Add support for multiple icon sizes for Mac platform apps

chrome/browser/extensions/image_loading_tracker.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_
 #pragma once
 
 #include <map>
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
+#include "ui/gfx/size.h"
 
 class Extension;
-class ExtensionResource;
 class SkBitmap;
 
 namespace gfx {
-  class Size;
+  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
 // SkBitmap 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 {
  public:
   enum CacheParam {
     CACHE,
     DONT_CACHE
   };
 
   class Observer {
    public:
     // Will be called when the image with the given index has loaded.
-    // The |image| is owned by the tracker, so the observer should make a copy
-    // if they need to access it after this call. |image| can be null if a valid
-    // image was not found or it failed to decode. |resource| is the
-    // ExtensionResource where the |image| came from and the |index| represents
-    // the index of the image just loaded (starts at 0 and increments every
-    // time LoadImage is called).
-    virtual void OnImageLoaded(SkBitmap* image,
-                               const ExtensionResource& resource,
+    // |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 single image to load from a extension resource.
+  struct ImageInfo {
+    ImageInfo(const ExtensionResource resource, gfx::Size max_size);
+    ~ImageInfo();
+    ExtensionResource resource;
+    gfx::Size max_size;

[Finnur, 2012/02/28 10:26:51]

I think it is worth calling out that the image will be resized if larger than
max_size, like we do in the comments for LoadImage below.

[sail, 2012/02/28 23:25:36]

Done.

[sail, 2012/02/28 23:25:36]

Done.

+  };
+
   explicit ImageLoadingTracker(Observer* observer);
   virtual ~ImageLoadingTracker();
 
   // 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.
   void LoadImage(const Extension* extension,
                  const ExtensionResource& resource,
                  const gfx::Size& max_size,
                  CacheParam cache);
 
+  // Same as LoadImage() above except it loads multiple images from the same

[Finnur, 2012/02/28 10:26:51]

nit: It bothers me a bit that we can't agree on whether to call a gfx::Image
object with multiple dimensions an *image* (as the object name implies) or
*images* (plural)... Here, we call it Images but when the return call comes we
call it Image. Any thoughts on how we can consolidate this?

[sail, 2012/02/28 23:25:36]

How about renaming this function LoadImage?

[Finnur, 2012/02/29 00:17:26]

The style guide doesn't like functions with same name but different params
(except in cases where the params are roughly equivalent (like std::string and
std::wstring)).

On 2012/02/28 23:25:36, sail wrote:

+  // extension. This is used to load multiple resolutions of the same image
+  // type.
+  void LoadImages(const Extension* extension,
+                  const std::vector<ImageInfo>& 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_; }
 
  private:
-  typedef std::map<int, const Extension*> LoadMap;
+  // Information for pending image load operation for one or more images.
+  struct PendingLoadInfo {
+    PendingLoadInfo();
+    ~PendingLoadInfo();
+
+    const Extension* extension;
+    // This is cached separate from |extension| incase the extension in

[Finnur, 2012/02/28 10:26:51]

nit: incase -> in case

[sail, 2012/02/28 23:25:36]

Done.

+    // unloaded.
+    std::string extension_id;
+    CacheParam cache;
+    size_t pending_count;
+    std::vector<SkBitmap> bitmaps;
+  };
+
+  // Maps an integer identifying a load request to a PendingLoadInfo.
+  typedef std::map<int, PendingLoadInfo> LoadMap;
 
   class ImageLoader;
 
   // When an image has finished loaded and been resized on the file thread, it
   // is posted back to this method on the original thread.  This method then
   // calls the observer's OnImageLoaded and deletes the ImageLoadingTracker if
   // it was the last image in the list. The |original_size| should be the size
   // of the image before any resizing was done.
   // |image| may be null if the file failed to decode.
   void OnImageLoaded(SkBitmap* image, const ExtensionResource& resource,
                      const gfx::Size& original_size, int id);
 
   // 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_;
 
-  // If LoadImage is told to cache the result an entry is added here. The
-  // integer identifies the id assigned to the request. If the extension is
-  // deleted while fetching the image the entry is removed from the map.
+  // Information for each LoadImage request is cached here. The integer
+  // identifies the id assigned to the request.

[Finnur, 2012/02/28 10:26:51]

nit: The reference to 'The integer' is probably a bit lost on people here. Not
sure how to improve on it, though. Feel free to ignore. :)

   LoadMap load_map_;
 
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageLoadingTracker);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_