From ce8aae1419f88ccc8b9c0615f7ddbef65a9bbbf4 Mon Sep 17 00:00:00 2001 From: Dean Herbert Date: Wed, 13 Jul 2022 15:01:55 +0900 Subject: [PATCH] Fix `Cocoa_GetWindowDisplayIndex` failing and causing a catastrophic crash With the introduction of this function, it is possible that for certain monitor and window configurations, creating an SDL window will cause a native crash. ``` Crashed Thread: 0 Dispatch queue: com.apple.main-thread Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000050 Exception Codes: 0x0000000000000001, 0x0000000000000050 Exception Note: EXC_CORPSE_NOTIFY Termination Reason: Namespace SIGNAL, Code 11 Segmentation fault: 11 Terminating Process: exc handler [56627] VM Region Info: 0x50 is not in any region. Bytes before following region: 140737486737328 REGION TYPE START - END [ VSIZE] PRT/MAX SHRMOD REGION DETAIL UNUSED SPACE AT START ---> VM_ALLOCATE 7fffffe75000-7fffffe76000 [ 4K] r-x/r-x SM=ALI Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 libSDL2.dylib 0x10247f665 SDL_UpdateFullscreenMode + 357 1 libSDL2.dylib 0x10247ec70 SDL_CreateWindow_REAL + 1504 2 ??? 0x111262de8 ??? 3 ??? 0x110c39fff ??? 4 libcoreclr.dylib 0x101fdf2a9 CallDescrWorkerInternal + 124 ``` Tracking thread from our end: https://github.com/ppy/osu-framework/issues/5190 Regressed with: https://github.com/libsdl-org/SDL/pull/5573 In testing, the window would not find a valid screen if created "hanging" off a primary display with a secondary display below it. In checking why this was the case, the `display_centre` was being calculated with a negative y origin, causing a final negative value falling outside all display bounds: ``` SDL error log [debug]: display_centre.y = -1296 + 1296 / 2 SDL error log [debug]: Display rect 0: 0 0 2560 1440 SDL error log [debug]: Display rect 1: 2560 -625 1080 2560 SDL error log [debug]: Display rect 2: 0 1440 1728 1296 ``` The method that was being used to find the current window using the frame origin/size seems unreliable, so I have opted to replace it with with a tried method (https://stackoverflow.com/a/40891902). Initial testing shows that this works with non-standard DPI screens, but further testing would be appreciated (cc @sezero / @misl6 from the original PR thread). --- src/video/cocoa/SDL_cocoawindow.m | 29 ++++++++++------------------- 1 file changed, 10 insertions(+), 19 deletions(-) diff --git a/src/video/cocoa/SDL_cocoawindow.m b/src/video/cocoa/SDL_cocoawindow.m index dca560ba9..3f5c04631 100644 --- a/src/video/cocoa/SDL_cocoawindow.m +++ b/src/video/cocoa/SDL_cocoawindow.m @@ -2230,9 +2230,6 @@ int Cocoa_GetWindowDisplayIndex(_THIS, SDL_Window * window) { @autoreleasepool { - NSRect displayframe; - SDL_Point display_center; - SDL_Rect sdl_display_rect; SDL_WindowData *data = (__bridge SDL_WindowData *) window->driverdata; /* Not recognized via CHECK_WINDOW_MAGIC */ @@ -2240,23 +2237,17 @@ Cocoa_GetWindowDisplayIndex(_THIS, SDL_Window * window) return 0; } - /* - Considering that we already have the display coordinates in which the window is placed (described via displayframe) - instead of checking in which display the window is placed, we should check which SDL display matches the display described - via displayframe. - */ - displayframe = data.nswindow.screen.frame; - - display_center.x = displayframe.origin.x + displayframe.size.width / 2; - display_center.y = displayframe.origin.y + displayframe.size.height / 2; - - for (int i = 0; i < SDL_GetNumVideoDisplays(); i++){ - SDL_GetDisplayBounds(i, &sdl_display_rect); - if (SDL_EnclosePoints(&display_center, 1, &sdl_display_rect, NULL)) { - return i; - } + NSArray *screens = [NSScreen screens]; + + int index = 0; + for (NSScreen *screen in screens) { + if (screen == data.nswindow.screen) + return index; + + index++; } - SDL_SetError("Couldn't find the display where the window is attached to."); + + SDL_SetError("Couldn't find the display where the window is attached."); return -1; }}