css-fonts/Fonts.html

Fri, 17 May 2013 17:03:30 +0900

author
John Daggett <jdaggett@mozilla.com>
date
Fri, 17 May 2013 17:03:30 +0900
changeset 8187
402870708eb9
parent 8178
ba0a2725b6cd
child 8197
1e26e4454f98
permissions
-rw-r--r--

[css-fonts] minor editorial tweaks

     1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
     2 "http://www.w3.org/TR/html4/strict.dtd">
     4 <html lang=en>
     5  <head><meta content="text/html;charset=utf-8" http-equiv=Content-Type>
     7   <title>CSS Fonts Module Level 3</title>
     8   <!--
     9       FIXME when publishing: copy the current default.css and link to
    10       "default.css" rather than "../default.css"
    11    -->
    12   <link href="../default.css" rel=stylesheet type="text/css">
    13   <link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
    14   <!-- I'm just experimenting here, don't get your bee in a bonnet -->
    15   <script src="http://use.typekit.com/xon2bky.js"
    16   type="text/javascript"></script>
    17   <script type="text/javascript">try{Typekit.load();}catch(e){}</script>
    19   <style type="text/css">
    21   body, th, td, h1, h2, h3, h4, h5, h6 {
    22     font-family: "myriad-pro", sans-serif !important;
    23   }
    25   body {
    26     padding: 2em 70px 2em 70px;
    27   }
    29   p + p, p.mtb {
    30     margin-top: 0.8em;
    31     text-indent: 0px;
    32   }
    34   #bolderlighter {
    35     width: 40%;
    36   }
    38   #bolderlighter th {
    39     text-align: center;
    40   }
    42   #fontformats td, #eventhandlers td, #fontformats th, #eventhandlers th {
    43     padding-right: 2em;
    44     text-align: left;
    45   }
    47   dd {
    48     margin-bottom: 1em;
    49   }
    51   #authors dd {
    52     margin-bottom: 0;
    53   }
    55   #fontstylematchingalg {
    56     list-style-type: lower-alpha;
    57   }
    59   #fontmatchingalg ul, #fontmatchingalg ol {
    60     margin-top: 0.8em;
    61   }
    63   #fontmatchingalg li + li {
    64     margin-top: 0.8em;
    65   }
    67   div.example {
    68     padding: 1em;
    69     margin-top: 1em;
    70   }
    72   div.example + div.example {
    73     margin-top: 2em;
    74   }
    76   div.figure {
    77     page-break-inside: avoid;
    78   }
    80   pre.prod { white-space: pre-wrap; margin: 1em 0 1em 2em }
    82   div.featex { 
    83     width: 700px;
    84   }
    86   div.featex img {
    87     margin: auto;
    88     display: block;
    89   }
    91   span.tag {
    92     font-family: monospace;
    93     font-size: 120%;
    94   }
    96   ol ol {
    97     list-style-type: lower-alpha;
    98   }
   100   .idl-code {
   101     font-weight: bold;
   102     color: #c50;
   103   }
   104   </style>
   105   <link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
   106   type="text/css">
   108  <body>
   109   <div class=head> <!--begin-logo-->
   110    <p><a href="http://www.w3.org/"><img alt=W3C height=48
   111     src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
   113    <h1>CSS Fonts Module Level 3</h1>
   115    <h2 class="no-num no-toc" id=editors-draft-17-may-2013>Editor's Draft 17
   116     May 2013</h2>
   118    <dl id=authors>
   119     <dt>This version:
   121     <dd><a
   122      href="http://dev.w3.org/csswg/css-fonts/">http://dev.w3.org/csswg/css-fonts/</a>
   123      <!-- <dd><a href="http://www.w3.org/TR/2013/ED-css3-fonts-20130517/">http://www.w3.org/TR/2013/ED-css3-fonts-20130517/</a> -->
   126     <dt>Latest version:
   128     <dd><a
   129      href="http://www.w3.org/TR/css3-fonts/">http://www.w3.org/TR/css3-fonts/</a>
   131     <dt>Latest editor's draft:
   133     <dd><a
   134      href="http://dev.w3.org/csswg/css-fonts/">http://dev.w3.org/csswg/css-fonts/</a>
   135      (<a
   136      href="https://dvcs.w3.org/hg/csswg/log/tip/css-fonts/Fonts.html">change
   137      log</a>)
   139     <dt>Previous version:
   141     <dd><a
   142      href="http://www.w3.org/TR/2013/WD-css3-fonts-20130212/">http://www.w3.org/TR/2013/WD-css3-fonts-20130212/</a>
   144     <dt>Issues List:
   146     <dd><a href="http://www.w3.org/Style/CSS/Tracker/products/18">CSS3 Fonts
   147      issues in Tracker</a>
   149     <dd><a
   150      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
   151      Fonts issues in Bugzilla</a>
   153     <dt>Discussion:
   155     <dd><a
   156      href="mailto:www-style@w3.org?subject=%5Bcss-fonts%5D%20feedback">www-style@w3.org</a>
   157      with subject line “<kbd>[css-fonts] <var>… message topic
   158      …</var></kbd>” (<a
   159      href="http://lists.w3.org/Archives/Public/www-style/"
   160      rel=discussion>archives</a>)
   162     <dt>Editor:
   164     <dd><a href="mailto:jdaggett@mozilla.com">John Daggett (Mozilla)</a>
   165    </dl>
   166    <!--begin-copyright-->
   167    <p class=copyright><a
   168     href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
   169     rel=license>Copyright</a> © 2013 <a href="http://www.w3.org/"><abbr
   170     title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a
   171     href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of
   172     Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr
   173     title="European Research Consortium for Informatics and
   174     Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>,
   175     <a href="http://ev.buaa.edu.cn/">Beihang</a>), All Rights Reserved. W3C
   176     <a
   177     href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
   178     <a
   179     href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
   180     and <a
   181     href="http://www.w3.org/Consortium/Legal/copyright-documents">document
   182     use</a> rules apply.</p>
   183    <!--end-copyright-->
   184    <hr title="Separator for header">
   185   </div>
   187   <h2 class="no-num no-toc" id=abstract>Abstract</h2>
   189   <p>This CSS3 module describes how font properties are specified and how
   190    font resources are loaded dynamically. The contents of this specification
   191    are a consolidation of content previously divided into <a
   192    href="http://www.w3.org/TR/2002/WD-css3-fonts-20020802/">CSS3 Fonts</a>
   193    and <a href="http://www.w3.org/TR/2002/WD-css3-webfonts-20020802/">CSS3
   194    Web Fonts</a> modules. The description of font load events was moved into
   195    the <a href="http://dev.w3.org/csswg/css3-font-load-events/">CSS3 Font
   196    Load Events</a> module.
   198   <h2 class="no-num no-toc" id=status>Status of this document</h2>
   199   <!--begin-status-->
   201   <p>This is a public copy of the editors' draft. It is provided for
   202    discussion only and may change at any moment. Its publication here does
   203    not imply endorsement of its contents by W3C. Don't cite this document
   204    other than as work in progress.
   206   <p>The (<a
   207    href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
   208    mailing list <a
   209    href="mailto:www-style@w3.org?Subject=%5Bcss3-fonts%5D%20PUT%20SUBJECT%20HERE">
   210    www-style@w3.org</a> (see <a
   211    href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
   212    discussion of this specification. When sending e-mail, please put the text
   213    “css3-fonts” in the subject, preferably like this:
   214    “[<!---->css3-fonts<!---->] <em>…summary of comment…</em>”
   216   <p>This document was produced by the <a
   217    href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of
   218    the <a href="http://www.w3.org/Style/">Style Activity</a>).
   220   <p>This document was produced by a group operating under the <a
   221    href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February
   222    2004 W3C Patent Policy</a>. W3C maintains a <a
   223    href="http://www.w3.org/2004/01/pp-impl/32061/status"
   224    rel=disclosure>public list of any patent disclosures</a> made in
   225    connection with the deliverables of the group; that page also includes
   226    instructions for disclosing a patent. An individual who has actual
   227    knowledge of a patent which the individual believes contains <a
   228    href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
   229    Claim(s)</a> must disclose the information in accordance with <a
   230    href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
   231    6 of the W3C Patent Policy</a>.</p>
   232   <!--end-status-->
   233   <!--
   234 <h3 class="no-num no-toc" id="atrisk">Features at risk</h3>
   236 <p>The following features are at risk and may be removed when exiting CR:</p>
   238 <ul>
   239 </ul>
   240 -->
   242   <h2 class="no-num no-toc" id=contents>Table of contents</h2>
   243   <!--begin-toc-->
   245   <ul class=toc>
   246    <li><a href="#introduction"><span class=secno>1 </span>Introduction</a>
   248    <li><a href="#typography-background"><span class=secno>2 </span>Typography
   249     Background</a>
   251    <li><a href="#basic-font-props"><span class=secno>3 </span>Basic Font
   252     Properties</a>
   253     <ul class=toc>
   254      <li><a href="#font-family-prop"><span class=secno>3.1 </span>Font
   255       family: the font-family property</a>
   256       <ul class=toc>
   257        <li><a href="#generic-font-families"><span class=secno>3.1.1
   258         </span>Generic font families</a>
   259       </ul>
   261      <li><a href="#font-weight-prop"><span class=secno>3.2 </span>Font
   262       weight: the font-weight property</a>
   264      <li><a href="#font-stretch-prop"><span class=secno>3.3 </span>Font
   265       width: the font-stretch property</a>
   267      <li><a href="#font-style-prop"><span class=secno>3.4 </span>Font style:
   268       the font-style property</a>
   270      <li><a href="#font-size-prop"><span class=secno>3.5 </span>Font size:
   271       the font-size property</a>
   273      <li><a href="#font-size-adjust-prop"><span class=secno>3.6
   274       </span>Relative sizing: the font-size-adjust property</a>
   276      <li><a href="#font-prop"><span class=secno>3.7 </span>Shorthand font
   277       property: the font property</a>
   279      <li><a href="#font-synthesis-prop"><span class=secno>3.8
   280       </span>Controlling synthetic faces: the font-synthesis property</a>
   281     </ul>
   283    <li><a href="#font-resources"><span class=secno>4 </span>Font
   284     Resources</a>
   285     <ul class=toc>
   286      <li><a href="#font-face-rule"><span class=secno>4.1 </span>The
   287       <code>@font-face</code> rule</a>
   289      <li><a href="#font-family-desc"><span class=secno>4.2 </span>Font
   290       family: the font-family descriptor</a>
   292      <li><a href="#src-desc"><span class=secno>4.3 </span>Font reference: the
   293       src descriptor</a>
   295      <li><a href="#font-prop-desc"><span class=secno>4.4 </span>Font property
   296       descriptors: the font-style, font-weight, font-stretch descriptors</a>
   298      <li><a href="#unicode-range-desc"><span class=secno>4.5 </span>Character
   299       range: the unicode-range descriptor</a>
   301      <li><a href="#font-rend-desc"><span class=secno>4.6 </span>Font
   302       features: the font-variant and font-feature-settings descriptors</a>
   304      <li><a href="#font-face-loading"><span class=secno>4.7 </span>Font
   305       loading guidelines</a>
   307      <li><a href="#same-origin-restriction"><span class=secno>4.8
   308       </span>Same-origin restriction for fonts</a>
   309       <ul class=toc>
   310        <li><a href="#default-same-origin-restriction"><span class=secno>4.8.1
   311         </span>Default same-origin restriction</a>
   313        <li><a href="#allowing-cross-origin-font-loading"><span
   314         class=secno>4.8.2 </span>Allowing cross-origin font loading</a>
   315       </ul>
   316     </ul>
   318    <li><a href="#font-matching-algorithm"><span class=secno>5 </span>Font
   319     Matching Algorithm</a>
   320     <ul class=toc>
   321      <li><a href="#font-family-casing"><span class=secno>5.1 </span>Case
   322       sensitivity of font family names</a>
   324      <li><a href="#font-style-matching"><span class=secno>5.2 </span>Matching
   325       font styles</a>
   327      <li><a href="#cluster-matching"><span class=secno>5.3 </span>Cluster
   328       matching</a>
   330      <li><a href="#char-handling-issues"><span class=secno>5.4
   331       </span>Character handling issues</a>
   333      <li><a href="#font-matching-changes"><span class=secno>5.5 </span>Font
   334       matching changes since CSS 2.1</a>
   336      <li><a href="#font-matching-examples"><span class=secno>5.6 </span>Font
   337       matching examples</a>
   338     </ul>
   340    <li><a href="#font-rend-props"><span class=secno>6 </span>Font Feature
   341     Properties</a>
   342     <ul class=toc>
   343      <li><a href="#glyph-selection-positioning"><span class=secno>6.1
   344       </span>Glyph selection and positioning</a>
   346      <li><a href="#language-specific-support"><span class=secno>6.2
   347       </span>Language-specific display</a>
   349      <li><a href="#font-kerning-prop"><span class=secno>6.3 </span>Kerning:
   350       the font-kerning property</a>
   352      <li><a href="#font-variant-ligatures-prop"><span class=secno>6.4
   353       </span>Ligatures: the font-variant-ligatures property</a>
   355      <li><a href="#font-variant-position-prop"><span class=secno>6.5
   356       </span>Subscript and superscript forms: the font-variant-position
   357       property</a>
   359      <li><a href="#font-variant-caps-prop"><span class=secno>6.6
   360       </span>Capitalization: the font-variant-caps property</a>
   362      <li><a href="#font-variant-numeric-prop"><span class=secno>6.7
   363       </span>Numerical formatting: the font-variant-numeric property</a>
   365      <li><a href="#font-variant-alternates-prop"><span class=secno>6.8
   366       </span>Alternates and swashes: the font-variant-alternates property</a>
   369      <li><a href="#font-feature-values"><span class=secno>6.9 </span>Defining
   370       font specific alternates: the <code>@font-feature-values</code>
   371       rule</a>
   373      <li><a href="#font-variant-east-asian-prop"><span class=secno>6.10
   374       </span>East Asian text rendering: the font-variant-east-asian
   375       property</a>
   377      <li><a href="#font-variant-prop"><span class=secno>6.11 </span>Overall
   378       shorthand for font rendering: the font-variant property</a>
   380      <li><a href="#font-feature-settings-prop"><span class=secno>6.12
   381       </span>Low-level font feature settings control: the
   382       font-feature-settings property</a>
   384      <li><a href="#font-language-override-prop"><span class=secno>6.13
   385       </span>Font language override: the font-language-override property</a>
   386     </ul>
   388    <li><a href="#font-feature-resolution"><span class=secno>7 </span>Font
   389     Feature Resolution </a>
   390     <ul class=toc>
   391      <li><a href="#default-features"><span class=secno>7.1 </span>Default
   392       features</a>
   394      <li><a href="#feature-precedence"><span class=secno>7.2 </span>Feature
   395       precedence</a>
   397      <li><a href="#feature-precedence-examples"><span class=secno>7.3
   398       </span>Feature precedence examples</a>
   399     </ul>
   401    <li><a href="#object-model"><span class=secno>8 </span>Object Model</a>
   402     <ul class=toc>
   403      <li><a href="#om-fontface"><span class=secno>8.1 </span>The
   404       <code>CSSFontFaceRule</code> interface</a>
   406      <li><a href="#om-fontfeaturevalues"><span class=secno>8.2 </span>The
   407       <code>CSSFontFeatureValuesRule</code> interface</a>
   408     </ul>
   410    <li class=no-num><a href="#platform-props-to-css">Appendix A: Mapping
   411     platform font properties to CSS properties</a>
   413    <li class=no-num><a href="#ch-ch-ch-changes">Changes</a>
   414     <ul class=toc>
   415      <li class=no-num><a href="#recent-changes"> Changes from the February
   416       2013 CSS3 Fonts Working Draft</a>
   417     </ul>
   419    <li class=no-num><a href="#acknowledgments">Acknowledgments</a>
   421    <li class=no-num><a href="#conformance"> Conformance</a>
   422     <ul class=toc>
   423      <li class=no-num><a href="#conventions"> Document Conventions</a>
   425      <li class=no-num><a href="#conformance-classes"> Conformance Classes</a>
   428      <li class=no-num><a href="#partial"> Partial Implementations</a>
   430      <li class=no-num><a href="#experimental"> Experimental
   431       Implementations</a>
   433      <li class=no-num><a href="#testing"> Non-Experimental
   434       Implementations</a>
   435     </ul>
   437    <li class=no-num><a href="#references">References</a>
   438     <ul class=toc>
   439      <li class=no-num><a href="#normative-references">Normative
   440       References</a>
   442      <li class=no-num><a href="#other-references">Other References</a>
   443     </ul>
   445    <li class=no-num><a href="#index">Index</a>
   447    <li class=no-num><a href="#property-index">Property index</a>
   448   </ul>
   449   <!--end-toc-->
   451   <h2 id=introduction><span class=secno>1 </span>Introduction</h2>
   453   <p>A font provides a resource containing the visual representation of
   454    characters. At the simplest level it contains information that maps
   455    character codes to shapes (called glyphs) that represent these characters.
   456    Fonts sharing a common design style are commonly grouped into font
   457    families classified by a set of standard font properties. Within a family,
   458    the shape displayed for a given character can vary by stroke weight, slant
   459    or relative width, among others. An individual font face is described by a
   460    unique combination of these properties. For a given range of text, CSS
   461    font properties are used to select a font family and a specific font face
   462    within that family to be used when rendering that text. As a simple
   463    example, to use the bold form of Helvetica one could use:
   465   <pre>body { 
   466     font-family: Helvetica; 
   467     font-weight: bold; 
   468 }</pre>
   470   <p>Font resources may be installed locally on the system on which a user
   471    agent is running or downloadable. For local font resources descriptive
   472    information can be obtained directly from the font resource. For
   473    downloadable font resources (sometimes referred to as web fonts), the
   474    descriptive information is included with the reference to the font
   475    resource.
   477   <p>Families of fonts typically don't contain a single face for each
   478    possible variation of font properties. The CSS font selection mechanism
   479    describes how to match a given set of CSS font properties to a single font
   480    face.
   482   <h2 id=typography-background><span class=secno>2 </span>Typography
   483    Background</h2>
   485   <p><em>This section is non-normative.</em>
   487   <p> Typographic traditions vary across the globe, so there is no unique way
   488    to classify all fonts across languages and cultures. For even common Latin
   489    letters, wide variations are possible:
   491   <div class=figure><img alt="variations in glyphs for a single character"
   492    src=aaaaaa.png>
   493    <p class=caption>One character, many glyph variations
   494   </div>
   496   <p>Differences in the anatomy of letterforms is one way to distinguish
   497    fonts. For Latin fonts, flourishes at the ends of a character's main
   498    strokes, or serifs, can distinguish a font from those without. Similar
   499    comparisons exist in non-Latin fonts between fonts with tapered strokes
   500    and those using primarily uniform strokes:
   502   <div class=figure><img alt="serif vs. non-serifs" src=serifvssansserif.png>
   503    <p class=caption>Letterforms with and without serifs
   504   </div>
   506   <div class=figure><img alt="serif vs. non-serifs for japanese"
   507    src=minchovsgothic.png>
   508    <p class=caption>Similar groupings for Japanese typefaces
   509   </div>
   511   <p>Fonts contain letterforms and the data needed to map characters to these
   512    letterforms. Often this may be a simple one-to-one mapping, but more
   513    complex mappings are also possible. The use of combining diacritic marks
   514    creates many variations for an underlying letterform:
   516   <div class=figure><img alt="diacritic marks" src=aaaaaa-diacritics.png>
   517    <p class=caption>Variations with diacritic marks
   518   </div>
   520   <p>A sequence of characters can be represented by a single glyph known as a
   521    ligature:
   523   <div class=figure><img alt="example of a fi ligature"
   524    src=final-ligature.png>
   525    <p class=caption>Ligature example
   526   </div>
   528   <p>Visual transformations based on textual context are often stylistic
   529    option in European languages. They are required to correctly render
   530    languages like Arabic, the lam and alef characters below <em>must</em> be
   531    combined when they exist in sequence:
   533   <div class=figure><img alt="lam alef ligature" src=lamaleflig.png>
   534    <p class=caption>Required Arabic ligature
   535   </div>
   537   <p>The relative complexity of these shaping transformations requires
   538    additional data within the font.
   540   <p>Sets of font faces with various stylistic variations are often grouped
   541    together into font families. In the simplest case a regular face is
   542    supplemented with bold and italic faces, but much more extensive groupings
   543    are possible. Variations in the thickness of letterform strokes, the <dfn
   544    id=weight>weight</dfn>, and the overall proportions of the letterform, the
   545    <dfn id=width>width</dfn>, are most common. In the example below, each
   546    letter uses a different font face within the Univers font family. The
   547    width used increases from top to bottom and the weight increases from left
   548    to right:
   550   <div class=figure><img alt="various width and weight variations within a
   551    single family" src=weightwidthvariations.png>
   552    <p class=caption>Weight and width variations within a single font family
   553   </div>
   555   <p>Creating fonts that support multiple scripts is a difficult task;
   556    designers need to understand the cultural traditions surrounding the use
   557    of type in different scripts and come up with letterforms that somehow
   558    share a common theme. Many languages often share a common script and each
   559    of these languages may have noticeable stylistic differences. For example,
   560    the Arabic script is shared by Persian and Urdu and Cyrillic is used with
   561    many languages, not just Russian.
   563   <p>The character map of a font defines the mapping of characters to glyphs
   564    for that font. If a document contains characters not supported by the
   565    character maps of the fonts contained in a font family list, a user agent
   566    may use a system font fallback procedure to locate an appropriate font
   567    that does. If no appropriate font can be found, some form of "missing
   568    glyph" character will be rendered by the user agent. System fallback can
   569    occur when the specified list of font families does not include a font
   570    that supports a given character.
   572   <p>Although the character map of a font maps a given character to a glyph
   573    for that character, modern font technologies such as OpenType and AAT
   574    (Apple Advanced Typography) provide ways of mapping a character to
   575    different glyphs based upon feature settings. Fonts in these formats allow
   576    these features to be embedded in the font itself and controlled by
   577    applications. Common typographic features which can be specified this way
   578    include ligatures, swashes, contextual alternates, proportional and
   579    tabular figures, and automatic fractions, to list just a few. For a visual
   580    overview of OpenType features, see the <a href="#OPENTYPE-FONT-GUIDE"
   581    rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
   583   <h2 id=basic-font-props><span class=secno>3 </span>Basic Font Properties</h2>
   585   <p>The particular font face used to render a character is determined by the
   586    font family and other font properties that apply to a given element. This
   587    structure allows settings to be varied independent of each other.</p>
   588   <!-- prop: font-family -->
   590   <h3 id=font-family-prop><span class=secno>3.1 </span>Font family: the <a
   591    href="#propdef-font-family">font-family</a> property</h3>
   593   <table class=propdef id=namefont-familyvalue-ltfamily-name-ltgen>
   594    <tbody>
   595     <tr>
   596      <td>Name:
   598      <td><dfn id=propdef-font-family>font-family</dfn>
   600     <tr>
   601      <td>Value:
   603      <td>[ &lt;family-name> | &lt;generic-family> ]#
   605     <tr>
   606      <td>Initial:
   608      <td>depends on user agent
   610     <tr>
   611      <td>Applies to:
   613      <td>all elements
   615     <tr>
   616      <td>Inherited:
   618      <td>yes
   620     <tr>
   621      <td>Percentages:
   623      <td>N/A
   625     <tr>
   626      <td>Media:
   628      <td>visual
   630     <tr>
   631      <td>Computed value:
   633      <td>as specified
   635     <tr>
   636      <td>Animatable:
   638      <td>no
   639   </table>
   641   <p>This property specifies a prioritized list of font family names or
   642    generic family names. A font family defines a set of faces that vary in
   643    weight, width or slope. CSS uses the combination of a family name with
   644    other style attributes to select an individual face. Using this selection
   645    mechanism, rather than selecting a face via the style name as is often
   646    done in design applications, allows some degree of regularity in textual
   647    display when fallback occurs.
   649   <p class=note>Designers should note that the CSS definition of font
   650    attributes used for selection are explicitly not intended to define a font
   651    taxonomy. A type designer's idea of a family may often extend to a set of
   652    faces that vary along axes other than just the standard axes of weight,
   653    width and slope. A family may extend to include both a set of serif faces
   654    and a set of sans-serif faces or vary along axes that are unique to that
   655    family. The CSS font selection mechanism merely provides a way to
   656    determine the “closest” substitute when substitution is necessary.
   658   <p>Unlike other CSS properties, component values are a comma-separated list
   659    indicating alternatives. A user agent iterates through the list of family
   660    names until it matches an available font that contains a glyph for the
   661    character to be rendered. This allows for differences in available fonts
   662    across platforms and for differences in the range of characters supported
   663    by individual fonts.
   665   <p>A font family name only specifies a name given to a set of font faces,
   666    it does not specify an individual face. For example, given the
   667    availability of the fonts below, Futura would match but Futura Medium
   668    would not:
   670   <div class=figure><img alt="family and face names"
   671    src=familyvsfacename.png>
   672    <p class=caption>Family and individual face names
   673   </div>
   675   <p>Consider the example below:
   677   <div class=example>
   678    <pre>body { 
   679     font-family: Helvetica, Verdana, sans-serif; 
   680 }</pre>
   682    <p>If Helvetica is available it will be used when rendering. If neither
   683     Helvetica nor Verdana is present, then the user-agent-defined sans serif
   684     font will be used.</p>
   685   </div>
   687   <p>There are two types of font family names:
   689   <dl>
   690    <dt>&lt;family-name&gt;
   692    <dd>The name of a font family of choice such as Helvetica or Verdana in
   693     the previous example.
   695    <dt>&lt;generic-family&gt;
   697    <dd> The following generic family keywords are defined: ‘<a
   698     href="#serif"><code class=property>serif</code></a>’, ‘<a
   699     href="#sans-serif"><code class=property>sans-serif</code></a>’, ‘<a
   700     href="#cursive"><code class=property>cursive</code></a>’, ‘<a
   701     href="#fantasy"><code class=property>fantasy</code></a>’, and ‘<a
   702     href="#monospace"><code class=property>monospace</code></a>’. These
   703     keywords can be used as a general fallback mechanism when an author's
   704     desired font choices are not available. As keywords, they must not be
   705     quoted. Authors are encouraged to append a generic font family as a last
   706     alternative for improved robustness.
   707   </dl>
   709   <p>Font family names must either be given quoted as <a
   710    href="//www.w3.org/TR/CSS21/syndata.html#strings">strings,</a> or unquoted
   711    as a sequence of one or more <a
   712    href="//www.w3.org/TR/CSS21/syndata.html#value-def-identifier">identifiers.</a>
   713    This means most punctuation characters and digits at the start of each
   714    token must be escaped in unquoted font family names.
   716   <p>To illustrate this, the following declarations are invalid:
   718   <pre>
   719 font-family: Red/Black, sans-serif;
   720 font-family: "Lucida" Grande, sans-serif;
   721 font-family: Ahem!, sans-serif;
   722 font-family: test@foo, sans-serif;
   723 font-family: #POUND, sans-serif;
   724 font-family: Hawaii 5-0, sans-serif;
   725 </pre>
   727   <p>If a sequence of identifiers is given as a font family name, the
   728    computed value is the name converted to a string by joining all the
   729    identifiers in the sequence by single spaces.
   731   <p>To avoid mistakes in escaping, it is recommended to quote font family
   732    names that contain white space, digits, or punctuation characters other
   733    than hyphens:
   735   <pre>
   736 body { font-family: "New Century Schoolbook", serif }
   738 &lt;BODY STYLE="font-family: '21st Century', fantasy">
   739 </pre>
   741   <p>Font family <em>names</em> that happen to be the same as a keyword value
   742    (‘<code class=property>inherit</code>’, ‘<a href="#serif"><code
   743    class=property>serif</code></a>’, ‘<a href="#sans-serif"><code
   744    class=property>sans-serif</code></a>’, ‘<a href="#monospace"><code
   745    class=property>monospace</code></a>’, ‘<a href="#fantasy"><code
   746    class=property>fantasy</code></a>’, and ‘<a href="#cursive"><code
   747    class=property>cursive</code></a>’) must be quoted to prevent confusion
   748    with the keywords with the same names. The keywords ‘<code
   749    class=property>initial</code>’ and ‘<code
   750    class=property>default</code>’ are reserved for future use and must also
   751    be quoted when used as font names. UAs must not consider these keywords as
   752    matching the ‘<code class=css>&lt;family-name&gt;</code>’ type.
   754   <p>The precise way a set of fonts are grouped into font families varies
   755    depending upon the platform font management API's. The Windows GDI API
   756    only allows four faces to be grouped into a family while the DirectWrite
   757    API and API's on OSX and other platforms support font families with a
   758    variety of weights, widths and slopes (see <a
   759    href="#platform-props-to-css">Appendix A</a> for more details).
   761   <p>Some font formats allow fonts to carry multiple localizations of the
   762    family name. User agents must recognize and correctly match all of these
   763    names independent of the underlying platform localization, system API used
   764    or document encoding:
   766   <div class=figure><img alt="examples of localized family names"
   767    src=localizedfamilynames.png>
   768    <p class=caption>Localized family names
   769   </div>
   771   <h4 id=generic-font-families><span class=secno>3.1.1 </span>Generic font
   772    families</h4>
   774   <p>All five generic font families are defined to exist in all CSS
   775    implementations (they need not necessarily map to five distinct actual
   776    fonts). User agents should provide reasonable default choices for the
   777    generic font families, which express the characteristics of each family as
   778    well as possible within the limits allowed by the underlying technology.
   779    User agents are encouraged to allow users to select alternative choices
   780    for the generic fonts.
   782   <h5 class="no-num no-toc"> <span class=index-def id=serif0 title="serif,
   783    definition of"><a name=serif-def><dfn id=serif>serif</dfn></a></span></h5>
   785   <p>Serif fonts represent the formal text style for a script. This often
   786    means but is not limited to glyphs that have finishing strokes, flared or
   787    tapering ends, or have actual serifed endings (including slab serifs).
   788    Serif fonts are typically proportionately-spaced. They often display a
   789    greater variation between thick and thin strokes than fonts from the ‘<a
   790    href="#sans-serif"><code class=property>sans-serif</code></a>’ generic
   791    font family. CSS uses the term ‘<a href="#serif"><code
   792    class=property>serif</code></a>’ to apply to a font for any script,
   793    although other names may be more familiar for particular scripts, such as
   794    Mincho (Japanese), Sung, Song or Kai (Chinese), Batang (Korean). For
   795    Arabic, the Naskh style would correspond to ‘<a href="#serif"><code
   796    class=property>serif</code></a>’ more due to its typographic role rather
   797    than its actual design style. Any font that is so described may be used to
   798    represent the generic ‘<a href="#serif"><code
   799    class=property>serif</code></a>’ family.
   801   <div class=figure><img alt="sample serif fonts" src=serifexamples.png>
   802    <p class=caption>Sample serif fonts
   803   </div>
   805   <h5 class="no-num no-toc"> <span class=index-def id=sans-serif0
   806    title="sans-serif, definition of"> <a name=sans-serif-def><dfn
   807    id=sans-serif>sans-serif</dfn></a></span></h5>
   809   <p>Glyphs in sans-serif fonts, as the term is used in CSS, are generally
   810    low contrast (vertical and horizontal stems have the close to the same
   811    thickness) and have stroke endings that are plain -- without any flaring,
   812    cross stroke, or other ornamentation. Sans-serif fonts are typically
   813    proportionately-spaced. They often have little variation between thick and
   814    thin strokes, compared to fonts from the ‘<a href="#serif"><code
   815    class=property>serif</code></a>’ family. CSS uses the term ‘<a
   816    href="#sans-serif"><code class=property>sans-serif</code></a>’ to apply
   817    to a font for any script, although other names may be more familiar for
   818    particular scripts, such as Gothic (Japanese), Hei (Chinese), or Gulim
   819    (Korean). Any font that is so described may be used to represent the
   820    generic ‘<a href="#sans-serif"><code
   821    class=property>sans-serif</code></a>’ family.
   823   <div class=figure><img alt="sample sans-serif fonts"
   824    src=sansserifexamples.png>
   825    <p class=caption>Sample sans-serif fonts
   826   </div>
   828   <h5 class="no-num no-toc"> <span class=index-def id=cursive0
   829    title="cursive, definition of"> <a name=cursive-def><dfn
   830    id=cursive>cursive</dfn></a></span></h5>
   832   <p>Glyphs in cursive fonts generally use a more informal script style, and
   833    the result looks more like handwritten pen or brush writing than printed
   834    letterwork. CSS uses the term ‘<a href="#cursive"><code
   835    class=property>cursive</code></a>’ to apply to a font for any script,
   836    although other names such as Chancery, Brush, Swing and Script are also
   837    used in font names.
   839   <div class=figure><img alt="sample cursive fonts" src=cursiveexamples.png>
   840    <p class=caption>Sample cursive fonts
   841   </div>
   843   <h5 class="no-num no-toc"> <span class=index-def id=fantasy0
   844    title="fantasy, definition of"> <a name=fantasy-def><dfn
   845    id=fantasy>fantasy</dfn></a></span></h5>
   847   <p>Fantasy fonts are primarily decorative or expressive fonts that contain
   848    playful representations of characters. These do not include Pi or Picture
   849    fonts which do not represent actual characters.
   851   <div class=figure><img alt="sample fantasy fonts" src=fantasyexamples.png>
   852    <p class=caption>Sample fantasy fonts
   853   </div>
   855   <h5 class="no-num no-toc"> <span class=index-def id=monospace0
   856    title="monospace, definition of"> <a name=monospace-def><dfn
   857    id=monospace>monospace</dfn></a></span></h5>
   859   <p>The sole criterion of a monospace font is that all glyphs have the same
   860    fixed width. This is often used to render samples of computer code.
   862   <div class=figure><img alt="sample monospace fonts"
   863    src=monospaceexamples.png>
   864    <p class=caption>Sample monospace fonts
   865   </div>
   866   <!-- prop: font-weight -->
   868   <h3 id=font-weight-prop><span class=secno>3.2 </span>Font weight: the <a
   869    href="#propdef-font-weight">font-weight</a> property</h3>
   871   <table class=propdef id=namefont-weightvaluenormal-bold-bolder-l>
   872    <tbody>
   873     <tr>
   874      <td>Name:
   876      <td><dfn id=propdef-font-weight>font-weight</dfn>
   878     <tr>
   879      <td>Value:
   881      <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
   882       | 700 | 800 | 900
   884     <tr>
   885      <td>Initial:
   887      <td>normal
   889     <tr>
   890      <td>Applies to:
   892      <td>all elements
   894     <tr>
   895      <td>Inherited:
   897      <td>yes
   899     <tr>
   900      <td>Percentages:
   902      <td>N/A
   904     <tr>
   905      <td>Media:
   907      <td>visual
   909     <tr>
   910      <td>Computed value:
   912      <td>numeric weight value (see description)
   914     <tr>
   915      <td>Animatable:
   917      <td>as <a
   918       href="http://dev.w3.org/csswg/css3-transitions/#animtype-font-weight">font
   919       weight</a>
   920   </table>
   922   <p>The <a class=noxref href="#font-weight-prop"><span
   923    class=property>‘<code class=property>font-weight</code>’</span></a>
   924    property specifies the weight of glyphs in the font, their degree of
   925    blackness or stroke thickness.
   927   <p>Values have the following meanings:
   929   <dl>
   930    <dt>100 to 900
   932    <dd>These values form an ordered sequence, where each number indicates a
   933     weight that is at least as dark as its predecessor. These roughly
   934     correspond to the commonly used weight names below:
   935   </dl>
   937   <ul>
   938    <li>100 - Thin
   940    <li>200 - Extra Light (Ultra Light)
   942    <li>300 - Light
   944    <li>400 - Normal
   946    <li>500 - Medium
   948    <li>600 - Semi Bold (Demi Bold)
   950    <li>700 - Bold
   952    <li>800 - Extra Bold (Ultra Bold)
   954    <li>900 - Black (Heavy)
   955   </ul>
   957   <dl>
   958    <dt><a href="#normal2"><strong>normal</strong></a>
   960    <dd>Same as ‘<code class=css>400</code>’.
   962    <dt><strong>bold</strong>
   964    <dd>Same as ‘<code class=css>700</code>’.
   966    <dt><strong>bolder</strong>
   968    <dd>Specifies a bolder weight than the inherited value.
   970    <dt><strong>lighter</strong>
   972    <dd>Specifies a lighter weight than the inherited value.
   973   </dl>
   975   <p>Font formats that use a scale other than a nine-step scale should map
   976    their scale onto the CSS scale so that 400 roughly corresponds with a face
   977    that would be labeled as Regular, Book, Roman and 700 roughly matches a
   978    face that would be labeled as Bold. Or weights may be inferred from the
   979    style names, ones that correspond roughly with the scale above. The scale
   980    is relative, so a face with a larger weight value must never appear
   981    lighter. If style names are used to infer weights, care should be taken to
   982    handle variations in style names across locales.
   984   <p>Quite often there are only a few weights available for a particular font
   985    family. When a weight is specified for which no face exists, a face with a
   986    nearby weight is used. In general, bold weights map to faces with heavier
   987    weights and light weights map to faces with lighter weights (see the <a
   988    href="#font-matching-algorithm">font matching section below</a> for a
   989    precise definition). The examples here illustrate which face is used for
   990    different weights, grey indicates a face for that weight does not exist so
   991    a face with a nearby weight is used:
   993   <div class=figure><img alt="weight mappings for a family with 400, 700 and
   994    900 weights" src=optimaweights.png>
   995    <p class=caption>Weight mappings for a font family with 400, 700 and 900
   996     weight faces
   997   </div>
   999   <div class=figure><img alt="weight mappings for a family with 300, 600
  1000    weights" src=hiraginoweights.png>
  1001    <p class=caption>Weight mappings for a font family with 300 and 600 weight
  1002     faces
  1003   </div>
  1005   <p>Although the practice is not well-loved by typographers, bold faces are
  1006    often synthesized by user agents for faces that lack actual bold faces.
  1007    For the purposes of style matching, these faces must be treated as if they
  1008    exist within the family. Authors can explicitly avoid this behavior by
  1009    using the ‘<a href="#propdef-font-synthesis"><code
  1010    class=property>font-synthesis</code></a>’ property.
  1012   <p>Specified values of ‘<code class=property>bolder</code>’ and
  1013    ‘<code class=property>lighter</code>’ indicate weights relative to the
  1014    weight of the parent element. The computed weight is calculated based on
  1015    the inherited ‘<a href="#propdef-font-weight"><code
  1016    class=property>font-weight</code></a>’ value using the chart below.
  1018   <table class=data id=bolderlighter summary="Bolder/lighter mappings">
  1019    <thead>
  1020     <tr>
  1021      <th>Inherited value
  1023      <th>bolder
  1025      <th>lighter
  1027    <tbody>
  1028     <tr>
  1029      <th>100
  1031      <td>400
  1033      <td>100
  1035     <tr>
  1036      <th>200
  1038      <td>400
  1040      <td>100
  1042     <tr>
  1043      <th>300
  1045      <td>400
  1047      <td>100
  1049     <tr>
  1050      <th>400
  1052      <td>700
  1054      <td>100
  1056     <tr>
  1057      <th>500
  1059      <td>700
  1061      <td>100
  1063     <tr>
  1064      <th>600
  1066      <td>900
  1068      <td>400
  1070     <tr>
  1071      <th>700
  1073      <td>900
  1075      <td>400
  1077     <tr>
  1078      <th>800
  1080      <td>900
  1082      <td>700
  1084     <tr>
  1085      <th>900
  1087      <td>900
  1089      <td>700
  1090   </table>
  1092   <p>The table above is equivalent to selecting the next relative bolder or
  1093    lighter face, given a font family containing normal and bold faces along
  1094    with a thin and a heavy face. Authors who desire finer control over the
  1095    exact weight values used for a given element may use numerical values
  1096    instead of relative weights.</p>
  1097   <!-- prop: font-stretch -->
  1099   <h3 id=font-stretch-prop><span class=secno>3.3 </span>Font width: the <a
  1100    href="#propdef-font-stretch">font-stretch</a> property</h3>
  1102   <table class=propdef id=namefont-stretchvaluenormal-ultra-conden>
  1103    <tbody>
  1104     <tr>
  1105      <td>Name:
  1107      <td><dfn id=propdef-font-stretch>font-stretch</dfn>
  1109     <tr>
  1110      <td>Value:
  1112      <td>normal | ultra-condensed | extra-condensed | condensed |
  1113       semi-condensed | semi-expanded | expanded | extra-expanded |
  1114       ultra-expanded
  1116     <tr>
  1117      <td>Initial:
  1119      <td>normal
  1121     <tr>
  1122      <td>Applies to:
  1124      <td>all elements
  1126     <tr>
  1127      <td>Inherited:
  1129      <td>yes
  1131     <tr>
  1132      <td>Percentages:
  1134      <td>N/A
  1136     <tr>
  1137      <td>Media:
  1139      <td>visual
  1141     <tr>
  1142      <td>Computed value:
  1144      <td>as specified
  1146     <tr>
  1147      <td>Animatable:
  1149      <td>as <a href="#font-stretch-animation">font stretch</a>
  1150   </table>
  1152   <p>The <a class=noxref href="#font-stretch-prop"><span
  1153    class=property>‘<code class=property>font-stretch</code>’</span></a>
  1154    property selects a normal, condensed, or expanded face from a font family.
  1155    Absolute keyword values have the following ordering, from narrowest to
  1156    widest:
  1158   <ul>
  1159    <li><code>ultra-condensed</code>
  1161    <li><code>extra-condensed</code>
  1163    <li><code>condensed</code>
  1165    <li><code>semi-condensed </code>
  1167    <li><code>normal</code>
  1169    <li><code>semi-expanded</code>
  1171    <li><code>expanded</code>
  1173    <li><code>extra-expanded</code>
  1175    <li><code>ultra-expanded</code>
  1176   </ul>
  1178   <p>The scale is relative, so a face with a font-stretch value higher in the
  1179    list above should never appear wider. When a face does not exist for a
  1180    given width, normal or condensed values map to a narrower face, otherwise
  1181    a wider face. Conversely, expanded values map to a wider face, otherwise a
  1182    narrower face. The figure below shows how the nine font-stretch property
  1183    settings affect font selection for font family containing a variety of
  1184    widths, grey indicates a width for which no face exists and a different
  1185    width is substituted:
  1187   <div class=figure><img alt="width mappings for a family with condensed,
  1188    normal and expanded faces" src=universwidths.png>
  1189    <p class=caption>Width mappings for a font family with condensed, normal
  1190     and expanded width faces
  1191   </div>
  1193   <p id=font-stretch-animation>Animation of font stretch: Font stretch is
  1194    interpolated in discrete steps. The interpolation happens as though the
  1195    ordered values are equally spaced real numbers. The interpolation result
  1196    is rounded to the nearest value, with values exactly halfway between two
  1197    values rounded towards the later value in the list above.</p>
  1198   <!-- prop: font-style -->
  1200   <h3 id=font-style-prop><span class=secno>3.4 </span>Font style: the <a
  1201    href="#propdef-font-style">font-style</a> property</h3>
  1203   <table class=propdef id=namefont-stylevaluenormal-italic-oblique>
  1204    <tbody>
  1205     <tr>
  1206      <td>Name:
  1208      <td><dfn id=propdef-font-style>font-style</dfn>
  1210     <tr>
  1211      <td>Value:
  1213      <td>normal | italic | oblique
  1215     <tr>
  1216      <td>Initial:
  1218      <td>normal
  1220     <tr>
  1221      <td>Applies to:
  1223      <td>all elements
  1225     <tr>
  1226      <td>Inherited:
  1228      <td>yes
  1230     <tr>
  1231      <td>Percentages:
  1233      <td>N/A
  1235     <tr>
  1236      <td>Media:
  1238      <td>visual
  1240     <tr>
  1241      <td>Computed value:
  1243      <td>as specified
  1245     <tr>
  1246      <td>Animatable:
  1248      <td>no
  1249   </table>
  1251   <p>The <a class=noxref href="#font-style-prop"><span
  1252    class=property>‘<code class=property>font-style</code>’</span></a>
  1253    property allows italic or oblique faces to be selected. Italic forms are
  1254    generally cursive in nature while oblique faces are typically sloped
  1255    versions of the regular face. Oblique faces can be simulated by
  1256    artificially sloping the glyphs of the regular face. Compare the
  1257    artificially sloped renderings of Palatino ‘<code
  1258    class=property>a</code>’ and Baskerville ‘<code
  1259    class=property>N</code>’ in grey with the actual italic versions:
  1261   <div class=figure><img alt="artificial sloping vs. real italics"
  1262    src=realvsfakeitalics.png>
  1263    <p class=caption>Artificial sloping versus real italics
  1264   </div>
  1266   <p>A value of ‘<a href="#normal2"><code
  1267    class=property>normal</code></a>’ selects a face that is classified as
  1268    ‘<a href="#normal2"><code class=property>normal</code></a>’, while
  1269    ‘<code class=property>oblique</code>’ selects a font that is labeled
  1270    ‘<code class=property>oblique</code>’. A value of ‘<code
  1271    class=property>italic</code>’ selects a font that is labeled ‘<code
  1272    class=property>italic</code>’, or, if that is not available, one labeled
  1273    ‘<code class=property>oblique</code>’. If no italic or oblique face is
  1274    available, oblique faces can be synthesized by rendering non-obliqued
  1275    faces with a right sloping transformation applied. When synthesizing these
  1276    faces, the transformation should apply to all glyphs in the same way and
  1277    not vary based on codepoint or due to horizontal or vertical line
  1278    orientation.
  1280   <p>Many scripts lack the tradition of mixing a cursive form within text
  1281    rendered with a normal face. Chinese, Japanese and Korean fonts almost
  1282    always lack italic or oblique faces. Fonts that support a mixture of
  1283    scripts will sometimes omit specific scripts such as Arabic from the set
  1284    of glyphs supported in the italic face. User agents should be careful
  1285    about making character map assumptions across faces.
  1287   <p class=issue>For synthetic italics in vertical runs of Chinese, Japanese,
  1288    or Korean text, is there a need to define explicitly the direction of the
  1289    faux oblique for runs that include a mixture of ideographic and Latin
  1290    text?</p>
  1291   <!-- prop: font-size -->
  1293   <h3 id=font-size-prop><span class=secno>3.5 </span>Font size: the <a
  1294    href="#propdef-font-size">font-size</a> property</h3>
  1296   <table class=propdef id=namefont-sizevalueltabsolute-size-ltrela>
  1297    <tbody>
  1298     <tr>
  1299      <td>Name:
  1301      <td><dfn id=propdef-font-size>font-size</dfn>
  1303     <tr>
  1304      <td>Value:
  1306      <td>&lt;absolute-size> | &lt;relative-size> | &lt;length> |
  1307       &lt;percentage>
  1309     <tr>
  1310      <td>Initial:
  1312      <td>medium
  1314     <tr>
  1315      <td>Applies to:
  1317      <td>all elements
  1319     <tr>
  1320      <td>Inherited:
  1322      <td>yes
  1324     <tr>
  1325      <td>Percentages:
  1327      <td>refer to parent element's font size
  1329     <tr>
  1330      <td>Media:
  1332      <td>visual
  1334     <tr>
  1335      <td>Computed value:
  1337      <td>absolute length
  1339     <tr>
  1340      <td>Animatable:
  1342      <td>as <a
  1343       href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
  1344   </table>
  1346   <p>This property indicates the desired height of glyphs from the font. For
  1347    scalable fonts, the font-size is a scale factor applied to the EM unit of
  1348    the font. (Note that certain glyphs may bleed outside their EM box.) For
  1349    non-scalable fonts, the font-size is converted into absolute units and
  1350    matched against the declared font-size of the font, using the same
  1351    absolute coordinate space for both of the matched values. Values have the
  1352    following meanings:
  1354   <dl>
  1355    <dt><a name=x18><span class=index-def id=ltabsolute-sizegt
  1356     title="&lt;absolute-size&gt;">
  1357     <strong>&lt;absolute-size&gt;</strong></span></a>
  1359    <dd> An <a class=value-def
  1360     name=value-def-absolute-size>&lt;absolute-size&gt;</a> keyword refers to
  1361     an entry in a table of font sizes computed and kept by the user agent.
  1362     Possible values are:
  1363     <p> [ xx-small | x-small | small | medium | large | x-large | xx-large ]</p>
  1365    <dt><a name=x19><span class=index-def id=ltrelative-sizegt
  1366     title="&lt;relative-size&gt;">
  1367     <strong>&lt;relative-size&gt;</strong></span></a>
  1369    <dd> A <a class=value-def
  1370     name=value-def-relative-size>&lt;relative-size&gt;</a> keyword is
  1371     interpreted relative to the table of font sizes and the computed ‘<a
  1372     href="#propdef-font-size"><code class=property>font-size</code></a>’ of
  1373     the parent element. Possible values are:
  1374     <p> [ larger | smaller ]
  1376     <p> For example, if the parent element has a font size of ‘<code
  1377      class=property>medium</code>’, a value of ‘<code
  1378      class=property>larger</code>’ will make the font size of the current
  1379      element be ‘<code class=property>large</code>’. If the parent
  1380      element's size is not close to a table entry, the user agent is free to
  1381      interpolate between table entries or round off to the closest one. The
  1382      user agent may have to extrapolate table values if the numerical value
  1383      goes beyond the keywords.
  1385    <dt><span class=index-inst id=ltlengthgt
  1386     title="&lt;length&gt;">&lt;length&gt;</span>
  1388    <dd>A length value specifies an absolute font size (independent of the
  1389     user agent's font table). Negative lengths are illegal.
  1391    <dt><span class=index-inst id=ltpercentagegt-
  1392     title="&lt;percentage&gt;">&lt;percentage&gt; </span>
  1394    <dd>A percentage value specifies an absolute font size relative to the
  1395     parent element's font size. Use of percentage values, or values in
  1396     ‘<code class=property>em</code>’s, leads to more robust and
  1397     cascadable style sheets.
  1398   </dl>
  1400   <p>The following table provides user agent guidelines for the absolute-size
  1401    scaling factor and their mapping to HTML heading and absolute font-sizes.
  1402    The ‘<code class=property>medium</code>’ value is used as the
  1403    reference middle value. The user agent may fine-tune these values for
  1404    different fonts or different types of display devices.
  1406   <table class=data>
  1407    <thead>
  1408     <tr>
  1409      <th>CSS absolute-size values
  1411      <th>xx-small
  1413      <th>x-small
  1415      <th>small
  1417      <th>medium
  1419      <th>large
  1421      <th>x-large
  1423      <th>xx-large
  1425      <th> 
  1427    <tbody>
  1428     <tr>
  1429      <th>scaling factor
  1431      <td>3/5
  1433      <td>3/4
  1435      <td>8/9
  1437      <td>1
  1439      <td>6/5
  1441      <td>3/2
  1443      <td>2/1
  1445      <td>3/1
  1447     <tr>
  1448      <th>HTML headings
  1450      <td>h6
  1452      <td> 
  1454      <td>h5
  1456      <td>h4
  1458      <td>h3
  1460      <td>h2
  1462      <td>h1
  1464      <td> 
  1466     <tr>
  1467      <th>HTML font sizes
  1469      <td>1
  1471      <td> 
  1473      <td>2
  1475      <td>3
  1477      <td>4
  1479      <td>5
  1481      <td>6
  1483      <td>7
  1484   </table>
  1486   <p class=note><em><strong>Note 1.</strong> To preserve readability, an UA
  1487    applying these guidelines should nevertheless avoid creating font-size
  1488    resulting in less than 9 device pixels per EM unit on a computer display
  1489    .</em>
  1491   <p class=note><em><strong>Note 2.</strong> In CSS1, the suggested scaling
  1492    factor between adjacent indexes was 1.5 which user experience proved to be
  1493    too large. In CSS2, the suggested scaling factor for computer screen
  1494    between adjacent indexes was 1.2 which still created issues for the small
  1495    sizes. The new scaling factor varies between each index to provide a
  1496    better readability.</em>
  1498   <p>The actual value of this property may differ from the computed value due
  1499    a numerical value on ‘<a href="#propdef-font-size-adjust"><code
  1500    class=property>font-size-adjust</code></a>’ and the unavailability of
  1501    certain font sizes.
  1503   <p>Child elements inherit the computed <a class=noxref
  1504    href="#font-size-prop"> <span class=property>‘<code
  1505    class=property>font-size</code>’</span></a> value (otherwise, the effect
  1506    of <a class=noxref href="#font-size-adjust-prop"><span
  1507    class=property>‘<code
  1508    class=property>font-size-adjust</code>’</span></a> would compound).
  1510   <div class=example>
  1511    <p style="display:none">Example(s):
  1513    <p>
  1515    <pre>p { font-size: 12pt; }
  1516 blockquote { font-size: larger }
  1517 em { font-size: 150% }
  1518 em { font-size: 1.5em }
  1519 </pre>
  1520   </div>
  1521   <!-- prop: font-size-adjust -->
  1523   <h3 id=font-size-adjust-prop><span class=secno>3.6 </span>Relative sizing:
  1524    the <a href="#propdef-font-size-adjust">font-size-adjust</a> property</h3>
  1526   <table class=propdef id=namefont-size-adjustvaluenone-auto-ltnum>
  1527    <tbody>
  1528     <tr>
  1529      <td>Name:
  1531      <td><dfn id=propdef-font-size-adjust>font-size-adjust</dfn>
  1533     <tr>
  1534      <td>Value:
  1536      <td>none | auto | &lt;number>
  1538     <tr>
  1539      <td>Initial:
  1541      <td>none
  1543     <tr>
  1544      <td>Applies to:
  1546      <td>all elements
  1548     <tr>
  1549      <td>Inherited:
  1551      <td>yes
  1553     <tr>
  1554      <td>Percentages:
  1556      <td>N/A
  1558     <tr>
  1559      <td>Media:
  1561      <td>visual
  1563     <tr>
  1564      <td>Computed value:
  1566      <td>as specified
  1568     <tr>
  1569      <td>Animatable:
  1571      <td>as <a
  1572       href="http://dev.w3.org/csswg/css3-transitions/#animtype-number">number</a>
  1573   </table>
  1575   <p>For any given font size, the apparent size and legibility of text varies
  1576    across fonts. For scripts such as Latin or Cyrillic that distinguish
  1577    between upper and lowercase letters, the relative height of lowercase
  1578    letters compared to their uppercase counterparts is a determining factor
  1579    of legibility. This is commonly referred to as the <a class=index-def
  1580    href="#aspect-value" id=aspect-value0 title="aspect value"><dfn
  1581    id=aspect-value>aspect value</dfn></a>. Precisely defined, it is equal to
  1582    the x-height of a font divided by the font size.
  1584   <p>In situations where font fallback occurs, fallback fonts may not share
  1585    the same aspect ratio as the desired font family and will thus appear less
  1586    readable. The font-size-adjust property is a way to preserve the
  1587    readability of text when font fallback occurs. It does this by adjusting
  1588    the font-size so that the x-height is the same regardless of the font
  1589    used.
  1591   <div class=example>
  1592    <p>The style defined below defines Verdana as the desired font family, but
  1593     if Verdana is not available Futura or Times will be used.</p>
  1595    <pre>p { 
  1596     font-family: Verdana, Futura, Times; 
  1599 &lt;p>Lorem ipsum dolor sit amet, ...&lt;/p>
  1600 </pre>
  1602    <p>Verdana has a relatively high aspect ratio, lowercase letters are
  1603     relatively tall compared to uppercase letters, so at small sizes text
  1604     appears legible. Times has a lower aspect ratio and so if fallback
  1605     occurs, the text will be less legible at small sizes than Verdana.</p>
  1606   </div>
  1608   <p>How text rendered in each of these fonts compares is shown below, the
  1609    columns show text rendered in Verdana, Futura and Times. The same
  1610    font-size value is used across cells within each row and red lines are
  1611    included to show the differences in x-height. In the upper half each row
  1612    is rendered in the same font-size value. The same is true for the lower
  1613    half but in this half the font-size-adjust property is also set so that
  1614    the actual font size is adjusted to preserve the x-height across each row.
  1615    Note how small text remains relatively legible across each row in the
  1616    lower half.
  1618   <div class=figure><img alt="text with and without font-size-adjust"
  1619    src=fontsizeadjust.png>
  1620    <p class=caption>Text with and without the use of font-size-adjust
  1621   </div>
  1623   <p>This property allows authors to specify an aspect value for an element
  1624    that will effectively preserve the x-height of the first choice font,
  1625    whether it is substituted or not. Values have the following meanings:
  1627   <dl>
  1628    <dt><strong>none</strong>
  1630    <dd>Do not preserve the font's x-height.
  1632    <dt><strong>auto</strong>
  1634    <dd>Behaves just like &lt;number>, except the number used is the aspect
  1635     value calculated by user agents for the first font in the list of fonts
  1636     defined for the initial value of the ‘<a
  1637     href="#descdef-font-family"><code
  1638     class=property>font-family</code></a>’ property. Effectively this is
  1639     the default font used when ‘<a href="#descdef-font-family"><code
  1640     class=property>font-family</code></a>’ is not otherwise specified.
  1641     <p>Authors can use this value to specify that font size should be
  1642      normalized across fonts based on the x-height without the need to
  1643      specify the aspect ratio explicitly.</p>
  1645    <dt><span class=index-inst id=ltnumbergt
  1646     title="&lt;number&gt;">&lt;number&gt;</span>
  1648    <dd>Specifies the aspect value used in the calculation below to calculate
  1649     the adjusted font size:
  1650     <pre>c  =  ( a / a' ) s 
  1651 </pre>
  1653     <p>where:</p>
  1655     <pre>s  =  font-size value
  1656 a  =  aspect value as specified by the font-size-adjust property
  1657 a' =  aspect value of actual font
  1658 c  =  adjusted font-size to use
  1659 </pre>
  1661     <p>This value applies to any font that is selected but in typical usage
  1662      it should be based on the aspect value of the first font in the
  1663      font-family list. If this is specified accurately, the <tt>(a/a')</tt>
  1664      term in the formula above is effectively 1 for the first font and no
  1665      adjustment occurs. If the value is specified inaccurately, text rendered
  1666      using the first font in the family list will display differently in
  1667      older user agents that don't support font-size-adjust.</p>
  1668   </dl>
  1670   <p>Authors can calculate the aspect value for a given font by comparing
  1671    spans with the same content but different font-size-adjust properties. If
  1672    the same font-size is used, the spans will match when the font-size-adjust
  1673    value is accurate for the given font.
  1675   <div class=example>
  1676    <p>Two spans with borders are used to determine the aspect value of a
  1677     font. The font-size is the same for both spans but the font-size-adjust
  1678     property is specified only for the right span. Starting with a value of
  1679     0.5, the aspect value can be adjusted until the borders around the two
  1680     letters line up.</p>
  1682    <pre>p {
  1683     font-family: Futura;
  1684     font-size: 500px;
  1687 span {
  1688     border: solid 1px red;
  1691 .adjust {
  1692     font-size-adjust: 0.5;
  1695 &lt;p>&lt;span>b&lt;/span>&lt;span class="adjust">b&lt;/span>&lt;/p>
  1696 </pre>
  1698    <div class=figure><img alt="Futura with an aspect value of 0.5"
  1699     src=beforefontsizeadjust.png>
  1700     <p class=caption>Futura with an aspect value of 0.5
  1701    </div>
  1703    <p>The box on the right is a bit bigger than the one on the left, so the
  1704     aspect value of this font is something less than 0.5. Adjust the value
  1705     until the boxes align.</p>
  1706   </div>
  1707   <!-- prop: font -->
  1708   <!-- jtdfix, crap, preprocessor is inserting links to descriptors rather than properties.  bert, make it stop... -->
  1709   <!-- <a href="#font-stretch-prop" class="noxref"><span class="property">'font-stretch'</span></a> -->
  1711   <h3 id=font-prop><span class=secno>3.7 </span>Shorthand font property: the
  1712    <a href="#propdef-font">font</a> property</h3>
  1714   <table class=propdef id=namefontvalue-ltlsquofont-stylersquo-ltf>
  1715    <tbody>
  1716     <tr>
  1717      <td>Name:
  1719      <td><dfn id=propdef-font>font</dfn>
  1721     <tr>
  1722      <td>Value:
  1724      <td>[ [ &lt;‘<a href="#propdef-font-style"><code
  1725       class=property>font-style</code></a>’> || &lt;font-variant-css21> ||
  1726       &lt;‘<a href="#propdef-font-weight"><code
  1727       class=property>font-weight</code></a>’> || &lt;‘<a
  1728       href="#propdef-font-stretch"><code
  1729       class=property>font-stretch</code></a>’> ]? &lt;‘<a
  1730       href="#propdef-font-size"><code class=property>font-size</code></a>’>
  1731       [ / &lt;‘<code class=property>line-height</code>’> ]? &lt;‘<a
  1732       href="#descdef-font-family"><code
  1733       class=property>font-family</code></a>’> ] | caption | icon | menu |
  1734       message-box | small-caption | status-bar
  1736     <tr>
  1737      <td>Initial:
  1739      <td>see individual properties
  1741     <tr>
  1742      <td>Applies to:
  1744      <td>all elements
  1746     <tr>
  1747      <td>Inherited:
  1749      <td>yes
  1751     <tr>
  1752      <td>Percentages:
  1754      <td>see individual properties
  1756     <tr>
  1757      <td>Media:
  1759      <td>visual
  1761     <tr>
  1762      <td>Computed value:
  1764      <td>see individual properties
  1766     <tr>
  1767      <td>Animatable:
  1769      <td>see individual properties
  1770   </table>
  1772   <p>The <span class=property>‘<a href="#propdef-font"><code
  1773    class=property>font</code></a>’</span> property is, except as described
  1774    below, a shorthand property for setting ‘<a
  1775    href="#propdef-font-style"><code class=property>font-style</code></a>’,
  1776    <span class=property>‘<a href="#propdef-font-variant"><code
  1777    class=property>font-variant</code></a>’</span>, <span
  1778    class=property>‘<a href="#propdef-font-weight"><code
  1779    class=property>font-weight</code></a>’</span>, <span
  1780    class=property>‘<a href="#propdef-font-stretch"><code
  1781    class=property>font-stretch</code></a>’</span>, <span
  1782    class=property>‘<a href="#propdef-font-size"><code
  1783    class=property>font-size</code></a>’</span>, ‘<code
  1784    class=property>line-height</code>’, <span class=property>‘<a
  1785    href="#descdef-font-family"><code
  1786    class=property>font-family</code></a>’</span> at the same place in the
  1787    stylesheet. Values for the <span class=property>‘<a
  1788    href="#propdef-font-variant"><code
  1789    class=property>font-variant</code></a>’</span> property may also be
  1790    included but only those supported in CSS 2.1, none of the font-variant
  1791    values added in this specification can be used in the <span
  1792    class=property>‘<a href="#propdef-font"><code
  1793    class=property>font</code></a>’</span> shorthand:
  1795   <pre
  1796    class=prod><dfn id=ltfont-variant-css21gt><var>&lt;font-variant-css21&gt;</var></dfn> = [normal | small-caps]</pre>
  1798   <p>The syntax of this property is based on a traditional typographical
  1799    shorthand notation to set multiple properties related to fonts.
  1801   <p>All font-related properties are first reset to their initial values,
  1802    including those listed in the preceding paragraph plus <span
  1803    class=property>‘<a href="#propdef-font-size-adjust"><code
  1804    class=property>font-size-adjust</code></a>’</span>, <span
  1805    class=property>‘<a href="#propdef-font-kerning"><code
  1806    class=property>font-kerning</code></a>’</span> and all font feature
  1807    properties. Then, those properties that are given explicit values in the
  1808    <span class=property>‘<a href="#propdef-font"><code
  1809    class=property>font</code></a>’</span> shorthand are set to those
  1810    values. For a definition of allowed and initial values, see the previously
  1811    defined properties. For reasons of backwards compatibility, it is not
  1812    possible to set <span class=property>‘<a
  1813    href="#propdef-font-size-adjust"><code
  1814    class=property>font-size-adjust</code></a>’</span> to anything other
  1815    than its initial value using the <span class=property>‘<a
  1816    href="#propdef-font"><code class=property>font</code></a>’</span>
  1817    shorthand property; instead, use the individual property.
  1819   <div class=example>
  1820    <p style="display:none">Example(s):
  1822    <p>
  1824    <pre>p { font: 12pt/14pt sans-serif }
  1825 p { font: 80% sans-serif }
  1826 p { font: x-large/110% &quot;new century schoolbook&quot;, serif }
  1827 p { font: bold italic large Palatino, serif }
  1828 p { font: normal small-caps 120%/120% fantasy }
  1829 p { font: condensed oblique 12pt &quot;Helvetica Neue&quot;, serif; }
  1830 </pre>
  1832    <p> In the second rule, the font size percentage value (‘<code
  1833     class=css>80%</code>’) refers to the computed ‘<a
  1834     href="#propdef-font-size"><code class=property>font-size</code></a>’ of
  1835     the parent element. In the third rule, the line height percentage
  1836     (‘<code class=css>110%</code>’) refers to the font size of the
  1837     element itself.
  1839    <p>The first three rules do not specify the <span class=property>‘<a
  1840     href="#propdef-font-variant"><code
  1841     class=property>font-variant</code></a>’</span> and <span
  1842     class=property>‘<a href="#propdef-font-weight"><code
  1843     class=property>font-weight</code></a>’</span> explicitly, so these
  1844     properties receive their initial values (‘<a href="#normal2"><code
  1845     class=property>normal</code></a>’). Notice that the font family name
  1846     "new century schoolbook", which contains spaces, is enclosed in quotes.
  1847     The fourth rule sets the <span class=property>‘<a
  1848     href="#propdef-font-weight"><code
  1849     class=property>font-weight</code></a>’</span> to ‘<code
  1850     class=property>bold</code>’, the <span class=property>‘<a
  1851     href="#propdef-font-style"><code
  1852     class=property>font-style</code></a>’</span> to ‘<code
  1853     class=property>italic</code>’, and implicitly sets <span
  1854     class=property>‘<a href="#propdef-font-variant"><code
  1855     class=property>font-variant</code></a>’</span> to ‘<a
  1856     href="#normal2"><code class=property>normal</code></a>’.
  1858    <p> The fifth rule sets the <span class=property>‘<a
  1859     href="#propdef-font-variant"><code
  1860     class=property>font-variant</code></a>’</span> (‘<a
  1861     href="#small-caps"><code class=property>small-caps</code></a>’), the
  1862     <span class=property>‘<a href="#propdef-font-size"><code
  1863     class=property>font-size</code></a>’</span> (120% of the parent's font
  1864     size), the <span class=property>‘<code
  1865     class=property>line-height</code>’</span> (120% of the font size) and
  1866     the <span class=property>‘<a href="#descdef-font-family"><code
  1867     class=property>font-family</code></a>’</span> (‘<a
  1868     href="#fantasy"><code class=property>fantasy</code></a>’). It follows
  1869     that the keyword ‘<a href="#normal2"><code
  1870     class=property>normal</code></a>’ applies to the two remaining
  1871     properties: <span class=property>‘<a href="#propdef-font-style"><code
  1872     class=property>font-style</code></a>’</span> and <span
  1873     class=property>‘<a href="#propdef-font-weight"><code
  1874     class=property>font-weight</code></a>’</span>.
  1876    <p>The sixth rule sets the <span class=property>‘<a
  1877     href="#propdef-font-style"><code
  1878     class=property>font-style</code></a>’</span>, <span
  1879     class=property>‘<a href="#propdef-font-stretch"><code
  1880     class=property>font-stretch</code></a>’</span>, <span
  1881     class=property>‘<a href="#propdef-font-size"><code
  1882     class=property>font-size</code></a>’</span>, and <span
  1883     class=property>‘<a href="#descdef-font-family"><code
  1884     class=property>font-family</code></a>’</span>, the other font
  1885     properties being set to their initial values.
  1886   </div>
  1888   <p>Since the ‘<a href="#propdef-font-stretch"><code
  1889    class=property>font-stretch</code></a>’ property was not defined in CSS
  1890    2.1, when using ‘<a href="#propdef-font-stretch"><code
  1891    class=property>font-stretch</code></a>’ values within ‘<a
  1892    href="#propdef-font"><code class=property>font</code></a>’ rules,
  1893    authors should include a extra version compatible with older user agents:
  1895   <pre>p {
  1896   font: 80% sans-serif;   /* for older user agents */
  1897   font: condensed 80% sans-serif;
  1898 }</pre>
  1900   <p>The following values refer to system fonts:
  1902   <dl>
  1903    <dt><strong>caption</strong>
  1905    <dd>The font used for captioned controls (e.g., buttons, drop-downs,
  1906     etc.).
  1908    <dt><strong>icon</strong>
  1910    <dd>The font used to label icons.
  1912    <dt><strong>menu</strong>
  1914    <dd>The font used in menus (e.g., dropdown menus and menu lists).
  1916    <dt><strong>message-box</strong>
  1918    <dd>The font used in dialog boxes.
  1920    <dt><strong>small-caption</strong>
  1922    <dd>The font used for labeling small controls.
  1924    <dt><strong>status-bar</strong>
  1926    <dd>The font used in window status bars.
  1927   </dl>
  1929   <p>System fonts may only be set as a whole; that is, the font family, size,
  1930    weight, style, etc. are all set at the same time. These values may then be
  1931    altered individually if desired. If no font with the indicated
  1932    characteristics exists on a given platform, the user agent should either
  1933    intelligently substitute (e.g., a smaller version of the ‘<code
  1934    class=property>caption</code>’ font might be used for the ‘<code
  1935    class=property>small-caption</code>’ font), or substitute a user agent
  1936    default font. As for regular fonts, if, for a system font, any of the
  1937    individual properties are not part of the operating system's available
  1938    user preferences, those properties should be set to their initial values.
  1940   <p>That is why this property is "almost" a shorthand property: system fonts
  1941    can only be specified with this property, not with <span
  1942    class=property>‘<a href="#descdef-font-family"><code
  1943    class=property>font-family</code></a>’</span> itself, so <span
  1944    class=property>‘<a href="#propdef-font"><code
  1945    class=property>font</code></a>’</span> allows authors to do more than
  1946    the sum of its subproperties. However, the individual properties such as
  1947    <span class=property>‘<a href="#propdef-font-weight"><code
  1948    class=property>font-weight</code></a>’</span> are still given values
  1949    taken from the system font, which can be independently varied.
  1951   <p>Note that the keywords used for the system fonts listed above are only
  1952    treated as keywords when they occur in the initial position, in other
  1953    positions the same string is treated as part of the font family name:
  1955   <pre>  font: menu;        /* use the font settings for system menus */
  1956   font: large menu;  /* use a font family named "menu" */</pre>
  1958   <div class=example>
  1959    <p style="display:none">Example(s):
  1961    <p>
  1963    <pre>button { font: 300 italic 1.3em/1.7em &quot;FB Armada&quot;, sans-serif }
  1964 button p { font: menu }
  1965 button p em { font-weight: bolder }
  1966 </pre>
  1968    <p>If the font used for dropdown menus on a particular system happened to
  1969     be, for example, 9-point Charcoal, with a weight of 600, then P elements
  1970     that were descendants of BUTTON would be displayed as if this rule were
  1971     in effect:
  1973    <pre>button p { font: 600 9pt Charcoal }
  1974 </pre>
  1976    <p>Because the <span class=property>‘<a href="#propdef-font"><code
  1977     class=property>font</code></a>’</span> shorthand resets to its initial
  1978     value any property not explicitly given a value, this has the same effect
  1979     as this declaration:
  1981    <pre>button p {
  1982   font-style: normal;
  1983   font-variant: normal;
  1984   font-weight: 600;
  1985   font-size: 9pt;
  1986   line-height: normal;
  1987   font-family: Charcoal
  1989 </pre>
  1990   </div>
  1991   <!-- prop: font-synthesis -->
  1993   <h3 id=font-synthesis-prop><span class=secno>3.8 </span>Controlling
  1994    synthetic faces: the <a href="#propdef-font-synthesis">font-synthesis</a>
  1995    property</h3>
  1997   <table class=propdef id=namefont-synthesisvaluenone-weight-style>
  1998    <tbody>
  1999     <tr>
  2000      <td>Name:
  2002      <td><dfn id=propdef-font-synthesis>font-synthesis</dfn>
  2004     <tr>
  2005      <td>Value:
  2007      <td>none | [ weight || style ]
  2009     <tr>
  2010      <td>Initial:
  2012      <td>weight style
  2014     <tr>
  2015      <td>Applies to:
  2017      <td>all elements
  2019     <tr>
  2020      <td>Inherited:
  2022      <td>yes
  2024     <tr>
  2025      <td>Percentages:
  2027      <td>N/A
  2029     <tr>
  2030      <td>Media:
  2032      <td>visual
  2034     <tr>
  2035      <td>Computed value:
  2037      <td>as specified
  2039     <tr>
  2040      <td>Animatable:
  2042      <td>no
  2043   </table>
  2045   <p>This property controls whether user agents are allowed to synthesize
  2046    bold or oblique font faces when a font family lacks bold or italic faces.
  2047    If ‘<a href="#weight"><code class=property>weight</code></a>’ is not
  2048    specified, user agents must not synthesize bold faces and if ‘<code
  2049    class=property>style</code>’ is not specified user agents must not
  2050    synthesize italic faces. A value of ‘<code class=property>none</code>’
  2051    disallows all synthetic faces.
  2053   <div class=example>
  2054    <p>The style rule below disables the use of synthetically obliqued Arabic:</p>
  2056    <pre>*:lang(ar) { font-synthesis: none; }
  2057 </pre>
  2058   </div>
  2060   <h2 id=font-resources><span class=secno>4 </span>Font Resources</h2>
  2062   <h3 id=font-face-rule><span class=secno>4.1 </span>The
  2063    <code>@font-face</code> rule</h3>
  2065   <p>The <code>@font-face</code> rule allows for linking to fonts that are
  2066    automatically activated when needed. This allows authors to select a font
  2067    that closely matches the design goals for a given page rather than
  2068    limiting the font choice to a set of fonts available on all platforms. A
  2069    set of font descriptors define the location of a font resource, either
  2070    locally or externally, along with the style characteristics of an
  2071    individual face. Multiple <code>@font-face</code> rules can be used to
  2072    construct font families with a variety of faces. Using CSS font matching
  2073    rules, a user agent can selectively download only those faces that are
  2074    needed for a given piece of text.
  2076   <p>In terms of the grammar, this specification defines the following
  2077    productions:
  2079   <pre><dfn id=fontfacerule>font_face_rule</dfn>
  2080   : FONT_FACE_SYM S* '{' S* descriptor_declaration? [ ';' S* descriptor_declaration? ]* '}' S*
  2083 <dfn id=descriptordeclaration>descriptor_declaration</dfn>
  2084   : property ':' S* expr
  2085   ;</pre>
  2087   <p>The following new definitions are introduced:
  2089   <pre>-    -|\\0{0,4}2d(\r\n|[ \t\r\n\f])?
  2090 F    f|\\0{0,4}(46|66)(\r\n|[ \t\r\n\f])?</pre>
  2092   <p>The following new token is introduced:
  2094   <pre>@{F}{O}{N}{T}{-}{F}{A}{C}{E} {return FONT_FACE_SYM;}</pre>
  2096   <p>Each <span class=index-inst id=font-face
  2097    title="@font-face"><code>@font-face</code></span> rule specifies a value
  2098    for every font descriptor, either implicitly or explicitly. Those not
  2099    given explicit values in the rule take the initial value listed with each
  2100    descriptor in this specification. These descriptors apply solely within
  2101    the context of the <code>@font-face</code> rule in which they are defined,
  2102    and do not apply to document language elements. There is no notion of
  2103    which elements the descriptors apply to or whether the values are
  2104    inherited by child elements. When a given descriptor occurs multiple times
  2105    in a given <code>@font-face</code> rule, only the last specified value is
  2106    used, all prior values for that descriptor are ignored.
  2108   <div class=example>
  2109    <p>To use a downloadable font called Gentium:</p>
  2111    <pre>
  2112 @font-face {
  2113   font-family: Gentium;
  2114   src: url(http://example.com/fonts/Gentium.ttf);
  2117 p { font-family: Gentium, serif; }
  2118 </pre>
  2120    <p>The user agent will download Gentium and use it when rendering text
  2121     within paragraph elements. If for some reason the site serving the font
  2122     is unavailable, the default serif font will be used.</p>
  2123   </div>
  2125   <p>A given set of <code>@font-face</code> rules define a set of fonts
  2126    available to containing documents. Multiple rules can be used to define a
  2127    family with a large set of faces. When font matching is done fonts defined
  2128    using these rules are considered before other available fonts on a system.
  2131   <p>Downloaded fonts are only available to documents that reference them,
  2132    the process of activating these fonts should not make them available to
  2133    other applications or to documents that don't directly link to the same
  2134    font. User agent implementers might consider it convenient to use
  2135    downloaded fonts when rendering characters in other documents for which no
  2136    other available font exists as part of the system font fallback procedure.
  2137    This would cause a security leak since the contents of one page would be
  2138    able to affect other pages, something an attacker could use as an attack
  2139    vector. These restrictions do not affect caching behavior, fonts are
  2140    cached the same way other web resources are cached.
  2142   <p>User agents which do not understand the <code>@font-face</code> rule
  2143    encounter the opening curly bracket and ignore forward until the closing
  2144    curly bracket. This at-rule conforms with the forward-compatible parsing
  2145    requirement of CSS, parsers may ignore these rules without error. Any
  2146    descriptors that are not recognized or implemented by a given user agent
  2147    must be ignored. <code>@font-face</code> rules require a font-family and
  2148    src descriptor, if either of these are missing the <code>@font-face</code>
  2149    must be ignored.
  2151   <p>In cases where user agents have limited platform resources or implement
  2152    the ability to disable downloadable font resources,
  2153    <code>@font-face</code> rules must simply be ignored; the behavior of
  2154    individual descriptors as defined in this specification should not be
  2155    altered.
  2157   <h3 id=font-family-desc><span class=secno>4.2 </span>Font family: the <a
  2158    href="#descdef-font-family">font-family</a> descriptor</h3>
  2160   <table class=descdef>
  2161    <tbody>
  2162     <tr>
  2163      <td>Name:
  2165      <td><dfn id=descdef-font-family>font-family</dfn>
  2167     <tr>
  2168      <td>Value:
  2170      <td>&lt;family-name>
  2172     <tr>
  2173      <td><em>Initial:</em>
  2175      <td>N/A
  2176   </table>
  2178   <p>This descriptor defines the font family name that will be used in all
  2179    CSS font family name matching, overriding font family names contained in
  2180    the underlying font data. If the font family name is the same as a font
  2181    family available in a given user's environment, it effectively hides the
  2182    underlying font for documents that use the stylesheet. This permits a web
  2183    author to freely choose font-family names without worrying about conflicts
  2184    with font family names present in a given user's environment. Errors
  2185    loading font data do not affect font name matching behavior. User agents
  2186    that apply platform font aliasing rules to font family names defined via
  2187    <code>@font-face</code> rules are considered non-conformant.
  2189   <h3 id=src-desc><span class=secno>4.3 </span>Font reference: the <a
  2190    href="#descdef-src">src</a> descriptor</h3>
  2192   <table class=descdef>
  2193    <tbody>
  2194     <tr>
  2195      <td>Name:
  2197      <td><dfn id=descdef-src>src</dfn>
  2199     <tr>
  2200      <td>Value:
  2202      <td>[ &lt;uri> [format(&lt;string>#)]? | &lt;font-face-name> ]#
  2204     <tr>
  2205      <td><em>Initial:</em>
  2207      <td>N/A
  2208   </table>
  2210   <p>This descriptor specifies the resource containing font data. It is
  2211    required, whether the font is downloadable or locally installed. Its value
  2212    is a prioritized, comma-separated list of external references or locally
  2213    installed font face names. When a font is needed the user agent iterates
  2214    over the set of references listed, using the first one it can successfully
  2215    activate. Fonts containing invalid data or local font faces that are not
  2216    found are ignored and the user agent loads the next font in the list
  2217    (platform substitutions for a given font must not be used).
  2219   <p>As with other URIs in CSS, the URI may be partial, in which case it is
  2220    resolved relative to the location of the style sheet containing the <span
  2221    class=index-inst id=font-face0
  2222    title="@font-face"><code>@font-face</code></span> rule. In the case of SVG
  2223    fonts, the URL points to an element within a document containing SVG font
  2224    definitions. If the element reference is omitted, a reference to the first
  2225    defined font is implied. Similarly, font container formats that can
  2226    contain more than one font must load one and only one of the fonts for a
  2227    given <code>@font-face</code> rule. Fragment identifiers are used to
  2228    indicate which font to load. If a container format lacks a defined
  2229    fragment identifier scheme, implementations should use a simple 1-based
  2230    indexing scheme (e.g. "font-collection#1" for the first font,
  2231    "font-collection#2" for the second font).
  2233   <pre>
  2234 src: url(fonts/simple.ttf);   /* load simple.ttf relative to stylesheet location */
  2235 src: url(/fonts/simple.ttf);  /* load simple.ttf from absolute location */
  2236 src: url(fonts.svg#simple);   /* load SVG font with id 'simple' */
  2237 </pre>
  2239   <p>External references consist of a URI, followed by an optional hint
  2240    describing the format of the font resource referenced by that URI. The
  2241    format hint contains a comma-separated list of format strings that denote
  2242    well-known font formats. Conformant user agents must skip downloading a
  2243    font resource if the format hints indicate only unsupported or unknown
  2244    font formats. If no format hints are supplied, the user agent should
  2245    download the font resource.
  2247   <pre>
  2248 /* load WOFF font if possible, otherwise use OpenType font */
  2249 @font-face {
  2250   font-family: bodytext;
  2251   src: url(ideal-sans-serif.woff) format("woff"),
  2252        url(basic-sans-serif.ttf) format("opentype");
  2254 </pre>
  2256   <p>Format strings defined by this specification:
  2258   <table class=data id=fontformats>
  2259    <thead>
  2260     <tr>
  2261      <th>String
  2263      <th>Font Format
  2265      <th>Common extensions
  2267    <tbody>
  2268     <tr>
  2269      <th>"woff"
  2271      <td><a href="http://www.w3.org/TR/WOFF/">WOFF (Web Open Font Format)</a>
  2273      <td>.woff
  2275     <tr>
  2276      <th>"truetype"
  2278      <td><a
  2279       href="http://www.microsoft.com/typography/otspec/default.htm">TrueType</a>
  2281      <td>.ttf
  2283     <tr>
  2284      <th>"opentype"
  2286      <td><a
  2287       href="http://www.microsoft.com/typography/otspec/default.htm">OpenType</a>
  2289      <td>.ttf, .otf
  2291     <tr>
  2292      <th>"embedded-opentype"
  2294      <td><a
  2295       href="http://www.w3.org/Submission/2008/SUBM-EOT-20080305/">Embedded
  2296       OpenType</a>
  2298      <td>.eot
  2300     <tr>
  2301      <th>"svg"
  2303      <td><a href="http://www.w3.org/TR/SVG/fonts.html">SVG Font</a>
  2305      <td>.svg, .svgz
  2306   </table>
  2308   <p>Given the overlap in common usage between TrueType and OpenType, the
  2309    format hints "truetype" and "opentype" must be considered as synonymous; a
  2310    format hint of "opentype" does not imply that the font contains Postscript
  2311    CFF style glyph data or that it contains OpenType layout information (see
  2312    <a href="#platform-props-to-css">Appendix A</a> for more background on
  2313    this).
  2315   <p>When authors would prefer to use a locally available copy of a given
  2316    font and download it if it's not, local() can be used. The locally
  2317    installed <span class=index-def id=ltfont-face-namegt
  2318    title="&lt;font-face-name&gt;"><a
  2319    name=value-def-font-face-name>&lt;font-face-name&gt;</a></span> is a
  2320    format-specific string that uniquely identifies a single font face within
  2321    a larger family. The syntax for a &lt;font-face-name&gt; is a unique font
  2322    face name enclosed by "local(" and ")".
  2324   <pre>
  2325 /* regular face of Gentium */
  2326 @font-face {
  2327   font-family: MyGentium;
  2328   src: local(Gentium),   /* use locally available Gentium */
  2329        url(Gentium.ttf); /* otherwise, download it */
  2331 </pre>
  2333   <p>The name can optionally be enclosed in quotes. For OpenType and TrueType
  2334    fonts, this string is used to match only the Postscript name or the full
  2335    font name in the name table of locally available fonts. Which is used
  2336    varies by platform and font, so authors should include both of these names
  2337    to assure proper matching across platforms.
  2339   <pre>
  2340 /* bold face of Gentium */
  2341 @font-face {
  2342   font-family: MyGentium;
  2343   src: local(Gentium Bold),   /* full font name */
  2344        local(Gentium-Bold),   /* Postscript name */
  2345        url(GentiumBold.ttf);  /* otherwise, download it */
  2346   font-weight: bold;
  2348 </pre>
  2350   <p>Just as a <code>@font-face</code> rule specifies the characteristics of
  2351    a single font within a family, the unique name used with local() specifies
  2352    a single font, not an entire font family. Defined in terms of OpenType
  2353    font data, the Postscript name is found in the font's <a
  2354    href="http://www.microsoft.com/typography/otspec/name.htm">name table</a>,
  2355    in the name record with nameID = 6 (see <a href="#OPENTYPE"
  2356    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> for more details). The
  2357    Postscript name is the commonly used key for all fonts on OSX and for
  2358    Postscript CFF fonts under Windows. The full font name (nameID = 4) is
  2359    used as a unique key for fonts with TrueType glyphs on Windows.
  2361   <p>For OpenType fonts with multiple localizations of the full font name,
  2362    the US English version is used (language ID = 0x409 for Windows and
  2363    language ID = 0 for Macintosh) or the first localization when a US English
  2364    full font name is not available (the OpenType specification recommends
  2365    that <a href="http://www.microsoft.com/typography/otspec/recom.htm">all
  2366    fonts minimally include US English names</a>). User agents that also match
  2367    other full font names, e.g. matching the Dutch name when the current
  2368    system locale is set to Dutch, are considered non-conformant. This is done
  2369    not to prefer English but to avoid matching inconsistencies across font
  2370    versions and OS localizations, since font style names (e.g. "Bold") are
  2371    frequently localized into many languages and the set of localizations
  2372    available varies widely across platform and font version. User agents that
  2373    match a concatenation of family name (nameID = 1) with style name (nameID
  2374    = 2) are considered non-conformant.
  2376   <p>This also allows for referencing faces that belong to larger families
  2377    that cannot otherwise be referenced.
  2379   <div class=example>
  2380    <p>Use a local font or reference an SVG font in another document:</p>
  2382    <pre>
  2383 @font-face {
  2384   font-family: Headline;
  2385   src: local(Futura-Medium), 
  2386        url(fonts.svg#MyGeometricModern) format("svg");
  2388 </pre>
  2390    <p>Create an alias for local Japanese fonts on different platforms:</p>
  2392    <pre>
  2393 @font-face {
  2394   font-family: jpgothic;
  2395   src: local(HiraKakuPro-W3), local(Meiryo), local(IPAPGothic);
  2397 </pre>
  2399    <p>Reference a font face that cannot be matched within a larger family:</p>
  2401    <pre>
  2402 @font-face {
  2403   font-family: Hoefler Text Ornaments;
  2404   /* has the same font properties as Hoefler Text Regular */
  2405   src: local(HoeflerText-Ornaments); 
  2407 </pre>
  2409    <p>Since localized fullnames should never match, a document with the
  2410     header style rules below would always render using the default serif
  2411     font, regardless whether a particular system locale parameter is set to
  2412     Finnish or not:</p>
  2414    <pre>
  2415 @font-face {
  2416   font-family: SectionHeader;
  2417   src: local("Arial Lihavoitu");  /* Finnish fullname for Arial Bold, should fail */
  2418   font-weight: bold;
  2421 h2 { font-family: SectionHeader, serif; }
  2422 </pre>
  2424    <p>A conformant user agent should never load the font ‘<code
  2425     class=css>gentium.eot</code>’ in the example below, since it is
  2426     included in the first definition of the ‘<a href="#descdef-src"><code
  2427     class=property>src</code></a>’ descriptor which is overridden by the
  2428     second definition in the same <code>@font-face</code> rule:</p>
  2430    <pre>
  2431 @font-face {
  2432   font-family: MainText;
  2433   src: url(gentium.eot); /* for use with older non-conformant user agents */
  2434   src: local("Gentium"), url(gentium.ttf);  /* Overrides src definition */
  2436 </pre>
  2437   </div>
  2439   <h3 id=font-prop-desc><span class=secno>4.4 </span>Font property
  2440    descriptors: the <a href="#descdef-font-style">font-style</a>, <a
  2441    href="#descdef-font-weight">font-weight</a>, <a
  2442    href="#descdef-font-stretch">font-stretch</a> descriptors</h3>
  2444   <table class=descdef>
  2445    <tbody>
  2446     <tr>
  2447      <td>Name:
  2449      <td><dfn id=descdef-font-style title="font-style
  2450       (descriptor)">font-style</dfn>
  2452     <tr>
  2453      <td>Value:
  2455      <td>normal | italic | oblique
  2457     <tr>
  2458      <td><em>Initial:</em>
  2460      <td>normal
  2461   </table>
  2463   <table class=descdef>
  2464    <tbody>
  2465     <tr>
  2466      <td>Name:
  2468      <td><dfn id=descdef-font-weight title="font-weight
  2469       (descriptor)">font-weight</dfn>
  2471     <tr>
  2472      <td>Value:
  2474      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
  2476     <tr>
  2477      <td><em>Initial:</em>
  2479      <td>normal
  2480   </table>
  2482   <table class=descdef>
  2483    <tbody>
  2484     <tr>
  2485      <td>Name:
  2487      <td><dfn id=descdef-font-stretch title="font-stretch
  2488       (descriptor)">font-stretch</dfn>
  2490     <tr>
  2491      <td>Value:
  2493      <td>normal | ultra-condensed | extra-condensed | condensed |
  2494       semi-condensed | semi-expanded | expanded | extra-expanded |
  2495       ultra-expanded
  2497     <tr>
  2498      <td><em>Initial:</em>
  2500      <td>normal
  2501   </table>
  2503   <p>These descriptors define the characteristics of a font face and are used
  2504    in the process of matching styles to specific faces. For a font family
  2505    defined with several <code>@font-face</code> rules, user agents can either
  2506    download all faces in the family or use these descriptors to selectively
  2507    download font faces that match actual styles used in document. The values
  2508    for these descriptors are the same as those for the corresponding font
  2509    properties except that relative keywords are not allowed, ‘<code
  2510    class=property>bolder</code>’ and ‘<code
  2511    class=property>lighter</code>’. If these descriptors are omitted,
  2512    default values are assumed.
  2514   <p>The value for these font face style attributes is used in place of the
  2515    style implied by the underlying font data. This allows authors to combine
  2516    faces in flexible combinations, even in situations where the original font
  2517    data was arranged differently. User agents that implement synthetic
  2518    bolding and obliqueing must only apply synthetic styling in cases where
  2519    the font descriptors imply this is needed, rather than based on the style
  2520    attributes implied by the font data.
  2522   <h3 id=unicode-range-desc><span class=secno>4.5 </span>Character range: the
  2523    <a href="#descdef-unicode-range">unicode-range</a> descriptor</h3>
  2525   <table class=descdef>
  2526    <tbody>
  2527     <tr>
  2528      <td>Name:
  2530      <td><dfn id=descdef-unicode-range>unicode-range</dfn>
  2532     <tr>
  2533      <td>Value:
  2535      <td>&lt;urange>#
  2537     <tr>
  2538      <td><em>Initial:</em>
  2540      <td>U+0-10FFFF
  2541   </table>
  2543   <p>This descriptor defines the range of Unicode characters supported by a
  2544    given font. The values of <span class=index-def id=lturangegt
  2545    title="&lt;urange&gt;"><a name=value-def-urange>&lt;urange&gt;</a></span>
  2546    are expressed using hexadecimal numbers prefixed by "U+" or "u+",
  2547    corresponding to <a href="http://www.unicode.org/charts/">Unicode
  2548    character code points</a>. The unicode-range descriptor serves as a hint
  2549    for user agents when deciding whether or not to download a font resource.
  2551   <p>Unicode range values are written using hexadecimal values and are ASCII
  2552    case-insensitive. Each is prefixed by "U+" or "u+" and multiple,
  2553    discontinuous ranges are separated by commas. Whitespace before or after
  2554    commas is ignored. Valid character code values vary between 0 and 10FFFF
  2555    inclusive. A single range has three basic forms:
  2557   <ul>
  2558    <li>a single code point (e.g. U+416)
  2560    <li>an interval value range (e.g. U+400-4ff)
  2562    <li>a range where trailing ‘<code class=css>?</code>’ characters imply
  2563     ‘<code class=css>any digit value</code>’ (e.g. U+4??)
  2564   </ul>
  2566   <p>Ranges that do not fit any of the above three forms are considered to be
  2567    parse errors and the descriptor is omitted. Interval ranges consisting of
  2568    a single code point are valid. Ranges specified with ‘?’ that lack an
  2569    initial digit (e.g. "U+???") are also valid, and are treated as if there
  2570    was a single 0 before the question marks (thus, "U+???" = "U+0???" =
  2571    "U+0000-0FFF"). "U+??????" is not a syntax error, even though "U+0??????"
  2572    would be. Ranges can overlap but interval ranges that descend (e.g.
  2573    U+400-32f) are invalid and omitted rather than treated as parse errors;
  2574    they have no effect on other ranges in a list of ranges. Ranges are
  2575    clipped to the domain of Unicode code points (currently 0 – 10FFFF
  2576    inclusive); a range entirely outside the domain is omitted. Without any
  2577    valid ranges, the descriptor is omitted. User agents may normalize the
  2578    list of ranges into a list that is different but represents the same set
  2579    of character code points.
  2581   <p>The character range can be a subset of the full <a
  2582    href="#character-map"><em>character map</em></a> of the underlying font.
  2583    The effective unicode-range used when mapping characters to fonts is the
  2584    intersection of the unicode range specified and the underlying <a
  2585    href="#character-map"><em>character map</em></a> of the font. This means
  2586    that authors do not need to define the unicode-range of a font precisely,
  2587    broad ranges for which a sparse set of code points are defined in the font
  2588    can be used. Code points outside of the defined unicode-range are ignored,
  2589    regardless of whether the font contains a glyph for that code point or
  2590    not. User agents that download fonts for characters outside the defined
  2591    unicode-range are considered non-conformant. Likewise, user agents that
  2592    render a character using a font resource for which the defined
  2593    unicode-range does not include that character are also considered
  2594    non-conformant.
  2596   <p>Example ranges for specific languages or characters:
  2598   <dl>
  2599    <dt>unicode-range: U+A5;
  2601    <dd>a single code point, the yen/yuan symbol
  2603    <dt>unicode-range: U+0-7F;
  2605    <dd>code range for basic ASCII characters
  2607    <dt>unicode-range: U+590-5ff;
  2609    <dd>code range for Hebrew characters
  2611    <dt>unicode-range: U+A5, U+4E00-9FFF, U+30??, U+FF00-FF9F;
  2613    <dd>code range for Japanese kanji, hiragana and katakana characters plus
  2614     yen/yuan symbol
  2615   </dl>
  2617   <div class=example>
  2618    <p>The BBC provides news services in a wide variety of languages, many
  2619     that are not well supported across all platforms. Using an
  2620     <code>@font-face</code> rule, the BBC could provide a font for any of
  2621     these languages, as it already does via a manual font download.</p>
  2623    <pre>
  2624 @font-face {
  2625   font-family: BBCBengali;
  2626   src: url(fonts/BBCBengali.ttf) format("opentype");
  2627   unicode-range: U+00-FF, U+980-9FF;
  2629 </pre>
  2630   </div>
  2632   <div class=example>
  2633    <p>Technical documents often require a wide range of symbols. The STIX
  2634     Fonts project is one project aimed at providing fonts to support a wide
  2635     range of technical typesetting in a standardized way. The example below
  2636     shows the use of a font that provides glyphs for many of the mathematical
  2637     and technical symbol ranges within Unicode:</p>
  2639    <pre>
  2640 @font-face {
  2641   font-family: STIXGeneral;
  2642   src: local(STIXGeneral), url(/stixfonts/STIXGeneral.otf);
  2643   unicode-range: U+000-49F, U+2000-27FF, U+2900-2BFF, U+1D400-1D7FF;
  2645 </pre>
  2646   </div>
  2648   <p>Multiple <code>@font-face</code> rules with different unicode ranges for
  2649    the same family and style descriptor values can be used to create
  2650    composite fonts that mix the glyphs from different fonts for different
  2651    scripts. This can be used to combine fonts that only contain glyphs for a
  2652    single script (e.g. Latin, Greek, Cyrillic) or it can be used by authors
  2653    as a way of segmenting a font into fonts for commonly used characters and
  2654    less frequently used characters. Since the user agent will only pull down
  2655    the fonts it needs this helps reduce page bandwidth.
  2657   <p>If the unicode ranges overlap for a set of <code>@font-face</code> rules
  2658    with the same family and style descriptor values, the rules are ordered in
  2659    the reverse order they were defined; the last rule defined is the first to
  2660    be checked for a given character.
  2662   <div class=example>
  2663    <p>This example shows how an author can override the glyphs used for Latin
  2664     characters in a Japanese font with glyphs from a different font. The
  2665     first rule specifies no range so it defaults to the entire range. The
  2666     range specified in the second rule overlaps but takes precedence because
  2667     it is defined later.</p>
  2669    <pre>
  2670 @font-face {
  2671   font-family: JapaneseWithGentium;
  2672   src: local(MSMincho);
  2673   /* no range specified, defaults to entire range */
  2676 @font-face {
  2677   font-family: JapaneseWithGentium;
  2678   src: url(../fonts/Gentium.ttf);
  2679   unicode-range: U+0-2FF;
  2681 </pre>
  2682   </div>
  2684   <div class=example>
  2685    <p>Consider a family constructed to optimize bandwidth by separating out
  2686     Latin, Japanese and other characters into different font files:</p>
  2688    <pre>
  2689 /* fallback font - size: 4.5MB */
  2690 @font-face {
  2691   font-family: DroidSans;
  2692   src: url(DroidSansFallback.ttf);
  2693   /* no range specified, defaults to entire range */
  2696 /* Japanese glyphs - size: 1.2MB */
  2697 @font-face {
  2698   font-family: DroidSans;
  2699   src: url(DroidSansJapanese.ttf);
  2700   unicode-range: U+3000-9FFF, U+ff??;
  2703 /* Latin, Greek, Cyrillic along with some 
  2704    punctuation and symbols - size: 190KB */
  2705 @font-face {
  2706   font-family: DroidSans;
  2707   src: url(DroidSans.ttf);
  2708   unicode-range: U+000-5FF, U+1e00-1fff, U+2000-2300;
  2710 </pre>
  2712    <p>For simple Latin text, only the font for Latin characters is
  2713     downloaded:</p>
  2715    <pre>
  2716 body { font-family: DroidSans; }
  2718 &lt;p>This is that&lt;/p>
  2719 </pre>
  2721    <p>In this case the user agent first checks the unicode-range for the font
  2722     containing Latin characters (DroidSans.ttf). Since all the characters
  2723     above are in the range U+0-5FF, the user agent downloads the font and
  2724     renders the text with that font.</p>
  2726    <p>Next, consider text that makes use of an arrow character (⇨):</p>
  2728    <pre>
  2729 &lt;p>This &amp;#x21e8; that&lt;p>
  2730 </pre>
  2732    <p>The user agent again first checks the unicode-range of the font
  2733     containing Latin characters. Since U+2000-2300 includes the arrow code
  2734     point (U+21E8), the user agent downloads the font. For this character
  2735     however the Latin font does not have a matching glyph, so the effective
  2736     unicode-range used for font matching excludes this code point. Next, the
  2737     user agent evaluates the Japanese font. The unicode-range for the
  2738     Japanese font, U+3000-9FFF and U+ff??, does not include U+21E8, so the
  2739     user agent does not download the Japanese font. Next the fallback font is
  2740     considered. The <code>@font-face</code> rule for the fallback font does
  2741     not define unicode-range so its value defaults to the range of all
  2742     Unicode code points. The fallback font is downloaded and used to render
  2743     the arrow character.</p>
  2744   </div>
  2746   <h3 id=font-rend-desc><span class=secno>4.6 </span>Font features: the <a
  2747    href="#descdef-font-variant">font-variant</a> and <a
  2748    href="#descdef-font-feature-settings">font-feature-settings</a>
  2749    descriptors</h3>
  2751   <table class=descdef>
  2752    <tbody>
  2753     <tr>
  2754      <td>Name:
  2756      <td><dfn id=descdef-font-variant title="font-variant
  2757       (descriptor)">font-variant</dfn>
  2759     <tr>
  2760      <td>Value:
  2762      <td>normal | [ &lt;common-lig-values&gt; ||
  2763       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  2764       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  2765       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  2766       character-variant(&lt;feature-value-name&gt;#) ||
  2767       swash(&lt;feature-value-name&gt;) ||
  2768       ornaments(&lt;feature-value-name&gt;) ||
  2769       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  2770       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  2771       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  2772       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  2773       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  2774       ruby ]
  2776     <tr>
  2777      <td><em>Initial:</em>
  2779      <td>normal
  2780   </table>
  2782   <table class=descdef>
  2783    <tbody>
  2784     <tr>
  2785      <td>Name:
  2787      <td><dfn id=descdef-font-feature-settings title="font-feature-settings
  2788       (descriptor)">font-feature-settings</dfn>
  2790     <tr>
  2791      <td>Value:
  2793      <td>normal | &lt;feature-tag-value&gt;#
  2795     <tr>
  2796      <td><em>Initial:</em>
  2798      <td>normal
  2799   </table>
  2801   <p>These descriptors define settings that apply when the font defined by an
  2802    <code>@font-face</code> rule is rendered. They do not affect font
  2803    selection. Values are identical to those defined for the corresponding
  2804    ‘<a href="#propdef-font-variant"><code
  2805    class=property>font-variant</code></a>’ and ‘<a
  2806    href="#propdef-font-feature-settings"><code
  2807    class=property>font-feature-settings</code></a>’ properties defined
  2808    below except that the value ‘<code class=property>inherit</code>’ is
  2809    omitted. When multiple font feature descriptors or properties are used,
  2810    the cumulative effect on text rendering is detailed in the section <a
  2811    href="#font-feature-resolution">Font Feature Resolution</a> below. In
  2812    cases where specific values define synthesized fallback for certain ‘<a
  2813    href="#propdef-font-variant"><code
  2814    class=property>font-variant</code></a>’ subproperties, the same
  2815    synthesized fallback applies when used within those values are used with
  2816    the <a href="#descdef-font-variant">‘<code
  2817    class=property>font-variant</code>’</a> descriptor.
  2819   <h3 id=font-face-loading><span class=secno>4.7 </span>Font loading
  2820    guidelines</h3>
  2822   <p>The <code>@font-face</code> rule is designed to allow lazy loading of
  2823    fonts, fonts are only downloaded when needed for use within a document. A
  2824    stylesheet can include <code>@font-face</code> rules for a library of
  2825    fonts of which only a select set are used; user agents must only download
  2826    those fonts that are referred to within the style rules applicable to a
  2827    given page. User agents that download all fonts defined in
  2828    <code>@font-face</code> rules without considering whether those fonts are
  2829    in fact used within a page are considered non-conformant. In cases where a
  2830    font might be downloaded in character fallback cases, user agents may
  2831    download a font if it's listed in a font list but is not actually used for
  2832    a given text run.
  2834   <pre>
  2835 @font-face {
  2836   font-family: GeometricModern;
  2837   src: url(font.ttf);
  2840 p {
  2841   /* font will be downloaded for pages with p elements */
  2842   font-family: GeometricModern, sans-serif;
  2845 h2 {
  2846   /* font may be downloaded for pages with h2 elements, even if Futura is available locally */
  2847   font-family: Futura, GeometricModern, sans-serif;
  2849 </pre>
  2851   <p>In cases where textual content is loaded before downloadable fonts are
  2852    available, user agents may render text as it would be rendered if
  2853    downloadable font resources are not available or they may render text
  2854    transparently with fallback fonts to avoid a flash of text using a
  2855    fallback font. In cases where the font download fails user agents must
  2856    display text, simply leaving transparent text is considered non-conformant
  2857    behavior. Authors are advised to use fallback fonts in their font lists
  2858    that closely match the vertical metrics of the downloadable fonts to avoid
  2859    large page reflows where possible.
  2861   <h3 id=same-origin-restriction><span class=secno>4.8 </span>Same-origin
  2862    restriction for fonts</h3>
  2864   <h4 id=default-same-origin-restriction><span class=secno>4.8.1
  2865    </span>Default same-origin restriction</h4>
  2866   <!-- TPAC 2011 Resolution to require same-origin restriction for loading fonts:
  2867   http://lists.w3.org/Archives/Public/www-style/2011Nov/0711.html
  2868   http://www.w3.org/2011/10/31-webapps-minutes.html#item02
  2869 -->
  2871   <p>User agents must implement a same-origin restriction when loading fonts
  2872    via the <code>@font-face</code> mechanism. This restriction limits the
  2873    loading of fonts for a given document to fonts loaded from the same
  2874    origin. Fonts can only be loaded via the same host, port, and method
  2875    combination as the containing document, using the <a
  2876    href="http://www.w3.org/TR/html5/browsers.html#origin">origin matching
  2877    algorithm</a> described in the <a href="#HTML5"
  2878    rel=biblioentry>[HTML5]<!--{{!HTML5}}--></a> specification. The origin of
  2879    the stylesheet containing <code>@font-face</code> rules is not used when
  2880    deciding whether a font is same origin or not, only the origin of the
  2881    containing document is used. The restriction applies to all font types.
  2883   <p>Given a document located at http://example.com/page.html, fonts defined
  2884    with ‘<a href="#descdef-src"><code class=property>src</code></a>’
  2885    definitions considered cross origin must not be loaded:
  2887   <pre>
  2888 /* same origin (i.e. domain, protocol, port match document) */
  2889 src: url(fonts/simple.ttf);                     
  2890 src: url(//fonts/simple.ttf);                     
  2892 /* cross origin, different protocol */
  2893 src: url(https://example.com/fonts/simple.ttf);              
  2895 /* cross origin, different domain */
  2896 src: url(http://another.example.com/fonts/simple.ttf); 
  2897 </pre>
  2899   <h4 id=allowing-cross-origin-font-loading><span class=secno>4.8.2
  2900    </span>Allowing cross-origin font loading</h4>
  2902   <p>User agents must also implement the ability to relax this restriction
  2903    using cross-site origin controls <a href="#CORS"
  2904    rel=biblioentry>[CORS]<!--{{!CORS}}--></a> for fonts loaded via HTTP.
  2905    Sites can explicitly allow cross-site downloading of font data using the
  2906    <code>Access-Control-Allow-Origin</code> HTTP header. For other protocols,
  2907    no explicit relaxation mechanism is defined or required.
  2909   <p>For font loads over HTTP, cross-origin requests must be made with the
  2910    following parameter settings which are used in conjunction with the <a
  2911    href="http://www.w3.org/TR/cors/#cross-origin-request-0"> <em>cross-origin
  2912    request algorithm</em></a> <a href="#CORS"
  2913    rel=biblioentry>[CORS]<!--{{!CORS}}--></a>:
  2915   <ul>
  2916    <li><em>request URL</em> — the URL of the font resource in the <a
  2917     href="#descdef-src"><code>src</code></a> descriptor
  2919    <li><em>request method</em> — GET
  2921    <li><em>author request headers</em> — none
  2923    <li><em>request entity body</em> — empty
  2925    <li><em>source origin</em> — the origin of the page which linked to the
  2926     stylesheet
  2928    <li><em>manual redirect flag</em> — false
  2930    <li><em>omit credentials flag</em> — true
  2932    <li><em>force preflight flag</em> — false
  2933   </ul>
  2935   <h2 id=font-matching-algorithm><span class=secno>5 </span>Font Matching
  2936    Algorithm</h2>
  2938   <p>The algorithm below describes how fonts are associated with individual
  2939    runs of text. For each character in the run a font family is chosen and a
  2940    particular font face is selected containing a glyph for that character.
  2942   <h3 id=font-family-casing><span class=secno>5.1 </span>Case sensitivity of
  2943    font family names</h3>
  2945   <p>As part of the font matching algorithm outlined below, user agents must
  2946    match font family names used in style rules with actual font family names
  2947    contained in fonts available in a given environment or defined via
  2948    <code>@font-face</code> rules. User agents must match these names case
  2949    insensitively, using the "Default Caseless Matching" algorithm outlined in
  2950    the Unicode specification <a href="#UNICODE6"
  2951    rel=biblioentry>[UNICODE6]<!--{{!UNICODE6}}--></a>. This algorithm is
  2952    detailed in section 3.13 entitled "Default Case Algorithms". Specifically,
  2953    the algorithm must be applied without normalizing the strings involved and
  2954    without applying any language-specific tailorings. The case folding method
  2955    specified by this algorithm uses the case mappings with status field
  2956    ‘<code class=property>C</code>’ or ‘<code class=property>F</code>’
  2957    in the CaseFolding.txt file of the Unicode Character Database.
  2959   <p class=note> Implementors should take care to verify that a given
  2960    caseless string comparison implementation uses this precise algorithm and
  2961    not assume that a given platform string matching routine follows it, as
  2962    many of these have locale-specific behavior or use some level of string
  2963    normalization.
  2965   <p class=note> For authors this means that font family names are matched
  2966    case insensitively, whether or not those names exist in a platform font or
  2967    in the <code>@font-face</code> rules contained in a stylesheet. Authors
  2968    should take care to ensure that names use a character sequence consistent
  2969    with the actual font family name, particularly when using combining
  2970    characters such as diacritical marks. For example, a family name that
  2971    contains an uppercase A (U+0041) followed by a combining ring (U+030A)
  2972    will <strong>not</strong> match a name that looks identical but which uses
  2973    the precomposed lowercase a-ring character (U+00E5) instead of the
  2974    combining sequence.
  2976   <h3 id=font-style-matching><span class=secno>5.2 </span>Matching font
  2977    styles</h3>
  2979   <p>The procedure for choosing fonts consists of iterating over the font
  2980    families determined by the font-family property, selecting a font face
  2981    with the appropriate style based on other font properties and then
  2982    determining whether a glyph exists for a given character. This is done
  2983    using the <dfn id=character-map>character map</dfn> of the font, data
  2984    which maps characters to the default glyph for that character. Codepoint
  2985    sequences consisting of a base character followed by a sequence of
  2986    combining characters are treated slightly differently, see the section on
  2987    <a href="#cluster-matching">cluster matching</a> below.
  2989   <p>For this procedure, the <dfn id=default-face>default face</dfn> for a
  2990    given font family is defined to be the face that would be selected if all
  2991    font style properties were set to their initial value.
  2993   <ol id=fontmatchingalg>
  2994    <li>Using the computed font property values for a given element, the user
  2995     agent starts with the first family name in the fontlist specified by the
  2996     <span class=property>‘<a href="#descdef-font-family"><code
  2997     class=property>font-family</code></a>’</span> property.
  2999    <li>If the family name is unquoted and is a generic family name, the user
  3000     agent looks up the appropriate font family name to be used. User agents
  3001     may choose the generic font family to use based on the language of the
  3002     containing element or the Unicode range of the character.
  3004    <li>For other family names, the user agent attempts to find the family
  3005     name among fonts defined via <code>@font-face</code> rules and then among
  3006     available system fonts, matching names with a case-insensitive comparison
  3007     as outlined <a href="#font-family-casing">in the section above</a>. On
  3008     systems containing fonts with multiple localized font family names, user
  3009     agents must match any of these names independent of the underlying system
  3010     locale or platform API used. If the font resources defined for a given
  3011     face in an @font-face rule are either not available or contain invalid
  3012     font data, then the face should be treated as not present in the family.
  3013     If no faces are present for a family defined via @font-face rules, the
  3014     family should be treated as missing; matching a platform font with the
  3015     same name must not occur in this case.
  3017    <li>If a font family match occurs, the user agent assembles the set of
  3018     font faces in that family and then narrows the set to a single face using
  3019     other font properties in the order given below:
  3020     <ol id=fontstylematchingalg>
  3021      <li><span class=property>‘<a href="#propdef-font-stretch"><code
  3022       class=property>font-stretch</code></a>’</span> is tried first. If the
  3023       matching set contains faces with width values matching the ‘<a
  3024       href="#propdef-font-stretch"><code
  3025       class=property>font-stretch</code></a>’ value, faces with other width
  3026       values are removed from the matching set. If there is no face that
  3027       exactly matches the width value the nearest width is used instead. If
  3028       the value of ‘<a href="#propdef-font-stretch"><code
  3029       class=property>font-stretch</code></a>’ is ‘<a
  3030       href="#normal2"><code class=property>normal</code></a>’ or one of the
  3031       condensed values, narrower width values are checked first, then wider
  3032       values. If the value of ‘<a href="#propdef-font-stretch"><code
  3033       class=property>font-stretch</code></a>’ is one of the expanded
  3034       values, wider values are checked first, followed by narrower values.
  3035       Once the closest matching width has been determined by this process,
  3036       faces with other widths are removed from the matching set.
  3038      <li><span class=property>‘<a href="#propdef-font-style"><code
  3039       class=property>font-style</code></a>’</span> is tried next. If the
  3040       value of ‘<a href="#propdef-font-style"><code
  3041       class=property>font-style</code></a>’ is ‘<code
  3042       class=property>italic</code>’, italic faces are checked first, then
  3043       oblique, then normal faces. If the value is ‘<code
  3044       class=property>oblique</code>’, oblique faces are checked first, then
  3045       italic faces and then normal faces. If the value is ‘<a
  3046       href="#normal2"><code class=property>normal</code></a>’, normal faces
  3047       are checked first, then oblique faces, then italic faces. Faces with
  3048       other style values are excluded from the matching set. User agents are
  3049       permitted to distinguish between italic and oblique faces within
  3050       platform font families but this is not required, they may treat all
  3051       italic or oblique faces as italic faces. However, within font families
  3052       defined via <code>@font-face</code> rules, italic and oblique faces
  3053       must be distinguished using the value of the ‘<a
  3054       href="#propdef-font-style"><code
  3055       class=property>font-style</code></a>’ descriptor.
  3057      <li><span class=property>‘<a href="#propdef-font-weight"><code
  3058       class=property>font-weight</code></a>’</span> is matched next, it
  3059       will always reduce the matching set to a single font face. If
  3060       bolder/lighter relative weights are used, the effective weight is
  3061       calculated based on the inherited weight value, as described in the
  3062       definition of the ‘<a href="#propdef-font-weight"><code
  3063       class=property>font-weight</code></a>’ property. Given the desired
  3064       weight and the weights of faces in the matching set after the steps
  3065       above, if the desired weight is available that face matches. Otherwise,
  3066       a weight is chosen using the rules below:
  3067       <ul>
  3068        <li>If the desired weight is less than 400, weights below the desired
  3069         weight are checked in descending order followed by weights above the
  3070         desired weight in ascending order until a match is found.
  3072        <li>If the desired weight is greater than 500, weights above the
  3073         desired weight are checked in ascending order followed by weights
  3074         below the desired weight in descending order until a match is found.
  3076        <li>If the desired weight is 400, 500 is checked first and then the
  3077         rule for desired weights less than 400 is used.
  3079        <li>If the desired weight is 500, 400 is checked first and then the
  3080         rule for desired weights less than 400 is used.
  3081       </ul>
  3083      <li><span class=property>‘<a href="#propdef-font-size"><code
  3084       class=property>font-size</code></a>’</span> must be matched within a
  3085       UA-dependent margin of tolerance. (Typically, sizes for scalable fonts
  3086       are rounded to the nearest whole pixel, while the tolerance for
  3087       bitmapped fonts could be as large as 20%.) Further computations, e.g.,
  3088       by ‘<code class=property>em</code>’ values in other properties, are
  3089       based on the <span class=property>‘<a href="#propdef-font-size"><code
  3090       class=property>font-size</code></a>’</span> value that is used, not
  3091       the one that is specified.
  3092     </ol>
  3094    <li>
  3095     <p>If no matching face exists or the matched face does not contain a
  3096      glyph for the character to be rendered, the next family name is selected
  3097      and the previous two steps repeated. Glyphs from other faces in the
  3098      family are not considered. The only exception is that user agents may
  3099      optionally substitute a synthetic version of the <a
  3100      href="#default-face"><em>default face</em></a> if that face supports a
  3101      given glyph (e.g. a synthetic italic version of the regular face may be
  3102      used if the italic face doesn't support glyphs for Arabic).</p>
  3103     <!-- resolution on the above: http://lists.w3.org/Archives/Public/www-style/2012Nov/0292.html -->
  3105     <p>If the matched font is defined via an <code>@font-face</code> rule and
  3106      needs to be downloaded, the font resource is downloaded. While the
  3107      download occurs, the user agent can either wait until the font is
  3108      downloaded or render once with substituted font metrics and render again
  3109      once the font is downloaded.</p>
  3111    <li>If there are no more font families to be evaluated and no matching
  3112     face has been found, then the user agent performs a <em>system font
  3113     fallback</em> procedure to find the best match for the character to be
  3114     rendered. The result of this procedure may vary across user agents.
  3116    <li>If a particular character cannot be displayed using any font, the user
  3117     agent should indicate by some means that a character is not being
  3118     displayed, displaying either a symbolic representation of the missing
  3119     glyph (e.g. using a <a
  3120     href="http://en.wikipedia.org/wiki/Last_resort_font">Last Resort
  3121     Font</a>) or using the missing character glyph from a default font.
  3122   </ol>
  3124   <h3 id=cluster-matching><span class=secno>5.3 </span>Cluster matching</h3>
  3126   <p>When text contains characters such as combining diacritics, ideally the
  3127    base character should be rendered using the same font as the diacritic,
  3128    this assures proper placement of the diacritic. For this reason, the font
  3129    matching algorithm for clusters is more specialized than the general case
  3130    of matching a single character by itself. For sequences containing
  3131    variation selectors, which indicate the precise glyph to be used for a
  3132    given character, user agents always attempt system font fallback to find
  3133    the appropriate glyph before using the default glyph of the base
  3134    character.
  3136   <p>A font is considered to <em>support</em> a given character if (1) the
  3137    character is contained in the font's <a
  3138    href="#character-map"><em>character map</em></a> and (2) if required by
  3139    the containing script, shaping information is available for that
  3140    character. Some legacy fonts may include a given character in the <a
  3141    href="#character-map"><em>character map</em></a> but lack the shaping
  3142    information (e.g. <a
  3143    href="http://www.microsoft.com/typography/otspec/ttochap1.htm">OpenType
  3144    layout tables</a> or <a
  3145    href="http://scripts.sil.org/cms/scripts/page.php?site_id=projects&amp;item_id=graphite_techAbout">Graphite
  3146    tables</a>) necessary for correctly rendering text runs containing that
  3147    character.
  3149   <p>A sequence of codepoints containing combining diacritics or other
  3150    modifiers is termed a grapheme cluster (see <a href="#CSS3TEXT"
  3151    rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a> for a more complete
  3152    description). For a given cluster containing a base character, <em>b</em>
  3153    and a sequence of combining characters <em>c1, c2…</em>, the entire
  3154    cluster is matched using these steps:
  3156   <ol>
  3157    <li>For each family in the font list, a face is chosen using the style
  3158     selection rules defined in the previous section.
  3159     <ol>
  3160      <li>If all characters in the sequence <em>b + c1 + c2 …</em> are
  3161       completely supported by the font, select this font for the sequence.
  3163      <li>If a sequence of multiple codepoints is canonically equivalent to a
  3164       single character and the font supports that character, select this font
  3165       for the sequence.
  3166     </ol>
  3168    <li>If no font was found in the font list in step 1:
  3169     <ol>
  3170      <li>If <em>c1</em> is a variation selector, system fallback must be used
  3171       to find a font that supports the full sequence of <em>b + c1</em>. If
  3172       no font on the system supports the full sequence, match the single
  3173       character <em>b</em> using the normal procedure for matching single
  3174       characters and ignore the variation selector. Note: a sequence with
  3175       more than one variation selector is treated as an encoding error and
  3176       the trailing selectors are ignored.
  3178      <li>Otherwise, the user agent may optionally use system font fallback to
  3179       match a font that supports the entire cluster.
  3180     </ol>
  3182    <li>If no font is found in step 2, use the matching sequence from step 1
  3183     to determine the longest sequence that is completely matched by a font in
  3184     the font list and attempt to match the remaining combining characters
  3185     separately using the rules for single characters.
  3186   </ol>
  3188   <h3 id=char-handling-issues><span class=secno>5.4 </span>Character handling
  3189    issues</h3>
  3191   <p>The procedure above is always performed on text runs containing Unicode
  3192    characters, documents using legacy encodings are assumed to have been
  3193    transcoded before matching fonts. For fonts containing <a
  3194    href="#character-map"><em title="character map">character maps</em></a>
  3195    for both legacy encodings and Unicode, the contents of the legacy encoding
  3196    <a href="#character-map"><em>character map</em></a> must have no effect on
  3197    the results of the font matching process.
  3199   <p>The font matching process does not assume that text runs are in either
  3200    normalized or denormalized form (see <a href="#CHARMOD-NORM"
  3201    rel=biblioentry>[CHARMOD-NORM]<!--{{CHARMOD-NORM}}--></a> for more
  3202    details). Layout engines often convert base character plus combining
  3203    character sequences into precomposed characters if they exist. The font
  3204    matching algorithm outlined here supports both ways and fonts can
  3205    generally support either but variations can occur. Authors should always
  3206    tailor their choice of fonts to their content, including whether that
  3207    content contains normalized or denormalized character streams.
  3209   <p>If a given character is a Private-Use Area Unicode codepoint and none of
  3210    the fonts in the fontlist contain a glyph for that codepoint, user agents
  3211    must display some form of missing glyph symbol for that character rather
  3212    than attempting system font fallback for that codepoint. When matching the
  3213    replacement character U+FFFD, user agents may skip the font matching
  3214    process and immediately display some form of missing glyph symbol, they
  3215    are not required to display the glyph from the font that would be selected
  3216    by the font matching process.
  3218   <p>In general, the fonts for a given family will all have the same or
  3219    similar <a href="#character-map"><em title="character map">character
  3220    maps</em></a>. The process outlined here is designed to handle even font
  3221    families containing faces with widely variant <a href="#character-map"><em
  3222    title="character map">character maps</em></a>. However, authors are
  3223    cautioned that the use of such families can lead to unexpected results.
  3225   <p>Optimizations of this process are allowed provided that an
  3226    implementation behaves as if the algorithm had been followed exactly.
  3227    Matching occurs in a well-defined order to insure that the results are as
  3228    consistent as possible across user agents, given an identical set of
  3229    available fonts and rendering technology.
  3231   <h3 id=font-matching-changes><span class=secno>5.5 </span>Font matching
  3232    changes since CSS 2.1</h3>
  3234   <p>The algorithm above is different from CSS 2.1 in a number of key places.
  3235    These changes were made to better reflect actual font matching behavior
  3236    across user agent implementations.
  3238   <p>Differences compared to the font matching algorithm in CSS 2.1:
  3240   <ul>
  3241    <li>The algorithm includes font-stretch matching.
  3243    <li>All possible font-style matching scenarios are delineated.
  3245    <li>Small-caps fonts are not matched as part of the font matching process,
  3246     they are now handled via font features.
  3248    <li>Unicode variation selector matching is required.
  3250    <li>Cluster sequences are matched as a unit.
  3251   </ul>
  3253   <h3 id=font-matching-examples><span class=secno>5.6 </span>Font matching
  3254    examples</h3>
  3256   <div class=example>
  3257    <p>It's useful to note that the CSS selector syntax may be used to create
  3258     language-sensitive typography. For example, some Chinese and Japanese
  3259     characters are unified to have the same Unicode code point, although the
  3260     abstract glyphs are not the same in the two languages.
  3262    <pre>*:lang(ja-jp) { font: 900 14pt/16pt &quot;Heisei Mincho W9&quot;, serif; }
  3263 *:lang(zh-tw) { font: 800 14pt/16.5pt &quot;Li Sung&quot;, serif; }
  3264 </pre>
  3266    <p>This selects any element that has the given language - Japanese or
  3267     Traditional Chinese - and uses the appropriate font.
  3268   </div>
  3270   <h2 id=font-rend-props><span class=secno>6 </span>Font Feature Properties</h2>
  3272   <p>Modern font technologies support a variety of advanced typographic and
  3273    language-specific font features. Using these features, a single font can
  3274    provide glyphs for a wide range of ligatures, contextual and stylistic
  3275    alternates, tabular and old-style figures, small capitals, automatic
  3276    fractions, swashes, and alternates specific to a given language. To allow
  3277    authors control over these font capabilities, the font-variant property
  3278    has been expanded for CSS3, it now functions as a shorthand for a set of
  3279    properties that provide control over stylistic font features.
  3281   <h3 id=glyph-selection-positioning><span class=secno>6.1 </span>Glyph
  3282    selection and positioning</h3>
  3284   <p>Simple fonts used for displaying Latin text use a very basic processing
  3285    model, fonts contain a <a href="#character-map"><em>character map</em></a>
  3286    which maps a given character to a glyph for that character. Glyphs for
  3287    subsequent characters are simply placed next in line along a run of text.
  3288    Font formats such as OpenType and AAT (Apple Advanced Typography) use a
  3289    richer processing model, the glyph for a given character can be chosen and
  3290    positioned not just based on a single character, but also based on
  3291    surrounding characters along with the language, script, and features
  3292    enabled for the text. Font features may be required for specific scripts,
  3293    or recommended as enabled by default or they may be stylistic features
  3294    meant to be used under author control.
  3296   <p>For a good visual overview of these features, see the <a
  3297    href="#OPENTYPE-FONT-GUIDE"
  3298    rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
  3299    For a detailed description of glyph processing for OpenType fonts, see <a
  3300    href="#WINDOWS-GLYPH-PROC"
  3301    rel=biblioentry>[WINDOWS-GLYPH-PROC]<!--{{WINDOWS-GLYPH-PROC}}--></a>.
  3303   <p>Stylistic font features can be classified into two broad categories,
  3304    ones that affect the harmonization of glyph shapes with the surrounding
  3305    context, such as kerning and ligature features, and those such as the
  3306    small-caps, subscript/superscript and alternate features that affect shape
  3307    selection.
  3309   <p>The subproperties of font-variant listed below are used to control these
  3310    stylistic font features; they do not control features that are required
  3311    for displaying certain scripts, such as the OpenType features used when
  3312    displaying Arabic or Indic language text. They affect glyph selection and
  3313    positioning, they do not affect font selection as described in the font
  3314    matching section (except in cases required for compatibility with CSS
  3315    2.1).
  3317   <p>To assure consistent behavior across user agents, the equivalent
  3318    OpenType property settings are listed for individual properties and must
  3319    be considered normative. When using other font formats these should be
  3320    used as a guideline to map CSS font feature property values to specific
  3321    font features.
  3323   <h3 id=language-specific-support><span class=secno>6.2
  3324    </span>Language-specific display</h3>
  3326   <p>OpenType also supports language-specific glyph selection and
  3327    positioning, so that text can be displayed correctly in cases where the
  3328    language dictates a specific display behavior. Languages often share a
  3329    common script but the shape of certain letters may vary across those
  3330    languages, such as the variations in certain Cyrillic letters used in
  3331    Russian and Bulgarian text. In Latin text, it's common to render "fi" with
  3332    an explicit fi-ligature that lacks a dot on the "i". However, in languages
  3333    such as Turkish which uses both a dotted-i and a dotless-i, it's important
  3334    to not use this ligature or use a specialized version that contains a dot
  3335    over the "i". The example below shows language-specific variations based
  3336    on stylistic traditions found in Spanish, Italian and French orthography:
  3338   <div class=featex><img alt="language specific forms, spanish"
  3339    src=locl-1.png></div>
  3341   <div class=featex><img alt="language specific forms, italian"
  3342    src=locl-2.png></div>
  3344   <div class=featex><img alt="language specific forms, french"
  3345    src=locl-3.png></div>
  3347   <p>If the content language of the element is known, according to the rules
  3348    of the <a
  3349    href="http://www.w3.org/TR/CSS21/conform.html#doclanguage">document
  3350    language</a>, user agents are required to infer the OpenType language
  3351    system from the content language and use that when selecting and
  3352    positioning glyphs using an OpenType font.
  3354   <p>For OpenType fonts, in some cases it may be necessary to explicitly
  3355    declare the OpenType language to be used, for example when displaying text
  3356    in a given language that uses the typographic conventions of another
  3357    language or when the font does not explicitly support a given language but
  3358    supports a language that shares common typographic conventions. The ‘<a
  3359    href="#propdef-font-language-override"><code
  3360    class=property>font-language-override</code></a>’ property is used for
  3361    this purpose.
  3363   <p class=issue>Should user agents be allowed to infer the OpenType language
  3364    or simply use only the default language system? Do we also need a
  3365    normative definition of how the script system is inferred?</p>
  3366   <!-- prop: font-kerning -->
  3368   <h3 id=font-kerning-prop><span class=secno>6.3 </span>Kerning: the <a
  3369    href="#propdef-font-kerning">font-kerning</a> property</h3>
  3371   <table class=propdef id=namefont-kerningvalueauto-normal-noneini>
  3372    <tbody>
  3373     <tr>
  3374      <td>Name:
  3376      <td><dfn id=propdef-font-kerning>font-kerning</dfn>
  3378     <tr>
  3379      <td>Value:
  3381      <td>auto | normal | none
  3383     <tr>
  3384      <td>Initial:
  3386      <td>auto
  3388     <tr>
  3389      <td>Applies to:
  3391      <td>all elements
  3393     <tr>
  3394      <td>Inherited:
  3396      <td>yes
  3398     <tr>
  3399      <td>Percentages:
  3401      <td>N/A
  3403     <tr>
  3404      <td>Media:
  3406      <td>visual
  3408     <tr>
  3409      <td>Computed value:
  3411      <td>as specified
  3413     <tr>
  3414      <td>Animatable:
  3416      <td>no
  3417   </table>
  3419   <p>Kerning is the contextual adjustment of inter-glyph spacing. This
  3420    property controls metric kerning, kerning that utilizes adjustment data
  3421    contained in the font. The value ‘<a href="#normal2"><code
  3422    class=property>normal</code></a>’ implies that kerning is applied while
  3423    the value ‘<code class=property>none</code>’ implies that kerning is
  3424    not applied when rendering text. If the value is ‘<code
  3425    class=property>auto</code>’, a user agent is free to choose whether
  3426    kerning is enabled or not by default and to vary that default based on the
  3427    underlying text script.
  3429   <p>For fonts that do not include kerning data this property will have no
  3430    visible effect. When rendering with OpenType fonts, the <a
  3431    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>
  3432    specification suggests that kerning be enabled by default. When kerning is
  3433    enabled, the OpenType <span class=tag>kern</span> feature is enabled (for
  3434    vertical text runs the <span class=tag>vkrn</span> feature is enabled).
  3435    User agents must also support fonts that only support kerning via data
  3436    contained in a ‘<code class=property>kern</code>’ font table, as
  3437    detailed in the OpenType specification. Authors may prefer to disable
  3438    kerning in situations where performance is more important that precise
  3439    appearance. If the ‘<code class=property>letter-spacing</code>’
  3440    property is defined, kerning adjustments are considered part of the
  3441    default spacing, letter spacing adjustments are made after kerning has
  3442    been applied.</p>
  3443   <!-- prop: font-variant-ligatures -->
  3445   <h3 id=font-variant-ligatures-prop><span class=secno>6.4 </span>Ligatures:
  3446    the <a href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
  3447    property</h3>
  3449   <table class=propdef id=namefont-variant-ligaturesvaluenormal-no>
  3450    <tbody>
  3451     <tr>
  3452      <td>Name:
  3454      <td><dfn id=propdef-font-variant-ligatures>font-variant-ligatures</dfn>
  3456     <tr>
  3457      <td>Value:
  3459      <td>normal | none | [ &lt;common-lig-values> ||
  3460       &lt;discretionary-lig-values> || &lt;historical-lig-values> ||
  3461       &lt;contextual-alt-values> ]
  3463     <tr>
  3464      <td>Initial:
  3466      <td>normal
  3468     <tr>
  3469      <td>Applies to:
  3471      <td>all elements
  3473     <tr>
  3474      <td>Inherited:
  3476      <td>yes
  3478     <tr>
  3479      <td>Percentages:
  3481      <td>N/A
  3483     <tr>
  3484      <td>Media:
  3486      <td>visual
  3488     <tr>
  3489      <td>Computed value:
  3491      <td>as specified
  3493     <tr>
  3494      <td>Animatable:
  3496      <td>no
  3497   </table>
  3499   <p>Ligatures and contextual forms are ways of combining glyphs to produce
  3500    more harmonized forms. A value of ‘<a href="#normal2"><code
  3501    class=property>normal</code></a>’ implies that common default features
  3502    are enabled, <a href="#font-feature-resolution">as described in detail in
  3503    the next section</a>. For OpenType fonts, common ligatures and contextual
  3504    forms are on by default, discretionary and historical ligatures are not. A
  3505    value of ‘<code class=property>none</code>’ implies that all types of
  3506    ligatures and contextual forms covered by this property are explicitly
  3507    disabled. In situations where ligatures are not considered necessary, this
  3508    may improve the speed of text rendering.
  3510   <pre
  3511    class=prod><dfn id=ltcommon-lig-values><var>&lt;common-lig-values></var></dfn>        = [ common-ligatures | no-common-ligatures ]</pre>
  3513   <pre
  3514    class=prod><dfn id=ltdiscretionary-lig-values><var>&lt;discretionary-lig-values></var></dfn> = [ discretionary-ligatures | no-discretionary-ligatures ]</pre>
  3516   <pre
  3517    class=prod><dfn id=lthistorical-lig-values><var>&lt;historical-lig-values></var></dfn>    = [ historical-ligatures | no-historical-ligatures ]</pre>
  3519   <pre
  3520    class=prod><dfn id=ltcontextual-alt-valuesgt><var>&lt;contextual-alt-values&gt;</var></dfn>    = [ contextual | no-contextual ]</pre>
  3522   <p>Individual values have the following meanings:
  3524   <dl>
  3525    <dt><dfn id=common-ligatures>common-ligatures</dfn>
  3527    <dd>Enables display of common ligatures (OpenType features: <span
  3528     class=tag>liga, clig</span>). For OpenType fonts, common ligatures are
  3529     enabled by default.
  3530   </dl>
  3532   <div class=featex><img alt="common ligature example" src=liga.png></div>
  3534   <dl>
  3535    <dt><dfn id=no-common-ligatures>no-common-ligatures</dfn>
  3537    <dd>Disables display of common ligatures (OpenType features: <span
  3538     class=tag>liga, clig</span>).
  3540    <dt><dfn id=discretionary-ligatures>discretionary-ligatures</dfn>
  3542    <dd>Enables display of discretionary ligatures (OpenType feature: <span
  3543     class=tag>dlig</span>). Which ligatures are discretionary, or optional,
  3544     is decided by the type designer so authors will need to refer to the
  3545     documentation of a given font to understand which ligatures are
  3546     considered discretionary.
  3547   </dl>
  3549   <div class=featex><img alt="discretionary ligature example" src=dlig.png></div>
  3551   <dl>
  3552    <dt><dfn id=no-discretionary-ligatures>no-discretionary-ligatures</dfn>
  3554    <dd>Disables display of discretionary ligatures (OpenType feature: <span
  3555     class=tag>dlig</span>).
  3557    <dt><dfn id=historical-ligatures>historical-ligatures</dfn>
  3559    <dd>Enables display of historical ligatures (OpenType feature: <span
  3560     class=tag>hlig</span>).
  3561   </dl>
  3563   <div class=featex><img alt="historical ligature example" src=hlig.png></div>
  3565   <dl>
  3566    <dt><dfn id=no-historical-ligatures>no-historical-ligatures</dfn>
  3568    <dd>Disables display of historical ligatures (OpenType feature: <span
  3569     class=tag>hlig</span>).
  3571    <dt><dfn id=contextual>contextual</dfn>
  3573    <dd>Enables display of contextual alternates (OpenType feature: <span
  3574     class=tag>calt</span>). Although not strictly a ligature feature, like
  3575     ligatures this feature is commonly used to harmonize the shapes of glyphs
  3576     with the surrounding context. For OpenType fonts, this feature is on by
  3577     default.
  3578   </dl>
  3580   <div class=featex><img alt="contextual alternate example" src=calt.png></div>
  3582   <dl>
  3583    <dt><dfn id=no-contextual>no-contextual</dfn>
  3585    <dd>Disables display of contextual alternates (OpenType feature: <span
  3586     class=tag>calt</span>).
  3587   </dl>
  3589   <p>Required ligatures, needed for correctly rendering complex scripts, are
  3590    not affected by the settings above, including ‘<code
  3591    class=property>none</code>’ (OpenType feature: <span
  3592    class=tag>rlig</span>).</p>
  3593   <!-- prop: font-variant-position -->
  3595   <h3 id=font-variant-position-prop><span class=secno>6.5 </span>Subscript
  3596    and superscript forms: the <a
  3597    href="#propdef-font-variant-position">font-variant-position</a> property</h3>
  3599   <table class=propdef id=namefont-variant-positionvaluenormal-sub>
  3600    <tbody>
  3601     <tr>
  3602      <td>Name:
  3604      <td><dfn id=propdef-font-variant-position>font-variant-position</dfn>
  3606     <tr>
  3607      <td>Value:
  3609      <td>normal | sub | super
  3611     <tr>
  3612      <td>Initial:
  3614      <td>normal
  3616     <tr>
  3617      <td>Applies to:
  3619      <td>all elements
  3621     <tr>
  3622      <td>Inherited:
  3624      <td>yes
  3626     <tr>
  3627      <td>Percentages:
  3629      <td>N/A
  3631     <tr>
  3632      <td>Media:
  3634      <td>visual
  3636     <tr>
  3637      <td>Computed value:
  3639      <td>as specified
  3641     <tr>
  3642      <td>Animatable:
  3644      <td>no
  3645   </table>
  3647   <p>This property is used to enable typographic subscript and superscript
  3648    glyphs. These are alternate glyphs designed within the same em-box as
  3649    default glyphs and are intended to be laid out on the same baseline as the
  3650    default glyphs, with no resizing or repositioning of the baseline. They
  3651    are explicitly designed to match the surrounding text and to be more
  3652    readable without affecting the line height.
  3654   <div class=figure><img alt="comparison between real subscript glyphs and
  3655    synthesized ones" src=realsubscripts.png>
  3656    <p class=caption>Subscript glyphs (top) vs. typical synthesized subscripts
  3657     (bottom)
  3658   </div>
  3660   <p>The values ‘<code class=property>sub</code>’ and ‘<code
  3661    class=property>super</code>’ imply the appropriate variant glyph is
  3662    displayed when available in the font (OpenType features: <span
  3663    class=tag>subs, sups</span>). A value of ‘<a href="#normal2"><code
  3664    class=property>normal</code></a>’ implies neither of these alternate
  3665    glyphs are substituted.
  3667   <p>Because of the semantic nature of subscripts and superscripts, when the
  3668    value is either ‘<code class=property>sub</code>’ or ‘<code
  3669    class=property>super</code>’ for a given contiguous run of text, if a
  3670    variant glyph is not available for all the characters in the run,
  3671    simulated glyphs must be synthesized for all characters using reduced
  3672    forms of the glyphs that would be used without this feature applied. This
  3673    is done to avoid a mixture of variant glyphs and synthesized ones that
  3674    would not align correctly.
  3676   <p>In the case of OpenType fonts that lack subscript or superscript glyphs
  3677    for a given character, user agents must use the appropriate subscript and
  3678    superscript metrics specified in the selected font's <a
  3679    href="http://www.microsoft.com/typography/otspec/os2.htm#subxs">OS/2
  3680    table</a> <a href="#OPENTYPE"
  3681    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> to calculate the size
  3682    and offset of the synthesized substitutes.
  3684   <p>In the past, user agents have used font-size and vertical-align to
  3685    simulate subscripts and superscripts for the <span class=tag>sub</span>
  3686    and <span class=tag>sup</span> elements. To allow a backwards compatible
  3687    way of defining subscripts and superscripts, it is recommended that
  3688    authors use conditional rules <a href="#CSS3-CONDITIONAL"
  3689    rel=biblioentry>[CSS3-CONDITIONAL]<!--{{CSS3-CONDITIONAL}}--></a> so that
  3690    older user agents will still render subscripts and superscripts via the
  3691    older mechanism.
  3693   <p>Authors should note that fonts typically only provide subscript and
  3694    superscript glyphs for a subset of all characters supported by the font.
  3695    While subscript and superscript glyphs are often available for Latin
  3696    numbers, glyphs for punctuation and letter characters are less frequently
  3697    provided. The synthetic fallback rules defined for this property assure
  3698    that subscripts and superscripts will always appear but the appearance may
  3699    not match author expectations if the font used does not provide the
  3700    appropriate alternate glyph for all characters contained in a subscript or
  3701    superscript.
  3703   <div class=figure><img alt="alternate superscripts vs. glyphs synthesized
  3704    using superscript metrics" src=superscript-alt-synth.png>
  3705    <p class=caption>Superscript alternate glyph (left), synthesized
  3706     superscript glyphs (middle), and incorrect mixture of the two (right)
  3707   </div>
  3709   <p>This property is not cumulative, applying it to subelements within a
  3710    subscript or superscript won't nest the placement of a subscript or
  3711    superscript glyph. Images contained within text runs where the value of
  3712    this property is ‘<code class=property>sub</code>’ or ‘<code
  3713    class=property>super</code>’ will be drawn just as they would if the
  3714    value was ‘<a href="#normal2"><code class=property>normal</code></a>’.
  3715    Likewise, text decorations such as underlines or emphasis marks will
  3716    render in the same position as they would for the default glyphs, since
  3717    this property does not affect the baseline position.
  3719   <p>Because of these limitations, font-variant-position is not recommended
  3720    for use in user agent stylesheets. Authors should use it in cases where
  3721    subscripts or superscripts will only contain the narrow range of
  3722    characters supported by the fonts specified.
  3724   <div class=example>
  3725    <p>A typical user agent default style for the <span class=tag>sub</span>
  3726     element:</p>
  3728    <pre>sub {
  3729   vertical-align: sub;
  3730   font-size: smaller;
  3731   line-height: normal;
  3733 </pre>
  3735    <p>Using font-variant-position to specify typographic subscripts in a way
  3736     that will still show subscripts in older user agents:</p>
  3738    <pre>@supports ( font-variant-position: sub ) {
  3740   sub {
  3741     vertical-align: inherit;
  3742     font-size: 100%;
  3743     line-height: inherit;
  3744     font-variant-position: sub;
  3748 </pre>
  3750    <p>User agents that support the ‘<a
  3751     href="#propdef-font-variant-position"><code
  3752     class=property>font-variant-position</code></a>’ property will select a
  3753     subscript variant glyph and render this without adjusting the baseline or
  3754     font-size. Older user agents will ignore the ‘<a
  3755     href="#propdef-font-variant-position"><code
  3756     class=property>font-variant-position</code></a>’ property definition
  3757     and use the standard defaults for subscripts.</p>
  3758   </div>
  3759   <!-- prop: font-variant-caps -->
  3761   <h3 id=font-variant-caps-prop><span class=secno>6.6 </span>Capitalization:
  3762    the <a href="#propdef-font-variant-caps">font-variant-caps</a> property</h3>
  3764   <table class=propdef id=namefont-variant-capsvaluenormal-small-c>
  3765    <tbody>
  3766     <tr>
  3767      <td>Name:
  3769      <td><dfn id=propdef-font-variant-caps>font-variant-caps</dfn>
  3771     <tr>
  3772      <td>Value:
  3774      <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
  3775       | unicase | titling-caps
  3777     <tr>
  3778      <td>Initial:
  3780      <td>normal
  3782     <tr>
  3783      <td>Applies to:
  3785      <td>all elements
  3787     <tr>
  3788      <td>Inherited:
  3790      <td>yes
  3792     <tr>
  3793      <td>Percentages:
  3795      <td>N/A
  3797     <tr>
  3798      <td>Media:
  3800      <td>visual
  3802     <tr>
  3803      <td>Computed value:
  3805      <td>as specified
  3807     <tr>
  3808      <td>Animatable:
  3810      <td>no
  3811   </table>
  3813   <p>Specifies control over capitalized forms.
  3815   <p>Individual values have the following meanings:
  3817   <dl>
  3818    <dt><dfn id=normal>normal</dfn>
  3820    <dd>None of the features listed below are enabled.
  3822    <dt><dfn id=small-caps>small-caps</dfn>
  3824    <dd>Enables display of small capitals (OpenType feature: <span
  3825     class=tag>smcp</span>). Small-caps glyphs typically use the form of
  3826     uppercase letters but are reduced to the size of lowercase letters.
  3827   </dl>
  3829   <div class=featex><img alt="small-caps example" src=smcp.png></div>
  3831   <dl>
  3832    <dt><dfn id=all-small-caps>all-small-caps</dfn>
  3834    <dd>Enables display of small capitals for both upper and lowercase letters
  3835     (OpenType features: <span class=tag>c2sc, smcp</span>).
  3837    <dt><dfn id=petite-caps>petite-caps</dfn>
  3839    <dd>Enables display of petite capitals (OpenType feature: <span
  3840     class=tag>pcap</span>).
  3842    <dt><dfn id=all-petite-caps>all-petite-caps</dfn>
  3844    <dd>Enables display of petite capitals for both upper and lowercase
  3845     letters (OpenType features: <span class=tag>c2pc, pcap</span>).
  3847    <dt><dfn id=unicase>unicase</dfn>
  3849    <dd>Enables display of mixture of small capitals for uppercase letters
  3850     with normal lowercase letters (OpenType feature: <span
  3851     class=tag>unic</span>).
  3853    <dt><dfn id=titling-caps>titling-caps</dfn>
  3855    <dd>Enables display of titling capitals (OpenType feature: <span
  3856     class=tag>titl</span>). Uppercase letter glyphs are often designed for
  3857     use with lowercase letters. When used in all uppercase titling sequences
  3858     they can appear too strong. Titling capitals are designed specifically
  3859     for this situation.
  3860   </dl>
  3862   <p>This property allows the selection of alternate glyphs used for small or
  3863    petite capitals or for titling. These glyphs are specifically designed to
  3864    blend well with the surrounding normal glyphs, to maintain the weight and
  3865    readability which suffers when text is simply resized to fit this purpose.
  3867   <p>The availability of these glyphs is based on whether a given feature is
  3868    defined or not in the feature list of the font. User agents can optionally
  3869    decide this on a per-script basis but should explicitly not decide this on
  3870    a per-character basis.
  3872   <p>Some fonts may only support a subset or none of the features described
  3873    for this property. For backwards compatibility with CSS 2.1, if ‘<a
  3874    href="#small-caps"><code class=property>small-caps</code></a>’ or ‘<a
  3875    href="#all-small-caps"><code class=property>all-small-caps</code></a>’
  3876    is specified but small-caps glyphs are not available for a given font,
  3877    user agents should simulate a small-caps font, for example by taking a
  3878    normal font and replacing the glyphs for lowercase letters with scaled
  3879    versions of the glyphs for uppercase characters (replacing the glyphs for
  3880    both upper and lowercase letters in the case of ‘<a
  3881    href="#all-small-caps"><code class=property>all-small-caps</code></a>’).
  3883   <div class=figure style="padding: 0; margin: auto;"><img alt="synthetic vs.
  3884    real small-caps" class=hires src=synthetic-vs-real-small-caps.png
  3885    width=512px>
  3886    <p class=caption>Synthetic vs. real small-caps
  3887   </div>
  3889   <p>To match the surrounding text, a font may provide alternate glyphs for
  3890    caseless characters when these features are enabled but when a user agent
  3891    simulates small capitals, it must not attempt to simulate alternates for
  3892    codepoints which are considered caseless.
  3894   <div class=figure style="padding: 0; margin: auto;"><img alt="caseless
  3895    characters with small-caps, all-small-caps enabled" class=hires
  3896    src=small-capitals-variations.png width=418px>
  3897    <p class=caption>Caseless characters with small-caps, all-small-caps
  3898     enabled
  3899   </div>
  3901   <p>If either ‘<a href="#petite-caps"><code
  3902    class=property>petite-caps</code></a>’ or ‘<a
  3903    href="#all-petite-caps"><code class=property>all-petite-caps</code></a>’
  3904    is specified for a font that doesn't support these features, the property
  3905    behaves as if ‘<a href="#small-caps"><code
  3906    class=property>small-caps</code></a>’ or ‘<a
  3907    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
  3908    respectively, had been specified. If ‘<a href="#unicase"><code
  3909    class=property>unicase</code></a>’ is specified for a font that doesn't
  3910    support that feature, the property behaves as if ‘<a
  3911    href="#small-caps"><code class=property>small-caps</code></a>’ was
  3912    applied only to lowercased uppercase letters. If ‘<a
  3913    href="#titling-caps"><code class=property>titling-caps</code></a>’ is
  3914    specified with a font that does not support this feature, this property
  3915    has no visible effect. When simulated small capital glyphs are used, for
  3916    scripts that lack uppercase and lowercase letters, ‘<a
  3917    href="#small-caps"><code class=property>small-caps</code></a>’, ‘<a
  3918    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
  3919    ‘<a href="#petite-caps"><code class=property>petite-caps</code></a>’,
  3920    ‘<a href="#all-petite-caps"><code
  3921    class=property>all-petite-caps</code></a>’ and ‘<a
  3922    href="#unicase"><code class=property>unicase</code></a>’ have no visible
  3923    effect.
  3925   <p>When casing transforms are used to simulate small capitals, the casing
  3926    transformations should match those used for the <span
  3927    class=property>‘<code class=property>text-transform</code>’</span>
  3928    property.
  3930   <p>As a last resort, unscaled uppercase letter glyphs in a normal font may
  3931    replace glyphs in a small-caps font so that the text appears in all
  3932    uppercase letters.
  3934   <div class=figure style="padding: 0; margin: auto;"><img alt="using
  3935    all-small-caps in acronym-laden text" class=hires
  3936    src=acronym-laden-text.png width=596px>
  3937    <p class=caption>Using small capitals to improve readability in
  3938     acronym-laden text
  3939   </div>
  3941   <div class=example>
  3942    <p>Quotes rendered italicised, with small-caps on the first line:</p>
  3944    <pre>blockquote            { font-style: italic; }
  3945 blockquote:first-line { font-variant: small-caps; }
  3947 &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>
  3948 </pre>
  3949   </div>
  3950   <!-- prop: font-variant-numeric -->
  3952   <h3 id=font-variant-numeric-prop><span class=secno>6.7 </span>Numerical
  3953    formatting: the <a
  3954    href="#propdef-font-variant-numeric">font-variant-numeric</a> property</h3>
  3956   <table class=propdef id=namefont-variant-numericvaluenormal-ltnu>
  3957    <tbody>
  3958     <tr>
  3959      <td>Name:
  3961      <td><dfn id=propdef-font-variant-numeric>font-variant-numeric</dfn>
  3963     <tr>
  3964      <td>Value:
  3966      <td>normal | [ &lt;numeric-figure-values&gt; ||
  3967       &lt;numeric-spacing-values&gt; || &lt;numeric-fraction-values&gt; ||
  3968       ordinal || slashed-zero ]
  3970     <tr>
  3971      <td>Initial:
  3973      <td>normal
  3975     <tr>
  3976      <td>Applies to:
  3978      <td>all elements
  3980     <tr>
  3981      <td>Inherited:
  3983      <td>yes
  3985     <tr>
  3986      <td>Percentages:
  3988      <td>N/A
  3990     <tr>
  3991      <td>Media:
  3993      <td>visual
  3995     <tr>
  3996      <td>Computed value:
  3998      <td>as specified
  4000     <tr>
  4001      <td>Animatable:
  4003      <td>no
  4004   </table>
  4006   <p>Specifies control over numerical forms.
  4008   <pre
  4009    class=prod><dfn id=ltnumeric-figure-valuesgt><var>&lt;numeric-figure-values&gt;</var></dfn>   = [ lining-nums | oldstyle-nums ]</pre>
  4011   <pre
  4012    class=prod><dfn id=ltnumeric-spacing-valuesgt><var>&lt;numeric-spacing-values&gt;</var></dfn>  = [ proportional-nums | tabular-nums ]</pre>
  4014   <pre
  4015    class=prod><dfn id=ltnumeric-fraction-valuesgt><var>&lt;numeric-fraction-values&gt;</var></dfn> = [ diagonal-fractions | stacked-fractions ]</pre>
  4017   <p>Individual values have the following meanings:
  4019   <dl>
  4020    <dt><dfn id=normal0>normal</dfn>
  4022    <dd>None of the features listed below are enabled.
  4024    <dt><dfn id=lining-nums>lining-nums</dfn>
  4026    <dd>Enables display of lining numerals (OpenType feature: <span
  4027     class=tag>lnum</span>).
  4029    <dt><dfn id=oldstyle-nums>oldstyle-nums</dfn>
  4031    <dd>Enables display of old-style numerals (OpenType feature: <span
  4032     class=tag>onum</span>).
  4034    <dt><dfn id=proportional-nums>proportional-nums</dfn>
  4036    <dd>Enables display of proportional numerals (OpenType feature: <span
  4037     class=tag>pnum</span>).
  4039    <dt><dfn id=tabular-nums>tabular-nums</dfn>
  4041    <dd>Enables display of tabular numerals (OpenType feature: <span
  4042     class=tag>tnum</span>).
  4043   </dl>
  4045   <p>The example below shows how these different properties can be combined
  4046    to influence the rendering of tabular data with fonts that support these
  4047    features. Within normal paragraph text, proportional numbers are used
  4048    while tabular numbers are used so that columns of numbers line up
  4049    properly:
  4051   <div class=figure style="padding: 0; margin: auto;"><img alt="combining
  4052    number styles" src=numberstyles.png>
  4053    <p class=caption>Using number styles
  4054   </div>
  4056   <dl>
  4057    <dt><dfn id=diagonal-fractions>diagonal-fractions</dfn>
  4059    <dd>Enables display of lining diagonal fractions (OpenType feature: <span
  4060     class=tag>frac</span>).
  4061   </dl>
  4063   <div class=featex><img alt="diagonal fraction example" src=frac.png></div>
  4065   <dl>
  4066    <dt><dfn id=stacked-fractions>stacked-fractions</dfn>
  4068    <dd>Enables display of lining stacked fractions (OpenType feature: <span
  4069     class=tag>afrc</span>).
  4070   </dl>
  4072   <div class=featex><img alt="stacked fraction example" src=afrc.png></div>
  4074   <dl>
  4075    <dt><dfn id=ordinal>ordinal</dfn>
  4077    <dd>Enables display of forms used with ordinal numbers (OpenType feature:
  4078     <span class=tag>ordn</span>).
  4080    <dt><dfn id=slashed-zero>slashed-zero</dfn>
  4082    <dd>Enables display of slashed zeros (OpenType feature: <span
  4083     class=tag>zero</span>).
  4084   </dl>
  4086   <div class=featex><img alt="slashed zero example" src=zero.png></div>
  4088   <div class=example id=steak-marinade>
  4089    <p>A simple flank steak marinade recipe, rendered with automatic fractions
  4090     and old-style numerals:</p>
  4092    <pre>.amount { font-variant-numeric: oldstyle-nums diagonal-fractions; }
  4094 &lt;h4>Steak marinade:&lt;/h4>
  4095 &lt;ul>
  4096   &lt;li>&lt;span class="amount">2&lt;/span> tbsp olive oil&lt;/li>
  4097   &lt;li>&lt;span class="amount">1&lt;/span> tbsp lemon juice&lt;/li>
  4098   &lt;li>&lt;span class="amount">1&lt;/span> tbsp soy sauce&lt;/li>
  4099   &lt;li>&lt;span class="amount">1 1/2&lt;/span> tbsp dry minced onion&lt;/li>
  4100   &lt;li>&lt;span class="amount">2 1/2&lt;/span> tsp italian seasoning&lt;/li>
  4101   &lt;li>Salt &amp;amp; pepper&lt;/li>
  4102 &lt;/ul>
  4104 &lt;p>Mix the meat with the marinade and let it sit covered in the refrigerator
  4105 for a few hours or overnight.&lt;/p>
  4106 </pre>
  4107   </div>
  4108   <!-- prop: font-variant-alternates -->
  4110   <h3 id=font-variant-alternates-prop><span class=secno>6.8 </span>Alternates
  4111    and swashes: the <a
  4112    href="#propdef-font-variant-alternates">font-variant-alternates</a>
  4113    property</h3>
  4115   <table class=propdef id=namefont-variant-alternatesvaluenormal-s>
  4116    <tbody>
  4117     <tr>
  4118      <td>Name:
  4120      <td><dfn
  4121       id=propdef-font-variant-alternates>font-variant-alternates</dfn>
  4123     <tr>
  4124      <td>Value:
  4126      <td>normal | [ stylistic(&lt;feature-value-name&gt;) || historical-forms
  4127       || styleset(&lt;feature-value-name&gt;#) ||
  4128       character-variant(&lt;feature-value-name&gt;#) ||
  4129       swash(&lt;feature-value-name&gt;) ||
  4130       ornaments(&lt;feature-value-name&gt;) ||
  4131       annotation(&lt;feature-value-name&gt;) ]
  4133     <tr>
  4134      <td>Initial:
  4136      <td>normal
  4138     <tr>
  4139      <td>Applies to:
  4141      <td>all elements
  4143     <tr>
  4144      <td>Inherited:
  4146      <td>yes
  4148     <tr>
  4149      <td>Percentages:
  4151      <td>N/A
  4153     <tr>
  4154      <td>Media:
  4156      <td>visual
  4158     <tr>
  4159      <td>Computed value:
  4161      <td>as specified
  4163     <tr>
  4164      <td>Animatable:
  4166      <td>no
  4167   </table>
  4169   <p>For any given character, fonts can provide a variety of alternate glyphs
  4170    in addition to the default glyph for that character. This property
  4171    provides control over the selection of these alternate glyphs.
  4173   <p>In cases where multiple alternates are possible, authors define a
  4174    <code>&lt;feature-value-name&gt;</code> using the
  4175    <code>@font-feature-values</code> rule described below to indicate the
  4176    specific alternate to be used. The nature of these alternates is font
  4177    specific, so the rule defines values for a specific font family or set of
  4178    families. When a particular value has not been defined for a given family,
  4179    the named value is treated as if the feature had omitted from the style
  4180    rule. If a given value is outside the range supported by a given font, the
  4181    value is ignored. These values never apply to generic font families, nor
  4182    to families selected as part of system font fallback. Values that behave
  4183    this way are marked as <em>font specific</em>.
  4185   <p>Individual values have the following meanings:
  4187   <dl>
  4188    <dt><dfn id=normal1>normal</dfn>
  4190    <dd>None of the features listed below are enabled.
  4192    <dt><dfn id=stylisticltfeature-value-namegt
  4193     title=stylistic>stylistic(&lt;feature-value-name&gt;)</dfn>
  4195    <dd>Enables display of stylistic alternates (<em>font specific</em>,
  4196     OpenType feature: <span class=tag>salt
  4197     &lt;feature-value-name&gt;</span>).
  4198   </dl>
  4200   <div class=featex><img alt="stylistic alternate example" src=salt.png></div>
  4202   <dl>
  4203    <dt><dfn id=historical-forms>historical-forms</dfn>
  4205    <dd>Enables display of historical forms (OpenType feature: <span
  4206     class=tag>hist</span>).
  4207   </dl>
  4209   <div class=featex><img alt="historical form example" src=hist.png></div>
  4211   <dl>
  4212    <dt><dfn id=stylesetltfeature-value-namegt
  4213     title=styleset>styleset(&lt;feature-value-name&gt;#)</dfn>
  4215    <dd>Enables display with stylistic sets (<em>font specific</em>, OpenType
  4216     feature: <span class=tag>ss&lt;feature-index&gt;</span> OpenType
  4217     currently defines <span class=tag>ss01</span> through <span
  4218     class=tag>ss20</span>).
  4219   </dl>
  4221   <div class=featex><img alt="styleset example" src=ssnn.png></div>
  4223   <dl>
  4224    <dt><dfn id=character-variantltfeature-value-namegt
  4225     title=character-variant>character-variant(&lt;feature-value-name&gt;#)</dfn>
  4228    <dd>Enables display of specific character variants (<em>font
  4229     specific</em>, OpenType feature: <span
  4230     class=tag>cv&lt;feature-index&gt;</span> OpenType currently defines <span
  4231     class=tag>cv01</span> through <span class=tag>cv99</span>).
  4233    <dt><dfn id=swashltfeature-value-namegt
  4234     title=swash>swash(&lt;feature-value-name&gt;)</dfn>
  4236    <dd>Enables display of swash glyphs (<em>font specific</em>, OpenType
  4237     feature: <span class=tag>swsh &lt;feature-index&gt;, cswh
  4238     &lt;feature-index&gt;</span>).
  4239   </dl>
  4241   <div class=featex><img alt="swash example" src=swsh.png></div>
  4243   <dl>
  4244    <dt><dfn id=ornamentsltfeature-value-namegt
  4245     title=ornaments>ornaments(&lt;feature-value-name&gt;)</dfn>
  4247    <dd>Enables replacement of default glyphs with ornaments, if provided in
  4248     the font (<em>font specific</em>, OpenType feature: <span class=tag>ornm
  4249     &lt;feature-index&gt;</span>). Some fonts may offer ornament glyphs as
  4250     alternates for a wide collection of characters; however, displaying
  4251     arbitrary characters (e.g., alphanumerics) as ornaments is poor practice
  4252     as it distorts the semantics of the data. Font designers are encouraged
  4253     to encode all ornaments (except those explicitly encoded in the Unicode
  4254     Dingbats blocks, etc.) as alternates for the bullet character (U+2022) to
  4255     allow authors to select the desired glyph using
  4256     &lt;feature-value-name&gt;.
  4257   </dl>
  4259   <div class=featex><img alt="ornaments example" src=ornm.png></div>
  4261   <dl>
  4262    <dt><dfn id=annotationltfeature-value-namegt
  4263     title=annotation>annotation(&lt;feature-value-name&gt;)</dfn>
  4265    <dd>Enables display of alternate annotation forms (<em>font specific</em>,
  4266     OpenType feature: <span class=tag>nalt &lt;feature-index&gt;</span>).
  4267   </dl>
  4269   <div class=featex><img alt="alternate annotation form example"
  4270    src=nalt.png></div>
  4272   <h3 id=font-feature-values><span class=secno>6.9 </span>Defining font
  4273    specific alternates: the <code>@font-feature-values</code> rule</h3>
  4275   <p>Several of the possible values of ‘<a
  4276    href="#propdef-font-variant-alternates"><code
  4277    class=property>font-variant-alternates</code></a>’ listed above are
  4278    labeled as "font specific". For these features fonts may define not just a
  4279    single glyph but a set of alternate glyphs with an index to select a given
  4280    alternate. Since these are font family specific, the
  4281    <code>@font-feature-values</code> rule is used to define named-values for
  4282    these indices for a given family.
  4284   <p>In the case of the swash Q in the example shown above, the swash could
  4285    be specified using these style rules:
  4287   <pre>
  4289 @font-feature-values Jupiter Sans {
  4290   @swash {
  4291     delicate: 1;
  4292     flowing: 2;
  4296 h2 { font-family: Jupiter Sans, sans-serif; }
  4298 /* show the second swash variant in h2 headings */
  4299 h2:first-letter { font-variant-alternates: swash(flowing); }
  4301 &lt;h2>Quick&lt;/h2></pre>
  4303   <p>When Jupiter Sans is present, the second alternate swash alternate will
  4304    be displayed. When not present, no swash character will be shown, since
  4305    the specific named-value "flowing" is only defined for the Jupiter Sans
  4306    family. The @-mark indicates the name of the property value for which a
  4307    named-value can be used. The name "flowing" is chosen by the author, the
  4308    values specified within a given font's data.
  4310   <p>In terms of the grammar, this specification defines the following
  4311    productions:
  4313   <pre><dfn id=fontfeaturevaluesrule>font_feature_values_rule</dfn>
  4314   : FONT_FEATURE_VALUES_SYM S* font_family_name_list S*
  4315     '{' S* feature_value_block? [ S* feature_value_block? ]* '}' S*
  4318 <dfn id=fontfamilynamelist>font_family_name_list</dfn>
  4319   : font_family_name [ S* ',' S* font_family_name ]*
  4322 <dfn id=fontfamilyname>font_family_name</dfn>
  4323   : STRING | [ IDENT [ S* IDENT ]* ]
  4326 <dfn id=featurevalueblock>feature_value_block</dfn>
  4327   : feature_type S*
  4328     '{' S* feature_value_definition? [ S* ';' S* feature_value_definition? ]* '}' S*
  4331 <dfn id=featuretype>feature_type</dfn>:
  4332   ATKEYWORD
  4335 <dfn id=featurevaluedefinition>feature_value_definition</dfn>
  4336   : IDENT S* ':' S* NUMBER [ S* NUMBER ]*
  4338 </pre>
  4340   <p>The following new token is introduced:
  4342   <pre>@{F}{O}{N}{T}{-}{F}{E}{A}{T}{U}{R}{E}{-}{V}{A}{L}{U}{E}{S}   {return FONT_FEATURE_VALUES_SYM;}
  4343 </pre>
  4345   <p>Feature value blocks are treated <a
  4346    href="http://www.w3.org/TR/CSS2/syndata.html#at-rules">similar to
  4347    at-rules</a>, they consist of everything up to the next block or
  4348    semi-colon, whichever comes first.
  4350   <p>Font feature values rules define a set of values for a specific font
  4351    feature as used for a given set of families. Effectively, they define a
  4352    mapping of ⟨family, feature, ident⟩ → ⟨values⟩ where
  4353    ⟨values⟩ are the indices used for specific features defined for a
  4354    given font.
  4356   <p>The font family list uses the same syntax as that used for the ‘<a
  4357    href="#descdef-font-family"><code class=property>font-family</code></a>’
  4358    property. Within feature value blocks, the feature type is ‘<code
  4359    class=css>@</code>’ followed by the name of the font-specific property
  4360    value (e.g. <a
  4361    href="#swashltfeature-value-namegt"><code>@swash</code></a>). The feature
  4362    type must match, using an ASCII case-insensitive comparison, one of the
  4363    <em>font specific</em> values of the <a
  4364    href="#propdef-font-variant-alternates"><code>font-variant-alternates</code></a>
  4365    property. The values associated with a given idenitifier are limited to
  4366    integer values 0 or greater.
  4368   <p>If syntax errors occur within the font family list, the entire rule must
  4369    be ignored. When syntax errors occur within a feature value definition,
  4370    such as invalid identifiers or values, the entire feature value definition
  4371    must be omitted, similar to the way syntax errors in style declarations
  4372    are handled. When the <code>&lt;feature-type></code> is invalid, the
  4373    entire associated feature value block must be ignored.
  4375   <pre>@font-feature-values Bongo {
  4376   @swash { ornate: 1; }
  4377   annotation { boxed: 4; } /* should be @annotation! */
  4378   @swash { double-loops: 1; flowing: -1; } /* negative value */
  4379   @ornaments ; /* incomplete definition */
  4380   @styleset { double-W: 14; sharp-terminals: 16 1 } /* missing ; */
  4381   <a href="http://www.angryalien.com/0504/shiningbunnies.html" style="text-decoration: none;">redrum</a>  /* random editing mistake */
  4382 }</pre>
  4384   <p>The example above is equivalent to:
  4386   <pre>@font-feature-values Bongo {
  4387   @swash { ornate: 1; }
  4388   @swash { double-loops: 1; }
  4389   @styleset { double-W: 14; sharp-terminals: 16 1; }
  4390 }</pre>
  4392   <p>If multiple <code>@font-feature-values</code> rules are defined for a
  4393    given family, the resulting values defined are the union of these rules.
  4394    This allows a set of named-values to be defined for a given font family
  4395    globally for a site and specific additions made per-page. If the same
  4396    &lt;feature-value-name&gt; is defined mulitple times for a given
  4397    font-variant value, the last defined value is used.
  4399   <pre>
  4400 site.css:
  4402   @font-feature-values Mercury Serif {
  4403     @styleset {
  4404       stacked-g: 3; /* "two-storey" versions of g, a */
  4405       stacked-a: 4;
  4409 page.css:
  4411   @font-feature-values Mercury Serif {
  4412     @styleset {
  4413       geometric-m: 7; /* alternate version of m */
  4417   body {
  4418     font-family: Mercury Serif, serif;
  4420     /* enable both the use of stacked g and alternate m */
  4421     font-variant-alternates: styleset(stacked-g, geometric-m);
  4422   }</pre>
  4424   <p>Only named font families are allowed for &lt;font-family&gt;, rules that
  4425    include generic or system fonts in the list of font families are
  4426    considered syntax errors and the contents of the rules are ignored.
  4427    However, if a user agent defines a generic font to be a specific named
  4428    font (e.g. Helvetica), the settings associated with that family name will
  4429    be used.
  4431   <p>For &lt;font-variant-property-value>, only font specific property value
  4432    names supported by the ‘<a href="#propdef-font-variant"><code
  4433    class=property>font-variant</code></a>’ property are recognized,
  4434    definitions for other value names cause a syntax error and are ignored.
  4435    Each property value that is font specific is clearly marked as such.
  4436    Feature value names follow the rules of CSS user identifiers and are
  4437    case-sensitive. They are unique only for a given set of font families and
  4438    font-variant property value; the same identifier used with a different
  4439    font-variant property value is treated as a separate and distinct value.
  4441   <p>Using a commonly named value allows authors to use a single style rule
  4442    to cover a set of fonts for which the underlying selector is different for
  4443    each font. If either font in the example below is found, a circled number
  4444    glyph will be used:
  4446   <pre>@font-feature-values Taisho Gothic {
  4447   @annotation { boxed: 1; circled: 4; }
  4450 @font-feature-values Otaru Kisa {
  4451   @annotation { circled: 1; black-boxed: 3; }
  4454 h3.title {
  4455   /* circled form defined for both fonts */
  4456   font-family: Taisho Gothic, Otaru Kisa;
  4457   font-variant: annotation(circled);
  4458 }</pre>
  4460   <p>Most font specific font-variant property values take a single value
  4461    (e.g. swash). The character-variant property value allows two values and
  4462    styleset allows an unlimited number. If a larger number of values are
  4463    assigned to a given name, a syntax error occurs and the entire
  4464    &lt;font-feature-values-declaration&gt; is ignored.
  4466   <p>For the styleset property value, multiple values indicate the style sets
  4467    to be enabled. Values between 1 and 99 enable OpenType features <span
  4468    class=tag>ss01</span> through <span class=tag>ss99</span>. However, the
  4469    OpenType standard only officially defines <span class=tag>ss01</span>
  4470    through <span class=tag>ss20</span>. Values greater than 99 or equal to 0
  4471    are ignored but do not generate a syntax error when parsed.
  4473   <pre>@font-feature-values Mars Serif {
  4474   @styleset { 
  4475     alt-g: 1;        /* implies ss01 = 1 */
  4476     curly-quotes: 3; /* implies ss03 = 1 */
  4477     code: 4 5;       /* implies ss04 = 1, ss05 = 1 */
  4480   @styleset {
  4481     dumb: 125;        /* &gt;99, ignored */
  4484   @swash {
  4485     swishy: 3 5;     /* more than 1 value for swash, syntax error */
  4489 p.codeblock {
  4490   /* implies ss03 = 1, ss04 = 1, ss05 = 1 */
  4491   font-variant-alternates: styleset(curly-quotes, code);
  4492 }</pre>
  4494   <p>For character-variant, a single value between 1 and 99 indicates the
  4495    enabling of OpenType feature <span class=tag>cv01</span> through <span
  4496    class=tag>cv99</span>. For OpenType fonts, values greater than 99 or equal
  4497    to 0 are ignored but do not generate a syntax error when parsed. When two
  4498    values are listed, the first value indicates the feature used and the
  4499    second the value passed for that feature. When two value names imply
  4500    different settings for the same underlying feature the last setting is
  4501    used.
  4503   <pre>@font-feature-values MM Greek {
  4504   @character-variant { alpha-2: 1 2; }   /* implies cv01 = 2 */
  4505   @character-variant { beta-3: 2 3; }    /* implies cv02 = 3 */
  4506   @character-variant { epsilon: 5 3 6; } /* more than 2 values, syntax error, ignored */
  4507   @character-variant { gamma: 12; }      /* implies cv12 = 1 */
  4508   @character-variant { zeta:   20 3; }   /* implies cv20 = 3 */
  4509   @character-variant { zeta-2: 20 2; }   /* implies cv20 = 2 */
  4510   @character-variant { silly: 105; }     /* &gt;99, ignored */
  4511   @character-variant { dumb: 323 3; }    /* &gt;99, ignored */
  4514 #title {
  4515   /* use the third alternate beta, first alternate gamma */
  4516   font-variant-alternates: character-variant(beta-3, gamma);
  4519 p {
  4520   /* zeta-2 follows zeta, implies cv20 = 2  */
  4521   font-variant-alternates: character-variant(zeta, zeta-2);
  4524 .special {
  4525   /* zeta follows zeta-2, implies cv20 = 3  */
  4526   font-variant-alternates: character-variant(zeta-2, zeta);
  4527 }</pre>
  4529   <p>See the <a href="#om-fontfeaturevalues">object model reference
  4530    section</a> for a description of the interfaces used to modify these rules
  4531    via the CSS Object Model.
  4533   <div class=figure><img alt="Matching text on Byzantine seals using
  4534    character variants" src=byzantineseal.png>
  4535    <p class=caption>Byzantine seal text displayed with character variants
  4536   </div>
  4538   <div class=example>
  4539    <p>In the figure above, the text in red is rendered using a font
  4540     containing character variants that mimic the character forms found on a
  4541     Byzantine seal from the 8th century A.D. Two lines below is the same text
  4542     displayed in a font without variants. Note the two variants for U and N
  4543     used on the seal.</p>
  4545    <pre>@font-feature-values Athena Ruby {
  4546   @character-variant {
  4547     leo-B: 2 1;
  4548     leo-M: 13 3;
  4549     leo-alt-N: 14 1;
  4550     leo-N: 14 2;
  4551     leo-T: 20 1; 
  4552     leo-U: 21 2;
  4553     leo-alt-U: 21 4;
  4557 p {
  4558   font-variant: discretionary-ligatures,
  4559                 character-variant(leo-B, leo-M, leo-N, leo-T, leo-U);
  4562 span.alt-N { 
  4563   font-variant-alternates: character-variant(leo-alt-N);
  4566 span.alt-U {
  4567   font-variant-alternates: character-variant(leo-alt-U);
  4570 &lt;p>ENO....UP͞RSTU&lt;span class="alt-U">U&lt;/span>͞&lt;span class="alt-U">U&lt;/span>ΚΑΙTỤẠG̣IUPNS&lt;/p>
  4572 &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> 
  4573 </pre>
  4574   </div>
  4576   <h3 id=font-variant-east-asian-prop><span class=secno>6.10 </span>East
  4577    Asian text rendering: the <a
  4578    href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
  4579    property</h3>
  4581   <table class=propdef id=namefont-variant-east-asianvaluenormal-l>
  4582    <tbody>
  4583     <tr>
  4584      <td>Name:
  4586      <td><dfn
  4587       id=propdef-font-variant-east-asian>font-variant-east-asian</dfn>
  4589     <tr>
  4590      <td>Value:
  4592      <td>normal | [ &lt;east-asian-variant-values&gt; ||
  4593       &lt;east-asian-width-values&gt; || ruby ]
  4595     <tr>
  4596      <td>Initial:
  4598      <td>normal
  4600     <tr>
  4601      <td>Applies to:
  4603      <td>all elements
  4605     <tr>
  4606      <td>Inherited:
  4608      <td>yes
  4610     <tr>
  4611      <td>Percentages:
  4613      <td>N/A
  4615     <tr>
  4616      <td>Media:
  4618      <td>visual
  4620     <tr>
  4621      <td>Computed value:
  4623      <td>as specified
  4625     <tr>
  4626      <td>Animatable:
  4628      <td>no
  4629   </table>
  4631   <p>Allows control of glyph substitution and sizing in East Asian text.
  4633   <pre
  4634    class=prod><dfn id=lteast-asian-variant-valuesgt><var>&lt;east-asian-variant-values&gt;</var></dfn> = [ jis78 | jis83 | jis90 | jis04 | simplified | traditional ]</pre>
  4636   <pre
  4637    class=prod><dfn id=lteast-asian-width-valuesgt><var>&lt;east-asian-width-values&gt;</var></dfn>   = [ full-width | proportional-width ]</pre>
  4639   <p>Individual values have the following meanings:
  4641   <dl>
  4642    <dt><dfn id=normal2>normal</dfn>
  4644    <dd>None of the features listed below are enabled.
  4646    <dt><dfn id=jis78>jis78</dfn>
  4648    <dd>Enables rendering of JIS78 forms (OpenType feature: <span
  4649     class=tag>jp78</span>).
  4650   </dl>
  4652   <div class=featex><img alt="JIS78 form example" src=jp78.png></div>
  4654   <dl>
  4655    <dt><dfn id=jis83>jis83</dfn>
  4657    <dd>Enables rendering of JIS83 forms (OpenType feature: <span
  4658     class=tag>jp83</span>).
  4660    <dt><dfn id=jis90>jis90</dfn>
  4662    <dd>Enables rendering of JIS90 forms (OpenType feature: <span
  4663     class=tag>jp90</span>).
  4665    <dt><dfn id=jis04>jis04</dfn>
  4667    <dd>Enables rendering of JIS2004 forms (OpenType feature: <span
  4668     class=tag>jp04</span>).
  4669     <p>The various JIS variants reflect the glyph forms defined in different
  4670      Japanese national standards. Fonts generally include glyphs defined by
  4671      the most recent national standard but it's sometimes necessary to use
  4672      older variants, to match signage for example.</p>
  4674    <dt><dfn id=simplified>simplified</dfn>
  4676    <dd>Enables rendering of simplified forms (OpenType feature: <span
  4677     class=tag>smpl</span>).
  4678     <p>The ‘<a href="#simplified"><code
  4679      class=property>simplified</code></a>’ and ‘<a
  4680      href="#traditional"><code class=property>traditional</code></a>’
  4681      values allow control over the glyph forms for characters which have been
  4682      simplified over time but for which the older, traditional form is still
  4683      used in some contexts. The exact set of characters and glyph forms will
  4684      vary to some degree by context for which a given font was designed.</p>
  4686    <dt><dfn id=traditional>traditional</dfn>
  4688    <dd>Enables rendering of traditional forms (OpenType feature: <span
  4689     class=tag>trad</span>).
  4690   </dl>
  4692   <div class=featex><img alt="tradtional form example" src=trad.png></div>
  4694   <dl>
  4695    <dt><dfn id=full-width>full-width</dfn>
  4697    <dd>Enables rendering of full-width variants (OpenType feature: <span
  4698     class=tag>fwid</span>).
  4700    <dt><dfn id=proportional-width>proportional-width</dfn>
  4702    <dd>Enables rendering of proportionally-spaced variants (OpenType feature:
  4703     <span class=tag>pwid</span>).
  4704   </dl>
  4706   <div class=featex><img alt="proportionally spaced Japanese example"
  4707    src=pwid.png></div>
  4709   <dl>
  4710    <dt><dfn id=ruby>ruby</dfn>
  4712    <dd>Enables display of ruby variant glyphs (OpenType feature: <span
  4713     class=tag>ruby</span>). Since ruby text is generally smaller than the
  4714     associated body text, font designers can design special glyphs for use
  4715     with ruby that are more readable than scaled down versions of the default
  4716     glyphs. Only glyph selection is affected, there is no associated font
  4717     scaling or other change that affects line layout. The red ruby text below
  4718     is shown with default glyphs (top) and with ruby variant glyphs (bottom).
  4719     Note the slight difference in stroke thickness.
  4720   </dl>
  4722   <div class=featex><img alt="ruby variant example" src=rubyshinkansen.png></div>
  4724   <h3 id=font-variant-prop><span class=secno>6.11 </span>Overall shorthand
  4725    for font rendering: the <a href="#propdef-font-variant">font-variant</a>
  4726    property</h3>
  4728   <table class=propdef id=namefont-variantvaluenormal-none-ltcommo>
  4729    <tbody>
  4730     <tr>
  4731      <td>Name:
  4733      <td><dfn id=propdef-font-variant>font-variant</dfn>
  4735     <tr>
  4736      <td>Value:
  4738      <td>normal | none | [ &lt;common-lig-values&gt; ||
  4739       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  4740       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  4741       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  4742       character-variant(&lt;feature-value-name&gt;#) ||
  4743       swash(&lt;feature-value-name&gt;) ||
  4744       ornaments(&lt;feature-value-name&gt;) ||
  4745       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  4746       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  4747       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  4748       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  4749       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  4750       ruby ]
  4752     <tr>
  4753      <td>Initial:
  4755      <td>normal
  4757     <tr>
  4758      <td>Applies to:
  4760      <td>all elements
  4762     <tr>
  4763      <td>Inherited:
  4765      <td>yes
  4767     <tr>
  4768      <td>Percentages:
  4770      <td>see individual properties
  4772     <tr>
  4773      <td>Media:
  4775      <td>visual
  4777     <tr>
  4778      <td>Computed value:
  4780      <td>see individual properties
  4782     <tr>
  4783      <td>Animatable:
  4785      <td>see individual properties
  4786   </table>
  4788   <p>The value ‘<a href="#normal2"><code
  4789    class=property>normal</code></a>’ resets all other font feature
  4790    properties to their inital value. The ‘<code
  4791    class=property>none</code>’ value sets ‘<a
  4792    href="#propdef-font-variant-ligatures"><code
  4793    class=property>font-variant-ligatures</code></a>’ to ‘<code
  4794    class=property>none</code>’ and resets all other font feature properties
  4795    to their initial value. Like other shorthands, using ‘<a
  4796    href="#propdef-font-variant"><code
  4797    class=property>font-variant</code></a>’ resets unspecified font-variant
  4798    subproperties to their initial values. It does not reset the values of
  4799    either ‘<a href="#propdef-font-language-override"><code
  4800    class=property>font-language-override</code></a>’ or ‘<a
  4801    href="#propdef-font-feature-settings"><code
  4802    class=property>font-feature-settings</code></a>’.
  4804   <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
  4805    font feature settings control: the <a
  4806    href="#propdef-font-feature-settings">font-feature-settings</a> property</h3>
  4808   <table class=propdef id=namefont-feature-settingsvaluenormal-ltf>
  4809    <tbody>
  4810     <tr>
  4811      <td>Name:
  4813      <td><dfn id=propdef-font-feature-settings>font-feature-settings</dfn>
  4815     <tr>
  4816      <td>Value:
  4818      <td>normal | &lt;feature-tag-value&gt;#
  4820     <tr>
  4821      <td>Initial:
  4823      <td>normal
  4825     <tr>
  4826      <td>Applies to:
  4828      <td>all elements
  4830     <tr>
  4831      <td>Inherited:
  4833      <td>yes
  4835     <tr>
  4836      <td>Percentages:
  4838      <td>N/A
  4840     <tr>
  4841      <td>Media:
  4843      <td>visual
  4845     <tr>
  4846      <td>Computed value:
  4848      <td>as specified
  4850     <tr>
  4851      <td>Animatable:
  4853      <td>no
  4854   </table>
  4856   <p>This property provides low-level control over OpenType font features. It
  4857    is intended as a way of providing access to font features that are not
  4858    widely used but are needed for a particular use case. A value of ‘<a
  4859    href="#normal2"><code class=property>normal</code></a>’ means that no
  4860    change in glyph selection or positioning occurs due to this property.
  4862   <p>
  4864   <pre>/* enable small caps and use second swash alternate */
  4865 font-feature-settings: "smcp", "swsh" 2;</pre>
  4867   <p>Feature tag values have the following syntax:
  4869   <pre
  4870    class=prod><dfn id=ltfeature-tag-valuegt><var>&lt;feature-tag-value&gt;</var></dfn> = &lt;string&gt; [ &lt;integer&gt; | on | off ]?</pre>
  4872   <p>The &lt;string&gt; is a case-sensitive OpenType feature tag. As
  4873    specified in the OpenType specification, feature tags contain four ASCII
  4874    characters. Tag strings longer or shorter than four characters, or
  4875    containing characters outside the U+20–7E codepoint range are invalid.
  4876    User agents must not use a feature tag created by truncating or padding
  4877    the string to four characters. Feature tags need only match a feature tag
  4878    defined in the font, they are not limited to explicitly registered
  4879    OpenType features. Fonts defining custom feature tags should follow the <a
  4880    href="http://www.microsoft.com/typography/otspec/featuretags.htm">tag name
  4881    rules</a> defined in the OpenType specification <a
  4882    href="#OPENTYPE-FEATURES"
  4883    rel=biblioentry>[OPENTYPE-FEATURES]<!--{{!OPENTYPE-FEATURES}}--></a>.
  4884    Feature tags not present in the font are ignored; a user agent must not
  4885    attempt to synthesize fallback behavior based on these feature tags.
  4887   <p>This means that explicitly disabling the <span class=tag>kern</span>
  4888    feature will not affect the application of kerning data found in the
  4889    ‘<code class=property>kern</code>’ table (as opposed to kerning data
  4890    associated with the <span class=tag>kern</span> feature in the ‘<code
  4891    class=property>GPOS</code>’ table). Authors should use the ‘<a
  4892    href="#propdef-font-kerning"><code
  4893    class=property>font-kerning</code></a>’ property to explictly enable or
  4894    disable kerning since this property affects both types of kerning.
  4896   <p>If present, a value indicates an index used for glyph selection. An
  4897    &lt;integer&gt; value must be 0 or greater. A value of 0 indicates that
  4898    the feature is disabled. For boolean features, a value of 1 enables the
  4899    feature. For non-boolean features, a value of 1 or greater enables the
  4900    feature and indicates the feature selection index. A value of ‘<code
  4901    class=property>on</code>’ is synonymous with 1 and ‘<code
  4902    class=property>off</code>’ is synonymous with 0. If the value is
  4903    omitted, a value of 1 is assumed.
  4905   <pre>
  4906 font-feature-settings: "dlig" 1;       /* dlig=1 enable discretionary ligatures */
  4907 font-feature-settings: "smcp" on;      /* smcp=1 enable small caps */
  4908 font-feature-settings: 'c2sc';         /* c2sc=1 enable caps to small caps */
  4909 font-feature-settings: "liga" off;     /* liga=0 no common ligatures */
  4910 font-feature-settings: "tnum", 'hist'; /* tnum=1, hist=1 enable tabular numbers and historical forms */
  4911 font-feature-settings: "tnum" "hist";  /* invalid, need a comma-delimited list */
  4912 font-feature-settings: "palin" off;    /* good idea but invalid tagname */
  4913 font-feature-settings: "PKRN";         /* PKRN=1 enable custom feature */
  4914 font-feature-settings: dlig;           /* invalid, tag must be a string */
  4915 </pre>
  4917   <p>Authors should generally use ‘<a href="#propdef-font-variant"><code
  4918    class=property>font-variant</code></a>’ and its related subproperties
  4919    whenever possible and only use this property for special cases where its
  4920    use is the only way of accessing a particular infrequently used font
  4921    feature.
  4923   <p>Although specifically defined for OpenType feature tags, feature tags
  4924    for other modern font formats that support font features may be added in
  4925    the future. Where possible, features defined for other font formats should
  4926    attempt to follow the pattern of registered OpenType tags.
  4928   <div class=example>
  4929    <p>The Japanese text below will be rendered with half-width kana
  4930     characters:</p>
  4932    <pre lang=ja>
  4933 body { font-feature-settings: "hwid"; /* Half-width OpenType feature */ }
  4935 &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>
  4936 </pre>
  4937   </div>
  4939   <h3 id=font-language-override-prop><span class=secno>6.13 </span>Font
  4940    language override: the <a
  4941    href="#propdef-font-language-override">font-language-override</a> property</h3>
  4943   <table class=propdef id=namefont-language-overridevaluenormal-lt>
  4944    <tbody>
  4945     <tr>
  4946      <td>Name:
  4948      <td><dfn id=propdef-font-language-override>font-language-override</dfn>
  4950     <tr>
  4951      <td>Value:
  4953      <td>normal | &lt;string&gt;
  4955     <tr>
  4956      <td>Initial:
  4958      <td>normal
  4960     <tr>
  4961      <td>Applies to:
  4963      <td>all elements
  4965     <tr>
  4966      <td>Inherited:
  4968      <td>yes
  4970     <tr>
  4971      <td>Percentages:
  4973      <td>N/A
  4975     <tr>
  4976      <td>Media:
  4978      <td>visual
  4980     <tr>
  4981      <td>Computed value:
  4983      <td>as specified
  4985     <tr>
  4986      <td>Animatable:
  4988      <td>no
  4989   </table>
  4991   <p>The value of ‘<a href="#normal2"><code
  4992    class=property>normal</code></a>’ implies that when rendering with
  4993    OpenType fonts the language of the document is used to infer the OpenType
  4994    language system, used to select language specific features when rendering.
  4995    The value of the &lt;string&gt; is a single three-letter OpenType <a
  4996    href="http://www.microsoft.com/typography/otspec/languagetags.htm">language
  4997    system tag</a>, defined in the layout tag registry of the OpenType
  4998    specification.
  5000   <div class=example>
  5001    <p>The <a href="http://www.un.org/en/documents/udhr/index.shtml">Universal
  5002     Declaration of Human Rights</a> has been translated into a wide variety
  5003     of languages. In Turkish, Article 9 of this document might be marked up
  5004     as below:</p>
  5006    <pre lang=tr>&lt;body lang="tr">
  5008 &lt;h4>Madde 9&lt;/h4>
  5009 &lt;p>Hiç kimse keyfi olarak tutuklanamaz, alıkonulanamaz veya sürülemez.&lt;/p>
  5010 </pre>
  5012    <p>Here the user agent uses the value of the ‘<code
  5013     class=property>lang</code>’ attribute when rendering text and
  5014     appropriately renders this text without ‘<code
  5015     class=property>fi</code>’ ligatures. There is no need to use the ‘<a
  5016     href="#propdef-font-language-override"><code
  5017     class=property>font-language-override</code></a>’ property.</p>
  5019    <p>However, a given font may lack support for a specific language. In this
  5020     situation authors may need to use the typographic conventions of a
  5021     related language that are supported by that font:</p>
  5023    <pre lang=mk>&lt;body lang="mk">     &lt;!-- Macedonian lang code --&gt;
  5025 body { font-language-override: "SRB"; /* Serbian OpenType language tag */ }
  5027 &lt;h4>Члeн 9&lt;/h4>
  5028 &lt;p>Никoj чoвeк нeмa дa бидe пoдлoжeн нa прoизвoлнo aпсeњe, притвoр или прoгoнувaњe.&lt;/p>
  5030 </pre>
  5032    <p>The Macedonian text here will be rendered using Serbian typographic
  5033     conventions, with the assumption that the font specified supports
  5034     Serbian.</p>
  5035   </div>
  5037   <p><a id=rendering-considerations></a>
  5039   <h2 id=font-feature-resolution><span class=secno>7 </span>Font Feature
  5040    Resolution</h2>
  5042   <p>As described in the previous section, font features can be enabled in a
  5043    variety of ways, either via the use of ‘<a
  5044    href="#propdef-font-variant"><code
  5045    class=property>font-variant</code></a>’ or ‘<a
  5046    href="#propdef-font-feature-settings"><code
  5047    class=property>font-feature-settings</code></a>’ in a style rule or
  5048    within an <code>@font-face</code> rule. The resolution order for the union
  5049    of these settings is defined below. Features defined via CSS properties
  5050    are applied on top of layout engine default features.
  5052   <h3 id=default-features><span class=secno>7.1 </span>Default features</h3>
  5054   <p>For OpenType fonts, user agents must enable the default features defined
  5055    in the OpenType documentation for a given script and writing mode.
  5056    Required ligatures, common ligatures and contextual forms must be enabled
  5057    by default (OpenType features: <span class=tag>rlig, liga, clig,
  5058    calt</span>), along with localized forms (OpenType feature: <span
  5059    class=tag>locl</span>), and features required for proper display of
  5060    composed characters and marks (OpenType features: <span class=tag>ccmp,
  5061    mark, mkmk</span>). These features must always be enabled, even when the
  5062    value of the ‘<a href="#propdef-font-variant"><code
  5063    class=property>font-variant</code></a>’ and ‘<a
  5064    href="#propdef-font-feature-settings"><code
  5065    class=property>font-feature-settings</code></a>’ properties is ‘<a
  5066    href="#normal2"><code class=property>normal</code></a>’. Individual
  5067    features are only disabled when explicitly overridden by the author, as
  5068    when ‘<a href="#propdef-font-variant-ligatures"><code
  5069    class=property>font-variant-ligatures</code></a>’ is set to ‘<a
  5070    href="#no-common-ligatures"><code
  5071    class=property>no-common-ligatures</code></a>’. For handling complex
  5072    scripts such as <a
  5073    href="http://www.microsoft.com/typography/otfntdev/arabicot/features.aspx">Arabic</a>,
  5074    <a
  5075    href="http://www.microsoft.com/typography/otfntdev/mongolot/features.htm">Mongolian</a>
  5076    or <a
  5077    href="http://www.microsoft.com/typography/otfntdev/devanot/features.aspx">Devanagari</a>
  5078    additional features are required. For upright text within vertical text
  5079    runs, vertical alternates (OpenType feature: <span class=tag>vert</span>)
  5080    must be enabled.
  5082   <h3 id=feature-precedence><span class=secno>7.2 </span>Feature precedence</h3>
  5084   <p>General and font specific font feature property settings are resolved in
  5085    the order below, in ascending precedence order. This ordering is used to
  5086    construct a combined list of font features that affect a given text run.
  5088   <ol>
  5089    <li>Font features enabled by default, including features required for a
  5090     given script.
  5092    <li>If the font is defined via an <code>@font-face</code> rule, the font
  5093     features implied by the font-variant descriptor in the
  5094     <code>@font-face</code> rule.
  5096    <li>If the font is defined via an <code>@font-face</code> rule, the font
  5097     features implied by the font-feature-settings descriptor in the
  5098     <code>@font-face</code> rule.
  5100    <li>Feature settings determined by properties other than ‘<a
  5101     href="#propdef-font-variant"><code
  5102     class=property>font-variant</code></a>’ or ‘<a
  5103     href="#propdef-font-feature-settings"><code
  5104     class=property>font-feature-settings</code></a>’. For example, setting
  5105     a non-default value for the ‘<code
  5106     class=property>letter-spacing</code>’ property disables ligatures.
  5108    <li>Font features implied by the value of the ‘<a
  5109     href="#propdef-font-variant"><code
  5110     class=property>font-variant</code></a>’ property, the related
  5111     font-variant subproperties and any other CSS property that may use
  5112     OpenType features (e.g. the ‘<a href="#propdef-font-kerning"><code
  5113     class=property>font-kerning</code></a>’ property).
  5115    <li>Font features implied by the value of ‘<a
  5116     href="#propdef-font-feature-settings"><code
  5117     class=property>font-feature-settings</code></a>’ property.
  5118   </ol>
  5120   <p>This ordering allows authors to set up a general set of defaults for
  5121    fonts within their <code>@font-face</code> rules, then override them with
  5122    property settings for specific elements. General property settings
  5123    override the settings in <code>@font-face</code> rules and low-level font
  5124    feature settings override ‘<a href="#propdef-font-variant"><code
  5125    class=property>font-variant</code></a>’ property settings.
  5127   <p>For situations where the combined list of font feature settings contains
  5128    more than one value for the same feature, the last value is used. When a
  5129    font lacks support for a given underlying font feature, text is simply
  5130    rendered as if that font feature was not enabled; font fallback does not
  5131    occur and no attempt is made to synthesize the feature except where
  5132    explicitly noted for specific properties.
  5134   <h3 id=feature-precedence-examples><span class=secno>7.3 </span>Feature
  5135    precedence examples</h3>
  5137   <div class=example>
  5138    <p>With the styles below, numbers are rendered proportionally when used
  5139     within a paragraph but are shown in tabular form within tables of prices:</p>
  5141    <pre>body { 
  5142   font-variant-numeric: proportional-nums; 
  5145 table.prices td {
  5146   font-variant-numeric: tabular-nums; 
  5148 </pre>
  5149   </div>
  5151   <div class=example>
  5152    <p>When the font-variant descriptor is used within an
  5153     <code>@font-face</code> rule, it only applies to the font defined by that
  5154     rule.</p>
  5156    <pre>@font-face {
  5157   font-family: MainText;
  5158   src: url(http://example.com/font.ttf);
  5159   font-variant: oldstyle-nums proportional-nums styleset(1,3);
  5162 body {
  5163   font-family: MainText, Helvetica;
  5166 table.prices td {
  5167   font-variant-numeric: tabular-nums; 
  5169 </pre>
  5171    <p>In this case, old-style numerals will be used throughout but only where
  5172     the font "MainText" is used. Just as in the previous example, tabular
  5173     values will be used in price tables since ‘<a
  5174     href="#tabular-nums"><code class=property>tabular-nums</code></a>’
  5175     appears in a general style rule and its use is mutually exclusive with
  5176     ‘<a href="#proportional-nums"><code
  5177     class=property>proportional-nums</code></a>’. Stylistic alternate sets
  5178     will only be used where MainText is used.</p>
  5179   </div>
  5181   <div class=example>
  5182    <p>The <code>@font-face</code> rule can also be used to access font
  5183     features in locally available fonts via the use of local() in the ‘<a
  5184     href="#descdef-src"><code class=property>src</code></a>’ descriptor of
  5185     the <code>@font-face</code> definition:</p>
  5187    <pre>@font-face {
  5188   font-family: BodyText;
  5189   src: local("HiraMaruPro-W4");
  5190   font-variant: proportional-width;
  5191   font-feature-settings: "ital"; /* Latin italics within CJK text feature */
  5194 body { font-family: BodyText, serif; }
  5195 </pre>
  5197    <p>If available, a Japanese font "Hiragino Maru Gothic" will be used. When
  5198     text rendering occurs, Japanese kana will be proportionally spaced and
  5199     Latin text will be italicised. Text rendered with the fallback serif font
  5200     will use default rendering properties.</p>
  5201   </div>
  5203   <div class=example>
  5204    <p>In the example below, discretionary ligatures are enabled only for a
  5205     downloadable font but are disabled within spans of class "special":</p>
  5207    <pre>@font-face {
  5208   font-family: main;
  5209   src: url(fonts/ffmeta.woff) format("woff");
  5210   font-variant: discretionary-ligatures;
  5213 body         { font-family: main, Helvetica; }
  5214 span.special { font-variant-ligatures: no-discretionary-ligatures; }
  5215 </pre>
  5217    <p>Adding an discretionary style rule with the <code>@font-face</code>
  5218     above:</p>
  5220    <pre>body         { font-family: main, Helvetica; }
  5221 span         { font-feature-settings: "dlig"; }
  5222 span.special { font-variant-ligatures: no-discretionary-ligatures; }
  5223 </pre>
  5225    <p>Within spans of class "special", discretionary ligatures <em>will</em>
  5226     be rendered. This is because both the ‘<a
  5227     href="#propdef-font-feature-settings"><code
  5228     class=property>font-feature-settings</code></a>’ and ‘<a
  5229     href="#propdef-font-variant-ligatures"><code
  5230     class=property>font-variant-ligatures</code></a>’ properties apply to
  5231     these spans. Although the ‘<code class=css>no-discretionary
  5232     ligatures</code>’ setting of ‘<a
  5233     href="#propdef-font-variant-ligatures"><code
  5234     class=property>font-variant-ligatures</code></a>’ effectively disables
  5235     the OpenType <span class=tag>dlig</span> feature, because the ‘<a
  5236     href="#propdef-font-feature-settings"><code
  5237     class=property>font-feature-settings</code></a>’ is resolved after
  5238     that, the ‘<code class=property>dlig</code>’ value reenables
  5239     discretionary ligatures.</p>
  5240   </div>
  5242   <h2 id=object-model><span class=secno>8 </span>Object Model</h2>
  5244   <p>The contents of <code>@font-face</code> and
  5245    <code>@font-feature-values</code> rules can be accessed via the following
  5246    extensions to the CSS Object Model.
  5248   <h3 id=om-fontface><span class=secno>8.1 </span>The <a
  5249    href="#cssfontfacerule"><code>CSSFontFaceRule</code></a> interface</h3>
  5251   <p>The <dfn id=cssfontfacerule>CSSFontFaceRule</dfn> interface represents a
  5252    <code>@font-face</code> rule.
  5254   <pre class=idl>
  5255 interface CSSFontFaceRule : CSSRule {
  5256   attribute DOMString family;
  5257   attribute DOMString src;
  5258   attribute DOMString style;
  5259   attribute DOMString weight;
  5260   attribute DOMString stretch;
  5261   attribute DOMString unicodeRange;
  5262   attribute DOMString variant;
  5263   attribute DOMString featureSettings;
  5264 }</pre>
  5266   <p>The DOM Level 2 Style specification <a href="#DOM-LEVEL-2-STYLE"
  5267    rel=biblioentry>[DOM-LEVEL-2-STYLE]<!--{{DOM-LEVEL-2-STYLE}}--></a>
  5268    defined a different variant of this rule. This definition supercedes that
  5269    one.
  5271   <h3 id=om-fontfeaturevalues><span class=secno>8.2 </span>The <a
  5272    href="#cssfontfeaturevaluesrule"><code>CSSFontFeatureValuesRule</code></a>
  5273    interface</h3>
  5275   <p>The <code>CSSRule</code> interface is extended as follows:
  5277   <pre class=idl>partial interface CSSRule {
  5278   const unsigned short FONT_FEATURE_VALUES_RULE = 14;
  5279 }</pre>
  5281   <p>The <dfn id=cssfontfeaturevaluesrule>CSSFontFeatureValuesRule</dfn>
  5282    interface represents a <code>@font-feature-values</code> rule.
  5284   <pre class=idl>interface CSSFontFeatureValuesRule : CSSRule {
  5285   readonly attribute DOMString familyList;
  5286   readonly attribute DOMString valueText;
  5287 };</pre>
  5289   <dl class=idl-attributes>
  5290    <dt><var>familyList</var> of type <code>DOMString</code>, readonly
  5292    <dd>The list of one or more font families for which a given set of feature
  5293     values is defined.
  5295    <dt><var>valueText</var> of type <code>DOMString</code>, readonly
  5297    <dd>Serialized set of feature values.
  5298   </dl>
  5300   <h2 class=no-num id=platform-props-to-css>Appendix A: Mapping platform font
  5301    properties to CSS properties</h2>
  5303   <p><em>This appendix is included as background for some of the problems and
  5304    situations that are described in other sections. It should be viewed as
  5305    informative only.</em>
  5307   <p>Font properties in CSS are designed to be independent of the underlying
  5308    font formats used; they can be used to specify bitmap fonts, Type1 fonts,
  5309    SVG fonts in addition to the common TrueType and OpenType fonts. But there
  5310    are facets of the TrueType and OpenType formats that often cause confusion
  5311    for authors and present challenges to implementers on different platforms.
  5313   <p>Originally developed at Apple, TrueType was designed as an outline font
  5314    format for both screen and print. Microsoft joined Apple in developing the
  5315    TrueType format and both platforms have supported TrueType fonts since
  5316    then. Font data in the TrueType format consists of a set of tables
  5317    distinguished with common four-letter tag names, each containing a
  5318    specific type of data. For example, naming information, including
  5319    copyright and license information, is stored in the ‘<code
  5320    class=property>name</code>’ table. The <a
  5321    href="#character-map"><em>character map</em></a> (‘<code
  5322    class=property>cmap</code>’) table contains a mapping of character
  5323    encodings to glyphs. Apple later added additional tables for supporting
  5324    enhanced typographic functionality; these are now called Apple Advanced
  5325    Typography, or AAT, fonts. Microsoft and Adobe developed a separate set of
  5326    tables for advanced typography and called their format OpenType <a
  5327    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>.
  5329   <p>In many cases the font data used under Microsoft Windows or Linux is
  5330    slightly different from the data used under Apple's Mac OS X because the
  5331    TrueType format allowed for explicit variation across platforms. This
  5332    includes font metrics, names and <a href="#character-map"><em>character
  5333    map</em></a> data.
  5335   <p>Specifically, font family name data is handled differently across
  5336    platforms. For TrueType and OpenType fonts these names are contained in
  5337    the ‘<code class=property>name</code>’ table, in name records with
  5338    name ID 1. Mulitple names can be stored for different locales but
  5339    Microsoft recommends fonts always include at least a US English version of
  5340    the name. On Windows, Microsoft made the decision for backwards
  5341    compatibility to limit this family name to a maximum of four faces; for
  5342    larger groupings the "preferred family" (name ID 16) or "WWS family" (name
  5343    ID 21) can be used. Other platforms such as OSX don't have this
  5344    limitation, the family name is used to define all possible groupings.
  5346   <p>Other name table data provides names used to uniquely identify a
  5347    specific face within a family. The full font name (name ID 4) and the
  5348    Postscript name (name ID 6) describe a single face uniquely. The bold face
  5349    of the Gill Sans family has a fullname of "Gill Sans Bold" and a
  5350    Postscript name of "GillSans-Bold". There can be multiple localized
  5351    versions of the fullname for a given face but the Postscript name is
  5352    always a unique name made from a limited set of ASCII characters.
  5354   <p>On various platforms, different names are used to search for a font. For
  5355    example, with the Windows GDI CreateIndirectFont API, either a family or
  5356    fullname can be used to lookup a face while on Mac OS X the
  5357    CTFontCreateWithName API call is used to lookup a given face using the
  5358    fullname and Postscript name. Under Linux, the fontconfig API allows fonts
  5359    to be searched using any of these names. In situations where platform
  5360    API's automatically substitute other font choices, it may be necessary to
  5361    verify a returned font matches a given name.
  5363   <p>The weight of a given face can be determined via the usWeightClass field
  5364    of the OS/2 table or inferred from the style name (name ID 2). Likewise,
  5365    the width can be determined via the usWidthClass of the OS/2 table or
  5366    inferred from the style name. For historical reasons related to synthetic
  5367    bolding at weights 200 or lower with the Windows GDI API, font designers
  5368    have sometimes skewed values in the OS/2 table to avoid these weights.
  5370   <p>Rendering complex scripts that use contextual shaping such as Thai,
  5371    Arabic and Devanagari requires features present only in OpenType or AAT
  5372    fonts. Currently, complex script rendering is supported on Windows and
  5373    Linux using OpenType font features while both OpenType and AAT font
  5374    features are used under Mac OS X.
  5376   <h2 class=no-num id=ch-ch-ch-changes>Changes</h2>
  5378   <h3 class=no-num id=recent-changes> Changes from the <a
  5379    href="http://www.w3.org/TR/2013/WD-css3-fonts-20130212/">February 2013
  5380    CSS3 Fonts Working Draft</a></h3>
  5382   <p>Major changes include:
  5384   <ul>
  5385    <li>Moved font load events into a separate <a
  5386     href="http://dev.w3.org/csswg/css3-font-load-events/">spec</a>
  5388    <li>Tightened error handling rules for <code>@font-feature-values</code>
  5389     rules
  5391    <li>Added grammar productions for <code>@font-face</code> and
  5392     <code>@font-feature-values</code> rules
  5394    <li>Tightened definition of synthetic oblique
  5395   </ul>
  5397   <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
  5399   <p>I'd like to thank Tal Leming, Jonathan Kew and Christopher Slye for all
  5400    their help and feedback. John Hudson was kind enough to take the time to
  5401    explain the subtleties of OpenType language tags and provided the example
  5402    of character variant usage for displaying text on Byzantine seals. Ken
  5403    Lunde and Eric Muller provided valuable feedback on CJK OpenType features
  5404    and Unicode variation selectors. The idea for supporting font features by
  5405    using font-variant subproperties originated with Håkon Wium Lie, Adam
  5406    Twardoch and Tal Leming. Elika Etemad supplied some of the initial design
  5407    ideas for the <code>@font-feature-values</code> rule. Thanks also to House
  5408    Industries for allowing the use of Ed Interlock in the discretionary
  5409    ligatures example.
  5411   <p>A special thanks to Robert Bringhurst for the sublime mind expansion
  5412    that is <em>The Elements of Typographic Style</em>.
  5414   <h2 class=no-num id=conformance> Conformance</h2>
  5416   <h3 class=no-num id=conventions> Document Conventions</h3>
  5418   <p>Conformance requirements are expressed with a combination of descriptive
  5419    assertions and RFC 2119 terminology. The key words “MUST”, “MUST
  5420    NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”,
  5421    “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the
  5422    normative parts of this document are to be interpreted as described in RFC
  5423    2119. However, for readability, these words do not appear in all uppercase
  5424    letters in this specification.
  5426   <p>All of the text of this specification is normative except sections
  5427    explicitly marked as non-normative, examples, and notes. <a
  5428    href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>
  5430   <p>Examples in this specification are introduced with the words “for
  5431    example” or are set apart from the normative text with
  5432    <code>class="example"</code>, like this:
  5434   <div class=example>
  5435    <p>This is an example of an informative example.
  5436   </div>
  5438   <p>Informative notes begin with the word “Note” and are set apart from
  5439    the normative text with <code>class="note"</code>, like this:
  5441   <p class=note>Note, this is an informative note.
  5443   <h3 class=no-num id=conformance-classes> Conformance Classes</h3>
  5445   <p>Conformance to CSS Fonts Level 3 Module is defined for three conformance
  5446    classes:
  5448   <dl>
  5449    <dt><dfn id=style-sheet title="style sheet!!as conformance class">style
  5450     sheet</dfn>
  5452    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
  5453     style sheet</a>.
  5455    <dt><dfn id=renderer>renderer</dfn>
  5457    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
  5458     that interprets the semantics of a style sheet and renders documents that
  5459     use them.
  5461    <dt><dfn id=authoring-tool>authoring tool</dfn>
  5463    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
  5464     that writes a style sheet.
  5465   </dl>
  5467   <p>A style sheet is conformant to CSS Fonts Level 3 Module if all of its
  5468    declarations that use properties defined in this module have values that
  5469    are valid according to the generic CSS grammar and the individual grammars
  5470    of each property as given in this module.
  5472   <p>A renderer is conformant to CSS Fonts Level 3 Module if, in addition to
  5473    interpreting the style sheet as defined by the appropriate specifications,
  5474    it supports all the features defined by CSS Fonts Level 3 Module by
  5475    parsing them correctly and rendering the document accordingly. However,
  5476    the inability of a UA to correctly render a document due to limitations of
  5477    the device does not make the UA non-conformant. (For example, a UA is not
  5478    required to render color on a monochrome monitor.)
  5480   <p>An authoring tool is conformant to CSS Fonts Level 3 Module if it writes
  5481    style sheets that are syntactically correct according to the generic CSS
  5482    grammar and the individual grammars of each feature in this module, and
  5483    meet all other conformance requirements of style sheets as described in
  5484    this module.
  5486   <h3 class=no-num id=partial> Partial Implementations</h3>
  5488   <p>So that authors can exploit the forward-compatible parsing rules to
  5489    assign fallback values, CSS renderers <strong>must</strong> treat as
  5490    invalid (and <a
  5491    href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore as
  5492    appropriate</a>) any at-rules, properties, property values, keywords, and
  5493    other syntactic constructs for which they have no usable level of support.
  5494    In particular, user agents <strong>must not</strong> selectively ignore
  5495    unsupported component values and honor supported values in a single
  5496    multi-value property declaration: if any value is considered invalid (as
  5497    unsupported values must be), CSS requires that the entire declaration be
  5498    ignored.
  5500   <h3 class=no-num id=experimental> Experimental Implementations</h3>
  5502   <p>To avoid clashes with future CSS features, the CSS2.1 specification
  5503    reserves a <a
  5504    href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
  5505    syntax</a> for proprietary and experimental extensions to CSS.
  5507   <p>Prior to a specification reaching the Candidate Recommendation stage in
  5508    the W3C process, all implementations of a CSS feature are considered
  5509    experimental. The CSS Working Group recommends that implementations use a
  5510    vendor-prefixed syntax for such features, including those in W3C Working
  5511    Drafts. This avoids incompatibilities with future changes in the draft.
  5513   <h3 class=no-num id=testing> Non-Experimental Implementations</h3>
  5515   <p>Once a specification reaches the Candidate Recommendation stage,
  5516    non-experimental implementations are possible, and implementors should
  5517    release an unprefixed implementation of any CR-level feature they can
  5518    demonstrate to be correctly implemented according to spec.
  5520   <p>To establish and maintain the interoperability of CSS across
  5521    implementations, the CSS Working Group requests that non-experimental CSS
  5522    renderers submit an implementation report (and, if necessary, the
  5523    testcases used for that implementation report) to the W3C before releasing
  5524    an unprefixed implementation of any CSS features. Testcases submitted to
  5525    W3C are subject to review and correction by the CSS Working Group.
  5527   <p>Further information on submitting testcases and implementation reports
  5528    can be found from on the CSS Working Group's website at <a
  5529    href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
  5530    Questions should be directed to the <a
  5531    href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
  5532    mailing list.
  5534   <h2 class=no-num id=references>References</h2>
  5536   <h3 class=no-num id=normative-references>Normative References</h3>
  5537   <!--begin-normative-->
  5538   <!-- Sorted by label -->
  5540   <dl class=bibliography>
  5541    <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
  5542     <!---->
  5544    <dt id=CHARMOD>[CHARMOD]
  5546    <dd>Martin J. Dürst; et al. <a
  5547     href="http://www.w3.org/TR/2005/REC-charmod-20050215/"><cite>Character
  5548     Model for the World Wide Web 1.0: Fundamentals.</cite></a> 15 February
  5549     2005. W3C Recommendation. URL: <a
  5550     href="http://www.w3.org/TR/2005/REC-charmod-20050215/">http://www.w3.org/TR/2005/REC-charmod-20050215/</a>
  5551     </dd>
  5552    <!---->
  5554    <dt id=CORS>[CORS]
  5556    <dd>Anne van Kesteren. <a
  5557     href="http://www.w3.org/TR/2013/CR-cors-20130129/"><cite>Cross-Origin
  5558     Resource Sharing.</cite></a> 29 January 2013. W3C Candidate
  5559     Recommendation. (Work in progress.) URL: <a
  5560     href="http://www.w3.org/TR/2013/CR-cors-20130129/">http://www.w3.org/TR/2013/CR-cors-20130129/</a>
  5561     </dd>
  5562    <!---->
  5564    <dt id=CSS21>[CSS21]
  5566    <dd>Bert Bos; et al. <a
  5567     href="http://www.w3.org/TR/2011/REC-CSS2-20110607"><cite>Cascading Style
  5568     Sheets Level 2 Revision 1 (CSS 2.1) Specification.</cite></a> 7 June
  5569     2011. W3C Recommendation. URL: <a
  5570     href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
  5571     </dd>
  5572    <!---->
  5574    <dt id=CSS3VAL>[CSS3VAL]
  5576    <dd>Håkon Wium Lie; Tab Atkins; Elika J. Etemad. <a
  5577     href="http://www.w3.org/TR/2012/CR-css3-values-20120828/"><cite>CSS
  5578     Values and Units Module Level 3.</cite></a> 28 August 2012. W3C Candidate
  5579     Recommendation. (Work in progress.) URL: <a
  5580     href="http://www.w3.org/TR/2012/CR-css3-values-20120828/">http://www.w3.org/TR/2012/CR-css3-values-20120828/</a>
  5581     </dd>
  5582    <!---->
  5584    <dt id=HTML5>[HTML5]
  5586    <dd>Ian Hickson. <a
  5587     href="http://www.w3.org/TR/2012/CR-html5-20121217/"><cite>HTML5.</cite></a>
  5588     17 December 2012. W3C Candidate Recommendation. (Work in progress.) URL:
  5589     <a
  5590     href="http://www.w3.org/TR/2012/CR-html5-20121217/">http://www.w3.org/TR/2012/CR-html5-20121217/</a>
  5591     </dd>
  5592    <!---->
  5594    <dt id=OPEN-FONT-FORMAT>[OPEN-FONT-FORMAT]
  5596    <dd><a
  5597     href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c052136_ISO_IEC_14496-22_2009(E).zip"><cite>Information
  5598     technology — Coding of audio-visual objects — Part 22: Open Font
  5599     Format.</cite></a> International Organization for Standardization.
  5600     ISO/IEC 14496-22:2009. URL: <a
  5601     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>
  5602     </dd>
  5603    <!---->
  5605    <dt id=OPENTYPE>[OPENTYPE]
  5607    <dd><a
  5608     href="http://www.microsoft.com/typography/otspec/default.htm"><cite>OpenType
  5609     specification.</cite></a> Microsoft. URL: <a
  5610     href="http://www.microsoft.com/typography/otspec/default.htm">http://www.microsoft.com/typography/otspec/default.htm</a>
  5611     </dd>
  5612    <!---->
  5614    <dt id=OPENTYPE-FEATURES>[OPENTYPE-FEATURES]
  5616    <dd><a
  5617     href="http://www.microsoft.com/typography/otspec/featurelist.htm"><cite>OpenType
  5618     feature registry.</cite></a> Microsoft. URL: <a
  5619     href="http://www.microsoft.com/typography/otspec/featurelist.htm">http://www.microsoft.com/typography/otspec/featurelist.htm</a>
  5620     </dd>
  5621    <!---->
  5623    <dt id=RFC2119>[RFC2119]
  5625    <dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
  5626     words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
  5627     RFC 2119. URL: <a
  5628     href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
  5629     </dd>
  5630    <!---->
  5632    <dt id=UAX15>[UAX15]
  5634    <dd>Mark Davis; Ken Whistler. <a
  5635     href="http://www.unicode.org/reports/tr15/"><cite>Unicode Normalization
  5636     Forms.</cite></a> 31 August 2012. Unicode Standard Annex #15. URL: <a
  5637     href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a>
  5638     </dd>
  5639    <!---->
  5641    <dt id=UAX29>[UAX29]
  5643    <dd>Mark Davis. <a
  5644     href="http://www.unicode.org/reports/tr29/"><cite>Unicode Text
  5645     Segmentation.</cite></a> 12 September 2012. Unicode Standard Annex #29.
  5646     URL: <a
  5647     href="http://www.unicode.org/reports/tr29/">http://www.unicode.org/reports/tr29/</a>
  5648     </dd>
  5649    <!---->
  5651    <dt id=UNICODE6>[UNICODE6]
  5653    <dd>The Unicode Consortium. <a
  5654     href="http://www.unicode.org/versions/Unicode6.2.0/"><cite>The Unicode
  5655     Standard, Version 6.2.0.</cite></a> Defined by: The Unicode Standard,
  5656     Version 6.2.0 URL: <a
  5657     href="http://www.unicode.org/versions/Unicode6.2.0/">http://www.unicode.org/versions/Unicode6.2.0/</a>
  5658     </dd>
  5659    <!---->
  5660   </dl>
  5661   <!--end-normative-->
  5662   <!--{{!CSS21}}-->
  5663   <!--{{!CSS3VAL}}-->
  5664   <!--{{!OPENTYPE}}-->
  5665   <!--{{!OPENTYPE-FEATURES}}-->
  5666   <!--{{!OPEN-FONT-FORMAT}}-->
  5667   <!--{{!UNICODE6}}-->
  5668   <!--{{!UAX15}}-->
  5669   <!--{{!UAX29}}-->
  5670   <!--{{!CORS}}-->
  5671   <!--{{!HTML5}}-->
  5672   <!--{{!CHARMOD}}-->
  5674   <h3 class=no-num id=other-references>Other References</h3>
  5675   <!--begin-informative-->
  5676   <!-- Sorted by label -->
  5678   <dl class=bibliography>
  5679    <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
  5680     <!---->
  5682    <dt id=AAT-FEATURES>[AAT-FEATURES]
  5684    <dd><a href="http://developer.apple.com/fonts/registry/"><cite>Apple
  5685     Advanced Typography font feature registry.</cite></a> Apple. URL: <a
  5686     href="http://developer.apple.com/fonts/registry/">http://developer.apple.com/fonts/registry/</a>
  5687     </dd>
  5688    <!---->
  5690    <dt id=ARABIC-TYPO>[ARABIC-TYPO]
  5692    <dd>Huda Smitshuijzen AbiFares. <cite>Arabic Typography: A Comprehensive
  5693     Sourcebook.</cite> Saqi Books. 2001. ISBN 0-86356-347-3.</dd>
  5694    <!---->
  5696    <dt id=CHARMOD-NORM>[CHARMOD-NORM]
  5698    <dd>François Yergeau; et al. <a
  5699     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/"><cite>Character
  5700     Model for the World Wide Web 1.0: Normalization.</cite></a> 1 May 2012.
  5701     W3C Working Draft. (Work in progress.) URL: <a
  5702     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/">http://www.w3.org/TR/2012/WD-charmod-norm-20120501/</a>
  5703     </dd>
  5704    <!---->
  5706    <dt id=CJKV-INFO-PROCESSING>[CJKV-INFO-PROCESSING]
  5708    <dd>Ken Lunde. <cite>CJKV Information Processing, Second Edition.</cite>
  5709     O'Reilly Media, Inc. 2009. ISBN 0-596-51447-1.</dd>
  5710    <!---->
  5712    <dt id=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]
  5714    <dd>L. David Baron. <a
  5715     href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/"><cite>CSS
  5716     Conditional Rules Module Level 3.</cite></a> 13 December 2012. W3C
  5717     Working Draft. (Work in progress.) URL: <a
  5718     href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/">http://www.w3.org/TR/2012/WD-css3-conditional-20121213/</a>
  5719     </dd>
  5720    <!---->
  5722    <dt id=CSS3TEXT>[CSS3TEXT]
  5724    <dd>Elika J. Etemad; Koji Ishii. <a
  5725     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/"><cite>CSS Text
  5726     Module Level 3.</cite></a> 13 November 2012. W3C Working Draft. (Work in
  5727     progress.) URL: <a
  5728     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/">http://www.w3.org/TR/2012/WD-css3-text-20121113/</a>
  5729     </dd>
  5730    <!---->
  5732    <dt id=DIGITAL-TYPOGRAPHY>[DIGITAL-TYPOGRAPHY]
  5734    <dd>Richard Rubinstein. <cite>Digital Typography, An Introduction to Type
  5735     and Composition for Computer System Design.</cite> Addison-Wesley. 1988.
  5736     ISBN 0-201-17633-5.</dd>
  5737    <!---->
  5739    <dt id=DOM-LEVEL-2-STYLE>[DOM-LEVEL-2-STYLE]
  5741    <dd>Chris Wilson; Philippe Le Hégaret; Vidur Apparao. <a
  5742     href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/"><cite>Document
  5743     Object Model (DOM) Level 2 Style Specification.</cite></a> 13 November
  5744     2000. W3C Recommendation. URL: <a
  5745     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>
  5746     </dd>
  5747    <!---->
  5749    <dt id=ELEMTYPO>[ELEMTYPO]
  5751    <dd>Robert Bringhurst. <cite>The Elements of Typographic Style, Version
  5752     4.</cite> Hartley &amp; Marks. 2013. ISBN 0-88179-212-8.</dd>
  5753    <!---->
  5755    <dt id=LANGCULTTYPE>[LANGCULTTYPE]
  5757    <dd>John D. Berry, Ed. <cite>Language Culture Type.</cite> Graphis. 2001.
  5758     ISBN 1-932026-01-0.</dd>
  5759    <!---->
  5761    <dt id=OPENTYPE-FONT-GUIDE>[OPENTYPE-FONT-GUIDE]
  5763    <dd><a
  5764     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf"><cite>OpenType
  5765     User Guide.</cite></a> FontShop International. URL: <a
  5766     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf">https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf</a>
  5767     </dd>
  5768    <!---->
  5770    <dt id=RASTER-TRAGEDY>[RASTER-TRAGEDY]
  5772    <dd>Beat Stamm. <a href="http://www.rastertragedy.com/"><cite>The Raster
  5773     Tragedy at Low-Resolution Revisited.</cite></a> 7 December 2011. URL: <a
  5774     href="http://www.rastertragedy.com/">http://www.rastertragedy.com/</a></dd>
  5775    <!---->
  5777    <dt id=WINDOWS-GLYPH-PROC>[WINDOWS-GLYPH-PROC]
  5779    <dd>John Hudson. <a
  5780     href="http://www.microsoft.com/typography/developers/opentype/default.htm"><cite>Windows
  5781     Glyph Processing.</cite></a> Microsoft Typogrraphy. URL: <a
  5782     href="http://www.microsoft.com/typography/developers/opentype/default.htm">http://www.microsoft.com/typography/developers/opentype/default.htm</a>
  5783     </dd>
  5784    <!---->
  5785   </dl>
  5786   <!--end-informative-->
  5787   <!--{{ARABIC-TYPO}}-->
  5788   <!--{{CJKV-INFO-PROCESSING}}-->
  5789   <!--{{DIGITAL-TYPOGRAPHY}}-->
  5790   <!--{{DOM-LEVEL-2-STYLE}}-->
  5791   <!--{{ELEMTYPO}}-->
  5792   <!--{{LANGCULTTYPE}}-->
  5793   <!--{{OPENTYPE-FONT-GUIDE}}-->
  5794   <!--{{RASTER-TRAGEDY}}-->
  5795   <!--{{WINDOWS-GLYPH-PROC}}-->
  5796   <!--{{CHARMOD-NORM}}-->
  5797   <!--{{AAT-FEATURES}}-->
  5798   <!--{{CSS3-CONDITIONAL}}-->
  5799   <!--{{CSS3TEXT}}-->
  5801   <h2 class=no-num id=index>Index</h2>
  5802   <!--begin-index-->
  5804   <ul class=indexlist>
  5805    <li>&lt;absolute-size&gt;, <a href="#ltabsolute-sizegt"
  5806     title="&lt;absolute-size&gt;"><strong>3.5</strong></a>
  5808    <li><var>&lt;common-lig-values></var>, <a href="#ltcommon-lig-values"
  5809     title="&lt;common-lig-values>"><strong>6.4</strong></a>
  5811    <li><var>&lt;contextual-alt-values&gt;</var>, <a
  5812     href="#ltcontextual-alt-valuesgt"
  5813     title="&lt;contextual-alt-values&gt;"><strong>6.4</strong></a>
  5815    <li><var>&lt;discretionary-lig-values></var>, <a
  5816     href="#ltdiscretionary-lig-values"
  5817     title="&lt;discretionary-lig-values>"><strong>6.4</strong></a>
  5819    <li><var>&lt;east-asian-variant-values&gt;</var>, <a
  5820     href="#lteast-asian-variant-valuesgt"
  5821     title="&lt;east-asian-variant-values&gt;"><strong>6.10</strong></a>
  5823    <li><var>&lt;east-asian-width-values&gt;</var>, <a
  5824     href="#lteast-asian-width-valuesgt"
  5825     title="&lt;east-asian-width-values&gt;"><strong>6.10</strong></a>
  5827    <li><var>&lt;feature-tag-value&gt;</var>, <a href="#ltfeature-tag-valuegt"
  5828     title="&lt;feature-tag-value&gt;"><strong>6.12</strong></a>
  5830    <li>&lt;font-face-name&gt;, <a href="#ltfont-face-namegt"
  5831     title="&lt;font-face-name&gt;"><strong>4.3</strong></a>
  5833    <li><var>&lt;font-variant-css21&gt;</var>, <a
  5834     href="#ltfont-variant-css21gt"
  5835     title="&lt;font-variant-css21&gt;"><strong>3.7</strong></a>
  5837    <li><var>&lt;historical-lig-values></var>, <a
  5838     href="#lthistorical-lig-values"
  5839     title="&lt;historical-lig-values>"><strong>6.4</strong></a>
  5841    <li>&lt;length&gt;, <a href="#ltlengthgt" title="&lt;length&gt;">3.5</a>
  5843    <li>&lt;number&gt;, <a href="#ltnumbergt" title="&lt;number&gt;">3.6</a>
  5845    <li><var>&lt;numeric-figure-values&gt;</var>, <a
  5846     href="#ltnumeric-figure-valuesgt"
  5847     title="&lt;numeric-figure-values&gt;"><strong>6.7</strong></a>
  5849    <li><var>&lt;numeric-fraction-values&gt;</var>, <a
  5850     href="#ltnumeric-fraction-valuesgt"
  5851     title="&lt;numeric-fraction-values&gt;"><strong>6.7</strong></a>
  5853    <li><var>&lt;numeric-spacing-values&gt;</var>, <a
  5854     href="#ltnumeric-spacing-valuesgt"
  5855     title="&lt;numeric-spacing-values&gt;"><strong>6.7</strong></a>
  5857    <li>&lt;percentage&gt;, <a href="#ltpercentagegt-"
  5858     title="&lt;percentage&gt;">3.5</a>
  5860    <li>&lt;relative-size&gt;, <a href="#ltrelative-sizegt"
  5861     title="&lt;relative-size&gt;"><strong>3.5</strong></a>
  5863    <li>&lt;urange&gt;, <a href="#lturangegt"
  5864     title="&lt;urange&gt;"><strong>4.5</strong></a>
  5866    <li>@font-face, <a href="#font-face" title="@font-face">4.1</a>, <a
  5867     href="#font-face0" title="@font-face">4.3</a>
  5869    <li>all-petite-caps, <a href="#all-petite-caps"
  5870     title=all-petite-caps><strong>6.6</strong></a>
  5872    <li>all-small-caps, <a href="#all-small-caps"
  5873     title=all-small-caps><strong>6.6</strong></a>
  5875    <li>annotation, <a href="#annotationltfeature-value-namegt"
  5876     title=annotation><strong>6.8</strong></a>
  5878    <li>aspect value, <a href="#aspect-value0" title="aspect
  5879     value"><strong>3.6</strong></a>
  5881    <li>authoring tool, <a href="#authoring-tool" title="authoring
  5882     tool"><strong>#</strong></a>
  5884    <li>character map, <a href="#character-map" title="character
  5885     map"><strong>5.2</strong></a>
  5887    <li>character-variant, <a href="#character-variantltfeature-value-namegt"
  5888     title=character-variant><strong>6.8</strong></a>
  5890    <li>common-ligatures, <a href="#common-ligatures"
  5891     title=common-ligatures><strong>6.4</strong></a>
  5893    <li>contextual, <a href="#contextual"
  5894     title=contextual><strong>6.4</strong></a>
  5896    <li>CSSFontFaceRule, <a href="#cssfontfacerule"
  5897     title=CSSFontFaceRule><strong>8.1</strong></a>
  5899    <li>CSSFontFeatureValuesRule, <a href="#cssfontfeaturevaluesrule"
  5900     title=CSSFontFeatureValuesRule><strong>8.2</strong></a>
  5902    <li>cursive, definition of, <a href="#cursive0" title="cursive, definition
  5903     of"><strong>#</strong></a>
  5905    <li>default face, <a href="#default-face" title="default
  5906     face"><strong>5.2</strong></a>
  5908    <li>descriptor_declaration, <a href="#descriptordeclaration"
  5909     title="descriptor_declaration"><strong>4.1</strong></a>
  5911    <li>diagonal-fractions, <a href="#diagonal-fractions"
  5912     title=diagonal-fractions><strong>6.7</strong></a>
  5914    <li>discretionary-ligatures, <a href="#discretionary-ligatures"
  5915     title=discretionary-ligatures><strong>6.4</strong></a>
  5917    <li>fantasy, definition of, <a href="#fantasy0" title="fantasy, definition
  5918     of"><strong>#</strong></a>
  5920    <li>feature_type, <a href="#featuretype"
  5921     title="feature_type"><strong>6.9</strong></a>
  5923    <li>feature_value_block, <a href="#featurevalueblock"
  5924     title="feature_value_block"><strong>6.9</strong></a>
  5926    <li>feature_value_definition, <a href="#featurevaluedefinition"
  5927     title="feature_value_definition"><strong>6.9</strong></a>
  5929    <li>font, <a href="#propdef-font" title=font><strong>3.7</strong></a>
  5931    <li>font-family, <a href="#descdef-font-family"
  5932     title=font-family><strong>4.2</strong></a>, <a
  5933     href="#propdef-font-family" title=font-family><strong>3.1</strong></a>
  5935    <li>font-feature-settings, <a href="#propdef-font-feature-settings"
  5936     title=font-feature-settings><strong>6.12</strong></a>
  5938    <li>font-feature-settings (descriptor), <a
  5939     href="#descdef-font-feature-settings" title="font-feature-settings
  5940     (descriptor)"><strong>4.6</strong></a>
  5942    <li>font-kerning, <a href="#propdef-font-kerning"
  5943     title=font-kerning><strong>6.3</strong></a>
  5945    <li>font-language-override, <a href="#propdef-font-language-override"
  5946     title=font-language-override><strong>6.13</strong></a>
  5948    <li>font-size, <a href="#propdef-font-size"
  5949     title=font-size><strong>3.5</strong></a>
  5951    <li>font-size-adjust, <a href="#propdef-font-size-adjust"
  5952     title=font-size-adjust><strong>3.6</strong></a>
  5954    <li>font-stretch, <a href="#propdef-font-stretch"
  5955     title=font-stretch><strong>3.3</strong></a>
  5957    <li>font-stretch (descriptor), <a href="#descdef-font-stretch"
  5958     title="font-stretch (descriptor)"><strong>4.4</strong></a>
  5960    <li>font-style, <a href="#propdef-font-style"
  5961     title=font-style><strong>3.4</strong></a>
  5963    <li>font-style (descriptor), <a href="#descdef-font-style"
  5964     title="font-style (descriptor)"><strong>4.4</strong></a>
  5966    <li>font-synthesis, <a href="#propdef-font-synthesis"
  5967     title=font-synthesis><strong>3.8</strong></a>
  5969    <li>font-variant, <a href="#propdef-font-variant"
  5970     title=font-variant><strong>6.11</strong></a>
  5972    <li>font-variant (descriptor), <a href="#descdef-font-variant"
  5973     title="font-variant (descriptor)"><strong>4.6</strong></a>
  5975    <li>font-variant-alternates, <a href="#propdef-font-variant-alternates"
  5976     title=font-variant-alternates><strong>6.8</strong></a>
  5978    <li>font-variant-caps, <a href="#propdef-font-variant-caps"
  5979     title=font-variant-caps><strong>6.6</strong></a>
  5981    <li>font-variant-east-asian, <a href="#propdef-font-variant-east-asian"
  5982     title=font-variant-east-asian><strong>6.10</strong></a>
  5984    <li>font-variant-ligatures, <a href="#propdef-font-variant-ligatures"
  5985     title=font-variant-ligatures><strong>6.4</strong></a>
  5987    <li>font-variant-numeric, <a href="#propdef-font-variant-numeric"
  5988     title=font-variant-numeric><strong>6.7</strong></a>
  5990    <li>font-variant-position, <a href="#propdef-font-variant-position"
  5991     title=font-variant-position><strong>6.5</strong></a>
  5993    <li>font-weight, <a href="#propdef-font-weight"
  5994     title=font-weight><strong>3.2</strong></a>
  5996    <li>font-weight (descriptor), <a href="#descdef-font-weight"
  5997     title="font-weight (descriptor)"><strong>4.4</strong></a>
  5999    <li>font_face_rule, <a href="#fontfacerule"
  6000     title="font_face_rule"><strong>4.1</strong></a>
  6002    <li>font_family_name, <a href="#fontfamilyname"
  6003     title="font_family_name"><strong>6.9</strong></a>
  6005    <li>font_family_name_list, <a href="#fontfamilynamelist"
  6006     title="font_family_name_list"><strong>6.9</strong></a>
  6008    <li>font_feature_values_rule, <a href="#fontfeaturevaluesrule"
  6009     title="font_feature_values_rule"><strong>6.9</strong></a>
  6011    <li>full-width, <a href="#full-width"
  6012     title=full-width><strong>6.10</strong></a>
  6014    <li>historical-forms, <a href="#historical-forms"
  6015     title=historical-forms><strong>6.8</strong></a>
  6017    <li>historical-ligatures, <a href="#historical-ligatures"
  6018     title=historical-ligatures><strong>6.4</strong></a>
  6020    <li>jis04, <a href="#jis04" title=jis04><strong>6.10</strong></a>
  6022    <li>jis78, <a href="#jis78" title=jis78><strong>6.10</strong></a>
  6024    <li>jis83, <a href="#jis83" title=jis83><strong>6.10</strong></a>
  6026    <li>jis90, <a href="#jis90" title=jis90><strong>6.10</strong></a>
  6028    <li>lining-nums, <a href="#lining-nums"
  6029     title=lining-nums><strong>6.7</strong></a>
  6031    <li>monospace, definition of, <a href="#monospace0" title="monospace,
  6032     definition of"><strong>#</strong></a>
  6034    <li>no-common-ligatures, <a href="#no-common-ligatures"
  6035     title=no-common-ligatures><strong>6.4</strong></a>
  6037    <li>no-contextual, <a href="#no-contextual"
  6038     title=no-contextual><strong>6.4</strong></a>
  6040    <li>no-discretionary-ligatures, <a href="#no-discretionary-ligatures"
  6041     title=no-discretionary-ligatures><strong>6.4</strong></a>
  6043    <li>no-historical-ligatures, <a href="#no-historical-ligatures"
  6044     title=no-historical-ligatures><strong>6.4</strong></a>
  6046    <li>normal, <a href="#normal" title=normal><strong>6.6</strong></a>, <a
  6047     href="#normal0" title=normal><strong>6.7</strong></a>, <a href="#normal1"
  6048     title=normal><strong>6.8</strong></a>, <a href="#normal2"
  6049     title=normal><strong>6.10</strong></a>
  6051    <li>oldstyle-nums, <a href="#oldstyle-nums"
  6052     title=oldstyle-nums><strong>6.7</strong></a>
  6054    <li>ordinal, <a href="#ordinal" title=ordinal><strong>6.7</strong></a>
  6056    <li>ornaments, <a href="#ornamentsltfeature-value-namegt"
  6057     title=ornaments><strong>6.8</strong></a>
  6059    <li>petite-caps, <a href="#petite-caps"
  6060     title=petite-caps><strong>6.6</strong></a>
  6062    <li>proportional-nums, <a href="#proportional-nums"
  6063     title=proportional-nums><strong>6.7</strong></a>
  6065    <li>proportional-width, <a href="#proportional-width"
  6066     title=proportional-width><strong>6.10</strong></a>
  6068    <li>renderer, <a href="#renderer" title=renderer><strong>#</strong></a>
  6070    <li>ruby, <a href="#ruby" title=ruby><strong>6.10</strong></a>
  6072    <li>sans-serif, definition of, <a href="#sans-serif0" title="sans-serif,
  6073     definition of"><strong>#</strong></a>
  6075    <li>serif, definition of, <a href="#serif0" title="serif, definition
  6076     of"><strong>#</strong></a>
  6078    <li>simplified, <a href="#simplified"
  6079     title=simplified><strong>6.10</strong></a>
  6081    <li>slashed-zero, <a href="#slashed-zero"
  6082     title=slashed-zero><strong>6.7</strong></a>
  6084    <li>small-caps, <a href="#small-caps"
  6085     title=small-caps><strong>6.6</strong></a>
  6087    <li>src, <a href="#descdef-src" title=src><strong>4.3</strong></a>
  6089    <li>stacked-fractions, <a href="#stacked-fractions"
  6090     title=stacked-fractions><strong>6.7</strong></a>
  6092    <li>style sheet
  6093     <ul>
  6094      <li>as conformance class, <a href="#style-sheet" title="style sheet, as
  6095       conformance class"><strong>#</strong></a>
  6096     </ul>
  6098    <li>styleset, <a href="#stylesetltfeature-value-namegt"
  6099     title=styleset><strong>6.8</strong></a>
  6101    <li>stylistic, <a href="#stylisticltfeature-value-namegt"
  6102     title=stylistic><strong>6.8</strong></a>
  6104    <li>swash, <a href="#swashltfeature-value-namegt"
  6105     title=swash><strong>6.8</strong></a>
  6107    <li>tabular-nums, <a href="#tabular-nums"
  6108     title=tabular-nums><strong>6.7</strong></a>
  6110    <li>titling-caps, <a href="#titling-caps"
  6111     title=titling-caps><strong>6.6</strong></a>
  6113    <li>traditional, <a href="#traditional"
  6114     title=traditional><strong>6.10</strong></a>
  6116    <li>unicase, <a href="#unicase" title=unicase><strong>6.6</strong></a>
  6118    <li>unicode-range, <a href="#descdef-unicode-range"
  6119     title=unicode-range><strong>4.5</strong></a>
  6121    <li>weight, <a href="#weight" title=weight><strong>2</strong></a>
  6123    <li>width, <a href="#width" title=width><strong>2</strong></a>
  6124   </ul>
  6125   <!--end-index-->
  6127   <h2 class=no-num id=property-index>Property index</h2>
  6128   <!--begin-properties-->
  6130   <table class=proptable>
  6131    <thead>
  6132     <tr>
  6133      <th>Property
  6135      <th>Values
  6137      <th>Initial
  6139      <th>Applies to
  6141      <th>Inh.
  6143      <th>Percentages
  6145      <th>Media
  6147    <tbody>
  6148     <tr>
  6149      <th><a class=property href="#propdef-font">font</a>
  6151      <td>[ [ &lt;‘font-style’> || &lt;font-variant-css21> ||
  6152       &lt;‘font-weight’> || &lt;‘font-stretch’> ]?
  6153       &lt;‘font-size’> [ / &lt;‘line-height’> ]?
  6154       &lt;‘font-family’> ] | caption | icon | menu | message-box |
  6155       small-caption | status-bar
  6157      <td>see individual properties
  6159      <td>all elements
  6161      <td>yes
  6163      <td>see individual properties
  6165      <td>visual
  6167     <tr>
  6168      <th><a class=property href="#descdef-font-family">font-family</a>
  6170      <td>[ &lt;family-name> | &lt;generic-family> ]#
  6172      <td>depends on user agent
  6174      <td>all elements
  6176      <td>yes
  6178      <td>N/A
  6180      <td>visual
  6182     <tr>
  6183      <th><a class=property
  6184       href="#propdef-font-feature-settings">font-feature-settings</a>
  6186      <td>normal | &lt;feature-tag-value&gt;#
  6188      <td>normal
  6190      <td>all elements
  6192      <td>yes
  6194      <td>N/A
  6196      <td>visual
  6198     <tr>
  6199      <th><a class=property href="#propdef-font-kerning">font-kerning</a>
  6201      <td>auto | normal | none
  6203      <td>auto
  6205      <td>all elements
  6207      <td>yes
  6209      <td>N/A
  6211      <td>visual
  6213     <tr>
  6214      <th><a class=property
  6215       href="#propdef-font-language-override">font-language-override</a>
  6217      <td>normal | &lt;string&gt;
  6219      <td>normal
  6221      <td>all elements
  6223      <td>yes
  6225      <td>N/A
  6227      <td>visual
  6229     <tr>
  6230      <th><a class=property href="#propdef-font-size">font-size</a>
  6232      <td>&lt;absolute-size> | &lt;relative-size> | &lt;length> |
  6233       &lt;percentage>
  6235      <td>medium
  6237      <td>all elements
  6239      <td>yes
  6241      <td>refer to parent element's font size
  6243      <td>visual
  6245     <tr>
  6246      <th><a class=property
  6247       href="#propdef-font-size-adjust">font-size-adjust</a>
  6249      <td>none | auto | &lt;number>
  6251      <td>none
  6253      <td>all elements
  6255      <td>yes
  6257      <td>N/A
  6259      <td>visual
  6261     <tr>
  6262      <th><a class=property href="#propdef-font-stretch">font-stretch</a>
  6264      <td>normal | ultra-condensed | extra-condensed | condensed |
  6265       semi-condensed | semi-expanded | expanded | extra-expanded |
  6266       ultra-expanded
  6268      <td>normal
  6270      <td>all elements
  6272      <td>yes
  6274      <td>N/A
  6276      <td>visual
  6278     <tr>
  6279      <th><a class=property href="#propdef-font-style">font-style</a>
  6281      <td>normal | italic | oblique
  6283      <td>normal
  6285      <td>all elements
  6287      <td>yes
  6289      <td>N/A
  6291      <td>visual
  6293     <tr>
  6294      <th><a class=property href="#propdef-font-synthesis">font-synthesis</a>
  6296      <td>none | [ weight || style ]
  6298      <td>weight style
  6300      <td>all elements
  6302      <td>yes
  6304      <td>N/A
  6306      <td>visual
  6308     <tr>
  6309      <th><a class=property href="#propdef-font-variant">font-variant</a>
  6311      <td>normal | none | [ &lt;common-lig-values&gt; ||
  6312       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  6313       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  6314       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  6315       character-variant(&lt;feature-value-name&gt;#) ||
  6316       swash(&lt;feature-value-name&gt;) ||
  6317       ornaments(&lt;feature-value-name&gt;) ||
  6318       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  6319       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  6320       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  6321       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  6322       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  6323       ruby ]
  6325      <td>normal
  6327      <td>all elements
  6329      <td>yes
  6331      <td>see individual properties
  6333      <td>visual
  6335     <tr>
  6336      <th><a class=property
  6337       href="#propdef-font-variant-alternates">font-variant-alternates</a>
  6339      <td>normal | [ stylistic(&lt;feature-value-name&gt;) || historical-forms
  6340       || styleset(&lt;feature-value-name&gt;#) ||
  6341       character-variant(&lt;feature-value-name&gt;#) ||
  6342       swash(&lt;feature-value-name&gt;) ||
  6343       ornaments(&lt;feature-value-name&gt;) ||
  6344       annotation(&lt;feature-value-name&gt;) ]
  6346      <td>normal
  6348      <td>all elements
  6350      <td>yes
  6352      <td>N/A
  6354      <td>visual
  6356     <tr>
  6357      <th><a class=property
  6358       href="#propdef-font-variant-caps">font-variant-caps</a>
  6360      <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
  6361       | unicase | titling-caps
  6363      <td>normal
  6365      <td>all elements
  6367      <td>yes
  6369      <td>N/A
  6371      <td>visual
  6373     <tr>
  6374      <th><a class=property
  6375       href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
  6377      <td>normal | [ &lt;east-asian-variant-values&gt; ||
  6378       &lt;east-asian-width-values&gt; || ruby ]
  6380      <td>normal
  6382      <td>all elements
  6384      <td>yes
  6386      <td>N/A
  6388      <td>visual
  6390     <tr>
  6391      <th><a class=property
  6392       href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
  6394      <td>normal | none | [ &lt;common-lig-values> ||
  6395       &lt;discretionary-lig-values> || &lt;historical-lig-values> ||
  6396       &lt;contextual-alt-values> ]
  6398      <td>normal
  6400      <td>all elements
  6402      <td>yes
  6404      <td>N/A
  6406      <td>visual
  6408     <tr>
  6409      <th><a class=property
  6410       href="#propdef-font-variant-numeric">font-variant-numeric</a>
  6412      <td>normal | [ &lt;numeric-figure-values&gt; ||
  6413       &lt;numeric-spacing-values&gt; || &lt;numeric-fraction-values&gt; ||
  6414       ordinal || slashed-zero ]
  6416      <td>normal
  6418      <td>all elements
  6420      <td>yes
  6422      <td>N/A
  6424      <td>visual
  6426     <tr>
  6427      <th><a class=property
  6428       href="#propdef-font-variant-position">font-variant-position</a>
  6430      <td>normal | sub | super
  6432      <td>normal
  6434      <td>all elements
  6436      <td>yes
  6438      <td>N/A
  6440      <td>visual
  6442     <tr>
  6443      <th><a class=property href="#propdef-font-weight">font-weight</a>
  6445      <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
  6446       | 700 | 800 | 900
  6448      <td>normal
  6450      <td>all elements
  6452      <td>yes
  6454      <td>N/A
  6456      <td>visual
  6457   </table>
  6458   <!--end-properties-->
  6459   <!--begin-descriptors-->
  6461   <table class=proptable>
  6462    <thead>
  6463     <tr>
  6464      <th>Descriptor
  6466      <th>Value
  6468      <th>Initial
  6470      <th>Percentages
  6472      <th>Media
  6474    <tbody>
  6475     <tr>
  6476      <th><a class=property href="#descdef-font-family">font-family</a>
  6478      <td>&lt;family-name>
  6480      <td>N/A
  6482     <tr>
  6483      <th><a class=property
  6484       href="#propdef-font-feature-settings">font-feature-settings</a>
  6486      <td>normal | &lt;feature-tag-value&gt;#
  6488      <td>normal
  6490     <tr>
  6491      <th><a class=property href="#propdef-font-stretch">font-stretch</a>
  6493      <td>normal | ultra-condensed | extra-condensed | condensed |
  6494       semi-condensed | semi-expanded | expanded | extra-expanded |
  6495       ultra-expanded
  6497      <td>normal
  6499     <tr>
  6500      <th><a class=property href="#propdef-font-style">font-style</a>
  6502      <td>normal | italic | oblique
  6504      <td>normal
  6506     <tr>
  6507      <th><a class=property href="#propdef-font-variant">font-variant</a>
  6509      <td>normal | [ &lt;common-lig-values&gt; ||
  6510       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  6511       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  6512       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  6513       character-variant(&lt;feature-value-name&gt;#) ||
  6514       swash(&lt;feature-value-name&gt;) ||
  6515       ornaments(&lt;feature-value-name&gt;) ||
  6516       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  6517       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  6518       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  6519       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  6520       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  6521       ruby ]
  6523      <td>normal
  6525     <tr>
  6526      <th><a class=property href="#propdef-font-weight">font-weight</a>
  6528      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
  6530      <td>normal
  6532     <tr>
  6533      <th><a class=property href="#descdef-src">src</a>
  6535      <td>[ &lt;uri> [format(&lt;string>#)]? | &lt;font-face-name> ]#
  6537      <td>N/A
  6539     <tr>
  6540      <th><a class=property href="#descdef-unicode-range">unicode-range</a>
  6542      <td>&lt;urange>#
  6544      <td>U+0-10FFFF
  6545   </table>
  6546   <!--end-descriptors-->
  6547   <script type="text/javascript">
  6548 window.onload = function () {
  6549   if (!("devicePixelRatio" in window && window.devicePixelRatio > 1)) return;
  6550   var i, hiresElements = document.getElementsByClassName("hires");
  6551   for (i = 0; i < hiresElements.length; i++) {
  6552     var h = hiresElements[i];
  6553     if (h.tagName != "IMG") continue;
  6554     var src = h.getAttribute("src");
  6555     var src2x = src.replace(/\.\w+$/, function(m) { return "@2x" + m; });
  6556     h.src = src2x;
  6559 </script>
  6560 </html>
  6561 <!-- Keep this comment at the end of the file
  6562 Local variables:
  6563 mode: sgml
  6564 sgml-declaration:"~/SGML/HTML4.decl"
  6565 sgml-default-doctype-name:"html"
  6566 sgml-minimize-attributes:t
  6567 sgml-nofill-elements:("pre" "style" "br")
  6568 sgml-live-element-indicator:t
  6569 sgml-omittag:nil
  6570 sgml-shorttag:nil
  6571 sgml-namecase-general:t
  6572 sgml-general-insert-case:lower
  6573 sgml-always-quote-attributes:t
  6574 sgml-indent-step:nil
  6575 sgml-indent-data:t
  6576 sgml-parent-document:nil
  6577 sgml-exposed-tags:nil
  6578 sgml-local-catalogs:nil
  6579 sgml-local-ecat-files:nil
  6580 End:
  6581 -->
  6582 <!-- 
  6584 to do:
  6586 - wording of OpenType family name handling
  6587 - handling combining sequences in the font matching algorithm
  6588 - fix-up fi ligature example
  6590 -->

mercurial