--- a/flys-artifacts/src/main/java/de/intevation/flys/exports/XYChartGenerator.java	Tue Dec 20 15:12:11 2011 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/exports/XYChartGenerator.java	Tue Dec 20 15:14:54 2011 +0000
@@ -950,8 +950,8 @@
      * Get renderer, from plot or cloned default renderer otherwise.
      */
     protected XYLineAndShapeRenderer getRenderer(XYPlot plot, int idx) {
-        // !TODO what if its a differencerenderer?!
         logger.debug("getRenderer: " + idx);
+
         XYLineAndShapeRenderer r =
             (XYLineAndShapeRenderer) plot.getRenderer(idx);
 
@@ -959,12 +959,19 @@
             return r;
         }
 
+        // Need a new renderer.
         if (idx == 0) {
             logger.warn("No default renderer set!");
             return new XYLineAndShapeRenderer();
         }
 
-        r = (XYLineAndShapeRenderer) plot.getRenderer(0);
+        // 'Default' (first) renderer is an area-renderer.
+        XYItemRenderer renderer = (XYItemRenderer) plot.getRenderer(0);
+        if (renderer instanceof StableXYDifferenceRenderer) {
+            return new XYLineAndShapeRenderer();
+        }
+
+        r = (XYLineAndShapeRenderer) renderer;
 
         try {
             return (XYLineAndShapeRenderer) r.clone();