One process at a time

Hi,

I want to have one process of my app running at a time. How can I do this?
OK, that's the basic question. Now I'll give some more details:
I'm making a control panel app. I've kept it pretty basic for testing purpose. So this is the code:

Code:

---

BOOL CALLBACK DlgProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
        switch(uMsg)
        {
        case WM_CLOSE:
                EndDialog(hWnd, 0);
                return true;
        }

        return false;
}

LONG CALLBACK CPlApplet(HWND  hwndCPl,       
                                                UINT  uMsg,       
                                                LONG  lParam1,
                                                LONG  lParam2)
{
        CPLINFO *                CL;

        switch (uMsg) {
        case CPL_INIT:      // first message, sent once
                        return true;
            break;
 
        case CPL_GETCOUNT:  // second message, sent once
            return 1;
 
        case CPL_INQUIRE: // third message, sent once per app
                        CL = (CPLINFO *) lParam2;

                        CL->idIcon        = IDI_MAIN;
                        CL->idInfo        = IDS_INFO;
                        CL->idName        = IDS_NAME;
                       
            break;
 
        case CPL_SELECT:    // applet icon selected
            break;
 
        case CPL_DBLCLK:    // applet icon double-clicked 
                        DialogBox(g_hMod, MAKEINTRESOURCE(IDD_DIALOG1), NULL, DlgProc);
                        break;
                       
        case CPL_STOP:      // sent once per app. before CPL_EXIT
            break;
 
        case CPL_EXIT:    // sent once before FreeLibrary is called
            break;
 
        default:
            break;
    }
        return 0;
}

---

So when it starts, I create a modal dialog box, without a parent. This is what I want (non parent) because then it is displayed in the taskbar. (or is there another way to put it there with a parent) But now if you create multiple instances of it, it kinda works and doesn't work. There's only one instance created (the second call does nothing, I don't know why), but the window doesn't get focus and that's also what I want.
If I give the dialog box a parent it does get focus (but like I said I want it in the task bar).
Is there a way around this?
And another question. I create control panels with "rundll32.exe shell32.dll,Control_RunDLL file.cpl". So there all controlled by rundll, which I guess only opens the control panel app one time, so subsequent calls to the same cpl are ignored?

I hope you could follow it, if not just say so and I'll try again :)

Joren

The way I ensure there is only one copy of my program running, I think that's what you mean, is to call CreateMutex() with a name unique to my application, then a call to GetLastError(). If the application created the mutex, then there are no other instances running, if there were, GetLastError() will return ERROR_ALREADY_EXISTS and I exit.

I have posted code for file mapping to tell if your app is already running, do a search.

If you want your app to appear in the task bar create a window, with a reg. class, and hide it. Or create it with 1x1 dimensions and move it if the user moves your dialog.