If we set a transform in push_stacking_context, it changes the internal
WebRender behaviour to make that stacking context a reference frame, and
things inside it are positioned differently. This is true even if the
transform is an identity transform.
In most cases we are hitting this and sending an identity transform
through, when in fact we want to be sending a None value to WebRender so
that it doesn't create reference frames. This is a partial fix, a proper
fix will be done in bug 1345577 by separating the CSS transform from the
other transforms that FrameLayerBuilder invents.
MozReview-Commit-ID: ElSs3hFMD2D
The only remaining callers of RelativeToParent() are in
StackingContextHelper itself, which we can remove now by having the SCH
take a parent SCH and use it instead of RelativeToParent(). This patch
implements this change.
This makes a failing test pass, because of how preserve-3d container
layers work. Specifically, preserve-3d container layers render their
descendants in z-order, not in tree order. If those children were assuming
that their parent had already pushed a stacking context, that assumption
may have been false because the parent might have not yet been rendered
because of z-ordering. By using the StackingContextHelper chain instead
of the layer tree ancestry, we fix the stacking-context-relative coordinates
being used in the descendant subtree of preserve-3d container layers.
MozReview-Commit-ID: HzZvBuAlMdB
This updates more code that was using RelativeToParent() to use the
stacking context helper's ToRelativeWr* functions instead. This get us
closer to breaking the assumption that the WR stacking context order maps
1:1 to the layer tree structure.
MozReview-Commit-ID: HQrbvCgPOW4
This uses the StackingContextHelper and typed helper functions in
WebRenderLayer to simplify WebRenderTextLayer::RenderLayer. It also
removes the implicit assumption in WebRenderTextLayer that the parent
layer pushed a stacking context, which is an assumption we will
probably break in the future.
MozReview-Commit-ID: CARoGVQd56i
This is needed in part 3 to update WebRenderTextLayer::RenderLayer, so
that it no longer assumes the parent container layer has pushed a
stacking context, and instead explicitly uses the StackingContextHelper.
MozReview-Commit-ID: 9twUmDgUipX
This class is a RAII class that can be used to push a stacking context
with properties from a WebRenderLayer. It can also then be used to
convert rects in the layer coordinate system to be relative to the
stacking context, which is what we want for passing to WR.
MozReview-Commit-ID: 1WVrfRYqLqc
