fix: incorrect cache validation logic causing cache false hit

[MaksimGalois]

Summary

In YGLayout.cpp, when calling newSizeIsStricterAndStillValid to check measure cache eligibility, the current constraint size is passed as net remaining space (availableHeight - marginColumn). However, the historical constraint lastSize is erroneously passed as gross space (lastAvailableHeight) without subtracting the margin.

This asymmetric comparison (comparing net space with gross space) leads Yoga to falsely assume that the available space has shrunk (triggering the lastSize > size branch) when the container actually grows. Consequently, a truncated cache result from a previously compressed pass is incorrectly reused.

Solution

Deduct the corresponding margin size (marginColumn / marginRow) from lastAvailableHeight / lastAvailableWidth respectively when calling newSizeIsStricterAndStillValid to ensure symmetrical net-to-net boundary comparisons.

Changelog

[C++] [Fixed] - Correct net layout space comparison in measure cache check by deducting margin.

Test Plan & Minimal Reproducible Example

Added a new dedicated unit test remeasure_when_container_grows_with_child_margin in YGMeasureCacheTest.cpp, which serves as a MRE for this specific bug.

• Before this fix: The test fails as the child incorrectly hits the stale measure cache and retains a compressed height of 5.0f instead of re-measuring to its desired height of 10.0f.
• After this fix: The test passes successfully with all assertions green.

Reproduction and Verification Steps:

1. First Layout Pass: The parent container is initialized with a restricted height (10.0f). Due to a child margin (5.0f), the net available space for the child is constrained to 5.0f. The child's measured layout height is compressed to 5.0f and cached erroneously.
2. Container Expansion: The parent container's height expands to 15.0f, releasing enough net available space (10.0f) to completely accommodate the child's desired target height (10.0f).
3. Second Layout Pass (The Bug Location):
   • Before this fix: Due to the asymmetric boundary check in newSizeIsStricterAndStillValid, Yoga incorrectly triggers a false cache hit during the second pass. It blindly reuses the stale, compressed height of 5.0f from the cache without re-measuring, causing the measureCount assertion to fail (retains 1 instead of 2).
   • After this fix: Symmetrical net-to-net boundary validation ensures that the cache is properly invalidated when space expands. Yoga correctly triggers a re-measurement (measureCount increments to 2) and the child layout height successfully recovers to its correct desired height of 10.0f. All assertions pass green.

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Project	Deployment	Actions	Updated (UTC)
yoga-website	Ready	Preview, Comment	May 25, 2026 7:56am

[meta-codesync]

@zeyap has imported this pull request. If you are a Meta employee, you can view this in D106414616.