code: private static void prepareTransparentGoing(boolean add, String transparentPageId) {
          Element p = Document.get().getBody();
          if (p != null) {
              String s = JQM4GWT_DLG_TRANSPARENT_GOING_PREFIX + transparentPageId;
              if (add) {
                  p.addClassName(JQM4GWT_DLG_TRANSPARENT_GOING);
                  p.addClassName(s);
              } else {
                  p.removeClassName(s);
                  String ss = JQMCommon.getStyleStartsWith(p, JQM4GWT_DLG_TRANSPARENT_GOING_PREFIX);
                  // checking for "opened dialog chain" case
                  if (Empty.is(ss)) p.removeClassName(JQM4GWT_DLG_TRANSPARENT_GOING);
              }
          }
      }
docs: GOING means from beforeShow till afterHide.