Joystick trackball motion event structure (event.jball.*)
Defined in SDL_events.h
typedef struct SDL_JoyBallEvent
{
Uint32 type; /**< SDL_JOYBALLMOTION */
Uint32 timestamp; /**< In milliseconds, populated using SDL_GetTicks() */
SDL_JoystickID which; /**< The joystick instance id */
Uint8 ball; /**< The joystick trackball index */
Uint8 padding1;
Uint8 padding2;
Uint8 padding3;
Sint16 xrel; /**< The relative motion in the X direction */
Sint16 yrel; /**< The relative motion in the Y direction */
} SDL_JoyBallEvent;