transformValues method
Transforms the x and y values to screen coordinates.
Implementation
@override
void transformValues() {
  points.clear();
  _drawIndexes.clear();
  _highPoints.clear();
  _lowPoints.clear();
  _startControlHighPoints.clear();
  _endControlHighPoints.clear();
  _fillPath.reset();
  _strokePath.reset();
  if (_xValues.isEmpty || _yValues.isEmpty) {
    return;
  }
  _calculatePoints(_xValues, _yValues);
  _createFillPath(
    _fillPath,
    _highPoints,
    _lowPoints,
    _startControlHighPoints,
    _endControlHighPoints,
  );
}