movie some video provider movie logic into an extension method

BizHawk.Client.EmuHawk/MainForm.Movie.cs

@@ -44,13 +44,7 @@ namespace BizHawk.Client.EmuHawk
 
 				if (movie.SavestateFramebuffer != null && Emulator.HasVideoProvider())
 				{
-					var b1 = movie.SavestateFramebuffer;
+					Emulator.AsVideoProvider().PopulateFromBuffer(movie.SavestateFramebuffer);
-					var b2 = Emulator.AsVideoProvider().GetVideoBuffer();
-					int len = Math.Min(b1.Length, b2.Length);
-					for (int i = 0; i < len; i++)
-					{
-						b2[i] = b1[i];
-					}
 				}
 
 				Emulator.ResetCounters();

BizHawk.Emulation.Common/Interfaces/Services/IVideoProvider.cs

@@ -1,4 +1,6 @@
-namespace BizHawk.Emulation.Common
+using System;
+
+namespace BizHawk.Emulation.Common
 {
 	/// <summary>
 	/// This service provides the ability to pass video output to the client
@@ -62,4 +64,24 @@
 		/// </summary>
 		int BackgroundColor { get; }
 	}
+
+	public static class VideoProviderExtensions
+	{
+		/// <summary>
+		/// Sets the frame buffer to the given frame buffer
+		/// Note: This sets the value returned by <see cref="IVideoProvider.GetVideoBuffer" />
+		/// which relies on the core to send a reference to the frame buffer instead of a copy,
+		/// in order to work
+		/// </summary>
+		public static void PopulateFromBuffer(this IVideoProvider videoProvider, int[] frameBuffer)
+		{
+			var b1 = frameBuffer;
+			var b2 = videoProvider.GetVideoBuffer();
+			int len = Math.Min(b1.Length, b2.Length);
+			for (int i = 0; i < len; i++)
+			{
+				b2[i] = b1[i];
+			}
+		}
+	}
 }