edit-menu:undo-callback in frame:standard-menus<%>

This method is called when the undo menu-item of the edit-menu menu is selected.

• (send a-frame:standard-menus edit-menu:undo-callback item evt) -> void
     item : (instance (derived-from menu-item%))
     evt : (instance control-event%)

  Defaultly bound to:

  (λ
   (menu evt)
   (let ((edit (get-edit-target-object)))
     (when (and edit (is-a? edit editor<%>))
       (send edit do-edit-operation 'undo)))
   #t)