The untransformation is done using the newly added UntransformTo() functions
which call Matrix4x4::ProjectRectBounds(), which returns an empty rectangle
if the result is not at least partially on the positive side of the w = 0 plane.
UntransformTo() returnis the transformed rectangle if it's not empty, and
Nothing() otherwise, making callers check for this case.
The patch also adds some assertions to places where we apply transforms we
know should be 2D (and thus didn't switch to use UntransformTo()), checking
that the transforms are in fact 2D.
We are trying to adjust for the async transform that gets applied to the scrollable container layer by applying a transform to the scrollbar layer. That means we also need to adjust our clip rect. The resolution compensation is not done for this reason (compensating for a transform on an ancestor layer), hence we don't need to adjust the clip rect for the resolution compensation.
The root scrollbars will no longer be a descendant of the layer with their corresponding frame metrics. But scrollbars for root scrollables still need adjustment for the resolution.
We still use the descendant check for the code which needs to be run if the scrollbars are a descendant of the layer with their corresponding frame metrics so that non-containerless root scrolling still works the same way.
The ref layer comes from the parent process, and hence a different scrollid space. If the scrollid on it's metrics happen to match a scrollbar from the child process we have a problem.
Containerless scrolling means that the pan zoom controller applies it's transforms (to compensate for differences between the state of layout the last time we painted and the current state as composited to the screen) to the layers that are scrolled instead of the container layer that contains the layers that scroll.
When running test_animations_omta.html there is a zoom of 1.306122 applied, and the page is scrolled down to 67 screen pixels (before the test starts, not sure why exactly). Gecko scrolls as close to 67 screen pixels as it can: 67/1.306122 = 51.29689 css pixels, which is 3077.813 appunits. Gecko scrolls to 3078 app units. When AsyncCompositionManager::TransformScrollableLayer runs we calculate the scroll position of gecko and the current scroll position that the pan zoom controller is using. Since there are no async pan or zoom operations taking place these should match. However when the gecko scroll position is calculated we get 3078/60*1.306122 = 67.0040586. So it applies a transform of 0.0040586 to the container layer for the transform that test_animations_omta.html is animating off main thread. When test_animations_omta.html reads the transform of this layer it fails because it's expecting 0 and 0.0040586 is outside of it's epsilon for considering it to be close enough.
Containerless scrolling means that the pan zoom controller applies it's transforms (to compensate for differences between the state of layout the last time we painted and the current state as composited to the screen) to the layers that are scrolled instead of the container layer that contains the layers that scroll.
When running test_animations_omta.html there is a zoom of 1.306122 applied, and the page is scrolled down to 67 screen pixels (before the test starts, not sure why exactly). Gecko scrolls as close to 67 screen pixels as it can: 67/1.306122 = 51.29689 css pixels, which is 3077.813 appunits. Gecko scrolls to 3078 app units. When AsyncCompositionManager::TransformScrollableLayer runs we calculate the scroll position of gecko and the current scroll position that the pan zoom controller is using. Since there are no async pan or zoom operations taking place these should match. However when the gecko scroll position is calculated we get 3078/60*1.306122 = 67.0040586. So it applies a transform of 0.0040586 to the container layer for the transform that test_animations_omta.html is animating off main thread. When test_animations_omta.html reads the transform of this layer it fails because it's expecting 0 and 0.0040586 is outside of it's epsilon for considering it to be close enough.
This patch is a fairly minimal rename of the AnimationPlayer interface. It
leaves a bunch of local variables and helper classes still using the word
"player". These will be addressed in subsequent patches that don't require DOM
peer review.
We define KeyframeEffectReadonly in KeyframeEffect.cpp since Web Animations also
defines KeyframeEffect and when we come to implement that I expect we'll define
it in the same class, maybe even using the same object.
This patch also adds a few missing includes in places where
KeyframeEffectReadonly is used so that we're not just cargo-culting it in.
