code: function (e, xy) {
      getMousePos = (typeof e.pageX === 'number' && !window.opera) ?
      function (e, xy) {
        return [e.pageX - xy[0], e.pageY - xy[1]]
      } : function (e, xy) {
        return [e.clientX + xy[2] - xy[0], e.clientY + xy[3] - xy[1]]
      };
      return getMousePos(e, xy);
    }
docs: attribute definitions