anchor.diff:  
   (defmethod medium-draw-rectangle* ((medium clx-medium) left top right bottom filled
                                      &aux (ink (medium-ink medium)))
  +  (declare (ignore ink))
     (let ((tr (sheet-native-transformation (medium-sheet medium))))
       (with-transformed-position (tr left top)
         (with-transformed-position (tr right bottom)
  
positive.code: 
  
  ;;; XXX: both PM and MM pixmaps should be freed with (xlib:free-pixmap pixmap)
  ;;; when not used. We do not do that right now.
  (defun compute-rgb-mask (drawable image)
  
negative.code:            (loop for y fixnum from 0 below height do
                  (let ((elt (aref idata y x)))
                    (setf (aref pdata y x) (ash elt -8)))))
        (put-image-recursively pm pm-gc pm-image width height 0 0)
        (xlib:free-gcontext pm-gc)
        (push #'(lambda () (xlib:free-pixmap pm)) ^cleanup)
        pm)))
  