isekai_wiki_app/lib/components/auto_wrap.dart

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

class AutoWrap extends StatefulWidget {
  final List<Widget> children;

  const AutoWrap({super.key, required this.children});

  @override
  State<StatefulWidget> createState() => _AutoWrapState();
}

class _AutoWrapState extends State<AutoWrap> {
  var _computed = false;
  var _isFirstBuild = true;
  final Map<int, double> _childWidth = {};
  var _isRow = true;

  void handleSizeChange(Size size, int id) {
    _childWidth[id] = size.width;
  }

  @override
  void didUpdateWidget(covariant AutoWrap oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (_isFirstBuild) {
      _isFirstBuild = false;
      var sum = _childWidth.values.reduce((value, element) => value + element);
      var width = context.size?.width ?? 0;

      setState(() {
        _computed = true;
        _isRow = sum < width;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    if (!_computed) {
      List<Widget> stackChildren = [];
      for (var i = 0; i < widget.children.length; i++) {
        // Only first child is visible
        stackChildren.add(
          Opacity(
            opacity: i == 0 ? 1 : 0,
            child: WidgetSizeOffsetWrapper(
              id: i,
              onSizeChange: handleSizeChange,
              child: widget.children[i],
            ),
          ),
        );
      }
      return Stack(
        children: stackChildren,
      );
    } else {
      if (_isRow) {
        return Row(children: widget.children);
      } else {
        return Column(children: widget.children);
      }
    }
  }
}

typedef OnWidgetSizeChange = void Function(Size size, int id);

class WidgetSizeRenderObject extends RenderProxyBox {
  final OnWidgetSizeChange onSizeChange;
  final int id;
  Size? currentSize;

  WidgetSizeRenderObject(this.onSizeChange, this.id);

  @override
  void performLayout() {
    super.performLayout();

    try {
      Size? newSize = child?.size;

      if (newSize != null && currentSize != newSize) {
        currentSize = newSize;
        WidgetsBinding.instance.addPostFrameCallback((_) {
          onSizeChange(newSize, id);
        });
      }
    } catch (e) {
      print(e);
    }
  }
}

class WidgetSizeOffsetWrapper extends SingleChildRenderObjectWidget {
  final OnWidgetSizeChange onSizeChange;
  final int id;

  const WidgetSizeOffsetWrapper({
    Key? key,
    required this.onSizeChange,
    required this.id,
    required Widget child,
  }) : super(key: key, child: child);

  @override
  RenderObject createRenderObject(BuildContext context) {
    return WidgetSizeRenderObject(onSizeChange, id);
  }
}