edit-menu:find-callback in frame:searchable-mixin

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

• (send a-frame:searchable-mixin edit-menu:find-callback item evt) -> void
     item : (instance (derived-from menu-item%))
     evt : (instance control-event%)

  Calls move-to-search-or-search.