half_circle_progress_bar_painter.dart

class _DiagramPainter extends CustomPainter {
  _DiagramPainter({
    required this.dotRadius,
    required this.startBarRadius,
    required this.layers,
    required this.layersSpacing,
    required this.dotsSpacing,
    required this.progress,
    required Color dotColor,
    required Color progressDotColor,
  })  : _paint = Paint()
          ..color = dotColor
          ..style = PaintingStyle.fill,
        _progressPaint = Paint()
          ..color = progressDotColor
          ..style = PaintingStyle.fill,
        _dotDiameter = dotRadius * 2,
        _dotsSizeWithSpacing = dotRadius * 2 + dotsSpacing;

  final double dotRadius;
  final double startBarRadius;
  final int layers;
  final double layersSpacing;
  final double dotsSpacing;
  final double progress;

  final Paint _paint;
  final Paint _progressPaint;

  final double _dotDiameter;
  final double _dotsSizeWithSpacing;

  static const _startAngle = 270.0;
  static const _circle = 360.0;
  static const _halfCircle = 180.0;

  @override
  void paint(Canvas canvas, Size size) {
    // implement this later
  }

  @override
  bool shouldRepaint(covariant _DiagramPainter oldDelegate) =>
      dotRadius != oldDelegate.dotRadius ||
      startBarRadius != oldDelegate.startBarRadius ||
      layers != oldDelegate.layers ||
      layersSpacing != oldDelegate.layersSpacing ||
      dotsSpacing != oldDelegate.dotsSpacing ||
      progress != oldDelegate.progress;
}