diff --git a/src/BizHawk.Client.Common/DisplayManager/IDisplayManagerForApi.cs b/src/BizHawk.Client.Common/DisplayManager/IDisplayManagerForApi.cs
new file mode 100644
index 0000000000..fb0f8a7dda
--- /dev/null
+++ b/src/BizHawk.Client.Common/DisplayManager/IDisplayManagerForApi.cs
@@ -0,0 +1,20 @@
+using System;
+using System.Drawing.Text;
+
+namespace BizHawk.Client.Common
+{
+	public interface IDisplayManagerForApi
+	{
+		PrivateFontCollection CustomFonts { get; }
+
+		OSDManager OSD { get; }
+
+		/// <summary>locks the lua surface called <paramref name="name"/></summary>
+		/// <exception cref="InvalidOperationException">already locked, or unknown surface</exception>
+		DisplaySurface LockLuaSurface(string name, bool clear = true);
+
+		/// <summary>unlocks this DisplaySurface which had better have been locked as a lua surface</summary>
+		/// <exception cref="InvalidOperationException">already unlocked</exception>
+		void UnlockLuaSurface(DisplaySurface surface);
+	}
+}
diff --git a/src/BizHawk.Client.EmuHawk/Api/ApiManager.cs b/src/BizHawk.Client.EmuHawk/Api/ApiManager.cs
index 1c1968e2d0..beae1623c7 100644
--- a/src/BizHawk.Client.EmuHawk/Api/ApiManager.cs
+++ b/src/BizHawk.Client.EmuHawk/Api/ApiManager.cs
@@ -37,7 +37,7 @@ namespace BizHawk.Client.EmuHawk
 			IEmulatorServiceProvider serviceProvider,
 			Action<string> logCallback,
 			IMainFormForApi mainForm,
-			DisplayManager displayManager,
+			IDisplayManagerForApi displayManager,
 			InputManager inputManager,
 			IMovieSession movieSession,
 			ToolManager toolManager,
@@ -49,7 +49,7 @@ namespace BizHawk.Client.EmuHawk
 			{
 				[typeof(Action<string>)] = logCallback,
 				[typeof(IMainFormForApi)] = mainForm,
-				[typeof(DisplayManager)] = displayManager,
+				[typeof(IDisplayManagerForApi)] = displayManager,
 				[typeof(IWindowCoordsTransformer)] = displayManager,
 				[typeof(InputManager)] = inputManager,
 				[typeof(IMovieSession)] = movieSession,
@@ -72,7 +72,7 @@ namespace BizHawk.Client.EmuHawk
 		public static IExternalApiProvider Restart(
 			IEmulatorServiceProvider serviceProvider,
 			IMainFormForApi mainForm,
-			DisplayManager displayManager,
+			IDisplayManagerForApi displayManager,
 			InputManager inputManager,
 			IMovieSession movieSession,
 			ToolManager toolManager,
@@ -89,7 +89,7 @@ namespace BizHawk.Client.EmuHawk
 			IEmulatorServiceProvider serviceProvider,
 			Action<string> logCallback,
 			IMainFormForApi mainForm,
-			DisplayManager displayManager,
+			IDisplayManagerForApi displayManager,
 			InputManager inputManager,
 			IMovieSession movieSession,
 			ToolManager toolManager,
diff --git a/src/BizHawk.Client.EmuHawk/Api/Libraries/GuiApi.cs b/src/BizHawk.Client.EmuHawk/Api/Libraries/GuiApi.cs
index 583e203f5d..2e88d8fcf1 100644
--- a/src/BizHawk.Client.EmuHawk/Api/Libraries/GuiApi.cs
+++ b/src/BizHawk.Client.EmuHawk/Api/Libraries/GuiApi.cs
@@ -18,7 +18,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private readonly Action<string> LogCallback;
 
-		private readonly DisplayManager _displayManager;
+		private readonly IDisplayManagerForApi _displayManager;
 
 		private readonly Dictionary<string, Image> _imageCache = new Dictionary<string, Image>();
 
@@ -46,7 +46,7 @@ namespace BizHawk.Client.EmuHawk
 
 		public bool HasGUISurface => _GUISurface != null;
 
-		public GuiApi(Action<string> logCallback, DisplayManager displayManager)
+		public GuiApi(Action<string> logCallback, IDisplayManagerForApi displayManager)
 		{
 			LogCallback = logCallback;
 			_displayManager = displayManager;
diff --git a/src/BizHawk.Client.EmuHawk/DisplayManager/DisplayManager.cs b/src/BizHawk.Client.EmuHawk/DisplayManager/DisplayManager.cs
index 4994a24594..706993d6ad 100644
--- a/src/BizHawk.Client.EmuHawk/DisplayManager/DisplayManager.cs
+++ b/src/BizHawk.Client.EmuHawk/DisplayManager/DisplayManager.cs
@@ -30,7 +30,7 @@ namespace BizHawk.Client.EmuHawk
 	/// Its job is to receive OSD and emulator outputs, and produce one single buffer (BitmapBuffer? Texture2d?) for display by the PresentationPanel.
 	/// Details TBD
 	/// </summary>
-	public class DisplayManager : IWindowCoordsTransformer, IDisposable
+	public class DisplayManager : IDisplayManagerForApi, IWindowCoordsTransformer, IDisposable
 	{
 		private class DisplayManagerRenderTargetProvider : IRenderTargetProvider
 		{
@@ -49,7 +49,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private readonly Func<bool> _getIsSecondaryThrottlingDisabled;
 
-		public readonly OSDManager OSD;
+		public OSDManager OSD { get; }
 
 		private Config GlobalConfig;
 
@@ -214,7 +214,7 @@ namespace BizHawk.Client.EmuHawk
 		/// <summary>
 		/// custom fonts that don't need to be installed on the user side
 		/// </summary>
-		public PrivateFontCollection CustomFonts = new PrivateFontCollection();
+		public PrivateFontCollection CustomFonts { get; } = new PrivateFontCollection();
 
 		private readonly TextureFrugalizer _videoTextureFrugalizer;
 		private readonly Dictionary<string, TextureFrugalizer> _luaSurfaceFrugalizers = new Dictionary<string, TextureFrugalizer>();
diff --git a/src/BizHawk.Client.EmuHawk/tools/Lua/Win32LuaLibraries.cs b/src/BizHawk.Client.EmuHawk/tools/Lua/Win32LuaLibraries.cs
index 8d0057fa6f..91dbab46ec 100644
--- a/src/BizHawk.Client.EmuHawk/tools/Lua/Win32LuaLibraries.cs
+++ b/src/BizHawk.Client.EmuHawk/tools/Lua/Win32LuaLibraries.cs
@@ -18,7 +18,7 @@ namespace BizHawk.Client.EmuHawk
 		public Win32LuaLibraries(
 			IEmulatorServiceProvider serviceProvider,
 			MainForm mainForm,
-			DisplayManager displayManager,
+			IDisplayManagerForApi displayManager,
 			InputManager inputManager,
 			Config config,
 			IEmulator emulator,
@@ -104,7 +104,7 @@ namespace BizHawk.Client.EmuHawk
 			EnumerateLuaFunctions(nameof(LuaCanvas), typeof(LuaCanvas), null); // add LuaCanvas to Lua function reference table
 		}
 
-		private readonly DisplayManager _displayManager;
+		private readonly IDisplayManagerForApi _displayManager;
 
 		private readonly InputManager _inputManager;