gistfile1.clj

(def mono-font
  (atom (Font. (if (is-mac)
                 "Monaco"
                 "Courier New")
               Font/PLAIN default-font-size)))

(defn change-font [myfn]
  (fn [myfont]
    (let [new-font (swap! myfont 
                          (fn [old-font]
                            (let [size (.getSize old-font)]
                              (.deriveFont font (myfn size)))))
          doc @current-doc]
      (doseq [area [:doc-text-area :repl-out-text-area :doc-in-text-area]]
        (.setFont (doc area) new-font)))))

(def inc-font (change-font inc))
(def dec-font (change-font dec))