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#10220 - Use UIScreen.maximumFramesPerSecond for dynamic slow frame threshold #15516

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#10220 - Use UIScreen.maximumFramesPerSecond for dynamic slow frame threshold #15516

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@JesusRojass
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@JesusRojass JesusRojass commented Nov 20, 2025

Discussion

Fix for #10220 by deriving slow-frame budget from UIScreen.maximumFramesPerSecond

User Statements:

  • Slow rendering values on tvOS approximately 150 times higher (~60%) than on iOS (<1%)
  • ProMotion devices reporting inaccurate frame metrics during refresh rate changes
  • 50Hz tvOS displays (Europe) incorrectly flagging smooth 18ms frames as slow
  • Static 60Hz assumption breaks on modern Apple hardware with variable refresh rates

What was done?

  • Replace fixed 16 ms with slowBudget = 1.0 / UIScreen.mainScreen.maximumFramesPerSecond (seconds). Keeps frozen at 700 ms. Behavior at 60 Hz preserved.
  • Cache maxFPS and recompute slowBudget only when needed.
  • Scoped refresh of the cache to tvOS on app-did-become-active.

Testing

All green ✅

Added tests:

  • 50 fps budget ~20 ms, 60 fps ~16.67 ms, 120 fps ~8.33 ms - assert slow/ok classification and frozen remains at 700 ms.
  • tvOS-specific test mirroring testSlowFrameIsRecorded.
  • Tests stub maximumFramesPerSecond locally to avoid global state.

API Changes

No API Changes

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@JesusRojass
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JesusRojass commented Nov 20, 2025

/gemini review

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Code Review

This pull request introduces a dynamic slow frame threshold based on UIScreen.maximumFramesPerSecond to improve frame metric accuracy on devices with variable refresh rates, such as ProMotion displays and 50Hz tvOS displays. The changes involve caching the maximum FPS and recalculating the slow frame budget when necessary, especially on tvOS when the screen mode changes. The implementation is solid and includes comprehensive unit tests for the new logic. My feedback includes a couple of suggestions to improve code maintainability by reducing duplication in both the implementation and the new tests.

eBlender
eBlender reviewed Nov 20, 2025
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@JesusRojass @eBlender