anchor.diff:                            (medium-gcontext from-drawable +background-ink+)
                             (round-coordinate from-x) (round-coordinate from-y)
                             (round width) (round height)
  -                          (or (medium-buffer to-drawable)
  -                              (sheet-xmirror (medium-sheet to-drawable)))
  +                          (sheet-xmirror (medium-sheet to-drawable))
                             (round-coordinate to-x) (round-coordinate to-y)))))))
   
   (defmethod medium-copy-area ((from-drawable clx-medium) from-x from-y width height
  
positive.code:   ((gc :initform nil)
     (last-medium-device-region :initform nil
                                :accessor last-medium-device-region)
     (clipping-region-tmp :initform (vector 0 0 0 0)
       :documentation "This object is reused to avoid consing in the
   most common case when configuring the clipping region.")
     (clipping-pixmap-cache
      :initform (cons +everywhere+ nil)
      :documentation "This object stores cons of the last non-rectangular clipping
  region and its clipping pixmap. This is looked up for optimization with region-equal."
      :accessor %clipping-pixmap-cache)
     (buffer :initform nil :accessor medium-buffer)))
  
  
  
negative.code:                     (medium-gcontext to-drawable +background-ink+)
                      (round-coordinate from-x) (round-coordinate from-y)
                      (round width) (round height)
                      (sheet-xmirror (medium-sheet to-drawable))
                      (round-coordinate to-x) (round-coordinate to-y))))
  
  (defmethod medium-copy-area ((from-drawable pixmap) from-x from-y width height
  