/**
  * Returns the drawing supplier from the plot.
  *
  * @return The drawing supplier (possibly <code>null</code>).
  */
 public DrawingSupplier getDrawingSupplier() {
   DrawingSupplier result = null;
   CategoryPlot cp = getPlot();
   if (cp != null) {
     result = cp.getDrawingSupplier();
   }
   return result;
 }