>We are currently trying to build an interface to a dll that works via window's events. The dll reads financial data and broadcasts it to various apps:
>
>For example in a VB app; part of the code looks like this:
>
>'declaring WIN32API functions
>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
>
>Global Const GWL_WNDWROC = -4
>
>Global Const WM_USER = &H400
>Global Const PM_GET_MSG = WM_USER
>Global Const PM_CONN_OK = WM_USER + 1
>Global Const PM_NO_CONN = WM_USER + 2
>Global Const PM_RECONNECTED = WM_USER + 3
>Global Const FINISH_INIT = WM_USER + 4
>Global Const PM_TRADE_MSG = WM_USER + 5
>Global hooked As Boolean
>
>Global lpPrevWndProc As Long
>
>
>Public Sub HookAgent(ByVal hWindow As Long)
>
> ' setting window proc to be the new window proc
> If Not hooked Then
> lpPrevWndProc = SetWindowLong(hWindow, GWL_WNDWROC, AddressOf NewWindowProc)
> hooked = True
> End If
>
>End Sub
>
>Public Sub UnHookAgent(ByVal hWindow As Long)
> Dim rc As Long
>
> ' returning window proc to be the original one
> If hooked Then
> rc = SetWindowLong(hWindow, GWL_WNDWROC, lpPrevWndProc)
> hooked = False
> End If
>End Sub
>
>Function NewWindowProc(ByVal hWin As Long, _
> ByVal uMsg As Long, _
> ByVal wParam As Long, _
> ByVal lParam As Long) As Long
>
> Dim rc As Boolean
>
> If ((uMsg = PM_CONN_OK) Or (uMsg = PM_NO_CONN) Or _
> (uMsg = PM_GET_MSG) Or (uMsg = PM_RECONNECTED)) Or _
> (uMsg = FINISH_INIT) Or (uMsg = PM_TRADE_MSG) Then
> rc = getMessages(uMsg, wParam, lParam)
> Else
> NewWindowProc = CallWindowProc(lpPrevWndProc, hWin, uMsg, _
> wParam, lParam)
> End If
>
>End Function
>
>(getmessages in registered in a dll)
>
>
>etc.
>
>
>However, we can not figure out how to get VFP to read the WM's , or to perform the callback performed in VB.
>
>
>
>Any help would be greatly appreciated.
>TIA
>
Eylon,

Simply put the answer is you can't do this in VFP. On the most basic level the reason is that there's no way to pass the address of the callback function (as you can do with VB via the AddressOf operator). Further, VFP's handling of messages is decidedly non standard. Sorry.