The scrollport size was previously fetched at refresh time from the
scroll ancestor paintable. Since it doesn't change between layouts,
precompute it alongside the other sticky constraints.
Previously `refresh_scroll_state()` reached back to PaintableBox for
sticky insets. Storing them on ScrollFrame makes it self-contained
for sticky offset computation.
Remove the public own_offset() getter from ScrollFrame and the
own_offset_for_frame_with_id() helper from ScrollState. The snapshot
creation in ScrollStateSnapshot now accesses m_own_offset directly
through a friend declaration. This ensures scroll offsets in the
painting pipeline are only read through snapshots.
Precompute the geometric data needed for sticky positioning during
scroll frame assignment. This avoids walking the paintable tree to query
containing blocks and ancestor geometry during scroll state refresh,
which runs on every scroll event.
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.
With this change we save a copy of of scroll state at the time of
recording a display list, instead of actual ScrollState pointer that
could be modifed by the main thread while display list is beings
rasterized on the rendering thread, which leads to a frame painted with
inconsistent scroll state.
Fixes https://github.com/LadybirdBrowser/ladybird/issues/4288
