comparison layer/WaveformLayer.h @ 156:b32282fefccd

* Tidy up inheritance hierarchy of model classes -- remove ZoomConstraint as
  a base class (make it a member instead) and remove virtual inheritances of
  QObject (no longer necessary).

 
 public:
     WaveformLayer();
     ~WaveformLayer();
 
-    virtual const ZoomConstraint *getZoomConstraint() const { return m_model; }
+    virtual const ZoomConstraint *getZoomConstraint() const {
+        return m_model ? m_model->getZoomConstraint() : 0;
+    }
     virtual const Model *getModel() const { return m_model; }
     virtual void paint(View *v, QPainter &paint, QRect rect) const;
 
     virtual QString getFeatureDescription(View *v, QPoint &) const;