fix: emitter throttling

packages/graphics/traits/emitter.trait.js

@@ -12,6 +12,7 @@ export class Emitter extends decorate(Trait) {
     this.emitters = {};
     this.ticker = new Ticker(1 / 10);
     this.ticker.on('tick', (elapsed) => {
+      this.updateFrequency();
       for (const key in this.emitters) {
         const emitter = this.emitters[key];
         emitter.tick(elapsed);
@@ -19,6 +20,39 @@ export class Emitter extends decorate(Trait) {
     });
   }
 
+  static addEmitter(emitter) {
+    if (!this._emitters) {
+      this._emitters = [];
+    }
+    this._emitters.push(emitter);
+  }
+
+  static particleCount() {
+    let particleCount = 0;
+    if (!this._emitters) {
+      return particleCount;
+    }
+    for (let i = 0; i < this._emitters.length; i++) {
+      const emitter = this._emitters[i];
+      particleCount += emitter.particleCount;
+    }
+    return particleCount;
+  }
+
+  static removeEmitter(emitter) {
+    const index = this._emitters.indexOf(emitter);
+    if (-1 === index) {
+      return;
+    }
+    this._emitters.splice(index, 1);
+  }
+
+  updateFrequency() {
+    const particleCount = this.constructor.particleCount();
+    const updatesPerSecond = Math.max(15, (60 - (particleCount / 10)));
+    this.ticker.frequency = 1 / updatesPerSecond;
+  }
+
   hooks() {
     return {
 
@@ -28,6 +62,7 @@ export class Emitter extends decorate(Trait) {
             const emitter = this.emitters[key];
             this.ticker.tick(elapsed);
             if (!emitter.hasParticles()) {
+              emitter.destroy();
               delete this.emitters[key];
             }
           }
@@ -43,6 +78,7 @@ export class Emitter extends decorate(Trait) {
 
       addEmitter: (key, emitter) => {
         this.emitters[key] = emitter;
+        this.constructor.addEmitter(emitter);
       },
 
       addEmitterRenderer: (key, renderer) => {