The Old New Thing
Practical development throughout the evolution of Windows.
Latest posts
C++ corner case: You can implement pure virtual functions in the base class
In our discussion , we saw that you can declare a pure virtual function with the syntax, and if you try to call one of these functions from the base class, you will get the dreaded R6025 - pure virtual function call error. In that article, I wrote that a pure virtual function is "a method which is declared by the base class, but for which no implementation is provided." That statement is false. You can provide an implementation for a pure virtual method in C++. "That's crazy talk," I hear you say. Okay, let's start talking crazy: What happens when the function constructs a ? Trick question, becau...
Happy 110th birthday, Professor Alyea
Professor Hubert Alyea would be 110 years old today, if he were still among us. (He passed away in 1996 at the ripe age of 93.) LIFE magazine called him the science teacher you wish you had for his engaging (and often explosive) chemistry demonstrations. He was called an "international grand master of lecture demonstrations" by Bassam Shakhashiri, noted chemist and author of several books on chemical demonstrations. I had the immense good fortune to attend one of his lectures. As he prepared his equipment, he casually popped a piece of dry ice in his mouth. (DO NOT TRY THIS AT HOME.) You can see a demonstrat...
How do I find out what size the window manager would have chosen for my window?
We saw some time ago how the window manager decides where to place a newly-created window if you pass the values when creating the window. But what if you want to filter the values first? If you pass an explicit upper left corner but pass for the width and height, then the bottom right corner will be down near the bottom right corner of the screen. Given that your code is buggy, is there a way I can ask how big you would have made the window, so I can go in and fix your mistake? If I try to resize it after the fact, there's an ugly flicker. I'm kind of disgusted that something this simple still doesn't work ...
Using the TAB key to navigate in non-dialogs, redux
You want to use the TAB key to navigate through a non-dialog, so you call in your message loop, but it doesn't work! The problem here is that you are passing the wrong window handle to . The first parameter to is the dialog-like window you want to be able to navigate through. But the code above passes the window that received the message, so you are basically telling the control to do TAB navigation within itself. And naturally, the result of that is that focus stays where it is, because if you ask a button, "Hey, could you move to your next tab stop?" the button is going to say, "Dude, I'm the only tab st...
I wrote my thesis on an airplane, for heaven's sake
As I wrote today's story, I recalled that I wrote the bulk of my thesis on an airplane. In longhand. Microsoft flew me out for an interview, so I had to endure two cross-country plane trips. I scheduled the interview on a Monday so that I would miss only one day of class, and among the things I brought with me was a notepad, which started the trip blank. I wasn't sure why I brought it, but I was sure it'd come in handy. And then I realized that I had a lot of time to kill, what with spare moments on the ground, in the air, back on the ground, waiting for my next interview, whatever. And during that time, I wro...
I wrote FAT on an airplane, for heaven’s sake
When you wrote code for 16-bit Windows, one of the things you spent time doing as part of performance tuning was deciding which functions should be grouped together in which segments. Code in 16-bit Windows executed out of code segments, each of which could be up to 64KB in size. When a code segment was loaded from disk, the entire segment was loaded, and when it was discarded, the entire segment was discarded. This meant that you could affect your application's performance in significant ways by choosing which functions go in which segments. For example, it was to your advantage to keep functions that are call...
But instead, they decided to build the Great Wheel
I dreamed that Seattle was building its own version of the Eiffel Tower. Just like the original, except that it was also a thrill ride similar to Round Up but you are seated. It turns out that the city of Seattle accepted my subconscious's instructions to replicate another city's famous landmark, but the message wasn't received loud and clear. Instead of making an Eiffel Tower knock-off, we decided to make a London Eye knock-off.
Printing the contents of the clipboard as text to stdout
The takes its stdin and puts it on the clipboard. But how do you get it out? That's today's Little Program. (I guess we could call it .) Okay, what do we have here? We open the clipboard and try to get the Unicode text on it. We then look for the null terminator within the first 0x10000000 bytes. Why do I stop at 256MB? Because I'm lazy and this lets me avoid worrying about integer overflow. This is a Little Program, remember. If you pass the command line switch, then the output is printed to stdout as the Unicode string itself. If you pass the command line switch, then the output is converted to AN...
What's the difference between CopyIcon and DuplicateIcon?
There are two functions that can be used to create one icon that is identical to another. One of them is . The other is . What's the difference? There isn't any difference. Both functions clone an icon. In fact, their implementations are basically line-for-line identical. Originally, there was just one function to clone an icon: . Windows 3.0 introduced Program Manager, and the developers of Program Manager wrote their own function called . Why? I have no idea. My guess is that they didn't realize that such a function already existed, so they inadvertently reinvented the wheel. Windows NT 3.1 came a...