Re: Run App only once

I want my app open only once. If a user opens a second instance I would
like to AfxMessageBox the user and make the original instance 'flash', then
close the second instance.

I have tried calling the following code in my App::InitInstance() - check
if this is the first instance and if it is, then register app, but it
doesn't work:

bool CCircaApp::FirstInstance()
{
CWnd* pWndMainFrm = (CMainFrame*) CWnd::FindWindow(_T("Circa_Main"),
NULL);

// Determine if another window with your class name exists (not this one
though!)...
if ((pWndMainFrm != NULL) && (pWndMainFrm != GetMainWnd()))
{
 CWnd* pWndChild = pWndMainFrm->GetLastActivePopup();

 AfxMessageBox("Another instance of Circa is already open");

 // Can't just bring the main window back because it doesn't
 // restore any tools that are also minimised, so just flash the
 // toolbar, so the user finds it again.
 pWndChild->FlashWindow(TRUE);

 // and you are done activating the previous one.
 return false;
}
// First instance. Proceed as normal.
else
 return true;
}

bool CCircaApp::RegisterApp()
{
// Register your unique class name that you wish to use
WNDCLASS wndcls;
memset(&wndcls, 0, sizeof(WNDCLASS)); // start with NULL defaults
wndcls.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;
wndcls.lpfnWndProc = ::DefWindowProc;
wndcls.hInstance = AfxGetInstanceHandle();
wndcls.hIcon = LoadIcon(IDR_MAINFRAME); // or load a different icon
wndcls.hCursor = LoadCursor( IDC_ARROW );
wndcls.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wndcls.lpszMenuName = NULL;
// Specify your own class name for using FindWindow later
wndcls.lpszClassName = _T("Circa_Main");
// Register the new class and exit if it fails
if(!AfxRegisterClass(&wndcls))
{
 TRACE("Class Registration Failed\n");
 return false;
}

return true;
}