[web-animation-2] Making currentTime and startTime CSSNumerish

web-animations-2/Overview.bs

@@ -171,11 +171,11 @@ Add:
 > 1.  If the [=iteration duration=] is auto, then perform the following steps.
 >     *   Set [=start delay=] and [=end delay=] to 0, as it is not
 >         possible to mix time and proportions.
->         
+>
 >         Note: Future versions may allow these properties to be assigned
 >         percentages, at which point the delays are only to be ignored if
 >         their values are expressed as times and not as percentages.
->         
+>
 >     Otherwise:
 >          1. Let <var>total time</var> be equal to |end time|
 >          1. Set [=start delay=] to be the result of evaluating
@@ -256,7 +256,7 @@ follows:
 
                     :   If |previous play state| is 'paused':
 
-                    :: If |previous progress| is resolved:
+                    ::  If |previous progress| is resolved:
 
                         1.  Set the flag |reset current time on resume| to true.
                         1.  Set [=start time=] to unresolved.
@@ -338,6 +338,36 @@ descendant effects and custom effects such that the first condition is:
 >     effect</a> or executing any <a>custom effects</a> associated with an
 >     <a>animation effect</a>.
 
+<h4 id='validating-a-css-numberish-time'>Validating a CSSNumberish time</h4>
+
+The procedure to <dfn>validate a CSSNumberish time</dfn> for an input
+value of <var>time</var> is based on the first condition that matches:
+
+<dl class="switch">
+
+    :   If <em>all</em> of the following conditions are true:
+
+        *   The animation is associated with a [=progress-based timeline=], and
+        *   <var>time</var> is not a CSSNumeric value with percent units:
+
+    ::  <a>throw</a> a <span class="exceptionname">TypeError</span>.
+    ::  return false;
+
+    :   If <em>all</em> of the following conditions are true:
+
+        *   The animation is not associated with a [=progress-based timeline=],
+            and
+        *   <var>time</var> is a CSSNumericValue, and
+        *   the units of time are not <a type lt="<time>">duration units</a>:
+
+    ::  <a>throw</a> a <span class="exceptionname">TypeError</span>.
+    ::  return false.
+
+    :   Oterwise
+    ::  return true.
+
+</dl>
+
 
 <h4 id='setting-the-current-time-of-an-animation'>Setting the current time of an
 Animation</h4>
@@ -357,31 +387,39 @@ an animation, <var>animation</var>, to <var>seek time</var> is as follows:
 
     1.   Abort these steps.
 
-1.  Update either <var>animation</var>'s <a>hold time</a> or
-    [=start time=] as follows:
+    1.  Let <var>valid seek time</var> be the result of running the
+        [=validate a CSSNumberish time=] procedure with <var>seek time</var>
+        as the input.
 
-    <dl class="switch">
+    1.  If <var>valid seek time</var> is false, abort this procedure.
 
-        :   If <em>any</em> of the following conditions are true:
+    1.  Update either <var>animation</var>'s <a>hold time</a> or
+        [=start time=] as follows:
 
-            *   <var>animation</var>'s <a>hold time</a> is
-                <a lt="unresolved">resolved</a>, or
-            *   <var>animation</var>'s [=start time=]
-                is <a lt="unresolved">unresolved</a>, or
-            *   <var>animation</var> has no associated <a>timeline</a> or the
-                associated <a>timeline</a> is
-                <a lt="inactive timeline">inactive</a>, or
-            *   <var>animation</var>'s [=playback rate=] is 0,
+        <dl class="switch">
 
-        ::  Set <var>animation</var>'s <a>hold time</a> to <var>seek time</var>.
+            :   If <em>any</em> of the following conditions are true:
 
-        :   Otherwise,
-        ::  Set <var>animation</var>'s [=start time=] to the result of evaluating
-            <code>|timeline time| - (|seek time| / [=playback rate=])</code>
-            where <var>timeline time</var> is the current <a>time value</a>
-            of <a>timeline</a> associated with <var>animation</var>.
+                *   <var>animation</var>'s <a>hold time</a> is
+                    <a lt="unresolved">resolved</a>, or
+                *   <var>animation</var>'s [=start time=]
+                    is <a lt="unresolved">unresolved</a>, or
+                *   <var>animation</var> has no associated <a>timeline</a> or
+                    the associated <a>timeline</a> is
+                    <a lt="inactive timeline">inactive</a>, or
+                *   <var>animation</var>'s [=playback rate=] is 0,
 
-    </dl>
+            ::  Set <var>animation</var>'s <a>hold time</a> to
+                <var>seek time</var>.
+
+            :   Otherwise,
+            ::  Set <var>animation</var>'s [=start time=] to the result of
+                evaluating
+                <code>|timeline time| - (|seek time| / [=playback rate=])</code>
+                where <var>timeline time</var> is the current <a>time value</a>
+                of <a>timeline</a> associated with <var>animation</var>.
+
+        </dl>
 
 1.  If <var>animation</var> has no associated <a>timeline</a> or the associated
     <a>timeline</a> is <a lt="inactive timeline">inactive</a>,
@@ -423,6 +461,12 @@ The procedure to <dfn>set the start time</dfn>
 of <a>animation</a>, <var>animation</var>, to <var>new start time</var>,
 is as follows:
 
+1.  Let <var>valid start time</var> be the result of running the
+    [=validate a CSSNumberish time=] procedure with
+    <var>new start time</var> as the input.
+
+1.  If <var>valid start time</var> is false, abort this procedure.
+
 1.  Let <var>timeline time</var> be the current <a>time value</a> of the
     <a>timeline</a> that <var>animation</var> is associated with.
     If there is no <a>timeline</a> associated with <var>animation</var> or the
@@ -2018,6 +2062,44 @@ partial interface AnimationTimeline {
 
 </div>
 
+<h3 id="the-animation-interface">The <code>Animation</code> interface</h3>
+
+Update the startTime and currentTime of the Animation interface as follows:
+
+<pre class="idl">
+[Exposed=Window]
+partial interface Animation : EventTarget {
+    attribute CSSNumberish?       startTime;
+    attribute CSSNumberish?       currentTime;
+};
+</pre>
+
+Replace [=start time=] and [=current time=] attribute descriptions with:
+
+<div class='attributes'>
+
+:   <dfn attribute for=Animation>startTime</dfn>
+::  Update the description as:
+
+    > The [=start time=] of this animation. When associated with a
+    > [=progress-based timeline=], [=start time=] must be returned as a
+    > {{CSSNumericValue}} with percent units. Otherwise [=start time=] must be
+    > returned as a double value, representing the time in units of
+    > milliseconds. Setting this attribute updates the [=start time=] using the
+    > procedure to <a>set the start time</a> of this object to the new value.
+
+:   <dfn attribute for=Animation>currentTime</dfn>
+::  update the description as:
+
+    > The <a>current time</a> of this animation. When associated with a
+    > [=progress-based timeline=], <a>current time</a> must be returned as a
+    > {{CSSNumericValue}}. with percent units. Otherwise <a>current time</a>
+    > must be returned as a double value, representing the time in units of
+    > milliseconds. Setting this attribute follows the procedure to
+    > <a>set the current time</a> of this object to the new value.
+
+</div>
+
 <h3 id="the-animationeffect-interface">The <code>AnimationEffect</code> interface</h3>
 
 <pre class='idl'>