comparison layer/Layer.h @ 947:e53a87a5efb2

Allow layers to be loaded without models if their layer class explicitly says it's OK (otherwise default template won't load, as it has an empty waveform layer)

 
     virtual const Model *getModel() const = 0;
     Model *getModel() {
 	return const_cast<Model *>(const_cast<const Layer *>(this)->getModel());
     }
-
+    
     /**
      * Return a zoom constraint object defining the supported zoom
      * levels for this layer.  If this returns zero, the layer will
      * support any integer zoom level.
      */

      * returned value is allocated on the heap and will be deleted by
      * the caller.
      */
     virtual RangeMapper *getNewVerticalZoomRangeMapper() const { return 0; }
 
+    /**
+     * Return true if this layer type can function without a model
+     * being set. If false (the default), the layer will not be loaded
+     * from a session if its model cannot be found.
+     */
+    virtual bool canExistWithoutModel() const { return false; }
+
 public slots:
     void showLayer(View *, bool show);
 
 signals:
     void modelChanged();