A variable controlling whether the system mouse acceleration curve is used for relative mouse motion.
Defined in SDL_hints.h
#define SDL_HINT_MOUSE_RELATIVE_SYSTEM_SCALE "SDL_MOUSE_RELATIVE_SYSTEM_SCALE"
This variable can be set to the following values:
If SDL_HINT_MOUSE_RELATIVE_SPEED_SCALE is set, that will override the system speed scale.