Manpages - SDL_JoystickGetBall.3

SDL_JoystickGetBall - Get relative trackball motion

#include “SDL.h”

int SDL_JoystickGetBall*(*SDL_Joystick *joystick, int ball, int *dx, int *dy);

Get the ball axis change.

Trackballs can only return relative motion since the last call to SDL_JoystickGetBall, these motion deltas a placed into dx and dy.

Returns 0 on success or -1 on failure

  int delta_x, delta_y;
  SDL_Joystick *joy;
  .
  .
  .
  SDL_JoystickUpdate();
  if(SDL_JoystickGetBall(joy, 0, &delta_x, &delta_y)==-1)
    printf("TrackBall Read Error!
  ");
  printf("Trackball Delta- X:%d, Y:%d
  ", delta_x, delta_y);

SDL_JoystickNumBalls