Martin Gerhardy
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.
An existing hint lets apps that don't need the timer resolution changed avoid
this, to save battery, etc, but this fixes several problems in timing, audio
callbacks not firing fast enough, etc.
Fixes Bugzilla #2944.
