Avoid hard depending on Direct3D 11.1, slighly optimize presentation

src/BizHawk.Bizware.Graphics.Controls/Controls/D3D11Control.cs

@@ -48,10 +48,12 @@ namespace BizHawk.Bizware.Graphics.Controls
 			=> Vsync = state;
 
 		public override void Begin()
-			=> _swapChain.SetBackBuffer();
+		{
+		}
 
 		public override void End()
-			=> _swapChain.SetBackBuffer();
+		{
+		}
 
 		public override void SwapBuffers()
 			=> _swapChain.PresentBuffer(ControlParameters);

src/BizHawk.Bizware.Graphics.Controls/GraphicsControl.cs

@@ -16,7 +16,8 @@ namespace BizHawk.Bizware.Graphics.Controls
 		public abstract void SetVsync(bool state);
 
 		/// <summary>
-		/// Swaps the buffers for this control
+		/// Swaps the buffers for this control.
+		/// Be aware, the owner IGL's current render target is undefined after calling this
 		/// </summary>
 		public abstract void SwapBuffers();
 

src/BizHawk.Bizware.Graphics/D3D11/D3D11SwapChain.cs

@@ -31,9 +31,10 @@ namespace BizHawk.Bizware.Graphics
 		{
 			public ID3D11Device Device;
 			public ID3D11DeviceContext Context;
+			public ID3D11DeviceContext1 Context1;
 			public ID3D11Texture2D BackBufferTexture;
 			public ID3D11RenderTargetView RTV;
-			public IDXGISwapChain1 SwapChain;
+			public IDXGISwapChain SwapChain;
 			public bool AllowsTearing;
 
 			public void Dispose()
@@ -41,6 +42,8 @@ namespace BizHawk.Bizware.Graphics
 				// Device/Context not owned by this class
 				Device = null;
 				Context = null;
+				Context1?.Dispose();
+				Context1 = null;
 				RTV?.Dispose();
 				RTV = null;
 				BackBufferTexture?.Dispose();
@@ -57,9 +60,10 @@ namespace BizHawk.Bizware.Graphics
 
 		private ID3D11Device Device => _resources.Device;
 		private ID3D11DeviceContext Context => _resources.Context;
+		private ID3D11DeviceContext1 Context1 => _resources.Context1;
 		private ID3D11Texture2D BackBufferTexture => _resources.BackBufferTexture;
 		private ID3D11RenderTargetView RTV => _resources.RTV;
-		private IDXGISwapChain1 SwapChain => _resources.SwapChain;
+		private IDXGISwapChain SwapChain => _resources.SwapChain;
 		private bool AllowsTearing => _resources.AllowsTearing;
 
 		internal D3D11SwapChain(SwapChainResources resources, Action<ControlParameters> resetDeviceCallback)
@@ -71,12 +75,9 @@ namespace BizHawk.Bizware.Graphics
 		public void Dispose()
 			=> _resources.Dispose();
 
-		public void SetBackBuffer()
-			=> Context.OMSetRenderTargets(RTV);
-
 		public void PresentBuffer(ControlParameters cp)
 		{
-			SetBackBuffer();
+			Context.OMSetRenderTargets(RTV);
 
 			PresentFlags presentFlags;
 			if (cp.Vsync)
@@ -95,6 +96,9 @@ namespace BizHawk.Bizware.Graphics
 			{
 				_resetDeviceCallback(cp);
 			}
+
+			// optimization hint to the GPU (note: not always available, needs Win8+ or Win7 with the Platform Update)
+			Context1?.DiscardView(RTV);
 		}
 
 		public void Refresh(ControlParameters cp)

src/BizHawk.Bizware.Graphics/D3D11/IGL_D3D11.cs

@@ -25,7 +25,8 @@ namespace BizHawk.Bizware.Graphics
 
 		private struct D3D11Resources : IDisposable
 		{
-			public IDXGIFactory2 Factory;
+			public IDXGIFactory1 Factory1;
+			public IDXGIFactory2 Factory2;
 			public ID3D11Device Device;
 			public ID3D11DeviceContext Context;
 			public ID3D11BlendState BlendEnableState;
@@ -40,8 +41,10 @@ namespace BizHawk.Bizware.Graphics
 			{
 				try
 				{
-					// we need IDXGIFactory2 for CreateSwapChainForHwnd
+					Factory1 = DXGI.CreateDXGIFactory1<IDXGIFactory1>();
-					Factory = DXGI.CreateDXGIFactory1<IDXGIFactory2>();
+					// we want IDXGIFactory2 for CreateSwapChainForHwnd
+					// however, it's not guaranteed to be available (only available in Win8+ or Win7 with the Platform Update)
+					Factory2 = Factory1.QueryInterfaceOrNull<IDXGIFactory2>();
 #if false
 					// use this to debug D3D11 calls
 					// note debug layer requires extra steps to use: https://learn.microsoft.com/en-us/windows/win32/direct3d11/overviews-direct3d-11-devices-layers#debug-layer
@@ -124,8 +127,11 @@ namespace BizHawk.Bizware.Graphics
 				Device?.Dispose();
 				Device = null;
 
-				Factory?.Dispose();
+				Factory2?.Dispose();
-				Factory = null;
+				Factory2 = null;
+
+				Factory1?.Dispose();
+				Factory1 = null;
 			}
 		}
 
@@ -133,7 +139,8 @@ namespace BizHawk.Bizware.Graphics
 		// these might need to be thrown out and recreated if the device is lost
 		private D3D11Resources _resources;
 
-		private IDXGIFactory2 Factory => _resources.Factory;
+		private IDXGIFactory1 Factory1 => _resources.Factory1;
+		private IDXGIFactory2 Factory2 => _resources.Factory2;
 		private ID3D11Device Device => _resources.Device;
 		private ID3D11DeviceContext Context => _resources.Context;
 		private ID3D11BlendState BlendEnableState => _resources.BlendEnableState;
@@ -166,7 +173,31 @@ namespace BizHawk.Bizware.Graphics
 			_resources.CreateResources();
 		}
 
-		private IDXGISwapChain1 CreateDXGISwapChain(D3D11SwapChain.ControlParameters cp)
+		private IDXGISwapChain CreateDXGISwapChain(D3D11SwapChain.ControlParameters cp)
+		{
+			IDXGISwapChain ret;
+
+			if (Factory2 is null)
+			{
+				// no Factory2, probably on Windows 7 without the Platform Update
+				// we can assume a simple legacy format is needed here
+				var sd = default(SwapChainDescription);
+				sd.BufferDescription = new(
+					width: cp.Width,
+					height: cp.Height,
+					refreshRate: new(0, 0),
+					format: Format.B8G8R8A8_UNorm);
+				sd.SampleDescription = SampleDescription.Default;
+				sd.BufferUsage = Usage.RenderTargetOutput;
+				sd.BufferCount = 2;
+				sd.OutputWindow = cp.Handle;
+				sd.Windowed = true;
+				sd.SwapEffect = SwapEffect.Discard;
+				sd.Flags = SwapChainFlags.None;
+
+				ret = Factory1.CreateSwapChain(Device, sd);
+			}
+			else
 			{
 				// this is the optimal swapchain model
 				// note however it requires windows 10+
@@ -183,20 +214,20 @@ namespace BizHawk.Bizware.Graphics
 					alphaMode: AlphaMode.Ignore,
 					flags: SwapChainFlags.AllowTearing);
 
-			IDXGISwapChain1 ret;
 				try
 				{
-				ret = Factory.CreateSwapChainForHwnd(Device, cp.Handle, sd);
+					ret = Factory2.CreateSwapChainForHwnd(Device, cp.Handle, sd);
 				}
 				catch
 				{
 					sd.SwapEffect = SwapEffect.Discard;
 					sd.Flags = SwapChainFlags.None;
-				ret = Factory.CreateSwapChainForHwnd(Device, cp.Handle, sd);
+					ret = Factory2.CreateSwapChainForHwnd(Device, cp.Handle, sd);
+				}
 			}
 
 			// don't allow DXGI to snoop alt+enter and such
-			using var parentFactory = ret.GetParent<IDXGIFactory2>();
+			using var parentFactory = ret.GetParent<IDXGIFactory>();
 			parentFactory.MakeWindowAssociation(cp.Handle, WindowAssociationFlags.IgnoreAll);
 			return ret;
 		}
@@ -330,10 +361,11 @@ namespace BizHawk.Bizware.Graphics
 
 			_controlSwapChain.Device = Device;
 			_controlSwapChain.Context = Context;
+			_controlSwapChain.Context1 = Context.QueryInterfaceOrNull<ID3D11DeviceContext1>();
 			_controlSwapChain.BackBufferTexture = bbTex;
 			_controlSwapChain.RTV = rtv;
 			_controlSwapChain.SwapChain = swapChain;
-			_controlSwapChain.AllowsTearing = (swapChain.Description1.Flags & SwapChainFlags.AllowTearing) != 0;
+			_controlSwapChain.AllowsTearing = (swapChain.Description.Flags & SwapChainFlags.AllowTearing) != 0;
 		}
 
 		public D3D11SwapChain CreateSwapChain(D3D11SwapChain.ControlParameters cp)
@@ -348,14 +380,15 @@ namespace BizHawk.Bizware.Graphics
 			var rtvd = new RenderTargetViewDescription(RenderTargetViewDimension.Texture2D, Format.B8G8R8A8_UNorm);
 			var rtv = Device.CreateRenderTargetView(bbTex, rtvd);
 
-			_controlSwapChain = new D3D11SwapChain.SwapChainResources
+			_controlSwapChain = new()
 			{
 				Device = Device,
 				Context = Context,
+				Context1 = Context.QueryInterfaceOrNull<ID3D11DeviceContext1>(),
 				BackBufferTexture = bbTex,
 				RTV = rtv,
 				SwapChain = swapChain,
-				AllowsTearing = (swapChain.Description1.Flags & SwapChainFlags.AllowTearing) != 0,
+				AllowsTearing = (swapChain.Description.Flags & SwapChainFlags.AllowTearing) != 0,
 			};
 
 			return new(_controlSwapChain, ResetDevice);