ImageSharp/src/ImageSharp.Drawing/Text/GlyphBuilder.cs

// <copyright file="GlyphBuilder.cs" company="James Jackson-South">
// Copyright (c) James Jackson-South and contributors.
// Licensed under the Apache License, Version 2.0.
// </copyright>

namespace ImageSharp.Drawing
{
    using System.Collections.Generic;
    using System.Numerics;

    using SixLabors.Fonts;
    using SixLabors.Shapes;

    /// <summary>
    /// rendering surface that Fonts can use to generate Shapes.
    /// </summary>
    internal class GlyphBuilder : IGlyphRenderer
    {
        private readonly PathBuilder builder = new PathBuilder();
        private readonly List<IPath> paths = new List<IPath>();
        private Vector2 currentPoint = default(Vector2);

        /// <summary>
        /// Initializes a new instance of the <see cref="GlyphBuilder"/> class.
        /// </summary>
        public GlyphBuilder()
            : this(Vector2.Zero)
        {
            // glyphs are renderd realative to bottom left so invert the Y axis to allow it to render on top left origin surface
            this.builder = new PathBuilder();
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="GlyphBuilder"/> class.
        /// </summary>
        /// <param name="origin">The origin.</param>
        public GlyphBuilder(Vector2 origin)
        {
            this.builder = new PathBuilder();
            this.builder.SetOrigin(origin);
        }

        /// <summary>
        /// Gets the paths that have been rendered by this.
        /// </summary>
        public IEnumerable<IPath> Paths => this.paths;

        /// <summary>
        /// Begins the glyph.
        /// </summary>
        /// <param name="location">The offset that the glyph will be rendered at.</param>
        void IGlyphRenderer.BeginGlyph(Vector2 location)
        {
            this.builder.Clear();
        }

        /// <summary>
        /// Begins the figure.
        /// </summary>
        void IGlyphRenderer.BeginFigure()
        {
            this.builder.StartFigure();
        }

        /// <summary>
        /// Draws a cubic bezier from the current point  to the <paramref name="point"/>
        /// </summary>
        /// <param name="secondControlPoint">The second control point.</param>
        /// <param name="thirdControlPoint">The third control point.</param>
        /// <param name="point">The point.</param>
        void IGlyphRenderer.CubicBezierTo(Vector2 secondControlPoint, Vector2 thirdControlPoint, Vector2 point)
        {
            this.builder.AddBezier(this.currentPoint, secondControlPoint, thirdControlPoint, point);
            this.currentPoint = point;
        }

        /// <summary>
        /// Ends the glyph.
        /// </summary>
        void IGlyphRenderer.EndGlyph()
        {
            this.paths.Add(this.builder.Build());
        }

        /// <summary>
        /// Ends the figure.
        /// </summary>
        void IGlyphRenderer.EndFigure()
        {
            this.builder.CloseFigure();
        }

        /// <summary>
        /// Draws a line from the current point  to the <paramref name="point"/>.
        /// </summary>
        /// <param name="point">The point.</param>
        void IGlyphRenderer.LineTo(Vector2 point)
        {
            this.builder.AddLine(this.currentPoint, point);
            this.currentPoint = point;
        }

        /// <summary>
        /// Moves to current point to the supplied vector.
        /// </summary>
        /// <param name="point">The point.</param>
        void IGlyphRenderer.MoveTo(Vector2 point)
        {
            this.builder.StartFigure();
            this.currentPoint = point;
        }

        /// <summary>
        /// Draws a quadratics bezier from the current point  to the <paramref name="point"/>
        /// </summary>
        /// <param name="secondControlPoint">The second control point.</param>
        /// <param name="point">The point.</param>
        void IGlyphRenderer.QuadraticBezierTo(Vector2 secondControlPoint, Vector2 point)
        {
            Vector2 c1 = (((secondControlPoint - this.currentPoint) * 2) / 3) + this.currentPoint;
            Vector2 c2 = (((secondControlPoint - point) * 2) / 3) + point;

            this.builder.AddBezier(this.currentPoint, c1, c2, point);
            this.currentPoint = point;
        }
    }
}