code: private int findItemNumber() 
      {
          ElementBox parent = getParent();
          int cnt = 0;
          for (int i = parent.getStartChild(); i < parent.getEndChild(); i++)
          {
              Box child = parent.getSubBox(i);
              if (child instanceof ListItemBox)
                  cnt++;
              if (child == this)
                  return cnt;
          }
          return 1;
      }
docs: Finds the item number. Currently this correspond to the number of list-item boxes before this box
  within the parent box.