}

> > Hi,

> >     Could someone please tell me how to use WaveOutOpen with window
> > handler callback? I used the below code to playback sound in my Visual
> > C++ program.

> > waveOutOpen(WaveIn,WAVE_MAPPER,Format,(DWORD)m_hWnd,0,CALLBACK_WINDOW)

> >     with m_hWnd being the window handle data member of my CWnd class
> > (the function is called in a modeless dialog, so the handle is actually
> > a handle of the dialog object, of the CDialog class, which is derived
> > from CWnd) . However, when I run the program in release build mode, it
> > give me illegal operation every time I finished recording and the my
> > window handler is called. There is no problem when I change to function
> > callback (waveOutProc). And when I disabled the window message handler,
> > no problem occured as well. So I think the problem really lies with my
> > window message handler.

> >     What is the correct way to implement our own window message
> > handlers?

> >     Hope someone could help me out! Thank you very much.

> > Yours sincerely,
> > Soon Chieh

> Your own window message handlers should have a line like this in the message
> map:

>  ON_MESSAGE(WM_SOME_MESSAGE, OnSomeMessage)

> and the message handler function *must* have a prototype like this:

>  LRESULT CSomeClass::OnSomeMessage(WPARAM wParam, LPARAM lParam);

> If you prototype the function with a void return it crashes in release build.

> --
> Scott McPhillips [VC++ MVP]

> LRESULT CSomeClass::OnSomeMessage(WPARAM wParam, LPARAM lParam)
> {    //my code
>      return 0; // 0 means the message was handled
> }

> The reason you must use exactly this prototype with ON_MESSAGE is that the MFC
> message router code constructs the call on the stack assuming this prototype.
> If you don't match it the stack gets corrupted.  The call construction code must
> be different for different messages, depending on Win32 message formats.

> Hey MS -- This is an extremely common newbie trap (three victims on the
> newsgroups just this morning).  The documentation for ON_MESSAGE fails to
> mention the required prototype.  It is mentioned under "User-Defined Handlers".
> The meaning of the return value is not explained in either place.

> --
> Scott McPhillips [VC++ MVP]