anchor.diff:    ((gc :initform nil)
      (picture :initform nil)
      (last-medium-device-region :initform nil
  -			      :accessor last-medium-device-region)
  +                              :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.")
  
positive.code: 
  (defmethod medium-gcontext :before ((medium clx-medium) ink)
    (let* ((port (port medium))
  	 (mirror (port-lookup-mirror port (medium-sheet medium))))
      (with-slots (gc) medium
        (unless gc
          (setq gc (xlib:create-gcontext :drawable mirror))
  
negative.code:              (let ((radius (/ (line-style-thickness line-style) 2)))
                 (do-sequence ((x y) coord-seq)
                   (let ((min-x (round-coordinate (- x radius)))
                         (min-y (round-coordinate (- y radius)))
                         (max-x (round-coordinate (+ x radius)))
                         (max-y (round-coordinate (+ y radius))))
                     (when (and (typep min-x '(signed-byte 16))
                                (typep min-y '(signed-byte 16)))
                       (xlib:draw-arc mirror gc min-x min-y
                                      (- max-x min-x) (- max-y min-y)
                                      0 (* 2 pi) t))))))))))
  
  (defmethod medium-draw-line* ((medium clx-medium) x1 y1 x2 y2)
    (let ((tr (sheet-native-transformation (medium-sheet medium))))
  