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Last time , we looked at the confusingly-named WM_ UPDATE­UI­STATE and WM_ CHANGE­UI­STATE messages. But how does the whole indicator thingie get off the ground? The default state for a window is to show all indicators. But as a special trick, the dialog manager will send a WM_...

I always get confused by the WM_ UPDATE­UI­STATE and WM_ CHANGE­UI­STATE messages, and I have to go figure them out each time I need to mess with them. So this time, I'm going to write it down so I don't forget. Because the act of writing it down helps me to remember. It's like...

What does GDI use BITMAP­INFO­HEADER. biXPels­Per­Meter and Set­Bitmap­Dimension­Ex for? Nothing. The BITMAP­INFO­HEADER. biXPels­Per­Meter and BITMAP­INFO­HEADER. biYPels­Per­Meter are completely ignored by GDI when loading...

Today's Little Program takes a rectangular portion of another application and continuously replicates it in its own client area. You might want to do this if you want to monitor a portion of an application like a custom progress bar, and the application doesn't use the Windows 7 taskbar progress indicator...

The original question from the customer was why they couldn't get named file mappings to work at all, but it turns out that the reason is that they were using the full path to the file as the name, even though backslashes have special meaning in file mapping names . Okay, that problem can be solved...

More than once, I'm seen somebody confused by how inline functions work. I have implemented a few inline functions in one of my cpp files, and I want to use it from other cpp files, so I declare them as extern . But sometimes I will get linker error 2019 (unresolved external) for the inline functions...

When you ask a mathematician to come up with a formula to solve a problem, you will get something that looks pretty, but that doesn't mean that it lends itself well to computation. For example, consider the binomial coefficient, traditionally written n C k or C ( n , k ) , and in more modern notation...

Today's Little program shows how to read mouse input from a console program. You might use this if you are writing a console-mode text editor with mouse support, or maybe you want to want to add mouse support to your roguelike game . But I'm not going to implement the game itself. Instead, I'm...

I'll assume that we all know what pidls are and how the shell namespace uses them. That's the prerequisite for today. A simple pidl is an item ID list that refers to a file or directory that may not actually exist. It's a way of playing "what if": "If there were a file or directory at this location...

A customer using Visual Studio wanted to know how to obtain the current value of the x64 RSP register from a C/C++ function. They noted that on the x86, you can drop to inline assembly, and on the ia64, you can use the __getReg intrinsic to retrieve the value of any register. There is no corresponding...

Today's Little Program takes the symbolic name for a shell property and returns a string suitable for display to the end-user, translated into the user's specified display language. #include <windows.h> #include <ole2.h> #include <propsys.h> #include <propkey.h> #include <atlbase...

Adam Rosenfield noted that " those sure are a lot of hoops you have to jump through to solve this unusual problem " of specifying which handles are inherited by a new process. Well, first of all, what's so wrong with that? You have to jump through a lot of hoops when you are in an unusual situation...

Is the Interlocked­Increment function broken? One person seemed to think so. We're finding that the Interlocked­Increment is producing duplicate values. Are there are any know bugs in Interlocked­Increment ? Because of course when something doesn't work, it's because you are...

Here are some strange but legal declarations in C/C++: int typedef a; short unsigned typedef b; By convention, the typedef keyword comes at the beginning of the line, but this is not actually required by the language. The above declarations are equivalent to typedef int a; typedef short unsigned...

Today's Little Program prints the current selection in all open Explorer windows. (This is an alternative to the C++ version that involves a ridiculous amount of typing.) var shellWindows = new ActiveXObject("Shell.Application").Windows(); for (var i = 0; i < shellWindows.Count; i++) { var...

While developing tests, a developer observed erratic behavior with respect to Co­Create­Instance : In my test, I call Co­Create­Instance and it fails with CO_ E_ NOT­INITIALIZED . Fair enough, because my test forgot to call Co­Initialize . But then I went and checked...

Opportunistic locks allow you to be notified when somebody else tries to access a file you have open. This is usually done if you want to use a file provided nobody else wants it. For example, you might be a search indexer that wants to extract information from a file, but if somebody opens the file...

A customer liaison asked whether it was legal to use Set­Parent to create a parent/child relationship between windows which belong to different processes. "If I remember correctly, the documentation for Set­Parent used to contain a stern warning that it is not supported, but that remark does...

Today's Little Program is a managed version of the text-extraction program from several years ago . It turns out that it's pretty easy in managed code because the accessibility folks sat down and wrote a whole framework for you, known as UI Automation . (Some people are under the mistaken impression...

A customer was having trouble with job objects, specifically, the customer found that a Wait­For­Single­Object on a job object was not completing even though all the processes in the job had exited. This is probably the most frustrating part of job objects: A job object does not become...

The Read­File and Write­File functions have a parameter called lp­Number­Of­Byte­Read , which is documented as __out_opt LPDWORD lpNumberOfBytesRead, // or __out_opt LPDWORD lpNumberOfBytesWritten, "Cool," you think. "That parameter is optional, and I can safely...

Suppose you have a TreeView control, and you created an item in it, and you want to move the HTREEITEM to a new parent. How do you do that? You can't, at least not all in one motion. You will have to delete the HTREEITEM and then re-create it in its new location. If you want to move an HTREEITEM...

The IMessage­Filter:: Handle­Incoming­Call method describes the incoming call by means of an INTERFACE­INFO structure: typedef struct tagINTERFACEINFO { LPUNKNOWN pUnk; IID iid; WORD wMethod; } INTERFACEINFO, *LPINTERFACEINFO; The wMethod is a zero-based index of...

Today's Little Program monitors windows as they come and go. When people contemplate doing this, they come up with ideas like installing a WH_CBT hook or a WH_SHELL hook, but one of the major problems with those types of hooks is that they are injected hooks. Injection is bad for a number of reasons...

A source of great consternation is the mysterious -1 return value from Get­Message : If there is an error, the return value is −1. For example, the function fails if hWnd is an invalid window handle or lpMsg is an invalid pointer. That paragraph has caused all sorts of havoc, because...