Implement a simple image cache for Sky in Dart. This doesn't yet do any eviction from the cache.

R=abarth@chromium.org, abarth

Review URL: https://codereview.chromium.org/1165753004

engine/core/loader/CanvasImageLoader.cpp

@@ -13,16 +13,13 @@ namespace blink {
 CanvasImageLoader::CanvasImageLoader(const String& src, PassOwnPtr<ImageLoaderCallback> callback)
   : callback_(callback) {
   // TODO(jackson): Figure out how to determine the proper base URL here
-  url_ = KURL(KURL(), src);
+  KURL url = KURL(KURL(), src);
+  fetcher_ = adoptPtr(new MojoFetcher(this, url));
 }
 
 CanvasImageLoader::~CanvasImageLoader() {
 }
 
-void CanvasImageLoader::load() {
-  fetcher_ = adoptPtr(new MojoFetcher(this, url_));
-}
-
 void CanvasImageLoader::OnReceivedResponse(mojo::URLResponsePtr response) {
   if (response->status_code != 200) {
     callback_->handleEvent(nullptr);

engine/core/loader/CanvasImageLoader.h

@@ -28,8 +28,6 @@ class CanvasImageLoader : public MojoFetcher::Client,
   }
   virtual ~CanvasImageLoader();
 
-  void load();
-
   // MojoFetcher::Client
   void OnReceivedResponse(mojo::URLResponsePtr) override;
 
@@ -43,8 +41,6 @@ class CanvasImageLoader : public MojoFetcher::Client,
   OwnPtr<MojoFetcher> fetcher_;
   OwnPtr<mojo::common::DataPipeDrainer> drainer_;
   RefPtr<SharedBuffer> buffer_;
-
-  KURL url_;
   OwnPtr<ImageLoaderCallback> callback_;
 };
 

engine/core/loader/ImageLoader.idl

@@ -6,5 +6,4 @@
   Constructor(DOMString src, ImageLoaderCallback callback),
   ImplementedAs=CanvasImageLoader,
 ] interface ImageLoader {
-    void load();
 };

engine/core/painting/Image.idl

@@ -6,6 +6,6 @@
   Constructor(),
   ImplementedAs=CanvasImage,
 ] interface Image {
-    readonly attribute long width;
-    readonly attribute long height;
+    readonly attribute long width;  // width in number of image pixels
+    readonly attribute long height; // height in number of image pixels
 };

examples/raw/spinning_image.dart

@@ -3,10 +3,13 @@
 // found in the LICENSE file.
 
 import 'dart:sky';
+import 'package:sky/framework/net/image_cache.dart' as image_cache;
 
 double timeBase = null;
 
 Image image = null;
+String url1 = "https://www.dartlang.org/logos/dart-logo.png";
+String url2 = "http://i2.kym-cdn.com/photos/images/facebook/000/581/296/c09.jpg";
 
 void beginFrame(double timeStamp) {
   if (timeBase == null) timeBase = timeStamp;
@@ -22,15 +25,32 @@ void beginFrame(double timeStamp) {
   view.scheduleFrame();
 }
 
+void handleImageLoad(result) {
+  if (result != image) {
+    print("${result.width}x${result.width} image loaded!");
+    image = result;
+    view.scheduleFrame();
+  } else {
+    print("Existing image was loaded again");
+  }
+}
+
+bool handleEvent(Event event) {
+  if (event.type == "pointerdown") {
+    return true;
+  }
+
+  if (event.type == "pointerup") {
+    image_cache.load(url2, handleImageLoad);
+    return true;
+  }
+
+  return false;
+}
+
 void main() {
-  new ImageLoader("https://www.dartlang.org/logos/dart-logo.png", (result) {
-    if (result != null) {
-      print("${result.width}x${result.width} image loaded!");
-      image = result;
-      view.scheduleFrame();
-    } else {
-      print("Image failed to load");
-    }
-  }).load();
+  image_cache.load(url1, handleImageLoad);
+  image_cache.load(url1, handleImageLoad);
+  view.setEventCallback(handleEvent);
   view.setBeginFrameCallback(beginFrame);
 }

sdk/BUILD.gn

@@ -93,6 +93,7 @@ dart_pkg("sdk") {
     "lib/framework/fn2.dart",
     "lib/framework/layout.dart",
     "lib/framework/net/fetch.dart",
+    "lib/framework/net/image_cache.dart",
     "lib/framework/node.dart",
     "lib/framework/reflect.dart",
     "lib/framework/rendering/render_block.dart",

sdk/lib/framework/net/image_cache.dart

@@ -0,0 +1,33 @@
+// Copyright 2015 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:sky' as sky;
+import 'dart:collection';
+
+final HashMap<String, List<sky.ImageLoaderCallback>> _pendingRequests =
+  new HashMap<String, List<sky.ImageLoaderCallback>>();
+
+final HashMap<String, sky.Image> _completedRequests =
+  new HashMap<String, sky.Image>();
+
+void load(String url, sky.ImageLoaderCallback callback) {
+  sky.Image result = _completedRequests[url];
+  if (result != null) {
+    callback(_completedRequests[url]);
+    return;
+  }
+
+  bool newRequest = false;
+  _pendingRequests.putIfAbsent(url, () {
+    newRequest = true;
+    return new List<sky.ImageLoaderCallback>();
+  }).add(callback);
+  if (newRequest) {
+    new sky.ImageLoader(url, (image) {
+      _completedRequests[url] = image;
+      _pendingRequests[url].forEach((c) => c(image));
+      _pendingRequests.remove(url);
+    });
+  }
+}