This applies the same pattern used for background-clip: text (commit
f2e6f70fbb).
Results in visible performance improvement in Discord app where
previously, according to profiles, we spent lots of time allocating
surfaces for masks.
Previously, both mask and clip-path were rendered to separate mutable
Gfx::Bitmap objects which forced CPU rasterization. They were then
combined using a CPU pixel-by-pixel operation before being returned
as an ImmutableBitmap.
Instead of including mask in the final bitmap as already rasterized
images, we now use display lists which opens opportunity to utilize
GPU if available.
Bitmap::apply_mask() and ApplyMaskBitmap display list command are no
longer used and have been removed.
Effects (opacity, blend mode, filters) must be applied in the parent's
coordinate space, before the element's transform. Previously this was
handled by manually switching to the parent's visual context when
applying effects at paint time.
By adding EffectsData to AccumulatedVisualContext and positioning it
before TransformData in the chain, effects are now naturally applied in
the correct order during display list replay, eliminating the special
case in StackingContext::paint().
For SVG filters that can generate content from empty elements (feFlood,
feImage, feTurbulence), a transparent FillRect command is emitted to
trigger the filter through the same AVC pipeline.
This moves filter resolution from display list recording time to
resolve_paint_properties(), caching the resolved values in CSS pixels
on PaintableBox. Device pixel conversion is now deferred until paint
time via to_gfx_filter().
This follows the existing pattern used for other paint-only properties
like box shadows and border radii.
Integrate AccumulatedVisualContext with display list recording and
playback. This is the main commit of the refactoring that delivers the
architectural improvements enabled by AccumulatedVisualContext.
Recording changes:
Each display list command now stores a single
RefPtr<AccumulatedVisualContext> instead of separate scroll_frame_id
and ClipFrame. The recorder simply captures the current accumulated
context when appending commands.
The before_paint()/after_paint() hooks that pushed/popped scroll frame
IDs are replaced by directly setting accumulated_visual_context on the
recorder before painting each element.
Playback changes:
The display list player now uses LCA (Lowest Common Ancestor) based
traversal to switch between visual contexts efficiently. When
transitioning from context A to context B:
1. Find the LCA of A and B in the context tree
2. Pop (restore) states back to the LCA depth
3. Push (save + apply) states from LCA down to B
This approach minimizes redundant save/restore operations. For example,
when rendering siblings that share a common scroll container, the
player keeps that scroll state applied and only switches the divergent
parts of their context chains.
Key deletions:
- Remove translate_by() from all 45 display list commands - commands
are now immutable
- Remove transform/perspective fields from PushStackingContext -
transforms are tracked via AccumulatedVisualContext
- Remove push_scroll_frame_id()/pop_scroll_frame_id() from
DisplayListRecorder
- Remove before_paint()/after_paint() hooks from Paintable
- Merge ApplyOpacity, ApplyCompositeAndBlendingOperator, ApplyFilter
into single ApplyEffects command
Stacking context painting changes:
The StackingContext::paint() method is significantly simplified.
Instead of building a PushStackingContextParams struct with transform
matrices and pushing/popping stacking contexts, it now:
1. Sets the accumulated visual context (which already contains
transforms)
2. Applies effects (opacity, blend mode, filters) if needed
3. Applies clip path if needed
4. Paints the content
5. Restores state
The visual state management that was interleaved throughout the
painting code is now handled uniformly by the context tree.
PaintContext dates back to a time when display lists didn't exist and it
truly represented "paint context". Renaming it to better align with its
current role.
83b6bc4 went too far by forbidding SVGSVGElement from establishing a
stacking context. This element type does follow the behavior of CSS
boxes, unlike inner SVG elements like `<rect>`, `<circle>`, etc., which
are not supposed to be aware of concepts like stacking contexts,
overflow clipping, scroll offsets, etc.
This change allows us to delete overrides of `before_paint()` and
`after_paint()` in SVGPaintable and SVGSVGPaintable, because display
list recording code has been rearranged to take care of clipping and
scrolling before recursing into SVGSVGPaintable descendants.
`Screenshot/images/css-transform-box-ref.png` expectation is updated and
fixes a bug where a rectangle at the very bottom of the page was not
clipped correctly.
`Screenshot/images/svg-filters-lb-website-ref.png` has a more subtle
difference, but if you look closely, you’ll see it matches other
browsers more closely now.
Previously, we always applied the enclosing clip rectangle for all paint
phases except overlays, and the own clip rectangle for the background
and foreground phases. The problem is that applying a clip rectangle
means emitting an AddClipRect display list item for each clip rectangle
in the containing block. With this change, we choose whether to include
the own clip based on the paint phase and this way avoid emitting
AddClipRect for enclosing clip rectangles twice.
These were only used in SVGSVGPaintable to apply scroll frame id, which
is already handled by `before_paint()` and `after_paint()` hooks in
PaintableBox.
This is a improved version of a73cd88f0c
The old commit was reverted in 552dd18696
The new version only paints an element into a new layer if background
blend modes other than normal are used. The rasterization performance
of most websites should therefore not suffer.
Co-Authored-By: Alexander Kalenik <kalenik.aliaksandr@gmail.com>
This reverts commit a73cd88f0c.
Emitting SaveLayer for each paintable made rasterization a lot slower
on every website because now Skia has to allocate enormous amounts of
temporary surfaces. Let's revert it for now and figure how to implement
it with less aggressive SaveLayer usage.
This reduces the number of `.cpp` files that need to be recompiled when
one of the below header files changes as follows:
Painting/Command.h: 1030 -> 61
Painting/DisplayList.h: 1030 -> 60
Painting/DisplayListRecorder.h: 557 -> 59
CSS filters work similarly to canvas filters, so it makes sense to have
Gfx::Filter that can be used by both libraries in an analogous way
as Gfx::Color.
ApplyOpacity internally calls canvas.saveLayer() which requires a
matching canvas.restore() to be called.
Fixes missing header on https://supabase.com/
ApplyFilter internally calls canvas.saveLayer() which requires a
matching canvas.restore() to be called.
Fixes painting on https://supabase.com/ regressed by
8562b0e33b
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
Now that the heap has no knowledge about a JavaScript realm and is
purely for managing the memory of the heap, it does not make sense
to name this function to say that it is a non-realm variant.
