// Copyright (c) 2012 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 UI_BASE_X_WORK_AREA_WATCHER_X_H_
#define UI_BASE_X_WORK_AREA_WATCHER_X_H_
#pragma once

#include "base/basictypes.h"
#include "base/memory/singleton.h"
#include "base/observer_list.h"
#include "ui/base/ui_export.h"
#include "ui/base/x/x11_util.h"

namespace ui {

class WorkAreaWatcherObserver;

namespace internal {
class RootWindowPropertyWatcherX;
}

// This is a helper class that is used to keep track of changes to work area.
// Add an observer to track changes.
class UI_EXPORT WorkAreaWatcherX {
 public:
  static WorkAreaWatcherX* GetInstance();
  static void AddObserver(WorkAreaWatcherObserver* observer);
  static void RemoveObserver(WorkAreaWatcherObserver* observer);

 private:
  friend struct DefaultSingletonTraits<WorkAreaWatcherX>;
  friend class ui::internal::RootWindowPropertyWatcherX;

  WorkAreaWatcherX();
  ~WorkAreaWatcherX();

  // Gets the atom for the default display for the property this class is
  // watching for.
  static Atom GetPropertyAtom();

  // Notify observers that the work area has changed.
  static void Notify();

  // Instance method that implements Notify().
  void NotifyWorkAreaChanged();

  ObserverList<WorkAreaWatcherObserver> observers_;

  DISALLOW_COPY_AND_ASSIGN(WorkAreaWatcherX);
};

}  // namespace ui

#endif  // UI_BASE_X_WORK_AREA_WATCHER_X_H_