gui-cs.Terminal.Gui/Terminal.Gui/Drawing/GradientFill.cs

namespace Terminal.Gui;

/// <summary>
///     Implementation of <see cref="IFill"/> that uses a color gradient (including
///     radial, diagonal etc.).
/// </summary>
public class GradientFill : IFill
{
    private readonly Dictionary<Point, Color> _map;

    /// <summary>
    ///     Creates a new instance of the <see cref="GradientFill"/> class that can return
    ///     color for any point in the given <paramref name="area"/> using the provided
    ///     <paramref name="gradient"/> and <paramref name="direction"/>.
    /// </summary>
    /// <param name="area"></param>
    /// <param name="gradient"></param>
    /// <param name="direction"></param>
    public GradientFill (Rectangle area, Gradient gradient, GradientDirection direction)
    {
        _map = gradient.BuildCoordinateColorMapping (area.Height - 1, area.Width - 1, direction)
                       .ToDictionary (
                                      kvp => new Point (kvp.Key.X + area.X, kvp.Key.Y + area.Y),
                                      kvp => kvp.Value);
    }

    /// <summary>
    ///     Returns the color to use for the given <paramref name="point"/> or Black if it
    ///     lies outside the prepared gradient area (see constructor).
    /// </summary>
    /// <param name="point"></param>
    /// <returns></returns>
    public Color GetColor (Point point)
    {
        if (_map.TryGetValue (point, out Color color))
        {
            return color;
        }

        return new (0, 0); // Default to black if point not found
    }
}