gistfile1.clj

(defn combined-key-code [key-code]
  (case key-code
    left-shift :shift
    right-shift :shift
    left-control :control
    right-control :control
    left-alt :alt
    alt-gr :alt
    nil))

(defn conj-if-not-nil [collection value]
  (if value
    (conj collection value)
    collection))

(defn update-keys-down [keys-down keyboard-event]
  (case (:type keyboard-event)
    :key-pressed (-> keys-down
                     (conj (:key-code keyboard-event))
                     (conj-if-not-nil (combined-key-code (:key-code keyboard-event))))
    :key-released (-> keys-down
                     (disj (:key-code keyboard-event))
                     (disj (combined-key-code (:key-code keyboard-event))))
    keys-down))