SDL_SetCursor doesn't work very well on Mac external monitors #12230
Description
My app wants to change the cursor when the mouse moves into a view in my Appkit-alike framework when the user has selected an icon in the collection view at the bottom.
On the built-in-to-the-laptop screen, the below code works perfectly every time. On either of the 2 external monitors plugged in, it works maybe 2-5% of the time (and once it's not working it seems to stay not working for the duration of the app). I can't find anything that correlates to it "working" on the external monitors.
- (void) _setCursor
{
NSLog(@"setting cursor");
if (_cursor)
SDL_DestroyCursor(_cursor);
if (_cursorImage == nil)
SDL_Log("no image!");
SDL_SetCursor(_arrowCursor);
else
{
int W = _cursorImage.width * _zoomFactor[_zoom];
int H = _cursorImage.height * _zoomFactor[_zoom];
SDL_Surface *scaled = SDL_CreateSurface(W, H, SDL_PIXELFORMAT_ABGR8888);
id<AZRenderer> azr = AZRenderer.renderer;
SDL_Surface *surface = [azr surfaceFor:_cursorImage.texture];
SDL_Rect srcRect = SDL_RECT(_cursorImage.srcRect);
SDL_BlitSurfaceScaled(surface, &srcRect,
scaled, NULL,
SDL_SCALEMODE_LINEAR);
SDL_DestroySurface(surface);
_cursor = SDL_CreateColorCursor(scaled, 0, 0);
if (!SDL_SetCursor(_cursor))
SDL_Log("setcursor failed: %s", SDL_GetError());
SDL_DestroySurface(scaled);
}
}
The call to SDL_SetCursor always succeeds, and in fact it looks as though the cursor is being set on the external monitor, but as soon as I move the mouse, it is reset to the arrow again - see attached video. I did manage to capture the single frame when the mouse doesn't move for a while, and the cursor stayed set, but that was a large video to upload :)
sdl_setcursor.mov
I added logging to every call of SDL_SetCursor in my app, and it never calls anything other than the above. In the debugger, the values always look fine (which again agrees with the set-then-reset theory).