packages/flutter/test/widgets/scrollable_semantics_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 'dart:ui';

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

import 'semantics_tester.dart';

void main() {
  SemanticsTester semantics;

  setUp(() {
    debugResetSemanticsIdCounter();
  });

  testWidgets('scrollable exposes the correct semantic actions', (WidgetTester tester) async {
    semantics = SemanticsTester(tester);
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: ListView(children: List<Widget>.generate(80, (int i) => Text('$i'))),
      ),
    );

    expect(semantics,includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollUp]));

    await flingUp(tester);
    expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollUp, SemanticsAction.scrollDown]));

    await flingDown(tester, repetitions: 2);
    expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollUp]));

    await flingUp(tester, repetitions: 5);
    expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollDown]));

    await flingDown(tester);
    expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.scrollUp, SemanticsAction.scrollDown]));

    semantics.dispose();
  });

  testWidgets('showOnScreen works in scrollable', (WidgetTester tester) async {
    semantics = SemanticsTester(tester); // enables semantics tree generation

    const double kItemHeight = 40.0;

    final List<Widget> containers = List<Widget>.generate(80, (int i) => MergeSemantics(
      child: SizedBox(
        height: kItemHeight,
        child: Text('container $i', textDirection: TextDirection.ltr),
      ),
    ));

    final ScrollController scrollController = ScrollController(
      initialScrollOffset: kItemHeight / 2,
    );

    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: ListView(
          controller: scrollController,
          children: containers,
        ),
      ),
    );

    expect(scrollController.offset, kItemHeight / 2);

    final int firstContainerId = tester.renderObject(find.byWidget(containers.first)).debugSemantics!.id;
    tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
    await tester.pump();
    await tester.pump(const Duration(seconds: 5));

    expect(scrollController.offset, 0.0);

    semantics.dispose();
  });

  testWidgets('showOnScreen works with pinned app bar and sliver list', (WidgetTester tester) async {
    semantics = SemanticsTester(tester); // enables semantics tree generation

    const double kItemHeight = 100.0;
    const double kExpandedAppBarHeight = 56.0;

    final List<Widget> containers = List<Widget>.generate(80, (int i) => MergeSemantics(
      child: SizedBox(
        height: kItemHeight,
        child: Text('container $i'),
      ),
    ));

    final ScrollController scrollController = ScrollController(
      initialScrollOffset: kItemHeight / 2,
    );

    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: Localizations(
        locale: const Locale('en', 'us'),
        delegates: const <LocalizationsDelegate<dynamic>>[
          DefaultWidgetsLocalizations.delegate,
          DefaultMaterialLocalizations.delegate,
        ],
        child: MediaQuery(
          data: const MediaQueryData(),
            child: Scrollable(
            controller: scrollController,
            viewportBuilder: (BuildContext context, ViewportOffset offset) {
              return Viewport(
                offset: offset,
                slivers: <Widget>[
                  const SliverAppBar(
                    pinned: true,
                    expandedHeight: kExpandedAppBarHeight,
                    flexibleSpace: FlexibleSpaceBar(
                      title: Text('App Bar'),
                    ),
                  ),
                  SliverList(
                    delegate: SliverChildListDelegate(containers),
                  ),
                ],
              );
            },
          ),
        ),
      ),
    ));

    expect(scrollController.offset, kItemHeight / 2);

    final int firstContainerId = tester.renderObject(find.byWidget(containers.first)).debugSemantics!.id;
    tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
    await tester.pump();
    await tester.pump(const Duration(seconds: 5));
    expect(tester.getTopLeft(find.byWidget(containers.first)).dy, kExpandedAppBarHeight);

    semantics.dispose();
  });

  testWidgets('showOnScreen works with pinned app bar and individual slivers', (WidgetTester tester) async {
    semantics = SemanticsTester(tester); // enables semantics tree generation

    const double kItemHeight = 100.0;
    const double kExpandedAppBarHeight = 256.0;


    final List<Widget> children = <Widget>[];
    final List<Widget> slivers = List<Widget>.generate(30, (int i) {
      final Widget child = MergeSemantics(
        child: SizedBox(
          height: 72.0,
          child: Text('Item $i'),
        ),
      );
      children.add(child);
      return SliverToBoxAdapter(
        child: child,
      );
    });

    final ScrollController scrollController = ScrollController(
      initialScrollOffset: 2.5 * kItemHeight,
    );

    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: MediaQuery(
        data: const MediaQueryData(),
        child: Localizations(
          locale: const Locale('en', 'us'),
          delegates: const <LocalizationsDelegate<dynamic>>[
            DefaultWidgetsLocalizations.delegate,
            DefaultMaterialLocalizations.delegate,
          ],
          child: Scrollable(
            controller: scrollController,
            viewportBuilder: (BuildContext context, ViewportOffset offset) {
              return Viewport(
                offset: offset,
                slivers: <Widget>[
                  const SliverAppBar(
                    pinned: true,
                    expandedHeight: kExpandedAppBarHeight,
                    flexibleSpace: FlexibleSpaceBar(
                      title: Text('App Bar'),
                    ),
                  ),
                  ...slivers,
                ],
              );
            },
          ),
        ),
      ),
    ));

    expect(scrollController.offset, 2.5 * kItemHeight);

    final int id0 = tester.renderObject(find.byWidget(children[0])).debugSemantics!.id;
    tester.binding.pipelineOwner.semanticsOwner!.performAction(id0, SemanticsAction.showOnScreen);
    await tester.pump();
    await tester.pump(const Duration(seconds: 5));
    expect(tester.getTopLeft(find.byWidget(children[0])).dy, kToolbarHeight);

    semantics.dispose();
  });

  testWidgets('correct scrollProgress', (WidgetTester tester) async {
    semantics = SemanticsTester(tester);

    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: ListView(children: List<Widget>.generate(80, (int i) => Text('$i'))),
    ));

    expect(semantics, includesNodeWith(
      scrollExtentMin: 0.0,
      scrollPosition: 0.0,
      scrollExtentMax: 520.0,
      actions: <SemanticsAction>[
        SemanticsAction.scrollUp,
      ],
    ));

    await flingUp(tester);

    expect(semantics, includesNodeWith(
      scrollExtentMin: 0.0,
      scrollPosition: 380.2,
      scrollExtentMax: 520.0,
      actions: <SemanticsAction>[
        SemanticsAction.scrollUp,
        SemanticsAction.scrollDown,
      ],
    ));

    await flingUp(tester);

    expect(semantics, includesNodeWith(
      scrollExtentMin: 0.0,
      scrollPosition: 520.0,
      scrollExtentMax: 520.0,
      actions: <SemanticsAction>[
        SemanticsAction.scrollDown,
      ],
    ));

    semantics.dispose();
  });

  testWidgets('correct scrollProgress for unbound', (WidgetTester tester) async {
    semantics = SemanticsTester(tester);

    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: ListView.builder(
        dragStartBehavior: DragStartBehavior.down,
        itemExtent: 20.0,
        itemBuilder: (BuildContext context, int index) {
          return Text('entry $index');
        },
      ),
    ));

    expect(semantics, includesNodeWith(
      scrollExtentMin: 0.0,
      scrollPosition: 0.0,
      scrollExtentMax: double.infinity,
      actions: <SemanticsAction>[
        SemanticsAction.scrollUp,
      ],
    ));

    await flingUp(tester);

    expect(semantics, includesNodeWith(
      scrollExtentMin: 0.0,
      scrollPosition: 380.2,
      scrollExtentMax: double.infinity,
      actions: <SemanticsAction>[
        SemanticsAction.scrollUp,
        SemanticsAction.scrollDown,
      ],
    ));

    await flingUp(tester);

    expect(semantics, includesNodeWith(
      scrollExtentMin: 0.0,
      scrollPosition: 760.4,
      scrollExtentMax: double.infinity,
      actions: <SemanticsAction>[
        SemanticsAction.scrollUp,
        SemanticsAction.scrollDown,
      ],
    ));

    semantics.dispose();
  });

  testWidgets('Semantics tree is populated mid-scroll', (WidgetTester tester) async {
    semantics = SemanticsTester(tester);

    final List<Widget> children = List<Widget>.generate(80, (int i) => SizedBox(
      height: 40.0,
      child: Text('Item $i'),
    ));
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: ListView(children: children),
      ),
    );

    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(ListView)));
    await gesture.moveBy(const Offset(0.0, -40.0));
    await tester.pump();

    expect(semantics, includesNodeWith(label: 'Item 1'));
    expect(semantics, includesNodeWith(label: 'Item 2'));
    expect(semantics, includesNodeWith(label: 'Item 3'));

    semantics.dispose();
  });

  testWidgets('Can toggle semantics on, off, on without crash', (WidgetTester tester) async {
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: ListView(
          children: List<Widget>.generate(40, (int i) {
            return SizedBox(
              height: 400.0,
              child: Text('item $i'),
            );
          }),
        ),
      ),
    );

    final TestSemantics expectedSemantics = TestSemantics.root(
      children: <TestSemantics>[
        TestSemantics.rootChild(
          children: <TestSemantics>[
            TestSemantics(
              flags: <SemanticsFlag>[
                SemanticsFlag.hasImplicitScrolling,
              ],
              actions: <SemanticsAction>[SemanticsAction.scrollUp],
              children: <TestSemantics>[
                TestSemantics(
                  label: r'item 0',
                  textDirection: TextDirection.ltr,
                ),
                TestSemantics(
                  label: r'item 1',
                  textDirection: TextDirection.ltr,
                ),
                TestSemantics(
                  flags: <SemanticsFlag>[
                    SemanticsFlag.isHidden,
                  ],
                  label: r'item 2',
                ),
              ],
            ),
          ],
        ),
      ],
    );

    // Start with semantics off.
    expect(tester.binding.pipelineOwner.semanticsOwner, isNull);

    // Semantics on
    semantics = SemanticsTester(tester);
    await tester.pumpAndSettle();
    expect(tester.binding.pipelineOwner.semanticsOwner, isNotNull);
    expect(semantics, hasSemantics(expectedSemantics, ignoreId: true, ignoreRect: true, ignoreTransform: true));

    // Semantics off
    semantics.dispose();
    await tester.pumpAndSettle();
    expect(tester.binding.pipelineOwner.semanticsOwner, isNull);

    // Semantics on
    semantics = SemanticsTester(tester);
    await tester.pumpAndSettle();
    expect(tester.binding.pipelineOwner.semanticsOwner, isNotNull);
    expect(semantics, hasSemantics(expectedSemantics, ignoreId: true, ignoreRect: true, ignoreTransform: true));

    semantics.dispose();
  }, semanticsEnabled: false);

  group('showOnScreen', () {

    const double kItemHeight = 100.0;

    late List<Widget> children;
    late ScrollController scrollController;
    late Widget widgetUnderTest;

    setUp(() {
      children = List<Widget>.generate(10, (int i) {
        return MergeSemantics(
          child: SizedBox(
            height: kItemHeight,
            child: Text('container $i'),
          ),
        );
      });

      scrollController = ScrollController(
        initialScrollOffset: kItemHeight / 2,
      );

      widgetUnderTest = Directionality(
        textDirection: TextDirection.ltr,
        child: Center(
          child: SizedBox(
            height: 2 * kItemHeight,
            child: ListView(
              controller: scrollController,
              children: children,
            ),
          ),
        ),
      );

    });

    testWidgets('brings item above leading edge to leading edge', (WidgetTester tester) async {
      semantics = SemanticsTester(tester); // enables semantics tree generation

      await tester.pumpWidget(widgetUnderTest);

      expect(scrollController.offset, kItemHeight / 2);

      final int firstContainerId = tester.renderObject(find.byWidget(children.first)).debugSemantics!.id;
      tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
      await tester.pumpAndSettle();

      expect(scrollController.offset, 0.0);

      semantics.dispose();
    });

    testWidgets('brings item below trailing edge to trailing edge', (WidgetTester tester) async {
      semantics = SemanticsTester(tester); // enables semantics tree generation

      await tester.pumpWidget(widgetUnderTest);

      expect(scrollController.offset, kItemHeight / 2);

      final int firstContainerId = tester.renderObject(find.byWidget(children[2])).debugSemantics!.id;
      tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
      await tester.pumpAndSettle();

      expect(scrollController.offset, kItemHeight);

      semantics.dispose();
    });

    testWidgets('does not change position of items already fully on-screen', (WidgetTester tester) async {
      semantics = SemanticsTester(tester); // enables semantics tree generation

      await tester.pumpWidget(widgetUnderTest);

      expect(scrollController.offset, kItemHeight / 2);

      final int firstContainerId = tester.renderObject(find.byWidget(children[1])).debugSemantics!.id;
      tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
      await tester.pumpAndSettle();

      expect(scrollController.offset, kItemHeight / 2);

      semantics.dispose();
    });
  });

  group('showOnScreen with negative children', () {
    const double kItemHeight = 100.0;

    late List<Widget> children;
    late ScrollController scrollController;
    late Widget widgetUnderTest;

    setUp(() {
      final Key center = GlobalKey();

      children = List<Widget>.generate(10, (int i) {
        return SliverToBoxAdapter(
          key: i == 5 ? center : null,
          child: MergeSemantics(
            key: ValueKey<int>(i),
            child: SizedBox(
              height: kItemHeight,
              child: Text('container $i'),
            ),
          ),
        );
      });

      scrollController = ScrollController(
        initialScrollOffset: -2.5 * kItemHeight,
      );

      // 'container 0' is at offset -500
      // 'container 1' is at offset -400
      // 'container 2' is at offset -300
      // 'container 3' is at offset -200
      // 'container 4' is at offset -100
      // 'container 5' is at offset 0

      widgetUnderTest = Directionality(
        textDirection: TextDirection.ltr,
        child: Center(
          child: SizedBox(
            height: 2 * kItemHeight,
            child: Scrollable(
              controller: scrollController,
              viewportBuilder: (BuildContext context, ViewportOffset offset) {
                return Viewport(
                  cacheExtent: 0.0,
                  offset: offset,
                  center: center,
                  slivers: children,
                );
              },
            ),
          ),
        ),
      );

    });

    testWidgets('brings item above leading edge to leading edge', (WidgetTester tester) async {
      semantics = SemanticsTester(tester); // enables semantics tree generation

      await tester.pumpWidget(widgetUnderTest);

      expect(scrollController.offset, -250.0);

      final int firstContainerId = tester.renderObject(find.byKey(const ValueKey<int>(2))).debugSemantics!.id;
      tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
      await tester.pumpAndSettle();

      expect(scrollController.offset, -300.0);

      semantics.dispose();
    });

    testWidgets('brings item below trailing edge to trailing edge', (WidgetTester tester) async {
      semantics = SemanticsTester(tester); // enables semantics tree generation

      await tester.pumpWidget(widgetUnderTest);

      expect(scrollController.offset, -250.0);

      final int firstContainerId = tester.renderObject(find.byKey(const ValueKey<int>(4))).debugSemantics!.id;
      tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
      await tester.pumpAndSettle();

      expect(scrollController.offset, -200.0);

      semantics.dispose();
    });

    testWidgets('does not change position of items already fully on-screen', (WidgetTester tester) async {
      semantics = SemanticsTester(tester); // enables semantics tree generation

      await tester.pumpWidget(widgetUnderTest);

      expect(scrollController.offset, -250.0);

      final int firstContainerId = tester.renderObject(find.byKey(const ValueKey<int>(3))).debugSemantics!.id;
      tester.binding.pipelineOwner.semanticsOwner!.performAction(firstContainerId, SemanticsAction.showOnScreen);
      await tester.pumpAndSettle();

      expect(scrollController.offset, -250.0);

      semantics.dispose();
    });

  });

  testWidgets('transform of inner node from useTwoPaneSemantics scrolls correctly with nested scrollables', (WidgetTester tester) async {
    semantics = SemanticsTester(tester); // enables semantics tree generation

    // Context: https://github.com/flutter/flutter/issues/61631
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: SingleChildScrollView(
          child: ListView(
            shrinkWrap: true,
            children: <Widget>[
              for (int i = 0; i < 50; ++i)
                Text('$i'),
            ],
          ),
        ),
      ),
    );

    final SemanticsNode rootScrollNode = semantics.nodesWith(actions: <SemanticsAction>[SemanticsAction.scrollUp]).single;
    final SemanticsNode innerListPane = semantics.nodesWith(ancestor: rootScrollNode, scrollExtentMax: 0).single;
    final SemanticsNode outerListPane = innerListPane.parent!;
    final List<SemanticsNode> hiddenNodes = semantics.nodesWith(flags: <SemanticsFlag>[SemanticsFlag.isHidden]).toList();

    // This test is only valid if some children are offscreen.
    // Increase the number of Text children if this assert fails.
    assert(hiddenNodes.length >= 3);

    // Scroll to end -> beginning -> middle to test both directions.
    final List<SemanticsNode> targetNodes = <SemanticsNode>[
      hiddenNodes.last,
      hiddenNodes.first,
      hiddenNodes[hiddenNodes.length ~/ 2],
    ];

    expect(nodeGlobalRect(innerListPane), nodeGlobalRect(outerListPane));

    for (final SemanticsNode node in targetNodes) {
      tester.binding.pipelineOwner.semanticsOwner!.performAction(node.id, SemanticsAction.showOnScreen);
      await tester.pumpAndSettle();

      expect(nodeGlobalRect(innerListPane), nodeGlobalRect(outerListPane));
    }

    semantics.dispose();
  });
}

Future<void> flingUp(WidgetTester tester, { int repetitions = 1 }) => fling(tester, const Offset(0.0, -200.0), repetitions);

Future<void> flingDown(WidgetTester tester, { int repetitions = 1 }) => fling(tester, const Offset(0.0, 200.0), repetitions);

Future<void> flingRight(WidgetTester tester, { int repetitions = 1 }) => fling(tester, const Offset(200.0, 0.0), repetitions);

Future<void> flingLeft(WidgetTester tester, { int repetitions = 1 }) => fling(tester, const Offset(-200.0, 0.0), repetitions);

Future<void> fling(WidgetTester tester, Offset offset, int repetitions) async {
  while (repetitions-- > 0) {
    await tester.fling(find.byType(ListView), offset, 1000.0);
    await tester.pump();
    await tester.pump(const Duration(seconds: 5));
  }
}

Rect nodeGlobalRect(SemanticsNode node) {
  Matrix4 globalTransform = node.transform ?? Matrix4.identity();
  for (SemanticsNode? parent = node.parent; parent != null; parent = parent.parent) {
    if (parent.transform != null) {
      globalTransform = parent.transform!.multiplied(globalTransform);
    }
  }
  return MatrixUtils.transformRect(globalTransform, node.rect);
}