code: private void addHoverHandlers(FocusPanel panel) {
  
          final CmsStyleVariable hoverVar = new CmsStyleVariable(panel);
          hoverVar.setValue(I_CmsLayoutBundle.INSTANCE.globalWidgetCss().openerNoHover());
          panel.addMouseOverHandler(new MouseOverHandler() {
  
              /**
               * @see com.google.gwt.event.dom.client.MouseOverHandler#onMouseOver(com.google.gwt.event.dom.client.MouseOverEvent)
               */
              public void onMouseOver(MouseOverEvent event) {
  
                  hoverVar.setValue(I_CmsLayoutBundle.INSTANCE.globalWidgetCss().openerHover());
              }
          });
  
          panel.addMouseOutHandler(new MouseOutHandler() {
  
              /**
               * @see com.google.gwt.event.dom.client.MouseOutHandler#onMouseOut(com.google.gwt.event.dom.client.MouseOutEvent)
               */
              public void onMouseOut(MouseOutEvent event) {
  
                  hoverVar.setValue(I_CmsLayoutBundle.INSTANCE.globalWidgetCss().openerNoHover());
              }
          });
  
      }
docs: Helper method for adding event handlers for a 'hover' effect to the opener.<p>
  
  @param panel the opener