User Tracking Mode cause crash

[paulsUsername]

Every time I set the user tracking mode to .followWithHeading I get a crash. I created a bare sample project below that replicated the error. I have tested on iPhone X, and iPad, both on 14.4.1 and both get the crash after a few seconds, maybe 20 at the most.

I am not calling it from a background thread.

https://github.com/paulsUsername/maplibre-error.git

=================================================================
Main Thread Checker: UI API called on a background thread: -[UIView superview]
PID: 9527, TID: 3803024, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103167fac -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 316
5   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
6   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
7   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
8   libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
9   libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
10  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
11  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
12  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8
2021-03-28 23:01:42.214336+0100 test-123[9527:3803024] [reports] Main Thread Checker: UI API called on a background thread: -[UIView superview]
PID: 9527, TID: 3803024, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103167fac -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 316
5   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
6   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
7   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
8   libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
9   libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
10  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
11  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
12  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8
=================================================================
Main Thread Checker: UI API called on a background thread: -[UIView bounds]
PID: 9527, TID: 3803024, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103168024 -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 436
5   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
6   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
7   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
8   libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
9   libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
10  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
11  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
12  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8
2021-03-28 23:01:42.334464+0100 test-123[9527:3803024] [reports] Main Thread Checker: UI API called on a background thread: -[UIView bounds]
PID: 9527, TID: 3803024, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103168024 -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 436
5   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
6   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
7   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
8   libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
9   libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
10  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
11  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
12  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8
=================================================================
Main Thread Checker: UI API called on a background thread: -[UIView setCenter:]
PID: 9527, TID: 3803024, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103103b00 -[MGLAnnotationView setCenter:] + 72
5   Mapbox                              0x0000000103168138 -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 712
6   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
7   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
8   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
9   libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
10  libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
11  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
12  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
13  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8
2021-03-28 23:01:42.464651+0100 test-123[9527:3803024] [reports] Main Thread Checker: UI API called on a background thread: -[UIView setCenter:]
PID: 9527, TID: 3803024, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103103b00 -[MGLAnnotationView setCenter:] + 72
5   Mapbox                              0x0000000103168138 -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 712
6   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
7   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
8   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
9   libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
10  libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
11  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
12  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
13  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8
=================================================================
Main Thread Checker: UI API called on a background thread: -[UIView frame]
PID: 9527, TID: 3803050, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103164278 -[MGLMapView edgePaddingForFollowingWithCourse] + 92
5   Mapbox                              0x0000000103168324 -[MGLMapView userLocationAnnotationViewCenter] + 252
6   Mapbox                              0x0000000103167f30 -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 192
7   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
8   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
9   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
10  libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
11  libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
12  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
13  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
14  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8
2021-03-28 23:01:46.983259+0100 test-123[9527:3803050] [reports] Main Thread Checker: UI API called on a background thread: -[UIView frame]
PID: 9527, TID: 3803050, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 0
Backtrace:
4   Mapbox                              0x0000000103164278 -[MGLMapView edgePaddingForFollowingWithCourse] + 92
5   Mapbox                              0x0000000103168324 -[MGLMapView userLocationAnnotationViewCenter] + 252
6   Mapbox                              0x0000000103167f30 -[MGLMapView updateUserLocationAnnotationViewAnimatedWithDuration:] + 192
7   Mapbox                              0x000000010316a974 __47-[MGLMapView locationManager:didUpdateHeading:]_block_invoke + 280
8   libdispatch.dylib                   0x00000001067cbce4 _dispatch_call_block_and_release + 24
9   libdispatch.dylib                   0x00000001067cd528 _dispatch_client_callout + 16
10  libdispatch.dylib                   0x00000001067cfcc4 _dispatch_queue_override_invoke + 888
11  libdispatch.dylib                   0x00000001067df048 _dispatch_root_queue_drain + 376
12  libdispatch.dylib                   0x00000001067df970 _dispatch_worker_thread2 + 152
13  libsystem_pthread.dylib             0x00000001c9c51568 _pthread_wqthread + 212
14  libsystem_pthread.dylib             0x00000001c9c54874 start_wqthread + 8

[rruu-map]

The problem lies in the didUpdateHeading method in the MGLMapView.mm code, remove the child thread, as follows:
// dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {
if ( ! self->_showsUserLocation || self.pan.state == UIGestureRecognizerStateBegan || newHeading.headingAccuracy < 0) return;

    self.userLocation.heading = newHeading;

    if (self.showsUserHeadingIndicator || self.userTrackingMode == MGLUserTrackingModeFollowWithHeading)
    {
        [self updateUserLocationAnnotationView];
    }

    if ([self.delegate respondsToSelector:@selector(mapView:didUpdateUserLocation:)])
    {
        [self.delegate mapView:self didUpdateUserLocation:self.userLocation];

        if (!self->_showsUserLocation) return;
    }

    CLLocationDirection headingDirection = (newHeading.trueHeading >= 0 ? newHeading.trueHeading : newHeading.magneticHeading);

    if (headingDirection >= 0 && self.userTrackingMode == MGLUserTrackingModeFollowWithHeading
        && self.userTrackingState != MGLUserTrackingStateBegan)
    {
        [self _setDirection:headingDirection animated:YES];
        [self updateUserLocationAnnotationView];
    }

// });