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 base::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 base::DefaultSingletonTraits<
  50       WtsRegistrationNotificationManager>;
  51
  52   void OnWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
  53     switch (message) {
  54       case WM_WTSSESSION_CHANGE:
  55         FOR_EACH_OBSERVER(WindowsSessionChangeObserver,
  56                           observer_list_,
  57                           OnSessionChange(wparam));
  58         break;
  59       case WM_DESTROY:
  60         RemoveSingletonHwndObserver();
  61         break;
  62     }
  63   }
  64
  65   void AddSingletonHwndObserver() {
  66     DCHECK(!singleton_hwnd_observer_);
  67     singleton_hwnd_observer_.reset(new gfx::SingletonHwndObserver(
  68         base::Bind(&WtsRegistrationNotificationManager::OnWndProc,
  69                    base::Unretained(this))));
  70     scoped_refptr<base::TaskRunner> task_runner;
  71     if (ViewsDelegate::GetInstance()) {
  72       task_runner = ViewsDelegate::GetInstance()->GetBlockingPoolTaskRunner();
  73     }
  74
  75     base::Closure wts_register =
  76         base::Bind(base::IgnoreResult(&WTSRegisterSessionNotification),
  77                    gfx::SingletonHwnd::GetInstance()->hwnd(),
  78                    NOTIFY_FOR_THIS_SESSION);
  79     if (task_runner) {
  80       task_runner->PostTask(FROM_HERE, wts_register);
  81     } else {
  82       wts_register.Run();
  83     }
  84   }
  85
  86   void RemoveSingletonHwndObserver() {
  87     if (!singleton_hwnd_observer_)
  88       return;
  89
  90     singleton_hwnd_observer_.reset(nullptr);
  91     // There is no race condition between this code and the worker thread.
  92     // RemoveSingletonHwndObserver is only called from two places:
  93     //   1) Destruction due to Singleton Destruction.
  94     //   2) WM_DESTROY fired by SingletonHwnd.
  95     // Under both cases we are in shutdown, which means no other worker threads
  96     // can be running.
  97     WTSUnRegisterSessionNotification(gfx::SingletonHwnd::GetInstance()->hwnd());
  98     FOR_EACH_OBSERVER(WindowsSessionChangeObserver,
  99                       observer_list_,
 100                       ClearCallback());
 101   }
 102
 103   base::ObserverList<WindowsSessionChangeObserver, true> observer_list_;
 104   scoped_ptr<gfx::SingletonHwndObserver> singleton_hwnd_observer_;
 105
 106   DISALLOW_COPY_AND_ASSIGN(WtsRegistrationNotificationManager);
 107 };
 108
 109 WindowsSessionChangeObserver::WindowsSessionChangeObserver(
 110     const WtsCallback& callback)
 111     : callback_(callback) {
 112   DCHECK(!callback_.is_null());
 113   WtsRegistrationNotificationManager::GetInstance()->AddObserver(this);
 114 }
 115
 116 WindowsSessionChangeObserver::~WindowsSessionChangeObserver() {
 117   ClearCallback();
 118 }
 119
 120 void WindowsSessionChangeObserver::OnSessionChange(WPARAM wparam) {
 121   callback_.Run(wparam);
 122 }
 123
 124 void WindowsSessionChangeObserver::ClearCallback() {
 125   if (!callback_.is_null()) {
 126     callback_.Reset();
 127     WtsRegistrationNotificationManager::GetInstance()->RemoveObserver(this);
 128   }
 129 }
 130
 131 }  // namespace views