Config: Detect (and warn about) missing fonts

config.org

@@ -724,6 +724,54 @@ aspects are nice, but on others I prefer Fira.
 #+attr_html: :class invertible :alt Screenshot of the fonts within Emacs.
 [[https://tecosaur.com/lfs/emacs-config/screenshots/font-face.png]]
 
+In addition to these fonts, Merriweather is used with =nov.el=, and Alegreya as a
+serifed proportional font used by =mixed-pitch-mode= for =writeroom-mode= with Org
+files.
+
+Because we care about how things look let's add a check to make sure we're told
+if the system doesn't have any of those fonts.
+
+#+name: detect-missing-fonts
+#+begin_src emacs-lisp :tangle no
+(defvar required-fonts '("JetBrainsMono.*" "Overpass" "JuliaMono" "IBM Plex Mono" "Merriweather" "Alegreya"))
+
+(defvar available-fonts
+  (delete-dups (or (font-family-list)
+                   (split-string (shell-command-to-string "fc-list : family")
+                                 "[,\n]"))))
+
+(defvar missing-fonts
+  (delq nil (mapcar
+             (lambda (font)
+               (unless (delq nil (mapcar (lambda (f)
+                                           (string-match-p (format "^%s$" font) f))
+                                         available-fonts))
+                 font))
+             required-fonts)))
+
+(if missing-fonts
+    (pp-to-string
+     `(add-hook! 'doom-init-ui-hook
+        (run-at-time nil nil
+                     (lambda ()
+                       (message "%s missing the following fonts: %s"
+                                (propertize "Warning!" 'face '(bold warning))
+                                (mapconcat (lambda (font)
+                                             (propertize font 'face 'font-lock-variable-name-face))
+                                           ',missing-fonts
+                                           ", "))
+                       (sleep-for 0.5)))))
+  ";; No missing fonts detected")
+#+end_src
+
+#+begin_src emacs-lisp :noweb no-export
+<<detect-missing-fonts()>>
+#+end_src
+
+This way whenever fonts are missing, after Doom's UI has initialised, a warning
+listing the missing fonts should appear for at least half a second.
+
+
 **** Theme and modeline
 ~doom-one~ is nice and all, but I find the ~vibrant~ variant nicer. Oh, and with the
 nice selection doom provides there's no reason for me to want the defaults.
@@ -8063,7 +8111,7 @@ export to a PDF.
                     (propertize "Success!" 'face '(bold success))
                     (propertize "doom sync" 'face 'font-lock-keyword-face)))
          (sleep-for 1))))
-  "")
+  ";; No missing LaTeX packags detected")
 #+end_src
 
 #+begin_src emacs-lisp :noweb no-export