fix(SUP-42730): Captions not showing after enabling (#219)

Issue:
When play the video with caption disabled, caption is not shown after enable the caption (when the caption is default)

Fix:
Listen to SUBTITLE_FRAG_PROCESSED (hls event) that's triggered after the captions request and parsing then hide the captions from our side.

Resolves SUP-42730

src/hls-adapter.ts

@@ -126,6 +126,7 @@ export default class HlsAdapter extends BaseMediaSourceAdapter {
   private _nativeTextTracksMap: any = {};
   private _lastLoadedFragSN: number = -1;
   private _sameFragSNLoadedCount: number = 0;
+  private _waitForSubtitleLoad: boolean = true;
   /**
    * an object containing all the events we bind and unbind to.
    * @member {Object} - _adapterEventsBindings
@@ -791,18 +792,27 @@ export default class HlsAdapter extends BaseMediaSourceAdapter {
     this._onTrackChanged(textTrack);
   }
 
+  private _onSubtitleFragProcessed(): void {
+    this._hls.subtitleTrack = -1;
+    this._waitForSubtitleLoad = false;
+    this._hls.off(Hlsjs.Events.SUBTITLE_FRAG_PROCESSED, this._onSubtitleFragProcessed, this._hls);
+  }
+
   /** Hide the text track
    * @function hideTextTrack
    * @returns {void}
    * @public
    */
   public hideTextTrack(): void {
-    if (this._hls) {
-      if (this._hls.subtitleTracks.length) {
-        this._hls.subtitleTrack = -1;
-      } else {
-        this.disableNativeTextTracks();
-      }
+    if (!this._hls){
+      return;
+    }
+    if (!this._hls.subtitleTracks.length) {
+      this.disableNativeTextTracks();
+    } else if (this._waitForSubtitleLoad){
+      this._hls.on(Hlsjs.Events.SUBTITLE_FRAG_PROCESSED, this. _onSubtitleFragProcessed, this._hls)
+    } else {
+      this._hls.subtitleTrack = -1;
     }
   }
 
@@ -1244,6 +1254,7 @@ export default class HlsAdapter extends BaseMediaSourceAdapter {
     for (const [event, callback] of Object.entries<(...parms: any) => any>(this._adapterEventsBindings)) {
       this._hls.off(event as keyof HlsListeners, callback);
     }
+    this._hls.off(Hlsjs.Events.SUBTITLE_FRAG_PROCESSED, this._onSubtitleFragProcessed, this._hls);
     this._videoElement.textTracks.onaddtrack = null;
     this._onRecoveredCallback = null;
     if (this._eventManager) {