Enable user change background image in settings page in Aura build.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 1220f5e686d7d2774802a452dd6e979e67d6de0c..12432078b7a2a08c7a1ddb82e4aedd792e5e38d2 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -8,6 +8,9 @@
 
 #include "ash/app_list/app_list.h"
 #include "ash/ash_switches.h"
+#include "ash/desktop_background/desktop_background_controller.h"
+#include "ash/desktop_background/desktop_background_resources.h"
+#include "ash/desktop_background/desktop_background_view.h"
 #include "ash/drag_drop/drag_drop_controller.h"
 #include "ash/focus_cycler.h"
 #include "ash/ime/input_method_event_filter.h"
@@ -474,6 +477,7 @@ void Shell::Init() {
   AddRootWindowEventFilter(tooltip_controller_.get());
 
   drag_drop_controller_.reset(new internal::DragDropController);
+  desktop_background_controller_.reset(new DesktopBackgroundController);
   power_button_controller_.reset(new PowerButtonController);
   video_detector_.reset(new VideoDetector);
   window_cycle_controller_.reset(new WindowCycleController);
@@ -539,6 +543,15 @@ void Shell::ToggleAppList() {
   app_list_->SetVisible(!app_list_->IsVisible());
 }
 
+void Shell::SetDesktopBackgroundWallpaper(const SkBitmap& wallpaper) {
+  if (desktop_background_mode_ == BACKGROUND_SOLID_COLOR)
+    return;
+  DCHECK(root_window_layout_->background_widget());
+  static_cast<internal::DesktopBackgroundView*>(
+      root_window_layout_->background_widget()->widget_delegate())->
+      SetWallpaper(wallpaper);
+}
+
 void Shell::SetDesktopBackgroundMode(BackgroundMode mode) {

[flackr, 2012/03/06 17:16:49]

I think this function should become SetDesktopBackgroundSolidColor() and
SetDesktopBackgroundWallpaper should change the desktop_background_mode_ if
necessary and set the background. This way if you currently have a solid color
set and select a background it will switch modes and set it. Also from a coding
perspective you can pass the background to set to the DesktopBackgroundView
constructor.

[bshe, 2012/03/06 19:56:16]

Just to confirm, your intention here is to enable the ability to switch between
solid color mode and image mode?

My understanding is that the solid color mode is only used in compact window
mode now. Unless we want to switch from compact mode to managed mode
dynamically, we dont need switch between solid color to image. 

To set a solid color background in managed mode, the current plan is to create
some solid color resources/images and draw them on screen using
DesktopBackgroundView.

I agree for solid color background, we should use the solid color mode for
memory efficiency. Do you want push this into this CL or should I just add a
TODO for now?

[flackr, 2012/03/06 20:25:28]

This is probably important, I think if we start supporting switching background
modes that this will break wallpaper switching (i.e. when you switch to solid
color mode selecting wallpapers won't do anything and when you switch back to
wallpaper mode it won't have a background until you select another wallpaper).
There is an accelerator in accelerator_controller.cc which changes background
modes on ctrl+alt+b if you compile with NDEBUG. You could test to see what
happens. I imagine this is okay as a TODO for now given that switching is not
allowed on release builds.

[bshe, 2012/03/07 19:50:44]

It seems the ToT build can't switch the color mode back and forth. I will create
a bug to track this. At the same time, I have modified my code according to your
suggestion so when user switch color mode, the user selected image will draw. 

   if (mode == BACKGROUND_SOLID_COLOR) {
     // Set a solid black background.