[Feature] Use librashader for .slangp (RetroArch) shader support

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

@@ -1,4 +1,4 @@
-// TODO
+// TODO
 // we could flag textures as 'actually' render targets (keep a reference to the render target?) which could allow us to convert between them more quickly in some cases
 
 using System.Collections.Generic;
@@ -112,6 +112,7 @@ protected DisplayManagerBase(
 			// `_apiHawkIDTo2DRenderer` is a new empty dict, members are lazily-initialised
 
 			RefreshUserShader();
+			RefreshLibrashader();
 		}
 
 		public void UpdateGlobals(Config config, IEmulator emulator)
@@ -158,6 +159,8 @@ public void Dispose()
 				s?.Dispose();
 			}
 
+			_librashaderFilter?.Dispose();
+
 			_theOneFont?.Dispose();
 			_renderer.Dispose();
 		}
@@ -222,6 +225,8 @@ private StringRenderer Font
 
 		private RetroShaderChain _shaderChainUser;
 
+		private LibrashaderFilter _librashaderFilter;
+
 		public abstract void ActivateOpenGLContext();
 
 		protected abstract void ActivateGraphicsControlContext();
@@ -231,6 +236,7 @@ private StringRenderer Font
 		public void RefreshUserShader()
 		{
 			_shaderChainUser?.Dispose();
+			_shaderChainUser = null;
 			if (File.Exists(GlobalConfig.DispUserFilterPath))
 			{
 				var fi = new FileInfo(GlobalConfig.DispUserFilterPath);
@@ -239,6 +245,25 @@ public void RefreshUserShader()
 			}
 		}
 
+		public void RefreshLibrashader()
+		{
+			Console.WriteLine($"[librashader] RefreshLibrashader called, path: {GlobalConfig.DispUserFilterPath}");
+			_librashaderFilter?.Dispose();
+			_librashaderFilter = null;
+			if (_gl is IGL_OpenGL && File.Exists(GlobalConfig.DispUserFilterPath))
+			{
+				Console.WriteLine("[librashader] Creating LibrashaderFilter");
+				_librashaderFilter = new LibrashaderFilter(GlobalConfig.DispUserFilterPath);
+			}
+			else
+			{
+				if (_gl is not IGL_OpenGL)
+					Console.WriteLine("[librashader] GL is not IGL_OpenGL, skipping librashader");
+				else if (!File.Exists(GlobalConfig.DispUserFilterPath))
+					Console.WriteLine("[librashader] Shader preset file not found");
+			}
+		}
+
 		private (int Left, int Top, int Right, int Bottom) CalculateCompleteContentPadding(bool user, bool source)
 		{
 			var padding = (Left: 0, Top: 0, Right: 0, Bottom: 0);
@@ -282,6 +307,7 @@ private FilterProgram BuildDefaultChain(Size chainInSize, Size chainOutSize, boo
 			// select user special FX shader chain
 			KeyValuePair<string, float>[] selectedChainProperties = null;
 			RetroShaderChain selectedChain = null;
+			bool useLibrashader = false;
 			switch (GlobalConfig.TargetDisplayFilter)
 			{
 				case 1 when _shaderChainHq2X is { Available: true }:
@@ -294,11 +320,15 @@ private FilterProgram BuildDefaultChain(Size chainInSize, Size chainOutSize, boo
 				case 3 when _shaderChainUser is { Available: true }:
 					selectedChain = _shaderChainUser;
 					break;
+				case 4 when _librashaderFilter != null:
+					useLibrashader = true;
+					break;
 			}
 
 			if (!includeUserFilters)
 			{
 				selectedChain = null;
+				useLibrashader = false;
 			}
 
 			var fCoreScreenControl = CreateCoreScreenControl();
@@ -362,6 +392,12 @@ private FilterProgram BuildDefaultChain(Size chainInSize, Size chainOutSize, boo
 				AppendRetroShaderChain(chain, "retroShader", selectedChain, selectedChainProperties);
 			}
 
+			// add librashader filter
+			if (useLibrashader)
+			{
+				chain.AddFilter(_librashaderFilter, "librashader");
+			}
+
 			// AutoPrescale makes no sense for a None final filter
 			if (GlobalConfig.DispAutoPrescale && GlobalConfig.DispFinalFilter != (int)FinalPresentation.eFilterOption.None)
 			{

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

@@ -0,0 +1,127 @@
+using System.Runtime.InteropServices;
+using System.Text;
+
+using BizHawk.Common;
+
+namespace BizHawk.Client.Common.Filters
+{
+	public static unsafe class Librashader
+	{
+		private const CallingConvention CC = CallingConvention.Cdecl;
+		private static bool _loaded = false;
+
+		public static bool IsLoaded => _loaded;
+
+		public static bool Load()
+		{
+			if (_loaded) return true;
+
+			Util.DebugWriteLine("[librashader] Attempting to load librashader.dll...");
+			try
+			{
+				libra_instance_abi_version();
+				Util.DebugWriteLine("[librashader] Successfully loaded librashader.dll");
+				_loaded = true;
+				return true;
+			}
+			catch (DllNotFoundException)
+			{
+				Util.DebugWriteLine("[librashader] Failed to load librashader.dll");
+				return false;
+			}
+		}
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern IntPtr libra_instance_abi_version();
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern IntPtr libra_instance_api_version();
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern IntPtr libra_preset_create(byte* filename, out IntPtr preset);
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern int libra_preset_free(ref IntPtr preset);
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern int libra_error_free(ref IntPtr error);
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern int libra_error_print(IntPtr error);
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern int libra_error_errno(IntPtr error);
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern IntPtr libra_gl_filter_chain_create(
+			ref IntPtr preset,
+			IntPtr loader,
+			[In] ref filter_chain_gl_opt_t options,
+			out IntPtr chain);
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern int libra_gl_filter_chain_frame(
+			ref IntPtr chain,
+			UIntPtr frame_count,
+			libra_image_gl_t image,
+			libra_image_gl_t output,
+			IntPtr viewport,
+			IntPtr mvp,
+			IntPtr options);
+
+		[DllImport("librashader", CallingConvention = CC)]
+		public static extern int libra_gl_filter_chain_free(ref IntPtr chain);
+
+		public static IntPtr PresetCreate(string filename, out IntPtr preset)
+		{
+			byte[] bytes = Encoding.UTF8.GetBytes(filename + "\0");
+			fixed (byte* ptr = bytes)
+			{
+				return libra_preset_create(ptr, out preset);
+			}
+		}
+
+		[StructLayout(LayoutKind.Sequential)]
+		public struct filter_chain_gl_opt_t
+		{
+			public UIntPtr version;
+			public ushort glsl_version;
+			[MarshalAs(UnmanagedType.U1)]
+			public bool use_dsa;
+			[MarshalAs(UnmanagedType.U1)]
+			public bool force_no_mipmaps;
+			[MarshalAs(UnmanagedType.U1)]
+			public bool disable_cache;
+		}
+
+		[StructLayout(LayoutKind.Sequential)]
+		public struct libra_image_gl_t
+		{
+			public uint handle;
+			public uint format;
+			public uint width;
+			public uint height;
+		}
+
+		[StructLayout(LayoutKind.Sequential)]
+		public struct libra_viewport_t
+		{
+			public float x;
+			public float y;
+			public uint width;
+			public uint height;
+		}
+
+		public static filter_chain_gl_opt_t CreateDefaultOptions()
+		{
+			return new filter_chain_gl_opt_t
+			{
+				version = new UIntPtr(1),
+				glsl_version = 330,
+				use_dsa = false,
+				force_no_mipmaps = false,
+				disable_cache = false,
+			};
+		}
+	}
+}