We will eventually use this in place of the various state flags stored on
AnimationCollection (e.g. mStyleRuleRefreshTime, mStyleChanging,
mHasPendingAnimationRestyle) as well as to do a more targetted update in
FlushAnimations and AddStyleUpdatesTo.
Since we want to track elements needing a restyle on EffectCompositor we need
to scope it to an nsPresContext rather than just making if a collection of
static methods.
This patch just moves a piece of functionality from
AnimationCollection::EnsureStyleRuleFor to the EffectCompositor. In subsequent
bugs we will move more and more of this functionality across until this
logic is fully contained in the EffectCompositor.
This restores the code removed in part 3 but adjusts it to iterate over
an effect set instead of an AnimationCollection. It also adds an early return
for the case where no compositor-animatable properties are found.
This added method should behave in an equivalent manner to the existing
CommonAnimationManager::GetAnimationsForCompositor except for the following
differences:
* It uses the EffectSet attached to a target element rather than one of the
AnimationCollection object on the owning element.
* It returns an array of Animation objects consisting of only those Animations
that actually have the specified property as opposed to the
AnimationCollection consisting of *all* CSS animations or *all* CSS
transitions for the element regardless of whether they run on the compositor
or not.
It may not be obvious why these two methods otherwise behave in an equivalent
fashion so the following explains how the existing code is mirrored in the new
method.
The existing code is as follows:
> AnimationCollection*
> CommonAnimationManager::GetAnimationsForCompositor(const nsIFrame* aFrame,
> nsCSSProperty aProperty)
> {
> AnimationCollection* collection = GetAnimationCollection(aFrame);
> if (!collection ||
> !collection->HasCurrentAnimationOfProperty(aProperty) ||
> !collection->CanPerformOnCompositorThread(aFrame)) {
> return nullptr;
> }
>
> // This animation can be done on the compositor.
> return collection;
> }
The new EffectCompositor::GetAnimationsForCompositor begins with two checks
performed at the beginning of CanPerformOnCompositorThread: the checks for
whether async animations are enabled or not and whether the frame has refused
async animations since these are cheap and it makes sense to check them first.
The next part of EffectCompositor::GetAnimationsForCompositor checks if there is
an EffectSet associated with the frame. This is equivalent to the check whether
|collection| is null or not above.
Following, we iterate through the effects in the EffectSet.
We first check if each effect is playing or not. In the above code,
HasCurrentAnimationOfProperty only checks if the effect is *current* or not.
However, CanPerformOnCompositorThread will only return true if it finds an
animation that can run on the compositor that is *playing*. Since playing is
a strict subset of current we only need to perform the more restrictive test.
Next we check if the effect should block running other animations on the
compositor. This is equivalent to the remainder of CanPerformOnCompositorThread.
Note that the order is important here. Only playing animations should block
other animations from running on the compositor. Furthermore, this needs to
happen before the following step since animations of property other than
|aProperty| can still block animations from running on the compositor.
Finally, we check if the effect has an animation of |aProperty|. This is
equivalent to the remainder of HasCurrentAnimationOfProperty.
If all these checks succeed, we add the effect's animation to the result to
return.
