying
     arbitrary characters (e.g., alphanumerics) as ornaments is poor practice
     as it distorts the semantics of the data. Font designers are encouraged
     to encode all ornaments (except those explicitly encoded in the Unicode
     Dingbats blocks, etc.) as alternates for the bullet character (U+2022) to
     allow authors to select the desired glyph using
     &lt;feature-value-name&gt;.
   </dl>
   <div class=featex><img alt="ornaments example" src=ornm.png></div>
   <dl>
    <dt><dfn id=annotationltfeature-value-namegt
     title=annotation>annotation(&lt;feature-value-name&gt;)</dfn>
    <dd>Enables display of alternate annotation forms (<em>font specific</em>,
     OpenType feature: <span class=tag>nalt &lt;feature-index&gt;</span>).
   </dl>
   <div class=featex><img alt="alternate annotation form example"
    src=nalt.png></div>
   <h3 id=font-feature-values><span class=secno>6.9 </span>Defining font
    specific alternates: the <code>@font-feature-values</code> rule</h3>
   <p>Several of the possible values of ‘<a
    href="#propdef-font-variant-alternates"><code
    class=property>font-variant-alternates</code></a>’ listed above are
    labeled as "font specific". For these features fonts may define not just a
    single glyph but a set of alternate glyphs with an index to select a given
    alternate. Since these are font family specific, the
    <code>@font-feature-values</code> rule is used to define named-values for
    these indices for a given family.
   <p>In the case of the swash Q in the example shown above, the swash could
    be specified using these style rules:
   <pre>
 @font-feature-values Jupiter Sans {
   @swash {
     delicate: 1;
     flowing: 2;
   }
 }
 h2 { font-family: Jupiter Sans, sans-serif; }
 /* show the second swash variant in h2 headings */
 h2:first-letter { font-variant-alternates: swash(flowing); }
 &lt;h2>Quick&lt;/h2></pre>
   <p>When Jupiter Sans is present, the second alternate swash alternate will
    be displayed. When not present, no swash character will be shown, since
    the specific named-value "flowing" is only defined for the Jupiter Sans
    family. The @-mark indicates the name of the property value for which a
    named-value can be used. The name "flowing" is chosen by the author.
   <p>The syntax of the <code>@font-feature-values</code> rule is defined as:
   <pre>@font-feature-values &lt;font-family># {
   @&lt;feature-type> {
     &lt;feature-ident> : &lt;feature-index>+;
     &lt;feature-ident> : &lt;feature-index>+;
     ...
   }
   ...
 }
 </pre>
   <p>where:
   <pre
    class=prod><dfn id=ltfont-familygt><var>&lt;font-family&gt;</var></dfn>         = font family name, same syntax as font-family property</pre>
   <pre
    class=prod><dfn id=ltfeature-typegt><var>&lt;feature-type&gt;</var></dfn>        = the name of one of the font specific font-variant property values
                         (e.g. swash, styleset, annotation)</pre>
   <pre
    class=prod><dfn id=ltfeature-identgt><var>&lt;feature-ident&gt;</var></dfn>       = a user-defined identifier used to describe a set of indices</pre>
   <pre
    class=prod><dfn id=ltfeature-indexgt><var>&lt;feature-index&gt;</var></dfn>       = an integer value greater than 0 specific to a given font or set of fonts</pre>
   <p>These <code>@font-feature-values</code> rules can appear anywhere within
    a stylesheet and are exposed bidirectionally across @import boundaries.
    Within each font feature values declaration, syntax errors such as unknown
    property value names, invalid identifiers or values result in the
    declaration being dropped, similar to the way syntax errors in style
    declarations are handled.
   <p>If multiple <code>@font-feature-values</code> rules are defined for a
    given family, the resulting values defined are the union of these rules.
    This allows a set of named-values to be defined for a given font family
    globally for a site and specific additions made per-page. If the same
    &lt;feature-value-name&gt; is defined mulitple times for a given
    font-variant value, the last defined value is used.
   <pre>
 site.css:
   @font-feature-values Mercury Serif {
     @styleset {
       stacked-g: 3; /* "two-storey" versions of g, a */
       stacked-a: 4;
     }
   }
 page.css:
   @font-feature-values Mercury Serif {
     @styleset {
       geometric-m: 7; /* alternate version of m */
     }
   }
   body {
     font-family: Mercury Serif, serif;
     /* enable both the use of stacked g and alternate m */
     font-variant-alternates: styleset(stacked-g, geometric-m);
   }</pre>
   <p>Only named font families are allowed for &lt;font-family&gt;, rules that
    include generic or system fonts in the list of font families are
    considered syntax errors and the contents of the rules are ignored.
    However, if a user agent defines a generic font to be a specific named
    font (e.g. Helvetica), the settings associated with that family name will
    be used.
   <p>For &lt;font-variant-property-value>, only font specific property value
    names supported by the ‘<a href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’ property are recognized,
    definitions for other value names cause a syntax error and are ignored.
    Each property value that is font specific is clearly marked as such.
    Feature value names follow the rules of CSS user identifiers and are
    case-sensitive. They are unique only for a given set of font families and
    font-variant property value; the same identifier used with a different
    font-variant property value is treated as a separate and distinct value.
   <p>Using a commonly named value allows authors to use a single style rule
    to cover a set of fonts for which the underlying selector is different for
    each font. If either font in the example below is found, a circled number
    glyph will be used:
   <pre>@font-feature-values Taisho Gothic {
   @annotation { boxed: 1; circled: 4; }
 }
 @font-feature-values Otaru Kisa {
   @annotation { circled: 1; black-boxed: 3; }
 }
 h3.title {
   /* circled form defined for both fonts */
   font-family: Taisho Gothic, Otaru Kisa;
   font-variant: annotation(circled);
 }</pre>
   <p>Most font specific font-variant property values take a single value
    (e.g. swash). The character-variant property value allows two values and
    styleset allows an unlimited number. If a larger number of values are
    assigned to a given name, a syntax error occurs and the entire
    &lt;font-feature-values-declaration&gt; is ignored.
   <p>For the styleset property value, multiple values indicate the style sets
    to be enabled. Values between 1 and 99 enable OpenType features <span
    class=tag>ss01</span> through <span class=tag>ss99</span>. However, the
    OpenType standard only officially defines <span class=tag>ss01</span>
    through <span class=tag>ss20</span>. Values greater than 99 or equal to 0
    are ignored but do not generate a syntax error when parsed.
   <pre>@font-feature-values Mars Serif {
   @styleset {
     alt-g: 1;        /* implies ss01 = 1 */
     curly-quotes: 3; /* implies ss03 = 1 */
     code: 4 5;       /* implies ss04 = 1, ss05 = 1 */
   }
   @styleset {
     dumb: 125;        /* &gt;99, ignored */
   }
   @swash {
     swishy: 3 5;     /* more than 1 value for swash, syntax error */
   }
 }
 p.codeblock {
   /* implies ss03 = 1, ss04 = 1, ss05 = 1 */
   font-variant-alternates: styleset(curly-quotes, code);
 }</pre>
   <p>For character-variant, a single value between 1 and 99 indicates the
    enabling of OpenType feature <span class=tag>cv01</span> through <span
    class=tag>cv99</span>. For OpenType fonts, values greater than 99 or equal
    to 0 are ignored but do not generate a syntax error when parsed. When two
    values are listed, the first value indicates the feature used and the
    second the value passed for that feature. When two value names imply
    different settings for the same underlying feature the last setting is
    used.
   <pre>@font-feature-values MM Greek {
   @character-variant { alpha-2: 1 2; }   /* implies cv01 = 2 */
   @character-variant { beta-3: 2 3; }    /* implies cv02 = 3 */
   @character-variant { epsilon: 5 3 6; } /* more than 2 values, syntax error, ignored */
   @character-variant { gamma: 12; }      /* implies cv12 = 1 */
   @character-variant { zeta:   20 3; }   /* implies cv20 = 3 */
   @character-variant { zeta-2: 20 2; }   /* implies cv20 = 2 */
   @character-variant { silly: 105; }     /* &gt;99, ignored */
   @character-variant { dumb: 323 3; }    /* &gt;99, ignored */
 }
 #title {
   /* use the third alternate beta, first alternate gamma */
   font-variant-alternates: character-variant(beta-3, gamma);
 }
 p {
   /* zeta-2 follows zeta, implies cv20 = 2  */
   font-variant-alternates: character-variant(zeta, zeta-2);
 }
 .special {
   /* zeta follows zeta-2, implies cv20 = 3  */
   font-variant-alternates: character-variant(zeta-2, zeta);
 }</pre>
   <p>See the <a href="#om-fontfeaturevalues">object model reference
    section</a> for a description of the interfaces used to modify these rules
    via the CSS Object Model.
   <div class=figure><img alt="Matching text on Byzantine seals using
    character variants" src=byzantineseal.png>
    <p class=caption>Byzantine seal text displayed with character variants
   </div>
   <div class=example>
    <p>In the figure above, the text in red is rendered using a font
     containing character variants that mimic the character forms found on a
     Byzantine seal from the 8th century A.D. Two lines below is the same text
     displayed in a font without variants. Note the two variants for U and N
     used on the seal.</p>
    <pre>@font-feature-values Athena Ruby {
   @character-variant {
     leo-B: 2 1;
     leo-M: 13 3;
     leo-alt-N: 14 1;
     leo-N: 14 2;
     leo-T: 20 1;
     leo-U: 21 2;
     leo-alt-U: 21 4;
   }
 }
 p {
   font-variant: discretionary-ligatures,
                 character-variant(leo-B, leo-M, leo-N, leo-T, leo-U);
 }
 span.alt-N {
   font-variant-alternates: character-variant(leo-alt-N);
 }
 span.alt-U {
   font-variant-alternates: character-variant(leo-alt-U);
 }
 &lt;p>ENO....UP͞RSTU&lt;span class="alt-U">U&lt;/span>͞&lt;span class="alt-U">U&lt;/span>ΚΑΙTỤẠG̣IUPNS&lt;/p>
 &lt;p>LEON|ΚΑΙCONSTA|NTI&lt;span class="alt-N">N&lt;/span>OS..|STOIBAṢ.|LIṢROM|AIO&lt;span class="alt-N">N&lt;/span>&lt;/p>
 </pre>
   </div>
   <h3 id=font-variant-east-asian-prop><span class=secno>6.10 </span>East
    Asian text rendering: the <a
    href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
    property</h3>
   <table class=propdef id=namefont-variant-east-asianvaluenormal-l>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn
       id=propdef-font-variant-east-asian>font-variant-east-asian</dfn>
     <tr>
      <td>Value:
      <td>normal | [ &lt;east-asian-variant-values&gt; ||
       &lt;east-asian-width-values&gt; || ruby ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>Allows control of glyph substitution and sizing in East Asian text.
   <pre
    class=prod><dfn id=lteast-asian-variant-valuesgt><var>&lt;east-asian-variant-values&gt;</var></dfn> = [ jis78 | jis83 | jis90 | jis04 | simplified | traditional ]</pre>
   <pre
    class=prod><dfn id=lteast-asian-width-valuesgt><var>&lt;east-asian-width-values&gt;</var></dfn>   = [ full-width | proportional-width ]</pre>
   <p>Individual values have the following meanings:
   <dl>
    <dt><dfn id=normal2>normal</dfn>
    <dd>None of the features listed below are enabled.
    <dt><dfn id=jis78>jis78</dfn>
    <dd>Enables rendering of JIS78 forms (OpenType feature: <span
     class=tag>jp78</span>).
   </dl>
   <div class=featex><img alt="JIS78 form example" src=jp78.png></div>
   <dl>
    <dt><dfn id=jis83>jis83</dfn>
    <dd>Enables rendering of JIS83 forms (OpenType feature: <span
     class=tag>jp83</span>).
    <dt><dfn id=jis90>jis90</dfn>
    <dd>Enables rendering of JIS90 forms (OpenType feature: <span
     class=tag>jp90</span>).
    <dt><dfn id=jis04>jis04</dfn>
    <dd>Enables rendering of JIS2004 forms (OpenType feature: <span
     class=tag>jp04</span>).
     <p>The various JIS variants reflect the glyph forms defined in different
      Japanese national standards. Fonts generally include glyphs defined by
      the most recent national standard but it's sometimes necessary to use
      older variants, to match signage for example.</p>
    <dt><dfn id=simplified>simplified</dfn>
    <dd>Enables rendering of simplified forms (OpenType feature: <span
     class=tag>smpl</span>).
     <p>The ‘<a href="#simplified"><code
      class=property>simplified</code></a>’ and ‘<a
      href="#traditional"><code class=property>traditional</code></a>’
      values allow control over the glyph forms for characters which have been
      simplified over time but for which the older, traditional form is still
      used in some contexts. The exact set of characters and glyph forms will
      vary to some degree by context for which a given font was designed.</p>
    <dt><dfn id=traditional>traditional</dfn>
    <dd>Enables rendering of traditional forms (OpenType feature: <span
     class=tag>trad</span>).
   </dl>
   <div class=featex><img alt="tradtional form example" src=trad.png></div>
   <dl>
    <dt><dfn id=full-width>full-width</dfn>
    <dd>Enables rendering of full-width variants (OpenType feature: <span
     class=tag>fwid</span>).
    <dt><dfn id=proportional-width>proportional-width</dfn>
    <dd>Enables rendering of proportionally-spaced variants (OpenType feature:
     <span class=tag>pwid</span>).
   </dl>
   <div class=featex><img alt="proportionally spaced Japanese example"
    src=pwid.png></div>
   <dl>
    <dt><dfn id=ruby>ruby</dfn>
    <dd>Enables display of ruby variant glyphs (OpenType feature: <span
     class=tag>ruby</span>). Since ruby text is generally smaller than the
     associated body text, font designers can design special glyphs for use
     with ruby that are more readable than scaled down versions of the default
     glyphs. Only glyph selection is affected, there is no associated font
     scaling or other change that affects line layout. The red ruby text below
     is shown with default glyphs (top) and with ruby variant glyphs (bottom).
     Note the slight difference in stroke thickness.
   </dl>
   <div class=featex><img alt="ruby variant example" src=rubyshinkansen.png></div>
   <h3 id=font-variant-prop><span class=secno>6.11 </span>Overall shorthand
    for font rendering: the <a href="#propdef-font-variant">font-variant</a>
    property</h3>
   <table class=propdef id=namefont-variantvaluenormal-none-ltcommo>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-variant>font-variant</dfn>
     <tr>
      <td>Value:
      <td>normal | none | [ &lt;common-lig-values&gt; ||
       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
       character-variant(&lt;feature-value-name&gt;#) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
       ruby ]
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>see individual properties
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>see individual properties
     <tr>
      <td>Animatable:
      <td>see individual properties
   </table>
   <p>The value ‘<a href="#normal2"><code
    class=property>normal</code></a>’ resets all other font feature
    properties to their inital value. The ‘<code
    class=property>none</code>’ value sets ‘<a
    href="#propdef-font-variant-ligatures"><code
    class=property>font-variant-ligatures</code></a>’ to ‘<code
    class=property>none</code>’ and resets all other font feature properties
    to their initial value. Like other shorthands, using ‘<a
    href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’ resets unspecified font-variant
    subproperties to their initial values. It does not reset the values of
    either ‘<a href="#propdef-font-language-override"><code
    class=property>font-language-override</code></a>’ or ‘<a
    href="#propdef-font-feature-settings"><code
    class=property>font-feature-settings</code></a>’.
   <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
    font feature settings control: the <a
    href="#propdef-font-feature-settings">font-feature-settings</a> property</h3>
   <table class=propdef id=namefont-feature-settingsvaluenormal-ltf>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-feature-settings>font-feature-settings</dfn>
     <tr>
      <td>Value:
      <td>normal | &lt;feature-tag-value&gt;#
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>This property provides low-level control over OpenType font features. It
    is intended as a way of providing access to font features that are not
    widely used but are needed for a particular use case. A value of ‘<a
    href="#normal2"><code class=property>normal</code></a>’ means that no
    change in glyph selection or positioning occurs due to this property.
   <p>
   <pre>/* enable small caps and use second swash alternate */
 font-feature-settings: "smcp", "swsh" 2;</pre>
   <p>Feature tag values have the following syntax:
   <pre
    class=prod><dfn id=ltfeature-tag-valuegt><var>&lt;feature-tag-value&gt;</var></dfn> = &lt;string&gt; [ &lt;integer&gt; | on | off ]?</pre>
   <p>The &lt;string&gt; is a case-sensitive OpenType feature tag. As
    specified in the OpenType specification, feature tags contain four ASCII
    characters. Tag strings longer or shorter than four characters, or
    containing characters outside the U+20–7E codepoint range are invalid.
    User agents must not use a feature tag created by truncating or padding
    the string to four characters. Feature tags need only match a feature tag
    defined in the font, they are not limited to explicitly registered
    OpenType features. Fonts defining custom feature tags should follow the <a
    href="http://www.microsoft.com/typography/otspec/featuretags.htm">tag name
    rules</a> defined in the OpenType specification <a
    href="#OPENTYPE-FEATURES"
    rel=biblioentry>[OPENTYPE-FEATURES]<!--{{!OPENTYPE-FEATURES}}--></a>.
    Feature tags not present in the font are ignored; a user agent must not
    attempt to synthesize fallback behavior based on these feature tags.
   <p>This means that explicitly disabling the <span class=tag>kern</span>
    feature will not affect the application of kerning data found in the
    ‘<code class=property>kern</code>’ table (as opposed to kerning data
    associated with the <span class=tag>kern</span> feature in the ‘<code
    class=property>GPOS</code>’ table). Authors should use the ‘<a
    href="#propdef-font-kerning"><code
    class=property>font-kerning</code></a>’ property to explictly enable or
    disable kerning since this property affects both types of kerning.
   <p>If present, a value indicates an index used for glyph selection. An
    &lt;integer&gt; value must be 0 or greater. A value of 0 indicates that
    the feature is disabled. For boolean features, a value of 1 enables the
    feature. For non-boolean features, a value of 1 or greater enables the
    feature and indicates the feature selection index. A value of ‘<code
    class=property>on</code>’ is synonymous with 1 and ‘<code
    class=property>off</code>’ is synonymous with 0. If the value is
    omitted, a value of 1 is assumed.
   <pre>
 font-feature-settings: "dlig" 1;       /* dlig=1 enable discretionary ligatures */
 font-feature-settings: "smcp" on;      /* smcp=1 enable small caps */
 font-feature-settings: 'c2sc';         /* c2sc=1 enable caps to small caps */
 font-feature-settings: "liga" off;     /* liga=0 no common ligatures */
 font-feature-settings: "tnum", 'hist'; /* tnum=1, hist=1 enable tabular numbers and historical forms */
 font-feature-settings: "tnum" "hist";  /* invalid, need a comma-delimited list */
 font-feature-settings: "palin" off;    /* good idea but invalid tagname */
 font-feature-settings: "PKRN";         /* PKRN=1 enable custom feature */
 font-feature-settings: dlig;           /* invalid, tag must be a string */
 </pre>
   <p>Authors should generally use ‘<a href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’ and its related subproperties
    whenever possible and only use this property for special cases where its
    use is the only way of accessing a particular infrequently used font
    feature.
   <p>Although specifically defined for OpenType feature tags, feature tags
    for other modern font formats that support font features may be added in
    the future. Where possible, features defined for other font formats should
    attempt to follow the pattern of registered OpenType tags.
   <div class=example>
    <p>The Japanese text below will be rendered with half-width kana
     characters:</p>
    <pre lang=ja>
 body { font-feature-settings: "hwid"; /* Half-width OpenType feature */ }
 &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>
 </pre>
   </div>
   <h3 id=font-language-override-prop><span class=secno>6.13 </span>Font
    language override: the <a
    href="#propdef-font-language-override">font-language-override</a> property</h3>
   <table class=propdef id=namefont-language-overridevaluenormal-lt>
    <tbody>
     <tr>
      <td>Name:
      <td><dfn id=propdef-font-language-override>font-language-override</dfn>
     <tr>
      <td>Value:
      <td>normal | &lt;string&gt;
     <tr>
      <td>Initial:
      <td>normal
     <tr>
      <td>Applies to:
      <td>all elements
     <tr>
      <td>Inherited:
      <td>yes
     <tr>
      <td>Percentages:
      <td>N/A
     <tr>
      <td>Media:
      <td>visual
     <tr>
      <td>Computed value:
      <td>as specified
     <tr>
      <td>Animatable:
      <td>no
   </table>
   <p>The value of ‘<a href="#normal2"><code
    class=property>normal</code></a>’ implies that when rendering with
    OpenType fonts the language of the document is used to infer the OpenType
    language system, used to select language specific features when rendering.
    The value of the &lt;string&gt; is a single three-letter OpenType <a
    href="http://www.microsoft.com/typography/otspec/languagetags.htm">language
    system tag</a>, defined in the layout tag registry of the OpenType
    specification.
   <div class=example>
    <p>The <a href="http://www.un.org/en/documents/udhr/index.shtml">Universal
     Declaration of Human Rights</a> has been translated into a wide variety
     of languages. In Turkish, Article 9 of this document might be marked up
     as below:</p>
    <pre lang=tr>&lt;body lang="tr">
 &lt;h4>Madde 9&lt;/h4>
 &lt;p>Hiç kimse keyfi olarak tutuklanamaz, alıkonulanamaz veya sürülemez.&lt;/p>
 </pre>
    <p>Here the user agent uses the value of the ‘<code
     class=property>lang</code>’ attribute when rendering text and
     appropriately renders this text without ‘<code
     class=property>fi</code>’ ligatures. There is no need to use the ‘<a
     href="#propdef-font-language-override"><code
     class=property>font-language-override</code></a>’ property.</p>
    <p>However, a given font may lack support for a specific language. In this
     situation authors may need to use the typographic conventions of a
     related language that are supported by that font:</p>
    <pre lang=mk>&lt;body lang="mk">     &lt;!-- Macedonian lang code --&gt;
 body { font-language-override: "SRB"; /* Serbian OpenType language tag */ }
 &lt;h4>Члeн 9&lt;/h4>
 &lt;p>Никoj чoвeк нeмa дa бидe пoдлoжeн нa прoизвoлнo aпсeњe, притвoр или прoгoнувaњe.&lt;/p>
 </pre>
    <p>The Macedonian text here will be rendered using Serbian typographic
     conventions, with the assumption that the font specified supports
     Serbian.</p>
   </div>
   <p><a id=rendering-considerations></a>
   <h2 id=font-feature-resolution><span class=secno>7 </span>Font Feature
    Resolution</h2>
   <p>As described in the previous section, font features can be enabled in a
    variety of ways, either via the use of ‘<a
    href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’ or ‘<a
    href="#propdef-font-feature-settings"><code
    class=property>font-feature-settings</code></a>’ in a style rule or
    within an <code>@font-face</code> rule. The resolution order for the union
    of these settings is defined below. Features defined via CSS properties
    are applied on top of layout engine default features.
   <h3 id=default-features><span class=secno>7.1 </span>Default features</h3>
   <p>For OpenType fonts, user agents must enable the default features defined
    in the OpenType documentation for a given script and writing mode.
    Required ligatures, common ligatures and contextual forms must be enabled
    by default (OpenType features: <span class=tag>rlig, liga, clig,
    calt</span>), along with localized forms (OpenType feature: <span
    class=tag>locl</span>), and features required for proper display of
    composed characters and marks (OpenType features: <span class=tag>ccmp,
    mark, mkmk</span>). These features must always be enabled, even when the
    value of the ‘<a href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’ and ‘<a
    href="#propdef-font-feature-settings"><code
    class=property>font-feature-settings</code></a>’ properties is ‘<a
    href="#normal2"><code class=property>normal</code></a>’. Individual
    features are only disabled when explicitly overridden by the author, as
    when ‘<a href="#propdef-font-variant-ligatures"><code
    class=property>font-variant-ligatures</code></a>’ is set to ‘<a
    href="#no-common-ligatures"><code
    class=property>no-common-ligatures</code></a>’. For handling complex
    scripts such as <a
    href="http://www.microsoft.com/typography/otfntdev/arabicot/features.aspx">Arabic</a>,
    <a
    href="http://www.microsoft.com/typography/otfntdev/mongolot/features.htm">Mongolian</a>
    or <a
    href="http://www.microsoft.com/typography/otfntdev/devanot/features.aspx">Devanagari</a>
    additional features are required. For upright text within vertical text
    runs, vertical alternates (OpenType feature: <span class=tag>vert</span>)
    must be enabled.
   <h3 id=feature-precedence><span class=secno>7.2 </span>Feature precedence</h3>
   <p>General and font specific font feature property settings are resolved in
    the order below, in ascending precedence order. This ordering is used to
    construct a combined list of font features that affect a given text run.
   <ol>
    <li>Font features enabled by default, including features required for a
     given script.
    <li>If the font is defined via an <code>@font-face</code> rule, the font
     features implied by the font-variant descriptor in the
     <code>@font-face</code> rule.
    <li>If the font is defined via an <code>@font-face</code> rule, the font
     features implied by the font-feature-settings descriptor in the
     <code>@font-face</code> rule.
    <li>Feature settings determined by properties other than ‘<a
     href="#propdef-font-variant"><code
     class=property>font-variant</code></a>’ or ‘<a
     href="#propdef-font-feature-settings"><code
     class=property>font-feature-settings</code></a>’. For example, setting
     a non-default value for the ‘<code
     class=property>letter-spacing</code>’ property disables ligatures.
    <li>Font features implied by the value of the ‘<a
     href="#propdef-font-variant"><code
     class=property>font-variant</code></a>’ property, the related
     font-variant subproperties and any other CSS property that may use
     OpenType features (e.g. the ‘<a href="#propdef-font-kerning"><code
     class=property>font-kerning</code></a>’ property).
    <li>Font features implied by the value of ‘<a
     href="#propdef-font-feature-settings"><code
     class=property>font-feature-settings</code></a>’ property.
   </ol>
   <p>This ordering allows authors to set up a general set of defaults for
    fonts within their <code>@font-face</code> rules, then override them with
    property settings for specific elements. General property settings
    override the settings in <code>@font-face</code> rules and low-level font
    feature settings override ‘<a href="#propdef-font-variant"><code
    class=property>font-variant</code></a>’ property settings.
   <p>For situations where the combined list of font feature settings contains
    more than one value for the same feature, the last value is used. When a
    font lacks support for a given underlying font feature, text is simply
    rendered as if that font feature was not enabled; font fallback does not
    occur and no attempt is made to synthesize the feature except where
    explicitly noted for specific properties.
   <h3 id=feature-precedence-examples><span class=secno>7.3 </span>Feature
    precedence examples</h3>
   <div class=example>
    <p>With the styles below, numbers are rendered proportionally when used
     within a paragraph but are shown in tabular form within tables of prices:</p>
    <pre>body {
   font-variant-numeric: proportional-nums;
 }
 table.prices td {
   font-variant-numeric: tabular-nums;
 }
 </pre>
   </div>
   <div class=example>
    <p>When the font-variant descriptor is used within an
     <code>@font-face</code> rule, it only applies to the font defined by that
     rule.</p>
    <pre>@font-face {
   font-family: MainText;
   src: url(http://example.com/font.ttf);
   font-variant: oldstyle-nums proportional-nums styleset(1,3);
 }
 body {
   font-family: MainText, Helvetica;
 }
 table.prices td {
   font-variant-numeric: tabular-nums;
 }
 </pre>
    <p>In this case, old-style numerals will be used throughout but only where
     the font "MainText" is used. Just as in the previous example, tabular
     values will be used in price tables since ‘<a
     href="#tabular-nums"><code class=property>tabular-nums</code></a>’
     appears in a general style rule and its use is mutually exclusive with
     ‘<a href="#proportional-nums"><code
     class=property>proportional-nums</code></a>’. Stylistic alternate sets
     will only be used where MainText is used.</p>
   </div>
   <div class=example>
    <p>The <code>@font-face</code> rule can also be used to access font
     features in locally available fonts via the use of local() in the ‘<a
     href="#descdef-src"><code class=property>src</code></a>’ descriptor of
     the <code>@font-face</code> definition:</p>
    <pre>@font-face {
   font-family: BodyText;
   src: local("HiraMaruPro-W4");
   font-variant: proportional-width;
   font-feature-settings: "ital"; /* Latin italics within CJK text feature */
 }
 body { font-family: BodyText, serif; }
 </pre>
    <p>If available, a Japanese font "Hiragino Maru Gothic" will be used. When
     text rendering occurs, Japanese kana will be proportionally spaced and
     Latin text will be italicised. Text rendered with the fallback serif font
     will use default rendering properties.</p>
   </div>
   <div class=example>
    <p>In the example below, discretionary ligatures are enabled only for a
     downloadable font but are disabled within spans of class "special":</p>
    <pre>@font-face {
   font-family: main;
   src: url(fonts/ffmeta.woff) format("woff");
   font-variant: discretionary-ligatures;
 }
 body         { font-family: main, Helvetica; }
 span.special { font-variant-ligatures: no-discretionary-ligatures; }
 </pre>
    <p>Adding an discretionary style rule with the <code>@font-face</code>
     above:</p>
    <pre>body         { font-family: main, Helvetica; }
 span         { font-feature-settings: "dlig"; }
 span.special { font-variant-ligatures: no-discretionary-ligatures; }
 </pre>
    <p>Within spans of class "special", discretionary ligatures <em>will</em>
     be rendered. This is because both the ‘<a
     href="#propdef-font-feature-settings"><code
     class=property>font-feature-settings</code></a>’ and ‘<a
     href="#propdef-font-variant-ligatures"><code
     class=property>font-variant-ligatures</code></a>’ properties apply to
     these spans. Although the ‘<code class=css>no-discretionary
     ligatures</code>’ setting of ‘<a
     href="#propdef-font-variant-ligatures"><code
     class=property>font-variant-ligatures</code></a>’ effectively disables
     the OpenType <span class=tag>dlig</span> feature, because the ‘<a
     href="#propdef-font-feature-settings"><code
     class=property>font-feature-settings</code></a>’ is resolved after
     that, the ‘<code class=property>dlig</code>’ value reenables
     discretionary ligatures.</p>
   </div>
   <h2 id=object-model><span class=secno>8 </span>Object Model</h2>
   <p>The contents of <code>@font-face</code> and
    <code>@font-feature-values</code> rules can be accessed via the following
    extensions to the CSS Object Model.
   <h3 id=om-fontface><span class=secno>8.1 </span>The <a
    href="#cssfontfacerule"><code>CSSFontFaceRule</code></a> interface</h3>
   <p>The <dfn id=cssfontfacerule>CSSFontFaceRule</dfn> interface represents a
    <code>@font-face</code> rule.
   <pre class=idl>
 interface CSSFontFaceRule : CSSRule {
   attribute DOMString family;
   attribute DOMString src;
   attribute DOMString style;
   attribute DOMString weight;
   attribute DOMString stretch;
   attribute DOMString unicodeRange;
   attribute DOMString variant;
   attribute DOMString featureSettings;
 }</pre>
   <p>The DOM Level 2 Style specification <a href="#DOM-LEVEL-2-STYLE"
    rel=biblioentry>[DOM-LEVEL-2-STYLE]<!--{{DOM-LEVEL-2-STYLE}}--></a>
    defined a different variant of this rule. This definition supercedes that
    one.
   <h3 id=om-fontfeaturevalues><span class=secno>8.2 </span>The <a
    href="#cssfontfeaturevaluesrule"><code>CSSFontFeatureValuesRule</code></a>
    interface</h3>
   <p>The <code>CSSRule</code> interface is extended as follows:
   <pre class=idl>partial interface CSSRule {
   const unsigned short FONT_FEATURE_VALUES_RULE = 14;
 }</pre>
   <p>The <dfn id=cssfontfeaturevaluesrule>CSSFontFeatureValuesRule</dfn>
    interface represents a <code>@font-feature-values</code> rule.
   <pre class=idl>interface CSSFontFeatureValuesRule : CSSRule {
   readonly attribute DOMString familyList;
   readonly attribute DOMString valueText;
 };</pre>
   <dl class=idl-attributes>
    <dt><var>familyList</var> of type <code>DOMString</code>, readonly
    <dd>The list of one or more font families for which a given set of feature
     values is defined.
    <dt><var>valueText</var> of type <code>DOMString</code>, readonly
    <dd>Serialized set of feature values.
   </dl>
   <h2 id=font-load-events><span class=secno>9 </span>Font Load Events</h2>
   <p>Since fonts defined via <code>@font-face</code> rules are loaded on
    demand, pages may need to know precisely when fonts have completed
    downloading before measuring text elements on the page or to show some
    form of interim user interface state.
   <h3 id=document-fontloader><span class=secno>9.1 </span>Extension to the
    <code>document</code> interface</h3>
   <p>To allow font loading to be tracked explicitly within content the
    following event target is added to the <code>document</code> of the page:
   <pre class=idl>partial interface Document {
   readonly attribute FontLoader fontloader;
 };
 </pre>
   <h3 id=fontloader-interface><span class=secno>9.2 </span>The
    <code>FontLoader</code> Interface</h3>
   <pre class=idl>dictionary CSSFontFaceLoadEventInit : EventInit {
   CSSFontFaceRule fontface = null;
   DOMError error = null;
 };
 dictionary LoadFontParameters {
   DOMString font;
   DOMString text = " ";
   FontsReadyCallback onsuccess;
   FontsReadyCallback onerror;
 };
 [Constructor(DOMString type, optional CSSFontFaceLoadEventInit eventInitDict)]
 interface CSSFontFaceLoadEvent : Event {
   readonly attribute CSSFontFaceRule fontface;
   readonly attribute DOMError error;
 }
 callback FontsReadyCallback = void ();
 interface FontLoader : EventTarget {
   // -- events for when loading state changes
   attribute EventHandler <a href="#fontloader-loading">onloading</a>;
   attribute EventHandler <a href="#fontloader-loadingdone">onloadingdone</a>;
   // -- events for each individual font load
   attribute EventHandler <a href="#fontloader-loadstart">onloadstart</a>;
   attribute EventHandler <a href="#fontloader-load">onload</a>;
   attribute EventHandler <a href="#fontloader-error">onerror</a>;
   // check and start load if appropriate
   // and fire callback when all loads complete
   void <a href="#fontloader-loadfont">loadFont</a>(LoadFontParameters params);
   // return whether all fonts in the fontlist are loaded
   // (does not initiate load if not available)
   boolean <a href="#fontloader-checkfont">checkFont</a>(DOMString font, optional DOMString text = " ");
   // async notify upon completion, pending layout changes
   void <a href="#fontloader-notifywhenfontsready">notifyWhenFontsReady</a>(FontsReadyCallback fontsReadyCallback);
   // loading state, true while one or more fonts loading, false otherwise
   readonly attribute boolean loading;
 };</pre>
   <p>Because font families defined with <code>@font-face</code> rules are
    loaded only when they are used, content sometimes needs to understand when
    the loading of fonts occurs. Authors can use the events and methods
    defined here to allow greater control over actions that are dependent upon
    the availability of specific fonts.
   <p>The term <dfn id=font-load>font load</dfn> is used below to indicate
    when the loading of content for a given <code>@font-face</code> rule
    completes. An <code>@font-face</code> rule may list multiple alternate
    resources within the ‘<a href="#descdef-src"><code
    class=property>src</code></a>’ descriptor, including references to local
    fonts, but the term font load only refers to the loading of the finally
    selected resource for a given rule, not to the loading of each individual
    resource.
   <h4 id=events><span class=secno>9.2.1 </span>Events</h4>
   <p>The following are the event handlers (and their corresponding event
    handler event types) that must be supported by <code>FontLoader</code>
    objects as IDL attributes:
   <table class=data id=eventhandlers>
    <thead>
     <tr>
      <th>Event handler
      <th>Event handler event type
    <tbody>
     <tr>
      <th><code class=idl-code>onloading</code>
      <td><code class=idl-code>loading</code>
     <tr>
      <th><code class=idl-code>onloadingdone</code>
      <td><code class=idl-code>loadingdone</code>
     <tr>
      <th><code class=idl-code>onloadstart</code>
      <td><code class=idl-code>loadstart</code>
     <tr>
      <th><code class=idl-code>onload</code>
      <td><code class=idl-code>load</code>
     <tr>
      <th><code class=idl-code>onerror</code>
      <td><code class=idl-code>error</code>
   </table>
   <p>To <dfn id=fire-a-font-load-event>fire a font load event</dfn> named
    <var>e</var> at a <code>FontLoader</code> target means to <a
    href="http://www.w3.org/TR/html5/webappapis.html#event-firing">fire a
    simple event</a> named <var>e</var> using the
    <code>CSSFontFaceLoadEvent</code> interface that also meets these
    conditions:
   <ol>
    <li>The <code class=idl-code>fontface</code> attribute is initialized to
     the given <var>font face rule</var>.
    <li>The <code class=idl-code>error</code> attribute is initialized to the
     given <var>error</var>.
   </ol>
   <p>When the user agent determines that one or more fonts defined via
    <code>@font-face</code> rules in a document <var>doc</var> need to be
    loaded, it must run the following steps:
   <ol>
    <li>Let <var>font loader</var> be the value of the <code
     class=idl-code>fontloader</code> attribute of <var>doc</var>.
    <li>Set the <code class=idl-code>loading</code> attribute of <var>font
     loader</var> to true.
    <li><a href="#fire-a-font-load-event">Fire a font load event</a> named <a
     id=fontloader-loading><code class=idl-code>"loading"</code></a> with
     <var>font face rule</var> and <var>error</var> at <var>font loader</var>.
    <li>When the user agent begins loading the first resource for a given
     <code>@font-face</code> rule, it must <a
     href="#fire-a-font-load-event">fire a font load event</a> named <a
     id=fontloader-loadstart><code class=idl-code>"loadstart"</code></a> with
     <var>font face</var> set to the <code>@font-face</code> rule that caused
     this load to start and <var>error</var> set to <code>????</code> at
     <var>font loader</var>.
   </ol>
   <p class=issue>What are the error types that should be used here?
   <p>The term “font load” covers any of the resources listed in the
    ‘src’ descriptor, including local fonts. When multiple resources are
    listed, the “font load” is the first resource in the list to
    successfully load or the error that occurs on the last resource for which
    a load is attempted.
   <p class=issue>Given that a set of <code>@font-face</code> rules might load
    concurrently, does it make sense to have a non-null value for the <code
    class=idl-code>"loading"</code> event?
   <p>When the user agent completes each font load for a document
    <var>doc</var>, it must run the following steps:
   <ol>
    <li>Let <var>font loader</var> be the value of the <code
     class=idl-code>fontloader</code> attribute of <var>doc</var>.
    <li>If none of the resources listed for the ‘<a
     href="#descdef-src"><code class=property>src</code></a>’ descriptor
     contain valid data, <a href="#fire-a-font-load-event">fire a font load
     event</a> named <a id=fontloader-error><code
     class=idl-code>"error"</code></a> with <var>font face</var> the
     <code>@font-face</code> rule that caused this load to start and
     <var>error</var> [something?] at <var>font loader</var>.
    <li>Otherwise, <a href="#fire-a-font-load-event">fire a font load
     event</a> named <a id=fontloader-load><code
     class=idl-code>"load"</code></a> with <var>font face</var> the
     <code>@font-face</code> rule that caused this load to start and
     <var>error</var> [something?] at <var>font loader</var>.
   </ol>
   <p>When the user agent completes the final font load for document
    <var>doc</var>, it must run the following steps:
   <ol>
    <li>Let <var>font loader</var> be the value of the <code
     class=idl-code>fontloader</code> attribute of <var>doc</var>.
    <li>Set the <code class=idl-code>loading</code> attribute of <var>font
     loader</var> to false.
    <li><a href="#fire-a-font-load-event">Fire a font load event</a> named <a
     id=fontloader-loadingdone><code class=idl-code>"loadingdone"</code></a>
     with <var>font face rule</var>, set to the last font to load, and
     <var>error</var> at <var>font loader</var>.
   </ol>
   <p>Note: For example, if three fonts are loaded at the same time, a <code
    class=idl-code>"loading"</code> event followed by three <code
    class=idl-code>"loadstart"</code> events and three <code
    class=idl-code>"load"</code> or <code class=idl-code>"error"</code>
    events, followed by a <code class=idl-code>"loadingdone"</code> event will
    occur.
   <h4 id=methods><span class=secno>9.2.2 </span>Methods</h4>
   <p>The methods <code class=idl-code>loadFont</code> and <code
    class=idl-code>checkFont</code> must determine whether all fonts in the
    given font list have been loaded and are available. If all fonts are
    available, <code class=idl-code>checkFont</code> must return true, false
    if one or more fonts are not available. In the case of <code
    class=idl-code>loadFont</code>, if any fonts are downloadable fonts and
    have not already been loaded, the user agent must initiate the load of
    each of these fonts.
   <p>The <a id=fontloader-loadfont><code
    class=idl-code>loadFont(params)</code></a> method must use these steps:
   <ol>
    <li>Parse the value of the <code class=idl-code>font</code> member of
     <code class=idl-code>params</code>, using the CSS value syntax of the
     ‘<a href="#propdef-font"><code class=property>font</code></a>’
     property.
    <li>If a syntax error occurs, return.
    <li>Otherwise, let <var>font family list</var> be the set of families and
     <var>font style</var> be the other font style attributes.
    <li>For each family in <var>font family list</var>, use the font matching
     rules to select the font faces that match the <var>font style</var>. In
     the case where these are font faces defined via <code>@font-face</code>
     rules, the use of ‘<a href="#descdef-unicode-range"><code
     class=property>unicode-range</code></a>’ means that this may be more
     than just a single font face.
    <li>Remove from the set of font faces all faces that have defined ‘<a
     href="#descdef-unicode-range"><code
     class=property>unicode-range</code></a>’ values that don't intersect
     the range of character values in the <code class=idl-code>text</code>
     member of <code class=idl-code>params</code> and set this to be the
     <var>font load list</var>.
    <li>For all of the font faces in the <var>font load list</var>, initiate
     the load of any font that has not already been loaded and return.
    <li>When all fonts in the <var>font load list</var> have been loaded, fire
     the appropriate callback handler. If all fonts loaded successfully, call
     the callback specified by the <code class=idl-code>onsuccess</code>
     member of <code class=idl-code>params</code>. If an error occurred with
     any one of the fonts in the <var>font load list</var> or if the list is
     empty, call the callback specified by the <code
     class=idl-code>onerror</code> member of <code
     class=idl-code>params</code>.
   </ol>
   <p>Callbacks for <code class=idl-code>loadFont</code> fire in addition to
    the callbacks that fire due to font event handlers.
   <p>The <a id=fontloader-checkfont><code class=idl-code>checkFont(font,
    text)</code></a> method must use these steps:
   <ol>
    <li>Parse the value of the <code class=idl-code>font</code> parameter,
     using the CSS value syntax of the ‘<a href="#propdef-font"><code
     class=property>font</code></a>’ property.
    <li>If a syntax error occurs, return <code class=idl-code>false</code>.
    <li>Otherwise, let <var>font family list</var> be the set of families and
     <var>font style</var> be the other font style attributes.
    <li>For each family in <var>font family list</var>, use the font matching
     rules to select the font faces that match the <var>font style</var>. In
     the case where these are font faces defined via <code>@font-face</code>
     rules, the use of ‘<a href="#descdef-unicode-range"><code
     class=property>unicode-range</code></a>’ means that this may be more
     than just a single font face.
    <li>Remove from the set of font faces all faces that have defined ‘<a
     href="#descdef-unicode-range"><code
     class=property>unicode-range</code></a>’ values that don't intersect
     the range of character values in the <code class=idl-code>text</code>
     parameter and set this to be the <var>font load list</var>.
    <li>If the <var>font load list</var> contains no font faces, return <code
     class=idl-code>false</code>.
    <li>If all fonts in the <var>font load list</var> have already
     successfully been loaded, return <code class=idl-code>true</code>.
     Otherwise, return <code class=idl-code>false</code>.
   </ol>
   <p>The <code class=idl-code>font</code> parameter of <code
    class=idl-code>checkFont</code> and the <code class=idl-code>font</code>
    member of <code class=idl-code>params</code> parameter of <code
    class=idl-code>loadFont</code> both specify the list of fonts to load.
    These values must be parsed using the same syntax as values for the CSS
    ‘<a href="#propdef-font"><code class=property>font</code></a>’
    property, the same way the <code class=idl-code>font</code> attribute of
    the <code>CanvasRenderingContext2D</code> is interpreted. <a href="#HTML5"
    rel=biblioentry>[HTML5]<!--{{!HTML5}}--></a> This yields a list of font
    families along with font style attributes.
   <p>Because the number of fonts loaded depends on the how many fonts are
    used for a given piece of text, in some cases whether fonts need to be
    loaded or not may not be known. The <a
    id=fontloader-notifywhenfontsready><code
    class=idl-code>notifyWhenFontsReady</code></a> method provides a way for
    authors to avoid having to keep track of which fonts have or haven't been
    loaded before examining content affected by which font is used.
   <p>The <code class=idl-code>notifyWhenFontsReady(fontsReadyCallback)</code>
    method must use these steps:
   <ol>
    <li>Let <var>font loader</var> be the value of the <code
     class=idl-code>fontloader</code> attribute of <var>doc</var>.
    <li>Add the value of the <code class=idl-code>fontsReadyCallback</code>
     parameter to the <var>notify</var> callback list of the <var>font
     loader</var> and return.
    <li>Once all pending layout operations have completed, determine whether
     font resources need to be loaded.
    <li>If no loads are in progress, copy the contents of the
     <var>notify</var> callback list to the <var>notify pending</var> list of
     the <var>font loader</var> and clear out the <var>notify</var> list.
     After the <code class=idl-code>"loadingdone"</code> event fires, call
     each of the callbacks in the <var>notify pending</var> list and clear out
     the <var>notify pending</var> list.
    <li>Otherwise, after all font loads complete and subsequent layout
     operations finish, again check whether loads are in progress. If no loads
     are in progress, execute the previous step. If fonts are still loading,
     continue waiting until those loads complete and repeat this step.
   </ol>
   <p>Authors should note here that the callback only fires once, the method
    needs to be called again when further font loads might occur. This method
    is similar to the callback function of the <code
    class=idl-code>"loadingdone"</code> event handler, except that in this
    case the callback will <strong>always</strong> get called, even when no
    font loads occur because the fonts in question are already loaded. It's a
    simple, easy way to sync code to font loads without the need to keep track
    of what fonts are needed and precisely when they load.
   <p>Note that the user agent may need to iterate over multiple font loads
    before the notify callback is called. This can occur with font fallback
    situations, where one font in the fontlist is loaded but doesn't contain a
    particular glyph and other fonts in the fontlist need to be loaded. The
    notify callback only fires after layout operations complete and no
    additional font loads are necessary.
   <h3 id=font-load-event-examples><span class=secno>9.3 </span>Font load
    event examples</h3>
   <div class=example>
    <p>To show content only after all font loads complete:</p>
    <pre>  document.fontloader.onloadingdone = function() {
     var content = document.getElementById("content");
     content.style.visibility = "visible";
   }
 </pre>
   </div>
   <div class=example>
    <p>Drawing text in a canvas with a downloadable font, explicitly
     initiating the font download and drawing upon completion:</p>
    <pre>  function drawStuff() {
     var ctx = document.getElementById("c").getContext("2d");
     ctx.fillStyle = "red";
     ctx.font = "50px MyDownloadableFont";
     ctx.fillText("Hello!", 100, 100);
   }
   document.fontloader.loadFont({font: "50px MyDownloadableFont",
                                 onsuccess: drawStuff,
                                 onerror: handleError});</pre>
   </div>
   <div class=example>
    <p>A rich text editing application may need to measure text elements after
     editing operations have taken place. Since style changes may or may not
     require additional fonts to be downloaded, or the fonts may already have
     been downloaded, the measurement procedures need to occur after those
     font loads complete:</p>
    <pre>  function measureTextElements() {
     // contents can now be measured using the metrics of
     // the downloadable font(s)
   }
   function doEditing() {
     // content/layout operations that may cause additional font loads
     document.fontloader.notifyWhenFontsReady(measureTextElements);
   }
 </pre>
   </div>
   <h2 class=no-num id=platform-props-to-css>Appendix A: Mapping platform font
    properties to CSS properties</h2>
   <p><em>This appendix is included as background for some of the problems and
    situations that are described in other sections. It should be viewed as
    informative only.</em>
   <p>Font properties in CSS are designed to be independent of the underlying
    font formats used; they can be used to specify bitmap fonts, Type1 fonts,
    SVG fonts in addition to the common TrueType and OpenType fonts. But there
    are facets of the TrueType and OpenType formats that often cause confusion
    for authors and present challenges to implementers on different platforms.
   <p>Originally developed at Apple, TrueType was designed as an outline font
    format for both screen and print. Microsoft joined Apple in developing the
    TrueType format and both platforms have supported TrueType fonts since
    then. Font data in the TrueType format consists of a set of tables
    distinguished with common four-letter tag names, each containing a
    specific type of data. For example, naming information, including
    copyright and license information, is stored in the ‘<code
    class=property>name</code>’ table. The <a
    href="#character-map"><em>character map</em></a> (‘<code
    class=property>cmap</code>’) table contains a mapping of character
    encodings to glyphs. Apple later added additional tables for supporting
    enhanced typographic functionality; these are now called Apple Advanced
    Typography, or AAT, fonts. Microsoft and Adobe developed a separate set of
    tables for advanced typography and called their format OpenType <a
    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>.
   <p>In many cases the font data used under Microsoft Windows or Linux is
    slightly different from the data used under Apple's Mac OS X because the
    TrueType format allowed for explicit variation across platforms. This
    includes font metrics, names and <a href="#character-map"><em>character
    map</em></a> data.
   <p>Specifically, font family name data is handled differently across
    platforms. For TrueType and OpenType fonts these names are contained in
    the ‘<code class=property>name</code>’ table, in name records with
    name ID 1. Mulitple names can be stored for different locales but
    Microsoft recommends fonts always include at least a US English version of
    the name. On Windows, Microsoft made the decision for backwards
    compatibility to limit this family name to a maximum of four faces; for
    larger groupings the "preferred family" (name ID 16) or "WWS family" (name
    ID 21) can be used. Other platforms such as OSX don't have this
    limitation, the family name is used to define all possible groupings.
   <p>Other name table data provides names used to uniquely identify a
    specific face within a family. The full font name (name ID 4) and the
    Postscript name (name ID 6) describe a single face uniquely. The bold face
    of the Gill Sans family has a fullname of "Gill Sans Bold" and a
    Postscript name of "GillSans-Bold". There can be multiple localized
    versions of the fullname for a given face but the Postscript name is
    always a unique name made from a limited set of ASCII characters.
   <p>On various platforms, different names are used to search for a font. For
    example, with the Windows GDI CreateIndirectFont API, either a family or
    fullname can be used to lookup a face while on Mac OS X the
    ATSFontFindFromName and ATSFontFindFromPostScriptName API calls are used
    to lookup a given face using the fullname and Postscript name. Under
    Linux, the fontconfig API allows fonts to be searched using any of these
    names. In situations where platform API's automatically substitute other
    font choices, it may be necessary to verify a returned font matches a
    given name.
   <p>The weight of a given face can be determined via the usWeightClass field
    of the OS/2 table or inferred from the style name (name ID 2). Likewise,
    the width can be determined via the usWidthClass of the OS/2 table or
    inferred from the style name. For historical reasons related to synthetic
    bolding at weights 200 or lower with the Windows GDI API, font designers
    have sometimes skewed values in the OS/2 table to avoid these weights.
   <p>Rendering complex scripts that use contextual shaping such as Thai,
    Arabic and Devanagari requires features present only in OpenType or AAT
    fonts. Currently, complex script rendering is supported on Windows and
    Linux using OpenType font features while AAT font features are used under
    Mac OS X. Apple has indicated it intends to support complex script
    rendering using OpenType font features in the future.
   <h2 class=no-num id=ch-ch-ch-changes>Changes</h2>
   <h3 class=no-num id=recent-changes> Changes from the <a
    href="http://www.w3.org/TR/2012/WD-css3-fonts-20121211/">December 2012
    CSS3 Fonts Working Draft</a></h3>
   <p>Major changes include:
   <ul>
    <li><code>loadFont</code> method takes a dictionary parameter that
     includes callbacks
    <li>Added example of system font names used as normal font family name
    <li>Added conformance section
    <li>Added CORS cross-origin request algorithm parameters
    <li>Added specification of Unicode caseless matching for font family names
     based on WG resolution
    <li>Include issue of synthetic oblique angle in CJK vertical text runs
    <li>Minor editorial tweaks hither and thither
   </ul>
   <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
   <p>I'd like to thank Tal Leming, Jonathan Kew and Christopher Slye for all
    their help and feedback. John Hudson was kind enough to take the time to
    explain the subtleties of OpenType language tags and provided the example
    of character variant usage for displaying text on Byzantine seals. Ken
    Lunde and Eric Muller provided valuable feedback on CJK OpenType features
    and Unicode variation selectors. The idea for supporting font features by
    using font-variant subproperties originated with Håkon Wium Lie, Adam
    Twardoch and Tal Leming. Elika Etemad supplied some of the initial design
    ideas for the <code>@font-feature-values</code> rule. Several members of
    the Google Fonts team provided helpful feedback on font load events, as
    did Boris Zbarsky, Jonas Sicking and ms2ger. Thanks also to House
    Industries for allowing the use of Ed Interlock in the discretionary
    ligatures example.
   <p>A special thanks to Robert Bringhurst for the sublime mind expansion
    that is <em>The Elements of Typographic Style</em>.
   <h2 class=no-num id=conformance> Conformance</h2>
   <h3 class=no-num id=conventions> Document Conventions</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
 . However, for readability, these words do not appear in all uppercase
    letters in this specification.
   <p>All of the text of this specification is normative except sections
    explicitly marked as non-normative, examples, and notes. <a
    href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>
   <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:
   <div class=example>
    <p>This is an example of an informative example.
   </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 class=note>Note, this is an informative note.
   <h3 class=no-num id=conformance-classes> Conformance Classes</h3>
   <p>Conformance to CSS Fonts Level 3 Module is defined for three conformance
    classes:
   <dl>
    <dt><dfn id=style-sheet title="style sheet!!as conformance class">style
     sheet</dfn>
    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
     style sheet</a>.
    <dt><dfn id=renderer>renderer</dfn>
    <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.
    <dt><dfn id=authoring-tool>authoring tool</dfn>
    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
     that writes a style sheet.
   </dl>
   <p>A style sheet is conformant to CSS Fonts Level 3 Module if all of its
    declarations that use properties defined in this module have values that
    are valid according to the generic CSS grammar and the individual grammars
    of each property as given in this module.
   <p>A renderer is conformant to CSS Fonts Level 3 Module if, in addition to
    interpreting the style sheet as defined by the appropriate specifications,
    it supports all the features defined by CSS Fonts Level 3 Module 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>An authoring tool is conformant to CSS Fonts Level 3 Module 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.
   <h3 class=no-num id=partial> Partial Implementations</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.
   <h3 class=no-num id=experimental> Experimental Implementations</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>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.
   <h3 class=no-num id=testing> Non-Experimental Implementations</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>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>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.
   <h2 class=no-num id=references>References</h2>
   <h3 class=no-num id=normative-references>Normative References</h3>
   <!--begin-normative-->
   <!-- Sorted by label -->
   <dl class=bibliography>
    <dt style="display: none"><!-- keeps the doc valid if the DL is empty -->
     <!---->
    <dt id=CHARMOD>[CHARMOD]
    <dd>Martin J. Dürst; et al. <a
     href="http://www.w3.org/TR/2005/REC-charmod-20050215/"><cite>Character
     Model for the World Wide Web 1.0: Fundamentals.</cite></a> 15 February
 . W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2005/REC-charmod-20050215/">http://www.w3.org/TR/2005/REC-charmod-20050215/</a>
     </dd>
    <!---->
    <dt id=CORS>[CORS]
    <dd>Anne van Kesteren. <a
     href="http://www.w3.org/TR/2013/CR-cors-20130129/"><cite>Cross-Origin
     Resource Sharing.</cite></a> 29 January 2013. W3C Candidate
     Recommendation. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2013/CR-cors-20130129/">http://www.w3.org/TR/2013/CR-cors-20130129/</a>
     </dd>
    <!---->
    <dt id=CSS21>[CSS21]
    <dd>Bert Bos; et al. <a
     href="http://www.w3.org/TR/2011/REC-CSS2-20110607/"><cite>Cascading Style
     Sheets Level 2 Revision 1 (CSS 2.1) Specification.</cite></a> 7 June
 . W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2011/REC-CSS2-20110607/">http://www.w3.org/TR/2011/REC-CSS2-20110607/</a>
     </dd>
    <!---->
    <dt id=CSS3VAL>[CSS3VAL]
    <dd>Håkon Wium Lie; Tab Atkins; Elika J. Etemad. <a
     href="http://www.w3.org/TR/2012/CR-css3-values-20120828/"><cite>CSS
     Values and Units Module Level 3.</cite></a> 28 August 2012. W3C Candidate
     Recommendation. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2012/CR-css3-values-20120828/">http://www.w3.org/TR/2012/CR-css3-values-20120828/</a>
     </dd>
    <!---->
    <dt id=HTML5>[HTML5]
    <dd>Ian Hickson. <a
     href="http://www.w3.org/TR/2012/CR-html5-20121217/"><cite>HTML5.</cite></a>
 December 2012. W3C Candidate Recommendation. (Work in progress.) URL:
     <a
     href="http://www.w3.org/TR/2012/CR-html5-20121217/">http://www.w3.org/TR/2012/CR-html5-20121217/</a>
     </dd>
    <!---->
    <dt id=OPEN-FONT-FORMAT>[OPEN-FONT-FORMAT]
    <dd><a
     href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c052136_ISO_IEC_14496-22_2009(E).zip"><cite>Information
     technology — Coding of audio-visual objects — Part 22: Open Font
     Format.</cite></a> International Organization for Standardization.
     ISO/IEC 14496-22:2009. URL: <a
     href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c052136_ISO_IEC_14496-22_2009(E).zip">http://standards.iso.org/ittf/PubliclyAvailableStandards/c052136_ISO_IEC_14496-22_2009(E).zip</a>
     </dd>
    <!---->
    <dt id=OPENTYPE>[OPENTYPE]
    <dd><a
     href="http://www.microsoft.com/typography/otspec/default.htm"><cite>OpenType
     specification.</cite></a> Microsoft. URL: <a
     href="http://www.microsoft.com/typography/otspec/default.htm">http://www.microsoft.com/typography/otspec/default.htm</a>
     </dd>
    <!---->
    <dt id=OPENTYPE-FEATURES>[OPENTYPE-FEATURES]
    <dd><a
     href="http://www.microsoft.com/typography/otspec/featurelist.htm"><cite>OpenType
     feature registry.</cite></a> Microsoft. URL: <a
     href="http://www.microsoft.com/typography/otspec/featurelist.htm">http://www.microsoft.com/typography/otspec/featurelist.htm</a>
     </dd>
    <!---->
    <dt id=RFC2119>[RFC2119]
    <dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
     words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
     RFC 2119. URL: <a
     href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
     </dd>
    <!---->
    <dt id=UAX15>[UAX15]
    <dd>Mark Davis; Ken Whistler. <a
     href="http://www.unicode.org/reports/tr15/"><cite>Unicode Normalization
     Forms.</cite></a> 31 August 2012. Unicode Standard Annex #15. URL: <a
     href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a>
     </dd>
    <!---->
    <dt id=UAX29>[UAX29]
    <dd>Mark Davis. <a
     href="http://www.unicode.org/reports/tr29/"><cite>Unicode Text
     Segmentation.</cite></a> 12 September 2012. Unicode Standard Annex #29.
     URL: <a
     href="http://www.unicode.org/reports/tr29/">http://www.unicode.org/reports/tr29/</a>
     </dd>
    <!---->
    <dt id=UNICODE6>[UNICODE6]
    <dd>The Unicode Consortium. <a
     href="http://www.unicode.org/versions/Unicode6.2.0/"><cite>The Unicode
     Standard, Version 6.2.0.</cite></a> Defined by: The Unicode Standard,
     Version 6.2.0 URL: <a
     href="http://www.unicode.org/versions/Unicode6.2.0/">http://www.unicode.org/versions/Unicode6.2.0/</a>
     </dd>
    <!---->
   </dl>
   <!--end-normative-->
   <!--{{!CSS21}}-->
   <!--{{!CSS3VAL}}-->
   <!--{{!OPENTYPE}}-->
   <!--{{!OPENTYPE-FEATURES}}-->
   <!--{{!OPEN-FONT-FORMAT}}-->
   <!--{{!UNICODE6}}-->
   <!--{{!UAX15}}-->
   <!--{{!UAX29}}-->
   <!--{{!CORS}}-->
   <!--{{!HTML5}}-->
   <!--{{!CHARMOD}}-->
   <h3 class=no-num id=other-references>Other References</h3>
   <!--begin-informative-->
   <!-- Sorted by label -->
   <dl class=bibliography>
    <dt style="display: none"><!-- keeps the doc valid if the DL is empty -->
     <!---->
    <dt id=AAT-FEATURES>[AAT-FEATURES]
    <dd><a href="http://developer.apple.com/fonts/registry/"><cite>Apple
     Advanced Typography font feature registry.</cite></a> Apple. URL: <a
     href="http://developer.apple.com/fonts/registry/">http://developer.apple.com/fonts/registry/</a>
     </dd>
    <!---->
    <dt id=ARABIC-TYPO>[ARABIC-TYPO]
    <dd>Huda Smitshuijzen AbiFares. <cite>Arabic Typography: A Comprehensive
     Sourcebook.</cite> Saqi Books. 2001. ISBN 0-86356-347-3.</dd>
    <!---->
    <dt id=CHARMOD-NORM>[CHARMOD-NORM]
    <dd>François Yergeau; et al. <a
     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/"><cite>Character
     Model for the World Wide Web 1.0: Normalization.</cite></a> 1 May 2012.
     W3C Working Draft. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/">http://www.w3.org/TR/2012/WD-charmod-norm-20120501/</a>
     </dd>
    <!---->
    <dt id=CJKV-INFO-PROCESSING>[CJKV-INFO-PROCESSING]
    <dd>Ken Lunde. <cite>CJKV Information Processing, Second Edition.</cite>
     O'Reilly Media, Inc. 2009. ISBN 0-596-51447-1.</dd>
    <!---->
    <dt id=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]
    <dd>L. David Baron. <a
     href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/"><cite>CSS
     Conditional Rules Module Level 3.</cite></a> 13 December 2012. W3C
     Working Draft. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/">http://www.w3.org/TR/2012/WD-css3-conditional-20121213/</a>
     </dd>
    <!---->
    <dt id=CSS3TEXT>[CSS3TEXT]
    <dd>Elika J. Etemad; Koji Ishii. <a
     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/"><cite>CSS Text
     Module Level 3.</cite></a> 13 November 2012. W3C Working Draft. (Work in
     progress.) URL: <a
     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/">http://www.w3.org/TR/2012/WD-css3-text-20121113/</a>
     </dd>
    <!---->
    <dt id=DIGITAL-TYPOGRAPHY>[DIGITAL-TYPOGRAPHY]
    <dd>Richard Rubinstein. <cite>Digital Typography, An Introduction to Type
     and Composition for Computer System Design.</cite> Addison-Wesley. 1988.
     ISBN 0-201-17633-5.</dd>
    <!---->
    <dt id=DOM-LEVEL-2-STYLE>[DOM-LEVEL-2-STYLE]
    <dd>Chris Wilson; Philippe Le Hégaret; Vidur Apparao. <a
     href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/"><cite>Document
     Object Model (DOM) Level 2 Style Specification.</cite></a> 13 November
 . W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/">http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/</a>
     </dd>
    <!---->
    <dt id=ELEMTYPO>[ELEMTYPO]
    <dd>Robert Bringhurst. <cite>The Elements of Typographic Style, Version
 .1.</cite> Hartley &amp; Marks. 2005. ISBN 0-88179-206-3.</dd>
    <!---->
    <dt id=LANGCULTTYPE>[LANGCULTTYPE]
    <dd>John D. Berry, Ed. <cite>Language Culture Type.</cite> Graphis. 2001.
     ISBN 1-932026-01-0.</dd>
    <!---->
    <dt id=OPENTYPE-FONT-GUIDE>[OPENTYPE-FONT-GUIDE]
    <dd><a
     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf"><cite>OpenType
     User Guide.</cite></a> FontShop International. URL: <a
     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf">https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf</a>
     </dd>
    <!---->
    <dt id=RASTER-TRAGEDY>[RASTER-TRAGEDY]
    <dd>Beat Stamm. <a href="http://www.rastertragedy.com/"><cite>The Raster
     Tragedy at Low-Resolution Revisited.</cite></a> 7 December 2011. URL: <a
     href="http://www.rastertragedy.com/">http://www.rastertragedy.com/</a></dd>
    <!---->
    <dt id=WINDOWS-GLYPH-PROC>[WINDOWS-GLYPH-PROC]
    <dd>John Hudson. <a
     href="http://www.microsoft.com/typography/developers/opentype/default.htm"><cite>Windows
     Glyph Processing.</cite></a> Microsoft Typogrraphy. URL: <a
     href="http://www.microsoft.com/typography/developers/opentype/default.htm">http://www.microsoft.com/typography/developers/opentype/default.htm</a>
     </dd>
    <!---->
   </dl>
   <!--end-informative-->
   <!--{{ARABIC-TYPO}}-->
   <!--{{CJKV-INFO-PROCESSING}}-->
   <!--{{DIGITAL-TYPOGRAPHY}}-->
   <!--{{DOM-LEVEL-2-STYLE}}-->
   <!--{{ELEMTYPO}}-->
   <!--{{LANGCULTTYPE}}-->
   <!--{{OPENTYPE-FONT-GUIDE}}-->
   <!--{{RASTER-TRAGEDY}}-->
   <!--{{WINDOWS-GLYPH-PROC}}-->
   <!--{{CHARMOD-NORM}}-->
   <!--{{AAT-FEATURES}}-->
   <!--{{CSS3-CONDITIONAL}}-->
   <!--{{CSS3TEXT}}-->
   <h2 class=no-num id=index>Index</h2>
   <!--begin-index-->
   <ul class=indexlist>
    <li>&lt;absolute-size&gt;, <a href="#ltabsolute-sizegt"
     title="&lt;absolute-size&gt;"><strong>3.5</strong></a>
    <li><var>&lt;common-lig-values></var>, <a href="#ltcommon-lig-values"
     title="&lt;common-lig-values>"><strong>6.4</strong></a>
    <li><var>&lt;contextual-alt-values&gt;</var>, <a
     href="#ltcontextual-alt-valuesgt"
     title="&lt;contextual-alt-values&gt;"><strong>6.4</strong></a>
    <li><var>&lt;discretionary-lig-values></var>, <a
     href="#ltdiscretionary-lig-values"
     title="&lt;discretionary-lig-values>"><strong>6.4</strong></a>
    <li><var>&lt;east-asian-variant-values&gt;</var>, <a
     href="#lteast-asian-variant-valuesgt"
     title="&lt;east-asian-variant-values&gt;"><strong>6.10</strong></a>
    <li><var>&lt;east-asian-width-values&gt;</var>, <a
     href="#lteast-asian-width-valuesgt"
     title="&lt;east-asian-width-values&gt;"><strong>6.10</strong></a>
    <li><var>&lt;feature-ident&gt;</var>, <a href="#ltfeature-identgt"
     title="&lt;feature-ident&gt;"><strong>6.9</strong></a>
    <li><var>&lt;feature-index&gt;</var>, <a href="#ltfeature-indexgt"
     title="&lt;feature-index&gt;"><strong>6.9</strong></a>
    <li><var>&lt;feature-tag-value&gt;</var>, <a href="#ltfeature-tag-valuegt"
     title="&lt;feature-tag-value&gt;"><strong>6.12</strong></a>
    <li><var>&lt;feature-type&gt;</var>, <a href="#ltfeature-typegt"
     title="&lt;feature-type&gt;"><strong>6.9</strong></a>
    <li>&lt;font-description&gt;, <a href="#ltfont-descriptiongt"
     title="&lt;font-description&gt;"><strong>4.1</strong></a>
    <li>&lt;font-face-name&gt;, <a href="#ltfont-face-namegt"
     title="&lt;font-face-name&gt;"><strong>4.3</strong></a>
    <li><var>&lt;font-family&gt;</var>, <a href="#ltfont-familygt"
     title="&lt;font-family&gt;"><strong>6.9</strong></a>
    <li><var>&lt;font-variant-css21&gt;</var>, <a
     href="#ltfont-variant-css21gt"
     title="&lt;font-variant-css21&gt;"><strong>3.7</strong></a>
    <li><var>&lt;historical-lig-values></var>, <a
     href="#lthistorical-lig-values"
     title="&lt;historical-lig-values>"><strong>6.4</strong></a>
    <li>&lt;length&gt;, <a href="#ltlengthgt" title="&lt;length&gt;">3.5</a>
    <li>&lt;number&gt;, <a href="#ltnumbergt" title="&lt;number&gt;">3.6</a>
    <li><var>&lt;numeric-figure-values&gt;</var>, <a
     href="#ltnumeric-figure-valuesgt"
     title="&lt;numeric-figure-values&gt;"><strong>6.7</strong></a>
    <li><var>&lt;numeric-fraction-values&gt;</var>, <a
     href="#ltnumeric-fraction-valuesgt"
     title="&lt;numeric-fraction-values&gt;"><strong>6.7</strong></a>
    <li><var>&lt;numeric-spacing-values&gt;</var>, <a
     href="#ltnumeric-spacing-valuesgt"
     title="&lt;numeric-spacing-values&gt;"><strong>6.7</strong></a>
    <li>&lt;percentage&gt;, <a href="#ltpercentagegt-"
     title="&lt;percentage&gt;">3.5</a>
    <li>&lt;relative-size&gt;, <a href="#ltrelative-sizegt"
     title="&lt;relative-size&gt;"><strong>3.5</strong></a>
    <li>&lt;urange&gt;, <a href="#lturangegt"
     title="&lt;urange&gt;"><strong>4.5</strong></a>
    <li>@font-face, <a href="#font-face"
     title="@font-face"><strong>4.1</strong></a>, <a href="#font-face0"
     title="@font-face">4.1</a>, <a href="#font-face1"
     title="@font-face">4.3</a>
    <li>all-petite-caps, <a href="#all-petite-caps"
     title=all-petite-caps><strong>6.6</strong></a>
    <li>all-small-caps, <a href="#all-small-caps"
     title=all-small-caps><strong>6.6</strong></a>
    <li>annotation, <a href="#annotationltfeature-value-namegt"
     title=annotation><strong>6.8</strong></a>
    <li>aspect value, <a href="#aspect-value0" title="aspect
     value"><strong>3.6</strong></a>
    <li>at-rules, <a href="#at-rule" title=at-rules>4.1</a>
    <li>authoring tool, <a href="#authoring-tool" title="authoring
     tool"><strong>#</strong></a>
    <li>character map, <a href="#character-map" title="character
     map"><strong>5.2</strong></a>
    <li>character-variant, <a href="#character-variantltfeature-value-namegt"
     title=character-variant><strong>6.8</strong></a>
    <li>common-ligatures, <a href="#common-ligatures"
     title=common-ligatures><strong>6.4</strong></a>
    <li>contextual, <a href="#contextual"
     title=contextual><strong>6.4</strong></a>
    <li>CSSFontFaceRule, <a href="#cssfontfacerule"
     title=CSSFontFaceRule><strong>8.1</strong></a>
    <li>CSSFontFeatureValuesRule, <a href="#cssfontfeaturevaluesrule"
     title=CSSFontFeatureValuesRule><strong>8.2</strong></a>
    <li>cursive, definition of, <a href="#cursive0" title="cursive, definition
     of"><strong>#</strong></a>
    <li>default face, <a href="#default-face" title="default
     face"><strong>5.2</strong></a>
    <li>diagonal-fractions, <a href="#diagonal-fractions"
     title=diagonal-fractions><strong>6.7</strong></a>
    <li>discretionary-ligatures, <a href="#discretionary-ligatures"
     title=discretionary-ligatures><strong>6.4</strong></a>
    <li>fantasy, definition of, <a href="#fantasy0" title="fantasy, definition
     of"><strong>#</strong></a>
    <li>fire a font load event, <a href="#fire-a-font-load-event" title="fire
     a font load event"><strong>9.2.1</strong></a>
    <li>font, <a href="#propdef-font" title=font><strong>3.7</strong></a>
    <li>font load, <a href="#font-load" title="font
     load"><strong>9.2</strong></a>
    <li>font-family, <a href="#descdef-font-family"
     title=font-family><strong>4.2</strong></a>, <a
     href="#propdef-font-family" title=font-family><strong>3.1</strong></a>
    <li>font-feature-settings, <a href="#propdef-font-feature-settings"
     title=font-feature-settings><strong>6.12</strong></a>
    <li>font-feature-settings (descriptor), <a
     href="#descdef-font-feature-settings" title="font-feature-settings
     (descriptor)"><strong>4.6</strong></a>
    <li>font-kerning, <a href="#propdef-font-kerning"
     title=font-kerning><strong>6.3</strong></a>
    <li>font-language-override, <a href="#propdef-font-language-override"
     title=font-language-override><strong>6.13</strong></a>
    <li>font-size, <a href="#propdef-font-size"
     title=font-size><strong>3.5</strong></a>
    <li>font-size-adjust, <a href="#propdef-font-size-adjust"
     title=font-size-adjust><strong>3.6</strong></a>
    <li>font-stretch, <a href="#propdef-font-stretch"
     title=font-stretch><strong>3.3</strong></a>
    <li>font-stretch (descriptor), <a href="#descdef-font-stretch"
     title="font-stretch (descriptor)"><strong>4.4</strong></a>
    <li>font-style, <a href="#propdef-font-style"
     title=font-style><strong>3.4</strong></a>
    <li>font-style (descriptor), <a href="#descdef-font-style"
     title="font-style (descriptor)"><strong>4.4</strong></a>
    <li>font-synthesis, <a href="#propdef-font-synthesis"
     title=font-synthesis><strong>3.8</strong></a>
    <li>font-variant, <a href="#propdef-font-variant"
     title=font-variant><strong>6.11</strong></a>
    <li>font-variant (descriptor), <a href="#descdef-font-variant"
     title="font-variant (descriptor)"><strong>4.6</strong></a>
    <li>font-variant-alternates, <a href="#propdef-font-variant-alternates"
     title=font-variant-alternates><strong>6.8</strong></a>
    <li>font-variant-caps, <a href="#propdef-font-variant-caps"
     title=font-variant-caps><strong>6.6</strong></a>
    <li>font-variant-east-asian, <a href="#propdef-font-variant-east-asian"
     title=font-variant-east-asian><strong>6.10</strong></a>
    <li>font-variant-ligatures, <a href="#propdef-font-variant-ligatures"
     title=font-variant-ligatures><strong>6.4</strong></a>
    <li>font-variant-numeric, <a href="#propdef-font-variant-numeric"
     title=font-variant-numeric><strong>6.7</strong></a>
    <li>font-variant-position, <a href="#propdef-font-variant-position"
     title=font-variant-position><strong>6.5</strong></a>
    <li>font-weight, <a href="#propdef-font-weight"
     title=font-weight><strong>3.2</strong></a>
    <li>font-weight (descriptor), <a href="#descdef-font-weight"
     title="font-weight (descriptor)"><strong>4.4</strong></a>
    <li>full-width, <a href="#full-width"
     title=full-width><strong>6.10</strong></a>
    <li>historical-forms, <a href="#historical-forms"
     title=historical-forms><strong>6.8</strong></a>
    <li>historical-ligatures, <a href="#historical-ligatures"
     title=historical-ligatures><strong>6.4</strong></a>
    <li>jis04, <a href="#jis04" title=jis04><strong>6.10</strong></a>
    <li>jis78, <a href="#jis78" title=jis78><strong>6.10</strong></a>
    <li>jis83, <a href="#jis83" title=jis83><strong>6.10</strong></a>
    <li>jis90, <a href="#jis90" title=jis90><strong>6.10</strong></a>
    <li>lining-nums, <a href="#lining-nums"
     title=lining-nums><strong>6.7</strong></a>
    <li>monospace, definition of, <a href="#monospace0" title="monospace,
     definition of"><strong>#</strong></a>
    <li>no-common-ligatures, <a href="#no-common-ligatures"
     title=no-common-ligatures><strong>6.4</strong></a>
    <li>no-contextual, <a href="#no-contextual"
     title=no-contextual><strong>6.4</strong></a>
    <li>no-discretionary-ligatures, <a href="#no-discretionary-ligatures"
     title=no-discretionary-ligatures><strong>6.4</strong></a>
    <li>no-historical-ligatures, <a href="#no-historical-ligatures"
     title=no-historical-ligatures><strong>6.4</strong></a>
    <li>normal, <a href="#normal" title=normal><strong>6.6</strong></a>, <a
     href="#normal0" title=normal><strong>6.7</strong></a>, <a href="#normal1"
     title=normal><strong>6.8</strong></a>, <a href="#normal2"
     title=normal><strong>6.10</strong></a>
    <li>oldstyle-nums, <a href="#oldstyle-nums"
     title=oldstyle-nums><strong>6.7</strong></a>
    <li>ordinal, <a href="#ordinal" title=ordinal><strong>6.7</strong></a>
    <li>ornaments, <a href="#ornamentsltfeature-value-namegt"
     title=ornaments><strong>6.8</strong></a>
    <li>petite-caps, <a href="#petite-caps"
     title=petite-caps><strong>6.6</strong></a>
    <li>proportional-nums, <a href="#proportional-nums"
     title=proportional-nums><strong>6.7</strong></a>
    <li>proportional-width, <a href="#proportional-width"
     title=proportional-width><strong>6.10</strong></a>
    <li>renderer, <a href="#renderer" title=renderer><strong>#</strong></a>
    <li>ruby, <a href="#ruby" title=ruby><strong>6.10</strong></a>
    <li>sans-serif, definition of, <a href="#sans-serif0" title="sans-serif,
     definition of"><strong>#</strong></a>
    <li>serif, definition of, <a href="#serif0" title="serif, definition
     of"><strong>#</strong></a>
    <li>simplified, <a href="#simplified"
     title=simplified><strong>6.10</strong></a>
    <li>slashed-zero, <a href="#slashed-zero"
     title=slashed-zero><strong>6.7</strong></a>
    <li>small-caps, <a href="#small-caps"
     title=small-caps><strong>6.6</strong></a>
    <li>src, <a href="#descdef-src" title=src><strong>4.3</strong></a>
    <li>stacked-fractions, <a href="#stacked-fractions"
     title=stacked-fractions><strong>6.7</strong></a>
    <li>style sheet
     <ul>
      <li>as conformance class, <a href="#style-sheet" title="style sheet, as
       conformance class"><strong>#</strong></a>
     </ul>
    <li>styleset, <a href="#stylesetltfeature-value-namegt"
     title=styleset><strong>6.8</strong></a>
    <li>stylistic, <a href="#stylisticltfeature-value-namegt"
     title=stylistic><strong>6.8</strong></a>
    <li>swash, <a href="#swashltfeature-value-namegt"
     title=swash><strong>6.8</strong></a>
    <li>tabular-nums, <a href="#tabular-nums"
     title=tabular-nums><strong>6.7</strong></a>
    <li>titling-caps, <a href="#titling-caps"
     title=titling-caps><strong>6.6</strong></a>
    <li>traditional, <a href="#traditional"
     title=traditional><strong>6.10</strong></a>
    <li>unicase, <a href="#unicase" title=unicase><strong>6.6</strong></a>
    <li>unicode-range, <a href="#descdef-unicode-range"
     title=unicode-range><strong>4.5</strong></a>
    <li>weight, <a href="#weight" title=weight><strong>2</strong></a>
    <li>width, <a href="#width" title=width><strong>2</strong></a>
   </ul>
   <!--end-index-->
   <h2 class=no-num id=property-index>Property index</h2>
   <!--begin-properties-->
   <table class=proptable>
    <thead>
     <tr>
      <th>Property
      <th>Values
      <th>Initial
      <th>Applies to
      <th>Inh.
      <th>Percentages
      <th>Media
    <tbody>
     <tr>
      <th><a class=property href="#propdef-font">font</a>
      <td>[ [ &lt;‘font-style’> || &lt;font-variant-css21> ||
       &lt;‘font-weight’> || &lt;‘font-stretch’> ]?
       &lt;‘font-size’> [ / &lt;‘line-height’> ]?
       &lt;‘font-family’> ] | caption | icon | menu | message-box |
       small-caption | status-bar
      <td>see individual properties
      <td>all elements
      <td>yes
      <td>see individual properties
      <td>visual
     <tr>
      <th><a class=property href="#descdef-font-family">font-family</a>
      <td>[ &lt;family-name> | &lt;generic-family> ]#
      <td>depends on user agent
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-feature-settings">font-feature-settings</a>
      <td>normal | &lt;feature-tag-value&gt;#
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-kerning">font-kerning</a>
      <td>auto | normal | none
      <td>auto
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-language-override">font-language-override</a>
      <td>normal | &lt;string&gt;
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-size">font-size</a>
      <td>&lt;absolute-size> | &lt;relative-size> | &lt;length> |
       &lt;percentage>
      <td>medium
      <td>all elements
      <td>yes
      <td>refer to parent element's font size
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-size-adjust">font-size-adjust</a>
      <td>none | auto | &lt;number>
      <td>none
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-stretch">font-stretch</a>
      <td>normal | ultra-condensed | extra-condensed | condensed |
       semi-condensed | semi-expanded | expanded | extra-expanded |
       ultra-expanded
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-style">font-style</a>
      <td>normal | italic | oblique
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-synthesis">font-synthesis</a>
      <td>none | [ weight || style ]
      <td>weight style
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-variant">font-variant</a>
      <td>normal | none | [ &lt;common-lig-values&gt; ||
       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
       character-variant(&lt;feature-value-name&gt;#) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
       ruby ]
      <td>normal
      <td>all elements
      <td>yes
      <td>see individual properties
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-alternates">font-variant-alternates</a>
      <td>normal | [ stylistic(&lt;feature-value-name&gt;) || historical-forms
       || styleset(&lt;feature-value-name&gt;#) ||
       character-variant(&lt;feature-value-name&gt;#) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-caps">font-variant-caps</a>
      <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
       | unicase | titling-caps
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
      <td>normal | [ &lt;east-asian-variant-values&gt; ||
       &lt;east-asian-width-values&gt; || ruby ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
      <td>normal | none | [ &lt;common-lig-values> ||
       &lt;discretionary-lig-values> || &lt;historical-lig-values> ||
       &lt;contextual-alt-values> ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-numeric">font-variant-numeric</a>
      <td>normal | [ &lt;numeric-figure-values&gt; ||
       &lt;numeric-spacing-values&gt; || &lt;numeric-fraction-values&gt; ||
       ordinal || slashed-zero ]
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property
       href="#propdef-font-variant-position">font-variant-position</a>
      <td>normal | sub | super
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#propdef-font-weight">font-weight</a>
      <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
       | 700 | 800 | 900
      <td>normal
      <td>all elements
      <td>yes
      <td>N/A
      <td>visual
   </table>
   <!--end-properties-->
   <!--begin-descriptors-->
   <table class=proptable>
    <thead>
     <tr>
      <th>Descriptor
      <th>Value
      <th>Initial
      <th>Percentages
      <th>Media
    <tbody>
     <tr>
      <th><a class=property href="#descdef-font-family">font-family</a>
      <td>&lt;family-name>
      <td>N/A
     <tr>
      <th><a class=property
       href="#propdef-font-feature-settings">font-feature-settings</a>
      <td>normal | &lt;feature-tag-value&gt;#
      <td>normal
     <tr>
      <th><a class=property href="#propdef-font-stretch">font-stretch</a>
      <td>normal | ultra-condensed | extra-condensed | condensed |
       semi-condensed | semi-expanded | expanded | extra-expanded |
       ultra-expanded
      <td>normal
     <tr>
      <th><a class=property href="#propdef-font-style">font-style</a>
      <td>normal | italic | oblique
      <td>normal
     <tr>
      <th><a class=property href="#propdef-font-variant">font-variant</a>
      <td>normal | [ &lt;common-lig-values&gt; ||
       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
       character-variant(&lt;feature-value-name&gt;#) ||
       swash(&lt;feature-value-name&gt;) ||
       ornaments(&lt;feature-value-name&gt;) ||
       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
       ruby ]
      <td>normal
     <tr>
      <th><a class=property href="#propdef-font-weight">font-weight</a>
      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
      <td>normal
     <tr>
      <th><a class=property href="#descdef-src">src</a>
      <td>[ &lt;uri> [format(&lt;string>#)]? | &lt;font-face-name> ]#
      <td>N/A
     <tr>
      <th><a class=property href="#descdef-unicode-range">unicode-range</a>
      <td>&lt;urange>#
      <td>U+0-10FFFF
   </table>
   <!--end-descriptors-->
   <script type="text/javascript">
 window.onload = function () {
   if (!("devicePixelRatio" in window && window.devicePixelRatio > 1)) return;
   var i, hiresElements = document.getElementsByClassName("hires");
   for (i = 0; i < hiresElements.length; i++) {
     var h = hiresElements[i];
     if (h.tagName != "IMG") continue;
     var src = h.getAttribute("src");
     var src2x = src.replace(/\.\w+$/, function(m) { return "@2x" + m; });
     h.src = src2x;
   }
 }
 </script>
 </html>
 <!-- Keep this comment at the end of the file
 Local variables:
 mode: sgml
 sgml-declaration:"~/SGML/HTML4.decl"
 sgml-default-doctype-name:"html"
 sgml-minimize-attributes:t
 sgml-nofill-elements:("pre" "style" "br")
 sgml-live-element-indicator:t
 sgml-omittag:nil
 sgml-shorttag:nil
 sgml-namecase-general:t
 sgml-general-insert-case:lower
 sgml-always-quote-attributes:t
 sgml-indent-step:nil
 sgml-indent-data:t
 sgml-parent-document:nil
 sgml-exposed-tags:nil
 sgml-local-catalogs:nil
 sgml-local-ecat-files:nil
 End:
 -->
 <!--
 to do:
 - wording of OpenType family name handling
 - handling combining sequences in the font matching algorithm
 - fix-up fi ligature example
 -->

Mercurial > drafts / annotate

css3-fonts/Overview.html@55bbedf65a90 (annotated)

css3-fonts/Overview.html