ImageSharp/ImageSharp.Drawing/Processing/Backends/CompositionSceneCommandBase.cs

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

#pragma warning disable SA1649 // Scene command types are grouped together in one file.

namespace SixLabors.ImageSharp.Drawing.Processing.Backends {
  /// <summary>
  /// Visitor contract for one flush-scoped composition scene command.
  /// </summary>
  public interface ICompositionSceneCommandVisitor
  {
      /// <summary>
      /// Visits one fill-path or layer-based composition command.
      /// </summary>
      /// <param name="command">The command being visited.</param>
      public void Visit(PathCompositionSceneCommand command);

      /// <summary>
      /// Visits one stroked path command.
      /// </summary>
      /// <param name="command">The command being visited.</param>
      public void Visit(StrokePathCompositionSceneCommand command);

      /// <summary>
      /// Visits one explicit stroked line-segment command.
      /// </summary>
      /// <param name="command">The command being visited.</param>
      public void Visit(LineSegmentCompositionSceneCommand command);

      /// <summary>
      /// Visits one explicit stroked polyline command.
      /// </summary>
      /// <param name="command">The command being visited.</param>
      public void Visit(PolylineCompositionSceneCommand command);
  }

  /// <summary>
  /// Base type for one draw-order command in a flush-scoped scene stream.
  /// </summary>
  public abstract class CompositionSceneCommand
  {
      /// <summary>
      /// Dispatches the command to a visitor without a per-item kind switch at the call site.
      /// </summary>
      /// <param name="visitor">The visitor receiving the command.</param>
      public abstract void Accept(ICompositionSceneCommandVisitor visitor);
  }

  /// <summary>
  /// Scene command wrapper for fill-path and layer-based composition commands.
  /// </summary>
  public sealed class PathCompositionSceneCommand : CompositionSceneCommand
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="PathCompositionSceneCommand"/> class.
      /// </summary>
      /// <param name="command">The wrapped composition command.</param>
      public PathCompositionSceneCommand(in CompositionCommand command)
          => this.Command = command;

      /// <summary>
      /// Gets the wrapped composition command.
      /// </summary>
      public CompositionCommand Command { get; internal set; }

      /// <inheritdoc />
      public override void Accept(ICompositionSceneCommandVisitor visitor) => visitor.Visit(this);
  }

  /// <summary>
  /// Scene command wrapper for stroked path commands.
  /// </summary>
  public sealed class StrokePathCompositionSceneCommand : CompositionSceneCommand
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="StrokePathCompositionSceneCommand"/> class.
      /// </summary>
      /// <param name="command">The wrapped stroke path command.</param>
      public StrokePathCompositionSceneCommand(in StrokePathCommand command)
          => this.Command = command;

      /// <summary>
      /// Gets the wrapped stroke path command.
      /// </summary>
      public StrokePathCommand Command { get; internal set; }

      /// <inheritdoc />
      public override void Accept(ICompositionSceneCommandVisitor visitor) => visitor.Visit(this);
  }

  /// <summary>
  /// Scene command wrapper for explicit stroked line-segment commands.
  /// </summary>
  public sealed class LineSegmentCompositionSceneCommand : CompositionSceneCommand
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="LineSegmentCompositionSceneCommand"/> class.
      /// </summary>
      /// <param name="command">The wrapped stroke line-segment command.</param>
      public LineSegmentCompositionSceneCommand(in StrokeLineSegmentCommand command)
          => this.Command = command;

      /// <summary>
      /// Gets the wrapped stroke line-segment command.
      /// </summary>
      public StrokeLineSegmentCommand Command { get; }

      /// <inheritdoc />
      public override void Accept(ICompositionSceneCommandVisitor visitor) => visitor.Visit(this);
  }

  /// <summary>
  /// Scene command wrapper for explicit stroked polyline commands.
  /// </summary>
  public sealed class PolylineCompositionSceneCommand : CompositionSceneCommand
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="PolylineCompositionSceneCommand"/> class.
      /// </summary>
      /// <param name="command">The wrapped stroke polyline command.</param>
      public PolylineCompositionSceneCommand(in StrokePolylineCommand command)
          => this.Command = command;

      /// <summary>
      /// Gets the wrapped stroke polyline command.
      /// </summary>
      public StrokePolylineCommand Command { get; }

      /// <inheritdoc />
      public override void Accept(ICompositionSceneCommandVisitor visitor) => visitor.Visit(this);
  }
}