Shutdown, Logoff API in Visual C++, MFC and Win32 – Article by Alok by thatsalok

This Visual C++ sample project using MFC is intended to either shutdown, logoff, or restart the computer at a given time or immediately. This is a Visual C++ Project using the concept of Win32 APIs with MFC. The Shutdown Timer application also uses System Tray Interface to handle it with menu options.

API for ShutDown:

The ExitWindowEx is the API which can be used in Visual C++ for shutting down a workstation. There is one more API for this purpose named InitiateSystemShutdown, but that API works only on Window 2000 and above. The ExitWindowEx API works directly
in Win9x/ME, but in Windows multi-user systems, it requires a special privilege before execution.

Here is the code for enabling that privilege for Windows multi-user platforms in Visual C++:

HANDLE hToken; // handle to process token 
TOKEN_PRIVILEGES tkp; // pointer to token structure
OpenProcessToken(GetCurrentProcess(),TOKEN_ADJUST_PRIVILEGES | 
       TOKEN_QUERY, &hToken); // Get the LUID for shutdown privilege.              
LookupPrivilegeValue(NULL, SE_SHUTDOWN_NAME, &tkp.Privileges[0].Luid); 
tkp.PrivilegeCount = 1; // one privilege to set
tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;   
// Get shutdown privilege for this process. 
AdjustTokenPrivileges(hToken, FALSE, &tkp, 0, (PTOKEN_PRIVILEGES) NULL, 0);
// Cannot test the return value of AdjustTokenPrivileges.  
if (GetLastError() != ERROR_SUCCESS)   
   MessageBox("AdjustTokenPrivileges enable failed.");

Now, ExitWindowsEx has two parameters. The function declaration in <Windows.h> looks like:

BOOL ExitWindowsEx

( UINT uFlags, DWORD dwReason );

And for uFlag, we have four options:

  1. EWX_LOGOFF: Logoff the current user.
  2. EWX_RESTART: Simply restart the computer.
  3. EWX_SHUTDOWN: Shut down but ‘AT’ style.
  4. EWX_POWEROFF: Shut down but
    ‘ATX’ style.

I think the above Win32 APIs are very simple, right?

System Tray Icon :

The next logical step to be understood is how to use the system tray icon and
the way it handles the messages. First, I will show you the code, after that, I
will describe to you the required details about the System Tray Icon handling.

//handling the ICON at System Tray Icon
sprintf(m_niData.szTip,"Shut Down Alarm :My Father Software inc @ 2003");


Now, here you see one new variable of type NOTIFYICONDATA Structure.

BOOL Shell_NotifyIcon(DWORD dwMessage, PNOTIFYICONDATA lpdata);

The NOTIFYICONDATA structure according to MSDN ‘Contains
information that the system needs to process taskbar status area messages’.
The variables are:

  1. cbSize: this variable is created to provide compatibility
    with other versions of NotifyIconData.
  2. hIcon: icon for the system tray.
  3. hWnd: handle to window which will handle the system tray icon
  4. szTip: show tip when mouse hovers over icon.
  5. CallbackMessage: application-defined message identifier. The
    system uses this identifier to send notifications to the window identified
    in hWnd. These notifications are sent when a mouse event occurs
    in the bounding rectangle of the icon, or when the icon is selected or
    activated with the keyboard.
  6. uFlag: this flag notifies the system which of the above
    variable to use or not.
  7. uID: any unique ID for Icon.

Now, Shell_NotifyIcon adds this icon to system tray. It takes
three parameters as arguments:

  1. NIM_ADD: add icon to system tray.
  2. NIM_DELETE: delete icon from system tray.
  3. NIM_MODIFY: modify the system tray icon (for e.g., when you
    connect to Yahoo! chat using Yahoo! messenger, the icon becomes active, and
    when you logoff, the icon becomes inactive).

Handling the system tray message:

Message Mapping: This notification is handled using MFC user defined messages .


Now, the code to handle message in MFC library (Visual C++ ) is :

void DlgShutDown::OnSystemBarMessage(WPARAM wParam, LPARAM lParam)
        case WM_LBUTTONDOWN:
            this- >ShowWindow(SW_SHOW);
            bMiniShow=FALSE; break;
        case WM_RBUTTONDOWN:
            CMenu mnu;
            //CMenu *PopUpMenu;
            CPoint pt;

This code demonstrates “Mouse Right Button Click” by which I show the popup menu when user clicks on system tray icon.

I think I have explained much about this software, but if has any problems, please forgive me. This is my first article in You can message me, I will try my best to help you and sort out my mistakes.

Download the Sample Project here.