anchor.diff:  
   (defun x-shear-callback (gadget shear)
     (declare (ignore gadget))
  -  (let ((viewer (find-pane-named *application-frame* 'viewer)))
  +  (let ((viewer (find-pane-named *application-frame* 'spectacle-pane)))
       (with-accessors ((image gadget-value)
                        (transform-parameters transform-parameters)
                        (transform transform))
  
positive.code: 
  (defun theta-callback (gadget degrees)
    (declare (ignore gadget))
    (let ((viewer (find-pane-named *application-frame* 'viewer)))
      (with-accessors ((image gadget-value)
                       (transform-parameters transform-parameters)
                       (transform transform))
  
negative.code: 
  (define-spectacle-command (com-redraw :name t)
      ()
    (let ((viewer (find-pane-named *application-frame* 'spectacle-pane)))
      (handle-repaint viewer (sheet-region viewer))))
  
  (define-spectacle-command (com-reset :name t)
      ()
    (let ((viewer (find-pane-named *application-frame* 'spectacle-pane)))
      (with-accessors ((image gadget-value)
                       (transform-parameters transform-parameters)
                       (transform transform))
          viewer
        (reset-sliders)
        (reset-transform-parameters transform-parameters)
        (setf transform nil))
      (handle-repaint viewer (sheet-region viewer))))
  
  (define-spectacle-command (com-quit :name t :keystroke (#\q :meta)) ()
  