AnimationCollection keeps a TimeStamp that records the refresh driver time when
the animation style rule was last updated. This is used for two purposes:
1. To determine when the style rule is out of date.
2. For animations that are partially throttled on the main thread, e.g.
transform animations that affect the scrollable region which we update every
200ms on the main thread.
In this bug we are removing all the overlapping bits of state used to track if
animations are up-to-date or not and replacing them with the hashmap stored on
the EffectCompositor which tracks which animations are currently in need of an
update. As a result, we would like to remove this style rule refresh time.
However, we will need something for case (2) from above.
This patch adds an animation rule refresh time to the EffectSet purely for the
purposes of partially-throttled animations so that we can later remove the style
rule refresh time from AnimationCollection.
As we gradually move logic from layout/style/AnimationCommon.cpp to
dom/animation/EffectSet and EffectCompositor it makes sense to let this class
live in its own file inside dom/animation where it is used.
--HG--
extra : rebase_source : aed0632a19800e0ef9d8fe1d03d0364bf1ccc4dc
This is needed in order to support script-generated animations since they do not
belong to any AnimationCollection.
This patch adopts the naming "animation rule" over "style rule". Currently we
are inconsistent about this (e.g. GetAnimationRule vs EnsureStyleRuleFor).
We don't do a mass rename here but just a few places near where we're touching.
Many of the other references to "style rule" will be revised in this bug or
related bugs so we can fix those references when we come to them.
--HG--
extra : rebase_source : e1f824029b39960915e056328447de256b6c1c6d
There are three situations when the cascade results of effects needs to be
updated.
1. The sets of effects (animations) has changed.
2. One or more effects have changed their "in effect" status.
3. Other style properties affecting the element have changing meaning that
animations applied at the animations-level of the cascade may now be
overridden or become active again.
We want to detect these situations so we can avoid updating the cascade when
none of these possibilities exist.
Currently we handle case 1 by calling UpdateCascadeResults at the appropriate
point in nsAnimationManager and nsTransitionManager when we build
animations/transtiions.
Case 2 only affects animations (since whether transitions are in effect or not
makes no difference to the cascade--they have a lower "composite order" than
animations and never overlap with each other so they can't override anything).
As a result, we handle it by adding a flag to CSSAnimation to track when an
animation was in effect last time we checked or not.
For case 3, we take care to call UpdateCascadeResults when the style context
changed in nsAnimationManager::CheckAnimationRule (called from
nsStyleSet::GetContext).
We want to generalize this detection to handle script-generated animations too.
In order to do that this patch introduces a flag to EffectSet that we will use
to mark when the cascade needs to be updated in cases 1 and 2. This patch also
sets the flag when we detect case 1. A subsequent patch sets the flag for
case 2.
Case 3 is more difficult to detect and so we simply maintain the existing
behavior of making nsAnimationManager::CheckAnimationRule unconditionally
update the cascade without checking if the "needs update" flag is set.
--HG--
extra : rebase_source : fc56b1bb5a98ae78b93a179c7a3b8af4724a06a1
This is so that when we have code like:
elem.animate({ opacity: 0 }, 1000)
the resulting Animation object is kept alive by |elem| based on the following
ownership chain:
elem --(strong)--> KeyframeEffectReadOnly --(strong)--> Animation
Now, there is an ownership cycle introduced here because KeyframeEffectReadOnly
objects also store owning references to their target elements. This is broken
when the Animation finishes (if it does not fill forwards) or is cancelled
since either event will trigger a call to
KeyframeEffectReadOnly::UpdateTargetRegistration.
If the Animation fills forwards, the resource will not be released until
it is cancelled. For Animations corresponding to CSS Animations / CSS
Transitions this happens when the Element is unbound or when the corresponding
style property is updated causing the animation to be replaced or removed.
For the general case of script-generated animations, however, this cycle won't
be broken until the Element is unbound and all external references to the
Animation or KeyframeEffectReadOnly are dropped.
It's unfortunate that we can't more aggressively prune these objects but it's
what the spec currently says. I've posted to the mailing list[1] about this but
have yet to find a good solution.
[1] https://lists.w3.org/Archives/Public/public-fx/2015OctDec/0029.html