请问_initGridSystem是不是有问题？

_class.prototype._initGridSystem = function _initGridSystem() {
var points = [];
var extent = void 0,
extent_1 = void 0,
c = void 0;

    this.layer.forEach(function (g) {
        if (!g.isVisible()) {
            return;
        }
        c = g._getPrjCoordinates();
        if (!extent) {
            extent = g._getPrjExtent();
            extent_1=g.getExtent();
        } else {
            //这里用投影的Extent做合并，并不是想要的结果，我理解extent是不是应该和extent_1是对应的extent 是投影坐标，extent_1是经纬度，但我这里测试了，并不对应
            extent = extent._combine(g._getPrjExtent());       
            extent_1=extent_1._combine(g.getExtent());        
        }
          
        points.push({
            x: c.x,
            y: c.y,
            id: g._getInternalId(),
            geometry: g
        });
    });
    this._markerExtent = extent;
    this._markerPoints = points;

}

在_combine方法中
this.projection.project({x:-13720.015920780175,y:6715329.280305414})={x:-1527305185.9768558,y:20037508.34278074}

this.projection.unproject({x:-1527305185.9768558,y:20037508.34278074})={x:-40.01592078017529,y:85.0511287798}

不是原来的坐标了

Start at _class.prototype._initGridSystem and trace _combine plus projection.project/unproject using the reported coordinates. Reproduce the mismatch and determine whether extent and extent_1 are combined in consistent coordinate systems. Done means the coordinate discrepancy is explained and the behavior is verified with a documented resolution or regression check.