prep work for easier OpenGL interop for cores

src/BizHawk.Bizware.BizwareGL/IGL.cs

@@ -159,7 +159,7 @@ namespace BizHawk.Bizware.BizwareGL
 
 		/// <summary>
 		/// In case you already have the texture ID (from an opengl emulator gpu core) you can get a Texture2d with it this way.
-		/// Otherwise, if this isn't an OpenGL frontend implementation, I guess... try reading the texturedata out of it and making a new texture?
+		/// Otherwise, if this isn't an OpenGL frontend implementation, the core is expected to readback the texture for GetVideoBuffer()
 		/// </summary>
 		Texture2d WrapGLTexture2d(IntPtr glTexId, int width, int height);
 

src/BizHawk.Bizware.BizwareGL/RenderTarget.cs

@@ -9,7 +9,6 @@ namespace BizHawk.Bizware.BizwareGL
 			Owner = owner;
 			Opaque = opaque;
 			Texture2d = tex;
-			tex.IsUpsideDown = true;
 		}
 
 		public override string ToString()

src/BizHawk.Bizware.Graphics/D3D9/IGL_D3D9.cs

@@ -683,8 +683,7 @@ namespace BizHawk.Bizware.Graphics
 
 		public Texture2d WrapGLTexture2d(IntPtr glTexId, int width, int height)
 		{
-			// not needed 1st pass (except for GL cores)
+			// only used for OpenGL
-			// TODO - need to rip the texture data. we had code for that somewhere...
 			return null;
 		}
 

src/BizHawk.Bizware.Graphics/OpenGL/IGL_OpenGL.cs

@@ -37,10 +37,7 @@ namespace BizHawk.Bizware.Graphics
 	{
 		public EDispMethod DispMethodEnum => EDispMethod.OpenGL;
 
-		private readonly SDL2OpenGLContext OffscreenContext;
+		private readonly GL GL;
-		private SDL2OpenGLContext ActiveContext;
-		private GL GL => ActiveContext.GL;
-
 		private readonly int _majorVersion, _minorVersion;
 		private readonly bool _forwardCompatible;
 
@@ -50,36 +47,20 @@ namespace BizHawk.Bizware.Graphics
 
 		public string API => "OPENGL";
 
-		public int Version
-		{
-			get
-			{
-				// doesnt work on older than gl3 maybe
-				// int major, minor;
-				// // other overloads may not exist...
-				// GL.GetInteger(GetPName.MajorVersion, out major);
-				// GL.GetInteger(GetPName.MinorVersion, out minor);
-
-				// supposedly the standard dictates that whatever junk is in the version string, some kind of version is at the beginning
-				// can be either in major_number.minor_number or major_number.minor_number.release_number, with vendor specific info afterwards
-				var versionString = GL.GetStringS(StringName.Version);
-				var versionParts = versionString.Split('.');
-				var major = int.Parse(versionParts[0]);
-				var minor = int.Parse(versionParts[1][0].ToString());
-				// getting a release number is too hard and not needed now
-				return major * 100 + minor * 10;
-			}
-		}
-
 		public IGL_OpenGL(int majorVersion, int minorVersion, bool forwardCompatible)
 		{
-			// create an offscreen context, so things can be done without a control
-			ActiveContext = OffscreenContext = new(majorVersion, minorVersion, forwardCompatible);
-
 			_majorVersion = majorVersion;
 			_minorVersion = minorVersion;
 			_forwardCompatible = forwardCompatible;
 
+			// we need an active context in order to acquire these functions
+			// technically, they could be different between contexts
+			// but with the exact same requested version and config that is highly unlikely in practice
+			using (new SDL2OpenGLContext(majorVersion, minorVersion, forwardCompatible))
+			{
+				GL = GL.GetApi(SDL2OpenGLContext.GetGLProcAddress);
+			}
+
 			// misc initialization
 			CreateRenderStates();
 		}
@@ -94,7 +75,6 @@ namespace BizHawk.Bizware.Graphics
 
 		public void Dispose()
 		{
-			OffscreenContext.Dispose();
 		}
 
 		public void Clear(BizClearBufferMask mask)
@@ -477,7 +457,7 @@ namespace BizHawk.Bizware.Graphics
 
 		public Texture2d WrapGLTexture2d(IntPtr glTexId, int width, int height)
 		{
-			return new(this, glTexId.ToInt32(), width, height);
+			return new(this, (uint)glTexId.ToInt32(), width, height) { IsUpsideDown = true };
 		}
 
 		public unsafe void LoadTextureData(Texture2d tex, BitmapBuffer bmp)
@@ -505,7 +485,7 @@ namespace BizHawk.Bizware.Graphics
 		{
 			// create a texture for it
 			var texId = GenTexture();
-			var tex = new Texture2d(this, texId, w, h);
+			var tex = new Texture2d(this, texId, w, h) { IsUpsideDown = true }; // TODO: The IsUpsideDown doesn't ever get used here it seems
 
 			GL.BindTexture(TextureTarget.Texture2D, texId);
 			GL.TexImage2D(TextureTarget.Texture2D, 0, InternalFormat.Rgba8, (uint)w, (uint)h, 0, PixelFormat.Bgra, PixelType.UnsignedByte, IntPtr.Zero.ToPointer());
@@ -839,26 +819,11 @@ namespace BizHawk.Bizware.Graphics
 		private VertexLayout sStatePendingVertexLayout;
 		private readonly HashSet<uint> sVertexAttribEnables = new();
 
-		private void ContextChangeCallback(SDL2OpenGLContext context)
+		private void ContextChangeCallback()
 		{
-			// null means the current context is being cleared
-			// set it back to the offscreen context
-			if (context is null)
-			{
-				OffscreenContext.MakeContextCurrent();
-				context = OffscreenContext;
-			}
-
 			sActiveTexture = -1;
 			sStatePendingVertexLayout = null;
 			sVertexAttribEnables.Clear();
-			ActiveContext = context;
-		}
-
-		public void MakeOffscreenContextCurrent()
-		{
-			OffscreenContext.MakeContextCurrent();
-			ContextChangeCallback(OffscreenContext);
 		}
 	}
 }

src/BizHawk.Bizware.Graphics/OpenGL/OpenGLControl.cs

@@ -11,7 +11,7 @@ namespace BizHawk.Bizware.Graphics
 		private readonly int _majorVersion;
 		private readonly int _minorVersion;
 		private readonly bool _forwardCompatible;
-		private readonly Action<SDL2OpenGLContext> _contextChangeCallback;
+		private readonly Action _contextChangeCallback;
 
 		public SDL2OpenGLContext Context { get; private set; }
 
@@ -21,7 +21,7 @@ namespace BizHawk.Bizware.Graphics
 			set => throw new NotImplementedException();
 		}
 
-		public OpenGLControl(int majorVersion, int minorVersion, bool forwardCompatible, Action<SDL2OpenGLContext> contextChangeCallback)
+		public OpenGLControl(int majorVersion, int minorVersion, bool forwardCompatible, Action contextChangeCallback)
 		{
 			_majorVersion = majorVersion;
 			_minorVersion = minorVersion;
@@ -59,8 +59,7 @@ namespace BizHawk.Bizware.Graphics
 		{
 			base.OnHandleCreated(e);
 			Context = new(Handle, _majorVersion, _minorVersion, _forwardCompatible);
-
+			_contextChangeCallback();
-			_contextChangeCallback(Context);
 		}
 
 		protected override void OnHandleDestroyed(EventArgs e)
@@ -69,7 +68,7 @@ namespace BizHawk.Bizware.Graphics
 
 			if (Context.IsCurrent)
 			{
-				_contextChangeCallback(null);
+				_contextChangeCallback();
 			}
 
 			Context.Dispose();
@@ -92,7 +91,7 @@ namespace BizHawk.Bizware.Graphics
 				if (!Context.IsCurrent)
 				{
 					Context.MakeContextCurrent();
-					_contextChangeCallback(Context);
+					_contextChangeCallback();
 				}
 			}
 		}
@@ -110,7 +109,8 @@ namespace BizHawk.Bizware.Graphics
 
 		public void End()
 		{
-			_contextChangeCallback(null);
+			SDL2OpenGLContext.MakeNoneCurrent();
+			_contextChangeCallback();
 		}
 
 		public void SwapBuffers()

src/BizHawk.Bizware.Graphics/OpenGL/SDL2OpenGLContext.cs

@@ -1,6 +1,5 @@
 using System;
-
+using System.Runtime.InteropServices;
-using Silk.NET.OpenGL.Legacy;
 
 using static SDL2.SDL;
 
@@ -9,7 +8,7 @@ namespace BizHawk.Bizware.Graphics
 	/// <summary>
 	/// Wraps an SDL2 OpenGL context
 	/// </summary>
-	internal class SDL2OpenGLContext : IDisposable
+	public class SDL2OpenGLContext : IDisposable
 	{
 		static SDL2OpenGLContext()
 		{
@@ -41,11 +40,50 @@ namespace BizHawk.Bizware.Graphics
 			SDL_SetHint(SDL_HINT_VIDEO_FOREIGN_WINDOW_OPENGL, "1");
 		}
 
+		[UnmanagedFunctionPointer(CallingConvention.Winapi)]
+		private delegate IntPtr glGetStringDelegate(int name);
+
+		private static readonly Lazy<int> _version = new(() =>
+		{
+			var prevWindow = SDL_GL_GetCurrentWindow();
+			var prevContext = SDL_GL_GetCurrentContext();
+
+			try
+			{
+				using (new SDL2OpenGLContext(2, 0, false))
+				{
+					var getStringFp = GetGLProcAddress("glGetString");
+					if (getStringFp == IntPtr.Zero) // uhhh?
+					{
+						return 0;
+					}
+
+					var getStringFunc = Marshal.GetDelegateForFunctionPointer<glGetStringDelegate>(getStringFp);
+					const int GL_VERSION = 0x1F02;
+					var version = getStringFunc(GL_VERSION);
+					if (version == IntPtr.Zero)
+					{
+						return 0;
+					}
+
+					var versionString = Marshal.PtrToStringAnsi(version);
+					var versionParts = versionString!.Split('.');
+					var major = int.Parse(versionParts[0]);
+					var minor = int.Parse(versionParts[1][0].ToString());
+					return major * 100 + minor;
+				}
+			}
+			finally
+			{
+				SDL_GL_MakeCurrent(prevWindow, prevContext);
+			}
+		});
+
+		public static int Version => _version.Value;
+
 		private IntPtr _sdlWindow;
 		private IntPtr _glContext;
 
-		public GL GL { get; private set; }
-
 		private void CreateContext(int majorVersion, int minorVersion, bool forwardCompatible)
 		{
 			if (SDL_GL_SetAttribute(SDL_GLattr.SDL_GL_CONTEXT_MAJOR_VERSION, majorVersion) != 0)
@@ -80,10 +118,6 @@ namespace BizHawk.Bizware.Graphics
 			{
 				throw new($"Could not create GL Context! SDL Error: {SDL_GetError()}");
 			}
-
-			// get GL functions
-			// these are specific towards a context, and so these are owned by the context here
-			GL = GL.GetApi(SDL_GL_GetProcAddress);
 		}
 
 		public SDL2OpenGLContext(IntPtr nativeWindowhandle, int majorVersion, int minorVersion, bool forwardCompatible)
@@ -146,6 +180,15 @@ namespace BizHawk.Bizware.Graphics
 			_ = SDL_GL_MakeCurrent(_sdlWindow, _glContext);
 		}
 
+		public static void MakeNoneCurrent()
+		{
+			// no-op if nothing is current
+			_ = SDL_GL_MakeCurrent(IntPtr.Zero, IntPtr.Zero);
+		}
+
+		public static IntPtr GetGLProcAddress(string proc)
+			=> SDL_GL_GetProcAddress(proc);
+
 		public void SetVsync(bool state)
 		{
 			if (!IsCurrent)

src/BizHawk.Client.Common/DisplayManager/DisplayManagerBase.cs

@@ -196,7 +196,9 @@ namespace BizHawk.Client.Common
 
 		private RetroShaderChain _shaderChainUser;
 
-		protected virtual void ActivateGLContext() => throw new NotImplementedException();
+		public virtual void ActivateOpenGLContext() => throw new NotImplementedException();
+
+		protected virtual void ActivateGraphicsControlContext() => throw new NotImplementedException();
 
 		protected virtual void SwapBuffersOfGraphicsControl() => throw new NotImplementedException();
 
@@ -771,12 +773,10 @@ namespace BizHawk.Client.Common
 
 		private FilterProgram UpdateSourceInternal(JobInfo job)
 		{
-			//no drawing actually happens. it's important not to begin drawing on a control
+			// no drawing actually happens
-			if (!job.Simulate/* && !job.Offscreen*/)
+			if (!job.Simulate)
 			{
-				// i don't want to do this for offscreen jobs
+				ActivateGraphicsControlContext();
-				// but it seems that would be required in case this context isn't active
-				ActivateGLContext();
 
 				if (job.ChainOutsize.Width == 0 || job.ChainOutsize.Height == 0)
 				{
@@ -791,17 +791,14 @@ namespace BizHawk.Client.Common
 			}
 
 			var videoProvider = job.VideoProvider;
+			var glTextureProvider = videoProvider as IGLTextureProvider;
 			var simulate = job.Simulate;
 			var chainOutsize = job.ChainOutsize;
 
-			//simulate = true;
-
-			var videoBuffer = videoProvider.GetVideoBuffer();
 			var bufferWidth = videoProvider.BufferWidth;
 			var bufferHeight = videoProvider.BufferHeight;
 			var presenterTextureWidth = bufferWidth;
 			var presenterTextureHeight = bufferHeight;
-			var isGlTextureId = videoBuffer.Length == 1;
 
 			var vw = videoProvider.VirtualWidth;
 			var vh = videoProvider.VirtualHeight;
@@ -854,23 +851,22 @@ namespace BizHawk.Client.Common
 			Texture2d videoTexture = null;
 			if (!simulate)
 			{
-				if (isGlTextureId)
+				if (glTextureProvider != null && _gl.DispMethodEnum == EDispMethod.OpenGL)
 				{
 					// FYI: this is a million years from happening on n64, since it's all geriatric non-FBO code
-					// is it workable for saturn?
+					videoTexture = _gl.WrapGLTexture2d(new(glTextureProvider.GetGLTexture()), bufferWidth, bufferHeight);
-					videoTexture = _gl.WrapGLTexture2d(new(videoBuffer[0]), bufferWidth, bufferHeight);
 				}
 				else
 				{
 					// wrap the VideoProvider data in a BitmapBuffer (no point to refactoring that many IVideoProviders)
-					bb = new(bufferWidth, bufferHeight, videoBuffer);
+					bb = new(bufferWidth, bufferHeight, videoProvider.GetVideoBuffer());
 					bb.DiscardAlpha();
 
 					//now, acquire the data sent from the videoProvider into a texture
 					videoTexture = _videoTextureFrugalizer.Get(bb);
 
 					// lets not use this. lets define BizwareGL to make clamp by default (TBD: check opengl)
-					// GL.SetTextureWrapMode(videoTexture, true);
+					// _gl.SetTextureWrapMode(videoTexture, true);
 				}
 			}
 
@@ -897,7 +893,6 @@ namespace BizHawk.Client.Common
 				fPresent.TextureSize = new(presenterTextureWidth, presenterTextureHeight);
 				fPresent.BackgroundColor = videoProvider.BackgroundColor;
 				fPresent.GuiRenderer = _renderer;
-				fPresent.Flip = isGlTextureId;
 				fPresent.Config_FixAspectRatio = GlobalConfig.DispFixAspectRatio;
 				fPresent.Config_FixScaleInteger = GlobalConfig.DispFixScaleInteger;
 				fPresent.Padding = (ClientExtraPadding.Left, ClientExtraPadding.Top, ClientExtraPadding.Right, ClientExtraPadding.Bottom);
@@ -932,7 +927,7 @@ namespace BizHawk.Client.Common
 
 		public void Blank()
 		{
-			ActivateGLContext();
+			ActivateGraphicsControlContext();
 			_gl.BeginScene();
 			_gl.BindRenderTarget(null);
 			_gl.SetClearColor(Color.Black);

src/BizHawk.Client.Common/DisplayManager/Filters/Gui.cs

@@ -435,7 +435,6 @@ namespace BizHawk.Client.Common.Filters
 		public int BackgroundColor;
 		public bool AutoPrescale;
 		public IGuiRenderer GuiRenderer;
-		public bool Flip;
 		public IGL GL;
 		private bool nop;
 		private LetterboxingLogic LL;
@@ -491,7 +490,7 @@ namespace BizHawk.Client.Common.Filters
 
 		public override void SetInputFormat(string channel, SurfaceState state)
 		{
-			bool need = state.SurfaceFormat.Size != OutputSize || FilterOption != eFilterOption.None || Flip;
+			bool need = state.SurfaceFormat.Size != OutputSize || FilterOption != eFilterOption.None;
 
 			if (!need)
 			{
@@ -575,14 +574,7 @@ namespace BizHawk.Client.Common.Filters
 				//this was handled earlier by another filter
 			}
 
-			GuiRenderer.Modelview.Translate(LL.vx, LL.vy);
+			GuiRenderer.Draw(InputTexture, LL.vx, LL.vy, LL.vw, LL.vh);
-			if (Flip)
-			{
-				GuiRenderer.Modelview.Scale(1, -1);
-				GuiRenderer.Modelview.Translate(0, -LL.vh);
-			}
-			GuiRenderer.Draw(InputTexture,0,0,LL.vw,LL.vh);
-
 			GuiRenderer.End();
 		}
 	}

src/BizHawk.Client.EmuHawk/DisplayManager/DisplayManager.cs

@@ -20,8 +20,6 @@ namespace BizHawk.Client.EmuHawk
 
 		private readonly PresentationPanel _presentationPanel; // well, its the final layer's target, at least
 
-		private readonly GLManager.ContextRef _crGraphicsControl;
-
 		private GraphicsControl _graphicsControl => _presentationPanel.GraphicsControl;
 
 		public DisplayManager(
@@ -36,14 +34,17 @@ namespace BizHawk.Client.EmuHawk
 		{
 			_presentationPanel = presentationPanel;
 			_getIsSecondaryThrottlingDisabled = getIsSecondaryThrottlingDisabled;
-
-			// setup the GL context manager, needed for coping with multiple opengl cores vs opengl display method
-			// but is it tho? --yoshi
-			// turns out it was, calling Instance getter here initialises it, and the encapsulated Activate call is necessary too --yoshi
-			_crGraphicsControl = GLManager.GetContextForGraphicsControl(_graphicsControl);
 		}
 
-		protected override void ActivateGLContext() => GLManager.Instance.Activate(_crGraphicsControl);
+		public override void ActivateOpenGLContext()
+		{
+			if (_gl.DispMethodEnum == EDispMethod.OpenGL)
+			{
+				_graphicsControl.Begin();
+			}
+		}
+
+		protected override void ActivateGraphicsControlContext() => _graphicsControl.Begin();
 
 		protected override Size GetGraphicsControlSize() => _graphicsControl.Size;
 

src/BizHawk.Client.EmuHawk/GLManager.cs

@@ -1,91 +0,0 @@
-using System;
-using BizHawk.Bizware.BizwareGL;
-using BizHawk.Bizware.Graphics;
-
-namespace BizHawk.Client.EmuHawk
-{
-	/// <summary>
-	/// This singleton class manages OpenGL contexts, in an effort to minimize context changes.
-	/// </summary>
-	public class GLManager : IDisposable
-	{
-		private GLManager()
-		{
-		}
-
-		public void Dispose()
-		{
-		}
-
-		private static readonly Lazy<GLManager> _lazyInstance = new(() => new());
-
-		public static GLManager Instance => _lazyInstance.Value;
-
-		public void ReleaseGLContext(object o)
-		{
-			var cr = (ContextRef)o;
-			cr.GL.Dispose();
-		}
-
-		public ContextRef CreateGLContext(int majorVersion, int minorVersion, bool forwardCompatible)
-		{
-			var gl = new IGL_OpenGL(majorVersion, minorVersion, forwardCompatible);
-			return new() { GL = gl };
-		}
-
-		public static ContextRef GetContextForGraphicsControl(GraphicsControl gc)
-		{
-			return new()
-			{
-				Gc = gc,
-				GL = gc.IGL
-			};
-		}
-
-		private ContextRef _activeContext;
-
-		public void Invalidate()
-		{
-			_activeContext = null;
-		}
-
-		public void Activate(ContextRef cr)
-		{
-			if (cr == _activeContext)
-			{
-				// D3D9 needs a begin signal to set the swap chain to the next backbuffer
-				if (cr.GL.DispMethodEnum is EDispMethod.D3D9)
-				{
-					cr.Gc.Begin();
-				}
-
-				return;
-			}
-
-			_activeContext = cr;
-
-			if (cr.Gc != null)
-			{
-				cr.Gc.Begin();
-			}
-			else
-			{
-				if (cr.GL is IGL_OpenGL gl)
-				{
-					gl.MakeOffscreenContextCurrent();
-				}
-			}
-		}
-
-		public void Deactivate()
-		{
-			//this is here for future use and tracking purposes.. however.. instead of relying on this, we should just make sure we always activate what we need before we use it
-		}
-
-		public class ContextRef
-		{
-			public IGL GL { get; set; }
-			public GraphicsControl Gc { get; set; }
-		}
-	}
-}

src/BizHawk.Client.EmuHawk/GraphicsImplementations/OpenGLProvider.cs

@@ -0,0 +1,30 @@
+using System;
+
+using BizHawk.Bizware.Graphics;
+using BizHawk.Emulation.Common;
+
+namespace BizHawk.Client.EmuHawk
+{
+	/// <summary>
+	/// Provides a way for a core to use OpenGL
+	/// </summary>
+	public class OpenGLProvider : IOpenGLProvider
+	{
+		public int GLVersion => SDL2OpenGLContext.Version;
+
+		public object RequestGLContext(int major, int minor, bool forwardCompatible)
+			=> new SDL2OpenGLContext(major, minor, forwardCompatible);
+
+		public void ReleaseGLContext(object context)
+			=> ((SDL2OpenGLContext)context).Dispose();
+
+		public void ActivateGLContext(object context)
+			=> ((SDL2OpenGLContext)context).MakeContextCurrent();
+
+		public void DeactivateGLContext()
+			=> SDL2OpenGLContext.MakeNoneCurrent();
+
+		public IntPtr GetGLProcAddress(string proc)
+			=> SDL2OpenGLContext.GetGLProcAddress(proc);
+	}
+}

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -226,7 +226,8 @@ namespace BizHawk.Client.EmuHawk
 				message => this.ModalMessageBox(message, "Warning", EMsgBoxIcon.Warning),
 				AddOnScreenMessage,
 				cfp,
-				prefs);
+				prefs,
+				new OpenGLProvider());
 		}
 
 		private void SetImages()
@@ -3837,6 +3838,7 @@ namespace BizHawk.Client.EmuHawk
 					//path = ioa_openrom.Path;
 				}
 
+				DisplayManager.ActivateOpenGLContext(); // required in case the core wants to created a shared OpenGL context
 				var result = loader.LoadRom(path, nextComm, ioaRetro?.CorePath, forcedCoreName: MovieSession.QueuedCoreName);
 
 				if (result) Game = loader.Game;

src/BizHawk.Client.EmuHawk/Program.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Diagnostics;
 using System.IO;
-using System.Linq;
 using System.Collections.Generic;
 using System.Reflection;
 using System.Runtime.InteropServices;
@@ -227,16 +226,14 @@ namespace BizHawk.Client.EmuHawk
 							return TryInitIGL(initialConfig.DispMethod = fallback.Method);
 						}
 					case EDispMethod.OpenGL:
-						var glOpenGL = new IGL_OpenGL(2, 0, false);
+						if (SDL2OpenGLContext.Version < 200)
-						if (glOpenGL.Version < 200)
 						{
 							// too old to use, GDI+ will be better
-							glOpenGL.Dispose();
 							var fallback = ChooseFallback();
 							new ExceptionBox(new Exception($"Initialization of OpenGL Display Method failed; falling back to {fallback.Name}")).ShowDialog();
 							return TryInitIGL(initialConfig.DispMethod = fallback.Method);
 						}
-						return CheckRenderer(glOpenGL);
+						return CheckRenderer(new IGL_OpenGL(2, 0, false));
 					default:
 					case EDispMethod.GdiPlus:
 						static GLControlWrapper_GdiPlus CreateGLControlWrapper(IGL_GdiPlus self) => new(self); // inlining as lambda causes crash, don't wanna know why --yoshi

src/BizHawk.Emulation.Common/CoreComms.cs

@@ -14,13 +14,15 @@ namespace BizHawk.Emulation.Common
 			Action<string> showMessage,
 			Action<string, int?> notifyMessage,
 			ICoreFileProvider coreFileProvider,
-			CorePreferencesFlags prefs
+			CorePreferencesFlags prefs,
+			IOpenGLProvider oglProvider
 			)
 		{
 			ShowMessage = showMessage;
 			Notify = notifyMessage;
 			CoreFileProvider = coreFileProvider;
 			CorePreferences = prefs;
+			OpenGLProvider = oglProvider;
 		}
 
 		public ICoreFileProvider CoreFileProvider { get; }
@@ -47,5 +49,10 @@ namespace BizHawk.Emulation.Common
 		/// Yeah, I put more stuff in corecomm. If you don't like it, change the settings/syncsettings stuff to support multiple "settings sets" to act like ini file sections kind of, so that we can hand a generic settings object to cores instead of strictly ones defined by the cores
 		/// </summary>
 		public CorePreferencesFlags CorePreferences { get; }
+
+		/// <summary>
+		/// Interface to provide OpenGL resources to the core
+		/// </summary>
+		public IOpenGLProvider OpenGLProvider { get; }
 	}
 }

src/BizHawk.Emulation.Common/Interfaces/IOpenGLProvider.cs

@@ -0,0 +1,44 @@
+using System;
+
+namespace BizHawk.Emulation.Common
+{
+	/// <summary>
+	/// Defines an interface for cores to obtain OpenGL contexts and functions
+	/// </summary>
+	public interface IOpenGLProvider
+	{
+		/// <summary>
+		/// OpenGL version, using major.minor.build format with decimal points ommitted (e.g. 1.2.3 turns into 123)
+		/// </summary>
+		public int GLVersion { get; }
+
+		/// <summary>
+		/// Requests an OpenGL context with specified major / minor / forwardCompatible
+		/// The requested OpenGL context will be shared with the current context
+		/// Note: creating a context implicitly makes that created context current
+		/// </summary>
+		public object RequestGLContext(int major, int minor, bool forwardCompatible);
+
+		/// <summary>
+		/// Frees this OpenGL context
+		/// </summary>
+		public void ReleaseGLContext(object context);
+
+		/// <summary>
+		/// Sets this OpenGL context to current
+		/// </summary>
+		public void ActivateGLContext(object context);
+
+		/// <summary>
+		/// Deactivates the current OpenGL context
+		/// No context will be current after this call
+		/// </summary>
+		public void DeactivateGLContext();
+
+		/// <summary>
+		/// Gets an OpenGL function pointer
+		/// The user must make a context active before using this
+		/// </summary>
+		public IntPtr GetGLProcAddress(string proc);
+	}
+}

src/BizHawk.Emulation.Common/Interfaces/Services/IGLTextureProvider.cs

@@ -0,0 +1,15 @@
+namespace BizHawk.Emulation.Common
+{
+	/// <summary>
+	/// This service is an extension of IVideoProvider, providing the ability to pass an OpenGL texture to the client
+	/// If available and the client is using OpenGL for display, this texture will be used
+	/// If unavailable or the client is not using OpenGL for display, the client will fall back to the base <see cref="IVideoProvider"/>
+	/// </summary>
+	public interface IGLTextureProvider : IVideoProvider, ISpecializedEmulatorService
+	{
+		/// <summary>
+		/// Returns an OpenGL texture of the current video content
+		/// </summary>
+		int GetGLTexture();
+	}
+}