code: function _getTipValueScale() {
      var attrs = this.getAttrsForLegend();
      var scale = void 0;
      Util.each(attrs, function (attr) {
        var tmpScale = attr.getScale(attr.type);
        if (tmpScale.isLinear) {
          // 如果指定字段是非position的，同时是连续的
          scale = tmpScale;
          return false;
        }
      });
  
      var xScale = this.getXScale();
      var yScale = this.getYScale();
  
      if (!scale && yScale && yScale.field === '..y') {
        return xScale;
      }
  
      return scale || yScale || xScale;
    }
docs: 获取值对应的度量