Utilities for working with hexagons on a hexagonal grid. Based on magnificent https://www.redblobgames.com/grids/hexagons/ article.

Zero dependencies. Framework agnostic. Use with Flutter, on Web, CLI, or anywhere Dart runs.

Example:

import 'package:hex_toolkit/hex_toolkit.dart';

void main() {
  var hexA = Hex.zero();
  var hexB = Hex(-5, -2, 7);

  print(hexA.neighbors());
  // Prints: [Hex(0, 1, -1), Hex(-1, 1, 0), Hex(-1, 0, 1), Hex(0, -1, 1), Hex(1, -1, 0), Hex(1, 0, -1)]

  print(hexA.distanceTo(hexB));
  // Prints: 7

  print(hexA.cheapestPathTo(hexB));
  // Prints: [Hex(0, 0, 0), Hex(-1, 0, 1), Hex(-2, 0, 2), Hex(-2, -1, 3), ...

  print(hexA.ring(3));
  // Prints: [Hex(3, -3, 0), Hex(3, -2, -1), Hex(3, -1, -2), Hex(3, 0, -3), ...

  // hexA.randomHexInArea(radius)
  // hexA.randomShape(50);
  // hexA.randomNeighbor();
  // hexA.randomNeighborWhere(filter);
}

Rendering in Flutter

How to paint

The library itself doesn't depend on Flutter, however the rendering is pretty straightforward:

class MyApp extends StatelessWidget {


  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: HexPainter(myHexesToPain),
      child: Container(),
    );
  }
}

class HexPainter extends CustomPainter {
  static const hexSize = 20.0;
  final List<Hex> toPaint;

  HexPainter(this.toPaint);

  @override
  void paint(Canvas canvas, Size size) {
    canvas.save();
    // Zero in the center
    canvas.translate(size.width / 2, size.height / 2);

    for (var hex in toPaint) {
      final paint = Paint()..color = Colors.red;

      // Just get the vertices ...
      var vertices = hex.vertices(hexSize).map((e) => Offset(e.x, e.y)).toList();

      // ... and draw them
      canvas.drawVertices(Vertices(VertexMode.triangleFan, vertices), BlendMode.plus, paint);
    }
    canvas.restore();
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) => true;
}

vertices() method returns a list o 6 points, which can be easily passed to drawVertices method. hexSize of the hex is it's "radius", see diagram at https://www.redblobgames.com/grids/hexagons/#basics

What to paint

In order to get a list of hexagons to paint, just find the corners and then iterate with two for loops:

Iterable<Hex> toDraw() sync* {

    Offset topLeft = Offset(x, y);
    Offset bottomRight = Offset(x + size.width, y + size.height);
    
    var topLeftHex = Hex.fromPixelPoint(PixelPoint(topLeft.dx, topLeft.dy), hexSize).cube.toGridOffset();
    var bottomRightHex = Hex.fromPixelPoint(PixelPoint(bottomRight.dx, bottomRight.dy), hexSize).cube.toGridOffset();

    for (int hx = topLeftHex.q; hx <= bottomRightHex.q; ++hx) {
        for (int hy = topLeftHex.r; hy <= bottomRightHex.r; ++hy) {
            yield Hex.fromOffset(GridOffset(hx, hy));
        }
    }
}

Glory to Hexagons!

... this "world generator" is not part of the library, but it's something you can easily whip out with this toolkit.

Once again, thanks to https://www.redblobgames.com/grids/hexagons/ for the inspiration.