css-fonts/Fonts.html@bf52664a49ae
css-fonts/Fonts.html
Thu, 30 May 2013 11:39:14 +0900
- author
- John Daggett <jdaggett@mozilla.com>
- date
- Thu, 30 May 2013 11:39:14 +0900
- changeset 8276
- bf52664a49ae
- parent 8272
- 5e29c9d80cca
- child 8277
- a09de2f3e565
- permissions
- -rw-r--r--
[css-fonts] rework font-kerning description
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-29-may-2013>Editor's Draft 29
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-20130529/">http://www.w3.org/TR/2013/ED-css3-fonts-20130529/</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&product=CSS&component=Fonts&bug_status=NEW&bug_status=ASSIGNED&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="#composite-fonts"><span class=secno>4.6 </span>Using
302 character ranges to define composite fonts</a>
304 <li><a href="#font-rend-desc"><span class=secno>4.7 </span>Font
305 features: the font-variant and font-feature-settings descriptors</a>
307 <li><a href="#font-face-loading"><span class=secno>4.8 </span>Font
308 loading guidelines</a>
310 <li><a href="#same-origin-restriction"><span class=secno>4.9
311 </span>Same-origin restriction for fonts</a>
312 <ul class=toc>
313 <li><a href="#default-same-origin-restriction"><span class=secno>4.9.1
314 </span>Default same-origin restriction</a>
316 <li><a href="#allowing-cross-origin-font-loading"><span
317 class=secno>4.9.2 </span>Allowing cross-origin font loading</a>
318 </ul>
319 </ul>
321 <li><a href="#font-matching-algorithm"><span class=secno>5 </span>Font
322 Matching Algorithm</a>
323 <ul class=toc>
324 <li><a href="#font-family-casing"><span class=secno>5.1 </span>Case
325 sensitivity of font family names</a>
327 <li><a href="#font-style-matching"><span class=secno>5.2 </span>Matching
328 font styles</a>
330 <li><a href="#cluster-matching"><span class=secno>5.3 </span>Cluster
331 matching</a>
333 <li><a href="#char-handling-issues"><span class=secno>5.4
334 </span>Character handling issues</a>
336 <li><a href="#font-matching-changes"><span class=secno>5.5 </span>Font
337 matching changes since CSS 2.1</a>
339 <li><a href="#font-matching-examples"><span class=secno>5.6 </span>Font
340 matching examples</a>
341 </ul>
343 <li><a href="#font-rend-props"><span class=secno>6 </span>Font Feature
344 Properties</a>
345 <ul class=toc>
346 <li><a href="#glyph-selection-positioning"><span class=secno>6.1
347 </span>Glyph selection and positioning</a>
349 <li><a href="#language-specific-support"><span class=secno>6.2
350 </span>Language-specific display</a>
352 <li><a href="#font-kerning-prop"><span class=secno>6.3 </span>Kerning:
353 the font-kerning property</a>
355 <li><a href="#font-variant-ligatures-prop"><span class=secno>6.4
356 </span>Ligatures: the font-variant-ligatures property</a>
358 <li><a href="#font-variant-position-prop"><span class=secno>6.5
359 </span>Subscript and superscript forms: the font-variant-position
360 property</a>
362 <li><a href="#font-variant-caps-prop"><span class=secno>6.6
363 </span>Capitalization: the font-variant-caps property</a>
365 <li><a href="#font-variant-numeric-prop"><span class=secno>6.7
366 </span>Numerical formatting: the font-variant-numeric property</a>
368 <li><a href="#font-variant-alternates-prop"><span class=secno>6.8
369 </span>Alternates and swashes: the font-variant-alternates property</a>
372 <li><a href="#font-feature-values"><span class=secno>6.9 </span>Defining
373 font specific alternates: the <code>@font-feature-values</code>
374 rule</a>
376 <li><a href="#font-variant-east-asian-prop"><span class=secno>6.10
377 </span>East Asian text rendering: the font-variant-east-asian
378 property</a>
380 <li><a href="#font-variant-prop"><span class=secno>6.11 </span>Overall
381 shorthand for font rendering: the font-variant property</a>
383 <li><a href="#font-feature-settings-prop"><span class=secno>6.12
384 </span>Low-level font feature settings control: the
385 font-feature-settings property</a>
387 <li><a href="#font-language-override-prop"><span class=secno>6.13
388 </span>Font language override: the font-language-override property</a>
389 </ul>
391 <li><a href="#font-feature-resolution"><span class=secno>7 </span>Font
392 Feature Resolution </a>
393 <ul class=toc>
394 <li><a href="#default-features"><span class=secno>7.1 </span>Default
395 features</a>
397 <li><a href="#feature-precedence"><span class=secno>7.2 </span>Feature
398 precedence</a>
400 <li><a href="#feature-precedence-examples"><span class=secno>7.3
401 </span>Feature precedence examples</a>
402 </ul>
404 <li><a href="#object-model"><span class=secno>8 </span>Object Model</a>
405 <ul class=toc>
406 <li><a href="#om-fontface"><span class=secno>8.1 </span>The
407 <code>CSSFontFaceRule</code> interface</a>
409 <li><a href="#om-fontfeaturevalues"><span class=secno>8.2 </span>The
410 <code>CSSFontFeatureValuesRule</code> interface</a>
411 </ul>
413 <li class=no-num><a href="#platform-props-to-css">Appendix A: Mapping
414 platform font properties to CSS properties</a>
416 <li class=no-num><a href="#ch-ch-ch-changes">Changes</a>
417 <ul class=toc>
418 <li class=no-num><a href="#recent-changes"> Changes from the February
419 2013 CSS3 Fonts Working Draft</a>
420 </ul>
422 <li class=no-num><a href="#acknowledgments">Acknowledgments</a>
424 <li class=no-num><a href="#conformance"> Conformance</a>
425 <ul class=toc>
426 <li class=no-num><a href="#conventions"> Document Conventions</a>
428 <li class=no-num><a href="#conformance-classes"> Conformance Classes</a>
431 <li class=no-num><a href="#partial"> Partial Implementations</a>
433 <li class=no-num><a href="#experimental"> Experimental
434 Implementations</a>
436 <li class=no-num><a href="#testing"> Non-Experimental
437 Implementations</a>
438 </ul>
440 <li class=no-num><a href="#references">References</a>
441 <ul class=toc>
442 <li class=no-num><a href="#normative-references">Normative
443 References</a>
445 <li class=no-num><a href="#other-references">Other References</a>
446 </ul>
448 <li class=no-num><a href="#index">Index</a>
450 <li class=no-num><a href="#property-index">Property index</a>
451 </ul>
452 <!--end-toc-->
454 <h2 id=introduction><span class=secno>1 </span>Introduction</h2>
456 <p>A font provides a resource containing the visual representation of
457 characters. At the simplest level it contains information that maps
458 character codes to shapes (called glyphs) that represent these characters.
459 Fonts sharing a common design style are commonly grouped into font
460 families classified by a set of standard font properties. Within a family,
461 the shape displayed for a given character can vary by stroke weight, slant
462 or relative width, among others. An individual font face is described by a
463 unique combination of these properties. For a given range of text, CSS
464 font properties are used to select a font family and a specific font face
465 within that family to be used when rendering that text. As a simple
466 example, to use the bold form of Helvetica one could use:
468 <pre>body {
469 font-family: Helvetica;
470 font-weight: bold;
471 }</pre>
473 <p>Font resources may be installed locally on the system on which a user
474 agent is running or downloadable. For local font resources descriptive
475 information can be obtained directly from the font resource. For
476 downloadable font resources (sometimes referred to as web fonts), the
477 descriptive information is included with the reference to the font
478 resource.
480 <p>Families of fonts typically don't contain a single face for each
481 possible variation of font properties. The CSS font selection mechanism
482 describes how to match a given set of CSS font properties to a single font
483 face.
485 <h2 id=typography-background><span class=secno>2 </span>Typography
486 Background</h2>
488 <p><em>This section is non-normative.</em>
490 <p> Typographic traditions vary across the globe, so there is no unique way
491 to classify all fonts across languages and cultures. For even common Latin
492 letters, wide variations are possible:
494 <div class=figure><img alt="variations in glyphs for a single character"
495 src=aaaaaa.png>
496 <p class=caption>One character, many glyph variations
497 </div>
499 <p>Differences in the anatomy of letterforms is one way to distinguish
500 fonts. For Latin fonts, flourishes at the ends of a character's main
501 strokes, or serifs, can distinguish a font from those without. Similar
502 comparisons exist in non-Latin fonts between fonts with tapered strokes
503 and those using primarily uniform strokes:
505 <div class=figure><img alt="serif vs. non-serifs" src=serifvssansserif.png>
506 <p class=caption>Letterforms with and without serifs
507 </div>
509 <div class=figure><img alt="serif vs. non-serifs for japanese"
510 src=minchovsgothic.png>
511 <p class=caption>Similar groupings for Japanese typefaces
512 </div>
514 <p>Fonts contain letterforms and the data needed to map characters to these
515 letterforms. Often this may be a simple one-to-one mapping, but more
516 complex mappings are also possible. The use of combining diacritic marks
517 creates many variations for an underlying letterform:
519 <div class=figure><img alt="diacritic marks" src=aaaaaa-diacritics.png>
520 <p class=caption>Variations with diacritic marks
521 </div>
523 <p>A sequence of characters can be represented by a single glyph known as a
524 ligature:
526 <div class=figure><img alt="example of a fi ligature"
527 src=final-ligature.png>
528 <p class=caption>Ligature example
529 </div>
531 <p>Visual transformations based on textual context are often stylistic
532 option in European languages. They are required to correctly render
533 languages like Arabic, the lam and alef characters below <em>must</em> be
534 combined when they exist in sequence:
536 <div class=figure><img alt="lam alef ligature" src=lamaleflig.png>
537 <p class=caption>Required Arabic ligature
538 </div>
540 <p>The relative complexity of these shaping transformations requires
541 additional data within the font.
543 <p>Sets of font faces with various stylistic variations are often grouped
544 together into font families. In the simplest case a regular face is
545 supplemented with bold and italic faces, but much more extensive groupings
546 are possible. Variations in the thickness of letterform strokes, the <dfn
547 id=weight>weight</dfn>, and the overall proportions of the letterform, the
548 <dfn id=width>width</dfn>, are most common. In the example below, each
549 letter uses a different font face within the Univers font family. The
550 width used increases from top to bottom and the weight increases from left
551 to right:
553 <div class=figure><img alt="various width and weight variations within a
554 single family" src=weightwidthvariations.png>
555 <p class=caption>Weight and width variations within a single font family
556 </div>
558 <p>Creating fonts that support multiple scripts is a difficult task;
559 designers need to understand the cultural traditions surrounding the use
560 of type in different scripts and come up with letterforms that somehow
561 share a common theme. Many languages often share a common script and each
562 of these languages may have noticeable stylistic differences. For example,
563 the Arabic script is shared by Persian and Urdu and Cyrillic is used with
564 many languages, not just Russian.
566 <p>The <a href="#character-map"><em>character map</em></a> of a font
567 defines the mapping of characters to glyphs for that font. If a document
568 contains characters not supported by the <a href="#character-map"><em
569 title="character map">character maps</em></a> of the fonts contained in a
570 font family list, a user agent may use a system font fallback procedure to
571 locate an appropriate font that does. If no appropriate font can be found,
572 some form of "missing glyph" character will be rendered by the user agent.
573 System fallback can occur when the specified list of font families does
574 not include a font that supports a given character.
576 <p>Although the <a href="#character-map"><em>character map</em></a> of a
577 font maps a given character to a glyph for that character, modern font
578 technologies such as OpenType and AAT (Apple Advanced Typography) provide
579 ways of mapping a character to different glyphs based upon feature
580 settings. Fonts in these formats allow these features to be embedded in
581 the font itself and controlled by applications. Common typographic
582 features which can be specified this way include ligatures, swashes,
583 contextual alternates, proportional and tabular figures, and automatic
584 fractions, to list just a few. For a visual overview of OpenType features,
585 see the <a href="#OPENTYPE-FONT-GUIDE"
586 rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
588 <h2 id=basic-font-props><span class=secno>3 </span>Basic Font Properties</h2>
590 <p>The particular font face used to render a character is determined by the
591 font family and other font properties that apply to a given element. This
592 structure allows settings to be varied independent of each other.</p>
593 <!-- prop: font-family -->
595 <h3 id=font-family-prop><span class=secno>3.1 </span>Font family: the <a
596 href="#propdef-font-family">font-family</a> property</h3>
598 <table class=propdef id=namefont-familyvalue-ltfamily-namegt-ltg>
599 <tbody>
600 <tr>
601 <td>Name:
603 <td><dfn id=propdef-font-family>font-family</dfn>
605 <tr>
606 <td>Value:
608 <td>[ <a href="#family-name-value"><var><family-name></var></a> |
609 <a href="#generic-family-value"><var><generic-family></var></a> ]
610 #
612 <tr>
613 <td>Initial:
615 <td>depends on user agent
617 <tr>
618 <td>Applies to:
620 <td>all elements
622 <tr>
623 <td>Inherited:
625 <td>yes
627 <tr>
628 <td>Percentages:
630 <td>N/A
632 <tr>
633 <td>Media:
635 <td>visual
637 <tr>
638 <td>Computed value:
640 <td>as specified
642 <tr>
643 <td>Animatable:
645 <td>no
646 </table>
648 <p>This property specifies a prioritized list of font family names or
649 generic family names. A font family defines a set of faces that vary in
650 weight, width or slope. CSS uses the combination of a family name with
651 other style attributes to select an individual face. Using this selection
652 mechanism, rather than selecting a face via the style name as is often
653 done in design applications, allows some degree of regularity in textual
654 display when fallback occurs.
656 <p class=note>Designers should note that the CSS definition of font
657 attributes used for selection are explicitly not intended to define a font
658 taxonomy. A type designer's idea of a family may often extend to a set of
659 faces that vary along axes other than just the standard axes of weight,
660 width and slope. A family may extend to include both a set of serif faces
661 and a set of sans-serif faces or vary along axes that are unique to that
662 family. The CSS font selection mechanism merely provides a way to
663 determine the “closest” substitute when substitution is necessary.
665 <p>Unlike other CSS properties, component values are a comma-separated list
666 indicating alternatives. A user agent iterates through the list of family
667 names until it matches an available font that contains a glyph for the
668 character to be rendered. This allows for differences in available fonts
669 across platforms and for differences in the range of characters supported
670 by individual fonts.
672 <p>A font family name only specifies a name given to a set of font faces,
673 it does not specify an individual face. For example, given the
674 availability of the fonts below, Futura would match but Futura Medium
675 would not:
677 <div class=figure><img alt="family and face names"
678 src=familyvsfacename.png>
679 <p class=caption>Family and individual face names
680 </div>
682 <p>Consider the example below:
684 <div class=example>
685 <pre>body {
686 font-family: Helvetica, Verdana, sans-serif;
687 }</pre>
689 <p>If Helvetica is available it will be used when rendering. If neither
690 Helvetica nor Verdana is present, then the user-agent-defined sans serif
691 font will be used.</p>
692 </div>
694 <p>There are two types of font family names:
696 <dl>
697 <dt><dfn id=family-name-value><var><family-name></var></dfn>
699 <dd>The name of a font family of choice such as Helvetica or Verdana in
700 the previous example.
702 <dt><dfn id=generic-family-value><var><generic-family></var></dfn>
704 <dd> The following generic family keywords are defined: ‘<a
705 href="#serif"><code class=property>serif</code></a>’, ‘<a
706 href="#sans-serif"><code class=property>sans-serif</code></a>’, ‘<a
707 href="#cursive"><code class=property>cursive</code></a>’, ‘<a
708 href="#fantasy"><code class=property>fantasy</code></a>’, and ‘<a
709 href="#monospace"><code class=property>monospace</code></a>’. These
710 keywords can be used as a general fallback mechanism when an author's
711 desired font choices are not available. As keywords, they must not be
712 quoted. Authors are encouraged to append a generic font family as a last
713 alternative for improved robustness.
714 </dl>
716 <p>Font family names other than generic families must either be given
717 quoted as <a
718 href="//www.w3.org/TR/CSS21/syndata.html#strings">strings,</a> or unquoted
719 as a sequence of one or more <a
720 href="//www.w3.org/TR/CSS21/syndata.html#value-def-identifier">identifiers.</a>
721 This means most punctuation characters and digits at the start of each
722 token must be escaped in unquoted font family names.
724 <p>To illustrate this, the following declarations are invalid:
726 <pre>
727 font-family: Red/Black, sans-serif;
728 font-family: "Lucida" Grande, sans-serif;
729 font-family: Ahem!, sans-serif;
730 font-family: test@foo, sans-serif;
731 font-family: #POUND, sans-serif;
732 font-family: Hawaii 5-0, sans-serif;
733 </pre>
735 <p>If a sequence of identifiers is given as a font family name, the
736 computed value is the name converted to a string by joining all the
737 identifiers in the sequence by single spaces.
739 <p>To avoid mistakes in escaping, it is recommended to quote font family
740 names that contain white space, digits, or punctuation characters other
741 than hyphens:
743 <pre>
744 body { font-family: "New Century Schoolbook", serif }
746 <BODY STYLE="font-family: '21st Century', fantasy">
747 </pre>
749 <p>Font family <em>names</em> that happen to be the same as a keyword value
750 (‘<code class=property>inherit</code>’, ‘<a href="#serif"><code
751 class=property>serif</code></a>’, ‘<a href="#sans-serif"><code
752 class=property>sans-serif</code></a>’, ‘<a href="#monospace"><code
753 class=property>monospace</code></a>’, ‘<a href="#fantasy"><code
754 class=property>fantasy</code></a>’, and ‘<a href="#cursive"><code
755 class=property>cursive</code></a>’) must be quoted to prevent confusion
756 with the keywords with the same names. The keywords ‘<code
757 class=property>initial</code>’ and ‘<code
758 class=property>default</code>’ are reserved for future use and must also
759 be quoted when used as font names. UAs must not consider these keywords as
760 matching the <a
761 href="#family-name-value"><var><family-name></var></a> type.
763 <p>The precise way a set of fonts are grouped into font families varies
764 depending upon the platform font management API's. The Windows GDI API
765 only allows four faces to be grouped into a family while the DirectWrite
766 API and API's on OSX and other platforms support font families with a
767 variety of weights, widths and slopes (see <a
768 href="#platform-props-to-css">Appendix A</a> for more details).
770 <p>Some font formats allow fonts to carry multiple localizations of the
771 family name. User agents must recognize and correctly match all of these
772 names independent of the underlying platform localization, system API used
773 or document encoding:
775 <div class=figure><img alt="examples of localized family names"
776 src=localizedfamilynames.png>
777 <p class=caption>Localized family names
778 </div>
780 <h4 id=generic-font-families><span class=secno>3.1.1 </span>Generic font
781 families</h4>
783 <p>All five generic font families are defined to exist in all CSS
784 implementations (they need not necessarily map to five distinct actual
785 fonts). User agents should provide reasonable default choices for the
786 generic font families, which express the characteristics of each family as
787 well as possible within the limits allowed by the underlying technology.
788 User agents are encouraged to allow users to select alternative choices
789 for the generic fonts.
791 <h5 class="no-num no-toc"> <span class=index-def id=serif0 title="serif,
792 definition of"><a name=serif-def><dfn id=serif>serif</dfn></a></span></h5>
794 <p>Serif fonts represent the formal text style for a script. This often
795 means but is not limited to glyphs that have finishing strokes, flared or
796 tapering ends, or have actual serifed endings (including slab serifs).
797 Serif fonts are typically proportionately-spaced. They often display a
798 greater variation between thick and thin strokes than fonts from the ‘<a
799 href="#sans-serif"><code class=property>sans-serif</code></a>’ generic
800 font family. CSS uses the term ‘<a href="#serif"><code
801 class=property>serif</code></a>’ to apply to a font for any script,
802 although other names may be more familiar for particular scripts, such as
803 Mincho (Japanese), Sung, Song or Kai (Chinese), Batang (Korean). For
804 Arabic, the Naskh style would correspond to ‘<a href="#serif"><code
805 class=property>serif</code></a>’ more due to its typographic role rather
806 than its actual design style. Any font that is so described may be used to
807 represent the generic ‘<a href="#serif"><code
808 class=property>serif</code></a>’ family.
810 <div class=figure><img alt="sample serif fonts" src=serifexamples.png>
811 <p class=caption>Sample serif fonts
812 </div>
814 <h5 class="no-num no-toc"> <span class=index-def id=sans-serif0
815 title="sans-serif, definition of"> <a name=sans-serif-def><dfn
816 id=sans-serif>sans-serif</dfn></a></span></h5>
818 <p>Glyphs in sans-serif fonts, as the term is used in CSS, are generally
819 low contrast (vertical and horizontal stems have the close to the same
820 thickness) and have stroke endings that are plain -- without any flaring,
821 cross stroke, or other ornamentation. Sans-serif fonts are typically
822 proportionately-spaced. They often have little variation between thick and
823 thin strokes, compared to fonts from the ‘<a href="#serif"><code
824 class=property>serif</code></a>’ family. CSS uses the term ‘<a
825 href="#sans-serif"><code class=property>sans-serif</code></a>’ to apply
826 to a font for any script, although other names may be more familiar for
827 particular scripts, such as Gothic (Japanese), Hei (Chinese), or Gulim
828 (Korean). Any font that is so described may be used to represent the
829 generic ‘<a href="#sans-serif"><code
830 class=property>sans-serif</code></a>’ family.
832 <div class=figure><img alt="sample sans-serif fonts"
833 src=sansserifexamples.png>
834 <p class=caption>Sample sans-serif fonts
835 </div>
837 <h5 class="no-num no-toc"> <span class=index-def id=cursive0
838 title="cursive, definition of"> <a name=cursive-def><dfn
839 id=cursive>cursive</dfn></a></span></h5>
841 <p>Glyphs in cursive fonts generally use a more informal script style, and
842 the result looks more like handwritten pen or brush writing than printed
843 letterwork. CSS uses the term ‘<a href="#cursive"><code
844 class=property>cursive</code></a>’ to apply to a font for any script,
845 although other names such as Chancery, Brush, Swing and Script are also
846 used in font names.
848 <div class=figure><img alt="sample cursive fonts" src=cursiveexamples.png>
849 <p class=caption>Sample cursive fonts
850 </div>
852 <h5 class="no-num no-toc"> <span class=index-def id=fantasy0
853 title="fantasy, definition of"> <a name=fantasy-def><dfn
854 id=fantasy>fantasy</dfn></a></span></h5>
856 <p>Fantasy fonts are primarily decorative or expressive fonts that contain
857 playful representations of characters. These do not include Pi or Picture
858 fonts which do not represent actual characters.
860 <div class=figure><img alt="sample fantasy fonts" src=fantasyexamples.png>
861 <p class=caption>Sample fantasy fonts
862 </div>
864 <h5 class="no-num no-toc"> <span class=index-def id=monospace0
865 title="monospace, definition of"> <a name=monospace-def><dfn
866 id=monospace>monospace</dfn></a></span></h5>
868 <p>The sole criterion of a monospace font is that all glyphs have the same
869 fixed width. This is often used to render samples of computer code.
871 <div class=figure><img alt="sample monospace fonts"
872 src=monospaceexamples.png>
873 <p class=caption>Sample monospace fonts
874 </div>
875 <!-- prop: font-weight -->
877 <h3 id=font-weight-prop><span class=secno>3.2 </span>Font weight: the <a
878 href="#propdef-font-weight">font-weight</a> property</h3>
880 <table class=propdef id=namefont-weightvaluenormal-bold-bolder-l>
881 <tbody>
882 <tr>
883 <td>Name:
885 <td><dfn id=propdef-font-weight>font-weight</dfn>
887 <tr>
888 <td>Value:
890 <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
891 | 700 | 800 | 900
893 <tr>
894 <td>Initial:
896 <td>normal
898 <tr>
899 <td>Applies to:
901 <td>all elements
903 <tr>
904 <td>Inherited:
906 <td>yes
908 <tr>
909 <td>Percentages:
911 <td>N/A
913 <tr>
914 <td>Media:
916 <td>visual
918 <tr>
919 <td>Computed value:
921 <td>numeric weight value (see description)
923 <tr>
924 <td>Animatable:
926 <td>as <a
927 href="http://dev.w3.org/csswg/css3-transitions/#animtype-font-weight">font
928 weight</a>
929 </table>
931 <p>The <a class=noxref href="#font-weight-prop"><span
932 class=property>‘<code class=property>font-weight</code>’</span></a>
933 property specifies the weight of glyphs in the font, their degree of
934 blackness or stroke thickness.
936 <p>Values have the following meanings:
938 <dl>
939 <dt>100 to 900
941 <dd>These values form an ordered sequence, where each number indicates a
942 weight that is at least as dark as its predecessor. These roughly
943 correspond to the commonly used weight names below:
944 </dl>
946 <ul>
947 <li>100 - Thin
949 <li>200 - Extra Light (Ultra Light)
951 <li>300 - Light
953 <li>400 - Normal
955 <li>500 - Medium
957 <li>600 - Semi Bold (Demi Bold)
959 <li>700 - Bold
961 <li>800 - Extra Bold (Ultra Bold)
963 <li>900 - Black (Heavy)
964 </ul>
966 <dl>
967 <dt><a href="#normal2"><strong>normal</strong></a>
969 <dd>Same as ‘<code class=css>400</code>’.
971 <dt><strong>bold</strong>
973 <dd>Same as ‘<code class=css>700</code>’.
975 <dt><strong>bolder</strong>
977 <dd>Specifies a bolder weight than the inherited value.
979 <dt><strong>lighter</strong>
981 <dd>Specifies a lighter weight than the inherited value.
982 </dl>
984 <p>Font formats that use a scale other than a nine-step scale should map
985 their scale onto the CSS scale so that 400 roughly corresponds with a face
986 that would be labeled as Regular, Book, Roman and 700 roughly matches a
987 face that would be labeled as Bold. Or weights may be inferred from the
988 style names, ones that correspond roughly with the scale above. The scale
989 is relative, so a face with a larger weight value must never appear
990 lighter. If style names are used to infer weights, care should be taken to
991 handle variations in style names across locales.
993 <p>Quite often there are only a few weights available for a particular font
994 family. When a weight is specified for which no face exists, a face with a
995 nearby weight is used. In general, bold weights map to faces with heavier
996 weights and light weights map to faces with lighter weights (see the <a
997 href="#font-matching-algorithm">font matching section below</a> for a
998 precise definition). The examples here illustrate which face is used for
999 different weights, grey indicates a face for that weight does not exist so
1000 a face with a nearby weight is used:
1002 <div class=figure><img alt="weight mappings for a family with 400, 700 and
1003 900 weights" src=optimaweights.png>
1004 <p class=caption>Weight mappings for a font family with 400, 700 and 900
1005 weight faces
1006 </div>
1008 <div class=figure><img alt="weight mappings for a family with 300, 600
1009 weights" src=hiraginoweights.png>
1010 <p class=caption>Weight mappings for a font family with 300 and 600 weight
1011 faces
1012 </div>
1014 <p>Although the practice is not well-loved by typographers, bold faces are
1015 often synthesized by user agents for faces that lack actual bold faces.
1016 For the purposes of style matching, these faces must be treated as if they
1017 exist within the family. Authors can explicitly avoid this behavior by
1018 using the ‘<a href="#propdef-font-synthesis"><code
1019 class=property>font-synthesis</code></a>’ property.
1021 <p>Specified values of ‘<code class=property>bolder</code>’ and
1022 ‘<code class=property>lighter</code>’ indicate weights relative to the
1023 weight of the parent element. The computed weight is calculated based on
1024 the inherited ‘<a href="#propdef-font-weight"><code
1025 class=property>font-weight</code></a>’ value using the chart below.
1027 <table class=data id=bolderlighter summary="Bolder/lighter mappings">
1028 <thead>
1029 <tr>
1030 <th>Inherited value
1032 <th>bolder
1034 <th>lighter
1036 <tbody>
1037 <tr>
1038 <th>100
1040 <td>400
1042 <td>100
1044 <tr>
1045 <th>200
1047 <td>400
1049 <td>100
1051 <tr>
1052 <th>300
1054 <td>400
1056 <td>100
1058 <tr>
1059 <th>400
1061 <td>700
1063 <td>100
1065 <tr>
1066 <th>500
1068 <td>700
1070 <td>100
1072 <tr>
1073 <th>600
1075 <td>900
1077 <td>400
1079 <tr>
1080 <th>700
1082 <td>900
1084 <td>400
1086 <tr>
1087 <th>800
1089 <td>900
1091 <td>700
1093 <tr>
1094 <th>900
1096 <td>900
1098 <td>700
1099 </table>
1101 <p>The table above is equivalent to selecting the next relative bolder or
1102 lighter face, given a font family containing normal and bold faces along
1103 with a thin and a heavy face. Authors who desire finer control over the
1104 exact weight values used for a given element may use numerical values
1105 instead of relative weights.</p>
1106 <!-- prop: font-stretch -->
1108 <h3 id=font-stretch-prop><span class=secno>3.3 </span>Font width: the <a
1109 href="#propdef-font-stretch">font-stretch</a> property</h3>
1111 <table class=propdef id=namefont-stretchvaluenormal-ultra-conden>
1112 <tbody>
1113 <tr>
1114 <td>Name:
1116 <td><dfn id=propdef-font-stretch>font-stretch</dfn>
1118 <tr>
1119 <td>Value:
1121 <td>normal | ultra-condensed | extra-condensed | condensed |
1122 semi-condensed | semi-expanded | expanded | extra-expanded |
1123 ultra-expanded
1125 <tr>
1126 <td>Initial:
1128 <td>normal
1130 <tr>
1131 <td>Applies to:
1133 <td>all elements
1135 <tr>
1136 <td>Inherited:
1138 <td>yes
1140 <tr>
1141 <td>Percentages:
1143 <td>N/A
1145 <tr>
1146 <td>Media:
1148 <td>visual
1150 <tr>
1151 <td>Computed value:
1153 <td>as specified
1155 <tr>
1156 <td>Animatable:
1158 <td>as <a href="#font-stretch-animation">font stretch</a>
1159 </table>
1161 <p>The <a class=noxref href="#font-stretch-prop"><span
1162 class=property>‘<code class=property>font-stretch</code>’</span></a>
1163 property selects a normal, condensed, or expanded face from a font family.
1164 Absolute keyword values have the following ordering, from narrowest to
1165 widest:
1167 <ul>
1168 <li><code>ultra-condensed</code>
1170 <li><code>extra-condensed</code>
1172 <li><code>condensed</code>
1174 <li><code>semi-condensed </code>
1176 <li><code>normal</code>
1178 <li><code>semi-expanded</code>
1180 <li><code>expanded</code>
1182 <li><code>extra-expanded</code>
1184 <li><code>ultra-expanded</code>
1185 </ul>
1187 <p>When a face does not exist for a given width, normal or condensed values
1188 map to a narrower face, otherwise a wider face. Conversely, expanded
1189 values map to a wider face, otherwise a narrower face. The figure below
1190 shows how the nine font-stretch property settings affect font selection
1191 for font family containing a variety of widths, grey indicates a width for
1192 which no face exists and a different width is substituted:
1194 <div class=figure><img alt="width mappings for a family with condensed,
1195 normal and expanded faces" src=universwidths.png>
1196 <p class=caption>Width mappings for a font family with condensed, normal
1197 and expanded width faces
1198 </div>
1200 <p id=font-stretch-animation>Animation of font stretch: Font stretch is
1201 interpolated in discrete steps. The interpolation happens as though the
1202 ordered values are equally spaced real numbers. The interpolation result
1203 is rounded to the nearest value, with values exactly halfway between two
1204 values rounded towards the later value in the list above.</p>
1205 <!-- prop: font-style -->
1207 <h3 id=font-style-prop><span class=secno>3.4 </span>Font style: the <a
1208 href="#propdef-font-style">font-style</a> property</h3>
1210 <table class=propdef id=namefont-stylevaluenormal-italic-oblique>
1211 <tbody>
1212 <tr>
1213 <td>Name:
1215 <td><dfn id=propdef-font-style>font-style</dfn>
1217 <tr>
1218 <td>Value:
1220 <td>normal | italic | oblique
1222 <tr>
1223 <td>Initial:
1225 <td>normal
1227 <tr>
1228 <td>Applies to:
1230 <td>all elements
1232 <tr>
1233 <td>Inherited:
1235 <td>yes
1237 <tr>
1238 <td>Percentages:
1240 <td>N/A
1242 <tr>
1243 <td>Media:
1245 <td>visual
1247 <tr>
1248 <td>Computed value:
1250 <td>as specified
1252 <tr>
1253 <td>Animatable:
1255 <td>no
1256 </table>
1258 <p>The <a class=noxref href="#font-style-prop"><span
1259 class=property>‘<code class=property>font-style</code>’</span></a>
1260 property allows italic or oblique faces to be selected. Italic forms are
1261 generally cursive in nature while oblique faces are typically sloped
1262 versions of the regular face. Oblique faces can be simulated by
1263 artificially sloping the glyphs of the regular face. Compare the
1264 artificially sloped renderings of Palatino ‘<code
1265 class=property>a</code>’ and Baskerville ‘<code
1266 class=property>N</code>’ in grey with the actual italic versions:
1268 <div class=figure><img alt="artificial sloping vs. real italics"
1269 src=realvsfakeitalics.png>
1270 <p class=caption>Artificial sloping versus real italics
1271 </div>
1273 <p>A value of ‘<a href="#normal2"><code
1274 class=property>normal</code></a>’ selects a face that is classified as
1275 ‘<a href="#normal2"><code class=property>normal</code></a>’, while
1276 ‘<code class=property>oblique</code>’ selects a font that is labeled
1277 ‘<code class=property>oblique</code>’. A value of ‘<code
1278 class=property>italic</code>’ selects a font that is labeled ‘<code
1279 class=property>italic</code>’, or, if that is not available, one labeled
1280 ‘<code class=property>oblique</code>’. If no italic or oblique face is
1281 available, oblique faces can be synthesized by rendering non-obliqued
1282 faces with a right sloping transformation applied. When synthesizing these
1283 faces, the transformation should apply to all glyphs in the same way and
1284 not vary based on codepoint or due to horizontal or vertical line
1285 orientation.
1287 <p>Many scripts lack the tradition of mixing a cursive form within text
1288 rendered with a normal face. Chinese, Japanese and Korean fonts almost
1289 always lack italic or oblique faces. Fonts that support a mixture of
1290 scripts will sometimes omit specific scripts such as Arabic from the set
1291 of glyphs supported in the italic face. User agents should be careful
1292 about making <a href="#character-map"><em>character map</em></a>
1293 assumptions across faces.
1295 <p class=issue>For synthetic italics in vertical runs of Chinese, Japanese,
1296 or Korean text, is there a need to define explicitly the direction of the
1297 faux oblique for runs that include a mixture of ideographic and Latin
1298 text?</p>
1299 <!-- prop: font-size -->
1301 <h3 id=font-size-prop><span class=secno>3.5 </span>Font size: the <a
1302 href="#propdef-font-size">font-size</a> property</h3>
1304 <table class=propdef id=namefont-sizevalueltabsolute-sizegt-ltre>
1305 <tbody>
1306 <tr>
1307 <td>Name:
1309 <td><dfn id=propdef-font-size>font-size</dfn>
1311 <tr>
1312 <td>Value:
1314 <td><a href="#absolute-size-value"><var><absolute-size></var></a>
1315 | <a href="#relative-size-value"><var><relative-size></var></a> |
1316 <a href="#length-size-value"><var><length></var></a> | <a
1317 href="#percentage-size-value"><var><percentage></var></a>
1319 <tr>
1320 <td>Initial:
1322 <td>medium
1324 <tr>
1325 <td>Applies to:
1327 <td>all elements
1329 <tr>
1330 <td>Inherited:
1332 <td>yes
1334 <tr>
1335 <td>Percentages:
1337 <td>refer to parent element's font size
1339 <tr>
1340 <td>Media:
1342 <td>visual
1344 <tr>
1345 <td>Computed value:
1347 <td>absolute length
1349 <tr>
1350 <td>Animatable:
1352 <td>as <a
1353 href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
1354 </table>
1356 <p>This property indicates the desired height of glyphs from the font. For
1357 scalable fonts, the font-size is a scale factor applied to the EM unit of
1358 the font. (Note that certain glyphs may bleed outside their EM box.) For
1359 non-scalable fonts, the font-size is converted into absolute units and
1360 matched against the declared font-size of the font, using the same
1361 absolute coordinate space for both of the matched values. Values have the
1362 following meanings:
1364 <dl>
1365 <dt><dfn id=absolute-size-value><var><absolute-size></var></dfn>
1367 <dd> An <a
1368 href="#absolute-size-value"><var><absolute-size></var></a> keyword
1369 refers to an entry in a table of font sizes computed and kept by the user
1370 agent. Possible values are:
1371 <p> [ xx-small | x-small | small | medium | large | x-large | xx-large ]</p>
1373 <dt><dfn id=relative-size-value><var><relative-size></var></dfn>
1375 <dd> A <a href="#relative-size-value"><var><relative-size></var></a>
1376 keyword is interpreted relative to the table of font sizes and the
1377 computed ‘<a href="#propdef-font-size"><code
1378 class=property>font-size</code></a>’ of the parent element. Possible
1379 values are:
1380 <p> [ larger | smaller ]
1382 <p> For example, if the parent element has a font size of ‘<code
1383 class=property>medium</code>’, a value of ‘<code
1384 class=property>larger</code>’ will make the font size of the current
1385 element be ‘<code class=property>large</code>’. If the parent
1386 element's size is not close to a table entry, the user agent is free to
1387 interpolate between table entries or round off to the closest one. The
1388 user agent may have to extrapolate table values if the numerical value
1389 goes beyond the keywords.
1391 <dt><dfn id=length-size-value><var><length></var></dfn>
1393 <dd>A length value specifies an absolute font size (independent of the
1394 user agent's font table). Negative lengths are illegal.
1396 <dt><dfn id=percentage-size-value><var><percentage></var></dfn>
1398 <dd>A percentage value specifies an absolute font size relative to the
1399 parent element's font size. Use of percentage values, or values in
1400 ‘<code class=property>em</code>’s, leads to more robust and
1401 cascadable style sheets.
1402 </dl>
1404 <p>The following table provides user agent guidelines for the absolute-size
1405 scaling factor and their mapping to HTML heading and absolute font-sizes.
1406 The ‘<code class=property>medium</code>’ value is used as the
1407 reference middle value. The user agent may fine-tune these values for
1408 different fonts or different types of display devices.
1410 <table class=data>
1411 <thead>
1412 <tr>
1413 <th>CSS absolute-size values
1415 <th>xx-small
1417 <th>x-small
1419 <th>small
1421 <th>medium
1423 <th>large
1425 <th>x-large
1427 <th>xx-large
1429 <th>
1431 <tbody>
1432 <tr>
1433 <th>scaling factor
1435 <td>3/5
1437 <td>3/4
1439 <td>8/9
1441 <td>1
1443 <td>6/5
1445 <td>3/2
1447 <td>2/1
1449 <td>3/1
1451 <tr>
1452 <th>HTML headings
1454 <td>h6
1456 <td>
1458 <td>h5
1460 <td>h4
1462 <td>h3
1464 <td>h2
1466 <td>h1
1468 <td>
1470 <tr>
1471 <th>HTML font sizes
1473 <td>1
1475 <td>
1477 <td>2
1479 <td>3
1481 <td>4
1483 <td>5
1485 <td>6
1487 <td>7
1488 </table>
1490 <p class=note><em><strong>Note 1.</strong> To preserve readability, an UA
1491 applying these guidelines should nevertheless avoid creating font-size
1492 resulting in less than 9 device pixels per EM unit on a computer
1493 display.</em>
1495 <p class=note><em><strong>Note 2.</strong> In CSS1, the suggested scaling
1496 factor between adjacent indexes was 1.5 which user experience proved to be
1497 too large. In CSS2, the suggested scaling factor for computer screen
1498 between adjacent indexes was 1.2 which still created issues for the small
1499 sizes. The new scaling factor varies between each index to provide a
1500 better readability.</em>
1502 <p>The actual value of this property may differ from the computed value due
1503 a numerical value on ‘<a href="#propdef-font-size-adjust"><code
1504 class=property>font-size-adjust</code></a>’ and the unavailability of
1505 certain font sizes.
1507 <p>Child elements inherit the computed <a class=noxref
1508 href="#font-size-prop"> <span class=property>‘<code
1509 class=property>font-size</code>’</span></a> value (otherwise, the effect
1510 of <a class=noxref href="#font-size-adjust-prop"><span
1511 class=property>‘<code
1512 class=property>font-size-adjust</code>’</span></a> would compound).
1514 <div class=example>
1515 <p style="display:none">Example(s):
1517 <p>
1519 <pre>p { font-size: 12pt; }
1520 blockquote { font-size: larger }
1521 em { font-size: 150% }
1522 em { font-size: 1.5em }
1523 </pre>
1524 </div>
1525 <!-- prop: font-size-adjust -->
1527 <h3 id=font-size-adjust-prop><span class=secno>3.6 </span>Relative sizing:
1528 the <a href="#propdef-font-size-adjust">font-size-adjust</a> property</h3>
1530 <table class=propdef id=namefont-size-adjustvaluenone-auto-ltnum>
1531 <tbody>
1532 <tr>
1533 <td>Name:
1535 <td><dfn id=propdef-font-size-adjust>font-size-adjust</dfn>
1537 <tr>
1538 <td>Value:
1540 <td>none | auto | <a
1541 href="#aspect-ratio-value"><var><number></var></a>
1543 <tr>
1544 <td>Initial:
1546 <td>none
1548 <tr>
1549 <td>Applies to:
1551 <td>all elements
1553 <tr>
1554 <td>Inherited:
1556 <td>yes
1558 <tr>
1559 <td>Percentages:
1561 <td>N/A
1563 <tr>
1564 <td>Media:
1566 <td>visual
1568 <tr>
1569 <td>Computed value:
1571 <td>as specified
1573 <tr>
1574 <td>Animatable:
1576 <td>as <a
1577 href="http://dev.w3.org/csswg/css3-transitions/#animtype-number">number</a>
1578 </table>
1580 <p>For any given font size, the apparent size and legibility of text varies
1581 across fonts. For scripts such as Latin or Cyrillic that distinguish
1582 between upper and lowercase letters, the relative height of lowercase
1583 letters compared to their uppercase counterparts is a determining factor
1584 of legibility. This is commonly referred to as the <a class=index-def
1585 href="#aspect-value" id=aspect-value0 title="aspect value"><dfn
1586 id=aspect-value>aspect value</dfn></a>. Precisely defined, it is equal to
1587 the x-height of a font divided by the font size.
1589 <p>In situations where font fallback occurs, fallback fonts may not share
1590 the same aspect ratio as the desired font family and will thus appear less
1591 readable. The font-size-adjust property is a way to preserve the
1592 readability of text when font fallback occurs. It does this by adjusting
1593 the font-size so that the x-height is the same regardless of the font
1594 used.
1596 <div class=example>
1597 <p>The style defined below defines Verdana as the desired font family, but
1598 if Verdana is not available Futura or Times will be used.</p>
1600 <pre>p {
1601 font-family: Verdana, Futura, Times;
1602 }
1604 <p>Lorem ipsum dolor sit amet, ...</p>
1605 </pre>
1607 <p>Verdana has a relatively high aspect ratio, lowercase letters are
1608 relatively tall compared to uppercase letters, so at small sizes text
1609 appears legible. Times has a lower aspect ratio and so if fallback
1610 occurs, the text will be less legible at small sizes than Verdana.</p>
1611 </div>
1613 <p>How text rendered in each of these fonts compares is shown below, the
1614 columns show text rendered in Verdana, Futura and Times. The same
1615 font-size value is used across cells within each row and red lines are
1616 included to show the differences in x-height. In the upper half each row
1617 is rendered in the same font-size value. The same is true for the lower
1618 half but in this half the font-size-adjust property is also set so that
1619 the actual font size is adjusted to preserve the x-height across each row.
1620 Note how small text remains relatively legible across each row in the
1621 lower half.
1623 <div class=figure><img alt="text with and without font-size-adjust"
1624 src=fontsizeadjust.png>
1625 <p class=caption>Text with and without the use of font-size-adjust
1626 </div>
1628 <p>This property allows authors to specify an aspect value for an element
1629 that will effectively preserve the x-height of the first choice font,
1630 whether it is substituted or not. Values have the following meanings:
1632 <dl>
1633 <dt><a href="#font-variant-ligatures-none-value"><strong>none</strong></a>
1636 <dd>Do not preserve the font's x-height.
1638 <dt><strong>auto</strong>
1640 <dd>Behaves just like <number>, except the number used is the aspect
1641 value calculated by user agents for the first font in the list of fonts
1642 defined for the initial value of the ‘<a
1643 href="#descdef-font-family"><code
1644 class=property>font-family</code></a>’ property. Effectively this is
1645 the default font used when ‘<a href="#descdef-font-family"><code
1646 class=property>font-family</code></a>’ is not otherwise specified.
1647 <p>Authors can use this value to specify that font size should be
1648 normalized across fonts based on the x-height without the need to
1649 specify the aspect ratio explicitly.</p>
1651 <dt><dfn id=aspect-ratio-value><var><number></var></dfn>
1653 <dd>Specifies the aspect value used in the calculation below to calculate
1654 the adjusted font size:
1655 <pre>c = ( a / a' ) s
1656 </pre>
1658 <p>where:</p>
1660 <pre>s = font-size value
1661 a = aspect value as specified by the font-size-adjust property
1662 a' = aspect value of actual font
1663 c = adjusted font-size to use
1664 </pre>
1666 <p>This value applies to any font that is selected but in typical usage
1667 it should be based on the aspect value of the first font in the
1668 font-family list. If this is specified accurately, the <tt>(a/a')</tt>
1669 term in the formula above is effectively 1 for the first font and no
1670 adjustment occurs. If the value is specified inaccurately, text rendered
1671 using the first font in the family list will display differently in
1672 older user agents that don't support font-size-adjust.</p>
1673 </dl>
1675 <p>Authors can calculate the aspect value for a given font by comparing
1676 spans with the same content but different font-size-adjust properties. If
1677 the same font-size is used, the spans will match when the font-size-adjust
1678 value is accurate for the given font.
1680 <div class=example>
1681 <p>Two spans with borders are used to determine the aspect value of a
1682 font. The font-size is the same for both spans but the font-size-adjust
1683 property is specified only for the right span. Starting with a value of
1684 0.5, the aspect value can be adjusted until the borders around the two
1685 letters line up.</p>
1687 <pre>p {
1688 font-family: Futura;
1689 font-size: 500px;
1690 }
1692 span {
1693 border: solid 1px red;
1694 }
1696 .adjust {
1697 font-size-adjust: 0.5;
1698 }
1700 <p><span>b</span><span class="adjust">b</span></p>
1701 </pre>
1703 <div class=figure><img alt="Futura with an aspect value of 0.5"
1704 src=beforefontsizeadjust.png>
1705 <p class=caption>Futura with an aspect value of 0.5
1706 </div>
1708 <p>The box on the right is a bit bigger than the one on the left, so the
1709 aspect value of this font is something less than 0.5. Adjust the value
1710 until the boxes align.</p>
1711 </div>
1712 <!-- prop: font -->
1713 <!-- jtdfix, crap, preprocessor is inserting links to descriptors rather than properties. bert, make it stop... -->
1714 <!-- <a href="#font-stretch-prop" class="noxref"><span class="property">'font-stretch'</span></a> -->
1716 <h3 id=font-prop><span class=secno>3.7 </span>Shorthand font property: the
1717 <a href="#propdef-font">font</a> property</h3>
1719 <table class=propdef id=namefontvalue-ltlsquofont-stylersquogt-l>
1720 <tbody>
1721 <tr>
1722 <td>Name:
1724 <td><dfn id=propdef-font>font</dfn>
1726 <tr>
1727 <td>Value:
1729 <td>[ [ <var><‘<a href="#propdef-font-style"><code
1730 class=property>font-style</code></a>’></var> || <a
1731 href="#font-variant-css21-values"><var><font-variant-css21></var></a>
1732 || <var><‘<a href="#propdef-font-weight"><code
1733 class=property>font-weight</code></a>’></var> || <var><‘<a
1734 href="#propdef-font-stretch"><code
1735 class=property>font-stretch</code></a>’</var> ]? <var><‘<a
1736 href="#propdef-font-size"><code
1737 class=property>font-size</code></a>’></var> [ / <var><‘<code
1738 class=property>line-height</code>’></var> ]? <var><‘<a
1739 href="#descdef-font-family"><code
1740 class=property>font-family</code></a>’></var> ] | caption | icon |
1741 menu | message-box | small-caption | status-bar
1743 <tr>
1744 <td>Initial:
1746 <td>see individual properties
1748 <tr>
1749 <td>Applies to:
1751 <td>all elements
1753 <tr>
1754 <td>Inherited:
1756 <td>yes
1758 <tr>
1759 <td>Percentages:
1761 <td>see individual properties
1763 <tr>
1764 <td>Media:
1766 <td>visual
1768 <tr>
1769 <td>Computed value:
1771 <td>see individual properties
1773 <tr>
1774 <td>Animatable:
1776 <td>see individual properties
1777 </table>
1779 <p>The <span class=property>‘<a href="#propdef-font"><code
1780 class=property>font</code></a>’</span> property is, except as described
1781 below, a shorthand property for setting ‘<a
1782 href="#propdef-font-style"><code class=property>font-style</code></a>’,
1783 <span class=property>‘<a href="#propdef-font-variant"><code
1784 class=property>font-variant</code></a>’</span>, <span
1785 class=property>‘<a href="#propdef-font-weight"><code
1786 class=property>font-weight</code></a>’</span>, <span
1787 class=property>‘<a href="#propdef-font-stretch"><code
1788 class=property>font-stretch</code></a>’</span>, <span
1789 class=property>‘<a href="#propdef-font-size"><code
1790 class=property>font-size</code></a>’</span>, ‘<code
1791 class=property>line-height</code>’, <span class=property>‘<a
1792 href="#descdef-font-family"><code
1793 class=property>font-family</code></a>’</span> at the same place in the
1794 stylesheet. Values for the <span class=property>‘<a
1795 href="#propdef-font-variant"><code
1796 class=property>font-variant</code></a>’</span> property may also be
1797 included but only those supported in CSS 2.1, none of the font-variant
1798 values added in this specification can be used in the <span
1799 class=property>‘<a href="#propdef-font"><code
1800 class=property>font</code></a>’</span> shorthand:
1802 <pre
1803 class=prod><dfn id=font-variant-css21-values><var><font-variant-css21></var></dfn> = [normal | small-caps]</pre>
1805 <p>The syntax of this property is based on a traditional typographical
1806 shorthand notation to set multiple properties related to fonts.
1808 <p>All subproperties of the ‘<a href="#propdef-font"><code
1809 class=property>font</code></a>’ property are first reset to their
1810 initial values, including those listed above plus <span
1811 class=property>‘<a href="#propdef-font-size-adjust"><code
1812 class=property>font-size-adjust</code></a>’</span>, <span
1813 class=property>‘<a href="#propdef-font-kerning"><code
1814 class=property>font-kerning</code></a>’</span>, subproperties of <span
1815 class=property>‘<a href="#propdef-font-variant"><code
1816 class=property>font-variant</code></a>’</span> and and <span
1817 class=property>‘<a href="#propdef-font-language-override"><code
1818 class=property>font-language-override</code></a>’</span>. Then, those
1819 properties that are given explicit values in the <span
1820 class=property>‘<a href="#propdef-font"><code
1821 class=property>font</code></a>’</span> shorthand are set to those
1822 values. For a definition of allowed and initial values, see the previously
1823 defined properties. For reasons of backwards compatibility, it is not
1824 possible to set <span class=property>‘<a
1825 href="#propdef-font-size-adjust"><code
1826 class=property>font-size-adjust</code></a>’</span> to anything other
1827 than its initial value using the <span class=property>‘<a
1828 href="#propdef-font"><code class=property>font</code></a>’</span>
1829 shorthand property; instead, use the individual property.
1831 <div class=example>
1832 <p style="display:none">Example(s):
1834 <p>
1836 <pre>p { font: 12pt/14pt sans-serif }
1837 p { font: 80% sans-serif }
1838 p { font: x-large/110% "new century schoolbook", serif }
1839 p { font: bold italic large Palatino, serif }
1840 p { font: normal small-caps 120%/120% fantasy }
1841 p { font: condensed oblique 12pt "Helvetica Neue", serif; }
1842 </pre>
1844 <p> In the second rule, the font size percentage value (‘<code
1845 class=css>80%</code>’) refers to the computed ‘<a
1846 href="#propdef-font-size"><code class=property>font-size</code></a>’ of
1847 the parent element. In the third rule, the line height percentage
1848 (‘<code class=css>110%</code>’) refers to the font size of the
1849 element itself.
1851 <p>The first three rules do not specify the <span class=property>‘<a
1852 href="#propdef-font-variant"><code
1853 class=property>font-variant</code></a>’</span> and <span
1854 class=property>‘<a href="#propdef-font-weight"><code
1855 class=property>font-weight</code></a>’</span> explicitly, so these
1856 properties receive their initial values (‘<a href="#normal2"><code
1857 class=property>normal</code></a>’). Notice that the font family name
1858 "new century schoolbook", which contains spaces, is enclosed in quotes.
1859 The fourth rule sets the <span class=property>‘<a
1860 href="#propdef-font-weight"><code
1861 class=property>font-weight</code></a>’</span> to ‘<code
1862 class=property>bold</code>’, the <span class=property>‘<a
1863 href="#propdef-font-style"><code
1864 class=property>font-style</code></a>’</span> to ‘<code
1865 class=property>italic</code>’, and implicitly sets <span
1866 class=property>‘<a href="#propdef-font-variant"><code
1867 class=property>font-variant</code></a>’</span> to ‘<a
1868 href="#normal2"><code class=property>normal</code></a>’.
1870 <p> The fifth rule sets the <span class=property>‘<a
1871 href="#propdef-font-variant"><code
1872 class=property>font-variant</code></a>’</span> (‘<a
1873 href="#small-caps"><code class=property>small-caps</code></a>’), the
1874 <span class=property>‘<a href="#propdef-font-size"><code
1875 class=property>font-size</code></a>’</span> (120% of the parent's font
1876 size), the <span class=property>‘<code
1877 class=property>line-height</code>’</span> (120% of the font size) and
1878 the <span class=property>‘<a href="#descdef-font-family"><code
1879 class=property>font-family</code></a>’</span> (‘<a
1880 href="#fantasy"><code class=property>fantasy</code></a>’). It follows
1881 that the keyword ‘<a href="#normal2"><code
1882 class=property>normal</code></a>’ applies to the two remaining
1883 properties: <span class=property>‘<a href="#propdef-font-style"><code
1884 class=property>font-style</code></a>’</span> and <span
1885 class=property>‘<a href="#propdef-font-weight"><code
1886 class=property>font-weight</code></a>’</span>.
1888 <p>The sixth rule sets the <span class=property>‘<a
1889 href="#propdef-font-style"><code
1890 class=property>font-style</code></a>’</span>, <span
1891 class=property>‘<a href="#propdef-font-stretch"><code
1892 class=property>font-stretch</code></a>’</span>, <span
1893 class=property>‘<a href="#propdef-font-size"><code
1894 class=property>font-size</code></a>’</span>, and <span
1895 class=property>‘<a href="#descdef-font-family"><code
1896 class=property>font-family</code></a>’</span>, the other font
1897 properties being set to their initial values.
1898 </div>
1900 <p>Since the ‘<a href="#propdef-font-stretch"><code
1901 class=property>font-stretch</code></a>’ property was not defined in CSS
1902 2.1, when using ‘<a href="#propdef-font-stretch"><code
1903 class=property>font-stretch</code></a>’ values within ‘<a
1904 href="#propdef-font"><code class=property>font</code></a>’ rules,
1905 authors should include a extra version compatible with older user agents:
1907 <pre>p {
1908 font: 80% sans-serif; /* for older user agents */
1909 font: condensed 80% sans-serif;
1910 }</pre>
1912 <p>The following values refer to system fonts:
1914 <dl>
1915 <dt><strong>caption</strong>
1917 <dd>The font used for captioned controls (e.g., buttons, drop-downs,
1918 etc.).
1920 <dt><strong>icon</strong>
1922 <dd>The font used to label icons.
1924 <dt><strong>menu</strong>
1926 <dd>The font used in menus (e.g., dropdown menus and menu lists).
1928 <dt><strong>message-box</strong>
1930 <dd>The font used in dialog boxes.
1932 <dt><strong>small-caption</strong>
1934 <dd>The font used for labeling small controls.
1936 <dt><strong>status-bar</strong>
1938 <dd>The font used in window status bars.
1939 </dl>
1941 <p>System fonts may only be set as a whole; that is, the font family, size,
1942 weight, style, etc. are all set at the same time. These values may then be
1943 altered individually if desired. If no font with the indicated
1944 characteristics exists on a given platform, the user agent should either
1945 intelligently substitute (e.g., a smaller version of the ‘<code
1946 class=property>caption</code>’ font might be used for the ‘<code
1947 class=property>small-caption</code>’ font), or substitute a user agent
1948 default font. As for regular fonts, if, for a system font, any of the
1949 individual properties are not part of the operating system's available
1950 user preferences, those properties should be set to their initial values.
1952 <p>That is why this property is "almost" a shorthand property: system fonts
1953 can only be specified with this property, not with <span
1954 class=property>‘<a href="#descdef-font-family"><code
1955 class=property>font-family</code></a>’</span> itself, so <span
1956 class=property>‘<a href="#propdef-font"><code
1957 class=property>font</code></a>’</span> allows authors to do more than
1958 the sum of its subproperties. However, the individual properties such as
1959 <span class=property>‘<a href="#propdef-font-weight"><code
1960 class=property>font-weight</code></a>’</span> are still given values
1961 taken from the system font, which can be independently varied.
1963 <p>Note that the keywords used for the system fonts listed above are only
1964 treated as keywords when they occur in the initial position, in other
1965 positions the same string is treated as part of the font family name:
1967 <pre> font: menu; /* use the font settings for system menus */
1968 font: large menu; /* use a font family named "menu" */</pre>
1970 <div class=example>
1971 <p style="display:none">Example(s):
1973 <p>
1975 <pre>button { font: 300 italic 1.3em/1.7em "FB Armada", sans-serif }
1976 button p { font: menu }
1977 button p em { font-weight: bolder }
1978 </pre>
1980 <p>If the font used for dropdown menus on a particular system happened to
1981 be, for example, 9-point Charcoal, with a weight of 600, then P elements
1982 that were descendants of BUTTON would be displayed as if this rule were
1983 in effect:
1985 <pre>button p { font: 600 9pt Charcoal }
1986 </pre>
1988 <p>Because the <span class=property>‘<a href="#propdef-font"><code
1989 class=property>font</code></a>’</span> shorthand resets to its initial
1990 value any property not explicitly given a value, this has the same effect
1991 as this declaration:
1993 <pre>button p {
1994 font-style: normal;
1995 font-variant: normal;
1996 font-weight: 600;
1997 font-size: 9pt;
1998 line-height: normal;
1999 font-family: Charcoal
2000 }
2001 </pre>
2002 </div>
2003 <!-- prop: font-synthesis -->
2005 <h3 id=font-synthesis-prop><span class=secno>3.8 </span>Controlling
2006 synthetic faces: the <a href="#propdef-font-synthesis">font-synthesis</a>
2007 property</h3>
2009 <table class=propdef id=namefont-synthesisvaluenone-weight-style>
2010 <tbody>
2011 <tr>
2012 <td>Name:
2014 <td><dfn id=propdef-font-synthesis>font-synthesis</dfn>
2016 <tr>
2017 <td>Value:
2019 <td>none | [ weight || style ]
2021 <tr>
2022 <td>Initial:
2024 <td>weight style
2026 <tr>
2027 <td>Applies to:
2029 <td>all elements
2031 <tr>
2032 <td>Inherited:
2034 <td>yes
2036 <tr>
2037 <td>Percentages:
2039 <td>N/A
2041 <tr>
2042 <td>Media:
2044 <td>visual
2046 <tr>
2047 <td>Computed value:
2049 <td>as specified
2051 <tr>
2052 <td>Animatable:
2054 <td>no
2055 </table>
2057 <p>This property controls whether user agents are allowed to synthesize
2058 bold or oblique font faces when a font family lacks bold or italic faces.
2059 If ‘<a href="#weight"><code class=property>weight</code></a>’ is not
2060 specified, user agents must not synthesize bold faces and if ‘<code
2061 class=property>style</code>’ is not specified user agents must not
2062 synthesize italic faces. A value of ‘<a
2063 href="#font-variant-ligatures-none-value"><code
2064 class=property>none</code></a>’ disallows all synthetic faces.
2066 <div class=example>
2067 <p>The style rule below disables the use of synthetically obliqued Arabic:</p>
2069 <pre>*:lang(ar) { font-synthesis: none; }
2070 </pre>
2071 </div>
2073 <h2 id=font-resources><span class=secno>4 </span>Font Resources</h2>
2075 <h3 id=font-face-rule><span class=secno>4.1 </span>The
2076 <code>@font-face</code> rule</h3>
2078 <p>The <code>@font-face</code> rule allows for linking to fonts that are
2079 automatically fetched and activated when needed. This allows authors to
2080 select a font that closely matches the design goals for a given page
2081 rather than limiting the font choice to a set of fonts available on all
2082 platforms. A set of font descriptors define the location of a font
2083 resource, either locally or externally, along with the style
2084 characteristics of an individual face. Multiple <code>@font-face</code>
2085 rules can be used to construct font families with a variety of faces.
2086 Using CSS font matching rules, a user agent can selectively download only
2087 those faces that are needed for a given piece of text.
2089 <p>The @font-face rule consists of the @font-face at-keyword followed by a
2090 block of descriptor declarations. In terms of the grammar, this
2091 specification defines the following productions:
2093 <pre><dfn id=fontfacerule>font_face_rule</dfn>
2094 : <a href="#fontfacesym"><i>FONT_FACE_SYM</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* '{' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#descriptordeclaration"><i>descriptor_declaration</i></a>? [ ';' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#descriptordeclaration"><i>descriptor_declaration</i></a>? ]* '}' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
2095 ;
2097 <dfn id=descriptordeclaration>descriptor_declaration</dfn>
2098 : <a href="http://www.w3.org/TR/CSS21/grammar.html#grammar"><i>property</i></a> ':' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/grammar.html#grammar"><i>expr</i></a>
2099 ;</pre>
2101 <p>The following new definitions are introduced:
2103 <pre>- -|\\0{0,4}2d(\r\n|[ \t\r\n\f])?
2104 F f|\\0{0,4}(46|66)(\r\n|[ \t\r\n\f])?</pre>
2106 <p>The following new token is introduced:
2108 <pre>@{F}{O}{N}{T}{-}{F}{A}{C}{E} {return <dfn id=fontfacesym>FONT_FACE_SYM</dfn>;}</pre>
2110 <p>Each <span class=index-inst id=font-face
2111 title="@font-face"><code>@font-face</code></span> rule specifies a value
2112 for every font descriptor, either implicitly or explicitly. Those not
2113 given explicit values in the rule take the initial value listed with each
2114 descriptor in this specification. These descriptors apply solely within
2115 the context of the <code>@font-face</code> rule in which they are defined,
2116 and do not apply to document language elements. There is no notion of
2117 which elements the descriptors apply to or whether the values are
2118 inherited by child elements. When a given descriptor occurs multiple times
2119 in a given <code>@font-face</code> rule, only the last descriptor
2120 declaration is used and all prior declarations for that descriptor are
2121 ignored.
2123 <div class=example>
2124 <p>To use a downloadable font called Gentium:</p>
2126 <pre>
2127 @font-face {
2128 font-family: Gentium;
2129 src: url(http://example.com/fonts/Gentium.ttf);
2130 }
2132 p { font-family: Gentium, serif; }
2133 </pre>
2135 <p>The user agent will download Gentium and use it when rendering text
2136 within paragraph elements. If for some reason the site serving the font
2137 is unavailable, the default serif font will be used.</p>
2138 </div>
2140 <p>A given set of <code>@font-face</code> rules define a set of fonts
2141 available for use within the documents that contain these rules. When font
2142 matching is done, fonts defined using these rules are considered before
2143 other available fonts on a system.
2145 <p>Downloaded fonts are only available to documents that reference them.
2146 The process of activating these fonts must not make them available to
2147 other applications or to documents that don't directly link to the same
2148 font. User agent implementers might consider it convenient to use
2149 downloaded fonts when rendering characters in other documents for which no
2150 other available font exists as part of the system font fallback procedure.
2151 However, this would cause a security leak since the contents of one page
2152 would be able to affect other pages, something an attacker could use as an
2153 attack vector. These restrictions do not affect caching behavior, fonts
2154 are cached the same way other web resources are cached.
2156 <p>This at-rule follows the forward-compatible parsing rules of CSS. Like
2157 properties in a declaration block, declarations of any descriptors that
2158 are not supported by the user agent must be ignored.
2159 <code>@font-face</code> rules require a font-family and src descriptor; if
2160 either of these are missing, the <code>@font-face</code> rule is invalid
2161 and must be ignored entirely.
2163 <p>In cases where user agents have limited platform resources or implement
2164 the ability to disable downloadable font resources,
2165 <code>@font-face</code> rules must simply be ignored; the behavior of
2166 individual descriptors as defined in this specification should not be
2167 altered.
2169 <h3 id=font-family-desc><span class=secno>4.2 </span>Font family: the <a
2170 href="#descdef-font-family">font-family</a> descriptor</h3>
2172 <table class=descdef>
2173 <tbody>
2174 <tr>
2175 <td>Name:
2177 <td><dfn id=descdef-font-family>font-family</dfn>
2179 <tr>
2180 <td>Value:
2182 <td><a href="#family-name-value"><var><family-name></var></a>
2184 <tr>
2185 <td><em>Initial:</em>
2187 <td>N/A
2188 </table>
2190 <p>This descriptor defines the font family name that will be used in all
2191 CSS font family name matching. It is required for the @font-face rule to
2192 be valid. It overrides the font family names contained in the underlying
2193 font data. If the font family name is the same as a font family available
2194 in a given user's environment, it effectively hides the underlying font
2195 for documents that use the stylesheet. This permits a web author to freely
2196 choose font-family names without worrying about conflicts with font family
2197 names present in a given user's environment. Likewise, platform
2198 substitutions for a given font family name must not be used.
2200 <h3 id=src-desc><span class=secno>4.3 </span>Font reference: the <a
2201 href="#descdef-src">src</a> descriptor</h3>
2203 <table class=descdef>
2204 <tbody>
2205 <tr>
2206 <td>Name:
2208 <td><dfn id=descdef-src>src</dfn>
2210 <tr>
2211 <td>Value:
2213 <td>[ <url> [format(<string> #)]? | <a
2214 href="#font-face-name-value"><var><font-face-name></var></a> ] #
2216 <tr>
2217 <td><em>Initial:</em>
2219 <td>N/A
2220 </table>
2222 <p>This descriptor specifies the resource containing font data. It is
2223 required for the <code>@font-face</code> rule to be valid. Its value is a
2224 prioritized, comma-separated list of external references or
2225 locally-installed font face names. When a font is needed the user agent
2226 iterates over the set of references listed, using the first one it can
2227 successfully activate. Fonts containing invalid data or local font faces
2228 that are not found are ignored and the user agent loads the next font in
2229 the list.
2231 <p>As with other URLs in CSS, the URL may be relative, in which case it is
2232 resolved relative to the location of the style sheet containing the <span
2233 class=index-inst id=font-face0
2234 title="@font-face"><code>@font-face</code></span> rule. In the case of SVG
2235 fonts, the URL points to an element within a document containing SVG font
2236 definitions. If the element reference is omitted, a reference to the first
2237 defined font is implied. Similarly, font container formats that can
2238 contain more than one font must load one and only one of the fonts for a
2239 given <code>@font-face</code> rule. Fragment identifiers are used to
2240 indicate which font to load. If a container format lacks a defined
2241 fragment identifier scheme, implementations should use a simple 1-based
2242 indexing scheme (e.g. "font-collection#1" for the first font,
2243 "font-collection#2" for the second font).
2245 <pre>
2246 src: url(fonts/simple.ttf); /* load simple.ttf relative to stylesheet location */
2247 src: url(/fonts/simple.ttf); /* load simple.ttf from absolute location */
2248 src: url(fonts.svg#simple); /* load SVG font with id 'simple' */
2249 </pre>
2251 <p>External references consist of a URL, followed by an optional hint
2252 describing the format of the font resource referenced by that URL. The
2253 format hint contains a comma-separated list of format strings that denote
2254 well-known font formats. Conformant user agents must skip downloading a
2255 font resource if the format hints indicate only unsupported or unknown
2256 font formats. If no format hints are supplied, the user agent should
2257 download the font resource.
2259 <pre>
2260 /* load WOFF font if possible, otherwise use OpenType font */
2261 @font-face {
2262 font-family: bodytext;
2263 src: url(ideal-sans-serif.woff) format("woff"),
2264 url(basic-sans-serif.ttf) format("opentype");
2265 }
2266 </pre>
2268 <p>Format strings defined by this specification:
2270 <table class=data id=fontformats>
2271 <thead>
2272 <tr>
2273 <th>String
2275 <th>Font Format
2277 <th>Common extensions
2279 <tbody>
2280 <tr>
2281 <th>"woff"
2283 <td><a href="http://www.w3.org/TR/WOFF/">WOFF (Web Open Font Format)</a>
2285 <td>.woff
2287 <tr>
2288 <th>"truetype"
2290 <td><a
2291 href="http://www.microsoft.com/typography/otspec/default.htm">TrueType</a>
2293 <td>.ttf
2295 <tr>
2296 <th>"opentype"
2298 <td><a
2299 href="http://www.microsoft.com/typography/otspec/default.htm">OpenType</a>
2301 <td>.ttf, .otf
2303 <tr>
2304 <th>"embedded-opentype"
2306 <td><a
2307 href="http://www.w3.org/Submission/2008/SUBM-EOT-20080305/">Embedded
2308 OpenType</a>
2310 <td>.eot
2312 <tr>
2313 <th>"svg"
2315 <td><a href="http://www.w3.org/TR/SVG/fonts.html">SVG Font</a>
2317 <td>.svg, .svgz
2318 </table>
2320 <p>Given the overlap in common usage between TrueType and OpenType, the
2321 format hints "truetype" and "opentype" must be considered as synonymous; a
2322 format hint of "opentype" does not imply that the font contains Postscript
2323 CFF style glyph data or that it contains OpenType layout information (see
2324 <a href="#platform-props-to-css">Appendix A</a> for more background on
2325 this).
2327 <p>When authors would prefer to use a locally available copy of a given
2328 font and download it if it's not, <code>local()</code> can be used. The
2329 locally-installed <dfn
2330 id=font-face-name-value><var><font-face-name></var></dfn> argument
2331 to <code>local()</code> is a format-specific string that uniquely
2332 identifies a single font face within a larger family. The syntax for a <a
2333 href="#font-face-name-value"><var><font-face-name></var></a> is a
2334 unique font face name enclosed by "local(" and ")". The name can
2335 optionally be enclosed in quotes. If unquoted, the unquoted font family
2336 name processing conventions apply; the name must be a sequence of
2337 identifiers separated by whitespace which is converted to a string by
2338 joining the identifiers together separated by a single space.
2340 <pre>
2341 /* regular face of Gentium */
2342 @font-face {
2343 font-family: MyGentium;
2344 src: local(Gentium), /* use locally available Gentium */
2345 url(Gentium.ttf); /* otherwise, download it */
2346 }
2347 </pre>
2349 <p>For OpenType and TrueType fonts, this string is used to match only the
2350 Postscript name or the full font name in the name table of locally
2351 available fonts. Which type of name is used varies by platform and font,
2352 so authors should include both of these names to assure proper matching
2353 across platforms. Platform substitutions for a given font name must not be
2354 used.
2356 <pre>
2357 /* bold face of Gentium */
2358 @font-face {
2359 font-family: MyGentium;
2360 src: local(Gentium Bold), /* full font name */
2361 local(Gentium-Bold), /* Postscript name */
2362 url(GentiumBold.ttf); /* otherwise, download it */
2363 font-weight: bold;
2364 }
2365 </pre>
2367 <p>Just as a <code>@font-face</code> rule specifies the characteristics of
2368 a single font within a family, the unique name used with
2369 <code>local()</code> specifies a single font, not an entire font family.
2370 Defined in terms of OpenType font data, the Postscript name is found in
2371 the font's <a
2372 href="http://www.microsoft.com/typography/otspec/name.htm">name table</a>,
2373 in the name record with nameID = 6 (see <a href="#OPENTYPE"
2374 rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> for more details). The
2375 Postscript name is the commonly used key for all fonts on OSX and for
2376 Postscript CFF fonts under Windows. The full font name (nameID = 4) is
2377 used as a unique key for fonts with TrueType glyphs on Windows.
2379 <p>For OpenType fonts with multiple localizations of the full font name,
2380 the US English version is used (language ID = 0x409 for Windows and
2381 language ID = 0 for Macintosh) or the first localization when a US English
2382 full font name is not available (the OpenType specification recommends
2383 that <a href="http://www.microsoft.com/typography/otspec/recom.htm">all
2384 fonts minimally include US English names</a>). User agents that also match
2385 other full font names, e.g. matching the Dutch name when the current
2386 system locale is set to Dutch, are considered non-conformant. This is done
2387 not to prefer English but to avoid matching inconsistencies across font
2388 versions and OS localizations, since font style names (e.g. "Bold") are
2389 frequently localized into many languages and the set of localizations
2390 available varies widely across platform and font version. User agents that
2391 match a concatenation of family name (nameID = 1) with style name (nameID
2392 = 2) are considered non-conformant.
2394 <p>This also allows for referencing faces that belong to larger families
2395 that cannot otherwise be referenced.
2397 <div class=example>
2398 <p>Use a local font or reference an SVG font in another document:</p>
2400 <pre>
2401 @font-face {
2402 font-family: Headline;
2403 src: local(Futura-Medium),
2404 url(fonts.svg#MyGeometricModern) format("svg");
2405 }
2406 </pre>
2408 <p>Create an alias for local Japanese fonts on different platforms:</p>
2410 <pre>
2411 @font-face {
2412 font-family: jpgothic;
2413 src: local(HiraKakuPro-W3), local(Meiryo), local(IPAPGothic);
2414 }
2415 </pre>
2417 <p>Reference a font face that cannot be matched within a larger family:</p>
2419 <pre>
2420 @font-face {
2421 font-family: Hoefler Text Ornaments;
2422 /* has the same font properties as Hoefler Text Regular */
2423 src: local(HoeflerText-Ornaments);
2424 }
2425 </pre>
2427 <p>Since localized fullnames never match, a document with the header style
2428 rules below would always render using the default serif font, regardless
2429 whether a particular system locale parameter is set to Finnish or not:</p>
2431 <pre>
2432 @font-face {
2433 font-family: SectionHeader;
2434 src: local("Arial Lihavoitu"); /* Finnish fullname for Arial Bold, should fail */
2435 font-weight: bold;
2436 }
2438 h2 { font-family: SectionHeader, serif; }
2439 </pre>
2441 <p>A conformant user agent would never load the font ‘<code
2442 class=css>gentium.eot</code>’ in the example below, since it is
2443 included in the first definition of the ‘<a href="#descdef-src"><code
2444 class=property>src</code></a>’ descriptor which is overridden by the
2445 second definition in the same <code>@font-face</code> rule:</p>
2447 <pre>
2448 @font-face {
2449 font-family: MainText;
2450 src: url(gentium.eot); /* for use with older non-conformant user agents */
2451 src: local("Gentium"), url(gentium.ttf); /* Overrides src definition */
2452 }
2453 </pre>
2454 </div>
2456 <h3 id=font-prop-desc><span class=secno>4.4 </span>Font property
2457 descriptors: the <a href="#descdef-font-style">font-style</a>, <a
2458 href="#descdef-font-weight">font-weight</a>, <a
2459 href="#descdef-font-stretch">font-stretch</a> descriptors</h3>
2461 <table class=descdef>
2462 <tbody>
2463 <tr>
2464 <td>Name:
2466 <td><dfn id=descdef-font-style title="font-style
2467 (descriptor)">font-style</dfn>
2469 <tr>
2470 <td>Value:
2472 <td>normal | italic | oblique
2474 <tr>
2475 <td><em>Initial:</em>
2477 <td>normal
2478 </table>
2480 <table class=descdef>
2481 <tbody>
2482 <tr>
2483 <td>Name:
2485 <td><dfn id=descdef-font-weight title="font-weight
2486 (descriptor)">font-weight</dfn>
2488 <tr>
2489 <td>Value:
2491 <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
2493 <tr>
2494 <td><em>Initial:</em>
2496 <td>normal
2497 </table>
2499 <table class=descdef>
2500 <tbody>
2501 <tr>
2502 <td>Name:
2504 <td><dfn id=descdef-font-stretch title="font-stretch
2505 (descriptor)">font-stretch</dfn>
2507 <tr>
2508 <td>Value:
2510 <td>normal | ultra-condensed | extra-condensed | condensed |
2511 semi-condensed | semi-expanded | expanded | extra-expanded |
2512 ultra-expanded
2514 <tr>
2515 <td><em>Initial:</em>
2517 <td>normal
2518 </table>
2520 <p>These descriptors define the characteristics of a font face and are used
2521 in the process of matching styles to specific faces. For a font family
2522 defined with several <code>@font-face</code> rules, user agents can either
2523 download all faces in the family or use these descriptors to selectively
2524 download font faces that match actual styles used in document. The values
2525 for these descriptors are the same as those for the corresponding font
2526 properties except that relative keywords are not allowed, ‘<code
2527 class=property>bolder</code>’ and ‘<code
2528 class=property>lighter</code>’. If these descriptors are omitted,
2529 initial values are assumed.
2531 <p>The value for these font face style attributes is used in place of the
2532 style implied by the underlying font data. This allows authors to combine
2533 faces in flexible combinations, even in situations where the original font
2534 data was arranged differently. User agents that implement synthetic
2535 bolding and obliquing must only apply synthetic styling in cases where the
2536 font descriptors imply this is needed, rather than based on the style
2537 attributes implied by the font data.
2539 <h3 id=unicode-range-desc><span class=secno>4.5 </span>Character range: the
2540 <a href="#descdef-unicode-range">unicode-range</a> descriptor</h3>
2542 <table class=descdef>
2543 <tbody>
2544 <tr>
2545 <td>Name:
2547 <td><dfn id=descdef-unicode-range>unicode-range</dfn>
2549 <tr>
2550 <td>Value:
2552 <td><a href="#urange-value"><var><urange></var></a> #
2554 <tr>
2555 <td><em>Initial:</em>
2557 <td>U+0-10FFFF
2558 </table>
2560 <p>This descriptor defines the set of Unicode codepoints that may be
2561 supported by the font face for which it is declared. The descriptor value
2562 is a comma-delimited list of Unicode range (<a
2563 href="#urange-value"><var><urange></var></a>) values. The union of
2564 these ranges defines the set of codepoints that serves as a hint for user
2565 agents when deciding whether or not to download a font resource for a
2566 given text run.
2568 <p>Each <dfn id=urange-value><var><urange></var></dfn> value is a <a
2569 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><code
2570 title="UNICODE-RANGE token">UNICODE-RANGE</code></a> token made up of a
2571 "U+" or "u+" prefix followed by a codepoint range in one of the three
2572 forms listed below. Ranges that do not fit one of the these forms are
2573 invalid and cause the declaration to be ignored.
2575 <dl>
2576 <dt>single codepoint (e.g. U+416)
2578 <dd>a valid Unicode codepoint, represented as one to six hexadecimal
2579 digits
2581 <dt>interval range (e.g. U+400-4ff)
2583 <dd>represented as two hyphen-separated valid Unicode codepoints
2584 indicating the inclusive start and end codepoints of a range
2586 <dt>wildcard range (e.g. U+4??)
2588 <dd>defined by the set of codepoints implied when trailing ‘<code
2589 class=css>?</code>’ characters signify any hexadeximal digit
2590 </dl>
2592 <p>Individual codepoints are written using hexadecimal values that
2593 correspond to <a href="http://www.unicode.org/charts/">Unicode character
2594 codepoints</a>. Valid Unicode codepoint values vary between 0 and 10FFFF
2595 inclusive. Digit values of codepoints are ASCII case-insensitive. For
2596 interval ranges, the start and end codepoints must be valid Unicode values
2597 and the end codepoint must be greater than or equal to the start
2598 codepoint.
2600 <p>Wildcard ranges specified with ‘?’ that lack an initial digit (e.g.
2601 "U+???") are valid and equivalent to a wildcard range with an initial zero
2602 digit (e.g. "U+0???" = "U+0000-0FFF"). Wildcard ranges that extend beyond
2603 the range of valid Unicode codepoints are invalid. Because of this, the
2604 maximum number of trailing ‘<code class=css>?</code>’ wildcard
2605 characters is five, even though the <a
2606 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><code
2607 title="UNICODE-RANGE token">UNICODE-RANGE</code></a> token accepts six.
2609 <p>Within the comma-delimited list of Unicode ranges in a ‘<a
2610 href="#descdef-unicode-range"><code
2611 class=property>unicode-range</code></a>’ descriptor declaration, ranges
2612 may overlap. The union of these ranges defines the set of codepoints for
2613 which the corresponding font may be used. User agents must not download or
2614 use the font for codepoints outside this set. User agents may normalize
2615 the list of ranges into a list that is different but represents the same
2616 set of codepoints.
2618 <p>The associated font might not contain glyphs for the entire set of
2619 codepoints defined by the ‘<a href="#descdef-unicode-range"><code
2620 class=property>unicode-range</code></a>’ descriptor. When the font is
2621 used the effective <a href="#character-map"><em>character map</em></a> is
2622 the intersection of the codepoints defined by ‘<a
2623 href="#descdef-unicode-range"><code
2624 class=property>unicode-range</code></a>’ with the font's <a
2625 href="#character-map"><em>character map</em></a>. This allows authors to
2626 define supported ranges in terms of broad ranges without worrying about
2627 the precise codepoint ranges supported by the underlying font.
2629 <h3 id=composite-fonts><span class=secno>4.6 </span>Using character ranges
2630 to define composite fonts</h3>
2632 <p>Multiple <code>@font-face</code> rules with different unicode ranges for
2633 the same family and style descriptor values can be used to create
2634 composite fonts that mix the glyphs from different fonts for different
2635 scripts. This can be used to combine fonts that only contain glyphs for a
2636 single script (e.g. Latin, Greek, Cyrillic) or it can be used by authors
2637 as a way of segmenting a font into fonts for commonly used characters and
2638 less frequently used characters. Since the user agent will only pull down
2639 the fonts it needs this helps reduce page bandwidth.
2641 <p>If the unicode ranges overlap for a set of <code>@font-face</code> rules
2642 with the same family and style descriptor values, the rules are ordered in
2643 the reverse order they were defined; the last rule defined is the first to
2644 be checked for a given character.
2646 <p>Example ranges for specific languages or characters:
2648 <dl>
2649 <dt>unicode-range: U+A5;
2651 <dd>a single code point, the yen/yuan symbol
2653 <dt>unicode-range: U+0-7F;
2655 <dd>code range for basic ASCII characters
2657 <dt>unicode-range: U+590-5ff;
2659 <dd>code range for Hebrew characters
2661 <dt>unicode-range: U+A5, U+4E00-9FFF, U+30??, U+FF00-FF9F;
2663 <dd>code range for Japanese kanji, hiragana and katakana characters plus
2664 yen/yuan symbol
2665 </dl>
2667 <div class=example>
2668 <p>The BBC provides news services in a wide variety of languages, many
2669 that are not well supported across all platforms. Using an
2670 <code>@font-face</code> rule, the BBC could provide a font for any of
2671 these languages, as it already does via a manual font download.</p>
2673 <pre>
2674 @font-face {
2675 font-family: BBCBengali;
2676 src: url(fonts/BBCBengali.ttf) format("opentype");
2677 unicode-range: U+00-FF, U+980-9FF;
2678 }
2679 </pre>
2680 </div>
2682 <div class=example>
2683 <p>Technical documents often require a wide range of symbols. The STIX
2684 Fonts project is one project aimed at providing fonts to support a wide
2685 range of technical typesetting in a standardized way. The example below
2686 shows the use of a font that provides glyphs for many of the mathematical
2687 and technical symbol ranges within Unicode:</p>
2689 <pre>
2690 @font-face {
2691 font-family: STIXGeneral;
2692 src: local(STIXGeneral), url(/stixfonts/STIXGeneral.otf);
2693 unicode-range: U+000-49F, U+2000-27FF, U+2900-2BFF, U+1D400-1D7FF;
2694 }
2695 </pre>
2696 </div>
2698 <div class=example>
2699 <p>This example shows how an author can override the glyphs used for Latin
2700 characters in a Japanese font with glyphs from a different font. The
2701 first rule specifies no range so it defaults to the entire range. The
2702 range specified in the second rule overlaps but takes precedence because
2703 it is defined later.</p>
2705 <pre>
2706 @font-face {
2707 font-family: JapaneseWithGentium;
2708 src: local(MSMincho);
2709 /* no range specified, defaults to entire range */
2710 }
2712 @font-face {
2713 font-family: JapaneseWithGentium;
2714 src: url(../fonts/Gentium.ttf);
2715 unicode-range: U+0-2FF;
2716 }
2717 </pre>
2718 </div>
2720 <div class=example>
2721 <p>Consider a family constructed to optimize bandwidth by separating out
2722 Latin, Japanese and other characters into different font files:</p>
2724 <pre>
2725 /* fallback font - size: 4.5MB */
2726 @font-face {
2727 font-family: DroidSans;
2728 src: url(DroidSansFallback.ttf);
2729 /* no range specified, defaults to entire range */
2730 }
2732 /* Japanese glyphs - size: 1.2MB */
2733 @font-face {
2734 font-family: DroidSans;
2735 src: url(DroidSansJapanese.ttf);
2736 unicode-range: U+3000-9FFF, U+ff??;
2737 }
2739 /* Latin, Greek, Cyrillic along with some
2740 punctuation and symbols - size: 190KB */
2741 @font-face {
2742 font-family: DroidSans;
2743 src: url(DroidSans.ttf);
2744 unicode-range: U+000-5FF, U+1e00-1fff, U+2000-2300;
2745 }
2746 </pre>
2748 <p>For simple Latin text, only the font for Latin characters is
2749 downloaded:</p>
2751 <pre>
2752 body { font-family: DroidSans; }
2754 <p>This is that</p>
2755 </pre>
2757 <p>In this case the user agent first checks the unicode-range for the font
2758 containing Latin characters (DroidSans.ttf). Since all the characters
2759 above are in the range U+0-5FF, the user agent downloads the font and
2760 renders the text with that font.</p>
2762 <p>Next, consider text that makes use of an arrow character (⇨):</p>
2764 <pre>
2765 <p>This &#x21e8; that<p>
2766 </pre>
2768 <p>The user agent again first checks the unicode-range of the font
2769 containing Latin characters. Since U+2000-2300 includes the arrow code
2770 point (U+21E8), the user agent downloads the font. For this character
2771 however the Latin font does not have a matching glyph, so the effective
2772 unicode-range used for font matching excludes this code point. Next, the
2773 user agent evaluates the Japanese font. The unicode-range for the
2774 Japanese font, U+3000-9FFF and U+ff??, does not include U+21E8, so the
2775 user agent does not download the Japanese font. Next the fallback font is
2776 considered. The <code>@font-face</code> rule for the fallback font does
2777 not define unicode-range so its value defaults to the range of all
2778 Unicode code points. The fallback font is downloaded and used to render
2779 the arrow character.</p>
2780 </div>
2782 <h3 id=font-rend-desc><span class=secno>4.7 </span>Font features: the <a
2783 href="#descdef-font-variant">font-variant</a> and <a
2784 href="#descdef-font-feature-settings">font-feature-settings</a>
2785 descriptors</h3>
2787 <table class=descdef>
2788 <tbody>
2789 <tr>
2790 <td>Name:
2792 <td><dfn id=descdef-font-variant title="font-variant
2793 (descriptor)">font-variant</dfn>
2795 <tr>
2796 <td>Value:
2798 <td>normal | none | [ <a
2799 href="#common-lig-values"><var><common-lig-values></var></a> ||
2800 <a
2801 href="#discretionary-lig-values"><var><discretionary-lig-values></var></a>
2802 || <a
2803 href="#historical-lig-values"><var><historical-lig-values></var></a>
2804 || <a
2805 href="#contextual-alt-values"><var><contextual-alt-values></var></a>
2806 || <a href="#stylistic"><var
2807 title=stylistic>stylistic(<feature-value-name>)</var></a> || <a
2808 href="#historical-forms"><var>historical-forms</var></a> || <a
2809 href="#styleset"><var
2810 title=styleset>styleset(<feature-value-name> #)</var></a> || <a
2811 href="#character-variant"><var
2812 title=character-variant>character-variant(<feature-value-name>
2813 #)</var></a> || <a href="#swash"><var
2814 title=swash>swash(<feature-value-name>)</var></a> || <a
2815 href="#ornaments"><var
2816 title=ornaments>ornaments(<feature-value-name>)</var></a> || <a
2817 href="#annotation"><var
2818 title=annotation>annotation(<feature-value-name>)</var></a> || [
2819 <a href="#small-caps"><i>small-caps</i></a> | <a
2820 href="#all-small-caps"><i>all-small-caps</i></a> | <a
2821 href="#petite-caps"><i>petite-caps</i></a> | <a
2822 href="#all-petite-caps"><i>all-petite-caps</i></a> | <a
2823 href="#unicase"><i>unicase</i></a> | <a
2824 href="#titling-caps"><i>titling-caps</i></a> ] || <a
2825 href="#numeric-figure-values"><var><numeric-figure-values></var></a>
2826 || <a
2827 href="#numeric-spacing-values"><var><numeric-spacing-values></var></a>
2828 || <a
2829 href="#numeric-fraction-values"><var><numeric-fraction-values></var></a>
2830 || <a href="#ordinal"><i>ordinal</i></a> || <a
2831 href="#slashed-zero"><i>slashed-zero</i></a> || <a
2832 href="#east-asian-variant-values"><var><east-asian-variant-values></var></a>
2833 || <a
2834 href="#east-asian-width-values"><var><east-asian-width-values></var></a>
2835 || <a href="#ruby"><i>ruby</i></a> ]
2837 <tr>
2838 <td><em>Initial:</em>
2840 <td>normal
2841 </table>
2843 <table class=descdef>
2844 <tbody>
2845 <tr>
2846 <td>Name:
2848 <td><dfn id=descdef-font-feature-settings title="font-feature-settings
2849 (descriptor)">font-feature-settings</dfn>
2851 <tr>
2852 <td>Value:
2854 <td>normal | <a
2855 href="#feature-tag-value"><var><feature-tag-value></var></a> #
2857 <tr>
2858 <td><em>Initial:</em>
2860 <td>normal
2861 </table>
2863 <p>These descriptors define initial settings that apply when the font
2864 defined by an <code>@font-face</code> rule is rendered. They do not affect
2865 font selection. Values are identical to those defined for the
2866 corresponding ‘<a href="#propdef-font-variant"><code
2867 class=property>font-variant</code></a>’ and ‘<a
2868 href="#propdef-font-feature-settings"><code
2869 class=property>font-feature-settings</code></a>’ properties defined
2870 below except that the value ‘<code class=property>inherit</code>’ is
2871 omitted. When multiple font feature descriptors or properties are used,
2872 the cumulative effect on text rendering is detailed in the section <a
2873 href="#font-feature-resolution">Font Feature Resolution</a> below. In
2874 cases where specific values define synthesized fallback for certain ‘<a
2875 href="#propdef-font-variant"><code
2876 class=property>font-variant</code></a>’ subproperties, the same
2877 synthesized fallback applies when used within those values are used with
2878 the <a href="#descdef-font-variant">‘<code
2879 class=property>font-variant</code>’</a> descriptor.
2881 <h3 id=font-face-loading><span class=secno>4.8 </span>Font loading
2882 guidelines</h3>
2884 <p>The <code>@font-face</code> rule is designed to allow lazy loading of
2885 font resources that are only downloaded when used within a document. A
2886 stylesheet can include <code>@font-face</code> rules for a library of
2887 fonts of which only a select set are used; user agents must only download
2888 those fonts that are referred to within the style rules applicable to a
2889 given page. User agents that download all fonts defined in
2890 <code>@font-face</code> rules without considering whether those fonts are
2891 in fact used within a page are considered non-conformant. In cases where a
2892 font might be downloaded in character fallback cases, user agents may
2893 download a font if it's listed in a font list but is not actually used for
2894 a given text run.
2896 <pre>
2897 @font-face {
2898 font-family: GeometricModern;
2899 src: url(font.ttf);
2900 }
2902 p {
2903 /* font will be downloaded for pages with p elements */
2904 font-family: GeometricModern, sans-serif;
2905 }
2907 h2 {
2908 /* font may be downloaded for pages with h2 elements, even if Futura is available locally */
2909 font-family: Futura, GeometricModern, sans-serif;
2910 }
2911 </pre>
2913 <p>In cases where textual content is loaded before downloadable fonts are
2914 available, user agents may render text as it would be rendered if
2915 downloadable font resources are not available or they may render text
2916 transparently with fallback fonts to avoid a flash of text using a
2917 fallback font. In cases where the font download fails user agents must
2918 display text, simply leaving transparent text is considered non-conformant
2919 behavior. Authors are advised to use fallback fonts in their font lists
2920 that closely match the vertical metrics of the downloadable fonts to avoid
2921 large page reflows where possible.
2923 <h3 id=same-origin-restriction><span class=secno>4.9 </span>Same-origin
2924 restriction for fonts</h3>
2926 <h4 id=default-same-origin-restriction><span class=secno>4.9.1
2927 </span>Default same-origin restriction</h4>
2928 <!-- TPAC 2011 Resolution to require same-origin restriction for loading fonts:
2929 http://lists.w3.org/Archives/Public/www-style/2011Nov/0711.html
2930 http://www.w3.org/2011/10/31-webapps-minutes.html#item02
2931 -->
2933 <p>User agents must implement a same-origin restriction when loading fonts
2934 via the <code>@font-face</code> mechanism. This restriction limits the
2935 loading of fonts for a given document to fonts loaded from the same
2936 origin. Fonts can only be loaded via the same host, port, and method
2937 combination as the containing document, using the <a
2938 href="http://www.w3.org/TR/html5/browsers.html#origin">origin matching
2939 algorithm</a> described in the <a href="#HTML5"
2940 rel=biblioentry>[HTML5]<!--{{!HTML5}}--></a> specification. The origin of
2941 the stylesheet containing <code>@font-face</code> rules is not used when
2942 deciding whether a font is same origin or not, only the origin of the
2943 containing document is used. The restriction applies to all font types.
2945 <p>Given a document located at http://example.com/page.html, fonts defined
2946 with ‘<a href="#descdef-src"><code class=property>src</code></a>’
2947 definitions considered cross origin must not be loaded:
2949 <pre>
2950 /* same origin (i.e. domain, protocol, port match document) */
2951 src: url(fonts/simple.ttf);
2952 src: url(//fonts/simple.ttf);
2954 /* cross origin, different protocol */
2955 src: url(https://example.com/fonts/simple.ttf);
2957 /* cross origin, different domain */
2958 src: url(http://another.example.com/fonts/simple.ttf);
2959 </pre>
2961 <h4 id=allowing-cross-origin-font-loading><span class=secno>4.9.2
2962 </span>Allowing cross-origin font loading</h4>
2964 <p>User agents must also implement the ability to relax this restriction
2965 using cross-site origin controls <a href="#CORS"
2966 rel=biblioentry>[CORS]<!--{{!CORS}}--></a> for fonts loaded via HTTP.
2967 Sites can explicitly allow cross-site downloading of font data using the
2968 <code>Access-Control-Allow-Origin</code> HTTP header. For other protocols,
2969 no explicit relaxation mechanism is defined or required.
2971 <p>For font loads over HTTP, cross-origin requests must be made with the
2972 following parameter settings which are used in conjunction with the <a
2973 href="http://www.w3.org/TR/cors/#cross-origin-request-0"> <em>cross-origin
2974 request algorithm</em></a> <a href="#CORS"
2975 rel=biblioentry>[CORS]<!--{{!CORS}}--></a>:
2977 <ul>
2978 <li><em>request URL</em> — the URL of the font resource in the <a
2979 href="#descdef-src"><code>src</code></a> descriptor
2981 <li><em>request method</em> — GET
2983 <li><em>author request headers</em> — none
2985 <li><em>request entity body</em> — empty
2987 <li><em>source origin</em> — the origin of the page which linked to the
2988 stylesheet
2990 <li><em>manual redirect flag</em> — false
2992 <li><em>omit credentials flag</em> — true
2994 <li><em>force preflight flag</em> — false
2995 </ul>
2997 <h2 id=font-matching-algorithm><span class=secno>5 </span>Font Matching
2998 Algorithm</h2>
3000 <p>The algorithm below describes how fonts are associated with individual
3001 runs of text. For each character in the run a font family is chosen and a
3002 particular font face is selected containing a glyph for that character.
3004 <h3 id=font-family-casing><span class=secno>5.1 </span>Case sensitivity of
3005 font family names</h3>
3007 <p>As part of the font matching algorithm outlined below, user agents must
3008 match font family names used in style rules with actual font family names
3009 contained in fonts available in a given environment or defined via
3010 <code>@font-face</code> rules. User agents must match these names case
3011 insensitively, using the "Default Caseless Matching" algorithm outlined in
3012 the Unicode specification <a href="#UNICODE6"
3013 rel=biblioentry>[UNICODE6]<!--{{!UNICODE6}}--></a>. This algorithm is
3014 detailed in section 3.13 entitled "Default Case Algorithms". Specifically,
3015 the algorithm must be applied without normalizing the strings involved and
3016 without applying any language-specific tailorings. The case folding method
3017 specified by this algorithm uses the case mappings with status field
3018 ‘<code class=property>C</code>’ or ‘<code class=property>F</code>’
3019 in the CaseFolding.txt file of the Unicode Character Database.
3021 <p class=note> Implementors should take care to verify that a given
3022 caseless string comparison implementation uses this precise algorithm and
3023 not assume that a given platform string matching routine follows it, as
3024 many of these have locale-specific behavior or use some level of string
3025 normalization.
3027 <p class=note> For authors this means that font family names are matched
3028 case insensitively, whether those names exist in a platform font or in the
3029 <code>@font-face</code> rules contained in a stylesheet. Authors should
3030 take care to ensure that names use a character sequence consistent with
3031 the actual font family name, particularly when using combining characters
3032 such as diacritical marks. For example, a family name that contains an
3033 uppercase A (U+0041) followed by a combining ring (U+030A) will
3034 <strong>not</strong> match a name that looks identical but which uses the
3035 precomposed lowercase a-ring character (U+00E5) instead of the combining
3036 sequence.
3038 <h3 id=font-style-matching><span class=secno>5.2 </span>Matching font
3039 styles</h3>
3041 <p>The procedure for choosing fonts consists of iterating over the font
3042 families determined by the font-family property, selecting a font face
3043 with the appropriate style based on other font properties and then
3044 determining whether a glyph exists for a given character. This is done
3045 using the <dfn id=character-map>character map</dfn> of the font, data
3046 which maps characters to the default glyph for that character. Codepoint
3047 sequences consisting of a base character followed by a sequence of
3048 combining characters are treated slightly differently, see the section on
3049 <a href="#cluster-matching">cluster matching</a> below.
3051 <p>For this procedure, the <dfn id=default-face>default face</dfn> for a
3052 given font family is defined to be the face that would be selected if all
3053 font style properties were set to their initial value.
3055 <ol id=fontmatchingalg>
3056 <li>Using the computed font property values for a given element, the user
3057 agent starts with the first family name in the fontlist specified by the
3058 <span class=property>‘<a href="#descdef-font-family"><code
3059 class=property>font-family</code></a>’</span> property.
3061 <li>If the family name is unquoted and is a generic family name, the user
3062 agent looks up the appropriate font family name to be used. User agents
3063 may choose the generic font family to use based on the language of the
3064 containing element or the Unicode range of the character.
3066 <li>For other family names, the user agent attempts to find the family
3067 name among fonts defined via <code>@font-face</code> rules and then among
3068 available system fonts, matching names with a case-insensitive comparison
3069 as outlined <a href="#font-family-casing">in the section above</a>. On
3070 systems containing fonts with multiple localized font family names, user
3071 agents must match any of these names independent of the underlying system
3072 locale or platform API used. If the font resources defined for a given
3073 face in an @font-face rule are either not available or contain invalid
3074 font data, then the face should be treated as not present in the family.
3075 If no faces are present for a family defined via @font-face rules, the
3076 family should be treated as missing; matching a platform font with the
3077 same name must not occur in this case.
3079 <li>If a font family match occurs, the user agent assembles the set of
3080 font faces in that family and then narrows the set to a single face using
3081 other font properties in the order given below:
3082 <ol id=fontstylematchingalg>
3083 <li><span class=property>‘<a href="#propdef-font-stretch"><code
3084 class=property>font-stretch</code></a>’</span> is tried first. If the
3085 matching set contains faces with width values matching the ‘<a
3086 href="#propdef-font-stretch"><code
3087 class=property>font-stretch</code></a>’ value, faces with other width
3088 values are removed from the matching set. If there is no face that
3089 exactly matches the width value the nearest width is used instead. If
3090 the value of ‘<a href="#propdef-font-stretch"><code
3091 class=property>font-stretch</code></a>’ is ‘<a
3092 href="#normal2"><code class=property>normal</code></a>’ or one of the
3093 condensed values, narrower width values are checked first, then wider
3094 values. If the value of ‘<a href="#propdef-font-stretch"><code
3095 class=property>font-stretch</code></a>’ is one of the expanded
3096 values, wider values are checked first, followed by narrower values.
3097 Once the closest matching width has been determined by this process,
3098 faces with other widths are removed from the matching set.
3100 <li><span class=property>‘<a href="#propdef-font-style"><code
3101 class=property>font-style</code></a>’</span> is tried next. If the
3102 value of ‘<a href="#propdef-font-style"><code
3103 class=property>font-style</code></a>’ is ‘<code
3104 class=property>italic</code>’, italic faces are checked first, then
3105 oblique, then normal faces. If the value is ‘<code
3106 class=property>oblique</code>’, oblique faces are checked first, then
3107 italic faces and then normal faces. If the value is ‘<a
3108 href="#normal2"><code class=property>normal</code></a>’, normal faces
3109 are checked first, then oblique faces, then italic faces. Faces with
3110 other style values are excluded from the matching set. User agents are
3111 permitted to distinguish between italic and oblique faces within
3112 platform font families but this is not required, they may treat all
3113 italic or oblique faces as italic faces. However, within font families
3114 defined via <code>@font-face</code> rules, italic and oblique faces
3115 must be distinguished using the value of the ‘<a
3116 href="#propdef-font-style"><code
3117 class=property>font-style</code></a>’ descriptor.
3119 <li><span class=property>‘<a href="#propdef-font-weight"><code
3120 class=property>font-weight</code></a>’</span> is matched next, it
3121 will always reduce the matching set to a single font face. If
3122 bolder/lighter relative weights are used, the effective weight is
3123 calculated based on the inherited weight value, as described in the
3124 definition of the ‘<a href="#propdef-font-weight"><code
3125 class=property>font-weight</code></a>’ property. Given the desired
3126 weight and the weights of faces in the matching set after the steps
3127 above, if the desired weight is available that face matches. Otherwise,
3128 a weight is chosen using the rules below:
3129 <ul>
3130 <li>If the desired weight is less than 400, weights below the desired
3131 weight are checked in descending order followed by weights above the
3132 desired weight in ascending order until a match is found.
3134 <li>If the desired weight is greater than 500, weights above the
3135 desired weight are checked in ascending order followed by weights
3136 below the desired weight in descending order until a match is found.
3138 <li>If the desired weight is 400, 500 is checked first and then the
3139 rule for desired weights less than 400 is used.
3141 <li>If the desired weight is 500, 400 is checked first and then the
3142 rule for desired weights less than 400 is used.
3143 </ul>
3145 <li><span class=property>‘<a href="#propdef-font-size"><code
3146 class=property>font-size</code></a>’</span> must be matched within a
3147 UA-dependent margin of tolerance. (Typically, sizes for scalable fonts
3148 are rounded to the nearest whole pixel, while the tolerance for
3149 bitmapped fonts could be as large as 20%.) Further computations, e.g.,
3150 by ‘<code class=property>em</code>’ values in other properties, are
3151 based on the <span class=property>‘<a href="#propdef-font-size"><code
3152 class=property>font-size</code></a>’</span> value that is used, not
3153 the one that is specified.
3154 </ol>
3156 <li>
3157 <p>If no matching face exists or the matched face does not contain a
3158 glyph for the character to be rendered, the next family name is selected
3159 and the previous two steps repeated. Glyphs from other faces in the
3160 family are not considered. The only exception is that user agents may
3161 optionally substitute a synthetic version of the <a
3162 href="#default-face"><em>default face</em></a> if that face supports a
3163 given glyph (e.g. a synthetic italic version of the regular face may be
3164 used if the italic face doesn't support glyphs for Arabic).</p>
3165 <!-- resolution on the above: http://lists.w3.org/Archives/Public/www-style/2012Nov/0292.html -->
3167 <p>If the matched font is defined via an <code>@font-face</code> rule and
3168 needs to be downloaded, the font resource is downloaded. While the
3169 download occurs, the user agent can either wait until the font is
3170 downloaded or render once with substituted font metrics and render again
3171 once the font is downloaded.</p>
3173 <li>If there are no more font families to be evaluated and no matching
3174 face has been found, then the user agent performs a <em>system font
3175 fallback</em> procedure to find the best match for the character to be
3176 rendered. The result of this procedure may vary across user agents.
3178 <li>If a particular character cannot be displayed using any font, the user
3179 agent should indicate by some means that a character is not being
3180 displayed, displaying either a symbolic representation of the missing
3181 glyph (e.g. using a <a
3182 href="http://en.wikipedia.org/wiki/Last_resort_font">Last Resort
3183 Font</a>) or using the missing character glyph from a default font.
3184 </ol>
3186 <h3 id=cluster-matching><span class=secno>5.3 </span>Cluster matching</h3>
3188 <p>When text contains characters such as combining diacritics, ideally the
3189 base character should be rendered using the same font as the diacritic,
3190 this assures proper placement of the diacritic. For this reason, the font
3191 matching algorithm for clusters is more specialized than the general case
3192 of matching a single character by itself. For sequences containing
3193 variation selectors, which indicate the precise glyph to be used for a
3194 given character, user agents always attempt system font fallback to find
3195 the appropriate glyph before using the default glyph of the base
3196 character.
3198 <p>A font is considered to <em>support</em> a given character if (1) the
3199 character is contained in the font's <a
3200 href="#character-map"><em>character map</em></a> and (2) if required by
3201 the containing script, shaping information is available for that
3202 character. Some legacy fonts may include a given character in the <a
3203 href="#character-map"><em>character map</em></a> but lack the shaping
3204 information (e.g. <a
3205 href="http://www.microsoft.com/typography/otspec/ttochap1.htm">OpenType
3206 layout tables</a> or <a
3207 href="http://scripts.sil.org/cms/scripts/page.php?site_id=projects&item_id=graphite_techAbout">Graphite
3208 tables</a>) necessary for correctly rendering text runs containing that
3209 character.
3211 <p>A sequence of codepoints containing combining diacritics or other
3212 modifiers is termed a grapheme cluster (see <a href="#CSS3TEXT"
3213 rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a> for a more complete
3214 description). For a given cluster containing a base character, <em>b</em>
3215 and a sequence of combining characters <em>c1, c2…</em>, the entire
3216 cluster is matched using these steps:
3218 <ol>
3219 <li>For each family in the font list, a face is chosen using the style
3220 selection rules defined in the previous section.
3221 <ol>
3222 <li>If all characters in the sequence <em>b + c1 + c2 …</em> are
3223 completely supported by the font, select this font for the sequence.
3225 <li>If a sequence of multiple codepoints is canonically equivalent to a
3226 single character and the font supports that character, select this font
3227 for the sequence.
3228 </ol>
3230 <li>If no font was found in the font list in step 1:
3231 <ol>
3232 <li>If <em>c1</em> is a variation selector, system fallback must be used
3233 to find a font that supports the full sequence of <em>b + c1</em>. If
3234 no font on the system supports the full sequence, match the single
3235 character <em>b</em> using the normal procedure for matching single
3236 characters and ignore the variation selector. Note: a sequence with
3237 more than one variation selector is treated as an encoding error and
3238 the trailing selectors are ignored.
3240 <li>Otherwise, the user agent may optionally use system font fallback to
3241 match a font that supports the entire cluster.
3242 </ol>
3244 <li>If no font is found in step 2, use the matching sequence from step 1
3245 to determine the longest sequence that is completely matched by a font in
3246 the font list and attempt to match the remaining combining characters
3247 separately using the rules for single characters.
3248 </ol>
3250 <h3 id=char-handling-issues><span class=secno>5.4 </span>Character handling
3251 issues</h3>
3253 <p>The procedure above is always performed on text runs containing Unicode
3254 characters, documents using legacy encodings are assumed to have been
3255 transcoded before matching fonts. For fonts containing <a
3256 href="#character-map"><em title="character map">character maps</em></a>
3257 for both legacy encodings and Unicode, the contents of the legacy encoding
3258 <a href="#character-map"><em>character map</em></a> must have no effect on
3259 the results of the font matching process.
3261 <p>The font matching process does not assume that text runs are in either
3262 normalized or denormalized form (see <a href="#CHARMOD-NORM"
3263 rel=biblioentry>[CHARMOD-NORM]<!--{{CHARMOD-NORM}}--></a> for more
3264 details). Layout engines often convert base character plus combining
3265 character sequences into precomposed characters if they exist. The font
3266 matching algorithm outlined here supports both ways and fonts can
3267 generally support either but variations can occur. Authors should always
3268 tailor their choice of fonts to their content, including whether that
3269 content contains normalized or denormalized character streams.
3271 <p>If a given character is a Private-Use Area Unicode codepoint and none of
3272 the fonts in the fontlist contain a glyph for that codepoint, user agents
3273 must display some form of missing glyph symbol for that character rather
3274 than attempting system font fallback for that codepoint. When matching the
3275 replacement character U+FFFD, user agents may skip the font matching
3276 process and immediately display some form of missing glyph symbol, they
3277 are not required to display the glyph from the font that would be selected
3278 by the font matching process.
3280 <p>In general, the fonts for a given family will all have the same or
3281 similar <a href="#character-map"><em title="character map">character
3282 maps</em></a>. The process outlined here is designed to handle even font
3283 families containing faces with widely variant <a href="#character-map"><em
3284 title="character map">character maps</em></a>. However, authors are
3285 cautioned that the use of such families can lead to unexpected results.
3287 <p>Optimizations of this process are allowed provided that an
3288 implementation behaves as if the algorithm had been followed exactly.
3289 Matching occurs in a well-defined order to insure that the results are as
3290 consistent as possible across user agents, given an identical set of
3291 available fonts and rendering technology.
3293 <h3 id=font-matching-changes><span class=secno>5.5 </span>Font matching
3294 changes since CSS 2.1</h3>
3296 <p>The algorithm above is different from CSS 2.1 in a number of key places.
3297 These changes were made to better reflect actual font matching behavior
3298 across user agent implementations.
3300 <p>Differences compared to the font matching algorithm in CSS 2.1:
3302 <ul>
3303 <li>The algorithm includes font-stretch matching.
3305 <li>All possible font-style matching scenarios are delineated.
3307 <li>Small-caps fonts are not matched as part of the font matching process,
3308 they are now handled via font features.
3310 <li>Unicode variation selector matching is required.
3312 <li>Cluster sequences are matched as a unit.
3313 </ul>
3315 <h3 id=font-matching-examples><span class=secno>5.6 </span>Font matching
3316 examples</h3>
3318 <div class=example>
3319 <p>It's useful to note that the CSS selector syntax may be used to create
3320 language-sensitive typography. For example, some Chinese and Japanese
3321 characters are unified to have the same Unicode code point, although the
3322 abstract glyphs are not the same in the two languages.
3324 <pre>*:lang(ja-jp) { font: 900 14pt/16pt "Heisei Mincho W9", serif; }
3325 *:lang(zh-tw) { font: 800 14pt/16.5pt "Li Sung", serif; }
3326 </pre>
3328 <p>This selects any element that has the given language - Japanese or
3329 Traditional Chinese - and uses the appropriate font.
3330 </div>
3332 <h2 id=font-rend-props><span class=secno>6 </span>Font Feature Properties</h2>
3334 <p>Modern font technologies support a variety of advanced typographic and
3335 language-specific font features. Using these features, a single font can
3336 provide glyphs for a wide range of ligatures, contextual and stylistic
3337 alternates, tabular and old-style figures, small capitals, automatic
3338 fractions, swashes, and alternates specific to a given language. To allow
3339 authors control over these font capabilities, the font-variant property
3340 has been expanded for CSS3, it now functions as a shorthand for a set of
3341 properties that provide control over stylistic font features.
3343 <h3 id=glyph-selection-positioning><span class=secno>6.1 </span>Glyph
3344 selection and positioning</h3>
3346 <p>Simple fonts used for displaying Latin text use a very basic processing
3347 model, fonts contain a <a href="#character-map"><em>character map</em></a>
3348 which maps a given character to a glyph for that character. Glyphs for
3349 subsequent characters are simply placed next in line along a run of text.
3350 Font formats such as OpenType and AAT (Apple Advanced Typography) use a
3351 richer processing model, the glyph for a given character can be chosen and
3352 positioned not just based on a single character, but also based on
3353 surrounding characters along with the language, script, and features
3354 enabled for the text. Font features may be required for specific scripts,
3355 or recommended as enabled by default or they may be stylistic features
3356 meant to be used under author control.
3358 <p>For a good visual overview of these features, see the <a
3359 href="#OPENTYPE-FONT-GUIDE"
3360 rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
3361 For a detailed description of glyph processing for OpenType fonts, see <a
3362 href="#WINDOWS-GLYPH-PROC"
3363 rel=biblioentry>[WINDOWS-GLYPH-PROC]<!--{{WINDOWS-GLYPH-PROC}}--></a>.
3365 <p>Stylistic font features can be classified into two broad categories,
3366 ones that affect the harmonization of glyph shapes with the surrounding
3367 context, such as kerning and ligature features, and those such as the
3368 small-caps, subscript/superscript and alternate features that affect shape
3369 selection.
3371 <p>The subproperties of font-variant listed below are used to control these
3372 stylistic font features; they do not control features that are required
3373 for displaying certain scripts, such as the OpenType features used when
3374 displaying Arabic or Indic language text. They affect glyph selection and
3375 positioning, they do not affect font selection as described in the font
3376 matching section (except in cases required for compatibility with CSS
3377 2.1).
3379 <p>To assure consistent behavior across user agents, the equivalent
3380 OpenType property settings are listed for individual properties and must
3381 be considered normative. When using other font formats these should be
3382 used as a guideline to map CSS font feature property values to specific
3383 font features.
3385 <h3 id=language-specific-support><span class=secno>6.2
3386 </span>Language-specific display</h3>
3388 <p>OpenType also supports language-specific glyph selection and
3389 positioning, so that text can be displayed correctly in cases where the
3390 language dictates a specific display behavior. Languages often share a
3391 common script but the shape of certain letters may vary across those
3392 languages, such as the variations in certain Cyrillic letters used in
3393 Russian and Bulgarian text. In Latin text, it's common to render "fi" with
3394 an explicit fi-ligature that lacks a dot on the "i". However, in languages
3395 such as Turkish which uses both a dotted-i and a dotless-i, it's important
3396 to not use this ligature or use a specialized version that contains a dot
3397 over the "i". The example below shows language-specific variations based
3398 on stylistic traditions found in Spanish, Italian and French orthography:
3400 <div class=featex><img alt="language specific forms, spanish"
3401 src=locl-1.png></div>
3403 <div class=featex><img alt="language specific forms, italian"
3404 src=locl-2.png></div>
3406 <div class=featex><img alt="language specific forms, french"
3407 src=locl-3.png></div>
3409 <p>If the content language of the element is known, according to the rules
3410 of the <a
3411 href="http://www.w3.org/TR/CSS21/conform.html#doclanguage">document
3412 language</a>, user agents are required to infer the OpenType language
3413 system from the content language and use that when selecting and
3414 positioning glyphs using an OpenType font.
3416 <p>For OpenType fonts, in some cases it may be necessary to explicitly
3417 declare the OpenType language to be used, for example when displaying text
3418 in a given language that uses the typographic conventions of another
3419 language or when the font does not explicitly support a given language but
3420 supports a language that shares common typographic conventions. The ‘<a
3421 href="#propdef-font-language-override"><code
3422 class=property>font-language-override</code></a>’ property is used for
3423 this purpose.</p>
3424 <!-- prop: font-kerning -->
3426 <h3 id=font-kerning-prop><span class=secno>6.3 </span>Kerning: the <a
3427 href="#propdef-font-kerning">font-kerning</a> property</h3>
3429 <table class=propdef id=namefont-kerningvalueauto-normal-noneini>
3430 <tbody>
3431 <tr>
3432 <td>Name:
3434 <td><dfn id=propdef-font-kerning>font-kerning</dfn>
3436 <tr>
3437 <td>Value:
3439 <td>auto | normal | none
3441 <tr>
3442 <td>Initial:
3444 <td>auto
3446 <tr>
3447 <td>Applies to:
3449 <td>all elements
3451 <tr>
3452 <td>Inherited:
3454 <td>yes
3456 <tr>
3457 <td>Percentages:
3459 <td>N/A
3461 <tr>
3462 <td>Media:
3464 <td>visual
3466 <tr>
3467 <td>Computed value:
3469 <td>as specified
3471 <tr>
3472 <td>Animatable:
3474 <td>no
3475 </table>
3477 <p>Kerning is the contextual adjustment of inter-glyph spacing. This
3478 property controls metric kerning, kerning that utilizes adjustment data
3479 contained in the font.
3481 <dl>
3482 <dt>auto
3484 <dd>Specifies that kerning is applied at the discretion of the user agent
3486 <dt>normal
3488 <dd>Specifies that kerning is applied
3490 <dt>none
3492 <dd>Specifies that kerning is not applied
3493 </dl>
3495 <p>For fonts that do not include kerning data this property will have no
3496 visible effect. When rendering with OpenType fonts, the <a
3497 href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>
3498 specification suggests that kerning be enabled by default. When kerning is
3499 enabled, the OpenType <span class=tag>kern</span> feature is enabled (for
3500 vertical text runs the <span class=tag>vkrn</span> feature is enabled
3501 instead). User agents must also support fonts that only support kerning
3502 via data contained in a <span class=tag>kern</span> font table, as
3503 detailed in the OpenType specification. If the ‘<code
3504 class=property>letter-spacing</code>’ property is defined, kerning
3505 adjustments are considered part of the default spacing and letter spacing
3506 adjustments are made after kerning has been applied.
3508 <p>When set to ‘<code class=property>auto</code>’, user agents can
3509 determine whether to apply kerning or not based on a number of factors:
3510 text size, script, or other factors that influence text processing speed.
3511 Authors who want proper kerning should use ‘<a href="#normal2"><code
3512 class=property>normal</code></a>’ to explicitly enable kerning.
3513 Likewise, some authors may prefer to disable kerning in situations where
3514 performance is more important than precise appearance. However, in
3515 well-designed modern implementations the use of kerning generally does not
3516 have a large impact on text rendering speed.</p>
3517 <!-- prop: font-variant-ligatures -->
3519 <h3 id=font-variant-ligatures-prop><span class=secno>6.4 </span>Ligatures:
3520 the <a href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
3521 property</h3>
3523 <table class=propdef id=namefont-variant-ligaturesvaluenormal-no>
3524 <tbody>
3525 <tr>
3526 <td>Name:
3528 <td><dfn id=propdef-font-variant-ligatures>font-variant-ligatures</dfn>
3530 <tr>
3531 <td>Value:
3533 <td>normal | none | [ <a
3534 href="#common-lig-values"><var><common-lig-values></var></a> ||
3535 <a
3536 href="#discretionary-lig-values"><var><discretionary-lig-values></var></a>
3537 || <a
3538 href="#historical-lig-values"><var><historical-lig-values></var></a>
3539 || <a
3540 href="#contextual-alt-values"><var><contextual-alt-values></var></a>
3541 ]
3543 <tr>
3544 <td>Initial:
3546 <td>normal
3548 <tr>
3549 <td>Applies to:
3551 <td>all elements
3553 <tr>
3554 <td>Inherited:
3556 <td>yes
3558 <tr>
3559 <td>Percentages:
3561 <td>N/A
3563 <tr>
3564 <td>Media:
3566 <td>visual
3568 <tr>
3569 <td>Computed value:
3571 <td>as specified
3573 <tr>
3574 <td>Animatable:
3576 <td>no
3577 </table>
3579 <p>Ligatures and contextual forms are ways of combining glyphs to produce
3580 more harmonized forms.
3582 <pre
3583 class=prod><dfn id=common-lig-values><var><common-lig-values></var></dfn> = [ <a href="#common-ligatures">common-ligatures</a> | <a href="#no-common-ligatures">no-common-ligatures</a> ]</pre>
3585 <pre
3586 class=prod><dfn id=discretionary-lig-values><var><discretionary-lig-values></var></dfn> = [ <a href="#discretionary-ligatures">discretionary-ligatures</a> | <a href="#no-discretionary-ligatures">no-discretionary-ligatures</a> ]</pre>
3588 <pre
3589 class=prod><dfn id=historical-lig-values><var><historical-lig-values></var></dfn> = [ <a href="#historical-ligatures">historical-ligatures</a> | <a href="#no-historical-ligatures">no-historical-ligatures</a> ]</pre>
3591 <pre
3592 class=prod><dfn id=contextual-alt-values><var><contextual-alt-values></var></dfn> = [ <a href="#contextual">contextual</a> | <a href="#no-contextual">no-contextual</a> ]</pre>
3594 <p>Individual values have the following meanings:
3596 <dl>
3597 <dt><dfn id=font-variant-ligatures-normal-value
3598 title="font-variant-ligatures normal value">normal</dfn>
3600 <dd>A value of ‘<a href="#normal2"><code
3601 class=property>normal</code></a>’ specifies that common default
3602 features are enabled, <a href="#font-feature-resolution">as described in
3603 detail in the next section</a>. For OpenType fonts, common ligatures and
3604 contextual forms are on by default, discretionary and historical
3605 ligatures are not.
3607 <dt><dfn id=font-variant-ligatures-none-value>none</dfn>
3609 <dd>Specifies that all types of ligatures and contextual forms covered by
3610 this property are explicitly disabled. In situations where ligatures are
3611 not considered necessary, this may improve the speed of text rendering.
3613 <dt><dfn id=common-ligatures>common-ligatures</dfn>
3615 <dd>Enables display of common ligatures (OpenType features: <span
3616 class=tag>liga, clig</span>). For OpenType fonts, common ligatures are
3617 enabled by default.
3618 </dl>
3620 <div class=featex><img alt="common ligature example" src=liga.png></div>
3622 <dl>
3623 <dt><dfn id=no-common-ligatures>no-common-ligatures</dfn>
3625 <dd>Disables display of common ligatures (OpenType features: <span
3626 class=tag>liga, clig</span>).
3628 <dt><dfn id=discretionary-ligatures>discretionary-ligatures</dfn>
3630 <dd>Enables display of discretionary ligatures (OpenType feature: <span
3631 class=tag>dlig</span>). Which ligatures are discretionary, or optional,
3632 is decided by the type designer so authors will need to refer to the
3633 documentation of a given font to understand which ligatures are
3634 considered discretionary.
3635 </dl>
3637 <div class=featex><img alt="discretionary ligature example" src=dlig.png></div>
3639 <dl>
3640 <dt><dfn id=no-discretionary-ligatures>no-discretionary-ligatures</dfn>
3642 <dd>Disables display of discretionary ligatures (OpenType feature: <span
3643 class=tag>dlig</span>).
3645 <dt><dfn id=historical-ligatures>historical-ligatures</dfn>
3647 <dd>Enables display of historical ligatures (OpenType feature: <span
3648 class=tag>hlig</span>).
3649 </dl>
3651 <div class=featex><img alt="historical ligature example" src=hlig.png></div>
3653 <dl>
3654 <dt><dfn id=no-historical-ligatures>no-historical-ligatures</dfn>
3656 <dd>Disables display of historical ligatures (OpenType feature: <span
3657 class=tag>hlig</span>).
3659 <dt><dfn id=contextual>contextual</dfn>
3661 <dd>Enables display of contextual alternates (OpenType feature: <span
3662 class=tag>calt</span>). Although not strictly a ligature feature, like
3663 ligatures this feature is commonly used to harmonize the shapes of glyphs
3664 with the surrounding context. For OpenType fonts, this feature is on by
3665 default.
3666 </dl>
3668 <div class=featex><img alt="contextual alternate example" src=calt.png></div>
3670 <dl>
3671 <dt><dfn id=no-contextual>no-contextual</dfn>
3673 <dd>Disables display of contextual alternates (OpenType feature: <span
3674 class=tag>calt</span>).
3675 </dl>
3677 <p>Required ligatures, needed for correctly rendering complex scripts, are
3678 not affected by the settings above, including ‘<a
3679 href="#font-variant-ligatures-none-value"><code
3680 class=property>none</code></a>’ (OpenType feature: <span
3681 class=tag>rlig</span>).</p>
3682 <!-- prop: font-variant-position -->
3684 <h3 id=font-variant-position-prop><span class=secno>6.5 </span>Subscript
3685 and superscript forms: the <a
3686 href="#propdef-font-variant-position">font-variant-position</a> property</h3>
3688 <table class=propdef id=namefont-variant-positionvaluenormal-sub>
3689 <tbody>
3690 <tr>
3691 <td>Name:
3693 <td><dfn id=propdef-font-variant-position>font-variant-position</dfn>
3695 <tr>
3696 <td>Value:
3698 <td>normal | sub | super
3700 <tr>
3701 <td>Initial:
3703 <td>normal
3705 <tr>
3706 <td>Applies to:
3708 <td>all elements
3710 <tr>
3711 <td>Inherited:
3713 <td>yes
3715 <tr>
3716 <td>Percentages:
3718 <td>N/A
3720 <tr>
3721 <td>Media:
3723 <td>visual
3725 <tr>
3726 <td>Computed value:
3728 <td>as specified
3730 <tr>
3731 <td>Animatable:
3733 <td>no
3734 </table>
3736 <p>This property is used to enable typographic subscript and superscript
3737 glyphs. These are alternate glyphs designed within the same em-box as
3738 default glyphs and are intended to be laid out on the same baseline as the
3739 default glyphs, with no resizing or repositioning of the baseline. They
3740 are explicitly designed to match the surrounding text and to be more
3741 readable without affecting the line height.
3743 <div class=figure><img alt="comparison between real subscript glyphs and
3744 synthesized ones" src=realsubscripts.png>
3745 <p class=caption>Subscript glyphs (top) vs. typical synthesized subscripts
3746 (bottom)
3747 </div>
3749 <p>The values ‘<code class=property>sub</code>’ and ‘<code
3750 class=property>super</code>’ imply the appropriate variant glyph is
3751 displayed when available in the font (OpenType features: <span
3752 class=tag>subs, sups</span>). A value of ‘<a href="#normal2"><code
3753 class=property>normal</code></a>’ specifies neither of these alternate
3754 glyphs are substituted.
3756 <p>Because of the semantic nature of subscripts and superscripts, when the
3757 value is either ‘<code class=property>sub</code>’ or ‘<code
3758 class=property>super</code>’ for a given contiguous run of text, if a
3759 variant glyph is not available for all the characters in the run,
3760 simulated glyphs must be synthesized for all characters using reduced
3761 forms of the glyphs that would be used without this feature applied. This
3762 is done to avoid a mixture of variant glyphs and synthesized ones that
3763 would not align correctly.
3765 <p>In the case of OpenType fonts that lack subscript or superscript glyphs
3766 for a given character, user agents must use the appropriate subscript and
3767 superscript metrics specified in the selected font's <a
3768 href="http://www.microsoft.com/typography/otspec/os2.htm#subxs">OS/2
3769 table</a> <a href="#OPENTYPE"
3770 rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a> to calculate the size
3771 and offset of the synthesized substitutes.
3773 <p>In the past, user agents have used font-size and vertical-align to
3774 simulate subscripts and superscripts for the <span class=tag>sub</span>
3775 and <span class=tag>sup</span> elements. To allow a backwards compatible
3776 way of defining subscripts and superscripts, it is recommended that
3777 authors use conditional rules <a href="#CSS3-CONDITIONAL"
3778 rel=biblioentry>[CSS3-CONDITIONAL]<!--{{CSS3-CONDITIONAL}}--></a> so that
3779 older user agents will still render subscripts and superscripts via the
3780 older mechanism.
3782 <p>Authors should note that fonts typically only provide subscript and
3783 superscript glyphs for a subset of all characters supported by the font.
3784 While subscript and superscript glyphs are often available for Latin
3785 numbers, glyphs for punctuation and letter characters are less frequently
3786 provided. The synthetic fallback rules defined for this property assure
3787 that subscripts and superscripts will always appear but the appearance may
3788 not match author expectations if the font used does not provide the
3789 appropriate alternate glyph for all characters contained in a subscript or
3790 superscript.
3792 <div class=figure><img alt="alternate superscripts vs. glyphs synthesized
3793 using superscript metrics" src=superscript-alt-synth.png>
3794 <p class=caption>Superscript alternate glyph (left), synthesized
3795 superscript glyphs (middle), and incorrect mixture of the two (right)
3796 </div>
3798 <p>This property is not cumulative, applying it to subelements within a
3799 subscript or superscript won't nest the placement of a subscript or
3800 superscript glyph. Images contained within text runs where the value of
3801 this property is ‘<code class=property>sub</code>’ or ‘<code
3802 class=property>super</code>’ will be drawn just as they would if the
3803 value was ‘<a href="#normal2"><code class=property>normal</code></a>’.
3804 Likewise, text decorations such as underlines or emphasis marks will
3805 render in the same position as they would for the default glyphs, since
3806 this property does not affect the baseline position.
3808 <p>Because of these limitations, font-variant-position is not recommended
3809 for use in user agent stylesheets. Authors should use it in cases where
3810 subscripts or superscripts will only contain the narrow range of
3811 characters supported by the fonts specified.
3813 <div class=example>
3814 <p>A typical user agent default style for the <span class=tag>sub</span>
3815 element:</p>
3817 <pre>sub {
3818 vertical-align: sub;
3819 font-size: smaller;
3820 line-height: normal;
3821 }
3822 </pre>
3824 <p>Using font-variant-position to specify typographic subscripts in a way
3825 that will still show subscripts in older user agents:</p>
3827 <pre>@supports ( font-variant-position: sub ) {
3829 sub {
3830 vertical-align: inherit;
3831 font-size: 100%;
3832 line-height: inherit;
3833 font-variant-position: sub;
3834 }
3836 }
3837 </pre>
3839 <p>User agents that support the ‘<a
3840 href="#propdef-font-variant-position"><code
3841 class=property>font-variant-position</code></a>’ property will select a
3842 subscript variant glyph and render this without adjusting the baseline or
3843 font-size. Older user agents will ignore the ‘<a
3844 href="#propdef-font-variant-position"><code
3845 class=property>font-variant-position</code></a>’ property definition
3846 and use the standard defaults for subscripts.</p>
3847 </div>
3848 <!-- prop: font-variant-caps -->
3850 <h3 id=font-variant-caps-prop><span class=secno>6.6 </span>Capitalization:
3851 the <a href="#propdef-font-variant-caps">font-variant-caps</a> property</h3>
3853 <table class=propdef id=namefont-variant-capsvaluenormal-small-c>
3854 <tbody>
3855 <tr>
3856 <td>Name:
3858 <td><dfn id=propdef-font-variant-caps>font-variant-caps</dfn>
3860 <tr>
3861 <td>Value:
3863 <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
3864 | unicase | titling-caps
3866 <tr>
3867 <td>Initial:
3869 <td>normal
3871 <tr>
3872 <td>Applies to:
3874 <td>all elements
3876 <tr>
3877 <td>Inherited:
3879 <td>yes
3881 <tr>
3882 <td>Percentages:
3884 <td>N/A
3886 <tr>
3887 <td>Media:
3889 <td>visual
3891 <tr>
3892 <td>Computed value:
3894 <td>as specified
3896 <tr>
3897 <td>Animatable:
3899 <td>no
3900 </table>
3902 <p>Specifies control over capitalized forms.
3904 <p>Individual values have the following meanings:
3906 <dl>
3907 <dt><dfn id=normal>normal</dfn>
3909 <dd>None of the features listed below are enabled.
3911 <dt><dfn id=small-caps>small-caps</dfn>
3913 <dd>Enables display of small capitals (OpenType feature: <span
3914 class=tag>smcp</span>). Small-caps glyphs typically use the form of
3915 uppercase letters but are reduced to the size of lowercase letters.
3916 </dl>
3918 <div class=featex><img alt="small-caps example" src=smcp.png></div>
3920 <dl>
3921 <dt><dfn id=all-small-caps>all-small-caps</dfn>
3923 <dd>Enables display of small capitals for both upper and lowercase letters
3924 (OpenType features: <span class=tag>c2sc, smcp</span>).
3926 <dt><dfn id=petite-caps>petite-caps</dfn>
3928 <dd>Enables display of petite capitals (OpenType feature: <span
3929 class=tag>pcap</span>).
3931 <dt><dfn id=all-petite-caps>all-petite-caps</dfn>
3933 <dd>Enables display of petite capitals for both upper and lowercase
3934 letters (OpenType features: <span class=tag>c2pc, pcap</span>).
3936 <dt><dfn id=unicase>unicase</dfn>
3938 <dd>Enables display of mixture of small capitals for uppercase letters
3939 with normal lowercase letters (OpenType feature: <span
3940 class=tag>unic</span>).
3942 <dt><dfn id=titling-caps>titling-caps</dfn>
3944 <dd>Enables display of titling capitals (OpenType feature: <span
3945 class=tag>titl</span>). Uppercase letter glyphs are often designed for
3946 use with lowercase letters. When used in all uppercase titling sequences
3947 they can appear too strong. Titling capitals are designed specifically
3948 for this situation.
3949 </dl>
3951 <p>This property allows the selection of alternate glyphs used for small or
3952 petite capitals or for titling. These glyphs are specifically designed to
3953 blend well with the surrounding normal glyphs, to maintain the weight and
3954 readability which suffers when text is simply resized to fit this purpose.
3956 <p>The availability of these glyphs is based on whether a given feature is
3957 defined or not in the feature list of the font. User agents can optionally
3958 decide this on a per-script basis but should explicitly not decide this on
3959 a per-character basis.
3961 <p>Some fonts may only support a subset or none of the features described
3962 for this property. For backwards compatibility with CSS 2.1, if ‘<a
3963 href="#small-caps"><code class=property>small-caps</code></a>’ or ‘<a
3964 href="#all-small-caps"><code class=property>all-small-caps</code></a>’
3965 is specified but small-caps glyphs are not available for a given font,
3966 user agents should simulate a small-caps font, for example by taking a
3967 normal font and replacing the glyphs for lowercase letters with scaled
3968 versions of the glyphs for uppercase characters (replacing the glyphs for
3969 both upper and lowercase letters in the case of ‘<a
3970 href="#all-small-caps"><code class=property>all-small-caps</code></a>’).
3972 <div class=figure style="padding: 0; margin: auto;"><img alt="synthetic vs.
3973 real small-caps" class=hires src=synthetic-vs-real-small-caps.png
3974 width=512px>
3975 <p class=caption>Synthetic vs. real small-caps
3976 </div>
3978 <p>To match the surrounding text, a font may provide alternate glyphs for
3979 caseless characters when these features are enabled but when a user agent
3980 simulates small capitals, it must not attempt to simulate alternates for
3981 codepoints which are considered caseless.
3983 <div class=figure style="padding: 0; margin: auto;"><img alt="caseless
3984 characters with small-caps, all-small-caps enabled" class=hires
3985 src=small-capitals-variations.png width=418px>
3986 <p class=caption>Caseless characters with small-caps, all-small-caps
3987 enabled
3988 </div>
3990 <p>If either ‘<a href="#petite-caps"><code
3991 class=property>petite-caps</code></a>’ or ‘<a
3992 href="#all-petite-caps"><code class=property>all-petite-caps</code></a>’
3993 is specified for a font that doesn't support these features, the property
3994 behaves as if ‘<a href="#small-caps"><code
3995 class=property>small-caps</code></a>’ or ‘<a
3996 href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
3997 respectively, had been specified. If ‘<a href="#unicase"><code
3998 class=property>unicase</code></a>’ is specified for a font that doesn't
3999 support that feature, the property behaves as if ‘<a
4000 href="#small-caps"><code class=property>small-caps</code></a>’ was
4001 applied only to lowercased uppercase letters. If ‘<a
4002 href="#titling-caps"><code class=property>titling-caps</code></a>’ is
4003 specified with a font that does not support this feature, this property
4004 has no visible effect. When simulated small capital glyphs are used, for
4005 scripts that lack uppercase and lowercase letters, ‘<a
4006 href="#small-caps"><code class=property>small-caps</code></a>’, ‘<a
4007 href="#all-small-caps"><code class=property>all-small-caps</code></a>’,
4008 ‘<a href="#petite-caps"><code class=property>petite-caps</code></a>’,
4009 ‘<a href="#all-petite-caps"><code
4010 class=property>all-petite-caps</code></a>’ and ‘<a
4011 href="#unicase"><code class=property>unicase</code></a>’ have no visible
4012 effect.
4014 <p>When casing transforms are used to simulate small capitals, the casing
4015 transformations should match those used for the <span
4016 class=property>‘<code class=property>text-transform</code>’</span>
4017 property.
4019 <p>As a last resort, unscaled uppercase letter glyphs in a normal font may
4020 replace glyphs in a small-caps font so that the text appears in all
4021 uppercase letters.
4023 <div class=figure style="padding: 0; margin: auto;"><img alt="using
4024 all-small-caps in acronym-laden text" class=hires
4025 src=acronym-laden-text.png width=596px>
4026 <p class=caption>Using small capitals to improve readability in
4027 acronym-laden text
4028 </div>
4030 <div class=example>
4031 <p>Quotes rendered italicised, with small-caps on the first line:</p>
4033 <pre>blockquote { font-style: italic; }
4034 blockquote:first-line { font-variant: small-caps; }
4036 <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></blockquote>
4037 </pre>
4038 </div>
4039 <!-- prop: font-variant-numeric -->
4041 <h3 id=font-variant-numeric-prop><span class=secno>6.7 </span>Numerical
4042 formatting: the <a
4043 href="#propdef-font-variant-numeric">font-variant-numeric</a> property</h3>
4045 <table class=propdef id=namefont-variant-numericvaluenormal-ltnu>
4046 <tbody>
4047 <tr>
4048 <td>Name:
4050 <td><dfn id=propdef-font-variant-numeric>font-variant-numeric</dfn>
4052 <tr>
4053 <td>Value:
4055 <td>normal | [ <a
4056 href="#numeric-figure-values"><var><numeric-figure-values></var></a>
4057 || <a
4058 href="#numeric-spacing-values"><var><numeric-spacing-values></var></a>
4059 || <a
4060 href="#numeric-fraction-values"><var><numeric-fraction-values></var></a>
4061 || <a href="#ordinal">ordinal</a> || <a
4062 href="#slashed-zero">slashed-zero</a> ]
4064 <tr>
4065 <td>Initial:
4067 <td>normal
4069 <tr>
4070 <td>Applies to:
4072 <td>all elements
4074 <tr>
4075 <td>Inherited:
4077 <td>yes
4079 <tr>
4080 <td>Percentages:
4082 <td>N/A
4084 <tr>
4085 <td>Media:
4087 <td>visual
4089 <tr>
4090 <td>Computed value:
4092 <td>as specified
4094 <tr>
4095 <td>Animatable:
4097 <td>no
4098 </table>
4100 <p>Specifies control over numerical forms.
4102 <pre
4103 class=prod><dfn id=numeric-figure-values><var><numeric-figure-values></var></dfn> = [ <a href="#lining-nums">lining-nums</a> | <a href="#oldstyle-nums">oldstyle-nums</a> ]</pre>
4105 <pre
4106 class=prod><dfn id=numeric-spacing-values><var><numeric-spacing-values></var></dfn> = [ <a href="#proportional-nums">proportional-nums</a> | <a href="#tabular-nums">tabular-nums</a> ]</pre>
4108 <pre
4109 class=prod><dfn id=numeric-fraction-values><var><numeric-fraction-values></var></dfn> = [ <a href="#diagonal-fractions">diagonal-fractions</a> | <a href="#stacked-fractions">stacked-fractions</a> ]</pre>
4111 <p>Individual values have the following meanings:
4113 <dl>
4114 <dt><dfn id=normal0>normal</dfn>
4116 <dd>None of the features listed below are enabled.
4118 <dt><dfn id=lining-nums>lining-nums</dfn>
4120 <dd>Enables display of lining numerals (OpenType feature: <span
4121 class=tag>lnum</span>).
4123 <dt><dfn id=oldstyle-nums>oldstyle-nums</dfn>
4125 <dd>Enables display of old-style numerals (OpenType feature: <span
4126 class=tag>onum</span>).
4128 <dt><dfn id=proportional-nums>proportional-nums</dfn>
4130 <dd>Enables display of proportional numerals (OpenType feature: <span
4131 class=tag>pnum</span>).
4133 <dt><dfn id=tabular-nums>tabular-nums</dfn>
4135 <dd>Enables display of tabular numerals (OpenType feature: <span
4136 class=tag>tnum</span>).
4137 </dl>
4139 <p>The example below shows how these different properties can be combined
4140 to influence the rendering of tabular data with fonts that support these
4141 features. Within normal paragraph text, proportional numbers are used
4142 while tabular numbers are used so that columns of numbers line up
4143 properly:
4145 <div class=figure style="padding: 0; margin: auto;"><img alt="combining
4146 number styles" src=numberstyles.png>
4147 <p class=caption>Using number styles
4148 </div>
4150 <dl>
4151 <dt><dfn id=diagonal-fractions>diagonal-fractions</dfn>
4153 <dd>Enables display of lining diagonal fractions (OpenType feature: <span
4154 class=tag>frac</span>).
4155 </dl>
4157 <div class=featex><img alt="diagonal fraction example" src=frac.png></div>
4159 <dl>
4160 <dt><dfn id=stacked-fractions>stacked-fractions</dfn>
4162 <dd>Enables display of lining stacked fractions (OpenType feature: <span
4163 class=tag>afrc</span>).
4164 </dl>
4166 <div class=featex><img alt="stacked fraction example" src=afrc.png></div>
4168 <dl>
4169 <dt><dfn id=ordinal>ordinal</dfn>
4171 <dd>Enables display of forms used with ordinal numbers (OpenType feature:
4172 <span class=tag>ordn</span>).
4174 <dt><dfn id=slashed-zero>slashed-zero</dfn>
4176 <dd>Enables display of slashed zeros (OpenType feature: <span
4177 class=tag>zero</span>).
4178 </dl>
4180 <div class=featex><img alt="slashed zero example" src=zero.png></div>
4182 <div class=example id=steak-marinade>
4183 <p>A simple flank steak marinade recipe, rendered with automatic fractions
4184 and old-style numerals:</p>
4186 <pre>.amount { font-variant-numeric: oldstyle-nums diagonal-fractions; }
4188 <h4>Steak marinade:</h4>
4189 <ul>
4190 <li><span class="amount">2</span> tbsp olive oil</li>
4191 <li><span class="amount">1</span> tbsp lemon juice</li>
4192 <li><span class="amount">1</span> tbsp soy sauce</li>
4193 <li><span class="amount">1 1/2</span> tbsp dry minced onion</li>
4194 <li><span class="amount">2 1/2</span> tsp italian seasoning</li>
4195 <li>Salt &amp; pepper</li>
4196 </ul>
4198 <p>Mix the meat with the marinade and let it sit covered in the refrigerator
4199 for a few hours or overnight.</p>
4200 </pre>
4201 </div>
4202 <!-- prop: font-variant-alternates -->
4204 <h3 id=font-variant-alternates-prop><span class=secno>6.8 </span>Alternates
4205 and swashes: the <a
4206 href="#propdef-font-variant-alternates">font-variant-alternates</a>
4207 property</h3>
4209 <table class=propdef id=namefont-variant-alternatesvaluenormal-s>
4210 <tbody>
4211 <tr>
4212 <td>Name:
4214 <td><dfn
4215 id=propdef-font-variant-alternates>font-variant-alternates</dfn>
4217 <tr>
4218 <td>Value:
4220 <td>normal | [ <a href="#stylistic"
4221 title=stylistic>stylistic(<feature-value-name>)</a> || <a
4222 href="#historical-forms">historical-forms</a> || <a href="#styleset"
4223 title=styleset>styleset(<feature-value-name> #)</a> || <a
4224 href="#character-variant"
4225 title=character-variant>character-variant(<feature-value-name>
4226 #)</a> || <a href="#swash"
4227 title=swash>swash(<feature-value-name>)</a> || <a
4228 href="#ornaments"
4229 title=ornaments>ornaments(<feature-value-name>)</a> || <a
4230 href="#annotation"
4231 title=annotation>annotation(<feature-value-name>)</a> ]
4233 <tr>
4234 <td>Initial:
4236 <td>normal
4238 <tr>
4239 <td>Applies to:
4241 <td>all elements
4243 <tr>
4244 <td>Inherited:
4246 <td>yes
4248 <tr>
4249 <td>Percentages:
4251 <td>N/A
4253 <tr>
4254 <td>Media:
4256 <td>visual
4258 <tr>
4259 <td>Computed value:
4261 <td>as specified
4263 <tr>
4264 <td>Animatable:
4266 <td>no
4267 </table>
4269 <p>For any given character, fonts can provide a variety of alternate glyphs
4270 in addition to the default glyph for that character. This property
4271 provides control over the selection of these alternate glyphs.
4273 <p>In cases where multiple alternates are possible, authors define a
4274 <code><feature-value-name></code> using the
4275 <code>@font-feature-values</code> rule described below to indicate the
4276 specific alternate to be used. The nature of these alternates is font
4277 specific, so the rule defines values for a specific font family or set of
4278 families. When a particular value has not been defined for a given family,
4279 the named value is treated as if the feature had omitted from the style
4280 rule. If a given value is outside the range supported by a given font, the
4281 value is ignored. These values never apply to generic font families, nor
4282 to families selected as part of system font fallback. Values that behave
4283 this way are marked as <em>font specific</em>.
4285 <p>Individual values have the following meanings:
4287 <dl>
4288 <dt><dfn id=normal1>normal</dfn>
4290 <dd>None of the features listed below are enabled.
4292 <dt><dfn id=stylistic
4293 title=stylistic>stylistic(<feature-value-name>)</dfn>
4295 <dd>Enables display of stylistic alternates (<em>font specific</em>,
4296 OpenType feature: <span class=tag>salt
4297 <feature-value-name></span>).
4298 </dl>
4300 <div class=featex><img alt="stylistic alternate example" src=salt.png></div>
4302 <dl>
4303 <dt><dfn id=historical-forms>historical-forms</dfn>
4305 <dd>Enables display of historical forms (OpenType feature: <span
4306 class=tag>hist</span>).
4307 </dl>
4309 <div class=featex><img alt="historical form example" src=hist.png></div>
4311 <dl>
4312 <dt><dfn id=styleset title=styleset>styleset(<feature-value-name>
4313 #)</dfn>
4315 <dd>Enables display with stylistic sets (<em>font specific</em>, OpenType
4316 feature: <span class=tag>ss<feature-index></span> OpenType
4317 currently defines <span class=tag>ss01</span> through <span
4318 class=tag>ss20</span>).
4319 </dl>
4321 <div class=featex><img alt="styleset example" src=ssnn.png></div>
4323 <dl>
4324 <dt><dfn id=character-variant
4325 title=character-variant>character-variant(<feature-value-name>
4326 #)</dfn>
4328 <dd>Enables display of specific character variants (<em>font
4329 specific</em>, OpenType feature: <span
4330 class=tag>cv<feature-index></span> OpenType currently defines <span
4331 class=tag>cv01</span> through <span class=tag>cv99</span>).
4333 <dt><dfn id=swash title=swash>swash(<feature-value-name>)</dfn>
4335 <dd>Enables display of swash glyphs (<em>font specific</em>, OpenType
4336 feature: <span class=tag>swsh <feature-index>, cswh
4337 <feature-index></span>).
4338 </dl>
4340 <div class=featex><img alt="swash example" src=swsh.png></div>
4342 <dl>
4343 <dt><dfn id=ornaments
4344 title=ornaments>ornaments(<feature-value-name>)</dfn>
4346 <dd>Enables replacement of default glyphs with ornaments, if provided in
4347 the font (<em>font specific</em>, OpenType feature: <span class=tag>ornm
4348 <feature-index></span>). Some fonts may offer ornament glyphs as
4349 alternates for a wide collection of characters; however, displaying
4350 arbitrary characters (e.g., alphanumerics) as ornaments is poor practice
4351 as it distorts the semantics of the data. Font designers are encouraged
4352 to encode all ornaments (except those explicitly encoded in the Unicode
4353 Dingbats blocks, etc.) as alternates for the bullet character (U+2022) to
4354 allow authors to select the desired glyph using
4355 <feature-value-name>.
4356 </dl>
4358 <div class=featex><img alt="ornaments example" src=ornm.png></div>
4360 <dl>
4361 <dt><dfn id=annotation
4362 title=annotation>annotation(<feature-value-name>)</dfn>
4364 <dd>Enables display of alternate annotation forms (<em>font specific</em>,
4365 OpenType feature: <span class=tag>nalt <feature-index></span>).
4366 </dl>
4368 <div class=featex><img alt="alternate annotation form example"
4369 src=nalt.png></div>
4371 <h3 id=font-feature-values><span class=secno>6.9 </span>Defining font
4372 specific alternates: the <code>@font-feature-values</code> rule</h3>
4374 <p>Several of the possible values of ‘<a
4375 href="#propdef-font-variant-alternates"><code
4376 class=property>font-variant-alternates</code></a>’ listed above are
4377 labeled as "font specific". For these features fonts may define not just a
4378 single glyph but a set of alternate glyphs with an index to select a given
4379 alternate. Since these are font family specific, the
4380 <code>@font-feature-values</code> rule is used to define named-values for
4381 these indices for a given family.
4383 <p>In the case of the swash Q in the example shown above, the swash could
4384 be specified using these style rules:
4386 <pre>
4388 @font-feature-values Jupiter Sans {
4389 @swash {
4390 delicate: 1;
4391 flowing: 2;
4392 }
4393 }
4395 h2 { font-family: Jupiter Sans, sans-serif; }
4397 /* show the second swash variant in h2 headings */
4398 h2:first-letter { font-variant-alternates: swash(flowing); }
4400 <h2>Quick</h2></pre>
4402 <p>When Jupiter Sans is present, the second alternate swash alternate will
4403 be displayed. When not present, no swash character will be shown, since
4404 the specific named-value "flowing" is only defined for the Jupiter Sans
4405 family. The @-mark indicates the name of the property value for which a
4406 named-value can be used. The name "flowing" is chosen by the author, the
4407 values specified within a given font's data.
4409 <p>In terms of the grammar, this specification defines the following
4410 productions:</p>
4411 <!--
4412 <pre><dfn>supports_rule</dfn>
4413 : <i>SUPPORTS_SYM</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>supports_condition</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>group_rule_body</i>
4414 ;
4416 <dfn>supports_condition</dfn>
4417 : <i>supports_negation</i> | <i>supports_conjunction</i> | <i>supports_disjunction</i> |
4418 <i>supports_condition_in_parens</i>
4419 ;
4421 <dfn>supports_condition_in_parens</dfn>
4422 : ( '(' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>supports_condition</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ')' ) | <i>supports_declaration_condition</i> |
4423 <i>general_enclosed</i>
4424 ;
4426 <dfn>supports_negation</dfn>
4427 : <a href="http://www.w3.org/TR/css3-mediaqueries/#syntax"><i>NOT</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i>
4428 ;
4430 <dfn>supports_conjunction</dfn>
4431 : <i>supports_condition_in_parens</i> ( <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <a href="http://www.w3.org/TR/css3-mediaqueries/#syntax"><i>AND</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i> )+
4432 ;
4434 <dfn>supports_disjunction</dfn>
4435 : <i>supports_condition_in_parens</i> ( <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>OR</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i> )+
4436 ;
4438 <dfn>supports_declaration_condition</dfn>
4439 : '(' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>declaration</i></a> ')'
4440 ;
4442 <dfn>general_enclosed</dfn>
4443 : ( <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>FUNCTION</i></a> | '(' ) ( <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>any</i></a> | <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>unused</i></a> )* ')'
4444 ;
4445 </pre>
4447 -->
4449 <pre><dfn id=fontfeaturevaluesrule>font_feature_values_rule</dfn>
4450 : <a href="#fontfeaturevaluessym"><i>FONT_FEATURE_VALUES_SYM</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#fontfamilynamelist"><i>font_family_name_list</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
4451 '{' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevalueblock"><i>feature_value_block</i></a>? [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevalueblock"><i>feature_value_block</i></a>? ]* '}' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
4452 ;
4454 <dfn id=fontfamilynamelist>font_family_name_list</dfn>
4455 : <a href="#fontfamilyname"><i>font_family_name</i></a> [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ',' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#fontfamilyname"><i>font_family_name</i></a> ]*
4456 ;
4458 <dfn id=fontfamilyname>font_family_name</dfn>
4459 : <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>STRING</i></a> | [ <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>IDENT</i></a> [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>IDENT</i></a> ]* ]
4460 ;
4462 <dfn id=featurevalueblock>feature_value_block</dfn>
4463 : <a href="#featuretype"><i>feature_type</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
4464 '{' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevaluedefinition"><i>feature_value_definition</i></a>? [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ';' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#featurevaluedefinition"><i>feature_value_definition</i></a>? ]* '}' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
4465 ;
4467 <dfn id=featuretype>feature_type</dfn>:
4468 <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>ATKEYWORD</i></a>
4469 ;
4471 <dfn id=featurevaluedefinition>feature_value_definition</dfn>
4472 : <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>IDENT</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ':' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>NUMBER</i></a> [ <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>NUMBER</i></a> ]*
4473 ;
4474 </pre>
4476 <p>The following new token is introduced:
4478 <pre>@{F}{O}{N}{T}{-}{F}{E}{A}{T}{U}{R}{E}{-}{V}{A}{L}{U}{E}{S} {return <dfn id=fontfeaturevaluessym>FONT_FEATURE_VALUES_SYM</dfn>;}
4479 </pre>
4481 <p>Feature value blocks are treated <a
4482 href="http://www.w3.org/TR/CSS2/syndata.html#at-rules">similar to
4483 at-rules</a>, they consist of everything up to the next block or
4484 semi-colon, whichever comes first.
4486 <p>Font feature values rules define a set of values for a specific font
4487 feature as used for a given set of families. Effectively, they define a
4488 mapping of ⟨family, feature, ident⟩ → ⟨values⟩ where
4489 ⟨values⟩ are the indices used for specific features defined for a
4490 given font.
4492 <p>The font family list uses the same syntax as that used for the ‘<a
4493 href="#descdef-font-family"><code class=property>font-family</code></a>’
4494 property. Within feature value blocks, the feature type is ‘<code
4495 class=css>@</code>’ followed by the name of the font-specific property
4496 value (e.g. <a href="#swash"><code>@swash</code></a>). The feature type
4497 must match, using an ASCII case-insensitive comparison, one of the
4498 <em>font specific</em> values of the <a
4499 href="#propdef-font-variant-alternates"><code>font-variant-alternates</code></a>
4500 property. The values associated with a given idenitifier are limited to
4501 integer values 0 or greater.
4503 <p>If syntax errors occur within the font family list, the entire rule must
4504 be ignored. When syntax errors occur within a feature value definition,
4505 such as invalid identifiers or values, the entire feature value definition
4506 must be omitted, similar to the way syntax errors in style declarations
4507 are handled. When the <code><feature-type></code> is invalid, the
4508 entire associated feature value block must be ignored.
4510 <pre>@font-feature-values Bongo {
4511 @swash { ornate: 1; }
4512 annotation { boxed: 4; } /* should be @annotation! */
4513 @swash { double-loops: 1; flowing: -1; } /* negative value */
4514 @ornaments ; /* incomplete definition */
4515 @styleset { double-W: 14; sharp-terminals: 16 1 } /* missing ; */
4516 <a href="http://www.angryalien.com/0504/shiningbunnies.html" style="text-decoration: none;">redrum</a> /* random editing mistake */
4517 }</pre>
4519 <p>The example above is equivalent to:
4521 <pre>@font-feature-values Bongo {
4522 @swash { ornate: 1; }
4523 @swash { double-loops: 1; }
4524 @styleset { double-W: 14; sharp-terminals: 16 1; }
4525 }</pre>
4527 <p>If multiple <code>@font-feature-values</code> rules are defined for a
4528 given family, the resulting values defined are the union of these rules.
4529 This allows a set of named-values to be defined for a given font family
4530 globally for a site and specific additions made per-page. If the same
4531 <feature-value-name> is defined mulitple times for a given
4532 font-variant value, the last defined value is used.
4534 <pre>
4535 site.css:
4537 @font-feature-values Mercury Serif {
4538 @styleset {
4539 stacked-g: 3; /* "two-storey" versions of g, a */
4540 stacked-a: 4;
4541 }
4542 }
4544 page.css:
4546 @font-feature-values Mercury Serif {
4547 @styleset {
4548 geometric-m: 7; /* alternate version of m */
4549 }
4550 }
4552 body {
4553 font-family: Mercury Serif, serif;
4555 /* enable both the use of stacked g and alternate m */
4556 font-variant-alternates: styleset(stacked-g, geometric-m);
4557 }</pre>
4559 <p>Only named font families are allowed for <font-family>, rules that
4560 include generic or system fonts in the list of font families are
4561 considered syntax errors and the contents of the rules are ignored.
4562 However, if a user agent defines a generic font to be a specific named
4563 font (e.g. Helvetica), the settings associated with that family name will
4564 be used.
4566 <p>For <font-variant-property-value>, only font specific property value
4567 names supported by the ‘<a href="#propdef-font-variant"><code
4568 class=property>font-variant</code></a>’ property are recognized,
4569 definitions for other value names cause a syntax error and are ignored.
4570 Each property value that is font specific is clearly marked as such.
4571 Feature value names follow the rules of CSS user identifiers and are
4572 case-sensitive. They are unique only for a given set of font families and
4573 font-variant property value; the same identifier used with a different
4574 font-variant property value is treated as a separate and distinct value.
4576 <p>Using a commonly named value allows authors to use a single style rule
4577 to cover a set of fonts for which the underlying selector is different for
4578 each font. If either font in the example below is found, a circled number
4579 glyph will be used:
4581 <pre>@font-feature-values Taisho Gothic {
4582 @annotation { boxed: 1; circled: 4; }
4583 }
4585 @font-feature-values Otaru Kisa {
4586 @annotation { circled: 1; black-boxed: 3; }
4587 }
4589 h3.title {
4590 /* circled form defined for both fonts */
4591 font-family: Taisho Gothic, Otaru Kisa;
4592 font-variant: annotation(circled);
4593 }</pre>
4595 <p>Most font specific font-variant property values take a single value
4596 (e.g. swash). The character-variant property value allows two values and
4597 styleset allows an unlimited number. If a larger number of values are
4598 assigned to a given name, a syntax error occurs and the entire
4599 <font-feature-values-declaration> is ignored.
4601 <p>For the styleset property value, multiple values indicate the style sets
4602 to be enabled. Values between 1 and 99 enable OpenType features <span
4603 class=tag>ss01</span> through <span class=tag>ss99</span>. However, the
4604 OpenType standard only officially defines <span class=tag>ss01</span>
4605 through <span class=tag>ss20</span>. Values greater than 99 or equal to 0
4606 are ignored but do not generate a syntax error when parsed.
4608 <pre>@font-feature-values Mars Serif {
4609 @styleset {
4610 alt-g: 1; /* implies ss01 = 1 */
4611 curly-quotes: 3; /* implies ss03 = 1 */
4612 code: 4 5; /* implies ss04 = 1, ss05 = 1 */
4613 }
4615 @styleset {
4616 dumb: 125; /* >99, ignored */
4617 }
4619 @swash {
4620 swishy: 3 5; /* more than 1 value for swash, syntax error */
4621 }
4622 }
4624 p.codeblock {
4625 /* implies ss03 = 1, ss04 = 1, ss05 = 1 */
4626 font-variant-alternates: styleset(curly-quotes, code);
4627 }</pre>
4629 <p>For character-variant, a single value between 1 and 99 indicates the
4630 enabling of OpenType feature <span class=tag>cv01</span> through <span
4631 class=tag>cv99</span>. For OpenType fonts, values greater than 99 or equal
4632 to 0 are ignored but do not generate a syntax error when parsed. When two
4633 values are listed, the first value indicates the feature used and the
4634 second the value passed for that feature. When two value names imply
4635 different settings for the same underlying feature the last setting is
4636 used.
4638 <pre>@font-feature-values MM Greek {
4639 @character-variant { alpha-2: 1 2; } /* implies cv01 = 2 */
4640 @character-variant { beta-3: 2 3; } /* implies cv02 = 3 */
4641 @character-variant { epsilon: 5 3 6; } /* more than 2 values, syntax error, ignored */
4642 @character-variant { gamma: 12; } /* implies cv12 = 1 */
4643 @character-variant { zeta: 20 3; } /* implies cv20 = 3 */
4644 @character-variant { zeta-2: 20 2; } /* implies cv20 = 2 */
4645 @character-variant { silly: 105; } /* >99, ignored */
4646 @character-variant { dumb: 323 3; } /* >99, ignored */
4647 }
4649 #title {
4650 /* use the third alternate beta, first alternate gamma */
4651 font-variant-alternates: character-variant(beta-3, gamma);
4652 }
4654 p {
4655 /* zeta-2 follows zeta, implies cv20 = 2 */
4656 font-variant-alternates: character-variant(zeta, zeta-2);
4657 }
4659 .special {
4660 /* zeta follows zeta-2, implies cv20 = 3 */
4661 font-variant-alternates: character-variant(zeta-2, zeta);
4662 }</pre>
4664 <p>See the <a href="#om-fontfeaturevalues">object model reference
4665 section</a> for a description of the interfaces used to modify these rules
4666 via the CSS Object Model.
4668 <div class=figure><img alt="Matching text on Byzantine seals using
4669 character variants" src=byzantineseal.png>
4670 <p class=caption>Byzantine seal text displayed with character variants
4671 </div>
4673 <div class=example>
4674 <p>In the figure above, the text in red is rendered using a font
4675 containing character variants that mimic the character forms found on a
4676 Byzantine seal from the 8th century A.D. Two lines below is the same text
4677 displayed in a font without variants. Note the two variants for U and N
4678 used on the seal.</p>
4680 <pre>@font-feature-values Athena Ruby {
4681 @character-variant {
4682 leo-B: 2 1;
4683 leo-M: 13 3;
4684 leo-alt-N: 14 1;
4685 leo-N: 14 2;
4686 leo-T: 20 1;
4687 leo-U: 21 2;
4688 leo-alt-U: 21 4;
4689 }
4690 }
4692 p {
4693 font-variant: discretionary-ligatures,
4694 character-variant(leo-B, leo-M, leo-N, leo-T, leo-U);
4695 }
4697 span.alt-N {
4698 font-variant-alternates: character-variant(leo-alt-N);
4699 }
4701 span.alt-U {
4702 font-variant-alternates: character-variant(leo-alt-U);
4703 }
4705 <p>ENO....UP͞RSTU<span class="alt-U">U</span>͞<span class="alt-U">U</span>ΚΑΙTỤẠG̣IUPNS</p>
4707 <p>LEON|ΚΑΙCONSTA|NTI<span class="alt-N">N</span>OS..|STOIBAṢ.|LIṢROM|AIO<span class="alt-N">N</span></p>
4708 </pre>
4709 </div>
4711 <h3 id=font-variant-east-asian-prop><span class=secno>6.10 </span>East
4712 Asian text rendering: the <a
4713 href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
4714 property</h3>
4716 <table class=propdef id=namefont-variant-east-asianvaluenormal-l>
4717 <tbody>
4718 <tr>
4719 <td>Name:
4721 <td><dfn
4722 id=propdef-font-variant-east-asian>font-variant-east-asian</dfn>
4724 <tr>
4725 <td>Value:
4727 <td>normal | [ <a
4728 href="#east-asian-variant-values"><var><east-asian-variant-values></var></a>
4729 || <a
4730 href="#east-asian-width-values"><var><east-asian-width-values></var></a>
4731 || <a href="#ruby">ruby</a> ]
4733 <tr>
4734 <td>Initial:
4736 <td>normal
4738 <tr>
4739 <td>Applies to:
4741 <td>all elements
4743 <tr>
4744 <td>Inherited:
4746 <td>yes
4748 <tr>
4749 <td>Percentages:
4751 <td>N/A
4753 <tr>
4754 <td>Media:
4756 <td>visual
4758 <tr>
4759 <td>Computed value:
4761 <td>as specified
4763 <tr>
4764 <td>Animatable:
4766 <td>no
4767 </table>
4769 <p>Allows control of glyph substitution and sizing in East Asian text.
4771 <pre
4772 class=prod><dfn id=east-asian-variant-values><var><east-asian-variant-values></var></dfn> = [ <a href="#jis78">jis78</a> | <a href="#jis83">jis83</a> | <a href="#jis90">jis90</a> | <a href="#jis04">jis04</a> | <a href="#simplified">simplified</a> | <a href="#traditional">traditional</a> ]</pre>
4774 <pre
4775 class=prod><dfn id=east-asian-width-values><var><east-asian-width-values></var></dfn> = [ <a href="#full-width">full-width</a> | <a href="#proportional-width">proportional-width</a> ]</pre>
4777 <p>Individual values have the following meanings:
4779 <dl>
4780 <dt><dfn id=normal2>normal</dfn>
4782 <dd>None of the features listed below are enabled.
4784 <dt><dfn id=jis78>jis78</dfn>
4786 <dd>Enables rendering of JIS78 forms (OpenType feature: <span
4787 class=tag>jp78</span>).
4788 </dl>
4790 <div class=featex><img alt="JIS78 form example" src=jp78.png></div>
4792 <dl>
4793 <dt><dfn id=jis83>jis83</dfn>
4795 <dd>Enables rendering of JIS83 forms (OpenType feature: <span
4796 class=tag>jp83</span>).
4798 <dt><dfn id=jis90>jis90</dfn>
4800 <dd>Enables rendering of JIS90 forms (OpenType feature: <span
4801 class=tag>jp90</span>).
4803 <dt><dfn id=jis04>jis04</dfn>
4805 <dd>Enables rendering of JIS2004 forms (OpenType feature: <span
4806 class=tag>jp04</span>).
4807 <p>The various JIS variants reflect the glyph forms defined in different
4808 Japanese national standards. Fonts generally include glyphs defined by
4809 the most recent national standard but it's sometimes necessary to use
4810 older variants, to match signage for example.</p>
4812 <dt><dfn id=simplified>simplified</dfn>
4814 <dd>Enables rendering of simplified forms (OpenType feature: <span
4815 class=tag>smpl</span>).
4816 <p>The ‘<a href="#simplified"><code
4817 class=property>simplified</code></a>’ and ‘<a
4818 href="#traditional"><code class=property>traditional</code></a>’
4819 values allow control over the glyph forms for characters which have been
4820 simplified over time but for which the older, traditional form is still
4821 used in some contexts. The exact set of characters and glyph forms will
4822 vary to some degree by context for which a given font was designed.</p>
4824 <dt><dfn id=traditional>traditional</dfn>
4826 <dd>Enables rendering of traditional forms (OpenType feature: <span
4827 class=tag>trad</span>).
4828 </dl>
4830 <div class=featex><img alt="tradtional form example" src=trad.png></div>
4832 <dl>
4833 <dt><dfn id=full-width>full-width</dfn>
4835 <dd>Enables rendering of full-width variants (OpenType feature: <span
4836 class=tag>fwid</span>).
4838 <dt><dfn id=proportional-width>proportional-width</dfn>
4840 <dd>Enables rendering of proportionally-spaced variants (OpenType feature:
4841 <span class=tag>pwid</span>).
4842 </dl>
4844 <div class=featex><img alt="proportionally spaced Japanese example"
4845 src=pwid.png></div>
4847 <dl>
4848 <dt><dfn id=ruby>ruby</dfn>
4850 <dd>Enables display of ruby variant glyphs (OpenType feature: <span
4851 class=tag>ruby</span>). Since ruby text is generally smaller than the
4852 associated body text, font designers can design special glyphs for use
4853 with ruby that are more readable than scaled down versions of the default
4854 glyphs. Only glyph selection is affected, there is no associated font
4855 scaling or other change that affects line layout. The red ruby text below
4856 is shown with default glyphs (top) and with ruby variant glyphs (bottom).
4857 Note the slight difference in stroke thickness.
4858 </dl>
4860 <div class=featex><img alt="ruby variant example" src=rubyshinkansen.png></div>
4862 <h3 id=font-variant-prop><span class=secno>6.11 </span>Overall shorthand
4863 for font rendering: the <a href="#propdef-font-variant">font-variant</a>
4864 property</h3>
4866 <table class=propdef id=namefont-variantvaluenormal-none-ltcommo>
4867 <tbody>
4868 <tr>
4869 <td>Name:
4871 <td><dfn id=propdef-font-variant>font-variant</dfn>
4873 <tr>
4874 <td>Value:
4876 <td>normal | none | [ <a
4877 href="#common-lig-values"><var><common-lig-values></var></a> ||
4878 <a
4879 href="#discretionary-lig-values"><var><discretionary-lig-values></var></a>
4880 || <a
4881 href="#historical-lig-values"><var><historical-lig-values></var></a>
4882 || <a
4883 href="#contextual-alt-values"><var><contextual-alt-values></var></a>
4884 || <a href="#stylistic"><var
4885 title=stylistic>stylistic(<feature-value-name>)</var></a> || <a
4886 href="#historical-forms"><var>historical-forms</var></a> || <a
4887 href="#styleset"><var
4888 title=styleset>styleset(<feature-value-name> #)</var></a> || <a
4889 href="#character-variant"><var
4890 title=character-variant>character-variant(<feature-value-name>
4891 #)</var></a> || <a href="#swash"><var
4892 title=swash>swash(<feature-value-name>)</var></a> || <a
4893 href="#ornaments"><var
4894 title=ornaments>ornaments(<feature-value-name>)</var></a> || <a
4895 href="#annotation"><var
4896 title=annotation>annotation(<feature-value-name>)</var></a> || [
4897 <a href="#small-caps"><i>small-caps</i></a> | <a
4898 href="#all-small-caps"><i>all-small-caps</i></a> | <a
4899 href="#petite-caps"><i>petite-caps</i></a> | <a
4900 href="#all-petite-caps"><i>all-petite-caps</i></a> | <a
4901 href="#unicase"><i>unicase</i></a> | <a
4902 href="#titling-caps"><i>titling-caps</i></a> ] || <a
4903 href="#numeric-figure-values"><var><numeric-figure-values></var></a>
4904 || <a
4905 href="#numeric-spacing-values"><var><numeric-spacing-values></var></a>
4906 || <a
4907 href="#numeric-fraction-values"><var><numeric-fraction-values></var></a>
4908 || <a href="#ordinal"><i>ordinal</i></a> || <a
4909 href="#slashed-zero"><i>slashed-zero</i></a> || <a
4910 href="#east-asian-variant-values"><var><east-asian-variant-values></var></a>
4911 || <a
4912 href="#east-asian-width-values"><var><east-asian-width-values></var></a>
4913 || <a href="#ruby"><i>ruby</i></a> ]
4915 <tr>
4916 <td>Initial:
4918 <td>normal
4920 <tr>
4921 <td>Applies to:
4923 <td>all elements
4925 <tr>
4926 <td>Inherited:
4928 <td>yes
4930 <tr>
4931 <td>Percentages:
4933 <td>see individual properties
4935 <tr>
4936 <td>Media:
4938 <td>visual
4940 <tr>
4941 <td>Computed value:
4943 <td>see individual properties
4945 <tr>
4946 <td>Animatable:
4948 <td>see individual properties
4949 </table>
4951 <p>The value ‘<a href="#normal2"><code
4952 class=property>normal</code></a>’ resets all other font feature
4953 properties to their inital value. The ‘<a
4954 href="#font-variant-ligatures-none-value"><code
4955 class=property>none</code></a>’ value sets ‘<a
4956 href="#propdef-font-variant-ligatures"><code
4957 class=property>font-variant-ligatures</code></a>’ to ‘<a
4958 href="#font-variant-ligatures-none-value"><code
4959 class=property>none</code></a>’ and resets all other font feature
4960 properties to their initial value. Like other shorthands, using ‘<a
4961 href="#propdef-font-variant"><code
4962 class=property>font-variant</code></a>’ resets unspecified font-variant
4963 subproperties to their initial values. It does not reset the values of
4964 either ‘<a href="#propdef-font-language-override"><code
4965 class=property>font-language-override</code></a>’ or ‘<a
4966 href="#propdef-font-feature-settings"><code
4967 class=property>font-feature-settings</code></a>’.
4969 <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
4970 font feature settings control: the <a
4971 href="#propdef-font-feature-settings">font-feature-settings</a> property</h3>
4973 <table class=propdef id=namefont-feature-settingsvaluenormal-ltf>
4974 <tbody>
4975 <tr>
4976 <td>Name:
4978 <td><dfn id=propdef-font-feature-settings>font-feature-settings</dfn>
4980 <tr>
4981 <td>Value:
4983 <td>normal | <a
4984 href="#feature-tag-value"><var><feature-tag-value></var></a> #
4986 <tr>
4987 <td>Initial:
4989 <td>normal
4991 <tr>
4992 <td>Applies to:
4994 <td>all elements
4996 <tr>
4997 <td>Inherited:
4999 <td>yes
5001 <tr>
5002 <td>Percentages:
5004 <td>N/A
5006 <tr>
5007 <td>Media:
5009 <td>visual
5011 <tr>
5012 <td>Computed value:
5014 <td>as specified
5016 <tr>
5017 <td>Animatable:
5019 <td>no
5020 </table>
5022 <p>This property provides low-level control over OpenType font features. It
5023 is intended as a way of providing access to font features that are not
5024 widely used but are needed for a particular use case. A value of ‘<a
5025 href="#normal2"><code class=property>normal</code></a>’ means that no
5026 change in glyph selection or positioning occurs due to this property.
5028 <p>
5030 <pre>/* enable small caps and use second swash alternate */
5031 font-feature-settings: "smcp", "swsh" 2;</pre>
5033 <p>Feature tag values have the following syntax:
5035 <pre
5036 class=prod><dfn id=feature-tag-value><var><feature-tag-value></var></dfn> = <string> [ <integer> | on | off ]?</pre>
5038 <p>The <string> is a case-sensitive OpenType feature tag. As
5039 specified in the OpenType specification, feature tags contain four ASCII
5040 characters. Tag strings longer or shorter than four characters, or
5041 containing characters outside the U+20–7E codepoint range are invalid.
5042 User agents must not use a feature tag created by truncating or padding
5043 the string to four characters. Feature tags need only match a feature tag
5044 defined in the font, they are not limited to explicitly registered
5045 OpenType features. Fonts defining custom feature tags should follow the <a
5046 href="http://www.microsoft.com/typography/otspec/featuretags.htm">tag name
5047 rules</a> defined in the OpenType specification <a
5048 href="#OPENTYPE-FEATURES"
5049 rel=biblioentry>[OPENTYPE-FEATURES]<!--{{!OPENTYPE-FEATURES}}--></a>.
5050 Feature tags not present in the font are ignored; a user agent must not
5051 attempt to synthesize fallback behavior based on these feature tags.
5053 <p>This means that explicitly disabling the <span class=tag>kern</span>
5054 feature will not affect the application of kerning data found in the
5055 ‘<code class=property>kern</code>’ table (as opposed to kerning data
5056 associated with the <span class=tag>kern</span> feature in the ‘<code
5057 class=property>GPOS</code>’ table). Authors should use the ‘<a
5058 href="#propdef-font-kerning"><code
5059 class=property>font-kerning</code></a>’ property to explictly enable or
5060 disable kerning since this property affects both types of kerning.
5062 <p>If present, a value indicates an index used for glyph selection. An
5063 <integer> value must be 0 or greater. A value of 0 indicates that
5064 the feature is disabled. For boolean features, a value of 1 enables the
5065 feature. For non-boolean features, a value of 1 or greater enables the
5066 feature and indicates the feature selection index. A value of ‘<code
5067 class=property>on</code>’ is synonymous with 1 and ‘<code
5068 class=property>off</code>’ is synonymous with 0. If the value is
5069 omitted, a value of 1 is assumed.
5071 <pre>
5072 font-feature-settings: "dlig" 1; /* dlig=1 enable discretionary ligatures */
5073 font-feature-settings: "smcp" on; /* smcp=1 enable small caps */
5074 font-feature-settings: 'c2sc'; /* c2sc=1 enable caps to small caps */
5075 font-feature-settings: "liga" off; /* liga=0 no common ligatures */
5076 font-feature-settings: "tnum", 'hist'; /* tnum=1, hist=1 enable tabular numbers and historical forms */
5077 font-feature-settings: "tnum" "hist"; /* invalid, need a comma-delimited list */
5078 font-feature-settings: "palin" off; /* good idea but invalid tagname */
5079 font-feature-settings: "PKRN"; /* PKRN=1 enable custom feature */
5080 font-feature-settings: dlig; /* invalid, tag must be a string */
5081 </pre>
5083 <p>When values greater than the range supported by the font are specified,
5084 the behavior is explicitly undefined. For boolean features, in general
5085 these will enable the feature. For non-boolean features, out of range
5086 values will in general be equivalent to a 0 value. However, in both cases
5087 the exact behavior will depend upon the way the font is designed
5088 (specifically, which type of lookup is used to define the feature).
5090 <p>Authors should generally use ‘<a href="#propdef-font-variant"><code
5091 class=property>font-variant</code></a>’ and its related subproperties
5092 whenever possible and only use this property for special cases where its
5093 use is the only way of accessing a particular infrequently used font
5094 feature.
5096 <p>Although specifically defined for OpenType feature tags, feature tags
5097 for other modern font formats that support font features may be added in
5098 the future. Where possible, features defined for other font formats should
5099 attempt to follow the pattern of registered OpenType tags.
5101 <div class=example>
5102 <p>The Japanese text below will be rendered with half-width kana
5103 characters:</p>
5105 <pre lang=ja>
5106 body { font-feature-settings: "hwid"; /* Half-width OpenType feature */ }
5108 <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</p>
5109 </pre>
5110 </div>
5112 <h3 id=font-language-override-prop><span class=secno>6.13 </span>Font
5113 language override: the <a
5114 href="#propdef-font-language-override">font-language-override</a> property</h3>
5116 <table class=propdef id=namefont-language-overridevaluenormal-lt>
5117 <tbody>
5118 <tr>
5119 <td>Name:
5121 <td><dfn id=propdef-font-language-override>font-language-override</dfn>
5123 <tr>
5124 <td>Value:
5126 <td>normal | <string>
5128 <tr>
5129 <td>Initial:
5131 <td>normal
5133 <tr>
5134 <td>Applies to:
5136 <td>all elements
5138 <tr>
5139 <td>Inherited:
5141 <td>yes
5143 <tr>
5144 <td>Percentages:
5146 <td>N/A
5148 <tr>
5149 <td>Media:
5151 <td>visual
5153 <tr>
5154 <td>Computed value:
5156 <td>as specified
5158 <tr>
5159 <td>Animatable:
5161 <td>no
5162 </table>
5164 <p>The value of ‘<a href="#normal2"><code
5165 class=property>normal</code></a>’ specifies that when rendering with
5166 OpenType fonts the content language of the element is used to infer the
5167 OpenType language system. The value of the <string> is a single
5168 three-letter OpenType <a
5169 href="http://www.microsoft.com/typography/otspec/languagetags.htm">language
5170 system tag</a>, defined in the layout tag registry of the OpenType
5171 specification. It indicates the OpenType language system to be used
5172 instead of the language system implied by the language of the element.
5174 <div class=example>
5175 <p>The <a href="http://www.un.org/en/documents/udhr/index.shtml">Universal
5176 Declaration of Human Rights</a> has been translated into a wide variety
5177 of languages. In Turkish, Article 9 of this document might be marked up
5178 as below:</p>
5180 <pre lang=tr><body lang="tr">
5182 <h4>Madde 9</h4>
5183 <p>Hiç kimse keyfi olarak tutuklanamaz, alıkonulanamaz veya sürülemez.</p>
5184 </pre>
5186 <p>Here the user agent uses the value of the ‘<code
5187 class=property>lang</code>’ attribute when rendering text and
5188 appropriately renders this text without ‘<code
5189 class=property>fi</code>’ ligatures. There is no need to use the ‘<a
5190 href="#propdef-font-language-override"><code
5191 class=property>font-language-override</code></a>’ property.</p>
5193 <p>However, a given font may lack support for a specific language. In this
5194 situation authors may need to use the typographic conventions of a
5195 related language that are supported by that font:</p>
5197 <pre lang=mk><body lang="mk"> <!-- Macedonian lang code -->
5199 body { font-language-override: "SRB"; /* Serbian OpenType language tag */ }
5201 <h4>Члeн 9</h4>
5202 <p>Никoj чoвeк нeмa дa бидe пoдлoжeн нa прoизвoлнo aпсeњe, притвoр или прoгoнувaњe.</p>
5204 </pre>
5206 <p>The Macedonian text here will be rendered using Serbian typographic
5207 conventions, with the assumption that the font specified supports
5208 Serbian.</p>
5209 </div>
5211 <p><a id=rendering-considerations></a>
5213 <h2 id=font-feature-resolution><span class=secno>7 </span>Font Feature
5214 Resolution</h2>
5216 <p>As described in the previous section, font features can be enabled in a
5217 variety of ways, either via the use of ‘<a
5218 href="#propdef-font-variant"><code
5219 class=property>font-variant</code></a>’ or ‘<a
5220 href="#propdef-font-feature-settings"><code
5221 class=property>font-feature-settings</code></a>’ in a style rule or
5222 within an <code>@font-face</code> rule. The resolution order for the union
5223 of these settings is defined below. Features defined via CSS properties
5224 are applied on top of layout engine default features.
5226 <h3 id=default-features><span class=secno>7.1 </span>Default features</h3>
5228 <p>For OpenType fonts, user agents must enable the default features defined
5229 in the OpenType documentation for a given script and writing mode.
5230 Required ligatures, common ligatures and contextual forms must be enabled
5231 by default (OpenType features: <span class=tag>rlig, liga, clig,
5232 calt</span>), along with localized forms (OpenType feature: <span
5233 class=tag>locl</span>), and features required for proper display of
5234 composed characters and marks (OpenType features: <span class=tag>ccmp,
5235 mark, mkmk</span>). These features must always be enabled, even when the
5236 value of the ‘<a href="#propdef-font-variant"><code
5237 class=property>font-variant</code></a>’ and ‘<a
5238 href="#propdef-font-feature-settings"><code
5239 class=property>font-feature-settings</code></a>’ properties is ‘<a
5240 href="#normal2"><code class=property>normal</code></a>’. Individual
5241 features are only disabled when explicitly overridden by the author, as
5242 when ‘<a href="#propdef-font-variant-ligatures"><code
5243 class=property>font-variant-ligatures</code></a>’ is set to ‘<a
5244 href="#no-common-ligatures"><code
5245 class=property>no-common-ligatures</code></a>’. For handling complex
5246 scripts such as <a
5247 href="http://www.microsoft.com/typography/otfntdev/arabicot/features.aspx">Arabic</a>,
5248 <a
5249 href="http://www.microsoft.com/typography/otfntdev/mongolot/features.htm">Mongolian</a>
5250 or <a
5251 href="http://www.microsoft.com/typography/otfntdev/devanot/features.aspx">Devanagari</a>
5252 additional features are required. For upright text within vertical text
5253 runs, vertical alternates (OpenType feature: <span class=tag>vert</span>)
5254 must be enabled.
5256 <h3 id=feature-precedence><span class=secno>7.2 </span>Feature precedence</h3>
5258 <p>General and font specific font feature property settings are resolved in
5259 the order below, in ascending precedence order. This ordering is used to
5260 construct a combined list of font features that affect a given text run.
5262 <ol>
5263 <li>Font features enabled by default, including features required for a
5264 given script.
5266 <li>If the font is defined via an <code>@font-face</code> rule, the font
5267 features implied by the font-variant descriptor in the
5268 <code>@font-face</code> rule.
5270 <li>If the font is defined via an <code>@font-face</code> rule, the font
5271 features implied by the font-feature-settings descriptor in the
5272 <code>@font-face</code> rule.
5274 <li>Feature settings determined by properties other than ‘<a
5275 href="#propdef-font-variant"><code
5276 class=property>font-variant</code></a>’ or ‘<a
5277 href="#propdef-font-feature-settings"><code
5278 class=property>font-feature-settings</code></a>’. For example, setting
5279 a non-default value for the ‘<code
5280 class=property>letter-spacing</code>’ property disables ligatures.
5282 <li>Font features implied by the value of the ‘<a
5283 href="#propdef-font-variant"><code
5284 class=property>font-variant</code></a>’ property, the related
5285 font-variant subproperties and any other CSS property that may use
5286 OpenType features (e.g. the ‘<a href="#propdef-font-kerning"><code
5287 class=property>font-kerning</code></a>’ property).
5289 <li>Font features implied by the value of ‘<a
5290 href="#propdef-font-feature-settings"><code
5291 class=property>font-feature-settings</code></a>’ property.
5292 </ol>
5294 <p>This ordering allows authors to set up a general set of defaults for
5295 fonts within their <code>@font-face</code> rules, then override them with
5296 property settings for specific elements. General property settings
5297 override the settings in <code>@font-face</code> rules and low-level font
5298 feature settings override ‘<a href="#propdef-font-variant"><code
5299 class=property>font-variant</code></a>’ property settings.
5301 <p>For situations where the combined list of font feature settings contains
5302 more than one value for the same feature, the last value is used. When a
5303 font lacks support for a given underlying font feature, text is simply
5304 rendered as if that font feature was not enabled; font fallback does not
5305 occur and no attempt is made to synthesize the feature except where
5306 explicitly noted for specific properties.
5308 <h3 id=feature-precedence-examples><span class=secno>7.3 </span>Feature
5309 precedence examples</h3>
5311 <div class=example>
5312 <p>With the styles below, numbers are rendered proportionally when used
5313 within a paragraph but are shown in tabular form within tables of prices:</p>
5315 <pre>body {
5316 font-variant-numeric: proportional-nums;
5317 }
5319 table.prices td {
5320 font-variant-numeric: tabular-nums;
5321 }
5322 </pre>
5323 </div>
5325 <div class=example>
5326 <p>When the font-variant descriptor is used within an
5327 <code>@font-face</code> rule, it only applies to the font defined by that
5328 rule.</p>
5330 <pre>@font-face {
5331 font-family: MainText;
5332 src: url(http://example.com/font.ttf);
5333 font-variant: oldstyle-nums proportional-nums styleset(1,3);
5334 }
5336 body {
5337 font-family: MainText, Helvetica;
5338 }
5340 table.prices td {
5341 font-variant-numeric: tabular-nums;
5342 }
5343 </pre>
5345 <p>In this case, old-style numerals will be used throughout but only where
5346 the font "MainText" is used. Just as in the previous example, tabular
5347 values will be used in price tables since ‘<a
5348 href="#tabular-nums"><code class=property>tabular-nums</code></a>’
5349 appears in a general style rule and its use is mutually exclusive with
5350 ‘<a href="#proportional-nums"><code
5351 class=property>proportional-nums</code></a>’. Stylistic alternate sets
5352 will only be used where MainText is used.</p>
5353 </div>
5355 <div class=example>
5356 <p>The <code>@font-face</code> rule can also be used to access font
5357 features in locally available fonts via the use of <code>local()</code>
5358 in the ‘<a href="#descdef-src"><code class=property>src</code></a>’
5359 descriptor of the <code>@font-face</code> definition:</p>
5361 <pre>@font-face {
5362 font-family: BodyText;
5363 src: local("HiraMaruPro-W4");
5364 font-variant: proportional-width;
5365 font-feature-settings: "ital"; /* Latin italics within CJK text feature */
5366 }
5368 body { font-family: BodyText, serif; }
5369 </pre>
5371 <p>If available, a Japanese font "Hiragino Maru Gothic" will be used. When
5372 text rendering occurs, Japanese kana will be proportionally spaced and
5373 Latin text will be italicised. Text rendered with the fallback serif font
5374 will use default rendering properties.</p>
5375 </div>
5377 <div class=example>
5378 <p>In the example below, discretionary ligatures are enabled only for a
5379 downloadable font but are disabled within spans of class "special":</p>
5381 <pre>@font-face {
5382 font-family: main;
5383 src: url(fonts/ffmeta.woff) format("woff");
5384 font-variant: discretionary-ligatures;
5385 }
5387 body { font-family: main, Helvetica; }
5388 span.special { font-variant-ligatures: no-discretionary-ligatures; }
5389 </pre>
5391 <p>Adding an discretionary style rule with the <code>@font-face</code>
5392 above:</p>
5394 <pre>body { font-family: main, Helvetica; }
5395 span { font-feature-settings: "dlig"; }
5396 span.special { font-variant-ligatures: no-discretionary-ligatures; }
5397 </pre>
5399 <p>Within spans of class "special", discretionary ligatures <em>will</em>
5400 be rendered. This is because both the ‘<a
5401 href="#propdef-font-feature-settings"><code
5402 class=property>font-feature-settings</code></a>’ and ‘<a
5403 href="#propdef-font-variant-ligatures"><code
5404 class=property>font-variant-ligatures</code></a>’ properties apply to
5405 these spans. Although the ‘<code class=css>no-discretionary
5406 ligatures</code>’ setting of ‘<a
5407 href="#propdef-font-variant-ligatures"><code
5408 class=property>font-variant-ligatures</code></a>’ effectively disables
5409 the OpenType <span class=tag>dlig</span> feature, because the ‘<a
5410 href="#propdef-font-feature-settings"><code
5411 class=property>font-feature-settings</code></a>’ is resolved after
5412 that, the ‘<code class=property>dlig</code>’ value reenables
5413 discretionary ligatures.</p>
5414 </div>
5416 <h2 id=object-model><span class=secno>8 </span>Object Model</h2>
5418 <p>The contents of <code>@font-face</code> and
5419 <code>@font-feature-values</code> rules can be accessed via the following
5420 extensions to the CSS Object Model.
5422 <h3 id=om-fontface><span class=secno>8.1 </span>The <a
5423 href="#cssfontfacerule"><code>CSSFontFaceRule</code></a> interface</h3>
5425 <p>The <dfn id=cssfontfacerule>CSSFontFaceRule</dfn> interface represents a
5426 <code>@font-face</code> rule.
5428 <pre class=idl>
5429 interface CSSFontFaceRule : CSSRule {
5430 attribute DOMString family;
5431 attribute DOMString src;
5432 attribute DOMString style;
5433 attribute DOMString weight;
5434 attribute DOMString stretch;
5435 attribute DOMString unicodeRange;
5436 attribute DOMString variant;
5437 attribute DOMString featureSettings;
5438 }</pre>
5440 <p>The DOM Level 2 Style specification <a href="#DOM-LEVEL-2-STYLE"
5441 rel=biblioentry>[DOM-LEVEL-2-STYLE]<!--{{DOM-LEVEL-2-STYLE}}--></a>
5442 defined a different variant of this rule. This definition supercedes that
5443 one.
5445 <h3 id=om-fontfeaturevalues><span class=secno>8.2 </span>The <a
5446 href="#cssfontfeaturevaluesrule"><code>CSSFontFeatureValuesRule</code></a>
5447 interface</h3>
5449 <p>The <code>CSSRule</code> interface is extended as follows:
5451 <pre class=idl>partial interface CSSRule {
5452 const unsigned short FONT_FEATURE_VALUES_RULE = 14;
5453 }</pre>
5455 <p>The <dfn id=cssfontfeaturevaluesrule>CSSFontFeatureValuesRule</dfn>
5456 interface represents a <code>@font-feature-values</code> rule.
5458 <pre class=idl>interface CSSFontFeatureValuesRule : CSSRule {
5459 readonly attribute DOMString familyList;
5460 readonly attribute DOMString valueText;
5461 };</pre>
5463 <dl class=idl-attributes>
5464 <dt><var>familyList</var> of type <code>DOMString</code>, readonly
5466 <dd>The list of one or more font families for which a given set of feature
5467 values is defined.
5469 <dt><var>valueText</var> of type <code>DOMString</code>, readonly
5471 <dd>Serialized set of feature values.
5472 </dl>
5474 <h2 class=no-num id=platform-props-to-css>Appendix A: Mapping platform font
5475 properties to CSS properties</h2>
5477 <p><em>This appendix is included as background for some of the problems and
5478 situations that are described in other sections. It should be viewed as
5479 informative only.</em>
5481 <p>Font properties in CSS are designed to be independent of the underlying
5482 font formats used; they can be used to specify bitmap fonts, Type1 fonts,
5483 SVG fonts in addition to the common TrueType and OpenType fonts. But there
5484 are facets of the TrueType and OpenType formats that often cause confusion
5485 for authors and present challenges to implementers on different platforms.
5487 <p>Originally developed at Apple, TrueType was designed as an outline font
5488 format for both screen and print. Microsoft joined Apple in developing the
5489 TrueType format and both platforms have supported TrueType fonts since
5490 then. Font data in the TrueType format consists of a set of tables
5491 distinguished with common four-letter tag names, each containing a
5492 specific type of data. For example, naming information, including
5493 copyright and license information, is stored in the ‘<code
5494 class=property>name</code>’ table. The <a
5495 href="#character-map"><em>character map</em></a> (‘<code
5496 class=property>cmap</code>’) table contains a mapping of character
5497 encodings to glyphs. Apple later added additional tables for supporting
5498 enhanced typographic functionality; these are now called Apple Advanced
5499 Typography, or AAT, fonts. Microsoft and Adobe developed a separate set of
5500 tables for advanced typography and called their format OpenType <a
5501 href="#OPENTYPE" rel=biblioentry>[OPENTYPE]<!--{{!OPENTYPE}}--></a>.
5503 <p>In many cases the font data used under Microsoft Windows or Linux is
5504 slightly different from the data used under Apple's Mac OS X because the
5505 TrueType format allowed for explicit variation across platforms. This
5506 includes font metrics, names and <a href="#character-map"><em>character
5507 map</em></a> data.
5509 <p>Specifically, font family name data is handled differently across
5510 platforms. For TrueType and OpenType fonts these names are contained in
5511 the ‘<code class=property>name</code>’ table, in name records with
5512 name ID 1. Mulitple names can be stored for different locales, but
5513 Microsoft recommends fonts always include at least a US English version of
5514 the name. On Windows, Microsoft made the decision for backwards
5515 compatibility to limit this family name to a maximum of four faces; for
5516 larger groupings the "preferred family" (name ID 16) or "WWS family" (name
5517 ID 21) can be used. Other platforms such as OSX don't have this
5518 limitation, so the family name is used to define all possible groupings.
5520 <p>Other name table data provides names used to uniquely identify a
5521 specific face within a family. The full font name (name ID 4) and the
5522 Postscript name (name ID 6) describe a single face uniquely. For example,
5523 the bold face of the Gill Sans family has a fullname of "Gill Sans Bold"
5524 and a Postscript name of "GillSans-Bold". There can be multiple localized
5525 versions of the fullname for a given face, but the Postscript name is
5526 always a unique name made from a limited set of ASCII characters.
5528 <p>On various platforms, different names are used to search for a font. For
5529 example, with the Windows GDI CreateIndirectFont API, either a family or
5530 fullname can be used to lookup a face, while on Mac OS X the
5531 CTFontCreateWithName API call is used to lookup a given face using the
5532 fullname and Postscript name. Under Linux, the fontconfig API allows fonts
5533 to be searched using any of these names. In situations where platform
5534 API's automatically substitute other font choices, it may be necessary to
5535 verify a returned font matches a given name.
5537 <p>The weight of a given face can be determined via the usWeightClass field
5538 of the OS/2 table or inferred from the style name (name ID 2). Likewise,
5539 the width can be determined via the usWidthClass of the OS/2 table or
5540 inferred from the style name. For historical reasons related to synthetic
5541 bolding at weights 200 or lower with the Windows GDI API, font designers
5542 have sometimes skewed values in the OS/2 table to avoid these weights.
5544 <p>Rendering complex scripts that use contextual shaping such as Thai,
5545 Arabic and Devanagari requires features present only in OpenType or AAT
5546 fonts. Currently, complex script rendering is supported on Windows and
5547 Linux using OpenType font features while both OpenType and AAT font
5548 features are used under Mac OS X.
5550 <h2 class=no-num id=ch-ch-ch-changes>Changes</h2>
5552 <h3 class=no-num id=recent-changes> Changes from the <a
5553 href="http://www.w3.org/TR/2013/WD-css3-fonts-20130212/">February 2013
5554 CSS3 Fonts Working Draft</a></h3>
5556 <p>Major changes include:
5558 <ul>
5559 <li>Moved font load events into a separate <a
5560 href="http://dev.w3.org/csswg/css3-font-load-events/">spec</a>
5562 <li>Tightened error handling rules for <code>@font-feature-values</code>
5563 rules
5565 <li>Added grammar productions for <code>@font-face</code> and
5566 <code>@font-feature-values</code> rules
5568 <li>Tightened definition of synthetic oblique
5570 <li>Revised definition of ‘<a href="#descdef-unicode-range"><code
5571 class=property>unicode-range</code></a>’ descriptor
5572 </ul>
5574 <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
5576 <p>I'd like to thank Tal Leming, Jonathan Kew and Christopher Slye for all
5577 their help and feedback. John Hudson was kind enough to take the time to
5578 explain the subtleties of OpenType language tags and provided the example
5579 of character variant usage for displaying text on Byzantine seals. Ken
5580 Lunde and Eric Muller provided valuable feedback on CJK OpenType features
5581 and Unicode variation selectors. The idea for supporting font features by
5582 using font-variant subproperties originated with Håkon Wium Lie, Adam
5583 Twardoch and Tal Leming. Elika Etemad supplied some of the initial design
5584 ideas for the <code>@font-feature-values</code> rule. Thanks also to House
5585 Industries for allowing the use of Ed Interlock in the discretionary
5586 ligatures example.
5588 <p>A special thanks to Robert Bringhurst for the sublime mind expansion
5589 that is <em>The Elements of Typographic Style</em>.
5591 <h2 class=no-num id=conformance> Conformance</h2>
5593 <h3 class=no-num id=conventions> Document Conventions</h3>
5595 <p>Conformance requirements are expressed with a combination of descriptive
5596 assertions and RFC 2119 terminology. The key words “MUST”, “MUST
5597 NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”,
5598 “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the
5599 normative parts of this document are to be interpreted as described in RFC
5600 2119. However, for readability, these words do not appear in all uppercase
5601 letters in this specification.
5603 <p>All of the text of this specification is normative except sections
5604 explicitly marked as non-normative, examples, and notes. <a
5605 href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>
5607 <p>Examples in this specification are introduced with the words “for
5608 example” or are set apart from the normative text with
5609 <code>class="example"</code>, like this:
5611 <div class=example>
5612 <p>This is an example of an informative example.
5613 </div>
5615 <p>Informative notes begin with the word “Note” and are set apart from
5616 the normative text with <code>class="note"</code>, like this:
5618 <p class=note>Note, this is an informative note.
5620 <h3 class=no-num id=conformance-classes> Conformance Classes</h3>
5622 <p>Conformance to CSS Fonts Level 3 Module is defined for three conformance
5623 classes:
5625 <dl>
5626 <dt><dfn id=style-sheet title="style sheet!!as conformance class">style
5627 sheet</dfn>
5629 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
5630 style sheet</a>.
5632 <dt><dfn id=renderer>renderer</dfn>
5634 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
5635 that interprets the semantics of a style sheet and renders documents that
5636 use them.
5638 <dt><dfn id=authoring-tool>authoring tool</dfn>
5640 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
5641 that writes a style sheet.
5642 </dl>
5644 <p>A style sheet is conformant to CSS Fonts Level 3 Module if all of its
5645 declarations that use properties defined in this module have values that
5646 are valid according to the generic CSS grammar and the individual grammars
5647 of each property as given in this module.
5649 <p>A renderer is conformant to CSS Fonts Level 3 Module if, in addition to
5650 interpreting the style sheet as defined by the appropriate specifications,
5651 it supports all the features defined by CSS Fonts Level 3 Module by
5652 parsing them correctly and rendering the document accordingly. However,
5653 the inability of a UA to correctly render a document due to limitations of
5654 the device does not make the UA non-conformant. (For example, a UA is not
5655 required to render color on a monochrome monitor.)
5657 <p>An authoring tool is conformant to CSS Fonts Level 3 Module if it writes
5658 style sheets that are syntactically correct according to the generic CSS
5659 grammar and the individual grammars of each feature in this module, and
5660 meet all other conformance requirements of style sheets as described in
5661 this module.
5663 <h3 class=no-num id=partial> Partial Implementations</h3>
5665 <p>So that authors can exploit the forward-compatible parsing rules to
5666 assign fallback values, CSS renderers <strong>must</strong> treat as
5667 invalid (and <a
5668 href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore as
5669 appropriate</a>) any at-rules, properties, property values, keywords, and
5670 other syntactic constructs for which they have no usable level of support.
5671 In particular, user agents <strong>must not</strong> selectively ignore
5672 unsupported component values and honor supported values in a single
5673 multi-value property declaration: if any value is considered invalid (as
5674 unsupported values must be), CSS requires that the entire declaration be
5675 ignored.
5677 <h3 class=no-num id=experimental> Experimental Implementations</h3>
5679 <p>To avoid clashes with future CSS features, the CSS2.1 specification
5680 reserves a <a
5681 href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
5682 syntax</a> for proprietary and experimental extensions to CSS.
5684 <p>Prior to a specification reaching the Candidate Recommendation stage in
5685 the W3C process, all implementations of a CSS feature are considered
5686 experimental. The CSS Working Group recommends that implementations use a
5687 vendor-prefixed syntax for such features, including those in W3C Working
5688 Drafts. This avoids incompatibilities with future changes in the draft.
5690 <h3 class=no-num id=testing> Non-Experimental Implementations</h3>
5692 <p>Once a specification reaches the Candidate Recommendation stage,
5693 non-experimental implementations are possible, and implementors should
5694 release an unprefixed implementation of any CR-level feature they can
5695 demonstrate to be correctly implemented according to spec.
5697 <p>To establish and maintain the interoperability of CSS across
5698 implementations, the CSS Working Group requests that non-experimental CSS
5699 renderers submit an implementation report (and, if necessary, the
5700 testcases used for that implementation report) to the W3C before releasing
5701 an unprefixed implementation of any CSS features. Testcases submitted to
5702 W3C are subject to review and correction by the CSS Working Group.
5704 <p>Further information on submitting testcases and implementation reports
5705 can be found from on the CSS Working Group's website at <a
5706 href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
5707 Questions should be directed to the <a
5708 href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
5709 mailing list.
5711 <h2 class=no-num id=references>References</h2>
5713 <h3 class=no-num id=normative-references>Normative References</h3>
5714 <!--begin-normative-->
5715 <!-- Sorted by label -->
5717 <dl class=bibliography>
5718 <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
5719 <!---->
5721 <dt id=CHARMOD>[CHARMOD]
5723 <dd>Martin J. Dürst; et al. <a
5724 href="http://www.w3.org/TR/2005/REC-charmod-20050215/"><cite>Character
5725 Model for the World Wide Web 1.0: Fundamentals.</cite></a> 15 February
5726 2005. W3C Recommendation. URL: <a
5727 href="http://www.w3.org/TR/2005/REC-charmod-20050215/">http://www.w3.org/TR/2005/REC-charmod-20050215/</a>
5728 </dd>
5729 <!---->
5731 <dt id=CORS>[CORS]
5733 <dd>Anne van Kesteren. <a
5734 href="http://www.w3.org/TR/2013/CR-cors-20130129/"><cite>Cross-Origin
5735 Resource Sharing.</cite></a> 29 January 2013. W3C Candidate
5736 Recommendation. (Work in progress.) URL: <a
5737 href="http://www.w3.org/TR/2013/CR-cors-20130129/">http://www.w3.org/TR/2013/CR-cors-20130129/</a>
5738 </dd>
5739 <!---->
5741 <dt id=CSS21>[CSS21]
5743 <dd>Bert Bos; et al. <a
5744 href="http://www.w3.org/TR/2011/REC-CSS2-20110607"><cite>Cascading Style
5745 Sheets Level 2 Revision 1 (CSS 2.1) Specification.</cite></a> 7 June
5746 2011. W3C Recommendation. URL: <a
5747 href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
5748 </dd>
5749 <!---->
5751 <dt id=CSS3VAL>[CSS3VAL]
5753 <dd>Håkon Wium Lie; Tab Atkins; Elika J. Etemad. <a
5754 href="http://www.w3.org/TR/2012/CR-css3-values-20120828/"><cite>CSS
5755 Values and Units Module Level 3.</cite></a> 28 August 2012. W3C Candidate
5756 Recommendation. (Work in progress.) URL: <a
5757 href="http://www.w3.org/TR/2012/CR-css3-values-20120828/">http://www.w3.org/TR/2012/CR-css3-values-20120828/</a>
5758 </dd>
5759 <!---->
5761 <dt id=HTML5>[HTML5]
5763 <dd>Ian Hickson. <a
5764 href="http://www.w3.org/TR/2012/CR-html5-20121217/"><cite>HTML5.</cite></a>
5765 17 December 2012. W3C Candidate Recommendation. (Work in progress.) URL:
5766 <a
5767 href="http://www.w3.org/TR/2012/CR-html5-20121217/">http://www.w3.org/TR/2012/CR-html5-20121217/</a>
5768 </dd>
5769 <!---->
5771 <dt id=OPEN-FONT-FORMAT>[OPEN-FONT-FORMAT]
5773 <dd><a
5774 href="http://standards.iso.org/ittf/PubliclyAvailableStandards/c052136_ISO_IEC_14496-22_2009(E).zip"><cite>Information
5775 technology — Coding of audio-visual objects — Part 22: Open Font
5776 Format.</cite></a> International Organization for Standardization.
5777 ISO/IEC 14496-22:2009. URL: <a
5778 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>
5779 </dd>
5780 <!---->
5782 <dt id=OPENTYPE>[OPENTYPE]
5784 <dd><a
5785 href="http://www.microsoft.com/typography/otspec/default.htm"><cite>OpenType
5786 specification.</cite></a> Microsoft. URL: <a
5787 href="http://www.microsoft.com/typography/otspec/default.htm">http://www.microsoft.com/typography/otspec/default.htm</a>
5788 </dd>
5789 <!---->
5791 <dt id=OPENTYPE-FEATURES>[OPENTYPE-FEATURES]
5793 <dd><a
5794 href="http://www.microsoft.com/typography/otspec/featurelist.htm"><cite>OpenType
5795 feature registry.</cite></a> Microsoft. URL: <a
5796 href="http://www.microsoft.com/typography/otspec/featurelist.htm">http://www.microsoft.com/typography/otspec/featurelist.htm</a>
5797 </dd>
5798 <!---->
5800 <dt id=RFC2119>[RFC2119]
5802 <dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
5803 words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
5804 RFC 2119. URL: <a
5805 href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
5806 </dd>
5807 <!---->
5809 <dt id=UAX15>[UAX15]
5811 <dd>Mark Davis; Ken Whistler. <a
5812 href="http://www.unicode.org/reports/tr15/"><cite>Unicode Normalization
5813 Forms.</cite></a> 31 August 2012. Unicode Standard Annex #15. URL: <a
5814 href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a>
5815 </dd>
5816 <!---->
5818 <dt id=UAX29>[UAX29]
5820 <dd>Mark Davis. <a
5821 href="http://www.unicode.org/reports/tr29/"><cite>Unicode Text
5822 Segmentation.</cite></a> 12 September 2012. Unicode Standard Annex #29.
5823 URL: <a
5824 href="http://www.unicode.org/reports/tr29/">http://www.unicode.org/reports/tr29/</a>
5825 </dd>
5826 <!---->
5828 <dt id=UNICODE6>[UNICODE6]
5830 <dd>The Unicode Consortium. <a
5831 href="http://www.unicode.org/versions/Unicode6.2.0/"><cite>The Unicode
5832 Standard, Version 6.2.0.</cite></a> Defined by: The Unicode Standard,
5833 Version 6.2.0 URL: <a
5834 href="http://www.unicode.org/versions/Unicode6.2.0/">http://www.unicode.org/versions/Unicode6.2.0/</a>
5835 </dd>
5836 <!---->
5837 </dl>
5838 <!--end-normative-->
5839 <!--{{!CSS21}}-->
5840 <!--{{!CSS3VAL}}-->
5841 <!--{{!OPENTYPE}}-->
5842 <!--{{!OPENTYPE-FEATURES}}-->
5843 <!--{{!OPEN-FONT-FORMAT}}-->
5844 <!--{{!UNICODE6}}-->
5845 <!--{{!UAX15}}-->
5846 <!--{{!UAX29}}-->
5847 <!--{{!CORS}}-->
5848 <!--{{!HTML5}}-->
5849 <!--{{!CHARMOD}}-->
5851 <h3 class=no-num id=other-references>Other References</h3>
5852 <!--begin-informative-->
5853 <!-- Sorted by label -->
5855 <dl class=bibliography>
5856 <dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
5857 <!---->
5859 <dt id=AAT-FEATURES>[AAT-FEATURES]
5861 <dd><a href="http://developer.apple.com/fonts/registry/"><cite>Apple
5862 Advanced Typography font feature registry.</cite></a> Apple. URL: <a
5863 href="http://developer.apple.com/fonts/registry/">http://developer.apple.com/fonts/registry/</a>
5864 </dd>
5865 <!---->
5867 <dt id=ARABIC-TYPO>[ARABIC-TYPO]
5869 <dd>Huda Smitshuijzen AbiFares. <cite>Arabic Typography: A Comprehensive
5870 Sourcebook.</cite> Saqi Books. 2001. ISBN 0-86356-347-3.</dd>
5871 <!---->
5873 <dt id=CHARMOD-NORM>[CHARMOD-NORM]
5875 <dd>François Yergeau; et al. <a
5876 href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/"><cite>Character
5877 Model for the World Wide Web 1.0: Normalization.</cite></a> 1 May 2012.
5878 W3C Working Draft. (Work in progress.) URL: <a
5879 href="http://www.w3.org/TR/2012/WD-charmod-norm-20120501/">http://www.w3.org/TR/2012/WD-charmod-norm-20120501/</a>
5880 </dd>
5881 <!---->
5883 <dt id=CJKV-INFO-PROCESSING>[CJKV-INFO-PROCESSING]
5885 <dd>Ken Lunde. <cite>CJKV Information Processing, Second Edition.</cite>
5886 O'Reilly Media, Inc. 2009. ISBN 0-596-51447-1.</dd>
5887 <!---->
5889 <dt id=CSS3-CONDITIONAL>[CSS3-CONDITIONAL]
5891 <dd>L. David Baron. <a
5892 href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/"><cite>CSS
5893 Conditional Rules Module Level 3.</cite></a> 13 December 2012. W3C
5894 Working Draft. (Work in progress.) URL: <a
5895 href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/">http://www.w3.org/TR/2012/WD-css3-conditional-20121213/</a>
5896 </dd>
5897 <!---->
5899 <dt id=CSS3TEXT>[CSS3TEXT]
5901 <dd>Elika J. Etemad; Koji Ishii. <a
5902 href="http://www.w3.org/TR/2012/WD-css3-text-20121113/"><cite>CSS Text
5903 Module Level 3.</cite></a> 13 November 2012. W3C Working Draft. (Work in
5904 progress.) URL: <a
5905 href="http://www.w3.org/TR/2012/WD-css3-text-20121113/">http://www.w3.org/TR/2012/WD-css3-text-20121113/</a>
5906 </dd>
5907 <!---->
5909 <dt id=DIGITAL-TYPOGRAPHY>[DIGITAL-TYPOGRAPHY]
5911 <dd>Richard Rubinstein. <cite>Digital Typography, An Introduction to Type
5912 and Composition for Computer System Design.</cite> Addison-Wesley. 1988.
5913 ISBN 0-201-17633-5.</dd>
5914 <!---->
5916 <dt id=DOM-LEVEL-2-STYLE>[DOM-LEVEL-2-STYLE]
5918 <dd>Chris Wilson; Philippe Le Hégaret; Vidur Apparao. <a
5919 href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/"><cite>Document
5920 Object Model (DOM) Level 2 Style Specification.</cite></a> 13 November
5921 2000. W3C Recommendation. URL: <a
5922 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>
5923 </dd>
5924 <!---->
5926 <dt id=ELEMTYPO>[ELEMTYPO]
5928 <dd>Robert Bringhurst. <cite>The Elements of Typographic Style, Version
5929 4.</cite> Hartley & Marks. 2013. ISBN 0-88179-212-8.</dd>
5930 <!---->
5932 <dt id=LANGCULTTYPE>[LANGCULTTYPE]
5934 <dd>John D. Berry, Ed. <cite>Language Culture Type.</cite> Graphis. 2001.
5935 ISBN 1-932026-01-0.</dd>
5936 <!---->
5938 <dt id=OPENTYPE-FONT-GUIDE>[OPENTYPE-FONT-GUIDE]
5940 <dd><a
5941 href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf"><cite>OpenType
5942 User Guide.</cite></a> FontShop International. URL: <a
5943 href="https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf">https://www.fontfont.com/staticcontent/downloads/FF_OT_User_Guide.pdf</a>
5944 </dd>
5945 <!---->
5947 <dt id=RASTER-TRAGEDY>[RASTER-TRAGEDY]
5949 <dd>Beat Stamm. <a href="http://www.rastertragedy.com/"><cite>The Raster
5950 Tragedy at Low-Resolution Revisited.</cite></a> 7 December 2011. URL: <a
5951 href="http://www.rastertragedy.com/">http://www.rastertragedy.com/</a></dd>
5952 <!---->
5954 <dt id=WINDOWS-GLYPH-PROC>[WINDOWS-GLYPH-PROC]
5956 <dd>John Hudson. <a
5957 href="http://www.microsoft.com/typography/developers/opentype/default.htm"><cite>Windows
5958 Glyph Processing.</cite></a> Microsoft Typogrraphy. URL: <a
5959 href="http://www.microsoft.com/typography/developers/opentype/default.htm">http://www.microsoft.com/typography/developers/opentype/default.htm</a>
5960 </dd>
5961 <!---->
5962 </dl>
5963 <!--end-informative-->
5964 <!--{{ARABIC-TYPO}}-->
5965 <!--{{CJKV-INFO-PROCESSING}}-->
5966 <!--{{DIGITAL-TYPOGRAPHY}}-->
5967 <!--{{DOM-LEVEL-2-STYLE}}-->
5968 <!--{{ELEMTYPO}}-->
5969 <!--{{LANGCULTTYPE}}-->
5970 <!--{{OPENTYPE-FONT-GUIDE}}-->
5971 <!--{{RASTER-TRAGEDY}}-->
5972 <!--{{WINDOWS-GLYPH-PROC}}-->
5973 <!--{{CHARMOD-NORM}}-->
5974 <!--{{AAT-FEATURES}}-->
5975 <!--{{CSS3-CONDITIONAL}}-->
5976 <!--{{CSS3TEXT}}-->
5978 <h2 class=no-num id=index>Index</h2>
5979 <!--begin-index-->
5981 <ul class=indexlist>
5982 <li><var><absolute-size></var>, <a href="#absolute-size-value"
5983 title="<absolute-size>"><strong>3.5</strong></a>
5985 <li><var><common-lig-values></var>, <a href="#common-lig-values"
5986 title="<common-lig-values>"><strong>6.4</strong></a>
5988 <li><var><contextual-alt-values></var>, <a
5989 href="#contextual-alt-values"
5990 title="<contextual-alt-values>"><strong>6.4</strong></a>
5992 <li><var><discretionary-lig-values></var>, <a
5993 href="#discretionary-lig-values"
5994 title="<discretionary-lig-values>"><strong>6.4</strong></a>
5996 <li><var><east-asian-variant-values></var>, <a
5997 href="#east-asian-variant-values"
5998 title="<east-asian-variant-values>"><strong>6.10</strong></a>
6000 <li><var><east-asian-width-values></var>, <a
6001 href="#east-asian-width-values"
6002 title="<east-asian-width-values>"><strong>6.10</strong></a>
6004 <li><var><family-name></var>, <a href="#family-name-value"
6005 title="<family-name>"><strong>3.1</strong></a>
6007 <li><var><feature-tag-value></var>, <a href="#feature-tag-value"
6008 title="<feature-tag-value>"><strong>6.12</strong></a>
6010 <li><var><font-face-name></var>, <a href="#font-face-name-value"
6011 title="<font-face-name>"><strong>4.3</strong></a>
6013 <li><var><font-variant-css21></var>, <a
6014 href="#font-variant-css21-values"
6015 title="<font-variant-css21>"><strong>3.7</strong></a>
6017 <li><var><generic-family></var>, <a href="#generic-family-value"
6018 title="<generic-family>"><strong>3.1</strong></a>
6020 <li><var><historical-lig-values></var>, <a
6021 href="#historical-lig-values"
6022 title="<historical-lig-values>"><strong>6.4</strong></a>
6024 <li><var><length></var>, <a href="#length-size-value"
6025 title="<length>"><strong>3.5</strong></a>
6027 <li><var><number></var>, <a href="#aspect-ratio-value"
6028 title="<number>"><strong>3.6</strong></a>
6030 <li><var><numeric-figure-values></var>, <a
6031 href="#numeric-figure-values"
6032 title="<numeric-figure-values>"><strong>6.7</strong></a>
6034 <li><var><numeric-fraction-values></var>, <a
6035 href="#numeric-fraction-values"
6036 title="<numeric-fraction-values>"><strong>6.7</strong></a>
6038 <li><var><numeric-spacing-values></var>, <a
6039 href="#numeric-spacing-values"
6040 title="<numeric-spacing-values>"><strong>6.7</strong></a>
6042 <li><var><percentage></var>, <a href="#percentage-size-value"
6043 title="<percentage>"><strong>3.5</strong></a>
6045 <li><var><relative-size></var>, <a href="#relative-size-value"
6046 title="<relative-size>"><strong>3.5</strong></a>
6048 <li><var><urange></var>, <a href="#urange-value"
6049 title="<urange>"><strong>4.5</strong></a>
6051 <li>@font-face, <a href="#font-face" title="@font-face">4.1</a>, <a
6052 href="#font-face0" title="@font-face">4.3</a>
6054 <li>all-petite-caps, <a href="#all-petite-caps"
6055 title=all-petite-caps><strong>6.6</strong></a>
6057 <li>all-small-caps, <a href="#all-small-caps"
6058 title=all-small-caps><strong>6.6</strong></a>
6060 <li>annotation, <a href="#annotation"
6061 title=annotation><strong>6.8</strong></a>
6063 <li>aspect value, <a href="#aspect-value0" title="aspect
6064 value"><strong>3.6</strong></a>
6066 <li>authoring tool, <a href="#authoring-tool" title="authoring
6067 tool"><strong>#</strong></a>
6069 <li>character map, <a href="#character-map" title="character
6070 map"><strong>5.2</strong></a>
6072 <li>character-variant, <a href="#character-variant"
6073 title=character-variant><strong>6.8</strong></a>
6075 <li>common-ligatures, <a href="#common-ligatures"
6076 title=common-ligatures><strong>6.4</strong></a>
6078 <li>contextual, <a href="#contextual"
6079 title=contextual><strong>6.4</strong></a>
6081 <li>CSSFontFaceRule, <a href="#cssfontfacerule"
6082 title=CSSFontFaceRule><strong>8.1</strong></a>
6084 <li>CSSFontFeatureValuesRule, <a href="#cssfontfeaturevaluesrule"
6085 title=CSSFontFeatureValuesRule><strong>8.2</strong></a>
6087 <li>cursive, definition of, <a href="#cursive0" title="cursive, definition
6088 of"><strong>#</strong></a>
6090 <li>default face, <a href="#default-face" title="default
6091 face"><strong>5.2</strong></a>
6093 <li>descriptor_declaration, <a href="#descriptordeclaration"
6094 title="descriptor_declaration"><strong>4.1</strong></a>
6096 <li>diagonal-fractions, <a href="#diagonal-fractions"
6097 title=diagonal-fractions><strong>6.7</strong></a>
6099 <li>discretionary-ligatures, <a href="#discretionary-ligatures"
6100 title=discretionary-ligatures><strong>6.4</strong></a>
6102 <li>fantasy, definition of, <a href="#fantasy0" title="fantasy, definition
6103 of"><strong>#</strong></a>
6105 <li>feature_type, <a href="#featuretype"
6106 title="feature_type"><strong>6.9</strong></a>
6108 <li>feature_value_block, <a href="#featurevalueblock"
6109 title="feature_value_block"><strong>6.9</strong></a>
6111 <li>feature_value_definition, <a href="#featurevaluedefinition"
6112 title="feature_value_definition"><strong>6.9</strong></a>
6114 <li>font, <a href="#propdef-font" title=font><strong>3.7</strong></a>
6116 <li>font-family, <a href="#descdef-font-family"
6117 title=font-family><strong>4.2</strong></a>, <a
6118 href="#propdef-font-family" title=font-family><strong>3.1</strong></a>
6120 <li>font-feature-settings, <a href="#propdef-font-feature-settings"
6121 title=font-feature-settings><strong>6.12</strong></a>
6123 <li>font-feature-settings (descriptor), <a
6124 href="#descdef-font-feature-settings" title="font-feature-settings
6125 (descriptor)"><strong>4.7</strong></a>
6127 <li>font-kerning, <a href="#propdef-font-kerning"
6128 title=font-kerning><strong>6.3</strong></a>
6130 <li>font-language-override, <a href="#propdef-font-language-override"
6131 title=font-language-override><strong>6.13</strong></a>
6133 <li>font-size, <a href="#propdef-font-size"
6134 title=font-size><strong>3.5</strong></a>
6136 <li>font-size-adjust, <a href="#propdef-font-size-adjust"
6137 title=font-size-adjust><strong>3.6</strong></a>
6139 <li>font-stretch, <a href="#propdef-font-stretch"
6140 title=font-stretch><strong>3.3</strong></a>
6142 <li>font-stretch (descriptor), <a href="#descdef-font-stretch"
6143 title="font-stretch (descriptor)"><strong>4.4</strong></a>
6145 <li>font-style, <a href="#propdef-font-style"
6146 title=font-style><strong>3.4</strong></a>
6148 <li>font-style (descriptor), <a href="#descdef-font-style"
6149 title="font-style (descriptor)"><strong>4.4</strong></a>
6151 <li>font-synthesis, <a href="#propdef-font-synthesis"
6152 title=font-synthesis><strong>3.8</strong></a>
6154 <li>font-variant, <a href="#propdef-font-variant"
6155 title=font-variant><strong>6.11</strong></a>
6157 <li>font-variant (descriptor), <a href="#descdef-font-variant"
6158 title="font-variant (descriptor)"><strong>4.7</strong></a>
6160 <li>font-variant-alternates, <a href="#propdef-font-variant-alternates"
6161 title=font-variant-alternates><strong>6.8</strong></a>
6163 <li>font-variant-caps, <a href="#propdef-font-variant-caps"
6164 title=font-variant-caps><strong>6.6</strong></a>
6166 <li>font-variant-east-asian, <a href="#propdef-font-variant-east-asian"
6167 title=font-variant-east-asian><strong>6.10</strong></a>
6169 <li>font-variant-ligatures, <a href="#propdef-font-variant-ligatures"
6170 title=font-variant-ligatures><strong>6.4</strong></a>
6172 <li>font-variant-ligatures normal value, <a
6173 href="#font-variant-ligatures-normal-value" title="font-variant-ligatures
6174 normal value"><strong>6.4</strong></a>
6176 <li>font-variant-numeric, <a href="#propdef-font-variant-numeric"
6177 title=font-variant-numeric><strong>6.7</strong></a>
6179 <li>font-variant-position, <a href="#propdef-font-variant-position"
6180 title=font-variant-position><strong>6.5</strong></a>
6182 <li>font-weight, <a href="#propdef-font-weight"
6183 title=font-weight><strong>3.2</strong></a>
6185 <li>font-weight (descriptor), <a href="#descdef-font-weight"
6186 title="font-weight (descriptor)"><strong>4.4</strong></a>
6188 <li>font_face_rule, <a href="#fontfacerule"
6189 title="font_face_rule"><strong>4.1</strong></a>
6191 <li>FONT_FACE_SYM, <a href="#fontfacesym"
6192 title="FONT_FACE_SYM"><strong>4.1</strong></a>
6194 <li>font_family_name, <a href="#fontfamilyname"
6195 title="font_family_name"><strong>6.9</strong></a>
6197 <li>font_family_name_list, <a href="#fontfamilynamelist"
6198 title="font_family_name_list"><strong>6.9</strong></a>
6200 <li>font_feature_values_rule, <a href="#fontfeaturevaluesrule"
6201 title="font_feature_values_rule"><strong>6.9</strong></a>
6203 <li>FONT_FEATURE_VALUES_SYM, <a href="#fontfeaturevaluessym"
6204 title="FONT_FEATURE_VALUES_SYM"><strong>6.9</strong></a>
6206 <li>full-width, <a href="#full-width"
6207 title=full-width><strong>6.10</strong></a>
6209 <li>historical-forms, <a href="#historical-forms"
6210 title=historical-forms><strong>6.8</strong></a>
6212 <li>historical-ligatures, <a href="#historical-ligatures"
6213 title=historical-ligatures><strong>6.4</strong></a>
6215 <li>jis04, <a href="#jis04" title=jis04><strong>6.10</strong></a>
6217 <li>jis78, <a href="#jis78" title=jis78><strong>6.10</strong></a>
6219 <li>jis83, <a href="#jis83" title=jis83><strong>6.10</strong></a>
6221 <li>jis90, <a href="#jis90" title=jis90><strong>6.10</strong></a>
6223 <li>lining-nums, <a href="#lining-nums"
6224 title=lining-nums><strong>6.7</strong></a>
6226 <li>monospace, definition of, <a href="#monospace0" title="monospace,
6227 definition of"><strong>#</strong></a>
6229 <li>no-common-ligatures, <a href="#no-common-ligatures"
6230 title=no-common-ligatures><strong>6.4</strong></a>
6232 <li>no-contextual, <a href="#no-contextual"
6233 title=no-contextual><strong>6.4</strong></a>
6235 <li>no-discretionary-ligatures, <a href="#no-discretionary-ligatures"
6236 title=no-discretionary-ligatures><strong>6.4</strong></a>
6238 <li>no-historical-ligatures, <a href="#no-historical-ligatures"
6239 title=no-historical-ligatures><strong>6.4</strong></a>
6241 <li>none, <a href="#font-variant-ligatures-none-value"
6242 title=none><strong>6.4</strong></a>
6244 <li>normal, <a href="#normal" title=normal><strong>6.6</strong></a>, <a
6245 href="#normal0" title=normal><strong>6.7</strong></a>, <a href="#normal1"
6246 title=normal><strong>6.8</strong></a>, <a href="#normal2"
6247 title=normal><strong>6.10</strong></a>
6249 <li>oldstyle-nums, <a href="#oldstyle-nums"
6250 title=oldstyle-nums><strong>6.7</strong></a>
6252 <li>ordinal, <a href="#ordinal" title=ordinal><strong>6.7</strong></a>
6254 <li>ornaments, <a href="#ornaments"
6255 title=ornaments><strong>6.8</strong></a>
6257 <li>petite-caps, <a href="#petite-caps"
6258 title=petite-caps><strong>6.6</strong></a>
6260 <li>proportional-nums, <a href="#proportional-nums"
6261 title=proportional-nums><strong>6.7</strong></a>
6263 <li>proportional-width, <a href="#proportional-width"
6264 title=proportional-width><strong>6.10</strong></a>
6266 <li>renderer, <a href="#renderer" title=renderer><strong>#</strong></a>
6268 <li>ruby, <a href="#ruby" title=ruby><strong>6.10</strong></a>
6270 <li>sans-serif, definition of, <a href="#sans-serif0" title="sans-serif,
6271 definition of"><strong>#</strong></a>
6273 <li>serif, definition of, <a href="#serif0" title="serif, definition
6274 of"><strong>#</strong></a>
6276 <li>simplified, <a href="#simplified"
6277 title=simplified><strong>6.10</strong></a>
6279 <li>slashed-zero, <a href="#slashed-zero"
6280 title=slashed-zero><strong>6.7</strong></a>
6282 <li>small-caps, <a href="#small-caps"
6283 title=small-caps><strong>6.6</strong></a>
6285 <li>src, <a href="#descdef-src" title=src><strong>4.3</strong></a>
6287 <li>stacked-fractions, <a href="#stacked-fractions"
6288 title=stacked-fractions><strong>6.7</strong></a>
6290 <li>style sheet
6291 <ul>
6292 <li>as conformance class, <a href="#style-sheet" title="style sheet, as
6293 conformance class"><strong>#</strong></a>
6294 </ul>
6296 <li>styleset, <a href="#styleset" title=styleset><strong>6.8</strong></a>
6298 <li>stylistic, <a href="#stylistic"
6299 title=stylistic><strong>6.8</strong></a>
6301 <li>swash, <a href="#swash" title=swash><strong>6.8</strong></a>
6303 <li>tabular-nums, <a href="#tabular-nums"
6304 title=tabular-nums><strong>6.7</strong></a>
6306 <li>titling-caps, <a href="#titling-caps"
6307 title=titling-caps><strong>6.6</strong></a>
6309 <li>traditional, <a href="#traditional"
6310 title=traditional><strong>6.10</strong></a>
6312 <li>unicase, <a href="#unicase" title=unicase><strong>6.6</strong></a>
6314 <li>unicode-range, <a href="#descdef-unicode-range"
6315 title=unicode-range><strong>4.5</strong></a>
6317 <li>weight, <a href="#weight" title=weight><strong>2</strong></a>
6319 <li>width, <a href="#width" title=width><strong>2</strong></a>
6320 </ul>
6321 <!--end-index-->
6323 <h2 class=no-num id=property-index>Property index</h2>
6324 <!--begin-properties-->
6326 <table class=proptable>
6327 <thead>
6328 <tr>
6329 <th>Property
6331 <th>Values
6333 <th>Initial
6335 <th>Applies to
6337 <th>Inh.
6339 <th>Percentages
6341 <th>Media
6343 <tbody>
6344 <tr>
6345 <th><a class=property href="#propdef-font">font</a>
6347 <td>[ [ <‘font-style’> || <font-variant-css21> ||
6348 <‘font-weight’> || <‘font-stretch’ ]?
6349 <‘font-size’> [ / <‘line-height’> ]?
6350 <‘font-family’> ] | caption | icon | menu | message-box |
6351 small-caption | status-bar
6353 <td>see individual properties
6355 <td>all elements
6357 <td>yes
6359 <td>see individual properties
6361 <td>visual
6363 <tr>
6364 <th><a class=property href="#descdef-font-family">font-family</a>
6366 <td>[ <family-name> | <generic-family> ] #
6368 <td>depends on user agent
6370 <td>all elements
6372 <td>yes
6374 <td>N/A
6376 <td>visual
6378 <tr>
6379 <th><a class=property
6380 href="#propdef-font-feature-settings">font-feature-settings</a>
6382 <td>normal | <feature-tag-value> #
6384 <td>normal
6386 <td>all elements
6388 <td>yes
6390 <td>N/A
6392 <td>visual
6394 <tr>
6395 <th><a class=property href="#propdef-font-kerning">font-kerning</a>
6397 <td>auto | normal | none
6399 <td>auto
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-language-override">font-language-override</a>
6413 <td>normal | <string>
6415 <td>normal
6417 <td>all elements
6419 <td>yes
6421 <td>N/A
6423 <td>visual
6425 <tr>
6426 <th><a class=property href="#propdef-font-size">font-size</a>
6428 <td><absolute-size> | <relative-size> | <length> |
6429 <percentage>
6431 <td>medium
6433 <td>all elements
6435 <td>yes
6437 <td>refer to parent element's font size
6439 <td>visual
6441 <tr>
6442 <th><a class=property
6443 href="#propdef-font-size-adjust">font-size-adjust</a>
6445 <td>none | auto | <number>
6447 <td>none
6449 <td>all elements
6451 <td>yes
6453 <td>N/A
6455 <td>visual
6457 <tr>
6458 <th><a class=property href="#propdef-font-stretch">font-stretch</a>
6460 <td>normal | ultra-condensed | extra-condensed | condensed |
6461 semi-condensed | semi-expanded | expanded | extra-expanded |
6462 ultra-expanded
6464 <td>normal
6466 <td>all elements
6468 <td>yes
6470 <td>N/A
6472 <td>visual
6474 <tr>
6475 <th><a class=property href="#propdef-font-style">font-style</a>
6477 <td>normal | italic | oblique
6479 <td>normal
6481 <td>all elements
6483 <td>yes
6485 <td>N/A
6487 <td>visual
6489 <tr>
6490 <th><a class=property href="#propdef-font-synthesis">font-synthesis</a>
6492 <td>none | [ weight || style ]
6494 <td>weight style
6496 <td>all elements
6498 <td>yes
6500 <td>N/A
6502 <td>visual
6504 <tr>
6505 <th><a class=property href="#propdef-font-variant">font-variant</a>
6507 <td>normal | none | [ <common-lig-values> ||
6508 <discretionary-lig-values> || <historical-lig-values> ||
6509 <contextual-alt-values> || stylistic(<feature-value-name>)
6510 || historical-forms || styleset(<feature-value-name> #) ||
6511 character-variant(<feature-value-name> #) ||
6512 swash(<feature-value-name>) ||
6513 ornaments(<feature-value-name>) ||
6514 annotation(<feature-value-name>) || [ small-caps | all-small-caps
6515 | petite-caps | all-petite-caps | unicase | titling-caps ] ||
6516 <numeric-figure-values> || <numeric-spacing-values> ||
6517 <numeric-fraction-values> || ordinal || slashed-zero ||
6518 <east-asian-variant-values> || <east-asian-width-values> ||
6519 ruby ]
6521 <td>normal
6523 <td>all elements
6525 <td>yes
6527 <td>see individual properties
6529 <td>visual
6531 <tr>
6532 <th><a class=property
6533 href="#propdef-font-variant-alternates">font-variant-alternates</a>
6535 <td>normal | [ stylistic(<feature-value-name>) || historical-forms
6536 || styleset(<feature-value-name> #) ||
6537 character-variant(<feature-value-name> #) ||
6538 swash(<feature-value-name>) ||
6539 ornaments(<feature-value-name>) ||
6540 annotation(<feature-value-name>) ]
6542 <td>normal
6544 <td>all elements
6546 <td>yes
6548 <td>N/A
6550 <td>visual
6552 <tr>
6553 <th><a class=property
6554 href="#propdef-font-variant-caps">font-variant-caps</a>
6556 <td>normal | small-caps | all-small-caps | petite-caps | all-petite-caps
6557 | unicase | titling-caps
6559 <td>normal
6561 <td>all elements
6563 <td>yes
6565 <td>N/A
6567 <td>visual
6569 <tr>
6570 <th><a class=property
6571 href="#propdef-font-variant-east-asian">font-variant-east-asian</a>
6573 <td>normal | [ <east-asian-variant-values> ||
6574 <east-asian-width-values> || ruby ]
6576 <td>normal
6578 <td>all elements
6580 <td>yes
6582 <td>N/A
6584 <td>visual
6586 <tr>
6587 <th><a class=property
6588 href="#propdef-font-variant-ligatures">font-variant-ligatures</a>
6590 <td>normal | none | [ <common-lig-values> ||
6591 <discretionary-lig-values> || <historical-lig-values> ||
6592 <contextual-alt-values> ]
6594 <td>normal
6596 <td>all elements
6598 <td>yes
6600 <td>N/A
6602 <td>visual
6604 <tr>
6605 <th><a class=property
6606 href="#propdef-font-variant-numeric">font-variant-numeric</a>
6608 <td>normal | [ <numeric-figure-values> ||
6609 <numeric-spacing-values> || <numeric-fraction-values> ||
6610 ordinal || slashed-zero ]
6612 <td>normal
6614 <td>all elements
6616 <td>yes
6618 <td>N/A
6620 <td>visual
6622 <tr>
6623 <th><a class=property
6624 href="#propdef-font-variant-position">font-variant-position</a>
6626 <td>normal | sub | super
6628 <td>normal
6630 <td>all elements
6632 <td>yes
6634 <td>N/A
6636 <td>visual
6638 <tr>
6639 <th><a class=property href="#propdef-font-weight">font-weight</a>
6641 <td>normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600
6642 | 700 | 800 | 900
6644 <td>normal
6646 <td>all elements
6648 <td>yes
6650 <td>N/A
6652 <td>visual
6653 </table>
6654 <!--end-properties-->
6655 <!--begin-descriptors-->
6657 <table class=proptable>
6658 <thead>
6659 <tr>
6660 <th>Descriptor
6662 <th>Value
6664 <th>Initial
6666 <th>Percentages
6668 <th>Media
6670 <tbody>
6671 <tr>
6672 <th><a class=property href="#descdef-font-family">font-family</a>
6674 <td><family-name>
6676 <td>N/A
6678 <tr>
6679 <th><a class=property
6680 href="#propdef-font-feature-settings">font-feature-settings</a>
6682 <td>normal | <feature-tag-value> #
6684 <td>normal
6686 <tr>
6687 <th><a class=property href="#propdef-font-stretch">font-stretch</a>
6689 <td>normal | ultra-condensed | extra-condensed | condensed |
6690 semi-condensed | semi-expanded | expanded | extra-expanded |
6691 ultra-expanded
6693 <td>normal
6695 <tr>
6696 <th><a class=property href="#propdef-font-style">font-style</a>
6698 <td>normal | italic | oblique
6700 <td>normal
6702 <tr>
6703 <th><a class=property href="#propdef-font-variant">font-variant</a>
6705 <td>normal | none | [ <common-lig-values> ||
6706 <discretionary-lig-values> || <historical-lig-values> ||
6707 <contextual-alt-values> || stylistic(<feature-value-name>)
6708 || historical-forms || styleset(<feature-value-name> #) ||
6709 character-variant(<feature-value-name> #) ||
6710 swash(<feature-value-name>) ||
6711 ornaments(<feature-value-name>) ||
6712 annotation(<feature-value-name>) || [ small-caps | all-small-caps
6713 | petite-caps | all-petite-caps | unicase | titling-caps ] ||
6714 <numeric-figure-values> || <numeric-spacing-values> ||
6715 <numeric-fraction-values> || ordinal || slashed-zero ||
6716 <east-asian-variant-values> || <east-asian-width-values> ||
6717 ruby ]
6719 <td>normal
6721 <tr>
6722 <th><a class=property href="#propdef-font-weight">font-weight</a>
6724 <td>normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
6726 <td>normal
6728 <tr>
6729 <th><a class=property href="#descdef-src">src</a>
6731 <td>[ <url> [format(<string> #)]? | <font-face-name> ] #
6733 <td>N/A
6735 <tr>
6736 <th><a class=property href="#descdef-unicode-range">unicode-range</a>
6738 <td><urange> #
6740 <td>U+0-10FFFF
6741 </table>
6742 <!--end-descriptors-->
6743 <script type="text/javascript">
6744 window.onload = function () {
6745 if (!("devicePixelRatio" in window && window.devicePixelRatio > 1)) return;
6746 var i, hiresElements = document.getElementsByClassName("hires");
6747 for (i = 0; i < hiresElements.length; i++) {
6748 var h = hiresElements[i];
6749 if (h.tagName != "IMG") continue;
6750 var src = h.getAttribute("src");
6751 var src2x = src.replace(/\.\w+$/, function(m) { return "@2x" + m; });
6752 h.src = src2x;
6753 }
6754 }
6755 </script>
6756 </html>
6757 <!-- Keep this comment at the end of the file
6758 Local variables:
6759 mode: sgml
6760 sgml-declaration:"~/SGML/HTML4.decl"
6761 sgml-default-doctype-name:"html"
6762 sgml-minimize-attributes:t
6763 sgml-nofill-elements:("pre" "style" "br")
6764 sgml-live-element-indicator:t
6765 sgml-omittag:nil
6766 sgml-shorttag:nil
6767 sgml-namecase-general:t
6768 sgml-general-insert-case:lower
6769 sgml-always-quote-attributes:t
6770 sgml-indent-step:nil
6771 sgml-indent-data:t
6772 sgml-parent-document:nil
6773 sgml-exposed-tags:nil
6774 sgml-local-catalogs:nil
6775 sgml-local-ecat-files:nil
6776 End:
6777 -->
6778 <!--
6780 to do:
6782 - wording of OpenType family name handling
6783 - handling combining sequences in the font matching algorithm
6784 - fix-up fi ligature example
6786 -->
