/// 
/// flutter test command:
/// `flutter test --update-goldens flutter_widget_rebuild_repaint_test.dart`
/// 

import 'dart:math';

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

///
/// widget rebuild, repaint test
///
void main() {
  testWidgets('StatefulWidget context', (WidgetTester tester) async {
    // set device size
    TestWidgetsFlutterBinding binding = tester.binding;
    binding.window.physicalSizeTestValue = Size(400, 700);
    binding.window.devicePixelRatioTestValue = 1.0;

    // prepare widget & finder
    var widget = StatefulBlock();
    var widgetFinder = find.byType(StatefulBlock);

    // 1st render ui
    await tester.pumpWidget(widget);
    await expectLater(
        widgetFinder, matchesGoldenFile('widget_rebuild_before.png'));

    // enable repaint rainbow
    debugRepaintRainbowEnabled = true;

    // trigger rebuild
    StatefulBlock.state.setState(() => 0);

    // 2nd render ui
    await tester.pumpWidget(widget);
    await expectLater(
        widgetFinder, matchesGoldenFile('widget_rebuild_after.png'));
  });
}

/// 有狀態 Block
class StatefulBlock extends StatefulWidget {
  static BlockState state;
  @override
  State<StatefulWidget> createState() => state = BlockState();
}

class BlockState extends State {
  @override
  Widget build(BuildContext context) {
    print('BlockState.build();');
    Color color = Random().nextInt(2) == 0 ? Colors.blue : Colors.red;
    return Container(color: color, padding: EdgeInsets.all(10));
  }
}