code: public static List<String> getSelectOptionValues(CmsObject cms, String rootPath, boolean allRemoved) {
  
          try {
              cms = OpenCms.initCmsObject(cms);
              cms.getRequestContext().setSiteRoot("");
              CmsADEConfigData adeConfig = OpenCms.getADEManager().lookupConfiguration(cms, rootPath);
              if (adeConfig.parent() != null) {
                  adeConfig = adeConfig.parent();
              }
  
              List<CmsSelectWidgetOption> options = getFormatterOptionsStatic(cms, adeConfig, rootPath, allRemoved);
              List<CmsSelectWidgetOption> typeOptions = getTypeOptionsStatic(cms, adeConfig, allRemoved);
              options.addAll(typeOptions);
              List<String> result = new ArrayList<String>(options.size());
              for (CmsSelectWidgetOption o : options) {
                  result.add(o.getValue());
              }
              return result;
          } catch (CmsException e) {
              // should never happen
              LOG.error(e.getLocalizedMessage(), e);
              return null;
          }
  
      }
docs: Returns all values that can be selected in the widget.
  @param cms the current CMS object
  @param rootPath the root path to the currently edited xml file (sitemap config)
  @param allRemoved flag, indicating if all inheritedly available formatters should be disabled
  @return all values that can be selected in the widget.