Game.cs

using System;
using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Input;

namespace OpenTkNoesisGui
{
    public class Game : GameWindow
    {
        private readonly float[] _vertices =
        {
            -0.5f, -0.5f, 0.0f, // Bottom-left vertex
             0.5f, -0.5f, 0.0f, // Bottom-right vertex
             0.0f,  0.5f, 0.0f  // Top vertex
        };
        private static Noesis.View _view = null;
        private int _vertexBufferObject;
        private int _vertexArrayObject;
        private Shader _shader;
        private double totalTime;

        public Game(int width, int height, string title)
            : base(width, height, GraphicsMode.Default, title)
        {
            NoesisInit();
        }

        protected override void OnLoad(EventArgs e)
        {
            GL.ClearColor(0.2f, 0.3f, 0.3f, 1.0f);
            _vertexBufferObject = GL.GenBuffer();
            GL.BindBuffer(BufferTarget.ArrayBuffer, _vertexBufferObject);
            GL.BufferData(BufferTarget.ArrayBuffer, _vertices.Length * sizeof(float), _vertices, BufferUsageHint.StaticDraw);

            _shader = new Shader("Shaders/shader.vert", "Shaders/shader.frag");
            _shader.Use();

            _vertexArrayObject = GL.GenVertexArray();
            GL.BindVertexArray(_vertexArrayObject);
            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 3 * sizeof(float), 0);
            GL.EnableVertexAttribArray(0);
            GL.BindBuffer(BufferTarget.ArrayBuffer, _vertexBufferObject);

            base.OnLoad(e);
        }

        protected override void OnRenderFrame(FrameEventArgs e)
        {
            totalTime += e.Time;
            // UI pre-render
            // Update view (layout, animations, ...)
            _view.Update(totalTime / 1000.0);

            // Offscreen rendering phase populates textures needed by the on-screen rendering
            _view.Renderer.UpdateRenderTree();
            _view.Renderer.RenderOffscreen();


            GL.Clear(ClearBufferMask.ColorBufferBit);
            _shader.Use();
            GL.BindVertexArray(_vertexArrayObject);
            GL.DrawArrays(PrimitiveType.Triangles, 0, 3);

            _view.Renderer.Render();

            SwapBuffers();
            base.OnRenderFrame(e);
        }

        protected override void OnUpdateFrame(FrameEventArgs e)
        {
            var input = Keyboard.GetState();

            if (input.IsKeyDown(Key.Escape))
            {
                Exit();
            }

            base.OnUpdateFrame(e);
        }

        protected override void OnResize(EventArgs e)
        {
            GL.Viewport(0, 0, Width, Height);
            _view.SetSize(Width, Height);
            base.OnResize(e);
        }

        protected override void OnUnload(EventArgs e)
        {
            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
            GL.BindVertexArray(0);
            GL.UseProgram(0);

            GL.DeleteBuffer(_vertexBufferObject);
            GL.DeleteVertexArray(_vertexArrayObject);

            GL.DeleteProgram(_shader.Handle);
            base.OnUnload(e);
        }

        protected override void OnMouseMove(MouseMoveEventArgs e)
        {
            var mouseState = Mouse.GetState();
            _view.MouseMove(mouseState.X, mouseState.Y);
        }

        protected override void OnMouseDown(MouseButtonEventArgs e)
        {
            if (e.Button == MouseButton.Left)
            {
                _view.MouseButtonDown(e.Mouse.X, e.Mouse.Y, Noesis.MouseButton.Left);
            }
        }

        protected override void OnMouseUp(MouseButtonEventArgs e)
        {
            if (e.Button == MouseButton.Left)
            {
                _view.MouseButtonUp(e.Mouse.X, e.Mouse.Y, Noesis.MouseButton.Left);
            }
        }

        /// Noesis GUI \o/
        static void NoesisInit()
        {
            Noesis.Log.SetLogCallback((level, channel, message) =>
            {
                if (channel == "")
                {
                    // [TRACE] [DEBUG] [INFO] [WARNING] [ERROR]
                    string[] prefixes = new string[] { "T", "D", "I", "W", "E" };
                    string prefix = (int)level < prefixes.Length ? prefixes[(int)level] : " ";
                    Console.WriteLine("[NOESIS/" + prefix + "] " + message);
                }
            });

            // Noesis initialization. This must be the first step before using any NoesisGUI functionality
            Noesis.GUI.Init();

            // For simplicity purposes we are not using resource providers in this sample. ParseXaml() is
            // enough if there is no extra XAML dependencies
            Noesis.Grid xaml = (Noesis.Grid)Noesis.GUI.ParseXaml(@"
                <Grid xmlns=""http://schemas.microsoft.com/winfx/2006/xaml/presentation"">
                    <Grid.Background>
                        <LinearGradientBrush StartPoint=""0,0"" EndPoint=""0,1"">
                            <GradientStop Offset=""0"" Color=""#FF123F61""/>
                            <GradientStop Offset=""0.6"" Color=""#FF0E4B79""/>
                            <GradientStop Offset=""0.7"" Color=""#FF106097""/>
                        </LinearGradientBrush>
                    </Grid.Background>
                    <Viewbox>
                        <StackPanel Margin=""50"">
                            <Button Content=""Hello World!"" Margin=""0,30,0,0""/>
                            <Rectangle Height=""5"" Margin=""-10,20,-10,0"">
                                <Rectangle.Fill>
                                    <RadialGradientBrush>
                                        <GradientStop Offset=""0"" Color=""#40000000""/>
                                        <GradientStop Offset=""1"" Color=""#00000000""/>
                                    </RadialGradientBrush>
                                </Rectangle.Fill>
                            </Rectangle>
                        </StackPanel>
                    </Viewbox>
                </Grid>");

            // View creation to render and interact with the user interface
            // We transfer the ownership to a global pointer instead of a Ptr<> because there is no way
            // in GLUT to do shutdown and we don't want the Ptr<> to be released at global time
            _view = Noesis.GUI.CreateView(xaml);
            _view.SetIsPPAAEnabled(true);

            // Renderer initialization with an OpenGL device
            _view.Renderer.Init(new Noesis.RenderDeviceGL());
        }
    }
}