Get the ball axis change since the last poll.
int SDL_JoystickGetBall(SDL_Joystick *joystick,
int ball, int *dx, int *dy);
|the SDL_Joystick to query
|the ball index to query; ball indices start at index 0
|stores the difference in the x axis position since the last poll
|stores the difference in the y axis position since the last poll
Returns 0 on success or a negative error code on failure; call SDL_GetError() for more information.
Trackballs can only return relative motion since the last call to SDL_JoystickGetBall(), these motion deltas are placed into
Most joysticks do not have trackballs.
This function is available since SDL 2.0.0.