Get the ball axis change since the last poll.
Defined in SDL_joystick.h
| joystick | the SDL_Joystick to query |
| ball | the ball index to query; ball indices start at index 0 |
| dx | stores the difference in the x axis position since the last poll |
| dy | 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 dx and dy.
Most joysticks do not have trackballs.
This function is available since SDL 2.0.0.