class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            Application.Initialize(
                (OperatingSystemType.Windows, new WindowsPlatform(), new SkiaDrawingFactory { UseGPU = true })
                , (OperatingSystemType.OSX, new CPF.Mac.MacPlatform(), new SkiaDrawingFactory { UseGPU = true })//如果需要支持Mac才需要
                , (OperatingSystemType.Linux, new CPF.Linux.LinuxPlatform(), new SkiaDrawingFactory { UseGPU = true })//如果需要支持Linux才需要
            );
            Application.Run(new Window2_1_Colors());
        }
    }

            Children.Add(new WindowFrame(this, new GLView
            {
                Width = "100%",
                Height = "100%",
                [nameof(GLView.GLLoaded)] = new CommandDescribe((s, e) => GLLoaded((GLView)s, (GLEventArgs)e)),
                [nameof(GLView.GLRender)] = new CommandDescribe((s, e) => GLRender((GLView)s, (GLEventArgs)e)),
                [nameof(GLView.MouseDown)] = new CommandDescribe((s, e) => MouseEvent((GLView)s, (MouseEventArgs)e)),
                [nameof(GLView.MouseUp)] = new CommandDescribe((s, e) => MouseEvent((GLView)s, (MouseEventArgs)e)),
                [nameof(GLView.MouseMove)] = new CommandDescribe((s, e) => MouseEvent((GLView)s, (MouseEventArgs)e)),
            })
            {
                MaximizeBox = true
            });

        GL gl;//可以保存為全局的字段
        void GLLoaded(GLView view, GLEventArgs args)
        {
            gl = GL.GetApi(args.Context.GetProcAddress);
        }

    class Context : OpenTK.IBindingsContext
    {//定義API綁定的上下文
        public IGlContext context;
        public IntPtr GetProcAddress(string procName)
        {
            return context.GetProcAddress(procName);
        }
    }

        void GLLoaded(GLView view, GLEventArgs args)
        {//初始化一次就行
             GL.LoadBindings(new Context { context = args.Context });
        }

        void GLRender(GLView view, GLEventArgs args)
        {
            gl.Enable(GLEnum.DepthTest);//開啟深度測試
            gl.DepthMask(true);

            //其他繪制代碼。。。。


            //開啟深度測試之后要關閉，否則會無法顯示界面，同樣的，如果開啟了其他功能，繪制結束后記得關閉，否則可能影響界面繪制。因為和界面共享OpenGL的上下文。
            gl.Disable(GLEnum.DepthTest);
        }