Merge pull request #13358 from MoonE/dispatch-events

Avoid event creation when there are no listeners

src/ol/Object.js

@@ -172,9 +172,13 @@ class BaseObject extends Observable {
   notify(key, oldValue) {
     let eventType;
     eventType = `change:${key}`;
-    this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    if (this.hasListener(eventType)) {
+      this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    }
     eventType = ObjectEventType.PROPERTYCHANGE;
-    this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    if (this.hasListener(eventType)) {
+      this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
+    }
   }
 
   /**

src/ol/events/Target.js

@@ -83,49 +83,50 @@ class Target extends Disposable {
    * @api
    */
   dispatchEvent(event) {
-    /** @type {import("./Event.js").default|Event} */
-    const evt = typeof event === 'string' ? new Event(event) : event;
-    const type = evt.type;
+    const isString = typeof event === 'string';
+    const type = isString ? event : event.type;
+    const listeners = this.listeners_ && this.listeners_[type];
+    if (!listeners) {
+      return;
+    }
+
+    const evt = isString ? new Event(event) : /** @type {Event} */ (event);
     if (!evt.target) {
       evt.target = this.eventTarget_ || this;
     }
-    const listeners = this.listeners_ && this.listeners_[type];
-    let propagate;
-    if (listeners) {
-      const dispatching = this.dispatching_ || (this.dispatching_ = {});
-      const pendingRemovals =
-        this.pendingRemovals_ || (this.pendingRemovals_ = {});
-      if (!(type in dispatching)) {
-        dispatching[type] = 0;
-        pendingRemovals[type] = 0;
-      }
-      ++dispatching[type];
-      for (let i = 0, ii = listeners.length; i < ii; ++i) {
-        if ('handleEvent' in listeners[i]) {
-          propagate = /** @type {import("../events.js").ListenerObject} */ (
-            listeners[i]
-          ).handleEvent(evt);
-        } else {
-          propagate = /** @type {import("../events.js").ListenerFunction} */ (
-            listeners[i]
-          ).call(this, evt);
-        }
-        if (propagate === false || evt.propagationStopped) {
-          propagate = false;
-          break;
-        }
-      }
-      --dispatching[type];
-      if (dispatching[type] === 0) {
-        let pr = pendingRemovals[type];
-        delete pendingRemovals[type];
-        while (pr--) {
-          this.removeEventListener(type, VOID);
-        }
-        delete dispatching[type];
-      }
-      return propagate;
+    const dispatching = this.dispatching_ || (this.dispatching_ = {});
+    const pendingRemovals =
+      this.pendingRemovals_ || (this.pendingRemovals_ = {});
+    if (!(type in dispatching)) {
+      dispatching[type] = 0;
+      pendingRemovals[type] = 0;
     }
+    ++dispatching[type];
+    let propagate;
+    for (let i = 0, ii = listeners.length; i < ii; ++i) {
+      if ('handleEvent' in listeners[i]) {
+        propagate = /** @type {import("../events.js").ListenerObject} */ (
+          listeners[i]
+        ).handleEvent(evt);
+      } else {
+        propagate = /** @type {import("../events.js").ListenerFunction} */ (
+          listeners[i]
+        ).call(this, evt);
+      }
+      if (propagate === false || evt.propagationStopped) {
+        propagate = false;
+        break;
+      }
+    }
+    if (--dispatching[type] === 0) {
+      let pr = pendingRemovals[type];
+      delete pendingRemovals[type];
+      while (pr--) {
+        this.removeEventListener(type, VOID);
+      }
+      delete dispatching[type];
+    }
+    return propagate;
   }
 
   /**

src/ol/source/Image.js

@@ -240,27 +240,25 @@ class ImageSource extends Source {
    */
   handleImageChange(event) {
     const image = /** @type {import("../Image.js").default} */ (event.target);
+    let type;
     switch (image.getState()) {
       case ImageState.LOADING:
         this.loading = true;
-        this.dispatchEvent(
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADSTART, image)
-        );
+        type = ImageSourceEventType.IMAGELOADSTART;
         break;
       case ImageState.LOADED:
         this.loading = false;
-        this.dispatchEvent(
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADEND, image)
-        );
+        type = ImageSourceEventType.IMAGELOADEND;
         break;
       case ImageState.ERROR:
         this.loading = false;
-        this.dispatchEvent(
-          new ImageSourceEvent(ImageSourceEventType.IMAGELOADERROR, image)
-        );
+        type = ImageSourceEventType.IMAGELOADERROR;
         break;
       default:
-      // pass
+        return;
+    }
+    if (this.hasListener(type)) {
+      this.dispatchEvent(new ImageSourceEvent(type, image));
     }
   }
 }

src/ol/source/Vector.js

@@ -457,10 +457,12 @@ class VectorSource extends Source {
       this.featuresRtree_.load(extents, geometryFeatures);
     }
 
-    for (let i = 0, length = newFeatures.length; i < length; i++) {
-      this.dispatchEvent(
-        new VectorSourceEvent(VectorEventType.ADDFEATURE, newFeatures[i])
-      );
+    if (this.hasListener(VectorEventType.ADDFEATURE)) {
+      for (let i = 0, length = newFeatures.length; i < length; i++) {
+        this.dispatchEvent(
+          new VectorSourceEvent(VectorEventType.ADDFEATURE, newFeatures[i])
+        );
+      }
     }
   }