method private _cb__down_opt_button_clicked = fun () ->
    match sopts_view.sopt_view#selection#get_selected_rows with
      | [path] ->
          if GTree.Path.get_depth path > 1 then
            let path_next = GTree.Path.copy path in
              GTree.Path.next path_next;
              if path_is_valid sopts_store path_next then
                i_bool (sopts_store#swap
                          (sopts_store#get_iter path)
                          (sopts_store#get_iter path_next))
      | _ ->
          ()