Changes ISpriteSource.Frames to be of type IReadOnlyList<ISpriteFrame>.

- Updated implementations to return a ReadOnlyList around an array (to reduce wasted memory from exposing lists or lazy enumerators around lists).
- Protect non-public ISpriteFrame classes by making them inner classes to prevent casting.
- Added an AsReadOnly extension method for lists.

OpenRA.Editor/RenderUtils.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -101,7 +101,7 @@ namespace OpenRA.Editor
 				}
 
 				bitmap.UnlockBits(data);
-				return new ResourceTemplate { Bitmap = bitmap, Info = info, Value = shp.Frames.Count() - 1 };
+				return new ResourceTemplate { Bitmap = bitmap, Info = info, Value = shp.Frames.Count - 1 };
 			}
 		}
 	}

OpenRA.Editor/TileSetRenderer.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -20,9 +20,9 @@ namespace OpenRA.Editor
 {
 	public class TileSetRenderer
 	{
+		public readonly int TileSize;
 		public TileSet TileSet;
 		Dictionary<ushort, List<byte[]>> templates;
-		public readonly int TileSize;
 
 		// Extract a square tile that the editor can render
 		byte[] ExtractSquareTile(ISpriteFrame frame)
@@ -61,7 +61,7 @@ namespace OpenRA.Editor
 			if (frames != null)
 			{
 				var ret = new List<byte[]>();
-				var srcFrames = source.Frames.ToArray();
+				var srcFrames = source.Frames;
 				foreach (var i in frames)
 					ret.Add(ExtractSquareTile(srcFrames[i]));
 

OpenRA.Game/FileFormats/R8Reader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made 
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -15,63 +15,66 @@ using OpenRA.Graphics;
 
 namespace OpenRA.FileFormats
 {
-	class R8Image : ISpriteFrame
-	{
-		public Size Size { get; private set; }
-		public Size FrameSize { get; private set; }
-		public float2 Offset { get; private set; }
-		public byte[] Data { get; set; }
-
-		public R8Image(Stream s)
-		{
-			// Scan forward until we find some data
-			var type = s.ReadUInt8();
-			while (type == 0)
-				type = s.ReadUInt8();
-
-			var width = s.ReadInt32();
-			var height = s.ReadInt32();
-			var x = s.ReadInt32();
-			var y = s.ReadInt32();
-
-			Size = new Size(width, height);
-			Offset = new int2(width/2 - x, height/2 - y);
-
-			/*var imageOffset = */s.ReadInt32();
-			var paletteOffset = s.ReadInt32();
-			var bpp = s.ReadUInt8();
-			if (bpp != 8)
-				throw new InvalidDataException("Error: {0} bits per pixel are not supported.".F(bpp));
-
-			var frameHeight = s.ReadUInt8();
-			var frameWidth = s.ReadUInt8();
-			FrameSize = new Size(frameWidth, frameHeight);
-
-			// Skip alignment byte
-			s.ReadUInt8();
-
-			Data = s.ReadBytes(width*height);
-
-			// Ignore palette
-			if (type == 1 && paletteOffset != 0)
-				s.Seek(520, SeekOrigin.Current);
-		}
-	}
-
 	public class R8Reader : ISpriteSource
 	{
-		readonly List<ISpriteFrame> frames = new List<ISpriteFrame>();
+		class R8Image : ISpriteFrame
-		public IEnumerable<ISpriteFrame> Frames { get { return frames; } }
+		{
+			public Size Size { get; private set; }
+			public Size FrameSize { get; private set; }
+			public float2 Offset { get; private set; }
+			public byte[] Data { get; set; }
+
+			public R8Image(Stream s)
+			{
+				// Scan forward until we find some data
+				var type = s.ReadUInt8();
+				while (type == 0)
+					type = s.ReadUInt8();
+
+				var width = s.ReadInt32();
+				var height = s.ReadInt32();
+				var x = s.ReadInt32();
+				var y = s.ReadInt32();
+
+				Size = new Size(width, height);
+				Offset = new int2(width / 2 - x, height / 2 - y);
+
+				/*var imageOffset = */
+				s.ReadInt32();
+				var paletteOffset = s.ReadInt32();
+				var bpp = s.ReadUInt8();
+				if (bpp != 8)
+					throw new InvalidDataException("Error: {0} bits per pixel are not supported.".F(bpp));
+
+				var frameHeight = s.ReadUInt8();
+				var frameWidth = s.ReadUInt8();
+				FrameSize = new Size(frameWidth, frameHeight);
+
+				// Skip alignment byte
+				s.ReadUInt8();
+
+				Data = s.ReadBytes(width * height);
+
+				// Ignore palette
+				if (type == 1 && paletteOffset != 0)
+					s.Seek(520, SeekOrigin.Current);
+			}
+		}
+
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
 		public bool CacheWhenLoadingTileset { get { return true; } }
 
 		public readonly int ImageCount;
 		public R8Reader(Stream stream)
 		{
+			var frames = new List<R8Image>();
 			while (stream.Position < stream.Length)
 			{
 				frames.Add(new R8Image(stream));
 				ImageCount++;
 			}
+
+			Frames = frames.ToArray().AsReadOnly();
 		}
 	}
 }

OpenRA.Game/FileFormats/ShpD2Reader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -9,83 +9,81 @@
 #endregion
 
 using System;
-using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
 using OpenRA.Graphics;
 
 namespace OpenRA.FileFormats
 {
-	[Flags] enum FormatFlags : int
-	{
-		PaletteTable = 1,
-		SkipFormat80 = 2,
-		VariableLengthTable = 4
-	}
-
-	class Frame : ISpriteFrame
-	{
-		public Size Size { get; private set; }
-		public Size FrameSize { get { return Size; } }
-		public float2 Offset { get { return float2.Zero; } }
-		public byte[] Data { get; set; }
-
-		public Frame(Stream s)
-		{
-			var flags = (FormatFlags)s.ReadUInt16();
-			s.Position += 1;
-			var width = s.ReadUInt16();
-			var height = s.ReadUInt8();
-			Size = new Size(width, height);
-
-			// Subtract header size
-			var dataLeft = s.ReadUInt16() - 10;
-			var dataSize = s.ReadUInt16();
-
-			byte[] table;
-			if ((flags & FormatFlags.PaletteTable) != 0)
-			{
-				var n = (flags & FormatFlags.VariableLengthTable) != 0 ? s.ReadUInt8() : (byte)16;
-				table = new byte[n];
-				for (var i = 0; i < n; i++)
-					table[i] = s.ReadUInt8();
-
-				dataLeft -= n;
-			}
-			else
-			{
-				table = new byte[256];
-				for (var i = 0; i < 256; i++)
-					table[i] = (byte)i;
-				table[1] = 0x7f;
-				table[2] = 0x7e;
-				table[3] = 0x7d;
-				table[4] = 0x7c;
-			}
-
-			Data = new byte[width * height];
-
-			// Decode image data
-			var compressed = s.ReadBytes(dataLeft);
-			if ((flags & FormatFlags.SkipFormat80) == 0)
-			{
-				var temp = new byte[dataSize];
-				Format80.DecodeInto(compressed, temp);
-				compressed = temp;
-			}
-
-			Format2.DecodeInto(compressed, Data, 0);
-
-			// Lookup values in lookup table
-			for (var j = 0; j < Data.Length; j++)
-				Data[j] = table[Data[j]];
-		}
-	}
-
 	public class ShpD2Reader : ISpriteSource
 	{
-		readonly List<ISpriteFrame> frames = new List<ISpriteFrame>();
+		[Flags] enum FormatFlags : int
-		public IEnumerable<ISpriteFrame> Frames { get { return frames; } }
+		{
+			PaletteTable = 1,
+			SkipFormat80 = 2,
+			VariableLengthTable = 4
+		}
+
+		class Frame : ISpriteFrame
+		{
+			public Size Size { get; private set; }
+			public Size FrameSize { get { return Size; } }
+			public float2 Offset { get { return float2.Zero; } }
+			public byte[] Data { get; set; }
+
+			public Frame(Stream s)
+			{
+				var flags = (FormatFlags)s.ReadUInt16();
+				s.Position += 1;
+				var width = s.ReadUInt16();
+				var height = s.ReadUInt8();
+				Size = new Size(width, height);
+
+				// Subtract header size
+				var dataLeft = s.ReadUInt16() - 10;
+				var dataSize = s.ReadUInt16();
+
+				byte[] table;
+				if ((flags & FormatFlags.PaletteTable) != 0)
+				{
+					var n = (flags & FormatFlags.VariableLengthTable) != 0 ? s.ReadUInt8() : (byte)16;
+					table = new byte[n];
+					for (var i = 0; i < n; i++)
+						table[i] = s.ReadUInt8();
+
+					dataLeft -= n;
+				}
+				else
+				{
+					table = new byte[256];
+					for (var i = 0; i < 256; i++)
+						table[i] = (byte)i;
+					table[1] = 0x7f;
+					table[2] = 0x7e;
+					table[3] = 0x7d;
+					table[4] = 0x7c;
+				}
+
+				Data = new byte[width * height];
+
+				// Decode image data
+				var compressed = s.ReadBytes(dataLeft);
+				if ((flags & FormatFlags.SkipFormat80) == 0)
+				{
+					var temp = new byte[dataSize];
+					Format80.DecodeInto(compressed, temp);
+					compressed = temp;
+				}
+
+				Format2.DecodeInto(compressed, Data, 0);
+
+				// Lookup values in lookup table
+				for (var j = 0; j < Data.Length; j++)
+					Data[j] = table[Data[j]];
+			}
+		}
+
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
 		public bool CacheWhenLoadingTileset { get { return false; } }
 
 		public ShpD2Reader(Stream s)
@@ -103,10 +101,12 @@ namespace OpenRA.FileFormats
 			for (var i = 0; i < imageCount + 1; i++)
 				offsets[i] = (twoByteOffset ? s.ReadUInt16() : s.ReadUInt32()) + 2;
 
-			for (var i = 0; i < imageCount; i++)
+			var frames = new Frame[imageCount];
+			Frames = frames.AsReadOnly();
+			for (var i = 0; i < frames.Length; i++)
 			{
 				s.Position = offsets[i];
-				frames.Add(new Frame(s));
+				frames[i] = new Frame(s);
 			}
 		}
 	}

OpenRA.Game/FileFormats/ShpReader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -17,50 +17,49 @@ using OpenRA.Graphics;
 
 namespace OpenRA.FileFormats
 {
-	enum Format { Format20 = 0x20, Format40 = 0x40, Format80 = 0x80 }
-
-	class ImageHeader : ISpriteFrame
-	{
-		public Size Size { get { return reader.Size; } }
-		public Size FrameSize { get { return reader.Size; } }
-		public float2 Offset { get { return float2.Zero; } }
-		public byte[] Data { get; set; }
-
-		public uint FileOffset;
-		public Format Format;
-
-		public uint RefOffset;
-		public Format RefFormat;
-		public ImageHeader RefImage;
-
-		ShpReader reader;
-		// Used by ShpWriter
-		public ImageHeader() { }
-
-		public ImageHeader(Stream stream, ShpReader reader)
-		{
-			this.reader = reader;
-			var data = stream.ReadUInt32();
-			FileOffset = data & 0xffffff;
-			Format = (Format)(data >> 24);
-
-			RefOffset = stream.ReadUInt16();
-			RefFormat = (Format)stream.ReadUInt16();
-		}
-
-		public void WriteTo(BinaryWriter writer)
-		{
-			writer.Write(FileOffset | ((uint)Format << 24));
-			writer.Write((ushort)RefOffset);
-			writer.Write((ushort)RefFormat);
-		}
-	}
-
 	public class ShpReader : ISpriteSource
 	{
-		readonly List<ImageHeader> headers = new List<ImageHeader>();
+		enum Format { Format20 = 0x20, Format40 = 0x40, Format80 = 0x80 }
-		Lazy<IEnumerable<ISpriteFrame>> spriteFrames;
+
-		public IEnumerable<ISpriteFrame> Frames { get { return spriteFrames.Value; } }
+		class ImageHeader : ISpriteFrame
+		{
+			public Size Size { get { return reader.Size; } }
+			public Size FrameSize { get { return reader.Size; } }
+			public float2 Offset { get { return float2.Zero; } }
+			public byte[] Data { get; set; }
+
+			public uint FileOffset;
+			public Format Format;
+
+			public uint RefOffset;
+			public Format RefFormat;
+			public ImageHeader RefImage;
+
+			ShpReader reader;
+
+			// Used by ShpWriter
+			public ImageHeader() { }
+
+			public ImageHeader(Stream stream, ShpReader reader)
+			{
+				this.reader = reader;
+				var data = stream.ReadUInt32();
+				FileOffset = data & 0xffffff;
+				Format = (Format)(data >> 24);
+
+				RefOffset = stream.ReadUInt16();
+				RefFormat = (Format)stream.ReadUInt16();
+			}
+
+			public void WriteTo(BinaryWriter writer)
+			{
+				writer.Write(FileOffset | ((uint)Format << 24));
+				writer.Write((ushort)RefOffset);
+				writer.Write((ushort)RefFormat);
+			}
+		}
+
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
 		public bool CacheWhenLoadingTileset { get { return false; } }
 		public readonly Size Size;
 
@@ -79,8 +78,10 @@ namespace OpenRA.FileFormats
 			Size = new Size(width, height);
 
 			stream.Position += 4;
-			for (var i = 0; i < imageCount; i++)
+			var headers = new ImageHeader[imageCount];
-				headers.Add(new ImageHeader(stream, this));
+			Frames = headers.AsReadOnly();
+			for (var i = 0; i < headers.Length; i++)
+				headers[i] = new ImageHeader(stream, this);
 
 			// Skip eof and zero headers
 			stream.Position += 16;
@@ -91,7 +92,6 @@ namespace OpenRA.FileFormats
 				var h = headers[i];
 				if (h.Format == Format.Format20)
 					h.RefImage = headers[i - 1];
-
 				else if (h.Format == Format.Format40 && !offsets.TryGetValue(h.RefOffset, out h.RefImage))
 					throw new InvalidDataException("Reference doesnt point to image data {0}->{1}".F(h.FileOffset, h.RefOffset));
 			}
@@ -101,8 +101,6 @@ namespace OpenRA.FileFormats
 
 			foreach (var h in headers)
 				Decompress(h);
-
-			spriteFrames = Exts.Lazy(() => headers.Cast<ISpriteFrame>());
 		}
 
 		void Decompress(ImageHeader h)

OpenRA.Game/FileFormats/ShpTSReader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -8,47 +8,42 @@
  */
 #endregion
 
-using System;
-using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
-using System.Linq;
 using OpenRA.Graphics;
 
 namespace OpenRA.FileFormats
 {
-	class FrameHeader : ISpriteFrame
-	{
-		public Size Size { get; private set; }
-		public Size FrameSize { get; private set; }
-		public float2 Offset { get; private set; }
-		public byte[] Data { get; set; }
-
-		public readonly uint FileOffset;
-		public readonly byte Format;
-
-		public FrameHeader(Stream stream, Size frameSize)
-		{
-			var x = stream.ReadUInt16();
-			var y = stream.ReadUInt16();
-			var width = stream.ReadUInt16();
-			var height = stream.ReadUInt16();
-
-			Offset = new float2(x + 0.5f * (width - frameSize.Width), y + 0.5f * (height - frameSize.Height));
-			Size = new Size(width, height);
-			FrameSize = frameSize;
-
-			Format = stream.ReadUInt8();
-			stream.Position += 11;
-			FileOffset = stream.ReadUInt32();
-		}
-	}
-
 	public class ShpTSReader : ISpriteSource
 	{
-		readonly List<FrameHeader> frames = new List<FrameHeader>();
+		class FrameHeader : ISpriteFrame
-		Lazy<IEnumerable<ISpriteFrame>> spriteFrames;
+		{
-		public IEnumerable<ISpriteFrame> Frames { get { return spriteFrames.Value; } }
+			public Size Size { get; private set; }
+			public Size FrameSize { get; private set; }
+			public float2 Offset { get; private set; }
+			public byte[] Data { get; set; }
+
+			public readonly uint FileOffset;
+			public readonly byte Format;
+
+			public FrameHeader(Stream stream, Size frameSize)
+			{
+				var x = stream.ReadUInt16();
+				var y = stream.ReadUInt16();
+				var width = stream.ReadUInt16();
+				var height = stream.ReadUInt16();
+
+				Offset = new float2(x + 0.5f * (width - frameSize.Width), y + 0.5f * (height - frameSize.Height));
+				Size = new Size(width, height);
+				FrameSize = frameSize;
+
+				Format = stream.ReadUInt8();
+				stream.Position += 11;
+				FileOffset = stream.ReadUInt32();
+			}
+		}
+
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
 		public bool CacheWhenLoadingTileset { get { return false; } }
 
 		public ShpTSReader(Stream stream)
@@ -59,8 +54,10 @@ namespace OpenRA.FileFormats
 			var size = new Size(width, height);
 			var frameCount = stream.ReadUInt16();
 
-			for (var i = 0; i < frameCount; i++)
+			var frames = new FrameHeader[frameCount];
-				frames.Add(new FrameHeader(stream, size));
+			Frames = frames.AsReadOnly();
+			for (var i = 0; i < frames.Length; i++)
+				frames[i] = new FrameHeader(stream, size);
 
 			for (var i = 0; i < frameCount; i++)
 			{
@@ -70,14 +67,16 @@ namespace OpenRA.FileFormats
 
 				stream.Position = f.FileOffset;
 
+				var frameSize = f.Size.Width * f.Size.Height;
+
 				// Uncompressed
 				if (f.Format == 1 || f.Format == 0)
-					f.Data = stream.ReadBytes(f.Size.Width * f.Size.Height);
+					f.Data = stream.ReadBytes(frameSize);
 
 				// Uncompressed scanlines
 				else if (f.Format == 2)
 				{
-					f.Data = new byte[f.Size.Width * f.Size.Height];
+					f.Data = new byte[frameSize];
 					for (var j = 0; j < f.Size.Height; j++)
 					{
 						var length = stream.ReadUInt16() - 2;
@@ -89,17 +88,15 @@ namespace OpenRA.FileFormats
 				// RLE-zero compressed scanlines
 				else if (f.Format == 3)
 				{
-					f.Data = new byte[f.Size.Width * f.Size.Height];
+					f.Data = new byte[frameSize];
-
 					for (var j = 0; j < f.Size.Height; j++)
 					{
 						var length = stream.ReadUInt16() - 2;
-						Format2.DecodeInto(stream.ReadBytes(length), f.Data, j * f.Size.Width);
+						var offset = f.Size.Width * j;
+						Format2.DecodeInto(stream.ReadBytes(length), f.Data, offset);
 					}
 				}
 			}
-
-			spriteFrames = Exts.Lazy(() => frames.Cast<ISpriteFrame>());
 		}
 	}
 }

OpenRA.Game/FileFormats/TmpRAReader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -8,7 +8,6 @@
  */
 #endregion
 
-using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
 using OpenRA.Graphics;
@@ -17,8 +16,7 @@ namespace OpenRA.FileFormats
 {
 	public class TmpRAReader : ISpriteSource
 	{
-		readonly List<ISpriteFrame> tiles = new List<ISpriteFrame>();
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
-		public IEnumerable<ISpriteFrame> Frames { get { return tiles; } }
 		public bool CacheWhenLoadingTileset { get { return false; } }
 
 		public TmpRAReader(Stream s)
@@ -35,15 +33,19 @@ namespace OpenRA.FileFormats
 			var indexStart = s.ReadInt32();
 
 			s.Position = indexStart;
-			foreach (var b in s.ReadBytes(indexEnd - indexStart))
+			var count = indexEnd - indexStart;
+			var tiles = new TmpTile[count];
+			Frames = tiles.AsReadOnly();
+			var tilesIndex = 0;
+			foreach (var b in s.ReadBytes(count))
 			{
 				if (b != 255)
 				{
 					s.Position = imgStart + b * width * height;
-					tiles.Add(new TmpTile(s.ReadBytes(width * height), size));
+					tiles[tilesIndex++] = new TmpTile(s.ReadBytes(width * height), size);
 				}
 				else
-					tiles.Add(new TmpTile(null, size));
+					tiles[tilesIndex++] = new TmpTile(null, size);
 			}
 		}
 	}

OpenRA.Game/FileFormats/TmpTDReader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -8,7 +8,6 @@
  */
 #endregion
 
-using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
 using OpenRA.Graphics;
@@ -36,8 +35,7 @@ namespace OpenRA.FileFormats
 
 	public class TmpTDReader : ISpriteSource
 	{
-		readonly List<ISpriteFrame> tiles = new List<ISpriteFrame>();
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
-		public IEnumerable<ISpriteFrame> Frames { get { return tiles; } }
 		public bool CacheWhenLoadingTileset { get { return false; } }
 
 		public TmpTDReader(Stream s)
@@ -53,15 +51,19 @@ namespace OpenRA.FileFormats
 			var indexStart = s.ReadInt32();
 
 			s.Position = indexStart;
-			foreach (var b in s.ReadBytes(indexEnd - indexStart))
+			var count = indexEnd - indexStart;
+			var tiles = new TmpTile[count];
+			Frames = tiles.AsReadOnly();
+			var tilesIndex = 0;
+			foreach (var b in s.ReadBytes(count))
 			{
 				if (b != 255)
 				{
 					s.Position = imgStart + b * width * height;
-					tiles.Add(new TmpTile(s.ReadBytes(width * height), size));
+					tiles[tilesIndex++] = new TmpTile(s.ReadBytes(width * height), size);
 				}
 				else
-					tiles.Add(new TmpTile(null, size));
+					tiles[tilesIndex++] = new TmpTile(null, size);
 			}
 		}
 	}

OpenRA.Game/FileFormats/TmpTSReader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -39,7 +39,7 @@ namespace OpenRA.FileFormats
 				for (var j = 0; j < width; j++)
 					Data[start + j] = s.ReadUInt8();
 
-				width += (i < size.Height / 2 - 1? 1 : -1) * 4;
+				width += (i < size.Height / 2 - 1 ? 1 : -1) * 4;
 			}
 
 			// Ignore Z-data for now
@@ -49,8 +49,7 @@ namespace OpenRA.FileFormats
 
 	public class TmpTSReader : ISpriteSource
 	{
-		readonly List<ISpriteFrame> tiles = new List<ISpriteFrame>();
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
-		public IEnumerable<ISpriteFrame> Frames { get { return tiles; } }
 		public bool CacheWhenLoadingTileset { get { return false; } }
 
 		public TmpTSReader(Stream s)
@@ -64,11 +63,14 @@ namespace OpenRA.FileFormats
 			for (var i = 0; i < offsets.Length; i++)
 				offsets[i] = s.ReadUInt32();
 
+			var tiles = new List<TmpTSTile>();
 			for (var i = 0; i < offsets.Length; i++)
 			{
 				s.Position = offsets[i];
 				tiles.Add(new TmpTSTile(s, size));
 			}
+
+			Frames = tiles.ToArray().AsReadOnly();
 		}
 	}
 }

OpenRA.Game/Graphics/SpriteSource.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -8,7 +8,6 @@
  */
 #endregion
 
-using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
 using OpenRA.FileFormats;
@@ -25,8 +24,7 @@ namespace OpenRA.Graphics
 
 	public interface ISpriteSource
 	{
-		// TODO: Change this to IReadOnlyList so users don't need to call .ToArray()
+		IReadOnlyList<ISpriteFrame> Frames { get; }
-		IEnumerable<ISpriteFrame> Frames { get; }
 		bool CacheWhenLoadingTileset { get; }
 	}
 

OpenRA.Game/Primitives/ReadOnlyList.cs

@@ -21,12 +21,20 @@ namespace OpenRA
 	/// duplicate it but provide a compatible interface that can be replaced
 	/// when we switch to .NET 4.5 or higher.
 	/// </remarks>
-	public interface IReadOnlyList<T> : IEnumerable<T>
+	public interface IReadOnlyList<out T> : IEnumerable<T>
 	{
 		int Count { get; }
 		T this[int index] { get; }
 	}
 
+	public static class ReadOnlyList
+	{
+		public static IReadOnlyList<T> AsReadOnly<T>(this IList<T> list)
+		{
+			return list as IReadOnlyList<T> ?? new ReadOnlyList<T>(list);
+		}
+	}
+
 	/// <summary>
 	/// A minimal read only list for .NET 4 implemented as a wrapper
 	/// around an IList.

OpenRA.Utility/Command.cs

@@ -233,7 +233,7 @@ namespace OpenRA.Utility
 		{
 			var srcImage = ShpReader.Load(args[1]);
 
-			var srcFrames = srcImage.Frames.ToArray();
+			var srcFrames = srcImage.Frames;
 			var destFrames = srcImage.Frames.ToArray();
 
 			for (var z = 3; z < args.Length - 2; z += 3)