anchor.diff:  ;;
   ;; --GB
   
  +(defparameter *3d-border-thickness* 2)
  +
   (defclass 3D-border-mixin ()
     ((border-width :initarg :border-width :initform 2)
      (border-style :initarg :border-style :initform :outset)
  
positive.code:                       ((:left) x1)
                        ((:right) (- x2 w))
                        ((:center) (/ (+ x1 x2 (- w)) 2))
                        (otherwise x1))  ;defensive programming
                      (case align-y
                        ((:top) (+ y1 as))
                        ((:center) (/ (+ y1 y2 (- as ds)) 2))
  
negative.code:     (draw-bordered-polygon pane (polygon-points (bounding-rectangle (sheet-region pane)))
                             :border-width border-width
                             :style border-style)))
  
  ;;; Common colors:
  
  