如何从画布CustomPaint中擦除/剪辑？

import 'package:flutter/material.dart';

class MyCustomClipper extends CustomClipper<Path> {
  @override
  Path getClip(Size size) {
    final path = Path();
    path.addRect(Rect.fromLTRB(0, 0, size.width, size.height));
    path.addRect(Rect.fromLTRB(100, 100, 200, 200)); // 要擦除的矩形区域
    return path;
  }

  @override
  bool shouldReclip(covariant CustomClipper<Path> oldClipper) {
    return true;
  }
}

class MyCustomPaint extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: _MyPainter(),
      size: Size(300, 300),
      foregroundPainter: _MyForegroundPainter(),
      child: Container(),
    );
  }
}

class _MyPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    // 在背景绘制内容
    // ...
  }

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

class _MyForegroundPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    // 在前景绘制内容
    canvas.clipPath(MyCustomClipper().getClip(size), clipOp: ClipOp.difference);
    canvas.drawColor(Colors.transparent, BlendMode.clear);
  }

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