css3-transitions/Overview.src.html

Sun, 03 Feb 2013 23:33:13 -0700

author
L. David Baron <dbaron@dbaron.org>
date
Sun, 03 Feb 2013 23:33:13 -0700
changeset 7300
6b5583cd39bb
parent 7299
be188be3a708
child 7301
3249d55edb05
permissions
-rw-r--r--

[css3-transitions] Fix incorrect use of single quotes in preprocessor input, which should only be used for CSS properties.

     1 <!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01//EN'
     2   'http://www.w3.org/TR/html4/strict.dtd'>
     4 <html lang="en">
     5 <head>
     6   <title>CSS Transitions</title>
     7   <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
     8   <link rel="stylesheet" type="text/css" href="../default.css">
     9   <style type="text/css">
    10     table.animatable-properties {
    11       border-collapse: collapse;
    12     }
    13     table.animatable-properties td {
    14       padding: 0.2em 1em;
    15       border: 1px solid black;
    16     }
    17     div.prod { margin: 1em 2em; }
    18   </style>
    19   <link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-ED.css">
    20 </head>
    22 <body>
    24 <div class="head">
    25 <!--logo-->
    27 <h1>CSS Transitions</h1>
    29 <h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
    30 <dl>
    31   <dt>This version:
    32     <dd>
    33     <a href="[VERSION]">
    34       http://dev.w3.org/csswg/css3-transitions/</a>
    35       <!--http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]/-->
    36   <dt>Latest version:
    37     <dd><a href="http://www.w3.org/TR/css3-transitions/">
    38       [LATEST]</a>
    39   <dt>Editor's draft:
    40     <dd><a href="http://dev.w3.org/csswg/[SHORTNAME]/">http://dev.w3.org/csswg/[SHORTNAME]/</a>
    41   <dt>Previous version:
    42     <dd><a href="http://www.w3.org/TR/2012/WD-css3-transitions-20120403/">
    43       http://www.w3.org/TR/2012/WD-css3-transitions-20120403/</a>
    44   <dt id="editors-list">Editors:
    45     <dd><a href="mailto:dino@apple.com">Dean Jackson</a> (<a
    46       href="http://www.apple.com/">Apple Inc</a>)
    47     <dd><a href="mailto:hyatt@apple.com">David Hyatt</a> (<a
    48       href="http://www.apple.com/">Apple Inc</a>)
    49     <dd><a href="mailto:cmarrin@apple.com">Chris Marrin</a> (<a
    50       href="http://www.apple.com/">Apple Inc</a>)
    51     <dd class=vcard><a class=fn href="http://dbaron.org/">L. David Baron</a> (<a
    52       class=org href="http://www.mozilla.org/">Mozilla</a>)
    54   <dt>Issues list:
    55     <dd><a href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&amp;product=CSS&amp;component=Transitions&amp;resolution=---&amp;cmdtype=doit">in Bugzilla</a>
    57   <dt>Discussion:</dt>
    58     <dd><a href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a> with subject line &ldquo;<kbd>[[SHORTNAME]] <var>&hellip; message topic &hellip;</var></kbd>&rdquo;
    60   <dt>Test suite:
    61     <dd>none yet
    62 </dl>
    64 <!--copyright-->
    66 <hr title="Separator for header">
    67 </div>
    69 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
    71 <p>CSS Transitions allows property changes in CSS values to occur smoothly
    72   over a specified duration.
    74 <h2 class="no-num no-toc" id="status">Status of this document</h2>
    75 <!--status-->
    77 <p>
    78   The <a href="ChangeLog">list of changes made to this specification</a> is
    79   available.
    80 </p>
    82 <h2 class="no-num no-toc" id="contents">Table of contents</h2>
    83 <!--toc-->
    86 <h2 id="introduction">Introduction</h2>
    88       <p><em>This section is not normative.</em>
    89       <p>
    90         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.
    91       </p>
    93 <h2 id="transitions"><a id="transitions-">Transitions</a></h2>
    94       <p>
    95         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.
    96       </p>
    97       <p>
    98         For example, suppose that transitions of one second have been defined on the <code class="property">'left'</code> and
    99         <code class="property">'background-color'</code> properties. The following diagram illustrates the effect of updating those properties on an element, in this case moving it to the right and changing the background from red to blue. This assumes other transition parameters still have their default values.
   100       </p>
   101       <div class="figure">
   102         <img src="transition1.png" alt="">
   103       </div>
   104       <p class="caption">
   105         Transitions of <code class="property">'left'</code> and <code class="property">'background-color'</code>
   106       </p>
   107       <p>
   108         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.
   109       </p>
   110       <p>
   111         Only animatable CSS properties can be transitioned. See the table at the end of this document for a list 
   112         of properties that are animatable.
   113       </p>
   114       <p>
   115         The transition for a property is defined using a number of new properties. For example:
   116       </p>
   117       <div class="example">
   118         <p style="display:none">
   119           Example(s):
   120         </p>
   121         <pre>
   122   div {
   123     transition-property: opacity;
   124     transition-duration: 2s;
   125   }
   126   </pre>The above example defines a transition on the <code class="property">'opacity'</code> property that, when a new value is assigned to it, will cause a smooth change between the old value and the new value over a period of two seconds.
   127       </div>
   128       <p>
   129         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:
   130       </p>
   131       <div class="example">
   132         <p style="display:none">
   133           Example(s):
   134         </p>
   135         <pre>
   136   div {
   137     transition-property: opacity, left;
   138     transition-duration: 2s, 4s;
   139   }
   141   </pre>This will cause the <code class="property">'opacity'</code> property to transition over a period of two seconds and the left property to transition over a period of four seconds.
   142       </div>
   144       <p id="list-matching">
   145         In the case where the lists of values in transition properties
   146         do not have the same length, the length of the
   147         'transition-property' list determines the number of items in
   148         each list examined when starting transitions.  The lists are
   149         matched up from the first value: excess values at the end are
   150         not used.  If one of the other properties doesn't have enough
   151         comma-separated values to match the number of values of
   152         'transition-property', the UA must calculate its used value by
   153         repeating the list of values until there are enough.  This
   154         truncation or repetition does not affect the computed value.
   155         <span class="note">
   156           Note: This is analogous to the behavior of the 'background-*'
   157           properties, with 'background-image' analogous to
   158           'transition-property'.
   159         </span>
   160       </p>
   162       <div class="example">
   163         <p style="display:none">
   164           Example(s):
   165         </p>
   166       <pre>
   167       div {
   168         transition-property: opacity, left, top, width;
   169         transition-duration: 2s, 1s;
   170       }
   171       </pre>The above example defines a transition on the <code class="property">'opacity'</code> property of 2 seconds duration, a
   172       transition on the <code class="property">'left'</code> property of 1
   173       second duration, a transition on the <code class="property">'top'</code> property of 2 seconds duration and a
   174       transition on the <code class="property">'width'</code> property of 1
   175       second duration.
   177       </div>
   179       <!-- ======================================================================================================= -->
   180       <h3 id="transition-property-property"><a id="the-transition-property-property-">
   181         The <code class="property">'transition-property'</code> Property
   182       </a></h3>
   183       <p>
   184         The <code class="property">'transition-property'</code> property specifies the name of the CSS property to which the transition is applied.
   185       </p>
   186       <div class="issue">
   187         We may ultimately want to support a keypath syntax for this property. A keypath syntax would enable different transitions to be specified for components of a property. For example the blur of a shadow could have a different transition than the color of a shadow.
   188       </div>
   189       <table class="propdef">
   190         <tbody>
   191           <tr>
   192             <td>
   193               <em>Name:</em>
   194             </td>
   195             <td>
   196               <dfn id="transition-property">transition-property</dfn>
   197             </td>
   198           </tr>
   199           <tr>
   200             <td>
   201               <em>Value:</em>
   202             </td>
   203             <td>
   204               none | <span>&lt;single-transition-property&gt;</span> [ ',' <span>&lt;single-transition-property&gt;</span> ]*
   205             </td>
   206           </tr>
   207           <tr>
   208             <td>
   209               <em>Initial:</em>
   210             </td>
   211             <td>
   212               all
   213             </td>
   214           </tr>
   215           <tr>
   216             <td>
   217               <em>Applies&nbsp;to:</em>
   218             </td>
   219             <td>
   220               all elements, :before and :after pseudo elements
   221             </td>
   222           </tr>
   223           <tr>
   224             <td>
   225               <em>Inherited:</em>
   226             </td>
   227             <td>
   228               no
   229             </td>
   230           </tr>
   231           <tr>
   232             <td>
   233               <em>Animatable:</em>
   234             </td>
   235             <td>
   236               no
   237             </td>
   238           </tr>
   239           <tr>
   240             <td>
   241               <em>Percentages:</em>
   242             </td>
   243             <td>
   244               N/A
   245             </td>
   246           </tr>
   247           <tr>
   248             <td>
   249               <em>Media:</em>
   250             </td>
   251             <td>
   252               visual
   253             </td>
   254           </tr>
   255           <tr>
   256             <td>
   257               <em>Computed value:</em>
   258             </td>
   259             <td>
   260               Same as specified value.
   261             </td>
   262           </tr>
   263           <tr>
   264             <td>
   265               <em>Canonical order:</em>
   266             </td>
   267             <td>
   268               <abbr title="follows order of property value definition">per grammar</abbr>
   269             </td>
   270           </tr>
   271         </tbody>
   272       </table>
   274       <div class="prod">
   275         <dfn id="single-transition-property">&lt;single-transition-property&gt;</dfn> = all | &lt;IDENT&gt;
   276       </div>
   278       <p>
   279         A value of ''none'' means that no property will transition.
   280         Otherwise, a list of properties to be transitioned, or the
   281         keyword ''all'' which indicates that all properties are to be
   282         transitioned, is given.
   283       </p>
   285       <p>
   286         If one of the identifiers listed is not a recognized property
   287         name or is not an animatable property, the implementation must
   288         still start transitions on the animatable properties in the
   289         list using the duration, delay, and timing function at their
   290         respective indices in the lists for 'transition-duration',
   291         'transition-delay', and 'transition-timing-function'.  In other
   292         words, unrecognized or non-animatable properties must be kept in
   293         the list to preserve the matching of indices.
   294       </p>
   296       <p>
   297         The keywords ''none'', ''inherit'', and ''initial'' are not
   298         permitted as items within a list of more that one identifier;
   299         any list that uses them is syntactically invalid.
   300         In other words, the &lt;IDENT&gt; production in
   301         <span>&lt;single-transition-property&gt;</span> matches any
   302         identifier other than these three keywords.
   303       </p>
   305       <p>
   306         For the keyword ''all'', or if one of the identifiers listed is a
   307         shorthand property, implementations must start transitions for
   308         any of its longhand sub-properties that are animatable (or, for
   309         ''all'', all animatable properties), using the duration, delay,
   310         and timing function at the index corresponding to the shorthand.
   311       </p>
   312       <p>
   313         If a property is specified multiple times in the value of
   314         'transition-property' (either on its own, via a shorthand that
   315         contains it, or via the ''all'' value), then the transition that
   316         starts uses the duration, delay, and timing function at the
   317         index corresponding to the <em>last</em> item in the value of
   318         'transition-property' that calls for animating that property.
   319       </p>
   320       <p class="note">
   321         Note:  The ''all'' value and 'all' shorthand
   322         property work in similar ways, so the
   323         ''all'' value is just like a shorthand that
   324         covers all properties.
   325       </p>
   327       <!-- ======================================================================================================= -->
   328       <h3 id="transition-duration-property"><a id="the-transition-duration-property-">
   329         The <code class="property">'transition-duration'</code> Property
   330       </a></h3>
   331       <p>
   332         The <code class="property">'transition-duration'</code> property defines the length of time that a transition takes.
   333       </p>
   334       <table class="propdef">
   335         <tbody>
   336           <tr>
   337             <td>
   338               <em>Name:</em>
   339             </td>
   340             <td>
   341               <dfn id="transition-duration">transition-duration</dfn>
   342             </td>
   343           </tr>
   344           <tr>
   345             <td>
   346               <em>Value:</em>
   347             </td>
   348             <td>
   349               <span>&lt;time&gt;</span> [, <span>&lt;time&gt;</span>]*
   350             </td>
   351           </tr>
   352           <tr>
   353             <td>
   354               <em>Initial:</em>
   355             </td>
   356             <td>
   357               0s
   358             </td>
   359           </tr>
   360           <tr>
   361             <td>
   362               <em>Applies&nbsp;to:</em>
   363             </td>
   364             <td>
   365               all elements, :before and :after pseudo elements
   366             </td>
   367           </tr>
   368           <tr>
   369             <td>
   370               <em>Inherited:</em>
   371             </td>
   372             <td>
   373               no
   374             </td>
   375           </tr>
   376           <tr>
   377             <td>
   378               <em>Animatable:</em>
   379             </td>
   380             <td>
   381               no
   382             </td>
   383           </tr>
   384           <tr>
   385             <td>
   386               <em>Percentages:</em>
   387             </td>
   388             <td>
   389               N/A
   390             </td>
   391           </tr>
   392           <tr>
   393             <td>
   394               <em>Media:</em>
   395             </td>
   396             <td>
   397               interactive
   398             </td>
   399           </tr>
   400           <tr>
   401             <td>
   402               <em>Computed value:</em>
   403             </td>
   404             <td>
   405               Same as specified value.
   406             </td>
   407           </tr>
   408           <tr>
   409             <td>
   410               <em>Canonical order:</em>
   411             </td>
   412             <td>
   413               <abbr title="follows order of property value definition">per grammar</abbr>
   414             </td>
   415           </tr>
   416         </tbody>
   417       </table>
   418       <p>
   419         This property specifies how long the transition from the old value to the new value should take. By default the value is ''0s'', meaning that the transition is immediate (i.e. there will be no animation). A negative value for <code class="property">transition-duration</code> renders the declaration invalid.
   420       </p>
   422       <!-- =======================================================================================================   
   423         -->
   425       <h3 id="transition-timing-function-property"><a id="transition-timing-function_tag">
   426         The <code class="property">'transition-timing-function'</code> Property
   427       </a></h3>
   428       <p>
   429         The <code class="property">'transition-timing-function'</code> property
   430         describes how the intermediate values used during a transition will be
   431         calculated. It allows for a transition to change speed over its
   432         duration. These effects are commonly called <em>easing</em> functions.
   433         In either case, a mathematical function that provides a smooth curve is
   434         used.
   435       </p>
   436       <p>
   437         Timing functions are either defined as a stepping function or 
   438         a <a
   439         href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
   440         B&eacute;zier curve</a>. 
   441         The timing function takes as its input
   442         the current elapsed percentage of the transition duration
   443         and outputs the percentage of the way the transition is
   444         from its start value to its end value.
   445         How this output is used is defined by
   446         the <a href="#animatable-types">interpolation rules</a>
   447         for the value type.
   448       </p>
   449       <p>
   450         A <a href="http://en.wikipedia.org/wiki/Step_function">stepping</a>
   451         function is defined by a number that divides the domain of operation
   452         into equally sized intervals. Each subsequent interval is a equal step
   453         closer to the goal state. The function also specifies whether the
   454         change in output percentage happens at the start or end of the
   455         interval (in other words, if 0% on the input percentage is the point
   456         of initial change).
   457       </p>
   458       <div class="figure">
   459         <img src="step.png" alt="The step timing function splits
   460           the function domain into a number of disjoint straight line
   461           segments. steps(1, start) is a function whose
   462           output value is 1 for all input values. steps(1, end) is a function whose
   463           output value is 0 for all input values less than 1, and output
   464           is 1 for the input value of 1. steps(3, start) is a function that
   465           divides the input domain into three segments, each 1/3 in length,
   466           and 1/3 above the previous segment, with the first segment starting
   467           at 1/3. steps(3, end) is a function that
   468           divides the input domain into three segments, each 1/3 in length,
   469           and 1/3 above the previous segment, with the first segment starting
   470           at 0.">
   471       </div>
   472       <p class="caption">
   473         Step timing functions
   474       </p>
   475       <p>
   476         A <a
   477         href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve#Cubic_B.C3.A9zier_curves">cubic
   478         B&eacute;zier curve</a> is defined by four control points, P<sub>0</sub>
   479         through P<sub>3</sub> (see Figure 1). P<sub>0</sub> and P<sub>3</sub>
   480         are always set to (0,0) and (1,1). The <code class="property">'transition-timing-function'</code> property is used
   481         to specify the values for points P<sub>1</sub> and P<sub>2</sub>. These
   482         can be set to preset values using the keywords listed below, or can be
   483         set to specific values using the <code class="css">'cubic-bezier'</code> function.
   484         In the <code class="css">'cubic-bezier'</code> function, P<sub>1</sub> and
   485         P<sub>2</sub> are each specified by both an X and Y value.
   486       </p>
   487       <div class="figure">
   488         <img src="TimingFunction.png" alt="The B&eacute;zier timing function is a
   489           smooth curve from point P0 = (0,0) to point P3 = (1,1). The
   490           length and orientation of the line segment P0-P1 determines
   491           the tangent and the curvature of the curve at P0 and the
   492           line segment P2-P3 does the same at P3.">
   493       </div>
   494       <p class="caption">
   495         B&eacute;zier Timing Function Control Points
   496       </p>
   497       <table class="propdef">
   498         <tbody>
   499           <tr>
   500             <td>
   501               <em>Name:</em>
   502             </td>
   503             <td>
   504               <dfn id="transition-timing-function">transition-timing-function</dfn>
   505             </td>
   506           </tr>
   507           <tr>
   508             <td>
   509               <em>Value:</em>
   510             </td>
   511             <td>
   512               <span>&lt;single-transition-timing-function&gt;</span> [ ',' <span>&lt;single-transition-timing-function&gt;</span> ]*
   513             </td>
   514           </tr>
   515           <tr>
   516             <td>
   517               <em>Initial:</em>
   518             </td>
   519             <td>
   520               ease
   521             </td>
   522           </tr>
   523           <tr>
   524             <td>
   525               <em>Applies&nbsp;to:</em>
   526             </td>
   527             <td>
   528               all elements, :before and :after pseudo elements
   529             </td>
   530           </tr>
   531           <tr>
   532             <td>
   533               <em>Inherited:</em>
   534             </td>
   535             <td>
   536               no
   537             </td>
   538           </tr>
   539           <tr>
   540             <td>
   541               <em>Animatable:</em>
   542             </td>
   543             <td>
   544               no
   545             </td>
   546           </tr>
   547           <tr>
   548             <td>
   549               <em>Percentages:</em>
   550             </td>
   551             <td>
   552               N/A
   553             </td>
   554           </tr>
   555           <tr>
   556             <td>
   557               <em>Media:</em>
   558             </td>
   559             <td>
   560               interactive
   561             </td>
   562           </tr>
   563           <tr>
   564             <td>
   565               <em>Computed value:</em>
   566             </td>
   567             <td>
   568               Same as specified value.
   569             </td>
   570           </tr>
   571           <tr>
   572             <td>
   573               <em>Canonical order:</em>
   574             </td>
   575             <td>
   576               <abbr title="follows order of property value definition">per grammar</abbr>
   577             </td>
   578           </tr>
   579         </tbody>
   580       </table>
   581       <div class="prod">
   582         <dfn id="single-transition-timing-function">&lt;single-transition-timing-function&gt;</dfn> = ease | linear | ease-in | ease-out | ease-in-out | step-start | step-end | steps(&lt;integer&gt;[, [ start | end ] ]?) | cubic-bezier(&lt;number&gt;, &lt;number&gt;, &lt;number&gt;, &lt;number&gt;)
   583       </div>
   584       <p>
   585         The timing functions have the following definitions.
   586       </p>
   587       <dl>
   588         <dt>
   589           ease
   590         </dt>
   591         <dd>
   592           The ease function is equivalent to cubic-bezier(0.25, 0.1, 0.25, 1).
   593         </dd>
   594         <dt>
   595           linear
   596         </dt>
   597         <dd>
   598           The linear function is equivalent to cubic-bezier(0, 0, 1, 1).
   599         </dd>
   600         <dt>
   601           ease-in
   602         </dt>
   603         <dd>
   604           The ease-in function is equivalent to cubic-bezier(0.42, 0, 1, 1).
   605         </dd>
   606         <dt>
   607           ease-out
   608         </dt>
   609         <dd>
   610           The ease-out function is equivalent to cubic-bezier(0, 0, 0.58, 1).
   611         </dd>
   612         <dt>
   613           ease-in-out
   614         </dt>
   615         <dd>
   616           The ease-in-out function is equivalent to cubic-bezier(0.42, 0, 0.58, 1)
   617         </dd>
   618         <dt>
   619           step-start
   620         </dt>
   621         <dd>
   622           The step-start function is equivalent to steps(1, start).
   623         </dd>
   624         <dt>
   625           step-end
   626         </dt>
   627         <dd>
   628           The step-end function is equivalent to steps(1, end).
   629         </dd>
   630         <dt>
   631           steps(&lt;integer&gt;[, [ start | end ] ]?)
   632         </dt>
   633         <dd>
   634           Specifies a stepping function, described above, taking two
   635           parameters. The first parameter specifies the number of intervals
   636           in the function. It must be a positive integer (greater than 0).
   637           The second parameter, which is optional, is
   638           either the value ''start'' or ''end'', and specifies the point
   639           at which the change of values occur within the interval.
   640           If the second parameter is omitted, it is given the value 'end'.
   641         </dd>
   642         <dt>
   643           cubic-bezier(&lt;number&gt;, &lt;number&gt;, &lt;number&gt;, &lt;number&gt;)
   644         </dt>
   645         <dd>
   646           Specifies a <a
   647           href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve">cubic-bezier
   648           curve</a>. The four values specify points P<sub>1</sub> and
   649           P<sub>2</sub> of the curve as (x1, y1, x2, y2). Both x values must be
   650           in the range [0, 1] or the definition is invalid. The y values can
   651           exceed this range.
   652         </dd>
   653       </dl><!-- ======================================================================================================= -->
   654       <h3 id="transition-delay-property"><a id="the-transition-delay-property-">
   655         The <code class="property">'transition-delay'</code> Property
   656       </a></h3>
   657       <p>
   658         The <code class="property">'transition-delay'</code> property defines when the transition will start. It allows a transition to begin execution some some period of time from when it is applied. A <code class="property">'transition-delay'</code> value of ''0s'' means the transition will execute as soon as the property is changed. Otherwise, the value specifies an offset from the moment the property is changed, and the transition will delay execution by that offset.
   659       </p>
   660       <p>
   661         If the value for <code class="property">'transition-delay'</code> is a negative time offset then the transition will execute the moment the property is changed, but will appear to have begun execution at the specified offset. That is, the transition will appear to begin part-way through its play cycle. In the case where a transition has implied starting values and a negative <code class="property">'transition-delay'</code>, the starting values are taken from the moment the property is changed.
   662       </p>
   663       <table class="propdef">
   664         <tbody>
   665           <tr>
   666             <td>
   667               <em>Name:</em>
   668             </td>
   669             <td>
   670               <dfn id="transition-delay">transition-delay</dfn>
   671             </td>
   672           </tr>
   673           <tr>
   674             <td>
   675               <em>Value:</em>
   676             </td>
   677             <td>
   678               <span>&lt;time&gt;</span> [, <span>&lt;time&gt;</span>]*
   679             </td>
   680           </tr>
   681           <tr>
   682             <td>
   683               <em>Initial:</em>
   684             </td>
   685             <td>
   686               0s
   687             </td>
   688           </tr>
   689           <tr>
   690             <td>
   691               <em>Applies&nbsp;to:</em>
   692             </td>
   693             <td>
   694               all elements, :before and :after pseudo elements
   695             </td>
   696           </tr>
   697           <tr>
   698             <td>
   699               <em>Inherited:</em>
   700             </td>
   701             <td>
   702               no
   703             </td>
   704           </tr>
   705           <tr>
   706             <td>
   707               <em>Animatable:</em>
   708             </td>
   709             <td>
   710               no
   711             </td>
   712           </tr>
   713           <tr>
   714             <td>
   715               <em>Percentages:</em>
   716             </td>
   717             <td>
   718               N/A
   719             </td>
   720           </tr>
   721           <tr>
   722             <td>
   723               <em>Media:</em>
   724             </td>
   725             <td>
   726               interactive
   727             </td>
   728           </tr>
   729           <tr>
   730             <td>
   731               <em>Computed value:</em>
   732             </td>
   733             <td>
   734               Same as specified value.
   735             </td>
   736           </tr>
   737           <tr>
   738             <td>
   739               <em>Canonical order:</em>
   740             </td>
   741             <td>
   742               <abbr title="follows order of property value definition">per grammar</abbr>
   743             </td>
   744           </tr>
   745         </tbody>
   746       </table><!-- ======================================================================================================= -->
   747       <h3 id="transition-shorthand-property"><a id="the-transition-shorthand-property-">
   748         The <code class="property">'transition'</code> Shorthand Property
   749       </a></h3>
   750       <p>
   751         The <code class="property">'transition'</code> shorthand property combines the four properties described above into a single property.
   752       </p>
   753       <table class="propdef">
   754         <tbody>
   755           <tr>
   756             <td>
   757               <em>Name:</em>
   758             </td>
   759             <td>
   760               <dfn id="transition">transition</dfn>
   761             </td>
   762           </tr>
   763           <tr>
   764             <td>
   765               <em>Value:</em>
   766             </td>
   767             <td>
   768               <span>&lt;single-transition&gt;</span> [ ',' <span>&lt;single-transition&gt;</span> ]*
   769             </td>
   770           </tr>
   771           <tr>
   772             <td>
   773               <em>Initial:</em>
   774             </td>
   775             <td>
   776               see individual properties
   777             </td>
   778           </tr>
   779           <tr>
   780             <td>
   781               <em>Applies&nbsp;to:</em>
   782             </td>
   783             <td>
   784               all elements, :before and :after pseudo elements
   785             </td>
   786           </tr>
   787           <tr>
   788             <td>
   789               <em>Inherited:</em>
   790             </td>
   791             <td>
   792               no
   793             </td>
   794           </tr>
   795           <tr>
   796             <td>
   797               <em>Animatable:</em>
   798             </td>
   799             <td>
   800               no
   801             </td>
   802           </tr>
   803           <tr>
   804             <td>
   805               <em>Percentages:</em>
   806             </td>
   807             <td>
   808               N/A
   809             </td>
   810           </tr>
   811           <tr>
   812             <td>
   813               <em>Media:</em>
   814             </td>
   815             <td>
   816               interactive
   817             </td>
   818           </tr>
   819           <tr>
   820             <td>
   821               <em>Computed value:</em>
   822             </td>
   823             <td>
   824               Same as specified value.
   825             </td>
   826           </tr>
   827           <tr>
   828             <td>
   829               <em>Canonical order:</em>
   830             </td>
   831             <td>
   832               <abbr title="follows order of property value definition">per grammar</abbr>
   833             </td>
   834           </tr>
   835         </tbody>
   836       </table>
   838       <div class="prod">
   839         <dfn id="single-transition">&lt;single-transition&gt;</dfn> = [ none | <span>&lt;single-transition-property&gt;</span> ] || <span>&lt;time&gt;</span> || <span>&lt;single-transition-timing-function&gt;</span> || <span>&lt;time&gt;</span>
   840       </div>
   842       <p>
   843         Note that order is important within the items in this property:
   844         the first value that can be parsed as a time is assigned to the
   845         transition-duration,
   846         and the second value that can be parsed as a time is assigned to
   847         transition-delay.
   848       </p>
   850       <p class="issue">
   851         An alternative proposal is to accept the font shorthand approach of
   852         using a "/" character between the values of the same type. e.g. 2s/4s would
   853         mean a duration of 2 seconds and a delay of 4 seconds.
   854       </p>
   856       <p>
   857         If there is more than one <span>&lt;single-transition&gt;</span> in the shorthand,
   858         and any of the transitions has
   859         ''none'' as the <span>&lt;single-transition-property&gt;</span>,
   860         then the declaration is invalid.
   861       </p>
   863       <h2 id="starting">
   864         Starting of transitions
   865       </h2>
   867       <p>
   868         When the computed value of an animatable property changes,
   869         implementations must decide what transitions to start based on
   870         the values of the 'transition-property', 'transition-duration',
   871         'transition-timing-function', and 'transition-delay' properties
   872         at the time the animatable property would first have its new
   873         computed value.
   874       </p>
   875       <div class="example" id="manual-reversing-example">
   876         <p style="display:none">
   877           Example(s):
   878         </p>
   879         <p>This provides a way for authors to specify different values
   880         of the 'transition-*' properties for the &ldquo;forward&rdquo;
   881         and &ldquo;reverse&rdquo; transitions (but see <a
   882         href="#reversing">below</a> for special reversing behavior when
   883         an <em>incomplete</em> transition is interrupted).  Authors can
   884         specify the value of 'transition-duration',
   885         'transition-timing-function', or 'transition-delay' in the same
   886         rule where they specify the value that triggers the transition,
   887         or can change these properties at the same time as they change
   888         the property that triggers the transition.  Since it's the new
   889         values of these 'transition-*' properties that affect the
   890         transition, these values will be used for the transitions
   891         <em>to</em> the associated transitioning values.  For example:
   892          </p>
   893         <pre>li {
   894   transition: background-color linear 1s;
   895   background: blue;
   896 }
   897 li:hover {
   898   background-color: green;
   899   transition-duration: 2s; /* applies to the transition *to* the :hover state */
   900 }</pre>
   901         <p>
   902           When a list item with these style rules enters the :hover
   903           state, the computed 'transition-duration' at the time that
   904           'background-color' would have its new value (''green'') is ''2s'',
   905           so the transition from 'blue' to 'green' takes 2 seconds.
   906           However, when the list item leaves the :hover state, the
   907           transition from ''green'' to ''blue'' takes 1 second.
   908         </p>
   909       </div>
   911       <p>
   912         When the computed value of a property changes, implementations
   913         must start transitions based on the relevant item (see <a
   914         href="#transition-property">the definition of
   915         'transition-property'</a>) in the computed value of
   916         'transition-property'.
   917         Corresponding to this item there are
   918         computed values of 'transition-duration' and 'transition-delay'
   919         (see <a href="#list-matching">the rules on matching lists</a>).
   920         Define the <dfn>combined duration</dfn> of the transition
   921         as the sum of max('transition-duration', ''0s'') and 'transition-delay'.
   922         When the combined duration is greater than ''0s'',
   923         then a transition starts based on the values of
   924         'transition-duration', 'transition-delay',
   925         and 'transition-timing-function';
   926         in other cases transitions do not occur.
   927       </p>
   929       <p>
   930         Since this specification does not define
   931         when computed values change, and thus what changes to
   932         computed values are considered simultaneous,
   933         authors should be aware that changing any of the transition
   934         properties a small amount of time after making a change that
   935         might transition can result in behavior that varies between
   936         implementations, since the changes might be considered
   937         simultaneous in some implementations but not others.
   938       </p>
   940       <p>
   941         Once the transition of a property has started, it must continue
   942         running based on the original timing function, duration, and
   943         delay, even if the 'transition-timing-function',
   944         'transition-duration', or 'transition-delay' property changes
   945         before the transition is complete.  However, if the
   946         'transition-property' property changes such that the transition
   947         would not have started, the transition must stop (and the
   948         property must immediately change to its final value).
   949       </p>
   951       <p>
   952         Implementations must not start a transition when the computed
   953         value of a property changes as a result of declarative animation
   954         (as opposed to scripted animation).
   955       </p>
   957       <p>
   958         Implementations also must not start a transition when the
   959         computed value changes because it is inherited (directly or
   960         indirectly) from another element that is transitioning the same
   961         property.
   962       </p>
   964       <h2 id="reversing">
   965         Automatically reversing interrupted transitions
   966       </h2>
   967       <p>
   968         A common type of transition effect is when a running transition is
   969         interrupted and the property is reset to its original value. An
   970         example is a hover effect on an element, where the pointer enters and
   971         exits the element before the effect has completed. If the outgoing and
   972         incoming transitions are executed using their specified durations and
   973         timing functions, the resulting effect can be distractingly
   974         asymmetric. Instead, the expected behavior is that the new transition
   975         should be the reverse of what has already executed.
   976       </p>
   978       <p>
   979         If a running transition with duration T, executing so far for duration TE, 
   980         from state A, to state B, is interrupted by
   981         a property change that would start a new transition back to state A, and
   982         all the transition attributes are the same (duration, delay and timing function),
   983         then the new transition must reverse the effect. The new transition must:
   984       </p>
   986       <ol>
   987         <li>
   988           Use the B and A states as its "from" and "to" states respectively. It
   989           does not use the current value as its from state, due to the rules below.
   990         </li>
   991         <li>
   992           Execute with the same duration T, but starting as if the transition had
   993           already begun, without any transition delay, at the moment which would
   994           cause the new transition to finish in TE from the moment of interruption. In other
   995           words, the new transition will execute as if it started T-TE in the past.
   996         </li>
   997         <li>
   998           Use a timing function that is the portion of the curve traversed up
   999           to the moment of interruption, followed in the opposite direction (towards
  1000           the starting point). This will make the transition appear as if it 
  1001           is playing backwards.
  1002         </li>
  1003         <li>
  1004           Ignore any transition delay.
  1005         </li>
  1006       </ol>
  1008       <p>
  1009         For example, suppose there is a transition with a duration of two
  1010         seconds. If this transition is interrupted after 0.5 seconds and the
  1011         property value assigned to the original value, then the new transition
  1012         effect will be the reverse of the original, as if it had begun
  1013         1.5 seconds in the past.
  1014       </p>
  1016       <p>
  1017         Note that by using the defined from and to states for the reversing
  1018         transition, it is also possible that it may reverse again, if
  1019         interrupted; for example, if the transition reversing to state A was
  1020         again interrupted by a property change to state B.
  1021       </p>
  1023       <p class="issue">Issue:
  1024         This introduces the concept of reversing a timing function,
  1025         which the spec has otherwise resisted doing, and also introduces
  1026         a discontinuity between transitions that have
  1027         almost completed (which get automatically reversed and thus have
  1028         their timing function reversed) and transitions that have fully
  1029         completed (where the reversal doesn't lead to the timing
  1030         function being reversed).  An alternative proposal that avoids
  1031         this is to follow the normal timing function algorithm, except
  1032         multiply the duration (and also shorten any negative delay) by
  1033         the (output) value of the transition timing function of the
  1034         incomplete transition at the time it was interrupted, and, to
  1035         account for multiple reverses in sequence, to divide by the
  1036         shortening applied to the transition being interrupted.  For
  1037         more details see this thread:
  1038         <a href="http://lists.w3.org/Archives/Public/www-style/2009Nov/thread.html#msg302">November 2009 part</a>,
  1039         <a href="http://lists.w3.org/Archives/Public/www-style/2009Dec/thread.html#msg319">December 2009 part</a>,
  1040         <a href="http://lists.w3.org/Archives/Public/www-style/2010Jan/thread.html#msg136">January 2010 part</a>.
  1041       </p>
  1043       <h2 id="transition-events"><a id="transition-events-">
  1044         Transition Events
  1045       </a></h2>
  1046       <p>
  1047         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>.
  1048         An event is fired for each property that undergoes a transition.
  1049         This allows a content developer to perform actions that synchronize
  1050         with the completion of a transition.
  1051       </p>
  1052       <p>
  1053         Each event provides the name of the property the transition is
  1054         associated with as well as the duration of the transition.
  1055       </p>
  1056       <dl>
  1057         <dt>
  1058           <b>Interface <i><a id="Events-TransitionEvent" name='Events-TransitionEvent'>TransitionEvent</a></i></b>
  1059         </dt>
  1060         <dd>
  1061           <p>
  1062             The <code>TransitionEvent</code> interface provides specific contextual information associated with transitions.
  1063           </p>
  1064           <dl>
  1065             <dt>
  1066               <b>IDL Definition</b>
  1067             </dt>
  1068             <dd>
  1069               <div class='idl-code'>
  1070                 <pre>
  1071   interface TransitionEvent : Event {
  1072     readonly attribute DOMString          propertyName;
  1073     readonly attribute float              elapsedTime;
  1074     readonly attribute DOMString          pseudoElement;
  1075     void               initTransitionEvent(in DOMString typeArg, 
  1076                                           in boolean canBubbleArg, 
  1077                                           in boolean cancelableArg, 
  1078                                           in DOMString propertyNameArg,
  1079                                           in float elapsedTimeArg,
  1080                                           in DOMString pseudoElementArg);
  1081   };
  1082   </pre>
  1083               </div>
  1084             </dd>
  1085             <dt>
  1086               <b>Attributes</b>
  1087             </dt>
  1088             <dd>
  1089               <dl>
  1090                 <dt>
  1091                   <code class='attribute-name'><a id="Events-TransitionEvent-propertyName" name='Events-TransitionEvent-propertyName'>propertyName</a></code> of type <code>DOMString</code>, readonly
  1092                 </dt>
  1093                 <dd>
  1094                   The name of the CSS property associated with the transition.
  1095                 </dd>
  1096               </dl>
  1097               <dl>
  1098                 <dt>
  1099                   <code class='attribute-name'><a id="Events-TransitionEvent-elapsedTime" name='Events-TransitionEvent-elapsedTime'>elapsedTime</a></code> of type <code>float</code>, readonly
  1100                 </dt>
  1101                 <dd>
  1102                   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>.
  1103                 </dd>
  1104               </dl>
  1105               <dl>
  1106                 <dt>
  1107                   <code class='attribute-name'><a id="Events-TransitionEvent-pseudoElement" name='Events-TransitionEvent-pseudoElement'>pseudoElement</a></code> of type <code>DOMString</code>, readonly
  1108                 </dt>
  1109                 <dd>
  1110                   The name (beginning with two colons) of the CSS
  1111                   pseudo-element on which the transition occured (in
  1112                   which case the target of the event is that
  1113                   pseudo-element's corresponding element), or the empty
  1114                   string if the transition occurred on an element (which
  1115                   means the target of the event is that element).
  1116                 </dd>
  1117               </dl>
  1118             </dd>
  1119             <dt>
  1120               <b>Methods</b>
  1121             </dt>
  1122             <dd>
  1123               <dl>
  1124                 <dt>
  1125                   <code class='method-name'><a id="Events-TransitionEvent-initTransitionEvent" name='Events-TransitionEvent-initTransitionEvent'>initTransitionEvent</a></code>
  1126                 </dt>
  1127                 <dd>
  1128                   <div class='method'>
  1129                     The <code>initTransitionEvent</code> method is used to
  1130                     initialize the value of a <code>TransitionEvent</code>
  1131                     created through the <a
  1132                     href='http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-DocumentEvent'><code>DocumentEvent</code></a>
  1133                     interface. This method may only be called before the
  1134                     <code>TransitionEvent</code> has been dispatched via the
  1135                     <code>dispatchEvent</code> method, though it may be called
  1136                     multiple times during that phase if necessary. If called
  1137                     multiple times, the final invocation takes precedence.
  1138                     <p class="issue">Should new events being created still
  1139                     have init*Event methods?</p>
  1140                     <div class='parameters'>
  1141                       <b>Parameters</b>
  1142                       <div class='paramtable'>
  1143                         <dl>
  1144                           <dt>
  1145                             <code class='parameter-name'>typeArg</code> of type <code>DOMString</code>
  1146                           </dt>
  1147                           <dd>
  1148                             Specifies the event type.<br>
  1149                           </dd>
  1150                           <dt>
  1151                             <code class='parameter-name'>canBubbleArg</code> of type <code>boolean</code>
  1152                           </dt>
  1153                           <dd>
  1154                             Specifies whether or not the event can bubble.<br>
  1155                           </dd>
  1156                           <dt>
  1157                             <code class='parameter-name'>cancelableArg</code> of type <code>boolean</code>
  1158                           </dt>
  1159                           <dd>
  1160                             Specifies whether or not the event's default action can be prevented. Since a TransitionEvent
  1161                             is purely for notification, there is no default action.<br>
  1162                           </dd>
  1163                           <dt>
  1164                             <code class='parameter-name'>propertyNameArg</code> of type <code>DOMString</code>
  1165                           </dt>
  1166                           <dd>
  1167                             Specifies the name of the property associated with the <a href='http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-Event'><code>Event</code></a>.
  1168                             (See the <a href="#Events-TransitionEvent-propertyName">propertyName</a> attribute.)
  1169                           </dd>
  1170                           <dt>
  1171                             <code class='parameter-name'>elapsedTimeArg</code> of type <code>float</code>
  1172                           </dt>
  1173                           <dd>
  1174                             Specifies the amount of time, in seconds, the transition has been running at the time of initialization.
  1175                             (See the <a href="#Events-TransitionEvent-elapsedTime">elapsedTime</a> attribute.)
  1176                           </dd>
  1177                           <dt>
  1178                             <code class='parameter-name'>pseudoElementArg</code> of type <code>DOMString</code>
  1179                           </dt>
  1180                           <dd>
  1181                             Specifies the pseudo-element on which the
  1182                             transition occurred.
  1183                             (See the <a href="#Events-TransitionEvent-pseudoElement">pseudoElement</a> attribute.)
  1184                             <span class="issue">Does adding this additional argument create any compatibility problems?</span>
  1185                           </dd>
  1186                         </dl>
  1187                       </div>
  1188                     </div><!-- parameters -->
  1189                     <div>
  1190                       <b>No Return Value</b>
  1191                     </div>
  1192                     <div>
  1193                       <b>No Exceptions</b>
  1194                     </div>
  1195                   </div><!-- method -->
  1196                 </dd>
  1197               </dl>
  1198             </dd>
  1199           </dl>
  1200         </dd>
  1201       </dl>
  1202       <p>
  1203         There is one type of transition event available.
  1204       </p>
  1205       <dl>
  1206         <dt>
  1207           <b>transitionend</b>
  1208         </dt>
  1209         <dd>
  1210           The <code>transitionend</code> event occurs at the completion of the transition. In the
  1211           case where a transition is removed before completion, such as if the
  1212           transition-property is removed, then the event will not fire.
  1213           <ul>
  1214             <li>Bubbles: Yes
  1215             </li>
  1216             <li>Cancelable: Yes
  1217             </li>
  1218             <li>Context Info: propertyName, elapsedTime
  1219             </li>
  1220           </ul>
  1221         </dd>
  1222       </dl>
  1224       <h2 id="animatable-types"><a id="animation-of-property-types-">
  1225         Animation of property types
  1226       </a></h2>
  1228       <p>
  1229         When interpolating between two values,
  1230         <i>V</i><sub>start</sub> and <i>V</i><sub>end</sub>,
  1231         interpolation is done using the output <i>p</i> of the timing function,
  1232         which gives the portion of the value space
  1233         that the interpolation has crossed.
  1234         Thus the result of the interpolation is
  1235         <i>V</i><sub>res</sub> =
  1236           (1 - <i>p</i>) &sdot; <i>V</i><sub>start</sub> +
  1237           <i>p</i> &sdot; <i>V</i><sub>end</sub>.
  1238       </p>
  1240       <p>
  1241         However, if this value (<i>V</i><sub>res</sub>)
  1242         is outside the allowed range of values for the property,
  1243         then it is clamped to that range.
  1244         This can occur if <i>p</i> is outside of the range 0 to 1,
  1245         which can occur if a timing function is specified
  1246         with a <i>y1</i> or <i>y2</i> that is outside the range 0 to 1.
  1247       </p>
  1249       <p>
  1250         The following describes how each property type undergoes transition or
  1251         animation.
  1252       </p>
  1254       <ul>
  1255         <li>
  1256           <strong>color</strong>: interpolated via red, green, blue and alpha
  1257           components (treating each as a number, see below).
  1258           The interpolation is done between premultiplied colors
  1259           (that is, colors for which the red, green, and blue components
  1260           specified have been multiplied by the alpha).
  1261         </li>
  1262         <li>
  1263           <strong>length</strong>: interpolated as real numbers.
  1264         </li>
  1265         <li>
  1266           <strong>percentage</strong>: interpolated as real numbers.
  1267         </li>
  1268         <li>
  1269           <strong>integer</strong>: interpolated via discrete steps (whole
  1270           numbers). The interpolation happens in real number space and is
  1271           converted to an integer using <code>floor()</code>.
  1272           <span class="issue">
  1273             This floor behavior is inconsistent with SMIL Animation /
  1274             SVG Animation.
  1275           </span>
  1276         </li>
  1277         <li>
  1278           <strong>font weight</strong>: interpolated via discrete steps
  1279           (multiples of 100). The interpolation happens in real number
  1280           space and is converted to an integer by rounding to the
  1281           nearest multiple of 100.
  1282           <span class="issue">
  1283             This round-to-nearest behavior is inconsistent with the
  1284             floor behavior used for integer types, but probably should
  1285             be consistent (one way or the other).
  1286           </span>
  1287         </li>
  1288         <li>
  1289           <strong>number</strong>: interpolated as real (floating point)
  1290           numbers.
  1291         </li>
  1292         <li>
  1293           <strong>transform list</strong>: see 
  1294             CSS Transforms specification [[!CSS3-TRANSFORMS]].
  1295         </li>
  1296         <li>
  1297           <strong>rectangle</strong>: interpolated via the x, y,
  1298           width and height components (treating each as a number).
  1299         </li>
  1300         <li>
  1301           <strong>visibility</strong>: if one of the values is
  1302           ''visible'', interpolated as a discrete step where values of the
  1303           timing function between 0 and 1 map to ''visible'' and other
  1304           values of the timing function (which occur only at the
  1305           start/end of the transition or as a result of ''cubic-bezier()''
  1306           functions with Y values outside of [0, 1]) map to the closer
  1307           endpoint; if neither value is ''visible'' then not interpolable.
  1308         </li>
  1309         <li>
  1310           <strong>shadow</strong>: interpolated via the color, x, y
  1311           and blur components (treating them as color and numbers where
  1312           appropriate). In the case where there are lists of shadows,
  1313           the shorter list is padded at the end with shadows whose
  1314           color is transparent and all lengths (x, y, blur) are 0.
  1315         </li>
  1316         <li>
  1317           <strong>gradient</strong>: interpolated via the
  1318           positions and colors of each stop. They must have the same type
  1319           (radial or linear) and same number of stops in order to be animated.
  1320           <span class="note">Note: [[CSS3-IMAGES]] may extend this
  1321           definition.</span>
  1322         </li>
  1323         <li>
  1324           <strong>paint server</strong> (SVG): interpolation is only supported
  1325           between: gradient to gradient and color to color. They then
  1326           work as above.
  1327         </li>
  1328         <li>
  1329           <strong>list of above types</strong>: If the lists have the
  1330           same number of items, each item in the list is interpolated using the
  1331           rules above. Otherwise the interpolation is determined by the property
  1332           rules. If the property extends its list by repeating values, then this
  1333           repeated form will be used in the interpolation (<code class="property">'background-position'</code>
  1334           is an example of a property that would transition between lists of different lengths). If
  1335           the property does not allow extending its list, then no interpolation
  1336           will occur.
  1337         </li>
  1338         <li>
  1339           <strong>a shorthand property</strong>: If any part of a
  1340           shorthand can be animated, then interpolation is performed as
  1341           if those animatable properties were individually specified.
  1342         </li>
  1343       </ul>
  1345       <p class="issue">Need to add a length-percentage-calc type.</p>
  1347       <p>Future specifications may define additional types that can
  1348       be animated.</p>
  1350       <h2 id="animatable-properties"><a id="animatable-properties-">
  1351         Animatable properties
  1352       </a></h2>
  1354       <!--
  1355       As resolved in
  1356       http://lists.w3.org/Archives/Public/www-style/2011Sep/0497.html
  1357       -->
  1358       <p>For properties that exist at the time this specification was
  1359       developed, this specification defines whether and how they are
  1360       animated.  However, future CSS specifications may define
  1361       additional properties, additional values for existing properties,
  1362       or additional animation behavior of existing values.  In order to
  1363       describe new animation behaviors and to have the definition of
  1364       animation behavior in a more appropriate location, future CSS
  1365       specifications should include an "Animatable:" line in the summary
  1366       of the property's definition (in addition to the other lines
  1367       described in [[CSS21]], <a
  1368       href="http://www.w3.org/TR/CSS21/about.html#property-defs">section
  1369       1.4.2</a>).  This line should say "no" to indicate that a property
  1370       cannot be animated or should reference an animation behavior
  1371       (which may be one of the behaviors in the <a
  1372       href="#animation-of-property-types-">Animation of property
  1373       types</a> section above, or may be a new behavior) to define how
  1374       the property animates.  Such definitions override those given in
  1375       this specification.</p>
  1377       <h3 id="animatable-css"><a id="properties-from-css-">
  1378         Properties from CSS
  1379       </a></h3>
  1381       <p class="issue">Need to define what listing comma-separated
  1382       things here means.  In particular, that they only apply when
  1383       both values fit the type, and that if one of the values is a
  1384       type not listed, or if two of the values are different types,
  1385       then the two values cannot be interpolated.</p>
  1387      <table class="animatable-properties">
  1388        <tr>
  1389          <th>Property Name</th>
  1390          <th>Type</th>
  1391        </tr>
  1392        <tr>
  1393          <td>background-color</td><td>color</tr>
  1394        <tr>
  1395          <td>background-position</td><td>percentage, length</td>
  1396        </tr>
  1397        <tr>
  1398          <td>border-bottom-color</td><td>color</td>
  1399        </tr>
  1400        <tr>
  1401          <td>border-bottom-width</td><td>length</td>
  1402        </tr>
  1403        <tr>
  1404          <td>border-left-color</td><td>color</td>
  1405        </tr>
  1406        <tr>
  1407          <td>border-left-width</td><td>length</td>
  1408        </tr>
  1409        <tr>
  1410          <td>border-right-color</td><td>color</td>
  1411        </tr>
  1412        <tr>
  1413          <td>border-right-width</td><td>length</td>
  1414        </tr>
  1415        <tr>
  1416          <td>border-spacing</td><td>length</td>
  1417        </tr>
  1418        <tr>
  1419          <td>border-top-color</td><td>color</td>
  1420        </tr>
  1421        <tr>
  1422          <td>border-top-width</td><td>length</td>
  1423        </tr>
  1424        <tr>
  1425          <td>bottom</td><td>length, percentage</td>
  1426        </tr>
  1427        <tr>
  1428          <td>clip</td><td>rectangle</td>
  1429        </tr>
  1430        <tr>
  1431          <td>color</td><td>color</td>
  1432        </tr>
  1433        <tr>
  1434          <td>crop <span class="issue">css3-content will likely advance slower than this specification, in which case this definition should move there</span></td><td>rectangle</td>
  1435        </tr>
  1436        <tr>
  1437          <td>font-size</td><td>length, percentage</td>
  1438        </tr>
  1439        <tr>
  1440          <td>font-weight</td><td>font weight</td>
  1441        </tr>
  1442        <tr>
  1443          <td>height</td><td>length, percentage</td>
  1444        </tr>
  1445        <tr>
  1446          <td>left</td><td>length, percentage</td>
  1447        </tr>
  1448        <tr>
  1449          <td>letter-spacing</td><td>length</td>
  1450        </tr>
  1451        <tr>
  1452          <td>line-height</td><td>number, length, percentage</td>
  1453        </tr>
  1454        <tr>
  1455          <td>margin-bottom</td><td>length</td>
  1456        </tr>
  1457        <tr>
  1458          <td>margin-left</td><td>length</td>
  1459        </tr>
  1460        <tr>
  1461          <td>margin-right</td><td>length</td>
  1462        </tr>
  1463        <tr>
  1464          <td>margin-top</td><td>length</td>
  1465        </tr>
  1466        <tr>
  1467          <td>max-height</td><td>length, percentage</td>
  1468        </tr>
  1469        <tr>
  1470          <td>max-width</td><td>length, percentage </td>
  1471        </tr>
  1472        <tr>
  1473          <td>min-height</td><td>length, percentage</td>
  1474        </tr>
  1475        <tr>
  1476          <td>min-width</td><td>length, percentage</td>
  1477        </tr>
  1478        <tr>
  1479          <td>opacity</td><td>number</td>
  1480        </tr>
  1481        <tr>
  1482          <td>outline-color</td><td>color</td>
  1483        </tr>
  1484        <tr>
  1485          <td>outline-offset</td><td>length</td>
  1486        </tr>
  1487        <tr>
  1488          <td>outline-width</td><td>length</td>
  1489        </tr>
  1490        <tr>
  1491          <td>padding-bottom</td><td>length</td>
  1492        </tr>
  1493        <tr>
  1494          <td>padding-left</td><td>length</td>
  1495        </tr>
  1496        <tr>
  1497          <td>padding-right</td><td>length</td>
  1498        </tr>
  1499        <tr>
  1500          <td>padding-top</td><td>length</td>
  1501        </tr>
  1502        <tr>
  1503          <td>right</td><td>length, percentage</td>
  1504        </tr>
  1505        <tr>
  1506          <td>text-indent</td><td>length, percentage</td>
  1507        </tr>
  1508        <tr>
  1509          <td>text-shadow</td><td>shadow</td>
  1510        </tr>
  1511        <tr>
  1512          <td>top</td><td>length, percentage</td>
  1513        </tr>
  1514        <tr>
  1515          <td>vertical-align</td><td>length, percentage</td>
  1516        </tr>
  1517        <tr>
  1518          <td>visibility</td><td>visibility</td>
  1519        </tr>
  1520        <tr>
  1521          <td>width</td><td>length, percentage</td>
  1522        </tr>
  1523        <tr>
  1524          <td>word-spacing</td><td>length, percentage</td>
  1525        </tr>
  1526        <tr>
  1527          <td>z-index</td><td>integer</td>
  1528        </tr>
  1529      </table>
  1531 <p class="issue">
  1532   This list omits the following properties that Gecko can animate, and
  1533   which likely should be included:
  1534   background-size,
  1535   border-*-radius,
  1536   box-shadow,
  1537   column-count,
  1538   column-gap,
  1539   column-rule-color,
  1540   column-rule-width,
  1541   column-width,
  1542   font-size-adjust,
  1543   font-stretch,
  1544   marker-offset,
  1545   text-decoration-color,
  1546   transform,
  1547   transform-origin.
  1548 </p>
  1550      <h3 id="animatable-svg"><a id="properties-from-svg-">
  1551        Properties from SVG
  1552      </a></h3>
  1554      <p>
  1555        All properties defined as animatable in the SVG specification, provided
  1556        they are one of the property types listed above.
  1557       </p>
  1559      <!-- <table>
  1560        <tr>
  1561          <th>Property Name</th><th>Type</th>
  1562        </tr>
  1563        <tr>
  1564          <td>stop-color</td><td>color</td>
  1565        </tr>
  1566        <tr>
  1567          <td>stop-opacity</td><td>float</td>
  1568        </tr>
  1569        <tr>
  1570          <td>fill</td><td>paint server</td>
  1571        </tr>
  1572        <tr>
  1573          <td>fill-opacity</td><td>float</td>
  1574        </tr>
  1575        <tr>
  1576          <td>stroke</td><td>paint server</td>
  1577        </tr>
  1578        <tr>
  1579          <td>stroke-dasharray</td><td>list of numbers</td>
  1580        </tr>
  1581        <tr>
  1582          <td>stroke-dashoffset</td><td>number</td>
  1583        </tr>
  1584        <tr>
  1585          <td>stroke-miterlimit</td><td>number</td>
  1586        </tr>
  1587        <tr>
  1588          <td>stroke-opacity</td><td>float</td>
  1589        </tr>
  1590        <tr>
  1591          <td>stroke-width</td><td>float</td>
  1592        </tr>
  1593        <tr>
  1594          <td>viewport-fill</td><td>color</td>
  1595        </tr>
  1596        <tr>
  1597          <td>viewport-fill-opacity</td><td>color</td>
  1598        </tr>
  1599       </table> -->
  1601 <h2 id="acknowledgments">Acknowledgments</h2>
  1603 <p>Thanks especially to the feedback from
  1604 Tab Atkins,
  1605 Carine Bournez,
  1606 Aryeh Gregor,
  1607 Vincent Hardy,
  1608 Cameron McCormack,
  1609 Alex Mogilevsky,
  1610 and all the rest of the
  1611 <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.</p>
  1613 <h2 id="references">References</h2>
  1615 <h3 class="no-num" id="normative-references">Normative references</h3>
  1616 <!--normative-->
  1618 <h3 class="no-num" id="other-references">Other references</h3>
  1619 <!--informative-->
  1623 <h2 class="no-num" id="property-index">Property index</h2>
  1624 <!-- properties -->
  1628 <h2 class="no-num" id="index">Index</h2>
  1629 <!--index-->
  1631 </body>
  1632 </html>
  1633 <!-- Keep this comment at the end of the file
  1634 Local variables:
  1635 mode: sgml
  1636 sgml-default-doctype-name:"html"
  1637 sgml-minimize-attributes:t
  1638 End:
  1639 -->

mercurial