# File gtk/sample/gtk-demo/changedisplay.rb, line 172
    def create_screen_frame
      frame, tree_view, button_vbox = create_frame('Screen')

      @screen_model = Gtk::ListStore.new(Integer, Gdk::Screen)
      tree_view.model = @screen_model

      column = Gtk::TreeViewColumn.new('Number',
                                       Gtk::CellRendererText.new,
                                       {'text' => SCREEN_COLUMN_NUMBER})
      tree_view.append_column(column)

      @screen_selection = tree_view.selection
      @screen_selection.signal_connect('changed') do |selection|
        @current_screen = if iter = selection.selected
                            iter.get_value(SCREEN_COLUMN_SCREEN)
                          else
                            nil
                          end
      end

      return frame
    end