comparison layer/Layer.h @ 949:e3c7da3d896e osx-retina

Merge from default branch

 
     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(LayerGeometryProvider *, bool show);
 
 signals:
     void modelChanged();