qr_corner_painter.dart

import 'package:flutter/material.dart';

class QRCornerPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = Colors.white
      ..style = PaintingStyle.fill;

    final cornerLength = size.width * 0.1;
    final cornerThickness = cornerLength * 0.2;

    // Top-left corner
    canvas.drawRect(Rect.fromLTWH(0, 0, cornerLength, cornerThickness), paint);
    canvas.drawRect(Rect.fromLTWH(0, 0, cornerThickness, cornerLength), paint);

    // Top-right corner
    canvas.drawRect(
        Rect.fromLTWH(
            size.width - cornerLength, 0, cornerLength, cornerThickness),
        paint);
    canvas.drawRect(
        Rect.fromLTWH(
            size.width - cornerThickness, 0, cornerThickness, cornerLength),
        paint);

    // Bottom-left corner
    canvas.drawRect(
        Rect.fromLTWH(
            0, size.height - cornerThickness, cornerLength, cornerThickness),
        paint);
    canvas.drawRect(
        Rect.fromLTWH(
            0, size.height - cornerLength, cornerThickness, cornerLength),
        paint);

    // Bottom-right corner
    canvas.drawRect(
        Rect.fromLTWH(size.width - cornerLength, size.height - cornerThickness,
            cornerLength, cornerThickness),
        paint);
    canvas.drawRect(
        Rect.fromLTWH(size.width - cornerThickness, size.height - cornerLength,
            cornerThickness, cornerLength),
        paint);
  }

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

Center(
  child: CustomPaint(
    size: Size.square(300),
      painter: QRCornerPainter(),
    ),
),