🔧 Optimize sidebar performance for deeply nested shapes

- Batch hover highlights using RAF to avoid long tasks from rapid events
- Run parent expansion asynchronously to not block selection
- Lazy-load children in layer items using IntersectionObserver
- Clarify expand-all-parents logic with explicit bindings

CHANGES.md

@@ -13,6 +13,7 @@
 - Remap references when renaming tokens [Taiga #10202](https://tree.taiga.io/project/penpot/us/10202)
 - Tokens panel nested path view [Taiga #9966](https://tree.taiga.io/project/penpot/us/9966)
 - Improve usability of lock and hide buttons in the layer panel. [Taiga #12916](https://tree.taiga.io/project/penpot/issue/12916)
+- Optimize sidebar performance for deeply nested shapes [Taiga #13017](https://tree.taiga.io/project/penpot/task/13017)
 
 ### :bug: Bugs fixed
 

common/src/app/common/files/helpers.cljc

@@ -526,20 +526,25 @@
           ids))
 
 (defn clean-loops
-  "Clean a list of ids from circular references."
+  "Clean a list of ids from circular references. Optimized fast-path for single selections."
   [objects ids]
-  (let [parent-selected?
-        (fn [id]
-          (let [parents (get-parent-ids objects id)]
-            (some ids parents)))
+  (if (<= (count ids) 1)
+    ;; For single selection, there can't be circularity; return as ordered-set.
+    (into (d/ordered-set) ids)
+    (let [ids-set (if (set? ids) ids (set ids))
+          parent-selected?
+          (fn [id]
+            ;; Stop early as soon as we find any selected parent
+            (let [parents (get-parent-ids objects id)]
+              (some #(contains? ids-set %) parents)))
 
-        add-element
-        (fn [result id]
-          (cond-> result
-            (not (parent-selected? id))
-            (conj id)))]
+          add-element
+          (fn [result id]
+            (cond-> result
+              (not (parent-selected? id))
+              (conj id)))]
 
-    (reduce add-element (d/ordered-set) ids)))
+      (reduce add-element (d/ordered-set) ids))))
 
 (defn- indexed-shapes
   "Retrieves a vector with the indexes for each element in the layer

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

@@ -61,6 +61,11 @@
 ;; Def micro-benchmark iterations
 (def micro-benchmark-iterations 1e6)
 
+;; Performance logs
+(defonce ^:private longtask-observer* (atom nil))
+(defonce ^:private stall-timer* (atom nil))
+(defonce ^:private current-op* (atom nil))
+
 ;; --- CONTEXT
 
 (defn- collect-context
@@ -464,3 +469,72 @@
 (defn event
   [props]
   (ptk/data-event ::event props))
+
+;; --- DEVTOOLS PERF LOGGING
+
+(defn install-long-task-observer! []
+  (when (and (some? (.-PerformanceObserver js/window)) (nil? @longtask-observer*))
+    (let [observer (js/PerformanceObserver.
+                    (fn [list _]
+                      (doseq [entry (.getEntries list)]
+                        (let [dur (.-duration entry)
+                              start (.-startTime entry)
+                              attrib (.-attribution entry)
+                              attrib-count (when attrib (.-length attrib))
+                              first-attrib (when (and attrib-count (> attrib-count 0)) (aget attrib 0))
+                              attrib-name (when first-attrib (.-name first-attrib))
+                              attrib-ctype (when first-attrib (.-containerType first-attrib))
+                              attrib-cid (when first-attrib (.-containerId first-attrib))
+                              attrib-csrc (when first-attrib (.-containerSrc first-attrib))]
+
+                          (.warn js/console (str "[perf] long task " (Math/round dur) "ms at " (Math/round start) "ms"
+                                                 (when first-attrib
+                                                   (str " attrib:name=" attrib-name
+                                                        " ctype=" attrib-ctype
+                                                        " cid=" attrib-cid
+                                                        " csrc=" attrib-csrc))))))))]
+      (.observe observer #js{:entryTypes #js["longtask"]})
+      (reset! longtask-observer* observer))))
+
+(defn start-event-loop-stall-logger!
+  "Log event loop stalls by measuring setInterval drift.
+  interval-ms: base interval
+  threshold-ms: drift over which we report"
+  [interval-ms threshold-ms]
+  (when (nil? @stall-timer*)
+    (let [last (atom (.now js/performance))
+          id (js/setInterval
+              (fn []
+                (let [now (.now js/performance)
+                      expected (+ @last interval-ms)
+                      drift (- now expected)
+                      current-op @current-op*
+                      measures (.getEntriesByType js/performance "measure")
+                      mlen (.-length measures)
+                      last-measure (when (> mlen 0) (aget measures (dec mlen)))
+                      meas-name (when last-measure (.-name last-measure))
+                      meas-detail (when last-measure (.-detail last-measure))
+                      meas-count (when meas-detail (unchecked-get meas-detail "count"))]
+                  (reset! last now)
+                  (when (> drift threshold-ms)
+                    (.warn js/console
+                           (str "[perf] event loop stall: " (Math/round drift) "ms"
+                                (when current-op (str " op=" current-op))
+                                (when meas-name (str " last=" meas-name))
+                                (when meas-count (str " count=" meas-count)))))))
+              interval-ms)]
+      (reset! stall-timer* id))))
+
+(defn init!
+  "Install perf observers in dev builds. Safe to call multiple times."
+  []
+  (when ^boolean js/goog.DEBUG
+    (install-long-task-observer!)
+    (start-event-loop-stall-logger! 50 100)
+    ;; Expose simple API on window for manual control in devtools
+    (let [api #js {:reset (fn []
+                            (try
+                              (.clearMarks js/performance)
+                              (.clearMeasures js/performance)
+                              (catch :default _ nil)))}]
+      (aset js/window "PenpotPerf" api))))

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

@@ -14,6 +14,87 @@
    [app.common.geom.shapes :as gsh]
    [app.common.types.path :as path]))
 
+;; =============================================================================
+;; Lazy Tree Wrapper
+;; =============================================================================
+;; This wrapper provides O(1) lookup by building an index lazily.
+;; The index is built once on first access and cached for subsequent lookups.
+
+(defn- build-index
+  "Builds a flat index from a tree structure. Returns {id -> shape-with-parent-id}"
+  ([root]
+   (build-index root nil (transient {})))
+  ([shape parent-id acc]
+   (let [id (dm/get-prop shape :id)
+         children (or (dm/get-prop shape :children)
+                      (dm/get-prop shape :shapes)
+                      [])
+         child-ids (mapv (fn [c] (if (map? c) (dm/get-prop c :id) c)) children)
+         shape-normalized (-> shape
+                              (assoc :parent-id parent-id)
+                              (assoc :shapes child-ids)
+                              (dissoc :children))
+         acc' (assoc! acc id shape-normalized)]
+     (reduce (fn [a child]
+               (if (map? child)
+                 (build-index child id a)
+                 a))
+             acc'
+             children))))
+
+(deftype TreeObjectsLookup [tree ^:mutable cached-index]
+  ILookup
+  (-lookup [_ k]
+    (when (nil? cached-index)
+      (set! cached-index (persistent! (build-index tree))))
+    (get cached-index k))
+  (-lookup [_ k not-found]
+    (when (nil? cached-index)
+      (set! cached-index (persistent! (build-index tree))))
+    (get cached-index k not-found))
+
+  ISeqable
+  (-seq [_]
+    (when (nil? cached-index)
+      (set! cached-index (persistent! (build-index tree))))
+    (seq cached-index))
+
+  ICounted
+  (-count [_]
+    (when (nil? cached-index)
+      (set! cached-index (persistent! (build-index tree))))
+    (count cached-index))
+
+  IFn
+  (-invoke [this k]
+    (-lookup this k))
+  (-invoke [this k not-found]
+    (-lookup this k not-found))
+
+  IAssociative
+  (-contains-key? [_ k]
+    (when (nil? cached-index)
+      (set! cached-index (persistent! (build-index tree))))
+    (contains? cached-index k))
+  (-assoc [_ k v]
+    (when (nil? cached-index)
+      (set! cached-index (persistent! (build-index tree))))
+    (assoc cached-index k v))
+
+  IIterable
+  (-iterator [_]
+    (when (nil? cached-index)
+      (set! cached-index (persistent! (build-index tree))))
+    (-iterator cached-index)))
+
+(defn- tree->lookup
+  "Wraps a tree structure in a lazy lookup that builds the index on first access.
+   Returns the tree as-is if it's already a flat map (no :id at root level)."
+  [tree]
+  (if (and (map? tree) (contains? tree :id))
+    (->TreeObjectsLookup tree nil)
+    tree))
+
 (defn lookup-profile
   ([state]
    (:profile state))
@@ -62,26 +143,46 @@
                         (:current-file-id state)
                         page-id))
   ([state file-id page-id]
-   (-> (lookup-page state file-id page-id)
-       (get :objects))))
+   (let [page (lookup-page state file-id page-id)
+         objects (:objects page)]
+     ;; Use lazy tree wrapper - builds index on first access, then O(1) lookups
+     (tree->lookup objects))))
+
+;; Small 1-slot memo to avoid recomputing the same selection normalization
+;; many times in hot paths (watchers, derived refs).
+(defonce ^:private last-process-selected
+  (atom {:objects nil :selected nil :omit-blocked? nil :result nil}))
 
 (defn process-selected
   ([objects selected]
    (process-selected objects selected nil))
 
   ([objects selected {:keys [omit-blocked?] :or {omit-blocked? false}}]
-   (let [selectable?
-         (fn [id]
-           (and (contains? objects id)
-                (or (not omit-blocked?)
-                    (not (dm/get-in objects [id :blocked] false)))))
-
-         selected
-         (cfh/clean-loops objects selected)]
-
-     (into (d/ordered-set)
-           (filter selectable?)
-           selected))))
+   (let [{c-objects :objects
+          c-selected :selected
+          c-omit-blocked? :omit-blocked?
+          c-result :result} @last-process-selected]
+     (if (and (identical? c-objects objects)
+              (= c-selected selected)
+              (= c-omit-blocked? omit-blocked?))
+       c-result
+       (let [;; Remove circular selections (child when parent is selected)
+             selected-cleaned (cfh/clean-loops objects selected)
+             ;; Fast path when not filtering blocked: only ensure id exists
+             selectable? (if omit-blocked?
+                           (fn [id]
+                             (and (contains? objects id)
+                                  (not (dm/get-in objects [id :blocked] false))))
+                           (fn [id]
+                             (contains? objects id)))
+             result (into (d/ordered-set)
+                          (filter selectable?)
+                          selected-cleaned)]
+         (reset! last-process-selected {:objects objects
+                                        :selected selected
+                                        :omit-blocked? omit-blocked?
+                                        :result result})
+         result)))))
 
 (defn split-text-shapes
   "Split text shapes from non-text shapes"

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

@@ -347,6 +347,12 @@
                                  (with-meta {:team-id team-id
                                              :file-id file-id}))))))
 
+              ;; Install dev perf observers once the workspace is ready
+              (->> stream
+                   (rx/filter (ptk/type? ::workspace-initialized))
+                   (rx/take 1)
+                   (rx/map (fn [_] (ev/init!))))
+
               (->> stream
                    (rx/filter (ptk/type? ::dps/persistence-notification))
                    (rx/take 1)

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

@@ -18,13 +18,13 @@
     ptk/UpdateEvent
     (update [_ state]
       (let [expand-fn (fn [expanded]
-                        (merge expanded
-                               (->> ids
-                                    (map #(cfh/get-parent-ids objects %))
-                                    flatten
-                                    (remove #(= % uuid/zero))
-                                    (map (fn [id] {id true}))
-                                    (into {}))))]
+                        (let [parents-seqs (map (fn [x] (cfh/get-parent-ids objects x)) ids)
+                              flat-parents (apply concat parents-seqs)
+                              non-root-parents (remove #(= % uuid/zero) flat-parents)
+                              distinct-parents (into #{} non-root-parents)]
+                          (merge expanded
+                                 (into {}
+                                       (map (fn [id] {id true}) distinct-parents)))))]
         (update-in state [:workspace-local :expanded] expand-fn)))))
 
 

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

@@ -264,10 +264,13 @@
 
     ptk/WatchEvent
     (watch [_ state _]
-      (let [objects (dsh/lookup-page-objects state)]
-        (rx/of
-         (dwc/expand-all-parents ids objects)
-         ::dwsp/interrupt)))))
+      (let [objects (dsh/lookup-page-objects state)
+            ;; Schedule expanding parents asynchronously to avoid blocking
+            ;; the event loop
+            expand-s (->> (rx/of (dwc/expand-all-parents ids objects))
+                          (rx/observe-on :async))
+            interrupt-s (rx/of ::dwsp/interrupt)]
+        (rx/merge expand-s interrupt-s)))))
 
 (defn select-all
   []

frontend/src/app/main/refs.cljs

@@ -305,7 +305,7 @@
   (l/derived #(dsh/lookup-shape % page-id shape-id) st/state =))
 
 (def workspace-page-objects
-  (l/derived dsh/lookup-page-objects st/state))
+  (l/derived dsh/lookup-page-objects st/state identical?))
 
 (def workspace-read-only?
   (l/derived :read-only? workspace-global))

frontend/src/app/main/ui/workspace/sidebar/layer_item.cljs

@@ -33,9 +33,24 @@
    [okulary.core :as l]
    [rumext.v2 :as mf]))
 
+;; Coalesce sidebar hover highlights to 1 frame to avoid long tasks
+(defonce ^:private sidebar-hover-queue (atom {:enter #{} :leave #{}}))
+(defonce ^:private sidebar-hover-pending? (atom false))
+
+(defn- schedule-sidebar-hover-flush []
+  (when (compare-and-set! sidebar-hover-pending? false true)
+    (ts/raf
+     (fn []
+       (let [{:keys [enter leave]} (swap! sidebar-hover-queue (constantly {:enter #{} :leave #{}}))]
+         (reset! sidebar-hover-pending? false)
+         (when (seq leave)
+           (apply st/emit! (map dw/dehighlight-shape leave)))
+         (when (seq enter)
+           (apply st/emit! (map dw/highlight-shape enter))))))))
+
 (mf/defc layer-item-inner
   {::mf/wrap-props false}
-  [{:keys [item depth parent-size name-ref children ref
+  [{:keys [item depth parent-size name-ref children ref style
            ;; Flags
            read-only? highlighted? selected? component-tree?
            filtered? expanded? dnd-over? dnd-over-top? dnd-over-bot? hide-toggle?
@@ -82,7 +97,8 @@
                     :dnd-over dnd-over?
                     :dnd-over-top dnd-over-top?
                     :dnd-over-bot dnd-over-bot?
-                    :root-board parent-board?)}
+                    :root-board parent-board?)
+            :style style}
       [:span {:class (stl/css-case
                       :tab-indentation true
                       :filtered filtered?)
@@ -165,10 +181,12 @@
 
      children]))
 
+;; Memoized for performance
 (mf/defc layer-item
   {::mf/props :obj
-   ::mf/memo true}
-  [{:keys [index item selected objects sortable? filtered? depth parent-size component-child? highlighted]}]
+   ::mf/wrap [mf/memo]}
+  [{:keys [index item selected objects sortable? filtered? depth parent-size component-child? highlighted style render-children?]
+    :or {render-children? true}}]
   (let [id                (:id item)
         blocked?          (:blocked item)
         hidden?           (:hidden item)
@@ -245,13 +263,21 @@
         (mf/use-fn
          (mf/deps id)
          (fn [_]
-           (st/emit! (dw/highlight-shape id))))
+           (swap! sidebar-hover-queue (fn [{:keys [enter leave] :as q}]
+                                        (-> q
+                                            (assoc :enter (conj enter id))
+                                            (assoc :leave (disj leave id)))))
+           (schedule-sidebar-hover-flush)))
 
         on-pointer-leave
         (mf/use-fn
          (mf/deps id)
          (fn [_]
-           (st/emit! (dw/dehighlight-shape id))))
+           (swap! sidebar-hover-queue (fn [{:keys [enter leave] :as q}]
+                                        (-> q
+                                            (assoc :enter (disj enter id))
+                                            (assoc :leave (conj leave id)))))
+           (schedule-sidebar-hover-flush)))
 
         on-context-menu
         (mf/use-fn
@@ -337,14 +363,18 @@
         component-tree? (or component-child? (ctk/instance-root? item) (ctk/instance-head? item))
 
         enable-drag      (mf/use-fn #(reset! drag-disabled* false))
-        disable-drag     (mf/use-fn #(reset! drag-disabled* true))]
+        disable-drag     (mf/use-fn #(reset! drag-disabled* true))
+
+        ;; Lazy loading of child elements via IntersectionObserver
+        children-count*  (mf/use-state 0)
+        children-count   (deref children-count*)
+        lazy-ref         (mf/use-ref nil)
+        observer-var     (mf/use-var nil)
+        chunk-size       50]
 
     (mf/with-effect [selected? selected]
       (let [single? (= (count selected) 1)
             node (mf/ref-val ref)
-            ;; NOTE: Neither get-parent-at nor get-parent-with-selector
-            ;; work if the component template changes, so we need to
-            ;; seek for an alternate solution. Maybe use-context?
             scroll-node (dom/get-parent-with-data node "scroll-container")
             parent-node (dom/get-parent-at node 2)
             first-child-node (dom/get-first-child parent-node)
@@ -362,6 +392,59 @@
         #(when (some? subid)
            (rx/dispose! subid))))
 
+    ;; Setup scroll-driven lazy loading when expanded
+    ;; and ensures selected children are loaded immediately
+    (mf/with-effect [expanded? (:shapes item) selected]
+      (let [shapes-vec (:shapes item)
+            total (count shapes-vec)]
+        (if expanded?
+          (let [;; Children are rendered in reverse order, so index 0 in render = last in shapes-vec
+                ;; Find if any selected id is a direct child and get its render index
+                selected-child-render-idx
+                (when (and (> total chunk-size) (seq selected))
+                  (let [shapes-reversed (vec (reverse shapes-vec))]
+                    (some (fn [sel-id]
+                            (let [idx (.indexOf shapes-reversed sel-id)]
+                              (when (>= idx 0) idx)))
+                          selected)))
+                ;; Load at least enough to include the selected child plus extra
+                ;; for context (so it can be centered in the scroll view)
+                min-count (if selected-child-render-idx
+                            (+ selected-child-render-idx chunk-size)
+                            chunk-size)]
+            (reset! children-count* (min total (max chunk-size min-count))))
+          (reset! children-count* 0)))
+      (fn []
+        (when-let [obs ^js @observer-var]
+          (.disconnect obs)
+          (reset! observer-var nil))))
+
+    ;; Re-observe sentinel whenever children-count changes (sentinel moves)
+    (mf/with-effect [children-count expanded?]
+      (let [total (count (:shapes item))
+            node (mf/ref-val ref)
+            scroll-node (dom/get-parent-with-data node "scroll-container")
+            lazy-node (mf/ref-val lazy-ref)]
+        ;; Disconnect previous observer
+        (when-let [obs ^js @observer-var]
+          (.disconnect obs)
+          (reset! observer-var nil))
+        ;; Setup new observer if there are more children to load
+        (when (and expanded?
+                   (< children-count total)
+                   scroll-node
+                   lazy-node)
+          (let [cb (fn [entries]
+                     (when (and (seq entries)
+                                (.-isIntersecting (first entries)))
+                       ;; Load next chunk when sentinel intersects
+                       (let [current @children-count*
+                             next-count (min total (+ current chunk-size))]
+                         (reset! children-count* next-count))))
+                observer (js/IntersectionObserver. cb #js {:root scroll-node})]
+            (.observe observer lazy-node)
+            (reset! observer-var observer)))))
+
     [:& layer-item-inner
      {:ref dref
       :item item
@@ -386,24 +469,32 @@
       :on-enable-drag enable-drag
       :on-disable-drag disable-drag
       :on-toggle-visibility toggle-visibility
-      :on-toggle-blocking toggle-blocking}
+      :on-toggle-blocking toggle-blocking
+      :style style}
 
-     (when (and (:shapes item) expanded?)
+     (when (and render-children?
+                (:shapes item)
+                expanded?)
        [:div {:class (stl/css-case
                       :element-children true
                       :parent-selected selected?
                       :sticky-children parent-board?)
               :data-testid (dm/str "children-" id)}
-        (for [[index id] (reverse (d/enumerate (:shapes item)))]
-          (when-let [item (get objects id)]
-            [:& layer-item
-             {:item item
-              :highlighted highlighted
-              :selected selected
-              :index index
-              :objects objects
-              :key (dm/str id)
-              :sortable? sortable?
-              :depth depth
-              :parent-size parent-size
-              :component-child? component-tree?}]))])]))
+        (let [all-children (reverse (d/enumerate (:shapes item)))
+              visible      (take children-count all-children)]
+          (for [[index id] visible]
+            (when-let [item (get objects id)]
+              [:& layer-item
+               {:item item
+                :highlighted highlighted
+                :selected selected
+                :index index
+                :objects objects
+                :key (dm/str id)
+                :sortable? sortable?
+                :depth depth
+                :parent-size parent-size
+                :component-child? component-tree?}])))
+        (when (< children-count (count (:shapes item)))
+          [:div {:ref lazy-ref
+                 :style {:min-height 1}}])])]))