auto-gsettings-theme.el

;; The following elisp automates switching my emacs theme between my preferred light and dark themes 
;; based on my system color-scheme preference.

;; Specify light and dark (day and night) themes
(setq cr/day-theme 'modus-operandi
      cr/night-theme 'modus-vivendi)

(defun cr/set-theme-by-gsettings-color-scheme ()
  "Sets the Doom Emacs theme based on the gsettings color-scheme preference"
  (let ((prefer-dark (string= "'prefer-dark'"
                              (string-clean-whitespace (shell-command-to-string "gsettings get org.gnome.desktop.interface color-scheme")))))
    (if prefer-dark
        ;; Only load the theme if its opposite is set
        (when (eq doom-theme cr/day-theme)
          (load-theme cr/night-theme t))
      (when (eq doom-theme cr/night-theme)
        (load-theme cr/day-theme t)))))

;; Cancel any timers running for this function
(cancel-function-timers 'cr/set-theme-by-gsettings-color-scheme)
;; Run function every 3 seconds to update the theme
(run-with-timer 0 3 'cr/set-theme-by-gsettings-color-scheme)