[two_dimensional_scrollables] TableView throws "The paint extent of the child has not been determined yet" while scrolling with trailing pinned rows/columns enabled #190800

// Temporary repro file: two_dimensional_scrollables trailing pinned layout bug
//
// Reliable repro: open the app and keep scrolling right (or press
// "Auto scroll right"); the paint assertion fires within seconds:
//   "The paint extent of the child has not been determined yet."
//
// The render tree right before the error shows stale cells with layoutOffset
// set but paintOffset=null and marked "not visible", meaning layout and paint
// get out of sync while scrolling with trailing pinned rows/columns enabled.
//
// Run: flutter run -t example/repro_bug.dart -d macos
import "dart:async";

import "package:flutter/material.dart";
import "package:two_dimensional_scrollables/two_dimensional_scrollables.dart";

void main() => runApp(const MaterialApp(home: Demo()));

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

  @override
  State<Demo> createState() => _DemoState();
}

class _DemoState extends State<Demo> {
  // Horizontal/vertical scroll controllers (start scrolled to the middle,
  // which makes the bug easier to hit).
  final ScrollController _h = ScrollController(initialScrollOffset: 1000);
  final ScrollController _v = ScrollController(initialScrollOffset: 1000);

  // Auto-scroll timer that keeps scrolling right to trigger the bug.
  Timer? _autoTimer;
  bool _autoScrolling = false;

  @override
  void dispose() {
    _autoTimer?.cancel();
    _h.dispose();
    _v.dispose();
    super.dispose();
  }

  /// Start/stop continuous auto-scroll to the right.
  void _toggleAutoScroll() {
    if (_autoScrolling) {
      _autoTimer?.cancel();
      setState(() => _autoScrolling = false);
      return;
    }
    setState(() => _autoScrolling = true);
    // Scroll 5px per frame; jump back to the start when reaching the end.
    _autoTimer = Timer.periodic(const Duration(milliseconds: 16), (_) {
      if (!_h.hasClients) return;
      final max = _h.position.maxScrollExtent;
      final target = _h.offset + 5;
      _h.jumpTo(target > max ? 0 : target);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("trailing pinned scroll repro")),
      body: Column(
        children: [
          Padding(
            padding: const EdgeInsets.all(16),
            child: FilledButton(
              onPressed: _toggleAutoScroll,
              child: Text(_autoScrolling ? "Stop auto scroll" : "Auto scroll right"),
            ),
          ),
          Expanded(
            child: Center(
              child: SizedBox(
                width: 600,
                height: 400,
                child: TableView.builder(
                  verticalDetails: ScrollableDetails.vertical(controller: _v),
                  horizontalDetails:
                      ScrollableDetails.horizontal(controller: _h),
                  columnCount: 30,
                  rowCount: 100,
                  pinnedColumnCount: 1,
                  trailingPinnedColumnCount: 2,
                  trailingPinnedRowCount: 1,
                  columnBuilder: (index) => const TableSpan(
                    extent: FixedTableSpanExtent(100),
                  ),
                  rowBuilder: (index) => const TableSpan(
                    extent: FixedTableSpanExtent(32),
                  ),
                  cellBuilder: (context, vicinity) => TableViewCell(
                    child: Center(
                      child: Text("${vicinity.row},${vicinity.column}"),
                    ),
                  ),
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}