Hi! I am currently finalizing a new app that uses Metal to render a 3D scene and a UIKit overlay to display controls for interacting with objects in the scene. The render loop is driven via a CADisplayLink with its preferredFramesPerSecond set to 60. I have recently noticed an issue where the app reports a steady 60 fps frame rate in the Xcode debug navigator, but still felt sluggish on the device. This feeling was only present on devices with ProMotion and often started after interactions with the UIKit overlay. I started investigating by using Metal System Trace and quickly found an explanation for the sluggish feeling: occasionally, the app would switch from its nominal 16ms-16ms-16ms cadence to 12ms-20ms-12ms, thus still averaging 60 fps, but with inconsistent frame times. Pictures of the timeline can be found here. I have tried setting the CAMetalLayer's presentsWithTransaction to true, waiting for the command buffer to be scheduled and then presenting the drawable, but, unfortunately, the problem persists. If anybody can think of a potential reason / solution for this, I would be very thankful.

I needed an infinite canvas for my app which is basically a drawing board where one can draw things using pen. So, I thought of having a very large custom UIView inside a UIScrollView. And in the custom view, I could keep drawing things. But, I ended up with a warning saying something like below and nothing drawn on screen. [<CALayer: 0x5584190> display]: Ignoring bogus layer size (50000, 50000) Which means, I can't have such a big CALayer to draw things. Now, solution? alternative? Then comes CATiledLayer. I made my large UIView backed by CATiledLayer now. After having a proper levelOfDetails and levelOfDetailsBias value, things worked like charm. Until I ended up facing another problem. Since, CATiledLayer caches drawing in different zoom levels if I try to scale the view after changing the drawing content the cached drawings appear and then the new contents get drawn. I don't find an option to invalidate caches in different levels. All the solutions I came across leads me to clear the entire contents of the CATiledLayer on drawing content change which won't help again. Do I miss something here? Is there a way with which I can clear caches at different levels? Or is there any other solutions which could solve my need? Can someone help me with this?

We have an iOS app in the App Store. Recently, we see in Organizer / Crashes for that app a new type of crash that seems bound to iOS 13 devices (21 devices affected in the last few weeks, all with iOS 13.1, .2, or .3). Xcode reports that the crashes occurred in QuartzCore, on CA::Render::Encoder::grow(unsigned long).Any idea what can it be and how it could be fixed? It doesn't look related to our code. Can it be a recent Apple bug? (We didn't have these crash reports before iOS 13.) Thank you in advance.Here is an extract from the crash log:OS Version: iPhone OS 13.3 (17C54) Release Type: User Baseband Version: n/a Report Version: 104 Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x0000000000000000, 0x0000000000000000 Exception Note: EXC_CORPSE_NOTIFY Triggered by Thread: 0 Thread 0 name: Thread 0 Crashed: 0 libsystem_kernel.dylib 0x0000000191d27ec4 __pthread_kill + 8 1 libsystem_pthread.dylib 0x0000000191c431d8 pthread_kill$VARIANT$mp + 136 (pthread.c:1458) 2 libsystem_c.dylib 0x0000000191b97844 abort + 100 (abort.c:110) 3 QuartzCore 0x00000001989af340 CA::Render::Encoder::grow(unsigned long) + 304 (render-coding.cpp:562) 4 QuartzCore 0x00000001989afa80 CA::Render::Encoder::encode_data_async(void const*, unsigned long, void (*)(void const*, void*), ... + 172 (render-coding.h:272) 5 QuartzCore 0x000000019886c358 CA::Render::Image::encode(CA::Render::Encoder*) const + 748 (render-image.cpp:401) 6 QuartzCore 0x000000019888510c CA::Render::Layer::encode(CA::Render::Encoder*) const + 112 (render-coding.h:388) 7 QuartzCore 0x00000001989b3c2c CA::Render::encode_set_object(CA::Render::Encoder*, unsigned long, unsigned int, CA::Render::Obje... + 192 (render-coding.cpp:2151) 8 QuartzCore 0x00000001988f78a4 invocation function for block in CA::Context::commit_transaction(CA::Transaction*, double) + 1568 (CAContextInternal.mm:1632) 9 QuartzCore 0x00000001989add88 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 364 (CALayer.mm:2647) 10 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 11 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 12 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 13 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 14 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 15 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 16 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 17 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 18 QuartzCore 0x00000001989add00 CA::Layer::commit_if_needed(CA::Transaction*, void (CA::Layer*, unsigned int, unsigned int) block... + 228 (CALayer.mm:2633) 19 QuartzCore 0x00000001988f6924 CA::Context::commit_transaction(CA::Transaction*, double) + 2872 (CAContextInternal.mm:2288) 20 QuartzCore 0x000000019891fc08 CA::Transaction::commit() + 676 (CATransactionInternal.mm:438) 21 UIKitCore 0x0000000195769698 -[_UIContextBinder updateBindableOrderWithTest:force:] + 704 (_UIContextBinder.m:280) 22 UIKitCore 0x0000000195769214 -[_UIContextBinder createContextsWithTest:creationAction:] + 100 (_UIContextBinder.m:233) 23 UIKitCore 0x00000001961d2510 -[UIWindowScene _prepareForResume] + 84 (UIWindowScene.m:712) 24 UIKitCore 0x00000001955e364c -[UIScene _emitSceneSettingsUpdateResponseForCompletion:afterSceneUpdateWork:] + 860 (UIScene.m:1055) 25 UIKitCore 0x00000001955e45b8 -[UIScene scene:didUpdateWithDiff:transitionContext:completion:] + 220 (UIScene.m:1315) 26 UIKitCore 0x0000000195b57248 -[UIApplicationSceneClientAgent scene:handleEvent:withCompletion:] + 464 (UIApplicationSceneClientAgent.m:80) 27 FrontBoardServices 0x0000000197051248 -[FBSSceneImpl updater:didUpdateSettings:withDiff:transitionContext:completion:] + 544 (FBSSceneImpl.m:551) 28 FrontBoardServices 0x0000000197075d28 __88-[FBSWorkspaceScenesClient sceneID:updateWithSettingsDiff:transitionContext:completion:]_bloc... + 120 (FBSWorkspaceScenesClient.m:356) 29 FrontBoardServices 0x000000019705af04 -[FBSWorkspace _calloutQueue_executeCalloutFromSource:withBlock:] + 232 (FBSWorkspace.m:357) 30 FrontBoardServices 0x0000000197075c5c __88-[FBSWorkspaceScenesClient sceneID:updateWithSettingsDiff:transitionContext:completion:]_bloc... + 184 (FBSWorkspaceScenesClient.m:355) 31 libdispatch.dylib 0x0000000191bfd184 _dispatch_client_callout + 16 (object.m:495) 32 libdispatch.dylib 0x0000000191ba5fd8 _dispatch_block_invoke_direct$VARIANT$mp + 224 (queue.c:466) 33 FrontBoardServices 0x000000019709a418 __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 40 (FBSSerialQueue.m:173) 34 FrontBoardServices 0x000000019709a0e4 -[FBSSerialQueue _queue_performNextIfPossible] + 404 (FBSSerialQueue.m:216) 35 FrontBoardServices 0x000000019709a60c -[FBSSerialQueue _performNextFromRunLoopSource] + 28 (FBSSerialQueue.m:247) 36 CoreFoundation 0x0000000191eaea00 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24 (CFRunLoop.c:1922) 37 CoreFoundation 0x0000000191eae958 __CFRunLoopDoSource0 + 80 (CFRunLoop.c:1956) 38 CoreFoundation 0x0000000191eae0f0 __CFRunLoopDoSources0 + 180 (CFRunLoop.c:1992) 39 CoreFoundation 0x0000000191ea923c __CFRunLoopRun + 1080 (CFRunLoop.c:2882) 40 CoreFoundation 0x0000000191ea8adc CFRunLoopRunSpecific + 464 (CFRunLoop.c:3192) 41 GraphicsServices 0x000000019be2e328 GSEventRunModal + 104 (GSEvent.c:2246) 42 UIKitCore 0x0000000195fa3ae0 UIApplicationMain + 1936 (UIApplication.m:4773) 43 <Our app name> 0x0000000100d9d32c main + 88 (main.m:14) 44 libdyld.dylib 0x0000000191d32360 start + 4