battery-status: Implement the battery-status API for chromeos.

content/browser/battery_status/battery_status_manager_chromeos.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 "base/memory/ref_counted.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/power_manager/power_supply_properties.pb.h"
+#include "chromeos/dbus/power_manager_client.h"
+#include "content/public/browser/browser_thread.h"
+#include "third_party/WebKit/public/platform/WebBatteryStatus.h"
+
+namespace content {
+
+namespace {
+
+class PowerManagerObserver
+    : public chromeos::PowerManagerClient::Observer,
+      public base::RefCountedThreadSafe<PowerManagerObserver> {
+ public:
+  explicit PowerManagerObserver(
+      const BatteryStatusService::BatteryUpdateCallback& callback)
+      : callback_(callback), currently_listening_(false) {}
+
+  // Starts listening for updates. It is safe to call this on any thread.
+  void Start() {
+    if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+      StartOnUI();
+    } else {
+      BrowserThread::PostTask(
+          BrowserThread::UI,
+          FROM_HERE,
+          base::Bind(&PowerManagerObserver::StartOnUI, this));
+    }
+  }
+
+  // Stops listening for updates. It is safe to call this on any thread.
+  void Stop() {
+    if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+      StopOnUI();
+    } else {
+      BrowserThread::PostTask(
+          BrowserThread::UI,
+          FROM_HERE,
+          base::Bind(&PowerManagerObserver::StopOnUI, this));
+    }
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<PowerManagerObserver>;
+
+  virtual ~PowerManagerObserver() {}
+
+  bool IsBatteryPresent(
+      const power_manager::PowerSupplyProperties& proto) const {
+    return proto.battery_state() !=
+           power_manager::PowerSupplyProperties_BatteryState_NOT_PRESENT;
+  }
+
+  bool IsUsbChargerConnected(
+      const power_manager::PowerSupplyProperties& proto) const {
+    return proto.external_power() ==
+           power_manager::PowerSupplyProperties_ExternalPower_USB;
+  }
+
+  bool IsBatteryCharging(
+      const power_manager::PowerSupplyProperties& proto) const {
+    return proto.battery_state() !=
+           power_manager::PowerSupplyProperties_BatteryState_DISCHARGING;
+  }
+
+  bool IsBatteryFull(const power_manager::PowerSupplyProperties& proto) const {
+    return proto.battery_state() ==
+           power_manager::PowerSupplyProperties_BatteryState_FULL;
+  }
+
+  double GetBatteryLevel(
+      const power_manager::PowerSupplyProperties& proto) const {
+    const double kMaxBatteryLevelProto = 100.f;
+    return proto.battery_percent() / kMaxBatteryLevelProto;
+  }
+
+  void StartOnUI() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    if (currently_listening_)
+      return;
+    chromeos::PowerManagerClient* power_client =
+        chromeos::DBusThreadManager::Get()->GetPowerManagerClient();
+    power_client->AddObserver(this);
+    power_client->RequestStatusUpdate();
+    currently_listening_ = true;
+  }
+
+  void StopOnUI() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    if (!currently_listening_)
+      return;
+    chromeos::DBusThreadManager::Get()->GetPowerManagerClient()->RemoveObserver(
+        this);
+    currently_listening_ = false;
+  }
+
+  // chromeos::PowerManagerClient::Observer:
+  virtual void PowerChanged(
+      const power_manager::PowerSupplyProperties& proto) OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    blink::WebBatteryStatus status;
+    // Use the default values if there is no battery in the system.
+    if (IsBatteryPresent(proto)) {
+      // The charging status is unreliable if a low power charger is connected
+      // (i.e. usb).
+      bool status_unreliable = IsUsbChargerConnected(proto);
+      // Battery time is unreliable if it is still being computed.
+      bool time_unreliable =
+          status_unreliable || proto.is_calculating_battery_time();
+
+      // Set |charging| only if the status is reliable. Otherwise, keep the
+      // default (which is |true|).
+      if (!status_unreliable)
+        status.charging = IsBatteryCharging(proto);
+
+      // Set |chargingTime| to +infinity if the battery is discharging, or if
+      // the time is unreliable. Keep the default value (which is 0) if the
+      // battery is full.
+      if (time_unreliable || !status.charging)
+        status.chargingTime = std::numeric_limits<double>::infinity();
+      else if (!IsBatteryFull(proto))
+        status.chargingTime = proto.battery_time_to_full_sec();
+
+      // Keep the default value for |dischargingTime| (which is +infinity) if
+      // the time is unreliable, or if the battery is charging.
+      if (!time_unreliable && !status.charging)
+        status.dischargingTime = proto.battery_time_to_empty_sec();
+
+      status.level = GetBatteryLevel(proto);
+    }
+    callback_.Run(status);
+  }
+
+  BatteryStatusService::BatteryUpdateCallback callback_;
+  bool currently_listening_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerManagerObserver);
+};
+
+class BatteryStatusManagerChromeOS
+    : public BatteryStatusManager,
+      public chromeos::PowerManagerClient::Observer {
+ public:
+  explicit BatteryStatusManagerChromeOS(
+      const BatteryStatusService::BatteryUpdateCallback& callback)
+      : observer_(new PowerManagerObserver(callback)) {}
+
+  virtual ~BatteryStatusManagerChromeOS() { observer_->Stop(); }
+
+ private:
+  // BatteryStatusManager:
+  virtual bool StartListeningBatteryChange() OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+    observer_->Start();
+    return true;
+  }
+
+  virtual void StopListeningBatteryChange() OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+    observer_->Stop();
+  }
+
+  scoped_refptr<PowerManagerObserver> observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(BatteryStatusManagerChromeOS);
+};
+
+}  // namespace
+
+// static
+scoped_ptr<BatteryStatusManager> BatteryStatusManager::Create(
+    const BatteryStatusService::BatteryUpdateCallback& callback) {
+  return scoped_ptr<BatteryStatusManager>(
+      new BatteryStatusManagerChromeOS(callback));
+}
+
+}  // namespace content