Skip creating snapshot clone when nobody is listening (for most updates)

packages/element/src/store.ts

@@ -68,6 +68,8 @@ type MicroActionsQueue = (() => void)[];
  * Store which captures the observed changes and emits them as `StoreIncrement` events.
  */
 export class Store {
+  // internally used by history
+  public readonly onDurableIncrementEmitter = new Emitter<[DurableIncrement]>();
   public readonly onStoreIncrementEmitter = new Emitter<
     [DurableIncrement | EphemeralIncrement]
   >();
@@ -265,6 +267,7 @@ export class Store {
       const increment = new DurableIncrement(change, storeDelta);
 
       // Notify listeners with the increment
+      this.onDurableIncrementEmitter.trigger(increment);
       this.onStoreIncrementEmitter.trigger(increment);
     }
   }
@@ -325,6 +328,17 @@ export class Store {
     appState: AppState | ObservedAppState | undefined,
   ) {
     const macroAction = this.getScheduledMacroAction();
+
+    // perf. optimisation, since "EVENTUALLY" does not update the snapshot,
+    // so if nobody is listening for increments, we don't need to even clone the snapshot
+    // as it's only needed for `StoreChange` computation inside `EphemeralIncrement`
+    if (
+      macroAction === CaptureUpdateAction.EVENTUALLY &&
+      !this.onStoreIncrementEmitter.subscribers.length
+    ) {
+      return;
+    }
+
     const nextSnapshot = this.maybeCloneSnapshot(
       macroAction,
       elements,

packages/excalidraw/components/App.tsx

@@ -2547,14 +2547,19 @@ class App extends React.Component<AppProps, AppState> {
       });
     }
 
-    this.store.onStoreIncrementEmitter.on((increment) => {
-      if (StoreIncrement.isDurable(increment)) {
-        this.history.record(increment.delta);
-      }
-
-      this.props.onIncrement?.(increment);
+    this.store.onDurableIncrementEmitter.on((increment) => {
+      this.history.record(increment.delta);
     });
 
+    const { onIncrement } = this.props;
+
+    // per. optimmisation, only subscribe if there is the `onIncrement` prop registered, to avoid unnecessary computation
+    if (onIncrement) {
+      this.store.onStoreIncrementEmitter.on((increment) => {
+        onIncrement(increment);
+      });
+    }
+
     this.scene.onUpdate(this.triggerRender);
     this.addEventListeners();
 
@@ -2614,6 +2619,7 @@ class App extends React.Component<AppProps, AppState> {
     this.eraserTrail.stop();
     this.onChangeEmitter.clear();
     this.store.onStoreIncrementEmitter.clear();
+    this.store.onDurableIncrementEmitter.clear();
     ShapeCache.destroy();
     SnapCache.destroy();
     clearTimeout(touchTimeout);