• Todd Volkert's avatar
    Add more flexible image API (#118966) · b319938e
    Todd Volkert authored
    This updates the framework to provide higher level wrappers around ui.instantiateImageCodecWithSize(). Functionally, this doesn't change anything (other than deprecating the older loadBuffer() method in favor of loadImage()), but it sets the stage for a simpler change that will allow us to provide a more flexible way to load sized images.
    
    #118543
    b319938e
scroll_aware_image_provider_test.dart 16 KB
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// 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' as ui show Image;

import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';

import '../painting/image_test_utils.dart';

void main() {

  late ui.Image testImage;

  setUpAll(() async {
    testImage = await createTestImage(width: 10, height: 10);
  });

  tearDown(() {
    imageCache.clear();
  });

  T findPhysics<T extends ScrollPhysics>(WidgetTester tester) {
    return Scrollable.of(find.byType(TestWidget).evaluate().first).position.physics as T;
  }

  ScrollMetrics findMetrics(WidgetTester tester) {
    return Scrollable.of(find.byType(TestWidget).evaluate().first).position;
  }

  testWidgets('ScrollAwareImageProvider does not delay if widget is not in scrollable', (WidgetTester tester) async {
    final GlobalKey<TestWidgetState> key = GlobalKey<TestWidgetState>();
    await tester.pumpWidget(TestWidget(key));

    final DisposableBuildContext context = DisposableBuildContext(key.currentState!);
    final TestImageProvider testImageProvider = TestImageProvider(testImage.clone());
    final ScrollAwareImageProvider<TestImageProvider> imageProvider = ScrollAwareImageProvider<TestImageProvider>(
      context: context,
      imageProvider: testImageProvider,
    );

    expect(testImageProvider.configuration, null);
    expect(imageCache.containsKey(testImageProvider), false);

    final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);

    expect(testImageProvider.configuration, ImageConfiguration.empty);
    expect(stream.completer, isNotNull);
    expect(stream.completer!.hasListeners, true);
    expect(imageCache.containsKey(testImageProvider), true);
    expect(imageCache.currentSize, 0);

    testImageProvider.complete();

    expect(imageCache.currentSize, 1);
  });

  testWidgets('ScrollAwareImageProvider does not delay if in scrollable that is not scrolling', (WidgetTester tester) async {
    final GlobalKey<TestWidgetState> key = GlobalKey<TestWidgetState>();
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: ListView(
        physics: RecordingPhysics(),
        children: <Widget>[
          TestWidget(key),
        ],
      ),
    ));

    final DisposableBuildContext context = DisposableBuildContext(key.currentState!);
    final TestImageProvider testImageProvider = TestImageProvider(testImage.clone());
    final ScrollAwareImageProvider<TestImageProvider> imageProvider = ScrollAwareImageProvider<TestImageProvider>(
      context: context,
      imageProvider: testImageProvider,
    );

    expect(testImageProvider.configuration, null);
    expect(imageCache.containsKey(testImageProvider), false);

    final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);

    expect(testImageProvider.configuration, ImageConfiguration.empty);
    expect(stream.completer, isNotNull);
    expect(stream.completer!.hasListeners, true);
    expect(imageCache.containsKey(testImageProvider), true);
    expect(imageCache.currentSize, 0);

    testImageProvider.complete();

    expect(imageCache.currentSize, 1);
    expect(findPhysics<RecordingPhysics>(tester).velocities, <double>[0]);
  });

  testWidgets('ScrollAwareImageProvider does not delay if in scrollable that is scrolling slowly', (WidgetTester tester) async {
    final List<GlobalKey<TestWidgetState>> keys = <GlobalKey<TestWidgetState>>[];
    final ScrollController scrollController = ScrollController();
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: ListView.builder(
        physics: RecordingPhysics(),
        controller: scrollController,
        itemBuilder: (BuildContext context, int index) {
          keys.add(GlobalKey<TestWidgetState>());
          return TestWidget(keys.last);
        },
        itemCount: 50,
      ),
    ));

    final DisposableBuildContext context = DisposableBuildContext(keys.last.currentState!);
    final TestImageProvider testImageProvider = TestImageProvider(testImage.clone());
    final ScrollAwareImageProvider<TestImageProvider> imageProvider = ScrollAwareImageProvider<TestImageProvider>(
      context: context,
      imageProvider: testImageProvider,
    );

    expect(testImageProvider.configuration, null);
    expect(imageCache.containsKey(testImageProvider), false);

    scrollController.animateTo(
      100,
      duration: const Duration(seconds: 2),
      curve: Curves.fastLinearToSlowEaseIn,
    );
    await tester.pump();
    final RecordingPhysics physics = findPhysics<RecordingPhysics>(tester);

    expect(physics.velocities.length, 0);
    final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);
    expect(physics.velocities.length, 1);
    expect(
      const ScrollPhysics().recommendDeferredLoading(
        physics.velocities.first,
        findMetrics(tester),
        find.byType(TestWidget).evaluate().first,
      ),
      false,
    );

    expect(testImageProvider.configuration, ImageConfiguration.empty);
    expect(stream.completer, isNotNull);
    expect(stream.completer!.hasListeners, true);
    expect(imageCache.containsKey(testImageProvider), true);
    expect(imageCache.currentSize, 0);

    testImageProvider.complete();

    expect(imageCache.currentSize, 1);
  });

  testWidgets('ScrollAwareImageProvider delays if in scrollable that is scrolling fast', (WidgetTester tester) async {
    final List<GlobalKey<TestWidgetState>> keys = <GlobalKey<TestWidgetState>>[];
    final ScrollController scrollController = ScrollController();
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: ListView.builder(
        physics: RecordingPhysics(),
        controller: scrollController,
        itemBuilder: (BuildContext context, int index) {
          keys.add(GlobalKey<TestWidgetState>());
          return TestWidget(keys.last);
        },
        itemCount: 50,
      ),
    ));

    final DisposableBuildContext context = DisposableBuildContext(keys.last.currentState!);
    final TestImageProvider testImageProvider = TestImageProvider(testImage.clone());
    final ScrollAwareImageProvider<TestImageProvider> imageProvider = ScrollAwareImageProvider<TestImageProvider>(
      context: context,
      imageProvider: testImageProvider,
    );

    expect(testImageProvider.configuration, null);
    expect(imageCache.containsKey(testImageProvider), false);

    scrollController.animateTo(
      3000,
      duration: const Duration(seconds: 2),
      curve: Curves.fastLinearToSlowEaseIn,
    );
    await tester.pump();
    final RecordingPhysics physics = findPhysics<RecordingPhysics>(tester);

    expect(physics.velocities.length, 0);
    final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);
    expect(physics.velocities.length, 1);
    expect(
      const ScrollPhysics().recommendDeferredLoading(
        physics.velocities.first,
        findMetrics(tester),
        find.byType(TestWidget).evaluate().first,
      ),
      true,
    );

    expect(testImageProvider.configuration, null);
    expect(stream.completer, null);

    expect(imageCache.containsKey(testImageProvider), false);
    expect(imageCache.currentSize, 0);

    await tester.pump(const Duration(seconds: 1));
    expect(physics.velocities.last, 0);

    expect(testImageProvider.configuration, ImageConfiguration.empty);
    expect(stream.completer, isNotNull);
    expect(stream.completer!.hasListeners, true);

    expect(imageCache.containsKey(testImageProvider), true);
    expect(imageCache.currentSize, 0);

    testImageProvider.complete();

    expect(imageCache.currentSize, 1);
  });

  testWidgets('ScrollAwareImageProvider delays if in scrollable that is scrolling fast and fizzles if disposed', (WidgetTester tester) async {
    final List<GlobalKey<TestWidgetState>> keys = <GlobalKey<TestWidgetState>>[];
    final ScrollController scrollController = ScrollController();
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: ListView.builder(
        physics: RecordingPhysics(),
        controller: scrollController,
        itemBuilder: (BuildContext context, int index) {
          keys.add(GlobalKey<TestWidgetState>());
          return TestWidget(keys.last);
        },
        itemCount: 50,
      ),
    ));

    final DisposableBuildContext context = DisposableBuildContext(keys.last.currentState!);
    final TestImageProvider testImageProvider = TestImageProvider(testImage.clone());
    final ScrollAwareImageProvider<TestImageProvider> imageProvider = ScrollAwareImageProvider<TestImageProvider>(
      context: context,
      imageProvider: testImageProvider,
    );

    expect(testImageProvider.configuration, null);
    expect(imageCache.containsKey(testImageProvider), false);

    scrollController.animateTo(
      3000,
      duration: const Duration(seconds: 2),
      curve: Curves.fastLinearToSlowEaseIn,
    );
    await tester.pump();
    final RecordingPhysics physics = findPhysics<RecordingPhysics>(tester);

    expect(physics.velocities.length, 0);
    final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);
    expect(physics.velocities.length, 1);
    expect(
      const ScrollPhysics().recommendDeferredLoading(
        physics.velocities.first,
        findMetrics(tester),
        find.byType(TestWidget).evaluate().first,
      ),
      true,
    );

    expect(testImageProvider.configuration, null);
    expect(stream.completer, null);

    expect(imageCache.containsKey(testImageProvider), false);
    expect(imageCache.currentSize, 0);

    // as if we had picked a context that scrolled out of the tree.
    context.dispose();

    await tester.pump(const Duration(seconds: 1));
    expect(physics.velocities.length, 1);

    expect(testImageProvider.configuration, null);
    expect(stream.completer, null);

    expect(imageCache.containsKey(testImageProvider), false);
    expect(imageCache.currentSize, 0);

    testImageProvider.complete();

    expect(imageCache.currentSize, 0);
  });

  testWidgets('ScrollAwareImageProvider resolves from ImageCache and does not set completer twice', (WidgetTester tester) async {
    final GlobalKey<TestWidgetState> key = GlobalKey<TestWidgetState>();
    final ScrollController scrollController = ScrollController();
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: SingleChildScrollView(
        physics: ControllablePhysics(),
        controller: scrollController,
        child: TestWidget(key),
      ),
    ));

    final DisposableBuildContext context = DisposableBuildContext(key.currentState!);
    final TestImageProvider testImageProvider = TestImageProvider(testImage.clone());
    final ScrollAwareImageProvider<TestImageProvider> imageProvider = ScrollAwareImageProvider<TestImageProvider>(
      context: context,
      imageProvider: testImageProvider,
    );

    expect(testImageProvider.configuration, null);
    expect(imageCache.containsKey(testImageProvider), false);

    final ControllablePhysics physics = findPhysics<ControllablePhysics>(tester);
    physics.recommendDeferredLoadingValue = true;

    final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);

    expect(testImageProvider.configuration, null);
    expect(stream.completer, null);
    expect(imageCache.containsKey(testImageProvider), false);
    expect(imageCache.currentSize, 0);

    // Simulate a case where someone else has managed to complete this stream -
    // so it can land in the cache right before we stop scrolling fast.
    // If we miss the early return, we will fail.
    testImageProvider.complete();

    imageCache.putIfAbsent(testImageProvider, () => testImageProvider.loadImage(testImageProvider, PaintingBinding.instance.instantiateImageCodecWithSize));
    // We've stopped scrolling fast.
    physics.recommendDeferredLoadingValue = false;
    await tester.idle();

    expect(imageCache.containsKey(testImageProvider), true);
    expect(imageCache.currentSize, 1);
    expect(testImageProvider.loadCallCount, 1);
    expect(stream.completer, null);
  });

  testWidgets('ScrollAwareImageProvider does not block LRU updates to image cache', (WidgetTester tester) async {
    final int oldSize = imageCache.maximumSize;
    imageCache.maximumSize = 1;

    final GlobalKey<TestWidgetState> key = GlobalKey<TestWidgetState>();
    final ScrollController scrollController = ScrollController();
    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: SingleChildScrollView(
        physics: ControllablePhysics(),
        controller: scrollController,
        child: TestWidget(key),
      ),
    ));

    final DisposableBuildContext context = DisposableBuildContext(key.currentState!);
    final TestImageProvider testImageProvider = TestImageProvider(testImage.clone());
    final ScrollAwareImageProvider<TestImageProvider> imageProvider = ScrollAwareImageProvider<TestImageProvider>(
      context: context,
      imageProvider: testImageProvider,
    );

    expect(testImageProvider.configuration, null);
    expect(imageCache.containsKey(testImageProvider), false);

    final ControllablePhysics physics = findPhysics<ControllablePhysics>(tester);
    physics.recommendDeferredLoadingValue = true;

    final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);

    expect(testImageProvider.configuration, null);
    expect(stream.completer, null);
    expect(imageCache.currentSize, 0);

    // Occupy the only slot in the cache with another image.
    final TestImageProvider testImageProvider2 = TestImageProvider(testImage.clone());
    testImageProvider2.complete();
    await precacheImage(testImageProvider2, context.context!);
    expect(imageCache.containsKey(testImageProvider), false);
    expect(imageCache.containsKey(testImageProvider2), true);
    expect(imageCache.currentSize, 1);

    // Complete the original image while we're still scrolling fast.
    testImageProvider.complete();
    stream.setCompleter(testImageProvider.loadImage(testImageProvider, PaintingBinding.instance.instantiateImageCodecWithSize));

    // Verify that this hasn't changed the cache state yet
    expect(imageCache.containsKey(testImageProvider), false);
    expect(imageCache.containsKey(testImageProvider2), true);
    expect(imageCache.currentSize, 1);
    expect(testImageProvider.loadCallCount, 1);

    await tester.pump();

    // After pumping a frame, the original image should be in the cache because
    // it took the LRU slot.
    expect(imageCache.containsKey(testImageProvider), true);
    expect(imageCache.containsKey(testImageProvider2), false);
    expect(imageCache.currentSize, 1);
    expect(testImageProvider.loadCallCount, 1);

    imageCache.maximumSize = oldSize;
  });
}

class TestWidget extends StatefulWidget {
  const TestWidget(Key? key) : super(key: key);

  @override
  State<TestWidget> createState() => TestWidgetState();
}

class TestWidgetState extends State<TestWidget> {
  @override
  Widget build(BuildContext context) => const SizedBox(height: 50);
}

class RecordingPhysics extends ScrollPhysics {
  RecordingPhysics({ super.parent });

  final List<double> velocities = <double>[];

  @override
  RecordingPhysics applyTo(ScrollPhysics? ancestor) {
    return RecordingPhysics(parent: buildParent(ancestor));
  }

  @override
  bool recommendDeferredLoading(double velocity, ScrollMetrics metrics, BuildContext context) {
    velocities.add(velocity);
    return super.recommendDeferredLoading(velocity, metrics, context);
  }
}

// Ignore this so that we can mutate whether we defer loading or not at specific
// times without worrying about actual scrolling mechanics.
// ignore: must_be_immutable
class ControllablePhysics extends ScrollPhysics {
  ControllablePhysics({ super.parent });

  bool recommendDeferredLoadingValue = false;

  @override
  ControllablePhysics applyTo(ScrollPhysics? ancestor) {
    return ControllablePhysics(parent: buildParent(ancestor));
  }

  @override
  bool recommendDeferredLoading(double velocity, ScrollMetrics metrics, BuildContext context) {
    return recommendDeferredLoadingValue;
  }
}