Chessistics/Scripts/Pieces/TrajectView.cs

using Godot;

namespace Chessistics.Scripts.Pieces;

public partial class TrajectView : Line2D
{
    public int PieceId { get; private set; }
    private Polygon2D? _arrow;

    public void Setup(int pieceId, Vector2 from, Vector2 to, Color color)
    {
        PieceId = pieceId;
        Width = 2.5f;
        DefaultColor = new Color(color, 0.35f);
        Antialiased = true;
        ClearPoints();
        AddPoint(from);
        AddPoint(to);
        ZIndex = -1;

        // Arrowhead at the end point
        var dir = (to - from).Normalized();
        var perp = new Vector2(-dir.Y, dir.X);
        float arrowSize = 8f;
        var tip = to - dir * 4f; // slightly inset from end
        var baseL = tip - dir * arrowSize + perp * arrowSize * 0.5f;
        var baseR = tip - dir * arrowSize - perp * arrowSize * 0.5f;

        _arrow = new Polygon2D
        {
            Polygon = [tip - Position, baseL - Position, baseR - Position],
            Color = new Color(color, 0.4f),
            Position = Vector2.Zero
        };
        // Position relative to parent, not this Line2D
        AddChild(_arrow);
    }
}