fitted_box_with_siblings 2.0.0

A Flutter widget that scales a first child like FittedBox while letting sibling widgets fill rects you compute alongside it.

example/lib/main.dart

import 'dart:async';

import 'package:fitted_box_with_siblings/fitted_box_with_siblings.dart';
import 'package:flutter/foundation.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 MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  Timer? _timer;

  @override
  void initState() {
    super.initState();
    _timer = Timer.periodic(const Duration(seconds: 1), (timer) {
      _incrementCounter();
    });
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Container(
        color: Colors.orange,
        child: FittedBoxWithSiblings(
          delegate: const _HeaderAndBoxDelegate(),
          children: [
            const Text('You have pushed the button\nthis many times:'),
            Container(
              width: double.infinity,
              height: double.infinity,
              alignment: Alignment.center,
              color: Colors.yellow,
              child: Text(
                '$_counter',
                style: Theme.of(context).textTheme.headlineMedium,
              ),
            ),
            Container(
              width: double.infinity,
              height: double.infinity,
              alignment: Alignment.center,
              color: Colors.blue,
              child: Text(
                'Next: ${_counter + 1}',
                style: Theme.of(context).textTheme.headlineMedium,
              ),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}

/// Places two header rects side by side across the top 100 pixels, with the
/// fitted box filling the rest.
///
/// The rects depend only on the constraints, so [shouldRelayout] returns
/// false and rebuilding with a new instance (e.g. every timer tick) does not
/// relayout.
class _HeaderAndBoxDelegate extends FittedBoxWithSiblingsDelegate {
  const _HeaderAndBoxDelegate();

  @override
  List<Rect> computeRects(BoxConstraints constraints, Size boxSize) {
    if (kDebugMode) {
      print('constraints=$constraints, boxSize=$boxSize');
    }
    final centerX = constraints.maxWidth / 2;
    return [
      Rect.fromLTWH(0, 100, constraints.maxWidth, constraints.maxHeight - 100),
      Rect.fromLTWH(0, 0, centerX, 100),
      Rect.fromLTWH(centerX, 0, centerX, 100),
    ];
  }

  @override
  bool shouldRelayout(_HeaderAndBoxDelegate oldDelegate) => false;
}