I have an MFC application that uses an ancient (circa 1999) third-party ActiveX control.
Since upgrading the project from VS2008 to VS2010, I’m having problems…
In the OnSize handler of the parent dialog IsWindow always returns false for the handle returned by control.GetSafeHwnd(), even when GetSafeHwnd() returns a non-NULL value. The rest of the control’s parent dialog is displayed fine, but it doesn’t seem to respond to any input.
I’ve seen this article, but GetSafeHwnd() isn’t returning NULL in this case (after the first time that it is called, which is before the control is instantiated).
The control does cause the trace message “Control wants to be windowless” to be output when it’s loaded. However it also does this when compiled in VS2008, so this may be a red herring. Searching for this message points me to creating a class derived from COleControlSite, and denying the control windowless-ness, but it seems there are no good example of this available, and as I say, it’s not clear that this is really the cause of the problem.
I’ve also found this issue mentioned on MSDN’s VS2010 porting page:
“An ActiveX control compiled by using Visual C++ 6.0, when embedded in
a dialog box in a project developed by using Visual C++ 2010, may
cause your program to assert at run time. In this situation, open the
ATL or MFC project associated with the ActiveX control in Visual C++
2010, and recompile it.. The assert will be in the file occcont.cpp,
on this line in source: ASSERT(IsWindow(pTemp->m_hWnd)).”
I assume that there’s something about VS6-compiled ActiveX controls that causes the window handles to be treated as invalid by the current Win32 implementation of IsWindow. The suggested solution is of course unhelpful as it’s a third-party control, and we can’t recompile it.
Has anyone managed to get around this?
I’ve already found solutions for VS2010 projects not running on Windows 2000, and errors linking to ODBC, but don’t seem to be able to find anything on this one.
Thanks,
Chris
I didn’t find a solution to this in the end – upgraded the controls to a VS2010-compatible version.