diff --git a/src/sink.h b/src/sink.h
--- a/src/sink.h
+++ b/src/sink.h
@@ -34,6 +34,8 @@ public:
     /// Disconnects a follower. Disconnecting an unconnected sink is
     /// an error.
     void disconnectFollower(Sink* sink);
+    /// Returns the connected source. `NULL` if it's not connected.
+    const Source* connectedSource() const;
 
 protected:
     /// Entry point for incoming data. Re-implementations should
@@ -46,11 +48,18 @@ protected:
     virtual bool hasX() const = 0;
     /// Returns number of channels
     virtual unsigned numChannels() const = 0;
+    /// Set by the connected source when its connected. When
+    /// disconnecting it's set to `NULL`.
+    ///
+    /// @important Trying to connect a source while its already
+    /// connected is an error.
+    void setSource(const Source* s);
 
     friend Source;
 
 private:
     QList<Sink*> followers;
+    const Source* source = NULL;   ///< source that this sink is connected to
 };
 
 #endif // SINK_H