Wayland does hit testing during teardown

[madebr]

During SDL_Quit, the wayland video driver might run the hit testing callback.
This callback might not be prepared to run with various destroyed resources and SDL partially shut down.

Reproducer:

• configure and build SDL3 with -DCMAKE_C_FLAGS="-DSDL_ASSERT_INVALID_PARAMS"
• run testshape test
• press escape

(The error does not always happen)

stacktrace:

SDL_ReadSurfacePixel_REAL SDL_surface.c:2813
SDL_ReadSurfacePixel SDL_dynapi_procs.h:738
ShapeHitTest testshape.c:23
pointer_dispatch_absolute_motion SDL_waylandevents.c:674
pointer_handle_frame SDL_waylandevents.c:1287
Wayland_DestroyWindow SDL_waylandwindow.c:3738
SDL_DestroyWindow_REAL SDL_video.c:4587
SDL_VideoQuit SDL_video.c:4699
SDL_QuitSubSystem_REAL SDL.c:671
SDL_Quit_REAL SDL.c:727
SDL_Quit SDL_dynapi_procs.h:725
main testshape.c:145

This can be fixed in testshape by not accessing the surface if it has been destroyed, but that would be the wrong approach imho.

SDL/test/testshape.c

Lines 18 to 30 in 0fb1177

	static SDL_HitTestResult SDLCALL ShapeHitTest(SDL_Window *window, const SDL_Point *area, void *userdata)
	{
	SDL_Surface *shape = (SDL_Surface *)userdata;
	Uint8 r, g, b, a;
	if (SDL_ReadSurfacePixel(shape, area->x, area->y, &r, &g, &b, &a)) {
	if (a != SDL_ALPHA_TRANSPARENT) {
	/* We'll just make everything draggable */
	return SDL_HITTEST_DRAGGABLE;
	}
	}
	return SDL_HITTEST_NORMAL;
	}