# File gtk/sample/gtk-demo/changedisplay.rb, line 239
    def query_change_display
      screen = self.window.screen

      toplevel = query_for_toplevel(screen,
                                    "Please select the toplevel\n"+
                                    "to move to the new screen")

      if toplevel
        toplevel.screen = @current_screen
      else
        screen.display.beep
      end
    end