dialog_button_bar_boxy.dart

import 'dart:math';

import 'package:boxy/boxy.dart';
import 'package:flutter/material.dart';

const darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: const MyHomePage(),
    );
  }
}

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

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Material(
      child: InkWell(
        child: const SizedBox.expand(),
        onTap: () {
          showDialog(
            context: context,
            builder: (context) => const MyDialog(),
          );
        },
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      content: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          const Text(
            'Lorem ipsum dolor sit amet, consectetur adipiscing elit.',
          ),
          const SizedBox(height: 16),
          CustomBoxy(
            delegate: MyOverflowBarBoxy(),
            children: [
              ElevatedButton(
                onPressed: () {},
                child: const Text('LOOOOOOOOOOONG'),
              ),
              ElevatedButton(
                onPressed: () {},
                child: const Text('Cancel'),
              ),
            ],
          ),
        ],
      ),
    );
  }
}

class MyOverflowBarBoxy extends BoxyDelegate {
  static const spacing = 8.0;
  static const verticalSpacing = 8.0;

  @override
  Size layout() {
    final child1 = children[0];
    final child2 = children[1];
    final child1Width = child1.render.getMaxIntrinsicWidth(double.infinity);
    final child2Width = child2.render.getMaxIntrinsicWidth(double.infinity);
    final desiredWidth = child1Width + child2Width + spacing;
    if (desiredWidth > constraints.maxWidth) {
      final childConstraints =
          BoxConstraints.tightFor(width: constraints.maxWidth);
      final child1Size = child1.layout(childConstraints);
      final child2Size = child2.layout(childConstraints);
      child2.position(Offset(0, child1Size.height + verticalSpacing));
      return Size(
        constraints.maxWidth,
        child1Size.height + child2Size.height + verticalSpacing,
      );
    } else {
      final child1Size =
          child1.layout(BoxConstraints.tightFor(width: child1Width));
      final child2Size =
          child2.layout(BoxConstraints.tightFor(width: child2Width));
      child2.position(Offset(child1Width + spacing, 0));
      return Size(
        child1Size.width + child2Size.width + spacing,
        max(child1Size.height, child2Size.height),
      );
    }
  }

  @override
  double maxIntrinsicHeight(double width) => 0;

  @override
  double minIntrinsicHeight(double width) => 0;

  @override
  double maxIntrinsicWidth(double height) => 0;

  @override
  double minIntrinsicWidth(double height) => 0;
}