(Flutter) Curved edge to a CustomPaint Widget

This is what I want to build:

(Just see the shape of the appBar and not the contents)

This is what I have:

I want the edge to be curved, and not so sharp.

Here is my code for the CustomPaint:

class LogoPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint();
    paint.color = Colors.blue;
    var path = Path();
    path.lineTo(0, size.height - size.height / 5);
    path.lineTo(size.width / 1.2, size.height);
    path.lineTo(size.width, size.height - size.height / 5);
    path.lineTo(size.width, 0);
    path.close();
    canvas.drawPath(path, paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}

How do I achieve this curved edge?

I have tried point.arcToPoint() and point.quadraticBezierTo(), but no success.

This isn't perfect, but you can fiddle with the numbers a bit more:

class LogoPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint();
    paint.color = Colors.blue;
    var path = Path();
    path.lineTo(0, size.height - size.height / 5);
    path.lineTo(size.width / 1.2, size.height);
    //Added this line
    path.relativeQuadraticBezierTo(15, 3, 30, -5);
    path.lineTo(size.width, size.height - size.height / 5);
    path.lineTo(size.width, 0);
    path.close();
    canvas.drawPath(path, paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}

This code gives this result: