# File gtk/sample/gtk-demo/cairo-operator.rb, line 64
    def operator_selector
      combo = Gtk::ComboBox.new
      operators = []
      Cairo.constants.each do |name|
        operators << name if /^OPERATOR_/ =~ name
      end
      operators.sort.each_with_index do |name, i|
        combo.append_text(name)
        combo.set_active(i) if Cairo.const_get(name) == @operator
      end

      combo.signal_connect("changed") do |widget|
        text = widget.active_text
        @operator = Cairo.const_get(text) if text
        @drawing_area.queue_draw
      end
      combo
    end