Anchor.forPos constructor
Implementation
factory Anchor.forPos(AnchorPos? pos, double width, double height) {
if (pos == null) return Anchor._(width, height, AnchorAlign.none);
if (pos.value is AnchorAlign) return Anchor._(width, height, pos.value);
if (pos.value is Anchor) return pos.value;
throw Exception('Unsupported AnchorPos value type: ${pos.runtimeType}.');
}