css-fonts/Fonts.html

Mon, 20 May 2013 17:48:43 +0800

author
John Daggett <jdaggett@mozilla.com>
date
Mon, 20 May 2013 17:48:43 +0800
changeset 8198
d4d9fa6daec2
parent 8197
1e26e4454f98
child 8213
6fc1fa06eae3
permissions
-rw-r--r--

[css-fonts] more editorial revisions

     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-20-may-2013>Editor's Draft 20
   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-20130520/">http://www.w3.org/TR/2013/ED-css3-fonts-20130520/</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>When a face does not exist for a given width, normal or condensed values
  1179    map to a narrower face, otherwise a wider face. Conversely, expanded
  1180    values map to a wider face, otherwise a narrower face. The figure below
  1181    shows how the nine font-stretch property settings affect font selection
  1182    for font family containing a variety of widths, grey indicates a width for
  1183    which no face exists and a different width is substituted:
  1185   <div class=figure><img alt="width mappings for a family with condensed,
  1186    normal and expanded faces" src=universwidths.png>
  1187    <p class=caption>Width mappings for a font family with condensed, normal
  1188     and expanded width faces
  1189   </div>
  1191   <p id=font-stretch-animation>Animation of font stretch: Font stretch is
  1192    interpolated in discrete steps. The interpolation happens as though the
  1193    ordered values are equally spaced real numbers. The interpolation result
  1194    is rounded to the nearest value, with values exactly halfway between two
  1195    values rounded towards the later value in the list above.</p>
  1196   <!-- prop: font-style -->
  1198   <h3 id=font-style-prop><span class=secno>3.4 </span>Font style: the <a
  1199    href="#propdef-font-style">font-style</a> property</h3>
  1201   <table class=propdef id=namefont-stylevaluenormal-italic-oblique>
  1202    <tbody>
  1203     <tr>
  1204      <td>Name:
  1206      <td><dfn id=propdef-font-style>font-style</dfn>
  1208     <tr>
  1209      <td>Value:
  1211      <td>normal | italic | oblique
  1213     <tr>
  1214      <td>Initial:
  1216      <td>normal
  1218     <tr>
  1219      <td>Applies to:
  1221      <td>all elements
  1223     <tr>
  1224      <td>Inherited:
  1226      <td>yes
  1228     <tr>
  1229      <td>Percentages:
  1231      <td>N/A
  1233     <tr>
  1234      <td>Media:
  1236      <td>visual
  1238     <tr>
  1239      <td>Computed value:
  1241      <td>as specified
  1243     <tr>
  1244      <td>Animatable:
  1246      <td>no
  1247   </table>
  1249   <p>The <a class=noxref href="#font-style-prop"><span
  1250    class=property>‘<code class=property>font-style</code>’</span></a>
  1251    property allows italic or oblique faces to be selected. Italic forms are
  1252    generally cursive in nature while oblique faces are typically sloped
  1253    versions of the regular face. Oblique faces can be simulated by
  1254    artificially sloping the glyphs of the regular face. Compare the
  1255    artificially sloped renderings of Palatino ‘<code
  1256    class=property>a</code>’ and Baskerville ‘<code
  1257    class=property>N</code>’ in grey with the actual italic versions:
  1259   <div class=figure><img alt="artificial sloping vs. real italics"
  1260    src=realvsfakeitalics.png>
  1261    <p class=caption>Artificial sloping versus real italics
  1262   </div>
  1264   <p>A value of ‘<a href="#normal2"><code
  1265    class=property>normal</code></a>’ selects a face that is classified as
  1266    ‘<a href="#normal2"><code class=property>normal</code></a>’, while
  1267    ‘<code class=property>oblique</code>’ selects a font that is labeled
  1268    ‘<code class=property>oblique</code>’. A value of ‘<code
  1269    class=property>italic</code>’ selects a font that is labeled ‘<code
  1270    class=property>italic</code>’, or, if that is not available, one labeled
  1271    ‘<code class=property>oblique</code>’. If no italic or oblique face is
  1272    available, oblique faces can be synthesized by rendering non-obliqued
  1273    faces with a right sloping transformation applied. When synthesizing these
  1274    faces, the transformation should apply to all glyphs in the same way and
  1275    not vary based on codepoint or due to horizontal or vertical line
  1276    orientation.
  1278   <p>Many scripts lack the tradition of mixing a cursive form within text
  1279    rendered with a normal face. Chinese, Japanese and Korean fonts almost
  1280    always lack italic or oblique faces. Fonts that support a mixture of
  1281    scripts will sometimes omit specific scripts such as Arabic from the set
  1282    of glyphs supported in the italic face. User agents should be careful
  1283    about making character map assumptions across faces.
  1285   <p class=issue>For synthetic italics in vertical runs of Chinese, Japanese,
  1286    or Korean text, is there a need to define explicitly the direction of the
  1287    faux oblique for runs that include a mixture of ideographic and Latin
  1288    text?</p>
  1289   <!-- prop: font-size -->
  1291   <h3 id=font-size-prop><span class=secno>3.5 </span>Font size: the <a
  1292    href="#propdef-font-size">font-size</a> property</h3>
  1294   <table class=propdef id=namefont-sizevalueltabsolute-size-ltrela>
  1295    <tbody>
  1296     <tr>
  1297      <td>Name:
  1299      <td><dfn id=propdef-font-size>font-size</dfn>
  1301     <tr>
  1302      <td>Value:
  1304      <td>&lt;absolute-size> | &lt;relative-size> | &lt;length> |
  1305       &lt;percentage>
  1307     <tr>
  1308      <td>Initial:
  1310      <td>medium
  1312     <tr>
  1313      <td>Applies to:
  1315      <td>all elements
  1317     <tr>
  1318      <td>Inherited:
  1320      <td>yes
  1322     <tr>
  1323      <td>Percentages:
  1325      <td>refer to parent element's font size
  1327     <tr>
  1328      <td>Media:
  1330      <td>visual
  1332     <tr>
  1333      <td>Computed value:
  1335      <td>absolute length
  1337     <tr>
  1338      <td>Animatable:
  1340      <td>as <a
  1341       href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
  1342   </table>
  1344   <p>This property indicates the desired height of glyphs from the font. For
  1345    scalable fonts, the font-size is a scale factor applied to the EM unit of
  1346    the font. (Note that certain glyphs may bleed outside their EM box.) For
  1347    non-scalable fonts, the font-size is converted into absolute units and
  1348    matched against the declared font-size of the font, using the same
  1349    absolute coordinate space for both of the matched values. Values have the
  1350    following meanings:
  1352   <dl>
  1353    <dt><a name=x18><span class=index-def id=ltabsolute-sizegt
  1354     title="&lt;absolute-size&gt;">
  1355     <strong>&lt;absolute-size&gt;</strong></span></a>
  1357    <dd> An <a class=value-def
  1358     name=value-def-absolute-size>&lt;absolute-size&gt;</a> keyword refers to
  1359     an entry in a table of font sizes computed and kept by the user agent.
  1360     Possible values are:
  1361     <p> [ xx-small | x-small | small | medium | large | x-large | xx-large ]</p>
  1363    <dt><a name=x19><span class=index-def id=ltrelative-sizegt
  1364     title="&lt;relative-size&gt;">
  1365     <strong>&lt;relative-size&gt;</strong></span></a>
  1367    <dd> A <a class=value-def
  1368     name=value-def-relative-size>&lt;relative-size&gt;</a> keyword is
  1369     interpreted relative to the table of font sizes and the computed ‘<a
  1370     href="#propdef-font-size"><code class=property>font-size</code></a>’ of
  1371     the parent element. Possible values are:
  1372     <p> [ larger | smaller ]
  1374     <p> For example, if the parent element has a font size of ‘<code
  1375      class=property>medium</code>’, a value of ‘<code
  1376      class=property>larger</code>’ will make the font size of the current
  1377      element be ‘<code class=property>large</code>’. If the parent
  1378      element's size is not close to a table entry, the user agent is free to
  1379      interpolate between table entries or round off to the closest one. The
  1380      user agent may have to extrapolate table values if the numerical value
  1381      goes beyond the keywords.
  1383    <dt><span class=index-inst id=ltlengthgt
  1384     title="&lt;length&gt;">&lt;length&gt;</span>
  1386    <dd>A length value specifies an absolute font size (independent of the
  1387     user agent's font table). Negative lengths are illegal.
  1389    <dt><span class=index-inst id=ltpercentagegt-
  1390     title="&lt;percentage&gt;">&lt;percentage&gt; </span>
  1392    <dd>A percentage value specifies an absolute font size relative to the
  1393     parent element's font size. Use of percentage values, or values in
  1394     ‘<code class=property>em</code>’s, leads to more robust and
  1395     cascadable style sheets.
  1396   </dl>
  1398   <p>The following table provides user agent guidelines for the absolute-size
  1399    scaling factor and their mapping to HTML heading and absolute font-sizes.
  1400    The ‘<code class=property>medium</code>’ value is used as the
  1401    reference middle value. The user agent may fine-tune these values for
  1402    different fonts or different types of display devices.
  1404   <table class=data>
  1405    <thead>
  1406     <tr>
  1407      <th>CSS absolute-size values
  1409      <th>xx-small
  1411      <th>x-small
  1413      <th>small
  1415      <th>medium
  1417      <th>large
  1419      <th>x-large
  1421      <th>xx-large
  1423      <th> 
  1425    <tbody>
  1426     <tr>
  1427      <th>scaling factor
  1429      <td>3/5
  1431      <td>3/4
  1433      <td>8/9
  1435      <td>1
  1437      <td>6/5
  1439      <td>3/2
  1441      <td>2/1
  1443      <td>3/1
  1445     <tr>
  1446      <th>HTML headings
  1448      <td>h6
  1450      <td> 
  1452      <td>h5
  1454      <td>h4
  1456      <td>h3
  1458      <td>h2
  1460      <td>h1
  1462      <td> 
  1464     <tr>
  1465      <th>HTML font sizes
  1467      <td>1
  1469      <td> 
  1471      <td>2
  1473      <td>3
  1475      <td>4
  1477      <td>5
  1479      <td>6
  1481      <td>7
  1482   </table>
  1484   <p class=note><em><strong>Note 1.</strong> To preserve readability, an UA
  1485    applying these guidelines should nevertheless avoid creating font-size
  1486    resulting in less than 9 device pixels per EM unit on a computer display
  1487    .</em>
  1489   <p class=note><em><strong>Note 2.</strong> In CSS1, the suggested scaling
  1490    factor between adjacent indexes was 1.5 which user experience proved to be
  1491    too large. In CSS2, the suggested scaling factor for computer screen
  1492    between adjacent indexes was 1.2 which still created issues for the small
  1493    sizes. The new scaling factor varies between each index to provide a
  1494    better readability.</em>
  1496   <p>The actual value of this property may differ from the computed value due
  1497    a numerical value on ‘<a href="#propdef-font-size-adjust"><code
  1498    class=property>font-size-adjust</code></a>’ and the unavailability of
  1499    certain font sizes.
  1501   <p>Child elements inherit the computed <a class=noxref
  1502    href="#font-size-prop"> <span class=property>‘<code
  1503    class=property>font-size</code>’</span></a> value (otherwise, the effect
  1504    of <a class=noxref href="#font-size-adjust-prop"><span
  1505    class=property>‘<code
  1506    class=property>font-size-adjust</code>’</span></a> would compound).
  1508   <div class=example>
  1509    <p style="display:none">Example(s):
  1511    <p>
  1513    <pre>p { font-size: 12pt; }
  1514 blockquote { font-size: larger }
  1515 em { font-size: 150% }
  1516 em { font-size: 1.5em }
  1517 </pre>
  1518   </div>
  1519   <!-- prop: font-size-adjust -->
  1521   <h3 id=font-size-adjust-prop><span class=secno>3.6 </span>Relative sizing:
  1522    the <a href="#propdef-font-size-adjust">font-size-adjust</a> property</h3>
  1524   <table class=propdef id=namefont-size-adjustvaluenone-auto-ltnum>
  1525    <tbody>
  1526     <tr>
  1527      <td>Name:
  1529      <td><dfn id=propdef-font-size-adjust>font-size-adjust</dfn>
  1531     <tr>
  1532      <td>Value:
  1534      <td>none | auto | &lt;number>
  1536     <tr>
  1537      <td>Initial:
  1539      <td>none
  1541     <tr>
  1542      <td>Applies to:
  1544      <td>all elements
  1546     <tr>
  1547      <td>Inherited:
  1549      <td>yes
  1551     <tr>
  1552      <td>Percentages:
  1554      <td>N/A
  1556     <tr>
  1557      <td>Media:
  1559      <td>visual
  1561     <tr>
  1562      <td>Computed value:
  1564      <td>as specified
  1566     <tr>
  1567      <td>Animatable:
  1569      <td>as <a
  1570       href="http://dev.w3.org/csswg/css3-transitions/#animtype-number">number</a>
  1571   </table>
  1573   <p>For any given font size, the apparent size and legibility of text varies
  1574    across fonts. For scripts such as Latin or Cyrillic that distinguish
  1575    between upper and lowercase letters, the relative height of lowercase
  1576    letters compared to their uppercase counterparts is a determining factor
  1577    of legibility. This is commonly referred to as the <a class=index-def
  1578    href="#aspect-value" id=aspect-value0 title="aspect value"><dfn
  1579    id=aspect-value>aspect value</dfn></a>. Precisely defined, it is equal to
  1580    the x-height of a font divided by the font size.
  1582   <p>In situations where font fallback occurs, fallback fonts may not share
  1583    the same aspect ratio as the desired font family and will thus appear less
  1584    readable. The font-size-adjust property is a way to preserve the
  1585    readability of text when font fallback occurs. It does this by adjusting
  1586    the font-size so that the x-height is the same regardless of the font
  1587    used.
  1589   <div class=example>
  1590    <p>The style defined below defines Verdana as the desired font family, but
  1591     if Verdana is not available Futura or Times will be used.</p>
  1593    <pre>p { 
  1594     font-family: Verdana, Futura, Times; 
  1597 &lt;p>Lorem ipsum dolor sit amet, ...&lt;/p>
  1598 </pre>
  1600    <p>Verdana has a relatively high aspect ratio, lowercase letters are
  1601     relatively tall compared to uppercase letters, so at small sizes text
  1602     appears legible. Times has a lower aspect ratio and so if fallback
  1603     occurs, the text will be less legible at small sizes than Verdana.</p>
  1604   </div>
  1606   <p>How text rendered in each of these fonts compares is shown below, the
  1607    columns show text rendered in Verdana, Futura and Times. The same
  1608    font-size value is used across cells within each row and red lines are
  1609    included to show the differences in x-height. In the upper half each row
  1610    is rendered in the same font-size value. The same is true for the lower
  1611    half but in this half the font-size-adjust property is also set so that
  1612    the actual font size is adjusted to preserve the x-height across each row.
  1613    Note how small text remains relatively legible across each row in the
  1614    lower half.
  1616   <div class=figure><img alt="text with and without font-size-adjust"
  1617    src=fontsizeadjust.png>
  1618    <p class=caption>Text with and without the use of font-size-adjust
  1619   </div>
  1621   <p>This property allows authors to specify an aspect value for an element
  1622    that will effectively preserve the x-height of the first choice font,
  1623    whether it is substituted or not. Values have the following meanings:
  1625   <dl>
  1626    <dt><strong>none</strong>
  1628    <dd>Do not preserve the font's x-height.
  1630    <dt><strong>auto</strong>
  1632    <dd>Behaves just like &lt;number>, except the number used is the aspect
  1633     value calculated by user agents for the first font in the list of fonts
  1634     defined for the initial value of the ‘<a
  1635     href="#descdef-font-family"><code
  1636     class=property>font-family</code></a>’ property. Effectively this is
  1637     the default font used when ‘<a href="#descdef-font-family"><code
  1638     class=property>font-family</code></a>’ is not otherwise specified.
  1639     <p>Authors can use this value to specify that font size should be
  1640      normalized across fonts based on the x-height without the need to
  1641      specify the aspect ratio explicitly.</p>
  1643    <dt><span class=index-inst id=ltnumbergt
  1644     title="&lt;number&gt;">&lt;number&gt;</span>
  1646    <dd>Specifies the aspect value used in the calculation below to calculate
  1647     the adjusted font size:
  1648     <pre>c  =  ( a / a' ) s 
  1649 </pre>
  1651     <p>where:</p>
  1653     <pre>s  =  font-size value
  1654 a  =  aspect value as specified by the font-size-adjust property
  1655 a' =  aspect value of actual font
  1656 c  =  adjusted font-size to use
  1657 </pre>
  1659     <p>This value applies to any font that is selected but in typical usage
  1660      it should be based on the aspect value of the first font in the
  1661      font-family list. If this is specified accurately, the <tt>(a/a')</tt>
  1662      term in the formula above is effectively 1 for the first font and no
  1663      adjustment occurs. If the value is specified inaccurately, text rendered
  1664      using the first font in the family list will display differently in
  1665      older user agents that don't support font-size-adjust.</p>
  1666   </dl>
  1668   <p>Authors can calculate the aspect value for a given font by comparing
  1669    spans with the same content but different font-size-adjust properties. If
  1670    the same font-size is used, the spans will match when the font-size-adjust
  1671    value is accurate for the given font.
  1673   <div class=example>
  1674    <p>Two spans with borders are used to determine the aspect value of a
  1675     font. The font-size is the same for both spans but the font-size-adjust
  1676     property is specified only for the right span. Starting with a value of
  1677     0.5, the aspect value can be adjusted until the borders around the two
  1678     letters line up.</p>
  1680    <pre>p {
  1681     font-family: Futura;
  1682     font-size: 500px;
  1685 span {
  1686     border: solid 1px red;
  1689 .adjust {
  1690     font-size-adjust: 0.5;
  1693 &lt;p>&lt;span>b&lt;/span>&lt;span class="adjust">b&lt;/span>&lt;/p>
  1694 </pre>
  1696    <div class=figure><img alt="Futura with an aspect value of 0.5"
  1697     src=beforefontsizeadjust.png>
  1698     <p class=caption>Futura with an aspect value of 0.5
  1699    </div>
  1701    <p>The box on the right is a bit bigger than the one on the left, so the
  1702     aspect value of this font is something less than 0.5. Adjust the value
  1703     until the boxes align.</p>
  1704   </div>
  1705   <!-- prop: font -->
  1706   <!-- jtdfix, crap, preprocessor is inserting links to descriptors rather than properties.  bert, make it stop... -->
  1707   <!-- <a href="#font-stretch-prop" class="noxref"><span class="property">'font-stretch'</span></a> -->
  1709   <h3 id=font-prop><span class=secno>3.7 </span>Shorthand font property: the
  1710    <a href="#propdef-font">font</a> property</h3>
  1712   <table class=propdef id=namefontvalue-ltlsquofont-stylersquo-ltf>
  1713    <tbody>
  1714     <tr>
  1715      <td>Name:
  1717      <td><dfn id=propdef-font>font</dfn>
  1719     <tr>
  1720      <td>Value:
  1722      <td>[ [ &lt;‘<a href="#propdef-font-style"><code
  1723       class=property>font-style</code></a>’> || &lt;font-variant-css21> ||
  1724       &lt;‘<a href="#propdef-font-weight"><code
  1725       class=property>font-weight</code></a>’> || &lt;‘<a
  1726       href="#propdef-font-stretch"><code
  1727       class=property>font-stretch</code></a>’> ]? &lt;‘<a
  1728       href="#propdef-font-size"><code class=property>font-size</code></a>’>
  1729       [ / &lt;‘<code class=property>line-height</code>’> ]? &lt;‘<a
  1730       href="#descdef-font-family"><code
  1731       class=property>font-family</code></a>’> ] | caption | icon | menu |
  1732       message-box | small-caption | status-bar
  1734     <tr>
  1735      <td>Initial:
  1737      <td>see individual properties
  1739     <tr>
  1740      <td>Applies to:
  1742      <td>all elements
  1744     <tr>
  1745      <td>Inherited:
  1747      <td>yes
  1749     <tr>
  1750      <td>Percentages:
  1752      <td>see individual properties
  1754     <tr>
  1755      <td>Media:
  1757      <td>visual
  1759     <tr>
  1760      <td>Computed value:
  1762      <td>see individual properties
  1764     <tr>
  1765      <td>Animatable:
  1767      <td>see individual properties
  1768   </table>
  1770   <p>The <span class=property>‘<a href="#propdef-font"><code
  1771    class=property>font</code></a>’</span> property is, except as described
  1772    below, a shorthand property for setting ‘<a
  1773    href="#propdef-font-style"><code class=property>font-style</code></a>’,
  1774    <span class=property>‘<a href="#propdef-font-variant"><code
  1775    class=property>font-variant</code></a>’</span>, <span
  1776    class=property>‘<a href="#propdef-font-weight"><code
  1777    class=property>font-weight</code></a>’</span>, <span
  1778    class=property>‘<a href="#propdef-font-stretch"><code
  1779    class=property>font-stretch</code></a>’</span>, <span
  1780    class=property>‘<a href="#propdef-font-size"><code
  1781    class=property>font-size</code></a>’</span>, ‘<code
  1782    class=property>line-height</code>’, <span class=property>‘<a
  1783    href="#descdef-font-family"><code
  1784    class=property>font-family</code></a>’</span> at the same place in the
  1785    stylesheet. Values for the <span class=property>‘<a
  1786    href="#propdef-font-variant"><code
  1787    class=property>font-variant</code></a>’</span> property may also be
  1788    included but only those supported in CSS 2.1, none of the font-variant
  1789    values added in this specification can be used in the <span
  1790    class=property>‘<a href="#propdef-font"><code
  1791    class=property>font</code></a>’</span> shorthand:
  1793   <pre
  1794    class=prod><dfn id=ltfont-variant-css21gt><var>&lt;font-variant-css21&gt;</var></dfn> = [normal | small-caps]</pre>
  1796   <p>The syntax of this property is based on a traditional typographical
  1797    shorthand notation to set multiple properties related to fonts.
  1799   <p>All subproperties of the ‘<a href="#propdef-font"><code
  1800    class=property>font</code></a>’ property are first reset to their
  1801    initial values, including those listed above plus <span
  1802    class=property>‘<a href="#propdef-font-size-adjust"><code
  1803    class=property>font-size-adjust</code></a>’</span>, <span
  1804    class=property>‘<a href="#propdef-font-kerning"><code
  1805    class=property>font-kerning</code></a>’</span>, subproperties of <span
  1806    class=property>‘<a href="#propdef-font-variant"><code
  1807    class=property>font-variant</code></a>’</span> and and <span
  1808    class=property>‘<a href="#propdef-font-language-override"><code
  1809    class=property>font-language-override</code></a>’</span>. Then, those
  1810    properties that are given explicit values in the <span
  1811    class=property>‘<a href="#propdef-font"><code
  1812    class=property>font</code></a>’</span> shorthand are set to those
  1813    values. For a definition of allowed and initial values, see the previously
  1814    defined properties. For reasons of backwards compatibility, it is not
  1815    possible to set <span class=property>‘<a
  1816    href="#propdef-font-size-adjust"><code
  1817    class=property>font-size-adjust</code></a>’</span> to anything other
  1818    than its initial value using the <span class=property>‘<a
  1819    href="#propdef-font"><code class=property>font</code></a>’</span>
  1820    shorthand property; instead, use the individual property.
  1822   <div class=example>
  1823    <p style="display:none">Example(s):
  1825    <p>
  1827    <pre>p { font: 12pt/14pt sans-serif }
  1828 p { font: 80% sans-serif }
  1829 p { font: x-large/110% &quot;new century schoolbook&quot;, serif }
  1830 p { font: bold italic large Palatino, serif }
  1831 p { font: normal small-caps 120%/120% fantasy }
  1832 p { font: condensed oblique 12pt &quot;Helvetica Neue&quot;, serif; }
  1833 </pre>
  1835    <p> In the second rule, the font size percentage value (‘<code
  1836     class=css>80%</code>’) refers to the computed ‘<a
  1837     href="#propdef-font-size"><code class=property>font-size</code></a>’ of
  1838     the parent element. In the third rule, the line height percentage
  1839     (‘<code class=css>110%</code>’) refers to the font size of the
  1840     element itself.
  1842    <p>The first three rules do not specify the <span class=property>‘<a
  1843     href="#propdef-font-variant"><code
  1844     class=property>font-variant</code></a>’</span> and <span
  1845     class=property>‘<a href="#propdef-font-weight"><code
  1846     class=property>font-weight</code></a>’</span> explicitly, so these
  1847     properties receive their initial values (‘<a href="#normal2"><code
  1848     class=property>normal</code></a>’). Notice that the font family name
  1849     "new century schoolbook", which contains spaces, is enclosed in quotes.
  1850     The fourth rule sets the <span class=property>‘<a
  1851     href="#propdef-font-weight"><code
  1852     class=property>font-weight</code></a>’</span> to ‘<code
  1853     class=property>bold</code>’, the <span class=property>‘<a
  1854     href="#propdef-font-style"><code
  1855     class=property>font-style</code></a>’</span> to ‘<code
  1856     class=property>italic</code>’, and implicitly sets <span
  1857     class=property>‘<a href="#propdef-font-variant"><code
  1858     class=property>font-variant</code></a>’</span> to ‘<a
  1859     href="#normal2"><code class=property>normal</code></a>’.
  1861    <p> The fifth rule sets the <span class=property>‘<a
  1862     href="#propdef-font-variant"><code
  1863     class=property>font-variant</code></a>’</span> (‘<a
  1864     href="#small-caps"><code class=property>small-caps</code></a>’), the
  1865     <span class=property>‘<a href="#propdef-font-size"><code
  1866     class=property>font-size</code></a>’</span> (120% of the parent's font
  1867     size), the <span class=property>‘<code
  1868     class=property>line-height</code>’</span> (120% of the font size) and
  1869     the <span class=property>‘<a href="#descdef-font-family"><code
  1870     class=property>font-family</code></a>’</span> (‘<a
  1871     href="#fantasy"><code class=property>fantasy</code></a>’). It follows
  1872     that the keyword ‘<a href="#normal2"><code
  1873     class=property>normal</code></a>’ applies to the two remaining
  1874     properties: <span class=property>‘<a href="#propdef-font-style"><code
  1875     class=property>font-style</code></a>’</span> and <span
  1876     class=property>‘<a href="#propdef-font-weight"><code
  1877     class=property>font-weight</code></a>’</span>.
  1879    <p>The sixth rule sets the <span class=property>‘<a
  1880     href="#propdef-font-style"><code
  1881     class=property>font-style</code></a>’</span>, <span
  1882     class=property>‘<a href="#propdef-font-stretch"><code
  1883     class=property>font-stretch</code></a>’</span>, <span
  1884     class=property>‘<a href="#propdef-font-size"><code
  1885     class=property>font-size</code></a>’</span>, and <span
  1886     class=property>‘<a href="#descdef-font-family"><code
  1887     class=property>font-family</code></a>’</span>, the other font
  1888     properties being set to their initial values.
  1889   </div>
  1891   <p>Since the ‘<a href="#propdef-font-stretch"><code
  1892    class=property>font-stretch</code></a>’ property was not defined in CSS
  1893    2.1, when using ‘<a href="#propdef-font-stretch"><code
  1894    class=property>font-stretch</code></a>’ values within ‘<a
  1895    href="#propdef-font"><code class=property>font</code></a>’ rules,
  1896    authors should include a extra version compatible with older user agents:
  1898   <pre>p {
  1899   font: 80% sans-serif;   /* for older user agents */
  1900   font: condensed 80% sans-serif;
  1901 }</pre>
  1903   <p>The following values refer to system fonts:
  1905   <dl>
  1906    <dt><strong>caption</strong>
  1908    <dd>The font used for captioned controls (e.g., buttons, drop-downs,
  1909     etc.).
  1911    <dt><strong>icon</strong>
  1913    <dd>The font used to label icons.
  1915    <dt><strong>menu</strong>
  1917    <dd>The font used in menus (e.g., dropdown menus and menu lists).
  1919    <dt><strong>message-box</strong>
  1921    <dd>The font used in dialog boxes.
  1923    <dt><strong>small-caption</strong>
  1925    <dd>The font used for labeling small controls.
  1927    <dt><strong>status-bar</strong>
  1929    <dd>The font used in window status bars.
  1930   </dl>
  1932   <p>System fonts may only be set as a whole; that is, the font family, size,
  1933    weight, style, etc. are all set at the same time. These values may then be
  1934    altered individually if desired. If no font with the indicated
  1935    characteristics exists on a given platform, the user agent should either
  1936    intelligently substitute (e.g., a smaller version of the ‘<code
  1937    class=property>caption</code>’ font might be used for the ‘<code
  1938    class=property>small-caption</code>’ font), or substitute a user agent
  1939    default font. As for regular fonts, if, for a system font, any of the
  1940    individual properties are not part of the operating system's available
  1941    user preferences, those properties should be set to their initial values.
  1943   <p>That is why this property is "almost" a shorthand property: system fonts
  1944    can only be specified with this property, not with <span
  1945    class=property>‘<a href="#descdef-font-family"><code
  1946    class=property>font-family</code></a>’</span> itself, so <span
  1947    class=property>‘<a href="#propdef-font"><code
  1948    class=property>font</code></a>’</span> allows authors to do more than
  1949    the sum of its subproperties. However, the individual properties such as
  1950    <span class=property>‘<a href="#propdef-font-weight"><code
  1951    class=property>font-weight</code></a>’</span> are still given values
  1952    taken from the system font, which can be independently varied.
  1954   <p>Note that the keywords used for the system fonts listed above are only
  1955    treated as keywords when they occur in the initial position, in other
  1956    positions the same string is treated as part of the font family name:
  1958   <pre>  font: menu;        /* use the font settings for system menus */
  1959   font: large menu;  /* use a font family named "menu" */</pre>
  1961   <div class=example>
  1962    <p style="display:none">Example(s):
  1964    <p>
  1966    <pre>button { font: 300 italic 1.3em/1.7em &quot;FB Armada&quot;, sans-serif }
  1967 button p { font: menu }
  1968 button p em { font-weight: bolder }
  1969 </pre>
  1971    <p>If the font used for dropdown menus on a particular system happened to
  1972     be, for example, 9-point Charcoal, with a weight of 600, then P elements
  1973     that were descendants of BUTTON would be displayed as if this rule were
  1974     in effect:
  1976    <pre>button p { font: 600 9pt Charcoal }
  1977 </pre>
  1979    <p>Because the <span class=property>‘<a href="#propdef-font"><code
  1980     class=property>font</code></a>’</span> shorthand resets to its initial
  1981     value any property not explicitly given a value, this has the same effect
  1982     as this declaration:
  1984    <pre>button p {
  1985   font-style: normal;
  1986   font-variant: normal;
  1987   font-weight: 600;
  1988   font-size: 9pt;
  1989   line-height: normal;
  1990   font-family: Charcoal
  1992 </pre>
  1993   </div>
  1994   <!-- prop: font-synthesis -->
  1996   <h3 id=font-synthesis-prop><span class=secno>3.8 </span>Controlling
  1997    synthetic faces: the <a href="#propdef-font-synthesis">font-synthesis</a>
  1998    property</h3>
  2000   <table class=propdef id=namefont-synthesisvaluenone-weight-style>
  2001    <tbody>
  2002     <tr>
  2003      <td>Name:
  2005      <td><dfn id=propdef-font-synthesis>font-synthesis</dfn>
  2007     <tr>
  2008      <td>Value:
  2010      <td>none | [ weight || style ]
  2012     <tr>
  2013      <td>Initial:
  2015      <td>weight style
  2017     <tr>
  2018      <td>Applies to:
  2020      <td>all elements
  2022     <tr>
  2023      <td>Inherited:
  2025      <td>yes
  2027     <tr>
  2028      <td>Percentages:
  2030      <td>N/A
  2032     <tr>
  2033      <td>Media:
  2035      <td>visual
  2037     <tr>
  2038      <td>Computed value:
  2040      <td>as specified
  2042     <tr>
  2043      <td>Animatable:
  2045      <td>no
  2046   </table>
  2048   <p>This property controls whether user agents are allowed to synthesize
  2049    bold or oblique font faces when a font family lacks bold or italic faces.
  2050    If ‘<a href="#weight"><code class=property>weight</code></a>’ is not
  2051    specified, user agents must not synthesize bold faces and if ‘<code
  2052    class=property>style</code>’ is not specified user agents must not
  2053    synthesize italic faces. A value of ‘<code class=property>none</code>’
  2054    disallows all synthetic faces.
  2056   <div class=example>
  2057    <p>The style rule below disables the use of synthetically obliqued Arabic:</p>
  2059    <pre>*:lang(ar) { font-synthesis: none; }
  2060 </pre>
  2061   </div>
  2063   <h2 id=font-resources><span class=secno>4 </span>Font Resources</h2>
  2065   <h3 id=font-face-rule><span class=secno>4.1 </span>The
  2066    <code>@font-face</code> rule</h3>
  2068   <p>The <code>@font-face</code> rule allows for linking to fonts that are
  2069    automatically fetched and activated when needed. This allows authors to
  2070    select a font that closely matches the design goals for a given page
  2071    rather than limiting the font choice to a set of fonts available on all
  2072    platforms. A set of font descriptors define the location of a font
  2073    resource, either locally or externally, along with the style
  2074    characteristics of an individual face. Multiple <code>@font-face</code>
  2075    rules can be used to construct font families with a variety of faces.
  2076    Using CSS font matching rules, a user agent can selectively download only
  2077    those faces that are needed for a given piece of text.
  2079   <p>The @font-face rule consists of the @font-face at-keyword followed by a
  2080    block of descriptor declarations. In terms of the grammar, this
  2081    specification defines the following productions:
  2083   <pre><dfn id=fontfacerule>font_face_rule</dfn>
  2084   : FONT_FACE_SYM S* '{' S* descriptor_declaration? [ ';' S* descriptor_declaration? ]* '}' S*
  2087 <dfn id=descriptordeclaration>descriptor_declaration</dfn>
  2088   : property ':' S* expr
  2089   ;</pre>
  2091   <p>The following new definitions are introduced:
  2093   <pre>-    -|\\0{0,4}2d(\r\n|[ \t\r\n\f])?
  2094 F    f|\\0{0,4}(46|66)(\r\n|[ \t\r\n\f])?</pre>
  2096   <p>The following new token is introduced:
  2098   <pre>@{F}{O}{N}{T}{-}{F}{A}{C}{E} {return FONT_FACE_SYM;}</pre>
  2100   <p>Each <span class=index-inst id=font-face
  2101    title="@font-face"><code>@font-face</code></span> rule specifies a value
  2102    for every font descriptor, either implicitly or explicitly. Those not
  2103    given explicit values in the rule take the initial value listed with each
  2104    descriptor in this specification. These descriptors apply solely within
  2105    the context of the <code>@font-face</code> rule in which they are defined,
  2106    and do not apply to document language elements. There is no notion of
  2107    which elements the descriptors apply to or whether the values are
  2108    inherited by child elements. When a given descriptor occurs multiple times
  2109    in a given <code>@font-face</code> rule, only the last descriptor
  2110    declaration is used and all prior declarations for that descriptor are
  2111    ignored.
  2113   <div class=example>
  2114    <p>To use a downloadable font called Gentium:</p>
  2116    <pre>
  2117 @font-face {
  2118   font-family: Gentium;
  2119   src: url(http://example.com/fonts/Gentium.ttf);
  2122 p { font-family: Gentium, serif; }
  2123 </pre>
  2125    <p>The user agent will download Gentium and use it when rendering text
  2126     within paragraph elements. If for some reason the site serving the font
  2127     is unavailable, the default serif font will be used.</p>
  2128   </div>
  2130   <p>A given set of <code>@font-face</code> rules define a set of fonts
  2131    available for use within the documents that contain these rules. When font
  2132    matching is done, fonts defined using these rules are considered before
  2133    other available fonts on a system.
  2135   <p>Downloaded fonts are only available to documents that reference them.
  2136    The process of activating these fonts must not make them available to
  2137    other applications or to documents that don't directly link to the same
  2138    font. User agent implementers might consider it convenient to use
  2139    downloaded fonts when rendering characters in other documents for which no
  2140    other available font exists as part of the system font fallback procedure.
  2141    However, this would cause a security leak since the contents of one page
  2142    would be able to affect other pages, something an attacker could use as an
  2143    attack vector. These restrictions do not affect caching behavior, fonts
  2144    are cached the same way other web resources are cached.
  2146   <p>This at-rule follows the forward-compatible parsing rules of CSS. Like
  2147    properties in a declaration block, declarations of any descriptors that
  2148    are not supported by the user agent must be ignored.
  2149    <code>@font-face</code> rules require a font-family and src descriptor; if
  2150    either of these are missing, the <code>@font-face</code> rule is invalid
  2151    and must be ignored entirely.
  2153   <p>In cases where user agents have limited platform resources or implement
  2154    the ability to disable downloadable font resources,
  2155    <code>@font-face</code> rules must simply be ignored; the behavior of
  2156    individual descriptors as defined in this specification should not be
  2157    altered.
  2159   <h3 id=font-family-desc><span class=secno>4.2 </span>Font family: the <a
  2160    href="#descdef-font-family">font-family</a> descriptor</h3>
  2162   <table class=descdef>
  2163    <tbody>
  2164     <tr>
  2165      <td>Name:
  2167      <td><dfn id=descdef-font-family>font-family</dfn>
  2169     <tr>
  2170      <td>Value:
  2172      <td>&lt;family-name>
  2174     <tr>
  2175      <td><em>Initial:</em>
  2177      <td>N/A
  2178   </table>
  2180   <p>This descriptor defines the font family name that will be used in all
  2181    CSS font family name matching. It is required for the @font-face rule to
  2182    be valid. It overrides the font family names contained in the underlying
  2183    font data. If the font family name is the same as a font family available
  2184    in a given user's environment, it effectively hides the underlying font
  2185    for documents that use the stylesheet. This permits a web author to freely
  2186    choose font-family names without worrying about conflicts with font family
  2187    names present in a given user's environment. Likewise, platform
  2188    substitutions for a given font family name must not be used.
  2190   <h3 id=src-desc><span class=secno>4.3 </span>Font reference: the <a
  2191    href="#descdef-src">src</a> descriptor</h3>
  2193   <table class=descdef>
  2194    <tbody>
  2195     <tr>
  2196      <td>Name:
  2198      <td><dfn id=descdef-src>src</dfn>
  2200     <tr>
  2201      <td>Value:
  2203      <td>[ &lt;url> [format(&lt;string>#)]? | &lt;font-face-name> ]#
  2205     <tr>
  2206      <td><em>Initial:</em>
  2208      <td>N/A
  2209   </table>
  2211   <p>This descriptor specifies the resource containing font data. It is
  2212    required for the <code>@font-face</code> rule to be valid. Its value is a
  2213    prioritized, comma-separated list of external references or locally
  2214    installed font face names. When a font is needed the user agent iterates
  2215    over the set of references listed, using the first one it can successfully
  2216    activate. Fonts containing invalid data or local font faces that are not
  2217    found are ignored and the user agent loads the next font in the list.
  2219   <p>As with other URLs in CSS, the URL 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 URL, followed by an optional hint
  2240    describing the format of the font resource referenced by that URL. 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, <code>local()</code> can be used. The
  2317    locally-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> argument
  2320    is a format-specific string that uniquely identifies a single font face
  2321    within a larger family. The syntax for a &lt;font-face-name&gt; is a
  2322    unique font 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. Platform substitutions for a
  2338    given font name must not be used.
  2340   <pre>
  2341 /* bold face of Gentium */
  2342 @font-face {
  2343   font-family: MyGentium;
  2344   src: local(Gentium Bold),   /* full font name */
  2345        local(Gentium-Bold),   /* Postscript name */
  2346        url(GentiumBold.ttf);  /* otherwise, download it */
  2347   font-weight: bold;
  2349 </pre>
  2351   <p>Just as a <code>@font-face</code> rule specifies the characteristics of
  2352    a single font within a family, the unique name used with
  2353    <code>local()</code> specifies a single font, not an entire font family.
  2354    Defined in terms of OpenType font data, the Postscript name is found in
  2355    the font's <a
  2356    href="http://www.microsoft.com/typography/otspec/name.htm">name table</a>,
  2357    in the name record with nameID = 6 (see <a href="#OPENTYPE"
  2358    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> for more details). The
  2359    Postscript name is the commonly used key for all fonts on OSX and for
  2360    Postscript CFF fonts under Windows. The full font name (nameID = 4) is
  2361    used as a unique key for fonts with TrueType glyphs on Windows.
  2363   <p>For OpenType fonts with multiple localizations of the full font name,
  2364    the US English version is used (language ID = 0x409 for Windows and
  2365    language ID = 0 for Macintosh) or the first localization when a US English
  2366    full font name is not available (the OpenType specification recommends
  2367    that <a href="http://www.microsoft.com/typography/otspec/recom.htm">all
  2368    fonts minimally include US English names</a>). User agents that also match
  2369    other full font names, e.g. matching the Dutch name when the current
  2370    system locale is set to Dutch, are considered non-conformant. This is done
  2371    not to prefer English but to avoid matching inconsistencies across font
  2372    versions and OS localizations, since font style names (e.g. "Bold") are
  2373    frequently localized into many languages and the set of localizations
  2374    available varies widely across platform and font version. User agents that
  2375    match a concatenation of family name (nameID = 1) with style name (nameID
  2376    = 2) are considered non-conformant.
  2378   <p>This also allows for referencing faces that belong to larger families
  2379    that cannot otherwise be referenced.
  2381   <div class=example>
  2382    <p>Use a local font or reference an SVG font in another document:</p>
  2384    <pre>
  2385 @font-face {
  2386   font-family: Headline;
  2387   src: local(Futura-Medium), 
  2388        url(fonts.svg#MyGeometricModern) format("svg");
  2390 </pre>
  2392    <p>Create an alias for local Japanese fonts on different platforms:</p>
  2394    <pre>
  2395 @font-face {
  2396   font-family: jpgothic;
  2397   src: local(HiraKakuPro-W3), local(Meiryo), local(IPAPGothic);
  2399 </pre>
  2401    <p>Reference a font face that cannot be matched within a larger family:</p>
  2403    <pre>
  2404 @font-face {
  2405   font-family: Hoefler Text Ornaments;
  2406   /* has the same font properties as Hoefler Text Regular */
  2407   src: local(HoeflerText-Ornaments); 
  2409 </pre>
  2411    <p>Since localized fullnames never match, a document with the header style
  2412     rules below would always render using the default serif font, regardless
  2413     whether a particular system locale parameter is set to Finnish or not:</p>
  2415    <pre>
  2416 @font-face {
  2417   font-family: SectionHeader;
  2418   src: local("Arial Lihavoitu");  /* Finnish fullname for Arial Bold, should fail */
  2419   font-weight: bold;
  2422 h2 { font-family: SectionHeader, serif; }
  2423 </pre>
  2425    <p>A conformant user agent would never load the font ‘<code
  2426     class=css>gentium.eot</code>’ in the example below, since it is
  2427     included in the first definition of the ‘<a href="#descdef-src"><code
  2428     class=property>src</code></a>’ descriptor which is overridden by the
  2429     second definition in the same <code>@font-face</code> rule:</p>
  2431    <pre>
  2432 @font-face {
  2433   font-family: MainText;
  2434   src: url(gentium.eot); /* for use with older non-conformant user agents */
  2435   src: local("Gentium"), url(gentium.ttf);  /* Overrides src definition */
  2437 </pre>
  2438   </div>
  2440   <h3 id=font-prop-desc><span class=secno>4.4 </span>Font property
  2441    descriptors: the <a href="#descdef-font-style">font-style</a>, <a
  2442    href="#descdef-font-weight">font-weight</a>, <a
  2443    href="#descdef-font-stretch">font-stretch</a> descriptors</h3>
  2445   <table class=descdef>
  2446    <tbody>
  2447     <tr>
  2448      <td>Name:
  2450      <td><dfn id=descdef-font-style title="font-style
  2451       (descriptor)">font-style</dfn>
  2453     <tr>
  2454      <td>Value:
  2456      <td>normal | italic | oblique
  2458     <tr>
  2459      <td><em>Initial:</em>
  2461      <td>normal
  2462   </table>
  2464   <table class=descdef>
  2465    <tbody>
  2466     <tr>
  2467      <td>Name:
  2469      <td><dfn id=descdef-font-weight title="font-weight
  2470       (descriptor)">font-weight</dfn>
  2472     <tr>
  2473      <td>Value:
  2475      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
  2477     <tr>
  2478      <td><em>Initial:</em>
  2480      <td>normal
  2481   </table>
  2483   <table class=descdef>
  2484    <tbody>
  2485     <tr>
  2486      <td>Name:
  2488      <td><dfn id=descdef-font-stretch title="font-stretch
  2489       (descriptor)">font-stretch</dfn>
  2491     <tr>
  2492      <td>Value:
  2494      <td>normal | ultra-condensed | extra-condensed | condensed |
  2495       semi-condensed | semi-expanded | expanded | extra-expanded |
  2496       ultra-expanded
  2498     <tr>
  2499      <td><em>Initial:</em>
  2501      <td>normal
  2502   </table>
  2504   <p>These descriptors define the characteristics of a font face and are used
  2505    in the process of matching styles to specific faces. For a font family
  2506    defined with several <code>@font-face</code> rules, user agents can either
  2507    download all faces in the family or use these descriptors to selectively
  2508    download font faces that match actual styles used in document. The values
  2509    for these descriptors are the same as those for the corresponding font
  2510    properties except that relative keywords are not allowed, ‘<code
  2511    class=property>bolder</code>’ and ‘<code
  2512    class=property>lighter</code>’. If these descriptors are omitted,
  2513    default values are assumed.
  2515   <p>The value for these font face style attributes is used in place of the
  2516    style implied by the underlying font data. This allows authors to combine
  2517    faces in flexible combinations, even in situations where the original font
  2518    data was arranged differently. User agents that implement synthetic
  2519    bolding and obliqueing must only apply synthetic styling in cases where
  2520    the font descriptors imply this is needed, rather than based on the style
  2521    attributes implied by the font data.
  2523   <h3 id=unicode-range-desc><span class=secno>4.5 </span>Character range: the
  2524    <a href="#descdef-unicode-range">unicode-range</a> descriptor</h3>
  2526   <table class=descdef>
  2527    <tbody>
  2528     <tr>
  2529      <td>Name:
  2531      <td><dfn id=descdef-unicode-range>unicode-range</dfn>
  2533     <tr>
  2534      <td>Value:
  2536      <td>&lt;urange>#
  2538     <tr>
  2539      <td><em>Initial:</em>
  2541      <td>U+0-10FFFF
  2542   </table>
  2544   <p>This descriptor defines the range of Unicode characters supported by a
  2545    given font. The values of <span class=index-def id=lturangegt
  2546    title="&lt;urange&gt;"><a name=value-def-urange>&lt;urange&gt;</a></span>
  2547    are expressed using hexadecimal numbers prefixed by "U+" or "u+",
  2548    corresponding to <a href="http://www.unicode.org/charts/">Unicode
  2549    character code points</a>. The unicode-range descriptor serves as a hint
  2550    for user agents when deciding whether or not to download a font resource.
  2552   <p>Unicode range values are written using hexadecimal values and are ASCII
  2553    case-insensitive. Each is prefixed by "U+" or "u+" and multiple,
  2554    discontinuous ranges are separated by commas. Whitespace before or after
  2555    commas is ignored. Valid character code values vary between 0 and 10FFFF
  2556    inclusive. A single range has three basic forms:
  2558   <ul>
  2559    <li>a single code point (e.g. U+416)
  2561    <li>an interval value range (e.g. U+400-4ff)
  2563    <li>a range where trailing ‘<code class=css>?</code>’ characters imply
  2564     ‘<code class=css>any digit value</code>’ (e.g. U+4??)
  2565   </ul>
  2567   <p>Ranges that do not fit any of the above three forms are considered to be
  2568    parse errors and the descriptor is omitted. Interval ranges consisting of
  2569    a single code point are valid. Ranges specified with ‘?’ that lack an
  2570    initial digit (e.g. "U+???") are also valid, and are treated as if there
  2571    was a single 0 before the question marks (thus, "U+???" = "U+0???" =
  2572    "U+0000-0FFF"). "U+??????" is not a syntax error, even though "U+0??????"
  2573    would be. Ranges can overlap but interval ranges that descend (e.g.
  2574    U+400-32f) are invalid and omitted rather than treated as parse errors;
  2575    they have no effect on other ranges in a list of ranges. Ranges are
  2576    clipped to the domain of Unicode code points (currently 0 – 10FFFF
  2577    inclusive); a range entirely outside the domain is omitted. Without any
  2578    valid ranges, the descriptor is omitted. User agents may normalize the
  2579    list of ranges into a list that is different but represents the same set
  2580    of character code points.
  2582   <p>The character range can be a subset of the full <a
  2583    href="#character-map"><em>character map</em></a> of the underlying font.
  2584    The effective unicode-range used when mapping characters to fonts is the
  2585    intersection of the unicode range specified and the underlying <a
  2586    href="#character-map"><em>character map</em></a> of the font. This means
  2587    that authors do not need to define the unicode-range of a font precisely,
  2588    broad ranges for which a sparse set of code points are defined in the font
  2589    can be used. Code points outside of the defined unicode-range are ignored,
  2590    regardless of whether the font contains a glyph for that code point or
  2591    not. User agents that download fonts for characters outside the defined
  2592    unicode-range are considered non-conformant. Likewise, user agents that
  2593    render a character using a font resource for which the defined
  2594    unicode-range does not include that character are also considered
  2595    non-conformant.
  2597   <p>Example ranges for specific languages or characters:
  2599   <dl>
  2600    <dt>unicode-range: U+A5;
  2602    <dd>a single code point, the yen/yuan symbol
  2604    <dt>unicode-range: U+0-7F;
  2606    <dd>code range for basic ASCII characters
  2608    <dt>unicode-range: U+590-5ff;
  2610    <dd>code range for Hebrew characters
  2612    <dt>unicode-range: U+A5, U+4E00-9FFF, U+30??, U+FF00-FF9F;
  2614    <dd>code range for Japanese kanji, hiragana and katakana characters plus
  2615     yen/yuan symbol
  2616   </dl>
  2618   <div class=example>
  2619    <p>The BBC provides news services in a wide variety of languages, many
  2620     that are not well supported across all platforms. Using an
  2621     <code>@font-face</code> rule, the BBC could provide a font for any of
  2622     these languages, as it already does via a manual font download.</p>
  2624    <pre>
  2625 @font-face {
  2626   font-family: BBCBengali;
  2627   src: url(fonts/BBCBengali.ttf) format("opentype");
  2628   unicode-range: U+00-FF, U+980-9FF;
  2630 </pre>
  2631   </div>
  2633   <div class=example>
  2634    <p>Technical documents often require a wide range of symbols. The STIX
  2635     Fonts project is one project aimed at providing fonts to support a wide
  2636     range of technical typesetting in a standardized way. The example below
  2637     shows the use of a font that provides glyphs for many of the mathematical
  2638     and technical symbol ranges within Unicode:</p>
  2640    <pre>
  2641 @font-face {
  2642   font-family: STIXGeneral;
  2643   src: local(STIXGeneral), url(/stixfonts/STIXGeneral.otf);
  2644   unicode-range: U+000-49F, U+2000-27FF, U+2900-2BFF, U+1D400-1D7FF;
  2646 </pre>
  2647   </div>
  2649   <p>Multiple <code>@font-face</code> rules with different unicode ranges for
  2650    the same family and style descriptor values can be used to create
  2651    composite fonts that mix the glyphs from different fonts for different
  2652    scripts. This can be used to combine fonts that only contain glyphs for a
  2653    single script (e.g. Latin, Greek, Cyrillic) or it can be used by authors
  2654    as a way of segmenting a font into fonts for commonly used characters and
  2655    less frequently used characters. Since the user agent will only pull down
  2656    the fonts it needs this helps reduce page bandwidth.
  2658   <p>If the unicode ranges overlap for a set of <code>@font-face</code> rules
  2659    with the same family and style descriptor values, the rules are ordered in
  2660    the reverse order they were defined; the last rule defined is the first to
  2661    be checked for a given character.
  2663   <div class=example>
  2664    <p>This example shows how an author can override the glyphs used for Latin
  2665     characters in a Japanese font with glyphs from a different font. The
  2666     first rule specifies no range so it defaults to the entire range. The
  2667     range specified in the second rule overlaps but takes precedence because
  2668     it is defined later.</p>
  2670    <pre>
  2671 @font-face {
  2672   font-family: JapaneseWithGentium;
  2673   src: local(MSMincho);
  2674   /* no range specified, defaults to entire range */
  2677 @font-face {
  2678   font-family: JapaneseWithGentium;
  2679   src: url(../fonts/Gentium.ttf);
  2680   unicode-range: U+0-2FF;
  2682 </pre>
  2683   </div>
  2685   <div class=example>
  2686    <p>Consider a family constructed to optimize bandwidth by separating out
  2687     Latin, Japanese and other characters into different font files:</p>
  2689    <pre>
  2690 /* fallback font - size: 4.5MB */
  2691 @font-face {
  2692   font-family: DroidSans;
  2693   src: url(DroidSansFallback.ttf);
  2694   /* no range specified, defaults to entire range */
  2697 /* Japanese glyphs - size: 1.2MB */
  2698 @font-face {
  2699   font-family: DroidSans;
  2700   src: url(DroidSansJapanese.ttf);
  2701   unicode-range: U+3000-9FFF, U+ff??;
  2704 /* Latin, Greek, Cyrillic along with some 
  2705    punctuation and symbols - size: 190KB */
  2706 @font-face {
  2707   font-family: DroidSans;
  2708   src: url(DroidSans.ttf);
  2709   unicode-range: U+000-5FF, U+1e00-1fff, U+2000-2300;
  2711 </pre>
  2713    <p>For simple Latin text, only the font for Latin characters is
  2714     downloaded:</p>
  2716    <pre>
  2717 body { font-family: DroidSans; }
  2719 &lt;p>This is that&lt;/p>
  2720 </pre>
  2722    <p>In this case the user agent first checks the unicode-range for the font
  2723     containing Latin characters (DroidSans.ttf). Since all the characters
  2724     above are in the range U+0-5FF, the user agent downloads the font and
  2725     renders the text with that font.</p>
  2727    <p>Next, consider text that makes use of an arrow character (⇨):</p>
  2729    <pre>
  2730 &lt;p>This &amp;#x21e8; that&lt;p>
  2731 </pre>
  2733    <p>The user agent again first checks the unicode-range of the font
  2734     containing Latin characters. Since U+2000-2300 includes the arrow code
  2735     point (U+21E8), the user agent downloads the font. For this character
  2736     however the Latin font does not have a matching glyph, so the effective
  2737     unicode-range used for font matching excludes this code point. Next, the
  2738     user agent evaluates the Japanese font. The unicode-range for the
  2739     Japanese font, U+3000-9FFF and U+ff??, does not include U+21E8, so the
  2740     user agent does not download the Japanese font. Next the fallback font is
  2741     considered. The <code>@font-face</code> rule for the fallback font does
  2742     not define unicode-range so its value defaults to the range of all
  2743     Unicode code points. The fallback font is downloaded and used to render
  2744     the arrow character.</p>
  2745   </div>
  2747   <h3 id=font-rend-desc><span class=secno>4.6 </span>Font features: the <a
  2748    href="#descdef-font-variant">font-variant</a> and <a
  2749    href="#descdef-font-feature-settings">font-feature-settings</a>
  2750    descriptors</h3>
  2752   <table class=descdef>
  2753    <tbody>
  2754     <tr>
  2755      <td>Name:
  2757      <td><dfn id=descdef-font-variant title="font-variant
  2758       (descriptor)">font-variant</dfn>
  2760     <tr>
  2761      <td>Value:
  2763      <td>normal | [ &lt;common-lig-values&gt; ||
  2764       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  2765       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  2766       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  2767       character-variant(&lt;feature-value-name&gt;#) ||
  2768       swash(&lt;feature-value-name&gt;) ||
  2769       ornaments(&lt;feature-value-name&gt;) ||
  2770       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  2771       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  2772       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  2773       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  2774       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  2775       ruby ]
  2777     <tr>
  2778      <td><em>Initial:</em>
  2780      <td>normal
  2781   </table>
  2783   <table class=descdef>
  2784    <tbody>
  2785     <tr>
  2786      <td>Name:
  2788      <td><dfn id=descdef-font-feature-settings title="font-feature-settings
  2789       (descriptor)">font-feature-settings</dfn>
  2791     <tr>
  2792      <td>Value:
  2794      <td>normal | &lt;feature-tag-value&gt;#
  2796     <tr>
  2797      <td><em>Initial:</em>
  2799      <td>normal
  2800   </table>
  2802   <p>These descriptors define default settings that apply when the font
  2803    defined by an <code>@font-face</code> rule is rendered. They do not affect
  2804    font selection. Values are identical to those defined for the
  2805    corresponding ‘<a href="#propdef-font-variant"><code
  2806    class=property>font-variant</code></a>’ and ‘<a
  2807    href="#propdef-font-feature-settings"><code
  2808    class=property>font-feature-settings</code></a>’ properties defined
  2809    below except that the value ‘<code class=property>inherit</code>’ is
  2810    omitted. When multiple font feature descriptors or properties are used,
  2811    the cumulative effect on text rendering is detailed in the section <a
  2812    href="#font-feature-resolution">Font Feature Resolution</a> below. In
  2813    cases where specific values define synthesized fallback for certain ‘<a
  2814    href="#propdef-font-variant"><code
  2815    class=property>font-variant</code></a>’ subproperties, the same
  2816    synthesized fallback applies when used within those values are used with
  2817    the <a href="#descdef-font-variant">‘<code
  2818    class=property>font-variant</code>’</a> descriptor.
  2820   <h3 id=font-face-loading><span class=secno>4.7 </span>Font loading
  2821    guidelines</h3>
  2823   <p>The <code>@font-face</code> rule is designed to allow lazy loading of
  2824    fonts, fonts are only downloaded when needed for use within a document. A
  2825    stylesheet can include <code>@font-face</code> rules for a library of
  2826    fonts of which only a select set are used; user agents must only download
  2827    those fonts that are referred to within the style rules applicable to a
  2828    given page. User agents that download all fonts defined in
  2829    <code>@font-face</code> rules without considering whether those fonts are
  2830    in fact used within a page are considered non-conformant. In cases where a
  2831    font might be downloaded in character fallback cases, user agents may
  2832    download a font if it's listed in a font list but is not actually used for
  2833    a given text run.
  2835   <pre>
  2836 @font-face {
  2837   font-family: GeometricModern;
  2838   src: url(font.ttf);
  2841 p {
  2842   /* font will be downloaded for pages with p elements */
  2843   font-family: GeometricModern, sans-serif;
  2846 h2 {
  2847   /* font may be downloaded for pages with h2 elements, even if Futura is available locally */
  2848   font-family: Futura, GeometricModern, sans-serif;
  2850 </pre>
  2852   <p>In cases where textual content is loaded before downloadable fonts are
  2853    available, user agents may render text as it would be rendered if
  2854    downloadable font resources are not available or they may render text
  2855    transparently with fallback fonts to avoid a flash of text using a
  2856    fallback font. In cases where the font download fails user agents must
  2857    display text, simply leaving transparent text is considered non-conformant
  2858    behavior. Authors are advised to use fallback fonts in their font lists
  2859    that closely match the vertical metrics of the downloadable fonts to avoid
  2860    large page reflows where possible.
  2862   <h3 id=same-origin-restriction><span class=secno>4.8 </span>Same-origin
  2863    restriction for fonts</h3>
  2865   <h4 id=default-same-origin-restriction><span class=secno>4.8.1
  2866    </span>Default same-origin restriction</h4>
  2867   <!-- TPAC 2011 Resolution to require same-origin restriction for loading fonts:
  2868   http://lists.w3.org/Archives/Public/www-style/2011Nov/0711.html
  2869   http://www.w3.org/2011/10/31-webapps-minutes.html#item02
  2870 -->
  2872   <p>User agents must implement a same-origin restriction when loading fonts
  2873    via the <code>@font-face</code> mechanism. This restriction limits the
  2874    loading of fonts for a given document to fonts loaded from the same
  2875    origin. Fonts can only be loaded via the same host, port, and method
  2876    combination as the containing document, using the <a
  2877    href="http://www.w3.org/TR/html5/browsers.html#origin">origin matching
  2878    algorithm</a> described in the <a href="#HTML5"
  2879    rel=biblioentry>[HTML5]<!--{{!HTML5}}--></a> specification. The origin of
  2880    the stylesheet containing <code>@font-face</code> rules is not used when
  2881    deciding whether a font is same origin or not, only the origin of the
  2882    containing document is used. The restriction applies to all font types.
  2884   <p>Given a document located at http://example.com/page.html, fonts defined
  2885    with ‘<a href="#descdef-src"><code class=property>src</code></a>’
  2886    definitions considered cross origin must not be loaded:
  2888   <pre>
  2889 /* same origin (i.e. domain, protocol, port match document) */
  2890 src: url(fonts/simple.ttf);                     
  2891 src: url(//fonts/simple.ttf);                     
  2893 /* cross origin, different protocol */
  2894 src: url(https://example.com/fonts/simple.ttf);              
  2896 /* cross origin, different domain */
  2897 src: url(http://another.example.com/fonts/simple.ttf); 
  2898 </pre>
  2900   <h4 id=allowing-cross-origin-font-loading><span class=secno>4.8.2
  2901    </span>Allowing cross-origin font loading</h4>
  2903   <p>User agents must also implement the ability to relax this restriction
  2904    using cross-site origin controls <a href="#CORS"
  2905    rel=biblioentry>[CORS]<!--{{!CORS}}--></a> for fonts loaded via HTTP.
  2906    Sites can explicitly allow cross-site downloading of font data using the
  2907    <code>Access-Control-Allow-Origin</code> HTTP header. For other protocols,
  2908    no explicit relaxation mechanism is defined or required.
  2910   <p>For font loads over HTTP, cross-origin requests must be made with the
  2911    following parameter settings which are used in conjunction with the <a
  2912    href="http://www.w3.org/TR/cors/#cross-origin-request-0"> <em>cross-origin
  2913    request algorithm</em></a> <a href="#CORS"
  2914    rel=biblioentry>[CORS]<!--{{!CORS}}--></a>:
  2916   <ul>
  2917    <li><em>request URL</em> — the URL of the font resource in the <a
  2918     href="#descdef-src"><code>src</code></a> descriptor
  2920    <li><em>request method</em> — GET
  2922    <li><em>author request headers</em> — none
  2924    <li><em>request entity body</em> — empty
  2926    <li><em>source origin</em> — the origin of the page which linked to the
  2927     stylesheet
  2929    <li><em>manual redirect flag</em> — false
  2931    <li><em>omit credentials flag</em> — true
  2933    <li><em>force preflight flag</em> — false
  2934   </ul>
  2936   <h2 id=font-matching-algorithm><span class=secno>5 </span>Font Matching
  2937    Algorithm</h2>
  2939   <p>The algorithm below describes how fonts are associated with individual
  2940    runs of text. For each character in the run a font family is chosen and a
  2941    particular font face is selected containing a glyph for that character.
  2943   <h3 id=font-family-casing><span class=secno>5.1 </span>Case sensitivity of
  2944    font family names</h3>
  2946   <p>As part of the font matching algorithm outlined below, user agents must
  2947    match font family names used in style rules with actual font family names
  2948    contained in fonts available in a given environment or defined via
  2949    <code>@font-face</code> rules. User agents must match these names case
  2950    insensitively, using the "Default Caseless Matching" algorithm outlined in
  2951    the Unicode specification <a href="#UNICODE6"
  2952    rel=biblioentry>[UNICODE6]<!--{{!UNICODE6}}--></a>. This algorithm is
  2953    detailed in section 3.13 entitled "Default Case Algorithms". Specifically,
  2954    the algorithm must be applied without normalizing the strings involved and
  2955    without applying any language-specific tailorings. The case folding method
  2956    specified by this algorithm uses the case mappings with status field
  2957    ‘<code class=property>C</code>’ or ‘<code class=property>F</code>’
  2958    in the CaseFolding.txt file of the Unicode Character Database.
  2960   <p class=note> Implementors should take care to verify that a given
  2961    caseless string comparison implementation uses this precise algorithm and
  2962    not assume that a given platform string matching routine follows it, as
  2963    many of these have locale-specific behavior or use some level of string
  2964    normalization.
  2966   <p class=note> For authors this means that font family names are matched
  2967    case insensitively, whether or not those names exist in a platform font or
  2968    in the <code>@font-face</code> rules contained in a stylesheet. Authors
  2969    should take care to ensure that names use a character sequence consistent
  2970    with the actual font family name, particularly when using combining
  2971    characters such as diacritical marks. For example, a family name that
  2972    contains an uppercase A (U+0041) followed by a combining ring (U+030A)
  2973    will <strong>not</strong> match a name that looks identical but which uses
  2974    the precomposed lowercase a-ring character (U+00E5) instead of the
  2975    combining sequence.
  2977   <h3 id=font-style-matching><span class=secno>5.2 </span>Matching font
  2978    styles</h3>
  2980   <p>The procedure for choosing fonts consists of iterating over the font
  2981    families determined by the font-family property, selecting a font face
  2982    with the appropriate style based on other font properties and then
  2983    determining whether a glyph exists for a given character. This is done
  2984    using the <dfn id=character-map>character map</dfn> of the font, data
  2985    which maps characters to the default glyph for that character. Codepoint
  2986    sequences consisting of a base character followed by a sequence of
  2987    combining characters are treated slightly differently, see the section on
  2988    <a href="#cluster-matching">cluster matching</a> below.
  2990   <p>For this procedure, the <dfn id=default-face>default face</dfn> for a
  2991    given font family is defined to be the face that would be selected if all
  2992    font style properties were set to their initial value.
  2994   <ol id=fontmatchingalg>
  2995    <li>Using the computed font property values for a given element, the user
  2996     agent starts with the first family name in the fontlist specified by the
  2997     <span class=property>‘<a href="#descdef-font-family"><code
  2998     class=property>font-family</code></a>’</span> property.
  3000    <li>If the family name is unquoted and is a generic family name, the user
  3001     agent looks up the appropriate font family name to be used. User agents
  3002     may choose the generic font family to use based on the language of the
  3003     containing element or the Unicode range of the character.
  3005    <li>For other family names, the user agent attempts to find the family
  3006     name among fonts defined via <code>@font-face</code> rules and then among
  3007     available system fonts, matching names with a case-insensitive comparison
  3008     as outlined <a href="#font-family-casing">in the section above</a>. On
  3009     systems containing fonts with multiple localized font family names, user
  3010     agents must match any of these names independent of the underlying system
  3011     locale or platform API used. If the font resources defined for a given
  3012     face in an @font-face rule are either not available or contain invalid
  3013     font data, then the face should be treated as not present in the family.
  3014     If no faces are present for a family defined via @font-face rules, the
  3015     family should be treated as missing; matching a platform font with the
  3016     same name must not occur in this case.
  3018    <li>If a font family match occurs, the user agent assembles the set of
  3019     font faces in that family and then narrows the set to a single face using
  3020     other font properties in the order given below:
  3021     <ol id=fontstylematchingalg>
  3022      <li><span class=property>‘<a href="#propdef-font-stretch"><code
  3023       class=property>font-stretch</code></a>’</span> is tried first. If the
  3024       matching set contains faces with width values matching the ‘<a
  3025       href="#propdef-font-stretch"><code
  3026       class=property>font-stretch</code></a>’ value, faces with other width
  3027       values are removed from the matching set. If there is no face that
  3028       exactly matches the width value the nearest width is used instead. If
  3029       the value of ‘<a href="#propdef-font-stretch"><code
  3030       class=property>font-stretch</code></a>’ is ‘<a
  3031       href="#normal2"><code class=property>normal</code></a>’ or one of the
  3032       condensed values, narrower width values are checked first, then wider
  3033       values. If the value of ‘<a href="#propdef-font-stretch"><code
  3034       class=property>font-stretch</code></a>’ is one of the expanded
  3035       values, wider values are checked first, followed by narrower values.
  3036       Once the closest matching width has been determined by this process,
  3037       faces with other widths are removed from the matching set.
  3039      <li><span class=property>‘<a href="#propdef-font-style"><code
  3040       class=property>font-style</code></a>’</span> is tried next. If the
  3041       value of ‘<a href="#propdef-font-style"><code
  3042       class=property>font-style</code></a>’ is ‘<code
  3043       class=property>italic</code>’, italic faces are checked first, then
  3044       oblique, then normal faces. If the value is ‘<code
  3045       class=property>oblique</code>’, oblique faces are checked first, then
  3046       italic faces and then normal faces. If the value is ‘<a
  3047       href="#normal2"><code class=property>normal</code></a>’, normal faces
  3048       are checked first, then oblique faces, then italic faces. Faces with
  3049       other style values are excluded from the matching set. User agents are
  3050       permitted to distinguish between italic and oblique faces within
  3051       platform font families but this is not required, they may treat all
  3052       italic or oblique faces as italic faces. However, within font families
  3053       defined via <code>@font-face</code> rules, italic and oblique faces
  3054       must be distinguished using the value of the ‘<a
  3055       href="#propdef-font-style"><code
  3056       class=property>font-style</code></a>’ descriptor.
  3058      <li><span class=property>‘<a href="#propdef-font-weight"><code
  3059       class=property>font-weight</code></a>’</span> is matched next, it
  3060       will always reduce the matching set to a single font face. If
  3061       bolder/lighter relative weights are used, the effective weight is
  3062       calculated based on the inherited weight value, as described in the
  3063       definition of the ‘<a href="#propdef-font-weight"><code
  3064       class=property>font-weight</code></a>’ property. Given the desired
  3065       weight and the weights of faces in the matching set after the steps
  3066       above, if the desired weight is available that face matches. Otherwise,
  3067       a weight is chosen using the rules below:
  3068       <ul>
  3069        <li>If the desired weight is less than 400, weights below the desired
  3070         weight are checked in descending order followed by weights above the
  3071         desired weight in ascending order until a match is found.
  3073        <li>If the desired weight is greater than 500, weights above the
  3074         desired weight are checked in ascending order followed by weights
  3075         below the desired weight in descending order until a match is found.
  3077        <li>If the desired weight is 400, 500 is checked first and then the
  3078         rule for desired weights less than 400 is used.
  3080        <li>If the desired weight is 500, 400 is checked first and then the
  3081         rule for desired weights less than 400 is used.
  3082       </ul>
  3084      <li><span class=property>‘<a href="#propdef-font-size"><code
  3085       class=property>font-size</code></a>’</span> must be matched within a
  3086       UA-dependent margin of tolerance. (Typically, sizes for scalable fonts
  3087       are rounded to the nearest whole pixel, while the tolerance for
  3088       bitmapped fonts could be as large as 20%.) Further computations, e.g.,
  3089       by ‘<code class=property>em</code>’ values in other properties, are
  3090       based on the <span class=property>‘<a href="#propdef-font-size"><code
  3091       class=property>font-size</code></a>’</span> value that is used, not
  3092       the one that is specified.
  3093     </ol>
  3095    <li>
  3096     <p>If no matching face exists or the matched face does not contain a
  3097      glyph for the character to be rendered, the next family name is selected
  3098      and the previous two steps repeated. Glyphs from other faces in the
  3099      family are not considered. The only exception is that user agents may
  3100      optionally substitute a synthetic version of the <a
  3101      href="#default-face"><em>default face</em></a> if that face supports a
  3102      given glyph (e.g. a synthetic italic version of the regular face may be
  3103      used if the italic face doesn't support glyphs for Arabic).</p>
  3104     <!-- resolution on the above: http://lists.w3.org/Archives/Public/www-style/2012Nov/0292.html -->
  3106     <p>If the matched font is defined via an <code>@font-face</code> rule and
  3107      needs to be downloaded, the font resource is downloaded. While the
  3108      download occurs, the user agent can either wait until the font is
  3109      downloaded or render once with substituted font metrics and render again
  3110      once the font is downloaded.</p>
  3112    <li>If there are no more font families to be evaluated and no matching
  3113     face has been found, then the user agent performs a <em>system font
  3114     fallback</em> procedure to find the best match for the character to be
  3115     rendered. The result of this procedure may vary across user agents.
  3117    <li>If a particular character cannot be displayed using any font, the user
  3118     agent should indicate by some means that a character is not being
  3119     displayed, displaying either a symbolic representation of the missing
  3120     glyph (e.g. using a <a
  3121     href="http://en.wikipedia.org/wiki/Last_resort_font">Last Resort
  3122     Font</a>) or using the missing character glyph from a default font.
  3123   </ol>
  3125   <h3 id=cluster-matching><span class=secno>5.3 </span>Cluster matching</h3>
  3127   <p>When text contains characters such as combining diacritics, ideally the
  3128    base character should be rendered using the same font as the diacritic,
  3129    this assures proper placement of the diacritic. For this reason, the font
  3130    matching algorithm for clusters is more specialized than the general case
  3131    of matching a single character by itself. For sequences containing
  3132    variation selectors, which indicate the precise glyph to be used for a
  3133    given character, user agents always attempt system font fallback to find
  3134    the appropriate glyph before using the default glyph of the base
  3135    character.
  3137   <p>A font is considered to <em>support</em> a given character if (1) the
  3138    character is contained in the font's <a
  3139    href="#character-map"><em>character map</em></a> and (2) if required by
  3140    the containing script, shaping information is available for that
  3141    character. Some legacy fonts may include a given character in the <a
  3142    href="#character-map"><em>character map</em></a> but lack the shaping
  3143    information (e.g. <a
  3144    href="http://www.microsoft.com/typography/otspec/ttochap1.htm">OpenType
  3145    layout tables</a> or <a
  3146    href="http://scripts.sil.org/cms/scripts/page.php?site_id=projects&amp;item_id=graphite_techAbout">Graphite
  3147    tables</a>) necessary for correctly rendering text runs containing that
  3148    character.
  3150   <p>A sequence of codepoints containing combining diacritics or other
  3151    modifiers is termed a grapheme cluster (see <a href="#CSS3TEXT"
  3152    rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a> for a more complete
  3153    description). For a given cluster containing a base character, <em>b</em>
  3154    and a sequence of combining characters <em>c1, c2…</em>, the entire
  3155    cluster is matched using these steps:
  3157   <ol>
  3158    <li>For each family in the font list, a face is chosen using the style
  3159     selection rules defined in the previous section.
  3160     <ol>
  3161      <li>If all characters in the sequence <em>b + c1 + c2 …</em> are
  3162       completely supported by the font, select this font for the sequence.
  3164      <li>If a sequence of multiple codepoints is canonically equivalent to a
  3165       single character and the font supports that character, select this font
  3166       for the sequence.
  3167     </ol>
  3169    <li>If no font was found in the font list in step 1:
  3170     <ol>
  3171      <li>If <em>c1</em> is a variation selector, system fallback must be used
  3172       to find a font that supports the full sequence of <em>b + c1</em>. If
  3173       no font on the system supports the full sequence, match the single
  3174       character <em>b</em> using the normal procedure for matching single
  3175       characters and ignore the variation selector. Note: a sequence with
  3176       more than one variation selector is treated as an encoding error and
  3177       the trailing selectors are ignored.
  3179      <li>Otherwise, the user agent may optionally use system font fallback to
  3180       match a font that supports the entire cluster.
  3181     </ol>
  3183    <li>If no font is found in step 2, use the matching sequence from step 1
  3184     to determine the longest sequence that is completely matched by a font in
  3185     the font list and attempt to match the remaining combining characters
  3186     separately using the rules for single characters.
  3187   </ol>
  3189   <h3 id=char-handling-issues><span class=secno>5.4 </span>Character handling
  3190    issues</h3>
  3192   <p>The procedure above is always performed on text runs containing Unicode
  3193    characters, documents using legacy encodings are assumed to have been
  3194    transcoded before matching fonts. For fonts containing <a
  3195    href="#character-map"><em title="character map">character maps</em></a>
  3196    for both legacy encodings and Unicode, the contents of the legacy encoding
  3197    <a href="#character-map"><em>character map</em></a> must have no effect on
  3198    the results of the font matching process.
  3200   <p>The font matching process does not assume that text runs are in either
  3201    normalized or denormalized form (see <a href="#CHARMOD-NORM"
  3202    rel=biblioentry>[CHARMOD-NORM]<!--{{CHARMOD-NORM}}--></a> for more
  3203    details). Layout engines often convert base character plus combining
  3204    character sequences into precomposed characters if they exist. The font
  3205    matching algorithm outlined here supports both ways and fonts can
  3206    generally support either but variations can occur. Authors should always
  3207    tailor their choice of fonts to their content, including whether that
  3208    content contains normalized or denormalized character streams.
  3210   <p>If a given character is a Private-Use Area Unicode codepoint and none of
  3211    the fonts in the fontlist contain a glyph for that codepoint, user agents
  3212    must display some form of missing glyph symbol for that character rather
  3213    than attempting system font fallback for that codepoint. When matching the
  3214    replacement character U+FFFD, user agents may skip the font matching
  3215    process and immediately display some form of missing glyph symbol, they
  3216    are not required to display the glyph from the font that would be selected
  3217    by the font matching process.
  3219   <p>In general, the fonts for a given family will all have the same or
  3220    similar <a href="#character-map"><em title="character map">character
  3221    maps</em></a>. The process outlined here is designed to handle even font
  3222    families containing faces with widely variant <a href="#character-map"><em
  3223    title="character map">character maps</em></a>. However, authors are
  3224    cautioned that the use of such families can lead to unexpected results.
  3226   <p>Optimizations of this process are allowed provided that an
  3227    implementation behaves as if the algorithm had been followed exactly.
  3228    Matching occurs in a well-defined order to insure that the results are as
  3229    consistent as possible across user agents, given an identical set of
  3230    available fonts and rendering technology.
  3232   <h3 id=font-matching-changes><span class=secno>5.5 </span>Font matching
  3233    changes since CSS 2.1</h3>
  3235   <p>The algorithm above is different from CSS 2.1 in a number of key places.
  3236    These changes were made to better reflect actual font matching behavior
  3237    across user agent implementations.
  3239   <p>Differences compared to the font matching algorithm in CSS 2.1:
  3241   <ul>
  3242    <li>The algorithm includes font-stretch matching.
  3244    <li>All possible font-style matching scenarios are delineated.
  3246    <li>Small-caps fonts are not matched as part of the font matching process,
  3247     they are now handled via font features.
  3249    <li>Unicode variation selector matching is required.
  3251    <li>Cluster sequences are matched as a unit.
  3252   </ul>
  3254   <h3 id=font-matching-examples><span class=secno>5.6 </span>Font matching
  3255    examples</h3>
  3257   <div class=example>
  3258    <p>It's useful to note that the CSS selector syntax may be used to create
  3259     language-sensitive typography. For example, some Chinese and Japanese
  3260     characters are unified to have the same Unicode code point, although the
  3261     abstract glyphs are not the same in the two languages.
  3263    <pre>*:lang(ja-jp) { font: 900 14pt/16pt &quot;Heisei Mincho W9&quot;, serif; }
  3264 *:lang(zh-tw) { font: 800 14pt/16.5pt &quot;Li Sung&quot;, serif; }
  3265 </pre>
  3267    <p>This selects any element that has the given language - Japanese or
  3268     Traditional Chinese - and uses the appropriate font.
  3269   </div>
  3271   <h2 id=font-rend-props><span class=secno>6 </span>Font Feature Properties</h2>
  3273   <p>Modern font technologies support a variety of advanced typographic and
  3274    language-specific font features. Using these features, a single font can
  3275    provide glyphs for a wide range of ligatures, contextual and stylistic
  3276    alternates, tabular and old-style figures, small capitals, automatic
  3277    fractions, swashes, and alternates specific to a given language. To allow
  3278    authors control over these font capabilities, the font-variant property
  3279    has been expanded for CSS3, it now functions as a shorthand for a set of
  3280    properties that provide control over stylistic font features.
  3282   <h3 id=glyph-selection-positioning><span class=secno>6.1 </span>Glyph
  3283    selection and positioning</h3>
  3285   <p>Simple fonts used for displaying Latin text use a very basic processing
  3286    model, fonts contain a <a href="#character-map"><em>character map</em></a>
  3287    which maps a given character to a glyph for that character. Glyphs for
  3288    subsequent characters are simply placed next in line along a run of text.
  3289    Font formats such as OpenType and AAT (Apple Advanced Typography) use a
  3290    richer processing model, the glyph for a given character can be chosen and
  3291    positioned not just based on a single character, but also based on
  3292    surrounding characters along with the language, script, and features
  3293    enabled for the text. Font features may be required for specific scripts,
  3294    or recommended as enabled by default or they may be stylistic features
  3295    meant to be used under author control.
  3297   <p>For a good visual overview of these features, see the <a
  3298    href="#OPENTYPE-FONT-GUIDE"
  3299    rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
  3300    For a detailed description of glyph processing for OpenType fonts, see <a
  3301    href="#WINDOWS-GLYPH-PROC"
  3302    rel=biblioentry>[WINDOWS-GLYPH-PROC]<!--{{WINDOWS-GLYPH-PROC}}--></a>.
  3304   <p>Stylistic font features can be classified into two broad categories,
  3305    ones that affect the harmonization of glyph shapes with the surrounding
  3306    context, such as kerning and ligature features, and those such as the
  3307    small-caps, subscript/superscript and alternate features that affect shape
  3308    selection.
  3310   <p>The subproperties of font-variant listed below are used to control these
  3311    stylistic font features; they do not control features that are required
  3312    for displaying certain scripts, such as the OpenType features used when
  3313    displaying Arabic or Indic language text. They affect glyph selection and
  3314    positioning, they do not affect font selection as described in the font
  3315    matching section (except in cases required for compatibility with CSS
  3316    2.1).
  3318   <p>To assure consistent behavior across user agents, the equivalent
  3319    OpenType property settings are listed for individual properties and must
  3320    be considered normative. When using other font formats these should be
  3321    used as a guideline to map CSS font feature property values to specific
  3322    font features.
  3324   <h3 id=language-specific-support><span class=secno>6.2
  3325    </span>Language-specific display</h3>
  3327   <p>OpenType also supports language-specific glyph selection and
  3328    positioning, so that text can be displayed correctly in cases where the
  3329    language dictates a specific display behavior. Languages often share a
  3330    common script but the shape of certain letters may vary across those
  3331    languages, such as the variations in certain Cyrillic letters used in
  3332    Russian and Bulgarian text. In Latin text, it's common to render "fi" with
  3333    an explicit fi-ligature that lacks a dot on the "i". However, in languages
  3334    such as Turkish which uses both a dotted-i and a dotless-i, it's important
  3335    to not use this ligature or use a specialized version that contains a dot
  3336    over the "i". The example below shows language-specific variations based
  3337    on stylistic traditions found in Spanish, Italian and French orthography:
  3339   <div class=featex><img alt="language specific forms, spanish"
  3340    src=locl-1.png></div>
  3342   <div class=featex><img alt="language specific forms, italian"
  3343    src=locl-2.png></div>
  3345   <div class=featex><img alt="language specific forms, french"
  3346    src=locl-3.png></div>
  3348   <p>If the content language of the element is known, according to the rules
  3349    of the <a
  3350    href="http://www.w3.org/TR/CSS21/conform.html#doclanguage">document
  3351    language</a>, user agents are required to infer the OpenType language
  3352    system from the content language and use that when selecting and
  3353    positioning glyphs using an OpenType font.
  3355   <p>For OpenType fonts, in some cases it may be necessary to explicitly
  3356    declare the OpenType language to be used, for example when displaying text
  3357    in a given language that uses the typographic conventions of another
  3358    language or when the font does not explicitly support a given language but
  3359    supports a language that shares common typographic conventions. The ‘<a
  3360    href="#propdef-font-language-override"><code
  3361    class=property>font-language-override</code></a>’ property is used for
  3362    this purpose.
  3364   <p class=issue>Should user agents be allowed to infer the OpenType language
  3365    or simply use only the default language system? Do we also need a
  3366    normative definition of how the script system is inferred?</p>
  3367   <!-- prop: font-kerning -->
  3369   <h3 id=font-kerning-prop><span class=secno>6.3 </span>Kerning: the <a
  3370    href="#propdef-font-kerning">font-kerning</a> property</h3>
  3372   <table class=propdef id=namefont-kerningvalueauto-normal-noneini>
  3373    <tbody>
  3374     <tr>
  3375      <td>Name:
  3377      <td><dfn id=propdef-font-kerning>font-kerning</dfn>
  3379     <tr>
  3380      <td>Value:
  3382      <td>auto | normal | none
  3384     <tr>
  3385      <td>Initial:
  3387      <td>auto
  3389     <tr>
  3390      <td>Applies to:
  3392      <td>all elements
  3394     <tr>
  3395      <td>Inherited:
  3397      <td>yes
  3399     <tr>
  3400      <td>Percentages:
  3402      <td>N/A
  3404     <tr>
  3405      <td>Media:
  3407      <td>visual
  3409     <tr>
  3410      <td>Computed value:
  3412      <td>as specified
  3414     <tr>
  3415      <td>Animatable:
  3417      <td>no
  3418   </table>
  3420   <p>Kerning is the contextual adjustment of inter-glyph spacing. This
  3421    property controls metric kerning, kerning that utilizes adjustment data
  3422    contained in the font. The value ‘<a href="#normal2"><code
  3423    class=property>normal</code></a>’ implies that kerning is applied while
  3424    the value ‘<code class=property>none</code>’ implies that kerning is
  3425    not applied when rendering text. If the value is ‘<code
  3426    class=property>auto</code>’, a user agent is free to choose whether
  3427    kerning is enabled or not by default and to vary that default based on the
  3428    underlying text script.
  3430   <p>For fonts that do not include kerning data this property will have no
  3431    visible effect. When rendering with OpenType fonts, the <a
  3432    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>
  3433    specification suggests that kerning be enabled by default. When kerning is
  3434    enabled, the OpenType <span class=tag>kern</span> feature is enabled (for
  3435    vertical text runs the <span class=tag>vkrn</span> feature is enabled).
  3436    User agents must also support fonts that only support kerning via data
  3437    contained in a ‘<code class=property>kern</code>’ font table, as
  3438    detailed in the OpenType specification. Authors may prefer to disable
  3439    kerning in situations where performance is more important that precise
  3440    appearance. If the ‘<code class=property>letter-spacing</code>’
  3441    property is defined, kerning adjustments are considered part of the
  3442    default spacing, letter spacing adjustments are made after kerning has
  3443    been applied.</p>
  3444   <!-- prop: font-variant-ligatures -->
  3446   <h3 id=font-variant-ligatures-prop><span class=secno>6.4 </span>Ligatures:
  3447    the <a href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
  3448    property</h3>
  3450   <table class=propdef id=namefont-variant-ligaturesvaluenormal-no>
  3451    <tbody>
  3452     <tr>
  3453      <td>Name:
  3455      <td><dfn id=propdef-font-variant-ligatures>font-variant-ligatures</dfn>
  3457     <tr>
  3458      <td>Value:
  3460      <td>normal | none | [ &lt;common-lig-values> ||
  3461       &lt;discretionary-lig-values> || &lt;historical-lig-values> ||
  3462       &lt;contextual-alt-values> ]
  3464     <tr>
  3465      <td>Initial:
  3467      <td>normal
  3469     <tr>
  3470      <td>Applies to:
  3472      <td>all elements
  3474     <tr>
  3475      <td>Inherited:
  3477      <td>yes
  3479     <tr>
  3480      <td>Percentages:
  3482      <td>N/A
  3484     <tr>
  3485      <td>Media:
  3487      <td>visual
  3489     <tr>
  3490      <td>Computed value:
  3492      <td>as specified
  3494     <tr>
  3495      <td>Animatable:
  3497      <td>no
  3498   </table>
  3500   <p>Ligatures and contextual forms are ways of combining glyphs to produce
  3501    more harmonized forms. A value of ‘<a href="#normal2"><code
  3502    class=property>normal</code></a>’ implies that common default features
  3503    are enabled, <a href="#font-feature-resolution">as described in detail in
  3504    the next section</a>. For OpenType fonts, common ligatures and contextual
  3505    forms are on by default, discretionary and historical ligatures are not. A
  3506    value of ‘<code class=property>none</code>’ implies that all types of
  3507    ligatures and contextual forms covered by this property are explicitly
  3508    disabled. In situations where ligatures are not considered necessary, this
  3509    may improve the speed of text rendering.
  3511   <pre
  3512    class=prod><dfn id=ltcommon-lig-values><var>&lt;common-lig-values></var></dfn>        = [ common-ligatures | no-common-ligatures ]</pre>
  3514   <pre
  3515    class=prod><dfn id=ltdiscretionary-lig-values><var>&lt;discretionary-lig-values></var></dfn> = [ discretionary-ligatures | no-discretionary-ligatures ]</pre>
  3517   <pre
  3518    class=prod><dfn id=lthistorical-lig-values><var>&lt;historical-lig-values></var></dfn>    = [ historical-ligatures | no-historical-ligatures ]</pre>
  3520   <pre
  3521    class=prod><dfn id=ltcontextual-alt-valuesgt><var>&lt;contextual-alt-values&gt;</var></dfn>    = [ contextual | no-contextual ]</pre>
  3523   <p>Individual values have the following meanings:
  3525   <dl>
  3526    <dt><dfn id=common-ligatures>common-ligatures</dfn>
  3528    <dd>Enables display of common ligatures (OpenType features: <span
  3529     class=tag>liga, clig</span>). For OpenType fonts, common ligatures are
  3530     enabled by default.
  3531   </dl>
  3533   <div class=featex><img alt="common ligature example" src=liga.png></div>
  3535   <dl>
  3536    <dt><dfn id=no-common-ligatures>no-common-ligatures</dfn>
  3538    <dd>Disables display of common ligatures (OpenType features: <span
  3539     class=tag>liga, clig</span>).
  3541    <dt><dfn id=discretionary-ligatures>discretionary-ligatures</dfn>
  3543    <dd>Enables display of discretionary ligatures (OpenType feature: <span
  3544     class=tag>dlig</span>). Which ligatures are discretionary, or optional,
  3545     is decided by the type designer so authors will need to refer to the
  3546     documentation of a given font to understand which ligatures are
  3547     considered discretionary.
  3548   </dl>
  3550   <div class=featex><img alt="discretionary ligature example" src=dlig.png></div>
  3552   <dl>
  3553    <dt><dfn id=no-discretionary-ligatures>no-discretionary-ligatures</dfn>
  3555    <dd>Disables display of discretionary ligatures (OpenType feature: <span
  3556     class=tag>dlig</span>).
  3558    <dt><dfn id=historical-ligatures>historical-ligatures</dfn>
  3560    <dd>Enables display of historical ligatures (OpenType feature: <span
  3561     class=tag>hlig</span>).
  3562   </dl>
  3564   <div class=featex><img alt="historical ligature example" src=hlig.png></div>
  3566   <dl>
  3567    <dt><dfn id=no-historical-ligatures>no-historical-ligatures</dfn>
  3569    <dd>Disables display of historical ligatures (OpenType feature: <span
  3570     class=tag>hlig</span>).
  3572    <dt><dfn id=contextual>contextual</dfn>
  3574    <dd>Enables display of contextual alternates (OpenType feature: <span
  3575     class=tag>calt</span>). Although not strictly a ligature feature, like
  3576     ligatures this feature is commonly used to harmonize the shapes of glyphs
  3577     with the surrounding context. For OpenType fonts, this feature is on by
  3578     default.
  3579   </dl>
  3581   <div class=featex><img alt="contextual alternate example" src=calt.png></div>
  3583   <dl>
  3584    <dt><dfn id=no-contextual>no-contextual</dfn>
  3586    <dd>Disables display of contextual alternates (OpenType feature: <span
  3587     class=tag>calt</span>).
  3588   </dl>
  3590   <p>Required ligatures, needed for correctly rendering complex scripts, are
  3591    not affected by the settings above, including ‘<code
  3592    class=property>none</code>’ (OpenType feature: <span
  3593    class=tag>rlig</span>).</p>
  3594   <!-- prop: font-variant-position -->
  3596   <h3 id=font-variant-position-prop><span class=secno>6.5 </span>Subscript
  3597    and superscript forms: the <a
  3598    href="#propdef-font-variant-position">font-variant-position</a> property</h3>
  3600   <table class=propdef id=namefont-variant-positionvaluenormal-sub>
  3601    <tbody>
  3602     <tr>
  3603      <td>Name:
  3605      <td><dfn id=propdef-font-variant-position>font-variant-position</dfn>
  3607     <tr>
  3608      <td>Value:
  3610      <td>normal | sub | super
  3612     <tr>
  3613      <td>Initial:
  3615      <td>normal
  3617     <tr>
  3618      <td>Applies to:
  3620      <td>all elements
  3622     <tr>
  3623      <td>Inherited:
  3625      <td>yes
  3627     <tr>
  3628      <td>Percentages:
  3630      <td>N/A
  3632     <tr>
  3633      <td>Media:
  3635      <td>visual
  3637     <tr>
  3638      <td>Computed value:
  3640      <td>as specified
  3642     <tr>
  3643      <td>Animatable:
  3645      <td>no
  3646   </table>
  3648   <p>This property is used to enable typographic subscript and superscript
  3649    glyphs. These are alternate glyphs designed within the same em-box as
  3650    default glyphs and are intended to be laid out on the same baseline as the
  3651    default glyphs, with no resizing or repositioning of the baseline. They
  3652    are explicitly designed to match the surrounding text and to be more
  3653    readable without affecting the line height.
  3655   <div class=figure><img alt="comparison between real subscript glyphs and
  3656    synthesized ones" src=realsubscripts.png>
  3657    <p class=caption>Subscript glyphs (top) vs. typical synthesized subscripts
  3658     (bottom)
  3659   </div>
  3661   <p>The values ‘<code class=property>sub</code>’ and ‘<code
  3662    class=property>super</code>’ imply the appropriate variant glyph is
  3663    displayed when available in the font (OpenType features: <span
  3664    class=tag>subs, sups</span>). A value of ‘<a href="#normal2"><code
  3665    class=property>normal</code></a>’ implies neither of these alternate
  3666    glyphs are substituted.
  3668   <p>Because of the semantic nature of subscripts and superscripts, when the
  3669    value is either ‘<code class=property>sub</code>’ or ‘<code
  3670    class=property>super</code>’ for a given contiguous run of text, if a
  3671    variant glyph is not available for all the characters in the run,
  3672    simulated glyphs must be synthesized for all characters using reduced
  3673    forms of the glyphs that would be used without this feature applied. This
  3674    is done to avoid a mixture of variant glyphs and synthesized ones that
  3675    would not align correctly.
  3677   <p>In the case of OpenType fonts that lack subscript or superscript glyphs
  3678    for a given character, user agents must use the appropriate subscript and
  3679    superscript metrics specified in the selected font's <a
  3680    href="http://www.microsoft.com/typography/otspec/os2.htm#subxs">OS/2
  3681    table</a> <a href="#OPENTYPE"
  3682    rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> to calculate the size
  3683    and offset of the synthesized substitutes.
  3685   <p>In the past, user agents have used font-size and vertical-align to
  3686    simulate subscripts and superscripts for the <span class=tag>sub</span>
  3687    and <span class=tag>sup</span> elements. To allow a backwards compatible
  3688    way of defining subscripts and superscripts, it is recommended that
  3689    authors use conditional rules <a href="#CSS3-CONDITIONAL"
  3690    rel=biblioentry>[CSS3-CONDITIONAL]<!--{{CSS3-CONDITIONAL}}--></a> so that
  3691    older user agents will still render subscripts and superscripts via the
  3692    older mechanism.
  3694   <p>Authors should note that fonts typically only provide subscript and
  3695    superscript glyphs for a subset of all characters supported by the font.
  3696    While subscript and superscript glyphs are often available for Latin
  3697    numbers, glyphs for punctuation and letter characters are less frequently
  3698    provided. The synthetic fallback rules defined for this property assure
  3699    that subscripts and superscripts will always appear but the appearance may
  3700    not match author expectations if the font used does not provide the
  3701    appropriate alternate glyph for all characters contained in a subscript or
  3702    superscript.
  3704   <div class=figure><img alt="alternate superscripts vs. glyphs synthesized
  3705    using superscript metrics" src=superscript-alt-synth.png>
  3706    <p class=caption>Superscript alternate glyph (left), synthesized
  3707     superscript glyphs (middle), and incorrect mixture of the two (right)
  3708   </div>
  3710   <p>This property is not cumulative, applying it to subelements within a
  3711    subscript or superscript won't nest the placement of a subscript or
  3712    superscript glyph. Images contained within text runs where the value of
  3713    this property is ‘<code class=property>sub</code>’ or ‘<code
  3714    class=property>super</code>’ will be drawn just as they would if the
  3715    value was ‘<a href="#normal2"><code class=property>normal</code></a>’.
  3716    Likewise, text decorations such as underlines or emphasis marks will
  3717    render in the same position as they would for the default glyphs, since
  3718    this property does not affect the baseline position.
  3720   <p>Because of these limitations, font-variant-position is not recommended
  3721    for use in user agent stylesheets. Authors should use it in cases where
  3722    subscripts or superscripts will only contain the narrow range of
  3723    characters supported by the fonts specified.
  3725   <div class=example>
  3726    <p>A typical user agent default style for the <span class=tag>sub</span>
  3727     element:</p>
  3729    <pre>sub {
  3730   vertical-align: sub;
  3731   font-size: smaller;
  3732   line-height: normal;
  3734 </pre>
  3736    <p>Using font-variant-position to specify typographic subscripts in a way
  3737     that will still show subscripts in older user agents:</p>
  3739    <pre>@supports ( font-variant-position: sub ) {
  3741   sub {
  3742     vertical-align: inherit;
  3743     font-size: 100%;
  3744     line-height: inherit;
  3745     font-variant-position: sub;
  3749 </pre>
  3751    <p>User agents that support the ‘<a
  3752     href="#propdef-font-variant-position"><code
  3753     class=property>font-variant-position</code></a>’ property will select a
  3754     subscript variant glyph and render this without adjusting the baseline or
  3755     font-size. Older user agents will ignore the ‘<a
  3756     href="#propdef-font-variant-position"><code
  3757     class=property>font-variant-position</code></a>’ property definition
  3758     and use the standard defaults for subscripts.</p>
  3759   </div>
  3760   <!-- prop: font-variant-caps -->
  3762   <h3 id=font-variant-caps-prop><span class=secno>6.6 </span>Capitalization:
  3763    the <a href="#propdef-font-variant-caps">font-variant-caps</a> property</h3>
  3765   <table class=propdef id=namefont-variant-capsvaluenormal-small-c>
  3766    <tbody>
  3767     <tr>
  3768      <td>Name:
  3770      <td><dfn id=propdef-font-variant-caps>font-variant-caps</dfn>
  3772     <tr>
  3773      <td>Value:
  3775      <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
  3776       | unicase | titling-caps
  3778     <tr>
  3779      <td>Initial:
  3781      <td>normal
  3783     <tr>
  3784      <td>Applies to:
  3786      <td>all elements
  3788     <tr>
  3789      <td>Inherited:
  3791      <td>yes
  3793     <tr>
  3794      <td>Percentages:
  3796      <td>N/A
  3798     <tr>
  3799      <td>Media:
  3801      <td>visual
  3803     <tr>
  3804      <td>Computed value:
  3806      <td>as specified
  3808     <tr>
  3809      <td>Animatable:
  3811      <td>no
  3812   </table>
  3814   <p>Specifies control over capitalized forms.
  3816   <p>Individual values have the following meanings:
  3818   <dl>
  3819    <dt><dfn id=normal>normal</dfn>
  3821    <dd>None of the features listed below are enabled.
  3823    <dt><dfn id=small-caps>small-caps</dfn>
  3825    <dd>Enables display of small capitals (OpenType feature: <span
  3826     class=tag>smcp</span>). Small-caps glyphs typically use the form of
  3827     uppercase letters but are reduced to the size of lowercase letters.
  3828   </dl>
  3830   <div class=featex><img alt="small-caps example" src=smcp.png></div>
  3832   <dl>
  3833    <dt><dfn id=all-small-caps>all-small-caps</dfn>
  3835    <dd>Enables display of small capitals for both upper and lowercase letters
  3836     (OpenType features: <span class=tag>c2sc, smcp</span>).
  3838    <dt><dfn id=petite-caps>petite-caps</dfn>
  3840    <dd>Enables display of petite capitals (OpenType feature: <span
  3841     class=tag>pcap</span>).
  3843    <dt><dfn id=all-petite-caps>all-petite-caps</dfn>
  3845    <dd>Enables display of petite capitals for both upper and lowercase
  3846     letters (OpenType features: <span class=tag>c2pc, pcap</span>).
  3848    <dt><dfn id=unicase>unicase</dfn>
  3850    <dd>Enables display of mixture of small capitals for uppercase letters
  3851     with normal lowercase letters (OpenType feature: <span
  3852     class=tag>unic</span>).
  3854    <dt><dfn id=titling-caps>titling-caps</dfn>
  3856    <dd>Enables display of titling capitals (OpenType feature: <span
  3857     class=tag>titl</span>). Uppercase letter glyphs are often designed for
  3858     use with lowercase letters. When used in all uppercase titling sequences
  3859     they can appear too strong. Titling capitals are designed specifically
  3860     for this situation.
  3861   </dl>
  3863   <p>This property allows the selection of alternate glyphs used for small or
  3864    petite capitals or for titling. These glyphs are specifically designed to
  3865    blend well with the surrounding normal glyphs, to maintain the weight and
  3866    readability which suffers when text is simply resized to fit this purpose.
  3868   <p>The availability of these glyphs is based on whether a given feature is
  3869    defined or not in the feature list of the font. User agents can optionally
  3870    decide this on a per-script basis but should explicitly not decide this on
  3871    a per-character basis.
  3873   <p>Some fonts may only support a subset or none of the features described
  3874    for this property. For backwards compatibility with CSS 2.1, if ‘<a
  3875    href="#small-caps"><code class=property>small-caps</code></a>’ or ‘<a
  3876    href="#all-small-caps"><code class=property>all-small-caps</code></a>’
  3877    is specified but small-caps glyphs are not available for a given font,
  3878    user agents should simulate a small-caps font, for example by taking a
  3879    normal font and replacing the glyphs for lowercase letters with scaled
  3880    versions of the glyphs for uppercase characters (replacing the glyphs for
  3881    both upper and lowercase letters in the case of ‘<a
  3882    href="#all-small-caps"><code class=property>all-small-caps</code></a>’).
  3884   <div class=figure style="padding: 0; margin: auto;"><img alt="synthetic vs.
  3885    real small-caps" class=hires src=synthetic-vs-real-small-caps.png
  3886    width=512px>
  3887    <p class=caption>Synthetic vs. real small-caps
  3888   </div>
  3890   <p>To match the surrounding text, a font may provide alternate glyphs for
  3891    caseless characters when these features are enabled but when a user agent
  3892    simulates small capitals, it must not attempt to simulate alternates for
  3893    codepoints which are considered caseless.
  3895   <div class=figure style="padding: 0; margin: auto;"><img alt="caseless
  3896    characters with small-caps, all-small-caps enabled" class=hires
  3897    src=small-capitals-variations.png width=418px>
  3898    <p class=caption>Caseless characters with small-caps, all-small-caps
  3899     enabled
  3900   </div>
  3902   <p>If either ‘<a href="#petite-caps"><code
  3903    class=property>petite-caps</code></a>’ or ‘<a
  3904    href="#all-petite-caps"><code class=property>all-petite-caps</code></a>’
  3905    is specified for a font that doesn't support these features, the property
  3906    behaves as if ‘<a href="#small-caps"><code
  3907    class=property>small-caps</code></a>’ or ‘<a
  3908    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
  3909    respectively, had been specified. If ‘<a href="#unicase"><code
  3910    class=property>unicase</code></a>’ is specified for a font that doesn't
  3911    support that feature, the property behaves as if ‘<a
  3912    href="#small-caps"><code class=property>small-caps</code></a>’ was
  3913    applied only to lowercased uppercase letters. If ‘<a
  3914    href="#titling-caps"><code class=property>titling-caps</code></a>’ is
  3915    specified with a font that does not support this feature, this property
  3916    has no visible effect. When simulated small capital glyphs are used, for
  3917    scripts that lack uppercase and lowercase letters, ‘<a
  3918    href="#small-caps"><code class=property>small-caps</code></a>’, ‘<a
  3919    href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
  3920    ‘<a href="#petite-caps"><code class=property>petite-caps</code></a>’,
  3921    ‘<a href="#all-petite-caps"><code
  3922    class=property>all-petite-caps</code></a>’ and ‘<a
  3923    href="#unicase"><code class=property>unicase</code></a>’ have no visible
  3924    effect.
  3926   <p>When casing transforms are used to simulate small capitals, the casing
  3927    transformations should match those used for the <span
  3928    class=property>‘<code class=property>text-transform</code>’</span>
  3929    property.
  3931   <p>As a last resort, unscaled uppercase letter glyphs in a normal font may
  3932    replace glyphs in a small-caps font so that the text appears in all
  3933    uppercase letters.
  3935   <div class=figure style="padding: 0; margin: auto;"><img alt="using
  3936    all-small-caps in acronym-laden text" class=hires
  3937    src=acronym-laden-text.png width=596px>
  3938    <p class=caption>Using small capitals to improve readability in
  3939     acronym-laden text
  3940   </div>
  3942   <div class=example>
  3943    <p>Quotes rendered italicised, with small-caps on the first line:</p>
  3945    <pre>blockquote            { font-style: italic; }
  3946 blockquote:first-line { font-variant: small-caps; }
  3948 &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>
  3949 </pre>
  3950   </div>
  3951   <!-- prop: font-variant-numeric -->
  3953   <h3 id=font-variant-numeric-prop><span class=secno>6.7 </span>Numerical
  3954    formatting: the <a
  3955    href="#propdef-font-variant-numeric">font-variant-numeric</a> property</h3>
  3957   <table class=propdef id=namefont-variant-numericvaluenormal-ltnu>
  3958    <tbody>
  3959     <tr>
  3960      <td>Name:
  3962      <td><dfn id=propdef-font-variant-numeric>font-variant-numeric</dfn>
  3964     <tr>
  3965      <td>Value:
  3967      <td>normal | [ &lt;numeric-figure-values&gt; ||
  3968       &lt;numeric-spacing-values&gt; || &lt;numeric-fraction-values&gt; ||
  3969       ordinal || slashed-zero ]
  3971     <tr>
  3972      <td>Initial:
  3974      <td>normal
  3976     <tr>
  3977      <td>Applies to:
  3979      <td>all elements
  3981     <tr>
  3982      <td>Inherited:
  3984      <td>yes
  3986     <tr>
  3987      <td>Percentages:
  3989      <td>N/A
  3991     <tr>
  3992      <td>Media:
  3994      <td>visual
  3996     <tr>
  3997      <td>Computed value:
  3999      <td>as specified
  4001     <tr>
  4002      <td>Animatable:
  4004      <td>no
  4005   </table>
  4007   <p>Specifies control over numerical forms.
  4009   <pre
  4010    class=prod><dfn id=ltnumeric-figure-valuesgt><var>&lt;numeric-figure-values&gt;</var></dfn>   = [ lining-nums | oldstyle-nums ]</pre>
  4012   <pre
  4013    class=prod><dfn id=ltnumeric-spacing-valuesgt><var>&lt;numeric-spacing-values&gt;</var></dfn>  = [ proportional-nums | tabular-nums ]</pre>
  4015   <pre
  4016    class=prod><dfn id=ltnumeric-fraction-valuesgt><var>&lt;numeric-fraction-values&gt;</var></dfn> = [ diagonal-fractions | stacked-fractions ]</pre>
  4018   <p>Individual values have the following meanings:
  4020   <dl>
  4021    <dt><dfn id=normal0>normal</dfn>
  4023    <dd>None of the features listed below are enabled.
  4025    <dt><dfn id=lining-nums>lining-nums</dfn>
  4027    <dd>Enables display of lining numerals (OpenType feature: <span
  4028     class=tag>lnum</span>).
  4030    <dt><dfn id=oldstyle-nums>oldstyle-nums</dfn>
  4032    <dd>Enables display of old-style numerals (OpenType feature: <span
  4033     class=tag>onum</span>).
  4035    <dt><dfn id=proportional-nums>proportional-nums</dfn>
  4037    <dd>Enables display of proportional numerals (OpenType feature: <span
  4038     class=tag>pnum</span>).
  4040    <dt><dfn id=tabular-nums>tabular-nums</dfn>
  4042    <dd>Enables display of tabular numerals (OpenType feature: <span
  4043     class=tag>tnum</span>).
  4044   </dl>
  4046   <p>The example below shows how these different properties can be combined
  4047    to influence the rendering of tabular data with fonts that support these
  4048    features. Within normal paragraph text, proportional numbers are used
  4049    while tabular numbers are used so that columns of numbers line up
  4050    properly:
  4052   <div class=figure style="padding: 0; margin: auto;"><img alt="combining
  4053    number styles" src=numberstyles.png>
  4054    <p class=caption>Using number styles
  4055   </div>
  4057   <dl>
  4058    <dt><dfn id=diagonal-fractions>diagonal-fractions</dfn>
  4060    <dd>Enables display of lining diagonal fractions (OpenType feature: <span
  4061     class=tag>frac</span>).
  4062   </dl>
  4064   <div class=featex><img alt="diagonal fraction example" src=frac.png></div>
  4066   <dl>
  4067    <dt><dfn id=stacked-fractions>stacked-fractions</dfn>
  4069    <dd>Enables display of lining stacked fractions (OpenType feature: <span
  4070     class=tag>afrc</span>).
  4071   </dl>
  4073   <div class=featex><img alt="stacked fraction example" src=afrc.png></div>
  4075   <dl>
  4076    <dt><dfn id=ordinal>ordinal</dfn>
  4078    <dd>Enables display of forms used with ordinal numbers (OpenType feature:
  4079     <span class=tag>ordn</span>).
  4081    <dt><dfn id=slashed-zero>slashed-zero</dfn>
  4083    <dd>Enables display of slashed zeros (OpenType feature: <span
  4084     class=tag>zero</span>).
  4085   </dl>
  4087   <div class=featex><img alt="slashed zero example" src=zero.png></div>
  4089   <div class=example id=steak-marinade>
  4090    <p>A simple flank steak marinade recipe, rendered with automatic fractions
  4091     and old-style numerals:</p>
  4093    <pre>.amount { font-variant-numeric: oldstyle-nums diagonal-fractions; }
  4095 &lt;h4>Steak marinade:&lt;/h4>
  4096 &lt;ul>
  4097   &lt;li>&lt;span class="amount">2&lt;/span> tbsp olive oil&lt;/li>
  4098   &lt;li>&lt;span class="amount">1&lt;/span> tbsp lemon juice&lt;/li>
  4099   &lt;li>&lt;span class="amount">1&lt;/span> tbsp soy sauce&lt;/li>
  4100   &lt;li>&lt;span class="amount">1 1/2&lt;/span> tbsp dry minced onion&lt;/li>
  4101   &lt;li>&lt;span class="amount">2 1/2&lt;/span> tsp italian seasoning&lt;/li>
  4102   &lt;li>Salt &amp;amp; pepper&lt;/li>
  4103 &lt;/ul>
  4105 &lt;p>Mix the meat with the marinade and let it sit covered in the refrigerator
  4106 for a few hours or overnight.&lt;/p>
  4107 </pre>
  4108   </div>
  4109   <!-- prop: font-variant-alternates -->
  4111   <h3 id=font-variant-alternates-prop><span class=secno>6.8 </span>Alternates
  4112    and swashes: the <a
  4113    href="#propdef-font-variant-alternates">font-variant-alternates</a>
  4114    property</h3>
  4116   <table class=propdef id=namefont-variant-alternatesvaluenormal-s>
  4117    <tbody>
  4118     <tr>
  4119      <td>Name:
  4121      <td><dfn
  4122       id=propdef-font-variant-alternates>font-variant-alternates</dfn>
  4124     <tr>
  4125      <td>Value:
  4127      <td>normal | [ stylistic(&lt;feature-value-name&gt;) || historical-forms
  4128       || styleset(&lt;feature-value-name&gt;#) ||
  4129       character-variant(&lt;feature-value-name&gt;#) ||
  4130       swash(&lt;feature-value-name&gt;) ||
  4131       ornaments(&lt;feature-value-name&gt;) ||
  4132       annotation(&lt;feature-value-name&gt;) ]
  4134     <tr>
  4135      <td>Initial:
  4137      <td>normal
  4139     <tr>
  4140      <td>Applies to:
  4142      <td>all elements
  4144     <tr>
  4145      <td>Inherited:
  4147      <td>yes
  4149     <tr>
  4150      <td>Percentages:
  4152      <td>N/A
  4154     <tr>
  4155      <td>Media:
  4157      <td>visual
  4159     <tr>
  4160      <td>Computed value:
  4162      <td>as specified
  4164     <tr>
  4165      <td>Animatable:
  4167      <td>no
  4168   </table>
  4170   <p>For any given character, fonts can provide a variety of alternate glyphs
  4171    in addition to the default glyph for that character. This property
  4172    provides control over the selection of these alternate glyphs.
  4174   <p>In cases where multiple alternates are possible, authors define a
  4175    <code>&lt;feature-value-name&gt;</code> using the
  4176    <code>@font-feature-values</code> rule described below to indicate the
  4177    specific alternate to be used. The nature of these alternates is font
  4178    specific, so the rule defines values for a specific font family or set of
  4179    families. When a particular value has not been defined for a given family,
  4180    the named value is treated as if the feature had omitted from the style
  4181    rule. If a given value is outside the range supported by a given font, the
  4182    value is ignored. These values never apply to generic font families, nor
  4183    to families selected as part of system font fallback. Values that behave
  4184    this way are marked as <em>font specific</em>.
  4186   <p>Individual values have the following meanings:
  4188   <dl>
  4189    <dt><dfn id=normal1>normal</dfn>
  4191    <dd>None of the features listed below are enabled.
  4193    <dt><dfn id=stylisticltfeature-value-namegt
  4194     title=stylistic>stylistic(&lt;feature-value-name&gt;)</dfn>
  4196    <dd>Enables display of stylistic alternates (<em>font specific</em>,
  4197     OpenType feature: <span class=tag>salt
  4198     &lt;feature-value-name&gt;</span>).
  4199   </dl>
  4201   <div class=featex><img alt="stylistic alternate example" src=salt.png></div>
  4203   <dl>
  4204    <dt><dfn id=historical-forms>historical-forms</dfn>
  4206    <dd>Enables display of historical forms (OpenType feature: <span
  4207     class=tag>hist</span>).
  4208   </dl>
  4210   <div class=featex><img alt="historical form example" src=hist.png></div>
  4212   <dl>
  4213    <dt><dfn id=stylesetltfeature-value-namegt
  4214     title=styleset>styleset(&lt;feature-value-name&gt;#)</dfn>
  4216    <dd>Enables display with stylistic sets (<em>font specific</em>, OpenType
  4217     feature: <span class=tag>ss&lt;feature-index&gt;</span> OpenType
  4218     currently defines <span class=tag>ss01</span> through <span
  4219     class=tag>ss20</span>).
  4220   </dl>
  4222   <div class=featex><img alt="styleset example" src=ssnn.png></div>
  4224   <dl>
  4225    <dt><dfn id=character-variantltfeature-value-namegt
  4226     title=character-variant>character-variant(&lt;feature-value-name&gt;#)</dfn>
  4229    <dd>Enables display of specific character variants (<em>font
  4230     specific</em>, OpenType feature: <span
  4231     class=tag>cv&lt;feature-index&gt;</span> OpenType currently defines <span
  4232     class=tag>cv01</span> through <span class=tag>cv99</span>).
  4234    <dt><dfn id=swashltfeature-value-namegt
  4235     title=swash>swash(&lt;feature-value-name&gt;)</dfn>
  4237    <dd>Enables display of swash glyphs (<em>font specific</em>, OpenType
  4238     feature: <span class=tag>swsh &lt;feature-index&gt;, cswh
  4239     &lt;feature-index&gt;</span>).
  4240   </dl>
  4242   <div class=featex><img alt="swash example" src=swsh.png></div>
  4244   <dl>
  4245    <dt><dfn id=ornamentsltfeature-value-namegt
  4246     title=ornaments>ornaments(&lt;feature-value-name&gt;)</dfn>
  4248    <dd>Enables replacement of default glyphs with ornaments, if provided in
  4249     the font (<em>font specific</em>, OpenType feature: <span class=tag>ornm
  4250     &lt;feature-index&gt;</span>). Some fonts may offer ornament glyphs as
  4251     alternates for a wide collection of characters; however, displaying
  4252     arbitrary characters (e.g., alphanumerics) as ornaments is poor practice
  4253     as it distorts the semantics of the data. Font designers are encouraged
  4254     to encode all ornaments (except those explicitly encoded in the Unicode
  4255     Dingbats blocks, etc.) as alternates for the bullet character (U+2022) to
  4256     allow authors to select the desired glyph using
  4257     &lt;feature-value-name&gt;.
  4258   </dl>
  4260   <div class=featex><img alt="ornaments example" src=ornm.png></div>
  4262   <dl>
  4263    <dt><dfn id=annotationltfeature-value-namegt
  4264     title=annotation>annotation(&lt;feature-value-name&gt;)</dfn>
  4266    <dd>Enables display of alternate annotation forms (<em>font specific</em>,
  4267     OpenType feature: <span class=tag>nalt &lt;feature-index&gt;</span>).
  4268   </dl>
  4270   <div class=featex><img alt="alternate annotation form example"
  4271    src=nalt.png></div>
  4273   <h3 id=font-feature-values><span class=secno>6.9 </span>Defining font
  4274    specific alternates: the <code>@font-feature-values</code> rule</h3>
  4276   <p>Several of the possible values of ‘<a
  4277    href="#propdef-font-variant-alternates"><code
  4278    class=property>font-variant-alternates</code></a>’ listed above are
  4279    labeled as "font specific". For these features fonts may define not just a
  4280    single glyph but a set of alternate glyphs with an index to select a given
  4281    alternate. Since these are font family specific, the
  4282    <code>@font-feature-values</code> rule is used to define named-values for
  4283    these indices for a given family.
  4285   <p>In the case of the swash Q in the example shown above, the swash could
  4286    be specified using these style rules:
  4288   <pre>
  4290 @font-feature-values Jupiter Sans {
  4291   @swash {
  4292     delicate: 1;
  4293     flowing: 2;
  4297 h2 { font-family: Jupiter Sans, sans-serif; }
  4299 /* show the second swash variant in h2 headings */
  4300 h2:first-letter { font-variant-alternates: swash(flowing); }
  4302 &lt;h2>Quick&lt;/h2></pre>
  4304   <p>When Jupiter Sans is present, the second alternate swash alternate will
  4305    be displayed. When not present, no swash character will be shown, since
  4306    the specific named-value "flowing" is only defined for the Jupiter Sans
  4307    family. The @-mark indicates the name of the property value for which a
  4308    named-value can be used. The name "flowing" is chosen by the author, the
  4309    values specified within a given font's data.
  4311   <p>In terms of the grammar, this specification defines the following
  4312    productions:
  4314   <pre><dfn id=fontfeaturevaluesrule>font_feature_values_rule</dfn>
  4315   : FONT_FEATURE_VALUES_SYM S* font_family_name_list S*
  4316     '{' S* feature_value_block? [ S* feature_value_block? ]* '}' S*
  4319 <dfn id=fontfamilynamelist>font_family_name_list</dfn>
  4320   : font_family_name [ S* ',' S* font_family_name ]*
  4323 <dfn id=fontfamilyname>font_family_name</dfn>
  4324   : STRING | [ IDENT [ S* IDENT ]* ]
  4327 <dfn id=featurevalueblock>feature_value_block</dfn>
  4328   : feature_type S*
  4329     '{' S* feature_value_definition? [ S* ';' S* feature_value_definition? ]* '}' S*
  4332 <dfn id=featuretype>feature_type</dfn>:
  4333   ATKEYWORD
  4336 <dfn id=featurevaluedefinition>feature_value_definition</dfn>
  4337   : IDENT S* ':' S* NUMBER [ S* NUMBER ]*
  4339 </pre>
  4341   <p>The following new token is introduced:
  4343   <pre>@{F}{O}{N}{T}{-}{F}{E}{A}{T}{U}{R}{E}{-}{V}{A}{L}{U}{E}{S}   {return FONT_FEATURE_VALUES_SYM;}
  4344 </pre>
  4346   <p>Feature value blocks are treated <a
  4347    href="http://www.w3.org/TR/CSS2/syndata.html#at-rules">similar to
  4348    at-rules</a>, they consist of everything up to the next block or
  4349    semi-colon, whichever comes first.
  4351   <p>Font feature values rules define a set of values for a specific font
  4352    feature as used for a given set of families. Effectively, they define a
  4353    mapping of ⟨family, feature, ident⟩ → ⟨values⟩ where
  4354    ⟨values⟩ are the indices used for specific features defined for a
  4355    given font.
  4357   <p>The font family list uses the same syntax as that used for the ‘<a
  4358    href="#descdef-font-family"><code class=property>font-family</code></a>’
  4359    property. Within feature value blocks, the feature type is ‘<code
  4360    class=css>@</code>’ followed by the name of the font-specific property
  4361    value (e.g. <a
  4362    href="#swashltfeature-value-namegt"><code>@swash</code></a>). The feature
  4363    type must match, using an ASCII case-insensitive comparison, one of the
  4364    <em>font specific</em> values of the <a
  4365    href="#propdef-font-variant-alternates"><code>font-variant-alternates</code></a>
  4366    property. The values associated with a given idenitifier are limited to
  4367    integer values 0 or greater.
  4369   <p>If syntax errors occur within the font family list, the entire rule must
  4370    be ignored. When syntax errors occur within a feature value definition,
  4371    such as invalid identifiers or values, the entire feature value definition
  4372    must be omitted, similar to the way syntax errors in style declarations
  4373    are handled. When the <code>&lt;feature-type></code> is invalid, the
  4374    entire associated feature value block must be ignored.
  4376   <pre>@font-feature-values Bongo {
  4377   @swash { ornate: 1; }
  4378   annotation { boxed: 4; } /* should be @annotation! */
  4379   @swash { double-loops: 1; flowing: -1; } /* negative value */
  4380   @ornaments ; /* incomplete definition */
  4381   @styleset { double-W: 14; sharp-terminals: 16 1 } /* missing ; */
  4382   <a href="http://www.angryalien.com/0504/shiningbunnies.html" style="text-decoration: none;">redrum</a>  /* random editing mistake */
  4383 }</pre>
  4385   <p>The example above is equivalent to:
  4387   <pre>@font-feature-values Bongo {
  4388   @swash { ornate: 1; }
  4389   @swash { double-loops: 1; }
  4390   @styleset { double-W: 14; sharp-terminals: 16 1; }
  4391 }</pre>
  4393   <p>If multiple <code>@font-feature-values</code> rules are defined for a
  4394    given family, the resulting values defined are the union of these rules.
  4395    This allows a set of named-values to be defined for a given font family
  4396    globally for a site and specific additions made per-page. If the same
  4397    &lt;feature-value-name&gt; is defined mulitple times for a given
  4398    font-variant value, the last defined value is used.
  4400   <pre>
  4401 site.css:
  4403   @font-feature-values Mercury Serif {
  4404     @styleset {
  4405       stacked-g: 3; /* "two-storey" versions of g, a */
  4406       stacked-a: 4;
  4410 page.css:
  4412   @font-feature-values Mercury Serif {
  4413     @styleset {
  4414       geometric-m: 7; /* alternate version of m */
  4418   body {
  4419     font-family: Mercury Serif, serif;
  4421     /* enable both the use of stacked g and alternate m */
  4422     font-variant-alternates: styleset(stacked-g, geometric-m);
  4423   }</pre>
  4425   <p>Only named font families are allowed for &lt;font-family&gt;, rules that
  4426    include generic or system fonts in the list of font families are
  4427    considered syntax errors and the contents of the rules are ignored.
  4428    However, if a user agent defines a generic font to be a specific named
  4429    font (e.g. Helvetica), the settings associated with that family name will
  4430    be used.
  4432   <p>For &lt;font-variant-property-value>, only font specific property value
  4433    names supported by the ‘<a href="#propdef-font-variant"><code
  4434    class=property>font-variant</code></a>’ property are recognized,
  4435    definitions for other value names cause a syntax error and are ignored.
  4436    Each property value that is font specific is clearly marked as such.
  4437    Feature value names follow the rules of CSS user identifiers and are
  4438    case-sensitive. They are unique only for a given set of font families and
  4439    font-variant property value; the same identifier used with a different
  4440    font-variant property value is treated as a separate and distinct value.
  4442   <p>Using a commonly named value allows authors to use a single style rule
  4443    to cover a set of fonts for which the underlying selector is different for
  4444    each font. If either font in the example below is found, a circled number
  4445    glyph will be used:
  4447   <pre>@font-feature-values Taisho Gothic {
  4448   @annotation { boxed: 1; circled: 4; }
  4451 @font-feature-values Otaru Kisa {
  4452   @annotation { circled: 1; black-boxed: 3; }
  4455 h3.title {
  4456   /* circled form defined for both fonts */
  4457   font-family: Taisho Gothic, Otaru Kisa;
  4458   font-variant: annotation(circled);
  4459 }</pre>
  4461   <p>Most font specific font-variant property values take a single value
  4462    (e.g. swash). The character-variant property value allows two values and
  4463    styleset allows an unlimited number. If a larger number of values are
  4464    assigned to a given name, a syntax error occurs and the entire
  4465    &lt;font-feature-values-declaration&gt; is ignored.
  4467   <p>For the styleset property value, multiple values indicate the style sets
  4468    to be enabled. Values between 1 and 99 enable OpenType features <span
  4469    class=tag>ss01</span> through <span class=tag>ss99</span>. However, the
  4470    OpenType standard only officially defines <span class=tag>ss01</span>
  4471    through <span class=tag>ss20</span>. Values greater than 99 or equal to 0
  4472    are ignored but do not generate a syntax error when parsed.
  4474   <pre>@font-feature-values Mars Serif {
  4475   @styleset { 
  4476     alt-g: 1;        /* implies ss01 = 1 */
  4477     curly-quotes: 3; /* implies ss03 = 1 */
  4478     code: 4 5;       /* implies ss04 = 1, ss05 = 1 */
  4481   @styleset {
  4482     dumb: 125;        /* &gt;99, ignored */
  4485   @swash {
  4486     swishy: 3 5;     /* more than 1 value for swash, syntax error */
  4490 p.codeblock {
  4491   /* implies ss03 = 1, ss04 = 1, ss05 = 1 */
  4492   font-variant-alternates: styleset(curly-quotes, code);
  4493 }</pre>
  4495   <p>For character-variant, a single value between 1 and 99 indicates the
  4496    enabling of OpenType feature <span class=tag>cv01</span> through <span
  4497    class=tag>cv99</span>. For OpenType fonts, values greater than 99 or equal
  4498    to 0 are ignored but do not generate a syntax error when parsed. When two
  4499    values are listed, the first value indicates the feature used and the
  4500    second the value passed for that feature. When two value names imply
  4501    different settings for the same underlying feature the last setting is
  4502    used.
  4504   <pre>@font-feature-values MM Greek {
  4505   @character-variant { alpha-2: 1 2; }   /* implies cv01 = 2 */
  4506   @character-variant { beta-3: 2 3; }    /* implies cv02 = 3 */
  4507   @character-variant { epsilon: 5 3 6; } /* more than 2 values, syntax error, ignored */
  4508   @character-variant { gamma: 12; }      /* implies cv12 = 1 */
  4509   @character-variant { zeta:   20 3; }   /* implies cv20 = 3 */
  4510   @character-variant { zeta-2: 20 2; }   /* implies cv20 = 2 */
  4511   @character-variant { silly: 105; }     /* &gt;99, ignored */
  4512   @character-variant { dumb: 323 3; }    /* &gt;99, ignored */
  4515 #title {
  4516   /* use the third alternate beta, first alternate gamma */
  4517   font-variant-alternates: character-variant(beta-3, gamma);
  4520 p {
  4521   /* zeta-2 follows zeta, implies cv20 = 2  */
  4522   font-variant-alternates: character-variant(zeta, zeta-2);
  4525 .special {
  4526   /* zeta follows zeta-2, implies cv20 = 3  */
  4527   font-variant-alternates: character-variant(zeta-2, zeta);
  4528 }</pre>
  4530   <p>See the <a href="#om-fontfeaturevalues">object model reference
  4531    section</a> for a description of the interfaces used to modify these rules
  4532    via the CSS Object Model.
  4534   <div class=figure><img alt="Matching text on Byzantine seals using
  4535    character variants" src=byzantineseal.png>
  4536    <p class=caption>Byzantine seal text displayed with character variants
  4537   </div>
  4539   <div class=example>
  4540    <p>In the figure above, the text in red is rendered using a font
  4541     containing character variants that mimic the character forms found on a
  4542     Byzantine seal from the 8th century A.D. Two lines below is the same text
  4543     displayed in a font without variants. Note the two variants for U and N
  4544     used on the seal.</p>
  4546    <pre>@font-feature-values Athena Ruby {
  4547   @character-variant {
  4548     leo-B: 2 1;
  4549     leo-M: 13 3;
  4550     leo-alt-N: 14 1;
  4551     leo-N: 14 2;
  4552     leo-T: 20 1; 
  4553     leo-U: 21 2;
  4554     leo-alt-U: 21 4;
  4558 p {
  4559   font-variant: discretionary-ligatures,
  4560                 character-variant(leo-B, leo-M, leo-N, leo-T, leo-U);
  4563 span.alt-N { 
  4564   font-variant-alternates: character-variant(leo-alt-N);
  4567 span.alt-U {
  4568   font-variant-alternates: character-variant(leo-alt-U);
  4571 &lt;p>ENO....UP͞RSTU&lt;span class="alt-U">U&lt;/span>͞&lt;span class="alt-U">U&lt;/span>ΚΑΙTỤẠG̣IUPNS&lt;/p>
  4573 &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> 
  4574 </pre>
  4575   </div>
  4577   <h3 id=font-variant-east-asian-prop><span class=secno>6.10 </span>East
  4578    Asian text rendering: the <a
  4579    href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
  4580    property</h3>
  4582   <table class=propdef id=namefont-variant-east-asianvaluenormal-l>
  4583    <tbody>
  4584     <tr>
  4585      <td>Name:
  4587      <td><dfn
  4588       id=propdef-font-variant-east-asian>font-variant-east-asian</dfn>
  4590     <tr>
  4591      <td>Value:
  4593      <td>normal | [ &lt;east-asian-variant-values&gt; ||
  4594       &lt;east-asian-width-values&gt; || ruby ]
  4596     <tr>
  4597      <td>Initial:
  4599      <td>normal
  4601     <tr>
  4602      <td>Applies to:
  4604      <td>all elements
  4606     <tr>
  4607      <td>Inherited:
  4609      <td>yes
  4611     <tr>
  4612      <td>Percentages:
  4614      <td>N/A
  4616     <tr>
  4617      <td>Media:
  4619      <td>visual
  4621     <tr>
  4622      <td>Computed value:
  4624      <td>as specified
  4626     <tr>
  4627      <td>Animatable:
  4629      <td>no
  4630   </table>
  4632   <p>Allows control of glyph substitution and sizing in East Asian text.
  4634   <pre
  4635    class=prod><dfn id=lteast-asian-variant-valuesgt><var>&lt;east-asian-variant-values&gt;</var></dfn> = [ jis78 | jis83 | jis90 | jis04 | simplified | traditional ]</pre>
  4637   <pre
  4638    class=prod><dfn id=lteast-asian-width-valuesgt><var>&lt;east-asian-width-values&gt;</var></dfn>   = [ full-width | proportional-width ]</pre>
  4640   <p>Individual values have the following meanings:
  4642   <dl>
  4643    <dt><dfn id=normal2>normal</dfn>
  4645    <dd>None of the features listed below are enabled.
  4647    <dt><dfn id=jis78>jis78</dfn>
  4649    <dd>Enables rendering of JIS78 forms (OpenType feature: <span
  4650     class=tag>jp78</span>).
  4651   </dl>
  4653   <div class=featex><img alt="JIS78 form example" src=jp78.png></div>
  4655   <dl>
  4656    <dt><dfn id=jis83>jis83</dfn>
  4658    <dd>Enables rendering of JIS83 forms (OpenType feature: <span
  4659     class=tag>jp83</span>).
  4661    <dt><dfn id=jis90>jis90</dfn>
  4663    <dd>Enables rendering of JIS90 forms (OpenType feature: <span
  4664     class=tag>jp90</span>).
  4666    <dt><dfn id=jis04>jis04</dfn>
  4668    <dd>Enables rendering of JIS2004 forms (OpenType feature: <span
  4669     class=tag>jp04</span>).
  4670     <p>The various JIS variants reflect the glyph forms defined in different
  4671      Japanese national standards. Fonts generally include glyphs defined by
  4672      the most recent national standard but it's sometimes necessary to use
  4673      older variants, to match signage for example.</p>
  4675    <dt><dfn id=simplified>simplified</dfn>
  4677    <dd>Enables rendering of simplified forms (OpenType feature: <span
  4678     class=tag>smpl</span>).
  4679     <p>The ‘<a href="#simplified"><code
  4680      class=property>simplified</code></a>’ and ‘<a
  4681      href="#traditional"><code class=property>traditional</code></a>’
  4682      values allow control over the glyph forms for characters which have been
  4683      simplified over time but for which the older, traditional form is still
  4684      used in some contexts. The exact set of characters and glyph forms will
  4685      vary to some degree by context for which a given font was designed.</p>
  4687    <dt><dfn id=traditional>traditional</dfn>
  4689    <dd>Enables rendering of traditional forms (OpenType feature: <span
  4690     class=tag>trad</span>).
  4691   </dl>
  4693   <div class=featex><img alt="tradtional form example" src=trad.png></div>
  4695   <dl>
  4696    <dt><dfn id=full-width>full-width</dfn>
  4698    <dd>Enables rendering of full-width variants (OpenType feature: <span
  4699     class=tag>fwid</span>).
  4701    <dt><dfn id=proportional-width>proportional-width</dfn>
  4703    <dd>Enables rendering of proportionally-spaced variants (OpenType feature:
  4704     <span class=tag>pwid</span>).
  4705   </dl>
  4707   <div class=featex><img alt="proportionally spaced Japanese example"
  4708    src=pwid.png></div>
  4710   <dl>
  4711    <dt><dfn id=ruby>ruby</dfn>
  4713    <dd>Enables display of ruby variant glyphs (OpenType feature: <span
  4714     class=tag>ruby</span>). Since ruby text is generally smaller than the
  4715     associated body text, font designers can design special glyphs for use
  4716     with ruby that are more readable than scaled down versions of the default
  4717     glyphs. Only glyph selection is affected, there is no associated font
  4718     scaling or other change that affects line layout. The red ruby text below
  4719     is shown with default glyphs (top) and with ruby variant glyphs (bottom).
  4720     Note the slight difference in stroke thickness.
  4721   </dl>
  4723   <div class=featex><img alt="ruby variant example" src=rubyshinkansen.png></div>
  4725   <h3 id=font-variant-prop><span class=secno>6.11 </span>Overall shorthand
  4726    for font rendering: the <a href="#propdef-font-variant">font-variant</a>
  4727    property</h3>
  4729   <table class=propdef id=namefont-variantvaluenormal-none-ltcommo>
  4730    <tbody>
  4731     <tr>
  4732      <td>Name:
  4734      <td><dfn id=propdef-font-variant>font-variant</dfn>
  4736     <tr>
  4737      <td>Value:
  4739      <td>normal | none | [ &lt;common-lig-values&gt; ||
  4740       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  4741       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  4742       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  4743       character-variant(&lt;feature-value-name&gt;#) ||
  4744       swash(&lt;feature-value-name&gt;) ||
  4745       ornaments(&lt;feature-value-name&gt;) ||
  4746       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  4747       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  4748       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  4749       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  4750       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  4751       ruby ]
  4753     <tr>
  4754      <td>Initial:
  4756      <td>normal
  4758     <tr>
  4759      <td>Applies to:
  4761      <td>all elements
  4763     <tr>
  4764      <td>Inherited:
  4766      <td>yes
  4768     <tr>
  4769      <td>Percentages:
  4771      <td>see individual properties
  4773     <tr>
  4774      <td>Media:
  4776      <td>visual
  4778     <tr>
  4779      <td>Computed value:
  4781      <td>see individual properties
  4783     <tr>
  4784      <td>Animatable:
  4786      <td>see individual properties
  4787   </table>
  4789   <p>The value ‘<a href="#normal2"><code
  4790    class=property>normal</code></a>’ resets all other font feature
  4791    properties to their inital value. The ‘<code
  4792    class=property>none</code>’ value sets ‘<a
  4793    href="#propdef-font-variant-ligatures"><code
  4794    class=property>font-variant-ligatures</code></a>’ to ‘<code
  4795    class=property>none</code>’ and resets all other font feature properties
  4796    to their initial value. Like other shorthands, using ‘<a
  4797    href="#propdef-font-variant"><code
  4798    class=property>font-variant</code></a>’ resets unspecified font-variant
  4799    subproperties to their initial values. It does not reset the values of
  4800    either ‘<a href="#propdef-font-language-override"><code
  4801    class=property>font-language-override</code></a>’ or ‘<a
  4802    href="#propdef-font-feature-settings"><code
  4803    class=property>font-feature-settings</code></a>’.
  4805   <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
  4806    font feature settings control: the <a
  4807    href="#propdef-font-feature-settings">font-feature-settings</a> property</h3>
  4809   <table class=propdef id=namefont-feature-settingsvaluenormal-ltf>
  4810    <tbody>
  4811     <tr>
  4812      <td>Name:
  4814      <td><dfn id=propdef-font-feature-settings>font-feature-settings</dfn>
  4816     <tr>
  4817      <td>Value:
  4819      <td>normal | &lt;feature-tag-value&gt;#
  4821     <tr>
  4822      <td>Initial:
  4824      <td>normal
  4826     <tr>
  4827      <td>Applies to:
  4829      <td>all elements
  4831     <tr>
  4832      <td>Inherited:
  4834      <td>yes
  4836     <tr>
  4837      <td>Percentages:
  4839      <td>N/A
  4841     <tr>
  4842      <td>Media:
  4844      <td>visual
  4846     <tr>
  4847      <td>Computed value:
  4849      <td>as specified
  4851     <tr>
  4852      <td>Animatable:
  4854      <td>no
  4855   </table>
  4857   <p>This property provides low-level control over OpenType font features. It
  4858    is intended as a way of providing access to font features that are not
  4859    widely used but are needed for a particular use case. A value of ‘<a
  4860    href="#normal2"><code class=property>normal</code></a>’ means that no
  4861    change in glyph selection or positioning occurs due to this property.
  4863   <p>
  4865   <pre>/* enable small caps and use second swash alternate */
  4866 font-feature-settings: "smcp", "swsh" 2;</pre>
  4868   <p>Feature tag values have the following syntax:
  4870   <pre
  4871    class=prod><dfn id=ltfeature-tag-valuegt><var>&lt;feature-tag-value&gt;</var></dfn> = &lt;string&gt; [ &lt;integer&gt; | on | off ]?</pre>
  4873   <p>The &lt;string&gt; is a case-sensitive OpenType feature tag. As
  4874    specified in the OpenType specification, feature tags contain four ASCII
  4875    characters. Tag strings longer or shorter than four characters, or
  4876    containing characters outside the U+20–7E codepoint range are invalid.
  4877    User agents must not use a feature tag created by truncating or padding
  4878    the string to four characters. Feature tags need only match a feature tag
  4879    defined in the font, they are not limited to explicitly registered
  4880    OpenType features. Fonts defining custom feature tags should follow the <a
  4881    href="http://www.microsoft.com/typography/otspec/featuretags.htm">tag name
  4882    rules</a> defined in the OpenType specification <a
  4883    href="#OPENTYPE-FEATURES"
  4884    rel=biblioentry>[OPENTYPE-FEATURES]<!--{{!OPENTYPE-FEATURES}}--></a>.
  4885    Feature tags not present in the font are ignored; a user agent must not
  4886    attempt to synthesize fallback behavior based on these feature tags.
  4888   <p>This means that explicitly disabling the <span class=tag>kern</span>
  4889    feature will not affect the application of kerning data found in the
  4890    ‘<code class=property>kern</code>’ table (as opposed to kerning data
  4891    associated with the <span class=tag>kern</span> feature in the ‘<code
  4892    class=property>GPOS</code>’ table). Authors should use the ‘<a
  4893    href="#propdef-font-kerning"><code
  4894    class=property>font-kerning</code></a>’ property to explictly enable or
  4895    disable kerning since this property affects both types of kerning.
  4897   <p>If present, a value indicates an index used for glyph selection. An
  4898    &lt;integer&gt; value must be 0 or greater. A value of 0 indicates that
  4899    the feature is disabled. For boolean features, a value of 1 enables the
  4900    feature. For non-boolean features, a value of 1 or greater enables the
  4901    feature and indicates the feature selection index. A value of ‘<code
  4902    class=property>on</code>’ is synonymous with 1 and ‘<code
  4903    class=property>off</code>’ is synonymous with 0. If the value is
  4904    omitted, a value of 1 is assumed.
  4906   <pre>
  4907 font-feature-settings: "dlig" 1;       /* dlig=1 enable discretionary ligatures */
  4908 font-feature-settings: "smcp" on;      /* smcp=1 enable small caps */
  4909 font-feature-settings: 'c2sc';         /* c2sc=1 enable caps to small caps */
  4910 font-feature-settings: "liga" off;     /* liga=0 no common ligatures */
  4911 font-feature-settings: "tnum", 'hist'; /* tnum=1, hist=1 enable tabular numbers and historical forms */
  4912 font-feature-settings: "tnum" "hist";  /* invalid, need a comma-delimited list */
  4913 font-feature-settings: "palin" off;    /* good idea but invalid tagname */
  4914 font-feature-settings: "PKRN";         /* PKRN=1 enable custom feature */
  4915 font-feature-settings: dlig;           /* invalid, tag must be a string */
  4916 </pre>
  4918   <p>Authors should generally use ‘<a href="#propdef-font-variant"><code
  4919    class=property>font-variant</code></a>’ and its related subproperties
  4920    whenever possible and only use this property for special cases where its
  4921    use is the only way of accessing a particular infrequently used font
  4922    feature.
  4924   <p>Although specifically defined for OpenType feature tags, feature tags
  4925    for other modern font formats that support font features may be added in
  4926    the future. Where possible, features defined for other font formats should
  4927    attempt to follow the pattern of registered OpenType tags.
  4929   <div class=example>
  4930    <p>The Japanese text below will be rendered with half-width kana
  4931     characters:</p>
  4933    <pre lang=ja>
  4934 body { font-feature-settings: "hwid"; /* Half-width OpenType feature */ }
  4936 &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>
  4937 </pre>
  4938   </div>
  4940   <h3 id=font-language-override-prop><span class=secno>6.13 </span>Font
  4941    language override: the <a
  4942    href="#propdef-font-language-override">font-language-override</a> property</h3>
  4944   <table class=propdef id=namefont-language-overridevaluenormal-lt>
  4945    <tbody>
  4946     <tr>
  4947      <td>Name:
  4949      <td><dfn id=propdef-font-language-override>font-language-override</dfn>
  4951     <tr>
  4952      <td>Value:
  4954      <td>normal | &lt;string&gt;
  4956     <tr>
  4957      <td>Initial:
  4959      <td>normal
  4961     <tr>
  4962      <td>Applies to:
  4964      <td>all elements
  4966     <tr>
  4967      <td>Inherited:
  4969      <td>yes
  4971     <tr>
  4972      <td>Percentages:
  4974      <td>N/A
  4976     <tr>
  4977      <td>Media:
  4979      <td>visual
  4981     <tr>
  4982      <td>Computed value:
  4984      <td>as specified
  4986     <tr>
  4987      <td>Animatable:
  4989      <td>no
  4990   </table>
  4992   <p>The value of ‘<a href="#normal2"><code
  4993    class=property>normal</code></a>’ implies that when rendering with
  4994    OpenType fonts the language of the document is used to infer the OpenType
  4995    language system, used to select language specific features when rendering.
  4996    The value of the &lt;string&gt; is a single three-letter OpenType <a
  4997    href="http://www.microsoft.com/typography/otspec/languagetags.htm">language
  4998    system tag</a>, defined in the layout tag registry of the OpenType
  4999    specification.
  5001   <div class=example>
  5002    <p>The <a href="http://www.un.org/en/documents/udhr/index.shtml">Universal
  5003     Declaration of Human Rights</a> has been translated into a wide variety
  5004     of languages. In Turkish, Article 9 of this document might be marked up
  5005     as below:</p>
  5007    <pre lang=tr>&lt;body lang="tr">
  5009 &lt;h4>Madde 9&lt;/h4>
  5010 &lt;p>Hiç kimse keyfi olarak tutuklanamaz, alıkonulanamaz veya sürülemez.&lt;/p>
  5011 </pre>
  5013    <p>Here the user agent uses the value of the ‘<code
  5014     class=property>lang</code>’ attribute when rendering text and
  5015     appropriately renders this text without ‘<code
  5016     class=property>fi</code>’ ligatures. There is no need to use the ‘<a
  5017     href="#propdef-font-language-override"><code
  5018     class=property>font-language-override</code></a>’ property.</p>
  5020    <p>However, a given font may lack support for a specific language. In this
  5021     situation authors may need to use the typographic conventions of a
  5022     related language that are supported by that font:</p>
  5024    <pre lang=mk>&lt;body lang="mk">     &lt;!-- Macedonian lang code --&gt;
  5026 body { font-language-override: "SRB"; /* Serbian OpenType language tag */ }
  5028 &lt;h4>Члeн 9&lt;/h4>
  5029 &lt;p>Никoj чoвeк нeмa дa бидe пoдлoжeн нa прoизвoлнo aпсeњe, притвoр или прoгoнувaњe.&lt;/p>
  5031 </pre>
  5033    <p>The Macedonian text here will be rendered using Serbian typographic
  5034     conventions, with the assumption that the font specified supports
  5035     Serbian.</p>
  5036   </div>
  5038   <p><a id=rendering-considerations></a>
  5040   <h2 id=font-feature-resolution><span class=secno>7 </span>Font Feature
  5041    Resolution</h2>
  5043   <p>As described in the previous section, font features can be enabled in a
  5044    variety of ways, either via the use of ‘<a
  5045    href="#propdef-font-variant"><code
  5046    class=property>font-variant</code></a>’ or ‘<a
  5047    href="#propdef-font-feature-settings"><code
  5048    class=property>font-feature-settings</code></a>’ in a style rule or
  5049    within an <code>@font-face</code> rule. The resolution order for the union
  5050    of these settings is defined below. Features defined via CSS properties
  5051    are applied on top of layout engine default features.
  5053   <h3 id=default-features><span class=secno>7.1 </span>Default features</h3>
  5055   <p>For OpenType fonts, user agents must enable the default features defined
  5056    in the OpenType documentation for a given script and writing mode.
  5057    Required ligatures, common ligatures and contextual forms must be enabled
  5058    by default (OpenType features: <span class=tag>rlig, liga, clig,
  5059    calt</span>), along with localized forms (OpenType feature: <span
  5060    class=tag>locl</span>), and features required for proper display of
  5061    composed characters and marks (OpenType features: <span class=tag>ccmp,
  5062    mark, mkmk</span>). These features must always be enabled, even when the
  5063    value of the ‘<a href="#propdef-font-variant"><code
  5064    class=property>font-variant</code></a>’ and ‘<a
  5065    href="#propdef-font-feature-settings"><code
  5066    class=property>font-feature-settings</code></a>’ properties is ‘<a
  5067    href="#normal2"><code class=property>normal</code></a>’. Individual
  5068    features are only disabled when explicitly overridden by the author, as
  5069    when ‘<a href="#propdef-font-variant-ligatures"><code
  5070    class=property>font-variant-ligatures</code></a>’ is set to ‘<a
  5071    href="#no-common-ligatures"><code
  5072    class=property>no-common-ligatures</code></a>’. For handling complex
  5073    scripts such as <a
  5074    href="http://www.microsoft.com/typography/otfntdev/arabicot/features.aspx">Arabic</a>,
  5075    <a
  5076    href="http://www.microsoft.com/typography/otfntdev/mongolot/features.htm">Mongolian</a>
  5077    or <a
  5078    href="http://www.microsoft.com/typography/otfntdev/devanot/features.aspx">Devanagari</a>
  5079    additional features are required. For upright text within vertical text
  5080    runs, vertical alternates (OpenType feature: <span class=tag>vert</span>)
  5081    must be enabled.
  5083   <h3 id=feature-precedence><span class=secno>7.2 </span>Feature precedence</h3>
  5085   <p>General and font specific font feature property settings are resolved in
  5086    the order below, in ascending precedence order. This ordering is used to
  5087    construct a combined list of font features that affect a given text run.
  5089   <ol>
  5090    <li>Font features enabled by default, including features required for a
  5091     given script.
  5093    <li>If the font is defined via an <code>@font-face</code> rule, the font
  5094     features implied by the font-variant descriptor in the
  5095     <code>@font-face</code> rule.
  5097    <li>If the font is defined via an <code>@font-face</code> rule, the font
  5098     features implied by the font-feature-settings descriptor in the
  5099     <code>@font-face</code> rule.
  5101    <li>Feature settings determined by properties other than ‘<a
  5102     href="#propdef-font-variant"><code
  5103     class=property>font-variant</code></a>’ or ‘<a
  5104     href="#propdef-font-feature-settings"><code
  5105     class=property>font-feature-settings</code></a>’. For example, setting
  5106     a non-default value for the ‘<code
  5107     class=property>letter-spacing</code>’ property disables ligatures.
  5109    <li>Font features implied by the value of the ‘<a
  5110     href="#propdef-font-variant"><code
  5111     class=property>font-variant</code></a>’ property, the related
  5112     font-variant subproperties and any other CSS property that may use
  5113     OpenType features (e.g. the ‘<a href="#propdef-font-kerning"><code
  5114     class=property>font-kerning</code></a>’ property).
  5116    <li>Font features implied by the value of ‘<a
  5117     href="#propdef-font-feature-settings"><code
  5118     class=property>font-feature-settings</code></a>’ property.
  5119   </ol>
  5121   <p>This ordering allows authors to set up a general set of defaults for
  5122    fonts within their <code>@font-face</code> rules, then override them with
  5123    property settings for specific elements. General property settings
  5124    override the settings in <code>@font-face</code> rules and low-level font
  5125    feature settings override ‘<a href="#propdef-font-variant"><code
  5126    class=property>font-variant</code></a>’ property settings.
  5128   <p>For situations where the combined list of font feature settings contains
  5129    more than one value for the same feature, the last value is used. When a
  5130    font lacks support for a given underlying font feature, text is simply
  5131    rendered as if that font feature was not enabled; font fallback does not
  5132    occur and no attempt is made to synthesize the feature except where
  5133    explicitly noted for specific properties.
  5135   <h3 id=feature-precedence-examples><span class=secno>7.3 </span>Feature
  5136    precedence examples</h3>
  5138   <div class=example>
  5139    <p>With the styles below, numbers are rendered proportionally when used
  5140     within a paragraph but are shown in tabular form within tables of prices:</p>
  5142    <pre>body { 
  5143   font-variant-numeric: proportional-nums; 
  5146 table.prices td {
  5147   font-variant-numeric: tabular-nums; 
  5149 </pre>
  5150   </div>
  5152   <div class=example>
  5153    <p>When the font-variant descriptor is used within an
  5154     <code>@font-face</code> rule, it only applies to the font defined by that
  5155     rule.</p>
  5157    <pre>@font-face {
  5158   font-family: MainText;
  5159   src: url(http://example.com/font.ttf);
  5160   font-variant: oldstyle-nums proportional-nums styleset(1,3);
  5163 body {
  5164   font-family: MainText, Helvetica;
  5167 table.prices td {
  5168   font-variant-numeric: tabular-nums; 
  5170 </pre>
  5172    <p>In this case, old-style numerals will be used throughout but only where
  5173     the font "MainText" is used. Just as in the previous example, tabular
  5174     values will be used in price tables since ‘<a
  5175     href="#tabular-nums"><code class=property>tabular-nums</code></a>’
  5176     appears in a general style rule and its use is mutually exclusive with
  5177     ‘<a href="#proportional-nums"><code
  5178     class=property>proportional-nums</code></a>’. Stylistic alternate sets
  5179     will only be used where MainText is used.</p>
  5180   </div>
  5182   <div class=example>
  5183    <p>The <code>@font-face</code> rule can also be used to access font
  5184     features in locally available fonts via the use of <code>local()</code>
  5185     in the ‘<a href="#descdef-src"><code class=property>src</code></a>’
  5186     descriptor of the <code>@font-face</code> definition:</p>
  5188    <pre>@font-face {
  5189   font-family: BodyText;
  5190   src: local("HiraMaruPro-W4");
  5191   font-variant: proportional-width;
  5192   font-feature-settings: "ital"; /* Latin italics within CJK text feature */
  5195 body { font-family: BodyText, serif; }
  5196 </pre>
  5198    <p>If available, a Japanese font "Hiragino Maru Gothic" will be used. When
  5199     text rendering occurs, Japanese kana will be proportionally spaced and
  5200     Latin text will be italicised. Text rendered with the fallback serif font
  5201     will use default rendering properties.</p>
  5202   </div>
  5204   <div class=example>
  5205    <p>In the example below, discretionary ligatures are enabled only for a
  5206     downloadable font but are disabled within spans of class "special":</p>
  5208    <pre>@font-face {
  5209   font-family: main;
  5210   src: url(fonts/ffmeta.woff) format("woff");
  5211   font-variant: discretionary-ligatures;
  5214 body         { font-family: main, Helvetica; }
  5215 span.special { font-variant-ligatures: no-discretionary-ligatures; }
  5216 </pre>
  5218    <p>Adding an discretionary style rule with the <code>@font-face</code>
  5219     above:</p>
  5221    <pre>body         { font-family: main, Helvetica; }
  5222 span         { font-feature-settings: "dlig"; }
  5223 span.special { font-variant-ligatures: no-discretionary-ligatures; }
  5224 </pre>
  5226    <p>Within spans of class "special", discretionary ligatures <em>will</em>
  5227     be rendered. This is because both the ‘<a
  5228     href="#propdef-font-feature-settings"><code
  5229     class=property>font-feature-settings</code></a>’ and ‘<a
  5230     href="#propdef-font-variant-ligatures"><code
  5231     class=property>font-variant-ligatures</code></a>’ properties apply to
  5232     these spans. Although the ‘<code class=css>no-discretionary
  5233     ligatures</code>’ setting of ‘<a
  5234     href="#propdef-font-variant-ligatures"><code
  5235     class=property>font-variant-ligatures</code></a>’ effectively disables
  5236     the OpenType <span class=tag>dlig</span> feature, because the ‘<a
  5237     href="#propdef-font-feature-settings"><code
  5238     class=property>font-feature-settings</code></a>’ is resolved after
  5239     that, the ‘<code class=property>dlig</code>’ value reenables
  5240     discretionary ligatures.</p>
  5241   </div>
  5243   <h2 id=object-model><span class=secno>8 </span>Object Model</h2>
  5245   <p>The contents of <code>@font-face</code> and
  5246    <code>@font-feature-values</code> rules can be accessed via the following
  5247    extensions to the CSS Object Model.
  5249   <h3 id=om-fontface><span class=secno>8.1 </span>The <a
  5250    href="#cssfontfacerule"><code>CSSFontFaceRule</code></a> interface</h3>
  5252   <p>The <dfn id=cssfontfacerule>CSSFontFaceRule</dfn> interface represents a
  5253    <code>@font-face</code> rule.
  5255   <pre class=idl>
  5256 interface CSSFontFaceRule : CSSRule {
  5257   attribute DOMString family;
  5258   attribute DOMString src;
  5259   attribute DOMString style;
  5260   attribute DOMString weight;
  5261   attribute DOMString stretch;
  5262   attribute DOMString unicodeRange;
  5263   attribute DOMString variant;
  5264   attribute DOMString featureSettings;
  5265 }</pre>
  5267   <p>The DOM Level 2 Style specification <a href="#DOM-LEVEL-2-STYLE"
  5268    rel=biblioentry>[DOM-LEVEL-2-STYLE]<!--{{DOM-LEVEL-2-STYLE}}--></a>
  5269    defined a different variant of this rule. This definition supercedes that
  5270    one.
  5272   <h3 id=om-fontfeaturevalues><span class=secno>8.2 </span>The <a
  5273    href="#cssfontfeaturevaluesrule"><code>CSSFontFeatureValuesRule</code></a>
  5274    interface</h3>
  5276   <p>The <code>CSSRule</code> interface is extended as follows:
  5278   <pre class=idl>partial interface CSSRule {
  5279   const unsigned short FONT_FEATURE_VALUES_RULE = 14;
  5280 }</pre>
  5282   <p>The <dfn id=cssfontfeaturevaluesrule>CSSFontFeatureValuesRule</dfn>
  5283    interface represents a <code>@font-feature-values</code> rule.
  5285   <pre class=idl>interface CSSFontFeatureValuesRule : CSSRule {
  5286   readonly attribute DOMString familyList;
  5287   readonly attribute DOMString valueText;
  5288 };</pre>
  5290   <dl class=idl-attributes>
  5291    <dt><var>familyList</var> of type <code>DOMString</code>, readonly
  5293    <dd>The list of one or more font families for which a given set of feature
  5294     values is defined.
  5296    <dt><var>valueText</var> of type <code>DOMString</code>, readonly
  5298    <dd>Serialized set of feature values.
  5299   </dl>
  5301   <h2 class=no-num id=platform-props-to-css>Appendix A: Mapping platform font
  5302    properties to CSS properties</h2>
  5304   <p><em>This appendix is included as background for some of the problems and
  5305    situations that are described in other sections. It should be viewed as
  5306    informative only.</em>
  5308   <p>Font properties in CSS are designed to be independent of the underlying
  5309    font formats used; they can be used to specify bitmap fonts, Type1 fonts,
  5310    SVG fonts in addition to the common TrueType and OpenType fonts. But there
  5311    are facets of the TrueType and OpenType formats that often cause confusion
  5312    for authors and present challenges to implementers on different platforms.
  5314   <p>Originally developed at Apple, TrueType was designed as an outline font
  5315    format for both screen and print. Microsoft joined Apple in developing the
  5316    TrueType format and both platforms have supported TrueType fonts since
  5317    then. Font data in the TrueType format consists of a set of tables
  5318    distinguished with common four-letter tag names, each containing a
  5319    specific type of data. For example, naming information, including
  5320    copyright and license information, is stored in the ‘<code
  5321    class=property>name</code>’ table. The <a
  5322    href="#character-map"><em>character map</em></a> (‘<code
  5323    class=property>cmap</code>’) table contains a mapping of character
  5324    encodings to glyphs. Apple later added additional tables for supporting
  5325    enhanced typographic functionality; these are now called Apple Advanced
  5326    Typography, or AAT, fonts. Microsoft and Adobe developed a separate set of
  5327    tables for advanced typography and called their format OpenType <a
  5328    href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>.
  5330   <p>In many cases the font data used under Microsoft Windows or Linux is
  5331    slightly different from the data used under Apple's Mac OS X because the
  5332    TrueType format allowed for explicit variation across platforms. This
  5333    includes font metrics, names and <a href="#character-map"><em>character
  5334    map</em></a> data.
  5336   <p>Specifically, font family name data is handled differently across
  5337    platforms. For TrueType and OpenType fonts these names are contained in
  5338    the ‘<code class=property>name</code>’ table, in name records with
  5339    name ID 1. Mulitple names can be stored for different locales but
  5340    Microsoft recommends fonts always include at least a US English version of
  5341    the name. On Windows, Microsoft made the decision for backwards
  5342    compatibility to limit this family name to a maximum of four faces; for
  5343    larger groupings the "preferred family" (name ID 16) or "WWS family" (name
  5344    ID 21) can be used. Other platforms such as OSX don't have this
  5345    limitation, the family name is used to define all possible groupings.
  5347   <p>Other name table data provides names used to uniquely identify a
  5348    specific face within a family. The full font name (name ID 4) and the
  5349    Postscript name (name ID 6) describe a single face uniquely. The bold face
  5350    of the Gill Sans family has a fullname of "Gill Sans Bold" and a
  5351    Postscript name of "GillSans-Bold". There can be multiple localized
  5352    versions of the fullname for a given face but the Postscript name is
  5353    always a unique name made from a limited set of ASCII characters.
  5355   <p>On various platforms, different names are used to search for a font. For
  5356    example, with the Windows GDI CreateIndirectFont API, either a family or
  5357    fullname can be used to lookup a face while on Mac OS X the
  5358    CTFontCreateWithName API call is used to lookup a given face using the
  5359    fullname and Postscript name. Under Linux, the fontconfig API allows fonts
  5360    to be searched using any of these names. In situations where platform
  5361    API's automatically substitute other font choices, it may be necessary to
  5362    verify a returned font matches a given name.
  5364   <p>The weight of a given face can be determined via the usWeightClass field
  5365    of the OS/2 table or inferred from the style name (name ID 2). Likewise,
  5366    the width can be determined via the usWidthClass of the OS/2 table or
  5367    inferred from the style name. For historical reasons related to synthetic
  5368    bolding at weights 200 or lower with the Windows GDI API, font designers
  5369    have sometimes skewed values in the OS/2 table to avoid these weights.
  5371   <p>Rendering complex scripts that use contextual shaping such as Thai,
  5372    Arabic and Devanagari requires features present only in OpenType or AAT
  5373    fonts. Currently, complex script rendering is supported on Windows and
  5374    Linux using OpenType font features while both OpenType and AAT font
  5375    features are used under Mac OS X.
  5377   <h2 class=no-num id=ch-ch-ch-changes>Changes</h2>
  5379   <h3 class=no-num id=recent-changes> Changes from the <a
  5380    href="http://www.w3.org/TR/2013/WD-css3-fonts-20130212/">February 2013
  5381    CSS3 Fonts Working Draft</a></h3>
  5383   <p>Major changes include:
  5385   <ul>
  5386    <li>Moved font load events into a separate <a
  5387     href="http://dev.w3.org/csswg/css3-font-load-events/">spec</a>
  5389    <li>Tightened error handling rules for <code>@font-feature-values</code>
  5390     rules
  5392    <li>Added grammar productions for <code>@font-face</code> and
  5393     <code>@font-feature-values</code> rules
  5395    <li>Tightened definition of synthetic oblique
  5396   </ul>
  5398   <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
  5400   <p>I'd like to thank Tal Leming, Jonathan Kew and Christopher Slye for all
  5401    their help and feedback. John Hudson was kind enough to take the time to
  5402    explain the subtleties of OpenType language tags and provided the example
  5403    of character variant usage for displaying text on Byzantine seals. Ken
  5404    Lunde and Eric Muller provided valuable feedback on CJK OpenType features
  5405    and Unicode variation selectors. The idea for supporting font features by
  5406    using font-variant subproperties originated with Håkon Wium Lie, Adam
  5407    Twardoch and Tal Leming. Elika Etemad supplied some of the initial design
  5408    ideas for the <code>@font-feature-values</code> rule. Thanks also to House
  5409    Industries for allowing the use of Ed Interlock in the discretionary
  5410    ligatures example.
  5412   <p>A special thanks to Robert Bringhurst for the sublime mind expansion
  5413    that is <em>The Elements of Typographic Style</em>.
  5415   <h2 class=no-num id=conformance> Conformance</h2>
  5417   <h3 class=no-num id=conventions> Document Conventions</h3>
  5419   <p>Conformance requirements are expressed with a combination of descriptive
  5420    assertions and RFC 2119 terminology. The key words “MUST”, “MUST
  5421    NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”,
  5422    “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the
  5423    normative parts of this document are to be interpreted as described in RFC
  5424    2119. However, for readability, these words do not appear in all uppercase
  5425    letters in this specification.
  5427   <p>All of the text of this specification is normative except sections
  5428    explicitly marked as non-normative, examples, and notes. <a
  5429    href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>
  5431   <p>Examples in this specification are introduced with the words “for
  5432    example” or are set apart from the normative text with
  5433    <code>class="example"</code>, like this:
  5435   <div class=example>
  5436    <p>This is an example of an informative example.
  5437   </div>
  5439   <p>Informative notes begin with the word “Note” and are set apart from
  5440    the normative text with <code>class="note"</code>, like this:
  5442   <p class=note>Note, this is an informative note.
  5444   <h3 class=no-num id=conformance-classes> Conformance Classes</h3>
  5446   <p>Conformance to CSS Fonts Level 3 Module is defined for three conformance
  5447    classes:
  5449   <dl>
  5450    <dt><dfn id=style-sheet title="style sheet!!as conformance class">style
  5451     sheet</dfn>
  5453    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
  5454     style sheet</a>.
  5456    <dt><dfn id=renderer>renderer</dfn>
  5458    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
  5459     that interprets the semantics of a style sheet and renders documents that
  5460     use them.
  5462    <dt><dfn id=authoring-tool>authoring tool</dfn>
  5464    <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
  5465     that writes a style sheet.
  5466   </dl>
  5468   <p>A style sheet is conformant to CSS Fonts Level 3 Module if all of its
  5469    declarations that use properties defined in this module have values that
  5470    are valid according to the generic CSS grammar and the individual grammars
  5471    of each property as given in this module.
  5473   <p>A renderer is conformant to CSS Fonts Level 3 Module if, in addition to
  5474    interpreting the style sheet as defined by the appropriate specifications,
  5475    it supports all the features defined by CSS Fonts Level 3 Module by
  5476    parsing them correctly and rendering the document accordingly. However,
  5477    the inability of a UA to correctly render a document due to limitations of
  5478    the device does not make the UA non-conformant. (For example, a UA is not
  5479    required to render color on a monochrome monitor.)
  5481   <p>An authoring tool is conformant to CSS Fonts Level 3 Module if it writes
  5482    style sheets that are syntactically correct according to the generic CSS
  5483    grammar and the individual grammars of each feature in this module, and
  5484    meet all other conformance requirements of style sheets as described in
  5485    this module.
  5487   <h3 class=no-num id=partial> Partial Implementations</h3>
  5489   <p>So that authors can exploit the forward-compatible parsing rules to
  5490    assign fallback values, CSS renderers <strong>must</strong> treat as
  5491    invalid (and <a
  5492    href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore as
  5493    appropriate</a>) any at-rules, properties, property values, keywords, and
  5494    other syntactic constructs for which they have no usable level of support.
  5495    In particular, user agents <strong>must not</strong> selectively ignore
  5496    unsupported component values and honor supported values in a single
  5497    multi-value property declaration: if any value is considered invalid (as
  5498    unsupported values must be), CSS requires that the entire declaration be
  5499    ignored.
  5501   <h3 class=no-num id=experimental> Experimental Implementations</h3>
  5503   <p>To avoid clashes with future CSS features, the CSS2.1 specification
  5504    reserves a <a
  5505    href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
  5506    syntax</a> for proprietary and experimental extensions to CSS.
  5508   <p>Prior to a specification reaching the Candidate Recommendation stage in
  5509    the W3C process, all implementations of a CSS feature are considered
  5510    experimental. The CSS Working Group recommends that implementations use a
  5511    vendor-prefixed syntax for such features, including those in W3C Working
  5512    Drafts. This avoids incompatibilities with future changes in the draft.
  5514   <h3 class=no-num id=testing> Non-Experimental Implementations</h3>
  5516   <p>Once a specification reaches the Candidate Recommendation stage,
  5517    non-experimental implementations are possible, and implementors should
  5518    release an unprefixed implementation of any CR-level feature they can
  5519    demonstrate to be correctly implemented according to spec.
  5521   <p>To establish and maintain the interoperability of CSS across
  5522    implementations, the CSS Working Group requests that non-experimental CSS
  5523    renderers submit an implementation report (and, if necessary, the
  5524    testcases used for that implementation report) to the W3C before releasing
  5525    an unprefixed implementation of any CSS features. Testcases submitted to
  5526    W3C are subject to review and correction by the CSS Working Group.
  5528   <p>Further information on submitting testcases and implementation reports
  5529    can be found from on the CSS Working Group's website at <a
  5530    href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
  5531    Questions should be directed to the <a
  5532    href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
  5533    mailing list.
  5535   <h2 class=no-num id=references>References</h2>
  5537   <h3 class=no-num id=normative-references>Normative References</h3>
  5538   <!--begin-normative-->
  5539   <!-- Sorted by label -->
  5541   <dl class=bibliography>
  5542    <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
  5543     <!---->
  5545    <dt id=CHARMOD>[CHARMOD]
  5547    <dd>Martin J. Dürst; et al. <a
  5548     href="http://www.w3.org/TR/2005/REC-charmod-20050215/"><cite>Character
  5549     Model for the World Wide Web 1.0: Fundamentals.</cite></a> 15 February
  5550     2005. W3C Recommendation. URL: <a
  5551     href="http://www.w3.org/TR/2005/REC-charmod-20050215/">http://www.w3.org/TR/2005/REC-charmod-20050215/</a>
  5552     </dd>
  5553    <!---->
  5555    <dt id=CORS>[CORS]
  5557    <dd>Anne van Kesteren. <a
  5558     href="http://www.w3.org/TR/2013/CR-cors-20130129/"><cite>Cross-Origin
  5559     Resource Sharing.</cite></a> 29 January 2013. W3C Candidate
  5560     Recommendation. (Work in progress.) URL: <a
  5561     href="http://www.w3.org/TR/2013/CR-cors-20130129/">http://www.w3.org/TR/2013/CR-cors-20130129/</a>
  5562     </dd>
  5563    <!---->
  5565    <dt id=CSS21>[CSS21]
  5567    <dd>Bert Bos; et al. <a
  5568     href="http://www.w3.org/TR/2011/REC-CSS2-20110607"><cite>Cascading Style
  5569     Sheets Level 2 Revision 1 (CSS 2.1) Specification.</cite></a> 7 June
  5570     2011. W3C Recommendation. URL: <a
  5571     href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
  5572     </dd>
  5573    <!---->
  5575    <dt id=CSS3VAL>[CSS3VAL]
  5577    <dd>Håkon Wium Lie; Tab Atkins; Elika J. Etemad. <a
  5578     href="http://www.w3.org/TR/2012/CR-css3-values-20120828/"><cite>CSS
  5579     Values and Units Module Level 3.</cite></a> 28 August 2012. W3C Candidate
  5580     Recommendation. (Work in progress.) URL: <a
  5581     href="http://www.w3.org/TR/2012/CR-css3-values-20120828/">http://www.w3.org/TR/2012/CR-css3-values-20120828/</a>
  5582     </dd>
  5583    <!---->
  5585    <dt id=HTML5>[HTML5]
  5587    <dd>Ian Hickson. <a
  5588     href="http://www.w3.org/TR/2012/CR-html5-20121217/"><cite>HTML5.</cite></a>
  5589     17 December 2012. W3C Candidate Recommendation. (Work in progress.) URL:
  5590     <a
  5591     href="http://www.w3.org/TR/2012/CR-html5-20121217/">http://www.w3.org/TR/2012/CR-html5-20121217/</a>
  5592     </dd>
  5593    <!---->
  5595    <dt id=OPEN-FONT-FORMAT>[OPEN-FONT-FORMAT]
  5597    <dd><a
  5598     href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c052136_ISO_IEC_14496-22_2009(E).zip"><cite>Information
  5599     technology — Coding of audio-visual objects — Part 22: Open Font
  5600     Format.</cite></a> International Organization for Standardization.
  5601     ISO/IEC 14496-22:2009. URL: <a
  5602     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>
  5603     </dd>
  5604    <!---->
  5606    <dt id=OPENTYPE>[OPENTYPE]
  5608    <dd><a
  5609     href="http://www.microsoft.com/typography/otspec/default.htm"><cite>OpenType
  5610     specification.</cite></a> Microsoft. URL: <a
  5611     href="http://www.microsoft.com/typography/otspec/default.htm">http://www.microsoft.com/typography/otspec/default.htm</a>
  5612     </dd>
  5613    <!---->
  5615    <dt id=OPENTYPE-FEATURES>[OPENTYPE-FEATURES]
  5617    <dd><a
  5618     href="http://www.microsoft.com/typography/otspec/featurelist.htm"><cite>OpenType
  5619     feature registry.</cite></a> Microsoft. URL: <a
  5620     href="http://www.microsoft.com/typography/otspec/featurelist.htm">http://www.microsoft.com/typography/otspec/featurelist.htm</a>
  5621     </dd>
  5622    <!---->
  5624    <dt id=RFC2119>[RFC2119]
  5626    <dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
  5627     words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
  5628     RFC 2119. URL: <a
  5629     href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
  5630     </dd>
  5631    <!---->
  5633    <dt id=UAX15>[UAX15]
  5635    <dd>Mark Davis; Ken Whistler. <a
  5636     href="http://www.unicode.org/reports/tr15/"><cite>Unicode Normalization
  5637     Forms.</cite></a> 31 August 2012. Unicode Standard Annex #15. URL: <a
  5638     href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a>
  5639     </dd>
  5640    <!---->
  5642    <dt id=UAX29>[UAX29]
  5644    <dd>Mark Davis. <a
  5645     href="http://www.unicode.org/reports/tr29/"><cite>Unicode Text
  5646     Segmentation.</cite></a> 12 September 2012. Unicode Standard Annex #29.
  5647     URL: <a
  5648     href="http://www.unicode.org/reports/tr29/">http://www.unicode.org/reports/tr29/</a>
  5649     </dd>
  5650    <!---->
  5652    <dt id=UNICODE6>[UNICODE6]
  5654    <dd>The Unicode Consortium. <a
  5655     href="http://www.unicode.org/versions/Unicode6.2.0/"><cite>The Unicode
  5656     Standard, Version 6.2.0.</cite></a> Defined by: The Unicode Standard,
  5657     Version 6.2.0 URL: <a
  5658     href="http://www.unicode.org/versions/Unicode6.2.0/">http://www.unicode.org/versions/Unicode6.2.0/</a>
  5659     </dd>
  5660    <!---->
  5661   </dl>
  5662   <!--end-normative-->
  5663   <!--{{!CSS21}}-->
  5664   <!--{{!CSS3VAL}}-->
  5665   <!--{{!OPENTYPE}}-->
  5666   <!--{{!OPENTYPE-FEATURES}}-->
  5667   <!--{{!OPEN-FONT-FORMAT}}-->
  5668   <!--{{!UNICODE6}}-->
  5669   <!--{{!UAX15}}-->
  5670   <!--{{!UAX29}}-->
  5671   <!--{{!CORS}}-->
  5672   <!--{{!HTML5}}-->
  5673   <!--{{!CHARMOD}}-->
  5675   <h3 class=no-num id=other-references>Other References</h3>
  5676   <!--begin-informative-->
  5677   <!-- Sorted by label -->
  5679   <dl class=bibliography>
  5680    <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
  5681     <!---->
  5683    <dt id=AAT-FEATURES>[AAT-FEATURES]
  5685    <dd><a href="http://developer.apple.com/fonts/registry/"><cite>Apple
  5686     Advanced Typography font feature registry.</cite></a> Apple. URL: <a
  5687     href="http://developer.apple.com/fonts/registry/">http://developer.apple.com/fonts/registry/</a>
  5688     </dd>
  5689    <!---->
  5691    <dt id=ARABIC-TYPO>[ARABIC-TYPO]
  5693    <dd>Huda Smitshuijzen AbiFares. <cite>Arabic Typography: A Comprehensive
  5694     Sourcebook.</cite> Saqi Books. 2001. ISBN 0-86356-347-3.</dd>
  5695    <!---->
  5697    <dt id=CHARMOD-NORM>[CHARMOD-NORM]
  5699    <dd>François Yergeau; et al. <a
  5700     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/"><cite>Character
  5701     Model for the World Wide Web 1.0: Normalization.</cite></a> 1 May 2012.
  5702     W3C Working Draft. (Work in progress.) URL: <a
  5703     href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/">http://www.w3.org/TR/2012/WD-charmod-norm-20120501/</a>
  5704     </dd>
  5705    <!---->
  5707    <dt id=CJKV-INFO-PROCESSING>[CJKV-INFO-PROCESSING]
  5709    <dd>Ken Lunde. <cite>CJKV Information Processing, Second Edition.</cite>
  5710     O'Reilly Media, Inc. 2009. ISBN 0-596-51447-1.</dd>
  5711    <!---->
  5713    <dt id=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]
  5715    <dd>L. David Baron. <a
  5716     href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/"><cite>CSS
  5717     Conditional Rules Module Level 3.</cite></a> 13 December 2012. W3C
  5718     Working Draft. (Work in progress.) URL: <a
  5719     href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/">http://www.w3.org/TR/2012/WD-css3-conditional-20121213/</a>
  5720     </dd>
  5721    <!---->
  5723    <dt id=CSS3TEXT>[CSS3TEXT]
  5725    <dd>Elika J. Etemad; Koji Ishii. <a
  5726     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/"><cite>CSS Text
  5727     Module Level 3.</cite></a> 13 November 2012. W3C Working Draft. (Work in
  5728     progress.) URL: <a
  5729     href="http://www.w3.org/TR/2012/WD-css3-text-20121113/">http://www.w3.org/TR/2012/WD-css3-text-20121113/</a>
  5730     </dd>
  5731    <!---->
  5733    <dt id=DIGITAL-TYPOGRAPHY>[DIGITAL-TYPOGRAPHY]
  5735    <dd>Richard Rubinstein. <cite>Digital Typography, An Introduction to Type
  5736     and Composition for Computer System Design.</cite> Addison-Wesley. 1988.
  5737     ISBN 0-201-17633-5.</dd>
  5738    <!---->
  5740    <dt id=DOM-LEVEL-2-STYLE>[DOM-LEVEL-2-STYLE]
  5742    <dd>Chris Wilson; Philippe Le Hégaret; Vidur Apparao. <a
  5743     href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/"><cite>Document
  5744     Object Model (DOM) Level 2 Style Specification.</cite></a> 13 November
  5745     2000. W3C Recommendation. URL: <a
  5746     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>
  5747     </dd>
  5748    <!---->
  5750    <dt id=ELEMTYPO>[ELEMTYPO]
  5752    <dd>Robert Bringhurst. <cite>The Elements of Typographic Style, Version
  5753     4.</cite> Hartley &amp; Marks. 2013. ISBN 0-88179-212-8.</dd>
  5754    <!---->
  5756    <dt id=LANGCULTTYPE>[LANGCULTTYPE]
  5758    <dd>John D. Berry, Ed. <cite>Language Culture Type.</cite> Graphis. 2001.
  5759     ISBN 1-932026-01-0.</dd>
  5760    <!---->
  5762    <dt id=OPENTYPE-FONT-GUIDE>[OPENTYPE-FONT-GUIDE]
  5764    <dd><a
  5765     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf"><cite>OpenType
  5766     User Guide.</cite></a> FontShop International. URL: <a
  5767     href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf">https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf</a>
  5768     </dd>
  5769    <!---->
  5771    <dt id=RASTER-TRAGEDY>[RASTER-TRAGEDY]
  5773    <dd>Beat Stamm. <a href="http://www.rastertragedy.com/"><cite>The Raster
  5774     Tragedy at Low-Resolution Revisited.</cite></a> 7 December 2011. URL: <a
  5775     href="http://www.rastertragedy.com/">http://www.rastertragedy.com/</a></dd>
  5776    <!---->
  5778    <dt id=WINDOWS-GLYPH-PROC>[WINDOWS-GLYPH-PROC]
  5780    <dd>John Hudson. <a
  5781     href="http://www.microsoft.com/typography/developers/opentype/default.htm"><cite>Windows
  5782     Glyph Processing.</cite></a> Microsoft Typogrraphy. URL: <a
  5783     href="http://www.microsoft.com/typography/developers/opentype/default.htm">http://www.microsoft.com/typography/developers/opentype/default.htm</a>
  5784     </dd>
  5785    <!---->
  5786   </dl>
  5787   <!--end-informative-->
  5788   <!--{{ARABIC-TYPO}}-->
  5789   <!--{{CJKV-INFO-PROCESSING}}-->
  5790   <!--{{DIGITAL-TYPOGRAPHY}}-->
  5791   <!--{{DOM-LEVEL-2-STYLE}}-->
  5792   <!--{{ELEMTYPO}}-->
  5793   <!--{{LANGCULTTYPE}}-->
  5794   <!--{{OPENTYPE-FONT-GUIDE}}-->
  5795   <!--{{RASTER-TRAGEDY}}-->
  5796   <!--{{WINDOWS-GLYPH-PROC}}-->
  5797   <!--{{CHARMOD-NORM}}-->
  5798   <!--{{AAT-FEATURES}}-->
  5799   <!--{{CSS3-CONDITIONAL}}-->
  5800   <!--{{CSS3TEXT}}-->
  5802   <h2 class=no-num id=index>Index</h2>
  5803   <!--begin-index-->
  5805   <ul class=indexlist>
  5806    <li>&lt;absolute-size&gt;, <a href="#ltabsolute-sizegt"
  5807     title="&lt;absolute-size&gt;"><strong>3.5</strong></a>
  5809    <li><var>&lt;common-lig-values></var>, <a href="#ltcommon-lig-values"
  5810     title="&lt;common-lig-values>"><strong>6.4</strong></a>
  5812    <li><var>&lt;contextual-alt-values&gt;</var>, <a
  5813     href="#ltcontextual-alt-valuesgt"
  5814     title="&lt;contextual-alt-values&gt;"><strong>6.4</strong></a>
  5816    <li><var>&lt;discretionary-lig-values></var>, <a
  5817     href="#ltdiscretionary-lig-values"
  5818     title="&lt;discretionary-lig-values>"><strong>6.4</strong></a>
  5820    <li><var>&lt;east-asian-variant-values&gt;</var>, <a
  5821     href="#lteast-asian-variant-valuesgt"
  5822     title="&lt;east-asian-variant-values&gt;"><strong>6.10</strong></a>
  5824    <li><var>&lt;east-asian-width-values&gt;</var>, <a
  5825     href="#lteast-asian-width-valuesgt"
  5826     title="&lt;east-asian-width-values&gt;"><strong>6.10</strong></a>
  5828    <li><var>&lt;feature-tag-value&gt;</var>, <a href="#ltfeature-tag-valuegt"
  5829     title="&lt;feature-tag-value&gt;"><strong>6.12</strong></a>
  5831    <li>&lt;font-face-name&gt;, <a href="#ltfont-face-namegt"
  5832     title="&lt;font-face-name&gt;"><strong>4.3</strong></a>
  5834    <li><var>&lt;font-variant-css21&gt;</var>, <a
  5835     href="#ltfont-variant-css21gt"
  5836     title="&lt;font-variant-css21&gt;"><strong>3.7</strong></a>
  5838    <li><var>&lt;historical-lig-values></var>, <a
  5839     href="#lthistorical-lig-values"
  5840     title="&lt;historical-lig-values>"><strong>6.4</strong></a>
  5842    <li>&lt;length&gt;, <a href="#ltlengthgt" title="&lt;length&gt;">3.5</a>
  5844    <li>&lt;number&gt;, <a href="#ltnumbergt" title="&lt;number&gt;">3.6</a>
  5846    <li><var>&lt;numeric-figure-values&gt;</var>, <a
  5847     href="#ltnumeric-figure-valuesgt"
  5848     title="&lt;numeric-figure-values&gt;"><strong>6.7</strong></a>
  5850    <li><var>&lt;numeric-fraction-values&gt;</var>, <a
  5851     href="#ltnumeric-fraction-valuesgt"
  5852     title="&lt;numeric-fraction-values&gt;"><strong>6.7</strong></a>
  5854    <li><var>&lt;numeric-spacing-values&gt;</var>, <a
  5855     href="#ltnumeric-spacing-valuesgt"
  5856     title="&lt;numeric-spacing-values&gt;"><strong>6.7</strong></a>
  5858    <li>&lt;percentage&gt;, <a href="#ltpercentagegt-"
  5859     title="&lt;percentage&gt;">3.5</a>
  5861    <li>&lt;relative-size&gt;, <a href="#ltrelative-sizegt"
  5862     title="&lt;relative-size&gt;"><strong>3.5</strong></a>
  5864    <li>&lt;urange&gt;, <a href="#lturangegt"
  5865     title="&lt;urange&gt;"><strong>4.5</strong></a>
  5867    <li>@font-face, <a href="#font-face" title="@font-face">4.1</a>, <a
  5868     href="#font-face0" title="@font-face">4.3</a>
  5870    <li>all-petite-caps, <a href="#all-petite-caps"
  5871     title=all-petite-caps><strong>6.6</strong></a>
  5873    <li>all-small-caps, <a href="#all-small-caps"
  5874     title=all-small-caps><strong>6.6</strong></a>
  5876    <li>annotation, <a href="#annotationltfeature-value-namegt"
  5877     title=annotation><strong>6.8</strong></a>
  5879    <li>aspect value, <a href="#aspect-value0" title="aspect
  5880     value"><strong>3.6</strong></a>
  5882    <li>authoring tool, <a href="#authoring-tool" title="authoring
  5883     tool"><strong>#</strong></a>
  5885    <li>character map, <a href="#character-map" title="character
  5886     map"><strong>5.2</strong></a>
  5888    <li>character-variant, <a href="#character-variantltfeature-value-namegt"
  5889     title=character-variant><strong>6.8</strong></a>
  5891    <li>common-ligatures, <a href="#common-ligatures"
  5892     title=common-ligatures><strong>6.4</strong></a>
  5894    <li>contextual, <a href="#contextual"
  5895     title=contextual><strong>6.4</strong></a>
  5897    <li>CSSFontFaceRule, <a href="#cssfontfacerule"
  5898     title=CSSFontFaceRule><strong>8.1</strong></a>
  5900    <li>CSSFontFeatureValuesRule, <a href="#cssfontfeaturevaluesrule"
  5901     title=CSSFontFeatureValuesRule><strong>8.2</strong></a>
  5903    <li>cursive, definition of, <a href="#cursive0" title="cursive, definition
  5904     of"><strong>#</strong></a>
  5906    <li>default face, <a href="#default-face" title="default
  5907     face"><strong>5.2</strong></a>
  5909    <li>descriptor_declaration, <a href="#descriptordeclaration"
  5910     title="descriptor_declaration"><strong>4.1</strong></a>
  5912    <li>diagonal-fractions, <a href="#diagonal-fractions"
  5913     title=diagonal-fractions><strong>6.7</strong></a>
  5915    <li>discretionary-ligatures, <a href="#discretionary-ligatures"
  5916     title=discretionary-ligatures><strong>6.4</strong></a>
  5918    <li>fantasy, definition of, <a href="#fantasy0" title="fantasy, definition
  5919     of"><strong>#</strong></a>
  5921    <li>feature_type, <a href="#featuretype"
  5922     title="feature_type"><strong>6.9</strong></a>
  5924    <li>feature_value_block, <a href="#featurevalueblock"
  5925     title="feature_value_block"><strong>6.9</strong></a>
  5927    <li>feature_value_definition, <a href="#featurevaluedefinition"
  5928     title="feature_value_definition"><strong>6.9</strong></a>
  5930    <li>font, <a href="#propdef-font" title=font><strong>3.7</strong></a>
  5932    <li>font-family, <a href="#descdef-font-family"
  5933     title=font-family><strong>4.2</strong></a>, <a
  5934     href="#propdef-font-family" title=font-family><strong>3.1</strong></a>
  5936    <li>font-feature-settings, <a href="#propdef-font-feature-settings"
  5937     title=font-feature-settings><strong>6.12</strong></a>
  5939    <li>font-feature-settings (descriptor), <a
  5940     href="#descdef-font-feature-settings" title="font-feature-settings
  5941     (descriptor)"><strong>4.6</strong></a>
  5943    <li>font-kerning, <a href="#propdef-font-kerning"
  5944     title=font-kerning><strong>6.3</strong></a>
  5946    <li>font-language-override, <a href="#propdef-font-language-override"
  5947     title=font-language-override><strong>6.13</strong></a>
  5949    <li>font-size, <a href="#propdef-font-size"
  5950     title=font-size><strong>3.5</strong></a>
  5952    <li>font-size-adjust, <a href="#propdef-font-size-adjust"
  5953     title=font-size-adjust><strong>3.6</strong></a>
  5955    <li>font-stretch, <a href="#propdef-font-stretch"
  5956     title=font-stretch><strong>3.3</strong></a>
  5958    <li>font-stretch (descriptor), <a href="#descdef-font-stretch"
  5959     title="font-stretch (descriptor)"><strong>4.4</strong></a>
  5961    <li>font-style, <a href="#propdef-font-style"
  5962     title=font-style><strong>3.4</strong></a>
  5964    <li>font-style (descriptor), <a href="#descdef-font-style"
  5965     title="font-style (descriptor)"><strong>4.4</strong></a>
  5967    <li>font-synthesis, <a href="#propdef-font-synthesis"
  5968     title=font-synthesis><strong>3.8</strong></a>
  5970    <li>font-variant, <a href="#propdef-font-variant"
  5971     title=font-variant><strong>6.11</strong></a>
  5973    <li>font-variant (descriptor), <a href="#descdef-font-variant"
  5974     title="font-variant (descriptor)"><strong>4.6</strong></a>
  5976    <li>font-variant-alternates, <a href="#propdef-font-variant-alternates"
  5977     title=font-variant-alternates><strong>6.8</strong></a>
  5979    <li>font-variant-caps, <a href="#propdef-font-variant-caps"
  5980     title=font-variant-caps><strong>6.6</strong></a>
  5982    <li>font-variant-east-asian, <a href="#propdef-font-variant-east-asian"
  5983     title=font-variant-east-asian><strong>6.10</strong></a>
  5985    <li>font-variant-ligatures, <a href="#propdef-font-variant-ligatures"
  5986     title=font-variant-ligatures><strong>6.4</strong></a>
  5988    <li>font-variant-numeric, <a href="#propdef-font-variant-numeric"
  5989     title=font-variant-numeric><strong>6.7</strong></a>
  5991    <li>font-variant-position, <a href="#propdef-font-variant-position"
  5992     title=font-variant-position><strong>6.5</strong></a>
  5994    <li>font-weight, <a href="#propdef-font-weight"
  5995     title=font-weight><strong>3.2</strong></a>
  5997    <li>font-weight (descriptor), <a href="#descdef-font-weight"
  5998     title="font-weight (descriptor)"><strong>4.4</strong></a>
  6000    <li>font_face_rule, <a href="#fontfacerule"
  6001     title="font_face_rule"><strong>4.1</strong></a>
  6003    <li>font_family_name, <a href="#fontfamilyname"
  6004     title="font_family_name"><strong>6.9</strong></a>
  6006    <li>font_family_name_list, <a href="#fontfamilynamelist"
  6007     title="font_family_name_list"><strong>6.9</strong></a>
  6009    <li>font_feature_values_rule, <a href="#fontfeaturevaluesrule"
  6010     title="font_feature_values_rule"><strong>6.9</strong></a>
  6012    <li>full-width, <a href="#full-width"
  6013     title=full-width><strong>6.10</strong></a>
  6015    <li>historical-forms, <a href="#historical-forms"
  6016     title=historical-forms><strong>6.8</strong></a>
  6018    <li>historical-ligatures, <a href="#historical-ligatures"
  6019     title=historical-ligatures><strong>6.4</strong></a>
  6021    <li>jis04, <a href="#jis04" title=jis04><strong>6.10</strong></a>
  6023    <li>jis78, <a href="#jis78" title=jis78><strong>6.10</strong></a>
  6025    <li>jis83, <a href="#jis83" title=jis83><strong>6.10</strong></a>
  6027    <li>jis90, <a href="#jis90" title=jis90><strong>6.10</strong></a>
  6029    <li>lining-nums, <a href="#lining-nums"
  6030     title=lining-nums><strong>6.7</strong></a>
  6032    <li>monospace, definition of, <a href="#monospace0" title="monospace,
  6033     definition of"><strong>#</strong></a>
  6035    <li>no-common-ligatures, <a href="#no-common-ligatures"
  6036     title=no-common-ligatures><strong>6.4</strong></a>
  6038    <li>no-contextual, <a href="#no-contextual"
  6039     title=no-contextual><strong>6.4</strong></a>
  6041    <li>no-discretionary-ligatures, <a href="#no-discretionary-ligatures"
  6042     title=no-discretionary-ligatures><strong>6.4</strong></a>
  6044    <li>no-historical-ligatures, <a href="#no-historical-ligatures"
  6045     title=no-historical-ligatures><strong>6.4</strong></a>
  6047    <li>normal, <a href="#normal" title=normal><strong>6.6</strong></a>, <a
  6048     href="#normal0" title=normal><strong>6.7</strong></a>, <a href="#normal1"
  6049     title=normal><strong>6.8</strong></a>, <a href="#normal2"
  6050     title=normal><strong>6.10</strong></a>
  6052    <li>oldstyle-nums, <a href="#oldstyle-nums"
  6053     title=oldstyle-nums><strong>6.7</strong></a>
  6055    <li>ordinal, <a href="#ordinal" title=ordinal><strong>6.7</strong></a>
  6057    <li>ornaments, <a href="#ornamentsltfeature-value-namegt"
  6058     title=ornaments><strong>6.8</strong></a>
  6060    <li>petite-caps, <a href="#petite-caps"
  6061     title=petite-caps><strong>6.6</strong></a>
  6063    <li>proportional-nums, <a href="#proportional-nums"
  6064     title=proportional-nums><strong>6.7</strong></a>
  6066    <li>proportional-width, <a href="#proportional-width"
  6067     title=proportional-width><strong>6.10</strong></a>
  6069    <li>renderer, <a href="#renderer" title=renderer><strong>#</strong></a>
  6071    <li>ruby, <a href="#ruby" title=ruby><strong>6.10</strong></a>
  6073    <li>sans-serif, definition of, <a href="#sans-serif0" title="sans-serif,
  6074     definition of"><strong>#</strong></a>
  6076    <li>serif, definition of, <a href="#serif0" title="serif, definition
  6077     of"><strong>#</strong></a>
  6079    <li>simplified, <a href="#simplified"
  6080     title=simplified><strong>6.10</strong></a>
  6082    <li>slashed-zero, <a href="#slashed-zero"
  6083     title=slashed-zero><strong>6.7</strong></a>
  6085    <li>small-caps, <a href="#small-caps"
  6086     title=small-caps><strong>6.6</strong></a>
  6088    <li>src, <a href="#descdef-src" title=src><strong>4.3</strong></a>
  6090    <li>stacked-fractions, <a href="#stacked-fractions"
  6091     title=stacked-fractions><strong>6.7</strong></a>
  6093    <li>style sheet
  6094     <ul>
  6095      <li>as conformance class, <a href="#style-sheet" title="style sheet, as
  6096       conformance class"><strong>#</strong></a>
  6097     </ul>
  6099    <li>styleset, <a href="#stylesetltfeature-value-namegt"
  6100     title=styleset><strong>6.8</strong></a>
  6102    <li>stylistic, <a href="#stylisticltfeature-value-namegt"
  6103     title=stylistic><strong>6.8</strong></a>
  6105    <li>swash, <a href="#swashltfeature-value-namegt"
  6106     title=swash><strong>6.8</strong></a>
  6108    <li>tabular-nums, <a href="#tabular-nums"
  6109     title=tabular-nums><strong>6.7</strong></a>
  6111    <li>titling-caps, <a href="#titling-caps"
  6112     title=titling-caps><strong>6.6</strong></a>
  6114    <li>traditional, <a href="#traditional"
  6115     title=traditional><strong>6.10</strong></a>
  6117    <li>unicase, <a href="#unicase" title=unicase><strong>6.6</strong></a>
  6119    <li>unicode-range, <a href="#descdef-unicode-range"
  6120     title=unicode-range><strong>4.5</strong></a>
  6122    <li>weight, <a href="#weight" title=weight><strong>2</strong></a>
  6124    <li>width, <a href="#width" title=width><strong>2</strong></a>
  6125   </ul>
  6126   <!--end-index-->
  6128   <h2 class=no-num id=property-index>Property index</h2>
  6129   <!--begin-properties-->
  6131   <table class=proptable>
  6132    <thead>
  6133     <tr>
  6134      <th>Property
  6136      <th>Values
  6138      <th>Initial
  6140      <th>Applies to
  6142      <th>Inh.
  6144      <th>Percentages
  6146      <th>Media
  6148    <tbody>
  6149     <tr>
  6150      <th><a class=property href="#propdef-font">font</a>
  6152      <td>[ [ &lt;‘font-style’> || &lt;font-variant-css21> ||
  6153       &lt;‘font-weight’> || &lt;‘font-stretch’> ]?
  6154       &lt;‘font-size’> [ / &lt;‘line-height’> ]?
  6155       &lt;‘font-family’> ] | caption | icon | menu | message-box |
  6156       small-caption | status-bar
  6158      <td>see individual properties
  6160      <td>all elements
  6162      <td>yes
  6164      <td>see individual properties
  6166      <td>visual
  6168     <tr>
  6169      <th><a class=property href="#descdef-font-family">font-family</a>
  6171      <td>[ &lt;family-name> | &lt;generic-family> ]#
  6173      <td>depends on user agent
  6175      <td>all elements
  6177      <td>yes
  6179      <td>N/A
  6181      <td>visual
  6183     <tr>
  6184      <th><a class=property
  6185       href="#propdef-font-feature-settings">font-feature-settings</a>
  6187      <td>normal | &lt;feature-tag-value&gt;#
  6189      <td>normal
  6191      <td>all elements
  6193      <td>yes
  6195      <td>N/A
  6197      <td>visual
  6199     <tr>
  6200      <th><a class=property href="#propdef-font-kerning">font-kerning</a>
  6202      <td>auto | normal | none
  6204      <td>auto
  6206      <td>all elements
  6208      <td>yes
  6210      <td>N/A
  6212      <td>visual
  6214     <tr>
  6215      <th><a class=property
  6216       href="#propdef-font-language-override">font-language-override</a>
  6218      <td>normal | &lt;string&gt;
  6220      <td>normal
  6222      <td>all elements
  6224      <td>yes
  6226      <td>N/A
  6228      <td>visual
  6230     <tr>
  6231      <th><a class=property href="#propdef-font-size">font-size</a>
  6233      <td>&lt;absolute-size> | &lt;relative-size> | &lt;length> |
  6234       &lt;percentage>
  6236      <td>medium
  6238      <td>all elements
  6240      <td>yes
  6242      <td>refer to parent element's font size
  6244      <td>visual
  6246     <tr>
  6247      <th><a class=property
  6248       href="#propdef-font-size-adjust">font-size-adjust</a>
  6250      <td>none | auto | &lt;number>
  6252      <td>none
  6254      <td>all elements
  6256      <td>yes
  6258      <td>N/A
  6260      <td>visual
  6262     <tr>
  6263      <th><a class=property href="#propdef-font-stretch">font-stretch</a>
  6265      <td>normal | ultra-condensed | extra-condensed | condensed |
  6266       semi-condensed | semi-expanded | expanded | extra-expanded |
  6267       ultra-expanded
  6269      <td>normal
  6271      <td>all elements
  6273      <td>yes
  6275      <td>N/A
  6277      <td>visual
  6279     <tr>
  6280      <th><a class=property href="#propdef-font-style">font-style</a>
  6282      <td>normal | italic | oblique
  6284      <td>normal
  6286      <td>all elements
  6288      <td>yes
  6290      <td>N/A
  6292      <td>visual
  6294     <tr>
  6295      <th><a class=property href="#propdef-font-synthesis">font-synthesis</a>
  6297      <td>none | [ weight || style ]
  6299      <td>weight style
  6301      <td>all elements
  6303      <td>yes
  6305      <td>N/A
  6307      <td>visual
  6309     <tr>
  6310      <th><a class=property href="#propdef-font-variant">font-variant</a>
  6312      <td>normal | none | [ &lt;common-lig-values&gt; ||
  6313       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  6314       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  6315       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  6316       character-variant(&lt;feature-value-name&gt;#) ||
  6317       swash(&lt;feature-value-name&gt;) ||
  6318       ornaments(&lt;feature-value-name&gt;) ||
  6319       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  6320       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  6321       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  6322       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  6323       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  6324       ruby ]
  6326      <td>normal
  6328      <td>all elements
  6330      <td>yes
  6332      <td>see individual properties
  6334      <td>visual
  6336     <tr>
  6337      <th><a class=property
  6338       href="#propdef-font-variant-alternates">font-variant-alternates</a>
  6340      <td>normal | [ stylistic(&lt;feature-value-name&gt;) || historical-forms
  6341       || styleset(&lt;feature-value-name&gt;#) ||
  6342       character-variant(&lt;feature-value-name&gt;#) ||
  6343       swash(&lt;feature-value-name&gt;) ||
  6344       ornaments(&lt;feature-value-name&gt;) ||
  6345       annotation(&lt;feature-value-name&gt;) ]
  6347      <td>normal
  6349      <td>all elements
  6351      <td>yes
  6353      <td>N/A
  6355      <td>visual
  6357     <tr>
  6358      <th><a class=property
  6359       href="#propdef-font-variant-caps">font-variant-caps</a>
  6361      <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
  6362       | unicase | titling-caps
  6364      <td>normal
  6366      <td>all elements
  6368      <td>yes
  6370      <td>N/A
  6372      <td>visual
  6374     <tr>
  6375      <th><a class=property
  6376       href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
  6378      <td>normal | [ &lt;east-asian-variant-values&gt; ||
  6379       &lt;east-asian-width-values&gt; || ruby ]
  6381      <td>normal
  6383      <td>all elements
  6385      <td>yes
  6387      <td>N/A
  6389      <td>visual
  6391     <tr>
  6392      <th><a class=property
  6393       href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
  6395      <td>normal | none | [ &lt;common-lig-values> ||
  6396       &lt;discretionary-lig-values> || &lt;historical-lig-values> ||
  6397       &lt;contextual-alt-values> ]
  6399      <td>normal
  6401      <td>all elements
  6403      <td>yes
  6405      <td>N/A
  6407      <td>visual
  6409     <tr>
  6410      <th><a class=property
  6411       href="#propdef-font-variant-numeric">font-variant-numeric</a>
  6413      <td>normal | [ &lt;numeric-figure-values&gt; ||
  6414       &lt;numeric-spacing-values&gt; || &lt;numeric-fraction-values&gt; ||
  6415       ordinal || slashed-zero ]
  6417      <td>normal
  6419      <td>all elements
  6421      <td>yes
  6423      <td>N/A
  6425      <td>visual
  6427     <tr>
  6428      <th><a class=property
  6429       href="#propdef-font-variant-position">font-variant-position</a>
  6431      <td>normal | sub | super
  6433      <td>normal
  6435      <td>all elements
  6437      <td>yes
  6439      <td>N/A
  6441      <td>visual
  6443     <tr>
  6444      <th><a class=property href="#propdef-font-weight">font-weight</a>
  6446      <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
  6447       | 700 | 800 | 900
  6449      <td>normal
  6451      <td>all elements
  6453      <td>yes
  6455      <td>N/A
  6457      <td>visual
  6458   </table>
  6459   <!--end-properties-->
  6460   <!--begin-descriptors-->
  6462   <table class=proptable>
  6463    <thead>
  6464     <tr>
  6465      <th>Descriptor
  6467      <th>Value
  6469      <th>Initial
  6471      <th>Percentages
  6473      <th>Media
  6475    <tbody>
  6476     <tr>
  6477      <th><a class=property href="#descdef-font-family">font-family</a>
  6479      <td>&lt;family-name>
  6481      <td>N/A
  6483     <tr>
  6484      <th><a class=property
  6485       href="#propdef-font-feature-settings">font-feature-settings</a>
  6487      <td>normal | &lt;feature-tag-value&gt;#
  6489      <td>normal
  6491     <tr>
  6492      <th><a class=property href="#propdef-font-stretch">font-stretch</a>
  6494      <td>normal | ultra-condensed | extra-condensed | condensed |
  6495       semi-condensed | semi-expanded | expanded | extra-expanded |
  6496       ultra-expanded
  6498      <td>normal
  6500     <tr>
  6501      <th><a class=property href="#propdef-font-style">font-style</a>
  6503      <td>normal | italic | oblique
  6505      <td>normal
  6507     <tr>
  6508      <th><a class=property href="#propdef-font-variant">font-variant</a>
  6510      <td>normal | [ &lt;common-lig-values&gt; ||
  6511       &lt;discretionary-lig-values&gt; || &lt;historical-lig-values&gt; ||
  6512       &lt;contextual-alt-values&gt; || stylistic(&lt;feature-value-name&gt;)
  6513       || historical-forms || styleset(&lt;feature-value-name&gt;#) ||
  6514       character-variant(&lt;feature-value-name&gt;#) ||
  6515       swash(&lt;feature-value-name&gt;) ||
  6516       ornaments(&lt;feature-value-name&gt;) ||
  6517       annotation(&lt;feature-value-name&gt;) || [ small-caps | all-small-caps
  6518       | petite-caps | all-petite-caps | unicase | titling-caps ] ||
  6519       &lt;numeric-figure-values&gt; || &lt;numeric-spacing-values&gt; ||
  6520       &lt;numeric-fraction-values&gt; || ordinal || slashed-zero ||
  6521       &lt;east-asian-variant-values&gt; || &lt;east-asian-width-values&gt; ||
  6522       ruby ]
  6524      <td>normal
  6526     <tr>
  6527      <th><a class=property href="#propdef-font-weight">font-weight</a>
  6529      <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
  6531      <td>normal
  6533     <tr>
  6534      <th><a class=property href="#descdef-src">src</a>
  6536      <td>[ &lt;url> [format(&lt;string>#)]? | &lt;font-face-name> ]#
  6538      <td>N/A
  6540     <tr>
  6541      <th><a class=property href="#descdef-unicode-range">unicode-range</a>
  6543      <td>&lt;urange>#
  6545      <td>U+0-10FFFF
  6546   </table>
  6547   <!--end-descriptors-->
  6548   <script type="text/javascript">
  6549 window.onload = function () {
  6550   if (!("devicePixelRatio" in window && window.devicePixelRatio > 1)) return;
  6551   var i, hiresElements = document.getElementsByClassName("hires");
  6552   for (i = 0; i < hiresElements.length; i++) {
  6553     var h = hiresElements[i];
  6554     if (h.tagName != "IMG") continue;
  6555     var src = h.getAttribute("src");
  6556     var src2x = src.replace(/\.\w+$/, function(m) { return "@2x" + m; });
  6557     h.src = src2x;
  6560 </script>
  6561 </html>
  6562 <!-- Keep this comment at the end of the file
  6563 Local variables:
  6564 mode: sgml
  6565 sgml-declaration:"~/SGML/HTML4.decl"
  6566 sgml-default-doctype-name:"html"
  6567 sgml-minimize-attributes:t
  6568 sgml-nofill-elements:("pre" "style" "br")
  6569 sgml-live-element-indicator:t
  6570 sgml-omittag:nil
  6571 sgml-shorttag:nil
  6572 sgml-namecase-general:t
  6573 sgml-general-insert-case:lower
  6574 sgml-always-quote-attributes:t
  6575 sgml-indent-step:nil
  6576 sgml-indent-data:t
  6577 sgml-parent-document:nil
  6578 sgml-exposed-tags:nil
  6579 sgml-local-catalogs:nil
  6580 sgml-local-ecat-files:nil
  6581 End:
  6582 -->
  6583 <!-- 
  6585 to do:
  6587 - wording of OpenType family name handling
  6588 - handling combining sequences in the font matching algorithm
  6589 - fix-up fi ligature example
  6591 -->

mercurial