miniblog

Screensavers

Back when I was a child, I was fascinated by screensavers, now a relic from the past. Imagine my surprise when I discovered (just recently, I must admit) that behind the scenes, a .scr file is just a Windows executable!

Well, that means that I could create my own screensaver, right? I just need to create a GUI app that renders fullscreen. Technically yes, but it needs to support some arguments so it can play nicely with the Control Panel configuration utility, namely /s for fullscreen mode, /c for configuration, and /p for the preview mode.
We can ignore the /s if we make the app render on fullscreen by default. To keep things simple, we only show a message dialog for /c indicating that we don't support configuration. /p is a little more complicated, as it involves getting a window handle and doing some wiring to make it work (that is, showing a preview of the screensaver on the Control Panel utility).
The next step is to decide what to render. We can try to replicate the now-missing Starfield screensaver.

This effect is based on projecting the 3D coordinates of each star onto a 2D plane using the following equations, while decreasing the Z value (the star's depth) on each iteration:

star_x = star.X / star.Z + SCREEN_WIDTH / 2;
star_y = star.Y / star.Z + SCREEN_HEIGHT / 2;

Quine

A quine is a program that outputs its own source code. There is something magical (or perhaps unsettling) about a program creating itself. Here is one in C#:

var s = """
var s = ""{1}
{0}
""{1};
System.Console.WriteLine(string.Format(s, s, (char)34));
""";
System.Console.WriteLine(string.Format(s, s, (char)34));

On naming

Naming is the eternal struggle of every software developer. Naming is hard, really hard, and not only for variables, methods, or classes, but also for processes and methodologies. This week, I spent more time in meetings than needed just to explain an internal process to our teams, simply because a poor choice of name was causing an uproar among departments. It turns out that knowing the true name of a thing is rarer than we think. Next time, think twice before sticking a name on something.

TIL: Quirkiness of C|C++

Digraphs! A legacy of C, inherited by C++, that, back in the day, was useful for writing some correct, although pretty obscure code due to some constraints on characters like '# { } [ ]'. Let's take a look at the following hello, world! program:

%:include<iostream>

using namespace std;

int main()
<%
    cout << "hello, world!" << std::endl;
    return 0;
%>

Pretty cool, right? Trigraphs also exist but they are disabled on most compilers by default. Please don't use them in production code.