Fix YouTube player readiness checks and improve polling logic for video playback

Jellyfin.Plugin.MediaBarEnhanced/Web/mediaBarEnhanced.js

@@ -2743,7 +2743,7 @@ const SlideshowManager = {
 
     if (!videoBackdrop && !hasRegisteredPlayer) return false;
 
-    if (videoBackdrop.tagName === 'VIDEO') {
+    if (videoBackdrop && videoBackdrop.tagName === 'VIDEO') {
       videoBackdrop.currentTime = 0;
       videoBackdrop.muted = STATE.slideshow.isMuted;
       if (!STATE.slideshow.isMuted) videoBackdrop.volume = 0.4;
@@ -2762,7 +2762,9 @@ const SlideshowManager = {
 
     // YouTube player
     const player = STATE.slideshow.videoPlayers && STATE.slideshow.videoPlayers[itemId];
-    if (player && typeof player.loadVideoById === 'function' && player._videoId) {
+    const playerIsReady = player && typeof player.loadVideoById === 'function' && player._videoId;
+
+    if (playerIsReady) {
       player.loadVideoById({
         videoId: player._videoId,
         startSeconds: player._startTime || 0,
@@ -2788,18 +2790,64 @@ const SlideshowManager = {
         }
       }, 1000);
       return true;
-    } else if (player && typeof player.seekTo === 'function') {
-      // Fallback if loadVideoById is not available or videoId missing but player object exists
-      const startTime = player._startTime || 0;
-      player.seekTo(startTime);
-      player.playVideo();
-      return true;
     }
 
-    // YouTube player not ready yet (still loading from preload) — mark for auto-play when onReady fires
+    // YouTube player exists but NOT fully ready yet.
-    if (videoBackdrop && videoBackdrop.id && videoBackdrop.id.startsWith('youtube-player-') && !player) {
+    // new YT.Player() returns an object immediately, but API methods like
-      console.log(`YouTube player for ${itemId} not ready yet, marking _pendingPlay`);
+    // loadVideoById and _videoId aren't available until onReady fires.
-      videoBackdrop._pendingPlay = true;
+    // onReady may have ALREADY fired (during preload), so we can't rely on
+    // _pendingPlay alone. Instead, poll for readiness.
+    const ytContainer = videoBackdrop || slide.querySelector(`[id^="youtube-player-"]`);
+    if (ytContainer && (ytContainer.tagName === 'IFRAME' || (ytContainer.id && ytContainer.id.startsWith('youtube-player-')))) {
+      console.log(`YouTube player for ${itemId} not ready yet, polling for readiness...`);
+      
+      // Also set _pendingPlay as fallback in case onReady hasn't fired yet
+      ytContainer._pendingPlay = true;
+
+      let attempts = 0;
+      const maxAttempts = 25; // 25 * 200ms = 5 seconds max
+      const pollInterval = setInterval(() => {
+        attempts++;
+        
+        // Stop if slide is no longer active (user navigated away)
+        if (!slide.classList.contains('active')) {
+          clearInterval(pollInterval);
+          return;
+        }
+
+        const p = STATE.slideshow.videoPlayers && STATE.slideshow.videoPlayers[itemId];
+        if (p && typeof p.loadVideoById === 'function' && p._videoId) {
+          clearInterval(pollInterval);
+          console.log(`YouTube player for ${itemId} now ready (after ${attempts * 200}ms), starting playback`);
+          
+          if (STATE.slideshow.isPaused) return;
+
+          p.loadVideoById({
+            videoId: p._videoId,
+            startSeconds: p._startTime || 0,
+            endSeconds: p._endTime
+          });
+
+          if (STATE.slideshow.isMuted) {
+            p.mute();
+          } else {
+            p.unMute();
+            p.setVolume(40);
+          }
+
+          // Pause slideshow timer when video starts if configured
+          if (CONFIG.waitForTrailerToEnd && STATE.slideshow.slideInterval) {
+            STATE.slideshow.slideInterval.stop();
+          }
+          return;
+        }
+
+        if (attempts >= maxAttempts) {
+          clearInterval(pollInterval);
+          console.warn(`YouTube player for ${itemId} failed to become ready after ${maxAttempts * 200}ms`);
+        }
+      }, 200);
+      
       return true;
     }