GUI_APP_MAIN
{
	LoginWindow login_window;

  	if (login_window.Run() != IDOK)
	{
                // The user click "Cancel" or "System close" button. So, we should finish app execution here.
                // I strongly encourage to use notation from 20 GUI Tutorial with Acceptor and Rejector.
                return;
	}
        
        // We should obtain information about the user somehow...
        // Store credentials when user press "Enter" or click on "OK" button in login screen...
        Credentials credentials = login_window.GetCrdentials(); 
        MainWindow(credentials).Run(); // <- Run main with authenticated user
}

// In any case there is no need for global variables, which in most cases are not optimal and cause bugs.