fixed bug in SetShuffle

backend/playbackengine.go

@@ -342,40 +342,54 @@ func (p *playbackEngine) GetLoopMode() LoopMode {
 	return p.loopMode
 }
 
-func (p *playbackEngine) GetNowPlayingIdxFrom(items []mediaprovider.MediaItem) int {
-	newNowPlayingIdx := -1
-	if p.nowPlayingIdx >= 0 && len(items) > p.nowPlayingIdx {
-		nowPlayingID := p.getPlayQueueItemAt(p.nowPlayingIdx).Metadata().ID
+func (p *playbackEngine) GetTrackIdxByIdFrom(items []mediaprovider.MediaItem, id string) int {
+	foundIdx := -1
 	for i, tr := range items {
-			if tr.Metadata().ID == nowPlayingID {
-				newNowPlayingIdx = i
+		if tr.Metadata().ID == id {
+			foundIdx = i
 			break
 		}
 	}
-	}
-	return newNowPlayingIdx
+	return foundIdx
 }
 
 func (p *playbackEngine) SetShuffle(shuffle bool) {
-	for _, cb := range p.onShuffleChange {
-		cb(shuffle)
-	}
 
 	if p.shuffle == shuffle {
 		return
 	}
+
+	for _, cb := range p.onShuffleChange {
+		cb(shuffle)
+	}
+	p.shuffle = shuffle
+
+	// guard against changing shuffle with an empty queue
+	if p.getPlayQueue() == nil || len(p.getPlayQueue()) == 0 {
+		return
+	}
+
 	newNowPlayingIdx := 0
 	if shuffle {
 		shuffledQueue := deepCopyMediaItemSlice(p.playQueue)
 		rand.Shuffle(len(shuffledQueue), func(i, j int) {
 			shuffledQueue[i], shuffledQueue[j] = shuffledQueue[j], shuffledQueue[i]
 		})
-		p.setShuffledPlayQueue(sharedutil.ReorderItems(shuffledQueue, []int{p.GetNowPlayingIdxFrom(shuffledQueue)}, 0))
+		if p.nowPlayingIdx >= 0 && len(p.getPlayQueue()) > p.nowPlayingIdx {
+			nowPlayingID := p.getPlayQueue()[p.nowPlayingIdx].Metadata().ID
+			p.setShuffledPlayQueue(sharedutil.ReorderItems(shuffledQueue, []int{p.GetTrackIdxByIdFrom(shuffledQueue, nowPlayingID)}, 0))
 		} else {
-		newNowPlayingIdx = p.GetNowPlayingIdxFrom(p.playQueue)
+			return
+		}
+	} else {
+		if p.nowPlayingIdx >= 0 && len(p.getShuffledPlayQueue()) > p.nowPlayingIdx {
+			nowPlayingID := p.getShuffledPlayQueue()[p.nowPlayingIdx].Metadata().ID
+			newNowPlayingIdx = p.GetTrackIdxByIdFrom(p.playQueue, nowPlayingID)
+		} else {
+			return
 		}
 
-	p.shuffle = shuffle
+	}
 
 	if p.nowPlayingIdx >= 0 && newNowPlayingIdx == -1 {
 		return

sharedutil/sharedutil.go

@@ -112,6 +112,9 @@ func TracksToIDs(tracks []*mediaprovider.Track) []string {
 // Reorder items and return a new track slice.
 // idxToMove must contain only valid indexes into tracks, and no repeats
 func ReorderItems[T any](items []T, idxToMove []int, insertIdx int) []T {
+	if len(items) < 2 {
+		return items
+	}
 	idxToMoveSet := ToSet(idxToMove)
 
 	newItems := make([]T, 0, len(items))