anchor.diff:    (let* ((port (port medium))
   	 (mirror (port-lookup-mirror port (medium-sheet medium)))
   	 (line-style (medium-line-style medium)))
  -    (with-slots (gc clipping-region-dirty) medium
  +    (with-slots (gc last-medium-device-region) medium
         (unless gc
   	(setq gc (xlib:create-gcontext :drawable mirror))
   	;; this is kind of false, since the :unit should be taken
  
positive.code:       (let ((fn (text-style-to-X-font port (medium-text-style medium))))
          (when (typep fn 'xlib:font)
            (setf (xlib:gcontext-font gc) fn)))
        (when clipping-region-dirty
          (%set-gc-clipping-region medium gc)
          (setf clipping-region-dirty nil))
        gc)))
  
  (defmethod medium-gcontext ((medium clx-medium) (ink (eql +transparent-ink+)))
  
negative.code:             ;; to clx :] we stick with :unsorted until that can be sorted out
              (setf (xlib:gcontext-clip-mask gc :unsorted) rect-seq)))))))
  
  
  (defgeneric medium-gcontext (medium ink))
  