[Win] Battery Status API: use SingletonHwnd for notifications.

content/browser/battery_status/battery_status_manager_win.cc

Index: content/browser/battery_status/battery_status_manager_win.cc
diff --git a/content/browser/battery_status/battery_status_manager_win.cc b/content/browser/battery_status/battery_status_manager_win.cc
index d998d5aca0e2ab6405e323d659aa894cf179ef34..273c429e1bdd2c5722ed58a79cc1a5b6a1e320a8 100644
--- a/content/browser/battery_status/battery_status_manager_win.cc
+++ b/content/browser/battery_status/battery_status_manager_win.cc
@@ -5,11 +5,10 @@
 #include "content/browser/battery_status/battery_status_manager_win.h"
 
 #include "base/memory/ref_counted.h"
-#include "base/strings/string16.h"
-#include "base/win/message_window.h"
 #include "base/win/windows_version.h"
 #include "content/browser/battery_status/battery_status_manager.h"
 #include "content/public/browser/browser_thread.h"
+#include "ui/gfx/win/singleton_hwnd.h"
 
 namespace content {
 
@@ -17,19 +16,19 @@ namespace {
 
 typedef BatteryStatusService::BatteryUpdateCallback BatteryCallback;
 
-const wchar_t kWindowClassName[] = L"BatteryStatusMessageWindow";
-
-// Message-only window for handling battery changes on Windows.
+// Listens to battery changes using a singleton message window.
 class BatteryStatusObserver
-    : public base::RefCountedThreadSafe<BatteryStatusObserver> {
+    : public gfx::SingletonHwnd::Observer,
+      public base::RefCountedThreadSafe<BatteryStatusObserver> {
  public:
   explicit BatteryStatusObserver(const BatteryCallback& callback)
       : power_handle_(NULL),
         battery_change_handle_(NULL),
-        callback_(callback) {
+        callback_(callback),
+        started_(false) {
   }
 
-  virtual ~BatteryStatusObserver() { DCHECK(!window_); }
+  virtual ~BatteryStatusObserver() { DCHECK(!started_); }
 
   void Start() {
     // Need to start on the UI thread to receive battery status notifications.
@@ -49,37 +48,38 @@ class BatteryStatusObserver
  private:
   void StartOnUI() {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-    if (window_)
+    if (started_)
       return;
 
-    if (CreateMessageWindow()) {
-      BatteryChanged();
-      // RegisterPowerSettingNotification function work from Windows Vista
-      // onwards. However even without them we will receive notifications,
-      // e.g. when a power source is connected.
-      // TODO(timvolodine) : consider polling for battery changes on windows
-      // versions prior to Vista, see crbug.com/402466.
-      power_handle_ =
-          RegisterNotification(&GUID_ACDC_POWER_SOURCE);
-      battery_change_handle_ =
-          RegisterNotification(&GUID_BATTERY_PERCENTAGE_REMAINING);
-    } else {
-      // Could not create a message window, execute callback with the default
-      // values.
-      callback_.Run(blink::WebBatteryStatus());
-    }
+    gfx::SingletonHwnd* message_window = gfx::SingletonHwnd::GetInstance();
+    message_window->AddObserver(this);
+
+    // RegisterPowerSettingNotification function work from Windows Vista
+    // onwards. However even without them we will receive notifications,
+    // e.g. when a power source is connected.
+    // TODO(timvolodine) : consider polling for battery changes on windows
+    // versions prior to Vista, see crbug.com/402466.
+    power_handle_ = RegisterNotification(&GUID_ACDC_POWER_SOURCE,
+                                         message_window->hwnd());
+    battery_change_handle_ =
+        RegisterNotification(&GUID_BATTERY_PERCENTAGE_REMAINING,
+                             message_window->hwnd());
+    BatteryChanged();
+    started_ = true;
   }
 
   void StopOnUI() {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-    if (!window_)
+    if (!started_)
       return;
 
     if (power_handle_)
       UnregisterNotification(power_handle_);
     if (battery_change_handle_)
       UnregisterNotification(battery_change_handle_);
-    window_.reset();
+
+    gfx::SingletonHwnd::GetInstance()->RemoveObserver(this);
+    started_ = false;
   }
 
   void BatteryChanged() {
@@ -90,29 +90,27 @@ class BatteryStatusObserver
       callback_.Run(blink::WebBatteryStatus());
   }
 
-  bool HandleMessage(UINT message,
-                     WPARAM wparam,
-                     LPARAM lparam,
-                     LRESULT* result) {
-    switch(message) {
-      case WM_POWERBROADCAST:
-        if (wparam == PBT_APMPOWERSTATUSCHANGE ||
-            wparam == PBT_POWERSETTINGCHANGE) {
-          BatteryChanged();
-        }
-        *result = NULL;
-        return true;
-      default:
-        return false;
+  // SingletonHwnd::Observer
+  void OnWndProc(HWND hwnd,
+                 UINT message,
+                 WPARAM wparam,
+                 LPARAM lparam) OVERRIDE {
+    if (message != WM_POWERBROADCAST)
+      return;
+
+    if (wparam == PBT_APMPOWERSTATUSCHANGE ||
+        wparam == PBT_POWERSETTINGCHANGE) {
+      BatteryChanged();
     }
   }
 
-  HPOWERNOTIFY RegisterNotification(LPCGUID power_setting) {
+  HPOWERNOTIFY RegisterNotification(LPCGUID power_setting, HWND hwnd) {
     if (base::win::GetVersion() < base::win::VERSION_VISTA)
       return NULL;
 
-    return RegisterPowerSettingNotification(window_->hwnd(), power_setting,
-                                     DEVICE_NOTIFY_WINDOW_HANDLE);
+    return RegisterPowerSettingNotification(hwnd,
+                                            power_setting,
+                                            DEVICE_NOTIFY_WINDOW_HANDLE);
   }
 
   BOOL UnregisterNotification(HPOWERNOTIFY handle) {
@@ -122,23 +120,10 @@ class BatteryStatusObserver
     return UnregisterPowerSettingNotification(handle);
   }
 
-  bool CreateMessageWindow() {
-    // TODO(timvolodine): consider reusing the message window of PowerMonitor.
-    window_.reset(new base::win::MessageWindow());
-    if (!window_->CreateNamed(base::Bind(&BatteryStatusObserver::HandleMessage,
-                                         base::Unretained(this)),
-                              base::string16(kWindowClassName))) {
-      LOG(ERROR) << "Failed to create message window: " << kWindowClassName;
-      window_.reset();
-      return false;
-    }
-    return true;
-  }
-
   HPOWERNOTIFY power_handle_;
   HPOWERNOTIFY battery_change_handle_;
   BatteryCallback callback_;
-  scoped_ptr<base::win::MessageWindow> window_;
+  bool started_;
 
   DISALLOW_COPY_AND_ASSIGN(BatteryStatusObserver);
 };