* Moved prev/next check into PlaylistInterface.

src/libtomahawk/PlaylistInterface.cpp

@@ -30,6 +30,9 @@ PlaylistInterface::PlaylistInterface ()
     : QObject()
     , m_latchMode( PlaylistModes::StayOnSong )
     , m_finished( false )
+    , m_prevAvail( false )
+    , m_nextAvail( false )
+    , m_currentIndex( -1 )
 {
     m_id = uuid();
 }
@@ -55,9 +58,9 @@ PlaylistInterface::nextResult() const
 
 
 Tomahawk::result_ptr
-PlaylistInterface::siblingResult( int itemsAway ) const
+PlaylistInterface::siblingResult( int itemsAway, qint64 rootIndex ) const
 {
-    qint64 idx = siblingIndex( itemsAway );
+    qint64 idx = siblingIndex( itemsAway, rootIndex );
     qint64 safetyCheck = -1;
 
     // If safetyCheck equals idx, this means the interface keeps returning the same item and we won't discover anything new - abort
@@ -168,3 +171,55 @@ PlaylistInterface::hasPreviousResult() const
 {
     return ( siblingResult( -1 ) );
 }
+
+
+void
+PlaylistInterface::onItemsChanged()
+{
+    if ( QThread::currentThread() != thread() )
+    {
+        QMetaObject::invokeMethod( this, "onItemsChanged", Qt::QueuedConnection );
+        return;
+    }
+
+    Tomahawk::result_ptr prevResult = siblingResult( -1, m_currentIndex );
+    Tomahawk::result_ptr nextResult = siblingResult( 1, m_currentIndex );
+
+    if ( prevResult )
+    {
+        bool avail = prevResult->toQuery()->playable();
+        if ( avail != m_prevAvail )
+        {
+            m_prevAvail = avail;
+            emit previousTrackAvailable();
+        }
+    }
+    else if ( m_prevAvail )
+    {
+        m_prevAvail = false;
+        emit previousTrackAvailable();
+    }
+
+    if ( nextResult )
+    {
+        bool avail = nextResult->toQuery()->playable();
+        if ( avail != m_nextAvail )
+        {
+            m_nextAvail = avail;
+            emit nextTrackAvailable();
+        }
+    }
+    else if ( m_nextAvail )
+    {
+        m_nextAvail = false;
+        emit nextTrackAvailable();
+    }
+}
+
+
+void
+PlaylistInterface::setCurrentIndex( qint64 index )
+{
+    m_currentIndex = index;
+    onItemsChanged();
+}

src/libtomahawk/PlaylistInterface.h

@@ -46,7 +46,7 @@ public:
     virtual int trackCount() const = 0;
 
     virtual Tomahawk::result_ptr currentItem() const = 0;
-    virtual void setCurrentIndex( qint64 index ) = 0;
+    virtual void setCurrentIndex( qint64 index );
 
     virtual bool hasNextResult() const;
     virtual bool hasPreviousResult() const;
@@ -54,7 +54,7 @@ public:
     virtual Tomahawk::result_ptr previousResult() const;
 
     virtual qint64 siblingIndex( int itemsAway, qint64 rootIndex = -1 ) const = 0;
-    virtual Tomahawk::result_ptr siblingResult( int itemsAway ) const;
+    virtual Tomahawk::result_ptr siblingResult( int itemsAway, qint64 rootIndex = -1 ) const;
 
     virtual Tomahawk::result_ptr resultAt( qint64 index ) const = 0;
     virtual Tomahawk::query_ptr queryAt( qint64 index ) const = 0;
@@ -100,11 +100,17 @@ signals:
     void previousTrackAvailable();
     void nextTrackAvailable();
 
+protected slots:
+    virtual void onItemsChanged();
+
 protected:
     virtual QList<Tomahawk::query_ptr> filterTracks( const QList<Tomahawk::query_ptr>& queries );
 
     PlaylistModes::LatchMode m_latchMode;
     bool m_finished;
+    mutable bool m_prevAvail;
+    mutable bool m_nextAvail;
+    mutable qint64 m_currentIndex;
 
 private:
     Q_DISABLE_COPY( PlaylistInterface )