Also NotifyRenderingChanged was on the canvas background color item, not the background image item.
Bug 818643 was a problem where the cache didn't get purged enough, but the fix meant we basically always purged the cached and never got to use it, making it useless. It meant that we purged the cache anytime the item has any type of invalidation whatsoever, even if the item would be drawn the same but the layer contents needed to be invalidated so that it would be redrawn (ie due to staying at the same position on screen but a different position in the layer).
This is really hacky, but NotifyRenderingChanged is only observed on one type of display item. So we just isolate the case where the only thing that changed is the offset (due to scrolling) and skip the NotifyRenderingChanged in that case.
Fix the size check in nsDisplayBackground::ShouldFixToViewport so that async
scrolling of fixed backgrounds works correctly when zoomed in on Firefox
Mobile. Also make IsFixedItem in nsDisplayList public and use it in
FrameLayerBuilder, so that fixed items are determined and treated consistently.
Separate out background layers into separate display-list items, so that
backgrounds that are a mix of fixed and non-fixed layers will be treated
individually.
Currently we return an extra out parameter on GetOpaqueRegion. This is ugly and it's also going to be inefficient
because in a followup patch I'm going to avoid calls to GetOpaqueRegion, but we still need to know whether the item
needs a transparent surface. So this patch removes that out parameter. Instead, we rely on the fact that only
Windows' glass-window-background display item needs to force a transparent surface, and there can only be one
of those per window. So we store a reference to it in the nsDisplayListBuilder if there is one, and then we can
efficiently tell if any leaf display item is the one that forces a transparent surface. For display items that
wrap a list, we continue to store whether they need to force a transparent surface in a boolean in the list.
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.
Implement GetChildList(ChildListID) and GetChildLists(nsTArray<ChildList>*)
for various frame classes. Remove GetAdditionalChildListName(PRInt32)
methods and associated macros and list index constants.
