NAME
	  fgluQuadricCallback -	define a callback for a	quadrics
	  object


     FORTRAN SPECIFICATION
	  SUBROUTINE fgluQuadricCallback( CHARACTER*8 quad,
					  INTEGER*4 which,
					  CHARACTER*8 (CallBackFunc)( )


     PARAMETERS
	  quad		Specifies the quadrics object (created with
			fgluNewQuadric).

	  which		Specifies the callback being defined.  The
			only valid value is GLU_ERROR.

	  CallBackFunc	Specifies the function to be called.

     DESCRIPTION
	  fgluQuadricCallback is used to define	a new callback to be
	  used by a quadrics object.  If the specified callback	is
	  already defined, then	it is replaced.	If CallBackFunc	is
	  NULL,	then any existing callback is erased.

	  The one legal	callback is GLU_ERROR:

	  GLU_ERROR	 The function is called	when an	error is
			 encountered. Its single argument is of	type
			 GLenum, and it	indicates the specific error
			 that occurred.	 Character strings describing
			 these errors can be retrieved with the
			 fgluErrorString call.

     SEE ALSO
	  fgluErrorString, fgluNewQuadric