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Another type of higher-order enumeration is composition, where one enumerator actually combines the results of multiple enumerators. (Everybody knows about derivation, but composition is another powerful concept in object-oriented programming. We've seen it before when building context menus.) In a producer-driven enumerator, you would implemen...

One type of higher-order enumeration is filtering, where one enumerator takes the output of another enumerator and removes some elements. In a producer-driven enumerator, you would implement filtering by substituting a new callback function that responds to callbacks on behalf of the client for items that should be filtered, and forwarding callb...

As we discovered in the previous two entries [second], the problem with enumeration is that somebody always loses. Now we will use fibers to fight back. Before you decide to use fibers in your programs, make sure to read the dire warnings at the end of this article. My goal here is to show one use of fibers, not to say that fibers are the answer ...

Last time, we looked at how a directory tree enumerator function would have been written if the person writing the enumerator (the producer) got to write the spec. Now let's look at what it would look like if the person consuming the enumerator wrote the spec: #include <windows.h> #include <shlwapi.h> #include <stdio.h> #includ...

The COM model for enumeration (enumeration objects) is biased towards making life easy for the consumer and hard for the producer. The enumeration object (producer) needs to be structured as a state machine, which can be quite onerous for complicated enumerators, for example, tree walking or composite enumeration. On the other hand, the callback...

When you set environment variables with the System control panel, the and variables are silently converted to their short file name equivalents (if possible). Why is that? For compatibility, of course. It is very common for batch files to assume that the paths referred to by the and environment variables do not contain any embedded space...

The CreateTimerQueueTimer function allows you to create one-shot timers by passing the WT_EXECUTEONLYONCE flag. The documentation says that you need to call the DeleteTimerQueueTimer function when you no longer need the timer. Why do you need to clean up one-shot timers? To answer this, I would like to introduce you to one of my favorite rhe...

Still more ways of saying the same thing. Why so many? Because each was invented by different people at different times to solve different problems. BOOL is the oldest one. Its definition is simply typedef int BOOL; The C programming language uses "int" as its boolean type, and Windows 1.0 was written back when C was the cool languag...

It's the other half of the missing IMarshal.

Creating that drag image was a bit of work. Fortunately, the listview control is willing to do some of the work for you. Throw away the OnLButtonDown function (and the HANDLE_MESSAGE that goes with it). Instead, we'll make the listview do all our presentation for us. BOOL OnCreate(HWND hwnd, LPCREATESTRUCT lpcs) { g_hwndChild = CreateWindow(...