Re: Run App only once

From:
David Wilkinson <no-reply@effisols.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
Mon, 16 Apr 2007 10:34:12 -0500
Message-ID:
<eADuqQDgHHA.2432@TK2MSFTNGP03.phx.gbl>
GT wrote:

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:iim223tffvs0pq5l6ntmr35438p3ol24k2@4ax.com...

From the OP

// 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);


Looks to me like an attempt to flash the window...

What is even weirder is that the OP casts the window to a CMainFrame*, and
why, exactly, a
window in some other process should be cast to a type in the current
process totally
escapes me.


This wasn't my code, just lifted from somewhere else, but casting the main
window to be a CMainFrame seems very logical because that's what type it
is - its another instance of the same app, so therefore is the same class!


GT:

But you are accesing it via the OS, which knows nothing about CMainFrame
(or C++ for that matter). The OS ::FindWindow() returns an HWND, for
which CWnd::FindWindow() creates a temporary CWnd object. But it is not
a CMainFrame.

If you were to use dynamic_cast then you would find the cast would fail.
And if you use C-style cast and try to call some CMainFrame member
function like GetActiveDocument() then your code will crash.

In this situation MFC is not helping any; I would just use
::FindWindow() and ::GetLastActivePopup() from the SDK.

--
David Wilkinson
Visual C++ MVP

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