This unifies the implementations of the element resize and the scroll
mouse inputs, so the actual code involved in handling the events can
be simplified, and it only should require one object per event.
The cursor override is now part of this ChromeWidget class as well, so
that the hit test's cursor doesn't need to be passed around as much.
Replace per-frame heap-allocated RefCounted ScrollFrame objects with a
single contiguous Vector<ScrollFrame> inside ScrollState. All frames for
a viewport are now stored in one allocation, using type-safe
ScrollFrameIndex instead of RefPtr pointers.
This reduces allocation churn, improves cache locality, and moves
parent-chain traversal (cumulative offset, nearest scrolling ancestor)
into ScrollState — similar to how visual context nodes were recently
consolidated into AccumulatedVisualContextTree.
Replace per-node heap-allocated AtomicRefCounted
AccumulatedVisualContext objects with a single contiguous Vector inside
AccumulatedVisualContextTree. All nodes for a frame are now stored in
one allocation, using type-safe VisualContextIndex instead of RefPtr
pointers.
This reduces allocation churn, improves cache locality, and opens the
door for future snapshotting of visual context state — similar to how
scroll offsets are snapshotted today.
Extract the pattern of inverse-transforming a screen position (removing
the effect of CSS transforms) into a helper method. Used to compute
mouse event offsets relative to the target element.
Extract the repeated pattern of transforming a rectangle from absolute
coordinates to viewport coordinates via the accumulated visual context
into a helper method.
Similar to transform_point_to_local(), but uses the descendants' visual
context which accounts for the element's own scroll offset. Used during
fragment hit testing in PaintableWithLines.
Extract the repeated pattern of transforming a screen position to local
coordinates via the accumulated visual context into a helper method.
This returns an Optional, unlike the existing
transform_to_local_coordinates() which falls back to the original
position. The old method is now implemented in terms of the new one.
With per-paintable display list command caching now in place, the
separate paint-only properties resolution phase is no longer needed.
Resolution now happens inline during painting and its cost is amortized
since it only runs on cache miss.
Move all property resolution to point of consumption:
- is_visible() and visible_for_hit_testing() compute on the fly
- Filter resolution moved to assign_accumulated_visual_contexts()
- Border radii, outlines computed on access
- Box shadows, backdrop filter resolved inline during painting
- Background resolution moved into paint_background()
- Mask resolution moved to StackingContext::paint()
- Text fragment and SVG stroke properties resolved during painting
Cache the display list commands produced by each PaintableBox's paint()
on a per-phase basis. On subsequent display list rebuilds, if a
paintable's cache is still valid, replay the recorded commands directly
— skipping paint() and all the property resolution it entails.
Besides saving time on property resolution, this also enables Skia to
reuse path tessellation results across frames — e.g. border paths are
preserved in the cache and don't need to be re-tessellated on every
repaint.
Rename Document::set_needs_display() to set_needs_repaint() and make it
private. External callers must now go through Node/Paintable which
route the request to the document internally.
Fix one existing misuse in AnimationEffect that was calling
document-level set_needs_display() instead of routing through the
target element's paintable.
This is preparation for per-paintable display list command caching:
repaint requests must go through specific paintables so their cached
command lists can be invalidated.
These rects are computed from immutable layout data but were
recomputed from scratch on every call, with the CSSPixels saturating
arithmetic showing up as a significant cost in profiles.
Cache them lazily alongside the existing m_absolute_rect cache.
This was 3.3% of CPU time while playing a YouTube video.
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.
Replace direct ScrollFrame access via own_scroll_frame_offset() with
ScrollStateSnapshot-based lookup. This aligns compute_scrollbar_data()
with the rest of the painting/hit-testing pipeline, which uses snapshots
for consistent, thread-safe scroll state.
Compute the perspective matrix on the fly during visual context
assignment instead of caching it in PaintableBox. This reduces
PaintableBox's size and keeps the logic closer to where it's used.
Instead of computing and caching the transform matrix and transform
origin on PaintableBox during resolve_paint_properties(), compute them
inline during assign_accumulated_visual_contexts() where they are
actually consumed. This makes PaintableBox smaller by not wasting space
for properties that are only consumed during AccumulatedVisualContext
tree construction.
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.
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.
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.
Reuse existing paintables during relayout to reduce GC allocation
pressure. Each paintable subclass implements reset_for_relayout()
to clear state before reuse.
This method was initially introduced to calculate the total paint area
including effects like box-shadows that paint outside the border box.
It was used in StackingContext for sizing bitmaps when painting
elements with opacity or transforms, and later for clip-path bounds.
This functionality is no longer needed as stacking context painting
and clip-path handling have been refactored to use different
approaches (AccumulatedVisualContext now handles clip-path).
When delegating mouse events to iframes, coordinate transformations
were not accounting for scroll offsets. This caused clicks inside
iframes to be incorrectly positioned when the parent page was scrolled.
Remove the now-obsolete ClipFrame infrastructure:
- Delete ClipFrame.h and ClipFrame.cpp
- Remove assign_clip_frames() from ViewportPaintable
- Remove enclosing_clip_frame and own_clip_frame from PaintableBox
- Remove m_clip_state HashMap from ViewportPaintable
Clip handling is now fully managed through AccumulatedVisualContext
nodes with ClipData.
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.
Introduce AccumulatedVisualContext, a tree structure that tracks the
cumulative visual state (scroll offsets, clip regions, transforms,
perspective) for each paintable box.
Motivation:
Before this change, visual state was fragmented across multiple
mechanisms:
- ClipFrame: Tracked clip rectangles, each storing its own
enclosing_scroll_frame_id to handle scroll offset adjustments
- scroll_frame_id: Passed separately to each display list command
- PushStackingContext: Stored transform matrices directly in the command
- Every display list command implemented translate_by() (45 methods
total) to allow scroll offset adjustment during playback
This fragmentation led to:
- Complex, error-prone coordinate transformation logic scattered
throughout the codebase
- Commands being mutated during playback to apply scroll offsets
- Duplicate logic between painting and hit testing for coordinate
transformations
Solution:
AccumulatedVisualContext builds a tree where each node represents a
single visual operation:
- ScrollData: A scroll frame with its ID
- ClipData: A clip rectangle with optional border radii
- TransformData: A 4x4 transform matrix with its origin
- PerspectiveData: A perspective projection matrix
Each PaintableBox stores a reference to its accumulated context node.
The tree structure naturally captures the parent-child relationships,
so traversing from any node to the root gives the complete chain of
visual transformations.
Benefits this enables (in subsequent commits):
- Display list commands become immutable - no more translate_by()
- Single RefPtr<AccumulatedVisualContext> replaces separate
scroll_frame_id and ClipFrame on commands
- LCA-based tree traversal during playback for efficient save/restore
- transform_point_for_hit_test() provides coordinate transformation for
hit testing using the same structure
Add ElementResizeAction to Page (maybe there's a better place). It's
just a mousemove delegate that updates styles on the target element.
Add ChromeMetrics for zoom-invariant chrome like scrollbar thumb
thickness, resize gripper size, paddings, etc. It's not user-stylable
but separates basic concerns in a way that a visually gifted
designer unlike myself can adjust to taste.
These values are pre-divided by zoom factor so that PaintableBox can
continue using device_pixels_per_css_pixel calls as normal.
The adjusted metrics are computed on demand from Page multiple times
per paint cycle, which is not ideal but avoids lifetime management and
atomics. Maybe someone with more surety about the painting flow control
can improve this, but it won't be a huge win. If profiling shows
this slowing paints, then Ladybird is in good shape.
Update PaintableBox to draw the resize gripper and deconflict
the scrollbars. Set apropriate cursors for scrollbars and gripper in
mousemove. We override EventHandler's cursor handling because nothing
should ever come between a man and his resize gripper.
Chrome metrics use the CSSPixels class. This is good because it's
broadly compatible but bad because they're actually different units
when zoom is not 1.0. If that's a problem, we could make a new type
or just use double.
This adds visit_edges(Cell::Visitor&) methods to various helper structs
that contain GC pointers, and makes sure they are called from owning
GC-heap-allocated objects as needed.
These were found by our Clang plugin after expanding its capabilities.
The added rules will be enforced by CI going forward.
The Transformation class wasn't really accomplishing anything. It still
had to store StyleValues, so it was basically the same as
TransformationStyleValue, with extra steps to convert from one to the
other. So... let's just use TransformationStyleValue instead!
Apart from moving code around, the behavior has changed a bit. We now
actually acknowledge unresolvable parameters and return an error when
we try to produce a matrix from them. Previously we just skipped over
them, which was pretty wrong. This gets us an extra pass in the
typed-om test.
We also get some slightly different results with our transform
serialization, because we're not converting to CSSPixels and back.
This function used layout node pointer to check if it's corresponding to
viewport. There is no need for that, since `is_viewport_paintable()`
does exactly the same check without going through layout node.
Before this change, you could only scroll the current hovered scroll
container, even if it was at the beginning or end and thus having no
effect.
Now, if it doesn't update, it will not be classed as handled and will
move onto the next scroll container.
