CallWindowProc - strange behavior - c++

Question

It definetly works, but in a strange way.
I'm replacing RichEdit control's procedure with
WNDPROC g_OrigREditText =
(WNDPROC)SetWindowLongPtr( g_hwnd_RichEdit, GWLP_WNDPROC, (LONG_PTR)REditWndProc);
Then, I SendMessage to RichEdit control using EM_REPLACESEL msg, and the text appears in the RichEdit control as it should. But when I replace standard procedure with my own, and process EM_REPLACESEL in mine own procedure, then the following scenario happens. Here's the code:
LRESULT CALLBACK REditWndProc( HWND hwnd, UINT msg, WPARAM wp, LPARAM lp )
{
switch( msg )
{
case EM_REPLACESEL:
{
int sdfsdf = 0;
CallWindowProc( (WNDPROC)g_OrigREditText, hwnd, msg, wp, lp );
break;
}
default:
return DefWindowProc( hwnd, msg, wp, lp);
break;
}
return 0;
}
Ok, I send an EM_REPLACESEL message to the RichEdit as usual and it works well, cos I catch operation pointer in "case EM_REPLACESEL" block.
Then CallWindowProc should do its job by passing parameters to the next procedure in the chain, but instead nothing happens, the text doesn't appear in a RichEdit control. Looks like something prevent the message to be passed to old procedure, but! if I replace g_OrigREditText with REditWndProc, then I catch the same UINT msg again, so it definetely pass parameters further, like it should.
So what's wrong with CallWindowProc or with my code, where should I dig to fix the problem?

Answer 1

The whole thing is called "subclassing" and this can be useful .
usually there are more events that occurs in relating with one message so change your code to this
LRESULT CALLBACK REditWndProc( HWND hwnd, UINT msg, WPARAM wp, LPARAM lp )
{
if( msg == EM_REPLACESEL)
{
// whatever you want
return TRUE;// comment this
// if you want to give it to the original proc.
}
return CallWindowProc( g_OrigREditText, hwnd, msg, wp, lp );
}