      /**
       * The constants used in this Content Widget.
       */
      public static interface CwConstants extends Constants,
          ContentWidget.CwConstants {
        String cwCustomButtonDescription();

        String cwCustomButtonName();

        String cwCustomButtonPush();

        String cwCustomButtonToggle();
      }

      /**
       * An instance of the constants.
       */
      private CwConstants constants;

      /**
       * Initialize this example.
       */
      @Override
      public Widget onInitialize() {
        // Create a panel to layout the widgets
        VerticalPanel vpanel = new VerticalPanel();
        HorizontalPanel pushPanel = new HorizontalPanel();
        pushPanel.setSpacing(10);
        HorizontalPanel togglePanel = new HorizontalPanel();
        togglePanel.setSpacing(10);

        // Combine all the panels
        vpanel.add(new HTML(constants.cwCustomButtonPush()));
        vpanel.add(pushPanel);
        vpanel.add(new HTML("<br><br>" + constants.cwCustomButtonToggle()));
        vpanel.add(togglePanel);

        // Add a normal PushButton
        PushButton normalPushButton = new PushButton(
            Showcase.images.gwtLogo().createImage());
        normalPushButton.ensureDebugId("cwCustomButton-push-normal");
        normalPushButton.addKeyboardListener(new KeyboardListenerAdapter());
        pushPanel.add(normalPushButton);

        // Add a disabled PushButton
        PushButton disabledPushButton = new PushButton(
            Showcase.images.gwtLogo().createImage());
        disabledPushButton.ensureDebugId("cwCustomButton-push-disabled");
        disabledPushButton.setEnabled(false);
        pushPanel.add(disabledPushButton);

        // Add a normal ToggleButton
        ToggleButton normalToggleButton = new ToggleButton(
            Showcase.images.gwtLogo().createImage());
        normalToggleButton.ensureDebugId("cwCustomButton-toggle-normal");
        normalToggleButton.addKeyboardListener(new KeyboardListenerAdapter());
        togglePanel.add(normalToggleButton);

        // Add a disabled ToggleButton
        ToggleButton disabledToggleButton = new ToggleButton(
            Showcase.images.gwtLogo().createImage());
        disabledToggleButton.ensureDebugId("cwCustomButton-toggle-disabled");
        disabledToggleButton.setEnabled(false);
        togglePanel.add(disabledToggleButton);

        // Return the panel
        return vpanel;
      }