`memmove` was showing up high in the profile when concatenating and
shorting display lists. This change drastically reduces the `memmove`
cost in exchange for some minor additional allocation cost.
Instead of producing a tree of stacking contexts, display list
generation now produces a flat list of display items and a tree of
stacking contexts. This will eventually allow display list construction
to produce and modify WebRender vertex buffers directly, removing the
overhead of display list conversion. This change also moves
layerization of the display list to the paint thread, since it isn't
currently useful for WebRender.
To accomplish this, display list generation now takes three passes of
the flow tree:
1. Calculation of absolute positions.
2. Collection of a tree of stacking contexts.
3. Creation of a list of display items.
After collection of display items, they are sorted based upon the index
of their parent stacking contexts and their position in CSS 2.1
Appendeix E stacking order.
This is a big change, but it actually simplifies display list generation.
absolutely-positioned flows separately when storing overflow.
This code dates back to the time when absolutely positioned flows were
ignored by all of their ancestors up to the containing block. This
hasn't been true for at least a year.
Closes#9306.
Closes#9309.
Is a partial fix for #9308.
There wasn't a good way to split this up, unfortunately.
With this change, the only remaining usage of the Servo-specific structures is
in layout_task, where the root node is received from the script task. \o/
Use the PrintTree utility to improve the readability of flow tree
dumps. Blocks and fragments are now split over two dump levels, because
otherwise they are impenetrable. Also start printing the restyle damage of
fragments.
Remove DisplayListBuildingResult
Always produce a DisplayList when processing nodes for display list
construction. StackingContexts are now added to the positioned content
section of DisplayLists. This makes the code a bit simpler and opens up
the possibility of producing a StackingContext in another section of
the DisplayList. This doesn't change behavior, but is a cleanup
prerequisite for proper inline stacking context support.
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This flag is no longer necessary, because stacking contexts can now
create layers lazily for content that needs to be stacked above a
layer. This should reduce the number of layers on pages, hopefully
reducing overdraw.
Always produce a DisplayList when processing nodes for display list
construction. StackingContexts are now added to the positioned content
section of DisplayLists. This makes the code a bit simpler and opens up
the possibility of producing a StackingContext in another section of
the DisplayList. This doesn't change behavior, but is a cleanup
prerequisite for proper inline stacking context support.
Mix stacking contexts into the positioned content list
Sometimes positioned content needs to be layered on top of stacking
contexts. The layer synthesis code can do this, but the current design
prevents it because stacking contexts are stored in a separate struct
member. In order to preserve tree order, mix stacking contexts into the
positioned content list, by adding a new StackingContextClass
DisplayItem. Such items do not have a base DisplayItem.
In some ways this simplifies the code, because we no longer have to
have a separate code path in the StackingContextLayerCreator.
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Sometimes positioned content needs to be layered on top of stacking
contexts. The layer synthesis code can do this, but the current design
prevents it because stacking contexts are stored in a separate struct
member. In order to preserve tree order, mix stacking contexts into the
positioned content list, by adding a new StackingContextClass
DisplayItem. Such items do not have a base DisplayItem.
In some ways this simplifies the code, because we no longer have to
have a separate code path in the StackingContextLayerCreator.
Fixes#7779.
Fixes#7983.
Fixes#8122.
Fixes#8310.
Flows never care about their own text-align, only the text-align of
their parent; change the text-align flags to account for that. Make the
"align descendants" rule use the flags instead of the current node's style.
Fixes#7301.
Currently pseudo-elements, like the fragments created for ::before and
::after, with layers will have the same LayerId as the body of their
owning fragments. Instead all LayerIds should be unique.
Fixes#2010.
StackingContexts that should be painted on top of StackingContexts that
are already layerized should automatically get their own layer. This
will ensure proper painting order.
account.
This necessitated changing overflow to be calculated by the parent flow
if relatively positioned children are present. That is because the
overflow regions cannot be calculated without knowing relative offsets,
which themselves cannot be calculated without knowing the parent size
(because of percentages). To accomplish this without sacrificing
parallelism in the non-relative case, this patch splits overflow into
"early" and "late" computation. Late overflow computation cannot be
parallelized across children, while early overflow computation can.
Makes the "Apple Music" text show up over the full-bleed promotional
background on apple.com.
