The bulk of this commit was generated by running:
run-clang-tidy.py \
-checks='-*,llvm-namespace-comment' \
-header-filter=^/.../mozilla-central/.* \
-fix
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.
Currently we use a world transform on the LayerManager. This gets passed to the
screen render target which adjusts the gl transform to accomplish the rotation.
This causes a lot of the system to have to know about the transform.
Instead we can just bake the transform into the root layer's shadow transform.
Everything now mostly just works.
This makes sense since the file no longer contains anything with the
nsTraceRefcnt name in it, and it will allow renaming nsTraceRefcntImpl
back to nsTraceRefcnt.
The bulk of this patch is fixing up pieces of code that infer the resolution
as the inverse of the scaling transform on the root layer. This used to be
how various bits of gfx code obtained the resolution, but now that we can set
the resolution on the actual presShell that contains the content, we can also
just read the resolution from the FrameMetrics directly.
