Asynchronously load wallpapers when user pod is selected.

ash/desktop_background/desktop_background_controller.cc

Index: ash/desktop_background/desktop_background_controller.cc
diff --git a/ash/desktop_background/desktop_background_controller.cc b/ash/desktop_background/desktop_background_controller.cc
index f6b56fd07a8cbb414f65d1662a2830edefa74d7c..95d3553e329524ceef693e04856ef2e4ac30d424 100644
--- a/ash/desktop_background/desktop_background_controller.cc
+++ b/ash/desktop_background/desktop_background_controller.cc
@@ -9,7 +9,9 @@
 #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"
@@ -19,22 +21,49 @@
 
 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() {
@@ -52,4 +81,14 @@ void DesktopBackgroundController::SetDesktopBackgroundSolidColorMode() {
   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