Re: Debug ASSERT when CDialog::DoModal() from PreTranslateMessage()
On Wed, 6 Feb 2008 10:01:42 -0800 (PST), PeteOlcott <PeteOlcott@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.)
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?
When do you call DoModal, before or after the original dialog is displayed?
(More to the point, before or after OnInitDialog?)
What message are you handling in PreTranslateMessage?
Which CWnd is the assertion referring to? The "parent" dialog, or the newly
created one?
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.)
--
Doug Harrison
Visual C++ MVP