feat: resume secondary track for current session

src/components/playback/playbackmanager.js

@@ -1488,6 +1488,24 @@ class PlaybackManager {
             return getPlayerData(player).subtitleStreamIndex;
         };
 
+        self.getSecondarySubtitleStreamIndex = function (player) {
+            player = player || self._currentPlayer;
+
+            try {
+                if (player && !enableLocalPlaylistManagement(player)) {
+                    return player.getSecondarySubtitleStreamIndex();
+                }
+            } catch (e) {
+                console.error(`Failed to get secondary stream index: ${e}`);
+            }
+
+            if (!player) {
+                throw new Error('player cannot be null');
+            }
+
+            return getPlayerData(player).secondarySubtitleStreamIndex;
+        };
+
         function getDeliveryMethod(subtitleStream) {
             // This will be null for internal subs for local items
             if (subtitleStream.DeliveryMethod) {

src/plugins/htmlVideoPlayer/plugin.js

@@ -186,6 +186,10 @@ function tryRemoveElement(elem) {
          * @type {number | undefined}
          */
         #subtitleTrackIndexToSetOnPlaying;
+        /**
+         * @type {number | undefined}
+         */
+        #secondarySubtitleTrackIndexToSetOnPlaying;
         /**
          * @type {number | null}
          */
@@ -474,6 +478,15 @@ function tryRemoveElement(elem) {
                     this.#subtitleTrackIndexToSetOnPlaying = -1;
                 }
             }
+            // Continue using the secondary track that has been set during this watch session
+            const currentSecondaryTrackIndex = playbackManager.getSecondarySubtitleStreamIndex();
+            this.#secondarySubtitleTrackIndexToSetOnPlaying = currentSecondaryTrackIndex == null ? -1 : currentSecondaryTrackIndex;
+            if (this.#secondarySubtitleTrackIndexToSetOnPlaying != null && this.#secondarySubtitleTrackIndexToSetOnPlaying >= 0) {
+                const initialSecondarySubtitleStream = options.mediaSource.MediaStreams[this.#secondarySubtitleTrackIndexToSetOnPlaying];
+                if (!initialSecondarySubtitleStream || initialSecondarySubtitleStream.DeliveryMethod !== 'External') {
+                    this.#secondarySubtitleTrackIndexToSetOnPlaying = -1;
+                }
+            }
 
             this.#audioTrackIndexToSetOnPlaying = options.playMethod === 'Transcode' ? null : options.mediaSource.DefaultAudioStreamIndex;
 
@@ -889,6 +902,16 @@ function tryRemoveElement(elem) {
             if (this.#audioTrackIndexToSetOnPlaying != null && this.canSetAudioStreamIndex()) {
                 this.setAudioStreamIndex(this.#audioTrackIndexToSetOnPlaying);
             }
+
+            if (this.#secondarySubtitleTrackIndexToSetOnPlaying != null && this.#secondarySubtitleTrackIndexToSetOnPlaying >= 0) {
+                /**
+                 * Using a 0ms timeout to set the secondary subtitles because of some weird race condition when
+                 * setting both primary and secondary tracks at the same time.
+                 * The `TextTrack` content and cues will somehow get mixed up and each track will play a mix of both languages.
+                 * Putting this in a timeout fixes it completely.
+                 */
+                setTimeout(() => this.setSecondarySubtitleStreamIndex(this.#secondarySubtitleTrackIndexToSetOnPlaying), 0);
+            }
         }
 
         /**