various: extended marker and timeline functionality

app/widget/timeruler/timeruler.h

@@ -45,6 +45,9 @@ protected:
 
   virtual void TimebaseChangedEvent(const rational& tb) override;
 
+protected slots:
+  virtual bool ShowContextMenu(const QPoint &p) override;
+
 private:
   void UpdateHeight();
 
@@ -64,9 +67,6 @@ private:
 
   PlaybackCache* playback_cache_;
 
-private slots:
-  void ShowContextMenu();
-
 };
 
 }