acdream/src/AcDream.App/Rendering/TextRenderGlStateScope.cs

using Silk.NET.OpenGL;

namespace AcDream.App.Rendering;

internal interface ITextRenderGlStateApi
{
    bool IsEnabled(EnableCap capability);

    int GetInteger(GetPName parameter);

    bool GetBoolean(GetPName parameter);

    void SetCapability(EnableCap capability, bool enabled);

    void DepthMask(bool enabled);

    void BlendFuncSeparate(
        BlendingFactor sourceRgb,
        BlendingFactor destinationRgb,
        BlendingFactor sourceAlpha,
        BlendingFactor destinationAlpha);

    void UseProgram(uint program);

    void BindVertexArray(uint vertexArray);

    void BindBuffer(BufferTargetARB target, uint buffer);

    void ActiveTexture(TextureUnit unit);

    void BindTexture(TextureTarget target, uint texture);
}

internal sealed class SilkTextRenderGlStateApi : ITextRenderGlStateApi
{
    private readonly GL _gl;

    public SilkTextRenderGlStateApi(GL gl) =>
        _gl = gl ?? throw new ArgumentNullException(nameof(gl));

    public bool IsEnabled(EnableCap capability) => _gl.IsEnabled(capability);

    public int GetInteger(GetPName parameter) => _gl.GetInteger(parameter);

    public bool GetBoolean(GetPName parameter) => _gl.GetBoolean(parameter);

    public void SetCapability(EnableCap capability, bool enabled)
    {
        if (enabled)
            _gl.Enable(capability);
        else
            _gl.Disable(capability);
    }

    public void DepthMask(bool enabled) => _gl.DepthMask(enabled);

    public void BlendFuncSeparate(
        BlendingFactor sourceRgb,
        BlendingFactor destinationRgb,
        BlendingFactor sourceAlpha,
        BlendingFactor destinationAlpha) =>
        _gl.BlendFuncSeparate(
            sourceRgb,
            destinationRgb,
            sourceAlpha,
            destinationAlpha);

    public void UseProgram(uint program) => _gl.UseProgram(program);

    public void BindVertexArray(uint vertexArray) => _gl.BindVertexArray(vertexArray);

    public void BindBuffer(BufferTargetARB target, uint buffer) =>
        _gl.BindBuffer(target, buffer);

    public void ActiveTexture(TextureUnit unit) => _gl.ActiveTexture(unit);

    public void BindTexture(TextureTarget target, uint texture) =>
        _gl.BindTexture(target, texture);
}

/// <summary>
/// Exact, focused state transaction for <see cref="TextRenderer.Flush"/>. It
/// captures every GL value that Flush or DrawLayer mutates, while avoiding the
/// dozens of unrelated synchronous reads made by the broad diagnostic scope.
/// </summary>
internal readonly struct TextRenderGlStateScope : IDisposable
{
    private readonly ITextRenderGlStateApi _gl;
    private readonly bool _depthTest;
    private readonly bool _blend;
    private readonly bool _cullFace;
    private readonly bool _alphaToCoverage;
    private readonly bool _multisample;
    private readonly bool _depthWrite;
    private readonly int _blendSourceRgb;
    private readonly int _blendDestinationRgb;
    private readonly int _blendSourceAlpha;
    private readonly int _blendDestinationAlpha;
    private readonly int _program;
    private readonly int _vertexArray;
    private readonly int _arrayBuffer;
    private readonly int _activeTexture;
    private readonly int _texture0Binding2D;

    public TextRenderGlStateScope(ITextRenderGlStateApi gl)
    {
        _gl = gl ?? throw new ArgumentNullException(nameof(gl));
        _depthTest = gl.IsEnabled(EnableCap.DepthTest);
        _blend = gl.IsEnabled(EnableCap.Blend);
        _cullFace = gl.IsEnabled(EnableCap.CullFace);
        _alphaToCoverage = gl.IsEnabled(EnableCap.SampleAlphaToCoverage);
        _multisample = gl.IsEnabled(EnableCap.Multisample);
        _depthWrite = gl.GetBoolean(GetPName.DepthWritemask);
        _blendSourceRgb = gl.GetInteger(GetPName.BlendSrcRgb);
        _blendDestinationRgb = gl.GetInteger(GetPName.BlendDstRgb);
        _blendSourceAlpha = gl.GetInteger(GetPName.BlendSrcAlpha);
        _blendDestinationAlpha = gl.GetInteger(GetPName.BlendDstAlpha);
        _program = gl.GetInteger(GetPName.CurrentProgram);
        _vertexArray = gl.GetInteger(GetPName.VertexArrayBinding);
        _arrayBuffer = gl.GetInteger(GetPName.ArrayBufferBinding);
        _activeTexture = gl.GetInteger(GetPName.ActiveTexture);

        try
        {
            gl.ActiveTexture(TextureUnit.Texture0);
            _texture0Binding2D = gl.GetInteger(GetPName.TextureBinding2D);
        }
        finally
        {
            gl.ActiveTexture((TextureUnit)_activeTexture);
        }
    }

    public void Dispose()
    {
        _gl.UseProgram((uint)_program);
        _gl.BindVertexArray((uint)_vertexArray);
        _gl.BindBuffer(BufferTargetARB.ArrayBuffer, (uint)_arrayBuffer);

        _gl.ActiveTexture(TextureUnit.Texture0);
        _gl.BindTexture(TextureTarget.Texture2D, (uint)_texture0Binding2D);
        _gl.ActiveTexture((TextureUnit)_activeTexture);

        _gl.DepthMask(_depthWrite);
        _gl.BlendFuncSeparate(
            (BlendingFactor)_blendSourceRgb,
            (BlendingFactor)_blendDestinationRgb,
            (BlendingFactor)_blendSourceAlpha,
            (BlendingFactor)_blendDestinationAlpha);
        _gl.SetCapability(EnableCap.DepthTest, _depthTest);
        _gl.SetCapability(EnableCap.Blend, _blend);
        _gl.SetCapability(EnableCap.CullFace, _cullFace);
        _gl.SetCapability(EnableCap.SampleAlphaToCoverage, _alphaToCoverage);
        _gl.SetCapability(EnableCap.Multisample, _multisample);
    }
}