Add a class to replace ImageLoadingTracker with a nicer API.

chrome/browser/extensions/image_loader.h

 // Copyright (c) 2012 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.
 
-#ifndef CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
-#define CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
+#ifndef CHROME_BROWSER_EXTENSIONS_IMAGE_LOADER_H_
+#define CHROME_BROWSER_EXTENSIONS_IMAGE_LOADER_H_
 
 #include <map>
-#include <string>
-#include <vector>
+#include <set>
 
-#include "base/compiler_specific.h"
+#include "base/callback_forward.h"
 #include "base/gtest_prod_util.h"
-#include "base/memory/ref_counted.h"
-#include "chrome/common/extensions/extension_icon_set.h"
+#include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/common/extensions/extension_resource.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
+#include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/base/layout.h"
-#include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/size.h"
 
-class SkBitmap;
-
-namespace extensions {
-class Extension;
-}
+class Profile;
 
 namespace gfx {
 class Image;
 }
 
-// The views need to load their icons asynchronously but might be deleted before
-// the images have loaded. This class encapsulates a loader class that stays
-// alive while the request is in progress (manages its own lifetime) and keeps
-// track of whether the view still cares about the icon loading.
-//
-// To use this class, have your class derive from ImageLoadingTracker::Observer,
-// and add a member variable ImageLoadingTracker tracker_. Then override
-// Observer::OnImageLoaded and call:
-//   tracker_.LoadImage(extension, resource, max_size, false);
-// ... and wait for OnImageLoaded to be called back on you with a pointer to the
-// ImageSkia loaded.
-// NOTE: if the image is available already (or the resource is not valid), the
-// Observer is notified immediately from the call to LoadImage. In other words,
-// by the time LoadImage returns the observer has been notified.
-//
-class ImageLoadingTracker : public content::NotificationObserver {
+namespace extensions {
+
+class Extension;
+
+// This class is responsible for asynchronously loading extension images and
+// calling a callback when an image is loaded.
+// The views need to load their icons asynchronously might be deleted before
+// the images have loaded. If you pass your callback using a weak_ptr, this
+// will make sure the callback won't be called after the view is deleted.
+class ImageLoader : public ProfileKeyedService {
  public:
-  enum CacheParam {
-    CACHE,
-    DONT_CACHE
-  };
-
-  class Observer {
-   public:
-    // Will be called when the image with the given index has loaded.
-    // |image| can be empty if a valid image was not found or it failed to
-    // decode. |extension_id| is the ID of the extension the images are loaded
-    // from.  |index| represents the index of the image just loaded (starts at 0
-    // and increments every time LoadImage is called).
-    virtual void OnImageLoaded(const gfx::Image& image,
-                               const std::string& extension_id,
-                               int index) = 0;
-
-   protected:
-    virtual ~Observer();
-  };
-
   // Information about a singe image representation to load from an extension
   // resource.
   struct ImageRepresentation {
     // Enum values to indicate whether to resize loaded bitmap when it is larger
     // than |desired_size| or always resize it.
     enum ResizeCondition {
       RESIZE_WHEN_LARGER,
       ALWAYS_RESIZE,
     };
 
     ImageRepresentation(const ExtensionResource& resource,
-                        ResizeCondition resize_method,
+                        ResizeCondition resize_condition,
                         const gfx::Size& desired_size,
                         ui::ScaleFactor scale_factor);
     ~ImageRepresentation();
 
     // Extension resource to load.
     ExtensionResource resource;
 
-    ResizeCondition resize_method;
+    ResizeCondition resize_condition;
 
     // When |resize_method| is ALWAYS_RESIZE or when the loaded image is larger
     // than |desired_size| it will be resized to these dimensions.
     gfx::Size desired_size;
 
     // |scale_factor| is used to construct the loaded gfx::ImageSkia.
     ui::ScaleFactor scale_factor;
   };
 
-  explicit ImageLoadingTracker(Observer* observer);
-  virtual ~ImageLoadingTracker();
+  // Returns the instance for the given profile, or NULL if none. This is
+  // a convenience wrapper around ImageLoaderFactory::GetForProfile.
+  static ImageLoader* Get(Profile* profile);
 
-  // Specify image resource to load. If the loaded image is larger than
-  // |max_size| it will be resized to those dimensions. IMPORTANT NOTE: this
-  // function may call back your observer synchronously (ie before it returns)
-  // if the image was found in the cache.
-  // Note this method loads a raw bitmap from the resource. All sizes given are
-  // assumed to be in pixels.
-  void LoadImage(const extensions::Extension* extension,
-                 const ExtensionResource& resource,
-                 const gfx::Size& max_size,
-                 CacheParam cache);
-
-  // Same as LoadImage() above except it loads multiple images from the same
-  // extension. This is used to load multiple resolutions of the same image
-  // type.
-  void LoadImages(const extensions::Extension* extension,
-                  const std::vector<ImageRepresentation>& info_list,
-                  CacheParam cache);
-
-  // Returns the ID used for the next image that is loaded. That is, the return
-  // value from this method corresponds to the int that is passed to
-  // OnImageLoaded() the next time LoadImage() is invoked.
-  int next_id() const { return next_id_; }
+  ImageLoader();
+  virtual ~ImageLoader();
 
   // Checks whether image is a component extension resource. Returns false
   // if a given |resource| does not have a corresponding image in bundled
   // resources. Otherwise fills |resource_id|.
   static bool IsComponentExtensionResource(
       const extensions::Extension* extension,
       const FilePath& resource_path,
       int* resource_id);
 
+  // Specify image resource to load. If the loaded image is larger than
+  // |max_size| it will be resized to those dimensions. IMPORTANT NOTE: this
+  // function may call back your callback synchronously (ie before it returns)
+  // if the image was found in the cache.

[kaiwang, 2012/11/29 03:57:37]

Looking at the code, I think the callback is always run asynchronously?

[Marijn Kruisselbrink, 2012/11/29 15:51:40]

Yeah, that's true; at the moment the callback is always run asynchronously. If
caching gets re-added in the future we'll at least keep the option of calling
the callback synchronously though. So I don't see a compelling reason to remove
this restriction evn though currently it is not being used.

+  // Note this method loads a raw bitmap from the resource. All sizes given are
+  // assumed to be in pixels.
+  void LoadImageAsync(const extensions::Extension* extension,
+                      const ExtensionResource& resource,
+                      const gfx::Size& max_size,
+                      const base::Callback<void(const gfx::Image&)>& callback);
+
+  // Same as LoadImage() above except it loads multiple images from the same
+  // extension. This is used to load multiple resolutions of the same image
+  // type.
+  void LoadImagesAsync(const extensions::Extension* extension,
+                       const std::vector<ImageRepresentation>& info_list,
+                       const base::Callback<void(const gfx::Image&)>& callback);
+
  private:
-  // Information for pending resource load operation for one or more image
-  // representations.
-  struct PendingLoadInfo {
-    PendingLoadInfo();
-    ~PendingLoadInfo();
+  struct LoadResult;
 
-    const extensions::Extension* extension;
-    // This is cached separate from |extension| in case the extension is
-    // unloaded.
-    std::string extension_id;
-    CacheParam cache;
-    size_t pending_count;
-    gfx::ImageSkia image_skia;
-  };
+  void LoadImagesOnBlockingPool(
+      const std::vector<ImageRepresentation>& info_list,
+      const std::vector<SkBitmap>& bitmaps,
+      const base::Callback<void(const gfx::Image&)>& callback);
 
-  // Maps an integer identifying a load request to a PendingLoadInfo.
-  typedef std::map<int, PendingLoadInfo> LoadMap;
-
-  class ImageLoader;
-
-  // Called on the calling thread when the bitmap finishes loading.
-  // |bitmap| may be null if the image file failed to decode.
-  void OnBitmapLoaded(const SkBitmap* bitmap,
-                      const ImageRepresentation& image_info,
-                      const gfx::Size& original_size,
-                      int id,
-                      bool should_cache);
-
-  // content::NotificationObserver method. If an extension is uninstalled while
-  // we're waiting for the image we remove the entry from load_map_.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
-
-  // The view that is waiting for the image to load.
-  Observer* observer_;
-
-  // ID to use for next image requested. This is an ever increasing integer.
-  int next_id_;
-
-  // The object responsible for loading the image on the File thread.
-  scoped_refptr<ImageLoader> loader_;
-
-  // Information for each LoadImage request is cached here. The integer
-  // identifies the id assigned to the request.
-  LoadMap load_map_;
-
-  content::NotificationRegistrar registrar_;
-
-  DISALLOW_COPY_AND_ASSIGN(ImageLoadingTracker);
+  void ReplyBack(
+      const std::vector<LoadResult>& load_result,
+      const base::Callback<void(const gfx::Image&)>& callback);
 };
 
-#endif  // CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_IMAGE_LOADER_H_