ImageSharp/SixLabors.Fonts/Tables/Cff/TransformingGlyphRenderer.cs

// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Numerics;
using System.Runtime.CompilerServices;
using SixLabors.Fonts.Rendering;

namespace SixLabors.Fonts.Tables.Cff {
  /// <summary>
  /// Used to apply a transform against any glyphs rendered by the engine.
  /// </summary>
  internal struct TransformingGlyphRenderer : IGlyphRenderer
  {
      private static readonly Vector2 YInverter = new(1, -1);
      private readonly IGlyphRenderer renderer;
      private Vector2 origin;
      private Vector2 scale;
      private Vector2 offset;
      private Matrix3x2 transform;

      /// <summary>
      /// Initializes a new instance of the <see cref="TransformingGlyphRenderer"/> struct.
      /// </summary>
      /// <param name="renderer">The underlying glyph renderer to delegate to.</param>
      /// <param name="origin">The origin point for rendering.</param>
      /// <param name="scale">The scale factor to apply.</param>
      /// <param name="offset">The offset to apply before transformation.</param>
      /// <param name="transform">The transformation matrix to apply.</param>
      public TransformingGlyphRenderer(IGlyphRenderer renderer, Vector2 origin, Vector2 scale, Vector2 offset, Matrix3x2 transform)
      {
          this.renderer = renderer;
          this.origin = origin;
          this.scale = scale;
          this.offset = offset;
          this.transform = transform;
          this.IsOpen = false;
      }

      /// <summary>
      /// Gets or sets a value indicating whether a figure is currently open.
      /// </summary>
      public bool IsOpen { get; set; }

      /// <inheritdoc/>
      public void BeginFigure()
      {
          this.IsOpen = true;
          this.renderer.BeginFigure();
      }

      /// <inheritdoc/>
      public bool BeginGlyph(in FontRectangle bounds, in GlyphRendererParameters parameters)
      {
          this.IsOpen = false;
          return this.renderer.BeginGlyph(in bounds, in parameters);
      }

      /// <inheritdoc/>
      public void BeginText(in FontRectangle bounds)
      {
          this.IsOpen = false;
          this.renderer.BeginText(in bounds);
      }

      /// <inheritdoc/>
      public void EndFigure()
      {
          this.IsOpen = false;
          this.renderer.EndFigure();
      }

      /// <inheritdoc/>
      public void EndGlyph()
      {
          this.IsOpen = false;
          this.renderer.EndGlyph();
      }

      /// <inheritdoc/>
      public void EndText()
      {
          this.IsOpen = false;
          this.renderer.EndText();
      }

      /// <inheritdoc/>
      public void LineTo(Vector2 point)
      {
          this.IsOpen = true;
          this.renderer.LineTo(this.Transform(point));
      }

      /// <inheritdoc/>
      public void MoveTo(Vector2 point)
      {
          if (this.IsOpen)
          {
              this.EndFigure();
          }

          this.BeginFigure();
          this.renderer.MoveTo(this.Transform(point));
          this.IsOpen = true;
      }

      /// <inheritdoc/>
      public void ArcTo(float radiusX, float radiusY, float rotationDegrees, bool largeArc, bool sweep, Vector2 point)
      {
          this.IsOpen = true;
          this.renderer.ArcTo(radiusX * this.scale.X, radiusY * this.scale.Y, rotationDegrees, largeArc, sweep, this.Transform(point));
      }

      /// <inheritdoc/>
      public void CubicBezierTo(Vector2 secondControlPoint, Vector2 thirdControlPoint, Vector2 point)
      {
          this.IsOpen = true;
          this.renderer.CubicBezierTo(this.Transform(secondControlPoint), this.Transform(thirdControlPoint), this.Transform(point));
      }

      /// <inheritdoc/>
      public void QuadraticBezierTo(Vector2 secondControlPoint, Vector2 point)
      {
          this.IsOpen = true;
          this.renderer.QuadraticBezierTo(this.Transform(secondControlPoint), this.Transform(point));
      }

      /// <inheritdoc/>
      public readonly TextDecorations EnabledDecorations()
          => this.renderer.EnabledDecorations();

      /// <inheritdoc/>
      public readonly void SetDecoration(TextDecorations textDecorations, Vector2 start, Vector2 end, float thickness)
          => this.renderer.SetDecoration(textDecorations, this.Transform(start), this.Transform(end), thickness);

      /// <summary>
      /// Applies the scale, offset, transform matrix, and Y-axis inversion to the given point.
      /// </summary>
      /// <param name="point">The point to transform.</param>
      /// <returns>The transformed point.</returns>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      private readonly Vector2 Transform(Vector2 point)
          => (Vector2.Transform((point * this.scale) + this.offset, this.transform) * YInverter) + this.origin;

      /// <inheritdoc/>
      public readonly void BeginLayer(Paint? paint, FillRule fillRule, ClipQuad? clipBounds)
          => this.renderer.BeginLayer(paint, fillRule, clipBounds);

      /// <inheritdoc/>
      public readonly void EndLayer() => this.renderer.EndLayer();
  }
}