⚡ Reuse uuid instances when decoding transit on the frontend (#12792)

common/src/app/common/transit.cljc

@@ -110,6 +110,37 @@
                (.set cache value kw)
                kw))))))
 
+#?(:cljs
+   (def ^:private uuid-cache-size
+     "Twice the ids of a very large page (~60k shapes), so decoding one
+     page does not rotate the cache."
+     131072))
+
+#?(:cljs (def ^:private recent-uuids (js/Map.)))
+#?(:cljs (def ^:private previous-uuids (js/Map.)))
+
+#?(:cljs
+   (defn clear-uuid-cache
+     "Forget the cached uuids, so the ids of a closed file can be freed."
+     []
+     (set! recent-uuids (js/Map.))
+     (set! previous-uuids (js/Map.))))
+
+#?(:cljs
+   (defn- read-uuid
+     "Give the same uuid instance for each value. Entries live in two
+     generations: when the recent one is full it becomes the previous one
+     and the older one is dropped, so the cache stays bounded."
+     [value]
+     (or (.get recent-uuids value)
+         (let [id (or (.get previous-uuids value)
+                      (parse-uuid value))]
+           (when (>= (.-size recent-uuids) uuid-cache-size)
+             (set! previous-uuids recent-uuids)
+             (set! recent-uuids (js/Map.)))
+           (.set recent-uuids value id)
+           id))))
+
 (add-handlers!
  #?@(:clj
      [{:id "file"
@@ -128,7 +159,7 @@
 
  #?(:cljs
     {:id "u"
-     :rfn parse-uuid})
+     :rfn read-uuid})
 
  #?(:cljs
     {:id ":"

frontend/src/app/main/data/workspace.cljs

@@ -21,6 +21,7 @@
    [app.common.math :as mth]
    [app.common.path-names :as cpn]
    [app.common.render-wasm.wasm :as wasm-state]
+   [app.common.transit :as t]
    [app.common.types.component :as ctc]
    [app.common.types.components-list :as ctkl]
    [app.common.types.shape :as cts]
@@ -631,6 +632,7 @@
 
     ptk/WatchEvent
     (watch [_ state _]
+      (t/clear-uuid-cache)
       (let [project-id (:current-project-id state)]
         (rx/of (dwn/finalize file-id)
                (dpj/finalize-project project-id)

frontend/src/app/worker/index.cljs

@@ -12,6 +12,7 @@
    [app.common.geom.rect :as grc]
    [app.common.logging :as log]
    [app.common.time :as ct]
+   [app.common.transit :as t]
    [app.worker.impl :as impl]
    [app.worker.selection :as selection]
    [app.worker.snap :as snap]
@@ -78,6 +79,7 @@
                     (update :pages-index dissoc page-id)
                     (update ::selection dissoc page-id)
                     (update ::snap dissoc page-id)))
+  (t/clear-uuid-cache)
   (log/dbg :hint "page index dropped" :id page-id ::log/sync? true)
   nil)