How can I make this not happen in the right and left corners?

Question

How can I make this not happen in the right and left corners? I am radiusing the corners with fromLTRBAndCorners. However, it breaks down while browsing the menu.

..lineTo(size.width, 0)
  ..lineTo(size.width, size.height)
  ..lineTo(0, size.height)
  ..addRect(Rect.fromPoints(const Offset(0, 100), Offset(size.width, 0)))
  ..addRRect(RRect.fromLTRBAndCorners(
    0,
    0,
    size.width.toDouble(),
    size.height.toDouble(),
    topLeft: const Radius.circular(50.0),
    topRight: const Radius.circular(50.0),
    bottomLeft: Radius.zero,
    bottomRight: Radius.zero,
  ))
  ..fillType = PathFillType.evenOdd
  ..close();
  canvas.drawPath(path, paint);

Answer 1

all code

late double loc;
  late double s;
  Color color;
  TextDirection textDirection;

  NavCustomPainter(double startingLoc, int itemsLength, this.color, this.textDirection) {
    final span = 1.0 / itemsLength;
    s = 0.2;
    double l = startingLoc + (span - s) / 2;
    loc = textDirection == TextDirection.rtl ? 0.8 - l : l;
  }

       @override
          void paint(Canvas canvas, Size size) {
            final paint = Paint()
              ..color = const Color.fromARGB(255, 87, 192, 241)
              ..style = PaintingStyle.fill
              ..maskFilter = MaskFilter.blur(BlurStyle.outer, convertRadiusToSigma(5));
        
            final path = Path()
              ..moveTo(0, 0)
              ..lineTo((loc - 0.1) * size.width, 0)
              ..cubicTo(
                (loc + s * 0.20) * size.width,
                size.height * 0.05,
                loc * size.width,
                size.height * 0.60,
                (loc + s * 0.50) * size.width,
                size.height * 0.60,
              )
              ..cubicTo(
                (loc + s) * size.width,
                size.height * 0.60,
                (loc + s - s * 0.20) * size.width,
                size.height * 0.05,
                (loc + s + 0.1) * size.width,
                0,
              )
              ..lineTo(size.width, 0)
              ..lineTo(size.width, size.height)
              ..lineTo(0, size.height)
              ..addRect(Rect.fromPoints(const Offset(0, 100), Offset(size.width, 0)))
              ..addRRect(RRect.fromLTRBAndCorners(
                0,
                0,
                size.width.toDouble(),
                size.height.toDouble(),
                topLeft: const Radius.circular(50.0),
                topRight: const Radius.circular(50.0),
                bottomLeft: Radius.zero,
                bottomRight: Radius.zero,
              ))
              ..fillType = PathFillType.evenOdd
              ..close();
              canvas.drawPath(path, paint);
          }