CurvedClipper.dart

  class CurvedClipper extends CustomClipper<Path> {
    @override
    Path getClip(Size size) {
      var path = new Path();
      path.lineTo(0.0, size.height - 40);
      path.quadraticBezierTo(
          size.width / 4, size.height, size.width / 2, size.height);
      path.quadraticBezierTo(
          size.width - (size.width / 4), size.height, size.width, size.height);
      path.lineTo(size.width, 0.0);
      path.close();
      return path;
    }

    @override
    bool shouldReclip(CustomClipper<Path> oldClipper) => true;
  }