glutSpaceballButtonFunc  - sets the Spaceball button call-
back for the current window.

glutSpaceballButtonFunc
	glutSpaceballButtonFunc(func) -> None

void glutSpaceballButtonFunc(void (*func)(int button, int state));

func      The new spaceball button callback function.

glutSpaceballButtonFunc sets the Spaceball button callback
for  the current window. The Spaceball button 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 button presses. The button param-
eter will be the button number (starting at one). The num-
ber of available Spaceball buttons can be determined  with
glutDeviceGet(GLUT_NUM_SPACEBALL_BUTTONS).  The  state  is
either GLUT_UP or GLUT_DOWN indicating whether  the  call-
back was due to a release or press respectively.

Registering  a  Spaceball button callback when a Spaceball
device is not available is ineffectual and not  an  error.
In this case, no Spaceball button callbacks will be gener-
ated.

Passing NULL to glutSpaceballButtonFunc disables the  gen-
eration  of  Spaceball button callbacks. When a new window
is created, no Spaceball button callback is initially reg-
istered.

glutSpaceballMotionFunc,   glutSpaceballRotateFunc,  glut-
MouseFunc,    glutButtonBoxFunc,     glutTabletButtonFunc,
glutJoystickFunc, glutDeviceGet

Mark J. Kilgard (mjk@nvidia.com)