Quick hack for cycling themes in Emacs

theme-cycling.el

;; Theme cycling.
;; NOTE: themes have to exist somewhere on disk, e.g in ~/.emacs.d/themes/
;; Set it with (setq custom-theme-directory "~/.emacs.d/themes/")

(defvar current-theme-index 0)
(defvar theme-list
  '(solarized-dark solarized-light)
  "List of themes to cycle through.")

(defun get-theme-name (idx)
  (nth idx theme-list))

(defun cycle-themes ()
  (interactive)
  (let* ((theme (get-theme-name current-theme-index))
         (next-theme-index (mod (+ 1 current-theme-index) (length theme-list)))
         (next-theme (get-theme-name next-theme-index)))
    (disable-theme theme)
    (setq current-theme-index next-theme-index)
    (load-theme next-theme)))

(when window-system
  (global-set-key (kbd "<f5>") 'cycle-themes)
  (load-theme (get-theme-name 0)))