-
Notifications
You must be signed in to change notification settings - Fork 791
Expand file tree
/
Copy pathFonts.html
More file actions
7173 lines (5451 loc) · 261 KB
/
Fonts.html
File metadata and controls
7173 lines (5451 loc) · 261 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang=en>
<head><meta content="text/html;charset=utf-8" http-equiv=Content-Type>
<title>CSS Fonts Module Level 3</title>
<!--
FIXME when publishing: copy the current default.css and link to
"default.css" rather than "../default.css"
-->
<link href="../default.css" rel=stylesheet type="text/css">
<link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
<!-- I'm just experimenting here, don't get your bee in a bonnet -->
<script src="http://use.typekit.com/xon2bky.js"
type="text/javascript"></script>
<script type="text/javascript">try{Typekit.load();}catch(e){}</script>
<style type="text/css">
body, th, td, h1, h2, h3, h4, h5, h6 {
font-family: "myriad-pro", sans-serif !important;
}
body {
padding: 2em 70px 2em 70px;
}
p + p, p.mtb {
margin-top: 0.8em;
text-indent: 0px;
}
#bolderlighter {
width: 40%;
}
#bolderlighter th {
text-align: center;
}
#fontformats td, #eventhandlers td, #fontformats th, #eventhandlers th {
padding-right: 2em;
text-align: left;
}
dd {
margin-bottom: 1em;
}
#authors dd {
margin-bottom: 0;
}
#fontstylematchingalg {
list-style-type: lower-alpha;
}
#fontmatchingalg ul, #fontmatchingalg ol {
margin-top: 0.8em;
}
#fontmatchingalg li + li {
margin-top: 0.8em;
}
div.example {
padding: 1em;
margin-top: 1em;
}
div.example + div.example {
margin-top: 2em;
}
div.figure {
page-break-inside: avoid;
}
pre.prod { white-space: pre-wrap; margin: 1em 0 1em 2em }
div.featex {
width: 700px;
}
div.featex img {
margin: auto;
display: block;
}
span.tag {
font-family: monospace;
font-size: 120%;
}
ol ol {
list-style-type: lower-alpha;
}
.idl-code {
font-weight: bold;
color: #c50;
}
</style>
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
type="text/css">
<script defer=defer
src="http://test.csswg.org/harness/annotate.js#CSS3-FONTS_DEV"
type="text/javascript"></script>
<body>
<div class=head> <!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt=W3C height=48
src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
<h1>CSS Fonts Module Level 3</h1>
<h2 class="no-num no-toc" id=editors-draft-7-june-2013>Editor's Draft 7
June 2013</h2>
<dl id=authors>
<dt>This version:
<dd><a
href="http://dev.w3.org/csswg/css-fonts/">http://dev.w3.org/csswg/css-fonts/</a>
<!-- <dd><a href="http://www.w3.org/TR/2013/ED-css3-fonts-20130607/">http://www.w3.org/TR/2013/ED-css3-fonts-20130607/</a> -->
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-fonts/">http://www.w3.org/TR/css3-fonts/</a>
<dt>Latest editor's draft:
<dd><a
href="http://dev.w3.org/csswg/css-fonts/">http://dev.w3.org/csswg/css-fonts/</a>
(<a
href="https://dvcs.w3.org/hg/csswg/log/tip/css-fonts/Fonts.html">change
log</a>)
<dt>Previous version:
<dd><a
href="http://www.w3.org/TR/2013/WD-css3-fonts-20130212/">http://www.w3.org/TR/2013/WD-css3-fonts-20130212/</a>
<dt>Issues List:
<dd><a href="http://www.w3.org/Style/CSS/Tracker/products/18">CSS3 Fonts
issues in Tracker</a>
<dd><a
href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Fonts&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED">CSS3
Fonts issues in Bugzilla</a>
<dt>Discussion:
<dd><a
href="mailto:www-style@w3.org?subject=%5Bcss-fonts%5D%20feedback">www-style@w3.org</a>
with subject line “<kbd>[css-fonts] <var>… message topic
…</var></kbd>” (<a
href="http://lists.w3.org/Archives/Public/www-style/"
rel=discussion>archives</a>)
<dt>Editor:
<dd><a href="mailto:jdaggett@mozilla.com">John Daggett (Mozilla)</a>
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2013 <a href="http://www.w3.org/"><abbr
title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of
Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr
title="European Research Consortium for Informatics and
Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>,
<a href="http://ev.buaa.edu.cn/">Beihang</a>), All Rights Reserved. W3C
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
and <a
href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>
<!--end-copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id=abstract>Abstract</h2>
<p>This CSS3 module describes how font properties are specified and how
font resources are loaded dynamically. The contents of this specification
are a consolidation of content previously divided into <a
href="http://www.w3.org/TR/2002/WD-css3-fonts-20020802/">CSS3 Fonts</a>
and <a href="http://www.w3.org/TR/2002/WD-css3-webfonts-20020802/">CSS3
Web Fonts</a> modules. The description of font load events was moved into
the <a href="http://dev.w3.org/csswg/css3-font-load-events/">CSS3 Font
Load Events</a> module.
<h2 class="no-num no-toc" id=status>Status of this document</h2>
<!--begin-status-->
<p>This is a public copy of the editors' draft. It is provided for
discussion only and may change at any moment. Its publication here does
not imply endorsement of its contents by W3C. Don't cite this document
other than as work in progress.
<p>The (<a
href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
mailing list <a
href="mailto:www-style@w3.org?Subject=%5Bcss3-fonts%5D%20PUT%20SUBJECT%20HERE">
www-style@w3.org</a> (see <a
href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
discussion of this specification. When sending e-mail, please put the text
“css3-fonts” in the subject, preferably like this:
“[<!---->css3-fonts<!---->] <em>…summary of comment…</em>”
<p>This document was produced by the <a
href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of
the <a href="http://www.w3.org/Style/">Style Activity</a>).
<p>This document was produced by a group operating under the <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February
2004 W3C Patent Policy</a>. W3C maintains a <a
href="http://www.w3.org/2004/01/pp-impl/32061/status"
rel=disclosure>public list of any patent disclosures</a> made in
connection with the deliverables of the group; that page also includes
instructions for disclosing a patent. An individual who has actual
knowledge of a patent which the individual believes contains <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
6 of the W3C Patent Policy</a>.</p>
<!--end-status-->
<!--
<h3 class="no-num no-toc" id="atrisk">Features at risk</h3>
<p>The following features are at risk and may be removed when exiting CR:</p>
<ul>
</ul>
-->
<h2 class="no-num no-toc" id=contents>Table of contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#introduction"><span class=secno>1 </span>Introduction</a>
<li><a href="#typography-background"><span class=secno>2 </span>Typography
Background</a>
<li><a href="#basic-font-props"><span class=secno>3 </span>Basic Font
Properties</a>
<ul class=toc>
<li><a href="#font-family-prop"><span class=secno>3.1 </span>Font
family: the font-family property</a>
<ul class=toc>
<li><a href="#generic-font-families"><span class=secno>3.1.1
</span>Generic font families</a>
</ul>
<li><a href="#font-weight-prop"><span class=secno>3.2 </span>Font
weight: the font-weight property</a>
<li><a href="#font-stretch-prop"><span class=secno>3.3 </span>Font
width: the font-stretch property</a>
<li><a href="#font-style-prop"><span class=secno>3.4 </span>Font style:
the font-style property</a>
<li><a href="#font-size-prop"><span class=secno>3.5 </span>Font size:
the font-size property</a>
<li><a href="#font-size-adjust-prop"><span class=secno>3.6
</span>Relative sizing: the font-size-adjust property</a>
<li><a href="#font-prop"><span class=secno>3.7 </span>Shorthand font
property: the font property</a>
<li><a href="#font-synthesis-prop"><span class=secno>3.8
</span>Controlling synthetic faces: the font-synthesis property</a>
</ul>
<li><a href="#font-resources"><span class=secno>4 </span>Font
Resources</a>
<ul class=toc>
<li><a href="#font-face-rule"><span class=secno>4.1 </span>The
<code>@font-face</code> rule</a>
<li><a href="#font-family-desc"><span class=secno>4.2 </span>Font
family: the font-family descriptor</a>
<li><a href="#src-desc"><span class=secno>4.3 </span>Font reference: the
src descriptor</a>
<li><a href="#font-prop-desc"><span class=secno>4.4 </span>Font property
descriptors: the font-style, font-weight, font-stretch descriptors</a>
<li><a href="#unicode-range-desc"><span class=secno>4.5 </span>Character
range: the unicode-range descriptor</a>
<li><a href="#composite-fonts"><span class=secno>4.6 </span>Using
character ranges to define composite fonts</a>
<li><a href="#font-rend-desc"><span class=secno>4.7 </span>Font
features: the font-variant and font-feature-settings descriptors</a>
<li><a href="#font-face-loading"><span class=secno>4.8 </span>Font
loading guidelines</a>
<li><a href="#same-origin-restriction"><span class=secno>4.9
</span>Same-origin restriction for fonts</a>
<ul class=toc>
<li><a href="#default-same-origin-restriction"><span class=secno>4.9.1
</span>Default same-origin restriction</a>
<li><a href="#allowing-cross-origin-font-loading"><span
class=secno>4.9.2 </span>Allowing cross-origin font loading</a>
</ul>
</ul>
<li><a href="#font-matching-algorithm"><span class=secno>5 </span>Font
Matching Algorithm</a>
<ul class=toc>
<li><a href="#font-family-casing"><span class=secno>5.1 </span>Case
sensitivity of font family names</a>
<li><a href="#font-style-matching"><span class=secno>5.2 </span>Matching
font styles</a>
<li><a href="#cluster-matching"><span class=secno>5.3 </span>Cluster
matching</a>
<li><a href="#char-handling-issues"><span class=secno>5.4
</span>Character handling issues</a>
<li><a href="#font-matching-changes"><span class=secno>5.5 </span>Font
matching changes since CSS 2.1</a>
<li><a href="#font-matching-examples"><span class=secno>5.6 </span>Font
matching examples</a>
</ul>
<li><a href="#font-rend-props"><span class=secno>6 </span>Font Feature
Properties</a>
<ul class=toc>
<li><a href="#glyph-selection-positioning"><span class=secno>6.1
</span>Glyph selection and positioning</a>
<li><a href="#language-specific-support"><span class=secno>6.2
</span>Language-specific display</a>
<li><a href="#font-kerning-prop"><span class=secno>6.3 </span>Kerning:
the font-kerning property</a>
<li><a href="#font-variant-ligatures-prop"><span class=secno>6.4
</span>Ligatures: the font-variant-ligatures property</a>
<li><a href="#font-variant-position-prop"><span class=secno>6.5
</span>Subscript and superscript forms: the font-variant-position
property</a>
<li><a href="#font-variant-caps-prop"><span class=secno>6.6
</span>Capitalization: the font-variant-caps property</a>
<li><a href="#font-variant-numeric-prop"><span class=secno>6.7
</span>Numerical formatting: the font-variant-numeric property</a>
<li><a href="#font-variant-alternates-prop"><span class=secno>6.8
</span>Alternates and swashes: the font-variant-alternates property</a>
<li><a href="#font-feature-values"><span class=secno>6.9 </span>Defining
font specific alternates: the <code>@font-feature-values</code>
rule</a>
<ul class=toc>
<li><a href="#basic-syntax"><span class=secno>6.9.1 </span>Basic
syntax</a>
<li><a href="#multi-valued-feature-value-definitions"><span
class=secno>6.9.2 </span>Multi-valued feature value definitions</a>
</ul>
<li><a href="#font-variant-east-asian-prop"><span class=secno>6.10
</span>East Asian text rendering: the font-variant-east-asian
property</a>
<li><a href="#font-variant-prop"><span class=secno>6.11 </span>Overall
shorthand for font rendering: the font-variant property</a>
<li><a href="#font-feature-settings-prop"><span class=secno>6.12
</span>Low-level font feature settings control: the
font-feature-settings property</a>
<li><a href="#font-language-override-prop"><span class=secno>6.13
</span>Font language override: the font-language-override property</a>
</ul>
<li><a href="#font-feature-resolution"><span class=secno>7 </span>Font
Feature Resolution </a>
<ul class=toc>
<li><a href="#default-features"><span class=secno>7.1 </span>Default
features</a>
<li><a href="#feature-precedence"><span class=secno>7.2 </span>Feature
precedence</a>
<li><a href="#feature-precedence-examples"><span class=secno>7.3
</span>Feature precedence examples</a>
</ul>
<li><a href="#object-model"><span class=secno>8 </span>Object Model</a>
<ul class=toc>
<li><a href="#om-fontface"><span class=secno>8.1 </span>The
<code>CSSFontFaceRule</code> interface</a>
<li><a href="#om-fontfeaturevalues"><span class=secno>8.2 </span>The
<code>CSSFontFeatureValuesRule</code> interface</a>
</ul>
<li class=no-num><a href="#platform-props-to-css">Appendix A: Mapping
platform font properties to CSS properties</a>
<li class=no-num><a href="#ch-ch-ch-changes">Changes</a>
<ul class=toc>
<li class=no-num><a href="#recent-changes"> Changes from the February
2013 CSS3 Fonts Working Draft</a>
</ul>
<li class=no-num><a href="#acknowledgments">Acknowledgments</a>
<li class=no-num><a href="#conformance"> Conformance</a>
<ul class=toc>
<li class=no-num><a href="#conventions"> Document Conventions</a>
<li class=no-num><a href="#conformance-classes"> Conformance Classes</a>
<li class=no-num><a href="#partial"> Partial Implementations</a>
<li class=no-num><a href="#experimental"> Experimental
Implementations</a>
<li class=no-num><a href="#testing"> Non-Experimental
Implementations</a>
</ul>
<li class=no-num><a href="#references">References</a>
<ul class=toc>
<li class=no-num><a href="#normative-references">Normative
References</a>
<li class=no-num><a href="#other-references">Other References</a>
</ul>
<li class=no-num><a href="#index">Index</a>
<li class=no-num><a href="#property-index">Property index</a>
</ul>
<!--end-toc-->
<h2 id=introduction><span class=secno>1 </span>Introduction</h2>
<p>A font provides a resource containing the visual representation of
characters. At the simplest level it contains information that maps
character codes to shapes (called glyphs) that represent these characters.
Fonts sharing a common design style are commonly grouped into font
families classified by a set of standard font properties. Within a family,
the shape displayed for a given character can vary by stroke weight, slant
or relative width, among others. An individual font face is described by a
unique combination of these properties. For a given range of text, CSS
font properties are used to select a font family and a specific font face
within that family to be used when rendering that text. As a simple
example, to use the bold form of Helvetica one could use:
<pre>body {
font-family: Helvetica;
font-weight: bold;
}</pre>
<p>Font resources may be installed locally on the system on which a user
agent is running or downloadable. For local font resources descriptive
information can be obtained directly from the font resource. For
downloadable font resources (sometimes referred to as web fonts), the
descriptive information is included with the reference to the font
resource.
<p>Families of fonts typically don't contain a single face for each
possible variation of font properties. The CSS font selection mechanism
describes how to match a given set of CSS font properties to a single font
face.
<h2 id=typography-background><span class=secno>2 </span>Typography
Background</h2>
<p><em>This section is non-normative.</em>
<p> Typographic traditions vary across the globe, so there is no unique way
to classify all fonts across languages and cultures. For even common Latin
letters, wide variations are possible:
<div class=figure><img alt="variations in glyphs for a single character"
src=aaaaaa.png>
<p class=caption>One character, many glyph variations
</div>
<p>Differences in the anatomy of letterforms is one way to distinguish
fonts. For Latin fonts, flourishes at the ends of a character's main
strokes, or serifs, can distinguish a font from those without. Similar
comparisons exist in non-Latin fonts between fonts with tapered strokes
and those using primarily uniform strokes:
<div class=figure><img alt="serif vs. non-serifs" src=serifvssansserif.png>
<p class=caption>Letterforms with and without serifs
</div>
<div class=figure><img alt="serif vs. non-serifs for japanese"
src=minchovsgothic.png>
<p class=caption>Similar groupings for Japanese typefaces
</div>
<p>Fonts contain letterforms and the data needed to map characters to these
letterforms. Often this may be a simple one-to-one mapping, but more
complex mappings are also possible. The use of combining diacritic marks
creates many variations for an underlying letterform:
<div class=figure><img alt="diacritic marks" src=aaaaaa-diacritics.png>
<p class=caption>Variations with diacritic marks
</div>
<p>A sequence of characters can be represented by a single glyph known as a
ligature:
<div class=figure><img alt="example of a fi ligature"
src=final-ligature.png>
<p class=caption>Ligature example
</div>
<p>Visual transformations based on textual context are often stylistic
option in European languages. They are required to correctly render
languages like Arabic, the lam and alef characters below <em>must</em> be
combined when they exist in sequence:
<div class=figure><img alt="lam alef ligature" src=lamaleflig.png>
<p class=caption>Required Arabic ligature
</div>
<p>The relative complexity of these shaping transformations requires
additional data within the font.
<p>Sets of font faces with various stylistic variations are often grouped
together into font families. In the simplest case a regular face is
supplemented with bold and italic faces, but much more extensive groupings
are possible. Variations in the thickness of letterform strokes, the <dfn
id=weight>weight</dfn>, and the overall proportions of the letterform, the
<dfn id=width>width</dfn>, are most common. In the example below, each
letter uses a different font face within the Univers font family. The
width used increases from top to bottom and the weight increases from left
to right:
<div class=figure><img alt="various width and weight variations within a
single family" src=weightwidthvariations.png>
<p class=caption>Weight and width variations within a single font family
</div>
<p>Creating fonts that support multiple scripts is a difficult task;
designers need to understand the cultural traditions surrounding the use
of type in different scripts and come up with letterforms that somehow
share a common theme. Many languages often share a common script and each
of these languages may have noticeable stylistic differences. For example,
the Arabic script is shared by Persian and Urdu and Cyrillic is used with
many languages, not just Russian.
<p>The <a href="#character-map"><em>character map</em></a> of a font
defines the mapping of characters to glyphs for that font. If a document
contains characters not supported by the <a href="#character-map"><em
title="character map">character maps</em></a> of the fonts contained in a
font family list, a user agent may use a <a
href="#system-font-fallback"><em>system font fallback</em></a> procedure
to locate an appropriate font that does. If no appropriate font can be
found, some form of "missing glyph" character will be rendered by the user
agent. System fallback can occur when the specified list of font families
does not include a font that supports a given character.
<p>Although the <a href="#character-map"><em>character map</em></a> of a
font maps a given character to a glyph for that character, modern font
technologies such as OpenType and AAT (Apple Advanced Typography) provide
ways of mapping a character to different glyphs based upon feature
settings. Fonts in these formats allow these features to be embedded in
the font itself and controlled by applications. Common typographic
features which can be specified this way include ligatures, swashes,
contextual alternates, proportional and tabular figures, and automatic
fractions, to list just a few. For a visual overview of OpenType features,
see the <a href="#OPENTYPE-FONT-GUIDE"
rel=biblioentry>[OPENTYPE-FONT-GUIDE]<!--{{OPENTYPE-FONT-GUIDE}}--></a>.
<h2 id=basic-font-props><span class=secno>3 </span>Basic Font Properties</h2>
<p>The particular font face used to render a character is determined by the
font family and other font properties that apply to a given element. This
structure allows settings to be varied independent of each other.</p>
<!-- prop: font-family -->
<h3 id=font-family-prop><span class=secno>3.1 </span>Font family: the <a
href="#propdef-font-family">font-family</a> property</h3>
<table class=propdef id=namefont-familyvalue-ltfamily-namegt-ltg>
<tbody>
<tr>
<td>Name:
<td><dfn id=propdef-font-family
title="font-family!!property">font-family</dfn>
<tr>
<td>Value:
<td>[ <a href="#family-name-value"><var><family-name></var></a> |
<a href="#generic-family-value"><var><generic-family></var></a> ]
#
<tr>
<td>Initial:
<td>depends on user agent
<tr>
<td>Applies to:
<td>all elements
<tr>
<td>Inherited:
<td>yes
<tr>
<td>Percentages:
<td>N/A
<tr>
<td>Media:
<td>visual
<tr>
<td>Computed value:
<td>as specified
<tr>
<td>Animatable:
<td>no
</table>
<p>This property specifies a prioritized list of font family names or
generic family names. A font family defines a set of faces that vary in
weight, width or slope. CSS uses the combination of a family name with
other style attributes to select an individual face. Using this selection
mechanism, rather than selecting a face via the style name as is often
done in design applications, allows some degree of regularity in textual
display when fallback occurs.
<p class=note>Designers should note that the CSS definition of font
attributes used for selection are explicitly not intended to define a font
taxonomy. A type designer's idea of a family may often extend to a set of
faces that vary along axes other than just the standard axes of weight,
width and slope. A family may extend to include both a set of serif faces
and a set of sans-serif faces or vary along axes that are unique to that
family. The CSS font selection mechanism merely provides a way to
determine the “closest” substitute when substitution is necessary.
<p>Unlike other CSS properties, component values are a comma-separated list
indicating alternatives. A user agent iterates through the list of family
names until it matches an available font that contains a glyph for the
character to be rendered. This allows for differences in available fonts
across platforms and for differences in the range of characters supported
by individual fonts.
<p>A font family name only specifies a name given to a set of font faces,
it does not specify an individual face. For example, given the
availability of the fonts below, Futura would match but Futura Medium
would not:
<div class=figure><img alt="family and face names"
src=familyvsfacename.png>
<p class=caption>Family and individual face names
</div>
<p>Consider the example below:
<div class=example>
<pre>body {
font-family: Helvetica, Verdana, sans-serif;
}</pre>
<p>If Helvetica is available it will be used when rendering. If neither
Helvetica nor Verdana is present, then the user-agent-defined sans serif
font will be used.</p>
</div>
<p>There are two types of font family names:
<dl>
<dt><dfn id=family-name-value><var><family-name></var></dfn>
<dd>The name of a font family of choice such as Helvetica or Verdana in
the previous example.
<dt><dfn id=generic-family-value><var><generic-family></var></dfn>
<dd> The following generic family keywords are defined: ‘<a
href="#serif"><code class=property>serif</code></a>’, ‘<a
href="#sans-serif"><code class=property>sans-serif</code></a>’, ‘<a
href="#cursive"><code class=property>cursive</code></a>’, ‘<a
href="#fantasy"><code class=property>fantasy</code></a>’, and ‘<a
href="#monospace"><code class=property>monospace</code></a>’. These
keywords can be used as a general fallback mechanism when an author's
desired font choices are not available. As keywords, they must not be
quoted. Authors are encouraged to append a generic font family as a last
alternative for improved robustness.
</dl>
<p>Font family names other than generic families must either be given
quoted as <a
href="//www.w3.org/TR/CSS21/syndata.html#strings">strings,</a> or unquoted
as a sequence of one or more <a
href="//www.w3.org/TR/CSS21/syndata.html#value-def-identifier">identifiers.</a>
This means most punctuation characters and digits at the start of each
token must be escaped in unquoted font family names.
<p>To illustrate this, the following declarations are invalid:
<pre>
font-family: Red/Black, sans-serif;
font-family: "Lucida" Grande, sans-serif;
font-family: Ahem!, sans-serif;
font-family: test@foo, sans-serif;
font-family: #POUND, sans-serif;
font-family: Hawaii 5-0, sans-serif;
</pre>
<p>If a sequence of identifiers is given as a font family name, the
computed value is the name converted to a string by joining all the
identifiers in the sequence by single spaces.
<p>To avoid mistakes in escaping, it is recommended to quote font family
names that contain white space, digits, or punctuation characters other
than hyphens:
<pre>
body { font-family: "New Century Schoolbook", serif }
<BODY STYLE="font-family: '21st Century', fantasy">
</pre>
<p>Font family <em>names</em> that happen to be the same as a keyword value
(‘<code class=property>inherit</code>’, ‘<a href="#serif"><code
class=property>serif</code></a>’, ‘<a href="#sans-serif"><code
class=property>sans-serif</code></a>’, ‘<a href="#monospace"><code
class=property>monospace</code></a>’, ‘<a href="#fantasy"><code
class=property>fantasy</code></a>’, and ‘<a href="#cursive"><code
class=property>cursive</code></a>’) must be quoted to prevent confusion
with the keywords with the same names. The keywords ‘<code
class=property>initial</code>’ and ‘<code
class=property>default</code>’ are reserved for future use and must also
be quoted when used as font names. UAs must not consider these keywords as
matching the <a
href="#family-name-value"><var><family-name></var></a> type.
<p>The precise way a set of fonts are grouped into font families varies
depending upon the platform font management API's. The Windows GDI API
only allows four faces to be grouped into a family while the DirectWrite
API and API's on OSX and other platforms support font families with a
variety of weights, widths and slopes (see <a
href="#platform-props-to-css">Appendix A</a> for more details).
<p>Some font formats allow fonts to carry multiple localizations of the
family name. User agents must recognize and correctly match all of these
names independent of the underlying platform localization, system API used
or document encoding:
<div class=figure><img alt="examples of localized family names"
src=localizedfamilynames.png>
<p class=caption>Localized family names
</div>
<h4 id=generic-font-families><span class=secno>3.1.1 </span>Generic font
families</h4>
<p>All five generic font families are defined to exist in all CSS
implementations (they need not necessarily map to five distinct actual
fonts). User agents should provide reasonable default choices for the
generic font families, which express the characteristics of each family as
well as possible within the limits allowed by the underlying technology.
User agents are encouraged to allow users to select alternative choices
for the generic fonts.
<h5 class="no-num no-toc"> <span class=index-def id=serif0 title="serif,
definition of"><a name=serif-def><dfn id=serif>serif</dfn></a></span></h5>
<p>Serif fonts represent the formal text style for a script. This often
means but is not limited to glyphs that have finishing strokes, flared or
tapering ends, or have actual serifed endings (including slab serifs).
Serif fonts are typically proportionately-spaced. They often display a
greater variation between thick and thin strokes than fonts from the ‘<a
href="#sans-serif"><code class=property>sans-serif</code></a>’ generic
font family. CSS uses the term ‘<a href="#serif"><code
class=property>serif</code></a>’ to apply to a font for any script,
although other names may be more familiar for particular scripts, such as
Mincho (Japanese), Sung, Song or Kai (Chinese), Batang (Korean). For
Arabic, the Naskh style would correspond to ‘<a href="#serif"><code
class=property>serif</code></a>’ more due to its typographic role rather
than its actual design style. Any font that is so described may be used to
represent the generic ‘<a href="#serif"><code
class=property>serif</code></a>’ family.
<div class=figure><img alt="sample serif fonts" src=serifexamples.png>
<p class=caption>Sample serif fonts
</div>
<h5 class="no-num no-toc"> <span class=index-def id=sans-serif0
title="sans-serif, definition of"> <a name=sans-serif-def><dfn
id=sans-serif>sans-serif</dfn></a></span></h5>
<p>Glyphs in sans-serif fonts, as the term is used in CSS, are generally
low contrast (vertical and horizontal stems have the close to the same
thickness) and have stroke endings that are plain -- without any flaring,
cross stroke, or other ornamentation. Sans-serif fonts are typically
proportionately-spaced. They often have little variation between thick and
thin strokes, compared to fonts from the ‘<a href="#serif"><code
class=property>serif</code></a>’ family. CSS uses the term ‘<a
href="#sans-serif"><code class=property>sans-serif</code></a>’ to apply
to a font for any script, although other names may be more familiar for
particular scripts, such as Gothic (Japanese), Hei (Chinese), or Gulim
(Korean). Any font that is so described may be used to represent the
generic ‘<a href="#sans-serif"><code
class=property>sans-serif</code></a>’ family.
<div class=figure><img alt="sample sans-serif fonts"
src=sansserifexamples.png>
<p class=caption>Sample sans-serif fonts
</div>
<h5 class="no-num no-toc"> <span class=index-def id=cursive0
title="cursive, definition of"> <a name=cursive-def><dfn
id=cursive>cursive</dfn></a></span></h5>
<p>Glyphs in cursive fonts generally use a more informal script style, and
the result looks more like handwritten pen or brush writing than printed
letterwork. CSS uses the term ‘<a href="#cursive"><code
class=property>cursive</code></a>’ to apply to a font for any script,
although other names such as Chancery, Brush, Swing and Script are also
used in font names.
<div class=figure><img alt="sample cursive fonts" src=cursiveexamples.png>
<p class=caption>Sample cursive fonts
</div>
<h5 class="no-num no-toc"> <span class=index-def id=fantasy0
title="fantasy, definition of"> <a name=fantasy-def><dfn
id=fantasy>fantasy</dfn></a></span></h5>
<p>Fantasy fonts are primarily decorative or expressive fonts that contain
playful representations of characters. These do not include Pi or Picture
fonts which do not represent actual characters.
<div class=figure><img alt="sample fantasy fonts" src=fantasyexamples.png>
<p class=caption>Sample fantasy fonts
</div>
<h5 class="no-num no-toc"> <span class=index-def id=monospace0
title="monospace, definition of"> <a name=monospace-def><dfn
id=monospace>monospace</dfn></a></span></h5>
<p>The sole criterion of a monospace font is that all glyphs have the same
fixed width. This is often used to render samples of computer code.
<div class=figure><img alt="sample monospace fonts"
src=monospaceexamples.png>
<p class=caption>Sample monospace fonts
</div>
<!-- prop: font-weight -->
<h3 id=font-weight-prop><span class=secno>3.2 </span>Font weight: the <a
href="#propdef-font-weight">font-weight</a> property</h3>
<table class=propdef id=namefont-weightvaluenormal-bold-bolder-l>
<tbody>
<tr>
<td>Name:
<td><dfn id=propdef-font-weight
title="font-weight!!property">font-weight</dfn>
<tr>
<td>Value:
<td><a href="#font-weight-normal-value"
title="normal!!font-weight">normal</a> | <a href="#bold">bold</a> | <a
href="#bolder">bolder</a> | <a href="#lighter">lighter</a> | <a
href="#font-weight-numeric-values" title="100...900 weight
values">100</a> | <a href="#font-weight-numeric-values"
title="100...900 weight values">200</a> | <a
href="#font-weight-numeric-values" title="100...900 weight
values">300</a> | <a href="#font-weight-numeric-values"
title="100...900 weight values">400</a> | <a
href="#font-weight-numeric-values" title="100...900 weight
values">500</a> | <a href="#font-weight-numeric-values"
title="100...900 weight values">600</a> | <a
href="#font-weight-numeric-values" title="100...900 weight
values">700</a> | <a href="#font-weight-numeric-values"
title="100...900 weight values">800</a> | <a
href="#font-weight-numeric-values" title="100...900 weight
values">900</a>
<tr>
<td>Initial:
<td>normal
<tr>
<td>Applies to:
<td>all elements
<tr>
<td>Inherited:
<td>yes
<tr>
<td>Percentages:
<td>N/A
<tr>
<td>Media:
<td>visual
<tr>
<td>Computed value:
<td>numeric weight value (see description)
<tr>
<td>Animatable:
<td>as <a
href="http://dev.w3.org/csswg/css3-transitions/#animtype-font-weight">font
weight</a>
</table>
<p>The <a href="#propdef-font-weight"
title="font-weight!!property">‘<code
class=property>font-weight</code>’</a> property specifies the weight of
glyphs in the font, their degree of blackness or stroke thickness.
<p>Values have the following meanings:
<dl>
<dt><dfn id=font-weight-numeric-values title="100...900 weight values">100
to 900</dfn>
<dd>These values form an ordered sequence, where each number indicates a
weight that is at least as dark as its predecessor. These roughly
correspond to the commonly used weight names below:
</dl>
<ul>
<li>100 - Thin
<li>200 - Extra Light (Ultra Light)
<li>300 - Light
<li>400 - Normal
<li>500 - Medium
<li>600 - Semi Bold (Demi Bold)
<li>700 - Bold
<li>800 - Extra Bold (Ultra Bold)
<li>900 - Black (Heavy)
</ul>
<dl>
<dt><dfn id=font-weight-normal-value
title="normal!!font-weight">normal</dfn>
<dd>Same as ‘<code class=css>400</code>’.