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[web-animations-1] Initialize start time of scroll animations to zero (#2075) #4842

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merged 6 commits into from
Apr 13, 2020
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[web-animations-1] Initialize start time of scroll animations to zero (#2075) #4842

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1fd6277
Initial change.
ogerchikov Mar 6, 2020
fc80ef2
Initialize start time of scroll animations to zero.
ogerchikov Mar 27, 2020
3df0083
Use monotonically increasing generalization of timelines instead of f…
ogerchikov Apr 2, 2020
441a771
Update play states.
ogerchikov Apr 8, 2020
5d11616
Addressed code review comments.
ogerchikov Apr 9, 2020
4806500
Addressed code review comments.
ogerchikov Apr 10, 2020
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48 changes: 17 additions & 31 deletions web-animations-1/Overview.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -828,31 +828,6 @@ follows:
<var>animation</var> with the <var>did seek</var> flag set to false, and
the <var>synchronously notify</var> flag set to false.

<h4 id="responding-to-a-newly-inactive-timeline">Responding to a newly inactive
timeline</h4>

Issue(2080): With the set of timelines defined in this level of this
specification, this situation is not expected to occur. As
a result, this section will likely be moved to a subsequent level
of this specification.

When the <a>timeline</a> associated with an <a>animation</a>,
<var>animation</var>, becomes newly <a lt="inactive timeline">inactive</a>,
if <var>animation</var>'s <a>previous current time</a> is <a
lt="unresolved">resolved</a>, the procedure to <a>silently set the current
time</a> of <var>animation</var> to <a>previous current time</a> is run.

<div class="note">

This step makes the behavior when an <a>animation</a>'s <a>timeline</a> becomes
<a lt="inactive timeline">inactive</a> consistent with when it is
disassociated with a <a>timeline</a>.
Furthermore, it ensures that the only occasion on which an <a>animation</a>
becomes <a lt="idle play state">idle</a>, is when the procedure to
<a>cancel an animation</a> is performed.

</div>

<h4 id="setting-the-associated-effect" oldids="setting-the-target-effect">Setting the associated effect of an animation</h4>

The procedure to <dfn>set the associated effect of an animation</dfn>,
Expand Down Expand Up @@ -1150,7 +1125,10 @@ as CSS Animations [[CSS-ANIMATIONS-1]].
condition from the following, if any:

<div class="switch">

: If |animation|'s <a>current time</a> is <a>unresolved</a>,
<a>start time</a> is <a>unresolved</a>, the associated <a>timeline</a>
is finite and the <var>auto-rewind</var> flag is true
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:: Set <var>animation</var>'s <a>start time</a> to zero.
: If |animation|'s [=effective playback rate=] &gt; 0,
the <var>auto-rewind</var> flag is true and <em>either</em>
<var>animation</var>'s:
Expand Down Expand Up @@ -1185,9 +1163,10 @@ as CSS Animations [[CSS-ANIMATIONS-1]].
1. Cancel that task.
1. Set <var>has pending ready promise</var> to true.

1. If the following three conditions are <em>all</em> satisfied:
1. If the following four conditions are <em>all</em> satisfied:

* |animation|'s [=hold time=] is [=unresolved=], and
* |animation|'s [=start time=] is [=unresolved=], and
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I'm not quite sure I follow this but I think it probably relates back to my comment here.

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This is required to avoid early exit if start time is set.

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I'm not sure about this. Won't this mean that calling play() on an already running animation makes it become pending? (Since the hold time is unresolved in that case but the start time is not -- previous we would abort the procedure in that case but now we won't.)

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We could probably fix the above by simply adding some extra flag to this procedure to indicate if we made a change that means that we need to wait for a pending task to run. This might be a more elegant way, however.

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Added the flag.

* |aborted pause| is false, and
* |animation| does <em>not</em> have a [=pending playback rate=],

Expand Down Expand Up @@ -1324,6 +1303,9 @@ follows:
perform the steps according to the first matching condition from below:

<div class="switch">
: If |animation|'s <a>start time</a> is <a>unresolved</a> and the
associated <a>timeline</a> is finite
:: Let <var>animation</var>'s <a>start time</a> be zero.
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(Presumably whatever we decide for the play procedure will also apply here.)

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Changed similarly to Play.


: If <var>animation</var>'s [=playback rate=] is &ge; 0,
:: Let <var>animation</var>'s <a>hold time</a> be zero.
Expand All @@ -1345,10 +1327,14 @@ follows:
1. If <var>has pending ready promise</var> is false,
set <var>animation</var>'s <a>current ready promise</a> to
<a>a new promise</a> in the <a>relevant Realm</a> of <var>animation</var>.
1. Schedule a task to be executed at the first possible moment after
the user agent has performed any processing necessary to suspend
the playback of
<var>animation</var>'s <a>associated effect</a>, if any.
1. Schedule a task to be executed at the first possible moment where
<em>both</em> of the following conditions are true:
* the user agent has performed any processing necessary to suspend
the playback of <var>animation</var>'s <a>associated effect</a>, if any.

* the animation is associated with a <a>timeline</a> that is not
<a lt="inactive timeline">inactive</a>.

The task shall perform the following steps:

1. Let <var>ready time</var> be the time value of the timeline associated
Expand Down