docs: protected String getResourcePath(CmsObject cms, I_CmsWidgetDialog dialog) {
  
          String result = null;
          if (dialog instanceof CmsDummyWidgetDialog) {
              result = ((CmsDummyWidgetDialog)dialog).getResource().getRootPath();
          } else if (dialog instanceof CmsDialog) {
              result = ((CmsDialog)dialog).getParamResource();
              if (result != null) {
                  result = cms.getRequestContext().addSiteRoot(result);
              }
          }
          return result;
      }