Add syntax helper for define once unnamed global instances.

frontend/uxbox/ui/workspace/base.cljs

@@ -1,4 +1,5 @@
 (ns uxbox.ui.workspace.base
+  (:require-macros [uxbox.util.syntax :refer [define-once]])
   (:require [beicon.core :as rx]
             [cats.labs.lens :as l]
             [uxbox.rstore :as rs]
@@ -88,7 +89,7 @@
        (rx/buffer 2 1)
        (rx/map coords-delta)))
 
-(defonce $$drag-subscription$$
+(define-once
   (as-> mouse-delta-s $
     (rx/filter #(deref shapes-dragging?) $)
     (rx/on-value $ (fn [delta]
@@ -113,7 +114,7 @@
      :width (- current-x start-x)
      :height (- current-y start-y)}))
 
-(defonce $$selrect-subscription$$
+(define-once
   (let [ss (as-> (rx/from-atom selrect-dragging?) $
              (rx/dedupe $)
              (rx/merge $ (rx/of false))

frontend/uxbox/util/syntax.cljc

@@ -0,0 +1,10 @@
+(ns uxbox.util.syntax
+  (:refer-clojure :exclude [defonce]))
+
+(defmacro define-once
+  [& body]
+  (let [sym (gensym "uxbox-")]
+    `(cljs.core/defonce ~sym
+       (do ~@body
+           nil))))
+