Main thread gets stuck on left mouse down

SDL Development
1

Hi,
My video player app runs on OSX 10.12.5. It has a window that runs borderless, fullscreen and in a non-resizable mode. Once in a while when I do the following use case, the main thread gets stuck trying to poll events.
My use case is:

  • Run the app, it runs in full screen(I use SDL_WINDOW_FULLSCREEN_DESKTOP)
  • Cmd-tab to go out of full screen to another app
  • Cmd-tab again to get back to my app
  • Press left mouse button, don’t release yet.
    After this point the main thread is stuck until I release the left mouse button and hence video rendering doesn’t happen anymore.

On debugging more, I see that thread 0 is stuck as shown below with sendEvent processing left mouse down. It comes out only after it receives a left mouse up. There are some frames below which show NSWindowResizing, but my window flag doesn’t have SDL_WINDOW_RESIZABLE set. Can someone help me solve this issue.

Thread 0:: CrBrowserMain Dispatch queue: com.apple.main-thread
0 libsystem_kernel.dylib 0x00007fffbe13d34a mach_msg_trap + 10
1 libsystem_kernel.dylib 0x00007fffbe13c797 mach_msg + 55
2 com.apple.CoreFoundation 0x00007fffa889d434 __CFRunLoopServiceMachPort + 212
3 com.apple.CoreFoundation 0x00007fffa889c8c1 __CFRunLoopRun + 1361
4 com.apple.CoreFoundation 0x00007fffa889c114 CFRunLoopRunSpecific + 420
5 com.apple.HIToolbox 0x00007fffa7dfdebc RunCurrentEventLoopInMode + 240
6 com.apple.HIToolbox 0x00007fffa7dfdcf1 ReceiveNextEventCommon + 432
7 com.apple.HIToolbox 0x00007fffa7dfdb26 _BlockUntilNextEventMatchingListInModeWithFilter + 71
8 com.apple.AppKit 0x00007fffa6396a54 _DPSNextEvent + 1120
9 com.apple.AppKit 0x00007fffa6b127ee -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 2796
10 com.apple.AppKit 0x00007fffa66f568d +[NSWindow(NSWindowResizing) _mouseHysteresisCheck:withExpiration:andDistance:finalMouseLocation:] + 525
11 com.apple.AppKit 0x00007fffa65eedb5 -[NSWindow(NSWindowResizing) _hitTestWithHysteresisCheck:forEvent:allowWindowDragging:] + 394
12 com.apple.AppKit 0x00007fffa6c8f0db -[NSWindow(NSEventRouting) _handleMouseDownEvent:isDelayedEvent:] + 1873
13 com.apple.AppKit 0x00007fffa6c8ca6c -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:] + 1942
14 com.apple.AppKit 0x00007fffa6c8bf0a -[NSWindow(NSEventRouting) sendEvent:] + 541
15 org.libsdl.SDL2 0x000000010d46d74a -[SDLWindow sendEvent:] + 90
16 com.apple.AppKit 0x00007fffa6b10681 -[NSApplication(NSEvent) sendEvent:] + 1145
17 org.libsdl.SDL2 0x000000010d46532b -[SDLApplication sendEvent:] + 139
18 org.libsdl.SDL2 0x000000010d466b2f Cocoa_PumpEvents + 495
19 org.libsdl.SDL2 0x000000010d44c1d5 SDL_PumpEvents_REAL + 53
20 org.libsdl.SDL2 0x000000010d44c2f5 SDL_WaitEventTimeout_REAL + 53
21 org.libsdl.SDL2 0x000000010d44c2b7 SDL_PollEvent_REAL + 23
22 org.libsdl.SDL2 0x000000010d51bb24 SDL_PollEvent + 36
23 libTest.dylib 0x000000010cf3e0e8 SDLEventProcessor::processEvents(int) + 568
24 Test 0x000000010cde6bba BrowserApp::RunAppMessageLoop(BAInstData*, CefStringBase, CefStringBase) + 810
25 Test 0x000000010ce04bbc main + 17980
26 libdyld.dylib 0x00007fffbe016235 start + 1

2

It seems like clicking on the edge of the screen in fullscreen desktop mode blocks the main thread…
I reproduced this on:

  • OSX 10.12.5
  • current hg SDL

I launched the SDLTest.xcodeproj in SDL/Xcode/SDLTest and ran the testgl2 target.

  • Pressed alt+enter to go fullscreen-desktop
  • move the mouse cursor to the top-left corner of the screen (also works on any edge)
  • click and hold the mouse, the spinning cube will stop

edit: seems like -windowWillEnterFullScreen: in SDL_cocoawindow.m is setting NSResizableWindowMask, which is why this is happening.

3

Thanks for the reply Eric.

Yes, that’s exactly my observation too. Once in fullscreen, I don’t see the need for this flag to be present. When I clear the flag in windowDidEnterFullScreen, the issue no longer repros.

Let me raise a bug for tracking this.