The Old New Thing

The easy way out is to just answer the question: What is the current Explorer window looking at?

November 26, 2010 Nov 26, 2010 11/26/10

Raymond Chen

A customer had the following question: We have an application which copies and pastes files. Our problem is that we want to paste the files into the folder which corresponds to the currently active Windows Explorer window. Right now, we're using , but we find this method unsatisfactory because we want to replace Explorer's default file copy ...

Consequences of using variables declared __declspec(thread)

November 22, 2010 Nov 22, 2010 11/22/10

Raymond Chen

As a prerequisite, I am going to assume that you understand how TLS works, and in particular how variables work. There's a quite thorough treatise on the subject by Ken Johnson (better known as Skywing), who comments quite frequently on this site. The series starts here and continues for a total of 8 installments, ending here. That last ...

One possible reason why ShellExecute returns SE_ERR_ACCESSDENIED and ShellExecuteEx returns ERROR_ACCESS_DENIED

November 18, 2010 Nov 18, 2010 11/18/10

Raymond Chen

(The strangely-phrased subject line is for search engine optimization.) A customer reported that when they called , the function sometimes fails with , depending on what they are trying to execute. (If they had tried they would have gotten the error .) After a good amount of back-and-forth examing file type registrations, a member of the ...

Why is there an LVN_ODSTATECHANGED notification when there's already a perfectly good LVN_ITEMCHANGED notification?

October 28, 2010 Oct 28, 2010 10/28/10

Raymond Chen

If you work with owner-data listviews, you take the responsibility for managing the data associated with each item in the list view. The list view control itself only knows how many items there are; when it needs information about an item, it asks you for it. It's the fancy name for a "virtual list view" control. When you use an ownerdata ...

When you call a function, your code doesn't resume execution until that function returns

October 25, 2010 Oct 25, 2010 10/25/10

Raymond Chen

Consider this code fragment: When calls , and has not yet returned, does continue executing? Does get called before returns? No, it does not. The basic structure of the C/C++ language imposes sequential execution. Control does not return to the function until returns control, either by reaching the end of the function or by an ...

How do I get the dimensions of a cursor or icon?

October 20, 2010 Oct 20, 2010 10/20/10

Raymond Chen

Given a or a , how do you get the dimensions of the icon or cursor? The function gets you most of the way there, returning you an structure which gives you the mask and color bitmaps (and the hotspot, if a cursor). You can then use the function to get the attributes of the bitmap. And then here's the tricky part: You have to massage the...

What does the FOF_NOCOPYSECURITYATTRIBS flag really do (or not do)?

October 15, 2010 Oct 15, 2010 10/15/10

Raymond Chen

In the old days, the shell copy engine didn't pay attention to ACLs. It just let the file system do whatever the default file system behavior was. The result was something like this: Perfectly logical, right? If a new file is created, then the security attributes are inherited from the container. If an existing file is moved, then its ...

The memcmp function reports the result of the comparison at the point of the first difference, but it can still read past that point

October 14, 2010 Oct 14, 2010 10/14/10

Raymond Chen

This story originally involved a more complex data structure, but that would have required too much explaining (with relatively little benefit since the data structure was not related to the moral of the story), so I'm going to retell it with double null-terminated strings as the data structure instead. Consider the following code to ...

How do I get the color depth of the screen?

October 13, 2010 Oct 13, 2010 10/13/10

Raymond Chen

How do I get the color depth of the screen? This question already makes an assumption that isn't always true, but we'll answer the question first, then discuss why the answer is wrong. If you have a device context for the screen, you can query the color depth with a simple arithmetic calculation: Now that you have the answer, I'll ...

Why does TaskDialog return immediately without showing a dialog? – Answer

October 8, 2010 Oct 8, 2010 10/8/10

Raymond Chen

Last time, I left an exercise to determine why the function was not actually displaying anything. The problem had nothing to do with an invalid window handle parameter and had all to do with original window being destroyed. My psychic powers told me that the window's handler called . As we learned some time ago, quit messages cause modal...