Fix "double rendering" in Lua/ApiHawk gui stuff

src/BizHawk.Bizware.Graphics/Interfaces/I2DRenderer.cs

@@ -29,6 +29,12 @@ namespace BizHawk.Bizware.Graphics
 		/// </summary>
 		void Clear();
 
+		/// <summary>
+		/// Discards any pending draw calls.
+		/// Similar to Clear(), except this won't insert a command to clear the target texture
+		/// </summary>
+		void Discard();
+
 		CompositingMode CompositingMode { set; }
 
 		void DrawBezier(Color color, Point pt1, Point pt2, Point pt3, Point pt4);

src/BizHawk.Bizware.Graphics/Renderers/ImGui2DRenderer.cs

@@ -302,6 +302,9 @@ namespace BizHawk.Bizware.Graphics
 			_hasClearPending = true;
 		}
 
+		public void Discard()
+			=> ResetDrawList();
+
 		protected bool EnableBlending { get; private set; }
 		private bool _pendingBlendEnable;
 

src/BizHawk.Client.Common/Api/Classes/EmuClientApi.cs

@@ -90,7 +90,7 @@ namespace BizHawk.Client.Common
 
 		public void DoFrameAdvance()
 		{
-			_mainForm.FrameAdvance();
+			_mainForm.FrameAdvance(discardApiHawkSurfaces: false); // we're rendering, so we don't want to discard
 			_mainForm.StepRunLoop_Throttle();
 			_mainForm.Render();
 		}

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

@@ -933,5 +933,13 @@ namespace BizHawk.Client.Common
 				renderer.Clear();
 			}
 		}
+
+		public void DiscardApiHawkSurfaces()
+		{
+			foreach (var renderer in _apiHawkIDTo2DRenderer.Values)
+			{
+				renderer.Discard();
+			}
+		}
 	}
 }

src/BizHawk.Client.Common/IMainFormForApi.cs

@@ -52,7 +52,7 @@ namespace BizHawk.Client.Common
 		bool FlushSaveRAM(bool autosave = false);
 
 		/// <remarks>only referenced from <c>EmuClientApi</c></remarks>
-		void FrameAdvance();
+		void FrameAdvance(bool discardApiHawkSurfaces = true);
 
 		void FrameBufferResized();
 

src/BizHawk.Client.EmuHawk/IMainFormForTools.cs

@@ -56,7 +56,7 @@ namespace BizHawk.Client.EmuHawk
 		bool EnsureCoreIsAccurate();
 
 		/// <remarks>only referenced from <see cref="TAStudio"/></remarks>
-		void FrameAdvance();
+		void FrameAdvance(bool discardApiHawkSurfaces = true);
 
 		/// <remarks>only referenced from <see cref="LuaConsole"/></remarks>
 		void FrameBufferResized();

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -2477,6 +2477,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			if (Config.DispSpeedupFeatures == 0)
 			{
+				DisplayManager.DiscardApiHawkSurfaces();
 				return;
 			}
 
@@ -3069,16 +3070,21 @@ namespace BizHawk.Client.EmuHawk
 			_throttle.Step(Config, Sound, allowSleep: true, forceFrameSkip: -1);
 		}
 
-		public void FrameAdvance()
+		public void FrameAdvance(bool discardApiHawkSurfaces)
 		{
 			PressFrameAdvance = true;
 			StepRunLoop_Core(true);
+			if (discardApiHawkSurfaces)
+			{
+				DisplayManager.DiscardApiHawkSurfaces();
+			}
 		}
 
 		public void SeekFrameAdvance()
 		{
 			PressFrameAdvance = true;
 			StepRunLoop_Core(true);
+			DisplayManager.DiscardApiHawkSurfaces();
 			PressFrameAdvance = false;
 		}