docs: function(mode, element) {
      if (!mode) return 0;
      if (mode == 'vertical')
        return ((this.offset[1] + element.offsetHeight) - this.ycomp) /
          element.offsetHeight;
      if (mode == 'horizontal')
        return ((this.offset[0] + element.offsetWidth) - this.xcomp) /
          element.offsetWidth;
    }