Re: Debug ASSERT when CDialog::DoModal() from PreTranslateMessage()

From:
"Mark Salsbery [MVP]" <MarkSalsbery[MVP]@newsgroup.nospam>
Newsgroups:
microsoft.public.vc.mfc
Date:
Wed, 6 Feb 2008 12:08:14 -0800
Message-ID:
<929075D2-7EF7-4E8E-9F48-2BCD3708D9E3@microsoft.com>
"PeteOlcott" <PeteOlcott@gmail.com> wrote in message
news:33771165-f298-4c98-9972-c3525ae2bb0b@d70g2000hsb.googlegroups.com...

On Feb 6, 12:38 pm, "Doug Harrison [MVP]" <d...@mvps.org> wrote:

On Wed, 6 Feb 2008 10:01:42 -0800 (PST), PeteOlcott
<PeteOlc...@gmail.com>
wrote:

I am creating and invoking a DialogBox within the
PreTranslateMessage() hander of another DialogBox. If I comment out
the DoModal() invocation, the exception is not thrown. If I leave it
in, the Debug Assertion Failed! message appears. The ASSERT statement
is located within MS Windows void CWnd::AssertValid(). What is going
on here? What can I do to make it work correctly?


Doing complicated stuff like showing a secondary dialog inside
PreTranslateMessage is not the best practice in the world, but I see no
reason it shouldn't work. Your best course of action is probably to take
a
cue from the function name and translate the message into a WM_COMMAND of
your choosing, which you post to yourself and receive in an ordinary
command handler function. This may well not solve your problem, and in
case
it doesn't, and for future reference when dealing with assertions, here
are
the questions that come to mind.

What *exactly* does the assertion say? (They're usually at least somewhat
descriptive and come with filename and line number info - for others to
make sense of the latter, you need to state your compiler version.)


Debug Assertion Failed!
My Program's FullPathName
File: wincore.cpp
Line: 886


You have the source code....what is causing the assertion at that line?

Mark

--
Mark Salsbery
Microsoft MVP - Visual C++

When does the assertion occur, before, during, or after DoModal? If
after,
are you returning true from PreTranslateMessage, or are you allowing the
dialog to continue processing the message?


The Debug Assertion occurs after the original PreTranslateMessage() is
called, it looks like it occurs within this function.

When do you call DoModal, before or after the original dialog is
displayed?
(More to the point, before or after OnInitDialog?)


After InitDialog()

What message are you handling in PreTranslateMessage?


#define SPECIAL_MESSAGE WM_USER + 1

Which CWnd is the assertion referring to? The "parent" dialog, or the
newly
created one?


It looks like it is the parent DialogBox

Can you invoke the secondary dialog successfully from an ordinary command
message handler, such as that for a button control? (If the answer is no,
you can be certain the PreTranslateMessage issue is a red herring.)


Yes this has been tested and it works fine. I Invoked another
DialogBox from a button on the original DialogBox.

--
Doug Harrison
Visual C++ MVP

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