css-ruby/Overview.src.html@9cea024667c6
css-ruby/Overview.src.html
Wed, 10 Jul 2013 19:08:33 -0700
- author
- fantasai <fantasai.cvs@inkedblade.net>
- date
- Wed, 10 Jul 2013 19:08:33 -0700
- changeset 8682
- 9cea024667c6
- parent 8663
- 8f5483049df7
- child 8833
- 0bd7993fcfef
- permissions
- -rw-r--r--
[css-ruby] Some fixup in the line breaking section
1 <!--
3 Issues:
4 bidi
5 box layout/sizing
7 Redo all examples with consistent font. (M+ 2p?)
9 -->
11 <!DOCTYPE html>
12 <html lang="en">
13 <head>
14 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
15 <title>CSS Ruby Module Level 1</title>
16 <link rel=contents href="#contents">
17 <link rel=index href="#index">
18 <link rel="stylesheet" type="text/css" href="../default.css">
19 <link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
20 <link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS].css">
21 </head>
23 <body class="h-entry">
25 <div class="head">
26 <!--logo-->
28 <h1 class="p-name">CSS Ruby Module Level 1</h1>
30 <h2 class="no-num no-toc">[LONGSTATUS] <time class="dt-updated" datetime="[CDATE]">[DATE]</time> <!-- for HTML4 doctype: <span class="value-title" title="[CDATE]">[DATE]</span></span> --> </h2>
31 <dl>
32 <dt>This version:
33 <dd><a class="u-url" href="[VERSION]">[VERSION]</a>
35 <dt>Latest version:
36 <dd><a href="http://www.w3.org/TR/[SHORTNAME]/">http://www.w3.org/TR/css3-ruby/</a>
38 <dt>Editor's draft:
39 <dd><a href="http://dev.w3.org/csswg/[SHORTNAME]/">http://dev.w3.org/csswg/[SHORTNAME]/</a>
40 (<a href="https://dvcs.w3.org/hg/csswg/log/tip/[SHORTNAME]/Overview.src.html">change log</a>)
42 <dt>Previous version:
43 <dd><a href="http://www.w3.org/TR/2011/WD-css3-ruby-20110630/">
44 http://www.w3.org/TR/2011/WD-css3-ruby-20110630/</a>
46 <dt>Issue Tracking:</dt>
47 <dd><a rel="issues" href="http://www.w3.org/Style/CSS/Tracker/products/FIXME">http://www.w3.org/Style/CSS/Tracker/products/FIXME</a>
49 <dt>Feedback:</dt>
50 <dd><a href="mailto:www-style@w3.org?subject=%5BSHORTNAME%5D%20feedback"
51 >www-style@w3.org</a>
52 with subject line “<kbd>[[SHORTNAME]]
53 <var>… message topic …</var></kbd>”
54 (<a rel="discussion" href="http://lists.w3.org/Archives/Public/www-style/"
55 >archives</a>)
57 <dt>Editors:
58 <dd class="p-author h-card vcard">
59 <a class="p-name fn u-url url" rel="author"
60 href="http://fantasai.inkedblade.net/contact">Elika J. Etemad</a>,
61 <a class="p-org org h-org" href="http://www.mozilla.org/">Mozilla</a>
62 <dd class="p-author h-card vcard">
63 <a class="p-name fn u-url url" rel="author"
64 href="mailto:koji.a.ishii@mail.rakuten.com">Koji Ishii</a>,
65 <span class="p-org org">Rakuten, Inc.</span>
66 <dd class="p-author h-card vcard">
67 <a class="p-name fn u-url url" rel="author"
68 href="mailto:ishida@w3.org">Richard Ishida</a>,
69 <span class="p-org org">W3C</span>
71 <dt>Former editors:
72 <dd>Michel Suignard, Microsoft
73 <dd>Marcin Sawicki, Microsoft
74 </dl>
76 <!--copyright-->
78 <hr title="Separator for header">
79 </div>
81 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
83 <p>
84 <span class="p-summary">
85 “Ruby” are short runs of text alongside the base text,
86 typically used in East Asian documents to indicate pronunciation
87 or to provide a short annotation.
88 This module describes the rendering model and formatting controls
89 related to displaying ruby annotations in CSS.
90 </span>
92 <a href="http://www.w3.org/TR/CSS/">CSS</a> is a language for describing
93 the rendering of structured documents (such as HTML and XML) on screen, on
94 paper, in speech, etc.
96 <h2 class="no-num no-toc" id="status">Status of this document</h2>
98 <!--status-->
100 <p>The following features are at risk: …
102 <h2 class="no-num no-toc" id="contents">
103 Table of Contents</h2>
105 <!--toc-->
107 <h2 id="intro">
108 Introduction</h2>
110 <p><em>This section is not normative.</em>
112 <h3 id="placement">
113 Module interactions</h3>
115 <p>This module extends the inline box model of CSS Level 2 [[!CSS21]]
116 to support ruby.
118 <p>None of the properties in this module apply to the <code>::first-line</code> or
119 <code>::first-letter</code> pseudo-elements.
121 <h3 id="values">
122 Values</h3>
124 <p>This specification follows the
125 <a href="http://www.w3.org/TR/CSS21/about.html#property-defs">CSS property
126 definition conventions</a> from [[!CSS21]]. Value types not defined in
127 this specification are defined in CSS Level 2 Revision 1 [[!CSS21]].
128 Other CSS modules may expand the definitions of these value types: for
129 example [[CSS3VAL]], when combined with this module, expands the
130 definition of the <var><length></var> value type as used in this specification.</p>
132 <p>In addition to the property-specific values listed in their definitions,
133 all properties defined in this specification also accept the
134 <a href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">inherit</a>
135 keyword as their property value. For readability it has not been repeated
136 explicitly.
138 <h3 id="conventions">
139 Document conventions</h3>
141 <p>Many typographical conventions in East Asian typography depend
142 on whether the character rendered is wide (CJK) or narrow (non-CJK).
143 There are a number of illustrations in this document
144 for which the following legend is used:
146 <dl>
147 <dt><img alt="Symbolic wide-cell glyph representation" width="39" height="39" src="images/fullwidth.gif">
148 <dd>Wide-cell glyph (e.g. Han) that is the <var>n</var>th character in the text run.
149 They are typically sized to 50% when used as annotations.
150 <dt><img alt="Symbolic narrow-cell glyph representation" width="19" height="39" src="images/halfwidth.gif">
151 <dd>Narrow-cell glyph (e.g. Roman) which is the <var>n</var>th glyph in the text run.
152 </dl>
154 <p>The orientation which the above symbols assume in the diagrams
155 corresponds to the orientation that the glyphs they represent
156 are intended to assume when rendered by the user agent.
157 Spacing between these characters in the diagrams is incidental,
158 unless intentionally changed to make a point.
160 <h3 id="ruby-def">
161 What is ruby?</h3>
163 <p><dfn>Ruby</dfn> is the commonly-used name for a run of text
164 that appears alongside another run of text (referred to as the “base”)
165 and serves as an annotation or a pronunciation guide associated with that run of text.
167 <p>The following figures show two examples of Ruby,
168 a simple case and one with more complicated structure.
170 <div class="example">
171 <p>In this first example, a single annotation is used to annotate the base text.
172 <div class="figure">
173 <p><img src="images/licence.png"
174 alt="Example of ruby applied on top of a Japanese expression">
175 <p class="caption">Example of ruby used in Japanese (simple case)
176 </div>
177 <p>In Japanese typography, this case is sometimes called
178 <i lang="ja">taigo</i> ruby or group-ruby (per-word ruby),
179 because the annotation as a whole is associated
180 with multi-character word (as a whole).
181 </div>
183 <div class="example">
184 <p>In this second example,
185 two levels of annotations are attached to a base sequence:
186 the hiragana characters on top refer to the pronunciation of each of the base kanji characters,
187 while the words “Keio” and “University” on the bottom are annotations describing the English translation.
188 <div class="figure">
189 <p><img src="images/ruby-univ.gif"
190 alt="Example showing complex ruby with annotation text over and under the base characters">
191 <p class="caption">Complex ruby with annotation text over and under the base characters
192 </div>
193 <p>
194 <p>Notice that to allow correct association between the hiragana characters and
195 their corresponding Kanji base characters,
196 the spacing between these Kanji characters is adjusted.
197 (This happens around the fourth Kanji character in the figure above.)
198 To avoid variable spacing between the Kanji characters in the example above
199 the hiragana annotations can be styled as a <i>collapsed annotation</i>,
200 which will look more like the group-ruby example earlier.
201 However because the base-annotation pairings are recorded in the ruby structure,
202 if the text breaks across lines, the annotation characters will stay
203 correctly paired with their respective base characters.
204 </div>
206 <p><i>Ruby</i> formatting as used in Japanese is described in JIS X-4051 [[JIS4051]] (in Japanese)
207 and in Requirements for Japanese Text Layout [[JLREQ]] (in English and Japanese)].
208 In HTML, ruby structure and markup to represent it is described
209 in the Ruby Markup Extension specification.
210 This module describes the CSS rendering model
211 and formatting controls relevant to ruby layout of such markup.
213 <h2 id="ruby-model">
214 Ruby Formatting Model</h2>
216 <p>The CSS ruby model is based on
217 the <a href="http://darobin.github.io/html-ruby/">HTML Ruby Markup Extension</a>
218 and <a href="http://www.w3.org/TR/ruby/">XHTML Ruby Annotation Recommendation</a> [[RUBY]].
219 In this model, a ruby structure consists of
220 one or more <dfn>ruby base</dfn> elements representing the base (annotated) text,
221 associated with one or more levels of <dfn>ruby annotation</dfn> elements representing the annotations.
222 The structure of ruby is similar to that of a table:
223 there are “rows” (the base text level, each annotation level)
224 and “columns” (each <i>ruby base</i> and its corresponding <i>ruby annotations</i>).
226 <p>Consecutive bases and annotations are grouped together into <dfn>ruby segments</dfn>.
227 Within a <i>ruby segment</i>, a <i>ruby annotation</i> may span multiple <i>ruby bases<i>.
229 <p class="note">In HTML, a single <code><ruby></code> element may contain multiple <i>ruby segments</i>.
230 (In the XHTML Ruby model, a single <code><ruby></code> element can only contain one <i>ruby segment</i>.)
232 <h3 id="ruby-display">
233 Ruby-specific 'display' property values</h3>
235 <p>For document languages (such as XML applications) that do not have pre-defined ruby elements,
236 authors must map document language elements to ruby elements;
237 this is done with the 'display' property.
239 <table class="propdef">
240 <tr>
241 <th>Name:
242 <td>display
243 <tr>
244 <th><a href="#values">New Values</a>:
245 <td>ruby | ruby-base | ruby-text | ruby-base-container | ruby-text-container
246 </table>
248 <p>The following new 'display' values assign ruby layout roles to an arbitrary element:
250 <dl>
251 <dt>''ruby''
252 <dd>Specifies that an element generates a <dfn title="ruby container | ruby container box">ruby container box</dfn>.
253 (Corresponds to HTML/XHTML <code><ruby></code> elements.)
254 <dt>''ruby-base''
255 <dd>Specifies that an element generates a <dfn title="ruby base box | ruby base">ruby base box</dfn>.
256 (Corresponds to HTML/XHTML <code><rb></code> elements.)
257 <dt>''ruby-text''
258 <dd>Specifies that an element generates a <dfn title="ruby annotation box | ruby annotation">ruby annotation box</dfn>.
259 (Corresponds to HTML/XHTML <code><rt></code> elements.)
260 <dt>''ruby-base-container''
261 <dd>Specifies that an element generates a <dfn title="ruby base container box | ruby base container">ruby base container box</dfn>.
262 (Corresponds to XHTML <code><rbc></code> elements; always implied in HTML.)
263 <dt>''ruby-text-container''
264 <dd>Specifies that an element generates a <dfn title="ruby annotation container box | ruby annotation container">ruby annotation container box</dfn>.
265 (Corresponds to HTML/XHTML <code><ruby></code> elements.)
266 </dl>
268 <h3 id="box-fixup">
269 Anonymous Ruby Box Generation</h3>
271 <p>The CSS model does not require that the document language
272 include elements that correspond to each of these components.
273 Missing parts of the structure are implied through the anonymous box generation rules
274 <a href="http://www.w3.org/TR/CSS21/tables.html#anonymous-boxes">similar to those used to normalize tables</a>. [[!CSS21]]
276 <ol>
277 <li>Any in-flow block-level boxes directly contained by a
278 <i>ruby container</i>,
279 <i>ruby base container</i>,
280 <i>ruby annotation container</i>,
281 <i>ruby base box</i>,
282 or <i>ruby annotation box</i>
283 are forced to be inline-level boxes,
284 and their 'display' value computed accordingly.
285 For example,
286 the 'display' property of an in-flow element with ''display: block''
287 parented by an element with ''display: ruby-text''
288 computes to ''inline-block''.
289 This computation occurs after any intermediary anonymous-box fixup
290 (such as that required by internal table elements).
292 <li>Any consecutive sequence of <i>ruby bases</i> not parented by a <i>ruby base container</i>
293 is wrapped in an anonymous <i>ruby base container</i>.
294 Similarly, any consecutive sequence of <i>ruby annotations</i> not parented by a <i>ruby annotation container</i>
295 is wrapped in an anonymous <i>ruby annotation container</i>.
297 <li>Within each <i>ruby base container</i>,
298 each sequence of inline-level boxes is wrapped in an anonymous <i>ruby base box</i>.
299 Similarly, within each <i>ruby annotation container</i>,
300 each sequence of inline-level boxes is wrapped in an anonymous <i>ruby annotation box</i>.
302 <li>A sequence of <i>ruby base containers</i> and/or <i>ruby annotation containers</i>
303 not parented by a <i>ruby container</i>
304 is wrapped in an anonymous <i>ruby container</i>.
305 </ol>
307 <p>At this point, all ruby layout structures are properly parented,
308 and the UA can start to associate bases with their annotations.
310 <p class="note">
311 Note that the UA is not required to create any of these anonymous boxes in its internal structures,
312 as long as pairing and layout behaves as if they existed.
314 <h3 id="pairing">
315 Ruby Pairing and Annotation Levels</h3>
317 <p>Within a ruby structure,
318 each <i>ruby base</i> is associated with <i>ruby annotations</i>
319 and vice versa.
320 A <i>ruby base</i> can be associated with at most one <i>ruby annotation</i> per annotation level.
321 If there are multiple annotation levels, it can therefore be associated with multiple <i>ruby annotations</i>.
322 A <i>ruby annotation</i> is associated with one or more <i>ruby bases</i>;
323 annotations can span multiple bases.
325 <p><dfn>Annotation pairing</dfn> is the process of associating
326 <i>ruby annotations</i> with <i>ruby bases</i>.
328 <ol>
329 <li>
330 <p>First, the ruby structure is divided into <i>ruby segments</i>,
331 each consisting of a single <i>ruby base container</i>
332 followed by one or more <i>ruby annotation containers</i>.
333 If the first child of a <i>ruby container</i> is a <i>ruby annotation container</i>,
334 an anonymous, empty <i>ruby base container</i> is assumed to exist before it.
335 Similarly, if the <i>ruby container</i> contains consecutive <i>ruby base containers</i>,
336 anonymous, empty <i>ruby annotation containers</i> are assumed to exist between them.
337 The <i>ruby base container</i> in each segment is thus associated
338 with each of the <i>ruby annotation containers</i> in that segment.
340 <p>Each <i>ruby annotation containers</i> in a <i>ruby segment</i>
341 represents one <dfn title="annotation level | level">level</dfn> of annotation:
342 the first one represents the first level of annotation,
343 the second one represents the second level of annotation,
344 and so on.
346 <li>Within each <i>ruby segment</i>,
347 each <i>ruby base box</i> in the <i>ruby base container</i>
348 is paired with one <i>ruby annotation box</i>
349 from each <i>ruby annotation container</i> in its <i>ruby segment</i>.
350 If there are not enough <i>ruby annotations</i> in a <i>ruby annotation container</i>,
351 the last one is associated with any excess <i>ruby bases</i>.
352 (If there are not any in the <i>ruby annotation container</i>, an anonymous empty one is assumed to exist.)
353 If there are not enough <i>ruby bases</i>,
354 any remaining <i>ruby annotations</i> are assumed to be associated
355 with empty, anonymous bases inserted at the end of the <i>ruby base container</i>.
357 <p>If an implementation supports ruby markup with explicit spanning
358 (e.g. XHTML Complex Ruby Annotations),
359 it must adjust the pairing rules to pair spanning annotations to multiple bases
360 appropriately.
361 </ol>
363 <p>A this point, ruby “columns” are defined,
364 each represented by a single <i>ruby base</i>
365 and associated with one <i>ruby annotation</i> (possibly an empty, anonymous one)
366 from each <i>annotation level</i>.
368 <h4 id="nested-pairing">
369 Nested Ruby</h4>
371 <p>When <i>ruby containers</i> are nested,
372 pairing begins with the deepest <i>ruby container</i>,
373 then expands out,
374 treating each <i>ruby container</i> nested within another <i>ruby container</i>
375 as a <i>ruby base</i>,
376 and associating each <i>ruby annotation</i>
377 associated with the nested <i>ruby container</i>
378 as being associated with (spanning) all of its <i>ruby bases</i>.
380 <p>Using nested <i>ruby containers</i> thus allows the representation
381 of complex spanning relationships.
383 <p class="issue">This shouldn't belong in Level 1. But HTML5 allows it, so we have to handle it. Yay HTML5.
385 <h3 id="autohide">
386 Autohiding Annotations</h3>
388 <p>If a <i>ruby annotation</i> has the exact same content as its base,
389 it is <dfn title="hidden ruby annotation | hidden annotation">hidden</dfn>.
390 Hiding a <i>ruby annotation</i> does not affect annotation pairing
391 or the block-axis positioning of boxes in other <i>levels</i>.
392 However the <i>hidden annotation</i> is not visible,
393 and it has no impact on layout
394 other than to separate adjacent sequences of <i>ruby annotation boxes</i> within its level,
395 as if they belonged to separate segments
396 and the <i>hidden annotation</i>’s base were not a <i>ruby base</i> but an intervening inline.
398 <div class="example">
399 <p>This is to allow correct inlined display of annotations
400 for Japanese words that are a mix of kanji and hirangana.
401 For example, the word <i>振り仮名</i> should be inlined as
402 <p class="figure">振り仮名(ふりがな)
403 <p>and therefore marked up as
404 <pre>
405 <!-- --><ruby>
406 <!-- --> <rb>振</rb><rb>り</rb><rb>仮</rb><rb>名</rb>
407 <!-- --> <rp>(</rp><rt>ふ</rt><rt>り</rt><rt>が</rt><rt>な</rt><rp>)</rp>
408 <!-- --><ruby></pre>
409 <p>However, when displayed as ruby, the “り” should be hidden
410 <div class="figure">
411 <p><img src="images/furigana-separate.png"
412 alt="Hiragana annotations for 振り仮名 appear, each above its base character.">
413 <p class="caption">Hiragana ruby for 振り仮名
414 </div>
415 </div>
417 <p class="note">
418 Future levels of CSS Ruby may add controls for this,
419 however in this level it is always forced.
421 <p>The content comparison for this auto-hiding behavior
422 takes place prior to white space collapsing.
423 <span class="issue">Is this easier? Or after collapsing is easier? We should do whatever is easier, as it really doesn't matter much which way to go.
425 <h3 id="white-space">
426 White Space</h3>
428 <p class="issue">I'm unsure exactly where space should be trimmed. :/
429 But pretty sure we need to keep spaces between things,
430 otherwise ruby only works for CJK.
432 <p><i>Collapsible</i> white space within a ruby structure is discarded
433 at the beginning and end of a <i>ruby container</i>,
434 and at the beginning/end of a <i>ruby annotation box</i> or <i>ruby base box</i> if white space is not its only contents.
435 Between <i>ruby segments</i>, between <i>ruby bases</i>, and between <i>ruby annotations</i>, however,
436 white space is not discarded.
437 If such white space is <i>collapsible</i>, it will collapse
438 following the standard <a href="http://www.w3.org/TR/css3-text/#white-space-rules">white space processing rules</a>. [[!CSS3TEXT]]
439 Between <i>ruby segments</i>, however,
440 the contextual text for determining collapsing behavior is given by the <i>ruby bases</i> on either side,
441 not the text on either side of the white space in the source document.
443 <div class="note">
444 <p>Note that the white space processing rules
445 cause a white space sequence containing a <i>segment break</i> (such as a line feed)
446 to <a href="http://www.w3.org/TR/css3-text/#line-break-transform">collapse to nothing</a> between CJK characters.
447 This means that CJK ruby can safely use white space for indentation of the ruby markup.
448 For example, the following markup will display without any spaces:
449 <pre>
450 <!-- --><ruby>
451 <!-- --> <rb>東</rb><rb>京</rb>
452 <!-- --> <rt>とう</rt><rt>きょう</rt>
453 <!-- --></ruby></pre>
454 <p>However, this markup will:
455 <pre>
456 <!-- --><ruby>
457 <!-- --> <rb>東</rb> <rb>京</rb>
458 <!-- --> <rt>とう</rt> <rt>きょう</rt>
459 <!-- --></ruby></pre>
460 </div>
462 <p>Any preserved white space is then wrapped in an anonymous box belonging to
463 the <i>ruby base container</i> (if between <i>ruby bases</i>),
464 <i>ruby annotation container</i> (if between <i>ruby annotations</i>),
465 or <i>ruby container</i> (if between <i>ruby segments</i>).
466 In the latter case, the text is considered part of the <i>base level</i>.
467 This box does not take part in pairing.
468 It merely ensures separation between adjacent bases/annotations.
470 <div class="example">
471 <p>These rules allow ruby to be used with space-separated scripts such as Latin.
472 For example,
473 <pre>
474 <!-- --><ruby>
475 <!-- --> <rb>W</rb><rb>W</rb><rb>W</rb>
476 <!-- --> <rt>World</rt> <rt>Wide</rt> <rt>Web</rt>
477 <!-- --></ruby></pre>
478 <p>They also ensure that annotated white space is preserved. For example,
479 <pre>
480 <!-- --><ruby>
481 <!-- --> <rb>Aerith</rb><rb> </rb><rb>Gainsboro</rb>
482 <!-- --> <rt>エアリス</rt><rt>・</rt><rt>ゲインズブール</rt>
483 <!-- --></ruby></pre>
484 </div>
486 <p class="issue">Specify how this impacts layout, or not.
488 <h3 id="ruby-layout">
489 Ruby layout</h3>
491 <p>When a ruby structure is laid out,
492 its base level is laid out on the line,
493 aligned according to its 'vertical-align' property
494 exactly as if its <i>bases</i> were a regular sequence of <i>inline</i> boxes.
495 Each <i>ruby base container</i> is sized and positioned
496 to contain exactly the full height of its <i>ruby bases</i>.
498 <p><i>Ruby annotations</i> associated with the base level
499 are then positioned with respect to their <i>ruby base boxes</i>
500 according to the applicable 'ruby-position' values.
501 <i>Ruby annotations</i> within a level (within a single <i>ruby container</i>)
502 are aligned to each other as if they were inline boxes
503 participating in the same inline formatting context.
504 Each <i>ruby annotation container</i> is sized and positioned
505 to contain exactly the full height of its <i>ruby annotations</i>.
507 <p>A ruby container (or fragment thereof)
508 measures as wide as the content of its widest level.
509 Similarly, <i>ruby base boxes</i> and <i>ruby annotation boxes</i>
510 within a ruby “column” have the measure of the widest content in that “column”.
511 In the case of spanning <i>annotations</i>
512 (whether actually spanning or pretending to span per 'ruby-collapse'),
513 the measures of the <i>ruby annotation box</i> and
514 the sum of its associated <i>ruby base boxes</i> must match.
516 <p>How the extra space is distributed
517 when ruby content is narrower than the measure of its box
518 is specified by the 'ruby-align' property.
520 <h4 id="inter-character-layout">
521 Inter-character ruby layout</h4>
523 <p>Inter-character annotations have special layout.
524 When 'ruby-position' indicates ''inter-character'' annotations, the affected <i>annotation boxes</i>
525 are spliced into and measured as part of the layout of the base level.
526 The <i>ruby base container</i> must be sized to include both the <i>base boxes</i>
527 as well as the ''inter-character'' <i>annotation boxes</i>
528 The affected <i>ruby annotation container</i> is similarly sized
529 so that its content box coincides with that of the <i>ruby base container</i>.
531 <p>For the purpose of laying out other levels of annotations,
532 an ''inter-character'' annotation effectively becomes part of its base.
533 <span class="issue">Or should it become a quasi-base between two bases?</span>
534 A spanning ''inter-character'' annotation is placed after
535 all the bases that it spans.
537 <h3 id="box-style">
538 Styling Ruby Boxes</h4>
540 <p>In most respects, ruby boxes can be styled similar to inline boxes.
541 However, the UA is not required to support
542 any of the box properties (borders, margins, padding),
543 any of the background properties or outline properties,
544 or any other property that illustrates the bounds of the box
545 on <i>ruby base container boxes</i>, <i>ruby annotation container boxes</i>,
546 or <a href="#nested-pairing">ruby-internal <i>ruby container boxes</i></a>.
547 The UA may implement these boxes simply as abstractions for inheritance
548 and control over the layout of their contents.
550 <p class="issue">
551 Alternatively... use margins to control offsets?
552 Or could line-height be adequate? Its centering behavior can be awkward.
554 <h3 id="line-breaks">
555 Ruby box and line breaking</h3>
557 <p>When there is not enough space for an entire <i>ruby container</i> to fit on the line,
558 the ruby may be broken wherever the base level allows a break.
559 Ruby most often breaks between base-annotation sets,
560 but if the line-breaking rules allow it, can also break within a <i>ruby base</i>
561 (and, in parallel, its associated <i>annotation boxes</i>).
563 <p>Whenever ruby breaks across lines, <i>ruby annotations</i> must stay
564 with their respective <i>bases</i>.
565 The line <em>must not</em> break between a <i>ruby base</i> and its <i>annotations</i>,
566 even in the case of ''inter-character'' <i>annotations</i>.
568 <div class="figure">
569 <img src="images/r-break-b.gif"
570 alt='Diagram showing the line breaking opportunity in a "Bopomofo" ruby'>
571 <p class="caption">''inter-character'' ruby line breaking opportunity
572 </div>
574 <h4 id="break-between">
575 Breaking between bases</h4>
577 <p>In typical cases, <i>ruby base boxes</i> and <i>ruby annotation boxes</i>
578 are styled to forbid internal line wrapping and do not contain forced breaks.
579 (See <a href="#default-stylesheet">Appendix A</a>.)
580 In such cases the <i>ruby container</i> can only break between adjacent <i>ruby bases</i>,
581 and only if no <i>ruby annotations</i> span those <i>ruby bases</i>.
583 <div class="figure">
584 <p><img src="images/r-break-a.gif"
585 alt="Diagram showing the line breaking opportunity in a complex ruby">
586 <p class="caption">Ruby line breaking opportunity
587 </div>
589 <p>Whether ruby can break between two adjacent <i>ruby bases</i>
590 is controlled by normal line-breaking rules for the affected text,
591 exactly as if the <i>ruby bases</i> were adjacent <i>inline</i> boxes.
592 (The annotations are ignored when determining soft wrap opportunities for the base level.)
594 <div class="example">
595 <p>For example, if two adjacent ruby bases are “蝴” and “蝶”,
596 the line may break between them,
597 because lines are normally allowed to break between two Han characters.
598 However, if 'word-break' is ''keep-all'', that line break is forbidden.
599 <pre><ruby>蝴<rt>hú</rt>蝶<rt>dié</rt></pre>
600 </div>
602 <p>Inter-base white space is significant for evaluating line break opportunities between <i>ruby bases</i>.
603 As with white space between inlines, it collapses when the line breaks there.
604 Similarly, annotation white space is also trimmed at a line break.
606 <div class="example">
607 <p>For example, given the following markup:
608 <pre><ruby><rb>one</rb> <rb>two</rb> <rt>1</rt> <rt>2</rt></ruby></pre>
609 <p>Due to the space, the line may break between “one” and “two“.
610 If the line breaks there, that space—and the space between “1” and “2”—disappears,
611 in accordance with standard CSS white space processing rules. [[CSS3TEXT]]
612 </div>
614 <h4 id="break-within">
615 Breaking within bases</h4>
617 <p class="issue">Fill in this section...
619 <p>There are no line breaking opportunities within ''inter-character'' <i>annotations</i>.
621 <h3 id="line-height">
622 Ruby box and line stacking</h3>
624 <p>The 'line-height' property controls spacing between lines in CSS.
625 When inline content on line is shorter than the 'line-height',
626 half-leading is added on either side of the content,
627 as specificed in <a href="http://www.w3.org/TR/CSS21/visudet.html#line-height">CSS2.1§10.8</a>. [[!CSS21]]
629 <p>In order to ensure consistent spacing of lines,
630 documents with ruby typically ensure that the 'line-height' is large enough
631 to accommodate ruby between lines of text.
632 Therefore, ordinarily, <i>ruby annotation containers</i> and <i>ruby annotation boxes</i>
633 do not contribute to the measured height of a line's inline contents;
634 any alignment (see 'vertical-align') and line-height calculations
635 are performed using only the <i>ruby base container</i>,
636 exactly as if it were a normal inline.
638 <p>However, if the 'line-height' specified on the <i>ruby container</i>
639 is less than the distance between
640 the top of the top <i>ruby annotation container</i>
641 and the bottom of the bottom <i>ruby annotation container</i>,
642 then additional leading is added
643 on the appropriate side of the <i>ruby base container</i>
644 such that if a block consisted of three lines
645 each containing ruby identical to this,
646 none of the <i>ruby containers</i> would overlap.
648 <p class="note">Note that this does not ensure that the <i>ruby annotations</i> remain within the line box.
649 It merely ensures that <em>if all lines had equal spacing</em>
650 and equivalent amounts and positioning of <i>ruby annotations</i>,
651 there would be enough room to avoid overlap.
653 <p>Authors should ensure appropriate 'line-height' and 'padding' to accommodate ruby,
654 and be particularly careful at the beginning or end of a block
655 and when a line contains inline-level content
656 (such as images, inline blocks, or elements shifted with 'vertical-align')
657 taller than the paragraph's default font size.
659 <div class="figure">
660 <p><img src="images/rlh-a.gif"
661 alt="The content of each line sits in the middle of its line height;
662 the additional space on each side is called half-leading.
663 Ruby fits between lines if it is smaller than twice the half-leading,
664 but this means that it occupies space belonging to the half-leading of the previous line.">
665 <p class="caption">Ruby annotations will often overflow the line;
666 authors should ensure content over/under a ruby-annotated line
667 is adequately spaced to leave room for the ruby.
668 </div>
670 <p class="note">More control over how ruby affects alignment and line layout
671 will be part of the CSS Line Layout Module Level 3.
672 Note, it is currently in the process of being rewritten;
673 the current drafts should not be relied upon.
675 <h2 id="ruby-props">
676 Ruby Properties</h2>
678 <p>The following properties are introduced to control ruby positioning and alignment.
680 <h3 id="rubypos">
681 Ruby positioning: the 'ruby-position' property</h3>
683 <table class="propdef">
684 <tr>
685 <th>Name:
686 <td><dfn>ruby-position</dfn>
687 <tr>
688 <th><a href="#values">Value</a>:
689 <td>[ over | under | inter-character ] && [ right | left ]
690 <tr>
691 <th>Initial:
692 <td>over right
693 <tr>
694 <th>Applies to:
695 <td>ruby annotation containers
696 <tr>
697 <th>Inherited:
698 <td>yes
699 <tr>
700 <th>Percentages:
701 <td>N/A
702 <tr>
703 <th>Media:
704 <td>visual
705 <tr>
706 <th>Computed value:
707 <td>specified value
708 <tr>
709 <th>Animatable:
710 <td>no
711 <tr>
712 <th>Canonical order:
713 <td><abbr title="follows order of property value definition">per grammar</abbr>
714 </table>
716 <p>This property controls position of the ruby text with respect to its base.
717 Values have the following meanings:
719 <p class="issue"><span class="issuehead">Issue-107: </span> Roland Steiner has requested the addition of an auto value as default. See <a href="http://www.w3.org/Search/Mail/Public/advanced_search?keywords=&hdr-1-name=subject&hdr-1-query=ruby-position%3A+undesirable+default+value+%27before%27+for+complex+ruby&hdr-2-name=from&hdr-2-query=&hdr-3-name=message-id&hdr-3-query=&period_month=&period_year=&index-grp=Public__FULL&index-type=t&type-index=www-style&resultsperpage=20&sortby=date">this thread</a> and <a href="http://www.w3.org/Search/Mail/Public/advanced_search?keywords=&hdr-1-name=subject&hdr-1-query=Styling+of+complex+Ruby&hdr-2-name=from&hdr-2-query=&hdr-3-name=message-id&hdr-3-query=&period_month=&period_year=&index-grp=Public__FULL&index-type=t&type-index=public-i18n-core&resultsperpage=20&sortby=date">this one</a>.</p>
720 <dl>
721 <dt><dfn title="ruby-position:over">''over''</dfn>
722 <dd>The ruby text appears <i>over</i> the base in horizontal text.
724 <div class="figure">
725 <p><img src="images/shinkansen-top.gif"
726 alt="Diagram of ruby glyph layout in horizontal mode with ruby text appearing above the base">
727 <p class="caption">Ruby over Japanese base text in horizontal layout
728 </div>
729 </dd>
731 <dt><dfn title="ruby-position:right">''right''</dfn>
732 <dd>The ruby text appears on the right side of the base in vertical text.
733 <div class="figure">
734 <p><img src="images/shinkansen-right.gif" width="33"
735 alt="Diagram of ruby glyph layout in vertical mode with ruby text apearing vertically on the right of the base">
736 <p class="caption">Ruby to the right of Japanese base text in vertical layout
737 </div>
738 </dd>
740 <dt><dfn title="ruby-position:under">''under''</dfn>
741 <dd>The ruby text appears under the base in horizontal text.
742 This is a relatively rare setting used in ideographic East Asian writing systems,
743 most easily found in educational text.
745 <div class="figure">
746 <p><img src="images/shinkansen-bottom.gif"
747 alt="Diagram of ruby glyph layout in horizontal mode with ruby text appearing below the base">
748 <p class="caption">Ruby under Japanese base text in horizontal layout
749 </div>
750 </dd>
752 <dt><dfn title="ruby-position:left">''left''</dfn>
753 <dd>The ruby text appears on the left side of the base in vertical text.
755 <div class="figure">
756 <p><img src="images/shinkansen-left.gif"
757 alt="Diagram of ruby glyph layout in vertical mode with ruby text apearing vertically on the left of the base">
758 <p class="caption">Ruby to the left of Japanese base text in vertical layout
759 </div>
760 </dd>
762 <dt><dfn title="ruby-position:inter-character">''inter-character''</dfn></dt>
763 <dd>
764 <p>The ruby text appears on the right of the base in horizontal text.
765 This value forces the 'writing-mode' of the <i>ruby annotation</i> to be vertical.
767 <p>This value is provided for the special case of traditional Chinese
768 as used especially in Taiwan:
769 ruby (made of <a href="#g-bopomofo">bopomofo</a> glyphs) in that context
770 appears vertically along the right side of the base glyph,
771 even when the layout of the base characters is horizontal:
773 <div class="figure">
774 <p><img src="images/bopomofo.gif"
775 alt="Example of Taiwanese-style ruby">
776 <p class="caption">“Bopomofo” ruby in traditional Chinese
777 (ruby text shown in blue for clarity) in horizontal layout
778 </div>
779 <p class="note">
780 Note that the user agent is responsible for ensuring the correct relative alignment and positioning of the glyphs,
781 including those corresponding to the tone marks, when displaying.
782 Tone marks are spacing characters that occur (in memory) at the end of the ruby text for each base character.
783 They are usually displayed in a separate column to the right of the bopomofo characters,
784 and the height of the tone mark depends on the number of characters in the syllable.
785 One tone mark, however, is placed above the bopomofo, not to the right of it.
786 <!-- See Taiwanese requirements doc for EPUB at http://epub-revision.googlecode.com/files/EGLS_TW_eng.ppt -->
787 </dd>
788 </dl>
790 <p>If multiple <i>ruby annotation containers</i> have the same 'ruby-position',
791 they stack along the block axis,
792 with lower levels of annotation closer to the base text.
794 <h3 id="collapsed-ruby">
795 Collapsed Ruby Annotations: the 'ruby-merge' property</h3>
797 <table class="propdef">
798 <tr>
799 <th>Name:
800 <td><dfn>ruby-merge</dfn>
801 <tr>
802 <th><a href="#values">Value</a>:
803 <td>separate | collapse | auto
804 <tr>
805 <th>Initial:
806 <td>separate
807 <tr>
808 <th>Applies to:
809 <td>ruby annotation containers
810 <tr>
811 <th>Inherited:
812 <td>yes
813 <tr>
814 <th>Percentages:
815 <td>N/A
816 <tr>
817 <th>Media:
818 <td>visual
819 <tr>
820 <th>Computed value:
821 <td>specified value
822 <tr>
823 <th>Animatable:
824 <td>no
825 <tr>
826 <th>Canonical order:
827 <td><abbr title="follows order of property value definition">per grammar</abbr>
828 </table>
830 <p>
831 This property controls how ruby annotation boxes should be rendered
832 when there are more than one in a ruby container box.
834 <p>Possible values:</p>
835 <dl>
836 <dt><dfn title="ruby-merge:separate">''separate''</dfn>
837 <dd>
838 <p>
839 Each ruby annotation box is rendered in the same column(s) as its corresponding base box(es).
840 This style is called “mono ruby” in [[JLREQ]].
842 <div class="example">
843 <p>For example, the following two markups render the same:
844 <pre><ruby>無<rt>む</ruby><ruby>常<rt>じょう</ruby></pre>
845 <p>and:
846 <pre><ruby style="ruby-merge:separate"><rb>無<rb>常<rt>む<rt>じょう</ruby></pre>
847 </div>
848 </dd>
850 <dt><dfn title="ruby-merge:collapse">''collapse''</dfn>
851 <dd>
852 <p>
853 All <i>ruby annotation boxes</i> within the same <i>ruby segment</i> on the same line are concatenated,
854 and laid out as if their contents belonged to a single <i>ruby annotation box</i>
855 spanning all their associated <i>ruby base boxes.
856 This style renders similar to “group ruby” in [[JLREQ]],
857 except that <i>ruby annotations</i> are kept together with their respective <i>ruby bases</i> when breaking lines.
858 </p>
860 <div class="example">
861 <p>The following two markups render the same both characters fit on one line:
862 <pre><ruby>無常<rt>むじょう</ruby></pre>
863 <p>and:
864 <pre><ruby style="ruby-merge:collapse"><rb>無<rb>常<rt>む<rt>じょう</ruby></pre>
865 <p>However, the second one renders the same as ''ruby-position: separate''
866 when the two bases are split across lines.
867 </div>
868 </dd>
870 <dt><dfn title="ruby-merge:auto">''auto''</dfn></dt>
871 <dd>
872 <p>
873 The user agent may use any algorithm to determine how each ruby annotation box
874 is rendered to its corresponding base box.
875 <div class="example">
876 <p>
877 One possible algorithm is described as Jukugo-ruby in [[JLREQ]].
878 <p>
879 Another, more simplified algorithm of Jukugo-ruby is
880 to render as Mono-ruby if all ruby annotation boxes fit within
881 advances of their corresponding base boxes,
882 and render as Group-ruby otherwise.
883 </p>
884 </div>
885 </dd>
886 </dl>
888 <h3 id="rubyalign">
889 Ruby Text Distribution: the 'ruby-align' property</h3>
891 <table class="propdef">
892 <tr>
893 <th>Name:
894 <td><dfn>ruby-align</dfn>
895 <tr>
896 <th><a href="#values">Value</a>:
897 <td>auto | start | center |
898 distribute-letter | distribute-space
899 <tr>
900 <th>Initial:
901 <td>auto
902 <tr>
903 <th>Applies to:
904 <td>ruby bases, ruby annotations, ruby base containers, ruby annotation containers
905 <tr>
906 <th>Inherited:
907 <td>yes
908 <tr>
909 <th>Percentages:
910 <td>N/A
911 <tr>
912 <th>Media:
913 <td>visual
914 <tr>
915 <th>Computed value:
916 <td>specified value (except for initial and inherit)
917 </table>
919 <p>This property specifies how text is distributed within the various ruby boxes
920 when their text contents exactly fill their respective boxes.
922 <p>Values have the following meanings:
923 <p class="issue"><span class="issuehead">Issue: </span> Tony Graham has <a href="http://www.w3.org/Style/XSL/Group/FO/wiki/Ruby#Treat_CSS3_.22ruby-align.22_As_Shorthand.3F">suggested </a>that distribute-letter and distribute-space be values of a ruby-group-distribution property, and line-edge be moved to a ruby-alignment-edge property, and that the rest be gathered under a ruby-alignment property. And that ruby-align become a shorthand.</p>
924 <dl>
925 <dt><dfn title="ruby-align:auto">''auto''</dfn></dt>
926 <dd>
927 <p>The user agent determines how the ruby contents are aligned.
928 This is the initial value.
929 The behavior recommended by [[JLREQ]] is for wide-cell ruby to be aligned in the 'distribute-space' mode:
930 <div class="figure">
931 <p><img width="145" height="91"
932 alt="Diagram of glyph layout in auto aligned ruby when ruby text is shorter than base"
933 src="images/ra-ds.gif" /><img width="145" height="91"
934 alt="Diagram of glyph layout in auto aligned ruby when ruby text is longer than base"
935 src="images/ra-ds-rb.gif" /></p>
936 <p><b>Figure 4.2.1</b>: Wide-cell text in 'auto' ruby alignment is
937 'distribute-space' justified</p>
938 </div>
940 <p>The recommended behavior for narrow-cell glyph ruby is to be
941 aligned in the 'center' mode.</p>
942 <div class="figure">
943 <p><img
944 alt="Diagram of glyph layout in auto aligned ruby when halfwidth ruby text is shorter than base"
945 width="145" height="91"
946 src="images/ra-c-h.gif" /><img
947 alt="Diagram of character layout in auto aligned ruby when ruby text is longer than narrow-width base"
948 width="145" height="91"
949 src="images/ra-c-rb-h.gif" /></p>
950 <p><b>Figure 4.2.2</b>: Narrow-width ruby text in 'auto' ruby alignment
951 is centered</p>
952 </div>
953 </dd>
955 <dt><dfn title="ruby-align:start">''start''</dfn></dt>
956 <dd>The ruby annotation content is aligned with the start edge of the base.
957 <div class="figure">
958 <p><img
959 alt="Diagram of glyph layout in left aligned ruby when ruby text is shorter than base"
960 width="145" height="91" src="images/ra-l.gif" /><img
961 width="145" height="91"
962 alt="Diagram of glyph layout in left aligned ruby when ruby text is longer than base"
963 src="images/ra-l-rb.gif" /></p>
964 <p><b>Figure 4.2.3</b>: Start ruby alignment</p>
965 </div>
966 </dd>
968 <dt><dfn title="ruby-align:center">''center''</dfn></dt>
969 <dd>The ruby text content is centered within the width of the base. If the
970 length of the base is smaller than the length of the ruby text, then the
971 base is centered within the width of the ruby text.
973 <div class="figure">
974 <p><img width="145" height="91"
975 alt="Diagram of glyph layout in center aligned ruby when ruby text is shorter than base"
976 src="images/ra-c.gif" /><img width="145" height="91"
977 alt="Diagram of glyph layout in center aligned ruby when ruby text is longer than base"
978 src="images/ra-c-rb.gif" /></p>
979 <p><b>Figure 4.2.4</b>: Center ruby alignment</p>
980 </div>
981 </dd>
983 <!--
984 <dt><strong>right</strong></dt>
985 <dd>The ruby text content is aligned with the end edge of the base.
986 <p class="issue"><span class="issuehead">Issue: </span> The i18n WG feels that end and right should not be synonymous, and proposed to drop right (there is no left/right in overhang)? See <a href="http://www.w3.org/Search/Mail/Public/advanced_search?keywords=&hdr-1-name=subject&hdr-1-query=[CSS3+Ruby]%20left/start+and+right/end&hdr-2-name=from&hdr-2-query=&hdr-3-name=message-id&hdr-3-query=&index-grp=Member__FULL+Public__FULL&index-type=t&type-index=public-i18n-core%40w3.org&resultsperpage=20&sortby=date">this thread</a>.</p>
987 <div class="figure">
988 <p><img class="example" width="145" height="91"
989 alt="Diagram of glyph layout in right aligned ruby when ruby text is shorter than base"
990 src="images/ra-r.gif" /><img class="example" width="145" height="91"
991 alt="Diagram of glyph layout in right aligned ruby when ruby text is longer than base"
992 src="images/ra-r-rb.gif" /></p>
993 <p><b>Figure 4.2.5</b>: End ruby alignment</p>
994 </div>
995 </dd>
996 -->
998 <dt><dfn title="ruby-align:distribute-letter">''distribute-letter''</dfn></dt>
999 <dd>If the width of the ruby text is smaller than that of the base, then
1000 the ruby text contents are evenly distributed across the width of the
1001 base, with the first and last ruby text glyphs lining up with the
1002 corresponding first and last base glyphs. If the width of the ruby text
1003 is at least the width of the base, then the letters of the base are
1004 evenly distributed across the width of the ruby text.
1006 <div class="figure">
1007 <p><img width="145" height="91"
1008 alt="Diagram of glyph layout in distribute-letter aligned ruby when ruby text is shorter than base"
1009 src="images/ra-dl.gif" /><img width="145" height="91"
1010 alt="Diagram of glyph layout in distribute-letter aligned ruby when ruby text is longer than base"
1011 src="images/ra-dl-rb.gif" /></p>
1012 <p><b>Figure 4.2.6</b>: Distribute-letter ruby alignment</p>
1013 </div>
1014 </dd>
1016 <dt><dfn title="ruby-align:distribute-space">''distribute-space''</dfn></dt>
1017 <dd>If the width of the ruby text is smaller than that of the base, then
1018 the ruby text contents are evenly distributed across the width of the
1019 base, with a certain amount of white space preceding the first and
1020 following the last character in the ruby text. That amount of white
1021 space is normally equal to half the amount of inter-character space of
1022 the ruby text. If the width of the ruby text is at least the width of
1023 the base, then the same type of space distribution applies to the base.
1024 In other words, if the base is shorter than the ruby text, the base is
1025 distribute-space aligned. This type of alignment
1026 is described by [[JLREQ]].
1028 <div class="figure">
1029 <p><img width="145" height="91"
1030 alt="Diagram of glyph layout in distribute-space aligned ruby when ruby text is shorter than base"
1031 src="images/ra-ds.gif" /><img width="145" height="91"
1032 alt="Diagram of glyph layout in distribute-space aligned ruby when ruby text is longer than base"
1033 src="images/ra-ds-rb.gif" /></p>
1034 <p><b>Figure 4.2.7</b>: Distribute-space ruby alignment</p>
1035 </div>
1036 </dd>
1038 <!--
1039 <dt><strong>line-edge</strong></dt>
1040 <dd>If the ruby text is not adjacent to a line edge, it is aligned as in
1041 'auto'. If it is adjacent to a line edge, then it is still aligned as in
1042 auto, but the side of the ruby text that touches the end of the line is
1043 lined up with the corresponding edge of the base. This type of alignment
1044 is described by [[JLREQ]]. This type of alignment is
1045 relevant only to the scenario where the ruby text is longer than the
1046 ruby base. In the other scenarios, this is just 'auto'.
1047 <div class="figure">
1048 <p><img class="example" width="146" height="109"
1049 alt="Diagram of glyph layout in line-edge aligned ruby when ruby text is shorter than base"
1050 src="images/ra-le-l.gif" /><img class="example" width="146"
1051 height="110"
1052 alt="Diagram of glyph layout in line-edge aligned ruby when ruby text is longer than base"
1053 src="images/ra-le-r.gif" /></p>
1054 <p><b>Figure 4.2.8</b>: Line edge ruby alignment</p>
1055 </div>
1056 </dd>
1057 -->
1058 </dl>
1060 <p>For a complex ruby with spanning elements, one additional consideration is
1061 required. If the spanning element spans multiple 'rows' (other rbc or rtc
1062 elements), and the ruby alignment requires space distribution among the
1063 'spanned' elements, a ratio must be determined among the 'columns' of spanned
1064 elements. This ratio is computed by taking into consideration the widest
1065 element within each column.</p>
1067 <h2 id="edge-effects">
1068 Edge Effects</h2>
1070 <h3 id="ruby-overhang">
1071 Overhanging Ruby</h3>
1073 <p>
1074 When <i>ruby annotation box</i> is longer than its corresponding <i>ruby base box</i>,
1075 the <i>ruby annotation box</i> may partially overhang adjacent boxes.
1076 </p>
1077 <p>
1078 This level of the specification does not define
1079 how much the overhang may be allowed, and under what conditions.
1080 </p>
1082 <p>If the ruby text is not allowed to overhang,
1083 then the ruby behaves like a traditional inline box,
1084 i.e. only its own contents are rendered within its boundaries
1085 and adjacent elements do not cross the box boundary:
1087 <div class="figure">
1088 <p><img src="images/ro-n.gif"
1089 alt="Diagram showing the ruby boxes interacting with adjacent text">
1090 <p class="caption">Simple ruby whose text is not allowed to overhang adjacent text
1091 </div>
1093 <p>However, if <i>ruby annotation</i> content is allowed to overhang adjacent elements
1094 and it happens to be wider than its base,
1095 then the adjacent content is partially rendered within the area of the <i>ruby container box</i>,
1096 while the <i>ruby annotation</i> may partially overlap the upper blank parts of the adjacent content:
1098 <div class="figure">
1099 <p><img src="images/ro-a.gif"
1100 alt="Diagram showing the ruby boxes interacting with adjacent text">
1101 <p class="caption">Simple ruby whose text is allowed to overhang adjacent text
1102 </div>
1104 <p>The <i>ruby annotations</i> related to a <i>ruby base</i>
1105 must never overhang another <i>ruby base</i>.
1107 <p>The alignment of the contents of the base or the ruby text
1108 is not affected by overhanging behavior.
1109 The alignment is achieved the same way regardless of the overhang behavior setting
1110 and it is computed before the space available for overlap is determined.
1111 It is controlled by the 'ruby-align' property.
1113 <p class="issue">
1114 I suspect overhanging interacts with alignment in some cases;
1115 might need to look into this later.
1117 <p>This entire logic applies the same way in vertical ideographic layout,
1118 only the dimension in which it works in such a layout is vertical,
1119 instead of horizontal.
1121 <div class="example">
1122 <p>
1123 The user agent may use [[JIS4051]] recommendation of
1124 using one ruby text character length as the maximum overhang length.
1125 Detailed rules for how ruby text can overhang adjacent characters for Japanese are described by [[JLREQ]].
1126 </p>
1127 </div>
1129 <h3 id="line-edge">
1130 Line-edge Alignment</h3>
1132 <p>
1133 When a <i>ruby annotation box</i> that is longer than its <i>ruby base</i>
1134 is at the start or end edge of a line,
1135 the user agent <em>may</em> force the side of the <i>ruby annotation</i> that touches the edge of the line
1136 to align to the corresponding edge of the base.
1137 This type of alignment is described by [[JLREQ]].
1138 </p>
1139 <p>
1140 This level of the specification does not provide a mechanism to control this behavior.
1141 </p>
1142 <div class="figure">
1143 <p><img src="images/ra-le-l.gif"
1144 alt="Diagram of glyph layout in line-edge aligned ruby when ruby text is shorter than base">
1145 <img src="images/ra-le-r.gif"
1146 alt="Diagram of glyph layout in line-edge aligned ruby when ruby text is longer than base">
1147 <p class="caption">Line-edge alignment
1148 </div>
1150 <!--
1151 <h3 id="rubyover">
1152 Ruby overhanging: the 'ruby-overhang' property</h3>
1154 <table class="propdef">
1155 <tr>
1156 <th>Name:
1157 <td><dfn>ruby-overhang</dfn>
1158 <tr>
1159 <th>Value:
1160 <td>auto | start | end | none
1161 <tr>
1162 <th>Initial:
1163 <td>none
1164 <tr>
1165 <th>Applies to:
1166 <td>the parent of elements with display: ruby-text
1167 <tr>
1168 <th>Inherited:
1169 <td>yes
1170 <tr>
1171 <th>Percentages:
1172 <td>N/A
1173 <tr>
1174 <th>Media:
1175 <td>visual
1176 <tr>
1177 <th>Computed value:
1178 <td>specified value (except for initial and inherit)
1179 </table>
1181 <p>This property determines whether, and on which side, ruby text is allowed
1182 to partially overhang any adjacent text in addition to its own base, when the
1183 ruby text is wider than the ruby base. Note that ruby text is never allowed to
1184 overhang glyphs belonging to another ruby base. <span class="issue"><span class="issuehead">Issue: </span> This rule must be broken if we are to allow support for jukugo ruby.</span> Also the user agent is free to assume
1185 a maximum amount by which ruby text may overhang adjacent text. The user agent may use
1186 the [[JIS4051]] recommendation of using one ruby text character
1187 length as the maximum overhang length. Detailed rules for how ruby text can overhang adjacent characters for Japanese are described by [[JLREQ]].</p>
1189 <p>Possible values:</p>
1190 <dl>
1191 <dt><strong>auto</strong></dt>
1192 <dd>The ruby text can overhang text adjacent to the base on either side. [[JLREQ]] and [[JIS4051]] specify the categories of characters that
1193 ruby text can overhang. The user agent is free to follow those recommendations or specify its own classes of
1194 characters to overhang. This is the initial value.
1195 <div class="figure">
1196 <p><img class="example" width="177" height="91"
1197 alt="Diagram of glyph layout in overhanging ruby" src="images/ro-a.gif" /></p>
1198 <p><b>Figure 4.3.1</b>: Ruby overhanging adjacent text</p>
1199 </div>
1200 </dd>
1201 <dt><strong>start</strong></dt>
1202 <dd>The ruby text can only overhang the text that precedes it. That means, for
1203 example, that ruby cannot overhang text that is to the right of it in
1204 horizontal LTR layout, and it cannot overhang text that is below it in
1205 vertical-ideographic layout.
1206 <div class="figure">
1207 <p><img class="example" width="199" height="91"
1208 alt="Diagram of glyph layout when ruby overhangs the preceding glyphs only"
1209 src="images/ro-s.gif" /></p>
1210 <p><b>Figure 4.3.2</b>: Ruby overhanging preceding text only</p>
1211 </div>
1212 </dd>
1213 <dt><strong>end</strong></dt>
1214 <dd>The ruby text can only overhang the text that follows it. That means, for
1215 example, that ruby cannot overhang text that is to the left of it in
1216 horizontal LTR layout, and it cannot overhang text that is above it in
1217 vertical-ideographic layout.
1218 <div class="figure">
1219 <p><img class="example" width="198" height="91"
1220 alt="Diagram of glyph layout when ruby overhangs the following characters only"
1221 src="images/ro-e.gif" /></p>
1222 <p><b>Figure 4.3.3</b>: Ruby overhanging following text only</p>
1223 </div>
1224 </dd>
1225 <dt><strong>none</strong></dt>
1226 <dd>The ruby text cannot overhang any text adjacent to its base, only its
1227 own base.
1229 <div class="figure">
1230 <p><img class="example" width="220" height="91"
1231 alt="Diagram of glyph layout in non-overhanging ruby"
1232 src="images/ro-n.gif" /></p>
1233 <p><b>Figure 4.3.4</b>: Ruby not allowed to overhang adjacent text</p>
1234 </div>
1235 </dd>
1236 </dl>
1238 <h3 id="rubyspan">
1239 Ruby annotation spanning: the 'ruby-span' property</h3>
1241 <table class="propdef">
1242 <tr>
1243 <th>Name:
1244 <td><dfn>ruby-span</dfn>
1245 <tr>
1246 <th>Value:
1247 <td>attr(x) | none
1248 <tr>
1249 <th>Initial:
1250 <td>none
1251 <tr>
1252 <th>Applies to:
1253 <td>elements with display: ruby-text
1254 <tr>
1255 <th>Inherited:
1256 <td>no
1257 <tr>
1258 <th>Percentages:
1259 <td>N/A
1260 <tr>
1261 <th>Media:
1262 <td>visual
1263 <tr>
1264 <th>Computed value:
1265 <td><number>
1266 </table>
1268 <p>This property controls the spanning behavior of annotation elements. </p>
1270 <p class="note"><span class="note-label">Note:</span> A XHTML user agent may also use the <samp>rbspan</samp>
1271 attribute to get the same effect.</p>
1273 <p>Possible values:</p>
1275 <dl>
1276 <dt><strong>attr(x)</strong></dt>
1277 <dd>The value of attribute 'x' as a string value. The string value is
1278 evaluated as a <number> to determine the number of ruby base elements to be
1279 spanned by the annotation element. If the <number> is '0', it is replaced by
1280 '1'.The <number> is the computed value. </dd>
1281 <dt>none</dt>
1282 <dd>No spanning. The computed value is '1'.</dd>
1283 </dl>
1285 <p>The following example shows an XML example using the 'display' property
1286 values associated with the 'ruby structure and the 'ruby-span' property</p>
1287 <pre class="xml">myruby { display: ruby; }
1288 myrbc { display: ruby-base-container; }
1289 myrb { display: ruby-base; }
1290 myrtc.before { display: ruby-text-container; ruby-position: before}
1291 myrtc.after { display: ruby-text-container; ruby-position: after}
1292 myrt { display: ruby-text; ruby-span: attr(rbspan); }
1293 ...
1294 <myruby>
1295 <myrbc>
1296 <myrb>10</myrb>
1297 <myrb>31</myrb>
1298 <myrb>2002</myrb>
1299 </myrbc>
1300 <myrtc class="before">
1301 <myrt>Month</myrt>
1302 <myrt>Day</myrt>
1303 <myrt>Year</myrt>
1304 </myrtc>
1305 <myrtc class="after">
1306 <myrt rbspan="3">Expiration Date</myrt>
1307 </myrtc>
1308 </myruby></pre>
1309 -->
1311 <h2 id="default-stylesheet" class="no-num">
1312 Appendix A: Default Style Sheet</h2>
1314 <p><em>This section is informative.</em>
1316 <h3 id="default-ua-ruby" class="no-num">
1317 <span class="secno">A.1</span> Supporting Ruby Layout</h3>
1319 <p>The following represents a default UA style sheet
1320 for rendering HTML and XHTML ruby markup as ruby layout:
1322 <pre>
1323 <!-- -->ruby { display: ruby; }
1324 <!-- -->rb { display: ruby-base; white-space: nowrap; }
1325 <!-- -->rt { display: ruby-text; white-space: nowrap; font-size: 50%; }
1326 <!-- -->rbc { display: ruby-base-container; }
1327 <!-- -->rtc { display: ruby-text-container; }</pre>
1329 <p>Additional rules for UAs supporting the relevant features of [[CSS3-TEXT-DECOR]] and [[CSS3-FONTS]]:
1330 <pre>rt { font-variant-east-asian: ruby; text-emphasis: none; }</pre>
1332 <p class="note">Authors should not use the above rules;
1333 a UA that supports ruby layout should provide these by default.
1335 <h3 id="default-inline" class="no-num">
1336 <span class="secno">A.2</span> Inlining Ruby Annotations</h3>
1338 <p>The following represents a sample style sheet
1339 for rendering HTML and XHTML ruby markup as inline annotations:
1341 <pre>ruby, rb, rt, rbc, rtc, rp {
1342 <!-- --> display: inline; white-space: inherit;
1343 <!-- --> font-variant-east-asian: inherit; text-emphasis: inherit; }</pre>
1345 <h3 id="default-parens" class="no-num">
1346 <span class="secno">A.3</span> Generating Parentheses</h3>
1348 <p>Unfortunately, because Selectors cannot match against text nodes,
1349 it's not possible with CSS to express rules that will automatically and correctly
1350 add parentheses to unparenthesized ruby annotations in HTML.
1351 (This is because HTML ruby allows implying the <i>ruby base</i> from raw text, without a corresponding element.)
1352 However, these rules will handle cases where either <code><rb></code>
1353 or <code><rtc></code> is used rigorously.
1355 <pre>
1356 <!-- -->/* Parens around <rtc> */
1357 <!-- -->rtc::before { content: "("; }
1358 <!-- -->rtc::after { content: ")"; }
1360 <!-- -->/* Parens before first <rt> not inside <rtc> */
1361 <!-- -->rb + rt::before,
1362 <!-- -->rtc + rt::before { content: "("; }
1364 <!-- -->/* Parens after <rt> not inside <rtc> */
1365 <!-- -->rb ~ rt:last-child::after,
1366 <!-- -->rt + rb::before { content: ")"; }
1367 <!-- -->rt + rtc::before { content: ")("; }</pre>
1369 <h2 id="glossary">
1370 Glossary</h2>
1371 <dl>
1372 <dt><a id="g-bopomofo"><strong><span
1373 lang="zh">Bopomofo</span></strong></a></dt>
1374 <dd>37 characters and 4 tone markings used as phonetics in Chinese,
1375 especially standard Mandarin.</dd>
1376 <dt><a id="g-hanja"><strong><span
1377 lang="ko">Hanja</span></strong></a></dt>
1378 <dd>Subset of the Korean writing system that utilizes ideographic
1379 characters borrowed or adapted from the Chinese writing system. Also see
1380 <a href="#g-kanji"><span lang="ja">Kanji</span></a>.</dd>
1381 <dt><a id="g-hiragana"><strong><span
1382 lang="ja">Hiragana</span></strong></a></dt>
1383 <dd>Japanese syllabic script, or character of that script. Rounded and
1384 cursive in appearance. Subset of the Japanese writing system, used together
1385 with kanji and katakana. In recent times, mostly used to write Japanese
1386 words when kanji are not available or appropriate, and word endings and
1387 particles. Also see <a
1388 href="#g-katakana"><span lang="ja">Katakana</span></a>.</dd>
1389 <dt><a id="g-ideogram"><strong>Ideograph</strong></a></dt>
1390 <dd>A character that is used to represent an idea, word, or word component,
1391 in contrast to a character from an alphabetic or syllabic script. The most
1392 well-known ideographic script is used (with some variation) in East Asia
1393 (China, Japan, Korea,...).</dd>
1394 <dt><a id="g-kana"><strong><span lang="ja">Kana</span></strong></a></dt>
1395 <dd>Collective term for hiragana and katakana.</dd>
1396 <dt><a id="g-kanji"><strong>Kanji</strong></a></dt>
1397 <dd>Japanese term for ideographs; ideographs used in Japanese. Subset of the
1398 Japanese writing system, used together with hiragana and katakana. Also see <a
1399 href="#g-hanja"><span lang="ko">Hanja</span></a>.</dd>
1400 <dt><a id="g-katakana"><strong><span
1401 lang="ja">Katakana</span></strong></a></dt>
1402 <dd>Japanese syllabic script, or character of that script. Angular in
1403 appearance. Subset of the Japanese writing system, used together with
1404 kanji and hiragana. In recent times, mainly used to write foreign words. Also see <a
1405 href="#g-hiragana"><span lang="ja">Hiragana</span></a>.</dd>
1406 <dt><a id="g-monoruby" name="g-monoruby"><strong>Mono-ruby</strong></a></dt>
1407 <dd>In Japanese typography: Ruby associated with a single character of
1408 the base text.</dd>
1409 <dt><a id="g-ruby"><strong>Ruby</strong></a></dt>
1410 <dd>A run of text that appears in the vicinity of another run of text and
1411 serves as an annotation or a pronunciation guide for that text.</dd>
1412 </dl>
1414 <h2 id="conformance">
1415 Conformance</h2>
1417 <h3 id="conventions">
1418 Document conventions</h3>
1420 <p>Conformance requirements are expressed with a combination of
1421 descriptive assertions and RFC 2119 terminology. The key words “MUST”,
1422 “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
1423 “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
1424 document are to be interpreted as described in RFC 2119.
1425 However, for readability, these words do not appear in all uppercase
1426 letters in this specification.
1428 <p>All of the text of this specification is normative except sections
1429 explicitly marked as non-normative, examples, and notes. [[!RFC2119]]</p>
1431 <p>Examples in this specification are introduced with the words “for example”
1432 or are set apart from the normative text with <code>class="example"</code>,
1433 like this:
1435 <div class="example">
1436 <p>This is an example of an informative example.</p>
1437 </div>
1439 <p>Informative notes begin with the word “Note” and are set apart from the
1440 normative text with <code>class="note"</code>, like this:
1442 <p class="note">Note, this is an informative note.</p>
1444 <h3 id="conformance-classes">
1445 Conformance classes</h3>
1447 <p>Conformance to CSS Ruby Module
1448 is defined for three conformance classes:
1449 <dl>
1450 <dt><dfn title="style sheet!!as conformance class">style sheet</dfn>
1451 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
1452 style sheet</a>.
1453 <dt><dfn>renderer</dfn></dt>
1454 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
1455 that interprets the semantics of a style sheet and renders
1456 documents that use them.
1457 <dt><dfn id="authoring-tool">authoring tool</dfn></dt>
1458 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
1459 that writes a style sheet.
1460 </dl>
1462 <p>A style sheet is conformant to CSS Ruby Module
1463 if all of its statements that use syntax defined in this module are valid
1464 according to the generic CSS grammar and the individual grammars of each
1465 feature defined in this module.
1467 <p>A renderer is conformant to CSS Ruby Module
1468 if, in addition to interpreting the style sheet as defined by the
1469 appropriate specifications, it supports all the features defined
1470 by CSS Ruby Module by parsing them correctly
1471 and rendering the document accordingly. However, the inability of a
1472 UA to correctly render a document due to limitations of the device
1473 does not make the UA non-conformant. (For example, a UA is not
1474 required to render color on a monochrome monitor.)
1476 <p>An authoring tool is conformant to CSS Ruby Module
1477 if it writes style sheets that are syntactically correct according to the
1478 generic CSS grammar and the individual grammars of each feature in
1479 this module, and meet all other conformance requirements of style sheets
1480 as described in this module.
1482 <h3 id="partial">
1483 Partial implementations</h3>
1485 <p>So that authors can exploit the forward-compatible parsing rules to
1486 assign fallback values, CSS renderers <strong>must</strong>
1487 treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore
1488 as appropriate</a>) any at-rules, properties, property values, keywords,
1489 and other syntactic constructs for which they have no usable level of
1490 support. In particular, user agents <strong>must not</strong> selectively
1491 ignore unsupported component values and honor supported values in a single
1492 multi-value property declaration: if any value is considered invalid
1493 (as unsupported values must be), CSS requires that the entire declaration
1494 be ignored.</p>
1496 <h3 id="experimental">
1497 Experimental implementations</h3>
1499 <p>To avoid clashes with future CSS features, the CSS2.1 specification
1500 reserves a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
1501 syntax</a> for proprietary and experimental extensions to CSS.
1503 <p>Prior to a specification reaching the Candidate Recommendation stage
1504 in the W3C process, all implementations of a CSS feature are considered
1505 experimental. The CSS Working Group recommends that implementations
1506 use a vendor-prefixed syntax for such features, including those in
1507 W3C Working Drafts. This avoids incompatibilities with future changes
1508 in the draft.
1509 </p>
1511 <h3 id="testing">
1512 Non-experimental implementations</h3>
1514 <p>Once a specification reaches the Candidate Recommendation stage,
1515 non-experimental implementations are possible, and implementors should
1516 release an unprefixed implementation of any CR-level feature they
1517 can demonstrate to be correctly implemented according to spec.
1519 <p>To establish and maintain the interoperability of CSS across
1520 implementations, the CSS Working Group requests that non-experimental
1521 CSS renderers submit an implementation report (and, if necessary, the
1522 testcases used for that implementation report) to the W3C before
1523 releasing an unprefixed implementation of any CSS features. Testcases
1524 submitted to W3C are subject to review and correction by the CSS
1525 Working Group.
1527 <p>Further information on submitting testcases and implementation reports
1528 can be found from on the CSS Working Group's website at
1529 <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
1530 Questions should be directed to the
1531 <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
1532 mailing list.
1534 <h2 class=no-num id="acknowledgments">
1535 Acknowledgments</h2>
1537 <p>This specification would not have been possible without the help from:</p>
1539 <p>Stephen Deach, Martin Dürst, Hideki Hiura(<span lang="ja">樋浦 秀樹</span>), Masayasu Ishikawa(<span lang="ja">石川
1540 雅康</span>), Chris
1541 Pratley, Takao Suzuki(<span lang="ja">鈴木 孝雄</span>), Frank Yung-Fong Tang, Chris Thrasher, Masafumi Yabe<span lang="ja">家辺
1542 勝文</span>), Steve Zilles.</p>
1544 <h2 class="no-num" id="changes">
1545 Changes</h2>
1547 <p>The following major changes have been made since the previous Working Draft:
1548 <dl>
1549 <dt>Remove 'ruby-span' and mentions of <code>rbspan</code>.
1550 <dd>
1551 Explicit spanning is not used in HTML ruby in favor of implicit spanning.
1552 This can't handle some pathological double-sided spanning cases,
1553 but there seems to be no requirement for these at the moment.
1554 (For implementations that support full complex XHTML Ruby,
1555 they can imply spanning from the markup the same magic way
1556 that we handle cell spanning from tables. It doesn't seem
1557 necessary to include controls this in Level 1.)
1559 <dt>Defer 'ruby-overhang' and ''ruby-align: line-end'' to Level 2.
1560 <dd>
1561 It's somewhat complicated, advanced feature.
1562 Proposal is to make this behavior UA-defined
1563 and provide some examples of acceptable options.
1565 <dt>Close issue requesting 'display: rp': use ''display: none''.
1566 <dd>
1567 The i18nwg added an issue requesting a display value for <rp> elements.
1568 They're supposed to be hidden when &tl;ruby> is displayed as ruby.
1569 But this is easily accomplished already with ''display: none''.
1571 <dt>Change 'ruby-position' values to match 'text-emphasis-position'.
1572 <dd>
1573 Other than ''inter-character'', which we need to keep,
1574 it makes more sense to align ruby positions with 'text-emphasis-position',
1575 which can correctly handle various combinations of horizontal/vertical preferences.
1577 <dt>Remove unused values of 'ruby-align'.
1578 <dd>
1579 'left', 'right', and 'end' are not needed.
1581 <dt>Added 'ruby-merge' property to control jukugo rendering.
1582 <dd>
1583 This is a stylistic effect, not a structural one;
1584 the previous model assumed that it was structural and suggested handling it by changing markup. :(
1586 <dt>Remove ''inline'' from 'ruby-position'.
1587 <dd>
1588 This is do-able via ''display: inline'' on all the ruby-related elements,
1589 see <a href="#default-inline">Appendix A</a>
1591 <dt>Added <a href="#default-style">Default Style</a> rules
1592 <dd>
1593 As requested by i18nwg.
1595 <dt>Wrote anonymous box generation rules
1596 <dd>
1597 And defined pairing of bases and annotations.
1598 Should now handle all the crazy proposed permutations of HTML ruby markup.
1599 </dl>
1601 <h2 class=no-num id="references">
1602 References</h2>
1604 <h3 class="no-num" id="normative-references">
1605 Normative references</h3>
1606 <!--normative-->
1608 <h3 class="no-num" id="other-references">
1609 Other references</h3>
1610 <!--informative-->
1612 <h2 class="no-num" id="index">
1613 Index</h2>
1614 <!--index-->
1616 <h2 class="no-num" id="property-index">
1617 Property index</h2>
1618 <!-- properties -->
1620 </body>
1621 </html>
1622 <!-- Keep this comment at the end of the file
1623 Local variables:
1624 mode: sgml
1625 sgml-declaration:"~/SGML/HTML4.decl"
1626 sgml-default-doctype-name:"html"
1627 sgml-minimize-attributes:t
1628 sgml-nofill-elements:("pre" "style" "br")
1629 sgml-live-element-indicator:t
1630 sgml-omittag:nil
1631 sgml-shorttag:nil
1632 sgml-namecase-general:t
1633 sgml-general-insert-case:lower
1634 sgml-always-quote-attributes:t
1635 sgml-indent-step:nil
1636 sgml-indent-data:t
1637 sgml-parent-document:nil
1638 sgml-exposed-tags:nil
1639 sgml-local-catalogs:nil
1640 sgml-local-ecat-files:nil
1641 End:
1642 -->
