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#region --- License ---

/* Licensed under the MIT/X11 license.

 * Copyright (c) 2006-2008 the OpenTK Team.

 * This notice may not be removed from any source distribution.

 * See license.txt for licensing detailed licensing details.

 */

#endregion

#region --- Using Directives ---

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

using System.Threading;

using System.Diagnostics;

using System.IO;

using OpenTK;

using OpenTK.Graphics;

using OpenTK.Graphics.OpenGL;

#endregion --- Using Directives ---

namespace Examples.Tutorial

{

    /// <summary>

    /// Demonstrates how to load and use a simple OpenGL shader program. Example is incomplete (documentation).

    /// </summary>

    [Example("First shader", ExampleCategory.OpenGL, "2.x", Documentation = "SimpleGLSL")]

    public class T10_GLSL_Cube : GameWindow

    {

        #region --- Fields ---

        static float angle = 0.0f, rotation_speed = 3.0f;

        int vertex_shader_object, fragment_shader_object, shader_program;

        int vertex_buffer_object, color_buffer_object, element_buffer_object;

        Shapes.Shape shape = new Examples.Shapes.Cube();

        #endregion

        #region --- Constructors ---

        public T10_GLSL_Cube()

            : base(800, 600, GraphicsMode.Default)

        { }

        #endregion

        #region OnLoad

        /// <summary>

        /// This is the place to load resources that change little

        /// during the lifetime of the GameWindow. In this case, we

        /// check for GLSL support, and load the shaders.

        /// </summary>

        /// <param name="e">Not used.</param>

        protected override void OnLoad(EventArgs e)

        {

            // Check for necessary capabilities:

            string version = GL.GetString(StringName.Version);

            int major = (int)version[0];

            int minor = (int)version[2];

            if (major < 2)

            {

                MessageBox.Show("You need at least OpenGL 2.0 to run this example. Aborting.", "GLSL not supported",

                    MessageBoxButtons.OK, MessageBoxIcon.Exclamation);

                this.Exit();

            }

            GL.ClearColor(Color.MidnightBlue);

            GL.Enable(EnableCap.DepthTest);

            CreateVBO();

            using (StreamReader vs = new StreamReader("Data/Shaders/Simple_VS.glsl"))

            using (StreamReader fs = new StreamReader("Data/Shaders/Simple_FS.glsl"))

                CreateShaders(vs.ReadToEnd(), fs.ReadToEnd(),

                    out vertex_shader_object, out fragment_shader_object,

                    out shader_program);

        }

        #endregion

        #region CreateShaders

        void CreateShaders(string vs, string fs,

            out int vertexObject, out int fragmentObject,

            out int program)

        {

            int status_code;

            string info;

            vertexObject = GL.CreateShader(ShaderType.VertexShader);

            fragmentObject = GL.CreateShader(ShaderType.FragmentShader);

            // Compile vertex shader

            GL.ShaderSource(vertexObject, vs);

            GL.CompileShader(vertexObject);

            GL.GetShaderInfoLog(vertexObject, out info);

            GL.GetShader(vertexObject, ShaderParameter.CompileStatus, out status_code);

            if (status_code != 1)

                throw new ApplicationException(info);

            // Compile vertex shader

            GL.ShaderSource(fragmentObject, fs);

            GL.CompileShader(fragmentObject);

            GL.GetShaderInfoLog(fragmentObject, out info);

            GL.GetShader(fragmentObject, ShaderParameter.CompileStatus, out status_code);

            if (status_code != 1)

                throw new ApplicationException(info);

            program = GL.CreateProgram();

            GL.AttachShader(program, fragmentObject);

            GL.AttachShader(program, vertexObject);

            GL.LinkProgram(program);

            GL.UseProgram(program);

        }

        #endregion

        #region private void CreateVBO()

        void CreateVBO()

        {

            int size;

            GL.GenBuffers(1, out vertex_buffer_object);

            GL.GenBuffers(1, out color_buffer_object);

            GL.GenBuffers(1, out element_buffer_object);

            // Upload the vertex buffer.

            GL.BindBuffer(BufferTarget.ArrayBuffer, vertex_buffer_object);

            GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(shape.Vertices.Length * 3 * sizeof(float)), shape.Vertices,

                BufferUsageHint.StaticDraw);

            GL.GetBufferParameter(BufferTarget.ArrayBuffer, BufferParameterName.BufferSize, out size);

            if (size != shape.Vertices.Length * 3 * sizeof(Single))

                throw new ApplicationException(String.Format(

                    "Problem uploading vertex buffer to VBO (vertices). Tried to upload {0} bytes, uploaded {1}.",

                    shape.Vertices.Length * 3 * sizeof(Single), size));

            // Upload the color buffer.

            GL.BindBuffer(BufferTarget.ArrayBuffer, color_buffer_object);

            GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(shape.Colors.Length * sizeof(int)), shape.Colors,

                BufferUsageHint.StaticDraw);

            GL.GetBufferParameter(BufferTarget.ArrayBuffer, BufferParameterName.BufferSize, out size);

            if (size != shape.Colors.Length * sizeof(int))

                throw new ApplicationException(String.Format(

                    "Problem uploading vertex buffer to VBO (colors). Tried to upload {0} bytes, uploaded {1}.",

                    shape.Colors.Length * sizeof(int), size));

            // Upload the index buffer (elements inside the vertex buffer, not color indices as per the IndexPointer function!)

            GL.BindBuffer(BufferTarget.ElementArrayBuffer, element_buffer_object);

            GL.BufferData(BufferTarget.ElementArrayBuffer, (IntPtr)(shape.Indices.Length * sizeof(Int32)), shape.Indices,

                BufferUsageHint.StaticDraw);

            GL.GetBufferParameter(BufferTarget.ElementArrayBuffer, BufferParameterName.BufferSize, out size);

            if (size != shape.Indices.Length * sizeof(int))

                throw new ApplicationException(String.Format(

                    "Problem uploading vertex buffer to VBO (offsets). Tried to upload {0} bytes, uploaded {1}.",

                    shape.Indices.Length * sizeof(int), size));

        }

        #endregion

        #region OnUnload

        protected override void OnUnload(EventArgs e)

        {

            if (shader_program != 0)

                GL.DeleteProgram(shader_program);

            if (fragment_shader_object != 0)

                GL.DeleteShader(fragment_shader_object);

            if (vertex_shader_object != 0)

                GL.DeleteShader(vertex_shader_object);

            if (vertex_buffer_object != 0)

                GL.DeleteBuffers(1, ref vertex_buffer_object);

            if (element_buffer_object != 0)

                GL.DeleteBuffers(1, ref element_buffer_object);

        }

        #endregion

        #region OnResize

        /// <summary>

        /// Called when the user resizes the window.

        /// </summary>

        /// <param name="e">Contains the new width/height of the window.</param>

        /// <remarks>

        /// You want the OpenGL viewport to match the window. This is the place to do it!

        /// </remarks>

        protected override void OnResize(EventArgs e)

        {

            GL.Viewport(0, 0, Width, Height);

            float aspect_ratio = Width / (float)Height;

            Matrix4 perpective = Matrix4.CreatePerspectiveFieldOfView(MathHelper.PiOver4, aspect_ratio, 1, 64);

            GL.MatrixMode(MatrixMode.Projection);

            GL.LoadMatrix(ref perpective);

        }

        #endregion

        #region OnUpdateFrame

        /// <summary>

        /// Prepares the next frame for rendering.

        /// </summary>

        /// <remarks>

        /// Place your control logic here. This is the place to respond to user input,

        /// update object positions etc.

        /// </remarks>

        protected override void OnUpdateFrame(FrameEventArgs e)

        {

            if (Keyboard[OpenTK.Input.Key.Escape])

                this.Exit();

            if (Keyboard[OpenTK.Input.Key.F11])

                if (WindowState != WindowState.Fullscreen)

                    WindowState = WindowState.Fullscreen;

                else

                    WindowState = WindowState.Normal;

        }

        #endregion

        #region OnRenderFrame

        /// <summary>

        /// Place your rendering code here.

        /// </summary>

        protected override void OnRenderFrame(FrameEventArgs e)

        {

            GL.Clear(ClearBufferMask.ColorBufferBit |

                     ClearBufferMask.DepthBufferBit);

            Matrix4 lookat = Matrix4.LookAt(0, 5, 5, 0, 0, 0, 0, 1, 0);

            GL.MatrixMode(MatrixMode.Modelview);

            GL.LoadMatrix(ref lookat);

            angle += rotation_speed * (float)e.Time;

            GL.Rotate(angle, 0.0f, 1.0f, 0.0f);

            GL.EnableClientState(EnableCap.VertexArray);

            GL.EnableClientState(EnableCap.ColorArray);

            GL.BindBuffer(BufferTarget.ArrayBuffer, vertex_buffer_object);

            GL.VertexPointer(3, VertexPointerType.Float, 0, IntPtr.Zero);

            GL.BindBuffer(BufferTarget.ArrayBuffer, color_buffer_object);

            GL.ColorPointer(4, ColorPointerType.UnsignedByte, 0, IntPtr.Zero);

            GL.BindBuffer(BufferTarget.ElementArrayBuffer, element_buffer_object);

            GL.DrawElements(BeginMode.Triangles, shape.Indices.Length,

                DrawElementsType.UnsignedInt, IntPtr.Zero);

            //GL.DrawArrays(GL.Enums.BeginMode.POINTS, 0, shape.Vertices.Length);

            GL.DisableClientState(EnableCap.VertexArray);

            GL.DisableClientState(EnableCap.ColorArray);

            //int error = GL.GetError();

            //if (error != 0)

            //    Debug.Print(Glu.ErrorString(Glu.Enums.ErrorCode.INVALID_OPERATION));

            SwapBuffers();

        }

        #endregion

        #region public static void Main()

        /// <summary>

        /// Entry point of this example.

        /// </summary>

        [STAThread]

        public static void Main()

        {

            using (T10_GLSL_Cube example = new T10_GLSL_Cube())

            {

                // Get the title and category  of this example using reflection.

                ExampleAttribute info = ((ExampleAttribute)example.GetType().GetCustomAttributes(false)[0]);

                example.Title = String.Format("OpenTK | {0} {1}: {2}", info.Category, info.Difficulty, info.Title);

                example.Run(30.0, 0.0);

            }

        }

        #endregion

    }

}