# File gtk/sample/gtk-demo/changedisplay.rb, line 329
    def open_display_cb
      dialog = Gtk::Dialog.new('Open Display',
                               self,
                               Gtk::Dialog::MODAL,
                               [Gtk::Stock::CANCEL, Gtk::Dialog::RESPONSE_CANCEL],
                               [Gtk::Stock::OK, Gtk::Dialog::RESPONSE_OK])

      dialog.default_response = Gtk::Dialog::RESPONSE_OK
      display_entry = Gtk::Entry.new
      display_entry.activates_default = true
      dialog_label =
        Gtk::Label.new("Please enter the name of\nthe new display\n")

      dialog.vbox.add(dialog_label)
      dialog.vbox.add(display_entry)

      display_entry.grab_focus
      dialog.vbox.show_all

      result = nil
      until result
        response_id = dialog.run
        break if response_id != Gtk::Dialog::RESPONSE_OK

        new_screen_name = display_entry.text

        unless new_screen_name.empty?
          begin
            result = Gdk::Dispaly.open(new_screen_name)
          rescue
            dialog_label.text = "Can't open display :\n\t%s\nplease try another one\n" % [new_screen_name]
          end
        end
      end
      dialog.destroy
    end