css-transitions/Overview.src.html@b8e4691d68cc
css-transitions/Overview.src.html
Tue, 19 Nov 2013 15:35:38 +0800
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- L. David Baron <dbaron@dbaron.org>
- date
- Tue, 19 Nov 2013 15:35:38 +0800
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[css-transitions] Better section title for reversing section.
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 <script src='http://test.csswg.org/harness/annotate.js#css-transitions-1_dev' type='text/javascript' defer></script>
8 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
9 <link rel="stylesheet" type="text/css" href="../default.css">
10 <style type="text/css">
11 table.animatable-properties {
12 border-collapse: collapse;
13 }
14 table.animatable-properties td {
15 padding: 0.2em 1em;
16 border: 1px solid black;
17 }
18 div.prod { margin: 1em 2em; }
19 </style>
20 <link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS].css">
21 </head>
23 <body>
25 <div class="head">
26 <!--logo-->
28 <h1>CSS Transitions</h1>
30 <h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
31 <dl>
32 <dt>This version:
33 <dd>
34 <a href="[VERSION]">[VERSION]</a>
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/css-transitions/">http://dev.w3.org/csswg/css-transitions/</a>
40 (<a href="https://dvcs.w3.org/hg/csswg/log/tip/css-transitions/Overview.src.html">change log</a>,
41 <a href="https://dvcs.w3.org/hg/csswg/log/tip/css3-transitions/Overview.src.html">older change log</a>)
42 <dt>Previous version:
43 <dd><a href="http://www.w3.org/TR/2013/WD-css3-transitions-20131119/">http://www.w3.org/TR/2013/WD-css3-transitions-20131119/</a>
44 <dt id="editors-list">Editors:
45 <dd><a href="mailto:dino@apple.com">Dean Jackson</a> (<a
46 href="http://www.apple.com/">Apple Inc</a>)
47 <dd><a href="mailto:hyatt@apple.com">David Hyatt</a> (<a
48 href="http://www.apple.com/">Apple Inc</a>)
49 <dd><a href="mailto:cmarrin@apple.com">Chris Marrin</a> (<a
50 href="http://www.apple.com/">Apple Inc</a>)
51 <dd class=vcard><a class=fn href="http://dbaron.org/">L. David Baron</a> (<a
52 class=org href="http://www.mozilla.org/">Mozilla</a>)
54 <dt>Issues list:
55 <dd><a href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Transitions&resolution=---&cmdtype=doit">in Bugzilla</a>
57 <dt>Feedback:
58 <dd><a href="mailto:www-style@w3.org?subject=%5Bcss-transitions%5D%20feedback">www-style@w3.org</a>
59 with subject line “<kbd>[css-transitions] <var>… message topic …</var></kbd>”
60 (<a rel="discussion" href="http://lists.w3.org/Archives/Public/www-style/">archives</a>)
62 <dt>Test suite:
63 <dd> <a href="http://test.csswg.org/suites/css-transitions-1/nightly-unstable/">http://test.csswg.org/suites/css-transitions-1/nightly-unstable/</a>
64 </dl>
66 <!--copyright-->
68 <hr title="Separator for header">
69 </div>
71 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
73 <p>CSS Transitions allows property changes in CSS values to occur smoothly
74 over a specified duration.
76 <h2 class="no-num no-toc" id="status">Status of this document</h2>
77 <!--status-->
79 <p>
80 <strong>This document</strong> is expected to be relatively close to
81 last call. While some issues raised have yet to be addressed, new
82 features are extremely unlikely to be considered for this level.
83 </p>
85 <h2 class="no-num no-toc" id="contents">Table of Contents</h2>
86 <!--toc-->
89 <h2 id="introduction">Introduction</h2>
91 <p><em>This section is not normative.</em>
92 <p>
93 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.
94 </p>
96 <h2 id="transitions"><a id="transitions-">Transitions</a></h2>
97 <p>
98 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.
99 </p>
100 <p>
101 For example, suppose that transitions of one second have been defined on the 'left' and
102 'background-color' 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.
103 </p>
104 <div class="figure">
105 <img src="transition1.png" alt="">
106 </div>
107 <p class="caption">
108 Transitions of 'left' and 'background-color'
109 </p>
110 <p>
111 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.
112 </p>
113 <p>
114 Only animatable CSS properties can be transitioned. See the table at the end of this document for a list
115 of properties that are animatable.
116 </p>
117 <p>
118 The transition for a property is defined using a number of new properties. For example:
119 </p>
120 <div class="example">
121 <p style="display:none">
122 Example(s):
123 </p>
124 <pre>
125 div {
126 transition-property: opacity;
127 transition-duration: 2s;
128 }
129 </pre>The above example defines a transition on the 'opacity' 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.
130 </div>
131 <p>
132 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:
133 </p>
134 <div class="example">
135 <p style="display:none">
136 Example(s):
137 </p>
138 <pre>
139 div {
140 transition-property: opacity, left;
141 transition-duration: 2s, 4s;
142 }
144 </pre>This will cause the 'opacity' property to transition over a period of two seconds and the left property to transition over a period of four seconds.
145 </div>
147 <p id="list-matching">
148 In the case where the lists of values in transition properties
149 do not have the same length, the length of the
150 'transition-property' list determines the number of items in
151 each list examined when starting transitions. The lists are
152 matched up from the first value: excess values at the end are
153 not used. If one of the other properties doesn't have enough
154 comma-separated values to match the number of values of
155 'transition-property', the UA must calculate its used value by
156 repeating the list of values until there are enough. This
157 truncation or repetition does not affect the computed value.
158 <span class="note">
159 Note: This is analogous to the behavior of the 'background-*'
160 properties, with 'background-image' analogous to
161 'transition-property'.
162 </span>
163 </p>
165 <div class="example">
166 <p style="display:none">
167 Example(s):
168 </p>
169 <pre>
170 div {
171 transition-property: opacity, left, top, width;
172 transition-duration: 2s, 1s;
173 }
174 </pre>The above example defines a transition on the 'opacity' property of 2 seconds duration, a
175 transition on the 'left' property of 1
176 second duration, a transition on the 'top' property of 2 seconds duration and a
177 transition on the 'width' property of 1
178 second duration.
180 </div>
182 <p>
183 While authors can use transitions to create dynamically changing content,
184 dynamically changing content can lead to seizures in some users.
185 For information on how to avoid content that can lead to seizures, see
186 <a href="http://www.w3.org/TR/WCAG20/#seizure">Guideline 2.3:
187 Seizures:
188 Do not design content in a way that is known to cause seizures</a>
189 ([[WCAG20]]).
190 </p>
192 <!-- ======================================================================================================= -->
193 <h3 id="transition-property-property"><a id="the-transition-property-property-">
194 The 'transition-property' Property
195 </a></h3>
196 <p>
197 The 'transition-property' property specifies the name of the CSS property to which the transition is applied.
198 </p>
199 <table class="propdef">
200 <tbody>
201 <tr>
202 <td>
203 <em>Name:</em>
204 </td>
205 <td>
206 <dfn id="transition-property">transition-property</dfn>
207 </td>
208 </tr>
209 <tr>
210 <td>
211 <em>Value:</em>
212 </td>
213 <td>
214 none | <span><single-transition-property></span> [ ',' <span><single-transition-property></span> ]*
215 </td>
216 </tr>
217 <tr>
218 <td>
219 <em>Initial:</em>
220 </td>
221 <td>
222 all
223 </td>
224 </tr>
225 <tr>
226 <td>
227 <em>Applies to:</em>
228 </td>
229 <td>
230 all elements, :before and :after pseudo elements
231 </td>
232 </tr>
233 <tr>
234 <td>
235 <em>Inherited:</em>
236 </td>
237 <td>
238 no
239 </td>
240 </tr>
241 <tr>
242 <td>
243 <em>Animatable:</em>
244 </td>
245 <td>
246 no
247 </td>
248 </tr>
249 <tr>
250 <td>
251 <em>Percentages:</em>
252 </td>
253 <td>
254 N/A
255 </td>
256 </tr>
257 <tr>
258 <td>
259 <em>Media:</em>
260 </td>
261 <td>
262 visual
263 </td>
264 </tr>
265 <tr>
266 <td>
267 <em>Computed value:</em>
268 </td>
269 <td>
270 Same as specified value.
271 </td>
272 </tr>
273 <tr>
274 <td>
275 <em>Canonical order:</em>
276 </td>
277 <td>
278 <abbr title="follows order of property value definition">per grammar</abbr>
279 </td>
280 </tr>
281 </tbody>
282 </table>
284 <div class="prod">
285 <dfn id="single-transition-property"><single-transition-property></dfn> = all | <IDENT>
286 </div>
288 <p>
289 A value of ''none'' means that no property will transition.
290 Otherwise, a list of properties to be transitioned, or the
291 keyword ''all'' which indicates that all properties are to be
292 transitioned, is given.
293 </p>
295 <p>
296 If one of the identifiers listed is not a recognized property
297 name or is not an animatable property, the implementation must
298 still start transitions on the animatable properties in the
299 list using the duration, delay, and timing function at their
300 respective indices in the lists for 'transition-duration',
301 'transition-delay', and 'transition-timing-function'. In other
302 words, unrecognized or non-animatable properties must be kept in
303 the list to preserve the matching of indices.
304 </p>
306 <p>
307 The keywords ''none'', ''inherit'', and ''initial'' are not
308 permitted as items within a list of more that one identifier;
309 any list that uses them is syntactically invalid.
310 In other words, the <IDENT> production in
311 <span><single-transition-property></span> matches any
312 identifier other than these three keywords.
313 </p>
315 <p>
316 For the keyword ''all'', or if one of the identifiers listed is a
317 shorthand property, implementations must start transitions for
318 any of its longhand sub-properties that are animatable (or, for
319 ''all'', all animatable properties), using the duration, delay,
320 and timing function at the index corresponding to the shorthand.
321 </p>
322 <p>
323 If a property is specified multiple times in the value of
324 'transition-property' (either on its own, via a shorthand that
325 contains it, or via the ''all'' value), then the transition that
326 starts uses the duration, delay, and timing function at the
327 index corresponding to the <em>last</em> item in the value of
328 'transition-property' that calls for animating that property.
329 </p>
330 <p class="note">
331 Note: The ''all'' value and 'all' shorthand
332 property work in similar ways, so the
333 ''all'' value is just like a shorthand that
334 covers all properties.
335 </p>
337 <!-- ======================================================================================================= -->
338 <h3 id="transition-duration-property"><a id="the-transition-duration-property-">
339 The 'transition-duration' Property
340 </a></h3>
341 <p>
342 The 'transition-duration' property defines the length of time that a transition takes.
343 </p>
344 <table class="propdef">
345 <tbody>
346 <tr>
347 <td>
348 <em>Name:</em>
349 </td>
350 <td>
351 <dfn id="transition-duration">transition-duration</dfn>
352 </td>
353 </tr>
354 <tr>
355 <td>
356 <em>Value:</em>
357 </td>
358 <td>
359 <span><time></span> [, <span><time></span>]*
360 </td>
361 </tr>
362 <tr>
363 <td>
364 <em>Initial:</em>
365 </td>
366 <td>
367 0s
368 </td>
369 </tr>
370 <tr>
371 <td>
372 <em>Applies to:</em>
373 </td>
374 <td>
375 all elements, :before and :after pseudo elements
376 </td>
377 </tr>
378 <tr>
379 <td>
380 <em>Inherited:</em>
381 </td>
382 <td>
383 no
384 </td>
385 </tr>
386 <tr>
387 <td>
388 <em>Animatable:</em>
389 </td>
390 <td>
391 no
392 </td>
393 </tr>
394 <tr>
395 <td>
396 <em>Percentages:</em>
397 </td>
398 <td>
399 N/A
400 </td>
401 </tr>
402 <tr>
403 <td>
404 <em>Media:</em>
405 </td>
406 <td>
407 interactive
408 </td>
409 </tr>
410 <tr>
411 <td>
412 <em>Computed value:</em>
413 </td>
414 <td>
415 Same as specified value.
416 </td>
417 </tr>
418 <tr>
419 <td>
420 <em>Canonical order:</em>
421 </td>
422 <td>
423 <abbr title="follows order of property value definition">per grammar</abbr>
424 </td>
425 </tr>
426 </tbody>
427 </table>
428 <p>
429 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 'transition-duration' renders the declaration invalid.
430 </p>
432 <!-- =======================================================================================================
433 -->
435 <h3 id="transition-timing-function-property"><a id="transition-timing-function_tag">
436 The 'transition-timing-function' Property
437 </a></h3>
438 <p>
439 The 'transition-timing-function' property
440 describes how the intermediate values used during a transition will be
441 calculated. It allows for a transition to change speed over its
442 duration. These effects are commonly called <em>easing</em> functions.
443 In either case, a mathematical function that provides a smooth curve is
444 used.
445 </p>
446 <p>
447 Timing functions are either defined as a stepping function or
448 a <a
449 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
450 Bézier curve</a>.
451 The timing function takes as its input
452 the current elapsed percentage of the transition duration
453 and outputs the percentage of the way the transition is
454 from its start value to its end value.
455 How this output is used is defined by
456 the <a href="#animatable-types">interpolation rules</a>
457 for the value type.
458 </p>
459 <p>
460 A <a href="http://en.wikipedia.org/wiki/Step_function">stepping</a>
461 function is defined by a number that divides the domain of operation
462 into equally sized intervals. Each subsequent interval is a equal step
463 closer to the goal state. The function also specifies whether the
464 change in output percentage happens at the start or end of the
465 interval (in other words, if 0% on the input percentage is the point
466 of initial change).
467 </p>
468 <div class="figure">
469 <img src="step.png" alt="The step timing function splits
470 the function domain into a number of disjoint straight line
471 segments. steps(1, start) is a function whose
472 output value is 1 for all input values. steps(1, end) is a function whose
473 output value is 0 for all input values less than 1, and output
474 is 1 for the input value of 1. steps(3, start) is a function that
475 divides the input domain into three segments, each 1/3 in length,
476 and 1/3 above the previous segment, with the first segment starting
477 at 1/3. steps(3, end) is a function that
478 divides the input domain into three segments, each 1/3 in length,
479 and 1/3 above the previous segment, with the first segment starting
480 at 0.">
481 </div>
482 <p class="caption">
483 Step timing functions
484 </p>
485 <p>
486 A <a
487 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
488 Bézier curve</a> is defined by four control points, P<sub>0</sub>
489 through P<sub>3</sub> (see Figure 1). P<sub>0</sub> and P<sub>3</sub>
490 are always set to (0,0) and (1,1). The 'transition-timing-function' property is used
491 to specify the values for points P<sub>1</sub> and P<sub>2</sub>. These
492 can be set to preset values using the keywords listed below, or can be
493 set to specific values using the ''cubic-bezier'' function.
494 In the ''cubic-bezier'' function, P<sub>1</sub> and
495 P<sub>2</sub> are each specified by both an X and Y value.
496 </p>
497 <div class="figure">
498 <img src="TimingFunction.png" alt="The Bézier timing function is a
499 smooth curve from point P0 = (0,0) to point P3 = (1,1). The
500 length and orientation of the line segment P0-P1 determines
501 the tangent and the curvature of the curve at P0 and the
502 line segment P2-P3 does the same at P3.">
503 </div>
504 <p class="caption">
505 Bézier Timing Function Control Points
506 </p>
507 <table class="propdef">
508 <tbody>
509 <tr>
510 <td>
511 <em>Name:</em>
512 </td>
513 <td>
514 <dfn id="transition-timing-function">transition-timing-function</dfn>
515 </td>
516 </tr>
517 <tr>
518 <td>
519 <em>Value:</em>
520 </td>
521 <td>
522 <span><single-transition-timing-function></span> [ ',' <span><single-transition-timing-function></span> ]*
523 </td>
524 </tr>
525 <tr>
526 <td>
527 <em>Initial:</em>
528 </td>
529 <td>
530 ease
531 </td>
532 </tr>
533 <tr>
534 <td>
535 <em>Applies to:</em>
536 </td>
537 <td>
538 all elements, :before and :after pseudo elements
539 </td>
540 </tr>
541 <tr>
542 <td>
543 <em>Inherited:</em>
544 </td>
545 <td>
546 no
547 </td>
548 </tr>
549 <tr>
550 <td>
551 <em>Animatable:</em>
552 </td>
553 <td>
554 no
555 </td>
556 </tr>
557 <tr>
558 <td>
559 <em>Percentages:</em>
560 </td>
561 <td>
562 N/A
563 </td>
564 </tr>
565 <tr>
566 <td>
567 <em>Media:</em>
568 </td>
569 <td>
570 interactive
571 </td>
572 </tr>
573 <tr>
574 <td>
575 <em>Computed value:</em>
576 </td>
577 <td>
578 Same as specified value.
579 </td>
580 </tr>
581 <tr>
582 <td>
583 <em>Canonical order:</em>
584 </td>
585 <td>
586 <abbr title="follows order of property value definition">per grammar</abbr>
587 </td>
588 </tr>
589 </tbody>
590 </table>
591 <div class="prod">
592 <dfn id="single-transition-timing-function"><single-transition-timing-function></dfn> = ease | linear | ease-in | ease-out | ease-in-out | step-start | step-end | steps(<integer>[, [ start | end ] ]?) | cubic-bezier(<number>, <number>, <number>, <number>)
593 </div>
594 <p>
595 The timing functions have the following definitions.
596 </p>
597 <dl>
598 <dt>
599 ease
600 </dt>
601 <dd>
602 The ease function is equivalent to cubic-bezier(0.25, 0.1, 0.25, 1).
603 </dd>
604 <dt>
605 linear
606 </dt>
607 <dd>
608 The linear function is equivalent to cubic-bezier(0, 0, 1, 1).
609 </dd>
610 <dt>
611 ease-in
612 </dt>
613 <dd>
614 The ease-in function is equivalent to cubic-bezier(0.42, 0, 1, 1).
615 </dd>
616 <dt>
617 ease-out
618 </dt>
619 <dd>
620 The ease-out function is equivalent to cubic-bezier(0, 0, 0.58, 1).
621 </dd>
622 <dt>
623 ease-in-out
624 </dt>
625 <dd>
626 The ease-in-out function is equivalent to cubic-bezier(0.42, 0, 0.58, 1)
627 </dd>
628 <dt>
629 step-start
630 </dt>
631 <dd>
632 The step-start function is equivalent to steps(1, start).
633 </dd>
634 <dt>
635 step-end
636 </dt>
637 <dd>
638 The step-end function is equivalent to steps(1, end).
639 </dd>
640 <dt>
641 steps(<integer>[, [ start | end ] ]?)
642 </dt>
643 <dd>
644 Specifies a stepping function, described above, taking two
645 parameters. The first parameter specifies the number of intervals
646 in the function. It must be a positive integer (greater than 0).
647 The second parameter, which is optional, is
648 either the value ''start'' or ''end'', and specifies the point
649 at which the change of values occur within the interval.
650 If the second parameter is omitted, it is given the value 'end'.
651 </dd>
652 <dt>
653 cubic-bezier(<number>, <number>, <number>, <number>)
654 </dt>
655 <dd>
656 Specifies a <a
657 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve">cubic-bezier
658 curve</a>. The four values specify points P<sub>1</sub> and
659 P<sub>2</sub> of the curve as (x1, y1, x2, y2). Both x values must be
660 in the range [0, 1] or the definition is invalid. The y values can
661 exceed this range.
662 </dd>
663 </dl><!-- ======================================================================================================= -->
664 <h3 id="transition-delay-property"><a id="the-transition-delay-property-">
665 The 'transition-delay' Property
666 </a></h3>
667 <p>
668 The 'transition-delay' 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 'transition-delay' 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.
669 </p>
670 <p>
671 If the value for 'transition-delay' 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 'transition-delay', the starting values are taken from the moment the property is changed.
672 </p>
673 <table class="propdef">
674 <tbody>
675 <tr>
676 <td>
677 <em>Name:</em>
678 </td>
679 <td>
680 <dfn id="transition-delay">transition-delay</dfn>
681 </td>
682 </tr>
683 <tr>
684 <td>
685 <em>Value:</em>
686 </td>
687 <td>
688 <span><time></span> [, <span><time></span>]*
689 </td>
690 </tr>
691 <tr>
692 <td>
693 <em>Initial:</em>
694 </td>
695 <td>
696 0s
697 </td>
698 </tr>
699 <tr>
700 <td>
701 <em>Applies to:</em>
702 </td>
703 <td>
704 all elements, :before and :after pseudo elements
705 </td>
706 </tr>
707 <tr>
708 <td>
709 <em>Inherited:</em>
710 </td>
711 <td>
712 no
713 </td>
714 </tr>
715 <tr>
716 <td>
717 <em>Animatable:</em>
718 </td>
719 <td>
720 no
721 </td>
722 </tr>
723 <tr>
724 <td>
725 <em>Percentages:</em>
726 </td>
727 <td>
728 N/A
729 </td>
730 </tr>
731 <tr>
732 <td>
733 <em>Media:</em>
734 </td>
735 <td>
736 interactive
737 </td>
738 </tr>
739 <tr>
740 <td>
741 <em>Computed value:</em>
742 </td>
743 <td>
744 Same as specified value.
745 </td>
746 </tr>
747 <tr>
748 <td>
749 <em>Canonical order:</em>
750 </td>
751 <td>
752 <abbr title="follows order of property value definition">per grammar</abbr>
753 </td>
754 </tr>
755 </tbody>
756 </table><!-- ======================================================================================================= -->
757 <h3 id="transition-shorthand-property"><a id="the-transition-shorthand-property-">
758 The 'transition' Shorthand Property
759 </a></h3>
760 <p>
761 The 'transition' shorthand property combines the four properties described above into a single property.
762 </p>
763 <table class="propdef">
764 <tbody>
765 <tr>
766 <td>
767 <em>Name:</em>
768 </td>
769 <td>
770 <dfn id="transition">transition</dfn>
771 </td>
772 </tr>
773 <tr>
774 <td>
775 <em>Value:</em>
776 </td>
777 <td>
778 <span><single-transition></span> [ ',' <span><single-transition></span> ]*
779 </td>
780 </tr>
781 <tr>
782 <td>
783 <em>Initial:</em>
784 </td>
785 <td>
786 see individual properties
787 </td>
788 </tr>
789 <tr>
790 <td>
791 <em>Applies to:</em>
792 </td>
793 <td>
794 all elements, :before and :after pseudo elements
795 </td>
796 </tr>
797 <tr>
798 <td>
799 <em>Inherited:</em>
800 </td>
801 <td>
802 no
803 </td>
804 </tr>
805 <tr>
806 <td>
807 <em>Animatable:</em>
808 </td>
809 <td>
810 no
811 </td>
812 </tr>
813 <tr>
814 <td>
815 <em>Percentages:</em>
816 </td>
817 <td>
818 N/A
819 </td>
820 </tr>
821 <tr>
822 <td>
823 <em>Media:</em>
824 </td>
825 <td>
826 interactive
827 </td>
828 </tr>
829 <tr>
830 <td>
831 <em>Computed value:</em>
832 </td>
833 <td>
834 see individual properties
835 </td>
836 </tr>
837 <tr>
838 <td>
839 <em>Canonical order:</em>
840 </td>
841 <td>
842 <abbr title="follows order of property value definition">per grammar</abbr>
843 </td>
844 </tr>
845 </tbody>
846 </table>
848 <div class="prod">
849 <dfn id="single-transition"><single-transition></dfn> = [ none | <span><single-transition-property></span> ] || <span><time></span> || <span><single-transition-timing-function></span> || <span><time></span>
850 </div>
852 <p>
853 Note that order is important within the items in this property:
854 the first value that can be parsed as a time is assigned to the
855 transition-duration,
856 and the second value that can be parsed as a time is assigned to
857 transition-delay.
858 </p>
860 <p>
861 If there is more than one <span><single-transition></span> in the shorthand,
862 and any of the transitions has
863 ''none'' as the <span><single-transition-property></span>,
864 then the declaration is invalid.
865 </p>
867 <h2 id="starting">
868 Starting of transitions
869 </h2>
871 <p>
872 When the computed value of an animatable property changes,
873 implementations must decide what transitions to start based on
874 the values of the 'transition-property', 'transition-duration',
875 'transition-timing-function', and 'transition-delay' properties
876 at the time the animatable property would first have its new
877 computed value.
878 This means that when one of these 'transition-*' properties
879 changes at the same time as
880 a property whose change might transition,
881 it is the <em>new</em> values of the 'transition-*' properties
882 that control the transition.
883 </p>
884 <div class="example" id="manual-reversing-example">
885 <p style="display:none">
886 Example(s):
887 </p>
888 <p>This provides a way for authors to specify different values
889 of the 'transition-*' properties for the “forward”
890 and “reverse” transitions (but see <a
891 href="#reversing">below</a> for special reversing behavior when
892 an <em>incomplete</em> transition is interrupted). Authors can
893 specify the value of 'transition-duration',
894 'transition-timing-function', or 'transition-delay' in the same
895 rule where they specify the value that triggers the transition,
896 or can change these properties at the same time as they change
897 the property that triggers the transition. Since it's the new
898 values of these 'transition-*' properties that affect the
899 transition, these values will be used for the transitions
900 <em>to</em> the associated transitioning values. For example:
901 </p>
902 <pre>li {
903 transition: background-color linear 1s;
904 background: blue;
905 }
906 li:hover {
907 background-color: green;
908 transition-duration: 2s; /* applies to the transition *to* the :hover state */
909 }</pre>
910 <p>
911 When a list item with these style rules enters the :hover
912 state, the computed 'transition-duration' at the time that
913 'background-color' would have its new value (''green'') is ''2s'',
914 so the transition from ''blue'' to ''green'' takes 2 seconds.
915 However, when the list item leaves the :hover state, the
916 transition from ''green'' to ''blue'' takes 1 second.
917 </p>
918 </div>
920 <p>
921 Various things can cause the computed style of an element to change,
922 or for an element to start or stop having computed style.
923 (For the purposes of this specification,
924 an element has computed style when it is in the document tree,
925 and does not have computed style when it is not in the document tree.)
926 These include
927 insertion and removal of elements from the document tree
928 (which both changes whether those elements have computed styles and
929 can change the styles of other elements through selector matching),
930 changes to the document tree that cause
931 changes to which selectors match elements,
932 changes to style sheets or style attributes,
933 and other things.
934 This specification does not define when computed styles are updated.
935 However,
936 when an implementation updates the computed style for an element
937 to reflect one of these changes,
938 it must update the computed style for all elements to reflect all
939 of these changes at the same time
940 (or at least it must be undetectable that it was done at a
941 different time).
942 This processing of a set of simultaneous style changes is called a
943 <dfn>style change event</dfn>.
944 (Implementations typically have a <span>style change event</span> to
945 correspond with their desired screen refresh rate,
946 and when up-to-date computed style is needed
947 for a script API that depends on it.)
948 </p>
950 <p>
951 Since this specification does not define
952 when a <span>style change event</span> occurs,
953 and thus what changes to computed values are considered simultaneous,
954 authors should be aware that changing any of the transition
955 properties a small amount of time after making a change that
956 might transition can result in behavior that varies between
957 implementations, since the changes might be considered
958 simultaneous in some implementations but not others.
959 </p>
961 <p>
962 When a <span>style change event</span> occurs,
963 implementations must start transitions based on
964 the computed styles that changed in that event.
965 If an element does not have a computed style
966 either before or after the style change event,
967 then transitions are not started for that element
968 in that style change event.
969 Otherwise,
970 define the <dfn>before-change style</dfn> as
971 the computed style for the element as of
972 the previous <span>style change event</span>,
973 except with any styles derived from declarative
974 animations such as CSS Transitions, CSS Animations
975 ([[CSS3-ANIMATIONS]]),
976 and SMIL Animations ([[SMIL-ANIMATION]], [[SVG11]])
977 updated to the current time.
978 Likewise, define the <dfn>after-change style</dfn> as
979 the computed style for the element based on the information
980 known at the start of that <span>style change event</span>,
981 in other words,
982 excluding any changes resulting from CSS Transitions
983 that start during that <span>style change event</span>.
984 </p>
986 <p class="issue">
987 This wording needs to handle already-running transitions better!
988 Need to cancel a transition that hasn't moved yet when we're
989 resetting to its start value! Define cancelling as not
990 firing transition events. And point to other occurrence of
991 cancelling in reversing section.
992 </p>
994 <div class="note">
995 <p>
996 Note that this definition of the <span>after-change style</span>
997 means that a single change
998 can start a transition on the same property
999 on both an ancestor element and its descendant element.
1000 This can happen when a property change is inherited
1001 from one element with 'transition-*' properties
1002 that say to animate the changing property
1003 to another element with 'transition-*' properties
1004 that also say to animate the changing property.
1005 </p>
1007 <p>
1008 When this happens, both transitions will run,
1009 and the transition on the descendant will override
1010 the transition on the ancestor
1011 because of the normal
1012 CSS cascading and inheritance rules ([[CSS3CASCADE]]).
1013 </p>
1015 <p>
1016 If the transition on the descendant completes before
1017 the transition on the ancestor,
1018 the descendant will then resume inheriting
1019 the (still transitioning) value from its parent.
1020 This effect is likely not a desirable effect,
1021 but it is essentially doing what the author asked for.
1022 </p>
1023 </div>
1025 <p>
1026 For each element with a <span>before-change style</span> and
1027 an <span>after-change style</span>,
1028 and each property (other than shorthands) for which
1029 the <span>before-change style</span> is different from
1030 the <span>after-change style</span>,
1031 implementations must
1032 start transitions based on the relevant item (see <a
1033 href="#transition-property">the definition of
1034 'transition-property'</a>) in the computed value of
1035 'transition-property'.
1036 Corresponding to this item there is
1037 a <span>matching transition duration</span>,
1038 a <span>matching transition delay</span>, and
1039 a <span>matching transition timing function</span>
1040 in the computed values of
1041 'transition-duration', 'transition-delay', and 'transition-timing-function'
1042 (see <a href="#list-matching">the rules on matching lists</a>).
1043 Define the <dfn>combined duration</dfn> of the transition
1044 as the sum of max(matching transition duration, ''0s'') and
1045 the matching transition-delay.
1046 When the combined duration is greater than ''0s'',
1047 then a transition starts based on the values of the
1048 matching transition duration, the matching transition delay,
1049 and the matching transition-timing-function;
1050 in other cases transitions do not occur.
1051 The <dfn>start time</dfn> of this transition is defined as
1052 the time of the <span>style change event</span> plus
1053 the matching transition delay.
1054 The <dfn>end time</dfn> of this transition is defined as
1055 the <span>start time</span> plus the matching transition duration.
1056 The <dfn>start value</dfn> of this transition is defined as
1057 the value of the transitioning property
1058 in the <span>before-change style</span>,
1059 and the <dfn>end value</dfn> of this transition is defined as
1060 the value of the transitioning property
1061 in the <span>after-change style</span>.
1062 Except in the cases described
1063 in the <a href="#reversing">section on reversing of
1064 transitions</a>,
1065 the <dfn>reversing-adjusted start value</dfn> is the same as
1066 the <span>start value</span>,
1067 and the <dfn>reversing shortening factor</dfn> is 1.
1068 </p>
1070 <p>
1071 Once the transition of a property has started, it must continue
1072 running based on the original timing function, duration, and
1073 delay, even if the 'transition-timing-function',
1074 'transition-duration', or 'transition-delay' property changes
1075 before the transition is complete. However, if the
1076 'transition-property' property changes such that the transition
1077 would not have started, the transition must stop (and the
1078 property must immediately change to its final value).
1079 </p>
1081 <p>
1082 Implementations must not start a transition when the computed
1083 value of a property changes as a result of declarative animation
1084 (as opposed to scripted animation).
1085 </p>
1087 <p>
1088 Implementations also must not start a transition when the
1089 computed value changes because it is inherited (directly or
1090 indirectly) from another element that is transitioning the same
1091 property.
1092 </p>
1094 <h3 id="reversing">
1095 Faster reversing of interrupted transitions
1096 </h3>
1097 <p>
1098 Many common transitions effects involve transitions between two states,
1099 such as the transition that occurs when the mouse pointer moves
1100 over a user interface element, and then later moves out of that element.
1101 With these effects, it is common for a running transition
1102 to be interrupted before it completes,
1103 and the property reset to the starting value of that transition.
1104 An example is a hover effect on an element,
1105 where a transition starts when the pointer enters the element,
1106 and then the pointer exits the element before the effect has completed.
1107 If the outgoing and incoming transitions
1108 are executed using their specified durations and timing functions,
1109 the resulting effect can be distractingly asymmetric
1110 because the second transition
1111 takes the full specified time to move a shortened distance.
1112 Instead, the expected behavior is that the second transition is shorter.
1113 </p>
1115 <p>
1116 To meet this expectation,
1117 when a transition is started for a property on an element
1118 (henceforth, the <dfn>new transition</dfn>)
1119 that has a currently-running transition whose
1120 <span>reversing-adjusted start value</span> is the same as the
1121 <span>end value</span> of the new transition
1122 (henceforth, the <dfn>old transition</dfn>), implementations
1123 must cancel the old transition <span class="issue">link to
1124 definition above</span> and adjust the new transition as follows
1125 (prior to following the rules for computing the <span>combined
1126 duration</span>, <span>start time</span>, and <span>end
1127 time</span>):
1128 </p>
1130 <ol>
1132 <li>
1133 The <span>reversing-adjusted start value</span> of the new
1134 transition is instead the the <span>end value</span> of the
1135 old transition.
1136 <span class="note">Note: This represents the logical start state of
1137 the transition, and allows some calculations to ignore that
1138 the transition started before that state was reached, which
1139 in turn allows repeated reversals of the same transition to
1140 work correctly.</span>
1141 </li>
1143 <li>
1144 The <span>reversing shortening factor</span> of the new
1145 transition is the absolute value, clamped to the range [0, 1],
1146 of the sum of:
1147 <ol>
1148 <li>the output of the timing function of the old transition
1149 at the time of the <span>style change event</span>,
1150 times the <span>reversing shortening factor</span> of the
1151 old transition</li>
1152 <li>1 minus the <span>reversing shortening factor</span> of
1153 the old transition.</li>
1154 </ol>
1155 <span class="note">Note: This represents the portion of the
1156 space between the <span>reversing-adjusted start value</span>
1157 and the <span>end value</span> that the old transition has
1158 traversed (in amounts of the value, not time), except with the
1159 absolute value and clamping to handle timing functions that
1160 have y1 or y2 outside the range [0, 1].</span>
1161 </li>
1163 <li>
1164 The matching transition-duration for the new transition is
1165 multiplied by the
1166 <span>reversing shortening factor</span>.
1167 </li>
1169 <li>
1170 If the matching transition-delay for the new transition is
1171 negative, it is also multiplied by the
1172 <span>reversing shortening factor</span>.
1173 </li>
1175 </ol>
1177 <p class="note">
1178 Note that these rules do not fully address the problem for
1179 transition patterns that involve more than two states.
1180 </p>
1182 <p class="note">
1183 Note that these rules lead to the entire timing function of the
1184 new transition being used, rather than jumping into the middle
1185 of a timing function, which can create a jarring effect.
1186 </p>
1188 <p class="note">
1189 This was one of several possibilities that was considered by the
1190 working group. See the
1191 <a href="transition-reversing-demo">reversing demo</a>
1192 demonstrating a number of them, leading to a working group
1193 resolution made on 2013-06-07 and edits made on 2013-11-11.
1194 </p>
1196 <h2 id="application">
1197 Application of transitions
1198 </h2>
1200 <p>
1201 When a property on an element is undergoing a transition
1202 (that is, when or after the transition has started and before the
1203 <span>end time</span> of the transition)
1204 the transition adds a style to the CSS cascade
1205 at the level defined for CSS Transitions in [[CSS3CASCADE]].
1206 </p>
1208 <p class="note">
1209 Note that this means that computed values
1210 resulting from CSS transitions
1211 can inherit to descendants just like
1212 any other computed values.
1213 In the normal case, this means that
1214 a transition of an inherited property
1215 applies to descendant elements
1216 just as an author would expect.
1217 </p>
1219 <p>
1220 Implementations must add this value to the cascade
1221 if and only if
1222 that property is not currently
1223 undergoing a CSS Animation ([[CSS3-ANIMATIONS]]) on the same element.
1224 </p>
1226 <p class="note">
1227 Note that this behavior of transitions not applying to the cascade
1228 when an animation on the same element and property is running
1229 does not affect whether the transition has started or ended.
1230 APIs that detect whether transitions are running
1231 (such as <a href="#transition-events">transition events</a>)
1232 still report that a transition is running.
1233 </p>
1235 <p>
1236 If the current time is at or before the
1237 <span>start time</span> of the transition
1238 (that is, during the delay phase of the transition),
1239 this value is a specified style that will compute
1240 to the <span>start value</span> of the transition.
1241 </p>
1243 <p>
1244 If the current time is after the
1245 <span>start time</span> of the transition
1246 (that is, during the duration phase of the transition),
1247 this value is a specified style that will compute
1248 to the <a href="#animatable-types">result of interpolating the property</a>
1249 using the <span>start value</span> of the transition as
1250 <var>V</var><sub>start</sub>,
1251 using the <span>end value</span> of the transition as
1252 <var>V</var><sub>end</sub>,
1253 and using (current time - start time) / (end time - start time)
1254 as the input to the timing function.
1255 </p>
1257 <h2 id="transition-events"><a id="transition-events-">
1258 Transition Events
1259 </a></h2>
1260 <p>
1261 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>.
1262 An event is fired for each property that undergoes a transition.
1263 This allows a content developer to perform actions that synchronize
1264 with the completion of a transition.
1265 </p>
1266 <p>
1267 Each event provides the name of the property the transition is
1268 associated with as well as the duration of the transition.
1269 </p>
1270 <dl>
1271 <dt>
1272 <b>Interface <dfn id="Events-TransitionEvent">TransitionEvent</dfn></b>
1273 </dt>
1274 <dd>
1275 <p>
1276 The <code>TransitionEvent</code> interface provides specific contextual information associated with transitions.
1277 </p>
1278 <dl>
1279 <dt>
1280 <b>IDL Definition</b>
1281 </dt>
1282 <dd>
1283 <div class='idl-code'>
1284 <pre>
1285 <span id="TransitionEvent">[Constructor(DOMString <var title="">type</var>, optional <i>TransitionEventInit</i> <var title="">transitionEventInitDict</var>)]
1286 interface TransitionEvent</span> : Event {
1287 readonly attribute DOMString <a href="#Events-TransitionEvent-propertyName">propertyName</a>;
1288 readonly attribute float <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a>;
1289 readonly attribute DOMString <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a>;
1290 };
1292 dictionary <dfn id="TransitionEventInit">TransitionEventInit</dfn> : <a class="external" href="https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#eventinit">EventInit</a> {
1293 DOMString <a href="#Events-TransitionEvent-propertyName">propertyName</a> = "";
1294 float <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a> = 0.0;
1295 DOMString <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a> = "";
1296 }
1297 </pre>
1298 </div>
1299 </dd>
1300 <dt>
1301 <b>Attributes</b>
1302 </dt>
1303 <dd>
1304 <dl>
1305 <dt>
1306 <code class='attribute-name'><dfn title="TransitionEvent::propertyName" id="Events-TransitionEvent-propertyName">propertyName</dfn></code> of type <code>DOMString</code>, readonly
1307 </dt>
1308 <dd>
1309 The name of the CSS property associated with the transition.
1310 </dd>
1311 </dl>
1312 <dl>
1313 <dt>
1314 <code class='attribute-name'><dfn title="TransitionEvent::elapsedTime" id="Events-TransitionEvent-elapsedTime">elapsedTime</dfn></code> of type <code>float</code>, readonly
1315 </dt>
1316 <dd>
1317 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>.
1318 </dd>
1319 </dl>
1320 <dl>
1321 <dt>
1322 <code class='attribute-name'><dfn title="TransitionEvent::pseudoElement" id="Events-TransitionEvent-pseudoElement">pseudoElement</dfn></code> of type <code>DOMString</code>, readonly
1323 </dt>
1324 <dd>
1325 The name (beginning with two colons) of the CSS
1326 pseudo-element on which the transition occured (in
1327 which case the target of the event is that
1328 pseudo-element's corresponding element), or the empty
1329 string if the transition occurred on an element (which
1330 means the target of the event is that element).
1331 </dd>
1332 </dl>
1333 </dd>
1334 </dl>
1335 <p>
1336 <code id="TransitionEvent-constructor">TransitionEvent(type, transitionEventInitDict)</code>
1337 is an <a class="external" href="https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#constructing-events">event constructor</a>.
1338 </p>
1339 </dd>
1340 </dl>
1341 <p>
1342 There is one type of transition event available.
1343 </p>
1344 <dl>
1345 <dt>
1346 <b><dfn>transitionend</dfn></b>
1347 </dt>
1348 <dd>
1349 The <code>transitionend</code> event occurs at the completion of the transition. In the
1350 case where a transition is removed before completion, such as if the
1351 transition-property is removed, then the event will not fire.
1352 <ul>
1353 <li>Bubbles: Yes
1354 </li>
1355 <li>Cancelable: Yes
1356 </li>
1357 <li>Context Info: propertyName, elapsedTime, pseudoElement
1358 </li>
1359 </ul>
1360 </dd>
1361 </dl>
1363 <h2 id="animatable-types"><a id="animation-of-property-types-">
1364 Animation of property types
1365 </a></h2>
1367 <p>
1368 When interpolating between two values,
1369 <var>V</var><sub>start</sub> and <var>V</var><sub>end</sub>,
1370 interpolation is done using the output <var>p</var> of the timing function,
1371 which gives the portion of the value space
1372 that the interpolation has crossed.
1373 Thus the result of the interpolation is
1374 <var>V</var><sub>res</sub> =
1375 (1 - <var>p</var>) ⋅ <var>V</var><sub>start</sub> +
1376 <var>p</var> ⋅ <var>V</var><sub>end</sub>.
1377 </p>
1379 <p>
1380 However, if this value (<var>V</var><sub>res</sub>)
1381 is outside the allowed range of values for the property,
1382 then it is clamped to that range.
1383 This can occur if <var>p</var> is outside of the range 0 to 1,
1384 which can occur if a timing function is specified
1385 with a <var>y1</var> or <var>y2</var> that is outside the range 0 to 1.
1386 </p>
1388 <p>
1389 The following describes how each property type undergoes transition or
1390 animation.
1391 </p>
1393 <ul>
1394 <li id="animtype-color">
1395 <strong>color</strong>: interpolated via red, green, blue and alpha
1396 components (treating each as a number, see below).
1397 The interpolation is done between premultiplied colors
1398 (that is, colors for which the red, green, and blue components
1399 specified have been multiplied by the alpha).
1400 </li>
1401 <li id="animtype-length">
1402 <strong>length</strong>: interpolated as real numbers.
1403 </li>
1404 <li id="animtype-percentage">
1405 <strong>percentage</strong>: interpolated as real numbers.
1406 </li>
1407 <li id="animtype-lpcalc">
1408 <strong>length, percentage, or calc</strong>: when both values
1409 are lengths, interpolated as lengths; when both values are
1410 percentages, interpolated as percentages; otherwise, both
1411 values are converted into a ''calc()'' function that is the
1412 sum of a length and a percentage (each possibly zero), and
1413 these ''calc()'' functions have each half interpolated as real
1414 numbers.
1415 </li>
1416 <li id="animtype-integer">
1417 <strong>integer</strong>: interpolated via discrete steps (whole
1418 numbers). The interpolation happens in real number space and is
1419 converted to an integer by rounding to the nearest integer, with
1420 values halfway between a pair of integers rounded towards
1421 positive infinity.
1422 </li>
1423 <li id="animtype-font-weight">
1424 <strong>font weight</strong>: interpolated via discrete steps
1425 (multiples of 100). The interpolation happens in real number
1426 space and is converted to an integer by rounding to the
1427 nearest multiple of 100, with values halfway between multiples
1428 of 100 rounded towards positive infinity.
1429 </li>
1430 <li id="animtype-number">
1431 <strong>number</strong>: interpolated as real (floating point)
1432 numbers.
1433 </li>
1434 <li id="animtype-rect">
1435 <strong>rectangle</strong>: interpolated via the x, y,
1436 width and height components (treating each as a number).
1437 </li>
1438 <li id="animtype-visibility">
1439 <strong>visibility</strong>: if one of the values is
1440 ''visible'', interpolated as a discrete step where values of the
1441 timing function between 0 and 1 map to ''visible'' and other
1442 values of the timing function (which occur only at the
1443 start/end of the transition or as a result of ''cubic-bezier()''
1444 functions with Y values outside of [0, 1]) map to the closer
1445 endpoint; if neither value is ''visible'' then not interpolable.
1446 </li>
1447 <li id="animtype-shadow-list">
1448 <strong>shadow list</strong>: Each shadow in the list is
1449 interpolated via the
1450 color (as <a href="#animtype-color">color</a>) component,
1451 and x, y, blur, and (when appropriate) spread
1452 (as <a href="#animtype-length">length</a>) components.
1453 For each shadow, if one input shadow is ''inset'' and the other
1454 is not, then the result for that shadow matches the inputs;
1455 otherwise the entire list is not interpolable.
1456 If the lists of shadows have different lengths,
1457 then the shorter list is padded at the end
1458 with shadows whose color is ''transparent'',
1459 all lengths are ''0'',
1460 and whose ''inset'' (or not) matches the longer list.
1461 </li>
1462 <li id="animtype-gradient">
1463 <strong>gradient</strong>: interpolated via the
1464 positions and colors of each stop. They must have the same type
1465 (radial or linear) and same number of stops in order to be animated.
1466 <span class="note">Note: [[CSS3-IMAGES]] may extend this
1467 definition.</span>
1468 </li>
1469 <li id="animtype-paintserver">
1470 <strong>paint server</strong> (SVG): interpolation is only supported
1471 between: gradient to gradient and color to color. They then
1472 work as above.
1473 </li>
1474 <li id="animtype-simple-list">
1475 <strong>simple list</strong> of other types:
1476 If the lists have the same number of items,
1477 and each pair of values can be interpolated,
1478 each item in the list is interpolated using
1479 the rules given for those types.
1480 Otherwise the values are not interpolable.
1481 </li>
1482 <li id="animtype-repeatable-list">
1483 <strong>repeatable list</strong> of other types:
1484 The result list has a length that is the least common multiple
1485 of the lengths of the input lists.
1486 Each item in the result is the interpolation of the value
1487 from each input list repeated to the length of the result list.
1488 If a pair of values cannot be interpolated, then the lists
1489 are not interpolable.
1490 <span class="note">
1491 The repeatable list concept ensures that a list that is
1492 conceptually repeated to a certain length (as
1493 'background-origin' is repeated to the length of the
1494 'background-image' list) or repeated infinitely will
1495 smoothly transition between any values, and so that the
1496 computed value will properly represent the result (and
1497 potentially be inherited correctly).
1498 </span>
1499 </li>
1500 </ul>
1502 <p>Future specifications may define additional types that can
1503 be animated.</p>
1505 <p>See the definition of 'transition-property' for how animation
1506 of shorthand properties and the ''all'' value is applied to any
1507 properties (in the shorthand) that can be animated.</p>
1509 <h2 id="animatable-properties"><a id="animatable-properties-">
1510 Animatable properties
1511 </a></h2>
1513 <!--
1514 As resolved in
1515 http://lists.w3.org/Archives/Public/www-style/2011Sep/0497.html
1516 -->
1518 <p>The definition of each CSS property defines
1519 when the values of that property can be interpolated
1520 by referring to the definitions of property types
1521 in the <a href="#animatable-types">previous section</a>.
1522 Values are animatable when
1523 both the from and the to values of the property have the type described.
1524 (When a composite type such as "length, percentage, or calc" is listed,
1525 this means that both values must fit into that composite type.)
1526 When multiple types are listed in the form "either A or B",
1527 both values must be of the same type to be interpolable.</p>
1529 <p>For properties that exist at the time this specification was
1530 developed, this specification defines whether and how they are
1531 animated. However, future CSS specifications may define
1532 additional properties, additional values for existing properties,
1533 or additional animation behavior of existing values. In order to
1534 describe new animation behaviors and to have the definition of
1535 animation behavior in a more appropriate location, future CSS
1536 specifications should include an "Animatable:" line in the summary
1537 of the property's definition (in addition to the other lines
1538 described in [[CSS21]], <a
1539 href="http://www.w3.org/TR/CSS21/about.html#property-defs">section
1540 1.4.2</a>). This line should say "no" to indicate that a property
1541 cannot be animated or should reference an animation behavior
1542 (which may be one of the behaviors in the <a
1543 href="#animation-of-property-types-">Animation of property
1544 types</a> section above, or may be a new behavior) to define how
1545 the property animates. Such definitions override those given in
1546 this specification.</p>
1548 <h3 id="animatable-css"><a id="properties-from-css-">
1549 Properties from CSS
1550 </a></h3>
1552 <p>
1553 The following definitions define the animation behavior for
1554 properties in CSS Level 2 Revision 1 ([[CSS21]]) and in Level 3 of
1555 the CSS Color Module ([[CSS3COLOR]]).
1556 </p>
1558 <table class="animatable-properties">
1559 <tr>
1560 <th>Property Name</th>
1561 <th>Type</th>
1562 </tr>
1563 <tr>
1564 <td>background-color</td><td>as <a href="#animtype-color">color</a></tr>
1565 <tr>
1566 <td>background-position</td><td>as <a href="#animtype-repeatable-list">repeatable list</a> of <a href="#animtype-simple-list">simple list</a> of <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1567 </tr>
1568 <tr>
1569 <td>border-bottom-color</td><td>as <a href="#animtype-color">color</a></td>
1570 </tr>
1571 <tr>
1572 <td>border-bottom-width</td><td>as <a href="#animtype-length">length</a></td>
1573 </tr>
1574 <tr>
1575 <td>border-left-color</td><td>as <a href="#animtype-color">color</a></td>
1576 </tr>
1577 <tr>
1578 <td>border-left-width</td><td>as <a href="#animtype-length">length</a></td>
1579 </tr>
1580 <tr>
1581 <td>border-right-color</td><td>as <a href="#animtype-color">color</a></td>
1582 </tr>
1583 <tr>
1584 <td>border-right-width</td><td>as <a href="#animtype-length">length</a></td>
1585 </tr>
1586 <tr>
1587 <td>border-spacing</td><td>as <a href="#animtype-simple-list">simple list</a> of <a href="#animtype-length">length</a></td>
1588 </tr>
1589 <tr>
1590 <td>border-top-color</td><td>as <a href="#animtype-color">color</a></td>
1591 </tr>
1592 <tr>
1593 <td>border-top-width</td><td>as <a href="#animtype-length">length</a></td>
1594 </tr>
1595 <tr>
1596 <td>bottom</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1597 </tr>
1598 <tr>
1599 <td>clip</td><td>as <a href="#animtype-rect">rectangle</a></td>
1600 </tr>
1601 <tr>
1602 <td>color</td><td>as <a href="#animtype-color">color</a></td>
1603 </tr>
1604 <tr>
1605 <td>font-size</td><td>as <a href="#animtype-length">length</a></td>
1606 </tr>
1607 <tr>
1608 <td>font-weight</td><td>as <a href="#animtype-font-weight">font weight</a></td>
1609 </tr>
1610 <tr>
1611 <td>height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1612 </tr>
1613 <tr>
1614 <td>left</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1615 </tr>
1616 <tr>
1617 <td>letter-spacing</td><td>as <a href="#animtype-length">length</a></td>
1618 </tr>
1619 <tr>
1620 <td>line-height</td><td>as either <a href="#animtype-number">number</a> or <a href="#animtype-length">length</a></td>
1621 </tr>
1622 <tr>
1623 <td>margin-bottom</td><td>as <a href="#animtype-length">length</a></td>
1624 </tr>
1625 <tr>
1626 <td>margin-left</td><td>as <a href="#animtype-length">length</a></td>
1627 </tr>
1628 <tr>
1629 <td>margin-right</td><td>as <a href="#animtype-length">length</a></td>
1630 </tr>
1631 <tr>
1632 <td>margin-top</td><td>as <a href="#animtype-length">length</a></td>
1633 </tr>
1634 <tr>
1635 <td>max-height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1636 </tr>
1637 <tr>
1638 <td>max-width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1639 </tr>
1640 <tr>
1641 <td>min-height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1642 </tr>
1643 <tr>
1644 <td>min-width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1645 </tr>
1646 <tr>
1647 <td>opacity</td><td>as <a href="#animtype-number">number</a></td>
1648 </tr>
1649 <tr>
1650 <td>outline-color</td><td>as <a href="#animtype-color">color</a></td>
1651 </tr>
1652 <tr>
1653 <td>outline-width</td><td>as <a href="#animtype-length">length</a></td>
1654 </tr>
1655 <tr>
1656 <td>padding-bottom</td><td>as <a href="#animtype-length">length</a></td>
1657 </tr>
1658 <tr>
1659 <td>padding-left</td><td>as <a href="#animtype-length">length</a></td>
1660 </tr>
1661 <tr>
1662 <td>padding-right</td><td>as <a href="#animtype-length">length</a></td>
1663 </tr>
1664 <tr>
1665 <td>padding-top</td><td>as <a href="#animtype-length">length</a></td>
1666 </tr>
1667 <tr>
1668 <td>right</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1669 </tr>
1670 <tr>
1671 <td>text-indent</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1672 </tr>
1673 <tr>
1674 <td>text-shadow</td><td>as <a href="#animtype-shadow-list">shadow list</a></td>
1675 </tr>
1676 <tr>
1677 <td>top</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1678 </tr>
1679 <tr>
1680 <td>vertical-align</td><td>as <a href="#animtype-length">length</a></td>
1681 </tr>
1682 <tr>
1683 <td>visibility</td><td>as <a href="#animtype-visibility">visibility</a></td>
1684 </tr>
1685 <tr>
1686 <td>width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1687 </tr>
1688 <tr>
1689 <td>word-spacing</td><td>as <a href="#animtype-length">length</a></td>
1690 </tr>
1691 <tr>
1692 <td>z-index</td><td>as <a href="#animtype-integer">integer</a></td>
1693 </tr>
1694 </table>
1696 <h3 id="animatable-svg"><a id="properties-from-svg-">
1697 Properties from SVG
1698 </a></h3>
1700 <p>
1701 All properties defined as animatable in the SVG specification, provided
1702 they are one of the property types listed above.
1703 </p>
1705 <!-- <table>
1706 <tr>
1707 <th>Property Name</th><th>Type</th>
1708 </tr>
1709 <tr>
1710 <td>stop-color</td><td>as <a href="#animtype-color">color</a></td>
1711 </tr>
1712 <tr>
1713 <td>stop-opacity</td><td>as <a href="#animtype-number">number</a></td>
1714 </tr>
1715 <tr>
1716 <td>fill</td><td>as <a href="#animtype-paintserver">paint server</a></td>
1717 </tr>
1718 <tr>
1719 <td>fill-opacity</td><td>as <a href="#animtype-number">number</a></td>
1720 </tr>
1721 <tr>
1722 <td>stroke</td><td>as <a href="#animtype-paintserver">paint server</a></td>
1723 </tr>
1724 <tr>
1725 <td>stroke-dasharray</td><td>as <a href="#animtype-repeatable-list">repeatable list</a> of <a href="#animtype-number">number</a></td>
1726 </tr>
1727 <tr>
1728 <td>stroke-dashoffset</td><td>as <a href="#animtype-number">number</a></td>
1729 </tr>
1730 <tr>
1731 <td>stroke-miterlimit</td><td>as <a href="#animtype-number">number</a></td>
1732 </tr>
1733 <tr>
1734 <td>stroke-opacity</td><td>as <a href="#animtype-number">number</a></td>
1735 </tr>
1736 <tr>
1737 <td>stroke-width</td><td>as <a href="#animtype-number">number</a></td>
1738 </tr>
1739 <tr>
1740 <td>viewport-fill</td><td>as <a href="#animtype-color">color</a></td>
1741 </tr>
1742 <tr>
1743 <td>viewport-fill-opacity</td><td>as <a href="#animtype-color">color</a></td>
1744 </tr>
1745 </table> -->
1747 <h2 id="changes">Changes since Working Draft of 19 November 2013</h2>
1749 <p>The following are the substantive changes made since the
1750 <a href="http://www.w3.org/TR/2013/WD-css3-transitions-20131119/">Working Draft
1751 dated 19 November 2013</a>:</p>
1753 <ul>
1754 <li class="issue">... ADD CHANGES HERE ...
1755 </ul>
1757 <p>For more details on these changes, see the version control <a href="https://dvcs.w3.org/hg/csswg/log/tip/css-transitions/Overview.src.html">change log</a>.</p>
1759 <p>For changes in earlier working drafts:</p>
1761 <ol>
1762 <li>see the <a href="http://www.w3.org/TR/2013/WD-css3-transitions-20131119/#changes">changes section in the 19 November 2013 Working Draft</a>
1763 <li>see the <a href="http://www.w3.org/TR/2013/WD-css3-transitions-20130212/ChangeLog">the ChangeLog</a> for changes in previous working drafts
1764 <li>For more details on these changes, see the version control change logs, which are split in two parts because of a file renaming: <a href="https://dvcs.w3.org/hg/csswg/log/tip/css-transitions/Overview.src.html">change log since 2013 March 28</a>, <a href="https://dvcs.w3.org/hg/csswg/log/tip/css3-transitions/Overview.src.html">change log before 2013 March 28</a>.
1765 </ol>
1767 <h2 id="acknowledgments">Acknowledgments</h2>
1769 <p>Thanks especially to the feedback from
1770 Tab Atkins,
1771 Carine Bournez,
1772 Aryeh Gregor,
1773 Vincent Hardy,
1774 Anne van Kesteren,
1775 Cameron McCormack,
1776 Alex Mogilevsky,
1777 and all the rest of the
1778 <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.</p>
1780 <h2 id="references">References</h2>
1782 <h3 class="no-num" id="normative-references">Normative references</h3>
1783 <!--normative-->
1785 <h3 class="no-num" id="other-references">Other references</h3>
1786 <!--informative-->
1790 <h2 class="no-num" id="property-index">Property index</h2>
1791 <!-- properties -->
1795 <h2 class="no-num" id="index">Index</h2>
1796 <!--index-->
1798 </body>
1799 </html>
1800 <!-- Keep this comment at the end of the file
1801 Local variables:
1802 mode: sgml
1803 sgml-default-doctype-name:"html"
1804 sgml-minimize-attributes:t
1805 End:
1806 -->
