Asynchronously load wallpapers when user pod is selected.

ash/desktop_background/desktop_background_controller.cc

 // 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.
 
 #include "ash/desktop_background/desktop_background_controller.h"
 
 #include "ash/desktop_background/desktop_background_view.h"
 #include "ash/shell.h"
 #include "ash/shell_factory.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/root_window_layout_manager.h"
+#include "base/bind.h"
 #include "base/logging.h"
+#include "base/threading/worker_pool.h"
 #include "grit/ui_resources.h"
 #include "ui/aura/window.h"
 #include "ui/gfx/compositor/layer.h"
 #include "ui/gfx/image/image.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 
-DesktopBackgroundController::DesktopBackgroundController() :
-  desktop_background_mode_(BACKGROUND_IMAGE) {
+DesktopBackgroundController::DesktopBackgroundController()
+    : desktop_background_mode_(BACKGROUND_IMAGE),
+      layout_(CENTER_CROPPED),
+      previous_index_(-1),
+      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+    wallpaper_ = NULL;

[Nikita (slow), 2012/04/25 16:47:48]

nit: align

[bshe, 2012/04/25 23:54:43]

Done.

 }
 
 DesktopBackgroundController::~DesktopBackgroundController() {
 }
 
+void DesktopBackgroundController::SetDefaultWallpaper(int index) {
+  if (previous_index_ == index)
+    return;
+  base::WorkerPool::PostTaskAndReply(

[Nikita (slow), 2012/04/25 16:47:48]

We should somehow cancel previous wallpaper load if it's in progress.
Or at least make sure that when OnWallpaperLoadCompleted would not be called by
that previous task i.e. preemption strategy is that new task always make sure
that previous task is cancelled and its result is ignored.

[bshe, 2012/04/25 23:54:43]

Done. The new wallpaper loading always make sure that previous task is cancelled
and its result is ignored.

+      FROM_HERE,
+      base::Bind(&DesktopBackgroundController::OnWallpaperLoadStarted,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 index),
+      base::Bind(&DesktopBackgroundController::OnWallpaperLoadCompleted,
+                 weak_ptr_factory_.GetWeakPtr()),
+      true);

[Nikita (slow), 2012/04/25 16:47:48]

nit:  /* task_is_slow */

[bshe, 2012/04/25 23:54:43]

Done.

+  previous_index_ = index;
+}
+
+void DesktopBackgroundController::SetGuestWallpaper() {
+  SetDefaultWallpaper(GetGuestWallpaperIndex());
+}
+
+void DesktopBackgroundController::SetLoggedInUserWallpaper() {
+  int index = Shell::GetInstance()->user_wallpaper_delegate()->
+      GetUserWallpaperIndex();
+  SetDefaultWallpaper(index);
+}
+
 void DesktopBackgroundController::SetDesktopBackgroundImageMode() {
   internal::RootWindowLayoutManager* root_window_layout =
       Shell::GetInstance()->root_window_layout();
-  int index = Shell::GetInstance()->user_wallpaper_delegate()->
-      GetUserWallpaperIndex();
   root_window_layout->SetBackgroundLayer(NULL);
-  internal::CreateDesktopBackground(GetWallpaper(index),
-                                    GetWallpaperInfo(index).layout);
-  desktop_background_mode_ = BACKGROUND_IMAGE;
+  if(wallpaper_) {
+    internal::CreateDesktopBackground(*wallpaper_, layout_);
+    desktop_background_mode_ = BACKGROUND_IMAGE;
+  }
 }
 
 void DesktopBackgroundController::SetDesktopBackgroundSolidColorMode() {
   // Set a solid black background.
   // TODO(derat): Remove this in favor of having the compositor only clear the
   // viewport when there are regions not covered by a layer:
   // http://crbug.com/113445
   Shell* shell = Shell::GetInstance();
   ui::Layer* background_layer = new ui::Layer(ui::LAYER_SOLID_COLOR);
   background_layer->SetColor(SK_ColorBLACK);
   shell->GetContainer(internal::kShellWindowId_DesktopBackgroundContainer)->
       layer()->Add(background_layer);
   shell->root_window_layout()->SetBackgroundLayer(background_layer);
   shell->root_window_layout()->SetBackgroundWidget(NULL);
   desktop_background_mode_ = BACKGROUND_SOLID_COLOR;
 }
 
+void DesktopBackgroundController::OnWallpaperLoadStarted(int index) {
+  wallpaper_ = ui::ResourceBundle::GetSharedInstance().GetImageNamed(
+      GetWallpaperInfo(index).id).ToSkBitmap();
+  layout_ = GetWallpaperInfo(index).layout;
+}
+
+void DesktopBackgroundController::OnWallpaperLoadCompleted() {
+  SetDesktopBackgroundImageMode();
+}
+
 }  // namespace ash