C++/VB - CPropertyPage::OnSetActive recursion or how can I extend CTabCtrl?

Asked By tenpoundnot

29-Jan-08 07:19 PM

I have an MFC application that uses PropertyPages and a PropertySheet
within a dialog as part of a GUI.  In addition there are other dialogs on the
screen which contain information that is specific to what is displayed on
each property page.  I've overriden the OnSetActive handler of the five
property pages I have so that I can update the other dialogs and make some
adjustments to what is displayed on the property page.  OnSetActive makes
some MFC calls including Wnd::RedrawWindow on a dialog within the property
page, and CWnd::ShowWindow on the dialogs outside the property page.  I only
call SetActivePage once in the entire application: on initialization.  I am
completely sure that SetActivePage is not called within OnSetActive.

I am using Visual C++ 2003 (version 7.1.6030).

My problem is that if I subject the property pages to some moderate stress
testing (i.e., lots of clicking) then sometimes the MFC calls within
OnSetActive will cause OnSetActive to be called again (recursively) by the
same thread, which is the main thread.  Realizing this I created a flag that
causes OnSetActive to bail out if recursion is detected.  I've observed that
this recursion always happens a multiple of 5 times, which is interesting
because I have 5 property pages / tabs.  It does not necessarily happen on
each tab, and it sometimes happens on tabs that weren't clicked, and
sometimes on tabs that were.  The strangest thing about this behaviour is
that the call stack does not show the recursion because it terminates in
Windows's OS dlls.  For this reason I don't know what part of MFC is causing
these effects.

Has anyone ever heard of or seen something like this?

I think that the problem may be related to some kind of latency between
the moment the CTabCtrl object within the property sheet is clicked and the
moment

OnSetActive is invoked.  If The user manages to click another tab in between
these two points in time, Windows's message queue will pick up the second
CTabCtrl click when it is handling my MFC ShowWindow and RedrawWindow calls
and then somehow get confused and cause 5 OnSetActive handlers to be invoked.

The easiest solution would be to somehow trap the CTabCtrl click, display
a WaitCursor and stop the user from clicking anything else until the
OnSetActive method has finished.  I don't know how to do this.  I've tried
overriding some of the property sheets methods but none get invoked.  I've
tried overriding the property page's OnKillActive, but the result was
unhelpful.  What I would really like is some way of extending the CTabCtrl
class and then overriding some of its event handlers, but it's unclear to me
how the CTabCtrl class is instantiated and what I would need to do.

Does anyone know of a way of overriding the CTabCtrl class that is used
together with a property page?  Does anyone know of any other way of trapping
when the CTabCtrl object is clicked?

Any insight would be appreciated.

30-Jan-08 02:54 AM

I'd try removing aspects of the code you have in the OnSetActive
handler to see which (if any) is allowing the recursion to occur. I'm
guessing that something you call is allowing another message loop to
run and that's then processing the mouse clicks and giving rise to the
issue.

Dave