Wed, 23 Apr 2014 18:02:06 +0900
[css-text] issues-lc-2013 updated up to 68
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5 <head>
6 <title>CSS Transitions</title>
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14 table.animatable-properties td {
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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> [ ',' <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> [, <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> [ ',' <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> [, <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> [ ',' <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 When the computed value of an animatable property changes,
875 implementations must decide what transitions to start based on
876 the values of the 'transition-property', 'transition-duration',
877 'transition-timing-function', and 'transition-delay' properties
878 at the time the animatable property would first have its new
879 computed value.
880 This means that when one of these 'transition-*' properties
881 changes at the same time as
882 a property whose change might transition,
883 it is the <em>new</em> values of the 'transition-*' properties
884 that control the transition.
885 </p>
886 <div class="example" id="manual-reversing-example">
887 <p style="display:none">
888 Example(s):
889 </p>
890 <p>This provides a way for authors to specify different values
891 of the 'transition-*' properties for the “forward”
892 and “reverse” transitions (but see <a
893 href="#reversing">below</a> for special reversing behavior when
894 an <em>incomplete</em> transition is interrupted). Authors can
895 specify the value of 'transition-duration',
896 'transition-timing-function', or 'transition-delay' in the same
897 rule where they specify the value that triggers the transition,
898 or can change these properties at the same time as they change
899 the property that triggers the transition. Since it's the new
900 values of these 'transition-*' properties that affect the
901 transition, these values will be used for the transitions
902 <em>to</em> the associated transitioning values. For example:
903 </p>
904 <pre>li {
905 transition: background-color linear 1s;
906 background: blue;
907 }
908 li:hover {
909 background-color: green;
910 transition-duration: 2s; /* applies to the transition *to* the :hover state */
911 }</pre>
912 <p>
913 When a list item with these style rules enters the :hover
914 state, the computed 'transition-duration' at the time that
915 'background-color' would have its new value (''green'') is ''2s'',
916 so the transition from ''blue'' to ''green'' takes 2 seconds.
917 However, when the list item leaves the :hover state, the
918 transition from ''green'' to ''blue'' takes 1 second.
919 </p>
920 </div>
922 <p>
923 Various things can cause the computed style of an element to change,
924 or for an element to start or stop having computed style.
925 (For the purposes of this specification,
926 an element has computed style when it is in the document tree,
927 and does not have computed style when it is not in the document tree.)
928 These include
929 insertion and removal of elements from the document tree
930 (which both changes whether those elements have computed styles and
931 can change the styles of other elements through selector matching),
932 changes to the document tree that cause
933 changes to which selectors match elements,
934 changes to style sheets or style attributes,
935 and other things.
936 This specification does not define when computed styles are updated.
937 However,
938 when an implementation updates the computed style for an element
939 to reflect one of these changes,
940 it must update the computed style for all elements to reflect all
941 of these changes at the same time
942 (or at least it must be undetectable that it was done at a
943 different time).
944 This processing of a set of simultaneous style changes is called a
945 <dfn>style change event</dfn>.
946 (Implementations typically have a <span>style change event</span> to
947 correspond with their desired screen refresh rate,
948 and when up-to-date computed style is needed
949 for a script API that depends on it.)
950 </p>
952 <p>
953 Since this specification does not define
954 when a <span>style change event</span> occurs,
955 and thus what changes to computed values are considered simultaneous,
956 authors should be aware that changing any of the transition
957 properties a small amount of time after making a change that
958 might transition can result in behavior that varies between
959 implementations, since the changes might be considered
960 simultaneous in some implementations but not others.
961 </p>
963 <p>
964 When a <span>style change event</span> occurs,
965 implementations must start transitions based on
966 the computed styles that changed in that event.
967 If an element does not have a computed style
968 either before or after the style change event,
969 then transitions are not started for that element
970 in that style change event.
971 Otherwise,
972 define the <dfn>before-change style</dfn> as
973 the computed style for the element as of
974 the previous <span>style change event</span>,
975 except with any styles derived from declarative
976 animations such as CSS Transitions, CSS Animations
977 ([[CSS3-ANIMATIONS]]),
978 and SMIL Animations ([[SMIL-ANIMATION]], [[SVG11]])
979 updated to the current time.
980 Likewise, define the <dfn>after-change style</dfn> as
981 the computed style for the element based on the information
982 known at the start of that <span>style change event</span>,
983 in other words,
984 excluding any changes resulting from CSS Transitions
985 that start during that <span>style change event</span>.
986 </p>
988 <p class="issue">
989 This wording needs to handle already-running transitions better!
990 Need to cancel a transition that hasn't moved yet when we're
991 resetting to its start value! Define canceling as not
992 firing transition events. And point to other occurrence of
993 canceling in reversing section.
994 </p>
996 <div class="note">
997 <p>
998 Note that this definition of the <span>after-change style</span>
999 means that a single change
1000 can start a transition on the same property
1001 on both an ancestor element and its descendant element.
1002 This can happen when a property change is inherited
1003 from one element with 'transition-*' properties
1004 that say to animate the changing property
1005 to another element with 'transition-*' properties
1006 that also say to animate the changing property.
1007 </p>
1009 <p>
1010 When this happens, both transitions will run,
1011 and the transition on the descendant will override
1012 the transition on the ancestor
1013 because of the normal
1014 CSS cascading and inheritance rules ([[CSS3CASCADE]]).
1015 </p>
1017 <p>
1018 If the transition on the descendant completes before
1019 the transition on the ancestor,
1020 the descendant will then resume inheriting
1021 the (still transitioning) value from its parent.
1022 This effect is likely not a desirable effect,
1023 but it is essentially doing what the author asked for.
1024 </p>
1025 </div>
1027 <p>
1028 For each element with a <span>before-change style</span> and
1029 an <span>after-change style</span>,
1030 and each property (other than shorthands) for which
1031 the <span>before-change style</span> is different from
1032 the <span>after-change style</span>,
1033 implementations must
1034 start transitions based on the relevant item (see <a
1035 href="#transition-property">the definition of
1036 'transition-property'</a>) in the computed value of
1037 'transition-property'.
1038 Corresponding to this item there is
1039 a <span>matching transition duration</span>,
1040 a <span>matching transition delay</span>, and
1041 a <span>matching transition timing function</span>
1042 in the computed values of
1043 'transition-duration', 'transition-delay', and 'transition-timing-function'
1044 (see <a href="#list-matching">the rules on matching lists</a>).
1045 Define the <dfn>combined duration</dfn> of the transition
1046 as the sum of max(matching transition duration, ''0s'') and
1047 the matching transition-delay.
1048 When the combined duration is greater than ''0s'',
1049 then a transition starts based on the values of the
1050 matching transition duration, the matching transition delay,
1051 and the matching transition-timing-function;
1052 in other cases transitions do not occur.
1053 The <dfn>start time</dfn> of this transition is defined as
1054 the time of the <span>style change event</span> plus
1055 the matching transition delay.
1056 The <dfn>end time</dfn> of this transition is defined as
1057 the <span>start time</span> plus the matching transition duration.
1058 The <dfn>start value</dfn> of this transition is defined as
1059 the value of the transitioning property
1060 in the <span>before-change style</span>,
1061 and the <dfn>end value</dfn> of this transition is defined as
1062 the value of the transitioning property
1063 in the <span>after-change style</span>.
1064 Except in the cases described
1065 in the <a href="#reversing">section on reversing of
1066 transitions</a>,
1067 the <dfn>reversing-adjusted start value</dfn> is the same as
1068 the <span>start value</span>,
1069 and the <dfn>reversing shortening factor</dfn> is 1.
1070 </p>
1072 <p>
1073 Once the transition of a property has started, it must continue
1074 running based on the original timing function, duration, and
1075 delay, even if the 'transition-timing-function',
1076 'transition-duration', or 'transition-delay' property changes
1077 before the transition is complete. However, if the
1078 'transition-property' property changes such that the transition
1079 would not have started, the transition must stop (and the
1080 property must immediately change to its final value).
1081 </p>
1083 <p>
1084 Implementations must not start a transition when the computed
1085 value of a property changes as a result of declarative animation
1086 (as opposed to scripted animation).
1087 </p>
1089 <p>
1090 Implementations also must not start a transition when the
1091 computed value changes because it is inherited (directly or
1092 indirectly) from another element that is transitioning the same
1093 property.
1094 </p>
1096 <h3 id="reversing">
1097 Faster reversing of interrupted transitions
1098 </h3>
1099 <p>
1100 Many common transitions effects involve transitions between two states,
1101 such as the transition that occurs when the mouse pointer moves
1102 over a user interface element, and then later moves out of that element.
1103 With these effects, it is common for a running transition
1104 to be interrupted before it completes,
1105 and the property reset to the starting value of that transition.
1106 An example is a hover effect on an element,
1107 where a transition starts when the pointer enters the element,
1108 and then the pointer exits the element before the effect has completed.
1109 If the outgoing and incoming transitions
1110 are executed using their specified durations and timing functions,
1111 the resulting effect can be distractingly asymmetric
1112 because the second transition
1113 takes the full specified time to move a shortened distance.
1114 Instead, the expected behavior is that the second transition is shorter.
1115 </p>
1117 <p>
1118 To meet this expectation,
1119 when a transition is started for a property on an element
1120 (henceforth, the <dfn>new transition</dfn>)
1121 that has a currently-running transition whose
1122 <span>reversing-adjusted start value</span> is the same as the
1123 <span>end value</span> of the new transition
1124 (henceforth, the <dfn>old transition</dfn>), implementations
1125 must cancel the old transition <span class="issue">link to
1126 definition above</span> and adjust the new transition as follows
1127 (prior to following the rules for computing the <span>combined
1128 duration</span>, <span>start time</span>, and <span>end
1129 time</span>):
1130 </p>
1132 <ol>
1134 <li>
1135 The <span>reversing-adjusted start value</span> of the new
1136 transition is instead the the <span>end value</span> of the
1137 old transition.
1138 <span class="note">Note: This represents the logical start state of
1139 the transition, and allows some calculations to ignore that
1140 the transition started before that state was reached, which
1141 in turn allows repeated reversals of the same transition to
1142 work correctly.</span>
1143 </li>
1145 <li>
1146 The <span>reversing shortening factor</span> of the new
1147 transition is the absolute value, clamped to the range [0, 1],
1148 of the sum of:
1149 <ol>
1150 <li>the output of the timing function of the old transition
1151 at the time of the <span>style change event</span>,
1152 times the <span>reversing shortening factor</span> of the
1153 old transition</li>
1154 <li>1 minus the <span>reversing shortening factor</span> of
1155 the old transition.</li>
1156 </ol>
1157 <span class="note">Note: This represents the portion of the
1158 space between the <span>reversing-adjusted start value</span>
1159 and the <span>end value</span> that the old transition has
1160 traversed (in amounts of the value, not time), except with the
1161 absolute value and clamping to handle timing functions that
1162 have y1 or y2 outside the range [0, 1].</span>
1163 </li>
1165 <li>
1166 The matching transition-duration for the new transition is
1167 multiplied by the
1168 <span>reversing shortening factor</span>.
1169 </li>
1171 <li>
1172 If the matching transition-delay for the new transition is
1173 negative, it is also multiplied by the
1174 <span>reversing shortening factor</span>.
1175 </li>
1177 </ol>
1179 <p class="note">
1180 Note that these rules do not fully address the problem for
1181 transition patterns that involve more than two states.
1182 </p>
1184 <p class="note">
1185 Note that these rules lead to the entire timing function of the
1186 new transition being used, rather than jumping into the middle
1187 of a timing function, which can create a jarring effect.
1188 </p>
1190 <p class="note">
1191 This was one of several possibilities that was considered by the
1192 working group. See the
1193 <a href="transition-reversing-demo">reversing demo</a>
1194 demonstrating a number of them, leading to a working group
1195 resolution made on 2013-06-07 and edits made on 2013-11-11.
1196 </p>
1198 <h2 id="application">
1199 Application of transitions
1200 </h2>
1202 <p>
1203 When a property on an element is undergoing a transition
1204 (that is, when or after the transition has started and before the
1205 <span>end time</span> of the transition)
1206 the transition adds a style to the CSS cascade
1207 at the level defined for CSS Transitions in [[CSS3CASCADE]].
1208 </p>
1210 <p class="note">
1211 Note that this means that computed values
1212 resulting from CSS transitions
1213 can inherit to descendants just like
1214 any other computed values.
1215 In the normal case, this means that
1216 a transition of an inherited property
1217 applies to descendant elements
1218 just as an author would expect.
1219 </p>
1221 <p>
1222 Implementations must add this value to the cascade
1223 if and only if
1224 that property is not currently
1225 undergoing a CSS Animation ([[CSS3-ANIMATIONS]]) on the same element.
1226 </p>
1228 <p class="note">
1229 Note that this behavior of transitions not applying to the cascade
1230 when an animation on the same element and property is running
1231 does not affect whether the transition has started or ended.
1232 APIs that detect whether transitions are running
1233 (such as <a href="#transition-events">transition events</a>)
1234 still report that a transition is running.
1235 </p>
1237 <p>
1238 If the current time is at or before the
1239 <span>start time</span> of the transition
1240 (that is, during the delay phase of the transition),
1241 this value is a specified style that will compute
1242 to the <span>start value</span> of the transition.
1243 </p>
1245 <p>
1246 If the current time is after the
1247 <span>start time</span> of the transition
1248 (that is, during the duration phase of the transition),
1249 this value is a specified style that will compute
1250 to the <a href="#animatable-types">result of interpolating the property</a>
1251 using the <span>start value</span> of the transition as
1252 <var>V</var><sub>start</sub>,
1253 using the <span>end value</span> of the transition as
1254 <var>V</var><sub>end</sub>,
1255 and using (current time - start time) / (end time - start time)
1256 as the input to the timing function.
1257 </p>
1259 <h2 id="transition-events"><a title="" id="transition-events-">
1260 Transition Events
1261 </a></h2>
1262 <p>
1263 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>.
1264 An event is fired for each property that undergoes a transition.
1265 This allows a content developer to perform actions that synchronize
1266 with the completion of a transition.
1267 </p>
1268 <p>
1269 Each event provides the name of the property the transition is
1270 associated with as well as the duration of the transition.
1271 </p>
1272 <dl>
1273 <dt>
1274 <b>Interface <dfn id="Events-TransitionEvent">TransitionEvent</dfn></b>
1275 </dt>
1276 <dd>
1277 <p>
1278 The <code>TransitionEvent</code> interface provides specific contextual information associated with transitions.
1279 </p>
1280 <dl>
1281 <dt>
1282 <b>IDL Definition</b>
1283 </dt>
1284 <dd>
1285 <div class='idl-code'>
1286 <pre>
1287 <span id="TransitionEvent">[Constructor(DOMString <var title="">type</var>, optional <i>TransitionEventInit</i> <var title="">transitionEventInitDict</var>)]
1288 interface TransitionEvent</span> : Event {
1289 readonly attribute DOMString <a href="#Events-TransitionEvent-propertyName">propertyName</a>;
1290 readonly attribute float <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a>;
1291 readonly attribute DOMString <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a>;
1292 };
1294 dictionary <dfn id="TransitionEventInit">TransitionEventInit</dfn> : <a class="external" href="https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#eventinit">EventInit</a> {
1295 DOMString <a href="#Events-TransitionEvent-propertyName">propertyName</a> = "";
1296 float <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a> = 0.0;
1297 DOMString <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a> = "";
1298 }
1299 </pre>
1300 </div>
1301 </dd>
1302 <dt>
1303 <b>Attributes</b>
1304 </dt>
1305 <dd>
1306 <dl>
1307 <dt>
1308 <code class='attribute-name'><dfn title="TransitionEvent::propertyName" id="Events-TransitionEvent-propertyName">propertyName</dfn></code> of type <code>DOMString</code>, readonly
1309 </dt>
1310 <dd>
1311 The name of the CSS property associated with the transition.
1312 </dd>
1313 </dl>
1314 <dl>
1315 <dt>
1316 <code class='attribute-name'><dfn title="TransitionEvent::elapsedTime" id="Events-TransitionEvent-elapsedTime">elapsedTime</dfn></code> of type <code>float</code>, readonly
1317 </dt>
1318 <dd>
1319 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>.
1320 </dd>
1321 </dl>
1322 <dl>
1323 <dt>
1324 <code class='attribute-name'><dfn title="TransitionEvent::pseudoElement" id="Events-TransitionEvent-pseudoElement">pseudoElement</dfn></code> of type <code>DOMString</code>, readonly
1325 </dt>
1326 <dd>
1327 The name (beginning with two colons) of the CSS
1328 pseudo-element on which the transition occurred (in
1329 which case the target of the event is that
1330 pseudo-element's corresponding element), or the empty
1331 string if the transition occurred on an element (which
1332 means the target of the event is that element).
1333 </dd>
1334 </dl>
1335 </dd>
1336 </dl>
1337 <p>
1338 <code id="TransitionEvent-constructor">TransitionEvent(type, transitionEventInitDict)</code>
1339 is an <a class="external" href="https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#constructing-events">event constructor</a>.
1340 </p>
1341 </dd>
1342 </dl>
1343 <p>
1344 There is one type of transition event available.
1345 </p>
1346 <dl>
1347 <dt>
1348 <b><dfn>transitionend</dfn></b>
1349 </dt>
1350 <dd>
1351 The <code>transitionend</code> event occurs at the completion of the transition. In the
1352 case where a transition is removed before completion, such as if the
1353 transition-property is removed, then the event will not fire.
1354 <ul>
1355 <li>Bubbles: Yes
1356 </li>
1357 <li>Cancelable: No
1358 </li>
1359 <li>Context Info: propertyName, elapsedTime, pseudoElement
1360 </li>
1361 </ul>
1362 </dd>
1363 </dl>
1365 <h2 id="animatable-types"><a title="" id="animation-of-property-types-">
1366 Animation of property types
1367 </a></h2>
1369 <p>
1370 When interpolating between two values,
1371 <var>V</var><sub>start</sub> and <var>V</var><sub>end</sub>,
1372 interpolation is done using the output <var>p</var> of the timing function,
1373 which gives the portion of the value space
1374 that the interpolation has crossed.
1375 Thus the result of the interpolation is
1376 <var>V</var><sub>res</sub> =
1377 (1 - <var>p</var>) ⋅ <var>V</var><sub>start</sub> +
1378 <var>p</var> ⋅ <var>V</var><sub>end</sub>.
1379 </p>
1381 <p>
1382 However, if this value (<var>V</var><sub>res</sub>)
1383 is outside the allowed range of values for the property,
1384 then it is clamped to that range.
1385 This can occur if <var>p</var> is outside of the range 0 to 1,
1386 which can occur if a timing function is specified
1387 with a <var>y1</var> or <var>y2</var> that is outside the range 0 to 1.
1388 </p>
1390 <p>
1391 The following describes how each property type undergoes transition or
1392 animation.
1393 </p>
1395 <ul>
1396 <li id="animtype-color">
1397 <strong>color</strong>: interpolated via red, green, blue and alpha
1398 components (treating each as a number, see below).
1399 The interpolation is done between premultiplied colors
1400 (that is, colors for which the red, green, and blue components
1401 specified have been multiplied by the alpha).
1402 </li>
1403 <li id="animtype-length">
1404 <strong>length</strong>: interpolated as real numbers.
1405 </li>
1406 <li id="animtype-percentage">
1407 <strong>percentage</strong>: interpolated as real numbers.
1408 </li>
1409 <li id="animtype-lpcalc">
1410 <strong>length, percentage, or calc</strong>: when both values
1411 are lengths, interpolated as lengths; when both values are
1412 percentages, interpolated as percentages; otherwise, both
1413 values are converted into a ''calc()'' function that is the
1414 sum of a length and a percentage (each possibly zero), and
1415 these ''calc()'' functions have each half interpolated as real
1416 numbers.
1417 </li>
1418 <li id="animtype-integer">
1419 <strong>integer</strong>: interpolated via discrete steps (whole
1420 numbers). The interpolation happens in real number space and is
1421 converted to an integer by rounding to the nearest integer, with
1422 values halfway between a pair of integers rounded towards
1423 positive infinity.
1424 </li>
1425 <li id="animtype-font-weight">
1426 <strong>font weight</strong>: interpolated via discrete steps
1427 (multiples of 100). The interpolation happens in real number
1428 space and is converted to an integer by rounding to the
1429 nearest multiple of 100, with values halfway between multiples
1430 of 100 rounded towards positive infinity.
1431 </li>
1432 <li id="animtype-number">
1433 <strong>number</strong>: interpolated as real (floating point)
1434 numbers.
1435 </li>
1436 <li id="animtype-rect">
1437 <strong>rectangle</strong>: interpolated via the x, y,
1438 width and height components (treating each as a number).
1439 </li>
1440 <li id="animtype-visibility">
1441 <strong>visibility</strong>: if one of the values is
1442 ''visible'', interpolated as a discrete step where values of the
1443 timing function between 0 and 1 map to ''visible'' and other
1444 values of the timing function (which occur only at the
1445 start/end of the transition or as a result of ''cubic-bezier()''
1446 functions with Y values outside of [0, 1]) map to the closer
1447 endpoint; if neither value is ''visible'' then not interpolable.
1448 </li>
1449 <li id="animtype-shadow-list">
1450 <strong>shadow list</strong>: Each shadow in the list is
1451 interpolated via the
1452 color (as <a href="#animtype-color">color</a>) component,
1453 and x, y, blur, and (when appropriate) spread
1454 (as <a href="#animtype-length">length</a>) components.
1455 For each shadow, if one input shadow is ''inset'' and the other
1456 is not, then the result for that shadow matches the inputs;
1457 otherwise the entire list is not interpolable.
1458 If the lists of shadows have different lengths,
1459 then the shorter list is padded at the end
1460 with shadows whose color is ''transparent'',
1461 all lengths are ''0'',
1462 and whose ''inset'' (or not) matches the longer list.
1463 </li>
1464 <li id="animtype-gradient">
1465 <strong>gradient</strong>: interpolated via the
1466 positions and colors of each stop. They must have the same type
1467 (radial or linear) and same number of stops in order to be animated.
1468 <span class="note">Note: [[CSS3-IMAGES]] may extend this
1469 definition.</span>
1470 </li>
1471 <li id="animtype-paintserver">
1472 <strong>paint server</strong> (SVG): interpolation is only supported
1473 between: gradient to gradient and color to color. They then
1474 work as above.
1475 </li>
1476 <li id="animtype-simple-list">
1477 <strong>simple list</strong> of other types:
1478 If the lists have the same number of items,
1479 and each pair of values can be interpolated,
1480 each item in the list is interpolated using
1481 the rules given for those types.
1482 Otherwise the values are not interpolable.
1483 </li>
1484 <li id="animtype-repeatable-list">
1485 <strong>repeatable list</strong> of other types:
1486 The result list has a length that is the least common multiple
1487 of the lengths of the input lists.
1488 Each item in the result is the interpolation of the value
1489 from each input list repeated to the length of the result list.
1490 If a pair of values cannot be interpolated, then the lists
1491 are not interpolable.
1492 <span class="note">
1493 The repeatable list concept ensures that a list that is
1494 conceptually repeated to a certain length (as
1495 'background-origin' is repeated to the length of the
1496 'background-image' list) or repeated infinitely will
1497 smoothly transition between any values, and so that the
1498 computed value will properly represent the result (and
1499 potentially be inherited correctly).
1500 </span>
1501 </li>
1502 </ul>
1504 <p>Future specifications may define additional types that can
1505 be animated.</p>
1507 <p>See the definition of 'transition-property' for how animation
1508 of shorthand properties and the ''all'' value is applied to any
1509 properties (in the shorthand) that can be animated.</p>
1511 <h2 id="animatable-properties"><a title="" id="animatable-properties-">
1512 Animatable properties
1513 </a></h2>
1515 <!--
1516 As resolved in
1517 http://lists.w3.org/Archives/Public/www-style/2011Sep/0497.html
1518 -->
1520 <p>The definition of each CSS property defines
1521 when the values of that property can be interpolated
1522 by referring to the definitions of property types
1523 in the <a href="#animatable-types">previous section</a>.
1524 Values are animatable when
1525 both the from and the to values of the property have the type described.
1526 (When a composite type such as "length, percentage, or calc" is listed,
1527 this means that both values must fit into that composite type.)
1528 When multiple types are listed in the form "either A or B",
1529 both values must be of the same type to be interpolable.</p>
1531 <p>For properties that exist at the time this specification was
1532 developed, this specification defines whether and how they are
1533 animated. However, future CSS specifications may define
1534 additional properties, additional values for existing properties,
1535 or additional animation behavior of existing values. In order to
1536 describe new animation behaviors and to have the definition of
1537 animation behavior in a more appropriate location, future CSS
1538 specifications should include an "Animatable:" line in the summary
1539 of the property's definition (in addition to the other lines
1540 described in [[CSS21]], <a
1541 href="http://www.w3.org/TR/CSS21/about.html#property-defs">section
1542 1.4.2</a>). This line should say "no" to indicate that a property
1543 cannot be animated or should reference an animation behavior
1544 (which may be one of the behaviors in the <a
1545 href="#animation-of-property-types-">Animation of property
1546 types</a> section above, or may be a new behavior) to define how
1547 the property animates. Such definitions override those given in
1548 this specification.</p>
1550 <h3 id="animatable-css"><a title="" id="properties-from-css-">
1551 Properties from CSS
1552 </a></h3>
1554 <p>
1555 The following definitions define the animation behavior for
1556 properties in CSS Level 2 Revision 1 ([[CSS21]]) and in Level 3 of
1557 the CSS Color Module ([[CSS3COLOR]]).
1558 </p>
1560 <table class="animatable-properties">
1561 <tr>
1562 <th>Property Name</th>
1563 <th>Type</th>
1564 </tr>
1565 <tr>
1566 <td>background-color</td><td>as <a href="#animtype-color">color</a></tr>
1567 <tr>
1568 <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>
1569 </tr>
1570 <tr>
1571 <td>border-bottom-color</td><td>as <a href="#animtype-color">color</a></td>
1572 </tr>
1573 <tr>
1574 <td>border-bottom-width</td><td>as <a href="#animtype-length">length</a></td>
1575 </tr>
1576 <tr>
1577 <td>border-left-color</td><td>as <a href="#animtype-color">color</a></td>
1578 </tr>
1579 <tr>
1580 <td>border-left-width</td><td>as <a href="#animtype-length">length</a></td>
1581 </tr>
1582 <tr>
1583 <td>border-right-color</td><td>as <a href="#animtype-color">color</a></td>
1584 </tr>
1585 <tr>
1586 <td>border-right-width</td><td>as <a href="#animtype-length">length</a></td>
1587 </tr>
1588 <tr>
1589 <td>border-spacing</td><td>as <a href="#animtype-simple-list">simple list</a> of <a href="#animtype-length">length</a></td>
1590 </tr>
1591 <tr>
1592 <td>border-top-color</td><td>as <a href="#animtype-color">color</a></td>
1593 </tr>
1594 <tr>
1595 <td>border-top-width</td><td>as <a href="#animtype-length">length</a></td>
1596 </tr>
1597 <tr>
1598 <td>bottom</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1599 </tr>
1600 <tr>
1601 <td>clip</td><td>as <a href="#animtype-rect">rectangle</a></td>
1602 </tr>
1603 <tr>
1604 <td>color</td><td>as <a href="#animtype-color">color</a></td>
1605 </tr>
1606 <tr>
1607 <td>font-size</td><td>as <a href="#animtype-length">length</a></td>
1608 </tr>
1609 <tr>
1610 <td>font-weight</td><td>as <a href="#animtype-font-weight">font weight</a></td>
1611 </tr>
1612 <tr>
1613 <td>height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1614 </tr>
1615 <tr>
1616 <td>left</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1617 </tr>
1618 <tr>
1619 <td>letter-spacing</td><td>as <a href="#animtype-length">length</a></td>
1620 </tr>
1621 <tr>
1622 <td>line-height</td><td>as either <a href="#animtype-number">number</a> or <a href="#animtype-length">length</a></td>
1623 </tr>
1624 <tr>
1625 <td>margin-bottom</td><td>as <a href="#animtype-length">length</a></td>
1626 </tr>
1627 <tr>
1628 <td>margin-left</td><td>as <a href="#animtype-length">length</a></td>
1629 </tr>
1630 <tr>
1631 <td>margin-right</td><td>as <a href="#animtype-length">length</a></td>
1632 </tr>
1633 <tr>
1634 <td>margin-top</td><td>as <a href="#animtype-length">length</a></td>
1635 </tr>
1636 <tr>
1637 <td>max-height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1638 </tr>
1639 <tr>
1640 <td>max-width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1641 </tr>
1642 <tr>
1643 <td>min-height</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1644 </tr>
1645 <tr>
1646 <td>min-width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1647 </tr>
1648 <tr>
1649 <td>opacity</td><td>as <a href="#animtype-number">number</a></td>
1650 </tr>
1651 <tr>
1652 <td>outline-color</td><td>as <a href="#animtype-color">color</a></td>
1653 </tr>
1654 <tr>
1655 <td>outline-width</td><td>as <a href="#animtype-length">length</a></td>
1656 </tr>
1657 <tr>
1658 <td>padding-bottom</td><td>as <a href="#animtype-length">length</a></td>
1659 </tr>
1660 <tr>
1661 <td>padding-left</td><td>as <a href="#animtype-length">length</a></td>
1662 </tr>
1663 <tr>
1664 <td>padding-right</td><td>as <a href="#animtype-length">length</a></td>
1665 </tr>
1666 <tr>
1667 <td>padding-top</td><td>as <a href="#animtype-length">length</a></td>
1668 </tr>
1669 <tr>
1670 <td>right</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1671 </tr>
1672 <tr>
1673 <td>text-indent</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1674 </tr>
1675 <tr>
1676 <td>text-shadow</td><td>as <a href="#animtype-shadow-list">shadow list</a></td>
1677 </tr>
1678 <tr>
1679 <td>top</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1680 </tr>
1681 <tr>
1682 <td>vertical-align</td><td>as <a href="#animtype-length">length</a></td>
1683 </tr>
1684 <tr>
1685 <td>visibility</td><td>as <a href="#animtype-visibility">visibility</a></td>
1686 </tr>
1687 <tr>
1688 <td>width</td><td>as <a href="#animtype-lpcalc">length, percentage, or calc</a></td>
1689 </tr>
1690 <tr>
1691 <td>word-spacing</td><td>as <a href="#animtype-length">length</a></td>
1692 </tr>
1693 <tr>
1694 <td>z-index</td><td>as <a href="#animtype-integer">integer</a></td>
1695 </tr>
1696 </table>
1698 <h3 id="animatable-svg"><a title="" id="properties-from-svg-">
1699 Properties from SVG
1700 </a></h3>
1702 <p>
1703 All properties defined as animatable in the SVG specification, provided
1704 they are one of the property types listed above.
1705 </p>
1707 <!-- <table>
1708 <tr>
1709 <th>Property Name</th><th>Type</th>
1710 </tr>
1711 <tr>
1712 <td>stop-color</td><td>as <a href="#animtype-color">color</a></td>
1713 </tr>
1714 <tr>
1715 <td>stop-opacity</td><td>as <a href="#animtype-number">number</a></td>
1716 </tr>
1717 <tr>
1718 <td>fill</td><td>as <a href="#animtype-paintserver">paint server</a></td>
1719 </tr>
1720 <tr>
1721 <td>fill-opacity</td><td>as <a href="#animtype-number">number</a></td>
1722 </tr>
1723 <tr>
1724 <td>stroke</td><td>as <a href="#animtype-paintserver">paint server</a></td>
1725 </tr>
1726 <tr>
1727 <td>stroke-dasharray</td><td>as <a href="#animtype-repeatable-list">repeatable list</a> of <a href="#animtype-number">number</a></td>
1728 </tr>
1729 <tr>
1730 <td>stroke-dashoffset</td><td>as <a href="#animtype-number">number</a></td>
1731 </tr>
1732 <tr>
1733 <td>stroke-miterlimit</td><td>as <a href="#animtype-number">number</a></td>
1734 </tr>
1735 <tr>
1736 <td>stroke-opacity</td><td>as <a href="#animtype-number">number</a></td>
1737 </tr>
1738 <tr>
1739 <td>stroke-width</td><td>as <a href="#animtype-number">number</a></td>
1740 </tr>
1741 <tr>
1742 <td>viewport-fill</td><td>as <a href="#animtype-color">color</a></td>
1743 </tr>
1744 <tr>
1745 <td>viewport-fill-opacity</td><td>as <a href="#animtype-color">color</a></td>
1746 </tr>
1747 </table> -->
1749 <h2 id="changes">Changes since Working Draft of 19 November 2013</h2>
1751 <p>The following are the substantive changes made since the
1752 <a href="http://www.w3.org/TR/2013/WD-css3-transitions-20131119/">Working Draft
1753 dated 19 November 2013</a>:</p>
1755 <ul>
1756 <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>
1757 <li class="issue">... ADD CHANGES HERE ...
1758 </ul>
1760 <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>
1762 <p>For changes in earlier working drafts:</p>
1764 <ol>
1765 <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>
1766 <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
1767 <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>.
1768 </ol>
1770 <h2 id="acknowledgments">Acknowledgments</h2>
1772 <p>Thanks especially to the feedback from
1773 Tab Atkins,
1774 Carine Bournez,
1775 Aryeh Gregor,
1776 Vincent Hardy,
1777 Anne van Kesteren,
1778 Cameron McCormack,
1779 Alex Mogilevsky,
1780 and all the rest of the
1781 <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.</p>
1783 <h2 id="references">References</h2>
1785 <h3 class="no-num" id="normative-references">Normative references</h3>
1786 <!--normative-->
1788 <h3 class="no-num" id="other-references">Other references</h3>
1789 <!--informative-->
1793 <h2 class="no-num" id="property-index">Property index</h2>
1794 <!-- properties -->
1798 <h2 class="no-num" id="index">Index</h2>
1799 <!--index-->
1801 </body>
1802 </html>
1803 <!-- Keep this comment at the end of the file
1804 Local variables:
1805 mode: sgml
1806 sgml-default-doctype-name:"html"
1807 sgml-minimize-attributes:t
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