Core.cs

using OpenTK.Graphics.OpenGL4;
using OpenTK.Mathematics;
using OpenTK.Windowing.Common;
using OpenTK.Windowing.Desktop;
using OpenTK.Windowing.GraphicsLibraryFramework;

namespace TextMeshRender;

public static class Core
{
    private static readonly GameWindow Window = new(
        GameWindowSettings.Default,
        new NativeWindowSettings
        {
            NumberOfSamples = 4,
        }
    );

    private static string _vertexShaderPath = null!;
    private static string _fragmentShaderPath = null!;

    public static Vector2i WindowSize {
        get => Window.Size;
        set => Window.Size = value;
    }
    
    public static string VertexShaderPath {
        get => _vertexShaderPath;
        set => _vertexShaderPath = value;
    }
    
    public static string FragmentShaderPath {
        get => _fragmentShaderPath;
        set => _fragmentShaderPath = value;
    }
    
    public static string Title {
        get => Window.Title;
        set => Window.Title = value;
    }
    
    public static VSyncMode VSync {
        get => Window.VSync;
        set => Window.VSync = value;
    }
    
    private static readonly List<Object2DMesh> Objects = [];
    private static Rect2D _target = null!;
    private static Text2D _fpsText = null!;
    private static Text2D _inputText = null!;
    private static Shader _shader = null!;
    private static void WindowOnLoad()
    {
        var vertexSource = File.ReadAllText(_vertexShaderPath);
        var fragmentSource = File.ReadAllText(_fragmentShaderPath);

        _shader = new Shader(vertexSource, fragmentSource);
        
        Object2DRenderer.RectMesh = new Mesh2D([
            // Top Left
            new Mesh2D.Vertex(new Vector2(0.0f,0.0f), new Vector2(0.0f, 0.0f)),
            // Top Right
            new Mesh2D.Vertex(new Vector2(1.0f,0.0f), new Vector2(1.0f, 0.0f)),
            // Bottom Left
            new Mesh2D.Vertex(new Vector2(0.0f,1.0f), new Vector2(0.0f, 1.0f)),
            // Bottom Right
            new Mesh2D.Vertex(new Vector2(1.0f,1.0f), new Vector2(1.0f, 1.0f)),
        ], [
            0, 1, 3,
            0, 2, 3
        ]);
        Object2DRenderer.TextShader = _shader;
        {
            var rect = new Rect2D(new Vector2(0.0f, 0.0f), new Vector2(100.0f, 100.0f), 0.0f)
            {
                Color = new Vector3(1.0f, 0.0f, 0.0f)
            };
            Objects.Add(rect);
            _target = rect;
        }
        var fontMesh = new FontMesh("fonts/Axiforma-Regular.ttf");
        {
            var tex = new Text2D(new Vector2(45.0f, 45.0f), new Vector2(1.0f, 1.0f), 0.0f, fontMesh)
            {
                Color = new Vector3(1.0f, 0.0f, 0.0f),
                Text = "The_Text",
            };
            Objects.Add(tex);
            _inputText = tex;
        }
        
        {
            var tex = new Text2D(new Vector2(45.0f, 400.0f), new Vector2(1.0f, 1.0f), 0.0f, fontMesh)
            {
                Color = new Vector3(1.0f, 0.0f, 0.0f),
                Text = "<FPS>",
            };
            Objects.Add(tex);
            _fpsText = tex;
        }
        
        
        GL.ClearColor(0.1f,0.1f,0.1f,1.0f);
        GL.Enable(EnableCap.Multisample);
        GL.Enable(EnableCap.LineSmooth);
        GL.Enable(EnableCap.PolygonSmooth);
        GL.Hint(HintTarget.LineSmoothHint, HintMode.Nicest);
        GL.Hint(HintTarget.PolygonSmoothHint, HintMode.Nicest);
    }
    private static void WindowOnRenderFrame(FrameEventArgs obj)
    {
        GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
        
        foreach (var object2D in Objects)
        {
            Object2DRenderer.Render(object2D, _shader, Window.ClientSize.X, Window.ClientSize.Y);
        }
        
        Window.SwapBuffers();
    }
    
    private static void WindowOnUpdateFrame(FrameEventArgs obj)
    {
        _target.Position = new Vector2(Window.MousePosition.X, Window.MousePosition.Y);
        _target.Rotation += (float)obj.Time * 20.0f;

        _fpsText.Text = $"FPS: {1.0f / obj.Time}";
    }

    private static void WindowOnResize(ResizeEventArgs obj)
    {
        GL.Viewport(0, 0, Window.ClientSize.X, Window.ClientSize.Y);
    }
    private static void WindowOnKeyDown(KeyboardKeyEventArgs obj)
    {
        switch (obj.Key)
        {
            case Keys.Backspace:
                if (!string.IsNullOrEmpty(_inputText.Text))
                {
                    _inputText.Text = _inputText.Text[..^1];
                }
                break;
            case Keys.Enter:
                _inputText.Text += '\n';
                break;

            case Keys.Escape:
                break;
        }
    }
    private static void WindowOnTextInput(TextInputEventArgs e)
    {
        var ch = e.AsString;
        _inputText.Text += ch;
    }
    public static void Start()
    {
        Window.Load += WindowOnLoad;
        Window.RenderFrame += WindowOnRenderFrame;
        Window.Resize += WindowOnResize;
        Window.UpdateFrame += WindowOnUpdateFrame;
        Window.KeyDown += WindowOnKeyDown;
        Window.TextInput += WindowOnTextInput;
        Window.Run();
    }
}