flutter_flutter/packages/flutter/test/widgets/scroll_activity_test.dart

// Copyright 2014 The Flutter 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/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter/physics.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';

List<Widget> children(int n) {
  return List<Widget>.generate(n, (int i) {
    return SizedBox(height: 100.0, child: Text('$i'));
  });
}

void main() {
  testWidgets('Scrolling with list view changes, leaving the overscroll', (
    WidgetTester tester,
  ) async {
    final ScrollController controller = ScrollController();
    addTearDown(controller.dispose);
    await tester.pumpWidget(
      MaterialApp(
        home: ListView(controller: controller, children: children(30)),
      ),
    );
    final double thirty = controller.position.maxScrollExtent;
    controller.jumpTo(thirty);
    await tester.pump();
    controller.jumpTo(thirty + 100.0); // past the end
    await tester.pump();
    await tester.pumpWidget(
      MaterialApp(
        home: ListView(controller: controller, children: children(31)),
      ),
    );
    expect(
      controller.position.pixels,
      thirty + 100.0,
    ); // has the same position, but no longer overscrolled
    expect(await tester.pumpAndSettle(), 1); // doesn't have ballistic animation...
    expect(controller.position.pixels, thirty + 100.0); // and ends up at the end
  });

  testWidgets('Scrolling with list view changes, remaining overscrolled', (
    WidgetTester tester,
  ) async {
    final ScrollController controller = ScrollController();
    addTearDown(controller.dispose);
    await tester.pumpWidget(
      MaterialApp(
        home: ListView(controller: controller, children: children(30)),
      ),
    );
    final double thirty = controller.position.maxScrollExtent;
    controller.jumpTo(thirty);
    await tester.pump();
    controller.jumpTo(thirty + 200.0); // past the end
    await tester.pump();
    await tester.pumpWidget(
      MaterialApp(
        home: ListView(controller: controller, children: children(31)),
      ),
    );
    expect(controller.position.pixels, thirty + 200.0); // has the same position, still overscrolled
    expect(await tester.pumpAndSettle(), 8); // now it goes ballistic...
    expect(controller.position.pixels, thirty + 100.0); // and ends up at the end
  });

  testWidgets('DrivenScrollActivity allows overriding applyMoveTo', (WidgetTester tester) async {
    final ScrollController controller = ScrollController();
    addTearDown(controller.dispose);
    final List<ScrollNotification> notifications = <ScrollNotification>[];
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: NotificationListener<ScrollNotification>(
          onNotification: (ScrollNotification notif) {
            if (notif is OverscrollNotification) {
              notifications.add(notif);
            }
            return false;
          },
          child: ListView(controller: controller, children: children(10)),
        ),
      ),
    );
    final ScrollPositionWithSingleContext position =
        controller.position as ScrollPositionWithSingleContext;
    final double end = position.maxScrollExtent;

    position.beginActivity(
      DrivenScrollActivity(
        position,
        from: 0,
        to: end + 10,
        duration: const Duration(milliseconds: 100),
        curve: Curves.linear,
        vsync: position.context.vsync,
      ),
    );
    await tester.pumpAndSettle();
    // The base DrivenScrollActivity caused overscroll.
    expect(notifications, hasLength(1));

    notifications.clear();
    controller.jumpTo(0);
    await tester.pump();

    position.beginActivity(
      _NoOverscrollDrivenScrollActivity(
        position,
        from: 0,
        to: end + 10,
        duration: const Duration(milliseconds: 100),
        curve: Curves.linear,
        vsync: position.context.vsync,
      ),
    );
    await tester.pumpAndSettle();
    // The _NoOverscrollDrivenScrollActivity avoided overscroll.
    expect(notifications, isEmpty);
  });

  testWidgets('Ability to keep a PageView at the end manually (issue 62209)', (
    WidgetTester tester,
  ) async {
    await tester.pumpWidget(const MaterialApp(home: PageView62209()));
    expect(find.text('Page 1'), findsOneWidget);
    expect(find.text('Page 100'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(-800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 2'), findsOneWidget);
    expect(find.text('Page 100'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(-800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 3'), findsOneWidget);
    expect(find.text('Page 100'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(-800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 4'), findsOneWidget);
    expect(find.text('Page 100'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(-800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 5'), findsOneWidget);
    expect(find.text('Page 100'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(-800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 5'), findsNothing);
    expect(find.text('Page 100'), findsOneWidget);
    await tester.tap(find.byType(TextButton)); // 6
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 6'), findsNothing);
    expect(find.text('Page 5'), findsNothing);
    expect(find.text('Page 100'), findsOneWidget);
    await tester.tap(find.byType(TextButton)); // 7
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 6'), findsNothing);
    expect(find.text('Page 7'), findsNothing);
    expect(find.text('Page 5'), findsNothing);
    expect(find.text('Page 100'), findsOneWidget);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 5'), findsOneWidget);
    expect(find.text('Page 100'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 4'), findsOneWidget);
    expect(find.text('Page 5'), findsNothing);
    expect(find.text('Page 100'), findsNothing);
    await tester.tap(find.byType(TextButton)); // 8
    await tester.pump();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 8'), findsNothing);
    expect(find.text('Page 4'), findsOneWidget);
    expect(find.text('Page 5'), findsNothing);
    expect(find.text('Page 100'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 3'), findsOneWidget);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 2'), findsOneWidget);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 6'), findsOneWidget);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 7'), findsOneWidget);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 8'), findsOneWidget);
    await tester.drag(find.byType(PageView62209), const Offset(800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 1'), findsOneWidget);
    await tester.tap(find.byType(TextButton)); // 9
    await tester.pump();
    expect(find.text('Page 1'), findsOneWidget);
    expect(find.text('Page 9'), findsNothing);
    await tester.drag(find.byType(PageView62209), const Offset(-800.0, 0.0));
    await tester.pump();
    expect(find.text('Page 9'), findsOneWidget);
  });

  testWidgets('Pointer is not ignored during trackpad scrolling.', (WidgetTester tester) async {
    final ScrollController controller = ScrollController();
    addTearDown(controller.dispose);
    int? lastTapped;
    int? lastHovered;
    await tester.pumpWidget(
      MaterialApp(
        home: ListView(
          controller: controller,
          children: List<Widget>.generate(30, (int i) {
            return SizedBox(
              height: 100.0,
              child: MouseRegion(
                onHover: (PointerHoverEvent event) {
                  lastHovered = i;
                },
                child: GestureDetector(
                  onTap: () {
                    lastTapped = i;
                  },
                  child: Text('$i'),
                ),
              ),
            );
          }),
        ),
      ),
    );
    final TestGesture touchGesture = await tester.createGesture(
      kind: PointerDeviceKind.touch, // ignore: avoid_redundant_argument_values
    );
    // Try mouse hovering while scrolling by touch
    await touchGesture.down(tester.getCenter(find.byType(ListView)));
    await tester.pump();
    await touchGesture.moveBy(const Offset(0, 200));
    await tester.pump();
    final TestGesture hoverGesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
    await hoverGesture.addPointer(location: tester.getCenter(find.text('3')));
    await hoverGesture.moveBy(const Offset(1, 1));
    await hoverGesture.removePointer(location: tester.getCenter(find.text('3')));
    await tester.pumpAndSettle();
    expect(
      controller.position.activity?.shouldIgnorePointer,
      isTrue,
    ); // Pointer is ignored for touch scrolling.
    expect(lastHovered, isNull);
    await touchGesture.up();
    await tester.pump();
    // Try mouse clicking during inertia after scrolling by touch
    await tester.fling(find.byType(ListView), const Offset(0, -200), 1000);
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 100));
    expect(
      controller.position.activity?.shouldIgnorePointer,
      isTrue,
    ); // Pointer is ignored following touch scrolling.
    await tester.tap(find.text('3'), warnIfMissed: false);
    expect(lastTapped, isNull);
    await tester.pumpAndSettle();

    controller.jumpTo(0);
    await tester.pump();
    final TestGesture trackpadGesture = await tester.createGesture(
      kind: PointerDeviceKind.trackpad,
    );
    // Try mouse hovering while scrolling with a trackpad
    await trackpadGesture.panZoomStart(tester.getCenter(find.byType(ListView)));
    await tester.pump();
    await trackpadGesture.panZoomUpdate(
      tester.getCenter(find.byType(ListView)),
      pan: const Offset(0, 200),
    );
    await tester.pump();
    await hoverGesture.addPointer(location: tester.getCenter(find.text('3')));
    await hoverGesture.moveBy(const Offset(1, 1));
    await hoverGesture.removePointer(location: tester.getCenter(find.text('3')));
    await tester.pumpAndSettle();
    expect(
      controller.position.activity?.shouldIgnorePointer,
      isFalse,
    ); // Pointer is not ignored for trackpad scrolling.
    expect(lastHovered, equals(3));
    await trackpadGesture.panZoomEnd();
    await tester.pump();
    // Try mouse clicking during inertia after scrolling with a trackpad
    await tester.trackpadFling(find.byType(ListView), const Offset(0, -200), 1000);
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 100));
    expect(
      controller.position.activity?.shouldIgnorePointer,
      isFalse,
    ); // Pointer is not ignored following trackpad scrolling.
    await tester.tap(find.text('3'));
    expect(lastTapped, equals(3));
    await tester.pumpAndSettle();
  });

  testWidgets('DrivenScrollActivity.simulation constructor', (WidgetTester tester) async {
    final ScrollController controller = ScrollController();
    addTearDown(controller.dispose);
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: ListView(controller: controller, children: children(10)),
      ),
    );
    final ScrollPositionWithSingleContext position =
        controller.position as ScrollPositionWithSingleContext;

    const double g = 9.8;
    position.beginActivity(
      DrivenScrollActivity.simulation(
        position,
        vsync: position.context.vsync,
        GravitySimulation(g, 0, 1000, 0),
      ),
    );
    await tester.pump();
    expect(position.pixels, 0.0);
    await tester.pump(const Duration(seconds: 1));
    expect(position.pixels, (1 / 2) * g);
    await tester.pump(const Duration(seconds: 1));
    expect(position.pixels, 2 * g);
  });

  test('$ScrollActivity dispatches memory events', () async {
    await expectLater(
      await memoryEvents(
        () => _ScrollActivity(_ScrollActivityDelegate()).dispose(),
        _ScrollActivity,
      ),
      areCreateAndDispose,
    );
  });

  test('$ScrollDragController dispatches memory events', () async {
    await expectLater(
      await memoryEvents(
        () => ScrollDragController(
          delegate: _ScrollActivityDelegate(),
          details: DragStartDetails(),
        ).dispose(),
        ScrollDragController,
      ),
      areCreateAndDispose,
    );
  });
}

class PageView62209 extends StatefulWidget {
  const PageView62209({super.key});

  @override
  State<PageView62209> createState() => _PageView62209State();
}

class _PageView62209State extends State<PageView62209> {
  int _nextPageNum = 1;
  final List<Carousel62209Page> _pages = <Carousel62209Page>[];

  @override
  void initState() {
    super.initState();
    for (int i = 0; i < 5; i++) {
      _pages.add(Carousel62209Page(key: Key('$_nextPageNum'), number: _nextPageNum++));
    }
    _pages.add(const Carousel62209Page(number: 100));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Expanded(child: Carousel62209(pages: _pages)),
          TextButton(
            child: const Text('ADD PAGE'),
            onPressed: () {
              setState(() {
                _pages.insert(
                  1,
                  Carousel62209Page(key: Key('$_nextPageNum'), number: _nextPageNum++),
                );
              });
            },
          ),
        ],
      ),
    );
  }
}

class Carousel62209Page extends StatelessWidget {
  const Carousel62209Page({required this.number, super.key});

  final int number;

  @override
  Widget build(BuildContext context) {
    return Center(child: Text('Page $number'));
  }
}

class Carousel62209 extends StatefulWidget {
  const Carousel62209({super.key, required this.pages});

  final List<Carousel62209Page> pages;

  @override
  State<Carousel62209> createState() => _Carousel62209State();
}

class _Carousel62209State extends State<Carousel62209> {
  // page variables
  late PageController _pageController;
  int _currentPage = 0;

  // controls updates outside of user interaction
  late List<Carousel62209Page> _pages;
  bool _jumpingToPage = false;

  @override
  void initState() {
    super.initState();
    _pages = widget.pages.toList();
    _pageController = PageController(keepPage: false);
  }

  @override
  void didUpdateWidget(Carousel62209 oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (!_jumpingToPage) {
      int newPage = -1;
      for (int i = 0; i < widget.pages.length; i++) {
        if (widget.pages[i].number == _pages[_currentPage].number) {
          newPage = i;
        }
      }
      if (newPage == _currentPage) {
        _pages = widget.pages.toList();
      } else {
        _jumpingToPage = true;
        SchedulerBinding.instance.addPostFrameCallback((_) {
          if (mounted) {
            setState(() {
              _pages = widget.pages.toList();
              _currentPage = newPage;
              _pageController.jumpToPage(_currentPage);
              SchedulerBinding.instance.addPostFrameCallback((_) {
                _jumpingToPage = false;
              });
            });
          }
        });
      }
    }
  }

  @override
  void dispose() {
    _pageController.dispose();
    super.dispose();
  }

  bool _handleScrollNotification(ScrollNotification notification) {
    if (notification is ScrollUpdateNotification) {
      final int page = _pageController.page!.round();
      if (!_jumpingToPage && _currentPage != page) {
        _currentPage = page;
      }
    }
    return true;
  }

  @override
  Widget build(BuildContext context) {
    return NotificationListener<ScrollNotification>(
      onNotification: _handleScrollNotification,
      child: PageView.builder(
        controller: _pageController,
        itemCount: _pages.length,
        itemBuilder: (BuildContext context, int index) {
          return _pages[index];
        },
      ),
    );
  }
}

class _NoOverscrollDrivenScrollActivity extends DrivenScrollActivity {
  _NoOverscrollDrivenScrollActivity(
    ScrollPositionWithSingleContext super.delegate, {
    required super.from,
    required super.to,
    required super.duration,
    required super.curve,
    required super.vsync,
  });

  ScrollPosition get _position => delegate as ScrollPosition;

  @override
  bool applyMoveTo(double value) {
    bool done = false;
    if (velocity >= 0.0 && value > _position.maxScrollExtent) {
      value = _position.maxScrollExtent;
      done = true;
    } else if (velocity <= 0.0 && value < _position.minScrollExtent) {
      value = _position.minScrollExtent;
      done = true;
    }
    if (!super.applyMoveTo(value)) {
      return false;
    }
    return !done;
  }
}

class _ScrollActivity extends ScrollActivity {
  _ScrollActivity(super.delegate);

  @override
  bool get isScrolling => false;

  @override
  bool get shouldIgnorePointer => true;

  @override
  double get velocity => 0.0;
}

class _ScrollActivityDelegate extends ScrollActivityDelegate {
  @override
  void applyUserOffset(double delta) {}

  @override
  AxisDirection get axisDirection => AxisDirection.down;

  @override
  void goBallistic(double velocity) {}

  @override
  void goIdle() {}

  @override
  double setPixels(double pixels) => 0.0;
}