This patch does several things. Sorry.
In BuildDisplayList implementations, instead of wrapping display items in nsDisplayClip, we
push clip state onto the nsDisplayListBuilder and give the display items an
explicit clip when they're created.
In FrameLayerBuilder, we use the explicit clips we find on display items instead of
computing our own.
We remove nsDisplayClip and everything that depends on it.
We remove ExplodeAnonymousChildLists. With nsDisplayClip gone, and
nsDisplayOptionEventGrabber removed in a previous patch, there are no
anonymous child lists.
nsDisplayItem::TryMerge implementations need to make sure they have the same
clip before being merged.
I ripped out the part of PruneDisplayListForExtraPage that adjusts clip rects.
As far as I can tell, it isn't actually necessary.
Previously we snapped the results of nsDisplayItem::GetBounds and
nsDisplayItem::GetOpaqueRegion internally. By tracking which display items were
inside transforms, we disabled snapping quite conservatively whenever an ancestor
had a transform, which is undesirable.
With this patch, we don't snap inside GetBounds or GetOpaqueRegion, but just return
a boolean flag indicating whether the item will draw with snapping or not. This flag
is conservative so that "true" means we will snap (if the graphics context has a transform
that allows snapping), but "false" means we might or might not snap (so it's always safe
to return false).
FrameLayerBuilder takes over responsibility for snapping item bounds. When it converts
display item bounds to layer pixel coordinates, it checks the snap flag returned from
the display item and checks whether the transform when we draw into the layer will be
a known scale (the ContainerParameters scale factors) plus integer translation. If both
are true, we snap the item bounds when converting to layer pixel coordinates. With
this approach, we can snap item bounds even when the items have ancestors with active
transforms.
layout-mentor: bz (mucho thanks!)
We make html canvas frame a container and render frames for its content which makes a lot of what we need for accessibility "just work".
layout-mentor: bz (mucho thanks!)
We make html canvas frame a container and render frames for its content which makes a lot of what we need for accessibility "just work".
This lets us avoid clamping the scale in more situations. We should only clamp the scale when we think
the scale is changing due to a changing transform --- the goal of clamping is to not have to redraw the content
too often when the content is zooming in or out.
This patch shouldn't change any behavior. It just passes the ContainerParameters around, which will contain scale factors that should have been
applied when BuildLayer returns a ContainerLayer.
This patch also adds an aTransform parameter to BuildContainerLayerFor, which nsDisplayTransform uses to set the
transform for the ContainerLayer. This way BuildContainerLayerFor knows what the container's transform is going to be
before constructing the children, which in the next patch will let us construct the children with the right resolution.
