transformValues method
Transforms the x and y values to screen coordinates.
Implementation
@override
void transformValues() {
  points.clear();
  _drawIndexes.clear();
  _highPoints.clear();
  _lowPoints.clear();
  if (_xValues.isEmpty || _topValues.isEmpty || _bottomValues.isEmpty) {
    return;
  }
  _fillPath.reset();
  _strokePath.reset();
  switch (series.emptyPointSettings.mode) {
    case EmptyPointMode.gap:
    case EmptyPointMode.zero:
    case EmptyPointMode.average:
      _calculatePoints(_xValues, _topValues, _bottomValues);
      break;
    case EmptyPointMode.drop:
      _calculateDropPoints(_xValues, _topValues, _bottomValues);
      break;
  }
  _createFillPath(_fillPath, _highPoints, _lowPoints);
}