Получить сообщение о переключении сессии в XP

//  Typically, an application does not need to be notified when a session switch
//  occurs. However, if the application needs to be aware when its desktop is
//  current, it can register for session switch notifications. Applications that
//  access the serial port or another shared resource on the computer should
//  check for this. To register for a notification, use the following function:
 

  function WTSRegisterSessionNotification( 
      hWnd: HWND ,    // Window handle 
      dwFlags: DWORD  // Flags 
      ): Bool;        // Return value 

{ 
  The registered HWND receives the message WM_WTSSESSION_CHANGE 
  through its WindowProc function. 

  In dwFlags you can specify: 

    a) NOTIFY_FOR_THIS_SESSION. A window is notified only about the session 
      change events that affect the session to which window belongs. 

    b) NOTIFY_FOR_ALL_SESSIONS. A window is notified for all session change 
      events. 

  The action happening on the session can be found in wParam code, which may 
  contain one of the following flags. 

  WTS_CONSOLE_CONNECT:        A session was connected to the console session. 
  WTS_CONSOLE_DISCONNECT:     A session was disconnected from the console session. 
  WTS_REMOTE_CONNECT:         A session was connected to the remote session. 
  WTS_REMOTE_DISCONNECT:      A session was disconnected from the remote session. 
  WTS_SESSION_LOGON:          A user has logged on to the session. 
  WTS_SESSION_LOGOFF:         A user has logged off the session. 
  WTS_SESSION_LOCK:           A session has been locked. 
  WTS_SESSION_UNLOCK:         A session has been unlocked. 
  WTS_SESSION_REMOTE_CONTROL: A session has changed its remote controlled status.


  lParam contains the sessionId for the session affected. 

  When your process no longer requires these notifications or is terminating, 
  it should call the following to unregister its notification. 

} 
  function WTSUnRegisterSesssionNotification( 
    hWnd: HWND // window handle. 
    ): Boolean; // Result 

{ 

  The HWND values passed to WTSRegisterSessionNotification are reference 
  counted, so you must call WTSUnRegisterSessionNotification exactly the same 
  number of times that you call WTSRegisterSessionNotification. 

  Applications can use the WTS_CONSOLE_CONNECT, WTS_CONSOLE_DISCONNECT, 
  WTS_REMOTE_CONNECT, WTS_REMOTE_DISCONNECT messages to track their state, as 
  well as to release and acquire console specific resources. 
} 

unit Wtsapi; 

interface 

{ (c) By Thomas Stutz 10. April 02 } 

uses 
  Windows;

const 
  // The WM_WTSSESSION_CHANGE message notifies applications of changes in session state. 
  WM_WTSSESSION_CHANGE = $2B1; 

  // wParam values: 
  WTS_CONSOLE_CONNECT = 1; 
  WTS_CONSOLE_DISCONNECT = 2; 
  WTS_REMOTE_CONNECT = 3; 
  WTS_REMOTE_DISCONNECT = 4; 
  WTS_SESSION_LOGON = 5; 
  WTS_SESSION_LOGOFF = 6; 
  WTS_SESSION_LOCK = 7; 
  WTS_SESSION_UNLOCK = 8; 
  WTS_SESSION_REMOTE_CONTROL = 9; 

  // Only session notifications involving the session attached to by the window 
  // identified by the hWnd parameter value are to be received. 
  NOTIFY_FOR_THIS_SESSION = 0; 
  // All session notifications are to be received. 
  NOTIFY_FOR_ALL_SESSIONS = 1; 


function RegisterSessionNotification(Wnd: HWND; dwFlags: DWORD): Boolean; 
function UnRegisterSessionNotification(Wnd: HWND): Boolean; 
function GetCurrentSessionID: Integer; 

implementation 

function RegisterSessionNotification(Wnd: HWND; dwFlags: DWORD): Boolean; 
  // The RegisterSessionNotification function registers the specified window
  // to receive session change notifications. 
  // Parameters: 
  // hWnd: Handle of the window to receive session change notifications. 
  // dwFlags: Specifies which session notifications are to be received: 
  // (NOTIFY_FOR_THIS_SESSION, NOTIFY_FOR_ALL_SESSIONS) 
type 
  TWTSRegisterSessionNotification = function(Wnd: HWND; dwFlags: DWORD): BOOL; stdcall; 
var 
  hWTSapi32dll: THandle; 
  WTSRegisterSessionNotification: TWTSRegisterSessionNotification; 
begin 
  Result := False; 
  hWTSAPI32DLL := LoadLibrary('Wtsapi32.dll'); 
  if (hWTSAPI32DLL > 0) then 
  begin 
    try @WTSRegisterSessionNotification := 
        GetProcAddress(hWTSAPI32DLL, 'WTSRegisterSessionNotification'); 
      if Assigned(WTSRegisterSessionNotification) then 
      begin 
        Result:= WTSRegisterSessionNotification(Wnd, dwFlags); 
      end; 
    finally 
      if hWTSAPI32DLL > 0 then 
        FreeLibrary(hWTSAPI32DLL); 
    end; 
  end; 
end; 

function UnRegisterSessionNotification(Wnd: HWND): Boolean; 
  // The RegisterSessionNotification function unregisters the specified window 
  // Parameters:
  // hWnd: Handle to the window 
type 
  TWTSUnRegisterSessionNotification = function(Wnd: HWND): BOOL; stdcall; 
var 
  hWTSapi32dll: THandle; 
  WTSUnRegisterSessionNotification: TWTSUnRegisterSessionNotification; 
begin 
  Result := False; 
  hWTSAPI32DLL := LoadLibrary('Wtsapi32.dll'); 
  if (hWTSAPI32DLL > 0) then 
  begin 
    try @WTSUnRegisterSessionNotification := 
        GetProcAddress(hWTSAPI32DLL, 'WTSUnRegisterSessionNotification'); 
      if Assigned(WTSUnRegisterSessionNotification) then 
      begin 
        Result:= WTSUnRegisterSessionNotification(Wnd); 
      end; 
    finally 
      if hWTSAPI32DLL > 0 then 
        FreeLibrary(hWTSAPI32DLL); 
    end; 
  end; 
end; 

function GetCurrentSessionID: Integer; 
 // Getting the session id from the current process 
type 
  TProcessIdToSessionId = function(dwProcessId: DWORD; pSessionId: DWORD): BOOL; stdcall; 
var 
  ProcessIdToSessionId: TProcessIdToSessionId; 
  hWTSapi32dll: THandle;
  Lib : THandle; 
  pSessionId : DWord; 
begin 
  Result := 0; 
  Lib := GetModuleHandle('kernel32'); 
  if Lib <> 0 then 
  begin 
    ProcessIdToSessionId := GetProcAddress(Lib, '1ProcessIdToSessionId'); 
    if Assigned(ProcessIdToSessionId) then 
    begin 
      ProcessIdToSessionId(GetCurrentProcessId(), DWORD(@pSessionId)); 
      Result:= pSessionId; 
    end; 
  end; 
end; 

end. 

// Example: 

unit Unit1; 

interface 

uses 
  Windows, Messages, {...},  Wtsapi; 

type 
  TForm1 = class(TForm) 
    procedure FormCreate(Sender: TObject); 
    procedure FormDestroy(Sender: TObject);
  private 
  { Private declarations } 
    FRegisteredSessionNotification : Boolean; 
    procedure AppMessage(var Msg: TMSG; var HAndled: Boolean); 
  end; 

var 
  Form1: TForm1; 

implementation 

{$R *.DFM} 

procedure TForm1.AppMessage(var Msg: TMSG; var Handled: Boolean); 
var 
  strReason: string; 
begin 
  Handled := False; 
  // Check for WM_WTSSESSION_CHANGE message 
  if Msg.Message = WM_WTSSESSION_CHANGE then 
  begin 
     case Msg.wParam of 
       WTS_CONSOLE_CONNECT: 
           strReason := 'WTS_CONSOLE_CONNECT'; 
       WTS_CONSOLE_DISCONNECT: 
           strReason := 'WTS_CONSOLE_DISCONNECT'; 
       WTS_REMOTE_CONNECT: 
           strReason := 'WTS_REMOTE_CONNECT'; 
       WTS_REMOTE_DISCONNECT: 
           strReason := 'WTS_REMOTE_DISCONNECT'; 
       WTS_SESSION_LOGON:
           strReason := 'WTS_SESSION_LOGON'; 
       WTS_SESSION_LOGOFF: 
           strReason := 'WTS_SESSION_LOGOFF'; 
       WTS_SESSION_LOCK: 
           strReason := 'WTS_SESSION_LOCK'; 
       WTS_SESSION_UNLOCK: 
           strReason := 'WTS_SESSION_UNLOCK'; 
       WTS_SESSION_REMOTE_CONTROL: 
           begin 
             strReason := 'WTS_SESSION_REMOTE_CONTROL'; 
             // GetSystemMetrics(SM_REMOTECONTROL); 
           end; 
      else 
        strReason := 'WTS_Unknown'; 
     end; 
   // Write strReason to a Memo 
   Memo1.Lines.Add(strReason + ' ' + IntToStr(msg.Lparam)); 
  end; 
end; 

procedure TForm1.FormCreate(Sender: TObject); 
begin 
  // register the window to receive session change notifications. 
  FRegisteredSessionNotification := RegisterSessionNotification(Handle, NOTIFY_FOR_THIS_SESSION); 
  Application.OnMessage := AppMessage; 
end; 

procedure TForm1.FormDestroy(Sender: TObject); 
begin 
  // unregister session change notifications. 
 if FRegisteredSessionNotification then
   UnRegisterSessionNotification(Handle); 
end; 

procedure TForm1.Button1Click(Sender: TObject); 
begin 
 // retrieve current session ID 
 ShowMessage(Inttostr(GetCurrentSessionID)); 
end;