main.dart

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(body: Center(child: _Example())),
    );
  }
}

class _Example extends StatefulWidget {
  const _Example();

  @override
  State<_Example> createState() => _ExampleState();
}

class _ExampleState extends State<_Example> {
  Widget build(BuildContext context) {
    return Column(
      children: [
        // can be const
        const ImprovedText(
          debugLabel: "const",
          textBuilder: _myText,
          styleBuilder: _bodyMedium,
        ),
        // cant be const yet because function literals cant be const
        ImprovedText(
          debugLabel: "not const",
          textBuilder:
              (context) => MaterialLocalizations.of(context).searchFieldLabel,
          styleBuilder: (context) => Theme.of(context).textTheme.bodyMedium,
        ),

        TextButton(child: Text("rebuild"), onPressed: () => setState(() {})),
      ],
    );
  }
}

TextStyle? _bodyMedium(BuildContext context) {
  return Theme.of(context).textTheme.bodyMedium;
}

String _myText(BuildContext context) {
  return MaterialLocalizations.of(context).searchFieldLabel;
}

class ImprovedText extends StatelessWidget {
  final TextStyle? Function(BuildContext) styleBuilder;
  final String Function(BuildContext) textBuilder;
  final String? debugLabel;

  const ImprovedText({
    required this.styleBuilder,
    required this.textBuilder,
    this.debugLabel,
  });

  Widget build(BuildContext context) {
    print("rebuild $debugLabel");
    return Text(textBuilder(context), style: styleBuilder(context));
  }
}