PRB: Event Firing Changes in MFC May Break Some Containers (157970)
The information in this article applies to:
- Microsoft Visual C++, 32-bit Enterprise Edition 4.2
- Microsoft Visual C++, 32-bit Professional Edition 4.2
This article was previously published under Q157970 SYMPTOMS
ActiveX Control containers implemented with Borland Delphi (and possibly
other containers as well) may not see events fired by ActiveX Controls
created with MFC version 4.2. The same container may have been able to
handle events fired by a version of the same control created with MFC 4.1
or earlier.
CAUSE
The problem is related to a change made in MFC 4.2's implementation of the
IConnectionPoint::Advise method. In MFC 4.1, the framework does a
QueryInterface on the passed in IUnknown specifying the GUID of the default
event set of the control.
In MFC 4.2, the framework was changed to do a QueryInterface on the passed
in IUnknown for IDispatch. Failing that, it queries for the event set
interface.
The change made to MFC 4.2 may make some containers unable to handle the
events fired by the control. The problem is usually related to the way the
container has implemented its control container support.
RESOLUTION
This problem has been addressed with the Visual C++ 4.2 patch. With this
patch, MFC's implementation of IConnectionPoint::Advise has been changed
back to doing an initial QueryInterface on the passed in IUnknown
specifying the GUID of the default event set of the control. Failing that,
it queries for IDispatch.
STATUS
This behavior is by design.
REFERENCES
For information on how to obtain the Visual C++ 4.2 patch, please see the
following article in the Microsoft Knowledge Base:
156934 PATCH: Visual C++ 4.2b Patch
| Modification Type: | Major | Last Reviewed: | 10/17/2003 |
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| Keywords: | kb3rdparty kbActivexEvents kbContainer kbCtrl kbfix kbprb KB157970 |
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