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iOS: Don't discard GPU state set before an engine runs - #191055
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This pull request refactors how the GPU availability state is updated and synchronized with the lifecycle state in FlutterEngine, moving the logic into a dedicated updateGpuAvailabilityFromLifecycleState method and adding corresponding unit tests. The review feedback correctly identifies a potential runtime crash on iOS 12 due to the unguarded use of scene-based APIs, suggesting wrapping the scene check in an @available(iOS 13.0, *) block.
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hellohuanlin
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Previously, a value assigned to `isGpuDisabled` before the engine ran was silently discarded: `createShell:` checked the current lifecycle state by assigning to the public property immediately before creating the shell, so the caller's value never actually reached `Shell::Create`. We now pass this through where it's safe to do so. The existing GPU state check is necessary: lifecycle notifications only report transitions, so an engine created while the app is already backgrounded won't receive one and needs to check the state explicitly on startup. However, the placement can be updated so we don't overwrite the user-specified state except when it's necessary (e.g. the user specified the GPU is enabled but the app is backgrounded). For apps, we can check `UIApplication.sharedApplication` directly. App extensions have no `sharedApplication` so need to check against the `UIScene`, but that's only reachable via a view that's been mounted in a window view hierarchy. As a result, we also need to check the state when we attach the view controller to see if it's different from the current state. In the case of an app extension where the view controller hasn't been mounted, the safest thing to do is leave the state alone. Enabling while backgrounded would result in the app being terminated. Fixes: flutter#190835 Issue: flutter#112232
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This was referenced Aug 18, 2026
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Previously, a value assigned to
isGpuDisabledbefore the engine ran was silently discarded:createShell:checked the current lifecycle state by assigning to the public property immediately before creating the shell, so the caller's value never actually reachedShell::Create. We now pass this through where it's safe to do so.The existing GPU state check is necessary: lifecycle notifications only report transitions, so an engine created while the app is already backgrounded won't receive one and needs to check the state explicitly on startup. However, the placement can be updated so we don't overwrite the user-specified state except when it's necessary (e.g. the user specified the GPU is enabled but the app is backgrounded).
For apps, we can check
UIApplication.sharedApplicationdirectly. App extensions have nosharedApplicationso need to check against theUIScene, but that's only reachable via a view that's been mounted in a window view hierarchy. As a result, we also need to check the state when we attach the view controller to see if it's different from the current state.In the case of an app extension where the view controller hasn't been mounted, the safest thing to do is leave the state alone. Enabling while backgrounded would result in the app being terminated.
Fixes: #190835
Issue: #112232
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