private double getWindowMinX() {
   double x = selection[0];
   if (x == overviewHandler.getData().getX(0)) {
     return firstDataPoint.getX();
   }
   return x;
 }
 private double getWindowMaxX() {
   double x = selection[1];
   SeriesData data = overviewHandler.getData();
   int size = data.length();
   if (size > 0 && x == data.getX(size - 1)) {
     return lastDataPoint.getX();
   }
   return x;
 }
 @Override
 public SeriesData getData() {
   return overviewHandler.getData();
 }