Graphics.cs

using System;

namespace Foster.Framework;

/// <summary>
/// The Core Graphics Module, used for Rendering
/// </summary>
public abstract class Graphics : AppModule
{
    /// <summary>
    /// The underlying Graphics API Name
    /// </summary>
    public string ApiName { get; protected set; } = "Unknown";

    /// <summary>
    /// The underlying Graphics API version
    /// </summary>
    public Version ApiVersion { get; protected set; } = new Version(0, 0, 0);

    /// <summary>
    /// The Underlying Graphics Device Name
    /// </summary>
    public string DeviceName { get; protected set; } = "Unknown";

    /// <summary>
    /// The Maximum Texture Width and Height supported, in pixels
    /// </summary>
    public int MaxTextureSize { get; protected set; } = 0;

    /// <summary>
    /// Whether the Frame Buffer origin is in the bottom left
    /// </summary>
    public bool OriginBottomLeft { get; protected set; } = false;

    /// <summary>
    /// The Renderer this Graphics Module implements
    /// </summary>
    public abstract Renderer Renderer { get; }

    protected Graphics() : base(200)
    {

    }

    protected internal override void Startup()
    {
        Log.Info($"{ApiName} {ApiVersion} ({DeviceName})");
    }

    /// <summary>
    /// Clears the Color of the Target
    /// </summary>
    public void Clear(RenderTarget target, Color color)
    {
        Clear(target, Framework.Clear.Color, color, 0, 0, new RectInt(0, 0, target.RenderWidth, target.RenderHeight));
    }

    /// <summary>
    /// Clears the Target
    /// </summary>
    public void Clear(RenderTarget target, Color color, float depth, int stencil)
    {
        Clear(target, Framework.Clear.All, color, depth, stencil, new RectInt(0, 0, target.RenderWidth, target.RenderHeight));
    }

    /// <summary>
    /// Clears the Target
    /// </summary>
    public void Clear(RenderTarget target, Clear flags, Color color, float depth, int stencil, RectInt viewport)
    {
        if (!target.Renderable)
            throw new Exception("Render Target cannot currently be drawn to");

        var bounds = new RectInt(0, 0, target.RenderWidth, target.RenderHeight);
        var clamped = viewport.OverlapRect(bounds);

        ClearInternal(target, flags, color, depth, stencil, clamped);
    }

    /// <summary>
    /// Clears the Target
    /// </summary>
    protected abstract void ClearInternal(RenderTarget target, Clear flags, Color color, float depth, int stencil, RectInt viewport);

    /// <summary>
    /// Draws the data from the Render pass to the Render Target.
    /// This will fail if the Target is not Drawable.
    /// </summary>
    public void Render(ref RenderPass pass)
    {
        if (!pass.Target.Renderable)
            throw new Exception("Render Target cannot currently be drawn to");

        if (!(pass.Target is FrameBuffer) && !(pass.Target is Window))
            throw new Exception("RenderTarget must be a Render Texture or a Window");

        if (pass.Mesh == null)
            throw new Exception("Mesh cannot be null when drawing");

        if (pass.Material == null)
            throw new Exception("Material cannot be null when drawing");

        if (pass.Mesh.InstanceCount > 0 && (pass.Mesh.InstanceFormat == null || (pass.Mesh.InstanceCount < pass.Mesh.InstanceCount)))
            throw new Exception("Trying to draw more Instances than exist in the Mesh");

        if (pass.Mesh.IndexCount < pass.MeshIndexStart + pass.MeshIndexCount)
            throw new Exception("Trying to draw more Indices than exist in the Mesh");

        if (pass.Viewport != null)
        {
            var bounds = new RectInt(0, 0, pass.Target.RenderWidth, pass.Target.RenderHeight);
            pass.Viewport = pass.Viewport.Value.OverlapRect(bounds);
        }

        RenderInternal(ref pass);
    }

    protected abstract void RenderInternal(ref RenderPass pass);

    /// <summary>
    /// Creates a new Color Texture of the given size
    /// </summary>
    protected internal abstract Texture.Platform CreateTexture(int width, int height, TextureFormat format);

    /// <summary>
    /// Creates a new render texture of the given size, with the given amount of color and depth buffers
    /// </summary>
    protected internal abstract FrameBuffer.Platform CreateFrameBuffer(int width, int height, TextureFormat[] attachments);

    /// <summary>
    /// Creates a new Shader from the Shader Source
    /// </summary>
    protected internal abstract Shader.Platform CreateShader(ShaderSource source);

    /// <summary>
    /// Creates a new Mesh
    /// </summary>
    protected internal abstract Mesh.Platform CreateMesh();

    /// <summary>
    /// Gets the Shader Source for the Batch2D
    /// </summary>
    protected internal abstract ShaderSource CreateShaderSourceBatch2D();

}