src/Tools/Graphview/shapes.scala

     }
   }
 
   object Dummy
   {
-    def shape(visualizer: Visualizer, d: Layout.Point): Shape =
+    def shape(visualizer: Visualizer, d: Layout.Point): Rectangle2D.Double =
     {
       val metrics = visualizer.metrics
       val w = metrics.space_width
       new Rectangle2D.Double((d.x - (w / 2)).floor, (d.y - (w / 2)).floor, w.ceil, w.ceil)
     }