Battery Status API: implementation for Windows.

content/browser/battery_status/battery_status_manager_win.cc

+// Copyright 2014 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 "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"
+
+namespace content {
+
+namespace {
+
+typedef BatteryStatusService::BatteryUpdateCallback BatteryCallback;
+
+const wchar_t kWindowClassName[] = L"BatteryStatusMessageWindow";
+
+// Message-only window for handling battery changes on Windows.
+class BatteryStatusObserver
+    : public base::RefCountedThreadSafe<BatteryStatusObserver> {
+ public:
+  explicit BatteryStatusObserver(const BatteryCallback& callback)
+       : power_handle_(NULL),
+        battery_change_handle_(NULL),
+        callback_(callback) {
+  }
+
+  virtual ~BatteryStatusObserver() { DCHECK(!window_); }
+
+  void Start() {
+    // Need to start on the UI thread to receive battery status notifications.
+    BrowserThread::PostTask(
+        BrowserThread::UI,
+        FROM_HERE,
+        base::Bind(&BatteryStatusObserver::StartOnUI, this));
+  }
+
+  void Stop() {
+    BrowserThread::PostTask(
+        BrowserThread::UI,
+        FROM_HERE,
+        base::Bind(&BatteryStatusObserver::StopOnUI, this));
+  }
+
+ private:
+  void StartOnUI() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    if (window_)
+      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_ =
+          RegisterPowerSettingNotification(&GUID_ACDC_POWER_SOURCE);
+      battery_change_handle_ =
+          RegisterPowerSettingNotification(&GUID_BATTERY_PERCENTAGE_REMAINING);
+    } else {
+      // Could not create a message window, execute callback with the default
+      // values.
+      callback_.Run(blink::WebBatteryStatus());
+    }
+  }
+
+  void StopOnUI() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    if (!window_)
+      return;
+
+    if (power_handle_)
+      UnregisterPowerSettingNotification(power_handle_);
+    if (battery_change_handle_)
+      UnregisterPowerSettingNotification(battery_change_handle_);
+    window_.reset();
+  }
+
+  void BatteryChanged() {
+    blink::WebBatteryStatus status;
+    SYSTEM_POWER_STATUS win_status;
+    if (GetSystemPowerStatus(&win_status))
+      status = ComputeWebBatteryStatus(win_status);
+
+    callback_.Run(status);
+  }
+
+  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;
+    }
+  }
+
+  HPOWERNOTIFY RegisterPowerSettingNotification(LPCGUID power_setting) {
+    if (base::win::GetVersion() < base::win::VERSION_VISTA)
+      return NULL;
+
+    typedef HPOWERNOTIFY (WINAPI* RegisterPowerSettingNotificationFunc)

[scottmg, 2014/08/13 23:39:52]

per previous comment, you don't need GetProcAddress, just call
RegisterPowerSettingNotification(...). the runtime guard at 112 is enough.

[timvolodine, 2014/08/14 15:34:34]

great, it magically works :) thanks.
Done.

+                         (HANDLE recipient, LPCGUID id, DWORD flags);
+
+    RegisterPowerSettingNotificationFunc register_func_ =

[scottmg, 2014/08/13 23:39:52]

(don't need it, but no trailing _ on locals)

[timvolodine, 2014/08/14 15:34:34]

Done.

+        reinterpret_cast<RegisterPowerSettingNotificationFunc>(
+            GetProcAddress(GetModuleHandleA("user32.dll"),
+                           "RegisterPowerSettingNotification"));
+
+    return register_func_ ? register_func_(window_->hwnd(), power_setting,
+                                           DEVICE_NOTIFY_WINDOW_HANDLE)
+                          : NULL;
+  }
+
+  BOOL UnregisterPowerSettingNotification(HPOWERNOTIFY handle) {
+    if (base::win::GetVersion() < base::win::VERSION_VISTA)
+      return FALSE;
+
+    typedef BOOL (WINAPI* UnregisterPowerSettingNotificationFunc)
+                 (HPOWERNOTIFY handle);
+
+    UnregisterPowerSettingNotificationFunc unregister_func_ =

[scottmg, 2014/08/13 23:39:52]

same here

[timvolodine, 2014/08/14 15:34:34]

Done.

+        reinterpret_cast<UnregisterPowerSettingNotificationFunc>(
+            GetProcAddress(GetModuleHandleA("user32.dll"),
+                           "UnregisterPowerSettingNotification"));
+
+    return unregister_func_ ? unregister_func_(handle) : FALSE;
+  }
+
+  bool CreateMessageWindow() {

[cpu_(ooo_6.6-7.5), 2014/08/13 23:29:06]

do we need to create a new window? I thought we already have a window singleton
that you can subscribe for messages?

[timvolodine, 2014/08/14 15:34:34]

not sure what window singleton you are referring to, but we may be able to reuse
the power_monitor message window. I'll need to check this because last time I
experimented with power_monitor it seemed that it can be not initialized yet at
the start of battery status api.. added a TODO.

+    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_;
+
+  DISALLOW_COPY_AND_ASSIGN(BatteryStatusObserver);
+};
+
+class BatteryStatusManagerWin : public BatteryStatusManager {
+ public:
+  explicit BatteryStatusManagerWin(const BatteryCallback& callback)
+      : battery_observer_(new BatteryStatusObserver(callback)) {}
+  virtual ~BatteryStatusManagerWin() { battery_observer_->Stop(); }
+
+ public:
+  // BatteryStatusManager:
+  virtual bool StartListeningBatteryChange() OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+    battery_observer_->Start();
+    return true;
+  }
+
+  virtual void StopListeningBatteryChange() OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+    battery_observer_->Stop();
+  }
+
+ private:
+  scoped_refptr<BatteryStatusObserver> battery_observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(BatteryStatusManagerWin);
+};
+
+}  // namespace
+
+blink::WebBatteryStatus ComputeWebBatteryStatus(
+    const SYSTEM_POWER_STATUS& win_status) {
+  blink::WebBatteryStatus status;
+  status.charging = win_status.ACLineStatus != WIN_AC_LINE_STATUS_OFFLINE;
+  // Set level if available. Otherwise keep the default value which is 1.
+  if (win_status.BatteryLifePercent != 255) {
+    // Convert percentage to a value between 0 and 1 with 2 significant digits.
+    status.level = static_cast<double>(win_status.BatteryLifePercent) / 100.;
+  }
+  if (!status.charging) {
+    // Set dischargingTime if available otherwise keep the default value,
+    // which is +Infinity.
+    if (win_status.BatteryLifeTime != (DWORD)-1)
+      status.dischargingTime = win_status.BatteryLifeTime;
+    status.chargingTime = std::numeric_limits<double>::infinity();
+  } else {
+    // Set chargingTime to +Infinity if not fully charged, otherwise leave the
+    // default value, which is 0.
+    if (status.level < 1)
+      status.chargingTime = std::numeric_limits<double>::infinity();
+  }
+  return status;
+}
+
+// static
+scoped_ptr<BatteryStatusManager> BatteryStatusManager::Create(
+    const BatteryStatusService::BatteryUpdateCallback& callback) {
+  return scoped_ptr<BatteryStatusManager>(
+      new BatteryStatusManagerWin(callback));
+}
+
+}  // namespace content