SDL_JoyBallEvent - Joystick trackball motion event structure

SDL_JoyBallEvent  is  a member of the SDL_Event union and is used when an event of type SDL_JOYBALLMOTION
       is reported.

       A SDL_JOYBALLMOTION event occurs when a user moves a trackball on the joystick. The field  which  is  the
       index of the joystick that reported the event and ball is the index of the trackball (for a more detailed
       explaination  see  the  Joysticksection). Trackballs only return relative motion, this is the change in
       position on the ball since it was last polled (last cycle of the event loop) and it is stored in xrel and
       yrel.

       SDL_JoyBallEvent - Joystick trackball motion event structure

SDL_Event, JoystickFunctions, SDL_JoystickEventState, SDL_JoystickGetBall

SDL                                          Tue 11 Sep 2001, 22:59                          SDL_JoyBallEvent(3)

typeSDL_JOYBALLMOTIONwhich               Joystick device index

       ball                Joystick trackball index

       xrel, yrel          The relative motion in the X/Y direction

       typedef struct{
         Uint8 type;
         Uint8 which;
         Uint8 ball;
         Sint16 xrel, yrel;
       } SDL_JoyBallEvent;