css3-overflow/Overview.src.html

Thu, 16 Aug 2012 15:28:42 -0700

author
L. David Baron <dbaron@dbaron.org>
date
Thu, 16 Aug 2012 15:28:42 -0700
changeset 6497
60743929aa4e
parent 6496
fa9023fd4cbf
child 7460
4a64a80a24d5
permissions
-rw-r--r--

Add issue about overflow vs. overflow-style that Florian pointed out.

dbaron@6470 1 <!DOCTYPE html>
dbaron@6470 2 <html lang="en">
dbaron@6470 3 <head>
dbaron@6470 4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
dbaron@6483 5 <title>CSS Overflow Module Level 3</title>
dbaron@6470 6 <link rel=contents href="#contents">
dbaron@6470 7 <link rel=index href="#index">
dbaron@6470 8 <link rel="stylesheet" type="text/css" href="../default.css">
dbaron@6470 9 <link rel="stylesheet" type="text/css"
dbaron@6470 10 href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS].css">
dbaron@6475 11 <style>
dbaron@6477 12 table.source-demo-pair {
dbaron@6477 13 width: 100%;
dbaron@6477 14 }
dbaron@6481 15
dbaron@6475 16 .in-cards-demo {
dbaron@6475 17 width: 13em;
dbaron@6475 18 height: 8em;
dbaron@6475 19
dbaron@6475 20 padding: 4px;
dbaron@6475 21 border: medium solid blue;
dbaron@6475 22 margin: 6px;
dbaron@6475 23
dbaron@6475 24 font: medium/1.3 Times New Roman, Times, serif;
dbaron@6475 25 white-space: nowrap;
dbaron@6475 26 }
dbaron@6481 27
dbaron@6477 28 .bouncy-columns-demo {
dbaron@6477 29 width: 6em;
dbaron@6477 30 height: 10em;
dbaron@6477 31 float: left;
dbaron@6477 32 margin: 1em;
dbaron@6477 33 font: medium/1.25 Times New Roman, Times, serif;
dbaron@6477 34 white-space: nowrap;
dbaron@6477 35 }
dbaron@6477 36 .bouncy-columns-demo.one {
dbaron@6477 37 background: aqua; color: black;
dbaron@6477 38 transform: rotate(-3deg);
dbaron@6477 39 }
dbaron@6477 40 .bouncy-columns-demo.two {
dbaron@6477 41 background: yellow; color: black;
dbaron@6477 42 transform: rotate(3deg);
dbaron@6477 43 }
dbaron@6479 44
dbaron@6480 45 .article-font-inherit-demo {
dbaron@6480 46 font: 1em/1.25 Times New Roman, Times, serif;
dbaron@6480 47 white-space: nowrap;
dbaron@6480 48 }
dbaron@6480 49 .article-font-inherit-demo.one {
dbaron@6480 50 width: 12em;
dbaron@6480 51 font-size: 1.5em;
dbaron@6480 52 margin-bottom: 1em;
dbaron@6480 53 height: 4em;
dbaron@6480 54 }
dbaron@6480 55 .article-font-inherit-demo.two {
dbaron@6480 56 width: 11em;
dbaron@6480 57 margin-left: 5em;
dbaron@6480 58 margin-right: 2em;
dbaron@6480 59 }
dbaron@6480 60
dbaron@6481 61 .dark-columns-demo {
dbaron@6481 62 width: 6em;
dbaron@6481 63 height: 10em;
dbaron@6481 64 float: left;
dbaron@6481 65 margin-right: 1em;
dbaron@6481 66 font: medium/1.25 Times New Roman, Times, serif;
dbaron@6481 67 white-space: nowrap;
dbaron@6481 68 }
dbaron@6481 69 .dark-columns-demo.one {
dbaron@6481 70 background: aqua; color: black;
dbaron@6481 71 }
dbaron@6481 72 .dark-columns-demo.one :link {
dbaron@6481 73 color: blue;
dbaron@6481 74 }
dbaron@6481 75 .dark-columns-demo.one :visited {
dbaron@6481 76 color: purple;
dbaron@6481 77 }
dbaron@6481 78 .dark-columns-demo.two {
dbaron@6481 79 background: navy; color: white;
dbaron@6481 80 }
dbaron@6481 81 .dark-columns-demo.two :link {
dbaron@6481 82 color: aqua;
dbaron@6481 83 }
dbaron@6481 84 .dark-columns-demo.two :visited {
dbaron@6481 85 color: fuchsia;
dbaron@6481 86 }
dbaron@6481 87
dbaron@6479 88 .article-max-lines-demo {
dbaron@6479 89 font: 1em/1.25 Times New Roman, Times, serif;
dbaron@6479 90 white-space: nowrap;
dbaron@6479 91 }
dbaron@6479 92 .article-max-lines-demo.one::first-letter {
dbaron@6479 93 font-size: 2em;
dbaron@6479 94 line-height: 0.9;
dbaron@6479 95 }
dbaron@6479 96 .article-max-lines-demo.one {
dbaron@6479 97 font-size: 1.5em;
dbaron@6479 98 width: 16em;
dbaron@6479 99 }
dbaron@6479 100 .article-max-lines-demo.two {
dbaron@6479 101 width: 11.5em;
dbaron@6479 102 float: left; margin-right: 1em;
dbaron@6479 103 }
dbaron@6479 104 .article-max-lines-demo.three {
dbaron@6479 105 width: 11.5em;
dbaron@6479 106 float: left;
dbaron@6479 107 }
dbaron@6475 108 </style>
dbaron@6470 109 </head>
dbaron@6470 110
dbaron@6470 111 <div class="head">
dbaron@6470 112 <!--logo-->
dbaron@6470 113
dbaron@6483 114 <h1>CSS Overflow Module Level 3</h1>
dbaron@6470 115
dbaron@6470 116 <h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
dbaron@6470 117 <dl>
dbaron@6470 118 <dt>This version:
dbaron@6483 119 <dd><a href="[VERSION]">http://www.w3.org/TR/[YEAR]/ED-css3-overflow-[CDATE]/</a>
dbaron@6470 120
dbaron@6470 121 <dt>Latest version:
dbaron@6470 122 <dd><a href="http://www.w3.org/TR/[SHORTNAME]/">http://www.w3.org/TR/[SHORTNAME]/</a>
dbaron@6470 123
dbaron@6470 124 <dt>Editor's draft:
dbaron@6470 125 <dd><a href="http://dev.w3.org/csswg/[SHORTNAME]/">http://dev.w3.org/csswg/[SHORTNAME]/</a>
dbaron@6470 126
dbaron@6470 127 <!--
dbaron@6470 128 <dt>Previous version:
dbaron@6470 129 <dd><a href="http://www.w3.org/PreviousVersionURI">
dbaron@6470 130 http://www.w3.org/PreviousVersionURI</a>
dbaron@6470 131 -->
dbaron@6470 132
dbaron@6470 133 <dt>Issue Tracking:</dt>
dbaron@6470 134 <dd>Maintained in document (only editor's draft is current)
dbaron@6470 135
dbaron@6470 136 <dt>Feedback:</dt>
dbaron@6470 137 <dd><a href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a> with subject line &ldquo;<kbd>[[SHORTNAME]] <var>&hellip; message topic &hellip;</var></kbd>&rdquo;
dbaron@6470 138
dbaron@6470 139 <dt>Editors:
dbaron@6470 140 <dd class="h-card vcard">
dbaron@6470 141 <a class="p-name fn u-url url" rel="author"
dbaron@6470 142 href="http://dbaron.org/">L. David Baron</a>,
dbaron@6470 143 <a class="p-org org" href="http://www.mozilla.org/">Mozilla</a>
dbaron@6470 144 </dl>
dbaron@6470 145
dbaron@6470 146 <!--copyright-->
dbaron@6470 147
dbaron@6470 148 <hr title="Separator for header">
dbaron@6470 149 </div>
dbaron@6470 150
dbaron@6470 151 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
dbaron@6470 152
dbaron@6470 153 <p>
dbaron@6470 154 <a href="http://www.w3.org/TR/CSS/">CSS</a> is
dbaron@6470 155 a language for describing
dbaron@6470 156 the rendering of structured documents (such as HTML and XML)
dbaron@6470 157 on screen, on paper, in speech, etc.
dbaron@6470 158 This module contains the features of CSS
dbaron@6470 159 relating to new mechanisms of overflow handling in visual media (e.g., screen or paper).
dbaron@6470 160 In interactive media,
dbaron@6470 161 it describes features that allow the overflow
dbaron@6470 162 from a fixed size container
dbaron@6470 163 to be handled by pagination (displaying one page at a time).
dbaron@6470 164 It also describes features, applying to all visual media,
dbaron@6470 165 that allow the contents of an element
dbaron@6484 166 to be spread across multiple fragments,
dbaron@6484 167 allowing the contents to flow across multiple regions
dbaron@6484 168 or to have different styles for different fragments.
dbaron@6470 169 </p>
dbaron@6470 170
dbaron@6470 171 <h2 class="no-num no-toc" id="status">Status of this document</h2>
dbaron@6470 172
dbaron@6470 173 <!--status-->
dbaron@6470 174
dbaron@6470 175 <p>The following features are at risk: &hellip;
dbaron@6470 176
dbaron@6470 177 <h2 class="no-num no-toc" id="contents">
dbaron@6470 178 Table of contents</h2>
dbaron@6470 179
dbaron@6470 180 <!--toc-->
dbaron@6470 181
dbaron@6470 182 <h2 id="intro">
dbaron@6470 183 Introduction</h2>
dbaron@6470 184
dbaron@6470 185 <p>
dbaron@6470 186 In CSS Level 1 [[CSS1]], placing more content than would fit
dbaron@6470 187 inside an element with a specified size
dbaron@6470 188 was generally an authoring error.
dbaron@6470 189 Doing so caused the content to extend
dbaron@6470 190 outside the bounds of the element,
dbaron@6470 191 which would likely cause
dbaron@6470 192 that content to overlap with other elements.
dbaron@6470 193 </p>
dbaron@6470 194
dbaron@6470 195 <p>
dbaron@6470 196 CSS Level 2 [[CSS21]] introduced the 'overflow' property,
dbaron@6470 197 which allows authors to have overflow be handled by scrolling,
dbaron@6470 198 which means it is no longer an authoring error.
dbaron@6470 199 It also allows authors to specify
dbaron@6470 200 that overflow is handled by clipping,
dbaron@6470 201 which makes sense when the author's intent
dbaron@6470 202 is that the content not be shown.
dbaron@6470 203 </p>
dbaron@6470 204
dbaron@6470 205 <p>
dbaron@6470 206 However, scrolling is not the only way
dbaron@6470 207 to present large amounts of content,
dbaron@6470 208 and may even not be the optimal way.
dbaron@6470 209 After all, the codex replaced the scroll
dbaron@6470 210 as the common format for large written works
dbaron@6470 211 because of its advantages.
dbaron@6470 212 </p>
dbaron@6470 213
dbaron@6470 214 <p>
dbaron@6470 215 This specification introduces
dbaron@6470 216 a mechanism for Web pages to specify
dbaron@6484 217 that an element of a page should handle overflow
dbaron@6470 218 through pagination rather than through scrolling.
dbaron@6470 219 </p>
dbaron@6470 220
dbaron@6470 221 <p>
dbaron@6470 222 This specification also extends the concept of overflow
dbaron@6470 223 in another direction.
dbaron@6484 224 Instead of requiring that authors specify a single area
dbaron@6470 225 into which the content of an element must flow,
dbaron@6484 226 this specification allows authors to specify multiple fragments,
dbaron@6470 227 each with their own dimensions and styles,
dbaron@6470 228 so that the content of the element can flow from one to the next,
dbaron@6470 229 using as many as needed to place the content without overflowing.
dbaron@6470 230 </p>
dbaron@6470 231
dbaron@6470 232 <p>
dbaron@6470 233 In both of these cases, implementations must
dbaron@6470 234 break the content in the block-progression dimension.
dbaron@6470 235 Implementations must do this is described
dbaron@6470 236 in the CSS Fragmentation Module [[!CSS3-BREAK]].
dbaron@6470 237 </p>
dbaron@6470 238
dbaron@6483 239 <h2 id="scrolling-overflow">Scrolling and hidden overflow</h2>
dbaron@6483 240
dbaron@6483 241 <p class="issue">
dbaron@6483 242 Move material from [[CSS21]] and [[CSS3BOX]] here.
dbaron@6483 243 </p>
dbaron@6470 244
dbaron@6470 245 <h2 id="paginated-overflow">Paginated overflow</h2>
dbaron@6470 246
dbaron@6497 247 <p class="issue">overflow:paginate or overflow:pages (or paged-x, paged-y, paged-x-controls, paged-y-controls as [[CSS3GCPM]] has?)</p>
dbaron@6470 248
dbaron@6470 249 <p class="issue">Ability to display N pages at once
dbaron@6470 250 rather than just one page at once?</p>
dbaron@6470 251
dbaron@6497 252 <p class="issue">
dbaron@6497 253 The current implementation of paginated overflow uses
dbaron@6497 254 the 'overflow'/'overflow-x'/'overflow-y' properties
dbaron@6497 255 rather than the 'overflow-style' property as proposed
dbaron@6497 256 in the [[CSS3GCPM]] draft
dbaron@6497 257 (which also matches the [[CSS3-MARQUEE]] proposal).
dbaron@6497 258 We should probably switch away from 'overflow-style',
dbaron@6497 259 but that's not 100% clear.
dbaron@6497 260 </p>
dbaron@6497 261
dbaron@6484 262 <h2 id="fragment-overflow">Fragment overflow</h2>
dbaron@6470 263
dbaron@6470 264 <p>
dbaron@6470 265 This section introduces and defines the meaning of
dbaron@6484 266 the new ''fragments'' value of the 'overflow' property.
dbaron@6470 267 </p>
dbaron@6470 268
dbaron@6470 269 <p>
dbaron@6484 270 When the computed value of 'overflow' for an element is ''fragments'',
dbaron@6470 271 and implementations would otherwise have created a box for the element,
dbaron@6491 272 then implementations must create a sequence of <dfn>fragment box</dfn>es
dbaron@6470 273 for that element.
dbaron@6491 274 (It is possible for an element with ''overflow: fragments''
dbaron@6491 275 to generate only one <i>fragment box</i>.
dbaron@6484 276 However, if an element's computed 'overflow' is not ''fragments'',
dbaron@6484 277 then its box is not a <i>fragment box</i>.)
dbaron@6484 278 Every <i>fragment box</i> is a fragmentation container,
dbaron@6491 279 and any overflow
dbaron@6491 280 that would cause that fragmentation container to fragment
dbaron@6491 281 causes another <i>fragment box</i> created as a next sibling
dbaron@6470 282 of the previous one.
dbaron@6470 283 <span class="issue">Or is it as though it's a next sibling of
dbaron@6470 284 the element? Need to figure out exactly how this interacts with
dbaron@6470 285 other box-level fixup.</span>
dbaron@6492 286 Additionally, if the <i>fragment box</i> is also
dbaron@6492 287 a multi-column box (as defined in [[!CSS3COL]]
dbaron@6492 288 <span class="issue">though it defines <i>multi-column element</i></span>)
dbaron@6492 289 any content that would lead to the creation of <i>overflow columns</i> [[!CSS3COL]]
dbaron@6492 290 instead is flown into an additional fragment box.
dbaron@6491 291 However, fragment boxes may themselves be broken
dbaron@6491 292 (due to fragmentation in a fragmentation context outside of them,
dbaron@6491 293 such as pages, columns, or other fragment boxes);
dbaron@6491 294 such breaking leads to fragments of the same fragment box
dbaron@6491 295 rather than multiple fragment boxes.
dbaron@6491 296 (This matters because fragment boxes may be styled by their index;
dbaron@6491 297 such breaking leads to multiple fragments of a fragment box
dbaron@6491 298 with a single index.
dbaron@6491 299 This design choice is so that
dbaron@6491 300 breaking a fragment box across pages does not break
dbaron@6491 301 the association of indices to particular pieces of content.)
dbaron@6491 302 <span class="issue">Should a forced break that breaks to
dbaron@6491 303 an outer fragmentation context cause a new fragment of a single
dbaron@6491 304 fragment box or a new fragment box?</span>
dbaron@6491 305 <span class="issue">Should we find a term other than
dbaron@6491 306 <i>fragment box</i> here to make this a little less confusing?</span>
dbaron@6470 307 </p>
dbaron@6470 308
dbaron@6470 309 <p class="issue">
dbaron@6491 310 What if we want to be able to style the pieces of an element
dbaron@6491 311 split within another type of fragmentation context?
dbaron@6491 312 These rules prevent ever using ''::nth-fragment()'' for that,
dbaron@6491 313 despite that the name seems the most logical name for such a feature.
dbaron@6470 314 </p>
dbaron@6470 315
dbaron@6475 316 <div class="example">
dbaron@6477 317 <table class="source-demo-pair"><tr><td><pre>&lt;!DOCTYPE HTML&gt;
dbaron@6475 318 &lt;title&gt;Breaking content into
dbaron@6475 319 equal-sized cards&lt;/title&gt;
dbaron@6475 320 &lt;style&gt;
dbaron@6475 321 .in-cards {
dbaron@6484 322 overflow: fragments;
dbaron@6475 323
dbaron@6475 324 width: 13em;
dbaron@6475 325 height: 8em;
dbaron@6475 326
dbaron@6475 327 padding: 4px;
dbaron@6475 328 border: medium solid blue;
dbaron@6475 329 margin: 6px;
dbaron@6475 330
dbaron@6475 331 font: medium/1.3 Times New
dbaron@6475 332 Roman, Times, serif;
dbaron@6475 333 }
dbaron@6475 334 &lt;/style&gt;
dbaron@6475 335 &lt;div class="in-cards"&gt;
dbaron@6475 336 In this example, the text in the div
dbaron@6475 337 is broken into a series of cards.
dbaron@6475 338 These cards all have the same style.
dbaron@6475 339 The presence of enough content to
dbaron@6475 340 overflow one of the cards causes
dbaron@6475 341 another one to be created. The second
dbaron@6475 342 card is created just like it's the
dbaron@6475 343 next sibling of the first.
dbaron@6477 344 &lt;/div&gt;</pre></td><td>
dbaron@6475 345 <div class="in-cards-demo">In this example, the text in the<br>div is broken into a series of<br>cards. These cards all have the<br>same style. The presence of<br>enough content to overflow<br>one of the cards causes another</div>
dbaron@6475 346 <div class="in-cards-demo">one to be created. The second<br>card is created just like it's the<br>next sibling of the first.</div>
dbaron@6475 347 </td></tr></table>
dbaron@6475 348 </div>
dbaron@6475 349
dbaron@6487 350 <p class="issue">
dbaron@6487 351 We should specify that ''overflow: fragments'' does not apply
dbaron@6487 352 to at least some table parts,
dbaron@6487 353 and perhaps other elements as well.
dbaron@6487 354 We need to determine exactly which ones.
dbaron@6487 355 </p>
dbaron@6487 356
dbaron@6488 357 <p class="issue">
dbaron@6488 358 This specification needs to say which type of
dbaron@6488 359 fragmentation context is created
dbaron@6488 360 so that it's clear which values of the 'break' property
dbaron@6488 361 cause breaks within this context.
dbaron@6488 362 We probably want ''break: regions'' to apply.
dbaron@6488 363 </p>
dbaron@6488 364
dbaron@6494 365 <p class="issue">
dbaron@6494 366 This specification needs a processing model
dbaron@6494 367 that will apply in cases where the layout containing the
dbaron@6494 368 fragments has characteristics that use the intrinsic size of the fragments
dbaron@6494 369 to change the amount of space available for them,
dbaron@6494 370 such as [[CSS3-GRID-LAYOUT]].
dbaron@6494 371 There has already been some work on such a processing model
dbaron@6494 372 in [[CSS3-REGIONS]],
dbaron@6494 373 and the work done on a model there,
dbaron@6494 374 and the editors of that specification,
dbaron@6494 375 should inform what happens in this specification.
dbaron@6494 376 </p>
dbaron@6494 377
dbaron@6484 378 <h3 id="fragment-styling">Fragment styling</h3>
dbaron@6470 379
dbaron@6484 380 <h4 id="fragment-pseudo-element">The ::nth-fragment() pseudo-element</h4>
dbaron@6470 381
dbaron@6470 382 <p>
dbaron@6484 383 The ::nth-fragment() pseudo-element is a pseudo-element
dbaron@6484 384 that describes some of the <i>fragment box</i>es generated by an element.
dbaron@6470 385 The argument to the pseudo-element takes the same syntax
dbaron@6470 386 as the argument to the :nth-child() pseudo-class
dbaron@6470 387 defined in [[!SELECT]], and has the same meaning
dbaron@6470 388 except that the number is relative to
dbaron@6484 389 <i>fragment box</i>es generated by the element
dbaron@6470 390 instead of siblings of the element.
dbaron@6470 391 </p>
dbaron@6470 392
dbaron@6470 393 <p class="note">
dbaron@6484 394 Selectors that allow addressing fragments
dbaron@6470 395 by counting from the end rather than the start
dbaron@6470 396 are intentionally not provided.
dbaron@6470 397 Such selectors would interfere with determining
dbaron@6484 398 the number of fragments.
dbaron@6470 399 </p>
dbaron@6470 400
dbaron@6489 401 <p class="issue">
dbaron@6489 402 Depending on future discussions,
dbaron@6489 403 this ''::nth-fragment(<var>an+b</var>)'' syntax
dbaron@6489 404 may be replaced with
dbaron@6489 405 the new ''::fragment:nth(<var>an+b</var>)'' syntax.
dbaron@6489 406 </p>
dbaron@6489 407
dbaron@6484 408 <h4 id="style-of-fragments">Styling of fragments</h4>
dbaron@6470 409
dbaron@6470 410 <p class="issue">
dbaron@6484 411 Should this apply to fragment overflow only,
dbaron@6470 412 or also to paginated overflow?
dbaron@6470 413 (If it applies,
dbaron@6470 414 then stricter property restrictions would be needed
dbaron@6470 415 for paginated overflow.)
dbaron@6470 416 </p>
dbaron@6470 417
dbaron@6470 418 <p>
dbaron@6484 419 In the absence of rules with ''::nth-fragment()'' pseudo-elements,
dbaron@6484 420 the computed style for each <i>fragment box</i>
dbaron@6470 421 is the computed style for the element
dbaron@6484 422 for which the <i>fragment box</i> was created.
dbaron@6484 423 However, the style for a <i>fragment box</i> is also influenced
dbaron@6470 424 by rules whose selector's <i>subject</i> [[!SELECT]]
dbaron@6484 425 has an ''::nth-fragment()'' pseudo-element,
dbaron@6484 426 if the 1-based number of the <i>fragment box</i> matches
dbaron@6484 427 that ''::nth-fragment()'' pseudo-element
dbaron@6484 428 and the selector (excluding the ''::nth-fragment()'' pseudo-element)
dbaron@6484 429 matches the element generating the fragments.
dbaron@6470 430 </p>
dbaron@6470 431
dbaron@6486 432 <p>
dbaron@6486 433 When determining the style of the <i>fragment box</i>,
dbaron@6486 434 these rules that match the fragment pseudo-element
dbaron@6486 435 cascade together with the rules that match the element,
dbaron@6486 436 with the fragment pseudo-element adding the specificity
dbaron@6486 437 of a pseudo-class to the specificity calculation.
dbaron@6486 438 <span class="issue">Does this need to be specified in
dbaron@6486 439 the cascading module as well?</span>
dbaron@6486 440 </p>
dbaron@6486 441
dbaron@6477 442 <div class="example">
dbaron@6477 443 <table class="source-demo-pair"><tr><td><pre>&lt;!DOCTYPE HTML&gt;
dbaron@6477 444 &lt;style&gt;
dbaron@6477 445 .bouncy-columns {
dbaron@6484 446 overflow: fragments;
dbaron@6477 447 width: 6em;
dbaron@6477 448 height: 10em;
dbaron@6477 449 float: left;
dbaron@6477 450 margin: 1em;
dbaron@6477 451 font: medium/1.25 Times New
dbaron@6477 452 Roman, Times, serif;
dbaron@6477 453 }
dbaron@6484 454 .bouncy-columns::nth-fragment(1) {
dbaron@6477 455 background: aqua; color: black;
dbaron@6477 456 transform: rotate(-3deg);
dbaron@6477 457 }
dbaron@6484 458 .bouncy-columns::nth-fragment(2) {
dbaron@6477 459 background: yellow; color: black;
dbaron@6477 460 transform: rotate(3deg);
dbaron@6477 461 }
dbaron@6477 462 &lt;/style&gt;
dbaron@6477 463 &lt;div class="bouncy-columns"&gt;
dbaron@6477 464 <i>...</i>
dbaron@6477 465 &lt;/div&gt;</pre></td><td>
dbaron@6477 466 <div class="bouncy-columns-demo one">In this<br>example, the<br>text in the div<br>is broken into<br>a series of<br>columns. The<br>author<br>probably</div>
dbaron@6477 467 <div class="bouncy-columns-demo two">intended the<br>text to fill two<br>columns. But<br>if it happens to<br>fill three<br>columns, the<br>third column is<br>still created. It</div>
dbaron@6484 468 <div class="bouncy-columns-demo">just doesn't<br>have any<br>fragment-specific<br>styling because<br>the author<br>didn't give it<br>any.</div>
dbaron@6477 469 </td></tr></table>
dbaron@6477 470 </div>
dbaron@6477 471
dbaron@6470 472 <p>
dbaron@6484 473 Styling an ''::nth-fragment()'' pseudo-element with the 'overflow'
dbaron@6490 474 property does take effect;
dbaron@6490 475 if a <i>fragment box</i> has a
dbaron@6490 476 computed value of 'overflow' other than ''fragments''
dbaron@6490 477 then that fragment box is the last fragment.
dbaron@6490 478 However, overriding ''overflow'' on the first fragment
dbaron@6490 479 does not cause the <i>fragment box</i> not to exist;
dbaron@6490 480 whether there are fragment boxes at all is determined by
dbaron@6490 481 the computed value of overflow for the element.
dbaron@6470 482 </p>
dbaron@6470 483
dbaron@6470 484 <p>
dbaron@6485 485 Styling an ''::nth-fragment()'' pseudo-element with the 'content'
dbaron@6485 486 property has no effect;
dbaron@6485 487 the computed value of 'content' for the fragment box
dbaron@6485 488 remains the same as the computed value of content for the element.
dbaron@6485 489 </p>
dbaron@6485 490
dbaron@6485 491 <p>
dbaron@6484 492 Specifying ''display: none'' for a <i>fragment box</i> causes
dbaron@6484 493 the fragment box with that index not to be generated.
dbaron@6470 494 However, in terms of the indices
dbaron@6484 495 used for matching ''::nth-fragment()'' pseudo-elements
dbaron@6484 496 of later fragment boxes,
dbaron@6470 497 it still counts as though it was generated.
dbaron@6470 498 However, since it is not generated, it does not contain any content.
dbaron@6470 499 </p>
dbaron@6470 500
dbaron@6470 501 <p class="issue">
dbaron@6470 502 Would it make more sense to forbid ''display:none''?
dbaron@6470 503 Or perhaps to forbid 'display', 'position', 'float',
dbaron@6470 504 and similar (in addition to 'overflow')?
dbaron@6470 505 </p>
dbaron@6470 506
dbaron@6470 507 <p>
dbaron@6470 508 To match the model for other pseudo-elements
dbaron@6470 509 where the pseudo-elements live inside their corresponding element,
dbaron@6484 510 declarations in ''::nth-fragment()'' pseudo-elements override
dbaron@6470 511 declarations in rules without the pseudo-element.
dbaron@6470 512 The relative priority within such declarations is determined
dbaron@6470 513 by normal cascading order (see [[!CSS21]]).
dbaron@6470 514 </p>
dbaron@6470 515
dbaron@6470 516 <p>
dbaron@6484 517 Styles specified on ''::nth-fragment()'' pseudo-elements
dbaron@6484 518 do affect inheritance to content within the <i>fragment box</i>.
dbaron@6484 519 In other words, the content within the <i>fragment box</i> must
dbaron@6484 520 inherit from the fragment box's style (i.e., the pseudo-element style)
dbaron@6470 521 rather than directly from the element.
dbaron@6484 522 This means that elements split between fragment boxes may
dbaron@6470 523 have different styles for different parts of the element.
dbaron@6470 524 </p>
dbaron@6470 525
dbaron@6472 526 <p class="issue">
dbaron@6472 527 This inheritance rule allows specifying styles indirectly
dbaron@6472 528 (by using explicit ''inherit'' or using default inheritance
dbaron@6472 529 on properties that don't apply to '':first-letter'')
dbaron@6472 530 that can't be specified directly
dbaron@6472 531 (based on the rules in the next section).
dbaron@6472 532 This is a problem.
dbaron@6484 533 The restrictions that apply to styling inside fragments
dbaron@6484 534 should also apply to inheritance from fragments.
dbaron@6472 535 </p>
dbaron@6472 536
dbaron@6480 537 <div class="example">
dbaron@6480 538 <table class="source-demo-pair"><tr><td><pre>&lt;!DOCTYPE HTML&gt;
dbaron@6480 539 &lt;style&gt;
dbaron@6480 540 .article {
dbaron@6484 541 overflow: fragments;
dbaron@6480 542 }
dbaron@6484 543 .article::nth-fragment(1) {
dbaron@6480 544 font-size: 1.5em;
dbaron@6480 545 margin-bottom: 1em;
dbaron@6480 546 height: 4em;
dbaron@6480 547 }
dbaron@6491 548 .article::nth-fragment(2) {
dbaron@6480 549 margin-left: 5em;
dbaron@6480 550 margin-right: 2em;
dbaron@6480 551 }
dbaron@6480 552 &lt;/style&gt;
dbaron@6480 553 &lt;div class="article"&gt;
dbaron@6480 554 The &lt;code&gt;font-size&lt;/code&gt; property<i>...</i>
dbaron@6480 555 &lt;/div&gt;</pre></td><td>
dbaron@6484 556 <div class="article-font-inherit-demo one">The <code>font-size</code> property<br>specified on the fragment<br>is inherited into the</div>
dbaron@6484 557 <div class="article-font-inherit-demo two">descendants of the fragment.<br>This means that inherited<br>properties can be used<br>reliably on a fragment, as in<br>this example.</div>
dbaron@6480 558 </td></tr></table>
dbaron@6480 559 </div>
dbaron@6478 560
dbaron@6484 561 <h4 id="style-in-fragments">Styling inside fragments</h4>
dbaron@6470 562
dbaron@6470 563 <p class="issue">
dbaron@6484 564 Should this apply to fragment overflow only,
dbaron@6470 565 or also to paginated overflow,
dbaron@6470 566 or even to pagination across pages?
dbaron@6470 567 </p>
dbaron@6470 568
dbaron@6470 569 <p>
dbaron@6484 570 The ''::nth-fragment()'' pseudo-element
dbaron@6470 571 can also be used to style
dbaron@6484 572 content inside of a <i>fragment box</i>.
dbaron@6470 573 Unlike the ''::first-line'' and ''::first-letter'' pseudo-elements,
dbaron@6484 574 the ''::nth-fragment()'' pseudo-element can be applied
dbaron@6470 575 to parts of the selector other than the subject:
dbaron@6470 576 in particular, it can match ancestors of the subject.
dbaron@6470 577 However, the only CSS properties applied
dbaron@6470 578 by rules with such selectors
dbaron@6470 579 are those that apply
dbaron@6470 580 to the ''::first-letter'' pseudo-element.
dbaron@6470 581 </p>
dbaron@6470 582
dbaron@6470 583 <p>
dbaron@6470 584 To be more precise,
dbaron@6484 585 when a rule's selector has ''::nth-fragment()'' pseudo-elements
dbaron@6470 586 attached to parts of the selector other than the subject,
dbaron@6470 587 the declarations in that rule apply to
dbaron@6470 588 a fragment (or pseudo-element thereof) when:
dbaron@6470 589 </p>
dbaron@6470 590 <ol>
dbaron@6470 591 <li>
dbaron@6470 592 the declarations are for properties that apply to the
dbaron@6470 593 ''::first-letter'' pseudo-element,
dbaron@6470 594 </li>
dbaron@6470 595 <li>
dbaron@6470 596 the declarations would apply to
dbaron@6470 597 that fragment (or pseudo-element thereof)
dbaron@6484 598 had those ''::nth-fragment()'' pseudo-elements been removed,
dbaron@6470 599 with a particular association between
dbaron@6470 600 each sequence of simple selectors and the element it matched,
dbaron@6470 601 and
dbaron@6470 602 </li>
dbaron@6470 603 <li>
dbaron@6484 604 for each removed ''::nth-fragment()'' pseudo-element,
dbaron@6484 605 the fragment lives within a <i>fragment box</i>
dbaron@6470 606 of the element associated in that association
dbaron@6470 607 with the selector that the pseudo-element was attached to,
dbaron@6470 608 and whose index matches the pseudo-element.
dbaron@6470 609 </li>
dbaron@6470 610 </ol>
dbaron@6470 611
dbaron@6481 612 <div class="example">
dbaron@6481 613 <table class="source-demo-pair"><tr><td><pre>&lt;!DOCTYPE HTML&gt;
dbaron@6481 614 &lt;style&gt;
dbaron@6481 615 .dark-columns {
dbaron@6484 616 overflow: fragments;
dbaron@6481 617 width: 6em;
dbaron@6481 618 height: 10em;
dbaron@6481 619 float: left;
dbaron@6481 620 margin-right: 1em;
dbaron@6481 621 font: medium/1.25 Times New
dbaron@6481 622 Roman, Times, serif;
dbaron@6481 623 }
dbaron@6484 624 .dark-columns::nth-fragment(1) {
dbaron@6481 625 background: aqua; color: black;
dbaron@6481 626 }
dbaron@6484 627 .dark-columns::nth-fragment(1) :link {
dbaron@6481 628 color: blue;
dbaron@6481 629 }
dbaron@6484 630 .dark-columns::nth-fragment(1) :visited {
dbaron@6481 631 color: purple;
dbaron@6481 632 }
dbaron@6484 633 .dark-columns::nth-fragment(2) {
dbaron@6481 634 background: navy; color: white;
dbaron@6481 635 }
dbaron@6484 636 .dark-columns::nth-fragment(2) :link {
dbaron@6481 637 color: aqua;
dbaron@6481 638 }
dbaron@6484 639 .dark-columns::nth-fragment(2) :visited {
dbaron@6481 640 color: fuchsia;
dbaron@6481 641 }
dbaron@6481 642 &lt;/style&gt;
dbaron@6481 643 &lt;div class="dark-columns"&gt;
dbaron@6481 644 <i>...</i>
dbaron@6481 645 &lt;/div&gt;</pre></td><td>
dbaron@6484 646 <div class="dark-columns-demo one">In this<br><a href="http://en.wiktionary.org/wiki/example">example</a>, the<br>text flows<br>from one<br>light-colored<br>fragment into<br>another<br>dark-colored</div>
dbaron@6484 647 <div class="dark-columns-demo two">fragment. We<br>therefore want<br>different styles<br>for <a href="http://www.w3.org/Provider/Style/IntoContext.html">hyperlinks</a><br>in the different<br>fragments.</div>
dbaron@6481 648 </td></tr></table>
dbaron@6481 649 </div>
dbaron@6481 650
dbaron@6478 651
dbaron@6470 652 <h3 id="max-lines">The 'max-lines' property</h3>
dbaron@6470 653
dbaron@6470 654 <p>
dbaron@6470 655 Authors may wish to style the opening lines of an element
dbaron@6470 656 with different styles
dbaron@6484 657 by putting those opening lines in a separate fragment.
dbaron@6470 658 However, since it may be difficult to predict the exact height
dbaron@6470 659 occupied by those lines
dbaron@6484 660 in order to restrict the first fragment to that height,
dbaron@6470 661 this specification introduces a 'max-lines' property
dbaron@6484 662 that forces a fragment to break
dbaron@6470 663 after a specified number of lines.
dbaron@6470 664 This forces a break after the given number of lines
dbaron@6470 665 contained within the element or its descendants,
dbaron@6470 666 as long as those lines are in the same block formatting context.
dbaron@6470 667 </p>
dbaron@6470 668
dbaron@6470 669 <table class=propdef>
dbaron@6470 670 <tr>
dbaron@6470 671 <th>Name:
dbaron@6470 672 <td><dfn>max-lines</dfn>
dbaron@6470 673 <tr>
dbaron@6470 674 <th><a href="#values">Value</a>:
dbaron@6470 675 <td>none | &lt;integer&gt;
dbaron@6470 676 <tr>
dbaron@6470 677 <th>Initial:
dbaron@6470 678 <td>none
dbaron@6470 679 <tr>
dbaron@6470 680 <th>Applies to:
dbaron@6484 681 <td>fragment boxes
dbaron@6470 682 <tr>
dbaron@6470 683 <th>Inherited:
dbaron@6470 684 <td>no
dbaron@6470 685 <tr>
dbaron@6482 686 <th>Animatable:
dbaron@6482 687 <td>as <a href="http://www.w3.org/TR/css3-transitions/#animatable-types">integer</a>
dbaron@6482 688 <tr>
dbaron@6470 689 <th>Percentages:
dbaron@6470 690 <td>N/A
dbaron@6470 691 <tr>
dbaron@6470 692 <th>Media:
dbaron@6470 693 <td>visual
dbaron@6470 694 <tr>
dbaron@6470 695 <th>Computed&nbsp;value:
dbaron@6470 696 <td>specified value
dbaron@6470 697 <tr>
dbaron@6470 698 <th>Canonical order:
dbaron@6470 699 <td><abbr title="follows order of property value definition">per grammar</abbr>
dbaron@6470 700 </table>
dbaron@6470 701
dbaron@6470 702 <dl>
dbaron@6470 703 <dt>none
dbaron@6470 704 <dd>
dbaron@6470 705 <p>
dbaron@6470 706 Breaks occur only as specified elsewhere.
dbaron@6470 707 </p>
dbaron@6470 708 </dd>
dbaron@6470 709
dbaron@6470 710 <dt>&lt;integer&gt;
dbaron@6470 711 <dd>
dbaron@6470 712 <p>
dbaron@6470 713 In addition to any breaks specified elsewhere,
dbaron@6470 714 a break is forced before any line that would exceed
dbaron@6470 715 the given number of lines
dbaron@6470 716 being placed inside the element
dbaron@6470 717 (excluding lines that are in
dbaron@6470 718 a different block formatting context from
dbaron@6470 719 the block formatting context to which
dbaron@6470 720 an unstyled child of the element would belong).
dbaron@6470 721 </p>
dbaron@6470 722
dbaron@6470 723 <p class="issue">
dbaron@6470 724 If there are multiple boundaries between this line
dbaron@6470 725 and the previous, where exactly (in terms of element
dbaron@6470 726 boundaries) is the break forced?
dbaron@6470 727 </p>
dbaron@6470 728
dbaron@6470 729 <p>
dbaron@6470 730 Only positive integers are accepted.
dbaron@6470 731 Zero or negative integers are a parse error.
dbaron@6470 732 </p>
dbaron@6470 733 </dd>
dbaron@6470 734 </dl>
dbaron@6470 735
dbaron@6484 736 <p class="issue">Should this apply to fragment overflow only, or also
dbaron@6470 737 to pagination?</p>
dbaron@6470 738
dbaron@6479 739 <div class="example">
dbaron@6479 740 <table class="source-demo-pair"><tr><td><pre>&lt;!DOCTYPE HTML&gt;
dbaron@6479 741 &lt;style&gt;
dbaron@6479 742 .article {
dbaron@6484 743 overflow: fragments;
dbaron@6479 744 }
dbaron@6479 745 .article::first-letter {
dbaron@6479 746 font-size: 2em;
dbaron@6479 747 line-height: 0.9;
dbaron@6479 748 }
dbaron@6484 749 .article::nth-fragment(1) {
dbaron@6479 750 font-size: 1.5em;
dbaron@6479 751 max-lines: 3;
dbaron@6479 752 }
dbaron@6491 753 .article::nth-fragment(2) {
dbaron@6479 754 column-count: 2;
dbaron@6479 755 }
dbaron@6479 756 &lt;/style&gt;
dbaron@6479 757 &lt;div class="article"&gt;
dbaron@6479 758 <i>...</i>
dbaron@6479 759 &lt;/div&gt;</pre></td><td>
dbaron@6479 760 <div class="article-max-lines-demo one">The max-lines property allows<br>authors to use a larger font for the first<br>few lines of an article. Without the</div>
dbaron@6479 761 <div class="article-max-lines-demo two">max-lines property, authors<br>might have to use the<br>'height' property instead, but<br>that would leave a slight gap<br>if the author miscalculated<br>how much height a given<br>number of lines would<br>occupy (which might be</div>
dbaron@6479 762 <div class="article-max-lines-demo three">particularly hard if the author<br>didn't know what text would<br>be filling the space, exactly<br>what font would be used, or<br>exactly which platform's font<br>rendering would be used to<br>display the font).</div>
dbaron@6479 763 </td></tr></table>
dbaron@6479 764 </div>
dbaron@6478 765
dbaron@6493 766 <h2 id="static-media">Overflow in static media</h2>
dbaron@6493 767
dbaron@6493 768 <p class="issue">
dbaron@6493 769 This specification should define useful behavior
dbaron@6493 770 for all values of 'overflow'
dbaron@6493 771 in static media (such as print).
dbaron@6493 772 Current implementation behavior is quite poor and
dbaron@6493 773 produces unexpected results when authors have not considered
dbaron@6493 774 what will happen when
dbaron@6493 775 the content they produce for interactive media
dbaron@6493 776 is printed.
dbaron@6493 777 </p>
dbaron@6493 778
dbaron@6470 779 <h2 id="conformance">
dbaron@6470 780 Conformance</h2>
dbaron@6470 781
dbaron@6470 782 <h3 id="placement">
dbaron@6470 783 Module interactions</h3>
dbaron@6470 784
dbaron@6470 785 <p>This module extends the 'overflow'
dbaron@6470 786 feature defined in [[CSS21]] section 11.1.1. It defines additional
dbaron@6470 787 overflow handling mechanisms that implementations must implement as
dbaron@6470 788 described in this module in order to conform to this module.</p>
dbaron@6470 789
dbaron@6470 790 <p>No properties in this module apply to the <code>::first-line</code> or
dbaron@6470 791 <code>::first-letter</code> pseudo-elements.</p>
dbaron@6470 792
dbaron@6470 793 <h3 id="values">
dbaron@6470 794 Values</h3>
dbaron@6470 795
dbaron@6470 796 <p>This specification follows the
dbaron@6470 797 <a href="http://www.w3.org/TR/CSS21/about.html#property-defs">CSS property
dbaron@6470 798 definition conventions</a> from [[!CSS21]]. Value types not defined in
dbaron@6470 799 this specification are defined in CSS Level 2 Revision 1 [[!CSS21]].
dbaron@6470 800 Other CSS modules may expand the definitions of these value types: for
dbaron@6470 801 example [[CSS3COLOR]], when combined with this module, expands the
dbaron@6470 802 definition of the &lt;color&gt; value type as used in this specification.</p>
dbaron@6470 803
dbaron@6470 804 <p>In addition to the property-specific values listed in their definitions,
dbaron@6470 805 all properties defined in this specification also accept the
dbaron@6470 806 <a href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">inherit</a>
dbaron@6470 807 keyword as their property value. For readability it has not been repeated
dbaron@6470 808 explicitly.
dbaron@6470 809
dbaron@6470 810
dbaron@6470 811 <h3 id="conventions">
dbaron@6470 812 Document conventions</h3>
dbaron@6470 813
dbaron@6470 814 <p>Conformance requirements are expressed with a combination of
dbaron@6470 815 descriptive assertions and RFC 2119 terminology. The key words “MUST”,
dbaron@6470 816 “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
dbaron@6470 817 “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
dbaron@6470 818 document are to be interpreted as described in RFC 2119.
dbaron@6470 819 However, for readability, these words do not appear in all uppercase
dbaron@6470 820 letters in this specification.
dbaron@6470 821
dbaron@6470 822 <p>All of the text of this specification is normative except sections
dbaron@6470 823 explicitly marked as non-normative, examples, and notes. [[!RFC2119]]</p>
dbaron@6470 824
dbaron@6470 825 <p>Examples in this specification are introduced with the words “for example”
dbaron@6470 826 or are set apart from the normative text with <code>class="example"</code>,
dbaron@6470 827 like this:
dbaron@6470 828
dbaron@6470 829 <div class="example">
dbaron@6470 830 <p>This is an example of an informative example.</p>
dbaron@6470 831 </div>
dbaron@6470 832
dbaron@6470 833 <p>Informative notes begin with the word “Note” and are set apart from the
dbaron@6470 834 normative text with <code>class="note"</code>, like this:
dbaron@6470 835
dbaron@6470 836 <p class="note">Note, this is an informative note.</p>
dbaron@6470 837
dbaron@6470 838 <h3 id="conformance-classes">
dbaron@6470 839 Conformance classes</h3>
dbaron@6470 840
dbaron@6483 841 <p>Conformance to CSS Overflow Module Level 3
dbaron@6470 842 is defined for three conformance classes:
dbaron@6470 843 <dl>
dbaron@6470 844 <dt><dfn title="style sheet!!as conformance class">style sheet</dfn>
dbaron@6470 845 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
dbaron@6470 846 style sheet</a>.
dbaron@6470 847 <dt><dfn>renderer</dfn></dt>
dbaron@6470 848 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
dbaron@6470 849 that interprets the semantics of a style sheet and renders
dbaron@6470 850 documents that use them.
dbaron@6470 851 <dt><dfn id="authoring-tool">authoring tool</dfn></dt>
dbaron@6470 852 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
dbaron@6470 853 that writes a style sheet.
dbaron@6470 854 </dl>
dbaron@6470 855
dbaron@6483 856 <p>A style sheet is conformant to CSS Overflow Module Level 3
dbaron@6470 857 if all of its statements that use syntax defined in this module are valid
dbaron@6470 858 according to the generic CSS grammar and the individual grammars of each
dbaron@6470 859 feature defined in this module.
dbaron@6470 860
dbaron@6483 861 <p>A renderer is conformant to CSS Overflow Module Level 3
dbaron@6470 862 if, in addition to interpreting the style sheet as defined by the
dbaron@6470 863 appropriate specifications, it supports all the features defined
dbaron@6483 864 by CSS Overflow Module Level 3 by parsing them correctly
dbaron@6470 865 and rendering the document accordingly. However, the inability of a
dbaron@6470 866 UA to correctly render a document due to limitations of the device
dbaron@6470 867 does not make the UA non-conformant. (For example, a UA is not
dbaron@6470 868 required to render color on a monochrome monitor.)
dbaron@6470 869
dbaron@6483 870 <p>An authoring tool is conformant to CSS Overflow Module Level 3
dbaron@6470 871 if it writes style sheets that are syntactically correct according to the
dbaron@6470 872 generic CSS grammar and the individual grammars of each feature in
dbaron@6470 873 this module, and meet all other conformance requirements of style sheets
dbaron@6470 874 as described in this module.
dbaron@6470 875
dbaron@6470 876 <h3 id="partial">
dbaron@6470 877 Partial implementations</h3>
dbaron@6470 878
dbaron@6470 879 <p>So that authors can exploit the forward-compatible parsing rules to
dbaron@6470 880 assign fallback values, CSS renderers <strong>must</strong>
dbaron@6470 881 treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore
dbaron@6470 882 as appropriate</a>) any at-rules, properties, property values, keywords,
dbaron@6470 883 and other syntactic constructs for which they have no usable level of
dbaron@6470 884 support. In particular, user agents <strong>must not</strong> selectively
dbaron@6470 885 ignore unsupported component values and honor supported values in a single
dbaron@6470 886 multi-value property declaration: if any value is considered invalid
dbaron@6470 887 (as unsupported values must be), CSS requires that the entire declaration
dbaron@6470 888 be ignored.</p>
dbaron@6470 889
dbaron@6470 890 <h3 id="experimental">
dbaron@6470 891 Experimental implementations</h3>
dbaron@6470 892
dbaron@6470 893 <p>To avoid clashes with future CSS features, the CSS2.1 specification
dbaron@6470 894 reserves a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
dbaron@6470 895 syntax</a> for proprietary and experimental extensions to CSS.
dbaron@6470 896
dbaron@6470 897 <p>Prior to a specification reaching the Candidate Recommendation stage
dbaron@6470 898 in the W3C process, all implementations of a CSS feature are considered
dbaron@6470 899 experimental. The CSS Working Group recommends that implementations
dbaron@6470 900 use a vendor-prefixed syntax for such features, including those in
dbaron@6470 901 W3C Working Drafts. This avoids incompatibilities with future changes
dbaron@6470 902 in the draft.
dbaron@6470 903 </p>
dbaron@6470 904
dbaron@6470 905 <h3 id="testing">
dbaron@6470 906 Non-experimental implementations</h3>
dbaron@6470 907
dbaron@6470 908 <p>Once a specification reaches the Candidate Recommendation stage,
dbaron@6470 909 non-experimental implementations are possible, and implementors should
dbaron@6470 910 release an unprefixed implementation of any CR-level feature they
dbaron@6470 911 can demonstrate to be correctly implemented according to spec.
dbaron@6470 912
dbaron@6470 913 <p>To establish and maintain the interoperability of CSS across
dbaron@6470 914 implementations, the CSS Working Group requests that non-experimental
dbaron@6470 915 CSS renderers submit an implementation report (and, if necessary, the
dbaron@6470 916 testcases used for that implementation report) to the W3C before
dbaron@6470 917 releasing an unprefixed implementation of any CSS features. Testcases
dbaron@6470 918 submitted to W3C are subject to review and correction by the CSS
dbaron@6470 919 Working Group.
dbaron@6470 920
dbaron@6470 921 <p>Further information on submitting testcases and implementation reports
dbaron@6470 922 can be found from on the CSS Working Group's website at
dbaron@6470 923 <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
dbaron@6470 924 Questions should be directed to the
dbaron@6470 925 <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
dbaron@6470 926 mailing list.
dbaron@6470 927
dbaron@6470 928 <h3 id="cr-exit-criteria">
dbaron@6470 929 CR exit criteria</h3>
dbaron@6470 930
dbaron@6470 931 <p class=issue>[Change or remove the following CR exit criteria if
dbaron@6470 932 the spec is not a module, but, e.g., a Note or a profile. This text was <a
dbaron@6470 933 href="http://www.w3.org/Style/CSS/Tracker/actions/44"> decided on 2008-06-04.</a>]</p>
dbaron@6470 934
dbaron@6470 935 <p>
dbaron@6470 936 For this specification to be advanced to Proposed Recommendation,
dbaron@6470 937 there must be at least two independent, interoperable implementations
dbaron@6470 938 of each feature. Each feature may be implemented by a different set of
dbaron@6470 939 products, there is no requirement that all features be implemented by
dbaron@6470 940 a single product. For the purposes of this criterion, we define the
dbaron@6470 941 following terms:
dbaron@6470 942
dbaron@6470 943 <dl>
dbaron@6470 944 <dt>independent <dd>each implementation must be developed by a
dbaron@6470 945 different party and cannot share, reuse, or derive from code
dbaron@6470 946 used by another qualifying implementation. Sections of code that
dbaron@6470 947 have no bearing on the implementation of this specification are
dbaron@6470 948 exempt from this requirement.
dbaron@6470 949
dbaron@6470 950 <dt>interoperable <dd>passing the respective test case(s) in the
dbaron@6470 951 official CSS test suite, or, if the implementation is not a Web
dbaron@6470 952 browser, an equivalent test. Every relevant test in the test
dbaron@6470 953 suite should have an equivalent test created if such a user
dbaron@6470 954 agent (UA) is to be used to claim interoperability. In addition
dbaron@6470 955 if such a UA is to be used to claim interoperability, then there
dbaron@6470 956 must one or more additional UAs which can also pass those
dbaron@6470 957 equivalent tests in the same way for the purpose of
dbaron@6470 958 interoperability. The equivalent tests must be made publicly
dbaron@6470 959 available for the purposes of peer review.
dbaron@6470 960
dbaron@6470 961 <dt>implementation <dd>a user agent which:
dbaron@6470 962
dbaron@6470 963 <ol class=inline>
dbaron@6470 964 <li>implements the specification.
dbaron@6470 965
dbaron@6470 966 <li>is available to the general public. The implementation may
dbaron@6470 967 be a shipping product or other publicly available version
dbaron@6470 968 (i.e., beta version, preview release, or “nightly build”).
dbaron@6470 969 Non-shipping product releases must have implemented the
dbaron@6470 970 feature(s) for a period of at least one month in order to
dbaron@6470 971 demonstrate stability.
dbaron@6470 972
dbaron@6470 973 <li>is not experimental (i.e., a version specifically designed
dbaron@6470 974 to pass the test suite and is not intended for normal usage
dbaron@6470 975 going forward).
dbaron@6470 976 </ol>
dbaron@6470 977 </dl>
dbaron@6470 978
dbaron@6470 979 <p>The specification will remain Candidate Recommendation for at least
dbaron@6470 980 six months.
dbaron@6470 981
dbaron@6470 982 <h2 class=no-num id="acknowledgments">
dbaron@6470 983 Acknowledgments</h2>
dbaron@6470 984
dbaron@6470 985 <p>
dbaron@6470 986 Thanks especially to the feedback from
dbaron@6496 987 Rossen Atanassov,
dbaron@6496 988 Bert Bos,
dbaron@6496 989 Tantek Çelik,
dbaron@6496 990 John Daggett,
dbaron@6496 991 fantasai,
dbaron@6496 992 Daniel Glazman,
dbaron@6496 993 Vincent Hardy,
dbaron@6470 994 H&aring;kon Wium Lie,
dbaron@6496 995 Peter Linss,
dbaron@6470 996 Florian Rivoal,
dbaron@6473 997 Alan Stearns,
dbaron@6496 998 Steve Zilles,
dbaron@6470 999 and all the rest of the
dbaron@6470 1000 <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.
dbaron@6470 1001 </p>
dbaron@6470 1002
dbaron@6470 1003 <h2 class=no-num id="references">
dbaron@6470 1004 References</h2>
dbaron@6470 1005
dbaron@6470 1006 <h3 class="no-num" id="normative-references">
dbaron@6470 1007 Normative references</h3>
dbaron@6470 1008 <!--normative-->
dbaron@6470 1009
dbaron@6470 1010 <h3 class="no-num" id="other-references">
dbaron@6470 1011 Other references</h3>
dbaron@6470 1012 <!--informative-->
dbaron@6470 1013
dbaron@6470 1014 <h2 class="no-num" id="index">
dbaron@6470 1015 Index</h2>
dbaron@6470 1016 <!--index-->
dbaron@6470 1017
dbaron@6470 1018 <h2 class="no-num" id="property-index">
dbaron@6470 1019 Property index</h2>
dbaron@6470 1020 <!-- properties -->
dbaron@6470 1021
dbaron@6470 1022 </body>
dbaron@6470 1023 </html>
dbaron@6470 1024 <!-- Keep this comment at the end of the file
dbaron@6470 1025 Local variables:
dbaron@6470 1026 mode: sgml
dbaron@6470 1027 sgml-declaration:"~/SGML/HTML4.decl"
dbaron@6470 1028 sgml-default-doctype-name:"html"
dbaron@6470 1029 sgml-minimize-attributes:t
dbaron@6470 1030 sgml-nofill-elements:("pre" "style" "br")
dbaron@6470 1031 sgml-live-element-indicator:t
dbaron@6470 1032 sgml-omittag:nil
dbaron@6470 1033 sgml-shorttag:nil
dbaron@6470 1034 sgml-namecase-general:t
dbaron@6470 1035 sgml-general-insert-case:lower
dbaron@6470 1036 sgml-always-quote-attributes:t
dbaron@6470 1037 sgml-indent-step:nil
dbaron@6470 1038 sgml-indent-data:t
dbaron@6470 1039 sgml-parent-document:nil
dbaron@6470 1040 sgml-exposed-tags:nil
dbaron@6470 1041 sgml-local-catalogs:nil
dbaron@6470 1042 sgml-local-ecat-files:nil
dbaron@6470 1043 End:
dbaron@6470 1044 -->
dbaron@6470 1045

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