Feat: [Envelope] allow passing an audio context (#3179)

* Feat: [Envelope] allow passing an audio context

* Cache volume

src/plugins/envelope.ts

@@ -21,6 +21,7 @@ export type EnvelopePluginOptions = {
   dragPointSize?: number
   dragPointFill?: string
   dragPointStroke?: string
+  audioContext?: AudioContext
 }
 
 const defaultOptions = {
@@ -254,6 +255,7 @@ class EnvelopePlugin extends BasePlugin<EnvelopePluginEvents, EnvelopePluginOpti
   private throttleTimeout: ReturnType<typeof setTimeout> | null = null
   private ac: AudioContext | null = null
   private gain: GainNode['gain'] | null = null
+  private volume = 1
 
   /**
    * Create a new Envelope plugin.
@@ -324,24 +326,27 @@ class EnvelopePlugin extends BasePlugin<EnvelopePluginEvents, EnvelopePluginOpti
    * Destroy the plugin instance.
    */
   public destroy() {
+    if (this.ac && this.ac !== this.options.audioContext) {
+      this.ac.close()
+    }
     this.polyline?.destroy()
-    this.ac?.close()
     super.destroy()
   }
 
   /**
    * Get the envelope volume.
    */
   public getCurrentVolume(): number {
-    return this.gain?.value || 0
+    return this.volume
   }
 
   /**
    * Set the envelope volume. 0..1 (more than 1 will boost the volume).
    */
   public setVolume(floatValue: number) {
+    this.volume = floatValue
     if (this.gain) {
-      this.gain.value = floatValue
+      this.gain.value = this.volume
     }
   }
 
@@ -355,6 +360,7 @@ class EnvelopePlugin extends BasePlugin<EnvelopePluginEvents, EnvelopePluginOpti
     options.volume = options.volume ?? this.wavesurfer.getVolume()
 
     this.initAudioContext(this.wavesurfer.getMediaElement())
+    this.setVolume(options.volume)
 
     this.subscriptions.push(
       this.wavesurfer.on('decode', (duration) => {
@@ -382,7 +388,7 @@ class EnvelopePlugin extends BasePlugin<EnvelopePluginEvents, EnvelopePluginOpti
   }
 
   private initAudioContext(mediaElement: HTMLMediaElement) {
-    const ac = new AudioContext()
+    const ac = this.options.audioContext || new AudioContext()
     const gainNode = ac.createGain()
     gainNode.gain.value = this.options.volume ?? 1
     gainNode.connect(ac.destination)
@@ -466,7 +472,7 @@ class EnvelopePlugin extends BasePlugin<EnvelopePluginEvents, EnvelopePluginOpti
 
     if (roundedVolume !== this.getCurrentVolume()) {
       this.setVolume(roundedVolume)
-      this.emit('volume-change', newVolume)
+      this.emit('volume-change', roundedVolume)
     }
   }
 }