Sub Classing

Why doesn't this do anything?

Form1
-----------------
Dim lpfnOld As Long
Private Sub Form_Load()
lpfnOld = SetWindowLong(Form1.hwnd, GWL_WNDPROC, AddressOf FrmWndProc)
End Sub
Private Sub Form_Unload(Cancel As Integer)
SetWindowLong Form1.hwnd, GWL_WNDPROC, lpfnOld
End Sub

Module1
-----------------
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Public Function FrmWndProc(ByVal hwnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
MsgBox "hello"
Select Case uMsg

Case WM_SETFOCUS
Form1.Caption = "Subclassed Form - Has Focus"
FrmWndProc = 0
Exit Function

Case WM_KILLFOCUS
Form1.Caption = "Subclassed Form - Lost Focus"
FrmWndProc = 0
Exit Function

End Select

FrmWndProc = CallWindowProc(lpfnOld, hwnd, uMsg, wParam, lParam)
End Function

This is the very first time I have tried this so I haven't got a clue.
-Thanks

First of all never use msgbox or any other flow breaking calls like doevents when you are subclassing. It's very unhealthy, use Debug.print instead.

I think that might fix it

From vbAccelerator:

Quote:

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When a form in your application is deactivated, Windows fires a WM_ACTIVATE message to the form. The wParam of this message tells you the reason the message has been fired:

wParam Meaning
0 Form deactivated
1 Form activated
2 Form activated by a mouse click

---

So try subclassing the WM_ACTIVATE instead of WM_SETFOCUS and WM_KILLFOCUS, AFAIK they won't work properly...

You don't have any of the constants declared either. Add these to your Module.

Code:

---

Const WM_SETFOCUS = &H7
Const WM_KILLFOCUS = &H8

---

I should have noticed that! Anyway, it works now. Thanks all.