glutSpaceballMotionFunc sets the Spaceball motion callback for the current window.
void glutSpaceballMotionFunc(void (*func)(int x, int y, int z));
glutSpaceballMotionFunc sets the Spaceball motion callback for the current window. The Spaceball motion callback for a window is called when the window has Spaceball input focus (normally, when the mouse is in the window) and the user generates Spaceball translations. The x, y, and z callback parameters indicate the translations along the X, Y, and Z axes. The callback parameters are normalized to be within the range of -1000 to 1000 inclusive.
Registering a Spaceball motion callback when a Spaceball device is not available has no effect and is not an error. In this case, no Spaceball motion callbacks will be generated.
Passing NULL to glutSpaceballMotionFunc disables the generation of Spaceball motion callbacks. When a new window is created, no Spaceball motion callback is initially registered.