int height = getRowHeight() + getRowMargin();
int r;
  public int rowAtPoint(Point point)  {    if (point != null)      {        int nrows = getRowCount();        int height = getRowHeight() + getRowMargin();        int y = point.y;        int r = y / height;        if (r < 0 || r >= nrows)          return -1;        else          return r;      }    else    return -1;  }