Associate scale with image more strongly in image resources

packages/flutter/lib/src/painting/box_painter.dart

@@ -668,10 +668,10 @@ class BackgroundImage {
       _imageResource.removeListener(_handleImageChanged);
   }
 
-  void _handleImageChanged(ui.Image resolvedImage) {
+  void _handleImageChanged(ImageInfo resolvedImage) {
     if (resolvedImage == null)
       return;
-    _image = resolvedImage;
+    _image = resolvedImage.image;
     final List<VoidCallback> localListeners =
       new List<VoidCallback>.from(_listeners);
     for (VoidCallback listener in localListeners)

packages/flutter/lib/src/rendering/image.dart

@@ -22,7 +22,7 @@ class RenderImage extends RenderBox {
     ui.Image image,
     double width,
     double height,
-    double scale,
+    double scale: 1.0,
     Color color,
     ImageFit fit,
     FractionalOffset alignment,
@@ -84,6 +84,7 @@ class RenderImage extends RenderBox {
   double get scale => _scale;
   double _scale;
   void set scale (double value) {
+    assert(value != null);
     if (value == _scale)
       return;
     _scale = value;
@@ -175,9 +176,8 @@ class RenderImage extends RenderBox {
     if (constraints.isTight || _image == null)
       return constraints.smallest;
 
-    double scale = _scale ?? 1.0;
-    double width = _image.width.toDouble() / scale;
-    double height = _image.height.toDouble() / scale;
+    double width = _image.width.toDouble() / _scale;
+    double height = _image.height.toDouble() / _scale;
     assert(width > 0.0);
     assert(height > 0.0);
     double aspectRatio = width / height;

packages/flutter/lib/src/services/asset_bundle.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:ui' as ui;
 import 'dart:ui_internals' as internals;
 import 'dart:typed_data';
 
@@ -48,8 +47,8 @@ abstract class CachingAssetBundle extends AssetBundle {
   final Map<String, Future<String>> _stringCache =
     new Map<String, Future<String>>();
 
-  Future<ui.Image> fetchImage(String key) async {
-    return await decodeImageFromDataPipe(await load(key));
+  Future<ImageInfo> fetchImage(String key) async {
+    return new ImageInfo(image: await decodeImageFromDataPipe(await load(key)));
   }
 
   ImageResource loadImage(String key) {

packages/flutter/lib/src/services/image_cache.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:ui' as ui;
 
 import 'package:mojo/mojo/url_response.mojom.dart';
 import 'package:quiver/collection.dart';
@@ -15,7 +14,7 @@ import 'image_resource.dart';
 /// Implements a way to retrieve an image, for example by fetching it from the network.
 /// Also used as a key in the image cache.
 abstract class ImageProvider {
-  Future<ui.Image> loadImage();
+  Future<ImageInfo> loadImage();
 }
 
 class _UrlFetcher implements ImageProvider {
@@ -23,13 +22,13 @@ class _UrlFetcher implements ImageProvider {
 
   _UrlFetcher(this._url);
 
-  Future<ui.Image> loadImage() async {
+  Future<ImageInfo> loadImage() async {
     UrlResponse response = await fetchUrl(_url);
     if (response.statusCode >= 400) {
       print("Failed (${response.statusCode}) to load image $_url");
       return null;
     }
-    return await decodeImageFromDataPipe(response.body);
+    return new ImageInfo(image: await decodeImageFromDataPipe(response.body));
   }
 
   bool operator ==(other) => other is _UrlFetcher && _url == other._url;

packages/flutter/lib/src/services/image_resource.dart

@@ -7,8 +7,14 @@ import 'dart:ui' as ui;
 
 import 'print.dart';
 
+class ImageInfo {
+  ImageInfo({ this.image, this.scale: 1.0 });
+  final ui.Image image;
+  final double scale;
+}
+
 /// A callback for when the image is available.
-typedef void ImageListener(ui.Image image);
+typedef void ImageListener(ImageInfo image);
 
 /// A handle to an image resource
 ///
@@ -16,21 +22,20 @@ typedef void ImageListener(ui.Image image);
 /// image object might change over time, either because the image is animating
 /// or because the underlying image resource was mutated.
 class ImageResource {
-  ImageResource(this._futureImage, { this.scale : 1.0 }) {
+  ImageResource(this._futureImage) {
     _futureImage.then(_handleImageLoaded, onError: (exception, stack) => _handleImageError('Failed to load image:', exception, stack));
   }
 
   bool _resolved = false;
-  Future<ui.Image> _futureImage;
-  ui.Image _image;
-  double scale;
+  Future<ImageInfo> _futureImage;
+  ImageInfo _image;
   final List<ImageListener> _listeners = new List<ImageListener>();
 
   /// The first concrete [ui.Image] object represented by this handle.
   ///
   /// Instead of receivingly only the first image, most clients will want to
   /// [addListener] to be notified whenever a a concrete image is available.
-  Future<ui.Image> get first => _futureImage;
+  Future<ImageInfo> get first => _futureImage;
 
   /// Adds a listener callback that is called whenever a concrete [ui.Image]
   /// object is available. Note: If a concrete image is available currently,
@@ -51,7 +56,7 @@ class ImageResource {
     _listeners.remove(listener);
   }
 
-  void _handleImageLoaded(ui.Image image) {
+  void _handleImageLoaded(ImageInfo image) {
     _image = image;
     _resolved = true;
     _notifyListeners();

packages/flutter/lib/src/widgets/asset_vendor.dart

@@ -5,7 +5,6 @@
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
-import 'dart:ui' as ui;
 
 import 'package:flutter/services.dart';
 import 'package:mojo/core.dart' as core;
@@ -51,13 +50,15 @@ class _ResolutionAwareAssetBundle extends _ResolvingAssetBundle {
 
   _ResolutionAwareAssetResolver get resolver => super.resolver;
 
-  Future<ui.Image> fetchImage(String key) async {
+  Future<ImageInfo> fetchImage(String key) async {
     core.MojoDataPipeConsumer pipe = await load(key);
     // At this point the key should be in our key cache, and the image
     // resource should be in our image cache
     double scale = resolver.getScale(keyCache[key]);
-    imageResourceCache[key].scale = scale;
-    return await decodeImageFromDataPipe(pipe);
+    return new ImageInfo(
+      image: await decodeImageFromDataPipe(pipe),
+      scale: scale
+    );
   }
 }
 

packages/flutter/lib/src/widgets/basic.dart

@@ -1508,7 +1508,7 @@ class RawImage extends LeafRenderObjectWidget {
     this.image,
     this.width,
     this.height,
-    this.scale,
+    this.scale: 1.0,
     this.color,
     this.fit,
     this.alignment,
@@ -1658,16 +1658,11 @@ class _ImageListenerState extends State<RawImageResource> {
     config.image.addListener(_handleImageChanged);
   }
 
-  // Note, we remember the resolved image and the scale together. If the
-  // source image resource is updated, we shouldn't grab its scale until
-  // it provides the associated resolved image.
-  ui.Image _resolvedImage;
-  double _scale;
+  ImageInfo _resolvedImage;
 
-  void _handleImageChanged(ui.Image resolvedImage) {
+  void _handleImageChanged(ImageInfo resolvedImage) {
     setState(() {
       _resolvedImage = resolvedImage;
-      _scale = config.image.scale;
     });
   }
 
@@ -1685,10 +1680,10 @@ class _ImageListenerState extends State<RawImageResource> {
 
   Widget build(BuildContext context) {
     return new RawImage(
-      image: _resolvedImage,
+      image: _resolvedImage?.image,
       width: config.width,
       height: config.height,
-      scale: _scale,
+      scale: _resolvedImage == null ? 1.0 : _resolvedImage.scale,
       color: config.color,
       fit: config.fit,
       alignment: config.alignment,