Circular List - by Simon Lightfoot - Humpday Q&A :: 26th June 2024 #Flutter #Dart https://www.youtube.com/watch?v=mMv9wRcKZrw

humpday_2024-07-24_1.dart

// MIT License
//
// Copyright (c) 2024 Simon Lightfoot
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
import 'dart:async';
import 'dart:math' as math;

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

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Home(),
    );
  }
}

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

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    return const Material(
      child: SafeArea(
        child: CircularList(),
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scrollable(
      controller: PrimaryScrollController.maybeOf(context),
      axisDirection: AxisDirection.right,
      physics: const BouncingScrollPhysics(),
      viewportBuilder: (BuildContext context, ViewportOffset position) {
        return Flow(
          delegate: CircularScrollDelegate(
            position: position,
            size: const Size.square(80.0),
          ),
          children: [
            for (int i = 0; i < Colors.accents.length; i++) //
              ColoredBox(
                color: Colors.accents[i],
                child: Center(child: Text('Item #$i')),
              ),
          ],
        );
      },
    );
  }
}

class CircularScrollDelegate extends FlowDelegate {
  CircularScrollDelegate({
    required this.position,
    required this.size,
  }) : super(repaint: position);

  final ViewportOffset position;
  final Size size;

  @override
  bool shouldRepaint(covariant CircularScrollDelegate oldDelegate) {
    return position != oldDelegate.position;
  }

  @override
  BoxConstraints getConstraintsForChild(int i, BoxConstraints constraints) {
    return BoxConstraints.tight(size);
  }

  @override
  void paintChildren(FlowPaintingContext context) {
    scheduleMicrotask(() {
      position.applyViewportDimension(context.size.width);
      position.applyContentDimensions(
        0.0,
        (size.width * context.childCount) - context.size.width,
      );
    });
    final centerX = (context.size.width - size.width) / 2;
    final centerY = (context.size.height - size.height) / 2;

    final phase = position.pixels / size.width;
    final rx = (context.size.width - size.width) / 2;
    final ry = (context.size.height - size.height) / 2;
    for (int i = 0; i < context.childCount; i++) {
      final e = i / context.childCount;
      final x = math.sin(e * math.pi * 2 - phase) * rx;
      final y = math.cos(e * math.pi * 2 - phase) * ry;
      // if (y < 0) {
      //   continue;
      // }
      context.paintChild(
        i,
        transform: Matrix4.translationValues(
          centerX + x,
          centerY + y,
          0.0,
        ),
      );
    }
  }
}