flutter-go/packages/flutter_web/test/material/scrollbar_test.dart

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter_web/material.dart';
import 'package:flutter_web/scheduler.dart';
import 'package:flutter_web_test/flutter_web_test.dart';

class TestCanvas implements Canvas {
  TestCanvas([this.invocations]);

  final List<Invocation> invocations;

  @override
  void noSuchMethod(Invocation invocation) {
    invocations?.add(invocation);
  }
}

void main() {
  testWidgets('Scrollbar doesn\'t show when tapping list',
      (WidgetTester tester) async {
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: Center(
        child: Container(
          decoration:
              BoxDecoration(border: Border.all(color: const Color(0xFFFFFF00))),
          height: 200.0,
          width: 300.0,
          child: Scrollbar(
            child: ListView(
              children: <Widget>[
                Container(height: 40.0, child: const Text('0')),
                Container(height: 40.0, child: const Text('1')),
                Container(height: 40.0, child: const Text('2')),
                Container(height: 40.0, child: const Text('3')),
                Container(height: 40.0, child: const Text('4')),
                Container(height: 40.0, child: const Text('5')),
                Container(height: 40.0, child: const Text('6')),
                Container(height: 40.0, child: const Text('7')),
              ],
            ),
          ),
        ),
      ),
    ));

    SchedulerBinding.instance.debugAssertNoTransientCallbacks(
        'Building a list with a scrollbar triggered an animation.');
    await tester.tap(find.byType(ListView));
    SchedulerBinding.instance.debugAssertNoTransientCallbacks(
        'Tapping a block with a scrollbar triggered an animation.');
    await tester.pump(const Duration(milliseconds: 200));
    await tester.pump(const Duration(milliseconds: 200));
    await tester.pump(const Duration(milliseconds: 200));
    await tester.pump(const Duration(milliseconds: 200));
    await tester.drag(find.byType(ListView), const Offset(0.0, -10.0));
    expect(SchedulerBinding.instance.transientCallbackCount, greaterThan(0));
    await tester.pump(const Duration(milliseconds: 200));
    await tester.pump(const Duration(milliseconds: 200));
    await tester.pump(const Duration(milliseconds: 200));
    await tester.pump(const Duration(milliseconds: 200));
  });

  testWidgets('ScrollbarPainter does not divide by zero',
      (WidgetTester tester) async {
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: Container(
        height: 200.0,
        width: 300.0,
        child: Scrollbar(
          child: ListView(
            children: <Widget>[
              Container(height: 40.0, child: const Text('0')),
            ],
          ),
        ),
      ),
    ));

    final CustomPaint custom = tester.widget(find
        .descendant(
            of: find.byType(Scrollbar), matching: find.byType(CustomPaint))
        .first);
    final dynamic scrollPainter = custom.foregroundPainter;
    // Dragging makes the scrollbar first appear.
    await tester.drag(find.text('0'), const Offset(0.0, -10.0));
    await tester.pump(const Duration(milliseconds: 200));
    await tester.pump(const Duration(milliseconds: 200));

    final ScrollMetrics metrics = FixedScrollMetrics(
        minScrollExtent: 0.0,
        maxScrollExtent: 0.0,
        pixels: 0.0,
        viewportDimension: 100.0,
        axisDirection: AxisDirection.down);
    scrollPainter.update(metrics, AxisDirection.down);

    final List<Invocation> invocations = <Invocation>[];
    final TestCanvas canvas = TestCanvas(invocations);
    scrollPainter.paint(canvas, const Size(10.0, 100.0));
    final Rect thumbRect = invocations.single.positionalArguments[0];
    expect(thumbRect.isFinite, isTrue);
  });

  // TODO(flutter_web): Renable, Web doesn't support Platform.iOS yet.
//  testWidgets('Adaptive scrollbar', (WidgetTester tester) async {
//    Widget viewWithScroll(TargetPlatform platform) {
//      return Directionality(
//        textDirection: TextDirection.ltr,
//        child: Theme(
//          data: ThemeData(
//              platform: platform
//          ),
//          child: Scrollbar(
//            child: SingleChildScrollView(
//              child: const SizedBox(width: 4000.0, height: 4000.0),
//            ),
//          ),
//        ),
//      );
//    }
//
//    await tester.pumpWidget(viewWithScroll(TargetPlatform.android));
//    await tester.drag(find.byType(SingleChildScrollView), const Offset(0.0, -10.0));
//    await tester.pump();
//    // Scrollbar fully showing
//    await tester.pump(const Duration(milliseconds: 500));
//    expect(find.byType(Scrollbar), paints..rect());
//
//    await tester.pumpWidget(viewWithScroll(TargetPlatform.iOS));
//    final TestGesture gesture = await tester.startGesture(
//        tester.getCenter(find.byType(SingleChildScrollView))
//    );
//    await gesture.moveBy(const Offset(0.0, -10.0));
//    await tester.drag(find.byType(SingleChildScrollView), const Offset(0.0, -10.0));
//    await tester.pump();
//    await tester.pump(const Duration(milliseconds: 200));
//    expect(find.byType(Scrollbar), paints..rrect());
//  });
}