anchor.diff:  			    (make-translation-transformation (- x x1) (- y y1))))
   		    (allocate-space child (round new-width) (round new-height)))))
   
  -;;; SPACER PANE
  -
  -(defclass spacer-pane (composite-pane)
  +;;; SPACING PANE
  +
  +(defclass spacing-pane (composite-pane)
     ((margin-width :initform nil :initarg :width)
      (margin-height :initform nil :initarg :height)
      (margin-max-width :initform nil :initarg :max-width)
      (margin-max-height :initform nil :initarg :max-height)
      (margin-min-width :initform nil :initarg :min-width)
      (margin-min-height :initform nil :initarg :min-height))
  -  (:documentation "The spacer pane will create a margin for his child.
  +  (:documentation "The spacing pane will create a margin for his child.
   The margin sizes (w h) are given with the :width and :height initargs.
  -During realization the child of the spacer will have as cordinates
  +During realization the child of the spacing will have as cordinates
    x = w/2 , y = h/2."))
   
  -(defmethod initialize-instance :after ((spacer spacer-pane) &rest ignore)
  +(defmethod initialize-instance :after ((spacing spacing-pane) &rest ignore)
     (declare (ignore ignore))
     (with-slots (margin-width margin-height
   	       margin-max-width margin-max-height
  -	       margin-min-width margin-min-height) spacer
  +	       margin-min-width margin-min-height) spacing
       (setf margin-width (or margin-width 0)
   	  margin-height (or margin-height 0)
   	  margin-max-width (or margin-max-width margin-width)
  
positive.code: 	  margin-min-width (or margin-min-width margin-width)
  	  margin-min-height (or margin-min-height margin-height))))
  
  (defun spacer-p (pane)
    (typep pane 'spacer-pane))
  
  (defmacro spacing ((&rest options) &body contents)
    `(make-pane 'spacer-pane ,@options :contents (list ,@contents)))
  
  (defmethod compose-space ((spacer spacer-pane))
    (compose-space (first (sheet-children spacer))))
  
  (defmethod allocate-space ((spacer spacer-pane) width height)
    (set-width-and-height spacer width height)
    (let* ((child (first (sheet-children spacer)))
  	 (margin-width (- (get-width spacer) (get-width child)))
  	 (margin-height (- (get-height spacer) (get-height child))))
      (setf margin-width
  	  (do-in (round (/ (* width margin-width) (get-size spacer)))
  		 (slot-value spacer 'margin-min-width)
  		 (slot-value spacer 'margin-max-width))
  	  margin-height
  	  (do-in (round (/ (* height margin-height) (get-size spacer nil)))
  		 (slot-value spacer 'margin-min-height)
  		 (slot-value spacer 'margin-max-height))
  	  (sheet-transformation child)
  	  (make-translation-transformation (/ margin-width 2)
  					   (/ margin-height 2)))
  
negative.code: 
  ;;; BORDER-PANE
  
  (defclass border-pane (spacing-pane)
    ((border-width :initarg :border-width :initform 1 :reader border-pane-width)
     )
    (:documentation ""))
  