This is a bug. I don't want to add so many levels of subviews. The detail of crash thread show as below: Thread 9 Crashed:: Dispatch queue: com.apple.root.user-interactive-qos 0 libsystem_kernel.dylib 0x00007fff73d39ad6 __abort_with_payload + 10 1 libsystem_kernel.dylib 0x00007fff73d3b3df abort_with_payload_wrapper_internal + 80 2 libsystem_kernel.dylib 0x00007fff73d3b411 abort_with_payload + 9 3 libsystem_c.dylib 0x00007fff73ca680b _os_crash_fmt.cold.1 + 55 4 libsystem_c.dylib 0x00007fff73c39e62 _os_crash_fmt + 154 5 com.apple.AppKit 0x00007fff37011e28 NSViewSendViewWillDrawToSubviews + 949 6 com.apple.AppKit 0x00007fff37011a49 _NSViewWillDraw + 45 7 com.apple.AppKit 0x00007fff3701169b -[_NSViewBackingLayer display] + 68 8 com.apple.QuartzCore 0x00007fff457cf1fd CA::Layer::display_if_needed(CA::Transaction*) + 757 9 com.apple.QuartzCore 0x00007fff457ad4b6 CA::Context::commit_transaction(CA::Transaction*, double) + 334 10 com.apple.QuartzCore 0x00007fff457ac0a0 CA::Transaction::commit() + 644 11 com.apple.AppKit 0x00007fff36f7eb74 NSPerformVisuallyAtomicChange + 154 12 com.apple.AppKit 0x00007fff371cda17 -[NSAnimation(NSInternal) _advanceTimeWithDisplayLink:] + 172 13 com.apple.AppKit 0x00007fff3712b624 -[NSScreenDisplayLink _fire] + 180 14 com.apple.AppKit 0x00007fff37878c62 ___NSRunLoopTimerCreateWithHandler_block_invoke + 34 15 com.apple.CoreFoundation 0x00007fff39cde4d8 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20 16 com.apple.CoreFoundation 0x00007fff39cde03e __CFRunLoopDoTimer + 872 17 com.apple.CoreFoundation 0x00007fff39cddb29 __CFRunLoopDoTimers + 322 18 com.apple.CoreFoundation 0x00007fff39cc277d __CFRunLoopRun + 1885 19 com.apple.CoreFoundation 0x00007fff39cc19c3 CFRunLoopRunSpecific + 466 20 com.apple.Foundation 0x00007fff3c37d1c8 -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 212 21 com.apple.AppKit 0x00007fff371cd930 -[NSAnimation(NSInternal) _runBlocking] + 344 22 com.apple.AppKit 0x00007fff371cd60d __42-[NSAnimation(NSInternal) _runInNewThread]_block_invoke + 97 23 libdispatch.dylib 0x00007fff73b7e6c4 _dispatch_call_block_and_release + 12 24 libdispatch.dylib 0x00007fff73b7f658 _dispatch_client_callout + 8 25 libdispatch.dylib 0x00007fff73b8daa8 _dispatch_root_queue_drain + 663 26 libdispatch.dylib 0x00007fff73b8e097 _dispatch_worker_thread2 + 92 27 libsystem_pthread.dylib 0x00007fff73ddd9f7 _pthread_wqthread + 220 28 libsystem_pthread.dylib 0x00007fff73ddcb77 start_wqthread + 15

crash log detail - https://developer.apple.com/forums/content/attachment/1ec0e841-10b7-4e32-a9d9-05ed486e9a81

crashReport_all.crash

I add a new crash report about Appkit. May be different from the top. crashReport2.txt