comparison layer/SpectrumLayer.h @ 267:4ed1446ad604

* more on measurement tool -- pull out some logic from pane to layer &c
  still more to do

     virtual void setProperties(const QXmlAttributes &);
 
     virtual bool getValueExtents(float &min, float &max,
                                  bool &logarithmic, QString &unit) const;
 
-    virtual bool getXScaleValue(View *v, int x,
+    virtual bool getXScaleValue(const View *v, int x,
                                 float &value, QString &unit) const;
 
     virtual bool isLayerScrollable(const View *) const { return false; }
 
     void setChannel(int);