import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: const Text('Varying Line Heights Bug Repro')),
        body: const Center(
          child: Padding(
            padding: EdgeInsets.all(16.0),
            child: VaryingLineHeightsTextField(),
          ),
        ),
      ),
    );
  }
}

class VaryingLineHeightsTextField extends StatefulWidget {
  const VaryingLineHeightsTextField({super.key});

  @override
  State<VaryingLineHeightsTextField> createState() =>
      _VaryingLineHeightsTextFieldState();
}

class _VaryingLineHeightsTextFieldState
    extends State<VaryingLineHeightsTextField> {
  late final TextEditingController _controller;

  @override
  void initState() {
    super.initState();
    _controller = VaryingTextInputController(
      text: 'Huge Line 1\nsmall line 2\nsmall line 3\nsmall line 4\n',
    );
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return TextField(
      controller: _controller,
      maxLines: null,
      style: const TextStyle(
        fontSize: 80,
        color: Colors.black,
      ), // default/fallback preferredLineHeight will be large (~80)
    );
  }
}

class VaryingTextInputController extends TextEditingController {
  VaryingTextInputController({super.text});

  @override
  TextSpan buildTextSpan({
    required BuildContext context,
    TextStyle? style,
    required bool withComposing,
  }) {
    return const TextSpan(
      style: TextStyle(fontSize: 80, color: Colors.black),
      children: <InlineSpan>[
        TextSpan(text: 'Huge Line\n'),
        TextSpan(text: 'small line 1\n', style: TextStyle(fontSize: 10)),
        TextSpan(text: 'small line 2\n', style: TextStyle(fontSize: 10)),
        TextSpan(text: 'small line 3\n', style: TextStyle(fontSize: 10)),
      ],
    );
  }
}