PRB: MFC Message Handler Not Called with PostThreadMessage()

RESOLUTION

The following code demonstrates how to call PostThreadMessage() in the InitInstance() of the CWinApp-derived class using a single-threaded application. The principle is the same for secondary threads except that the code shown here would be put in your alternate CWinThread-derived class.

Visual C++ 4.2 does support handling messages posted to threads. For more information, see ON_THREAD_MESSAGE in the Visual C++ 4.2 documentation.

NOTE: MFC worker threads do not have a message loop/pump associated with them so you must use a user-interface thread.

Sample Code

/* Compile options needed:

   standard MFC project generated by AppWizard */ 

BOOL CThreadMsgApp::PreTranslateMessage(MSG* pMsg)
{
    // Is it the Message you want?
    // You can use a switch statement but because this is
    // only looking for one message, you can use the if/else
    if (pMsg->message == WM_USER+2268)
    {
        // Call the function to handle this message
   OnReceivedCommand(pMsg->wParam,pMsg->lParam);
        // Tell MFC no more processing is needed
        return TRUE;
    }
    else
        // Call MFC to have it continue processing the message
        return CWinThread::PreTranslateMessage(pMsg);
}

BOOL CThreadMsgApp::InitInstance()
{
    WPARAM wParam;
    LPARAM lParam;
    wParam = MAKEWPARAM(0,0); // We can put whatever we
    lParam = MAKELPARAM(0,0); // want in wParam & lParam

    // Send the user-defined Thread Message
    // m_nThreadID is a member of CWinThread that holds the thread ID
    PostThreadMessage(m_nThreadID, WM_USER+2268, wParam, lParam);

    return TRUE;
}

void CThreadMsgApp::OnReceivedCommand(WPARAM wParam, LPARAM lParam)
{
    // You can do whatever you want in here, this is simply
    // sending output to the debug window
    TRACE0("Received WM_USER+2268!!\n");
}