drawParkingMarker function Null safety

Implementation

Future<BitmapDescriptor> drawParkingMarker(ThemeData theme, Parking parking) async {
  print("drawing bb");
  final recorder = new ui.PictureRecorder();
  final double w = 120;
  final double h = 140;
  final double ht = 30;
  final double wt = 40;

  final canvas = new Canvas(
      recorder,
      Rect.fromPoints(Offset(0.0, 0.0), Offset(w+wt, h+ht)));

  final fill = Paint()
    ..color = theme.primaryColor
    ..style = PaintingStyle.fill;

  final bg = RRect.fromRectAndRadius(
    Rect.fromPoints( Offset(0.0, 0.0),  Offset(w, h)),
    Radius.circular(20),
  );
  final rectPath = Path()..addRRect(bg);
  canvas.drawShadow(rectPath, Colors.grey, 4, false);
  canvas.drawPath(rectPath, fill);

  //triangle
  var path = Path();
  path.moveTo(w/2, h+ht);
  path.lineTo((w-wt)/2, h);
  path.lineTo((w+wt)/2, h);
  path.close();
  final filltriangle = Paint()
    ..color = theme.primaryColor
    ..style = PaintingStyle.fill;
  canvas.drawPath(path, filltriangle);

  //title
  final pText = TextSpan(
      text: 'P',
      style: theme.textTheme.headline2!.apply(
          color: Colors.white
      )
  );
  final pTextPainter = TextPainter(
    text: pText,
    textDirection: TextDirection.ltr,
  );
  pTextPainter.layout(
    minWidth: 0,
    maxWidth: w,
  );
  // spaces
  final sText = TextSpan(
      text: parking.spacesAvailable.toString(),
      style: theme.textTheme.headline4!.apply(
          color: Colors.white,
          fontWeightDelta: 2
      )
  );
  final sTextPainter = TextPainter(
    text: sText,
    textDirection: TextDirection.ltr,
  );
  sTextPainter.layout(
    minWidth: 0,
    maxWidth: w,
  );
  var spacing = (h - pTextPainter.height - sTextPainter.height)/5;
  pTextPainter.paint(canvas, Offset(
      (w - pTextPainter.width)/2,
      2*spacing)
  );
  sTextPainter.paint(canvas, Offset(
      (w - sTextPainter.width)/2,
      (3*spacing)+pTextPainter.height)
  );

  final picture = recorder.endRecording();
  final img = await picture.toImage(124, 170);
  final byteData = await img.toByteData(format: ui.ImageByteFormat.png);
  var pngBytes = byteData!.buffer.asUint8List();
  var bs64 = base64Encode(pngBytes);
  print(pngBytes);
  print(bs64);
  print("drawing_bmp");
  return BitmapDescriptor.fromBytes(pngBytes);
}