CarPlay App Hang: CPMapTemplate.isPanningInterfaceVisible blocks main thread

[LukasB-DEV]

I’m seeing an App Hang (main‑thread stall) in CarPlay that appears to be caused by a synchronous call to CPMapTemplate.isPanningInterfaceVisible inside MapTemplate._invalidate().

What I see (Sentry):

• Main thread blocked in CPMapTemplate.isPanningInterfaceVisible
• Call stack: MapTemplate._invalidate → AutoPlayTemplate.invalidate → HybridAutoPlay.setRootTemplate (async job)
• System frame: semaphore_timedwait_trap

Environment:

• iOS 26.2
• iPhone 17 Pro (arm64)
• Real CarPlay session (not simulator)
• App version 1.2.4 (production)

Reproduction (best‑effort):

1. Connect iPhone to real CarPlay
2. App launches and sets CPMapTemplate as root
3. Quickly toggle the panning interface (via pan button) while UI updates trigger invalidate() (e.g. header/actions update or navigation start/stop)
4. Occasionally the app hangs for ~2s on the main thread and Sentry reports “App hanging”

This seems timing‑sensitive and may be specific to newer iOS/CarPlay behavior.

Why I think this is the cause:
CPMapTemplate.isPanningInterfaceVisible appears to use an internal semaphore/IPC. If called synchronously on the main thread while CarPlay is changing panning state, it can block briefly. Our stack trace shows the hang inside that call.

Proposed fix (minimal):

• Cache panning interface state using mapTemplateDidShowPanningInterface / mapTemplateDidDismissPanningInterface
• Replace direct isPanningInterfaceVisible access in _invalidate() / onPanButtonPress / zoom handling with the cached flag
• Optionally defer invalidate() from the delegate callbacks to the next runloop (DispatchQueue.main.async) to avoid re‑entrancy during CarPlay callbacks

Would you like me to open a PR with this change?

Thanks!

[g4rb4g3]

Nice catch, we didn't spot that so far.
Caching this in map template sounds like a good plan. I'd be very happy about a PR. 🙂

[LukasB-DEV]

created: #33

[g4rb4g3]

fixed with #33, thanks for your support @LukasB-DEV