Minimize black screen during the boot with multi displays

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_controller_observer.h"
 #include "ash/desktop_background/desktop_background_view.h"
 #include "ash/desktop_background/desktop_background_widget_controller.h"
 #include "ash/desktop_background/user_wallpaper_delegate.h"
@@ skipping 114 matching lines @@
 
   scoped_ptr<WallpaperData> wallpaper_data_;
 
   const WallpaperInfo info_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperLoader);
 };
 
 DesktopBackgroundController::DesktopBackgroundController()
     : locked_(false),
-      desktop_background_mode_(BACKGROUND_SOLID_COLOR),
+      desktop_background_mode_(BACKGROUND_NONE),
       background_color_(kTransparentColor),
       weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
 }
 
 DesktopBackgroundController::~DesktopBackgroundController() {
   CancelPendingWallpaperOperation();
 }
 
 gfx::ImageSkia DesktopBackgroundController::GetWallpaper() const {
   if (current_wallpaper_.get())
@@ skipping 27 matching lines @@
   if (wallpaper_loader_.get())
     return wallpaper_loader_->idr();
   else if (current_wallpaper_.get())
     return current_wallpaper_->wallpaper_info.idr;
   else
     return -1;
 }
 
 void DesktopBackgroundController::OnRootWindowAdded(
     aura::RootWindow* root_window) {
+  // The background hasn't set yet.

[bshe, 2013/01/25 21:46:34]

Just curiosity, if we skip the installation here, when do we install the
background widget on the second screen? Would this function get called twice?

[oshima, 2013/01/25 21:51:49]

This can be called during the boot, before the background is set
by startup process. The background will set after all root windows are created.

[Daniel Erat, 2013/01/26 15:52:30]

nit: s/hasn't set/hasn't been set/

[oshima, 2013/01/26 23:10:42]

Done.

+  if (desktop_background_mode_ == BACKGROUND_NONE)
+    return;
+
   // Handle resolution change for "built-in" images.
   if (BACKGROUND_IMAGE == desktop_background_mode_ &&
       current_wallpaper_.get()) {
     gfx::Size root_window_size = root_window->GetHostSize();
     // Loads a higher resolution wallpaper if new root window is larger than
     // small screen.
     if (kSmallWallpaperMaxWidth < root_window_size.width() ||
         kSmallWallpaperMaxHeight < root_window_size.height()) {
       current_wallpaper_.reset(NULL);
       ash::Shell::GetInstance()->user_wallpaper_delegate()->
@@ skipping 147 matching lines @@
       component = new internal::DesktopBackgroundWidgetController(widget);
       break;
     }
     case BACKGROUND_SOLID_COLOR: {
       ui::Layer* layer = SetColorLayerForContainer(background_color_,
                                                    root_window,
                                                    container_id);
       component = new internal::DesktopBackgroundWidgetController(layer);
       break;
     }
-    default: {

[oshima, 2013/01/25 21:22:52]

removing default as desktop_background_mode_ is enum.

+    case BACKGROUND_NONE:

[bshe, 2013/01/25 21:46:34]

nit: Could you wrap the following with {} to be consistent?

[oshima, 2013/01/25 21:51:49]

{} is necessary when you create variables, which doesn't apply here. I don't
think we need {} just for consistency,
but I can be convinced either way. Dan, WDTY?

[Daniel Erat, 2013/01/26 15:52:30]

I'd vote for leaving out the curly brackets.

       NOTREACHED();
-    }
+      return;
   }
   // Ensure we're only observing the root window once. Don't rely on a window
   // property check as those can be cleared by tests resetting the background.
   if (!root_window->HasObserver(this))
     root_window->AddObserver(this);
 
   internal::AnimatingDesktopController* animating_controller =
       root_window->GetProperty(kAnimatingDesktopController);
   if (animating_controller)
     animating_controller->StopAnimating();
@@ skipping 43 matching lines @@
   }
   return moved;
 }
 
 int DesktopBackgroundController::GetBackgroundContainerId(bool locked) {
   return locked ? internal::kShellWindowId_LockScreenBackgroundContainer :
                   internal::kShellWindowId_DesktopBackgroundContainer;
 }
 
 }  // namespace ash