We've been using PencilKit in our app for a couple of years now, but have run into a significant slowdown recently. It coincided with a shift to iPadOS 17, but possibly that's a coincidence.
It seems to occur when we add PKStroke elements to a PKDrawing (programatically). Previously this has refreshed on-screen instantly, but now it's so slow we can sometime see the new stroke progressively drawing on-screen. I profiled the running app and the lag seems to entirely occur within the following call sequence:
2563 -[PKDrawingConcrete addNewStroke:]
2494 -[PKDrawing setNeedsRecognitionUpdate]
2434 -[NSUserDefaults(NSUserDefaults) boolForKey:]
2419 _CFPreferencesGetAppBooleanValueWithContainer
2417 _CFPreferencesCopyAppValueWithContainerAndConfiguration
2399 -[_CFXPreferences copyAppValueForKey:identifier:container:configurationURL:]
2395 -[_CFXPreferences withSearchListForIdentifier:container:cloudConfigurationURL:perform:]
2394 normalizeQuintuplet
2367 __108-[_CFXPreferences(SearchListAdditions) withSearchListForIdentifier:container:cloudConfigurationURL:perform:]_block_invoke
2338 __76-[_CFXPreferences copyAppValueForKey:identifier:container:configurationURL:]_block_invoke
2336 -[CFPrefsSource copyValueForKey:]
2332 -[CFPrefsSearchListSource alreadylocked_copyValueForKey:]
1924 -[CFPrefsSearchListSource alreadylocked_copyValueForKey:].cold.1
1921 _os_log_debug_impl
1918 _os_log
1914 _os_log_impl_flatten_and_send
1829 _os_log_impl_stream
1811 _os_activity_stream_reflect
1205 dispatch_block_perform
1199 _dispatch_block_invoke_direct
1195 _dispatch_client_callout
1194 ___os_activity_stream_reflect_block_invoke
1188 _xpc_pipe_simpleroutine
882 _xpc_send_serializer
867 _xpc_pipe_mach_msg
859 mach_msg
859 mach_msg_overwrite
855 mach_msg2_internal
853 0x1cf7701d8
Up to 'addNewStroke' this makes sense. But where is it going with 'PKDrawing setNeedsRecognitionUpdate'? This ultimately seems to be hitting some kind of lock, which I assume is the cause of the lag.
Any suggestions for why this is happening or a means of avoiding it would be much appreciated.
