#region License
/* FNA - XNA4 Reimplementation for Desktop Platforms
 * Copyright 2009-2016 Ethan Lee and the MonoGame Team
 *
 * Released under the Microsoft Public License.
 * See LICENSE for details.
 */
#endregion

#region THREADED_GL Option
// #define THREADED_GL
/* Ah, so I see you've run into some issues with threaded GL...
 *
 * This class is designed to handle rendering coming from multiple threads, but
 * if you're too wreckless with how many threads are calling the GL, this will
 * hang.
 *
 * With THREADED_GL we instead allow you to run threaded rendering using
 * multiple GL contexts. This is more flexible, but much more dangerous.
 *
 * Basically, if you have to enable this, you should feel very bad.
 * -flibit
 */
#endregion

#region DISABLE_THREADING Option
// #define DISABLE_THREADING
/* Perhaps you read the above option and thought to yourself:
 * "Wow, only an idiot would need threads for their graphics code!"
 *
 * For those of you who are particularly well-behaved with your renderer and
 * don't ever call anything on a thread at all, you can enable this define and
 * cut out a _ton_ of garbage generation that's caused by our attempt to force
 * things to the main thread.
 *
 * Enjoy the boost, you've earned it.
 * -flibit
 */
#endregion

#region Using Statements
using System;
using System.Collections.Concurrent;
using System.Runtime.InteropServices;
using System.Threading;

using SDL2;
#endregion

namespace Microsoft.Xna.Framework.Graphics
{
	internal partial class OpenGLDevice : IGLDevice
	{
		#region OpenGL Texture Container Class

		private class OpenGLTexture : IGLTexture
		{
			public uint Handle
			{
				get;
				private set;
			}

			public GLenum Target
			{
				get;
				private set;
			}

			public bool HasMipmaps
			{
				get;
				private set;
			}

			public TextureAddressMode WrapS;
			public TextureAddressMode WrapT;
			public TextureAddressMode WrapR;
			public TextureFilter Filter;
			public float Anistropy;
			public int MaxMipmapLevel;
			public float LODBias;

			public OpenGLTexture(
				uint handle,
				GLenum target,
				int levelCount
			) {
				Handle = handle;
				Target = target;
				HasMipmaps = levelCount > 1;

				WrapS = TextureAddressMode.Wrap;
				WrapT = TextureAddressMode.Wrap;
				WrapR = TextureAddressMode.Wrap;
				Filter = TextureFilter.Linear;
				Anistropy = 4.0f;
				MaxMipmapLevel = 0;
				LODBias = 0.0f;
			}

			// We can't set a SamplerState Texture to null, so use this.
			private OpenGLTexture()
			{
				Handle = 0;
				Target = GLenum.GL_TEXTURE_2D; // FIXME: Assumption! -flibit
			}
			public static readonly OpenGLTexture NullTexture = new OpenGLTexture();
		}

		#endregion

		#region OpenGL Renderbuffer Container Class

		private class OpenGLRenderbuffer : IGLRenderbuffer
		{
			public uint Handle
			{
				get;
				private set;
			}

			public OpenGLRenderbuffer(uint handle)
			{
				Handle = handle;
			}
		}

		#endregion

		#region OpenGL Buffer Container Class

		private class OpenGLBuffer : IGLBuffer
		{
			public uint Handle
			{
				get;
				private set;
			}

			public IntPtr BufferSize
			{
				get;
				private set;
			}

			public GLenum Dynamic
			{
				get;
				private set;
			}

			public OpenGLBuffer(
				uint handle,
				IntPtr bufferSize,
				GLenum dynamic
			) {
				Handle = handle;
				BufferSize = bufferSize;
				Dynamic = dynamic;
			}

			private OpenGLBuffer()
			{
				Handle = 0;
			}
			public static readonly OpenGLBuffer NullBuffer = new OpenGLBuffer();
		}

		#endregion

		#region OpenGL Effect Container Class

		private class OpenGLEffect : IGLEffect
		{
			public IntPtr EffectData
			{
				get;
				private set;
			}

			public IntPtr GLEffectData
			{
				get;
				private set;
			}

			public OpenGLEffect(IntPtr effect, IntPtr glEffect)
			{
				EffectData = effect;
				GLEffectData = glEffect;
			}
		}

		#endregion

		#region OpenGL Query Container Class

		private class OpenGLQuery : IGLQuery
		{
			public uint Handle
			{
				get;
				private set;
			}

			public OpenGLQuery(uint handle)
			{
				Handle = handle;
			}
		}

		#endregion

		#region Blending State Variables

		public Color BlendFactor
		{
			get
			{
				return blendColor;
			}
			set
			{
				if (value != blendColor)
				{
					blendColor = value;
					glBlendColor(
						blendColor.R / 255.0f,
						blendColor.G / 255.0f,
						blendColor.B / 255.0f,
						blendColor.A / 255.0f
					);
				}
			}
		}

		public int MultiSampleMask
		{
			get
			{
				return multisampleMask;
			}
			set
			{
				if (value != multisampleMask && supportsMultisampling)
				{
					if (value == -1)
					{
						glDisable(GLenum.GL_SAMPLE_MASK);
					}
					else
					{
						if (multisampleMask == -1)
						{
							glEnable(GLenum.GL_SAMPLE_MASK);
						}
						// FIXME: index...? -flibit
						glSampleMaski(0, (uint) value);
					}
					multisampleMask = value;
				}
			}
		}

		private bool alphaBlendEnable = false;
		private Color blendColor = Color.Transparent;
		private BlendFunction blendOp = BlendFunction.Add;
		private BlendFunction blendOpAlpha = BlendFunction.Add;
		private Blend srcBlend = Blend.One;
		private Blend dstBlend = Blend.Zero;
		private Blend srcBlendAlpha = Blend.One;
		private Blend dstBlendAlpha = Blend.Zero;
		private ColorWriteChannels colorWriteEnable = ColorWriteChannels.All;
		private ColorWriteChannels colorWriteEnable1 = ColorWriteChannels.All;
		private ColorWriteChannels colorWriteEnable2 = ColorWriteChannels.All;
		private ColorWriteChannels colorWriteEnable3 = ColorWriteChannels.All;
		private int multisampleMask = -1; // AKA 0xFFFFFFFF

		#endregion

		#region Depth State Variables

		private bool zEnable = false;
		private bool zWriteEnable = false;
		private CompareFunction depthFunc = CompareFunction.Less;

		#endregion

		#region Stencil State Variables

		public int ReferenceStencil
		{
			get
			{
				return stencilRef;
			}
			set
			{
				if (value != stencilRef)
				{
					stencilRef = value;
					if (separateStencilEnable)
					{
						glStencilFuncSeparate(
							GLenum.GL_FRONT,
							XNAToGL.CompareFunc[(int) stencilFunc],
							stencilRef,
							stencilMask
						);
						glStencilFuncSeparate(
							GLenum.GL_BACK,
							XNAToGL.CompareFunc[(int) ccwStencilFunc],
							stencilRef,
							stencilMask
						);
					}
					else
					{
						glStencilFunc(
							XNAToGL.CompareFunc[(int) stencilFunc],
							stencilRef,
							stencilMask
						);
					}
				}
			}
		}

		private bool stencilEnable = false;
		private int stencilWriteMask = -1; // AKA 0xFFFFFFFF, ugh -flibit
		private bool separateStencilEnable = false;
		private int stencilRef = 0;
		private int stencilMask = -1; // AKA 0xFFFFFFFF, ugh -flibit
		private CompareFunction stencilFunc = CompareFunction.Always;
		private StencilOperation stencilFail = StencilOperation.Keep;
		private StencilOperation stencilZFail = StencilOperation.Keep;
		private StencilOperation stencilPass = StencilOperation.Keep;
		private CompareFunction ccwStencilFunc = CompareFunction.Always;
		private StencilOperation ccwStencilFail = StencilOperation.Keep;
		private StencilOperation ccwStencilZFail = StencilOperation.Keep;
		private StencilOperation ccwStencilPass = StencilOperation.Keep;

		#endregion

		#region Rasterizer State Variables

		private bool scissorTestEnable = false;
		private CullMode cullFrontFace = CullMode.None;
		private FillMode fillMode = FillMode.Solid;
		private float depthBias = 0.0f;
		private float slopeScaleDepthBias = 0.0f;
		private bool multiSampleEnable = true;

		#endregion

		#region Viewport State Variables

		/* These two aren't actually empty rects by default in OpenGL,
		 * but we don't _really_ know the starting window size, so
		 * force apply this when the GraphicsDevice is initialized.
		 * -flibit
		 */
		private Rectangle scissorRectangle =  new Rectangle(
			0,
			0,
			0,
			0
		);
		private Rectangle viewport = new Rectangle(
			0,
			0,
			0,
			0
		);
		private float depthRangeMin = 0.0f;
		private float depthRangeMax = 1.0f;

		#endregion

		#region Texture Collection Variables

		private OpenGLTexture[] Textures;

		#endregion

		#region Buffer Binding Cache Variables

		private uint currentVertexBuffer = 0;
		private uint currentIndexBuffer = 0;

		// ld, or LastDrawn, effect/vertex attributes
		private int ldBaseVertex = -1;
		private VertexDeclaration ldVertexDeclaration = null;
		private IntPtr ldPointer = IntPtr.Zero;
		private IntPtr ldEffect = IntPtr.Zero;
		private IntPtr ldTechnique = IntPtr.Zero;
		private uint ldPass = 0;

		#endregion

		#region Render Target Cache Variables

		private uint currentReadFramebuffer = 0;
		private uint currentDrawFramebuffer = 0;
		private uint targetFramebuffer = 0;
		private uint resolveFramebufferRead = 0;
		private uint resolveFramebufferDraw = 0;
		private uint[] currentAttachments;
		private GLenum[] currentAttachmentTypes;
		private int currentDrawBuffers;
		private GLenum[] drawBuffersArray;
		private uint currentRenderbuffer;
		private DepthFormat currentDepthStencilFormat;

		#endregion

		#region Clear Cache Variables

		private Vector4 currentClearColor = new Vector4(0, 0, 0, 0);
		private float currentClearDepth = 1.0f;
		private int currentClearStencil = 0;

		#endregion

		#region Private OpenGL Context Variable

		private IntPtr glContext;

		#endregion

		#region Faux-Backbuffer Variable

		public IGLBackbuffer Backbuffer
		{
			get;
			private set;
		}

		#endregion

		#region OpenGL Device Capabilities

		public bool SupportsDxt1
		{
			get;
			private set;
		}

		public bool SupportsS3tc
		{
			get;
			private set;
		}

		public bool SupportsHardwareInstancing
		{
			get;
			private set;
		}

		public int MaxTextureSlots
		{
			get;
			private set;
		}

		public int MaxMultiSampleCount
		{
			get;
			private set;
		}

		private bool supportsMultisampling;
		private bool supportsFauxBackbuffer;
		private bool supportsBaseVertex;

		#endregion

		#region Private Vertex Attribute Cache

		private class VertexAttribute
		{
			public uint CurrentBuffer;
			public IntPtr CurrentPointer;
			public VertexElementFormat CurrentFormat;
			public bool CurrentNormalized;
			public int CurrentStride;
			public VertexAttribute()
			{
				CurrentBuffer = 0;
				CurrentPointer = IntPtr.Zero;
				CurrentFormat = VertexElementFormat.Single;
				CurrentNormalized = false;
				CurrentStride = 0;
			}
		}
		private VertexAttribute[] attributes;
		private bool[] attributeEnabled;
		private bool[] previousAttributeEnabled;
		private int[] attributeDivisor;
		private int[] previousAttributeDivisor;

		#endregion

		#region Private MojoShader Interop

		private string shaderProfile;
		private IntPtr shaderContext;

		private IntPtr currentEffect = IntPtr.Zero;
		private IntPtr currentTechnique = IntPtr.Zero;
		private uint currentPass = 0;

		private int flipViewport = 1;

		private bool effectApplied = false;

		private static IntPtr glGetProcAddress(string name, IntPtr d)
		{
			return SDL.SDL_GL_GetProcAddress(name);
		}
		private static MojoShader.MOJOSHADER_glGetProcAddress GLGetProcAddress = glGetProcAddress;

		#endregion

		#region Private Graphics Object Disposal Queues

		private ConcurrentQueue<IGLTexture> GCTextures = new ConcurrentQueue<IGLTexture>();
		private ConcurrentQueue<IGLRenderbuffer> GCDepthBuffers = new ConcurrentQueue<IGLRenderbuffer>();
		private ConcurrentQueue<IGLBuffer> GCVertexBuffers = new ConcurrentQueue<IGLBuffer>();
		private ConcurrentQueue<IGLBuffer> GCIndexBuffers = new ConcurrentQueue<IGLBuffer>();
		private ConcurrentQueue<IGLEffect> GCEffects = new ConcurrentQueue<IGLEffect>();
		private ConcurrentQueue<IGLQuery> GCQueries = new ConcurrentQueue<IGLQuery>();

		#endregion

		#region Private Profile-specific Variables

		private bool useES2;
		private bool useCoreProfile;
		private uint vao;

		#endregion

		#region Private Static SDL2 Bug Workaround

		private static void GetWindowDimensions(
			PresentationParameters presentationParameters,
			out int width,
			out int height
		) {
			if (presentationParameters.IsFullScreen)
			{
				/* FIXME: SDL2 bug!
				 * SDL's a little weird about SDL_GetWindowSize.
				 * If you call it early enough (for example,
				 * Game.Initialize()), it reports outdated ints.
				 * So you know what, let's just use this.
				 * -flibit
				 */
				SDL.SDL_DisplayMode mode;
				SDL.SDL_GetCurrentDisplayMode(
					SDL.SDL_GetWindowDisplayIndex(
						presentationParameters.DeviceWindowHandle
					),
					out mode
				);
				width = mode.w;
				height = mode.h;
			}
			else
			{
				SDL.SDL_GetWindowSize(
					presentationParameters.DeviceWindowHandle,
					out width,
					out height
				);
			}
		}

		#endregion

		#region Public Constructor

		public OpenGLDevice(
			PresentationParameters presentationParameters
		) {
			// Create OpenGL context
			glContext = SDL.SDL_GL_CreateContext(
				presentationParameters.DeviceWindowHandle
			);

			// Check for a possible ES context
			int flags;
			int es2Flag = (int) SDL.SDL_GLprofile.SDL_GL_CONTEXT_PROFILE_ES;
			SDL.SDL_GL_GetAttribute(SDL.SDL_GLattr.SDL_GL_CONTEXT_PROFILE_MASK, out flags);
			useES2 = (flags & es2Flag) == es2Flag;

			// Check for a possible Core context
			int coreFlag = (int) SDL.SDL_GLprofile.SDL_GL_CONTEXT_PROFILE_CORE;
			useCoreProfile = (flags & coreFlag) == coreFlag;

			// Init threaded GL crap where applicable
			InitThreadedGL(
				presentationParameters.DeviceWindowHandle
			);

			// Initialize entry points
			LoadGLEntryPoints();

			shaderProfile = MojoShader.MOJOSHADER_glBestProfile(
				GLGetProcAddress,
				IntPtr.Zero,
				null,
				null,
				IntPtr.Zero
			);
			shaderContext = MojoShader.MOJOSHADER_glCreateContext(
				shaderProfile,
				GLGetProcAddress,
				IntPtr.Zero,
				null,
				null,
				IntPtr.Zero
			);
			MojoShader.MOJOSHADER_glMakeContextCurrent(shaderContext);

			// Print GL information
			FNAPlatform.Log("OpenGL Device: " + glGetString(GLenum.GL_RENDERER));
			FNAPlatform.Log("OpenGL Driver: " + glGetString(GLenum.GL_VERSION));
			FNAPlatform.Log("OpenGL Vendor: " + glGetString(GLenum.GL_VENDOR));
			FNAPlatform.Log("MojoShader Profile: " + shaderProfile);

			// Load the extension list, initialize extension-dependent components
			string extensions;
			if (useCoreProfile)
			{
				extensions = string.Empty;
				int numExtensions;
				glGetIntegerv(GLenum.GL_NUM_EXTENSIONS, out numExtensions);
				for (uint i = 0; i < numExtensions; i += 1)
				{
					extensions += glGetStringi(GLenum.GL_EXTENSIONS, i) + " ";
				}
			}
			else
			{
				extensions = glGetString(GLenum.GL_EXTENSIONS);
			}
			SupportsS3tc = (
				extensions.Contains("GL_EXT_texture_compression_s3tc") ||
				extensions.Contains("GL_OES_texture_compression_S3TC") ||
				extensions.Contains("GL_EXT_texture_compression_dxt3") ||
				extensions.Contains("GL_EXT_texture_compression_dxt5")
			);
			SupportsDxt1 = (
				SupportsS3tc ||
				extensions.Contains("GL_EXT_texture_compression_dxt1")
			);

			/* Check the max multisample count, override parameters if necessary */
			int maxSamples = 0;
			if (supportsMultisampling)
			{
				glGetIntegerv(GLenum.GL_MAX_SAMPLES, out maxSamples);
			}
			MaxMultiSampleCount = maxSamples;
			presentationParameters.MultiSampleCount = Math.Min(
				presentationParameters.MultiSampleCount,
				MaxMultiSampleCount
			);

			// Initialize the faux-backbuffer
			int winWidth, winHeight;
			GetWindowDimensions(
				presentationParameters,
				out winWidth,
				out winHeight
			);
			if (	winWidth != presentationParameters.BackBufferWidth ||
				winHeight != presentationParameters.BackBufferHeight ||
				presentationParameters.MultiSampleCount > 0	)
			{
				if (!supportsFauxBackbuffer)
				{
					throw new NoSuitableGraphicsDeviceException(
						"Your hardware does not support the faux-backbuffer!" +
						"\n\nKeep the window/backbuffer resolution the same."
					);
				}
				Backbuffer = new OpenGLBackbuffer(
					this,
					presentationParameters.BackBufferWidth,
					presentationParameters.BackBufferHeight,
					presentationParameters.DepthStencilFormat,
					presentationParameters.MultiSampleCount
				);
			}
			else
			{
				Backbuffer = new NullBackbuffer(
					presentationParameters.BackBufferWidth,
					presentationParameters.BackBufferHeight
				);
			}

			// Initialize texture collection array
			int numSamplers;
			glGetIntegerv(GLenum.GL_MAX_TEXTURE_IMAGE_UNITS, out numSamplers);
			Textures = new OpenGLTexture[numSamplers];
			for (int i = 0; i < numSamplers; i += 1)
			{
				Textures[i] = OpenGLTexture.NullTexture;
			}
			MaxTextureSlots = numSamplers;

			// Initialize vertex attribute state arrays
			int numAttributes;
			glGetIntegerv(GLenum.GL_MAX_VERTEX_ATTRIBS, out numAttributes);
			attributes = new VertexAttribute[numAttributes];
			attributeEnabled = new bool[numAttributes];
			previousAttributeEnabled = new bool[numAttributes];
			attributeDivisor = new int[numAttributes];
			previousAttributeDivisor = new int[numAttributes];
			for (int i = 0; i < numAttributes; i += 1)
			{
				attributes[i] = new VertexAttribute();
				attributeEnabled[i] = false;
				previousAttributeEnabled[i] = false;
				attributeDivisor[i] = 0;
				previousAttributeDivisor[i] = 0;
			}

			// Initialize render target FBO and state arrays
			int numAttachments;
			glGetIntegerv(GLenum.GL_MAX_DRAW_BUFFERS, out numAttachments);
			currentAttachments = new uint[numAttachments];
			currentAttachmentTypes = new GLenum[numAttachments];
			drawBuffersArray = new GLenum[numAttachments];
			for (int i = 0; i < numAttachments; i += 1)
			{
				currentAttachments[i] = 0;
				currentAttachmentTypes[i] = GLenum.GL_TEXTURE_2D;
				drawBuffersArray[i] = GLenum.GL_COLOR_ATTACHMENT0 + i;
			}
			currentDrawBuffers = 0;
			currentRenderbuffer = 0;
			currentDepthStencilFormat = DepthFormat.None;
			glGenFramebuffers(1, out targetFramebuffer);
			glGenFramebuffers(1, out resolveFramebufferRead);
			glGenFramebuffers(1, out resolveFramebufferDraw);

			// Generate and bind a VAO, to shut Core up
			if (useCoreProfile)
			{
				glGenVertexArrays(1, out vao);
				glBindVertexArray(vao);
			}
		}

		#endregion

		#region Dispose Method

		public void Dispose()
		{
			if (useCoreProfile)
			{
				glBindVertexArray(0);
				glDeleteVertexArrays(1, ref vao);
			}
			glDeleteFramebuffers(1, ref resolveFramebufferRead);
			resolveFramebufferRead = 0;
			glDeleteFramebuffers(1, ref resolveFramebufferDraw);
			resolveFramebufferDraw = 0;
			glDeleteFramebuffers(1, ref targetFramebuffer);
			targetFramebuffer = 0;
			if (Backbuffer is OpenGLBackbuffer)
			{
				(Backbuffer as OpenGLBackbuffer).Dispose();
			}
			Backbuffer = null;
			MojoShader.MOJOSHADER_glMakeContextCurrent(IntPtr.Zero);
			MojoShader.MOJOSHADER_glDestroyContext(shaderContext);

#if THREADED_GL
			SDL.SDL_GL_DeleteContext(BackgroundContext.context);
#endif
			SDL.SDL_GL_DeleteContext(glContext);
		}

		#endregion

		#region Window Backbuffer Reset Method

		public void ResetBackbuffer(
			PresentationParameters presentationParameters,
			bool renderTargetBound
		) {
			int winWidth, winHeight;
			GetWindowDimensions(
				presentationParameters,
				out winWidth,
				out winHeight
			);
			bool useFauxBackbuffer = (	winWidth != presentationParameters.BackBufferWidth ||
							winHeight != presentationParameters.BackBufferHeight ||
							presentationParameters.MultiSampleCount > 0	);
			if (useFauxBackbuffer)
			{
				if (Backbuffer is NullBackbuffer)
				{
					if (!supportsFauxBackbuffer)
					{
						throw new NoSuitableGraphicsDeviceException(
							"Your hardware does not support the faux-backbuffer!" +
							"\n\nKeep the window/backbuffer resolution the same."
						);
					}
					Backbuffer = new OpenGLBackbuffer(
						this,
						presentationParameters.BackBufferWidth,
						presentationParameters.BackBufferHeight,
						presentationParameters.DepthStencilFormat,
						presentationParameters.MultiSampleCount
					);
				}
				else
				{
					Backbuffer.ResetFramebuffer(
						presentationParameters,
						renderTargetBound
					);
				}
			}
			else
			{
				if (Backbuffer is OpenGLBackbuffer)
				{
					(Backbuffer as OpenGLBackbuffer).Dispose();
					Backbuffer = new NullBackbuffer(
						presentationParameters.BackBufferWidth,
						presentationParameters.BackBufferHeight
					);
				}
				else
				{
					Backbuffer.ResetFramebuffer(
						presentationParameters,
						renderTargetBound
					);
				}
			}
		}

		#endregion

		#region Window SwapBuffers Method

		public void SwapBuffers(
			Rectangle? sourceRectangle,
			Rectangle? destinationRectangle,
			IntPtr overrideWindowHandle
		) {
			/* Only the faux-backbuffer supports presenting
			 * specific regions given to Present().
			 * -flibit
			 */
			if (Backbuffer is OpenGLBackbuffer)
			{
				int srcX, srcY, srcW, srcH;
				int dstX, dstY, dstW, dstH;
				if (sourceRectangle.HasValue)
				{
					srcX = sourceRectangle.Value.X;
					srcY = sourceRectangle.Value.Y;
					srcW = sourceRectangle.Value.Width;
					srcH = sourceRectangle.Value.Height;
				}
				else
				{
					srcX = 0;
					srcY = 0;
					srcW = Backbuffer.Width;
					srcH = Backbuffer.Height;
				}
				if (destinationRectangle.HasValue)
				{
					dstX = destinationRectangle.Value.X;
					dstY = destinationRectangle.Value.Y;
					dstW = destinationRectangle.Value.Width;
					dstH = destinationRectangle.Value.Height;
				}
				else
				{
					dstX = 0;
					dstY = 0;
					SDL.SDL_GetWindowSize(
						overrideWindowHandle,
						out dstW,
						out dstH
					);
				}

				if (scissorTestEnable)
				{
					glDisable(GLenum.GL_SCISSOR_TEST);
				}

				if (	Backbuffer.MultiSampleCount > 0 &&
					(srcX != dstX || srcY != dstY || srcW != dstW || srcH != dstH)	)
				{
					/* We have to resolve the renderbuffer to a texture first.
					 * For whatever reason, we can't blit a multisample renderbuffer
					 * to the backbuffer. Not sure why, but oh well.
					 * -flibit
					 */
					OpenGLBackbuffer glBack = Backbuffer as OpenGLBackbuffer;
					if (glBack.Texture == 0)
					{
						glGenTextures(1, out glBack.Texture);
						glBindTexture(GLenum.GL_TEXTURE_2D, glBack.Texture);
						glTexImage2D(
							GLenum.GL_TEXTURE_2D,
							0,
							(int) GLenum.GL_RGBA,
							glBack.Width,
							glBack.Height,
							0,
							GLenum.GL_RGBA,
							GLenum.GL_UNSIGNED_BYTE,
							IntPtr.Zero
						);
						glBindTexture(Textures[0].Target, Textures[0].Handle);
					}
					BindFramebuffer(resolveFramebufferDraw);
					glFramebufferTexture2D(
						GLenum.GL_FRAMEBUFFER,
						GLenum.GL_COLOR_ATTACHMENT0,
						GLenum.GL_TEXTURE_2D,
						glBack.Texture,
						0
					);
					BindReadFramebuffer(glBack.Handle);
					glBlitFramebuffer(
						0, 0, glBack.Width, glBack.Height,
						0, 0, glBack.Width, glBack.Height,
						GLenum.GL_COLOR_BUFFER_BIT,
						GLenum.GL_LINEAR
					);
					BindReadFramebuffer(resolveFramebufferDraw);
				}
				else
				{
					BindReadFramebuffer((Backbuffer as OpenGLBackbuffer).Handle);
				}
				BindDrawFramebuffer(0);

				glBlitFramebuffer(
					srcX, srcY, srcW, srcH,
					dstX, dstY, dstW, dstH,
					GLenum.GL_COLOR_BUFFER_BIT,
					GLenum.GL_LINEAR
				);

				BindFramebuffer(0);

				if (scissorTestEnable)
				{
					glEnable(GLenum.GL_SCISSOR_TEST);
				}

				SDL.SDL_GL_SwapWindow(
					overrideWindowHandle
				);

				BindFramebuffer((Backbuffer as OpenGLBackbuffer).Handle);
			}
			else
			{
				// Nothing left to do, just swap!
				SDL.SDL_GL_SwapWindow(
					overrideWindowHandle
				);
			}

#if !DISABLE_THREADING && !THREADED_GL
			RunActions();
#endif
			IGLTexture gcTexture;
			while (GCTextures.TryDequeue(out gcTexture))
			{
				DeleteTexture(gcTexture);
			}
			IGLRenderbuffer gcDepthBuffer;
			while (GCDepthBuffers.TryDequeue(out gcDepthBuffer))
			{
				DeleteRenderbuffer(gcDepthBuffer);
			}
			IGLBuffer gcBuffer;
			while (GCVertexBuffers.TryDequeue(out gcBuffer))
			{
				DeleteVertexBuffer(gcBuffer);
			}
			while (GCIndexBuffers.TryDequeue(out gcBuffer))
			{
				DeleteIndexBuffer(gcBuffer);
			}
			IGLEffect gcEffect;
			while (GCEffects.TryDequeue(out gcEffect))
			{
				DeleteEffect(gcEffect);
			}
			IGLQuery gcQuery;
			while (GCQueries.TryDequeue(out gcQuery))
			{
				DeleteQuery(gcQuery);
			}
		}

		#endregion

		#region GL Object Disposal Wrappers

		public void AddDisposeTexture(IGLTexture texture)
		{
			if (IsOnMainThread())
			{
				DeleteTexture(texture);
			}
			else
			{
				GCTextures.Enqueue(texture);
			}
		}

		public void AddDisposeRenderbuffer(IGLRenderbuffer renderbuffer)
		{
			if (IsOnMainThread())
			{
				DeleteRenderbuffer(renderbuffer);
			}
			else
			{
				GCDepthBuffers.Enqueue(renderbuffer);
			}
		}

		public void AddDisposeVertexBuffer(IGLBuffer buffer)
		{
			if (IsOnMainThread())
			{
				DeleteVertexBuffer(buffer);
			}
			else
			{
				GCVertexBuffers.Enqueue(buffer);
			}
		}

		public void AddDisposeIndexBuffer(IGLBuffer buffer)
		{
			if (IsOnMainThread())
			{
				DeleteIndexBuffer(buffer);
			}
			else
			{
				GCIndexBuffers.Enqueue(buffer);
			}
		}

		public void AddDisposeEffect(IGLEffect effect)
		{
			if (IsOnMainThread())
			{
				DeleteEffect(effect);
			}
			else
			{
				GCEffects.Enqueue(effect);
			}
		}

		public void AddDisposeQuery(IGLQuery query)
		{
			if (IsOnMainThread())
			{
				DeleteQuery(query);
			}
			else
			{
				GCQueries.Enqueue(query);
			}
		}

		#endregion

		#region String Marker Method

		public void SetStringMarker(string text)
		{
#if DEBUG
			byte[] chars = System.Text.Encoding.ASCII.GetBytes(text);
			glStringMarkerGREMEDY(chars.Length, chars);
#endif
		}

		#endregion

		#region Drawing Methods

		public void DrawIndexedPrimitives(
			PrimitiveType primitiveType,
			int baseVertex,
			int minVertexIndex,
			int numVertices,
			int startIndex,
			int primitiveCount,
			IndexBuffer indices
		) {
			// Unsigned short or unsigned int?
			bool shortIndices = indices.IndexElementSize == IndexElementSize.SixteenBits;

			// Bind the index buffer
			BindIndexBuffer(indices.buffer);

			// Draw!
			glDrawRangeElementsBaseVertex(
				XNAToGL.Primitive[(int) primitiveType],
				minVertexIndex,
				minVertexIndex + numVertices - 1,
				XNAToGL.PrimitiveVerts(primitiveType, primitiveCount),
				shortIndices ?
					GLenum.GL_UNSIGNED_SHORT :
					GLenum.GL_UNSIGNED_INT,
				(IntPtr) (startIndex * (shortIndices ? 2 : 4)),
				baseVertex
			);
		}

		public void DrawInstancedPrimitives(
			PrimitiveType primitiveType,
			int baseVertex,
			int minVertexIndex,
			int numVertices,
			int startIndex,
			int primitiveCount,
			int instanceCount,
			IndexBuffer indices
		) {
			// Note that minVertexIndex and numVertices are NOT used!

			// Bind the index buffer
			BindIndexBuffer(indices.buffer);

			// Unsigned short or unsigned int?
			bool shortIndices = indices.IndexElementSize == IndexElementSize.SixteenBits;

			// Draw!
			glDrawElementsInstancedBaseVertex(
				XNAToGL.Primitive[(int) primitiveType],
				XNAToGL.PrimitiveVerts(primitiveType, primitiveCount),
				shortIndices ?
					GLenum.GL_UNSIGNED_SHORT :
					GLenum.GL_UNSIGNED_INT,
				(IntPtr) (startIndex * (shortIndices ? 2 : 4)),
				instanceCount,
				baseVertex
			);
		}

		public void DrawPrimitives(
			PrimitiveType primitiveType,
			int vertexStart,
			int primitiveCount
		) {
			// Draw!
			glDrawArrays(
				XNAToGL.Primitive[(int) primitiveType],
				vertexStart,
				XNAToGL.PrimitiveVerts(primitiveType, primitiveCount)
			);
		}

		public void DrawUserIndexedPrimitives(
			PrimitiveType primitiveType,
			IntPtr vertexData,
			int vertexOffset,
			int numVertices,
			IntPtr indexData,
			int indexOffset,
			IndexElementSize indexElementSize,
			int primitiveCount
		) {
			// Unbind current index buffer.
			BindIndexBuffer(OpenGLBuffer.NullBuffer);

			// Unsigned short or unsigned int?
			bool shortIndices = indexElementSize == IndexElementSize.SixteenBits;

			// Draw!
			glDrawRangeElements(
				XNAToGL.Primitive[(int) primitiveType],
				0,
				numVertices - 1,
				XNAToGL.PrimitiveVerts(primitiveType, primitiveCount),
				shortIndices ?
					GLenum.GL_UNSIGNED_SHORT :
					GLenum.GL_UNSIGNED_INT,
				(IntPtr) (
					indexData.ToInt64() +
					(indexOffset * (shortIndices ? 2 : 4))
				)
			);
		}

		public void DrawUserPrimitives(
			PrimitiveType primitiveType,
			IntPtr vertexData,
			int vertexOffset,
			int primitiveCount
		) {
			// Draw!
			glDrawArrays(
				XNAToGL.Primitive[(int) primitiveType],
				vertexOffset,
				XNAToGL.PrimitiveVerts(primitiveType, primitiveCount)
			);
		}

		#endregion

		#region State Management Methods

		public void SetViewport(Viewport vp, bool renderTargetBound)
		{
			// Flip viewport when target is not bound
			if (!renderTargetBound)
			{
				vp.Y = Backbuffer.Height - vp.Y - vp.Height;
			}

			if (vp.Bounds != viewport)
			{
				viewport = vp.Bounds;
				glViewport(
					viewport.X,
					viewport.Y,
					viewport.Width,
					viewport.Height
				);
			}

			if (vp.MinDepth != depthRangeMin || vp.MaxDepth != depthRangeMax)
			{
				depthRangeMin = vp.MinDepth;
				depthRangeMax = vp.MaxDepth;
				glDepthRange((double) depthRangeMin, (double) depthRangeMax);
			}
		}

		public void SetScissorRect(
			Rectangle scissorRect,
			bool renderTargetBound
		) {
			// Flip rectangle when target is not bound
			if (!renderTargetBound)
			{
				scissorRect.Y = viewport.Height - scissorRect.Y - scissorRect.Height;
			}

			if (scissorRect != scissorRectangle)
			{
				scissorRectangle = scissorRect;
				glScissor(
					scissorRectangle.X,
					scissorRectangle.Y,
					scissorRectangle.Width,
					scissorRectangle.Height
				);
			}
		}

		public void SetBlendState(BlendState blendState)
		{
			bool newEnable = (
				!(	blendState.ColorSourceBlend == Blend.One &&
					blendState.ColorDestinationBlend == Blend.Zero &&
					blendState.AlphaSourceBlend == Blend.One &&
					blendState.AlphaDestinationBlend == Blend.Zero	)
			);
			if (newEnable != alphaBlendEnable)
			{
				alphaBlendEnable = newEnable;
				ToggleGLState(GLenum.GL_BLEND, alphaBlendEnable);
			}

			if (alphaBlendEnable)
			{
				if (blendState.BlendFactor != blendColor)
				{
					blendColor = blendState.BlendFactor;
					glBlendColor(
						blendColor.R / 255.0f,
						blendColor.G / 255.0f,
						blendColor.B / 255.0f,
						blendColor.A / 255.0f
					);
				}

				if (	blendState.ColorSourceBlend != srcBlend ||
					blendState.ColorDestinationBlend != dstBlend ||
					blendState.AlphaSourceBlend != srcBlendAlpha ||
					blendState.AlphaDestinationBlend != dstBlendAlpha	)
				{
					srcBlend = blendState.ColorSourceBlend;
					dstBlend = blendState.ColorDestinationBlend;
					srcBlendAlpha = blendState.AlphaSourceBlend;
					dstBlendAlpha = blendState.AlphaDestinationBlend;
					glBlendFuncSeparate(
						XNAToGL.BlendMode[(int) srcBlend],
						XNAToGL.BlendMode[(int) dstBlend],
						XNAToGL.BlendMode[(int) srcBlendAlpha],
						XNAToGL.BlendMode[(int) dstBlendAlpha]
					);
				}

				if (	blendState.ColorBlendFunction != blendOp ||
					blendState.AlphaBlendFunction != blendOpAlpha	)
				{
					blendOp = blendState.ColorBlendFunction;
					blendOpAlpha = blendState.AlphaBlendFunction;
					glBlendEquationSeparate(
						XNAToGL.BlendEquation[(int) blendOp],
						XNAToGL.BlendEquation[(int) blendOpAlpha]
					);
				}
			}

			if (blendState.ColorWriteChannels != colorWriteEnable)
			{
				colorWriteEnable = blendState.ColorWriteChannels;
				glColorMask(
					(colorWriteEnable & ColorWriteChannels.Red) != 0,
					(colorWriteEnable & ColorWriteChannels.Green) != 0,
					(colorWriteEnable & ColorWriteChannels.Blue) != 0,
					(colorWriteEnable & ColorWriteChannels.Alpha) != 0
				);
			}
			/* FIXME: So how exactly do we factor in
			 * COLORWRITEENABLE for buffer 0? Do we just assume that
			 * the default is just buffer 0, and all other calls
			 * update the other write masks afterward? Or do we
			 * assume that COLORWRITEENABLE only touches 0, and the
			 * other 3 buffers are left alone unless we don't have
			 * EXT_draw_buffers2?
			 * -flibit
			 */
			if (blendState.ColorWriteChannels1 != colorWriteEnable1)
			{
				colorWriteEnable1 = blendState.ColorWriteChannels1;
				glColorMaskIndexedEXT(
					1,
					(colorWriteEnable1 & ColorWriteChannels.Red) != 0,
					(colorWriteEnable1 & ColorWriteChannels.Green) != 0,
					(colorWriteEnable1 & ColorWriteChannels.Blue) != 0,
					(colorWriteEnable1 & ColorWriteChannels.Alpha) != 0
				);
			}
			if (blendState.ColorWriteChannels2 != colorWriteEnable2)
			{
				colorWriteEnable2 = blendState.ColorWriteChannels2;
				glColorMaskIndexedEXT(
					2,
					(colorWriteEnable2 & ColorWriteChannels.Red) != 0,
					(colorWriteEnable2 & ColorWriteChannels.Green) != 0,
					(colorWriteEnable2 & ColorWriteChannels.Blue) != 0,
					(colorWriteEnable2 & ColorWriteChannels.Alpha) != 0
				);
			}
			if (blendState.ColorWriteChannels3 != colorWriteEnable3)
			{
				colorWriteEnable3 = blendState.ColorWriteChannels3;
				glColorMaskIndexedEXT(
					3,
					(colorWriteEnable3 & ColorWriteChannels.Red) != 0,
					(colorWriteEnable3 & ColorWriteChannels.Green) != 0,
					(colorWriteEnable3 & ColorWriteChannels.Blue) != 0,
					(colorWriteEnable3 & ColorWriteChannels.Alpha) != 0
				);
			}

			if (blendState.MultiSampleMask != multisampleMask && supportsMultisampling)
			{
				if (blendState.MultiSampleMask == -1)
				{
					glDisable(GLenum.GL_SAMPLE_MASK);
				}
				else
				{
					if (multisampleMask == -1)
					{
						glEnable(GLenum.GL_SAMPLE_MASK);
					}
					// FIXME: index...? -flibit
					glSampleMaski(0, (uint) blendState.MultiSampleMask);
				}
				multisampleMask = blendState.MultiSampleMask;
			}
		}

		public void SetDepthStencilState(DepthStencilState depthStencilState)
		{
			if (depthStencilState.DepthBufferEnable != zEnable)
			{
				zEnable = depthStencilState.DepthBufferEnable;
				ToggleGLState(GLenum.GL_DEPTH_TEST, zEnable);
			}

			if (zEnable)
			{
				if (depthStencilState.DepthBufferWriteEnable != zWriteEnable)
				{
					zWriteEnable = depthStencilState.DepthBufferWriteEnable;
					glDepthMask(zWriteEnable);
				}

				if (depthStencilState.DepthBufferFunction != depthFunc)
				{
					depthFunc = depthStencilState.DepthBufferFunction;
					glDepthFunc(XNAToGL.CompareFunc[(int) depthFunc]);
				}
			}

			if (depthStencilState.StencilEnable != stencilEnable)
			{
				stencilEnable = depthStencilState.StencilEnable;
				ToggleGLState(GLenum.GL_STENCIL_TEST, stencilEnable);
			}

			if (stencilEnable)
			{
				if (depthStencilState.StencilWriteMask != stencilWriteMask)
				{
					stencilWriteMask = depthStencilState.StencilWriteMask;
					glStencilMask(stencilWriteMask);
				}

				// TODO: Can we split StencilFunc/StencilOp up nicely? -flibit
				if (	depthStencilState.TwoSidedStencilMode != separateStencilEnable ||
					depthStencilState.ReferenceStencil != stencilRef ||
					depthStencilState.StencilMask != stencilMask ||
					depthStencilState.StencilFunction != stencilFunc ||
					depthStencilState.CounterClockwiseStencilFunction != ccwStencilFunc ||
					depthStencilState.StencilFail != stencilFail ||
					depthStencilState.StencilDepthBufferFail != stencilZFail ||
					depthStencilState.StencilPass != stencilPass ||
					depthStencilState.CounterClockwiseStencilFail != ccwStencilFail ||
					depthStencilState.CounterClockwiseStencilDepthBufferFail != ccwStencilZFail ||
					depthStencilState.CounterClockwiseStencilPass != ccwStencilPass	)
				{
					separateStencilEnable = depthStencilState.TwoSidedStencilMode;
					stencilRef = depthStencilState.ReferenceStencil;
					stencilMask = depthStencilState.StencilMask;
					stencilFunc = depthStencilState.StencilFunction;
					stencilFail = depthStencilState.StencilFail;
					stencilZFail = depthStencilState.StencilDepthBufferFail;
					stencilPass = depthStencilState.StencilPass;
					if (separateStencilEnable)
					{
						ccwStencilFunc = depthStencilState.CounterClockwiseStencilFunction;
						ccwStencilFail = depthStencilState.CounterClockwiseStencilFail;
						ccwStencilZFail = depthStencilState.CounterClockwiseStencilDepthBufferFail;
						ccwStencilPass = depthStencilState.CounterClockwiseStencilPass;
						glStencilFuncSeparate(
							GLenum.GL_FRONT,
							XNAToGL.CompareFunc[(int) stencilFunc],
							stencilRef,
							stencilMask
						);
						glStencilFuncSeparate(
							GLenum.GL_BACK,
							XNAToGL.CompareFunc[(int) ccwStencilFunc],
							stencilRef,
							stencilMask
						);
						glStencilOpSeparate(
							GLenum.GL_FRONT,
							XNAToGL.GLStencilOp[(int) stencilFail],
							XNAToGL.GLStencilOp[(int) stencilZFail],
							XNAToGL.GLStencilOp[(int) stencilPass]
						);
						glStencilOpSeparate(
							GLenum.GL_BACK,
							XNAToGL.GLStencilOp[(int) ccwStencilFail],
							XNAToGL.GLStencilOp[(int) ccwStencilZFail],
							XNAToGL.GLStencilOp[(int) ccwStencilPass]
						);
					}
					else
					{
						glStencilFunc(
							XNAToGL.CompareFunc[(int) stencilFunc],
							stencilRef,
							stencilMask
						);
						glStencilOp(
							XNAToGL.GLStencilOp[(int) stencilFail],
							XNAToGL.GLStencilOp[(int) stencilZFail],
							XNAToGL.GLStencilOp[(int) stencilPass]
						);
					}
				}
			}
		}

		public void ApplyRasterizerState(
			RasterizerState rasterizerState,
			bool renderTargetBound
		) {
			if (rasterizerState.ScissorTestEnable != scissorTestEnable)
			{
				scissorTestEnable = rasterizerState.ScissorTestEnable;
				ToggleGLState(GLenum.GL_SCISSOR_TEST, scissorTestEnable);
			}

			CullMode actualMode;
			if (renderTargetBound)
			{
				actualMode = rasterizerState.CullMode;
			}
			else
			{
				// When not rendering offscreen the faces change order.
				if (rasterizerState.CullMode == CullMode.None)
				{
					actualMode = rasterizerState.CullMode;
				}
				else
				{
					actualMode = (
						rasterizerState.CullMode == CullMode.CullClockwiseFace ?
							CullMode.CullCounterClockwiseFace :
							CullMode.CullClockwiseFace
					);
				}
			}
			if (actualMode != cullFrontFace)
			{
				if ((actualMode == CullMode.None) != (cullFrontFace == CullMode.None))
				{
					ToggleGLState(GLenum.GL_CULL_FACE, actualMode != CullMode.None);
				}
				cullFrontFace = actualMode;
				if (cullFrontFace != CullMode.None)
				{
					glFrontFace(XNAToGL.FrontFace[(int) cullFrontFace]);
				}
			}

			if (rasterizerState.FillMode != fillMode)
			{
				fillMode = rasterizerState.FillMode;
				glPolygonMode(
					GLenum.GL_FRONT_AND_BACK,
					XNAToGL.GLFillMode[(int) fillMode]
				);
			}

			// FIXME: Floating point equality comparisons used for speed -flibit
			float realDepthBias = rasterizerState.DepthBias * XNAToGL.DepthBiasScale[
				renderTargetBound ?
					(int) currentDepthStencilFormat :
					(int) Backbuffer.DepthFormat
			];
			if (	realDepthBias != depthBias ||
				rasterizerState.SlopeScaleDepthBias != slopeScaleDepthBias	)
			{
				if (	realDepthBias == 0.0f &&
					rasterizerState.SlopeScaleDepthBias == 0.0f)
				{
					// We're changing to disabled bias, disable!
					glDisable(GLenum.GL_POLYGON_OFFSET_FILL);
				}
				else
				{
					if (depthBias == 0.0f && slopeScaleDepthBias == 0.0f)
					{
						// We're changing away from disabled bias, enable!
						glEnable(GLenum.GL_POLYGON_OFFSET_FILL);
					}
					glPolygonOffset(
						rasterizerState.SlopeScaleDepthBias,
						realDepthBias
					);
				}
				depthBias = realDepthBias;
				slopeScaleDepthBias = rasterizerState.SlopeScaleDepthBias;
			}

			/* FIXME: This doesn't actually work on like 99% of setups!
			 * For whatever reason people decided that they didn't have to obey
			 * GL_MULTISAMPLE's value when it was disabled.
			 *
			 * If they could do it for D3D9 I fail to see why they couldn't for
			 * OpenGL. Idiots.
			 *
			 * -flibit
			 */
			if (rasterizerState.MultiSampleAntiAlias != multiSampleEnable)
			{
				multiSampleEnable = rasterizerState.MultiSampleAntiAlias;
				ToggleGLState(GLenum.GL_MULTISAMPLE, multiSampleEnable);
			}
		}

		public void VerifySampler(int index, Texture texture, SamplerState sampler)
		{
			if (texture == null)
			{
				if (Textures[index] != OpenGLTexture.NullTexture)
				{
					if (index != 0)
					{
						glActiveTexture(GLenum.GL_TEXTURE0 + index);
					}
					glBindTexture(Textures[index].Target, 0);
					if (index != 0)
					{
						// Keep this state sane. -flibit
						glActiveTexture(GLenum.GL_TEXTURE0);
					}
					Textures[index] = OpenGLTexture.NullTexture;
				}
				return;
			}

			OpenGLTexture tex = texture.texture as OpenGLTexture;

			if (	tex == Textures[index] &&
				sampler.AddressU == tex.WrapS &&
				sampler.AddressV == tex.WrapT &&
				sampler.AddressW == tex.WrapR &&
				sampler.Filter == tex.Filter &&
				sampler.MaxAnisotropy == tex.Anistropy &&
				sampler.MaxMipLevel == tex.MaxMipmapLevel &&
				sampler.MipMapLevelOfDetailBias == tex.LODBias	)
			{
				// Nothing's changing, forget it.
				return;
			}

			// Set the active texture slot
			if (index != 0)
			{
				glActiveTexture(GLenum.GL_TEXTURE0 + index);
			}

			// Bind the correct texture
			if (tex != Textures[index])
			{
				if (tex.Target != Textures[index].Target)
				{
					// If we're changing targets, unbind the old texture first!
					glBindTexture(Textures[index].Target, 0);
				}
				glBindTexture(tex.Target, tex.Handle);
				Textures[index] = tex;
			}

			// Apply the sampler states to the GL texture
			if (sampler.AddressU != tex.WrapS)
			{
				tex.WrapS = sampler.AddressU;
				glTexParameteri(
					tex.Target,
					GLenum.GL_TEXTURE_WRAP_S,
					XNAToGL.Wrap[(int) tex.WrapS]
				);
			}
			if (sampler.AddressV != tex.WrapT)
			{
				tex.WrapT = sampler.AddressV;
				glTexParameteri(
					tex.Target,
					GLenum.GL_TEXTURE_WRAP_T,
					XNAToGL.Wrap[(int) tex.WrapT]
				);
			}
			if (sampler.AddressW != tex.WrapR)
			{
				tex.WrapR = sampler.AddressW;
				glTexParameteri(
					tex.Target,
					GLenum.GL_TEXTURE_WRAP_R,
					XNAToGL.Wrap[(int) tex.WrapR]
				);
			}
			if (	sampler.Filter != tex.Filter ||
				sampler.MaxAnisotropy != tex.Anistropy	)
			{
				tex.Filter = sampler.Filter;
				tex.Anistropy = sampler.MaxAnisotropy;
				glTexParameteri(
					tex.Target,
					GLenum.GL_TEXTURE_MAG_FILTER,
					XNAToGL.MagFilter[(int) tex.Filter]
				);
				glTexParameteri(
					tex.Target,
					GLenum.GL_TEXTURE_MIN_FILTER,
					tex.HasMipmaps ?
						XNAToGL.MinMipFilter[(int) tex.Filter] :
						XNAToGL.MinFilter[(int) tex.Filter]
				);
				glTexParameterf(
					tex.Target,
					GLenum.GL_TEXTURE_MAX_ANISOTROPY_EXT,
					(tex.Filter == TextureFilter.Anisotropic) ?
						Math.Max(tex.Anistropy, 1.0f) :
						1.0f
				);
			}
			if (sampler.MaxMipLevel != tex.MaxMipmapLevel)
			{
				tex.MaxMipmapLevel = sampler.MaxMipLevel;
				glTexParameteri(
					tex.Target,
					GLenum.GL_TEXTURE_BASE_LEVEL,
					tex.MaxMipmapLevel
				);
			}
			if (sampler.MipMapLevelOfDetailBias != tex.LODBias)
			{
				System.Diagnostics.Debug.Assert(!useES2);
				tex.LODBias = sampler.MipMapLevelOfDetailBias;
				glTexParameterf(
					tex.Target,
					GLenum.GL_TEXTURE_LOD_BIAS,
					tex.LODBias
				);
			}

			if (index != 0)
			{
				// Keep this state sane. -flibit
				glActiveTexture(GLenum.GL_TEXTURE0);
			}
		}

		#endregion

		#region Effect Methods

		public IGLEffect CreateEffect(byte[] effectCode)
		{
			IntPtr effect = IntPtr.Zero;
			IntPtr glEffect = IntPtr.Zero;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			effect = MojoShader.MOJOSHADER_parseEffect(
				shaderProfile,
				effectCode,
				(uint) effectCode.Length,
				null,
				0,
				null,
				0,
				null,
				null,
				IntPtr.Zero
			);
			glEffect = MojoShader.MOJOSHADER_glCompileEffect(effect);
			if (glEffect == IntPtr.Zero)
			{
				throw new InvalidOperationException(
					MojoShader.MOJOSHADER_glGetError()
				);
			}

#if !DISABLE_THREADING
			});
#endif

			return new OpenGLEffect(effect, glEffect);
		}

		private void DeleteEffect(IGLEffect effect)
		{
			IntPtr glEffectData = (effect as OpenGLEffect).GLEffectData;
			if (glEffectData == currentEffect)
			{
				MojoShader.MOJOSHADER_glEffectEndPass(currentEffect);
				MojoShader.MOJOSHADER_glEffectEnd(currentEffect);
				currentEffect = IntPtr.Zero;
				currentTechnique = IntPtr.Zero;
				currentPass = 0;
			}
			MojoShader.MOJOSHADER_glDeleteEffect(glEffectData);
			MojoShader.MOJOSHADER_freeEffect(effect.EffectData);
		}

		public IGLEffect CloneEffect(IGLEffect cloneSource)
		{
			IntPtr effect = IntPtr.Zero;
			IntPtr glEffect = IntPtr.Zero;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			effect = MojoShader.MOJOSHADER_cloneEffect(cloneSource.EffectData);
			glEffect = MojoShader.MOJOSHADER_glCompileEffect(effect);
			if (glEffect == IntPtr.Zero)
			{
				throw new InvalidOperationException(
					MojoShader.MOJOSHADER_glGetError()
				);
			}

#if !DISABLE_THREADING
			});
#endif

			return new OpenGLEffect(effect, glEffect);
		}

		public void ApplyEffect(
			IGLEffect effect,
			IntPtr technique,
			uint pass,
			ref MojoShader.MOJOSHADER_effectStateChanges stateChanges
		) {
			effectApplied = true;
			IntPtr glEffectData = (effect as OpenGLEffect).GLEffectData;
			if (glEffectData == currentEffect)
			{
				if (technique == currentTechnique && pass == currentPass)
				{
					MojoShader.MOJOSHADER_glEffectCommitChanges(currentEffect);
					return;
				}
				MojoShader.MOJOSHADER_glEffectEndPass(currentEffect);
				MojoShader.MOJOSHADER_glEffectBeginPass(currentEffect, pass);
				currentTechnique = technique;
				currentPass = pass;
				return;
			}
			else if (currentEffect != IntPtr.Zero)
			{
				MojoShader.MOJOSHADER_glEffectEndPass(currentEffect);
				MojoShader.MOJOSHADER_glEffectEnd(currentEffect);
			}
			uint whatever;
			MojoShader.MOJOSHADER_glEffectBegin(
				glEffectData,
				out whatever,
				0,
				ref stateChanges
			);
			MojoShader.MOJOSHADER_glEffectBeginPass(
				glEffectData,
				pass
			);
			currentEffect = glEffectData;
			currentTechnique = technique;
			currentPass = pass;
		}

		public void BeginPassRestore(
			IGLEffect effect,
			ref MojoShader.MOJOSHADER_effectStateChanges changes
		) {
			IntPtr glEffectData = (effect as OpenGLEffect).GLEffectData;
			uint whatever;
			MojoShader.MOJOSHADER_glEffectBegin(
				glEffectData,
				out whatever,
				1,
				ref changes
			);
			MojoShader.MOJOSHADER_glEffectBeginPass(
				glEffectData,
				0
			);
			effectApplied = true;
		}

		public void EndPassRestore(IGLEffect effect)
		{
			IntPtr glEffectData = (effect as OpenGLEffect).GLEffectData;
			MojoShader.MOJOSHADER_glEffectEndPass(glEffectData);
			MojoShader.MOJOSHADER_glEffectEnd(glEffectData);
			effectApplied = true;
		}

		#endregion

		#region glVertexAttribPointer/glVertexAttribDivisor Methods

		public void ApplyVertexAttributes(
			VertexBufferBinding[] bindings,
			int numBindings,
			bool bindingsUpdated,
			int baseVertex
		) {
			if (supportsBaseVertex)
			{
				baseVertex = 0;
			}

			if (	bindingsUpdated ||
				baseVertex != ldBaseVertex ||
				currentEffect != ldEffect ||
				currentTechnique != ldTechnique ||
				currentPass != ldPass ||
				effectApplied	)
			{
				/* There's this weird case where you can have multiple vertbuffers,
				 * but they will have overlapping attributes. It seems like the
				 * first buffer gets priority, so start with the last one so the
				 * first buffer's attributes are what's bound at the end.
				 * -flibit
				 */
				for (int i = numBindings - 1; i >= 0; i -= 1)
				{
					BindVertexBuffer(bindings[i].VertexBuffer.buffer);
					VertexDeclaration vertexDeclaration = bindings[i].VertexBuffer.VertexDeclaration;
					IntPtr basePtr = (IntPtr) (
						vertexDeclaration.VertexStride *
						(bindings[i].VertexOffset + baseVertex)
					);
					foreach (VertexElement element in vertexDeclaration.elements)
					{
						int attribLoc = MojoShader.MOJOSHADER_glGetVertexAttribLocation(
							XNAToGL.VertexAttribUsage[(int) element.VertexElementUsage],
							element.UsageIndex
						);
						if (attribLoc == -1)
						{
							// Stream not in use!
							continue;
						}
						attributeEnabled[attribLoc] = true;
						VertexAttribute attr = attributes[attribLoc];
						uint buffer = (bindings[i].VertexBuffer.buffer as OpenGLBuffer).Handle;
						IntPtr ptr = basePtr + element.Offset;
						VertexElementFormat format = element.VertexElementFormat;
						bool normalized = XNAToGL.VertexAttribNormalized(element);
						if (	attr.CurrentBuffer != buffer ||
							attr.CurrentPointer != ptr ||
							attr.CurrentFormat != element.VertexElementFormat ||
							attr.CurrentNormalized != normalized ||
							attr.CurrentStride != vertexDeclaration.VertexStride	)
						{
							glVertexAttribPointer(
								attribLoc,
								XNAToGL.VertexAttribSize[(int) format],
								XNAToGL.VertexAttribType[(int) format],
								normalized,
								vertexDeclaration.VertexStride,
								ptr
							);
							attr.CurrentBuffer = buffer;
							attr.CurrentPointer = ptr;
							attr.CurrentFormat = format;
							attr.CurrentNormalized = normalized;
							attr.CurrentStride = vertexDeclaration.VertexStride;
						}
						if (SupportsHardwareInstancing)
						{
							attributeDivisor[attribLoc] = bindings[i].InstanceFrequency;
						}
					}
				}
				FlushGLVertexAttributes();

				ldBaseVertex = baseVertex;
				ldEffect = currentEffect;
				ldTechnique = currentTechnique;
				ldPass = currentPass;
				effectApplied = false;
				ldVertexDeclaration = null;
				ldPointer = IntPtr.Zero;
			}

			MojoShader.MOJOSHADER_glProgramReady();
			MojoShader.MOJOSHADER_glProgramViewportFlip(flipViewport);
		}

		public void ApplyVertexAttributes(
			VertexDeclaration vertexDeclaration,
			IntPtr ptr,
			int vertexOffset
		) {
			BindVertexBuffer(OpenGLBuffer.NullBuffer);
			IntPtr basePtr = ptr + (vertexDeclaration.VertexStride * vertexOffset);

			if (	vertexDeclaration != ldVertexDeclaration ||
				basePtr != ldPointer ||
				currentEffect != ldEffect ||
				currentTechnique != ldTechnique ||
				currentPass != ldPass ||
				effectApplied	)
			{
				foreach (VertexElement element in vertexDeclaration.elements)
				{
					int attribLoc = MojoShader.MOJOSHADER_glGetVertexAttribLocation(
						XNAToGL.VertexAttribUsage[(int) element.VertexElementUsage],
						element.UsageIndex
					);
					if (attribLoc == -1)
					{
						// Stream not used!
						continue;
					}
					attributeEnabled[attribLoc] = true;
					VertexAttribute attr = attributes[attribLoc];
					IntPtr finalPtr = basePtr + element.Offset;
					bool normalized = XNAToGL.VertexAttribNormalized(element);
					if (	attr.CurrentBuffer != 0 ||
						attr.CurrentPointer != finalPtr ||
						attr.CurrentFormat != element.VertexElementFormat ||
						attr.CurrentNormalized != normalized ||
						attr.CurrentStride != vertexDeclaration.VertexStride	)
					{
						glVertexAttribPointer(
							attribLoc,
							XNAToGL.VertexAttribSize[(int) element.VertexElementFormat],
							XNAToGL.VertexAttribType[(int) element.VertexElementFormat],
							normalized,
							vertexDeclaration.VertexStride,
							finalPtr
						);
						attr.CurrentBuffer = 0;
						attr.CurrentPointer = finalPtr;
						attr.CurrentFormat = element.VertexElementFormat;
						attr.CurrentNormalized = normalized;
						attr.CurrentStride = vertexDeclaration.VertexStride;
					}
					if (SupportsHardwareInstancing)
					{
						attributeDivisor[attribLoc] = 0;
					}
				}
				FlushGLVertexAttributes();

				ldVertexDeclaration = vertexDeclaration;
				ldPointer = ptr;
				ldEffect = currentEffect;
				ldTechnique = currentTechnique;
				ldPass = currentPass;
				effectApplied = false;
				ldBaseVertex = -1;
			}

			MojoShader.MOJOSHADER_glProgramReady();
			MojoShader.MOJOSHADER_glProgramViewportFlip(flipViewport);
		}

		private void FlushGLVertexAttributes()
		{
			for (int i = 0; i < attributes.Length; i += 1)
			{
				if (attributeEnabled[i])
				{
					attributeEnabled[i] = false;
					if (!previousAttributeEnabled[i])
					{
						glEnableVertexAttribArray(i);
						previousAttributeEnabled[i] = true;
					}
				}
				else if (previousAttributeEnabled[i])
				{
					glDisableVertexAttribArray(i);
					previousAttributeEnabled[i] = false;
				}

				int divisor = attributeDivisor[i];
				if (divisor != previousAttributeDivisor[i])
				{
					glVertexAttribDivisor(i, divisor);
					previousAttributeDivisor[i] = divisor;
				}
			}
		}

		#endregion

		#region glGenBuffers Methods

		public IGLBuffer GenVertexBuffer(
			bool dynamic,
			int vertexCount,
			int vertexStride
		) {
			OpenGLBuffer result = null;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			uint handle;
			glGenBuffers(1, out handle);

			result = new OpenGLBuffer(
				handle,
				(IntPtr) (vertexStride * vertexCount),
				dynamic ? GLenum.GL_STREAM_DRAW : GLenum.GL_STATIC_DRAW
			);

			BindVertexBuffer(result);
			glBufferData(
				GLenum.GL_ARRAY_BUFFER,
				result.BufferSize,
				IntPtr.Zero,
				result.Dynamic
			);

#if !DISABLE_THREADING
			});
#endif

			return result;
		}

		public IGLBuffer GenIndexBuffer(
			bool dynamic,
			int indexCount,
			IndexElementSize indexElementSize
		) {
			OpenGLBuffer result = null;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			uint handle;
			glGenBuffers(1, out handle);

			result = new OpenGLBuffer(
				handle,
				(IntPtr) (indexCount * (indexElementSize == IndexElementSize.SixteenBits ? 2 : 4)),
				dynamic ? GLenum.GL_STREAM_DRAW : GLenum.GL_STATIC_DRAW
			);

			BindIndexBuffer(result);
			glBufferData(
				GLenum.GL_ELEMENT_ARRAY_BUFFER,
				result.BufferSize,
				IntPtr.Zero,
				result.Dynamic
			);

#if !DISABLE_THREADING
			});
#endif

			return result;
		}

		#endregion

		#region glBindBuffer Methods

		private void BindVertexBuffer(IGLBuffer buffer)
		{
			uint handle = (buffer as OpenGLBuffer).Handle;
			if (handle != currentVertexBuffer)
			{
				glBindBuffer(GLenum.GL_ARRAY_BUFFER, handle);
				currentVertexBuffer = handle;
			}
		}

		private void BindIndexBuffer(IGLBuffer buffer)
		{
			uint handle = (buffer as OpenGLBuffer).Handle;
			if (handle != currentIndexBuffer)
			{
				glBindBuffer(GLenum.GL_ELEMENT_ARRAY_BUFFER, handle);
				currentIndexBuffer = handle;
			}
		}

		#endregion

		#region glSetBufferData Methods

		public void SetVertexBufferData<T>(
			IGLBuffer buffer,
			int elementSizeInBytes,
			int offsetInBytes,
			T[] data,
			int startIndex,
			int elementCount,
			SetDataOptions options
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			BindVertexBuffer(buffer);

			if (options == SetDataOptions.Discard)
			{
				glBufferData(
					GLenum.GL_ARRAY_BUFFER,
					buffer.BufferSize,
					IntPtr.Zero,
					(buffer as OpenGLBuffer).Dynamic
				);
			}

			GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);

			glBufferSubData(
				GLenum.GL_ARRAY_BUFFER,
				(IntPtr) offsetInBytes,
				(IntPtr) (elementSizeInBytes * elementCount),
				(IntPtr) (dataHandle.AddrOfPinnedObject().ToInt64() + startIndex * elementSizeInBytes)
			);

			dataHandle.Free();

#if !DISABLE_THREADING
			});
#endif
		}

		public void SetIndexBufferData<T>(
			IGLBuffer buffer,
			int offsetInBytes,
			T[] data,
			int startIndex,
			int elementCount,
			SetDataOptions options
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			BindIndexBuffer(buffer);

			if (options == SetDataOptions.Discard)
			{
				glBufferData(
					GLenum.GL_ELEMENT_ARRAY_BUFFER,
					buffer.BufferSize,
					IntPtr.Zero,
					(buffer as OpenGLBuffer).Dynamic
				);
			}

			GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);

			int elementSizeInBytes = Marshal.SizeOf(typeof(T));
			glBufferSubData(
				GLenum.GL_ELEMENT_ARRAY_BUFFER,
				(IntPtr) offsetInBytes,
				(IntPtr) (elementSizeInBytes * elementCount),
				(IntPtr) (dataHandle.AddrOfPinnedObject().ToInt64() + startIndex * elementSizeInBytes)
			);

			dataHandle.Free();

#if !DISABLE_THREADING
			});
#endif
		}

		#endregion

		#region glGetBufferData Methods

		public void GetVertexBufferData<T>(
			IGLBuffer buffer,
			int offsetInBytes,
			T[] data,
			int startIndex,
			int elementCount,
			int vertexStride
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			BindVertexBuffer(buffer);

			GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);

			glGetBufferSubData(
				GLenum.GL_ARRAY_BUFFER,
				(IntPtr) offsetInBytes,
				(IntPtr) (elementCount * vertexStride),
				dataHandle.AddrOfPinnedObject() + (startIndex * Marshal.SizeOf(typeof(T)))
			);

			dataHandle.Free();

#if !DISABLE_THREADING
			});
#endif
		}

		public void GetIndexBufferData<T>(
			IGLBuffer buffer,
			int offsetInBytes,
			T[] data,
			int startIndex,
			int elementCount
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			BindIndexBuffer(buffer);

			GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);

			int typeSize = Marshal.SizeOf(typeof(T));
			glGetBufferSubData(
				GLenum.GL_ELEMENT_ARRAY_BUFFER,
				(IntPtr) offsetInBytes,
				(IntPtr) (elementCount * typeSize),
				dataHandle.AddrOfPinnedObject() + (startIndex * typeSize)
			);

			dataHandle.Free();

#if !DISABLE_THREADING
			});
#endif
		}

		#endregion

		#region glDeleteBuffers Methods

		private void DeleteVertexBuffer(IGLBuffer buffer)
		{
			uint handle = (buffer as OpenGLBuffer).Handle;
			if (handle == currentVertexBuffer)
			{
				glBindBuffer(GLenum.GL_ARRAY_BUFFER, 0);
				currentVertexBuffer = 0;
			}
			for (int i = 0; i < attributes.Length; i += 1)
			{
				if (handle == attributes[i].CurrentBuffer)
				{
					// Force the next vertex attrib update!
					attributes[i].CurrentBuffer = uint.MaxValue;
				}
			}
			glDeleteBuffers(1, ref handle);
		}

		private void DeleteIndexBuffer(IGLBuffer buffer)
		{
			uint handle = (buffer as OpenGLBuffer).Handle;
			if (handle == currentIndexBuffer)
			{
				glBindBuffer(GLenum.GL_ELEMENT_ARRAY_BUFFER, 0);
				currentIndexBuffer = 0;
			}
			glDeleteBuffers(1, ref handle);
		}

		#endregion

		#region glCreateTexture Methods

		private OpenGLTexture CreateTexture(
			GLenum target,
			int levelCount
		) {
			uint handle;
			glGenTextures(1, out handle);
			OpenGLTexture result = new OpenGLTexture(
				handle,
				target,
				levelCount
			);
			BindTexture(result);
			glTexParameteri(
				result.Target,
				GLenum.GL_TEXTURE_WRAP_S,
				XNAToGL.Wrap[(int) result.WrapS]
			);
			glTexParameteri(
				result.Target,
				GLenum.GL_TEXTURE_WRAP_T,
				XNAToGL.Wrap[(int) result.WrapT]
			);
			glTexParameteri(
				result.Target,
				GLenum.GL_TEXTURE_WRAP_R,
				XNAToGL.Wrap[(int) result.WrapR]
			);
			glTexParameteri(
				result.Target,
				GLenum.GL_TEXTURE_MAG_FILTER,
				XNAToGL.MagFilter[(int) result.Filter]
			);
			glTexParameteri(
				result.Target,
				GLenum.GL_TEXTURE_MIN_FILTER,
				result.HasMipmaps ?
					XNAToGL.MinMipFilter[(int) result.Filter] :
					XNAToGL.MinFilter[(int) result.Filter]
			);
			glTexParameterf(
				result.Target,
				GLenum.GL_TEXTURE_MAX_ANISOTROPY_EXT,
				(result.Filter == TextureFilter.Anisotropic) ? Math.Max(result.Anistropy, 1.0f) : 1.0f
			);
			glTexParameteri(
				result.Target,
				GLenum.GL_TEXTURE_BASE_LEVEL,
				result.MaxMipmapLevel
			);
			if (!useES2)
			{
				glTexParameterf(
					result.Target,
					GLenum.GL_TEXTURE_LOD_BIAS,
					result.LODBias
				);
			}
			return result;
		}

		public IGLTexture CreateTexture2D(
			SurfaceFormat format,
			int width,
			int height,
			int levelCount
		) {
			OpenGLTexture result = null;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			result = CreateTexture(
				GLenum.GL_TEXTURE_2D,
				levelCount
			);

			GLenum glFormat = XNAToGL.TextureFormat[(int) format];
			GLenum glInternalFormat = XNAToGL.TextureInternalFormat[(int) format];
			if (glFormat == GLenum.GL_COMPRESSED_TEXTURE_FORMATS)
			{
				for (int i = 0; i < levelCount; i += 1)
				{
					int levelWidth = Math.Max(width >> i, 1);
					int levelHeight = Math.Max(height >> i, 1);
					glCompressedTexImage2D(
						GLenum.GL_TEXTURE_2D,
						i,
						(int) glInternalFormat,
						levelWidth,
						levelHeight,
						0,
						((levelWidth + 3) / 4) * ((levelHeight + 3) / 4) * Texture.GetFormatSize(format),
						IntPtr.Zero
					);
				}
			}
			else
			{
				GLenum glType = XNAToGL.TextureDataType[(int) format];
				for (int i = 0; i < levelCount; i += 1)
				{
					glTexImage2D(
						GLenum.GL_TEXTURE_2D,
						i,
						(int) glInternalFormat,
						Math.Max(width >> i, 1),
						Math.Max(height >> i, 1),
						0,
						glFormat,
						glType,
						IntPtr.Zero
					);
				}
			}

#if !DISABLE_THREADING
			});
#endif

			return result;
		}

		public IGLTexture CreateTexture3D(
			SurfaceFormat format,
			int width,
			int height,
			int depth,
			int levelCount
		) {
			OpenGLTexture result = null;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			result = CreateTexture(
				GLenum.GL_TEXTURE_3D,
				levelCount
			);

			GLenum glFormat = XNAToGL.TextureFormat[(int) format];
			GLenum glInternalFormat = XNAToGL.TextureInternalFormat[(int) format];
			GLenum glType = XNAToGL.TextureDataType[(int) format];
			for (int i = 0; i < levelCount; i += 1)
			{
				glTexImage3D(
					GLenum.GL_TEXTURE_3D,
					i,
					(int) glInternalFormat,
					Math.Max(width >> i, 1),
					Math.Max(height >> i, 1),
					Math.Max(depth >> i, 1),
					0,
					glFormat,
					glType,
					IntPtr.Zero
				);
			}

#if !DISABLE_THREADING
			});
#endif

			return result;
		}

		public IGLTexture CreateTextureCube(
			SurfaceFormat format,
			int size,
			int levelCount
		) {
			OpenGLTexture result = null;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			result = CreateTexture(
				GLenum.GL_TEXTURE_CUBE_MAP,
				levelCount
			);

			GLenum glFormat = XNAToGL.TextureFormat[(int) format];
			GLenum glInternalFormat = XNAToGL.TextureInternalFormat[(int) format];
			if (glFormat == GLenum.GL_COMPRESSED_TEXTURE_FORMATS)
			{
				for (int i = 0; i < 6; i += 1)
				{
					for (int l = 0; l < levelCount; l += 1)
					{
						int levelSize = Math.Max(size >> l, 1);
						glCompressedTexImage2D(
							GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + i,
							l,
							(int) glInternalFormat,
							levelSize,
							levelSize,
							0,
							((levelSize + 3) / 4) * ((levelSize + 3) / 4) * Texture.GetFormatSize(format),
							IntPtr.Zero
						);
					}
				}
			}
			else
			{
				GLenum glType = XNAToGL.TextureDataType[(int) format];
				for (int i = 0; i < 6; i += 1)
				{
					for (int l = 0; l < levelCount; l += 1)
					{
						int levelSize = Math.Max(size >> l, 1);
						glTexImage2D(
							GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + i,
							l,
							(int) glInternalFormat,
							levelSize,
							levelSize,
							0,
							glFormat,
							glType,
							IntPtr.Zero
						);
					}
				}
			}

#if !DISABLE_THREADING
			});
#endif

			return result;
		}

		#endregion

		#region glTexSubImage Methods

		public void SetTextureData2D<T>(
			IGLTexture texture,
			SurfaceFormat format,
			int x,
			int y,
			int w,
			int h,
			int level,
			T[] data,
			int startIndex,
			int elementCount
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif
			BindTexture(texture);

			GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);
			int elementSizeInBytes = Marshal.SizeOf(typeof(T));
			int startByte = startIndex * elementSizeInBytes;
			IntPtr dataPtr = (IntPtr) (dataHandle.AddrOfPinnedObject().ToInt64() + startByte);

			GLenum glFormat = XNAToGL.TextureFormat[(int) format];
			try
			{
				if (glFormat == GLenum.GL_COMPRESSED_TEXTURE_FORMATS)
				{
					int dataLength;
					if (elementCount > 0)
					{
						dataLength = elementCount * elementSizeInBytes;
					}
					else
					{
						dataLength = data.Length - startByte;
					}

					/* Note that we're using glInternalFormat, not glFormat.
					 * In this case, they should actually be the same thing,
					 * but we use glFormat somewhat differently for
					 * compressed textures.
					 * -flibit
					 */
					glCompressedTexSubImage2D(
						GLenum.GL_TEXTURE_2D,
						level,
						x,
						y,
						w,
						h,
						XNAToGL.TextureInternalFormat[(int) format],
						dataLength,
						dataPtr
					);
				}
				else
				{
					// Set pixel alignment to match texel size in bytes
					int packSize = Texture.GetFormatSize(format);
					if (packSize != 4)
					{
						glPixelStorei(
							GLenum.GL_UNPACK_ALIGNMENT,
							packSize
						);
					}

					glTexSubImage2D(
						GLenum.GL_TEXTURE_2D,
						level,
						x,
						y,
						w,
						h,
						glFormat,
						XNAToGL.TextureDataType[(int) format],
						dataPtr
					);

					// Keep this state sane -flibit
					if (packSize != 4)
					{
						glPixelStorei(
							GLenum.GL_UNPACK_ALIGNMENT,
							4
						);
					}
				}
			}
			finally
			{
				dataHandle.Free();
			}

#if !DISABLE_THREADING
			});
#endif
		}

		public void SetTextureData3D<T>(
			IGLTexture texture,
			SurfaceFormat format,
			int level,
			int left,
			int top,
			int right,
			int bottom,
			int front,
			int back,
			T[] data,
			int startIndex,
			int elementCount
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif
			BindTexture(texture);

			GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);
			try
			{
				glTexSubImage3D(
					GLenum.GL_TEXTURE_3D,
					level,
					left,
					top,
					front,
					right - left,
					bottom - top,
					back - front,
					XNAToGL.TextureFormat[(int) format],
					XNAToGL.TextureDataType[(int) format],
					(IntPtr) (dataHandle.AddrOfPinnedObject().ToInt64() + startIndex * Marshal.SizeOf(typeof(T)))
				);
			}
			finally
			{
				dataHandle.Free();
			}

#if !DISABLE_THREADING
			});
#endif
		}

		public void SetTextureDataCube<T>(
			IGLTexture texture,
			SurfaceFormat format,
			int xOffset,
			int yOffset,
			int width,
			int height,
			CubeMapFace cubeMapFace,
			int level,
			T[] data,
			int startIndex,
			int elementCount
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif
			BindTexture(texture);

			GCHandle dataHandle = GCHandle.Alloc(data, GCHandleType.Pinned);
			int elementSizeInBytes = Marshal.SizeOf(typeof(T));
			int startByte = startIndex * elementSizeInBytes;
			IntPtr dataPtr = (IntPtr) (dataHandle.AddrOfPinnedObject().ToInt64() + startByte);

			GLenum glFormat = XNAToGL.TextureFormat[(int) format];
			try
			{
				if (glFormat == GLenum.GL_COMPRESSED_TEXTURE_FORMATS)
				{
					int dataLength;
					if (elementCount > 0)
					{
						dataLength = elementCount * elementSizeInBytes;
					}
					else
					{
						dataLength = data.Length - startByte;
					}

					/* Note that we're using glInternalFormat, not glFormat.
					 * In this case, they should actually be the same thing,
					 * but we use glFormat somewhat differently for
					 * compressed textures.
					 * -flibit
					 */
					glCompressedTexSubImage2D(
						GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + (int) cubeMapFace,
						level,
						xOffset,
						yOffset,
						width,
						height,
						XNAToGL.TextureInternalFormat[(int) format],
						dataLength,
						dataPtr
					);
				}
				else
				{
					glTexSubImage2D(
						GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + (int) cubeMapFace,
						level,
						xOffset,
						yOffset,
						width,
						height,
						glFormat,
						XNAToGL.TextureDataType[(int) format],
						dataPtr
					);
				}
			}
			finally
			{
				dataHandle.Free();
			}

#if !DISABLE_THREADING
			});
#endif
		}

		public void SetTextureData2DPointer(
			Texture2D texture,
			IntPtr ptr
		) {
			BindTexture(texture.texture);
			// Set pixel alignment to match texel size in bytes
			int packSize = Texture.GetFormatSize(texture.Format);
			if (packSize != 4)
			{
				glPixelStorei(
					GLenum.GL_UNPACK_ALIGNMENT,
					packSize
				);
			}
			glTexSubImage2D(
				GLenum.GL_TEXTURE_2D,
				0,
				0,
				0,
				texture.Width,
				texture.Height,
				XNAToGL.TextureFormat[(int) texture.Format],
				XNAToGL.TextureDataType[(int) texture.Format],
				ptr
			);
			// Keep this state sane -flibit
			if (packSize != 4)
			{
				glPixelStorei(GLenum.GL_UNPACK_ALIGNMENT, 4);
			}
		}

		#endregion

		#region glGetTexImage Methods

		public void GetTextureData2D<T>(
			IGLTexture texture,
			SurfaceFormat format,
			int width,
			int height,
			int level,
			Rectangle? rect,
			T[] data,
			int startIndex,
			int elementCount
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			if (ReadTargetIfApplicable(
				texture,
				width,
				height,
				level,
				data,
				rect
			)) {
				return;
			}

			BindTexture(texture);
			GLenum glFormat = XNAToGL.TextureFormat[(int) format];
			if (glFormat == GLenum.GL_COMPRESSED_TEXTURE_FORMATS)
			{
				throw new NotImplementedException("GetData, CompressedTexture");
			}
			else if (rect == null)
			{
				// Just throw the whole texture into the user array.
				GCHandle ptr = GCHandle.Alloc(data, GCHandleType.Pinned);
				try
				{
					glGetTexImage(
						GLenum.GL_TEXTURE_2D,
						0,
						glFormat,
						XNAToGL.TextureDataType[(int) format],
						ptr.AddrOfPinnedObject()
					);
				}
				finally
				{
					ptr.Free();
				}
			}
			else
			{
				// Get the whole texture...
				T[] texData = new T[width * height];
				GCHandle ptr = GCHandle.Alloc(texData, GCHandleType.Pinned);
				try
				{
					glGetTexImage(
						GLenum.GL_TEXTURE_2D,
						0,
						glFormat,
						XNAToGL.TextureDataType[(int) format],
						ptr.AddrOfPinnedObject()
					);
				}
				finally
				{
					ptr.Free();
				}

				// Now, blit the rect region into the user array.
				Rectangle region = rect.Value;
				int curPixel = -1;
				for (int row = region.Y; row < region.Y + region.Height; row += 1)
				{
					for (int col = region.X; col < region.X + region.Width; col += 1)
					{
						curPixel += 1;
						if (curPixel < startIndex)
						{
							// If we're not at the start yet, just keep going...
							continue;
						}
						if (curPixel > elementCount)
						{
							// If we're past the end, we're done!
							return;
						}
						data[curPixel - startIndex] = texData[(row * width) + col];
					}
				}
			}

#if !DISABLE_THREADING
			});
#endif
		}

		public void GetTextureDataCube<T>(
			IGLTexture texture,
			SurfaceFormat format,
			int size,
			CubeMapFace cubeMapFace,
			int level,
			Rectangle? rect,
			T[] data,
			int startIndex,
			int elementCount
		) where T : struct {
#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			BindTexture(texture);
			GLenum glFormat = XNAToGL.TextureFormat[(int) format];
			if (glFormat == GLenum.GL_COMPRESSED_TEXTURE_FORMATS)
			{
				throw new NotImplementedException("GetData, CompressedTexture");
			}
			else if (rect == null)
			{
				// Just throw the whole texture into the user array.
				GCHandle ptr = GCHandle.Alloc(data, GCHandleType.Pinned);
				try
				{
					glGetTexImage(
						GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + (int) cubeMapFace,
						0,
						glFormat,
						XNAToGL.TextureDataType[(int) format],
						ptr.AddrOfPinnedObject()
					);
				}
				finally
				{
					ptr.Free();
				}
			}
			else
			{
				// Get the whole texture...
				T[] texData = new T[size * size];
				GCHandle ptr = GCHandle.Alloc(texData, GCHandleType.Pinned);
				try
				{
					glGetTexImage(
						GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + (int) cubeMapFace,
						0,
						glFormat,
						XNAToGL.TextureDataType[(int) format],
						ptr.AddrOfPinnedObject()
					);
				}
				finally
				{
					ptr.Free();
				}

				// Now, blit the rect region into the user array.
				Rectangle region = rect.Value;
				int curPixel = -1;
				for (int row = region.Y; row < region.Y + region.Height; row += 1)
				{
					for (int col = region.X; col < region.X + region.Width; col += 1)
					{
						curPixel += 1;
						if (curPixel < startIndex)
						{
							// If we're not at the start yet, just keep going...
							continue;
						}
						if (curPixel > elementCount)
						{
							// If we're past the end, we're done!
							return;
						}
						data[curPixel - startIndex] = texData[(row * size) + col];
					}
				}
			}

#if !DISABLE_THREADING
			});
#endif
		}

		#endregion

		#region glBindTexture Method

		private void BindTexture(IGLTexture texture)
		{
			OpenGLTexture tex = texture as OpenGLTexture;
			if (tex.Target != Textures[0].Target)
			{
				glBindTexture(Textures[0].Target, 0);
			}
			if (tex != Textures[0])
			{
				glBindTexture(
					tex.Target,
					tex.Handle
				);
			}
			Textures[0] = tex;
		}

		#endregion

		#region glDeleteTexture Method

		private void DeleteTexture(IGLTexture texture)
		{
			uint handle = (texture as OpenGLTexture).Handle;
			for (int i = 0; i < currentAttachments.Length; i += 1)
			{
				if (handle == currentAttachments[i])
				{
					// Force an attachment update, this no longer exists!
					currentAttachments[i] = uint.MaxValue;
				}
			}
			glDeleteTextures(1, ref handle);
		}

		#endregion

		#region glReadPixels Methods

		public void ReadBackbuffer<T>(
			T[] data,
			int startIndex,
			int elementCount,
			Rectangle? rect
		) where T : struct {
			if (startIndex > 0 || elementCount != data.Length)
			{
				throw new NotImplementedException(
					"ReadBackbuffer startIndex/elementCount"
				);
			}

			uint prevReadBuffer = currentReadFramebuffer;
			BindReadFramebuffer(
				(Backbuffer is OpenGLBackbuffer) ?
					(Backbuffer as OpenGLBackbuffer).Handle :
					0
			);

			int x;
			int y;
			int w;
			int h;
			if (rect != null)
			{
				x = rect.Value.X;
				y = rect.Value.Y;
				w = rect.Value.Width;
				h = rect.Value.Height;
			}
			else
			{
				x = 0;
				y = 0;
				w = Backbuffer.Width;
				h = Backbuffer.Height;
			}

			GCHandle handle = GCHandle.Alloc(data, GCHandleType.Pinned);
			try
			{
				glReadPixels(
					x,
					y,
					w,
					h,
					GLenum.GL_RGBA,
					GLenum.GL_UNSIGNED_BYTE,
					handle.AddrOfPinnedObject()
				);
			}
			finally
			{
				handle.Free();
			}

			BindReadFramebuffer(prevReadBuffer);

			// Now we get to do a software-based flip! Yes, really! -flibit
			int pitch = w * 4 / Marshal.SizeOf(typeof(T));
			T[] tempRow = new T[pitch];
			for (int row = 0; row < h / 2; row += 1)
			{
				Array.Copy(data, row * pitch, tempRow, 0, pitch);
				Array.Copy(data, (h - row - 1) * pitch, data, row * pitch, pitch);
				Array.Copy(tempRow, 0, data, (h - row - 1) * pitch, pitch);
			}
		}

		/// <summary>
		/// Attempts to read the texture data directly from the FBO using glReadPixels
		/// </summary>
		/// <typeparam name="T">Texture data type</typeparam>
		/// <param name="texture">The texture to read from</param>
		/// <param name="width">The texture width</param>
		/// <param name="height">The texture height</param>
		/// <param name="level">The texture level</param>
		/// <param name="data">The texture data array</param>
		/// <param name="rect">The portion of the image to read from</param>
		/// <returns>True if we successfully read the texture data</returns>
		private bool ReadTargetIfApplicable<T>(
			IGLTexture texture,
			int width,
			int height,
			int level,
			T[] data,
			Rectangle? rect
		) where T : struct {
			bool texUnbound = (	currentDrawBuffers != 1 ||
						currentAttachments[0] != (texture as OpenGLTexture).Handle	);
			if (texUnbound && !useES2)
			{
				return false;
			}

			int x;
			int y;
			int w;
			int h;
			if (rect.HasValue)
			{
				x = rect.Value.X;
				y = rect.Value.Y;
				w = rect.Value.Width;
				h = rect.Value.Height;
			}
			else
			{
				x = 0;
				y = 0;
				w = width;
				h = height;
			}

			uint prevReadBuffer = currentReadFramebuffer;
			uint prevWriteBuffer = currentDrawFramebuffer;
			if (texUnbound)
			{
				BindFramebuffer(resolveFramebufferRead);
				glFramebufferTexture2D(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_COLOR_ATTACHMENT0,
					GLenum.GL_TEXTURE_2D,
					(texture as OpenGLTexture).Handle,
					level
				);
			}
			else
			{
				BindReadFramebuffer(targetFramebuffer);
			}

			/* glReadPixels should be faster than reading
			 * back from the render target if we are already bound.
			 */
			GCHandle handle = GCHandle.Alloc(data, GCHandleType.Pinned);
			try
			{
				glReadPixels(
					x,
					y,
					w,
					h,
					GLenum.GL_RGBA, // FIXME: Assumption!
					GLenum.GL_UNSIGNED_BYTE,
					handle.AddrOfPinnedObject()
				);
			}
			finally
			{
				handle.Free();
			}

			if (texUnbound)
			{
				if (prevReadBuffer == prevWriteBuffer)
				{
					BindFramebuffer(prevReadBuffer);
				}
				else
				{
					BindReadFramebuffer(prevReadBuffer);
					BindDrawFramebuffer(prevWriteBuffer);
				}
			}
			else
			{
				BindReadFramebuffer(prevReadBuffer);
			}
			return true;
		}

		#endregion

		#region RenderTarget->Texture Method

		public void ResolveTarget(RenderTargetBinding target)
		{
			if ((target.RenderTarget as IRenderTarget).MultiSampleCount > 0)
			{
				uint prevBuffer = currentDrawFramebuffer;

				// Set up the texture framebuffer
				GLenum textureTarget;
				int width, height;
				if (target.RenderTarget is RenderTarget2D)
				{
					textureTarget = GLenum.GL_TEXTURE_2D;
					Texture2D target2D = (target.RenderTarget as Texture2D);
					width = target2D.Width;
					height = target2D.Height;
				}
				else
				{
					textureTarget = GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + (int) target.CubeMapFace;
					TextureCube targetCube = (target.RenderTarget as TextureCube);
					width = targetCube.Size;
					height = targetCube.Size;
				}
				BindFramebuffer(resolveFramebufferDraw);
				glFramebufferTexture2D(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_COLOR_ATTACHMENT0,
					textureTarget,
					(target.RenderTarget.texture as OpenGLTexture).Handle,
					0
				);

				// Set up the renderbuffer framebuffer
				BindFramebuffer(resolveFramebufferRead);
				glFramebufferRenderbuffer(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_COLOR_ATTACHMENT0,
					GLenum.GL_RENDERBUFFER,
					((target.RenderTarget as IRenderTarget).ColorBuffer as OpenGLRenderbuffer).Handle
				);

				// Blit!
				if (scissorTestEnable)
				{
					glDisable(GLenum.GL_SCISSOR_TEST);
				}
				BindDrawFramebuffer(resolveFramebufferDraw);
				glBlitFramebuffer(
					0, 0, width, height,
					0, 0, width, height,
					GLenum.GL_COLOR_BUFFER_BIT,
					GLenum.GL_LINEAR
				);
				if (scissorTestEnable)
				{
					glEnable(GLenum.GL_SCISSOR_TEST);
				}

				BindFramebuffer(prevBuffer);
			}

			// If the target has mipmaps, regenerate them now
			if (target.RenderTarget.LevelCount > 1)
			{
				OpenGLTexture prevTex = Textures[0];
				BindTexture(target.RenderTarget.texture);
				glGenerateMipmap((target.RenderTarget.texture as OpenGLTexture).Target);
				BindTexture(prevTex);
			}
		}

		#endregion

		#region Framebuffer Methods

		private void BindFramebuffer(uint handle)
		{
			if (	currentReadFramebuffer != handle &&
				currentDrawFramebuffer != handle	)
			{
				glBindFramebuffer(
					GLenum.GL_FRAMEBUFFER,
					handle
				);
				currentReadFramebuffer = handle;
				currentDrawFramebuffer = handle;
			}
			else if (currentReadFramebuffer != handle)
			{
				BindReadFramebuffer(handle);
			}
			else if (currentDrawFramebuffer != handle)
			{
				BindDrawFramebuffer(handle);
			}
		}

		private void BindReadFramebuffer(uint handle)
		{
			if (handle == currentReadFramebuffer)
			{
				return;
			}

			glBindFramebuffer(
				GLenum.GL_READ_FRAMEBUFFER,
				handle
			);

			currentReadFramebuffer = handle;
		}

		private void BindDrawFramebuffer(uint handle)
		{
			if (handle == currentDrawFramebuffer)
			{
				return;
			}

			glBindFramebuffer(
				GLenum.GL_DRAW_FRAMEBUFFER,
				handle
			);

			currentDrawFramebuffer = handle;
		}

		#endregion

		#region Renderbuffer Methods

		public IGLRenderbuffer GenRenderbuffer(
			int width,
			int height,
			SurfaceFormat format,
			int multiSampleCount
		) {
			uint handle = 0;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			glGenRenderbuffers(1, out handle);
			glBindRenderbuffer(
				GLenum.GL_RENDERBUFFER,
				handle
			);
			if (multiSampleCount > 0)
			{
				glRenderbufferStorageMultisample(
					GLenum.GL_RENDERBUFFER,
					multiSampleCount,
					XNAToGL.TextureInternalFormat[(int) format],
					width,
					height
				);
			}
			else
			{
				glRenderbufferStorage(
					GLenum.GL_RENDERBUFFER,
					XNAToGL.TextureInternalFormat[(int) format],
					width,
					height
				);
			}
			glBindRenderbuffer(
				GLenum.GL_RENDERBUFFER,
				0
			);

#if !DISABLE_THREADING
			});
#endif

			return new OpenGLRenderbuffer(handle);
		}

		public IGLRenderbuffer GenRenderbuffer(
			int width,
			int height,
			DepthFormat format,
			int multiSampleCount
		) {
			uint handle = 0;

#if !DISABLE_THREADING
			ForceToMainThread(() => {
#endif

			glGenRenderbuffers(1, out handle);
			glBindRenderbuffer(
				GLenum.GL_RENDERBUFFER,
				handle
			);
			if (multiSampleCount > 0)
			{
				glRenderbufferStorageMultisample(
					GLenum.GL_RENDERBUFFER,
					multiSampleCount,
					XNAToGL.DepthStorage[(int) format],
					width,
					height
				);
			}
			else
			{
				glRenderbufferStorage(
					GLenum.GL_RENDERBUFFER,
					XNAToGL.DepthStorage[(int) format],
					width,
					height
				);
			}
			glBindRenderbuffer(
				GLenum.GL_RENDERBUFFER,
				0
			);

#if !DISABLE_THREADING
			});
#endif

			return new OpenGLRenderbuffer(handle);
		}

		private void DeleteRenderbuffer(IGLRenderbuffer renderbuffer)
		{
			uint handle = (renderbuffer as OpenGLRenderbuffer).Handle;
			if (handle == currentRenderbuffer)
			{
				// Force a renderbuffer update, this no longer exists!
				currentRenderbuffer = uint.MaxValue;
			}
			glDeleteRenderbuffers(1, ref handle);
		}

		#endregion

		#region glEnable/glDisable Method

		private void ToggleGLState(GLenum feature, bool enable)
		{
			if (enable)
			{
				glEnable(feature);
			}
			else
			{
				glDisable(feature);
			}
		}

		#endregion

		#region glClear Method

		public void Clear(ClearOptions options, Vector4 color, float depth, int stencil)
		{
			// glClear depends on the scissor rectangle!
			if (scissorTestEnable)
			{
				glDisable(GLenum.GL_SCISSOR_TEST);
			}

			bool clearTarget = (options & ClearOptions.Target) == ClearOptions.Target;
			bool clearDepth = (options & ClearOptions.DepthBuffer) == ClearOptions.DepthBuffer;
			bool clearStencil = (options & ClearOptions.Stencil) == ClearOptions.Stencil;

			// Get the clear mask, set the clear properties if needed
			GLenum clearMask = GLenum.GL_ZERO;
			if (clearTarget)
			{
				clearMask |= GLenum.GL_COLOR_BUFFER_BIT;
				if (!color.Equals(currentClearColor))
				{
					glClearColor(
						color.X,
						color.Y,
						color.Z,
						color.W
					);
					currentClearColor = color;
				}
				// glClear depends on the color write mask!
				if (colorWriteEnable != ColorWriteChannels.All)
				{
					// FIXME: ColorWriteChannels1/2/3? -flibit
					glColorMask(true, true, true, true);
				}
			}
			if (clearDepth)
			{
				clearMask |= GLenum.GL_DEPTH_BUFFER_BIT;
				if (depth != currentClearDepth)
				{
					glClearDepth((double) depth);
					currentClearDepth = depth;
				}
				// glClear depends on the depth write mask!
				if (!zWriteEnable)
				{
					glDepthMask(true);
				}
			}
			if (clearStencil)
			{
				clearMask |= GLenum.GL_STENCIL_BUFFER_BIT;
				if (stencil != currentClearStencil)
				{
					glClearStencil(stencil);
					currentClearStencil = stencil;
				}
				// glClear depends on the stencil write mask!
				if (stencilWriteMask != -1)
				{
					// AKA 0xFFFFFFFF, ugh -flibit
					glStencilMask(-1);
				}
			}

			// CLEAR!
			glClear(clearMask);

			// Clean up after ourselves.
			if (scissorTestEnable)
			{
				glEnable(GLenum.GL_SCISSOR_TEST);
			}
			if (clearTarget && colorWriteEnable != ColorWriteChannels.All)
			{
				// FIXME: ColorWriteChannels1/2/3? -flibit
				glColorMask(
					(colorWriteEnable & ColorWriteChannels.Red) != 0,
					(colorWriteEnable & ColorWriteChannels.Blue) != 0,
					(colorWriteEnable & ColorWriteChannels.Green) != 0,
					(colorWriteEnable & ColorWriteChannels.Alpha) != 0
				);
			}
			if (clearDepth && !zWriteEnable)
			{
				glDepthMask(false);
			}
			if (clearStencil && stencilWriteMask != -1) // AKA 0xFFFFFFFF, ugh -flibit
			{
				glStencilMask(stencilWriteMask);
			}
		}

		#endregion

		#region SetRenderTargets Method

		public void SetRenderTargets(
			RenderTargetBinding[] renderTargets,
			IGLRenderbuffer renderbuffer,
			DepthFormat depthFormat
		) {
			// Bind the right framebuffer, if needed
			if (renderTargets == null)
			{
				BindFramebuffer(
					(Backbuffer is OpenGLBackbuffer) ?
						(Backbuffer as OpenGLBackbuffer).Handle :
						0
				);
				flipViewport = 1;
				return;
			}
			else
			{
				BindFramebuffer(targetFramebuffer);
				flipViewport = -1;
			}

			int i;
			uint[] attachments = new uint[renderTargets.Length];
			GLenum[] attachmentTypes = new GLenum[renderTargets.Length];
			for (i = 0; i < renderTargets.Length; i += 1)
			{
				IGLRenderbuffer colorBuffer = (renderTargets[i].RenderTarget as IRenderTarget).ColorBuffer;
				if (colorBuffer != null)
				{
					attachments[i] = (colorBuffer as OpenGLRenderbuffer).Handle;
					attachmentTypes[i] = GLenum.GL_RENDERBUFFER;
				}
				else
				{
					attachments[i] = (renderTargets[i].RenderTarget.texture as OpenGLTexture).Handle;
					if (renderTargets[i].RenderTarget is RenderTarget2D)
					{
						attachmentTypes[i] = GLenum.GL_TEXTURE_2D;
					}
					else
					{
						attachmentTypes[i] = GLenum.GL_TEXTURE_CUBE_MAP_POSITIVE_X + (int) renderTargets[i].CubeMapFace;
					}
				}
			}

			// Update the color attachments, DrawBuffers state
			for (i = 0; i < attachments.Length; i += 1)
			{
				if (attachments[i] != currentAttachments[i])
				{
					if (currentAttachments[i] != 0)
					{
						if (	attachmentTypes[i] != GLenum.GL_RENDERBUFFER &&
							currentAttachmentTypes[i] == GLenum.GL_RENDERBUFFER	)
						{
							glFramebufferRenderbuffer(
								GLenum.GL_FRAMEBUFFER,
								GLenum.GL_COLOR_ATTACHMENT0 + i,
								GLenum.GL_RENDERBUFFER,
								0
							);
						}
						else if (	attachmentTypes[i] == GLenum.GL_RENDERBUFFER &&
								currentAttachmentTypes[i] != GLenum.GL_RENDERBUFFER	)
						{
							glFramebufferTexture2D(
								GLenum.GL_FRAMEBUFFER,
								GLenum.GL_COLOR_ATTACHMENT0 + i,
								currentAttachmentTypes[i],
								0,
								0
							);
						}
					}
					if (attachmentTypes[i] == GLenum.GL_RENDERBUFFER)
					{
						glFramebufferRenderbuffer(
							GLenum.GL_FRAMEBUFFER,
							GLenum.GL_COLOR_ATTACHMENT0 + i,
							GLenum.GL_RENDERBUFFER,
							attachments[i]
						);
					}
					else
					{
						glFramebufferTexture2D(
							GLenum.GL_FRAMEBUFFER,
							GLenum.GL_COLOR_ATTACHMENT0 + i,
							attachmentTypes[i],
							attachments[i],
							0
						);
					}
					currentAttachments[i] = attachments[i];
					currentAttachmentTypes[i] = attachmentTypes[i];
				}
				else if (attachmentTypes[i] != currentAttachmentTypes[i])
				{
					// Texture cube face change!
					glFramebufferTexture2D(
						GLenum.GL_FRAMEBUFFER,
						GLenum.GL_COLOR_ATTACHMENT0 + i,
						attachmentTypes[i],
						attachments[i],
						0
					);
					currentAttachmentTypes[i] = attachmentTypes[i];
				}
			}
			while (i < currentAttachments.Length)
			{
				if (currentAttachments[i] != 0)
				{
					if (currentAttachmentTypes[i] == GLenum.GL_RENDERBUFFER)
					{
						glFramebufferRenderbuffer(
							GLenum.GL_FRAMEBUFFER,
							GLenum.GL_COLOR_ATTACHMENT0 + i,
							GLenum.GL_RENDERBUFFER,
							0
						);
					}
					else
					{
						glFramebufferTexture2D(
							GLenum.GL_FRAMEBUFFER,
							GLenum.GL_COLOR_ATTACHMENT0 + i,
							currentAttachmentTypes[i],
							0,
							0
						);
					}
					currentAttachments[i] = 0;
					currentAttachmentTypes[i] = GLenum.GL_TEXTURE_2D;
				}
				i += 1;
			}
			if (attachments.Length != currentDrawBuffers)
			{
				glDrawBuffers(attachments.Length, drawBuffersArray);
				currentDrawBuffers = attachments.Length;
			}

			// Update the depth/stencil attachment
			/* FIXME: Notice that we do separate attach calls for the stencil.
			 * We _should_ be able to do a single attach for depthstencil, but
			 * some drivers (like Mesa) cannot into GL_DEPTH_STENCIL_ATTACHMENT.
			 * Use XNAToGL.DepthStencilAttachment when this isn't a problem.
			 * -flibit
			 */
			uint handle;
			if (renderbuffer == null)
			{
				handle = 0;
			}
			else
			{
				handle = (renderbuffer as OpenGLRenderbuffer).Handle;
			}
			if (handle != currentRenderbuffer)
			{
				if (currentDepthStencilFormat == DepthFormat.Depth24Stencil8)
				{
					glFramebufferRenderbuffer(
						GLenum.GL_FRAMEBUFFER,
						GLenum.GL_STENCIL_ATTACHMENT,
						GLenum.GL_RENDERBUFFER,
						0
					);
				}
				currentDepthStencilFormat = depthFormat;
				glFramebufferRenderbuffer(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_DEPTH_ATTACHMENT,
					GLenum.GL_RENDERBUFFER,
					handle
				);
				if (currentDepthStencilFormat == DepthFormat.Depth24Stencil8)
				{
					glFramebufferRenderbuffer(
						GLenum.GL_FRAMEBUFFER,
						GLenum.GL_STENCIL_ATTACHMENT,
						GLenum.GL_RENDERBUFFER,
						handle
					);
				}
				currentRenderbuffer = handle;
			}
		}

		#endregion

		#region Query Object Methods

		public IGLQuery CreateQuery()
		{
			uint handle;
			glGenQueries(1, out handle);
			return new OpenGLQuery(handle);
		}

		private void DeleteQuery(IGLQuery query)
		{
			uint handle = (query as OpenGLQuery).Handle;
			glDeleteQueries(
				1,
				ref handle
			);
		}

		public void QueryBegin(IGLQuery query)
		{
			glBeginQuery(
				GLenum.GL_SAMPLES_PASSED,
				(query as OpenGLQuery).Handle
			);
		}

		public void QueryEnd(IGLQuery query)
		{
			// May need to check active queries...?
			glEndQuery(
				GLenum.GL_SAMPLES_PASSED
			);
		}

		public bool QueryComplete(IGLQuery query)
		{
			uint result;
			glGetQueryObjectuiv(
				(query as OpenGLQuery).Handle,
				GLenum.GL_QUERY_RESULT_AVAILABLE,
				out result
			);
			return result != 0;
		}

		public int QueryPixelCount(IGLQuery query)
		{
			uint result;
			glGetQueryObjectuiv(
				(query as OpenGLQuery).Handle,
				GLenum.GL_QUERY_RESULT,
				out result
			);
			return (int) result;
		}

		#endregion

		#region XNA->GL Enum Conversion Class

		private static class XNAToGL
		{
			public static readonly GLenum[] TextureFormat = new GLenum[]
			{
				GLenum.GL_RGBA,				// SurfaceFormat.Color
				GLenum.GL_RGB,				// SurfaceFormat.Bgr565
				GLenum.GL_BGRA,				// SurfaceFormat.Bgra5551
				GLenum.GL_BGRA,				// SurfaceFormat.Bgra4444
				GLenum.GL_COMPRESSED_TEXTURE_FORMATS,	// SurfaceFormat.Dxt1
				GLenum.GL_COMPRESSED_TEXTURE_FORMATS,	// SurfaceFormat.Dxt3
				GLenum.GL_COMPRESSED_TEXTURE_FORMATS,	// SurfaceFormat.Dxt5
				GLenum.GL_RG,				// SurfaceFormat.NormalizedByte2
				GLenum.GL_RGBA,				// SurfaceFormat.NormalizedByte4
				GLenum.GL_RGBA,				// SurfaceFormat.Rgba1010102
				GLenum.GL_RG,				// SurfaceFormat.Rg32
				GLenum.GL_RGBA,				// SurfaceFormat.Rgba64
				GLenum.GL_LUMINANCE,			// SurfaceFormat.Alpha8
				GLenum.GL_RED,				// SurfaceFormat.Single
				GLenum.GL_RG,				// SurfaceFormat.Vector2
				GLenum.GL_RGBA,				// SurfaceFormat.Vector4
				GLenum.GL_RED,				// SurfaceFormat.HalfSingle
				GLenum.GL_RG,				// SurfaceFormat.HalfVector2
				GLenum.GL_RGBA,				// SurfaceFormat.HalfVector4
				GLenum.GL_RGBA				// SurfaceFormat.HdrBlendable
			};

			public static readonly GLenum[] TextureInternalFormat = new GLenum[]
			{
				GLenum.GL_RGBA8,				// SurfaceFormat.Color
				GLenum.GL_RGB8,					// SurfaceFormat.Bgr565
				GLenum.GL_RGB5_A1,				// SurfaceFormat.Bgra5551
				GLenum.GL_RGBA4,				// SurfaceFormat.Bgra4444
				GLenum.GL_COMPRESSED_RGBA_S3TC_DXT1_EXT,	// SurfaceFormat.Dxt1
				GLenum.GL_COMPRESSED_RGBA_S3TC_DXT3_EXT,	// SurfaceFormat.Dxt3
				GLenum.GL_COMPRESSED_RGBA_S3TC_DXT5_EXT,	// SurfaceFormat.Dxt5
				GLenum.GL_RG8,					// SurfaceFormat.NormalizedByte2
				GLenum.GL_RGBA8,				// SurfaceFormat.NormalizedByte4
				GLenum.GL_RGB10_A2_EXT,				// SurfaceFormat.Rgba1010102
				GLenum.GL_RG16,					// SurfaceFormat.Rg32
				GLenum.GL_RGBA16,				// SurfaceFormat.Rgba64
				GLenum.GL_LUMINANCE8,				// SurfaceFormat.Alpha8
				GLenum.GL_R32F,					// SurfaceFormat.Single
				GLenum.GL_RG32F,				// SurfaceFormat.Vector2
				GLenum.GL_RGBA32F,				// SurfaceFormat.Vector4
				GLenum.GL_R16F,					// SurfaceFormat.HalfSingle
				GLenum.GL_RG16F,				// SurfaceFormat.HalfVector2
				GLenum.GL_RGBA16F,				// SurfaceFormat.HalfVector4
				GLenum.GL_RGBA16F				// SurfaceFormat.HdrBlendable
			};

			public static readonly GLenum[] TextureDataType = new GLenum[]
			{
				GLenum.GL_UNSIGNED_BYTE,			// SurfaceFormat.Color
				GLenum.GL_UNSIGNED_SHORT_5_6_5,			// SurfaceFormat.Bgr565
				GLenum.GL_UNSIGNED_SHORT_5_5_5_1,		// SurfaceFormat.Bgra5551
				GLenum.GL_UNSIGNED_SHORT_4_4_4_4,		// SurfaceFormat.Bgra4444
				GLenum.GL_ZERO,					// NOPE
				GLenum.GL_ZERO,					// NOPE
				GLenum.GL_ZERO,					// NOPE
				GLenum.GL_BYTE,					// SurfaceFormat.NormalizedByte2
				GLenum.GL_BYTE,					// SurfaceFormat.NormalizedByte4
				GLenum.GL_UNSIGNED_INT_10_10_10_2,		// SurfaceFormat.Rgba1010102
				GLenum.GL_UNSIGNED_SHORT,			// SurfaceFormat.Rg32
				GLenum.GL_UNSIGNED_SHORT,			// SurfaceFormat.Rgba64
				GLenum.GL_UNSIGNED_BYTE,			// SurfaceFormat.Alpha8
				GLenum.GL_FLOAT,				// SurfaceFormat.Single
				GLenum.GL_FLOAT,				// SurfaceFormat.Vector2
				GLenum.GL_FLOAT,				// SurfaceFormat.Vector4
				GLenum.GL_HALF_FLOAT,				// SurfaceFormat.HalfSingle
				GLenum.GL_HALF_FLOAT,				// SurfaceFormat.HalfVector2
				GLenum.GL_HALF_FLOAT,				// SurfaceFormat.HalfVector4
				GLenum.GL_HALF_FLOAT				// SurfaceFormat.HdrBlendable
			};

			public static readonly GLenum[] BlendMode = new GLenum[]
			{
				GLenum.GL_ONE,				// Blend.One
				GLenum.GL_ZERO,				// Blend.Zero
				GLenum.GL_SRC_COLOR,			// Blend.SourceColor
				GLenum.GL_ONE_MINUS_SRC_COLOR,		// Blend.InverseSourceColor
				GLenum.GL_SRC_ALPHA,			// Blend.SourceAlpha
				GLenum.GL_ONE_MINUS_SRC_ALPHA,		// Blend.InverseSourceAlpha
				GLenum.GL_DST_COLOR,			// Blend.DestinationColor
				GLenum.GL_ONE_MINUS_DST_COLOR,		// Blend.InverseDestinationColor
				GLenum.GL_DST_ALPHA,			// Blend.DestinationAlpha
				GLenum.GL_ONE_MINUS_DST_ALPHA,		// Blend.InverseDestinationAlpha
				GLenum.GL_CONSTANT_COLOR,		// Blend.BlendFactor
				GLenum.GL_ONE_MINUS_CONSTANT_COLOR,	// Blend.InverseBlendFactor
				GLenum.GL_SRC_ALPHA_SATURATE		// Blend.SourceAlphaSaturation
			};

			public static readonly GLenum[] BlendEquation = new GLenum[]
			{
				GLenum.GL_FUNC_ADD,			// BlendFunction.Add
				GLenum.GL_FUNC_SUBTRACT,		// BlendFunction.Subtract
				GLenum.GL_FUNC_REVERSE_SUBTRACT,	// BlendFunction.ReverseSubtract
				GLenum.GL_MAX,				// BlendFunction.Max
				GLenum.GL_MIN				// BlendFunction.Min
			};

			public static readonly GLenum[] CompareFunc = new GLenum[]
			{
				GLenum.GL_ALWAYS,	// CompareFunction.Always
				GLenum.GL_NEVER,	// CompareFunction.Never
				GLenum.GL_LESS,		// CompareFunction.Less
				GLenum.GL_LEQUAL,	// CompareFunction.LessEqual
				GLenum.GL_EQUAL,	// CompareFunction.Equal
				GLenum.GL_GEQUAL,	// CompareFunction.GreaterEqual
				GLenum.GL_GREATER,	// CompareFunction.Greater
				GLenum.GL_NOTEQUAL	// CompareFunction.NotEqual
			};

			public static readonly GLenum[] GLStencilOp = new GLenum[]
			{
				GLenum.GL_KEEP,		// StencilOperation.Keep
				GLenum.GL_ZERO,		// StencilOperation.Zero
				GLenum.GL_REPLACE,	// StencilOperation.Replace
				GLenum.GL_INCR_WRAP,	// StencilOperation.Increment
				GLenum.GL_DECR_WRAP,	// StencilOperation.Decrement
				GLenum.GL_INCR,		// StencilOperation.IncrementSaturation
				GLenum.GL_DECR,		// StencilOperation.DecrementSaturation
				GLenum.GL_INVERT	// StencilOperation.Invert
			};

			public static readonly GLenum[] FrontFace = new GLenum[]
			{
				GLenum.GL_ZERO,	// NOPE
				GLenum.GL_CW,	// CullMode.CullClockwiseFace
				GLenum.GL_CCW	// CullMode.CullCounterClockwiseFace
			};

			public static readonly GLenum[] GLFillMode = new GLenum[]
			{
				GLenum.GL_FILL,	// FillMode.Solid
				GLenum.GL_LINE	// FillMode.WireFrame
			};

			public static readonly int[] Wrap = new int[]
			{
				(int) GLenum.GL_REPEAT,			// TextureAddressMode.Wrap
				(int) GLenum.GL_CLAMP_TO_EDGE,		// TextureAddressMode.Clamp
				(int) GLenum.GL_MIRRORED_REPEAT		// TextureAddressMode.Mirror
			};

			public static readonly int[] MagFilter = new int[]
			{
				(int) GLenum.GL_LINEAR,		// TextureFilter.Linear
				(int) GLenum.GL_NEAREST,	// TextureFilter.Point
				(int) GLenum.GL_LINEAR,		// TextureFilter.Anisotropic
				(int) GLenum.GL_LINEAR,		// TextureFilter.LinearMipPoint
				(int) GLenum.GL_NEAREST,	// TextureFilter.PointMipLinear
				(int) GLenum.GL_NEAREST,	// TextureFilter.MinLinearMagPointMipLinear
				(int) GLenum.GL_NEAREST,	// TextureFilter.MinLinearMagPointMipPoint
				(int) GLenum.GL_LINEAR,		// TextureFilter.MinPointMagLinearMipLinear
				(int) GLenum.GL_LINEAR		// TextureFilter.MinPointMagLinearMipPoint
			};

			public static readonly int[] MinMipFilter = new int[]
			{
				(int) GLenum.GL_LINEAR_MIPMAP_LINEAR,	// TextureFilter.Linear
				(int) GLenum.GL_NEAREST_MIPMAP_NEAREST,	// TextureFilter.Point
				(int) GLenum.GL_LINEAR_MIPMAP_LINEAR,	// TextureFilter.Anisotropic
				(int) GLenum.GL_LINEAR_MIPMAP_NEAREST,	// TextureFilter.LinearMipPoint
				(int) GLenum.GL_NEAREST_MIPMAP_LINEAR,	// TextureFilter.PointMipLinear
				(int) GLenum.GL_LINEAR_MIPMAP_LINEAR,	// TextureFilter.MinLinearMagPointMipLinear
				(int) GLenum.GL_LINEAR_MIPMAP_NEAREST,	// TextureFilter.MinLinearMagPointMipPoint
				(int) GLenum.GL_NEAREST_MIPMAP_LINEAR,	// TextureFilter.MinPointMagLinearMipLinear
				(int) GLenum.GL_NEAREST_MIPMAP_NEAREST	// TextureFilter.MinPointMagLinearMipPoint
			};

			public static readonly int[] MinFilter = new int[]
			{
				(int) GLenum.GL_LINEAR,		// TextureFilter.Linear
				(int) GLenum.GL_NEAREST,	// TextureFilter.Point
				(int) GLenum.GL_LINEAR,		// TextureFilter.Anisotropic
				(int) GLenum.GL_LINEAR,		// TextureFilter.LinearMipPoint
				(int) GLenum.GL_NEAREST,	// TextureFilter.PointMipLinear
				(int) GLenum.GL_LINEAR,		// TextureFilter.MinLinearMagPointMipLinear
				(int) GLenum.GL_LINEAR,		// TextureFilter.MinLinearMagPointMipPoint
				(int) GLenum.GL_NEAREST,	// TextureFilter.MinPointMagLinearMipLinear
				(int) GLenum.GL_NEAREST		// TextureFilter.MinPointMagLinearMipPoint
			};

			public static readonly GLenum[] DepthStencilAttachment = new GLenum[]
			{
				GLenum.GL_ZERO,				// NOPE
				GLenum.GL_DEPTH_ATTACHMENT,		// DepthFormat.Depth16
				GLenum.GL_DEPTH_ATTACHMENT,		// DepthFormat.Depth24
				GLenum.GL_DEPTH_STENCIL_ATTACHMENT	// DepthFormat.Depth24Stencil8
			};

			public static readonly GLenum[] DepthStorage = new GLenum[]
			{
				GLenum.GL_ZERO,			// NOPE
				GLenum.GL_DEPTH_COMPONENT16,	// DepthFormat.Depth16
				GLenum.GL_DEPTH_COMPONENT24,	// DepthFormat.Depth24
				GLenum.GL_DEPTH24_STENCIL8	// DepthFormat.Depth24Stencil8
			};

			public static readonly float[] DepthBiasScale = new float[]
			{
				0.0f,				// DepthFormat.None
				(float) ((1 << 16) - 1),	// DepthFormat.Depth16
				(float) ((1 << 24) - 1),	// DepthFormat.Depth24
				(float) ((1 << 24) - 1)		// DepthFormat.Depth24Stencil8
			};

			public static readonly MojoShader.MOJOSHADER_usage[] VertexAttribUsage = new MojoShader.MOJOSHADER_usage[]
			{
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_POSITION,		// VertexElementUsage.Position
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_COLOR,		// VertexElementUsage.Color
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_TEXCOORD,		// VertexElementUsage.TextureCoordinate
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_NORMAL,		// VertexElementUsage.Normal
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_BINORMAL,		// VertexElementUsage.Binormal
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_TANGENT,		// VertexElementUsage.Tangent
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_BLENDINDICES,	// VertexElementUsage.BlendIndices
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_BLENDWEIGHT,	// VertexElementUsage.BlendWeight
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_DEPTH,		// VertexElementUsage.Depth
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_FOG,		// VertexElementUsage.Fog
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_POINTSIZE,		// VertexElementUsage.PointSize
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_SAMPLE,		// VertexElementUsage.Sample
				MojoShader.MOJOSHADER_usage.MOJOSHADER_USAGE_TESSFACTOR		// VertexElementUsage.TessellateFactor
			};

			public static readonly int[] VertexAttribSize = new int[]
			{
					1,	// VertexElementFormat.Single
					2,	// VertexElementFormat.Vector2
					3,	// VertexElementFormat.Vector3
					4,	// VertexElementFormat.Vector4
					4,	// VertexElementFormat.Color
					4,	// VertexElementFormat.Byte4
					2,	// VertexElementFormat.Short2
					4,	// VertexElementFormat.Short4
					2,	// VertexElementFormat.NormalizedShort2
					4,	// VertexElementFormat.NormalizedShort4
					2,	// VertexElementFormat.HalfVector2
					4	// VertexElementFormat.HalfVector4
			};

			public static readonly GLenum[] VertexAttribType = new GLenum[]
			{
				GLenum.GL_FLOAT,		// VertexElementFormat.Single
				GLenum.GL_FLOAT,		// VertexElementFormat.Vector2
				GLenum.GL_FLOAT,		// VertexElementFormat.Vector3
				GLenum.GL_FLOAT,		// VertexElementFormat.Vector4
				GLenum.GL_UNSIGNED_BYTE,	// VertexElementFormat.Color
				GLenum.GL_UNSIGNED_BYTE,	// VertexElementFormat.Byte4
				GLenum.GL_SHORT,		// VertexElementFormat.Short2
				GLenum.GL_SHORT,		// VertexElementFormat.Short4
				GLenum.GL_SHORT,		// VertexElementFormat.NormalizedShort2
				GLenum.GL_SHORT,		// VertexElementFormat.NormalizedShort4
				GLenum.GL_HALF_FLOAT,		// VertexElementFormat.HalfVector2
				GLenum.GL_HALF_FLOAT		// VertexElementFormat.HalfVector4
			};

			public static bool VertexAttribNormalized(VertexElement element)
			{
				return (	element.VertexElementUsage == VertexElementUsage.Color ||
						element.VertexElementFormat == VertexElementFormat.NormalizedShort2 ||
						element.VertexElementFormat == VertexElementFormat.NormalizedShort4	);
			}

			public static readonly GLenum[] Primitive = new GLenum[]
			{
				GLenum.GL_TRIANGLES,		// PrimitiveType.TriangleList
				GLenum.GL_TRIANGLE_STRIP,	// PrimitiveType.TriangleStrip
				GLenum.GL_LINES,		// PrimitiveType.LineList
				GLenum.GL_LINE_STRIP,		// PrimitiveType.LineStrip
			};

			public static int PrimitiveVerts(PrimitiveType primitiveType, int primitiveCount)
			{
				switch (primitiveType)
				{
					case PrimitiveType.TriangleList:
						return primitiveCount * 3;
					case PrimitiveType.TriangleStrip:
						return primitiveCount + 2;
					case PrimitiveType.LineList:
						return primitiveCount * 2;
					case PrimitiveType.LineStrip:
						return primitiveCount + 1;
				}
				throw new NotSupportedException();
			}
		}

		#endregion

		#region The Faux-Backbuffer

		private class OpenGLBackbuffer : IGLBackbuffer
		{
			public uint Handle
			{
				get;
				private set;
			}

			public int Width
			{
				get;
				private set;
			}

			public int Height
			{
				get;
				private set;
			}

			public DepthFormat DepthFormat
			{
				get;
				private set;
			}

			public int MultiSampleCount
			{
				get;
				private set;
			}

			public uint Texture;

			private uint colorAttachment;
			private uint depthStencilAttachment;
			private OpenGLDevice glDevice;

			public OpenGLBackbuffer(
				OpenGLDevice device,
				int width,
				int height,
				DepthFormat depthFormat,
				int multiSampleCount
			) {
				Width = width;
				Height = height;

				glDevice = device;
				DepthFormat = depthFormat;
				MultiSampleCount = multiSampleCount;
				Texture = 0;

				// Generate and bind the FBO.
				uint handle;
				glDevice.glGenFramebuffers(1, out handle);
				Handle = handle;
				glDevice.BindFramebuffer(Handle);

				// Create and attach the color buffer
				glDevice.glGenRenderbuffers(1, out colorAttachment);
				glDevice.glBindRenderbuffer(GLenum.GL_RENDERBUFFER, colorAttachment);
				if (multiSampleCount > 0)
				{
					glDevice.glRenderbufferStorageMultisample(
						GLenum.GL_RENDERBUFFER,
						multiSampleCount,
						GLenum.GL_RGBA8,
						width,
						height
					);
				}
				else
				{
					glDevice.glRenderbufferStorage(
						GLenum.GL_RENDERBUFFER,
						GLenum.GL_RGBA8,
						width,
						height
					);
				}
				glDevice.glFramebufferRenderbuffer(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_COLOR_ATTACHMENT0,
					GLenum.GL_RENDERBUFFER,
					colorAttachment
				);

				if (depthFormat == DepthFormat.None)
				{
					// Don't bother creating a depth/stencil buffer.
					depthStencilAttachment = 0;

					// Keep this state sane.
					glDevice.glBindRenderbuffer(GLenum.GL_RENDERBUFFER, 0);

					return;
				}

				// Create and attach the depth/stencil buffer
				glDevice.glGenRenderbuffers(1, out depthStencilAttachment);
				glDevice.glBindRenderbuffer(GLenum.GL_RENDERBUFFER, depthStencilAttachment);
				if (multiSampleCount > 0)
				{
					glDevice.glRenderbufferStorageMultisample(
						GLenum.GL_RENDERBUFFER,
						multiSampleCount,
						XNAToGL.DepthStorage[(int) depthFormat],
						width,
						height
					);
				}
				else
				{
					glDevice.glRenderbufferStorage(
						GLenum.GL_RENDERBUFFER,
						XNAToGL.DepthStorage[(int) depthFormat],
						width,
						height
					);
				}
				glDevice.glFramebufferRenderbuffer(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_DEPTH_ATTACHMENT,
					GLenum.GL_RENDERBUFFER,
					depthStencilAttachment
				);
				if (depthFormat == DepthFormat.Depth24Stencil8)
				{
					glDevice.glFramebufferRenderbuffer(
						GLenum.GL_FRAMEBUFFER,
						GLenum.GL_STENCIL_ATTACHMENT,
						GLenum.GL_RENDERBUFFER,
						depthStencilAttachment
					);
				}

				// Keep this state sane.
				glDevice.glBindRenderbuffer(GLenum.GL_RENDERBUFFER, 0);
			}

			public void Dispose()
			{
				uint handle = Handle;
				glDevice.BindFramebuffer(0);
				glDevice.glDeleteFramebuffers(1, ref handle);
				glDevice.glDeleteRenderbuffers(1, ref colorAttachment);
				if (depthStencilAttachment != 0)
				{
					glDevice.glDeleteRenderbuffers(1, ref depthStencilAttachment);
				}
				if (Texture != 0)
				{
					glDevice.glDeleteTextures(1, ref Texture);
				}
				glDevice = null;
				Handle = 0;
			}

			public void ResetFramebuffer(
				PresentationParameters presentationParameters,
				bool renderTargetBound
			) {
				Width = presentationParameters.BackBufferWidth;
				Height = presentationParameters.BackBufferHeight;

				DepthFormat depthFormat = presentationParameters.DepthStencilFormat;
				MultiSampleCount = presentationParameters.MultiSampleCount;
				if (Texture != 0)
				{
					glDevice.glDeleteTextures(1, ref Texture);
					Texture = 0;
				}

				if (renderTargetBound)
				{
					glDevice.glBindFramebuffer(
						GLenum.GL_FRAMEBUFFER, Handle
					);
				}

				// Detach color attachment
				glDevice.glFramebufferRenderbuffer(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_COLOR_ATTACHMENT0,
					GLenum.GL_RENDERBUFFER,
					0
				);

				// Detach depth/stencil attachment, if applicable
				if (depthStencilAttachment != 0)
				{
					glDevice.glFramebufferRenderbuffer(
						GLenum.GL_FRAMEBUFFER,
						GLenum.GL_DEPTH_ATTACHMENT,
						GLenum.GL_RENDERBUFFER,
						0
					);
					if (DepthFormat == DepthFormat.Depth24Stencil8)
					{
						glDevice.glFramebufferRenderbuffer(
							GLenum.GL_FRAMEBUFFER,
							GLenum.GL_STENCIL_ATTACHMENT,
							GLenum.GL_RENDERBUFFER,
							0
						);
					}
				}

				// Update our color attachment to the new resolution.
				glDevice.glBindRenderbuffer(
					GLenum.GL_RENDERBUFFER,
					colorAttachment
				);
				if (MultiSampleCount > 0)
				{
					glDevice.glRenderbufferStorageMultisample(
						GLenum.GL_RENDERBUFFER,
						MultiSampleCount,
						GLenum.GL_RGBA8,
						Width,
						Height
					);
				}
				else
				{
					glDevice.glRenderbufferStorage(
						GLenum.GL_RENDERBUFFER,
						GLenum.GL_RGBA8,
						Width,
						Height
					);
				}
				glDevice.glFramebufferRenderbuffer(
					GLenum.GL_FRAMEBUFFER,
					GLenum.GL_COLOR_ATTACHMENT0,
					GLenum.GL_RENDERBUFFER,
					colorAttachment
				);

				// Generate/Delete depth/stencil attachment, if needed
				if (depthFormat == DepthFormat.None)
				{
					if (depthStencilAttachment != 0)
					{
						glDevice.glDeleteRenderbuffers(
							1,
							ref depthStencilAttachment
						);
						depthStencilAttachment = 0;
					}
				}
				else if (depthStencilAttachment == 0)
				{
					glDevice.glGenRenderbuffers(
						1,
						out depthStencilAttachment
					);
				}

				// Update the depth/stencil buffer, if applicable
				if (depthStencilAttachment != 0)
				{
					glDevice.glBindRenderbuffer(
						GLenum.GL_RENDERBUFFER,
						depthStencilAttachment
					);
					if (MultiSampleCount > 0)
					{
						glDevice.glRenderbufferStorageMultisample(
							GLenum.GL_RENDERBUFFER,
							MultiSampleCount,
							XNAToGL.DepthStorage[(int)depthFormat],
							Width,
							Height
						);
					}
					else
					{
						glDevice.glRenderbufferStorage(
							GLenum.GL_RENDERBUFFER,
							XNAToGL.DepthStorage[(int)depthFormat],
							Width,
							Height
						);
					}
					glDevice.glFramebufferRenderbuffer(
						GLenum.GL_FRAMEBUFFER,
						GLenum.GL_DEPTH_ATTACHMENT,
						GLenum.GL_RENDERBUFFER,
						depthStencilAttachment
					);
					if (depthFormat == DepthFormat.Depth24Stencil8)
					{
						glDevice.glFramebufferRenderbuffer(
							GLenum.GL_FRAMEBUFFER,
							GLenum.GL_STENCIL_ATTACHMENT,
							GLenum.GL_RENDERBUFFER,
							depthStencilAttachment
						);
					}
				}
				DepthFormat = depthFormat;

				if (renderTargetBound)
				{
					glDevice.glBindFramebuffer(
						GLenum.GL_FRAMEBUFFER,
						glDevice.targetFramebuffer
					);
				}

				// Keep this state sane.
				glDevice.glBindRenderbuffer(GLenum.GL_RENDERBUFFER, 0);
			}
		}

		#endregion

		#region The Faux-Faux-Backbuffer

		private class NullBackbuffer : IGLBackbuffer
		{
			public int Width
			{
				get;
				private set;
			}

			public int Height
			{
				get;
				private set;
			}

			public DepthFormat DepthFormat
			{
				get
				{
					// Constant, per SDL2_GameWindow
					return DepthFormat.Depth24Stencil8;
				}
			}

			public int MultiSampleCount
			{
				get
				{
					// Constant, per SDL2_GameWindow
					return 0;
				}
			}

			public NullBackbuffer(int width, int height)
			{
				Width = width;
				Height = height;
			}

			public void ResetFramebuffer(
				PresentationParameters presentationParameters,
				bool renderTargetBound
			) {
				Width = presentationParameters.BackBufferWidth;
				Height = presentationParameters.BackBufferHeight;
			}
		}

		#endregion

		#region Threaded GL Nonsense

		private int mainThreadId;

		private bool IsOnMainThread()
		{
			return mainThreadId == Thread.CurrentThread.ManagedThreadId;
		}

		private void InitThreadedGL(IntPtr window)
		{
			mainThreadId = Thread.CurrentThread.ManagedThreadId;
#if THREADED_GL
			// Create a background context
			SDL.SDL_GL_SetAttribute(SDL.SDL_GLattr.SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
			WindowInfo = window;
			BackgroundContext = new GL_ContextHandle()
			{
				context = SDL.SDL_GL_CreateContext(window)
			};

			// Make the foreground context current.
			SDL.SDL_GL_MakeCurrent(window, glContext);

			// We're going to need glFlush, so load this entry point.
			glFlush = (Flush) Marshal.GetDelegateForFunctionPointer(
				SDL.SDL_GL_GetProcAddress("glFlush"),
				typeof(Flush)
			);
#endif
		}

#if !DISABLE_THREADING

#if THREADED_GL
		private class GL_ContextHandle
		{
			public IntPtr context;
		}
		private GL_ContextHandle BackgroundContext;
		private IntPtr WindowInfo;
		private delegate void Flush();
		private Flush glFlush;

#else
		private System.Collections.Generic.List<Action> actions = new System.Collections.Generic.List<Action>();
		private void RunActions()
		{
			lock (actions)
			{
				foreach (Action action in actions)
				{
					action();
				}
				actions.Clear();
			}
		}
#endif

		private void ForceToMainThread(Action action)
		{
			// If we're already on the main thread, just call the action.
			if (mainThreadId == Thread.CurrentThread.ManagedThreadId)
			{
				action();
				return;
			}

#if THREADED_GL
			lock (BackgroundContext)
			{
				// Make the context current on this thread.
				SDL.SDL_GL_MakeCurrent(WindowInfo, BackgroundContext.context);

				// Execute the action.
				action();

				// Must flush the GL calls now before we release the context.
				glFlush();

				// Free the threaded context for the next threaded call...
				SDL.SDL_GL_MakeCurrent(WindowInfo, IntPtr.Zero);
			}
#else
			ManualResetEventSlim resetEvent = new ManualResetEventSlim(false);
			lock (actions)
			{
				actions.Add(() =>
				{
					action();
					resetEvent.Set();
				});
			}
			resetEvent.Wait();
#endif
		}

#endif // !DISABLE_THREADING

		#endregion
	}
}