packages/flutter/test/widgets/image_resolution_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 'dart:async';
import 'dart:typed_data';
import 'dart:ui' as ui show Image;

import 'package:flutter/rendering.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:meta/meta.dart';

class TestImage extends ui.Image {
  TestImage(this.scale);
  final double scale;

  @override
  int get width => (48*scale).floor();

  @override
  int get height => (48*scale).floor();

  @override
  void dispose() { }
}

class TestByteData implements ByteData {
  TestByteData(this.scale);
  final double scale;

  @override
  dynamic noSuchMethod(Invocation invocation) => null;
}

String testManifest = '''
{
  "assets/image.png" : [
    "assets/1.5x/image.png",
    "assets/2.0x/image.png",
    "assets/3.0x/image.png",
    "assets/4.0x/image.png"
  ]
}
''';

class TestAssetBundle extends CachingAssetBundle {
  @override
  Future<ByteData> load(String key) {
    ByteData data;
    switch (key) {
      case 'assets/image.png':
        data = new TestByteData(1.0);
        break;
      case 'assets/1.5x/image.png':
        data = new TestByteData(1.5);
        break;
      case 'assets/2.0x/image.png':
        data = new TestByteData(2.0);
        break;
      case 'assets/3.0x/image.png':
        data = new TestByteData(3.0);
        break;
      case 'assets/4.0x/image.png':
        data = new TestByteData(4.0);
        break;
    }
    return new SynchronousFuture<ByteData>(data);
  }

  @override
  Future<String> loadString(String key, { bool cache: true }) {
    if (key == 'AssetManifest.json')
      return new SynchronousFuture<String>(testManifest);
    return null;
  }

  @override
  String toString() => '$runtimeType@$hashCode()';
}

class TestAssetImage extends AssetImage {
  TestAssetImage(String name) : super(name);

  @override
  Future<ImageInfo> loadAsync(AssetBundleImageKey key) {
    ImageInfo result;
    key.bundle.load(key.name).then((ByteData data) {
      decodeImage(data).then((ui.Image image) {
        result = new ImageInfo(image: image, scale: key.scale);
      });
    });
    assert(result != null);
    return new SynchronousFuture<ImageInfo>(result);
  }

  @override
  Future<ui.Image> decodeImage(@checked TestByteData data) {
    return new SynchronousFuture<ui.Image>(new TestImage(data.scale));
  }
}

Widget buildImageAtRatio(String image, Key key, double ratio, bool inferSize) {
  const double windowSize = 500.0; // 500 logical pixels
  const double imageSize = 200.0; // 200 logical pixels

  return new MediaQuery(
    data: new MediaQueryData(
      size: const Size(windowSize, windowSize),
      devicePixelRatio: ratio,
      padding: const EdgeInsets.all(0.0)
    ),
    child: new DefaultAssetBundle(
      bundle: new TestAssetBundle(),
      child: new Center(
        child: inferSize ?
          new Image(
            key: key,
            image: new TestAssetImage(image)
          ) :
          new Image(
            key: key,
            image: new TestAssetImage(image),
            height: imageSize,
            width: imageSize,
            fit: ImageFit.fill
          )
      )
    )
  );
}

RenderImage getRenderImage(WidgetTester tester, Key key) {
  return tester.renderObject/*<RenderImage>*/(find.byKey(key));
}
TestImage getTestImage(WidgetTester tester, Key key) {
  return tester.renderObject/*<RenderImage>*/(find.byKey(key)).image;
}

Future<Null> pumpTreeToLayout(WidgetTester tester, Widget widget) {
  Duration pumpDuration = const Duration(milliseconds: 0);
  EnginePhase pumpPhase = EnginePhase.layout;
  return tester.pumpWidget(widget, pumpDuration, pumpPhase);
}

void main() {
  String image = 'assets/image.png';

  testWidgets('Image for device pixel ratio 1.0', (WidgetTester tester) async {
    const double ratio = 1.0;
    Key key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false));
    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
    expect(getTestImage(tester, key).scale, 1.0);
    key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true));
    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
    expect(getTestImage(tester, key).scale, 1.0);
  });

  testWidgets('Image for device pixel ratio 0.5', (WidgetTester tester) async {
    const double ratio = 0.5;
    Key key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false));
    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
    expect(getTestImage(tester, key).scale, 1.0);
    key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true));
    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
    expect(getTestImage(tester, key).scale, 1.0);
  });

  testWidgets('Image for device pixel ratio 1.5', (WidgetTester tester) async {
    const double ratio = 1.5;
    Key key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false));
    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
    expect(getTestImage(tester, key).scale, 1.5);
    key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true));
    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
    expect(getTestImage(tester, key).scale, 1.5);
  });

  testWidgets('Image for device pixel ratio 1.75', (WidgetTester tester) async {
    const double ratio = 1.75;
    Key key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false));
    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
    expect(getTestImage(tester, key).scale, 1.5);
    key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true));
    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
    expect(getTestImage(tester, key).scale, 1.5);
  });

  testWidgets('Image for device pixel ratio 2.3', (WidgetTester tester) async {
    const double ratio = 2.3;
    Key key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false));
    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
    expect(getTestImage(tester, key).scale, 2.0);
    key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true));
    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
    expect(getTestImage(tester, key).scale, 2.0);
  });

  testWidgets('Image for device pixel ratio 3.7', (WidgetTester tester) async {
    const double ratio = 3.7;
    Key key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false));
    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
    expect(getTestImage(tester, key).scale, 4.0);
    key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true));
    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
    expect(getTestImage(tester, key).scale, 4.0);
  });

  testWidgets('Image for device pixel ratio 5.1', (WidgetTester tester) async {
    const double ratio = 5.1;
    Key key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, false));
    expect(getRenderImage(tester, key).size, const Size(200.0, 200.0));
    expect(getTestImage(tester, key).scale, 4.0);
    key = new GlobalKey();
    await pumpTreeToLayout(tester, buildImageAtRatio(image, key, ratio, true));
    expect(getRenderImage(tester, key).size, const Size(48.0, 48.0));
    expect(getTestImage(tester, key).scale, 4.0);
  });

}