1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CHROME_BROWSER_UI_AURA_ACTIVE_DESKTOP_MONITOR_H_
6#define CHROME_BROWSER_UI_AURA_ACTIVE_DESKTOP_MONITOR_H_
7
8#include "base/basictypes.h"
9#include "base/compiler_specific.h"
10#include "chrome/browser/ui/host_desktop.h"
11#include "ui/aura/env_observer.h"
12
13// Tracks the most-recently activated host desktop type by observing
14// WindowTreeHost activations.
15class ActiveDesktopMonitor : public aura::EnvObserver {
16 public:
17  // Constructs an ActiveDesktopMonitor which initially uses |initial_desktop|
18  // as the |last_activated_desktop_| until a root window is activated.
19  explicit ActiveDesktopMonitor(chrome::HostDesktopType initial_desktop);
20  virtual ~ActiveDesktopMonitor();
21
22  // Returns the host desktop type of the most-recently activated
23  // WindowTreeHost. This desktop type may no longer exist (e.g., the Ash
24  // desktop may have closed since being active, and no RWHs on the native
25  // desktop have yet been activated).
26  static chrome::HostDesktopType GetLastActivatedDesktopType();
27
28 private:
29  // Returns true if |host| is a DesktopWindowTreeHost.
30  static bool IsDesktopWindow(aura::WindowTreeHost* host);
31
32  // aura::EnvObserver methods.
33  virtual void OnWindowInitialized(aura::Window* window) OVERRIDE;
34  virtual void OnHostActivated(aura::WindowTreeHost* host) OVERRIDE;
35
36  static ActiveDesktopMonitor* g_instance_;
37  chrome::HostDesktopType last_activated_desktop_;
38
39  DISALLOW_COPY_AND_ASSIGN(ActiveDesktopMonitor);
40};
41
42#endif  // CHROME_BROWSER_UI_AURA_ACTIVE_DESKTOP_MONITOR_H_
43