I want to implement a simple specialized window manager for presentations (not user-controllable) that supports only the following operations:
I don't need any user input, button/titles, ...
What existing window manager should I use as example? There are many little "hello world" window managers, but they usually does not support desktop switching.
You don't need to reimplement the wheel.
openbox will do everything you mention and more besides.
Simply edit the rc.xml to disable the root menu, and re-launch.
Openbox also allows per app setting so that certain applications can open on a particular desktop by default, or with a particular size, or open hidden.
It also supports wildcards in the window selection, so that settings can apply to all windows.
devilspie2 is a window matching utility that can perform actions whenever a window opens.
It is highly hackable and the code is available on github. It will match windows by name/class/etc when they open, and perform actions on them. (including matching all windows and moving them to a different desktop. It will work with most window managers.
Based on the original devilspie which does not have Lua scripting, but is configured using s-exprs instead.
xdotool will also allow you to perform complex actions on windows without hacking any code. It will even fake user input (mouse/kbd) if you need it.