If I’m not already very familiar with X, how am I supposed to know that?

The purpose of this code is not to provide a useful WM.

It's to illustrate the minimum, in case you want to play with it and become very familiar with X.

How to draw my own window decorations is exactly what I'd be interested in learning.

Twm, dwm or aewm might be good places to start for that

I would expect their code to be written in ancient C. Probably not an easy read (I once tried to figure out how to use non-bitmap fonts by reading xterm's code - so I could help Paul Mattes in adding my font to x3270, but came out with a headache).

Every line of code has paragraphs of text describing what it does.

We read it, but, still it's hard for someone with little experience with X window managers (fun story - I built a minimal graphical WM for the Apple II that fit in 1K) to have an idea.

Also, I'm a visual thinker - nothing picks my curiosity about software like a nice screenshot.