Re: CPropertySheet::PreTranslateMessage in VS2005

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 20 Jul 2006 09:58:04 -0500

Message-ID:

<ps5vb2lgkc3mjphkmhgc4rhbjuoiepaam4@4ax.com>

On Thu, 20 Jul 2006 05:56:02 -0700, juan@msdnCompany.com
<juan@newsgroup.nospam> wrote:

I have converted over my MFC application from VS2003 to VS2005. I was
getting some inconsistent crashing due to a change made in the MFC library to
the CPropertySheet::PreTranslateMessage method. Added to the method was the
following code

    if (NULL == PropSheet_GetCurrentPageHwnd(m_hWnd))
    {
        DestroyWindow();
        return TRUE;
    }

I think the code was added for modeless windows, but it caused my modal
sheet to crash, because it was being destroyed behind my back. I overrode
the method to work around it, but thought I would mention it if anyone else
happened to have the problem.

How to reproduce:
I have a property sheet that on the first page it is filling a grid in
OnInitDialog. Now there are cases when the grid cannot be filled and the
user is presented with another property sheet during the fill. The
additional modal property sheet will get information from the user that will
be used by the grid to complete the fill. Now all this by itself will not
cause the window to be destroyed, BUT if the fill takes a while AND the user
switches focus to a different application window, then the change in the
pretranslate method will cause my original property sheet to be destroyed. I
played with using different parent handles for the sheets and that did not
fix the problem either.

You could probably fix this problem by failing the OnInitDialog and posting
a message to yourself to show the second property sheet or otherwise
indicating to the creator of the first one that you need to show it. I
think what's happening is that you're entering a message loop when you show
the second property sheet, and switching away from your app is causing the
first one to receive posted messages (the only kind that go through
PreTranslateMessage, such as mouse and keyboard) while it's stuck in
OnInitDialog and its initialization is incomplete. As much as possible, I'd
try to let OnInitDialog and similar handlers run their course without
interrupting their execution with new dialog boxes or property sheets.

--
Doug Harrison
Visual C++ MVP