services/device/time_zone_monitor/time_zone_monitor.h

// 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.

#ifndef SERVICES_DEVICE_TIME_ZONE_MONITOR_TIME_ZONE_MONITOR_H_
#define SERVICES_DEVICE_TIME_ZONE_MONITOR_TIME_ZONE_MONITOR_H_

#include <memory>

#include "base/macros.h"
#include "base/threading/thread_checker.h"
#include "mojo/public/cpp/bindings/binding_set.h"
#include "mojo/public/cpp/bindings/interface_ptr_set.h"
#include "services/device/public/interfaces/time_zone_monitor.mojom.h"

template <class T>
class scoped_refptr;

namespace base {
class SequencedTaskRunner;
}

namespace device {

// TimeZoneMonitor watches the system time zone, and notifies renderers
// when it changes. Some renderer code caches the system time zone, so
// this notification is necessary to inform such code that cached
// timezone data may have become invalid. Due to sandboxing, it is not
// possible for renderer processes to monitor for system time zone
// changes themselves, so this must happen in the browser process.
//
// Sandboxing also may prevent renderer processes from reading the time
// zone when it does change, so platforms may have to deal with this in
// platform-specific ways:
//  - Mac uses a sandbox hole defined in content/renderer/renderer.sb.
//  - Linux-based platforms use ProxyLocaltimeCallToBrowser in
//    content/zygote/zygote_main_linux.cc and HandleLocaltime in
//    content/browser/renderer_host/sandbox_ipc_linux.cc to override
//    localtime in renderer processes with custom code that calls
//    localtime in the browser process via Chrome IPC.

class TimeZoneMonitor : public device::mojom::TimeZoneMonitor {
 public:
  // Returns a new TimeZoneMonitor object (likely a subclass) specific to the
  // platform. Inject |file_task_runner| to enable running blocking file
  // operations on it when necessary.
  static std::unique_ptr<TimeZoneMonitor> Create(
      scoped_refptr<base::SequencedTaskRunner> file_task_runner);

  ~TimeZoneMonitor() override;

  void Bind(device::mojom::TimeZoneMonitorRequest request);

 protected:
  TimeZoneMonitor();

  // Notify all callbacks that the system time zone may have changed.
  void NotifyClients();

 private:
  base::ThreadChecker thread_checker_;

  // device::mojom::device::mojom::TimeZoneMonitor:
  void AddClient(device::mojom::TimeZoneMonitorClientPtr client) override;

  mojo::BindingSet<device::mojom::TimeZoneMonitor> bindings_;
  mojo::InterfacePtrSet<device::mojom::TimeZoneMonitorClient> clients_;
  DISALLOW_COPY_AND_ASSIGN(TimeZoneMonitor);
};

}  // namespace device

#endif  // SERVICES_DEVICE_TIME_ZONE_MONITOR_TIME_ZONE_MONITOR_H_