Re: SendMessage WM_NOTIFY across process

I make no apologies for the tattiness of my code I just wanted the
mechanism to work and tried lot's
of things out. Anyhow, I decided to redouble my efforts and have found
out exactly why this doesn't work.

Examining the call stack you can see that CWnd::OnNotify the first
parameter has value 0x000001aa.
This is the window's ID (426 decimal). In the next call to CMainFrame
this has morphed into an nID
parameter of 0x00003c38.

  mfc71d.dll!CCmdTarget::OnCmdMsg(unsigned int nID=0x00003c38, int
nCode=0x0000fffe, void * pExtra=0x0013fb74, AFX_CMDHANDLERINFO *
pHandlerInfo=0x00000000) Line 383 + 0x18 C++
  mfc71d.dll!CFrameWnd::OnCmdMsg(unsigned int nID=0x00003c38, int
nCode=0x004efffe, void * pExtra=0x0013fb74, AFX_CMDHANDLERINFO *
pHandlerInfo=0x00000000) Line 897 + 0x18 C++
  WmNotify.exe!CMainFrame::OnCmdMsg(unsigned int nID=0x00003c38, int
nCode=0x004efffe, void * pExtra=0x0013fb74, AFX_CMDHANDLERINFO *
pHandlerInfo=0x00000000) Line 170 C++
  mfc71d.dll!CWnd::OnNotify(unsigned int __formal=0x000001aa, long
lParam=0x00037970, long * pResult=0x0013fc70) Line 2576 C++
  mfc71d.dll!CWnd::OnWndMsg(unsigned int message=0x0000004e, unsigned
int wParam=0x000001aa, long lParam=0x00037970, long *
pResult=0x0013fca4) Line 1771 + 0x28 C++
  mfc71d.dll!CWnd::WindowProc(unsigned int message=0x0000004e,
unsigned int wParam=0x000001aa, long lParam=0x00037970) Line 1745 +
0x1e C++

This is the reason why:

BOOL CWnd::OnNotify(WPARAM, LPARAM lParam, LRESULT* pResult)
{
    ASSERT(pResult != NULL);
    NMHDR* pNMHDR = (NMHDR*)lParam;
    HWND hWndCtrl = pNMHDR->hwndFrom;

    // get the child ID from the window itself
    UINT_PTR nID = _AfxGetDlgCtrlID(hWndCtrl);

OnNotify ignores the NMHDR.idFrom field and instead recalculates it
from _AfxGetDlgCtrlID(hWndCtrl).
Now the hWndFrom that I passed was from my MainFrame window so the ID
becomes that of my MainFrame
window and not the control.

I think some of you hinted at this. The HWND and ID should both tie
up.

Breaking out a WM_NOTIFY message in the command map looks like this:

BOOL CMainFrame::OnCmdMsg(UINT nID, int nCode, void* pExtra,
AFX_CMDHANDLERINFO* pHandlerInfo)
{
   TRACE(_T("HIWORD(nCode) = %x\n"), HIWORD(nCode));
   TRACE(_T("LOWORD(nCode) = %x\n"), LOWORD(nCode));
   TRACE(_T("WM_NOTIFY = %x\n"), WM_NOTIFY);
   TRACE(_T("NM_CLICK = %x\n"), NM_CLICK);
   // TODO: Add your specialized code here and/or call the base class
   if ( (HIWORD(nCode) == WM_NOTIFY) && (LOWORD(nCode) ==
LOWORD(NM_CLICK)) )
   {
      CString str;
      str.Format(_T("nID = %ld, nCode = %ld\n"), nID, nCode);
      TRACE(str);
   }
   return CFrameWnd::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);
}

You have to do LOWORD(nCode) == LOWORD(NM_CLICK) because
only the low word of NM_CLICK (defined as 0xFFFFFFFE) is placed into
nCode.

As an aside it appears impossible to write a program where the
mainframe notifies itself
(*VIA STATIC MAP ENTRIES*) as the Mainframe's ID is decided at run-
time.

Well, I said I was trying something arcane out. Now to get back to
looking at RemoteSendMessage API or whatever
it's called.