HelloMy system is Xcode 9.3, High Sierra 10.13.4.I have an NSWindow containing only a subclass of NSOpenGLView. The view is displaying a simple texture. If I grab the corner of my window and start resizing, after a few seconds dragging the window edge around I get the following crash:*** Assertion failure in -[MyOpenGLView _enableNeedsDisplayInRectNotifications], /BuildRoot/Library/Caches/com.apple.xbs/Sources/AppKit/AppKit-1561.40.112/AppKit.subproj/NSView.m:18293 [General] Overflowed needs display in rect posting count.The crash always occurs. If I move the mouse more slowly, it takes a little more time to occur. Move the mouse faster and the crash happens sooner.I post the full stack trace below. Note that at no point is any of my code listed in the stack. I do not call setNeedsDisplay or setNeedsDisplayInRect: anywhere in response to resizing the window. My gl reshape method is empty. There is no recursion happening in drawRect:.I can workaround the issue by adding these empty overrides to my view:- (void)_enableNeedsDisplayInRectNotifications { } - (void)_disableNeedsDisplayInRectNotifications { }It looks and smells like a bug in AppKit. But what is triggering it?Thanks in advanceFull stack trace:** Assertion failure in -[MyOpenGLView _enableNeedsDisplayInRectNotifications], /BuildRoot/Library/Caches/com.apple.xbs/Sources/AppKit/AppKit-1561.40.112/AppKit.subproj/NSView.m:18293 2018-04-18 12:08:14.785967-0700 MyApp[22899:701655] [General] Overflowed needs display in rect posting count. 2018-04-18 12:08:14.790419-0700 MyApp[22899:701655] [General] ( 0 CoreFoundation 0x00007fff504d932b __exceptionPreprocess + 171 1 libobjc.A.dylib 0x00007fff77b53c76 objc_exception_throw + 48 2 CoreFoundation 0x00007fff504df0c2 +[NSException raise:format:arguments:] + 98 3 Foundation 0x00007fff525fb340 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193 4 AppKit 0x00007fff4e2a9a32 -[NSView(NSInternal) _enableNeedsDisplayInRectNotifications] + 202 5 AppKit 0x00007fff4e06829f -[NSPortalView layout] + 361 6 AppKit 0x00007fff4e299ad0 _NSViewLayout + 587 7 AppKit 0x00007fff4da93eff -[NSView _layoutSubtreeWithOldSize:] + 437 8 AppKit 0x00007fff4da94178 -[NSView _layoutSubtreeWithOldSize:] + 1070 9 AppKit 0x00007fff4da94178 -[NSView _layoutSubtreeWithOldSize:] + 1070 10 AppKit 0x00007fff4da94178 -[NSView _layoutSubtreeWithOldSize:] + 1070 11 AppKit 0x00007fff4e2a082c -[NSView _layoutSubtreeIfNeededAndAllowTemporaryEngine:] + 1380 12 AppKit 0x00007fff4dab16ef -[NSWindow(NSConstraintBasedLayout) _layoutViewTree] + 163 13 AppKit 0x00007fff4da9888a -[NSWindow _setFrame:updateBorderViewSize:] + 1124 14 AppKit 0x00007fff4dab0c67 -[NSWindow _oldPlaceWindow:] + 604 15 AppKit 0x00007fff4dab021a -[NSWindow _setFrameCommon:display:stashSize:] + 3108 16 AppKit 0x00007fff4daaf5e9 -[NSWindow _setFrame:display:allowImplicitAnimation:stashSize:] + 222 17 AppKit 0x00007fff4daaf504 -[NSWindow setFrame:display:] + 67 18 AppKit 0x00007fff4e4f23e9 -[NSWindow(NSWindowResizing) _resizeSetFrame:withEvent:] + 124 19 AppKit 0x00007fff4dd1a37f -[NSWindow(NSWindowResizing) _resizeWithEvent:] + 3060 20 AppKit 0x00007fff4e258422 -[NSTitledFrame attemptResizeWithEvent:] + 177 21 AppKit 0x00007fff4dc243dd -[NSThemeFrame handleMouseDown:] + 297 22 AppKit 0x00007fff4dc24603 -[NSThemeFrame mouseDown:] + 30 23 AppKit 0x00007fff4e325d6d -[NSWindow(NSEventRouting) _handleMouseDownEvent:isDelayedEvent:] + 5891 24 AppKit 0x00007fff4e3229c4 -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:] + 2359 25 AppKit 0x00007fff4e321c70 -[NSWindow(NSEventRouting) sendEvent:] + 497 26 AppKit 0x00007fff4e183236 -[NSApplication(NSEvent) sendEvent:] + 2462 27 AppKit 0x00007fff4d9e38b5 -[NSApplication run] + 812 28 AppKit 0x00007fff4d9b2a72 NSApplicationMain + 804 29 MyApp 0x000000010003208a main + 170 30 libdyld.dylib 0x00007fff7876d015 start + 1 31 ??? 0x0000000000000001 0x0 + 1 ) 2018-04-18 12:08:14.791393-0700 MyApp[22899:701655] *** Assertion failure in -[MyOpenGLView _disableNeedsDisplayInRectNotifications], /BuildRoot/Library/Caches/com.apple.xbs/Sources/AppKit/AppKit-1561.40.112/AppKit.subproj/NSView.m:18297 2018-04-18 12:08:14.792496-0700 MyApp[22899:701655] [General] An uncaught exception was raised 2018-04-18 12:08:14.792513-0700 MyApp[22899:701655] [General] Unbalanced needs display in rect posting count. 2018-04-18 12:08:14.792573-0700 MyApp[22899:701655] [General] ( 0 CoreFoundation 0x00007fff504d932b __exceptionPreprocess + 171 1 libobjc.A.dylib 0x00007fff77b53c76 objc_exception_throw + 48 2 CoreFoundation 0x00007fff504df0c2 +[NSException raise:format:arguments:] + 98 3 Foundation 0x00007fff525fb340 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193 4 AppKit 0x00007fff4e2a9af2 -[NSView(NSInternal) _disableNeedsDisplayInRectNotifications] + 190 5 AppKit 0x00007fff4e06876b -[_NSPortalView2 setSourceView:] + 166 6 AppKit 0x00007fff4e06802a -[NSPortalView dealloc] + 89 7 libobjc.A.dylib 0x00007fff77b49087 _ZN12_GLOBAL__N_119AutoreleasePoolPage3popEPv + 817 8 CoreFoundation 0x00007fff50412a56 _CFAutoreleasePoolPop + 22 9 Foundation 0x00007fff525378ad -[NSAutoreleasePool drain] + 144 10 AppKit 0x00007fff4d9e3990 -[NSApplication run] + 1031 11 AppKit 0x00007fff4d9b2a72 NSApplicationMain + 804 12 MyApp 0x000000010003208a main + 170 13 libdyld.dylib 0x00007fff7876d015 start + 1 14 ??? 0x0000000000000001 0x0 + 1 ) 2018-04-18 12:08:14.793037-0700 MyApp[22899:701655] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unbalanced needs display in rect posting count.' *** First throw call stack: ( 0 CoreFoundation 0x00007fff504d932b __exceptionPreprocess + 171 1 libobjc.A.dylib 0x00007fff77b53c76 objc_exception_throw + 48 2 CoreFoundation 0x00007fff504df0c2 +[NSException raise:format:arguments:] + 98 3 Foundation 0x00007fff525fb340 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193 4 AppKit 0x00007fff4e2a9af2 -[NSView(NSInternal) _disableNeedsDisplayInRectNotifications] + 190 5 AppKit 0x00007fff4e06876b -[_NSPortalView2 setSourceView:] + 166 6 AppKit 0x00007fff4e06802a -[NSPortalView dealloc] + 89 7 libobjc.A.dylib 0x00007fff77b49087 _ZN12_GLOBAL__N_119AutoreleasePoolPage3popEPv + 817 8 CoreFoundation 0x00007fff50412a56 _CFAutoreleasePoolPop + 22 9 Foundation 0x00007fff525378ad -[NSAutoreleasePool drain] + 144 10 AppKit 0x00007fff4d9e3990 -[NSApplication run] + 1031 11 AppKit 0x00007fff4d9b2a72 NSApplicationMain + 804 12 MyApp 0x000000010003208a main + 170 13 libdyld.dylib 0x00007fff7876d015 start + 1 14 ??? 0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException