C / C++ / MFC

/*  This function is called by the Windows function DispatchMessage()  */

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int wWidth, wHeight;
    int bWidth, bHeight;
    RECT btnRect;
    HWND btnHwnd;
    switch (message)                  /* handle the messages */
    {
        case WM_DESTROY:
            PostQuitMessage (0);       /* send a WM_QUIT to the message queue */
            break;

        case WM_SIZE:
            // get size of the parent window's client area
            wWidth = LOWORD(lParam);
            wHeight = HIWORD(lParam);

            //  get RECT of the button (in parent's client coords)
            btnHwnd = GetDlgItem(hwnd, IDC_BUTTON1);
            GetWindowRect(btnHwnd, &btnRect);

            // determine it's dimensions
            bWidth = btnRect.right - btnRect.left;
            bHeight = btnRect.bottom - btnRect.top;

            // move it so that it retains its width and height, and is centered on the parent window.
            SetWindowPos(btnHwnd, HWND_TOP, (wWidth-bWidth)/2, (wHeight-bHeight)/2, bWidth, bHeight, SWP_SHOWWINDOW);
            break;

        default:                      /* for messages that we don't deal with */
            return DefWindowProc (hwnd, message, wParam, lParam);
    }

    return 0;
}

Shy Agam wrote:

But how do I go about making my DLL able to talk with my app when used by another external application?

Cedric Moonen wrote:

However, if you explicitely load your dll (by using LoadLibrary), you can place it anywhere you want and specify the path of the dll in the call to LoadLibrary.