Launching application via CreateProcess but cant seem to PeekMessage?

Question

I have a simple (windows) application that launches another application using the CreateProcess function. It then gets the correct hwnd by using EnumWindows and the process id of the newly created process.

After the hwnd has been gained, the 'main loop' of my applications begins. This loop continues until the application started by CreateProcess is no longer running.

Everything works perfectly, until I try to use PeekMessage to peek at the messages being sent to the application I have launched - It seems that no messages at all are being recognized by my application, but the program that was launched (via CreateProcess) is running as normal, doing everything it should..

What I am trying to achieve, is to remove certain messages from being sent to the application, mainly various F-keys (F1, F2..F12 keys), but also, if possible, I would like to change the menu shown in the application (I dont know the technical name for the menu I mean, its the one you see what you click on the application icon in the top right corner) - I want to add a small 'about' option.

If anyone could point out what I am doing wrong within my code, or to a better alternative for stopping certain keypresses from reaching the launched application, I would be very grateful.

Many thanks in advance. :)

Here is the code I currently have:

VOID PerformLaunch(LPWSTR lpAppName, LPTSTR lpCmdLine) {
    STARTUPINFO si;
    PROCESS_INFORMATION pi;
    DWORD dwLoopExitCode = NULL;
    BOOL cpBool = FALSE;
    BOOL finishedLoop = FALSE;
    MSG message = { 0 };

    ZeroMemory(&pi, sizeof(PROCESS_INFORMATION));
    ZeroMemory(&si, sizeof(STARTUPINFO));
    si.cb = sizeof(STARTUPINFO);

    cpBool = CreateProcess(lpAppName, lpCmdLine, NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi);
    if (!cpBool) {
        MessageBox(Game_HWND, L"Could not start process!", L"Error:", MB_OK | MB_ICONERROR);
    }

    //-- Enumerate windows until Game_HWND && Game_Hook are not NULL.
    while (Game_Hook == NULL) {
        EnumWindows(MainEnumGameWindProc, pi.dwProcessId);
    }

    while (!finishedLoop) {
        DWORD dwWC = WaitForSingleObject(pi.hProcess, 0);
        if ((dwWC == WAIT_FAILED) || (dwWC == WAIT_OBJECT_0)|| (dwWC == WAIT_ABANDONED)) {
            DWORD dwExitCode;
            GetExitCodeProcess(pi.hProcess, &dwExitCode);
            CloseHandle(pi.hThread);
            CloseHandle(pi.hProcess);
            dwLoopExitCode = dwExitCode;
            finishedLoop = TRUE;
        }
        else {
            if (PeekMessage(&message, Game_HWND, 0, 0, PM_REMOVE)) {
                TranslateMessage(&message);
                DispatchMessage(&message);
                if (WM_QUIT == message.message) {
                    finishedLoop = TRUE;
                    break;
                }
            }
        }
    }
}

Answer 1

PeekMessage retrieves messages only from the message queue, associated with the its calling thread. Window, which messages you are trying to peek belongs to the different thread, so PeekMessage with its handle will never give you anything. You could either install a hook, or subclass its window procedure.

Answer 2

You can't intercept another message loop like that. Remember, that process will be doing its own message pump - it's not okay for you to be dispatching its messages, and I expect things would go very weird if you do.

The correct way is to set a hook. Use the SetWindowsHookEx function to install a hook on that window.

• Reference for SetWindowsHookEx