copy method
Implementation
@override
copy(source) {
super.copy(source);
points = [];
for (var i = 0, l = source.points.length; i < l; i++) {
var point = source.points[i];
points.add(point.clone());
}
closed = source.closed;
curveType = source.curveType;
tension = source.tension;
return this;
}