Report App Hangs

[philipphofmann]

The watchdog can terminate an app when it is not responsive for a few seconds. This results in a hard crash with the code 0x8badf00d ("ate bad food"). Having the app hanging for a few seconds and being terminated by the watchdog is a bad user experience. It would be beneficial for our users to detect shorter unresponsiveness of the app before leading to a crash to improve their apps. We could give them the possibility to configure a threshold in milliseconds for the unresponsiveness of their app and send an event to Sentry when the app hangs longer than the configured threshold.

https://getsentry.atlassian.net/browse/MOBILE-256

[marandaneto]

similar to Android ANR, we probably need to investigate grouping when doing this as it can't be too noisy either.

[philipphofmann]

Maybe we can use a CADisplayLink on iOS, Mac Catalyst, and tvOS and a CVDisplayLink on macOS to be able to detect this.

[philipphofmann]

We already use CADisplayLink for detecting slow and frozen frames. We could use this logic to detect the app not being responsive.

[philipphofmann]

This could be solved with a CFRunLoopObserver as pointed out here #1645 (comment).