ImageSharp/SixLabors.Fonts/Rendering/IGlyphRenderer.cs

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

using System.Numerics;

namespace SixLabors.Fonts.Rendering {
  /// <summary>
  /// A surface that can have a glyph rendered to it as a series of actions.
  /// </summary>
  public interface IGlyphRenderer
  {
      /// <summary>
      /// Called before any glyphs have been rendered.
      /// </summary>
      /// <param name="bounds">The rectangle within the text will be rendered.</param>
      public void BeginText(in FontRectangle bounds);

      /// <summary>
      /// Called once all glyphs have completed rendering.
      /// </summary>
      public void EndText();

      /// <summary>
      /// Begins the glyph.
      /// </summary>
      /// <param name="bounds">The bounds the glyph will be rendered at and at what size.</param>
      /// <param name="parameters">
      /// The set of parameters that uniquely represents a version of a glyph at particular font size, font family, font style and DPI.
      /// </param>
      /// <returns>
      /// Returns <see langword="true"/> if the glyph should be rendered otherwise it returns <see langword="false"/>.
      /// </returns>
      public bool BeginGlyph(in FontRectangle bounds, in GlyphRendererParameters parameters);

      /// <summary>
      /// Ends the glyph.
      /// </summary>
      public void EndGlyph();

      /// <summary>
      /// Begins a new painted layer with the specified paint and fill rule.
      /// All geometry commands issued after this call belong to the layer until <see cref="EndLayer"/> is called.
      /// </summary>
      /// <param name="paint">The paint definition.</param>
      /// <param name="fillRule">The fill rule to use when rasterizing this layer.</param>
      /// <param name="clipBounds">The optional clip bounds to apply when rasterizing this layer.</param>
      public void BeginLayer(Paint? paint, FillRule fillRule, ClipQuad? clipBounds);

      /// <summary>
      /// Ends the current painted layer.
      /// </summary>
      public void EndLayer();

      /// <summary>
      /// Begins the figure.
      /// </summary>
      public void BeginFigure();

      /// <summary>
      /// Sets a new start point to draw lines from.
      /// </summary>
      /// <param name="point">The point.</param>
      public void MoveTo(Vector2 point);

      /// <summary>
      /// Draw a straight line connecting the previous point to <paramref name="point"/>.
      /// </summary>
      /// <param name="point">The point.</param>
      public void LineTo(Vector2 point);

      /// <summary>
      /// Draw a quadratic bezier curve connecting the previous point to <paramref name="point"/>.
      /// </summary>
      /// <param name="secondControlPoint">The second control point.</param>
      /// <param name="point">The point.</param>
      public void QuadraticBezierTo(Vector2 secondControlPoint, Vector2 point);

      /// <summary>
      /// Draw a cubic bezier curve connecting the previous point to <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>
      public void CubicBezierTo(Vector2 secondControlPoint, Vector2 thirdControlPoint, Vector2 point);

      /// <summary>
      /// <para>
      /// Adds an elliptical arc to the current figure. The arc curves from the last point to <paramref name="point"/>,
      /// choosing one of four possible routes: clockwise or counterclockwise, and smaller or larger.
      /// </para>
      /// <para>
      /// The arc sweep is always less than 360 degrees. The method appends a line
      /// to the last point if either radii are zero, or if last point is equal to <paramref name="point"/>.
      /// In addition the method scales the radii to fit last point and <paramref name="point"/> if both
      /// are greater than zero but too small to describe an arc.
      /// </para>
      /// </summary>
      /// <param name="radiusX">The x-radius of the ellipsis.</param>
      /// <param name="radiusY">The y-radius of the ellipsis.</param>
      /// <param name="rotation">The rotation along the X-axis; measured in degrees clockwise.</param>
      /// <param name="largeArc">
      /// The large arc flag, and is <see langword="false"/> if an arc spanning less than or equal to 180 degrees
      /// is chosen, or <see langword="true"/> if an arc spanning greater than 180 degrees is chosen.
      /// </param>
      /// <param name="sweep">
      /// The sweep flag, and is <see langword="false"/> if the line joining center to arc sweeps through decreasing
      /// angles, or <see langword="true"/> if it sweeps through increasing angles.
      /// </param>
      /// <param name="point">The end point of the arc.</param>
      public void ArcTo(float radiusX, float radiusY, float rotation, bool largeArc, bool sweep, Vector2 point);

      /// <summary>
      /// Ends the figure.
      /// </summary>
      public void EndFigure();

      /// <summary>
      /// Provides a callback to enable custom logic to request decoration details.
      /// A custom <see cref="TextRun"/> might use alternative triggers to determine what decorations it needs access to.
      /// </summary>
      /// <returns>The text decorations the render wants render info for.</returns>
      public TextDecorations EnabledDecorations();

      /// <summary>
      /// Sets the details of a text decoration to be rendered.
      /// This only gets called if the decoration type was requested via <see cref="EnabledDecorations"/>
      /// and after the glyph has been rendered via <see cref="BeginGlyph"/> and <see cref="EndGlyph"/>.
      /// </summary>
      /// <param name="textDecorations">The type of decoration these details correspond to.</param>
      /// <param name="start">The start position from where to draw the decorations from.</param>
      /// <param name="end">The end position from where to draw the decorations to.</param>
      /// <param name="thickness">The thickness to draw the decoration.</param>
      public void SetDecoration(TextDecorations textDecorations, Vector2 start, Vector2 end, float thickness);
  }
}