add platformer window infrastructure

Platformer/Util/Buffer.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Runtime.InteropServices;
+using OpenTK.Graphics.OpenGL4;
+
+namespace Platformer.Util
+{
+    public class Buffer : GlObj
+    {
+        public Buffer() : base(GL.GenBuffer())
+        {
+        }
+
+        public void SetData<T>(T[] data, BufferUsageHint usage = BufferUsageHint.StaticDraw) where T : struct
+        {
+            GL.BindBuffer(BufferTarget.ArrayBuffer, this);
+            GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(data.Length * Marshal.SizeOf(typeof(T))), data, usage);
+            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
+        }
+    }
+}

Platformer/Util/GlObj.cs

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+namespace Platformer.Util
+{
+    public abstract class GlObj
+    {
+        public readonly int Id;
+
+        public GlObj(int id)
+        {
+            Id = id;
+        }
+
+        public static implicit operator int(GlObj o) => o.Id;
+    }
+}

Platformer/Util/Program.cs

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+using OpenTK.Graphics.OpenGL4;
+
+namespace Platformer.Util
+{
+    public class Program : GlObj
+    {
+        public Program() : base(GL.CreateProgram())
+        {
+        }
+
+        public static Program Link(params Shader[] shaders)
+        {
+            var p = new Program();
+            foreach (var s in shaders)
+                GL.AttachShader(p, s);
+            GL.LinkProgram(p);
+            return p;
+        }
+    }
+}

Platformer/Util/Shader.cs

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+using System;
+using System.Collections.Generic;
+using System.IO;
+using OpenTK.Graphics.OpenGL4;
+
+namespace Platformer.Util
+{
+    public class Shader : GlObj
+    {
+        private static Dictionary<string, ShaderType> _shaderTypes = new Dictionary<string, ShaderType>()
+        {
+            [".vert"] = ShaderType.VertexShader,
+            [".frag"] = ShaderType.FragmentShader,
+            [".geom"] = ShaderType.GeometryShader,
+            [".comp"] = ShaderType.ComputeShader,
+        };
+
+        public Shader(ShaderType type) : base(GL.CreateShader(type))
+        {
+        }
+
+        public static Shader Compile(ShaderType type, string source)
+        {
+            var s = new Shader(type);
+            GL.ShaderSource(s, source);
+            GL.CompileShader(s);
+            return s;
+        }
+
+        public static Shader Compile(string filename)
+        {
+            var ext = Path.GetExtension(filename);
+
+            if (!_shaderTypes.ContainsKey(ext))
+                throw new InvalidOperationException($"Can't infer shader type for {filename}");
+
+            return Compile(_shaderTypes[ext], File.ReadAllText(filename));
+        }
+    }
+}

Platformer/Util/VertexArray.cs

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+using OpenTK.Graphics.OpenGL4;
+
+namespace Platformer.Util
+{
+    public class VertexArray : GlObj
+    {
+        public VertexArray() : base(GL.GenVertexArray())
+        {
+        }
+
+        public void VertexPointer(Buffer buffer, int index, int size,
+            VertexAttribPointerType type = VertexAttribPointerType.Float,
+            bool normalized = false, int stride = 0, int offset = 0)
+        {
+            GL.BindVertexArray(this);
+            
+            GL.BindBuffer(BufferTarget.ArrayBuffer, buffer);
+            GL.VertexAttribPointer(index, size, type, normalized, stride, offset);
+            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
+            
+            GL.EnableVertexArrayAttrib(this, index);
+            
+            GL.BindVertexArray(0);
+        }
+    }
+}