anchor.diff:  (defmethod handle-event ((pane slider-pane) (event pointer-motion-event))
     (with-slots (armed) pane
       (when (eq armed ':button-press)
  -      (let ((value (convert-position-to-value pane (pointer-event-y event))))
  +      (let ((value (convert-position-to-value pane
  +					      (if (eq (gadget-orientation pane) :vertical)
  +						  (pointer-event-y event)
  +						  (pointer-event-x event)))))
   	(setf (gadget-value pane :invoke-callback nil) value)
   	(drag-callback pane (gadget-client pane) (gadget-id pane) value)
   	(dispatch-repaint pane (sheet-region pane))))))
  
positive.code: 		 :initarg :show-value-p
  		 :accessor gadget-show-value-p)))
  
  (defmethod drag-callback ((pane slider-pane) client gadget-id value)
    (declare (ignore client gadget-id))
    (when (slider-drag-callback pane)
  
negative.code: 			 range-gadget-mixin
  			 gadget-color-mixin)
    ()
    (:documentation "The value is a real number, and default value for orientation is :vertical, and can never be nil."))
    
  (defclass slider-pane (slider-gadget)
    ((drag-callback :initform nil
  