Thu, 12 Jul 2012 17:37:16 -0700
Say that future specifications may define additional types.
1 <!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01//EN'
2 'http://www.w3.org/TR/html4/strict.dtd'>
4 <html lang="en">
5 <head>
6 <title>CSS Transitions</title>
7 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
8 <link rel="stylesheet" type="text/css" href="../default.css">
9 <style type="text/css">
10 table.animatable-properties {
11 border-collapse: collapse;
12 }
13 table.animatable-properties td {
14 padding: 0.2em 1em;
15 border: 1px solid black;
16 }
17 </style>
18 <link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-ED.css">
19 </head>
21 <body>
23 <div class="head">
24 <!--logo-->
26 <h1>CSS Transitions</h1>
28 <h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
29 <dl>
30 <dt>This version:
31 <dd>
32 <a href="[VERSION]">
33 http://dev.w3.org/csswg/css3-transitions/</a>
34 <!--http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]/-->
35 <dt>Latest version:
36 <dd><a href="http://www.w3.org/TR/css3-transitions/">
37 [LATEST]</a>
38 <dt>Editor's draft:
39 <dd><a href="http://dev.w3.org/csswg/[SHORTNAME]/">http://dev.w3.org/csswg/[SHORTNAME]/</a>
40 <dt>Previous version:
41 <dd><a href="http://www.w3.org/TR/2012/WD-css3-transitions-20120403/">
42 http://www.w3.org/TR/2012/WD-css3-transitions-20120403/</a>
43 <dt id="editors-list">Editors:
44 <dd><a href="mailto:dino@apple.com">Dean Jackson</a> (<a
45 href="http://www.apple.com/">Apple Inc</a>)
46 <dd><a href="mailto:hyatt@apple.com">David Hyatt</a> (<a
47 href="http://www.apple.com/">Apple Inc</a>)
48 <dd><a href="mailto:cmarrin@apple.com">Chris Marrin</a> (<a
49 href="http://www.apple.com/">Apple Inc</a>)
50 <dd class=vcard><a class=fn href="http://dbaron.org/">L. David Baron</a> (<a
51 class=org href="http://www.mozilla.org/">Mozilla</a>)
53 <dt>Issues list:
54 <dd><a href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Transitions&resolution=---&cmdtype=doit">in Bugzilla</a>
56 <dt>Discussion:</dt>
57 <dd><a href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a> with subject line “<kbd>[[SHORTNAME]] <var>… message topic …</var></kbd>”
59 <dt>Test suite:
60 <dd>none yet
61 </dl>
63 <!--copyright-->
65 <hr title="Separator for header">
66 </div>
68 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
70 <p>CSS Transitions allows property changes in CSS values to occur smoothly
71 over a specified duration.
73 <h2 class="no-num no-toc" id="status">Status of this document</h2>
74 <!--status-->
76 <p>
77 The <a href="ChangeLog">list of changes made to this specification</a> is
78 available.
79 </p>
81 <h2 class="no-num no-toc" id="contents">Table of contents</h2>
82 <!--toc-->
85 <h2 id="introduction">Introduction</h2>
87 <p><em>This section is not normative.</em>
88 <p>
89 This document introduces new CSS features to enable <em>implicit transitions</em>, which describe how CSS properties can be made to change smoothly from one value to another over a given duration.
90 </p>
92 <h2 id="transitions"><a id="transitions-">Transitions</a></h2>
93 <p>
94 Normally when the value of a CSS property changes, the rendered result is instantly updated, with the affected elements immediately changing from the old property value to the new property value. This section describes a way to specify transitions using new CSS properties. These properties are used to animate smoothly from the old state to the new state over time.
95 </p>
96 <p>
97 For example, suppose that transitions of one second have been defined on the <code class="property">'left'</code> and
98 <code class="property">'background-color'</code> properties. The following diagram illustrates the effect of updating those properties on an element, in this case moving it to the right and changing the background from red to blue. This assumes other transition parameters still have their default values.
99 </p>
100 <div class="figure">
101 <img src="transition1.png" alt="">
102 </div>
103 <p class="caption">
104 Transitions of <code class="property">'left'</code> and <code class="property">'background-color'</code>
105 </p>
106 <p>
107 Transitions are a presentational effect. The computed value of a property transitions over time from the old value to the new value. Therefore if a script queries the computed style of a property as it is transitioning, it will see an intermediate value that represents the current animated value of the property.
108 </p>
109 <p>
110 Only animatable CSS properties can be transitioned. See the table at the end of this document for a list
111 of properties that are animatable.
112 </p>
113 <p>
114 The transition for a property is defined using a number of new properties. For example:
115 </p>
116 <div class="example">
117 <p style="display:none">
118 Example(s):
119 </p>
120 <pre>
121 div {
122 transition-property: opacity;
123 transition-duration: 2s;
124 }
125 </pre>The above example defines a transition on the <code class="property">'opacity'</code> property that, when a new value is assigned to it, will cause a smooth change between the old value and the new value over a period of two seconds.
126 </div>
127 <p>
128 Each of the transition properties accepts a comma-separated list, allowing multiple transitions to be defined, each acting on a different property. In this case, the individual transitions take their parameters from the same index in all the lists. For example:
129 </p>
130 <div class="example">
131 <p style="display:none">
132 Example(s):
133 </p>
134 <pre>
135 div {
136 transition-property: opacity, left;
137 transition-duration: 2s, 4s;
138 }
140 </pre>This will cause the <code class="property">'opacity'</code> property to transition over a period of two seconds and the left property to transition over a period of four seconds.
141 </div>
143 <p id="list-matching">
144 In the case where the lists of values in transition properties
145 do not have the same length, the length of the
146 'transition-property' list determines the number of items in
147 each list examined when starting transitions. The lists are
148 matched up from the first value: excess values at the end are
149 not used. If one of the other properties doesn't have enough
150 comma-separated values to match the number of values of
151 'transition-property', the UA must calculate its used value by
152 repeating the list of values until there are enough. This
153 truncation or repetition does not affect the computed value.
154 <span class="note">
155 Note: This is analogous to the behavior of the 'background-*'
156 properties, with 'background-image' analogous to
157 'transition-property'.
158 </span>
159 </p>
161 <div class="example">
162 <p style="display:none">
163 Example(s):
164 </p>
165 <pre>
166 div {
167 transition-property: opacity, left, top, width;
168 transition-duration: 2s, 1s;
169 }
170 </pre>The above example defines a transition on the <code class="property">'opacity'</code> property of 2 seconds duration, a
171 transition on the <code class="property">'left'</code> property of 1
172 second duration, a transition on the <code class="property">'top'</code> property of 2 seconds duration and a
173 transition on the <code class="property">'width'</code> property of 1
174 second duration.
176 </div>
178 <!-- ======================================================================================================= -->
179 <h3 id=transition-property-property><a id=the-transition-property-property->
180 The <code class="property">'transition-property'</code> Property
181 </a></h3>
182 <p>
183 The <code class="property">'transition-property'</code> property specifies the name of the CSS property to which the transition is applied.
184 </p>
185 <div class="issue">
186 We may ultimately want to support a keypath syntax for this property. A keypath syntax would enable different transitions to be specified for components of a property. For example the blur of a shadow could have a different transition than the color of a shadow.
187 </div>
188 <table class="propdef">
189 <tbody>
190 <tr>
191 <td>
192 <em>Name:</em>
193 </td>
194 <td>
195 <dfn id="transition-property">transition-property</dfn>
196 </td>
197 </tr>
198 <tr>
199 <td>
200 <em>Value:</em>
201 </td>
202 <td>
203 none | [ all | <IDENT> ] [ ',' [ all | <IDENT> ] ]*
204 </td>
205 </tr>
206 <tr>
207 <td>
208 <em>Initial:</em>
209 </td>
210 <td>
211 all
212 </td>
213 </tr>
214 <tr>
215 <td>
216 <em>Applies to:</em>
217 </td>
218 <td>
219 all elements, :before and :after pseudo elements
220 </td>
221 </tr>
222 <tr>
223 <td>
224 <em>Inherited:</em>
225 </td>
226 <td>
227 no
228 </td>
229 </tr>
230 <tr>
231 <td>
232 <em>Percentages:</em>
233 </td>
234 <td>
235 N/A
236 </td>
237 </tr>
238 <tr>
239 <td>
240 <em>Media:</em>
241 </td>
242 <td>
243 visual
244 </td>
245 </tr>
246 <tr>
247 <td>
248 <em>Computed value:</em>
249 </td>
250 <td>
251 Same as specified value.
252 </td>
253 </tr>
254 </tbody>
255 </table>
257 <p>
258 A value of 'none' means that no property will transition.
259 Otherwise, a list of properties to be transitioned, or the
260 keyword 'all' which indicates that all properties are to be
261 transitioned, is given.
262 </p>
264 <p>
265 If one of the identifiers listed is not a recognized property
266 name or is not an animatable property, the implementation must
267 still start transitions on the animatable properties in the
268 list using the duration, delay, and timing function at their
269 respective indices in the lists for 'transition-duration',
270 'transition-delay', and 'transition-timing-function'. In other
271 words, unrecognized or non-animatable properties must be kept in
272 the list to preserve the matching of indices.
273 </p>
274 <p class="issue">
275 Are 'none', 'inherit', and 'initial' allowed as items in
276 a list of identifiers (of length greater than one)?
277 </p>
278 <p>
279 For the keyword 'all', or if one of the identifiers listed is a
280 shorthand property, implementations must start transitions for
281 any of its longhand sub-properties that are animatable (or, for
282 'all', all animatable properties), using the duration, delay,
283 and timing function at the index corresponding to the shorthand.
284 </p>
285 <p>
286 If a property is specified multiple times in the value of
287 'transition-property' (either on its own, via a shorthand that
288 contains it, or via the 'all' value), then the transition that
289 starts uses the duration, delay, and timing function at the
290 index corresponding to the <em>last</em> item in the value of
291 'transition-property' that calls for animating that property.
292 </p>
293 <p class="note">
294 Note: The <code class="property">all</code> value and shorthand
295 properties work in similar ways, so the <code
296 class="property">all</code> value is just like a shorthand that
297 covers all properties.
298 </p>
300 <!-- ======================================================================================================= -->
301 <h3 id=transition-duration-property><a id=the-transition-duration-property->
302 The <code class="property">'transition-duration'</code> Property
303 </a></h3>
304 <p>
305 The <code class="property">'transition-duration'</code> property defines the length of time that a transition takes.
306 </p>
307 <table class="propdef">
308 <tbody>
309 <tr>
310 <td>
311 <em>Name:</em>
312 </td>
313 <td>
314 <dfn id="transition-duration">transition-duration</dfn>
315 </td>
316 </tr>
317 <tr>
318 <td>
319 <em>Value:</em>
320 </td>
321 <td>
322 <time> [, <time>]*
323 </td>
324 </tr>
325 <tr>
326 <td>
327 <em>Initial:</em>
328 </td>
329 <td>
330 0s
331 </td>
332 </tr>
333 <tr>
334 <td>
335 <em>Applies to:</em>
336 </td>
337 <td>
338 all elements, :before and :after pseudo elements
339 </td>
340 </tr>
341 <tr>
342 <td>
343 <em>Inherited:</em>
344 </td>
345 <td>
346 no
347 </td>
348 </tr>
349 <tr>
350 <td>
351 <em>Percentages:</em>
352 </td>
353 <td>
354 N/A
355 </td>
356 </tr>
357 <tr>
358 <td>
359 <em>Media:</em>
360 </td>
361 <td>
362 interactive
363 </td>
364 </tr>
365 <tr>
366 <td>
367 <em>Computed value:</em>
368 </td>
369 <td>
370 Same as specified value.
371 </td>
372 </tr>
373 </tbody>
374 </table>
375 <p>
376 This property specifies how long the transition from the old value to the new value should take. By default the value is '0s', meaning that the transition is immediate (i.e. there will be no animation). A negative value for <code class="property">transition-duration</code> renders the declaration invalid.
377 </p>
379 <!-- =======================================================================================================
380 -->
382 <h3 id=transition-timing-function-property><a id=transition-timing-function_tag>
383 The <code class="property">'transition-timing-function'</code> Property
384 </a></h3>
385 <p>
386 The <code class="property">'transition-timing-function'</code> property
387 describes how the intermediate values used during a transition will be
388 calculated. It allows for a transition to change speed over its
389 duration. These effects are commonly called <em>easing</em> functions.
390 In either case, a mathematical function that provides a smooth curve is
391 used.
392 </p>
393 <p>
394 Timing functions are either defined as a stepping function or
395 a <a
396 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
397 Bézier curve</a>.
398 The timing function takes as its input
399 the current elapsed percentage of the transition duration
400 and outputs the percentage of the way the transition is
401 from its start value to its end value.
402 How this output is used is defined by
403 the <a href="#animatable-types">interpolation rules</a>
404 for the value type.
405 </p>
406 <p>
407 A <a href="http://en.wikipedia.org/wiki/Step_function">stepping</a>
408 function is defined by a number that divides the domain of operation
409 into equally sized intervals. Each subsequent interval is a equal step
410 closer to the goal state. The function also specifies whether the
411 change in output percentage happens at the start or end of the
412 interval (in other words, if 0% on the input percentage is the point
413 of initial change).
414 </p>
415 <div class="figure">
416 <img src="step.png" alt="The step timing function splits
417 the function domain into a number of disjoint straight line
418 segments. steps(1, start) is a function whose
419 output value is 1 for all input values. steps(1, end) is a function whose
420 output value is 0 for all input values less than 1, and output
421 is 1 for the input value of 1. steps(3, start) is a function that
422 divides the input domain into three segments, each 1/3 in length,
423 and 1/3 above the previous segment, with the first segment starting
424 at 1/3. steps(3, end) is a function that
425 divides the input domain into three segments, each 1/3 in length,
426 and 1/3 above the previous segment, with the first segment starting
427 at 0.">
428 </div>
429 <p class="caption">
430 Step timing functions
431 </p>
432 <p>
433 A <a
434 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
435 Bézier curve</a> is defined by four control points, P<sub>0</sub>
436 through P<sub>3</sub> (see Figure 1). P<sub>0</sub> and P<sub>3</sub>
437 are always set to (0,0) and (1,1). The <code class="property">'transition-timing-function'</code> property is used
438 to specify the values for points P<sub>1</sub> and P<sub>2</sub>. These
439 can be set to preset values using the keywords listed below, or can be
440 set to specific values using the <code class="css">'cubic-bezier'</code> function.
441 In the <code class="css">'cubic-bezier'</code> function, P<sub>1</sub> and
442 P<sub>2</sub> are each specified by both an X and Y value.
443 </p>
444 <div class="figure">
445 <img src="TimingFunction.png" alt="The Bézier timing function is a
446 smooth curve from point P0 = (0,0) to point P3 = (1,1). The
447 length and orientation of the line segment P0-P1 determines
448 the tangent and the curvature of the curve at P0 and the
449 line segment P2-P3 does the same at P3.">
450 </div>
451 <p class="caption">
452 Bézier Timing Function Control Points
453 </p>
454 <table class="propdef">
455 <tbody>
456 <tr>
457 <td>
458 <em>Name:</em>
459 </td>
460 <td>
461 <dfn id="transition-timing-function">transition-timing-function</dfn>
462 </td>
463 </tr>
464 <tr>
465 <td>
466 <em>Value:</em>
467 </td>
468 <td>
469 [ ease | linear | ease-in | ease-out | ease-in-out | step-start | step-end | steps(<integer>[, [ start | end ] ]?) | cubic-bezier(<number>, <number>, <number>, <number>) ] [, [ ease | linear | ease-in | ease-out | ease-in-out | step-start | step-end | steps(<number>[, [ start | end ] ]?) | cubic-bezier(<number>, <number>, <number>, <number>) ] ]*
470 </td>
471 </tr>
472 <tr>
473 <td>
474 <em>Initial:</em>
475 </td>
476 <td>
477 ease
478 </td>
479 </tr>
480 <tr>
481 <td>
482 <em>Applies to:</em>
483 </td>
484 <td>
485 all elements, :before and :after pseudo elements
486 </td>
487 </tr>
488 <tr>
489 <td>
490 <em>Inherited:</em>
491 </td>
492 <td>
493 no
494 </td>
495 </tr>
496 <tr>
497 <td>
498 <em>Percentages:</em>
499 </td>
500 <td>
501 N/A
502 </td>
503 </tr>
504 <tr>
505 <td>
506 <em>Media:</em>
507 </td>
508 <td>
509 interactive
510 </td>
511 </tr>
512 <tr>
513 <td>
514 <em>Computed value:</em>
515 </td>
516 <td>
517 Same as specified value.
518 </td>
519 </tr>
520 </tbody>
521 </table>
522 <p>
523 The timing functions have the following definitions.
524 </p>
525 <dl>
526 <dt>
527 ease
528 </dt>
529 <dd>
530 The ease function is equivalent to cubic-bezier(0.25, 0.1, 0.25, 1.0).
531 </dd>
532 <dt>
533 linear
534 </dt>
535 <dd>
536 The linear function is equivalent to cubic-bezier(0.0, 0.0, 1.0, 1.0).
537 </dd>
538 <dt>
539 ease-in
540 </dt>
541 <dd>
542 The ease-in function is equivalent to cubic-bezier(0.42, 0, 1.0, 1.0).
543 </dd>
544 <dt>
545 ease-out
546 </dt>
547 <dd>
548 The ease-out function is equivalent to cubic-bezier(0, 0, 0.58, 1.0).
549 </dd>
550 <dt>
551 ease-in-out
552 </dt>
553 <dd>
554 The ease-in-out function is equivalent to cubic-bezier(0.42, 0, 0.58, 1.0)
555 </dd>
556 <dt>
557 step-start
558 </dt>
559 <dd>
560 The step-start function is equivalent to steps(1, start).
561 </dd>
562 <dt>
563 step-end
564 </dt>
565 <dd>
566 The step-end function is equivalent to steps(1, end).
567 </dd>
568 <dt>
569 steps(<integer>[, [ start | end ] ]?)
570 </dt>
571 <dd>
572 Specifies a stepping function, described above, taking two
573 parameters. The first parameter specifies the number of intervals
574 in the function. It must be a positive integer (greater than 0).
575 The second parameter, which is optional, is
576 either the value 'start' or 'end', and specifies the point
577 at which the change of values occur within the interval.
578 If the second parameter is omitted, it is given the value 'end'.
579 </dd>
580 <dt>
581 cubic-bezier(<number>, <number>, <number>, <number>)
582 </dt>
583 <dd>
584 Specifies a <a
585 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve">cubic-bezier
586 curve</a>. The four values specify points P<sub>1</sub> and
587 P<sub>2</sub> of the curve as (x1, y1, x2, y2). Both x values must be
588 in the range [0, 1] or the definition is invalid. The y values can
589 exceed this range.
590 </dd>
591 </dl><!-- ======================================================================================================= -->
592 <h3 id=transition-delay-property><a id=the-transition-delay-property->
593 The <code class="property">'transition-delay'</code> Property
594 </a></h3>
595 <p>
596 The <code class="property">'transition-delay'</code> property defines when the transition will start. It allows a transition to begin execution some some period of time from when it is applied. A <code class="property">'transition-delay'</code> value of '0s' means the transition will execute as soon as the property is changed. Otherwise, the value specifies an offset from the moment the property is changed, and the transition will delay execution by that offset.
597 </p>
598 <p>
599 If the value for <code class="property">'transition-delay'</code> is a negative time offset then the transition will execute the moment the property is changed, but will appear to have begun execution at the specified offset. That is, the transition will appear to begin part-way through its play cycle. In the case where a transition has implied starting values and a negative <code class="property">'transition-delay'</code>, the starting values are taken from the moment the property is changed.
600 </p>
601 <table class="propdef">
602 <tbody>
603 <tr>
604 <td>
605 <em>Name:</em>
606 </td>
607 <td>
608 <dfn id="transition-delay">transition-delay</dfn>
609 </td>
610 </tr>
611 <tr>
612 <td>
613 <em>Value:</em>
614 </td>
615 <td>
616 <time> [, <time>]*
617 </td>
618 </tr>
619 <tr>
620 <td>
621 <em>Initial:</em>
622 </td>
623 <td>
624 0s
625 </td>
626 </tr>
627 <tr>
628 <td>
629 <em>Applies to:</em>
630 </td>
631 <td>
632 all elements, :before and :after pseudo elements
633 </td>
634 </tr>
635 <tr>
636 <td>
637 <em>Inherited:</em>
638 </td>
639 <td>
640 no
641 </td>
642 </tr>
643 <tr>
644 <td>
645 <em>Percentages:</em>
646 </td>
647 <td>
648 N/A
649 </td>
650 </tr>
651 <tr>
652 <td>
653 <em>Media:</em>
654 </td>
655 <td>
656 interactive
657 </td>
658 </tr>
659 <tr>
660 <td>
661 <em>Computed value:</em>
662 </td>
663 <td>
664 Same as specified value.
665 </td>
666 </tr>
667 </tbody>
668 </table><!-- ======================================================================================================= -->
669 <h3 id=transition-shorthand-property><a id=the-transition-shorthand-property->
670 The <code class="property">'transition'</code> Shorthand Property
671 </a></h3>
672 <p>
673 The <code class="property">'transition'</code> shorthand property combines the four properties described above into a single property.
674 </p>
675 <p>
676 Note that order is important in this property. The first value that can be
677 parsed as a time is assigned to the transition-duration. The second value that
678 can be parsed as a time is assigned to transition-delay.
679 </p>
680 <p class="issue">
681 An alternative proposal is to accept the font shorthand approach of
682 using a "/" character between the values of the same type. e.g. 2s/4s would
683 mean a duration of 2 seconds and a delay of 4 seconds.
684 </p>
685 <table class="propdef">
686 <tbody>
687 <tr>
688 <td>
689 <em>Name:</em>
690 </td>
691 <td>
692 <dfn id="transition">transition</dfn>
693 </td>
694 </tr>
695 <tr>
696 <td>
697 <em>Value:</em>
698 </td>
699 <td>
700 [<'transition-property'> || <'transition-duration'> || <'transition-timing-function'> || <'transition-delay'> [, [<'transition-property'> || <'transition-duration'> || <'transition-timing-function'> || <'transition-delay'>]]*
701 </td>
702 </tr>
703 <tr>
704 <td>
705 <em>Initial:</em>
706 </td>
707 <td>
708 see individual properties
709 </td>
710 </tr>
711 <tr>
712 <td>
713 <em>Applies to:</em>
714 </td>
715 <td>
716 all elements, :before and :after pseudo elements
717 </td>
718 </tr>
719 <tr>
720 <td>
721 <em>Inherited:</em>
722 </td>
723 <td>
724 no
725 </td>
726 </tr>
727 <tr>
728 <td>
729 <em>Percentages:</em>
730 </td>
731 <td>
732 N/A
733 </td>
734 </tr>
735 <tr>
736 <td>
737 <em>Media:</em>
738 </td>
739 <td>
740 interactive
741 </td>
742 </tr>
743 <tr>
744 <td>
745 <em>Computed value:</em>
746 </td>
747 <td>
748 Same as specified value.
749 </td>
750 </tr>
751 </tbody>
752 </table>
754 <h2 id="starting">
755 Starting of transitions
756 </h2>
758 <p>
759 When the computed value of an animatable property changes,
760 implementations must decide what transitions to start based on
761 the values of the 'transition-property', 'transition-duration',
762 'transition-timing-function', and 'transition-delay' properties
763 at the time the animatable property would first have its new
764 computed value.
765 </p>
766 <div class="example" id="manual-reversing-example">
767 <p style="display:none">
768 Example(s):
769 </p>
770 <p>This provides a way for authors to specify different values
771 of the 'transition-*' properties for the “forward”
772 and “reverse” transitions (but see <a
773 href="#reversing">below</a> for special reversing behavior when
774 an <em>incomplete</em> transition is interrupted). Authors can
775 specify the value of 'transition-duration',
776 'transition-timing-function', or 'transition-delay' in the same
777 rule where they specify the value that triggers the transition,
778 or can change these properties at the same time as they change
779 the property that triggers the transition. Since it's the new
780 values of these 'transition-*' properties that affect the
781 transition, these values will be used for the transitions
782 <em>to</em> the associated transitioning values. For example:
783 </p>
784 <pre>li {
785 transition: background-color linear 1s;
786 background: blue;
787 }
788 li:hover {
789 background-color: green;
790 transition-duration: 2s; /* applies to the transition *to* the :hover state */
791 }</pre>
792 <p>
793 When a list item with these style rules enters the :hover
794 state, the computed 'transition-duration' at the time that
795 'background-color' would have its new value ('green') is '2s',
796 so the transition from 'blue' to 'green' takes 2 seconds.
797 However, when the list item leaves the :hover state, the
798 transition from 'green' to 'blue' takes 1 second.
799 </p>
800 </div>
802 <p>
803 When the computed value of a property changes, implementations
804 must start transitions based on the relevant item (see <a
805 href="#transition-property">the definition of
806 'transition-property'</a>) in the computed value of
807 'transition-property'.
808 Corresponding to this item there are
809 computed values of 'transition-duration' and 'transition-delay'
810 (see <a href="#list-matching">the rules on matching lists</a>).
811 Define the <dfn>combined duration</dfn> of the transition
812 as the sum of max('transition-duration', '0s') and 'transition-delay'.
813 When the combined duration is greater than '0s',
814 then a transition starts based on the values of
815 'transition-duration', 'transition-delay',
816 and 'transition-timing-function';
817 in other cases transitions do not occur.
818 </p>
820 <p>
821 Since this specification does not define
822 when computed values change, and thus what changes to
823 computed values are considered simultaneous,
824 authors should be aware that changing any of the transition
825 properties a small amount of time after making a change that
826 might transition can result in behavior that varies between
827 implementations, since the changes might be considered
828 simultaneous in some implementations but not others.
829 </p>
830 <p class="note">Say something about simultaneity</p>
832 <p>
833 Once the transition of a property has started, it must continue
834 running based on the original timing function, duration, and
835 delay, even if the 'transition-timing-function',
836 'transition-duration', or 'transition-delay' property changes
837 before the transition is complete. However, if the
838 'transition-property' property changes such that the transition
839 would not have started, the transition must stop (and the
840 property must immediately change to its final value).
841 </p>
843 <p>
844 Implementations must not start a transition when the computed
845 value of a property changes as a result of declarative animation
846 (as opposed to scripted animation).
847 </p>
849 <p>
850 Implementations also must not start a transition when the
851 computed value changes because it is inherited (directly or
852 indirectly) from another element that is transitioning the same
853 property.
854 </p>
856 <h2 id="reversing">
857 Automatically reversing interrupted transitions
858 </h2>
859 <p>
860 A common type of transition effect is when a running transition is
861 interrupted and the property is reset to its original value. An
862 example is a hover effect on an element, where the pointer enters and
863 exits the element before the effect has completed. If the outgoing and
864 incoming transitions are executed using their specified durations and
865 timing functions, the resulting effect can be distractingly
866 asymmetric. Instead, the expected behavior is that the new transition
867 should be the reverse of what has already executed.
868 </p>
870 <p>
871 If a running transition with duration T, executing so far for duration TE,
872 from state A, to state B, is interrupted by
873 a property change that would start a new transition back to state A, and
874 all the transition attributes are the same (duration, delay and timing function),
875 then the new transition must reverse the effect. The new transition must:
876 </p>
878 <ol>
879 <li>
880 Use the B and A states as its "from" and "to" states respectively. It
881 does not use the current value as its from state, due to the rules below.
882 </li>
883 <li>
884 Execute with the same duration T, but starting as if the transition had
885 already begun, without any transition delay, at the moment which would
886 cause the new transition to finish in TE from the moment of interruption. In other
887 words, the new transition will execute as if it started T-TE in the past.
888 </li>
889 <li>
890 Use a timing function that is the portion of the curve traversed up
891 to the moment of interruption, followed in the opposite direction (towards
892 the starting point). This will make the transition appear as if it
893 is playing backwards.
894 </li>
895 <li>
896 Ignore any transition delay.
897 </li>
898 </ol>
900 <p>
901 For example, suppose there is a transition with a duration of two
902 seconds. If this transition is interrupted after 0.5 seconds and the
903 property value assigned to the original value, then the new transition
904 effect will be the reverse of the original, as if it had begun
905 1.5 seconds in the past.
906 </p>
908 <p>
909 Note that by using the defined from and to states for the reversing
910 transition, it is also possible that it may reverse again, if
911 interrupted; for example, if the transition reversing to state A was
912 again interrupted by a property change to state B.
913 </p>
915 <p class="issue">Issue:
916 This introduces the concept of reversing a timing function,
917 which the spec has otherwise resisted doing, and also introduces
918 a discontinuity between transitions that have
919 almost completed (which get automatically reversed and thus have
920 their timing function reversed) and transitions that have fully
921 completed (where the reversal doesn't lead to the timing
922 function being reversed). An alternative proposal that avoids
923 this is to follow the normal timing function algorithm, except
924 multiply the duration (and also shorten any negative delay) by
925 the (output) value of the transition timing function of the
926 incomplete transition at the time it was interrupted, and, to
927 account for multiple reverses in sequence, to divide by the
928 shortening applied to the transition being interrupted. For
929 more details see this thread:
930 <a href="http://lists.w3.org/Archives/Public/www-style/2009Nov/thread.html#msg302">November 2009 part</a>,
931 <a href="http://lists.w3.org/Archives/Public/www-style/2009Dec/thread.html#msg319">December 2009 part</a>,
932 <a href="http://lists.w3.org/Archives/Public/www-style/2010Jan/thread.html#msg136">January 2010 part</a>.
933 </p>
935 <h2 id=transition-events><a id=transition-events->
936 Transition Events
937 </a></h2>
938 <p>
939 The completion of a CSS Transition generates a corresponding <a href="http://www.w3.org/TR/DOM-Level-2-Events/events.html">DOM Event</a>.
940 An event is fired for each property that undergoes a transition.
941 This allows a content developer to perform actions that synchronize
942 with the completion of a transition.
943 </p>
944 <p>
945 Each event provides the name of the property the transition is
946 associated with as well as the duration of the transition.
947 </p>
948 <dl>
949 <dt>
950 <b>Interface <i><a id="Events-TransitionEvent" name='Events-TransitionEvent'>TransitionEvent</a></i></b>
951 </dt>
952 <dd>
953 <p>
954 The <code>TransitionEvent</code> interface provides specific contextual information associated with transitions.
955 </p>
956 <dl>
957 <dt>
958 <b>IDL Definition</b>
959 </dt>
960 <dd>
961 <div class='idl-code'>
962 <pre>
963 interface TransitionEvent : Event {
964 readonly attribute DOMString propertyName;
965 readonly attribute float elapsedTime;
966 readonly attribute DOMString pseudoElement;
967 void initTransitionEvent(in DOMString typeArg,
968 in boolean canBubbleArg,
969 in boolean cancelableArg,
970 in DOMString propertyNameArg,
971 in float elapsedTimeArg,
972 in DOMString pseudoElementArg);
973 };
974 </pre>
975 </div>
976 </dd>
977 <dt>
978 <b>Attributes</b>
979 </dt>
980 <dd>
981 <dl>
982 <dt>
983 <code class='attribute-name'><a id="Events-TransitionEvent-propertyName" name='Events-TransitionEvent-propertyName'>propertyName</a></code> of type <code>DOMString</code>, readonly
984 </dt>
985 <dd>
986 The name of the CSS property associated with the transition.
987 </dd>
988 </dl>
989 <dl>
990 <dt>
991 <code class='attribute-name'><a id="Events-TransitionEvent-elapsedTime" name='Events-TransitionEvent-elapsedTime'>elapsedTime</a></code> of type <code>float</code>, readonly
992 </dt>
993 <dd>
994 The amount of time the transition has been running, in seconds, when this event fired. Note that this value is not affected by the value of <code class="property">transition-delay</code>.
995 </dd>
996 </dl>
997 <dl>
998 <dt>
999 <code class='attribute-name'><a id="Events-TransitionEvent-pseudoElement" name='Events-TransitionEvent-pseudoElement'>pseudoElement</a></code> of type <code>DOMString</code>, readonly
1000 </dt>
1001 <dd>
1002 The name (beginning with two colons) of the CSS
1003 pseudo-element on which the transition occured (in
1004 which case the target of the event is that
1005 pseudo-element's corresponding element), or the empty
1006 string if the transition occurred on an element (which
1007 means the target of the event is that element).
1008 </dd>
1009 </dl>
1010 </dd>
1011 <dt>
1012 <b>Methods</b>
1013 </dt>
1014 <dd>
1015 <dl>
1016 <dt>
1017 <code class='method-name'><a id="Events-TransitionEvent-initTransitionEvent" name='Events-TransitionEvent-initTransitionEvent'>initTransitionEvent</a></code>
1018 </dt>
1019 <dd>
1020 <div class='method'>
1021 The <code>initTransitionEvent</code> method is used to
1022 initialize the value of a <code>TransitionEvent</code>
1023 created through the <a
1024 href='http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-DocumentEvent'><code>DocumentEvent</code></a>
1025 interface. This method may only be called before the
1026 <code>TransitionEvent</code> has been dispatched via the
1027 <code>dispatchEvent</code> method, though it may be called
1028 multiple times during that phase if necessary. If called
1029 multiple times, the final invocation takes precedence.
1030 <p class="issue">Should new events being created still
1031 have init*Event methods?</p>
1032 <div class='parameters'>
1033 <b>Parameters</b>
1034 <div class='paramtable'>
1035 <dl>
1036 <dt>
1037 <code class='parameter-name'>typeArg</code> of type <code>DOMString</code>
1038 </dt>
1039 <dd>
1040 Specifies the event type.<br>
1041 </dd>
1042 <dt>
1043 <code class='parameter-name'>canBubbleArg</code> of type <code>boolean</code>
1044 </dt>
1045 <dd>
1046 Specifies whether or not the event can bubble.<br>
1047 </dd>
1048 <dt>
1049 <code class='parameter-name'>cancelableArg</code> of type <code>boolean</code>
1050 </dt>
1051 <dd>
1052 Specifies whether or not the event's default action can be prevented. Since a TransitionEvent
1053 is purely for notification, there is no default action.<br>
1054 </dd>
1055 <dt>
1056 <code class='parameter-name'>propertyNameArg</code> of type <code>DOMString</code>
1057 </dt>
1058 <dd>
1059 Specifies the name of the property associated with the <a href='http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-Event'><code>Event</code></a>.
1060 (See the <a href="#Events-TransitionEvent-propertyName">propertyName</a> attribute.)
1061 </dd>
1062 <dt>
1063 <code class='parameter-name'>elapsedTimeArg</code> of type <code>float</code>
1064 </dt>
1065 <dd>
1066 Specifies the amount of time, in seconds, the transition has been running at the time of initialization.
1067 (See the <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a> attribute.)
1068 </dd>
1069 <dt>
1070 <code class='parameter-name'>pseudoElementArg</code> of type <code>DOMString</code>
1071 </dt>
1072 <dd>
1073 Specifies the pseudo-element on which the
1074 transition occurred.
1075 (See the <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a> attribute.)
1076 <span class="issue">Does adding this additional argument create any compatibility problems?</span>
1077 </dd>
1078 </dl>
1079 </div>
1080 </div><!-- parameters -->
1081 <div>
1082 <b>No Return Value</b>
1083 </div>
1084 <div>
1085 <b>No Exceptions</b>
1086 </div>
1087 </div><!-- method -->
1088 </dd>
1089 </dl>
1090 </dd>
1091 </dl>
1092 </dd>
1093 </dl>
1094 <p>
1095 There is one type of transition event available.
1096 </p>
1097 <dl>
1098 <dt>
1099 <b>transitionend</b>
1100 </dt>
1101 <dd>
1102 The 'transitionend' event occurs at the completion of the transition. In the
1103 case where a transition is removed before completion, such as if the
1104 transition-property is removed, then the event will not fire.
1105 <ul>
1106 <li>Bubbles: Yes
1107 </li>
1108 <li>Cancelable: Yes
1109 </li>
1110 <li>Context Info: propertyName, elapsedTime
1111 </li>
1112 </ul>
1113 </dd>
1114 </dl>
1116 <h2 id="animatable-types"><a id=animation-of-property-types->
1117 Animation of property types
1118 </a></h2>
1120 <p>
1121 When interpolating between two values,
1122 <i>V</i><sub>start</sub> and <i>V</i><sub>end</sub>,
1123 interpolation is done using the output <i>p</i> of the timing function,
1124 which gives the portion of the value space
1125 that the interpolation has crossed.
1126 Thus the result of the interpolation is
1127 <i>V</i><sub>res</sub> =
1128 (1 - <i>p</i>) ⋅ <i>V</i><sub>start</sub> +
1129 <i>p</i> ⋅ <i>V</i><sub>end</sub>.
1130 </p>
1132 <p>
1133 The following describes how each property type undergoes transition or
1134 animation.
1135 </p>
1137 <ul>
1138 <li>
1139 <strong>color</strong>: interpolated via red, green, blue and alpha
1140 components (treating each as a number, see below).
1141 <div class="issue">Issue: Are the colors interpolated in
1142 premultiplied space or non-premultiplied space?</div>
1143 </li>
1144 <li>
1145 <strong>length</strong>: interpolated as real numbers.
1146 </li>
1147 <li>
1148 <strong>percentage</strong>: interpolated as real numbers.
1149 </li>
1150 <li>
1151 <strong>integer</strong>: interpolated via discrete steps (whole
1152 numbers). The interpolation happens in real number space and is
1153 converted to an integer using <code>floor()</code>.
1154 <span class="issue">
1155 This floor behavior is inconsistent with SMIL Animation /
1156 SVG Animation.
1157 </span>
1158 </li>
1159 <li>
1160 <strong>font weight</strong>: interpolated via discrete steps
1161 (multiples of 100). The interpolation happens in real number
1162 space and is converted to an integer by rounding to the
1163 nearest multiple of 100.
1164 <span class="issue">
1165 This round-to-nearest behavior is inconsistent with the
1166 floor behavior used for integer types, but probably should
1167 be consistent (one way or the other).
1168 </span>
1169 </li>
1170 <li>
1171 <strong>number</strong>: interpolated as real (floating point)
1172 numbers.
1173 </li>
1174 <li>
1175 <strong>transform list</strong>: see
1176 CSS Transforms specification [[!CSS3-TRANSFORMS]].
1177 </li>
1178 <li>
1179 <strong>rectangle</strong>: interpolated via the x, y,
1180 width and height components (treating each as a number).
1181 </li>
1182 <li>
1183 <strong>visibility</strong>: if one of the values is
1184 'visible', interpolated as a discrete step where values of the
1185 timing function between 0 and 1 map to 'visible' and other
1186 values of the timing function (which occur only at the
1187 start/end of the transition or as a result of 'cubic-bezier()'
1188 functions with Y values outside of [0, 1]) map to the closer
1189 endpoint; if neither value is 'visible' then not interpolable.
1190 </li>
1191 <li>
1192 <strong>shadow</strong>: interpolated via the color, x, y
1193 and blur components (treating them as color and numbers where
1194 appropriate). In the case where there are lists of shadows,
1195 the shorter list is padded at the end with shadows whose
1196 color is transparent and all lengths (x, y, blur) are 0.
1197 </li>
1198 <li>
1199 <strong>gradient</strong>: interpolated via the
1200 positions and colors of each stop. They must have the same type
1201 (radial or linear) and same number of stops in order to be animated.
1202 <span class="note">Note: [[CSS3-IMAGES]] may extend this
1203 definition.</span>
1204 </li>
1205 <li>
1206 <strong>paint server</strong> (SVG): interpolation is only supported
1207 between: gradient to gradient and color to color. They then
1208 work as above.
1209 </li>
1210 <li>
1211 <strong>list of above types</strong>: If the lists have the
1212 same number of items, each item in the list is interpolated using the
1213 rules above. Otherwise the interpolation is determined by the property
1214 rules. If the property extends its list by repeating values, then this
1215 repeated form will be used in the interpolation (<code class="property">'background-position'</code>
1216 is an example of a property that would transition between lists of different lengths). If
1217 the property does not allow extending its list, then no interpolation
1218 will occur.
1219 </li>
1220 <li>
1221 <strong>a shorthand property</strong>: If any part of a
1222 shorthand can be animated, then interpolation is performed as
1223 if those animatable properties were individually specified.
1224 </li>
1225 </ul>
1227 <p class="issue">Issue: Need to describe handling of out-of-range
1228 values that can result from cubic-bezier(). Clamping values to the
1229 allowed range is probably the best solution.</p>
1231 <p>Future specifications may define additional types that can
1232 be animated.</p>
1234 <h2 id=animatable-properties><a id=animatable-properties->
1235 Animatable properties
1236 </a></h2>
1238 <!--
1239 As resolved in
1240 http://lists.w3.org/Archives/Public/www-style/2011Sep/0497.html
1241 -->
1242 <p>For properties that exist at the time this specification was
1243 developed, this specification defines whether and how they are
1244 animated. However, future CSS specifications may define
1245 additional properties, additional values for existing properties,
1246 or additional animation behavior of existing values. In order to
1247 describe new animation behaviors and to have the definition of
1248 animation behavior in a more appropriate location, future CSS
1249 specifications should include an "Animatable:" line in the summary
1250 of the property's definition (in addition to the other lines
1251 described in [[CSS21]], <a
1252 href="http://www.w3.org/TR/CSS21/about.html#property-defs">section
1253 1.4.2</a>). This line should say "no" to indicate that a property
1254 cannot be animated or should reference an animation behavior
1255 (which may be one of the behaviors in the <a
1256 href="#animation-of-property-types-">Animation of property
1257 types</a> section above, or may be a new behavior) to define how
1258 the property animates. Such definitions override those given in
1259 this specification.</p>
1261 <h3 id=animatable-css><a id=properties-from-css->
1262 Properties from CSS
1263 </a></h3>
1265 <table class="animatable-properties">
1266 <tr>
1267 <th>Property Name</th>
1268 <th>Type</th>
1269 </tr>
1270 <tr>
1271 <td>background-color</td><td>color</tr>
1272 <tr>
1273 <td>background-position</td><td>percentage, length</td>
1274 </tr>
1275 <tr>
1276 <td>border-bottom-color</td><td>color</td>
1277 </tr>
1278 <tr>
1279 <td>border-bottom-width</td><td>length</td>
1280 </tr>
1281 <tr>
1282 <td>border-left-color</td><td>color</td>
1283 </tr>
1284 <tr>
1285 <td>border-left-width</td><td>length</td>
1286 </tr>
1287 <tr>
1288 <td>border-right-color</td><td>color</td>
1289 </tr>
1290 <tr>
1291 <td>border-right-width</td><td>length</td>
1292 </tr>
1293 <tr>
1294 <td>border-spacing</td><td>length</td>
1295 </tr>
1296 <tr>
1297 <td>border-top-color</td><td>color</td>
1298 </tr>
1299 <tr>
1300 <td>border-top-width</td><td>length</td>
1301 </tr>
1302 <tr>
1303 <td>bottom</td><td>length, percentage</td>
1304 </tr>
1305 <tr>
1306 <td>clip</td><td>rectangle</td>
1307 </tr>
1308 <tr>
1309 <td>color</td><td>color</td>
1310 </tr>
1311 <tr>
1312 <td>crop <span class="issue">css3-content will likely advance slower than this specification, in which case this definition should move there</span></td><td>rectangle</td>
1313 </tr>
1314 <tr>
1315 <td>font-size</td><td>length, percentage</td>
1316 </tr>
1317 <tr>
1318 <td>font-weight</td><td>font weight</td>
1319 </tr>
1320 <tr>
1321 <td>height</td><td>length, percentage</td>
1322 </tr>
1323 <tr>
1324 <td>left</td><td>length, percentage</td>
1325 </tr>
1326 <tr>
1327 <td>letter-spacing</td><td>length</td>
1328 </tr>
1329 <tr>
1330 <td>line-height</td><td>number, length, percentage</td>
1331 </tr>
1332 <tr>
1333 <td>margin-bottom</td><td>length</td>
1334 </tr>
1335 <tr>
1336 <td>margin-left</td><td>length</td>
1337 </tr>
1338 <tr>
1339 <td>margin-right</td><td>length</td>
1340 </tr>
1341 <tr>
1342 <td>margin-top</td><td>length</td>
1343 </tr>
1344 <tr>
1345 <td>max-height</td><td>length, percentage</td>
1346 </tr>
1347 <tr>
1348 <td>max-width</td><td>length, percentage </td>
1349 </tr>
1350 <tr>
1351 <td>min-height</td><td>length, percentage</td>
1352 </tr>
1353 <tr>
1354 <td>min-width</td><td>length, percentage</td>
1355 </tr>
1356 <tr>
1357 <td>opacity</td><td>number</td>
1358 </tr>
1359 <tr>
1360 <td>outline-color</td><td>color</td>
1361 </tr>
1362 <tr>
1363 <td>outline-offset</td><td>integer</td>
1364 </tr>
1365 <tr>
1366 <td>outline-width</td><td>length</td>
1367 </tr>
1368 <tr>
1369 <td>padding-bottom</td><td>length</td>
1370 </tr>
1371 <tr>
1372 <td>padding-left</td><td>length</td>
1373 </tr>
1374 <tr>
1375 <td>padding-right</td><td>length</td>
1376 </tr>
1377 <tr>
1378 <td>padding-top</td><td>length</td>
1379 </tr>
1380 <tr>
1381 <td>right</td><td>length, percentage</td>
1382 </tr>
1383 <tr>
1384 <td>text-indent</td><td>length, percentage</td>
1385 </tr>
1386 <tr>
1387 <td>text-shadow</td><td>shadow</td>
1388 </tr>
1389 <tr>
1390 <td>top</td><td>length, percentage</td>
1391 </tr>
1392 <tr>
1393 <td>vertical-align</td><td>length, percentage</td>
1394 </tr>
1395 <tr>
1396 <td>visibility</td><td>visibility</td>
1397 </tr>
1398 <tr>
1399 <td>width</td><td>length, percentage</td>
1400 </tr>
1401 <tr>
1402 <td>word-spacing</td><td>length, percentage</td>
1403 </tr>
1404 <tr>
1405 <td>z-index</td><td>integer</td>
1406 </tr>
1407 </table>
1409 <p class="issue">
1410 This list omits the following properties that Gecko can animate, and
1411 which likely should be included:
1412 background-size,
1413 border-*-radius,
1414 box-shadow,
1415 column-count,
1416 column-gap,
1417 column-rule-color,
1418 column-rule-width,
1419 column-width,
1420 font-size-adjust,
1421 font-stretch,
1422 marker-offset,
1423 text-decoration-color,
1424 transform,
1425 transform-origin.
1426 </p>
1428 <h3 id=animatable-svg><a id=properties-from-svg->
1429 Properties from SVG
1430 </a></h3>
1432 <p>
1433 All properties defined as animatable in the SVG specification, provided
1434 they are one of the property types listed above.
1435 </p>
1437 <!-- <table>
1438 <tr>
1439 <th>Property Name</th><th>Type</th>
1440 </tr>
1441 <tr>
1442 <td>stop-color</td><td>color</td>
1443 </tr>
1444 <tr>
1445 <td>stop-opacity</td><td>float</td>
1446 </tr>
1447 <tr>
1448 <td>fill</td><td>paint server</td>
1449 </tr>
1450 <tr>
1451 <td>fill-opacity</td><td>float</td>
1452 </tr>
1453 <tr>
1454 <td>stroke</td><td>paint server</td>
1455 </tr>
1456 <tr>
1457 <td>stroke-dasharray</td><td>list of numbers</td>
1458 </tr>
1459 <tr>
1460 <td>stroke-dashoffset</td><td>number</td>
1461 </tr>
1462 <tr>
1463 <td>stroke-miterlimit</td><td>number</td>
1464 </tr>
1465 <tr>
1466 <td>stroke-opacity</td><td>float</td>
1467 </tr>
1468 <tr>
1469 <td>stroke-width</td><td>float</td>
1470 </tr>
1471 <tr>
1472 <td>viewport-fill</td><td>color</td>
1473 </tr>
1474 <tr>
1475 <td>viewport-fill-opacity</td><td>color</td>
1476 </tr>
1477 </table> -->
1479 <h2 id="acknowledgments">Acknowledgments</h2>
1481 <p>Thanks especially to the feedback from
1482 Tab Atkins,
1483 Aryeh Gregor,
1484 Vincent Hardy,
1485 Cameron McCormack,
1486 Alex Mogilevsky,
1487 and all the rest of the
1488 <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.</p>
1490 <h2 id="references">References</h2>
1492 <h3 class="no-num" id=normative-references>Normative references</h3>
1493 <!--normative-->
1495 <h3 class="no-num" id=other-references>Other references</h3>
1496 <!--informative-->
1500 <h2 class="no-num" id=property-index>Property index</h2>
1501 <!-- properties -->
1505 <h2 class="no-num" id="index">Index</h2>
1506 <!--index-->
1508 </body>
1509 </html>
1510 <!-- Keep this comment at the end of the file
1511 Local variables:
1512 mode: sgml
1513 sgml-default-doctype-name:"html"
1514 sgml-minimize-attributes:t
1515 End:
1516 -->