VB Forum / COM / March 2005

Dear Tony,
Thank you so much for the hint about window stations. I had no idea that
something like that existed although now that I have read up on them it
makes absolute sense for such a system to be in effect.

I have been tinkering around with a test application (only has code for
the Window Stations stuff) that I call through the same COM+ component
on the same machine.
The future is looking very bleak as I am trying to marry the worlds of
VB and VC++ and it's not going very well.
I will attach my code in hope that someone (maybe you Tony) will be able
to make any comments.
This is new territory for me and I have not fully understood how the low
 level distinction of a process and thread in VC++ can be reflected in
VB to take full advantage of the functions that deal with Window Stations.
The theory is briefly (merging on adequately) described at:
http://msdn.microsoft.com/library/en-us/dllproc/base/window_station_and_desktop_
functions.asp

Looking forward to hearing from you!

My code so far (the fso stuff is for error logging):

'API function declarations
Public Declare Function SetProcessWindowStation Lib "user32" (ByVal
hWinSta As Long) As Long
Public Declare Function OpenWindowStation Lib "user32" Alias
"OpenWindowStationA" (ByVal lpszWinSta As String, ByVal fInherit As
Long, ByVal dwDesiredAccess As Long) As Long
Public Declare Function OpenInputDesktop Lib "user32" (ByVal dwFlags As
Long, ByVal fInherit As Long, ByVal dwDesiredAccess As Long) As Long
Public Declare Function SetThreadDesktop Lib "user32" (ByVal hDesktop As
Long) As Long

'The window station we wish to assign to the application
Public Const INTERACTIVE_WINDOW_STATION = "Winsta0"

'ACCESS_MASK values
Public Const MAXIMUM_ALLOWED = &H2000000
Public Const GENERIC_ALL = &H10000000
Public Const GENERIC_READ_AND_WRITE = &HC0000000

'Handle to the window station
Dim hndWindowStation As Long

'Handle to the desktop
Dim hndDesktop As Long

Sub Main()
    Dim lngReturn As Integer
    Dim fso As New FileSystemObject, txt As TextStream

    hndWindowStation = OpenWindowStation(INTERACTIVE_WINDOW_STATION, 0,
GENERIC_READ_AND_WRITE)

    If IsNull(hndWindowStation) Then
        Set txt = fso.CreateTextFile(App.Path & "\log.log", True, False)
        txt.WriteLine ("Window Station Handle IS NULL")
        txt.Close
        Set txt = Nothing

        End
    Else
        lngReturn = SetProcessWindowStation(hndWindowStation)

        If lngReturn = 0 Then
            Set txt = fso.CreateTextFile(App.Path & "\log.log", True,
False)
            txt.WriteLine ("SetProcessWindowStation " & Err.LastDllError)
            txt.Close
            Set txt = Nothing

            End
        End If

        hndDesktop = OpenInputDesktop(0, 0, GENERIC_READ_AND_WRITE)

        If IsNull(hndDesktop) Then
            Set txt = fso.CreateTextFile(App.Path & "\log.log", True,
False)
            txt.WriteLine ("Desktop Handle IS NULL")
            txt.Close
            Set txt = Nothing

            End
        Else
            lngReturn = SetThreadDesktop(hndDesktop)

            If lngReturn = 0 Then
                Set txt = fso.CreateTextFile(App.Path & "\log.log",
True, False)
                txt.WriteLine ("SetThreadDesktop " & Err.LastDllError)
                txt.Close
                Set txt = Nothing

                End
            End If
        End If
    End If

    Set fso = Nothing

    Load Form1
End Sub