glutSpaceballRotateFunc sets the Spaceball rotation callback for the current window.
void glutSpaceballRotateFunc(void (*func)(int x, int y, int z));
glutSpaceballRotateFunc sets the Spaceball rotate callback for the current window. The Spaceball rotate 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 rotations. The x, y, and z callback parameters indicate the rotation along the X, Y, and Z axes. The callback parameters are normalized to be within the range of -1800 to 1800 inclusive.
Registering a Spaceball rotate callback when a Spaceball device is not available is ineffectual and not an error. In this case, no Spaceball rotate callbacks will be generated.
Passing NULL to glutSpaceballRotateFunc disables the generation of Spaceball rotate callbacks. When a new window is created, no Spaceball rotate callback is initially registered.