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Bug 3015

Summary: grab mouse inconsistent state
Product: SDL Reporter: Martin Gerhardy <martin.gerhardy>
Component: videoAssignee: Ryan C. Gordon <icculus>
Status: ASSIGNED --- QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: icculus, yv.sharma
Version: HG 2.0Keywords: target-2.0.4
Hardware: x86_64   
OS: Linux   

Description Martin Gerhardy 2015-06-15 06:45:04 UTC 
Not sure - but I think there might be a logic flaw in SDL_SetWindowGrab.

The problem here is that this modifies the window flags and e.g. sets 
SDL_WINDOW_INPUT_GRABBED - but the _this->grabbed_window pointer is not 
yet set.

Then in SDL_UpdateWindowGrab the _this->grabbed_window pointer is only 
set if the function pointer _this->SetWindowGrab is not NULL. But if 
this is NULL, the _this->grabbed_window pointer is never set, but every 
future call to any of the grab functions include an assert for:  
SDL_assert(!_this->grabbed_window || ((_this->grabbed_window->flags & 
SDL_WINDOW_INPUT_GRABBED) != 0));

That means the first call works, the second always fails and triggers 
the assert.
Comment 1 Sam Lantinga 2015-06-16 06:44:54 UTC 
Okay, I think this is fixed:
https://hg.libsdl.org/SDL/rev/885b6b5c8426

I don't have an environment where I can easily test this, can you verify the fix?

Thanks!
Comment 2 Martin Gerhardy 2015-06-16 07:43:29 UTC 
Still triggered.

Assertion failure at SDL_GetGrabbedWindow_REAL (/home/mgerhardy/dev/caveexpress/src/libs/SDL/src/video/SDL_video.c:2180), triggered 1 time:
  '!_this->grabbed_window || ((_this->grabbed_window->flags & SDL_WINDOW_INPUT_GRABBED) != 0)'
Comment 3 Martin Gerhardy 2015-06-16 07:44:02 UTC 
reopen - see my previous comment
Comment 4 Martin Gerhardy 2015-06-16 07:48:20 UTC 
looks like SDL_SetWindowGrab and SDL_UpdateWindowGrab compute different "SDL_bool grabbed" states
Comment 5 Ryan C. Gordon 2015-06-16 14:42:30 UTC 
This one is my bug, taking it.

--ryan.
Comment 6 Yash 2015-07-21 04:40:35 UTC 
Hi Ryan

Any fix so far ?
Comment 7 Ryan C. Gordon 2015-12-31 08:54:32 UTC 
Actually, I'm trying to find a way to trigger that assertion and can't.

Martin, is this still happening to you?

--ryan.
Comment 8 Martin Gerhardy 2015-12-31 10:22:28 UTC 
hm. I can't reproduce the assert anymore - but for my code the grabbing and ungrabbing doesn't work at all anymore. I always have the mouse grabbed (software renderer - as there might be grabbing issues... e.g. I only receive mouse move event in software render mode after I at least once alt+tabbed away)

will try a different renderer to double check.
Comment 9 Martin Gerhardy 2015-12-31 10:59:47 UTC 
Assertion failure at SDL_GetGrabbedWindow_REAL (/home/mgerhardy/dev/caveexpress/src/libs/sdl2/src/video/SDL_video.c:2283), triggered 1 time:
  '!_this->grabbed_window || ((_this->grabbed_window->flags & SDL_WINDOW_INPUT_GRABBED) != 0)'

still happens on latest hg rev.

void SDLFrontend::toggleGrabMouse () {
#if SDL_VERSION_ATLEAST(2, 0, 4)
	const bool grabMouse = SDL_GetGrabbedWindow() == _window;
#else
	const bool grabMouse = Config.isGrabMouse();
#endif
	if (grabMouse) {
		SDL_SetWindowGrab(_window, SDL_FALSE);
		Log::info(LOG_GFX, "Mouse grab is now deactivated");
		Config.setGrabMouse(false);
	} else {
		SDL_SetWindowGrab(_window, SDL_TRUE);
		Log::info(LOG_GFX, "Mouse grab is now activated");
		Config.setGrabMouse(true);
	}
}

this is the code that I use to trigger it.