Subclassing again...

[Joshwa]

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

Here is the relevant 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?

[Joshwa]

Yes, I've declared it:

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.

[Joshwa]

' ************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]

[Sam Finch]

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

[Joshwa]

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.

[Sam Finch]

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.

[Joshwa]

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/

[Joshwa]

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

[Joshwa]

$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?

[Joshwa]

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