source: [view]
var shapes = group.children;
var feature = shapes[0];
var bbox = feature.getBoundingBox();
this._arround = dojo.clone(bbox);
dojo.forEach(shapes, function(item){
var _bbox = item.getBoundingBox();
this._arround.x = Math.min(this._arround.x, _bbox.x);
this._arround.y = Math.min(this._arround.y, _bbox.y);
},this);