--- a/Framework/Layers/ILayerSource.h	Tue May 16 22:12:41 2017 +0200
+++ b/Framework/Layers/ILayerSource.h	Wed May 17 22:03:09 2017 +0200
@@ -36,6 +36,10 @@
       {
       }
 
+      // Triggered as soon as the source has enough information to
+      // answer to "GetExtent()"
+      virtual void NotifyGeometryReady(ILayerSource& source) = 0;
+      
       // Triggered if the extent or the content of the volume has changed
       virtual void NotifySourceChange(ILayerSource& source) = 0;
 
@@ -67,5 +71,7 @@
                            const SliceGeometry& viewportSlice) = 0;
 
     virtual void ScheduleLayerCreation(const SliceGeometry& viewportSlice) = 0;
+
+    virtual void Start() = 0;
   };
 }