LibWeb: Reuse block-independent intrinsic widths

[awesomekling]

Canonicalize intrinsic inline-size cache keys across assigned block sizes when a horizontal subtree has no cross-axis dependency. Preserve separate entries for orthogonal flows, aspect-ratio transfers, and wrapping column flex containers.

Cache the subtree dependency under the existing intrinsic-size epoch so mutations invalidate it without repeated scans. This avoids thousands of repeated measurement layouts in text-heavy flex content.

Benchmark     Old Score     New Score       Score Improvement  Old Total Time (ms)    New Total Time (ms)      Speedup
------------  ------------  ------------  -------------------  ---------------------  ---------------------  ---------
Speedometer2  77.25 ± 0.57  76.69 ± 0.83                0.993  6.42 ± 0.58            6.43 ± 0.63                0.998
Speedometer3  4.29 ± 0.75   4.38 ± 0.46                 1.021  6.26 ± 1.52            6.07 ± 0.41                1.032
StyleBench    61.69 ± 3.58  61.84 ± 5.18                1.002  4.13 ± 0.28            4.12 ± 0.31                1.003

[coderabbitai]

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: 6a621450-80ef-418b-97ea-0850f2e73d2f

📥 Commits

Reviewing files that changed from the base of the PR and between d84b1ff and f1fb04c.

📒 Files selected for processing (4)

• Libraries/LibWeb/Rust/src/layout/layout_node_arena.rs
• Libraries/LibWeb/Rust/src/layout/sizing_context.rs
• Tests/LibWeb/Text/expected/Layout/wrapping-column-flex-intrinsic-width.txt
• Tests/LibWeb/Text/input/Layout/wrapping-column-flex-intrinsic-width.html

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

The layout node arena now caches whether inline size depends on block size. The cache uses node generation and intrinsic cache epoch validation. SizingContext detects cross-axis dependencies and conditionally includes block size in min-content, paired max-content, and intrinsic measurement cache keys. A new wrapping column flex layout test verifies an intrinsic width of 90.

Sequence Diagram(s)

sequenceDiagram
  participant LayoutTest
  participant SizingContext
  participant LayoutNodeArena
  participant IntrinsicCache
  LayoutTest->>SizingContext: request intrinsic inline measurement
  SizingContext->>LayoutNodeArena: determine block-size dependency
  LayoutNodeArena->>IntrinsicCache: read or compute dependency fact
  IntrinsicCache-->>LayoutNodeArena: dependency result
  LayoutNodeArena-->>SizingContext: normalized cache key
  SizingContext->>IntrinsicCache: lookup or create measurement
  IntrinsicCache-->>LayoutTest: computed intrinsic width

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Possibly related PRs

• LadybirdBrowser/ladybird#10904: Modifies the same intrinsic-size cache structures and inline intrinsic measurement behavior.
• LadybirdBrowser/ladybird#10949: Introduces the SizingContext intrinsic measurement caching used by this change.
• LadybirdBrowser/ladybird#11152: Extends intrinsic sizing cache logic with block-size dependency detection.

Suggested reviewers: kalenikaliaksandr

Merge Risk: ⚪ Minimal · up to f1fb0

The change is merge-ready after normal checks and review; no actionable merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description accurately covers intrinsic inline-size cache-key canonicalization, dependency caching, invalidation, preserved dependency cases, and regression coverage.
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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