(let [start-xy-chan  (om/get-state owner :start-xy-chan)
      change-xy-chan (om/get-state owner :change-xy-chan)
      end-xy-chan    (om/get-state owner :end-xy-chan)]
        (go
          (loop []
            (let [[x0 y0] (<! start-xy-chan)]
              (loop []
                (let [[[x1 y1] ch] (alts! [change-xy-chan end-xy-chan])
                      dx (- x0 x1)
                      dy (- y0 y1)]
                  (om/transact! app
                    (fn [{:keys [currentUser] :as all}]
                      (update-in all [:users currentUser :position]
                        (let [zoom (get-in all [:users currentUser :zoom])]
                          (fn [[x y]]
                            [(+ x (/ dx zoom)) (+ y (/ dy zoom))]))))))
                (if (= ch change-xy-chan)
                  (recur))))
            (recur))))