BUG: EnumDesktopWindows Might Enumerate the Wrong Desktop (198590)


The information in this article applies to:

  • Microsoft Windows NT Server 4.0
  • Microsoft Windows NT Workstation 4.0
  • Microsoft Win32 Application Programming Interface (API)
This article was previously published under Q198590

SYMPTOMS

If a desktop has no child windows, a call to EnumDesktopWindows may enumerate windows on a different desktop.

CAUSE

This is caused by a bug in the operating system.

RESOLUTION

To ensure that EnumDesktopWindows is enumerating the intended desktop, use GetWindowThreadProcessID, GetThreadDesktop, and/or GetUserObjectInformation functions to verify that the desktop is correct.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

This bug will affect those applications that attempt to enumerate a desktop immediately after it has been created, or in a scenario where there are currently no child windows of the desktop.

The following code snippet uses GetThreadDesktop() to validate that the correct desktop is being enumerated. Be sure to free any desktop handles opened with GetThreadDesktop() by calling CloseDesktop(). 

   HDESK hdesk;
   hdesk = GetThreadDesktop( GetCurrentThreadId() );
   EnumDesktopWindows( hdesk, EnumProc, (LPARAM)hdesk );
   .
   .
   .
   return;


   BOOL CALLBACK EnumProc( HWND hwnd, LPARAM lParam )
   {


      DWORD dwThreadId;
      HDESK hdesk;


      dwThreadId = GetWindowThreadProcessId( hwnd, NULL );
      hdesk = GetThreadDesktop( dwThreadId );


      if( hdesk && hdesk != (HDESK)lParam ) {
        return FALSE;
      } else {
        // now certain this is the desktop we want to enumerate
        .
        .
        .
      }


      return TRUE;


   }
Modification Type:MinorLast Reviewed:3/21/2005
Keywords:kbBug kbpending kbScreenSaver KB198590
©2004 Microsoft Corporation. All rights reserved.