SDL Library Documentation
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# SDL_JoyBallEvent

## Name

SDL_JoyBallEvent -- Joystick trackball motion event structure

## Structure Definition

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

## Structure Data

`type` | `SDL_JOYBALLMOTION`
`which` | Joystick device index
`ball` | Joystick trackball index
`xrel`, `yrel` | The relative motion in the X/Y direction

## Description

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 Joystick section). 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`.

## See Also

SDL_Event, Joystick Functions, `SDL_JoystickEventState`, `SDL_JoystickGetBall`

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