when loading a movie, gracefully handle a movie/rom system id mismatch

BizHawk.Client.Common/BizHawk.Client.Common.csproj

@@ -104,6 +104,7 @@
     <Compile Include="config\ToolDialogSettings.cs" />
     <Compile Include="ControllerBinding.cs" />
     <Compile Include="CoreFileProvider.cs" />
+    <Compile Include="ExceptionClasses.cs" />
     <Compile Include="FirmwareManager.cs" />
     <Compile Include="GLManager.cs">
       <SubType>Code</SubType>

BizHawk.Client.Common/ExceptionClasses.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace BizHawk.Client.Common
+{
+	public class MoviePlatformMismatchException : InvalidOperationException
+	{
+		public MoviePlatformMismatchException(string message) : base(message)
+		{
+
+		}
+	}
+}

BizHawk.Client.Common/movie/MovieSession.cs

@@ -443,7 +443,11 @@ namespace BizHawk.Client.Common
 				movie.Load();
 				if (movie.SystemID != Global.Emulator.SystemId)
 				{
-					throw new InvalidOperationException("Movie does not match the currently loaded system, unable to load");
+					throw new MoviePlatformMismatchException(
+						string.Format(
+						"Movie system Id ({0}) does not match the currently loaded platform ({1}), unable to load",
+						movie.SystemID,
+						Global.Emulator.SystemId));
 				}
 			}
 

BizHawk.Client.EmuHawk/MainForm.Movie.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Windows.Forms;
 
 using BizHawk.Client.Common;
 using BizHawk.Emulation.Common;
@@ -14,7 +15,15 @@ namespace BizHawk.Client.EmuHawk
 	{
 		public void StartNewMovie(IMovie movie, bool record)
 		{
-			Global.MovieSession.QueueNewMovie(movie, record);
+			try
+			{
+				Global.MovieSession.QueueNewMovie(movie, record);
+			}
+			catch (MoviePlatformMismatchException ex)
+			{
+				MessageBox.Show(this, ex.Message, "Movie/Platform Mismatch", MessageBoxButtons.OK, MessageBoxIcon.Error);
+				return;
+			}
 
 			LoadRom(GlobalWin.MainForm.CurrentlyOpenRom);