code: public static void main(final String[] args) {
          LookAndFeelManager.get().init();
  
          final ComboButton comboButton1 = new ComboButton();
          comboButton1.addButton("Foo!", IconUtils.ACTION_ADD_DARK, true);
          comboButton1.addButton("Boo!", IconUtils.ACTION_REMOVE_DARK, true);
  
          final ComboButton comboButton2 = new ComboButton();
          comboButton2.addButton("Foo!", IconUtils.ACTION_ADD_DARK, false);
          comboButton2.addButton("Boo!", IconUtils.ACTION_REMOVE_DARK, false);
          comboButton2.addButton("Mrr!", IconUtils.ACTION_REFRESH, true);
          comboButton2.addButton("Rrrh!", IconUtils.ACTION_DRILL_TO_DETAIL, true);
  
          final DCPanel panel = new DCPanel(WidgetUtils.COLOR_DEFAULT_BACKGROUND);
          panel.add(comboButton1);
          panel.add(comboButton2);
  
          final JButton regularButton = WidgetFactory.createDefaultButton("Regular button", IconUtils.ACTION_ADD_DARK);
          panel.add(regularButton);
  
          final JFrame frame = new JFrame("test");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.setSize(500, 400);
          frame.add(panel);
  
          frame.pack();
          frame.setVisible(true);
      }
docs: a simple test app