docs: private void actionPreview(CmsHistoryResourceBean bean) {
  
          CmsGwtDialogExtension ext = new CmsGwtDialogExtension(A_CmsUI.get(), new I_CmsUpdateListener<String>() {
  
              public void onUpdate(List<String> updatedItems) {
  
                  // nothing to do
              }
          });
          OfflineOnline offOnline = null;
          if (bean.getVersion().isOffline()) {
              offOnline = OfflineOnline.offline;
          }
          if (bean.getVersion().isOnline()) {
              offOnline = OfflineOnline.online;
          }
          ext.showPreview(bean.getStructureId(), bean.getVersion().getVersionNumber(), offOnline);
      }