csswg-drafts/css3-fonts/Fonts.html at 54fd2ae76f78c98db3ca72afb896b53bfa6ad54b · w3c/csswg-drafts · GitHub

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">

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

  <title>CSS3 Module: Fonts</title>
  <!--
      FIXME when publishing: copy the current default.css and link to
      "default.css" rather than "../default.css"
   -->
  <link href="../default.css" rel=stylesheet type="text/css">
  <link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
  type="text/css">

  <style type="text/css">

  body {
    padding: 2em 70px 2em 70px;
  }

  p + p, p.mtb {
    margin-top: 0.8em;
    text-indent: 0px;
  }

  #fontformats {
    margin-left: 2em;
    text-align: left;
  }

  #fontformats td {
    padding-right: 2em;
  }

  dd {
    margin-bottom: 1em;
  }

  pre {
  	font-size: 100%;
  }

  #authors dd {
    margin-bottom: 0;
  }

  #fontstylematchingalg {
    list-style-type: lower-alpha;
  }

  #fontmatchingalg ul, #fontmatchingalg ol {
    margin-top: 0.8em;
  }

  #fontmatchingalg li + li {
    margin-top: 0.8em;
  }

  div.example {
    padding: 1em;
    margin-top: 1em;
  }

  div.example + div.example {
    margin-top: 2em;
  }

  div.figure {
    page-break-inside: avoid;
  }

  </style>

 <body>
  <div class=head> <!--begin-logo-->
   <p><a href="http://www.w3.org/"><img alt=W3C height=48
    src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->

   <h1>CSS Fonts Module Level 3</h1>

   <h2 class="no-num no-toc" id=editors>Editor's Draft 21 January 2009</h2>

   <dl id=authors>
    <dt>This version:

    <dd><a
     href="http://dev.w3.org/csswg/css3-fonts/">http://dev.w3.org/csswg/css3-fonts/</a>


    <dt>Latest version:

    <dd><a
     href="http://www.w3.org/TR/css3-fonts/">http://www.w3.org/TR/css3-fonts/</a>

    <dt>Latest editor's draft:

    <dd><a
     href="http://dev.w3.org/csswg/css3-fonts/">http://dev.w3.org/csswg/css3-fonts/</a>

    <dt>Previous version (CSS3 Fonts):

    <dd><a
     href="http://www.w3.org/TR/2002/WD-css3-fonts-20020802">http://www.w3.org/TR/2002/WD-css3-fonts-20020802</a>

    <dt>Previous version (CSS3 Web Fonts):

    <dd><a
     href="http://www.w3.org/TR/2002/WD-css3-webfonts-20020802">http://www.w3.org/TR/2002/WD-css3-webfonts-20020802</a>

    <dt>Editor:

    <dd><a href="mailto:jdaggett@mozilla.com">John Daggett (Mozilla)</a>
   </dl>
   <!--begin-copyright-->
   <p class=copyright><a
    href="http://www.w
8096
3.org/Consortium/Legal/ipr-notice#Copyright"
    rel=license>Copyright</a> &copy; 2009 <a
    href="http://www.w3.org/"><acronym title="World Wide Web
    Consortium">W3C</acronym></a><sup>&reg;</sup> (<a
    href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute
    of Technology">MIT</acronym></a>, <a
    href="http://www.ercim.org/"><acronym title="European Research Consortium
    for Informatics and Mathematics">ERCIM</acronym></a>, <a
    href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
    href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
    <a
    href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
    and <a
    href="http://www.w3.org/Consortium/Legal/copyright-documents">document
    use</a> rules apply.</p>
   <!--end-copyright-->
   <hr title="Separator for header">
  </div>
  <!--
Note: this draft is still undergoing some major editing, so portions of
it may appear quite incoherent or inconsistent at times.  Please wait a
month or so before sending out flames...
-->
  <!--
To do:
 - font matching examples
 - polish font matching algorithm, deal with bolder/lighter matching
 - clean up font-weight wording, better definition of bolder/lighter
 - same for wider/narrower
 - specifics of SVG font reference handling
 - finish examples for unicode-range
 - italic/oblique substitution issue
 - font-size
 - move font-variant into font rendering section
 - font shorthand
 - TrueType/OpenType nitty gritty
 - make intro more concise and relevant to rest of the spec, point out specific general problems
 - illustrations of localized bold, italic names?
-->

  <h2 class="no-num no-toc" id=abstract>Abstract</h2>

  <p>This CSS3 module describes how font properties are specified and how
   font resources are loaded dynamically. The contents of this specification
   are a consolidation of content previously divided into CSS3 Fonts and CSS3
   Web Fonts modules.

  <h2 class="no-num no-toc" id=status>Status of this document</h2>
  <!--begin-status-->

  <p>This is a public copy of the editors' draft. It is provided for
   discussion only and may change at any moment. Its publication here does
   not imply endorsement of its contents by W3C. Don't cite this document
   other than as work in progress.

  <p>The (<a
   href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
   mailing list <a href="mailto:www-style@w3.org">www-style@w3.org</a> (see
   <a href="http://www.w3.org/Mail/Request">instructions</a>) is preferred
   for discussion of this specification. When sending e-mail, please put the
   text &#8220;css3-fonts&#8221; in the subject, preferably like this:
   &#8220;[<!---->css3-fonts<!---->] <em>&hellip;summary of
   comment&hellip;</em>&#8221;

  <p>This document was produced by the <a href="/Style/CSS/members">CSS
   Working Group</a> (part of the <a href="/Style/">Style Activity</a>).

  <p>This document was produced by a group operating under the <a
   href="/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent
   Policy</a>. W3C maintains a <a href="/2004/01/pp-impl/32061/status"
   rel=disclosure>public list of any patent disclosures</a> made in
   connection with the deliverables of the group; that page also includes
   instructions for disclosing a patent. An individual who has actual
   knowledge of a patent which the individual believes contains <a
   href="/Consortium/Patent-Policy-20040205/#def-essential">Essential
   Claim(s)</a> must disclose the information in accordance with <a
   href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the
   W3C Patent Policy</a>.</p>
  <!--end-status-->

  <h2 class="no-num no-toc" id=contents>Table of contents</h2>
  <!--begin-toc-->

  <ul class=toc>
   <li><a href="#introduction"><span class=secno>1 </span>Introduction</a>

   <li><a href="#typography"><span class=secno>2 </span>Typography
    Background</a>

   <li><a href="#font-properties"><span class=secno>3 </span>Font
    properties</a>
    <ul class=toc>
     <li><a href="#font-family"><span class=secno>3.1 </span>Font family: the
      &lsquo;<code class=property>font-family</code>&rsquo; property</a>
      <ul class=toc>
       <li><a href="#generic"><span class=secno>3.1.1 </span>Generic font
        families</a>
      </ul>

     <li><a href="#font-weight"><span class=secno>3.2 </span>Font weight: the
      &lsquo;<code class=property>font-weight</code>&rsquo; property</a>

     <li><a href="#font-proportion"><span class=secno>3.3 </span>Font
      proportion: the &lsquo;<code class=property>font-stretch</code>&rsquo;
      property</a>

     <li><a href="#font-style"><span class=secno>3.4 </span>Font style: the
      &lsquo;<code class=property>font-style</code>&rsquo; property</a>

     <li><a href="#small"><span class=secno>3.5 </span>Small caps: the
      &lsquo;<code class=property>font-variant</code>&rsquo; property</a>

     <li><a href="#font-size"><span class=secno>3.6 </span>Font size: the
      &lsquo;<code class=property>font-size</code>&rsquo; property</a>

     <li><a href="#relative"><span class=secno>3.7 </span>Relative sizing:
      the &lsquo;<code class=property>font-size-adjust</code>&rsquo;
      property</a>

     <li><a href="#shorthand"><span class=secno>3.8 </span>Shorthand font
      property: the &lsquo;<code class=property>font</code>&rsquo;
      property</a>
    </ul>

   <li><a href="#font-resources"><span class=secno>4 </span>Font
    resources</a>
    <ul class=toc>
     <li><a href="#the-font-face"><span class=secno>4.1 </span>The @font-face
      rule</a>

     <li><a href="#font-family0"><span class=secno>4.2 </span>Font family:
      the &lsquo;<code class=property>font-family</code>&rsquo;
      descriptor</a>

     <li><a href="#font-reference"><span class=secno>4.3 </span>Font
      reference: the &lsquo;<code class=property>src</code>&rsquo;
      descriptor</a>

     <li><a href="#font-property"><span class=secno>4.4 </span>Font property
      descriptors: the &lsquo;<code class=property>font-style</code>&rsquo;,
      &lsquo;<code class=property>font-weight</code>&rsquo;, &lsquo;<code
      class=property>font-stretch</code>&
F328
amp;rsquo; descriptors</a>

     <li><a href="#character"><span class=secno>4.5 </span>Character range:
      the &lsquo;<code class=property>unicode-range</code>&rsquo;
      descriptor</a>
    </ul>

   <li><a href="#font-matching"><span class=secno>5 </span>Font matching
    algorithm</a>
    <ul class=toc>
     <li><a href="#examples"><span class=secno>5.1 </span>Examples of font
      matching</a>
    </ul>

   <li><a href="#font-rendering"><span class=secno>6 </span>Font rendering
    properties</a>

   <li class=no-num><a href="#appendix">Appendix A: Mapping CSS properties to
    font features</a>

   <li class=no-num><a href="#appendix0">Appendix B: Font licensing
    issues</a>

   <li class=no-num><a href="#acknowledgments">Acknowledgments</a>

   <li class=no-num><a href="#references">References</a>
    <ul class=toc>
     <li class=no-num><a href="#normative">Normative</a>

     <li class=no-num><a href="#informative">Informative</a>
    </ul>

   <li class=no-num><a href="#index">Index</a>

   <li class=no-num><a href="#property-index">Property index</a>
  </ul>
  <!--end-toc-->

  <h2 id=introduction><span class=secno>1 </span>Introduction</h2>

  <p>Font properties in CSS determine which fonts are used when rendering
   text. Fonts represent collections of letterforms, or glyphs, that uniquely
   describe the visual appearance of the underlying characters. Fonts are
   often grouped into font families that share a common aesthetic. In CSS,
   font families are specified by name but a particular face within a family
   is selected based on the value of other font properties. To specify text
   in bold Helvetica, one could use:

  <pre>
p { font-family: Helvetica; font-weight: bold; }
</pre>

  <p>When an exact match doesn't exist for a particular combination of style
   attributes, CSS defines a specific way in which another face is chosen.
   Font properties are independent of each other, allowing text to be
   rendered similarly even in environments where the set of available fonts
   is different. In addition to the font properties defined in CSS2.1, CSS3
   defines the @font-face rule which specifies font resources that can be
   downloaded when needed, often referred to as "web fonts".

  <h2 id=typography><span class=secno>2 </span>Typography Background</h2>
  <!--
 - Wide variation in character forms, glyphs
 - Use of diacritics adds complications to even "simple" alphabets
 - Examples from Czech, Slovak, African romanizations
 - Vietnamese stacking example
 - General use of ligatures
 - Required for languages such as Arabic
 - Problems with creating "universal fonts"
-->

  <p><em>This section is included as background for some of the problems and
   situations that are described in other sections. It should be viewed as
   informative only.</em>

  <p> Typographic traditions vary across the globe so there is no unique way
   to classify all fonts across languages and cultures. For even common Latin
   letters, wide variations are possible:

  <div class=figure><img src=aaaaaa.png>
   <p class=caption>One character, many glyph variations
  </div>

  <p>Differences in the anatomy of letterforms is one way to distinguish
   fonts. For Latin fonts, flourishes at the ends of a character's main
   strokes, or serifs, can distinguish a font from those without. Similar
   comparisons exist in non-Latin fonts between fonts with tapered strokes
   and those using primarily uniform strokes:

  <div class=figure><img src=serifvssansserif.png>
   <p class=caption>Letterforms with and without serifs
  </div>

  <div class=figure><img src=minchovsgothic.png>
   <p class=caption>Similar groupings for Japanese typefaces
  </div>

  <p>Fonts contain letterforms and the data needed to map characters to these
   letterforms. Often this may be a simple one-to-one mapping but more
   complex mappings are also possible. The use of combining diacritic marks
   creates many variations for an underlying letterform:

  <div class=figure><img src=aaaaaa-diacritics.png>
   <p class=caption>Variations with diacritic marks
  </div>
  <!-- Include stacking diacritics?  Hmm, Vietnamese example? -->

  <p>A sequence of characters can be represented by a single glyph known as a
   ligature:

  <div class=figure><img src=final-ligature.png>
   <p class=caption>Ligature example
  </div>

  <p>Visual transformations based on textual context like this may be a
   stylistic option for European langauges but are required to correctly
   render languages like Arabic; the lam and alef characters below
   <em>must</em> be combined when they exist in sequence:

  <div class=figure><img src=lamaleflig.png>
   <p class=caption>Required Arabic ligature
  </div>

  <p>The relative complexity of these shaping transformations requires
   additional data within the font.

  <p>Sets of font faces with various stylistic variations are often grouped
   together into font families. In the simplest case a regular face is
   supplemented with bold and italic faces but much more extensive groupings
   are possible. Variations in the thickness of letterform strokes, or the
   weight, or the overall proportions of the letterform, or the width, are
   most common. In the example below, each letter uses a different font face
   within the Univers font family. The width used increases from top to
   bottom and the weight increases from left to right:

  <div class=figure><img src=weightwidthvariations.png>
   <p class=caption>Weight and width variations within a single font family
  </div>

  <p>Creating fonts that support multiple scripts is a difficult task;
   designers need to understand the cultural traditions surronding the use of
   type in different scripts and come up with letterforms that somehow share
   a common theme. Many languages often share a common script and each of
   these languages may have noticeable stylistic differences. The Arabic
   script is shared by Persian and Urdu and Cyrillic is used with many
   languages, not just Russian.

  <p>Fonts provide a character map that details the set of characters for
   they have glyphs. If a document contains characters not supported by a
   specified font, a user agent may revert to a system font fallback
   procedure to find glyphs to render these characters correctly. If no font
   can be found, some form of "missing glyph" character is rendered by the
   user agent. Often these are the result of authors failing to explicitly
   indicate the encoding used by a document.

  <h2 id=font-properties><span class=secno>3 </span>Font properties</h2>

  <p>The particular font face used to render a character is determined by the
   font family and other font properties that apply to a given element. This
   structure allows settings to be varied independent of each other.</p>
  <!-- prop: font-family -->

  <h3 id=font-family><span class=secno>3.1 </span>Font family: the
   &lsquo;<code class=property><a
   href="#font-family2">font-family</a></code>&rsquo; property</h3>

  <table class=propdef id=namefont-family>
   <tbody>
    <tr>
     <td>Name:

     <td><dfn id=font-family1>font-family</dfn>

    <tr>
     <td>Value:

     <td>[[ &lt;family-name> | &lt;generic-family> ] [, &lt;family-name>|
      &lt;generic-family>]* ] | inherit

    <tr>
     <td>Initial:

     <td>depends on user agent

    <tr>
     <td>Applies to:

     <td>all elements

    <tr>
     <td>Inherited:

     <td>yes

    <tr>
     <td>Percentages:

     <td>N/A

    <tr>
     <td>Media:

     <td>visual

    <tr>
     <td>Computed&nbsp;value:

     <td>as specified
  </table>

  <p>This property specifies a prioritized list of font family names or
   generic family names. A user agent iterates through the list of family
   names until it matches an available font that contains a glyph for the
   character to be rendered. This allows for differences in available fonts
   across across platforms and for differences in the range of characters
   supported by individual fonts.

  <p>A font family name only specifies a name given to a set of font faces,
   it does not specify an individual face. Given the availability of the
   fonts below, Futura would match but Futura Medium would not:

  <div class=figure><img src=familyvsfacename.png>
   <p class=caption>Family and individual face names
  </div>

  <p>Some font formats support the use of multiple family names for different
   localizations. User agents should recognize any of these names independent
   of the underlying platform localization, system API used or document
   encoding:

  <div class=figure><img src=localizedfamilynames.png>
   <p class=caption>Localized family names
  </div>

  <p>Consider the example below:

  <div class=example>
   <pre>body {
    font-family: Helvetica, Verdana, sans-serif;
}</pre>
  </div>

  <p>If Helvetica is available it will be used when rendering. If neither
   Helvetica or Verdana is present, then the user agent defined sans serif
   font will be used.

  <p>There are two types of font family names:

  <dl>
   <dt>&lt;family-name&gt;

   <dd>The name of a font family of choice such as Helvetica or Verdana in
    the previous example. Font family names containing more than one word
    should be quoted. If quoting is omitted, whitespace characters before and
    after the font family name are ignored and any sequence of whitespace
    characters inside the font name is converted to a single space. Depending
    upon the font format used, font family names may be case-sensitive.

   <dt>&lt;generic-family&gt;

   <dd> The following generic family keywords are defined: &lsquo;<code
    class=property><a href="#serif">serif</a></code>&rsquo;, &lsquo;<code
    class=property><a href="#sans-serif">sans-serif</a></code>&rsquo;,
    &lsquo;<code class=property><a href="#cursive">cursive</a></code>&rsquo;,
    &lsquo;<code class=property><a href="#fantasy">fantasy</a></code>&rsquo;,
    and &lsquo;<code class=property><a
    href="#monospace">monospace</a></code>&rsquo;. These keywords can be used
    as a general fallback mechanism when an author's desired font choices are
    not available. As keywords, they should not be quoted. Authors are
    encouraged to append a generic font family as a last alternative for
    improved robustness.
  </dl>

  <h4 id=generic><span class=secno>3.1.1 </span>Generic font families</h4>

  <p>All five generic font families are defined to exist in all CSS
   implementations (they need not necessarily map to five distinct actual
   fonts). User agents should provide reasonable default choices for the
   generic font families, which express the characteristics of each family as
   well as possible within the limits allowed by the underlying technology.
   User agents are encouraged to allow users to select alternative choices
   for the generic fonts.

  <h5 class="no-num no-toc"> <span class=index-def id=serif0 title="serif,
   definition of"><a name=serif-def><dfn id=serif>serif</dfn></a></span></h5>

  <p>Glyphs of serif fonts, as the term is used in CSS, have finishing
   strokes, flared or tapering ends, or have actual serifed endings
   (including slab serifs). Serif fonts are typically proportionately-spaced.
   They often display a greater variation between thick and thin strokes than
   fonts from the &lsquo;<code class=property><a
   href="#sans-serif">sans-serif</a></code>&rsquo; generic font family. CSS
   uses the term &lsquo;<code class=property><a
   href="#serif">serif</a></code>&rsquo; to apply to a font for any script,
   although other names may be more familiar for particular scripts, such as
   Mincho (Japanese), Sung or Song (Chinese), Batang (Korean). Any font that
   is so described may be used to represent the generic &lsquo;<code
   class=property><a href="#serif">serif</a></code>&rsquo; family.

  <div class=figure><img src=serifexamples.png>
   <p class=caption>Sample serif fonts
  </div>

  <h5 class="no-num no-toc"> <span class=index-def id=sans-serif0
   title="sans-serif, definition of"> <a name=sans-serif-def><dfn
   id=sans-serif>sans-serif</dfn></a></span></h5>

  <p>Glyphs in sans-serif fonts, as the term is used in CSS, have stroke
   endings that are plain -- without any flaring, cross stroke, or other
   ornamentation. Sans-serif fonts are typically proportionately-spaced. They
   often have little variation between thick and thin strokes, compared to
   fonts from the &lsquo;<code class=property><a
   href="#serif">serif</a></code>&rsquo; family. CSS uses the term
   &lsquo;<code class=property><a
   href="#sans-serif">sans-serif</a></code>&rsquo; to apply to a font for any
   script, although other names may be more familiar for particular scripts,
   such as Gothic (Japanese), Kai (Chinese), or Gulim (Korean). Any font that
   is so described may be used to represent the generic &lsquo;<code
   class=property><a href="#sans-serif">sans-serif</a></code>&rsquo; family.

  <p class=issue>Kai for Chinese looks wrong, looks to be a serif-like face.

  <div class=figure><img src=sansserifexamples.png>
   <p class=caption>Sample sans-serif fonts
  </div>

  <h5 class="no-num no-toc"> <span class=index-def id=cursive0
   title="cursive, definition of"> <a name=cursive-def><dfn
   id=cursive>cursive</dfn></a></span></h5>

  <p>Glyphs in cursive fonts generally have either joining strokes or other
   cursive characteristics beyond those of italic typefaces. The glyphs are
   partially or completely connected, and the result looks more like
   handwritten pen or brush writing than printed letterwork. Some scripts,
   such as Arabic, are almost always cursive. CSS uses the term &lsquo;<code
   class=property><a href="#cursive">cursive</a></code>&rsquo; to apply to a
   font for any script, although other names such as Chancery, Brush, Swing
   and Script are also used in font names.

  <div class=figure><img src=cursiveexamples.png>
   <p class=caption>Sample cursive fonts
  </div>

  <h5 class="no-num no-toc"> <span class=index-def id=fantasy0
   title="fantasy, definition of"> <a name=fantasy-def><dfn
   id=fantasy>fantasy</dfn></a></span></h5>

  <p>Fantasy fonts are primarily decorative fonts that contain playful
   representations of characters. These do not include Pi or Picture fonts
   which do not represent actual characters.

  <div class=figure><img src=fantasyexamples.png>
   <p class=caption>Sample fantasy fonts

  <h5 class="no-num no-toc"> <span class=index-def id=monospace0
   title="monospace, definition of"> <a name=monospace-def><dfn
   id=monospace>monospace</dfn></a></span></h5>

  <p>The sole criterion of a monospace font is that all glyphs have the same
   fixed width. This is often used to render samples of computer code.

  <div class=figure><img src=monospaceexamples.png>
   <p class=caption>Sample monospace fonts
  </div>
  <!-- prop: font-weight -->

  <h3 id=font-weight><span class=secno>3.2 </span>Font weight: the
   &lsquo;<code class=property><a
   href="#font-weight1">font-weight</a></code>&rsquo; property</h3>

  <table class=propdef id=namefont-weight>
   <tbody>
    <tr>
     <td>Name:

     <td><dfn id=font-weight0>font-weight</dfn>

    <tr>
     <td>Value:

     <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
      | 700 | 800 | 900 | inherit

    <tr>
     <td>Initial:

     <td>normal

    <tr>
     <td>Applies to:

     <td>all elements

    <tr>
     <td>Inherited:

     <td>yes

    <tr>
     <td>Percentages:

     <td>N/A

    <tr>
     <td>Media:

     <td>visual

    <tr>
     <td>Computed&nbsp;value:

     <td>see description
  </table>

  <p>The <a class=noxref href="#font-weight"><span
   class=property>&lsquo;<code
   class=property>font-weight</code>&rsquo;</span></a> property specifies
   weight of glyphs in the font, their degree of blackness or stroke
   thickness.

  <p>Values have the following meanings:

  <dl>
   <dt>100 to 900

   <dd>These values form an ordered sequence, where each number indicates a
    weight that is at least as dark as its predecessor. These roughly
    correspond to the commonly used weight names below:
  </dl>

  <ul>
   <li>100 - Thin

   <li>200 - Extra Light (Ultra Light)

   <li>300 - Light

   <li>400 - Normal

   <li>500 - Medium

   <li>600 - Semi Bold (Demi Bold)

   <li>700 - Bold

   <li>800 - Extra Bold (Ultra Bold)

   <li>900 - Black (Heavy)
  </ul>

  <dl>
   <dt><strong>normal</strong>

   <dd>Same as &lsquo;<code class=css>400</code>&rsquo;.

   <dt><strong>bold</strong>

   <dd>Same as &lsquo;<code class=css>700</code>&rsquo;.

   <dt><strong>bolder</strong>

   <dd>Specifies the weight of the face bolder than the inherited value.

   <dt><strong>lighter</strong>

   <dd>Specifies the weight of the face lighter than the inherited value.
  </dl>

  <p>Font formats that use a scale other than a nine step scale should map
   their scale onto the CSS scale so that 400 roughly corresponds with a face
   that would be labeled as Regular, Book, Roman and 700 roughly matches a
   face that would be labeled as Bold. Or weights may be inferred from the
   style names, ones that correspond roughly with the scale above. The scale
   is relative, so a face with a larger weight should never appear lighter.
   If style names are used to infer weights, care should be taken to handle
   common variations in different locales:

  <p>Quite often there are only a few weights available for a particular font
   family. When a weight is specified for which no face exists, a face with a
   nearby weight is used. In general, bold weights map to faces with heavier
   weights and light weights map to faces with lighter weights (see the font
   matching section below for a precise definition). The examples here
   illustrate which face is used for different weights, grey indicates a face
   for that weight does not exist so a face with a nearby weight is used:

  <div class=figure><img src=optimaweights.png>
   <p class=caption>Weight mappings for a font family with 400, 700 and 900
    weight faces
  </div>

  <div class=figure><img src=hiraginoweights.png>
   <p class=caption>Weight mappings for a font family with 300 and 600 weight
    faces
  </div>

  <p>Description of how bolder and lighter work. They are relative to an
   inherited value and "accumulate". Child elements inherit the given weight
   plus the accumulated relative bolder/lighter values.

  <p>Although not well-loved by typographers, bold faces are often
   synthesized by user agents for faces that lack actual bold faces. The use
   of the lighter/bolder can lead to strange interactions with synthetic
   bolding.</p>
  <!-- prop: font-stretch -->

  <h3 id=font-proportion><span class=secno>3.3 </span>Font proportion: the
   &lsquo;<code class=property><a
   href="#font-stretch0">font-stretch</a></code>&rsquo; property</h3>

  <table class=propdef id=namefont-stretch>
   <tbody>
    <tr>
     <td>Name:

     <td><dfn id=font-stretch>font-stretch</dfn>

    <tr>
     <td>Value:

     <td>normal | wider | narrower | ultra-condensed | extra-condensed |
      condensed | semi-condensed | semi-expanded | expanded | extra-expanded
      | ultra-expanded | inherit

    <tr>
     <td>Initial:

     <td>normal

    <tr>
     <td>Applies to:

     <td>all elements

    <tr>
     <td>Inherited:

     <td>yes

    <tr>
     <td>Percentages:

     <td>N/A

    <tr>
     <td>Media:

     <td>visual

    <tr>
     <td>Computed&nbsp;value:

     <td>as specified
  </table>

  <p>The <a class=noxref href="#font-stretch"><span
   class=property>&lsquo;<code
   class=property>font-stretch</code>&rsquo;</span></a> property selects a
   normal, condensed, or expanded face from a font family. Absolute keyword
   values have the following ordering, from narrowest to widest:

  <ul>
   <li>Ultra Condensed

   <li>Extra Condensed

   <li>Condensed

   <li>Semi Condensed

   <li>Normal

   <li>Semi Expanded

   <li>Expanded

   <li>Extra Expanded

   <li>Ultra Expanded
  </ul>

  <p>The relative keyword &lsquo;<code class=property>wider</code>&rsquo;
   sets the value to the next expanded value above the inherited value (while
   not increasing it above &lsquo;<code
   class=property>ultra-expanded</code>&rsquo;); the relative keyword
   &lsquo;<code class=property>narrower</code>&rsquo; sets the value to the
   next condensed value below the inherited value (while not decreasing it
   below &lsquo;<code class=property>ultra-condensed</code>&rsquo;).

  <p class=issue>Do we really need all these keywords?!? Would
   ultra-expanded, expanded, normal, condensed, ultra-condensed suffice?

  <p class=issue>What about synthesized condensed/expanded? What are the
   "filling in the holes" rules, non-normal values map away from normal?</p>
  <!-- prop: font-style -->

  <h3 id=font-style><span class=secno>3.4 </span>Font style: the &lsquo;<code
   class=property><a href="#font-style1">font-style</a></code>&rsquo;
   property</h3>

  <table class=propdef id=namefont-style>
   <tbody>
    <tr>
     <td>Name:

     <td><dfn id=font-style0>font-style</dfn>

    <tr>
     <td>Value:

     <td>normal | italic | oblique | inherit

    <tr>
     <td>Initial:

     <td>normal

    <tr>
     <td>Applies to:

     <td>all elements

    <tr>
     <td>Inherited:

<
8096
/div>
     <td>yes

    <tr>
     <td>Percentages:

     <td>N/A

    <tr>
     <td>Media:

     <td>visual

    <tr>
     <td>Computed&nbsp;value:

     <td>as specified
  </table>

  <p>The <a class=noxref href="#font-style"><span class=property>&lsquo;<code
   class=property>font-style</code>&rsquo;</span></a> property allows italic
   or oblique faces to be selected. Italic forms are generally cursive in
   nature while oblique faces are typically sloped versions of the regular
   face. Oblique faces can be simulated by artificially sloping the glyphs of
   the regular face. Compare the artificially sloped renderings of Palatino
   &lsquo;<code class=property>a</code>&rsquo; and Baskerville &lsquo;<code
   class=property>N</code>&rsquo; in grey with the actual italic versions:

  <div class=figure><img src=realvsfakeitalics.png>
   <p class=caption>Artificial sloping versus real italics
  </div>

  <p>A value of &lsquo;<code class=property>normal</code>&rsquo; selects a
   face that is classified as &lsquo;<code
   class=property>normal</code>&rsquo;, while &lsquo;<code
   class=property>oblique</code>&rsquo; selects a font that is labeled
   &lsquo;<code class=property>oblique</code>&rsquo;. A value of &lsquo;<code
   class=property>italic</code>&rsquo; selects a font that is labeled
   &lsquo;<code class=property>italic</code>&rsquo;, or, if that is not
   available, one labeled &lsquo;<code class=property>oblique</code>&rsquo;.
   If no italic or oblique faces is available, an oblique face can by
   synthesized by rendering the normal face with a sloping transformation
   applied.

  <div class=figure>
   <p class=caption>Common localizations of italic and oblique names
  </div>

  <p>Many scripts lack the tradition of mixing a cursive form within text
   rendered with a normal face. Chinese, Japanese and Korean fonts almost
   always lack italic or oblique faces. Fonts that support a mixture of
   scripts will sometimes omit specific scripts such as Arabic from the set
   of glyphs supported in the italic face. User agents should be careful
   about making character map assumptions across faces.

  <p class=issue>What is the existing behavior for oblique? Is it actually
   <em>ever</em> relevant, i.e. is there a font that defines both italic and
   oblique faces? Or is it effectively an alias for italic?</p>
  <!-- prop: font-variant -->

  <h3 id=small><span class=secno>3.5 </span>Small caps: the &lsquo;<code
   class=property><a href="#font-variant">font-variant</a></code>&rsquo;
   property</h3>

  <table class=propdef id=namefont-variant>
   <tbody>
    <tr>
     <td>Name:

     <td><dfn id=font-variant>font-variant</dfn>

    <tr>
     <td>Value:

     <td>normal | small-caps | inherit

    <tr>
     <td>Initial:

     <td>normal

    <tr>
     <td>Applies to:

     <td>all elements

    <tr>
     <td>Inherited:

     <td>yes

    <tr>
     <td>Percentages:

     <td>N/A

    <tr>
     <td>Media:

     <td>visual

    <tr>
     <td>Computed&nbsp;value:

     <td>as specified
  </table>

  <ul>
   <li>small-caps

   <li>used to select alternate glyphs if available in font

   <li>can be simulated using sized versions of uppercase glyphs
  </ul>

  <p>In a small-caps font, the glyphs for lowercase letters look similar to
   the uppercase ones, but in a smaller size and with slightly different
   proportions. The <a class=noxref href="#font-variant"><span
   class=property>&lsquo;<code