code: protected void addDisplayType(
          CmsXmlContentDefinition contentDefinition,
          String elementName,
          DisplayType displayType)
      throws CmsXmlException {
  
          if (contentDefinition.getSchemaType(elementName) == null) {
              throw new CmsXmlException(
                  Messages.get().container(Messages.ERR_XMLCONTENT_CONFIG_ELEM_UNKNOWN_1, elementName));
          }
          m_displayTypes.put(elementName, displayType);
      }
docs: Adds the given element to the compact view set.<p>
  
  @param contentDefinition the XML content definition this XML content handler belongs to
  @param elementName the element name
  @param displayType the display type to use for the element widget
  
  @throws CmsXmlException in case an unknown element name is used