anchor.diff:         ((,window :pointer) (,x :double) (,y :double))
        ,@body))
   
  -(defun set-key-callback (callback-name)
  -  (%glfw:set-key-callback (cffi:get-callback callback-name)))
  -
  -(defun set-char-callback (callback-name)
  -  (%glfw:set-char-callback (cffi:get-callback callback-name)))
  -
  -(defun set-mouse-button-callback (callback-name)
  -  (%glfw:set-mouse-button-callback (cffi:get-callback callback-name)))
  -
  -(defun set-cursor-position-callback (callback-name)
  -  (%glfw:set-cursor-position-callback (cffi:get-callback callback-name)))
  -
  -(defun set-cursor-enter-callback (callback-name)
  -  (%glfw:set-cursor-enter-callback (cffi:get-callback callback-name)))
  -
  -(defun set-scroll-callback (callback-name)
  -  (%glfw:set-scroll-callback (cffi:get-callback callback-name)))
  +(defun set-key-callback (callback-name &optional (window *window*))
  +  (%glfw:set-key-callback window (cffi:get-callback callback-name)))
  +
  +(defun set-char-callback (callback-name &optional (window *window*))
  +  (%glfw:set-char-callback window (cffi:get-callback callback-name)))
  +
  +(defun set-mouse-button-callback (callback-name &optional (window *window*))
  +  (%glfw:set-mouse-button-callback window (cffi:get-callback callback-name)))
  +
  +(defun set-cursor-position-callback (callback-name &optional (window *window*))
  +  (%glfw:set-cursor-position-callback window (cffi:get-callback callback-name)))
  +
  +(defun set-cursor-enter-callback (callback-name &optional (window *window*))
  +  (%glfw:set-cursor-enter-callback window (cffi:get-callback callback-name)))
  +
  +(defun set-scroll-callback (callback-name &optional (window *window*))
  +  (%glfw:set-scroll-callback window (cffi:get-callback callback-name)))
   
   (import-export %glfw:joystick-present-p %glfw:get-joystick-axes %glfw:get-joystick-buttons %glfw:get-joystick-name)
   
  
positive.code:    def-cursor-pos-callback
     def-cursor-enter-callback
     def-scroll-callback
     set-char-callback
     set-mouse-button-callback
     set-cursor-position-callback
  
negative.code:      (if (%glfw:init)
  	 (unwind-protect
  	      (progn
  		,@body)
  	   (%glfw:terminate))
  	 (error "Error initializing glfw."))))
  