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.h"
+
+#include <windows.h>
+#include "base/memory/ref_counted.h"
+#include "base/win/windows_version.h"
+#include "base/win/wrapped_window_proc.h"
+#include "content/public/browser/browser_thread.h"
+#include "third_party/WebKit/public/platform/WebBatteryStatus.h"
+
+namespace content {
+
+namespace {
+
+typedef BatteryStatusService::BatteryUpdateCallback BatteryCallback;
+
+const wchar_t kWindowClassName[] = L"BatteryStatusMessageWindow";
+
+void ComputeWebBatteryStatus(const SYSTEM_POWER_STATUS& win_status,
+                             blink::WebBatteryStatus& status) {
+  bool on_battery = win_status.ACLineStatus == 0;
+  status.charging = !on_battery;  // not offline

[mlamouri (slow - plz ping), 2014/08/07 16:40:47]

Couldn't you do:
 status.charging = win_status.ACLineStatus != 0;

Then use |!status.charging| instead of |on_battery| ?

[timvolodine, 2014/08/11 19:43:41]

Done.

+  // 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 3 significant digits.
+    status.level = round(win_status.BatteryLifePercent * 10) / 1000.f;
+  }
+  if (on_battery) {
+    // Set dischargingTime if available otherwise keep the default value,
+    // which is +Infinity.
+    if (win_status.BatteryLifeTime != -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();

[mlamouri (slow - plz ping), 2014/08/07 16:40:47]

Can't you use status.BatteryFullLifeTime?

[timvolodine, 2014/08/11 19:43:41]

according to the documentation BatteryFullLifeTime is "The number of seconds of
battery life when at full charge", so not usable for the purpose of
chargingTime.

+  }
+}
+
+// Message-only window for handling battery changes on Windows.
+class BatteryStatusObserver
+    : public base::RefCountedThreadSafe<BatteryStatusObserver> {
+ public:
+  explicit BatteryStatusObserver(const BatteryCallback& callback)
+      : register_func_(NULL),
+        unregister_func_(NULL),
+        instance_(NULL),
+        message_hwnd_(NULL),
+        power_handle_(NULL),
+        battery_change_handle_(NULL),
+        callback_(callback) {
+    InitPowerSettingFunctions();
+  }
+
+  virtual ~BatteryStatusObserver() { DCHECK(!message_hwnd_); }
+
+  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 (message_hwnd_)
+      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.
+      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 (!message_hwnd_)
+      return;
+
+    if (power_handle_)
+      UnregisterPowerSettingNotification(power_handle_);
+    if (battery_change_handle_)
+      UnregisterPowerSettingNotification(battery_change_handle_);
+    DestroyWindow(message_hwnd_);
+    UnregisterClass(kWindowClassName, instance_);
+    message_hwnd_ = NULL;
+  }
+
+  static LRESULT CALLBACK WndProcThunk(HWND hwnd,
+                                       UINT message,
+                                       WPARAM wparam,
+                                       LPARAM lparam) {
+  BatteryStatusObserver* msg_wnd = reinterpret_cast<BatteryStatusObserver*>(
+      GetWindowLongPtr(hwnd, GWLP_USERDATA));
+    switch(message) {
+      case WM_POWERBROADCAST:
+        if (wparam == PBT_APMPOWERSTATUSCHANGE ||
+            wparam == PBT_POWERSETTINGCHANGE) {
+          msg_wnd->BatteryChanged();
+        }
+        return true;
+      default:
+        return ::DefWindowProc(hwnd, message, wparam, lparam);
+    }
+  }
+
+  void BatteryChanged() {
+    blink::WebBatteryStatus status;
+    SYSTEM_POWER_STATUS win_status;
+    if (GetSystemPowerStatus(&win_status))
+      ComputeWebBatteryStatus(win_status, status);
+
+    callback_.Run(status);
+  }
+
+  HPOWERNOTIFY RegisterPowerSettingNotification(LPCGUID power_setting) {
+    return register_func_ ? register_func_(message_hwnd_, power_setting,
+                                           DEVICE_NOTIFY_WINDOW_HANDLE)
+                          : NULL;
+  }
+
+  BOOL UnregisterPowerSettingNotification(HPOWERNOTIFY handle) {
+    return unregister_func_ ? unregister_func_(handle) : FALSE;
+  }
+
+  void InitPowerSettingFunctions() {
+    if (base::win::GetVersion() < base::win::VERSION_VISTA)
+      return;

[mlamouri (slow - plz ping), 2014/08/07 16:40:47]

If that means that we don't get any event before Vista (ie. XP) unless the
battery mode is toggled, that's a problem. I wouldn't block shipping this in M38
just for that but we need to fix that in a follow-up.

Could you open a bug and mark it as blocking bug 122593.

We should consider polling at a very high interval like 30s to 5 minutes.

[timvolodine, 2014/08/11 19:43:41]

Done. added a crbug.

+
+    HMODULE user32 = GetModuleHandleA("user32.dll");

[scottmg, 2014/08/08 21:32:19]

I believe user32 is delayload, so you can just runtime-guard this, but call the
functions normally and avoid the extra members.

[timvolodine, 2014/08/11 19:43:41]

Done.

+    register_func_ = reinterpret_cast<RegisterPowerSettingNotificationFunc>(
+        GetProcAddress(user32, "RegisterPowerSettingNotification"));
+    unregister_func_ = reinterpret_cast<UnregisterPowerSettingNotificationFunc>(
+        GetProcAddress(user32, "UnregisterPowerSettingNotification"));
+    DCHECK(register_func_ && unregister_func_);
+  }
+
+  bool CreateMessageWindow() {

[scottmg, 2014/08/08 21:32:19]

can we use base::win::MessageWindow here?

[timvolodine, 2014/08/11 19:43:41]

yes. thanks for noticing this, done.

+    WNDCLASSEX window_class;
+    base::win::InitializeWindowClass(kWindowClassName,
+        &base::win::WrappedWindowProc<BatteryStatusObserver::WndProcThunk>,
+        0, 0, 0, NULL, NULL, NULL, NULL, NULL, &window_class);
+    instance_ = window_class.hInstance;
+    ATOM clazz = RegisterClassEx(&window_class);
+    DCHECK(clazz);
+    message_hwnd_ = CreateWindowEx(WS_EX_NOACTIVATE, kWindowClassName,
+        NULL, WS_POPUP, 0, 0, 0, 0, NULL, NULL, instance_, NULL);
+    if (!message_hwnd_)
+      return false;
+    SetWindowLongPtr(message_hwnd_, GWLP_USERDATA,
+                     reinterpret_cast<LONG_PTR>(this));
+    return true;
+  }
+
+  typedef HPOWERNOTIFY (WINAPI* RegisterPowerSettingNotificationFunc)
+                       (HANDLE recipient, LPCGUID id, DWORD flags);
+  RegisterPowerSettingNotificationFunc register_func_;
+
+  typedef BOOL (WINAPI* UnregisterPowerSettingNotificationFunc)
+               (HPOWERNOTIFY handle);
+  UnregisterPowerSettingNotificationFunc unregister_func_;
+
+  HMODULE instance_;
+  HWND message_hwnd_;
+  HPOWERNOTIFY power_handle_;
+  HPOWERNOTIFY battery_change_handle_;
+  BatteryCallback callback_;
+
+  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
+
+// static
+scoped_ptr<BatteryStatusManager> BatteryStatusManager::Create(
+    const BatteryStatusService::BatteryUpdateCallback& callback) {
+  return scoped_ptr<BatteryStatusManager>(
+      new BatteryStatusManagerWin(callback));
+}
+
+}  // namespace content