visionOS: Moving window with a Map causes app to freeze

Question

Created Feb ’24

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I'm developing a map-based app for visionOS. The loads map data from a server, using JSON. It works just fine, but I noticed the following effect: If I move the app's window around, it freezes; either on the first movement, or on one of the subsequent ones. The map cannot be panned anymore, and all other UI elements lose their interactivity as well.

I noticed this issue before, when I was opening the map on app startup (and here it even happened without moving the window). Since I added a short delay, this was resolved. There was no log message in this case.

However, when I noticed that it also happens if I move the window around, I saw that Xcode logs an error:

+[UIView setAnimationsEnabled:] being called from a background thread. Performing any operation from a background thread on UIView or a subclass is not supported and may result in unexpected and insidious behavior. trace=(
	0   UIKitCore                           0x0000000185824a24 __42+[UIView(Animation) setAnimationsEnabled:]_block_invoke + 112
	1   libdispatch.dylib                   0x0000000102a327e4 _dispatch_client_callout + 16
	2   libdispatch.dylib                   0x0000000102a34284 _dispatch_once_callout + 84
	3   UIKitCore                           0x0000000185824ad8 +[UIView(Animation) performWithoutAnimation:] + 56
	4   SwiftUI                             0x00000001c68cf1e0 OUTLINED_FUNCTION_136 + 10376
	5   SwiftUI                             0x00000001c782bebc OUTLINED_FUNCTION_12 + 22864
	6   SwiftUI                             0x00000001c78285e8 OUTLINED_FUNCTION_12 + 8316
	7   SwiftUI                             0x00000001c787c288 OUTLINED_FUNCTION_20 + 39264
	8   SwiftUI                             0x00000001c787c2cc OUTLINED_FUNCTION_20 + 39332
	9   UIKitCore                           0x000000018582fc24 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1496
	10  QuartzCore                          0x000000018a05cf00 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 440
	11  QuartzCore                          0x000000018a068ad0 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 124
	12  QuartzCore                          0x0000000189f80498 _ZN2CA7Context18commit_transactionEPNS_11TransactionEdPd + 460
	13  QuartzCore                          0x0000000189fb00b0 _ZN2CA11Transaction6commitEv + 652
	14  VectorKit                           0x00000001938ee620 _ZN2md12HoverSupport18updateHoverProxiesERKNSt3__16vectorINS1_10shared_ptrINS_5LabelEEEN3geo12StdAllocatorIS5_N3mdm9AllocatorEEEEE + 2468
	15  VectorKit                           0x0000000193afd1cc _ZN2md15StandardLabeler16layoutForDisplayERKNS_13LayoutContextE + 156
	16  VectorKit                           0x0000000193cf133c _ZN2md16CompositeLabeler16layoutForDisplayERKNS_13LayoutContextE + 52
	17  VectorKit                           0x0000000193abf318 _ZN2md12LabelManager6layoutERKNS_13LayoutContextEPKNS_20CartographicRendererERKNSt3__113unordered_setINS7_10shared_ptrINS_12LabelMapTileEEENS7_4hashISB_EENS7_8equal_toISB_EEN3geo12StdAllocatorISB_N3mdm9AllocatorEEEEERNS_8PassListE + 2904
	18  VectorKit                           0x0000000193cad464 _ZN2md9realistic16LabelRenderLayer6layoutERKNS_13LayoutContextE + 464
	19  VectorKit                           0x0000000193658b54 _ZNSt3__110__function6__funcIZN2md9realistic20RealisticRenderLayer5frameERNS2_13LayoutContextEE3$_0NS_9allocatorIS7_EEFvvEEclEv + 180
	20  VectorKit                           0x00000001936584cc ___ZN3geo9TaskQueue14queueAsyncTaskENSt3__110shared_ptrINS_4TaskEEEPU28objcproto17OS_dispatch_group8NSObject_block_invoke + 80
	21  libdispatch.dylib                   0x0000000102a30f98 _dispatch_call_block_and_release + 24
	22  libdispatch.dylib                   0x0000000102a327e4 _dispatch_client_callout + 16
	23  libdispatch.dylib                   0x0000000102a3aa80 _dispatch_lane_serial_drain + 916
	24  libdispatch.dylib                   0x0000000102a3b7c4 _dispatch_lane_invoke + 420
	25  libdispatch.dylib                   0x0000000102a3c794 _dispatch_workloop_invoke + 864
	26  libdispatch.dylib                   0x0000000102a481a0 _dispatch_root_queue_drain_deferred_wlh + 324
	27  libdispatch.dylib                   0x0000000102a475fc _dispatch_workloop_worker_thread + 488
	28  libsystem_pthread.dylib             0x0000000103b0f924 _pthread_wqthread + 284
	29  libsystem_pthread.dylib             0x0000000103b0e6e4 start_wqthread + 8

I disabled all my withAnimation() statements, and the problem persists. I also thought it might be related to my own network fetches, but I think all apply their changes on the main thread. And when I turn on network logging for my own fetching logic, I do not see any data coming in. I also do not think there should be a reason for it.

How can I debug such a situation, so I know, which call actually threw this message? I'd like to know if it is my code or a bug in the SwiftUI map itself.

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Answer 1

waldgeist OP

Feb ’24

I just noticed that the logs appeared since I added a toolbar to the window. Without these, the app still freezes, but without any logs. That's the reason why I noticed them just yesterday.

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Answer 2

waldgeist OP

Feb ’24

Another observation: It also happens if I popup a new window, interact with that window, and then click into the map window again. It seems to be related to the window receiving user gestures again. Interestingly, it does not happen if I close the second window right away.

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Answer 3

jlilest OP

Feb ’24

I notice the log mentions the animation is happening on a background thread. I would look to see if you have anything running in background updating state values. SwifUI seems to be more sensitive to that than UIKit is.

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