code: public void setOpenerVisible(boolean visible) {
  
          if (visible) {
              m_opener.removeStyleName(OpenCmsTheme.BUTTON_INVISIBLE);
          } else {
              m_opener.addStyleName(OpenCmsTheme.BUTTON_INVISIBLE);
          }
      }
docs: Shows or hides the opener button.<p>
  
  @param visible true if the opener should be shown, else false