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

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

using System.Numerics;
using SixLabors.Fonts.Rendering;
using SixLabors.Fonts.Unicode;

namespace SixLabors.Fonts.Tables.Cff {
  /// <summary>
  /// Represents a glyph metric from a particular Compact Font Face.
  /// </summary>
  internal class CffGlyphMetrics : FontGlyphMetrics
  {
      private CffGlyphData glyphData;

      /// <summary>
      /// Initializes a new instance of the <see cref="CffGlyphMetrics"/> class with text attribute parameters.
      /// </summary>
      /// <param name="fontMetrics">The font metrics.</param>
      /// <param name="glyphId">The glyph identifier.</param>
      /// <param name="codePoint">The Unicode code point.</param>
      /// <param name="glyphData">The CFF glyph data containing the charstring program.</param>
      /// <param name="bounds">The glyph bounding box.</param>
      /// <param name="advanceWidth">The advance width.</param>
      /// <param name="advanceHeight">The advance height.</param>
      /// <param name="leftSideBearing">The left side bearing.</param>
      /// <param name="topSideBearing">The top side bearing.</param>
      /// <param name="unitsPerEM">The units per em.</param>
      /// <param name="textAttributes">The text attributes.</param>
      /// <param name="textDecorations">The text decorations.</param>
      /// <param name="glyphType">The glyph type.</param>
      internal CffGlyphMetrics(
          StreamFontMetrics fontMetrics,
          ushort glyphId,
          CodePoint codePoint,
          CffGlyphData glyphData,
          Bounds bounds,
          ushort advanceWidth,
          ushort advanceHeight,
          short leftSideBearing,
          short topSideBearing,
          ushort unitsPerEM,
          TextAttributes textAttributes,
          TextDecorations textDecorations,
          GlyphType glyphType)
          : base(
                fontMetrics,
                glyphId,
                codePoint,
                bounds,
                advanceWidth,
                advanceHeight,
                leftSideBearing,
                topSideBearing,
                unitsPerEM,
                textAttributes,
                textDecorations,
                glyphType)
          => this.glyphData = glyphData;

      /// <summary>
      /// Initializes a new instance of the <see cref="CffGlyphMetrics"/> class with offset, scale, and text run parameters.
      /// </summary>
      /// <param name="fontMetrics">The font metrics.</param>
      /// <param name="glyphId">The glyph identifier.</param>
      /// <param name="codePoint">The Unicode code point.</param>
      /// <param name="glyphData">The CFF glyph data containing the charstring program.</param>
      /// <param name="bounds">The glyph bounding box.</param>
      /// <param name="advanceWidth">The advance width.</param>
      /// <param name="advanceHeight">The advance height.</param>
      /// <param name="leftSideBearing">The left side bearing.</param>
      /// <param name="topSideBearing">The top side bearing.</param>
      /// <param name="unitsPerEM">The units per em.</param>
      /// <param name="offset">The glyph offset.</param>
      /// <param name="scaleFactor">The scale factor.</param>
      /// <param name="textRun">The text run for rendering.</param>
      /// <param name="glyphType">The glyph type.</param>
      internal CffGlyphMetrics(
          StreamFontMetrics fontMetrics,
          ushort glyphId,
          CodePoint codePoint,
          CffGlyphData glyphData,
          Bounds bounds,
          ushort advanceWidth,
          ushort advanceHeight,
          short leftSideBearing,
          short topSideBearing,
          ushort unitsPerEM,
          Vector2 offset,
          Vector2 scaleFactor,
          TextRun textRun,
          GlyphType glyphType)
          : base(
                fontMetrics,
                glyphId,
                codePoint,
                bounds,
                advanceWidth,
                advanceHeight,
                leftSideBearing,
                topSideBearing,
                unitsPerEM,
                offset,
                scaleFactor,
                textRun,
                glyphType)
          => this.glyphData = glyphData;

      /// <inheritdoc/>
      internal override FontGlyphMetrics CloneForRendering(TextRun textRun)
          => new CffGlyphMetrics(
              this.FontMetrics,
              this.GlyphId,
              this.CodePoint,
              this.glyphData,
              this.Bounds,
              this.AdvanceWidth,
              this.AdvanceHeight,
              this.LeftSideBearing,
              this.TopSideBearing,
              this.UnitsPerEm,
              this.Offset,
              this.ScaleFactor,
              textRun,
              this.GlyphType);

      /// <inheritdoc/>
      internal override void RenderTo(
          IGlyphRenderer renderer,
          int graphemeIndex,
          Vector2 glyphOrigin,
          Vector2 decorationOrigin,
          GlyphLayoutMode mode,
          TextOptions options)
      {
          // https://www.unicode.org/faq/unsup_char.html
          if (ShouldSkipGlyphRendering(this.CodePoint))
          {
              return;
          }

          float pointSize = this.TextRun.Font?.Size ?? options.Font.Size;
          float dpi = options.Dpi;

          glyphOrigin *= dpi;
          decorationOrigin *= dpi;
          float scaledPPEM = this.GetScaledSize(pointSize, dpi);

          Matrix3x2 rotation = GetRotationMatrix(mode);
          FontRectangle box = this.GetBoundingBox(mode, glyphOrigin, scaledPPEM);
          GlyphRendererParameters parameters = new(this, this.TextRun, pointSize, dpi, mode, graphemeIndex);

          if (renderer.BeginGlyph(in box, in parameters))
          {
              if (!UnicodeUtility.ShouldRenderWhiteSpaceOnly(this.CodePoint))
              {
                  Vector2 scale = new Vector2(scaledPPEM) / this.ScaleFactor;

                  // Apply the CFF FontMatrix to convert charstring coordinates to design units.
                  // The normalized FontMatrix (fontMatrix * unitsPerEM) is identity for the default
                  // [0.001, 0, 0, 0.001, 0, 0] with upm=1000.
                  if (this.glyphData.FontMatrix is double[] fm)
                  {
                      float upm = this.UnitsPerEm;
                      scale *= new Vector2((float)(fm[0] * upm), (float)(fm[3] * upm));
                  }

                  Vector2 scaledOffset = this.Offset * scale;
                  this.glyphData.RenderTo(renderer, glyphOrigin, scale, scaledOffset, rotation);
              }

              renderer.EndGlyph();
              this.RenderDecorationsTo(renderer, decorationOrigin, mode, rotation, scaledPPEM, options);
          }
      }
  }
}