gobang/lib/widgets/board_painter.dart

import 'package:flutter/cupertino.dart';
import 'package:gobang/models/position.dart';
import 'package:gobang/utils/constants.dart';

/// 棋盘 + 棋子绘制；最后一手支持缩放入场与高亮光圈。
class BoardPainter extends CustomPainter {
  BoardPainter({
    required this.pieces,
    required this.version,
    this.lastMoveScale = 1,
    this.lastMovePulse = 0,
  });

  final List<Position> pieces;
  final int version;
  final double lastMoveScale;
  final double lastMovePulse;

  @override
  void paint(Canvas canvas, Size size) {
    final cell = size.width / (kBoardSize - 1);
    final bg = Paint()
      ..isAntiAlias = true
      ..style = PaintingStyle.fill
      ..color = const Color(0x77cdb175);
    canvas.drawRect(Offset.zero & size, bg);

    final line = Paint()
      ..style = PaintingStyle.stroke
      ..color = CupertinoColors.systemGrey6
      ..strokeWidth = 1;
    for (var i = 0; i < kBoardSize; i++) {
      final o = cell * i;
      canvas.drawLine(Offset(0, o), Offset(size.width, o), line);
      canvas.drawLine(Offset(o, 0), Offset(o, size.height), line);
    }

    final radius = cell / 2 - 2;
    final fill = Paint()..style = PaintingStyle.fill;
    final lastIndex = pieces.length - 1;

    for (var i = 0; i < pieces.length; i++) {
      final p = pieces[i];
      final isLast = i == lastIndex;
      final center = Offset(p.dx, p.dy);
      final scale = isLast ? lastMoveScale.clamp(0.0, 1.2) : 1.0;
      final r = radius * scale;

      if (isLast && lastMovePulse > 0) {
        final ring = Paint()
          ..style = PaintingStyle.stroke
          ..strokeWidth = 2.5
          ..color = const Color(0xE0E53935).withValues(
            alpha: 0.85 * lastMovePulse,
          );
        canvas.drawCircle(center, radius * (1.15 + 0.45 * lastMovePulse), ring);
      }

      fill.color = p.chess.color;
      if (p.chessShape.shape == 1) {
        canvas.drawCircle(center, r, fill);
      } else {
        canvas.drawRect(
          Rect.fromCircle(center: center, radius: r),
          fill,
        );
      }

      // 最后一手中心小三角标记，方便辨认落点
      if (isLast && scale > 0.85) {
        final mark = Paint()
          ..style = PaintingStyle.fill
          ..color = const Color(0xFFE53935);
        final s = radius * 0.28;
        final path = Path()
          ..moveTo(center.dx, center.dy - s)
          ..lineTo(center.dx - s * 0.9, center.dy + s * 0.7)
          ..lineTo(center.dx + s * 0.9, center.dy + s * 0.7)
          ..close();
        canvas.drawPath(path, mark);
      }
    }
  }

  @override
  bool shouldRepaint(covariant BoardPainter oldDelegate) {
    return oldDelegate.version != version ||
        oldDelegate.lastMoveScale != lastMoveScale ||
        oldDelegate.lastMovePulse != lastMovePulse;
  }
}