After toggling shuffle, track down the new playback index and prepare the next track.

src/musikbox/app/model/TrackList.cpp

@@ -106,6 +106,10 @@ TrackPtr TrackList::Get(size_t index) {
     return query->Result();
 }
 
+DBID TrackList::GetId(size_t index) {
+    return this->ids.at(index);
+}
+
 void TrackList::CopyFrom(TrackList& from) {
     this->Clear();
 
@@ -115,6 +119,11 @@ void TrackList::CopyFrom(TrackList& from) {
         std::back_inserter(this->ids));
 }
 
+int TrackList::IndexOf(DBID id) {
+    auto it = std::find(this->ids.begin(), this->ids.end(), id);
+    return (it == this->ids.end()) ? -1 : it - this->ids.begin();
+}
+
 void TrackList::Shuffle() {
     std::random_shuffle(this->ids.begin(), this->ids.end());
 }

src/musikbox/app/model/TrackList.h

@@ -50,6 +50,8 @@ namespace musik {
                 size_t Count();
                 void Add(const DBID& id);
                 musik::core::TrackPtr Get(size_t index);
+                DBID GetId(size_t index);
+                int IndexOf(DBID id);
                 void ClearCache();
                 void Clear();
                 void Swap(TrackList& list);

src/musikbox/app/service/PlaybackService.cpp

@@ -133,16 +133,33 @@ void PlaybackService::SetRepeatMode(RepeatMode mode) {
 
 void PlaybackService::ToggleShuffle() {
     boost::recursive_mutex::scoped_lock lock(this->playlistMutex);
-    if (this->unshuffled.Count() > 0) {
+
+    /* remember the ID of the playing track -- we're going to need to look
+    it up after the shuffle */
+    DBID id = -1;
+    if (this->index < this->playlist.Count()) {
+        id = this->playlist.GetId(this->index);
+    }
+
+    if (this->unshuffled.Count() > 0) { /* shuffled -> unshuffled */
         this->playlist.Clear();
         this->playlist.Swap(this->unshuffled);
         this->Shuffled(false);
     }
-    else {
+    else { /* unshuffled -> shuffle */
         this->unshuffled.CopyFrom(this->playlist);
         this->playlist.Shuffle();
         this->Shuffled(true);
     }
+
+    /* find the new playback index and prefetch the next track */
+    if (id != -1) {
+        int index = this->playlist.IndexOf(id);
+        if (index != -1) {
+            this->index = index;
+            POST(this, MESSAGE_PREPARE_NEXT_TRACK, 0, 0);
+        }
+    }
 }
 
 void PlaybackService::ProcessMessage(IMessage &message) {