getOuterPath method

@override Path getOuterPath(Rect host, Rect? guest)

Creates a Path that describes the outline of the shape.

The host is the bounding rectangle of the shape.

The guest is the bounding rectangle of the shape for which a notch will be made. It is null when there is no guest.

Implementation

@override
Path getOuterPath(Rect host, Rect? guest) {
  if (guest == null || !host.overlaps(guest)) return Path()..addRect(host);

  // The guest's shape is a circle bounded by the guest rectangle.
  // So the guest's radius is half the guest width.
  final notchRadius = guest.width / 2.0;

  const s1 = 15.0;
  const s2 = 1.0;

  final r = notchRadius;
  final a = -1.0 * r - s2;
  final b = host.top - guest.center.dy;

  final n2 = math.sqrt(b * b * r * r * (a * a + b * b - r * r));
  final p2xA = ((a * r * r) - n2) / (a * a + b * b);
  final p2xB = ((a * r * r) + n2) / (a * a + b * b);
  final p2yA = -math.sqrt(r * r - p2xA * p2xA);
  final p2yB = -math.sqrt(r * r - p2xB * p2xB);

  final p = List<Offset>.filled(6, Offset.zero, growable: false);
  // p0, p1, and p2 are the control points for segment A.
  p[0] = Offset(a - s1, b);
  p[1] = Offset(a, b);
  final cmp = b < 0 ? -1.0 : 1.0;
  p[2] = cmp * p2yA > cmp * p2yB ? Offset(p2xA, p2yA) : Offset(p2xB, p2yB);

  // p3, p4, and p5 are the control points for segment B, which is a mirror
  // of segment A around the y axis.
  p[3] = Offset(-1.0 * p[2].dx, p[2].dy);
  p[4] = Offset(-1.0 * p[1].dx, p[1].dy);
  p[5] = Offset(-1.0 * p[0].dx, p[0].dy);

  // translate all points back to the absolute coordinate system.
  for (var i = 0; i < p.length; i += 1) {
    p[i] = p[i] + guest.center;
    //p[i] += padding;
  }

  return radius > 0
      ? (Path()
        ..moveTo(host.left, host.top + radius)
        ..arcToPoint(Offset(host.left + radius, host.top),
            radius: Radius.circular(radius))
        ..lineTo(p[0].dx, p[0].dy)
        ..quadraticBezierTo(p[1].dx, p[1].dy, p[2].dx, p[2].dy)
        ..arcToPoint(
          p[3],
          radius: Radius.circular(notchRadius),
          clockwise: true,
        )
        ..quadraticBezierTo(p[4].dx, p[4].dy, p[5].dx, p[5].dy)
        ..lineTo(host.right - radius, host.top)
        ..arcToPoint(Offset(host.right, host.top + radius),
            radius: Radius.circular(radius))
        ..lineTo(host.right, host.bottom)
        ..lineTo(host.left, host.bottom)
        ..close())
      : (Path()
        ..moveTo(host.left, host.top)
        ..lineTo(p[0].dx, p[0].dy)
        ..quadraticBezierTo(p[1].dx, p[1].dy, p[2].dx, p[2].dy)
        ..arcToPoint(
          p[3],
          radius: Radius.circular(notchRadius),
          clockwise: true,
        )
        ..quadraticBezierTo(p[4].dx, p[4].dy, p[5].dx, p[5].dy)
        ..lineTo(host.right, host.top)
        ..lineTo(host.right, host.bottom)
        ..lineTo(host.left, host.bottom)
        ..close());
}