diff --git a/OpenRA.Editor/Form1.cs b/OpenRA.Editor/Form1.cs
index b12540232b..f8ac9c94e8 100644
--- a/OpenRA.Editor/Form1.cs
+++ b/OpenRA.Editor/Form1.cs
@@ -4,6 +4,7 @@ using System.Drawing;
 using System.IO;
 using System.Windows.Forms;
 using OpenRA.FileFormats;
+using System.Drawing.Imaging;
 
 namespace OpenRA.Editor
 {
@@ -22,13 +23,13 @@ namespace OpenRA.Editor
 			foreach (var pkg in manifest.Packages) FileSystem.Mount(pkg);
 
 			// load the map
-			var map = new Map(new Folder("mods/ra/maps/mjolnir"));
+			var map = new Map(new Folder("mods/ra/maps/scm01ea"));
 
 			// we're also going to need a tileset...
 			var tsinfo = fileMapping[Pair.New(mods[0], map.Theater)];
 			var tileset = new TileSet("tileset.til", "templates.ini", tsinfo.First);
 
-			var palette = new Palette( FileSystem.Open( map.Theater.ToLowerInvariant() + ".pal" ), true);
+			var palette = new Palette(FileSystem.Open(map.Theater.ToLowerInvariant() + ".pal"), true);
 
 			surface1.TileSet = tileset;
 			surface1.Map = map;
@@ -36,7 +37,7 @@ namespace OpenRA.Editor
 
 			// construct the palette of tiles
 
-			foreach( var n in tileset.tiles.Keys )
+			foreach (var n in tileset.tiles.Keys)
 			{
 				try
 				{
@@ -94,18 +95,27 @@ namespace OpenRA.Editor
 			var tile = ts.tiles[n];
 
 			var bitmap = new Bitmap(24 * template.Size.X, 24 * template.Size.Y);
+			var data = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height),
+				ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
 
-			for( var u = 0; u < template.Size.X; u++ )
-				for( var v = 0; v < template.Size.Y; v++ )
-					if (template.TerrainType.ContainsKey(u + v * template.Size.X))
-					{
-						var rawImage = tile.TileBitmapBytes[u + v * template.Size.X];
-						for (var i = 0; i < 24; i++)
-							for (var j = 0; j < 24; j++)
-								bitmap.SetPixel(u * 24 + i, v * 24 + j, p.GetColor(rawImage[i + 24 * j]));
-					}
+			unsafe
+			{
+				int* q = (int*)data.Scan0.ToPointer();
+				var stride = data.Stride >> 2;
 
+				for (var u = 0; u < template.Size.X; u++)
+					for (var v = 0; v < template.Size.Y; v++)
+						if (template.TerrainType.ContainsKey(u + v * template.Size.X))
+						{
+							var rawImage = tile.TileBitmapBytes[u + v * template.Size.X];
+							for (var i = 0; i < 24; i++)
+								for (var j = 0; j < 24; j++)
+									q[(v * 24 + j) * stride + u * 24 + i] = p.GetColor(rawImage[i + 24 * j]).ToArgb();
+						}
+			}
+
+			bitmap.UnlockBits(data);
 			return bitmap;
 		}
 	}
-}
+}
\ No newline at end of file
diff --git a/OpenRA.Editor/Surface.cs b/OpenRA.Editor/Surface.cs
index e014bb0ead..20e8350115 100644
--- a/OpenRA.Editor/Surface.cs
+++ b/OpenRA.Editor/Surface.cs
@@ -27,7 +27,7 @@ namespace OpenRA.Editor
 			UpdateStyles();
 		}
 
-		static readonly Pen RedPen = new Pen(Color.Red);
+		static readonly Pen CordonPen = new Pen(Color.Red);
 		int2 MousePos;
 
 		protected override void OnMouseMove(MouseEventArgs e)
@@ -86,9 +86,6 @@ namespace OpenRA.Editor
 			var bitmap = new Bitmap(ChunkSize * 24, ChunkSize * 24);
 			bitmap.SetPixel(0, 0, Color.Green);
 
-			var hx = Math.Min(Map.Width - u * ChunkSize, ChunkSize);
-			var hy = Math.Min(Map.Height - v * ChunkSize, ChunkSize);
-
 			var data = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), 
 				ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
 
@@ -97,8 +94,8 @@ namespace OpenRA.Editor
 				int* p = (int*)data.Scan0.ToPointer();
 				var stride = data.Stride >> 2;
 
-				for (var i = 0; i < hx; i++)
-					for (var j = 0; j < hy; j++)
+				for (var i = 0; i < ChunkSize; i++)
+					for (var j = 0; j < ChunkSize; j++)
 					{
 						var tr = Map.MapTiles[u * ChunkSize + i, v * ChunkSize + j];
 						var tile = TileSet.tiles[tr.type];
@@ -126,14 +123,17 @@ namespace OpenRA.Editor
 			if (Map == null) return;
 			if (TileSet == null) return;
 
-			for( var u = Map.TopLeft.X - Map.TopLeft.X % ChunkSize; u < Map.BottomRight.X; u += ChunkSize )
-				for (var v = Map.TopLeft.Y - Map.TopLeft.Y % ChunkSize; v < Map.BottomRight.Y; v += ChunkSize)
+			for( var u = Map.TopLeft.X - Map.TopLeft.X % ChunkSize; u <= Map.BottomRight.X; u += ChunkSize )
+				for (var v = Map.TopLeft.Y - Map.TopLeft.Y % ChunkSize; v <= Map.BottomRight.Y; v += ChunkSize)
 				{
 					var x = new int2(u/ChunkSize,v/ChunkSize);
 					if (!Chunks.ContainsKey(x)) Chunks[x] = RenderChunk(u / ChunkSize, v / ChunkSize);
 					e.Graphics.DrawImage(Chunks[x], (24 * ChunkSize * x + Offset).ToPoint());
 				}
 
+			e.Graphics.DrawRectangle(CordonPen,
+				new Rectangle(Map.XOffset * 24 + Offset.X, Map.YOffset * 24 + Offset.Y, Map.Width * 24, Map.Height * 24));
+
 			if (Brush.Second != null)
 				e.Graphics.DrawImage(Brush.Second,
 					(24 * GetBrushLocation() + Offset).ToPoint());
diff --git a/OpenRA.FileFormats/Session.cs b/OpenRA.FileFormats/Session.cs
index ff9254630e..5bd59eceeb 100644
--- a/OpenRA.FileFormats/Session.cs
+++ b/OpenRA.FileFormats/Session.cs
@@ -86,6 +86,9 @@ namespace OpenRA.FileFormats
 			ShellmapUid = yaml["ShellmapUid"].Value;
 		}
 
-		static string[] YamlList(Dictionary<string, MiniYaml> ys, string key) { return ys[key].Nodes.Keys.ToArray(); }
+		static string[] YamlList(Dictionary<string, MiniYaml> ys, string key)
+		{
+			return ys.ContainsKey(key) ? ys[key].Nodes.Keys.ToArray() : new string[] { };
+		}
 	}
 }