feat(nixos): Add initial NixOS & EXWM configuration

Adds configuratio for using Emacs as a window manager, because clear
that is an extremely sane thing to do.

init/nixos.el

@@ -0,0 +1,57 @@
+;; Configure additional settings if this is one of my NixOS machines
+;; (i.e. if ExWM is required)
+;; -*- lexical-binding: t; -*-
+
+(require 's)
+(require 'f)
+
+(defvar is-nixos
+  (let ((os-f "/etc/os-release"))
+    (s-contains?
+     "NixOS" (if (f-file? os-f) (f-read os-f)))))
+
+(if is-nixos
+    (progn
+      (message "Running on NixOS, configuring ExWM.")
+      (require 'exwm)
+      (require 'exwm-config)
+
+      ;; Start with one workspace (make more as needed)
+      (setq exwm-workspace-number 1)
+      ;; Make class name the buffer name
+      (add-hook 'exwm-update-class-hook
+                (lambda ()
+                  (exwm-workspace-rename-buffer exwm-class-name)))
+
+      ;; 's-r': Reset
+      (exwm-input-set-key (kbd "s-r") #'exwm-reset)
+      ;; 's-w': Switch workspace
+      (exwm-input-set-key (kbd "s-w") #'exwm-workspace-switch)
+      ;; 's-N': Switch to certain workspace
+      (dotimes (i 10)
+        (exwm-input-set-key (kbd (format "s-%d" i))
+                            `(lambda ()
+                               (interactive)
+                               (exwm-workspace-switch-create ,i))))
+
+      ;; Launch applications with completion (dmenu style!)
+      (exwm-input-set-key (kbd "s-p") #'helm-run-external-command)
+
+      ;; Line-editing shortcuts
+      (exwm-input-set-simulation-keys
+       '(([?\C-b] . left)
+         ([?\C-f] . right)
+         ([?\C-p] . up)
+         ([?\C-n] . down)
+         ([?\C-a] . home)
+         ([?\C-e] . end)
+         ([?\M-v] . prior)
+         ([?\C-v] . next)
+         ([?\C-d] . delete)
+         ([?\C-k] . (S-end delete))))
+
+      ;; Enable EXWM
+      (exwm-enable)
+      (fringe-mode 1)))
+
+(provide 'nixos)