-
Notifications
You must be signed in to change notification settings - Fork 790
Expand file tree
/
Copy pathOverview.html
More file actions
7155 lines (5055 loc) · 219 KB
/
Overview.html
File metadata and controls
7155 lines (5055 loc) · 219 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
4B74
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 Text Level 4</title>
<link href="../default.css" rel=stylesheet type="text/css">
<style type="text/css">
.egbidiwsaA,.egbidiwsbB,.egbidiwsaB,.egbidiwsbC
{ white-space:pre;font-size:80%;font-family:monospace; vertical-align:2px; margin:1px }
.egbidiwsaA { background:lime;padding:2px; }
.egbidiwsbB { border:2px solid blue }
.egbidiwsaB { background:yellow;border:2px dotted white }
.egbidiwsbC { border:2px dotted red }
.char { border: 1px dotted gray; }
.quarter { font-size: 25%; }
tt[lang="ja"] { font-family: "MS Gothic", "Osaka", monospace }
</style>
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
type="text/css">
<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 Text Level 4</h1>
<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 6 January 2012</h2>
<dl>
<dt>This version:
<dd><a href="http://dev.w3.org/csswg/css3-text/">$Date: 2012/01/06
22:37:37 $ (CVS $Revision$)</a> <!--
<dd><a href="http://www.w3.org/TR/2012/WD-css3-text-20120106/">http://www.w3.org/TR/2012/WD-css3-text-20120106/</a></dd>
-->
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-text">http://www.w3.org/TR/css3-text</a>
<dt>Latest editor's draft:
<dd><a
href="http://dev.w3.org/csswg/css3-text/">http://dev.w3.org/csswg/css3-text/</a>
<dt>Previous version:
<dd><a
href="http://www.w3.org/TR/2011/WD-css3-text-20110901/">http://www.w3.org/TR/2011/WD-css3-text-20110901/</a>
<dt>Editors:
<dd><a href="http://fantasai.inkedblade.net/contact">Elika J. Etemad</a>
(Mozilla)
<dd><a href="mailto:kojiishi@gluesoft.co.jp">Koji Ishii</a> (Invited
Expert)
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2012 <a
href="http://www.w3.org/"><acronym
title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><acronym
title="Massachusetts Institute of Technology">MIT</acronym></a>, <a
href="http://www.ercim.eu/"><acronym
title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>,
<a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
and <a
href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>
<!--end-copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id=abstract>Abstract</h2>
<p>This CSS3 module defines properties for text manipulation and specifies
their processing model. It covers line breaking, justification and
alignment, white space handling, text decoration and text transformation.
<h2 class="no-num no-toc" id=status>Status of This Document</h2>
<p><em>This section describes the status of this document at the time of
its publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical report
can be found in the <a href="http://www.w3.org/TR/">W3C technical reports
index at http://www.w3.org/TR/.</a></em>
<p>Publication as a Working Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or
obsoleted by other documents at any time. It is inappropriate to cite this
document as other than work in progress.
<p>This CSS module has been produced as a combined effort of the <a
href="http://www.w3.org/International/Activity">W3C Internationalization
Activity</a>, and the <a href="http://www.w3.org/Style/Activity">Style
Activity</a> and is maintained by the <a
href="http://www.w3.org/Style/CSS/members">CSS Working Group</a>. It also
includes contributions made by participants in the <a
href="http://www.w3.org/Style/XSL/Group/">XSL Working Group</a> (<a
href="http://cgi.w3.org/MemberAccess/AccessRequest">members only</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><strong>Feedback on this draft should be posted to the (<a
href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
mailing list <a
href="mailto:www-style@w3.org">www-style@w3.org</a></strong> (see <a
href="http://www.w3.org/Mail/Request">instructions</a>) <strong>with
<kbd>[css3-text]</kbd> in the subject line.</strong> You are strongly
encouraged to complain if you see something stupid in this draft. The
editors will do their best to respond to all feedback.
<p><strong>If you have implemented properties from the <a
href="http://www.w3.org/TR/2003/CR-css3-text-20030514/">May 2003 CSS3 Text
CR</a></strong> <em>please</em> let us know so we can take that into
account as we redraft the spec. You can post to <a
href="http://lists.w3.org/Archives/Public/www-style/">www-style</a>
(public), post to the <a
href="http://lists.w3.org/Archives/Member/w3c-css-wg/">CSS WG mailing
list</a> (<a
href="http://cgi.w3.org/MemberAccess/AccessRequest">Member-restricted</a>),
or <a href="http://fantasai.inkedblade.net/contact">email fantasai
directly</a> (personal).
<p>The following features are at risk and may be cut from the spec during
its CR period if there are no (correct) implementations:
<ul>
<li>the <length> values of the ‘<a href="#tab-size0"><code
class=property>tab-size</code></a>’ property
<li>the ‘<a href="#hanging-punctuation0"><code
class=property>hanging-punctuation</code></a>’ property
<li>the percentage values of ‘<a href="#letter-spacing0"><code
class=property>letter-spacing</code></a>’ and ‘<a
href="#word-spacing0"><code class=property>word-spacing</code></a>’
<li>the ‘<code class=css>hyphenate-limit-*</code>’ properties
<li>the ‘<a href="#text-spacing"><code
class=property>text-spacing</code></a>’ property
<li>the ‘<a href="#text-decoration-skip0"><code
class=property>text-decoration-skip</code></a>’ property /
‘<code class=css>ink</code>’ value
<li>the ‘<a href="#text-emphasis-skip0"><code
class=property>text-emphasis-skip</code></a>’ property
<li><span class=issue>audit draft and add more here</span>
</ul>
<h2 class="no-num no-toc" id=contents> Table of Contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#intro"><span class=secno>1. </span> Introduction</a>
<ul class=toc>
<li><a href="#placement"><span class=secno>1.1. </span> Module
Interactions</a>
<li><a href="#values"><span class=secno>1.2. </span> Values</a>
<li><a href="#terms"><span class=secno>1.3. </span> Terminology</a>
</ul>
<li><a href="#transforming"><span class=secno>2. </span> Transforming
Text</a>
<ul class=toc>
<li><a href="#text-transform"><span class=secno>2.1. </span>
Transforming Text: the ‘<code
class=property>text-transform</code>’ property</a>
</ul>
<li><a href="#white-space-processing"><span class=secno>3. </span> White
Space Processing</a>
<ul class=toc>
<li><a href="#white-space-collapsing"><span class=secno>3.1. </span>
White Space Collapsing: the ‘<code
class=property>text-space-collapse</code>’ property</a>
<li><a href="#tab-size"><span class=secno>3.2. </span> Tab Character
Size: the ‘<code class=property>tab-size</code>’
property</a>
<li><a href="#white-space-rules"><span class=secno>3.3. </span> The
White Space Processing Rules</a>
<ul class=toc>
<li><a href="#egbidiwscollapse"><span class=secno>3.3.1. </span>
Example of bidirectionality with white space collapsing</a>
<li><a href="#line-break-transform"><span class=secno>3.3.2. </span>
Line Feed Transformation Rules</a>
<li><a href="#white-space-summary"><span class=secno>3.3.3. </span>
Informative Summary of White Space Collapsing Effects</a>
</ul>
<li><a href="#white-space"><span class=secno>3.4. </span> White Space
and Text Wrapping Shorthand: the ‘<code
class=property>white-space</code>’ property</a>
</ul>
<li><a href="#line-breaking"><span class=secno>4. </span> Line Breaking
and Word Boundaries</a>
<ul class=toc>
<li><a href="#line-break"><span class=secno>4.1. </span> Line Breaking
Strictness: the ‘<code class=property>line-break</code>’
property</a>
<li><a href="#word-break"><span class=secno>4.2. </span> Word Breaking
Rules: the ‘<code class=property>word-break</code>’
property</a>
</ul>
<li><a href="#hyphenation"><span class=secno>5. </span>Hyphenation</a>
<ul class=toc>
<li><a href="#hyphens"><span class=secno>5.1. </span>Hyphenation
Control: the ‘<code class=property>hyphens</code>’
property</a>
<li><a href="#hyphenate-character"><span class=secno>5.2. </span>
Hyphens: the ‘<code
class=property>hyphenate-character</code>’ property</a>
<li><a href="#hyphenate-size-limits"><span class=secno>5.3. </span>
Hyphenation Size Limit: the ‘<code
class=property>hyphenate-limit-zone</code>’ property</a>
<li><a href="#hyphenate-char-limits"><span class=secno>5.4. </span>
Hyphenation Character Limits: the ‘<code
class=property>hyphenate-limit-chars</code>’ property</a>
<li><a href="#hyphenate-line-limits"><span class=secno>5.5. </span>
Hyphenation Line Limits: the ‘<code
class=property>hyphenate-limit-lines</code>’ and ‘<code
class=property>hyphenate-limit-last</code>’ properties</a>
</ul>
<li><a href="#wrapping"><span class=secno>6. </span> Text Wrapping</a>
<ul class=toc>
<li><a href="#text-wrap"><span class=secno>6.1. </span> Text Wrap
Settings: the ‘<code class=property>text-wrap</code>’
property</a>
<ul class=toc>
<li><a href="#example-avoid"><span class=secno>6.1.1. </span> Example
of using ‘<code class=css>text-wrap: avoid</code>’ in
presenting a footer</a>
</ul>
<li><a href="#overflow-wrap"><span class=secno>6.2. </span> Emergency
Wrapping: the ‘<code class=property>overflow-wrap</code>’
property</a>
</ul>
<li><a href="#justification"><span class=secno>7. </span> Alignment and
Justification</a>
<ul class=toc>
<li><a href="#text-align"><span class=secno>7.1. </span> Text Alignment:
the ‘<code class=property>text-align</code>’ property</a>
<ul class=toc>
<li><a href="#character-alignment"><span class=secno>7.1.1.
</span>Details on Character-based Alignment in a Table Column</a>
</ul>
<li><a href="#text-align-last"><span class=secno>7.2. </span> Last Line
Alignment: the ‘<code
class=property>text-align-last</code>’ property</a>
<li><a href="#text-justify"><span class=secno>7.3. </span> Justification
Method: the ‘<code class=property>text-justify</code>’
property</a>
</ul>
<li><a href="#spacing"><span class=secno>8. </span> Spacing</a>
<ul class=toc>
<li><a href="#word-spacing"><span class=secno>8.1. </span> Word Spacing:
the ‘<code class=property>word-spacing</code>’ property</a>
<li><a href="#letter-spacing"><span class=secno>8.2. </span> Tracking:
the ‘<code class=property>letter-spacing</code>’
property</a>
<li><a href="#text-spacing-prop"><span class=secno>8.3. </span>
Character Class Spacing: the ‘<code
class=property>text-spacing</code>’ property</a>
<ul class=toc>
<li><a href="#fullwidth-collapsing"><span class=secno>8.3.1. </span>
Fullwidth Punctuation Collapsing</a>
<li><a href="#text-spacing-classes"><span class=secno>8.3.2. </span>
Text Spacing Character Classes</a>
</ul>
</ul>
<li><a href="#edge-effects"><span class=secno>9. </span> Edge Effects</a>
<ul class=toc>
<li><a href="#text-indent"><span class=secno>9.1. </span> First Line
Indentation: the ‘<code class=property>text-indent</code>’
property</a>
<li><a href="#hanging-punctuation"><span class=secno>9.2. </span>
Hanging Punctuation: the ‘<code
class=property>hanging-punctuation</code>’ property</a>
</ul>
<li><a href="#decoration"><span class=secno>10. </span> Text
Decoration</a>
<ul class=toc>
<li><a href="#line-decoration"><span class=secno>10.1. </span> Line
Decoration: Underline, Overline, and Strike-Through</a>
<ul class=toc>
<li><a href="#text-decoration-line"><span class=secno>10.1.1. </span>
Text Decoration Lines: the ‘<code
class=property>text-decoration-line</code>’ property</a>
<li><a href="#text-decoration-color"><span class=secno>10.1.2. </span>
Text Decoration Color: the ‘<code
class=property>text-decoration-color</code>’ property</a>
<li><a href="#text-decoration-style"><span class=secno>10.1.3. </span>
Text Decoration Style: the ‘<code
class=property>text-decoration-style</code>’ property</a>
<li><a href="#text-decoration"><span class=secno>10.1.4. </span> Text
Decoration Shorthand: the ‘<code
class=property>text-decoration</code>’ property</a>
<li><a href="#text-decoration-skip"><span class=secno>10.1.5. </span>
Text Decoration Line Continuity: the ‘<code
class=property>text-decoration-skip</code>’ property</a>
<li><a href="#text-underline-position"><span class=secno>10.1.6.
</span> Text Underline Position: the ‘<code
class=property>text-underline-position</code>’ property</a>
</ul>
<li><a href="#emphasis-marks"><span class=secno>10.2. </span> Emphasis
Marks</a>
<ul class=toc>
<li><a href="#text-emphasis-style"><span class=secno>10.2.1. </span>
Emphasis Mark Style: the ‘<code
class=property>text-emphasis-style</code>’ property</a>
<li><a href="#text-emphasis-color"><span class=secno>10.2.2. </span>
Emphasis Mark Color: the ‘<code
class=property>text-emphasis-color</code>’ property</a>
<li><a href="#text-emphasis"><span class=secno>10.2.3. </span>
Emphasis Mark Shorthand: the ‘<code
class=property>text-emphasis</code>’ property</a>
<li><a href="#text-emphasis-position"><span class=secno>10.2.4.
</span> Emphasis Mark Position: the ‘<code
class=property>text-emphasis-position</code>’ property</a>
<li><a href="#text-emphasis-skip"><span class=secno>10.2.5. </span>
Emphasis Mark Skip: the ‘<code
class=property>text-emphasis-skip</code>’ property</a>
</ul>
<li><a href="#text-shadow"><span class=secno>10.3. </span> Text Shadows:
the ‘<code class=property>text-shadow</code>’ property</a>
</ul>
<li><a href="#conformance"><span class=secno>11. </span> Conformance</a>
<ul class=toc>
<li><a href="#conventions"><span class=secno>11.1. </span> Document
Conventions</a>
<li><a href="#conformance-classes"><span class=secno>11.2. </span>
Conformance Classes</a>
<li><a href="#partial"><span class=secno>11.3. </span> Partial
Implementations</a>
<li><a href="#experimental"><span class=secno>11.4. </span> Experimental
Implementations</a>
<li><a href="#testing"><span class=secno>11.5. </span>Non-Experimental
Implementations</a>
<li><a href="#cr-exit-criteria"><span class=secno>11.6. </span> CR Exit
Criteria</a>
</ul>
<li class=no-num><a href="#acknowledgements"> Appendix A:
Acknowledgements</a>
<li class=no-num><a href="#appendix-b-references">Appendix B:
References</a>
<ul class=toc>
<li class=no-num><a href="#normative-ref">Normative references</a>
<li class=no-num><a href="#informative-ref">Informative references</a>
</ul>
<li class=no-num><a href="#changes">Appendix C: Changes</a>
<ul class=toc>
<li class=no-num><a href="#recent-changes"> Changes from the April 2011
CSS3 Text <abbr title="Working Draft">WD</abbr></a>
<li class=no-num><a href="#recent-changes"> Changes from the April 2011
CSS3 Text <abbr title="Working Draft">WD</abbr></a>
</ul>
<li class=no-num><a href="#default-stylesheet">Appendix D: Default UA
Stylesheet</a>
<li class=no-num><a href="#script-groups">Appendix E: Scripts and
Spacing</a>
<li class=no-num><a href="#small-kana">Appendix F: Small Kana Mappings</a>
<li class=no-num><a
href="#appendix-g-text-processing-order-of-oper">Appendix G: Text
Processing Order of Operations</a>
<li class=no-num><a href="#appendix-h-full-property-index">Appendix H:
Full Property Index</a>
<li class=no-num><a href="#traditions">Appendix J: Cultural
Correlations</a>
</ul>
<!--end-toc-->
<h2 id=intro><span class=secno>1. </span> Introduction</h2>
<p>[document here]
<p class=issue>This draft describes features that are specific to certain
scripts. There is an ongoing discussion about where these features belong:
in existing CSS properties, in new CSS properties, or perhaps in other
specifications.
<h3 id=placement><span class=secno>1.1. </span> Module Interactions</h3>
<p>This module replaces and extends the text-level features defined in <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> chapter 16.
<h3 id=values><span class=secno>1.2. </span> Values</h3>
<p>This specification follows the <a
href="http://www.w3.org/TR/CSS21/about.html#property-defs">CSS property
definition conventions</a> from <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Value types not defined in
this specification are defined in CSS Level 2 Revision 1 <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Other CSS
modules may expand the definitions of these value types: for example <a
href="#CSS3COLOR" rel=biblioentry>[CSS3COLOR]<!--{{CSS3COLOR}}--></a>,
when combined with this module, expands the definition of the
<color> value type as used in this specification.
<p>In addition to the property-specific values listed in their definitions,
all properties defined in this specification also accept the <a
href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">inherit</a>
keyword as their property value. For readability it has not been repeated
explicitly.
<h3 id=terms><span class=secno>1.3. </span> Terminology</h3>
<p id=grapheme-cluster>A <dfn id=grapheme-cluster0>grapheme cluster</dfn>
is what a language user considers to be a character or a basic unit of the
script. The term is described in detail in the Unicode Technical Report:
Text Boundaries <a href="#UAX29"
rel=biblioentry>[UAX29]<!--{{!UAX29}}--></a>. This specification uses the
<em>extended grapheme cluster</em> definition in <a href="#UAX29"
rel=biblioentry>[UAX29]<!--{{!UAX29}}--></a> (not the <em>legacy grapheme
cluster</em> definition). The UA may further tailor the definition as
allowed by Unicode. Within this specification, the ambiguous term <dfn
id=character>character</dfn> is used as a friendlier synonym for <a
href="#grapheme-cluster0"><i>grapheme cluster</i></a>. See <a
href="http://dev.w3.org/csswg/css3-writing-modes/#character-properties">Characters
and Properties</a> for how to determine the Unicode properties of a
character.
<p id=letter>A <dfn id=letter0>letter</dfn> for the purpose of this
specification is a <a href="#character"><i>character</i></a> belonging to
one of the Letter or Number general categories in Unicode. <a
href="#UAX44" rel=biblioentry>[UAX44]<!--{{!UAX44}}--></a>
<h2 id=transforming><span class=secno>2. </span> Transforming Text</h2>
<h3 id=text-transform><span class=secno>2.1. </span> <a name=caps-prop></a>
Transforming Text: the ‘<a href="#text-transform0"><code
class=property>text-transform</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=text-transform0>text-transform</dfn>
<tr>
<th>Value:
<td>none | [ [ capitalize | uppercase | lowercase ] || full-width ||
full-size-kana ]
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>as specified
</table>
<p>This property transforms text for styling purposes. Values have the
following meanings:
<dl>
<dt><dfn id=none title="text-transform:none">‘<code
class=css>none</code>’</dfn>
<dd>No effects.
<dt><dfn id=capitalize title="text-transform:capitalize">‘<code
class=css>capitalize</code>’</dfn>
<dd>Puts the first <a href="#letter0"><i>letter</i></a> of each word in
titlecase; other characters are unaffected.
<dt><dfn id=uppercase title="text-transform:uppercase">‘<code
class=css>uppercase</code>’</dfn>
<dd>Puts all characters in uppercase.
<dt><dfn id=lowercase title="text-transform:lowercase">‘<code
class=css>lowercase</code>’</dfn>
<dd>Puts all characters in lowercase.
<dt><dfn id=full-width title="text-transform:full-width">‘<code
class=css>full-width</code>’</dfn>
<dd>Puts all characters in fullwidth form. If the character does not have
a corresponding fullwidth form, it is left as is. This value is typically
used to typeset Latin characters and digits like ideographic characters.
<dt><dfn id=full-size-kana
title="text-transform:full-size-kana">‘<code
class=css>full-size-kana</code>’</dfn>
<dd>Converts all small Kana characters to normal Kana. This value is
typically used for ruby annotation text, where all small Kana should be
drawn as large Kana.
</dl>
<p>The case mapping rules for the character repertoire specified by the
Unicode Standard can be found on the Unicode Consortium Web site <a
href="#UNICODE" rel=biblioentry>[UNICODE]<!--{{!UNICODE}}--></a>. The UA
must use the full case mappings for Unicode characters, including any
conditional casing rules, as defined in Default Case Algorithm section. If
(and only if) the content language of the element is, according to the
rules of the document language, known, then any appropriate
language-specific rules must be applied as well. These minimally include,
but are not limited to, the language-specific rules in Unicode's <a
href="http://www.unicode.org/Public/UNIDATA/SpecialCasing.txt">SpecialCasing.txt</a>.
<div class=example>
<p>For example, in Turkish there are two “i”s, one with a
dot—“İ” and “i”— and one
without—“I” and “ı”. Thus the usual case
mappings between “I” and “i” are replaced with a
different set of mappings to their respective undotted/dotted
counterparts, which do not exist in English. This mapping must only take
effect if the language is known to be Turkish or Azeri; in other
languages, the usual mapping of “I” and “i” is
required. This rule is thus conditionally defined in Unicode's
SpecialCasing.txt file.
</div>
<!--
<div class="example">
<p>An example where the UA may choose to include rules beyond those
in Unicode is Greek. In Greek, if the entire word is in upper case,
accents are dropped or transformed
http://blogs.msdn.com/b/michkap/archive/2006/08/18/706383.aspx
</div>
-->
<p>The definition of "word" used for ‘<code
class=css>capitalize</code>’ is UA-dependent; <a href="#UAX29"
rel=biblioentry>[UAX29]<!--{{!UAX29}}--></a> is suggested (but not
required) for determining such word boundaries. Authors should not expect
‘<code class=css>capitalize</code>’ to follow
language-specific titlecasing conventions (such as skipping articles in
English).
<p>The definition of fullwidth and halfwidth forms can be found on the
Unicode consortium web site at <a href="#UAX11"
rel=biblioentry>[UAX11]<!--{{!UAX11}}--></a>. The mapping to fullwidth
form is defined by taking code points with the <wide> or the
<narrow> tag in their Decomposition_Mapping in <a href="#UAX44"
rel=biblioentry>[UAX44]<!--{{!UAX44}}--></a>. For the <narrow> tag,
the mapping is from the code point to the decomposition (minus
<narrow> tag), and for the <wide> tag, the mapping is from the
decomposition (minus the <wide> tag) back to the original code
point.
<p>The mappings for small Kana to normal Kana are defined in <a
href="#small-kana">Small Kana Mappings</a>.
<p>When multiple values are specified and therefore multiple
transformations need to be applied, they are applied in the following
order:
<ol>
<li>‘<code class=css>capitalize</code>’, ‘<code
class=css>uppercase</code>’, and ‘<code
class=css>lowercase</code>’
<li>‘<code class=css>full-width</code>’
<li>‘<code class=css>full-size-kana</code>’
</ol>
<p>Text transformation happens after <a href="#white-space-rules">white
space processing</a>, which means that ‘<code
class=css>full-width</code>’ transforms only preserved U+0020 spaces
to U+3000.
<div class=example>
<p>The following example converts the ASCII characters in abbreviations in
Japanese to their fullwidth variants so that they lay out and line break
like ideographs:
<pre>abbr:lang(ja) { text-transform: full-width; }</pre>
</div>
<p class=issue>All-caps text sometimes has special typographic
considerations. For example: Punctuation and number glyphs might be
adjusted for the higher "center of gravity" (see the <a
href="http://www.microsoft.com/typography/otspec/features_ae.htm#case">case</a>
feature in OpenType). Should we turn that on by default, as they suggest?
<p class=issue>CSS may introduce the ability to create custom mapping
tables for less common text transforms, such as by an ‘<a
href="#text-transform0"><code class=css>@text-transform</code></a>’
rule similar to ‘<code class=css>@counter-style</code>’ from
<a href="#CSS3LIST" rel=biblioentry>[CSS3LIST]<!--{{CSS3LIST}}--></a>, and
this mechanism may be used to replace ‘<code
class=css>full-size-kana</code>’.
<h2 id=white-space-processing><span class=secno>3. </span> White Space
Processing</h2>
<p>The source text of a document often contains formatting that is not
relevant to the final rendering: for example, breaking the source into
segments (lines) for ease of editing or adding white space characters such
as tabs and spaces to indent the source code. CSS white space processing
allows the author to control interpretation of such formatting: to
preserve or collapse it away when rendering the document.
<p id=segment-normalization> In the document source, segments can be
delimited by carriage returns (U+000D), linefeeds (U+000A) or a
combination (U+000D U+000A), or by some other mechanism, such as the SGML
RECORD-START and RECORD-END tokens. If no segmentation rules are specified
for the document language, each line feed (U+000A), carriage return
(U+000D) and CRLF sequence (U+000D U+000A) in the text is considered a
segment break. (This default rule also applies to generated content.) In
CSS, each such segment break is treated as a single line feed character
(U+000A).
<p>White space processing in CSS interprets white space characters only for
rendering: it has no effect on the underlying document data.
<p class=note>Note that the document parser may have not only normalized
segment breaks, but also collapsed other space characters or otherwise
processed white space according to markup rules. Because CSS processing
occurs <em>after</em> the parsing stage, it is not possible to restore
these characters for styling. Therefore, some of the behavior specified
below can be affected by these limitations and may be user agent
dependent.
<p>Control characters (Unicode class Cc) other than tab (U+0009), line feed
(U+000A), space (U+0020), and the bidi formatting characters
(U+202<var>x</
A292
var>) should be rendered as invisible zero-width characters.
UAs may instead treat them as visible characters. (Note, however, that
this will usually result in them being rendered as missing glyphs.) <span
class=issue>What's the line-breaking behavior? Effects on joining? Can we
just copy the behavior of some zero-width Unicode character?</span>
<h3 id=white-space-collapsing><span class=secno>3.1. </span> White Space
Collapsing: the ‘<a href="#text-space-collapse"><code
class=property>text-space-collapse</code></a>’ property</h3>
<p class=issue>This section is still under discussion and may change in
future drafts.
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=text-space-collapse>text-space-collapse</dfn>
<tr>
<th>Value:
<td>collapse | discard | [ [preserve | preserve-breaks] && [ trim-inner
|| consume-before || consume-after ]
<tr>
<th>Initial:
<td>collapse
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>specified value
</table>
<p class=issue>Need a property name
<p>This property declares whether and how <a
href="#white-space-processing">white space</a> inside the element is
collapsed. Values have the following meanings, which must be interpreted
according to the <a href="#white-space-rules">white space processing
rules</a>:
<dl>
<dt><dfn id=collapse0 title="white-space:collapse">‘<code
class=css>collapse</code>’</dfn>
<dd>This value directs user agents to collapse sequences of white space
into a single character (or <a href="#line-break-transform">in some
cases</a>, no character).
<dt><dfn id=preserve title="white-space:preserve">‘<code
class=css>preserve</code>’</dfn>
<dd>This value prevents user agents from collapsing sequences of white
space. Line feeds are preserved as forced line breaks.
<dt><dfn id=preserve-breaks
title="white-space:preserve-breaks">‘<code
class=css>preserve-breaks</code>’</dfn>
<dd>This value collapses white space as for ‘<code
class=css>collapse</code>’, but preserves line feeds as forced line
breaks.
<dt><dfn id=discard title="white-space:discard">‘<code
class=css>discard</code>’</dfn>
<dd>This value directs user agents to "discard" all white space in the
element.
<dt><dfn id=trim-inner title="white-space:trim-inner">‘<code
class=css>trim-inner</code>’</dfn>
<dd>For block containers this value directs UAs to discard all whitespace
at the beginning of the element up to and including the last line feed
before the first non-white-space character in the element as well as to
discard all white space at the end of the element starting with the first
line feed after the last non-white-space character in the element. For
other elements this value directs UAs to discard all whitespace at the
beginning and end of the element.
<dt><dfn id=consume-before title="white-space:consume-before">‘<code
class=css>consume-before</code>’</dfn>
<dd>This value directs the UA to collapse all collapsible whitespace
immediately before the start of the element.
<dt><dfn id=consume-after title="white-space:consume-after">‘<code
class=css>consume-after</code>’</dfn>
<dd>This value directs the UA to collapse all collapsible whitespace
immediately after the end of the element.
</dl>
<div class=example>
<p>The following style rules implement MathML's white space processing:
<pre>
<!-- -->@namespace m "http://www.w3.org/1998/Math/MathML";
<!-- -->m|* {
<!-- --> text-space-collapse: discard;
<!-- -->}
<!-- -->m|mi, m|mn, m|mo, m|ms, m|mtext {
<!-- --> text-space-collapse: trim-inner;
<!-- -->}</pre>
</div>
<p class=issue>It's been pointed out that ‘<code
class=css>trim-inner</code>’, ‘<code
class=css>consume-before</code>’, and ‘<code
class=css>consume-after</code>’ won't work well because ‘<a
href="#text-space-collapse"><code
class=property>text-space-collapse</code></a>’ is inherited, meaning
that inserting a <span> or >div> would cause more white space to be
removed than otherwise.
<h3 id=tab-size><span class=secno>3.2. </span> Tab Character Size: the
‘<a href="#tab-size0"><code
class=property>tab-size</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=tab-size0>tab-size</dfn>
<tr>
<th>Value:
<td><integer> | <length>
<tr>
<th>Initial:
<td>8
<tr&
692E
gt;
<th>Applies to:
<td>block containers
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>specified value
</table>
<p>This property determines the measure of the tab character (U+0009) when
rendered. Integers represent the measure in space characters (U+0020).
Negative integers are not allowed.
<h3 id=white-space-rules><span class=secno>3.3. </span> The White Space
Processing Rules</h3>
<p>White space processing affects only spaces (U+0020), tabs (U+0009), and
(<a href="#segment-normalization">post-normalization</a>) line feeds
(U+00A0).
<p>For each inline (including anonymous inlines) within an inline
formatting context, white space characters are handled as follows,
ignoring bidi formatting characters as if they were not there:
<ul>
<li id=collapse>
<p>If ‘<a href="#text-space-collapse"><code
class=property>text-space-collapse</code></a>’ is set to
‘<code class=css>collapse</code>’ or ‘<code
class=css>preserve-breaks</code>’, white space characters are
considered <dfn id=collapsible>collapsible</dfn> and are processed by
performing the following steps:</p>
<ol>
<li>All spaces and tabs immediately preceding or following a line feed
character are removed.
<li>If ‘<a href="#text-space-collapse"><code
class=property>text-space-collapse</code></a>’ is not
‘<code class=css>preserve-breaks</code>’, line feed
characters are transformed for rendering according to the <a
href="#line-break-transform">line feed transformation rules</a>.
<li>Every tab is converted to a space (U+0020).
<li>Any space immediately following another collapsible space
—even one outside the boundary of the inline—is removed.
However, if removing this space would eliminate a line breaking
opportunity in the text, that opportunity is still considered to exist.
<li>A collapsible space immediately preceding an element with
‘<code class=css>consume-before</code>’ is removed. Such
removed spaces do not indicate a line breaking opportunity in the text.
<li>Any collapsible spaces after the end of an element with ‘<code
class=css>consume-after</code>’ are removed. Such removed spaces
do not indicate a line breaking opportunity in the text.
</ol>
<li>
<p>If ‘<a href="#text-space-collapse"><code
class=property>text-space-collapse</code></a>’ is set to
‘<code class=css>preserve</code>’, any sequence of spaces
unbroken by an element boundary is treated as a sequence of non-breaking
spaces. However, a line breaking opportunity exists at the end of the
sequence.
<li>
<p>If ‘<a href="#text-space-collapse"><code
class=property>text-space-collapse</code></a>’ is set to
‘<code class=css>discard</code>’, the first white space
character in every white space sequence is converted to a zero width
non-joiner (U+200C) and the rest of the sequence is removed.</p>
</ul>
<p>Then, the entire block is rendered. Inlines are laid out, taking bidi
reordering into account, and wrapping as specified by the ‘<a
href="#text-wrap0"><code class=property>text-wrap</code></a>’
property.
<p>As each line is laid out,
<ol>
<li>A sequence of collapsible spaces at the beginning of a line is
removed.
<li>Each tab is rendered as a horizontal shift that lines up the start
edge of the next glyph with the next tab stop. Tab stops occur at points
that are multiples of the width of a space (U+0020) rendered in the
block's font from the block's starting content edge. How many spaces is
given by the ‘<a href="#tab-size0"><code
class=property>tab-size</code></a>’ property.