cheets: add wallpaper observer to arc_wallpaper_service.

chrome/browser/chromeos/arc/arc_wallpaper_service.cc

 // Copyright 2016 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 "chrome/browser/chromeos/arc/arc_wallpaper_service.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 13 matching lines @@
 #include "ui/gfx/image/image.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/image/image_util.h"
 
 using user_manager::UserManager;
 
 namespace arc {
 
 namespace {
 
+constexpr uint32_t kMinOnWallpaperChangedVersion = 1;
 constexpr char kAndroidWallpaperFilename[] = "android.jpg";
 
 // Sets a decoded bitmap as the wallpaper.
 void SetBitmapAsWallpaper(const SkBitmap& bitmap) {
   // Make the SkBitmap immutable as we won't modify it. This is important
   // because otherwise it gets duplicated during painting, wasting memory.
   SkBitmap immutable_bitmap(bitmap);
   immutable_bitmap.setImmutable();
   gfx::ImageSkia image = gfx::ImageSkia::CreateFrom1xBitmap(immutable_bitmap);
   image.MakeThreadSafe();
@@ skipping 30 matching lines @@
 ArcWallpaperService::ArcWallpaperService(ArcBridgeService* bridge_service)
     : ArcService(bridge_service), binding_(this) {
   arc_bridge_service()->wallpaper()->AddObserver(this);
 }
 
 ArcWallpaperService::~ArcWallpaperService() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   // Make sure the callback is never called after destruction. It is safe to
   // call Cancel() even when there is no in-flight request.
   ImageDecoder::Cancel(this);
+  ash::WmShell* wm_shell = ash::WmShell::Get();
+  if (wm_shell && wm_shell->wallpaper_controller()) {
+    wm_shell->wallpaper_controller()->RemoveObserver(this);
+  }
   arc_bridge_service()->wallpaper()->RemoveObserver(this);
 }
 
 void ArcWallpaperService::OnInstanceReady() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   mojom::WallpaperInstance* wallpaper_instance =
       arc_bridge_service()->wallpaper()->instance();
   if (!wallpaper_instance) {
     LOG(DFATAL) << "OnWallpaperInstanceReady called, "
                 << "but no wallpaper instance found";
     return;
   }
   wallpaper_instance->Init(binding_.CreateInterfacePtrAndBind());
+  ash::WmShell::Get()->wallpaper_controller()->AddObserver(this);
 }
 
 void ArcWallpaperService::SetWallpaper(mojo::Array<uint8_t> png_data) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   ImageDecoder::Cancel(this);
   ImageDecoder::StartWithOptions(this, png_data.PassStorage(),
                                  ImageDecoder::ROBUST_PNG_CODEC, true);
 }
 
 void ArcWallpaperService::GetWallpaper(const GetWallpaperCallback& callback) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   ash::WallpaperController* wc = ash::WmShell::Get()->wallpaper_controller();
   gfx::ImageSkia wallpaper = wc->GetWallpaper();
   base::PostTaskAndReplyWithResult(
       content::BrowserThread::GetBlockingPool(), FROM_HERE,
       base::Bind(&EncodeImagePng, wallpaper), callback);
 }
 
 void ArcWallpaperService::OnImageDecoded(const SkBitmap& bitmap) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   SetBitmapAsWallpaper(bitmap);
 }
 
 void ArcWallpaperService::OnDecodeImageFailed() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   LOG(ERROR) << "Failed to decode wallpaper image.";
 }
 
+void ArcWallpaperService::OnWallpaperDataChanged() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  mojom::WallpaperInstance* instance =
+      GetWallpaperInstance(kMinOnWallpaperChangedVersion);
+  if (!instance) {
+    ash::WmShell::Get()->wallpaper_controller()->RemoveObserver(this);

[Luis Héctor Chávez, 2016/09/16 19:58:11]

It's better to do this in the OnInstanceClosed() rather than here.

[Muyuan, 2016/09/16 20:19:08]

I see. So here is a question:
Is there a guarantee that Android side will be torn down before CrOS side? In
other words, is OnInstanceClosed() always guaranteed to be called prior to
~ArcWallpaperService()? I'm asking this because if it's true, the removal of
WallpaperObserver in ~ArcWallpaperService() could be moved here.

[Luis Héctor Chávez, 2016/09/16 20:27:37]

There are cases where Android outlives Chrome, but are error cases. I'd rather
have two places where the observer is removed (because the second removal is a
no-op): one in OnInstanceClosed() (for symmetry with OnInstanceReady()) and one
in the destructor (for safety). If you omit the latter, the destructor of the
ObserverList will DCHECK since not all Observers were removed.

[Muyuan, 2016/09/16 20:48:56]

Done.

+    return;
+  }
+  instance->OnWallpaperChanged();
+}
+
+mojom::WallpaperInstance* ArcWallpaperService::GetWallpaperInstance(
+    uint32_t min_version) {
+  uint32_t version = arc_bridge_service()->wallpaper()->version();
+  if (version < min_version) {
+    VLOG(1) << "ARC wallpaper instance is too old. required: " << min_version
+            << ", actual: " << version;
+    return nullptr;
+  }
+
+  mojom::WallpaperInstance* instance =
+      arc_bridge_service()->wallpaper()->instance();
+  if (!instance) {
+    VLOG(2) << "ARC wallpaper instance is not ready.";
+  }
+
+  return instance;
+}
+
 }  // namespace arc