Speed up custom wallpaper switching time and wallpaper manager code refactor

chrome/browser/chromeos/login/wallpaper_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_CHROMEOS_LOGIN_WALLPAPER_LOADER_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_WALLPAPER_LOADER_H_
+
+#include <map>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "chrome/browser/image_decoder.h"
+
+class MessageLoop;
+class SkBitmap;
+
+namespace chromeos {
+
+// Callback used to inidicate that wallpaper has been loaded.
+typedef base::Callback<void(const SkBitmap& wallpaper)> LoadedCallback;
+
+// A facility to read and decode a custom wallpaper asynchronously in the IO
+// thread. Returns the image in the form of an SkBitmap.
+class WallpaperLoader : public base::RefCountedThreadSafe<WallpaperLoader>,
+                        public ImageDecoder::Delegate {
+ public:
+  WallpaperLoader();
+
+  // Start reading the image from |filepath| on the file thread. Calls
+  // |loaded_cb| when image has been successfully loaded.
+  // If |save_raw_image| is true, save the loaded image to |save_to_path|.
+  void Start(const std::string& filepath,
+             bool save_raw_image,
+             const std::string& save_to_path,
+             const LoadedCallback& loaded_cb);
+
+ private:
+  friend class base::RefCountedThreadSafe<WallpaperLoader>;
+
+  // Contains attributes we need to know about each wallpaper we decode.
+  struct WallpaperInfo {
+    WallpaperInfo(bool save_raw_image,
+                  const std::string& save_to_path,
+                  const LoadedCallback& loaded_cb);
+    ~WallpaperInfo();
+
+    bool save_raw_image;
+    std::string save_to_path;
+    LoadedCallback loaded_cb;
+  };
+
+  typedef std::map<const ImageDecoder*, WallpaperInfo> WallpaperInfoMap;
+
+  virtual ~WallpaperLoader();
+
+  // Method that reads the file on the file thread and starts decoding it in
+  // sandboxed process.
+  void LoadImage(const std::string& filepath,
+                 const WallpaperInfo& wallpaper_info);
+
+  // ImageDecoder::Delegate implementation.
+  virtual void OnImageDecoded(const ImageDecoder* decoder,
+                              const SkBitmap& decoded_image) OVERRIDE;
+  virtual void OnDecodeImageFailed(const ImageDecoder* decoder) OVERRIDE;
+
+  // The message loop object of the thread in which we notify the delegate.
+  MessageLoop* target_message_loop_;
+
+  // Holds info structures about all wallpapers we're trying to decode.
+  // Accessed only on FILE thread.
+  WallpaperInfoMap wallpaper_info_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(WallpaperLoader);
+
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_WALLPAPER_LOADER_H_