The Old New Thing

What happens if I call KillTimer with a NULL hwnd?

May 31, 2012 May 31, 2012 05/31/12

Raymond Chen

A customer discovered a bug in their code and wanted some information on how serious it was, so they could assess how urgently they need to issue a fix. We have code that calls with a valid window handle, but then we destroy the window before we get around to calling . When we finally do call , we do so with a window handle. The calls are ...

What does a STATUS_OBJECT_TYPE_MISMATCH exception in LeaveCriticalSection mean?

May 30, 2012 May 30, 2012 05/30/12

Raymond Chen

It means the same thing as a exception...

If my window hosts multiple windowless ActiveX controls, which one do I call IOleInPlaceActiveObject::TranslateAccelerator and IOleInPlaceObjectWindowless::OnWindowMessage on?

May 28, 2012 May 28, 2012 05/28/12

Raymond Chen

Commenter Farproc asks how one goes about hosting two windowless ActiveX controls in a single window. In particular, "none of the documentation explains how to choose which control to send and on?" Actually, the documentation does say. The documentation for says, "Active in-place objects must always be given the first chance at ...

The extern "C" specifier disables C++ mangling, but that doesn't mean it disables mangling

May 25, 2012 May 25, 2012 05/25/12

Raymond Chen

The MSDN documentation on dllexport contains the following enigmatic paragraph, or at least did at the time I wrote this article: dllexport of a C++ function will expose the function with C++ name mangling. If C++ name mangling is not desired, either use a .def file (EXPORTS keyword) or declare the function as extern "C". I've seen this ...

How do I prevent unchecked checkboxes in my listview control from disappearing?

May 24, 2012 May 24, 2012 05/24/12

Raymond Chen

A customer asked, "I have a listview control in report view with the extended style. I noticed that unchecked checkboxes are not visible until I hover over the corresponding item. Is it possible to get the checkboxes to be visible all the time?" I was kind of puzzled by this question because the default behavior of the list view control is ...

GUIDs are designed to be unique, not random

May 23, 2012 May 23, 2012 05/23/12

Raymond Chen

A customer liaison asked, "My customer is looking for information on the GUID generation algorithm. They need to select N items randomly from a pool of M (jury selection), and their proposed algorithm is to assign each item a GUID, then sort the items by GUID and take the first N." (I've seen similar questions regarding using ...