Nested WIdget experiment

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  const MyHomePage({
    Key? key,
    required this.title,
  }) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String _text = "OPT_1";
  
  bool isNested = false;
  
  void changeMode() {
    setState(() {
      isNested = !isNested;
    });
  }

  void changeText() {
    setState(() {
      if (_text == "OPT_1") {
        _text = "OPT_2";
      } else {
        _text = "OPT_1";
      }
    });
  }

  Widget _nestedOption() {
    return NestedWidget(
      children: [
        (child) {
          print("Nested widget rebuilt!");
          return Padding(
            padding: const EdgeInsets.all(1),
            child: child,
          );
        }
      ],
      child: Text(_text),
    );
  }

  Widget _normalOption() {
    return CustomPaddingForLog(
      child: Text(_text),
    );
  }

  @override
  Widget build(BuildContext context) {
    print("Rebuilt in parent");

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Column(
        children: [
          Expanded(
            child: isNested ? _nestedOption() : _normalOption(),
          ),
          Row(
            children: [
              ElevatedButton(
                onPressed: changeText,
                child: const Text("Rebuilt"),
              ),
              ElevatedButton(
                onPressed: changeMode,
                child: const Text("Change mode"),
              ),
            ],
          ),
        ],
      ),
    );
  }
}

class CustomPaddingForLog extends StatelessWidget {
  const CustomPaddingForLog({required this.child});
  
  final Widget child;
  
  @override
  Widget build(BuildContext context) {
    print("Rebuilt in normal");
    return Padding(
      padding: const EdgeInsets.all(1),
      child: child,
    );
  }
}

typedef SingleChildWidgetConstructor = Widget Function(Widget child);

class NestedWidget extends StatelessWidget {
  const NestedWidget({
    Key? key,
    required this.children,
    required this.child,
  }) : super(key: key);
  final List<SingleChildWidgetConstructor> children;
  final Widget child;
  @override
  Widget build(BuildContext context) {
    Widget nestedChild = child;
    for (final constructor in children.reversed) {
      return constructor(nestedChild);
    }
    return nestedChild;
  }
}