anchor.diff:     (frames :initform (make-hash-table))
      (application-frame-recording-p :initform nil))
     (:panes
  -   (options-pane
  -    (vertically ()
  +   (category-test-pane
  +    (horizontally (:equalize-height t)
         (1/8 (labelling (:label "Category")
                (clim-extensions:lowering ()
                  (scrolling (:scroll-bar :vertical)
  
positive.code:   (list-pane-down 'category-selector))
  
  (define-drawing-tests-command (com-drawing-tests-change-test-up :keystroke :up) ()
    (list-pane-up 'test-selector))
  
  (define-drawing-tests-command (com-drawing-tests-change-test-down :keystroke :down) ()
    (list-pane-down 'test-selector))
  
  (defmethod handle-event ((pane drawing-app-pane) (event keyboard-event))
    (case (keyboard-event-key-name event)
  
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))
  