/* Establish the currentRange of bases covered by the
    currentFeature of this renderer
 */
 public double[] establishRange(SeqFeatureI sf, int pos, int tier, boolean use_set) {
   double range[];
   if (sf == null || (!use_set && (sf.canHaveChildren()))) {
     range = baseEditor.getRangeAtPosition(tier, pos);
   } else {
     range = new double[2];
     range[0] = (double) baseEditor.basePairToPos(sf.getLow());
     range[1] = (double) baseEditor.basePairToPos(sf.getHigh());
   }
   return range;
 }