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LibWeb: Avoid redundant wheel hit test target recording - #11139

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awesomekling merged 1 commit into
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awesomekling:hitme
Aug 15, 2026
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LibWeb: Avoid redundant wheel hit test target recording#11139
awesomekling merged 1 commit into
LadybirdBrowser:masterfrom
awesomekling:hitme

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Avoid recording per-box wheel hit test targets when the viewport is the only wheel-scrollable candidate. The compositor already falls back to the viewport after checking blocking and main-thread wheel regions.

Track non-viewport candidates while building the visual context tree, so viewport-only pages do not pay for another traversal. Memoize target resolution when element scrollers exist. Reject non-scrollable overflow styles before measuring overflow geometry.

Add coverage for viewport fallback without explicit targets. Update display list expectations to omit the redundant commands.

Avoid recording per-box wheel hit test targets when the viewport is the
only wheel-scrollable candidate. The compositor already falls back to
the viewport after checking blocking and main-thread wheel regions.

Track non-viewport candidates while building the visual context tree,
so viewport-only pages do not pay for another traversal. Memoize target
resolution when element scrollers exist. Reject non-scrollable overflow
styles before measuring overflow geometry.

Add coverage for viewport fallback without explicit targets. Update
display list expectations to omit the redundant commands.
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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info
⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 36f34788-f060-48b1-ade8-31ca10aa5ed9

📥 Commits

Reviewing files that changed from the base of the PR and between d3df8e0 and 0d23346.

📒 Files selected for processing (72)
  • Libraries/LibWeb/Painting/DisplayListRecordingContext.h
  • Libraries/LibWeb/Painting/Paintable.cpp
  • Libraries/LibWeb/Painting/ViewportPaintable.cpp
  • Libraries/LibWeb/Painting/ViewportPaintable.h
  • Tests/LibWeb/Text/expected/async-scrolling/blocking-wheel-event-region-hit-testing.txt
  • Tests/LibWeb/Text/expected/async-scrolling/blocking-wheel-listener-invalidation.txt
  • Tests/LibWeb/Text/expected/async-scrolling/nested-navigable-wheel-admission.txt
  • Tests/LibWeb/Text/expected/async-scrolling/sticky-areas.txt
  • Tests/LibWeb/Text/expected/async-scrolling/viewport-wheel-target-fast-path.txt
  • Tests/LibWeb/Text/expected/css/text-underline-position.txt
  • Tests/LibWeb/Text/expected/display_list/abspos-inside-nested-opacity-inside-relpos.txt
  • Tests/LibWeb/Text/expected/display_list/abspos-inside-opacity-inside-relpos.txt
  • Tests/LibWeb/Text/expected/display_list/animated-transform-visual-context-update.txt
  • Tests/LibWeb/Text/expected/display_list/background-attachment-change-repaints.txt
  • Tests/LibWeb/Text/expected/display_list/background-attachment-fixed.txt
  • Tests/LibWeb/Text/expected/display_list/block-in-inline-no-border-for-phantom-inline-box.txt
  • Tests/LibWeb/Text/expected/display_list/border-inner-corner-right-angle-all-edges.txt
  • Tests/LibWeb/Text/expected/display_list/button-with-text-decoration.txt
  • Tests/LibWeb/Text/expected/display_list/canvas-compositor-surface.txt
  • Tests/LibWeb/Text/expected/display_list/clip-auto-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/clip-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/clip-path-empty-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/clip-path-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/clip-positioned-descendants.txt
  • Tests/LibWeb/Text/expected/display_list/contenteditable-caret.txt
  • Tests/LibWeb/Text/expected/display_list/css-clip-property.txt
  • Tests/LibWeb/Text/expected/display_list/dashed-border-with-border-radius.txt
  • Tests/LibWeb/Text/expected/display_list/deep-branching-tree.txt
  • Tests/LibWeb/Text/expected/display_list/double-border-with-asymmetric-radii.txt
  • Tests/LibWeb/Text/expected/display_list/fieldset-background-with-legend.txt
  • Tests/LibWeb/Text/expected/display_list/fixed-position.txt
  • Tests/LibWeb/Text/expected/display_list/grid-gap-rounding.txt
  • Tests/LibWeb/Text/expected/display_list/iframe-compositor-surface.txt
  • Tests/LibWeb/Text/expected/display_list/image-object-fit-cover-clip.txt
  • Tests/LibWeb/Text/expected/display_list/input-caret.txt
  • Tests/LibWeb/Text/expected/display_list/input-focus-switch-selection-and-caret.txt
  • Tests/LibWeb/Text/expected/display_list/mask-image-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/mask-type-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/mix-blend-mode-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/mixed-sibling-contexts.txt
  • Tests/LibWeb/Text/expected/display_list/multiline-inline-color-change-inside-opacity.txt
  • Tests/LibWeb/Text/expected/display_list/multiline-inline-opacity.txt
  • Tests/LibWeb/Text/expected/display_list/multiline-inline-paint-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/nested-branches.txt
  • Tests/LibWeb/Text/expected/display_list/opaque-background-image-blend.txt
  • Tests/LibWeb/Text/expected/display_list/page-focus-rendering.txt
  • Tests/LibWeb/Text/expected/display_list/patterned-border-on-a-short-side.txt
  • Tests/LibWeb/Text/expected/display_list/patterned-border-sharing-corners.txt
  • Tests/LibWeb/Text/expected/display_list/perspective-basic.txt
  • Tests/LibWeb/Text/expected/display_list/perspective-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/positioned-with-transformed-ancestor.txt
  • Tests/LibWeb/Text/expected/display_list/relative-with-inline-transformed-intermediate.txt
  • Tests/LibWeb/Text/expected/display_list/repeated-svg-background-is-display-list.txt
  • Tests/LibWeb/Text/expected/display_list/sibling-overflow-containers.txt
  • Tests/LibWeb/Text/expected/display_list/sibling-transforms.txt
  • Tests/LibWeb/Text/expected/display_list/simple-overflow-hidden.txt
  • Tests/LibWeb/Text/expected/display_list/skip-zero-area-clip-commands.txt
  • Tests/LibWeb/Text/expected/display_list/solid-border-edge-before-a-groove-edge.txt
  • Tests/LibWeb/Text/expected/display_list/solid-border-edges-with-a-dashed-edge.txt
  • Tests/LibWeb/Text/expected/display_list/svg-foreignobject-mask-after-relayout.txt
  • Tests/LibWeb/Text/expected/display_list/svg-in-img-is-nested.txt
  • Tests/LibWeb/Text/expected/display_list/svg-overflow-on-inner-elements.txt
  • Tests/LibWeb/Text/expected/display_list/svg-transform-with-opacity.txt
  • Tests/LibWeb/Text/expected/display_list/text-decoration-underline-partial-selection.txt
  • Tests/LibWeb/Text/expected/display_list/textarea-caret.txt
  • Tests/LibWeb/Text/expected/display_list/three-way-branch.txt
  • Tests/LibWeb/Text/expected/display_list/transform-basic.txt
  • Tests/LibWeb/Text/expected/display_list/transform-invertibility-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/transform-nested.txt
  • Tests/LibWeb/Text/expected/display_list/transform-with-clip.txt
  • Tests/LibWeb/Text/expected/display_list/z-index-change-no-double-paint.txt
  • Tests/LibWeb/Text/input/async-scrolling/viewport-wheel-target-fast-path.html
💤 Files with no reviewable changes (64)
  • Tests/LibWeb/Text/expected/async-scrolling/sticky-areas.txt
  • Tests/LibWeb/Text/expected/display_list/three-way-branch.txt
  • Tests/LibWeb/Text/expected/display_list/fixed-position.txt
  • Tests/LibWeb/Text/expected/display_list/background-attachment-fixed.txt
  • Tests/LibWeb/Text/expected/display_list/textarea-caret.txt
  • Tests/LibWeb/Text/expected/async-scrolling/blocking-wheel-event-region-hit-testing.txt
  • Tests/LibWeb/Text/expected/display_list/solid-border-edges-with-a-dashed-edge.txt
  • Tests/LibWeb/Text/expected/display_list/opaque-background-image-blend.txt
  • Tests/LibWeb/Text/expected/display_list/deep-branching-tree.txt
  • Tests/LibWeb/Text/expected/display_list/image-object-fit-cover-clip.txt
  • Tests/LibWeb/Text/expected/display_list/double-border-with-asymmetric-radii.txt
  • Tests/LibWeb/Text/expected/display_list/css-clip-property.txt
  • Tests/LibWeb/Text/expected/display_list/solid-border-edge-before-a-groove-edge.txt
  • Tests/LibWeb/Text/expected/css/text-underline-position.txt
  • Tests/LibWeb/Text/expected/display_list/canvas-compositor-surface.txt
  • Tests/LibWeb/Text/expected/display_list/transform-basic.txt
  • Tests/LibWeb/Text/expected/display_list/grid-gap-rounding.txt
  • Tests/LibWeb/Text/expected/display_list/svg-overflow-on-inner-elements.txt
  • Tests/LibWeb/Text/expected/async-scrolling/nested-navigable-wheel-admission.txt
  • Tests/LibWeb/Text/expected/display_list/transform-nested.txt
  • Tests/LibWeb/Text/expected/display_list/nested-branches.txt
  • Tests/LibWeb/Text/expected/display_list/patterned-border-on-a-short-side.txt
  • Tests/LibWeb/Text/expected/display_list/abspos-inside-opacity-inside-relpos.txt
  • Tests/LibWeb/Text/expected/display_list/perspective-basic.txt
  • Tests/LibWeb/Text/expected/async-scrolling/blocking-wheel-listener-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/svg-in-img-is-nested.txt
  • Tests/LibWeb/Text/expected/display_list/svg-transform-with-opacity.txt
  • Tests/LibWeb/Text/expected/display_list/clip-positioned-descendants.txt
  • Tests/LibWeb/Text/expected/display_list/fieldset-background-with-legend.txt
  • Tests/LibWeb/Text/expected/display_list/button-with-text-decoration.txt
  • Tests/LibWeb/Text/expected/display_list/input-caret.txt
  • Tests/LibWeb/Text/expected/display_list/transform-invertibility-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/iframe-compositor-surface.txt
  • Tests/LibWeb/Text/expected/display_list/page-focus-rendering.txt
  • Tests/LibWeb/Text/expected/display_list/text-decoration-underline-partial-selection.txt
  • Tests/LibWeb/Text/expected/display_list/mask-type-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/input-focus-switch-selection-and-caret.txt
  • Tests/LibWeb/Text/expected/display_list/repeated-svg-background-is-display-list.txt
  • Tests/LibWeb/Text/expected/display_list/skip-zero-area-clip-commands.txt
  • Tests/LibWeb/Text/expected/display_list/mixed-sibling-contexts.txt
  • Tests/LibWeb/Text/expected/display_list/transform-with-clip.txt
  • Tests/LibWeb/Text/expected/display_list/mask-image-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/positioned-with-transformed-ancestor.txt
  • Tests/LibWeb/Text/expected/display_list/clip-path-empty-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/contenteditable-caret.txt
  • Tests/LibWeb/Text/expected/display_list/block-in-inline-no-border-for-phantom-inline-box.txt
  • Tests/LibWeb/Text/expected/display_list/sibling-transforms.txt
  • Tests/LibWeb/Text/expected/display_list/simple-overflow-hidden.txt
  • Tests/LibWeb/Text/expected/display_list/svg-foreignobject-mask-after-relayout.txt
  • Tests/LibWeb/Text/expected/display_list/sibling-overflow-containers.txt
  • Tests/LibWeb/Text/expected/display_list/dashed-border-with-border-radius.txt
  • Tests/LibWeb/Text/expected/display_list/abspos-inside-nested-opacity-inside-relpos.txt
  • Tests/LibWeb/Text/expected/display_list/background-attachment-change-repaints.txt
  • Tests/LibWeb/Text/expected/display_list/z-index-change-no-double-paint.txt
  • Tests/LibWeb/Text/expected/display_list/clip-path-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/relative-with-inline-transformed-intermediate.txt
  • Tests/LibWeb/Text/expected/display_list/clip-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/patterned-border-sharing-corners.txt
  • Tests/LibWeb/Text/expected/display_list/clip-auto-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/animated-transform-visual-context-update.txt
  • Tests/LibWeb/Text/expected/display_list/multiline-inline-paint-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/border-inner-corner-right-angle-all-edges.txt
  • Tests/LibWeb/Text/expected/display_list/perspective-invalidation.txt
  • Tests/LibWeb/Text/expected/display_list/mix-blend-mode-invalidation.txt

📝 Walkthrough

Walkthrough

The PR adds wheel hit-test target recording controls and per-paintable caching. Paintable now resolves targets through containing blocks, fixed-position contexts, and the viewport. ViewportPaintable tracks non-viewport scroll-target candidates. Scrollability checks validate overflow types before measuring geometry. Async-scrolling and display-list expectations are updated to remove unnecessary compositor wheel-target entries. A viewport fast-path test verifies the new behavior.

Sequence Diagram(s)

sequenceDiagram
  participant Paintable
  participant DisplayListRecordingContext
  participant ViewportPaintable
  participant DisplayList
  Paintable->>DisplayListRecordingContext: resolve cached wheel target
  DisplayListRecordingContext-->>Paintable: return VisualContextIndex or no target
  Paintable->>ViewportPaintable: check non-viewport scroll candidate
  ViewportPaintable-->>Paintable: return candidate state
  Paintable->>DisplayListRecordingContext: cache target or skip recording
  DisplayListRecordingContext->>DisplayList: emit wheel target when required
Loading

Possibly related PRs

Suggested reviewers: kalenikaliaksandr

Merge Risk: ⚪ Minimal · up to 0d233

This change removes redundant viewport-only wheel target recording and updates coverage and display-list expectations; no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 3
✅ Passed checks (3 passed)
Check name Status Explanation
Description check ✅ Passed The description directly matches the changes to wheel hit-test target recording, viewport fallback, memoization, overflow checks, and related tests.
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.

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@awesomekling
awesomekling merged commit a997bfa into LadybirdBrowser:master Aug 15, 2026
14 of 15 checks passed
@awesomekling
awesomekling deleted the hitme branch August 15, 2026 11:08
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