interval_progressbar_abstract.dart

abstract class IntervalProgressPainter extends CustomPainter {
  final int max;
  final int progress;
  final int intervalSize;
  final Color highlightColor;
  final Color defaultColor;
  final Color intervalColor;
  final Color intervalHighlightColor;
  final double radius;
  final bool reverse;

  final Paint _paint = Paint()
    ..style = PaintingStyle.fill
    ..isAntiAlias = true;

  Rect bound;

  @override
  @mustCallSuper
  void paint(Canvas canvas, Size size) {
    if (progress > max) {
      throw Exception("progress must <= max");
    }
    bound = Offset.zero & size;
    Size blockSize = calBlockSize();
    for (int i = 0; i < max; i++) {
      paintBlock(canvas, i, blockSize);
    }
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    final old = oldDelegate as IntervalProgressPainter;
    return old.max != max ||
        old.progress != progress ||
        old.intervalSize != intervalSize ||
        old.intervalColor != intervalColor ||
        old.defaultColor != defaultColor ||
        old.highlightColor != highlightColor ||
        old.intervalHighlightColor != intervalHighlightColor ||
        old.radius != radius;
  }

  bool highlightBlock(int index) =>
      reverse ? index >= (max - progress) : index < progress;

  bool highlightInterval(int index) =>
      reverse ? index >= (max - progress - 1) : index < progress - 1;

  void paintBlock(Canvas canvas, int blockIndex, Size blockSize);

  Size calBlockSize();

  bool shouldDrawStartRadius(int index) => index == 0 && radius > 0;

  bool shouldDrawEndRadius(int index) => index == max - 1 && radius > 0;

  bool shouldDrawInterval(int index) =>
      index != max - 1 &&
      (intervalColor != IntervalProgressBar.TRANSPARENT ||
          intervalHighlightColor != IntervalProgressBar.TRANSPARENT);
}