code: function (e) {
      var node = ReactDOM.findDOMNode(this),
        numTabsMod = this.ctx.ownerId == this.memberId ? 0 : 1,
        tabWidth = node.offsetWidth / (this.tabKeys.length + numTabsMod),
        distance = e.pageX - node.getBoundingClientRect().left,
        index = parseInt(distance / tabWidth);
  
      this.tabWidth = tabWidth;
      return index;
    }
docs: /* TODO: proper name.