CupertinoSheetRoute top gap can reveal lower routes when multiple sheets are stacked #187057

import 'package:flutter/cupertino.dart';

void main() {
  runApp(const SystemCupertinoSheetDemoApp());
}

class SystemCupertinoSheetDemoApp extends StatelessWidget {
  const SystemCupertinoSheetDemoApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const CupertinoApp(
      home: _DemoHomePage(),
    );
  }
}

class _DemoHomePage extends StatelessWidget {
  const _DemoHomePage();

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      child: ColoredBox(
        color: const Color(0xff006edb),
        child: Center(
          child: CupertinoButton.filled(
            onPressed: () => _showSystemSheet(context, level: 2),
            child: const Text('Open Sheet 2'),
          ),
        ),
      ),
    );
  }
}

void _showSystemSheet(BuildContext context, {required int level}) {
  showCupertinoSheet<void>(
    context: context,
    scrollableBuilder:
        (BuildContext context, ScrollController scrollController) {
          return _SystemSheetPage(level: level);
        },
  );
}

class _SystemSheetPage extends StatelessWidget {
  const _SystemSheetPage({required this.level});

  final int level;

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      child: Center(
        child: CupertinoButton.filled(
          onPressed: level >= 4
              ? () => Navigator.of(context, rootNavigator: true).pop()
              : () => _showSystemSheet(context, level: level + 1),
          child: Text(level >= 4 ? 'Close Sheet 4' : 'Open Sheet ${level + 1}'),
        ),
      ),
    );
  }
}