use strings to connect nodes

This makes the node system somewhat more high-level with the intent of making
working with them far more flexible and stable. By making the architecture more
abstracted, it becomes far less rigid which should allow us to do even more
with it and make it much less crash prone.

app/node/output/viewer/viewer.h

@@ -59,17 +59,7 @@ public:
   void ShiftAudioCache(const rational& from, const rational& to);
   void ShiftCache(const rational& from, const rational& to);
 
-  NodeInput* texture_input() const
-  {
-    return texture_input_;
-  }
-
-  NodeInput* samples_input() const
-  {
-    return samples_input_;
-  }
-
-  virtual void InvalidateCache(const TimeRange& range, const InputConnection& from) override;
+  virtual void InvalidateCache(const TimeRange& range, const QString& from, int element = -1) override;
 
   const VideoParams& video_params() const
   {
@@ -106,11 +96,6 @@ public:
    */
   QVector<Track *> GetUnlockedTracks() const;
 
-  NodeInput* track_input(Track::Type type) const
-  {
-    return track_inputs_.at(type);
-  }
-
   TrackList* track_list(Track::Type type) const
   {
     return track_lists_.at(type);
@@ -132,6 +117,10 @@ public:
 
   virtual void EndOperation() override;
 
+  static const QString kTextureInput;
+  static const QString kSamplesInput;
+  static const QString kTrackInputFormat;
+
 signals:
   void TimebaseChanged(const rational&);
 
@@ -149,19 +138,20 @@ signals:
   void TrackAdded(Track* track);
   void TrackRemoved(Track* track);
 
+  void TextureInputChanged();
+
+protected:
+  void InputConnectedEvent(const QString &input, int element, const NodeOutput &output) override;
+
+  void InputDisconnectedEvent(const QString &input, int element, const NodeOutput &output) override;
+
 private:
   QUuid uuid_;
 
-  NodeInput* texture_input_;
-
-  NodeInput* samples_input_;
-
   VideoParams video_params_;
 
   AudioParams audio_params_;
 
-  QVector<NodeInput*> track_inputs_;
-
   QVector<TrackList*> track_lists_;
 
   QVector<Track*> track_cache_;