anchor.diff:    (list-pane-down 'category-selector))
   
   (define-drawing-tests-command (com-drawing-tests-change-test-up :keystroke :up) ()
  -  (list-pane-up 'test-selector))
  +  (unless (list-pane-up 'test-selector)
  +    (list-pane-up 'category-selector)))
   
   (define-drawing-tests-command (com-drawing-tests-change-test-down :keystroke :down) ()
  -  (list-pane-down 'test-selector))
  +  (unless (list-pane-down 'test-selector)
  +    (list-pane-down 'category-selector)))
   
   (defmethod handle-event ((pane drawing-app-pane) (event keyboard-event))
     (case (keyboard-event-key-name event)
  
positive.code:           "side-by-side view with the renderer output"))))
     (backend-pane
      (labelling (:label "Backend")
        (make-pane 'application-pane
                   :name 'backend-output
                   :min-width *width*
                   :min-height *height*
                   :display-time nil
                   :display-function #'display-backend-output
                   :end-of-line-action :wrap
                   :end-of-page-action :wrap)))
     (render-pane
      (labelling (:label "Render")
        (make-pane 'application-pane
                   :name 'render-output
                   :min-width *width*
                   :min-height *height*
                   :display-time nil
                   :display-function #'display-render-output
                   :end-of-line-action :wrap
                   :end-of-page-action :wrap)))
     (description-pane
      (spacing (:thickness 3)
        (clim-extensions:lowering ()
  
negative.code: 
  (defun list-pane-up (pane-name)
    (let* ((pane (find-pane-named *application-frame* pane-name))
           (items (clime:list-pane-items pane))
           (current (gadget-value pane))
           (pos (when current (position current items))))
      (when (and pos (not (zerop pos)))
        (setf (gadget-value pane :invoke-callback t)
              (elt items (1- pos))))))
  
  (defun list-pane-down (pane-name)
    (let* ((pane (find-pane-named *application-frame* pane-name))
           (items (clime:list-pane-items pane))
           (current (gadget-value pane))
           (pos (when current (position current items))))
      (when (and pos (< pos (1- (length items))))
        (setf (gadget-value pane :invoke-callback t)
              (elt items (1+ pos))))))
  
  (define-drawing-tests-command (com-drawing-tests-change-category-up :keystroke (:left :meta)) ()
    (list-pane-up 'category-selector))
  