This means that, unlike most other tiling window managers, Penrose is not a
binary that you install on your system. Instead, you use it like a normal
dependency in your own crate for writing your own window manager. Don't worry,
the top level API is well documented and a lot of things will work out of the
box, and if you fancy digging deeper you'll find lots of opportunities to
customise things to your liking.
The docs for penrose are written using mdBook and published to GitHub Pages here. They cover some more general concepts about how to get up and running as opposed to the crate docs on docs.rs which are more aimed at covering the APIs themselves.
The current development version of the docs can be found here.
If you want to have a look at how it all comes together then the examples directory of this repo has several different starting points for you to begin with and my personal set up can be found here. (You almost certainly don't want to use my set up in full but it should serve as a good reference for what a real use case looks like!)
Penrose was born out of my failed attempts to refactor the dwm codebase into
something that I could more easily understand and hack on. While I very much
admire and aim for minimalism in code, I personally feel that it becomes a problem
when your code base starts playing code golf to keep things short for the sake of it.
I certainly won't claim that Penrose has the cleanest code base you've ever seen,
but it should be readible in addition to being fast.
I've also tried my hand at Xmonad in the past. I love the set-ups people can achive with it (this one is a personal favourite) but doing everything in Haskell was a deal breaker for me. I'm sure many people will say the same thing about Rust but then at least I'm giving you some more options!
With Penrose, a simple window manager can be written in about 5 minutes and under
100 lines of code. It will be pretty minimal but each additional feature (such as a
status bar, scratch-pads, custom layouts, dynamic menus...) can be added in as
little as a single line. If the functionality you want isn't available however
then that leads us on to...
dwm patches, qtile lazy APIs, i3 IPC configuration; all of these definitely work but they are not what I'm after. Again, the Xmonad model of companion libraries that you bring in and use as part of writing your own window manager has always felt like the right model for me for extending the window manager.
Penrose provides a set of traits and APIs for extending the minimal core library
that is provided out of the box. By default you essentially get an event loop and
a nice clean split between the "pure" state manipulation APIs for managing your
windows and a "diff and render" layer that interacts with the X server. There are
enough built-in pieces to show how everything works and then some more interesting
/ useful code available in the extensions module.
Parsing a config file and dynamically switching behaviour on the contents adds a
large amount of complexity to the code: not to mention the need for validating
the config file! By default, Penrose is configured statically in your main.rs
and compiled each time you want to make changes (similar to Xmonad and dwm).
There is no built-in support for hot reloading of changes or wrappers around the
main window manager process.
That said, the extensibility of Penrose means that you are definately able to define
your own config file format and parse that as part of your startup, if that is something
you want.
The choice is yours!
There are several places where Penrose makes use of external programs for
utility functionality (reading the user's key-map or spawning a program launcher
for example), but core window manager functionality is contained in the pure state
data structures. This makes it a lot simpler to maintain the codebase and (importantly)
provide a nice API to work with for extending the behaviour of your window manager.
As you might expect, you can definitely write your own extensions that provide
some sort of IPC or client/server style mechanism if you want to mirror the
kinds of things possible in other window managers such as i3 or bspwm, but
that is not going to be supported in the core of the library itself.