deserialize method

Implementation

@override
Offset? deserialize(String? str) {
  if (str == null) return null;
  final map = jsonDecode(str);
  if (map is Map) {
    return Offset(
      DartUtil.safeDouble(map['dx']),
      DartUtil.safeDouble(map['dy']),
    );
  } else {
    return null;
  }
}