Subclassing again...

Something is amiss... When I do SetWindowLong it fails, and I can't figure out why.

Here is the relevant code:

Code:

---

Sub SubClass(hWnd As Long)
    hPrevWndProc = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf WindowProc)
    If hPrevWndProc <> 0 Then
        bIsSubclassed = True
    End If
End Sub

---

Except hPrevWndProc always ends up as zero.

What is happening here?

Thanks,
--Josh

Is hPrevWndProc a Public/Global variable?

Yes, I've declared it:

Code:

---

Public hPrevWndProc As Long

---

in the module that has both SubClass and WindowProc.

Post your SubClass routine up and I'll see if I can find a fault.

Code:

---


' ************module1.bas ****************

Declare Function GetLastError Lib "kernel32" () As Long
Declare Sub SetLastError Lib "kernel32" (ByVal dwErrCode As Long)
Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" ( _
  ByVal lpPrevWndFunc As Long, _
  ByVal hwnd As Long, ByVal Msg As Long, _
  ByVal wParam As Long, _
  ByVal lParam As Long) As Long
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" ( _
  ByVal hwnd As Long, _
  ByVal nIndex As Long, _
  ByVal dwNewLong As Long) As Long
Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" ( _
  ByVal hWnd1 As Long, _
  ByVal hWnd2 As Long, _
  ByVal lpsz1 As String, _
  ByVal lpsz2 As String) As Long
Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
  ByVal hwnd As Long, _
  ByVal wMsg As Long, _
  ByVal wParam As Long, _
  lParam As Any) As Long
Public Const WM_WINDOWPOSCHANGING = &H46
Public Const GWL_WNDPROC = (-4)
Public bIsSubclassed As Boolean
Public hPrevWndProc As Long
 
 
Public Function GetMonitor(Who As String)
  Dim sWho As String
  Dim IM_Top As Long
  sWho = Who & " - Instant Message"
  IM_Top = FindWindow(vbNullString, sWho)
  GetMonitor = FindWindowEx(IM_Top, 0, "_Oscar_Static", vbNullString)
End Function


Sub SubClass(hwnd As Long)
    SetLastError (0)
    hPrevWndProc = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf WindowProc)
    frmDebug.rtfDebug.TextRTF = hPrevWndProc
    If hPrevWndProc <> 0 Then
        bIsSubclassed = True
       
    End If
End Sub

Sub UnSubClass(hwnd As Long)
    Dim lRet As Long
    If bIsSubclassed Then
        lRet = SetWindowLong(hwnd, GWL_WNDPROC, hPrevWndProc)
        bIsSubclassed = False
    End If
End Sub

Public Function WindowProc( _
  ByVal hwnd As Long, _
  ByVal iMsg As Long, _
  ByVal wParam As Long, _
  ByVal lParam As Long)

    Select Case iMsg
        Case WM_WINDOWPOSCHANGING
            frmDebug.rtfDebug.TextRTF = "IM Transmitted or Recieved!"
    End Select
   
    WindowProc = CallWindowProc(hPrevWndProc, hwnd, iMsg, wParam, lParam)
End Function


' *************** frmDebug ************************

 Public lMonitor As Long
 Const GWL_WNDPROC = (-4)
 Option Explicit
 

Private Sub Form_Load()
    lMonitor = GetMonitor("JoshWand1")
    rtfDebug.TextRTF = ""
    Call SubClass(lMonitor)
End Sub


Private Sub Form_Unload(Cancel As Integer)
    UnSubClass (lMonitor)
End Sub

---

[Edited by Joshwa on 08-03-2000 at 01:40 PM]

you are trying to subclass a monitor, I've never used monitors, so don't know what they are but when you subclass you have to subclass a window, the hWnd parameter has to be a valid Window Handle, otherwise the function will just return 0, like it's doing

the "monitor" is just my name for the child window that recieves messages when an IM comes in (class _Oscar_Static).

If you look at the GetMonitor function it just finds the window of that class and returns the handle. This part of the program works fine and always returns a handle.

oh yes, a monitor is also something else in the API, I'm not sure what though, The only reason that SetwindowLong would return Zero is if a bad window function is used, Check the value of Err.LastDllError on the line after setwindowlong, tell me what it is.

value of Err.LastDllError after SetWindowLong is 0.

It looks to me like your trying to subclass an AIM window. You can't do this using vb alone. You'll need to use a 3rd party control to subclass outside your own process, or learn the necessary C++ in order to accomplish this. Desaware has outstanding components for global subclassing (as well as a bunch of other goodies), and I highly recommend you check them out at www.desaware.com

-Joe Jordan
Ignite Software
http://www.IgniteSoft.com/

Are there any freeware/GPL subclassing controls out there? I can't afford $200 of extra software for this capability...

I don't know of any freeware global subclassing controls... but if your a student you can fax them a copy of your student id and get it for $100 instead of $200 :)

$100 is still not cheap by any means... I'll do a little research now that I know what I'm looking for...

Could I accomplish this in VB using hooks?

After a bit of research it appears I can't do it with hooks; I'd still need the C++ DLL (I don't have VC++) to be able to do anything.

I've been looking for the custom controls, but all I can find is SpyWorks ($$) and MsgBlast.VBX (written for VB 2.0).

Does anyone know of any other (free!) cross-process subclassing DLL's/Controls?

It'd be nice to do this the right way (subclassing) instead of lamely polling the window on a timer (resource-hog).

Thanks a million,
--Josh