ui/views/win/windows_session_change_observer.cc

   1 // Copyright 2015 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 #include "ui/views/win/windows_session_change_observer.h"
   6
   7 #include <wtsapi32.h>
   8 #pragma comment(lib, "wtsapi32.lib")
   9
  10 #include "base/bind.h"
  11 #include "base/bind_helpers.h"
  12 #include "base/callback.h"
  13 #include "base/location.h"
  14 #include "base/memory/ref_counted.h"
  15 #include "base/memory/scoped_ptr.h"
  16 #include "base/memory/singleton.h"
  17 #include "base/observer_list.h"
  18 #include "base/task_runner.h"
  19 #include "ui/gfx/win/singleton_hwnd.h"
  20 #include "ui/gfx/win/singleton_hwnd_observer.h"
  21 #include "ui/views/views_delegate.h"
  22
  23 namespace views {
  24
  25 class WindowsSessionChangeObserver::WtsRegistrationNotificationManager {
  26  public:
  27   static WtsRegistrationNotificationManager* GetInstance() {
  28     return Singleton<WtsRegistrationNotificationManager>::get();
  29   }
  30
  31   WtsRegistrationNotificationManager() {
  32     AddSingletonHwndObserver();
  33   }
  34
  35   ~WtsRegistrationNotificationManager() {
  36     RemoveSingletonHwndObserver();
  37   }
  38
  39   void AddObserver(WindowsSessionChangeObserver* observer) {
  40     DCHECK(singleton_hwnd_observer_);
  41     observer_list_.AddObserver(observer);
  42   }
  43
  44   void RemoveObserver(WindowsSessionChangeObserver* observer) {
  45     observer_list_.RemoveObserver(observer);
  46   }
  47
  48  private:
  49   friend struct DefaultSingletonTraits<WtsRegistrationNotificationManager>;
  50
  51   void OnWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
  52     switch (message) {
  53       case WM_WTSSESSION_CHANGE:
  54         FOR_EACH_OBSERVER(WindowsSessionChangeObserver,
  55                           observer_list_,
  56                           OnSessionChange(wparam));
  57         break;
  58       case WM_DESTROY:
  59         RemoveSingletonHwndObserver();
  60         break;
  61     }
  62   }
  63
  64   void AddSingletonHwndObserver() {
  65     DCHECK(!singleton_hwnd_observer_);
  66     singleton_hwnd_observer_.reset(new gfx::SingletonHwndObserver(
  67         base::Bind(&WtsRegistrationNotificationManager::OnWndProc,
  68                    base::Unretained(this))));
  69     scoped_refptr<base::TaskRunner> task_runner;
  70     if (ViewsDelegate::GetInstance()) {
  71       task_runner = ViewsDelegate::GetInstance()->GetBlockingPoolTaskRunner();
  72     }
  73
  74     base::Closure wts_register =
  75         base::Bind(base::IgnoreResult(&WTSRegisterSessionNotification),
  76                    gfx::SingletonHwnd::GetInstance()->hwnd(),
  77                    NOTIFY_FOR_THIS_SESSION);
  78     if (task_runner) {
  79       task_runner->PostTask(FROM_HERE, wts_register);
  80     } else {
  81       wts_register.Run();
  82     }
  83   }
  84
  85   void RemoveSingletonHwndObserver() {
  86     if (!singleton_hwnd_observer_)
  87       return;
  88
  89     singleton_hwnd_observer_.reset(nullptr);
  90     // There is no race condition between this code and the worker thread.
  91     // RemoveSingletonHwndObserver is only called from two places:
  92     //   1) Destruction due to Singleton Destruction.
  93     //   2) WM_DESTROY fired by SingletonHwnd.
  94     // Under both cases we are in shutdown, which means no other worker threads
  95     // can be running.
  96     WTSUnRegisterSessionNotification(gfx::SingletonHwnd::GetInstance()->hwnd());
  97     FOR_EACH_OBSERVER(WindowsSessionChangeObserver,
  98                       observer_list_,
  99                       ClearCallback());
 100   }
 101
 102   base::ObserverList<WindowsSessionChangeObserver, true> observer_list_;
 103   scoped_ptr<gfx::SingletonHwndObserver> singleton_hwnd_observer_;
 104
 105   DISALLOW_COPY_AND_ASSIGN(WtsRegistrationNotificationManager);
 106 };
 107
 108 WindowsSessionChangeObserver::WindowsSessionChangeObserver(
 109     const WtsCallback& callback)
 110     : callback_(callback) {
 111   DCHECK(!callback_.is_null());
 112   WtsRegistrationNotificationManager::GetInstance()->AddObserver(this);
 113 }
 114
 115 WindowsSessionChangeObserver::~WindowsSessionChangeObserver() {
 116   ClearCallback();
 117 }
 118
 119 void WindowsSessionChangeObserver::OnSessionChange(WPARAM wparam) {
 120   callback_.Run(wparam);
 121 }
 122
 123 void WindowsSessionChangeObserver::ClearCallback() {
 124   if (!callback_.is_null()) {
 125     callback_.Reset();
 126     WtsRegistrationNotificationManager::GetInstance()->RemoveObserver(this);
 127   }
 128 }
 129
 130 }  // namespace views