The Old New Thing

Code - The Old New Thing

How do I override the default icon selection algorithm?

October 5, 2012 Oct 5, 2012 10/5/12
Raymond Chen
The usual way of loading an icon from a resource is to use the or function and letting the window manager's icon selection algorithm decide which image to use based on the images available in the icon, the desired icon size, and the current color depth. A customer wanted to override that algorithm, because the window manager uses the ...

Why aren't environment variables being expanded in my RGS file?

September 27, 2012 Sep 27, 2012 09/27/12
Raymond Chen
A customer was having trouble with their RGS file. I want to include the below line in a .rgs file: When I do this, registering of the dll fails with 80002009. Any help? If I change it to then the registration succeeds (but of course now contains a hard-coded path). A common problem people have when asking a question is assuming ...

Sabotaging yourself: Closing a handle and then using it

September 26, 2012 Sep 26, 2012 09/26/12
Raymond Chen
A customer reported a problem with the function: I have a DLL with an function and an function. The code goes like this: Under certain conditions, the function is called twice, and the function is correspondingly called twice. Under these conditions, if I run the code on a single-processor system with hyperthreading disabled, then ...

How can I implement SAFEARRAY.ToString() without going insane?

September 21, 2012 Sep 21, 2012 09/21/12
Raymond Chen
A colleague needed some help with manipulating s. I have some generic code to execute WMI queries and store the result as strings. Normally, does the work, but doesn't know how to convert arrays (e.g. ). And there doesn't seem to be an easy way to convert the array element-by-element because expects a pointer to an object of the ...

How do I invoke a verb on an IShellItemArray?

September 20, 2012 Sep 20, 2012 09/20/12
Raymond Chen
A customer wanted to invoke a command on multiple items at once. I have an , and I want to invoke a verb with that array as the parameter. I know that I can invoke a verb on a single by the code below, but how do I pass an entire array? The function invokes the command by extracting the pidl, then asking to invoke the command on the...

How do you deal with an input stream that may or may not contain Unicode data?

September 17, 2012 Sep 17, 2012 09/17/12
Raymond Chen
Dewi Morgan reinterpreted a question from a Suggestion Box of times past as "How do you deal with an input stream that may or may not contain Unicode data?" A related question from Dave wondered how applications that use to store data could ensure that the data is interpreted in the same code page by the recipient. "If I send a .txt file to ...

IShellFolder::BindToObject is a high-traffic method; don't do any heavy lifting

September 14, 2012 Sep 14, 2012 09/14/12
Raymond Chen
A customer observed that once the user visited their shell extension, Explorer ran really slowly. (Actually, it took a while just to get to this point, but I'll skip the early investigations because they aren't relevant to the story.) Some investigation showed that Explorer's tree view was calling into the shell extension, which was in turn ...

When you transfer control across stack frames, all the frames in between need to be in on the joke

September 10, 2012 Sep 10, 2012 09/10/12
Raymond Chen
Chris Hill suggests discussing the use of structured exception handling as it relates to the window manager, and specifically the implications for applications which raise exceptions from a callback. If you plan on raising an exception and handling it in a function higher up the stack, all the stack frames in between need to be be in on ...