fix coding style

For indexed PNGs, we only need to allocate a palette large enough to accommodate the number of indexed colours in the image. For images that don't use all 256 colours, this slightly reduces the memory usage for these images.

.github/workflows/ci.yml

@@ -15,10 +15,10 @@ jobs:
 
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install .NET 6.0
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.0.x'
 
@@ -39,7 +39,7 @@ jobs:
 
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Check Code
         run: |
@@ -57,10 +57,10 @@ jobs:
 
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install .NET 6.0
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.0.x'
 

.github/workflows/documentation.yml

@@ -1,6 +1,9 @@
 name: Deploy Documentation
 
 on:
+  push:
+    branches: [ bleed ]
+    tags: [ 'release-*', 'playtest-*' ]
   workflow_dispatch:
     inputs:
       tag:
@@ -12,18 +15,49 @@ permissions:
   contents: read  #  to fetch code (actions/checkout)
 
 jobs:
-  wiki:
-    name: Update Wiki
+  prepare:
+    name: Prepare version strings
     if: github.repository == 'openra/openra'
     runs-on: ubuntu-22.04
     steps:
+      - name: Prepare environment variables
+        run: |
+          if [ "${{ github.event_name }}" = "push" ]; then
+            if [ "${{ github.ref_type }}" = "tag" ]; then
+              VERSION_TYPE=`echo "${GITHUB_REF#refs/tags/}" | cut -d"-" -f1`
+              echo "GIT_TAG=${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV
+              echo "VERSION_TYPE=$VERSION_TYPE" >> $GITHUB_ENV
+            else
+              echo "GIT_TAG=bleed" >> $GITHUB_ENV
+              echo "VERSION_TYPE=bleed" >> $GITHUB_ENV
+            fi
+          else
+            VERSION_TYPE=`echo "${{ github.event.inputs.tag }}" | cut -d"-" -f1`
+            echo "GIT_TAG=${{ github.event.inputs.tag }}" >> $GITHUB_ENV
+            echo "VERSION_TYPE=$VERSION_TYPE" >> $GITHUB_ENV
+          fi
+    outputs:
+      git_tag: ${{ env.GIT_TAG }}
+      version_type: ${{ env.VERSION_TYPE }}
+
+  wiki:
+    name: Update Wiki
+    needs: prepare
+    if: github.repository == 'openra/openra' && needs.prepare.outputs.version_type != 'bleed'
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Debug output
+        run: |
+          echo ${{ needs.prepare.outputs.git_tag }}
+          echo ${{ needs.prepare.outputs.version_type }}
+
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.inputs.tag }}
+          ref: ${{ needs.prepare.outputs.git_tag }}
 
       - name: Install .NET 6
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.0.x'
 
@@ -32,49 +66,53 @@ jobs:
           make all
 
       - name: Clone Wiki
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: openra/openra.wiki
           token: ${{ secrets.DOCS_TOKEN }}
           path: wiki
 
       - name: Update Wiki (Playtest)
-        if: startsWith(github.event.inputs.tag, 'playtest-')
-        env:
-          GIT_TAG: ${{ github.event.inputs.tag }}
+        if: startsWith(needs.prepare.outputs.git_tag, 'playtest-')
         run: |
-          ./utility.sh all --settings-docs "${GIT_TAG}" > "wiki/Settings (playtest).md"
+          ./utility.sh all --settings-docs "${{ needs.prepare.outputs.git_tag }}" > "wiki/Settings (playtest).md"
 
       - name: Update Wiki (Release)
-        if: startsWith(github.event.inputs.tag, 'release-')
-        env:
-          GIT_TAG: ${{ github.event.inputs.tag }}
+        if: startsWith(needs.prepare.outputs.git_tag, 'release-')
         run: |
-          ./utility.sh all --settings-docs "${GIT_TAG}" > "wiki/Settings.md"
+          ./utility.sh all --settings-docs "${{ needs.prepare.outputs.git_tag }}" > "wiki/Settings.md"
 
       - name: Push Wiki
-        env:
-          GIT_TAG: ${{ github.event.inputs.tag }}
         run: |
           cd wiki
           git config --local user.email "actions@github.com"
           git config --local user.name "GitHub Actions"
-          git add --all
-          git commit -m "Update auto-generated documentation for ${GIT_TAG}"
-          git push origin master
+          git status
+          git diff-index --quiet HEAD || \
+          (
+            git add --all && \
+            git commit -m "Update auto-generated documentation for ${{ needs.prepare.outputs.git_tag }}" && \
+            git push origin master
+          )
 
   docs:
     name: Update docs.openra.net
+    needs: prepare
     if: github.repository == 'openra/openra'
     runs-on: ubuntu-22.04
     steps:
+      - name: Debug output
+        run: |
+          echo ${{ needs.prepare.outputs.git_tag }}
+          echo ${{ needs.prepare.outputs.version_type }}
+
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.inputs.tag }}
+          ref: ${{ needs.prepare.outputs.git_tag }}
 
       - name: Install .NET 6
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.0.x'
 
@@ -82,62 +120,31 @@ jobs:
         run: |
           make all
 
-      - name: Clone docs.openra.net (Playtest)
-        if: startsWith(github.event.inputs.tag, 'playtest-')
-        uses: actions/checkout@v3
+      # version_type is release/playtest/bleed - the name of the target branch.
+      - name: Clone docs.openra.net
+        uses: actions/checkout@v4
         with:
           repository: openra/docs
           token: ${{ secrets.DOCS_TOKEN }}
           path: docs
-          ref: playtest
+          ref: ${{ needs.prepare.outputs.version_type }}
 
-      - name: Clone docs.openra.net (Release)
-        if: startsWith(github.event.inputs.tag, 'release-')
-        uses: actions/checkout@v3
-        with:
-          repository: openra/docs
-          token: ${{ secrets.DOCS_TOKEN }}
-          path: docs
-          ref: release
-
-      - name: Update docs.openra.net (Playtest)
-        if: startsWith(github.event.inputs.tag, 'playtest-')
-        env:
-          GIT_TAG: ${{ github.event.inputs.tag }}
+      - name: Generate docs files
         run: |
-          ./utility.sh all --docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/traits.md"
-          ./utility.sh all --weapon-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/weapons.md"
-          ./utility.sh all --sprite-sequence-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/sprite-sequences.md"
-          ./utility.sh all --lua-docs "${GIT_TAG}" > "docs/api/lua.md"
+          ./utility.sh all --docs "${{ needs.prepare.outputs.git_tag }}" | python3 ./packaging/format-docs.py > "docs/api/traits.md"
+          ./utility.sh all --weapon-docs "${{ needs.prepare.outputs.git_tag }}" | python3 ./packaging/format-docs.py > "docs/api/weapons.md"
+          ./utility.sh all --sprite-sequence-docs "${{ needs.prepare.outputs.git_tag }}" | python3 ./packaging/format-docs.py > "docs/api/sprite-sequences.md"
+          ./utility.sh all --lua-docs "${{ needs.prepare.outputs.git_tag }}" > "docs/api/lua.md"
 
-      - name: Update docs.openra.net (Release)
-        if: startsWith(github.event.inputs.tag, 'release-')
-        env:
-          GIT_TAG: ${{ github.event.inputs.tag }}
-        run: |
-          ./utility.sh all --docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/traits.md"
-          ./utility.sh all --weapon-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/weapons.md"
-          ./utility.sh all --sprite-sequence-docs "${GIT_TAG}" | python3 ./packaging/format-docs.py > "docs/api/sprite-sequences.md"
-          ./utility.sh all --lua-docs "${GIT_TAG}" > "docs/api/lua.md"
-
-      - name: Commit docs.openra.net
-        env:
-          GIT_TAG: ${{ github.event.inputs.tag }}
+      - name: Update docs.openra.net
         run: |
           cd docs
           git config --local user.email "actions@github.com"
           git config --local user.name "GitHub Actions"
-          git add api/*.md
-          git commit -m "Update auto-generated documentation for ${GIT_TAG}"
-
-      - name: Push docs.openra.net (Release)
-        if: startsWith(github.event.inputs.tag, 'release-')
-        run: |
-          cd docs
-          git push origin release
-
-      - name: Push docs.openra.net (Playtest)
-        if: startsWith(github.event.inputs.tag, 'playtest-')
-        run: |
-          cd docs
-          git push origin playtest
+          git status
+          git diff-index --quiet HEAD || \
+          (
+            git add api/*.md && \
+            git commit -m "Update auto-generated documentation for ${{ needs.prepare.outputs.git_tag }}" && \
+            git push origin ${{ needs.prepare.outputs.version_type }}
+          )

.github/workflows/packaging.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Prepare Environment
         run: echo "GIT_TAG=${GITHUB_REF#refs/tags/}" >> ${GITHUB_ENV}
@@ -40,10 +40,10 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install .NET 6.0
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.0.x'
 
@@ -70,10 +70,10 @@ jobs:
     runs-on: macos-11
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install .NET 6.0
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.0.x'
 
@@ -105,10 +105,10 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install .NET 6.0
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: '6.0.x'
 

AUTHORS

@@ -150,6 +150,7 @@ Also thanks to:
     * Teemu Nieminen (Temeez)
     * Thomas Christlieb (ThomasChr)
     * Tim Mylemans (gecko)
+    * Tinix
     * Tirili
     * Tomas Einarsson (Mesacer)
     * Tom van Leth (tovl)

Directory.Build.props

@@ -33,7 +33,7 @@
     <Optimize>false</Optimize>
     <!-- Enable only for Debug builds to improve compile-time performance for Release builds -->
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
-    <!-- Enabling GenerateDocumentationFile is required for IDE0005 (Remove unnecessary import) 
+    <!-- Enabling GenerateDocumentationFile is required for IDE0005 (Remove unnecessary import)
       rule to run in command line builds. https://github.com/dotnet/roslyn/issues/41640
       Enable only for Debug builds to improve compile-time performance for Release builds -->
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
@@ -51,8 +51,10 @@
     </ItemGroup>
   </Target>
 
-  <!-- StyleCop -->
+  <!-- StyleCop/Roslynator -->
   <ItemGroup>
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.435" PrivateAssets="All" />
+    <!-- Roslynator analyzers fail to run under Mono (AD0001) -->
+    <PackageReference Include="Roslynator.Analyzers" Version="4.2.0" PrivateAssets="All" Condition="'$(MSBuildRuntimeType)'!='Mono'" />
   </ItemGroup>
 </Project>

OpenRA.Game/Activities/Activity.cs

@@ -146,18 +146,22 @@ namespace OpenRA.Activities
 		}
 
 		/// <summary>
+		/// <para>
 		/// Called every tick to run activity logic. Returns false if the activity should
 		/// remain active, or true if it is complete. Cancelled activities must ensure they
 		/// return the actor to a consistent state before returning true.
-		///
+		/// </para>
+		/// <para>
 		/// Child activities can be queued using QueueChild, and these will be ticked
 		/// instead of the parent while they are active. Activities that need to run logic
 		/// in parallel with child activities should set ChildHasPriority to false and
 		/// manually call TickChildren.
-		///
+		/// </para>
+		/// <para>
 		/// Queuing one or more child activities and returning true is valid, and causes
 		/// the activity to be completed immediately (without ticking again) once the
 		/// children have completed.
+		/// </para>
 		/// </summary>
 		public virtual bool Tick(Actor self)
 		{
@@ -222,10 +226,11 @@ namespace OpenRA.Activities
 		}
 
 		/// <summary>
-		/// Prints the activity tree, starting from the top or optionally from a given origin.
-		///
+		/// <para>Prints the activity tree, starting from the top or optionally from a given origin.</para>
+		/// <para>
 		/// Call this method from any place that's called during a tick, such as the Tick() method itself or
 		/// the Before(First|Last)Run() methods. The origin activity will be marked in the output.
+		/// </para>
 		/// </summary>
 		/// <param name="self">The actor performing this activity.</param>
 		/// <param name="origin">Activity from which to start traversing, and which to mark. If null, mark the calling activity, and start traversal from the top.</param>

OpenRA.Game/Actor.cs

@@ -71,7 +71,12 @@ namespace OpenRA
 		public IEffectiveOwner EffectiveOwner { get; }
 		public IOccupySpace OccupiesSpace { get; }
 		public ITargetable[] Targetables { get; }
-		public IEnumerable<ITargetablePositions> EnabledTargetablePositions { get; private set; }
+		public IEnumerable<ITargetablePositions> EnabledTargetablePositions { get; }
+		readonly ICrushable[] crushables;
+		public ICrushable[] Crushables
+		{
+			get => crushables ?? throw new InvalidOperationException($"Crushables for {Info.Name} are not initialized.");
+		}
 
 		public bool IsIdle => CurrentActivity == null;
 		public bool IsDead => Disposed || (health != null && health.IsDead);
@@ -155,6 +160,7 @@ namespace OpenRA
 				var targetablesList = new List<ITargetable>();
 				var targetablePositionsList = new List<ITargetablePositions>();
 				var syncHashesList = new List<SyncHash>();
+				var crushablesList = new List<ICrushable>();
 
 				foreach (var traitInfo in Info.TraitsInConstructOrder())
 				{
@@ -181,6 +187,7 @@ namespace OpenRA
 					{ if (trait is ITargetable t) targetablesList.Add(t); }
 					{ if (trait is ITargetablePositions t) targetablePositionsList.Add(t); }
 					{ if (trait is ISync t) syncHashesList.Add(new SyncHash(t)); }
+					{ if (trait is ICrushable t) crushablesList.Add(t); }
 				}
 
 				resolveOrders = resolveOrdersList.ToArray();
@@ -195,6 +202,7 @@ namespace OpenRA
 				EnabledTargetablePositions = targetablePositions.Where(Exts.IsTraitEnabled);
 				enabledTargetableWorldPositions = EnabledTargetablePositions.SelectMany(tp => tp.TargetablePositions(this));
 				SyncHashes = syncHashesList.ToArray();
+				crushables = crushablesList.ToArray();
 			}
 		}
 

OpenRA.Game/CVec.cs

@@ -61,14 +61,14 @@ namespace OpenRA
 
 		public static readonly CVec[] Directions =
 		{
-			new CVec(-1, -1),
-			new CVec(-1,  0),
-			new CVec(-1,  1),
-			new CVec(0, -1),
-			new CVec(0,  1),
-			new CVec(1, -1),
-			new CVec(1,  0),
-			new CVec(1,  1),
+			new(-1, -1),
+			new(-1,  0),
+			new(-1,  1),
+			new(0, -1),
+			new(0,  1),
+			new(1, -1),
+			new(1,  0),
+			new(1,  1),
 		};
 
 		#region Scripting interface

OpenRA.Game/CryptoUtil.cs

@@ -22,6 +22,9 @@ namespace OpenRA
 		// Fixed byte pattern for the OID header
 		static readonly byte[] OIDHeader = { 0x30, 0xD, 0x6, 0x9, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0xD, 0x1, 0x1, 0x1, 0x5, 0x0 };
 
+		static readonly char[] HexUpperAlphabet = "0123456789ABCDEF".ToArray();
+		static readonly char[] HexLowerAlphabet = "0123456789abcdef".ToArray();
+
 		public static string PublicKeyFingerprint(RSAParameters parameters)
 		{
 			// Public key fingerprint is defined as the SHA1 of the modulus + exponent bytes
@@ -53,33 +56,33 @@ namespace OpenRA
 				using (var s = new MemoryStream(data))
 				{
 					// SEQUENCE
-					s.ReadByte();
+					s.ReadUInt8();
 					ReadTLVLength(s);
 
 					// SEQUENCE -> fixed header junk
-					s.ReadByte();
+					s.ReadUInt8();
 					var headerLength = ReadTLVLength(s);
 					s.Position += headerLength;
 
 					// SEQUENCE -> BIT_STRING
-					s.ReadByte();
+					s.ReadUInt8();
 					ReadTLVLength(s);
-					s.ReadByte();
+					s.ReadUInt8();
 
 					// SEQUENCE -> BIT_STRING -> SEQUENCE
-					s.ReadByte();
+					s.ReadUInt8();
 					ReadTLVLength(s);
 
 					// SEQUENCE -> BIT_STRING -> SEQUENCE -> INTEGER (modulus)
-					s.ReadByte();
+					s.ReadUInt8();
 					var modulusLength = ReadTLVLength(s);
-					s.ReadByte();
+					s.ReadUInt8();
 					var modulus = s.ReadBytes(modulusLength - 1);
 
 					// SEQUENCE -> BIT_STRING -> SEQUENCE -> INTEGER (exponent)
-					s.ReadByte();
+					s.ReadUInt8();
 					var exponentLength = ReadTLVLength(s);
-					s.ReadByte();
+					s.ReadUInt8();
 					var exponent = s.ReadBytes(exponentLength - 1);
 
 					return new RSAParameters
@@ -158,13 +161,13 @@ namespace OpenRA
 
 		static int ReadTLVLength(Stream s)
 		{
-			var length = s.ReadByte();
+			var length = s.ReadUInt8();
 			if (length < 0x80)
 				return length;
 
-			var data = new byte[4];
-			s.ReadBytes(data, 0, Math.Min(length & 0x7F, 4));
-			return BitConverter.ToInt32(data.ToArray(), 0);
+			Span<byte> data = stackalloc byte[4];
+			s.ReadBytes(data[..Math.Min(length & 0x7F, 4)]);
+			return BitConverter.ToInt32(data);
 		}
 
 		static int TripletFullLength(int dataLength)
@@ -249,19 +252,44 @@ namespace OpenRA
 
 		public static string SHA1Hash(Stream data)
 		{
-			using (var csp = SHA1.Create())
-				return new string(csp.ComputeHash(data).SelectMany(a => a.ToString("x2")).ToArray());
+			using var csp = SHA1.Create();
+			return ToHex(csp.ComputeHash(data), true);
 		}
 
 		public static string SHA1Hash(byte[] data)
 		{
-			using (var csp = SHA1.Create())
-				return new string(csp.ComputeHash(data).SelectMany(a => a.ToString("x2")).ToArray());
+			using var csp = SHA1.Create();
+			return ToHex(csp.ComputeHash(data), true);
 		}
 
 		public static string SHA1Hash(string data)
 		{
 			return SHA1Hash(Encoding.UTF8.GetBytes(data));
 		}
+
+		public static string ToHex(ReadOnlySpan<byte> source, bool lowerCase = false)
+		{
+			if (source.Length == 0)
+				return string.Empty;
+
+			// excessively avoid stack overflow if source is too large (considering that we're allocating a new string)
+			var buffer = source.Length <= 256 ? stackalloc char[source.Length * 2] : new char[source.Length * 2];
+			return ToHexInternal(source, buffer, lowerCase);
+		}
+
+		static string ToHexInternal(ReadOnlySpan<byte> source, Span<char> buffer, bool lowerCase)
+		{
+			var sourceIndex = 0;
+			var alphabet = lowerCase ? HexLowerAlphabet : HexUpperAlphabet;
+
+			for (var i = 0; i < buffer.Length; i += 2)
+			{
+				var b = source[sourceIndex++];
+				buffer[i] = alphabet[b >> 4];
+				buffer[i + 1] = alphabet[b & 0xF];
+			}
+
+			return new string(buffer);
+		}
 	}
 }

OpenRA.Game/ExternalMods.cs

@@ -66,6 +66,7 @@ namespace OpenRA
 			// Several types of support directory types are available, depending on
 			// how the player has installed and launched the game.
 			// Read registration metadata from all of them
+			var stringPool = new HashSet<string>(); // Reuse common strings in YAML
 			foreach (var source in GetSupportDirs(ModRegistration.User | ModRegistration.System))
 			{
 				var metadataPath = Path.Combine(source, "ModMetadata");
@@ -76,7 +77,7 @@ namespace OpenRA
 				{
 					try
 					{
-						var yaml = MiniYaml.FromStream(File.OpenRead(path), path).First().Value;
+						var yaml = MiniYaml.FromFile(path, stringPool: stringPool).First().Value;
 						LoadMod(yaml, path);
 					}
 					catch (Exception e)
@@ -94,17 +95,17 @@ namespace OpenRA
 
 			if (sheetBuilder != null)
 			{
-				var iconNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon");
+				var iconNode = yaml.NodeWithKeyOrDefault("Icon");
 				if (iconNode != null && !string.IsNullOrEmpty(iconNode.Value.Value))
 					using (var stream = new MemoryStream(Convert.FromBase64String(iconNode.Value.Value)))
 						mod.Icon = sheetBuilder.Add(new Png(stream));
 
-				var icon2xNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon2x");
+				var icon2xNode = yaml.NodeWithKeyOrDefault("Icon2x");
 				if (icon2xNode != null && !string.IsNullOrEmpty(icon2xNode.Value.Value))
 					using (var stream = new MemoryStream(Convert.FromBase64String(icon2xNode.Value.Value)))
 						mod.Icon2x = sheetBuilder.Add(new Png(stream), 1f / 2);
 
-				var icon3xNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon3x");
+				var icon3xNode = yaml.NodeWithKeyOrDefault("Icon3x");
 				if (icon3xNode != null && !string.IsNullOrEmpty(icon3xNode.Value.Value))
 					using (var stream = new MemoryStream(Convert.FromBase64String(icon3xNode.Value.Value)))
 						mod.Icon3x = sheetBuilder.Add(new Png(stream), 1f / 3);
@@ -122,7 +123,7 @@ namespace OpenRA
 				return;
 
 			var key = ExternalMod.MakeKey(mod);
-			var yaml = new MiniYamlNode("Registration", new MiniYaml("", new List<MiniYamlNode>()
+			var yaml = new MiniYamlNode("Registration", new MiniYaml("", new[]
 			{
 				new MiniYamlNode("Id", mod.Id),
 				new MiniYamlNode("Version", mod.Metadata.Version),
@@ -131,17 +132,21 @@ namespace OpenRA
 				new MiniYamlNode("LaunchArgs", new[] { "Game.Mod=" + mod.Id }.Concat(launchArgs).JoinWith(", "))
 			}));
 
+			var iconNodes = new List<MiniYamlNode>();
+
 			using (var stream = mod.Package.GetStream("icon.png"))
 				if (stream != null)
-					yaml.Value.Nodes.Add(new MiniYamlNode("Icon", Convert.ToBase64String(stream.ReadAllBytes())));
+					iconNodes.Add(new MiniYamlNode("Icon", Convert.ToBase64String(stream.ReadAllBytes())));
 
 			using (var stream = mod.Package.GetStream("icon-2x.png"))
 				if (stream != null)
-					yaml.Value.Nodes.Add(new MiniYamlNode("Icon2x", Convert.ToBase64String(stream.ReadAllBytes())));
+					iconNodes.Add(new MiniYamlNode("Icon2x", Convert.ToBase64String(stream.ReadAllBytes())));
 
 			using (var stream = mod.Package.GetStream("icon-3x.png"))
 				if (stream != null)
-					yaml.Value.Nodes.Add(new MiniYamlNode("Icon3x", Convert.ToBase64String(stream.ReadAllBytes())));
+					iconNodes.Add(new MiniYamlNode("Icon3x", Convert.ToBase64String(stream.ReadAllBytes())));
+
+			yaml = yaml.WithValue(yaml.Value.WithNodesAppended(iconNodes));
 
 			var sources = new HashSet<string>();
 			if (registration.HasFlag(ModRegistration.System))
@@ -201,7 +206,7 @@ namespace OpenRA
 					string modKey = null;
 					try
 					{
-						var yaml = MiniYaml.FromStream(File.OpenRead(path), path).First().Value;
+						var yaml = MiniYaml.FromFile(path).First().Value;
 						var m = FieldLoader.Load<ExternalMod>(yaml);
 						modKey = ExternalMod.MakeKey(m);
 

OpenRA.Game/Exts.cs

@@ -22,15 +22,14 @@ namespace OpenRA
 {
 	public static class Exts
 	{
-		public static bool IsUppercase(this string str)
+		public static string FormatInvariant(this string format, params object[] args)
 		{
-			return string.Compare(str.ToUpperInvariant(), str, false) == 0;
+			return string.Format(CultureInfo.InvariantCulture, format, args);
 		}
 
-		public static T WithDefault<T>(T def, Func<T> f)
+		public static string FormatCurrent(this string format, params object[] args)
 		{
-			try { return f(); }
-			catch { return def; }
+			return string.Format(CultureInfo.CurrentCulture, format, args);
 		}
 
 		public static Lazy<T> Lazy<T>(Func<T> p) { return new Lazy<T>(p); }
@@ -131,11 +130,35 @@ namespace OpenRA
 			return ret;
 		}
 
+		public static T GetOrAdd<T>(this HashSet<T> set, T value)
+		{
+			if (!set.TryGetValue(value, out var ret))
+				set.Add(ret = value);
+			return ret;
+		}
+
+		public static T GetOrAdd<T>(this HashSet<T> set, T value, Func<T, T> createFn)
+		{
+			if (!set.TryGetValue(value, out var ret))
+				set.Add(ret = createFn(value));
+			return ret;
+		}
+
 		public static int IndexOf<T>(this T[] array, T value)
 		{
 			return Array.IndexOf(array, value);
 		}
 
+		public static T FirstOrDefault<T>(this T[] array, Predicate<T> match)
+		{
+			return Array.Find(array, match);
+		}
+
+		public static T FirstOrDefault<T>(this List<T> list, Predicate<T> match)
+		{
+			return list.Find(match);
+		}
+
 		public static T Random<T>(this IEnumerable<T> ts, MersenneTwister r)
 		{
 			return Random(ts, r, true);
@@ -148,7 +171,7 @@ namespace OpenRA
 
 		static T Random<T>(IEnumerable<T> ts, MersenneTwister r, bool throws)
 		{
-			var xs = ts as ICollection<T>;
+			var xs = ts as IReadOnlyCollection<T>;
 			xs ??= ts.ToList();
 			if (xs.Count == 0)
 			{
@@ -303,9 +326,9 @@ namespace OpenRA
 
 			// Adjust for other rounding modes
 			if (round == ISqrtRoundMode.Nearest && remainder > root)
-				root += 1;
+				root++;
 			else if (round == ISqrtRoundMode.Ceiling && root * root < number)
-				root += 1;
+				root++;
 
 			return root;
 		}
@@ -344,9 +367,9 @@ namespace OpenRA
 
 			// Adjust for other rounding modes
 			if (round == ISqrtRoundMode.Nearest && remainder > root)
-				root += 1;
+				root++;
 			else if (round == ISqrtRoundMode.Ceiling && root * root < number)
-				root += 1;
+				root++;
 
 			return root;
 		}
@@ -356,6 +379,11 @@ namespace OpenRA
 			return number * 46341 / 32768;
 		}
 
+		public static int MultiplyBySqrtTwoOverTwo(int number)
+		{
+			return (int)(number * 23170L / 32768L);
+		}
+
 		public static int IntegerDivisionRoundingAwayFromZero(int dividend, int divisor)
 		{
 			var quotient = Math.DivRem(dividend, divisor, out var remainder);
@@ -493,17 +521,22 @@ namespace OpenRA
 			return result;
 		}
 
-		public static int ParseIntegerInvariant(string s)
-		{
-			return int.Parse(s, NumberStyles.Integer, NumberFormatInfo.InvariantInfo);
-		}
-
-		public static byte ParseByte(string s)
+		public static byte ParseByteInvariant(string s)
 		{
 			return byte.Parse(s, NumberStyles.Integer, NumberFormatInfo.InvariantInfo);
 		}
 
-		public static bool TryParseIntegerInvariant(string s, out int i)
+		public static short ParseInt16Invariant(string s)
+		{
+			return short.Parse(s, NumberStyles.Integer, NumberFormatInfo.InvariantInfo);
+		}
+
+		public static int ParseInt32Invariant(string s)
+		{
+			return int.Parse(s, NumberStyles.Integer, NumberFormatInfo.InvariantInfo);
+		}
+
+		public static bool TryParseInt32Invariant(string s, out int i)
 		{
 			return int.TryParse(s, NumberStyles.Integer, NumberFormatInfo.InvariantInfo, out i);
 		}
@@ -513,6 +546,26 @@ namespace OpenRA
 			return long.TryParse(s, NumberStyles.Integer, NumberFormatInfo.InvariantInfo, out i);
 		}
 
+		public static string ToStringInvariant(this byte i)
+		{
+			return i.ToString(NumberFormatInfo.InvariantInfo);
+		}
+
+		public static string ToStringInvariant(this byte i, string format)
+		{
+			return i.ToString(format, NumberFormatInfo.InvariantInfo);
+		}
+
+		public static string ToStringInvariant(this int i)
+		{
+			return i.ToString(NumberFormatInfo.InvariantInfo);
+		}
+
+		public static string ToStringInvariant(this int i, string format)
+		{
+			return i.ToString(format, NumberFormatInfo.InvariantInfo);
+		}
+
 		public static bool IsTraitEnabled<T>(this T trait)
 		{
 			return trait is not IDisabledTrait disabledTrait || !disabledTrait.IsTraitDisabled;
@@ -562,11 +615,6 @@ namespace OpenRA
 		{
 			return new LineSplitEnumerator(str.AsSpan(), separator);
 		}
-
-		public static bool TryParseInt32Invariant(string s, out int i)
-		{
-			return int.TryParse(s, NumberStyles.Integer, NumberFormatInfo.InvariantInfo, out i);
-		}
 	}
 
 	public ref struct LineSplitEnumerator
@@ -581,7 +629,7 @@ namespace OpenRA
 			Current = default;
 		}
 
-		public LineSplitEnumerator GetEnumerator() => this;
+		public readonly LineSplitEnumerator GetEnumerator() => this;
 
 		public bool MoveNext()
 		{

OpenRA.Game/FieldLoader.cs

@@ -87,6 +87,7 @@ namespace OpenRA
 				{ typeof(WAngle), ParseWAngle },
 				{ typeof(WRot), ParseWRot },
 				{ typeof(CPos), ParseCPos },
+				{ typeof(CPos[]), ParseCPosArray },
 				{ typeof(CVec), ParseCVec },
 				{ typeof(CVec[]), ParseCVecArray },
 				{ typeof(BooleanExpression), ParseBooleanExpression },
@@ -118,7 +119,7 @@ namespace OpenRA
 
 		static object ParseInt(string fieldName, Type fieldType, string value, MemberInfo field)
 		{
-			if (Exts.TryParseIntegerInvariant(value, out var res))
+			if (Exts.TryParseInt32Invariant(value, out var res))
 			{
 				if (res >= 0 && res < BoxedInts.Length)
 					return BoxedInts[res];
@@ -195,11 +196,11 @@ namespace OpenRA
 			if (value != null)
 			{
 				var parts = value.Split(SplitComma);
-				if (parts.Length == 3)
-				{
-					if (WDist.TryParse(parts[0], out var rx) && WDist.TryParse(parts[1], out var ry) && WDist.TryParse(parts[2], out var rz))
-						return new WVec(rx, ry, rz);
-				}
+				if (parts.Length == 3
+					&& WDist.TryParse(parts[0], out var rx)
+					&& WDist.TryParse(parts[1], out var ry)
+					&& WDist.TryParse(parts[2], out var rz))
+					return new WVec(rx, ry, rz);
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -219,8 +220,8 @@ namespace OpenRA
 				for (var i = 0; i < vecs.Length; ++i)
 				{
 					if (WDist.TryParse(parts[3 * i], out var rx)
-							&& WDist.TryParse(parts[3 * i + 1], out var ry)
-							&& WDist.TryParse(parts[3 * i + 2], out var rz))
+						&& WDist.TryParse(parts[3 * i + 1], out var ry)
+						&& WDist.TryParse(parts[3 * i + 2], out var rz))
 						vecs[i] = new WVec(rx, ry, rz);
 				}
 
@@ -235,13 +236,11 @@ namespace OpenRA
 			if (value != null)
 			{
 				var parts = value.Split(SplitComma);
-				if (parts.Length == 3)
-				{
-					if (WDist.TryParse(parts[0], out var rx)
-						&& WDist.TryParse(parts[1], out var ry)
-						&& WDist.TryParse(parts[2], out var rz))
-						return new WPos(rx, ry, rz);
-				}
+				if (parts.Length == 3
+					&& WDist.TryParse(parts[0], out var rx)
+					&& WDist.TryParse(parts[1], out var ry)
+					&& WDist.TryParse(parts[2], out var rz))
+					return new WPos(rx, ry, rz);
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -249,7 +248,7 @@ namespace OpenRA
 
 		static object ParseWAngle(string fieldName, Type fieldType, string value, MemberInfo field)
 		{
-			if (Exts.TryParseIntegerInvariant(value, out var res))
+			if (Exts.TryParseInt32Invariant(value, out var res))
 				return new WAngle(res);
 			return InvalidValueAction(value, fieldType, fieldName);
 		}
@@ -259,13 +258,11 @@ namespace OpenRA
 			if (value != null)
 			{
 				var parts = value.Split(SplitComma);
-				if (parts.Length == 3)
-				{
-					if (Exts.TryParseIntegerInvariant(parts[0], out var rr)
-							&& Exts.TryParseIntegerInvariant(parts[1], out var rp)
-							&& Exts.TryParseIntegerInvariant(parts[2], out var ry))
-						return new WRot(new WAngle(rr), new WAngle(rp), new WAngle(ry));
-				}
+				if (parts.Length == 3
+					&& Exts.TryParseInt32Invariant(parts[0], out var rr)
+					&& Exts.TryParseInt32Invariant(parts[1], out var rp)
+					&& Exts.TryParseInt32Invariant(parts[2], out var ry))
+					return new WRot(new WAngle(rr), new WAngle(rp), new WAngle(ry));
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -278,10 +275,33 @@ namespace OpenRA
 				var parts = value.Split(SplitComma, StringSplitOptions.RemoveEmptyEntries);
 				if (parts.Length == 3)
 					return new CPos(
-						Exts.ParseIntegerInvariant(parts[0]),
-						Exts.ParseIntegerInvariant(parts[1]),
-						Exts.ParseByte(parts[2]));
-				return new CPos(Exts.ParseIntegerInvariant(parts[0]), Exts.ParseIntegerInvariant(parts[1]));
+						Exts.ParseInt32Invariant(parts[0]),
+						Exts.ParseInt32Invariant(parts[1]),
+						Exts.ParseByteInvariant(parts[2]));
+				return new CPos(Exts.ParseInt32Invariant(parts[0]), Exts.ParseInt32Invariant(parts[1]));
+			}
+
+			return InvalidValueAction(value, fieldType, fieldName);
+		}
+
+		static object ParseCPosArray(string fieldName, Type fieldType, string value, MemberInfo field)
+		{
+			if (value != null)
+			{
+				var parts = value.Split(SplitComma);
+
+				if (parts.Length % 2 != 0)
+					return InvalidValueAction(value, fieldType, fieldName);
+
+				var vecs = new CPos[parts.Length / 2];
+				for (var i = 0; i < vecs.Length; i++)
+				{
+					if (int.TryParse(parts[2 * i], out var rx)
+							&& int.TryParse(parts[2 * i + 1], out var ry))
+						vecs[i] = new CPos(rx, ry);
+				}
+
+				return vecs;
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -292,7 +312,7 @@ namespace OpenRA
 			if (value != null)
 			{
 				var parts = value.Split(SplitComma, StringSplitOptions.RemoveEmptyEntries);
-				return new CVec(Exts.ParseIntegerInvariant(parts[0]), Exts.ParseIntegerInvariant(parts[1]));
+				return new CVec(Exts.ParseInt32Invariant(parts[0]), Exts.ParseInt32Invariant(parts[1]));
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -385,7 +405,7 @@ namespace OpenRA
 
 				var ints = new int2[parts.Length / 2];
 				for (var i = 0; i < ints.Length; i++)
-					ints[i] = new int2(Exts.ParseIntegerInvariant(parts[2 * i]), Exts.ParseIntegerInvariant(parts[2 * i + 1]));
+					ints[i] = new int2(Exts.ParseInt32Invariant(parts[2 * i]), Exts.ParseInt32Invariant(parts[2 * i + 1]));
 
 				return ints;
 			}
@@ -398,7 +418,7 @@ namespace OpenRA
 			if (value != null)
 			{
 				var parts = value.Split(SplitComma, StringSplitOptions.RemoveEmptyEntries);
-				return new Size(Exts.ParseIntegerInvariant(parts[0]), Exts.ParseIntegerInvariant(parts[1]));
+				return new Size(Exts.ParseInt32Invariant(parts[0]), Exts.ParseInt32Invariant(parts[1]));
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -412,7 +432,7 @@ namespace OpenRA
 				if (parts.Length != 2)
 					return InvalidValueAction(value, fieldType, fieldName);
 
-				return new int2(Exts.ParseIntegerInvariant(parts[0]), Exts.ParseIntegerInvariant(parts[1]));
+				return new int2(Exts.ParseInt32Invariant(parts[0]), Exts.ParseInt32Invariant(parts[1]));
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -460,10 +480,10 @@ namespace OpenRA
 			{
 				var parts = value.Split(SplitComma, StringSplitOptions.RemoveEmptyEntries);
 				return new Rectangle(
-					Exts.ParseIntegerInvariant(parts[0]),
-					Exts.ParseIntegerInvariant(parts[1]),
-					Exts.ParseIntegerInvariant(parts[2]),
-					Exts.ParseIntegerInvariant(parts[3]));
+					Exts.ParseInt32Invariant(parts[0]),
+					Exts.ParseInt32Invariant(parts[1]),
+					Exts.ParseInt32Invariant(parts[2]),
+					Exts.ParseInt32Invariant(parts[3]));
 			}
 
 			return InvalidValueAction(value, fieldType, fieldName);
@@ -500,7 +520,7 @@ namespace OpenRA
 			if (yaml == null)
 				return Activator.CreateInstance(fieldType);
 
-			var dict = Activator.CreateInstance(fieldType, yaml.Nodes.Count);
+			var dict = Activator.CreateInstance(fieldType, yaml.Nodes.Length);
 			var arguments = fieldType.GetGenericArguments();
 			var addMethod = fieldType.GetMethod(nameof(Dictionary<object, object>.Add), arguments);
 			var addArgs = new object[2];
@@ -531,7 +551,7 @@ namespace OpenRA
 			if (string.IsNullOrEmpty(value))
 				return null;
 
-			var innerType = fieldType.GetGenericArguments().First();
+			var innerType = fieldType.GetGenericArguments()[0];
 			var innerValue = GetValue("Nullable<T>", innerType, value, field);
 			return fieldType.GetConstructor(new[] { innerType }).Invoke(new[] { innerValue });
 		}

OpenRA.Game/FieldSaver.cs

@@ -15,6 +15,7 @@ using System.ComponentModel;
 using System.Globalization;
 using System.Linq;
 using System.Reflection;
+using System.Text;
 using OpenRA.Primitives;
 
 namespace OpenRA
@@ -58,7 +59,7 @@ namespace OpenRA
 
 			return new MiniYaml(
 				null,
-				fields.Select(info => new MiniYamlNode(info.YamlName, FormatValue(o, info.Field))).ToList());
+				fields.Select(info => new MiniYamlNode(info.YamlName, FormatValue(o, info.Field))));
 		}
 
 		public static MiniYamlNode SaveField(object o, string field)
@@ -84,7 +85,7 @@ namespace OpenRA
 			// This is only for documentation generation
 			if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Dictionary<,>))
 			{
-				var result = "";
+				var result = new StringBuilder();
 				var dict = (System.Collections.IDictionary)v;
 				foreach (var kvp in dict)
 				{
@@ -94,10 +95,10 @@ namespace OpenRA
 					var formattedKey = FormatValue(key);
 					var formattedValue = FormatValue(value);
 
-					result += $"{formattedKey}: {formattedValue}{Environment.NewLine}";
+					result.Append($"{formattedKey}: {formattedValue}{Environment.NewLine}");
 				}
 
-				return result;
+				return result.ToString();
 			}
 
 			if (v is DateTime d)

OpenRA.Game/FileFormats/Png.cs

@@ -16,6 +16,7 @@ using System.Linq;
 using System.Net;
 using System.Text;
 using ICSharpCode.SharpZipLib.Checksum;
+using ICSharpCode.SharpZipLib.Zip.Compression;
 using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
 using OpenRA.Graphics;
 using OpenRA.Primitives;
@@ -45,12 +46,13 @@ namespace OpenRA.FileFormats
 			var data = new List<byte>();
 			Type = SpriteFrameType.Rgba32;
 
+			byte bitDepth = 8;
 			while (true)
 			{
 				var length = IPAddress.NetworkToHostOrder(s.ReadInt32());
-				var type = Encoding.UTF8.GetString(s.ReadBytes(4));
+				var type = s.ReadASCII(4);
 				var content = s.ReadBytes(length);
-				/*var crc = */s.ReadInt32();
+				s.ReadInt32(); // crc
 
 				if (!headerParsed && type != "IHDR")
 					throw new InvalidDataException("Invalid PNG file - header does not appear first.");
@@ -66,7 +68,7 @@ namespace OpenRA.FileFormats
 							Width = IPAddress.NetworkToHostOrder(ms.ReadInt32());
 							Height = IPAddress.NetworkToHostOrder(ms.ReadInt32());
 
-							var bitDepth = ms.ReadUInt8();
+							bitDepth = ms.ReadUInt8();
 							var colorType = (PngColorType)ms.ReadUInt8();
 							if (IsPaletted(bitDepth, colorType))
 								Type = SpriteFrameType.Indexed8;
@@ -76,7 +78,7 @@ namespace OpenRA.FileFormats
 							Data = new byte[Width * Height * PixelStride];
 
 							var compression = ms.ReadUInt8();
-							/*var filter = */ms.ReadUInt8();
+							ms.ReadUInt8(); // filter
 							var interlace = ms.ReadUInt8();
 
 							if (compression != 0)
@@ -92,8 +94,8 @@ namespace OpenRA.FileFormats
 
 						case "PLTE":
 						{
-							Palette = new Color[256];
-							for (var i = 0; i < length / 3; i++)
+							Palette = new Color[length / 3];
+							for (var i = 0; i < Palette.Length; i++)
 							{
 								var r = ms.ReadUInt8(); var g = ms.ReadUInt8(); var b = ms.ReadUInt8();
 								Palette[i] = Color.FromArgb(r, g, b);
@@ -136,14 +138,34 @@ namespace OpenRA.FileFormats
 								{
 									var pxStride = PixelStride;
 									var rowStride = Width * pxStride;
+									var pixelsPerByte = 8 / bitDepth;
+									var sourceRowStride = Exts.IntegerDivisionRoundingAwayFromZero(rowStride, pixelsPerByte);
 
 									Span<byte> prevLine = new byte[rowStride];
 									for (var y = 0; y < Height; y++)
 									{
 										var filter = (PngFilter)ds.ReadUInt8();
-										ds.ReadBytes(Data, y * rowStride, rowStride);
+										ds.ReadBytes(Data, y * rowStride, sourceRowStride);
 										var line = Data.AsSpan(y * rowStride, rowStride);
 
+										// If the source has a bit depth of 1, 2 or 4 it packs multiple pixels per byte.
+										// Unpack to bit depth of 8, yielding 1 pixel per byte.
+										// This makes life easier for consumers of palleted data.
+										if (bitDepth < 8)
+										{
+											var mask = 0xFF >> (8 - bitDepth);
+											for (var i = sourceRowStride - 1; i >= 0; i--)
+											{
+												var packed = line[i];
+												for (var j = 0; j < pixelsPerByte; j++)
+												{
+													var dest = i * pixelsPerByte + j;
+													if (dest < line.Length) // Guard against last byte being only partially packed
+														line[dest] = (byte)(packed >> (8 - (j + 1) * bitDepth) & mask);
+												}
+											}
+										}
+
 										switch (filter)
 										{
 											case PngFilter.None:
@@ -269,7 +291,7 @@ namespace OpenRA.FileFormats
 
 		static bool IsPaletted(byte bitDepth, PngColorType colorType)
 		{
-			if (bitDepth == 8 && colorType == (PngColorType.Indexed | PngColorType.Color))
+			if (bitDepth <= 8 && colorType == (PngColorType.Indexed | PngColorType.Color))
 				return true;
 
 			if (bitDepth == 8 && colorType == (PngColorType.Color | PngColorType.Alpha))
@@ -287,10 +309,10 @@ namespace OpenRA.FileFormats
 
 			var typeBytes = Encoding.ASCII.GetBytes(type);
 			output.Write(IPAddress.HostToNetworkOrder((int)input.Length));
-			output.WriteArray(typeBytes);
+			output.Write(typeBytes);
 
 			var data = input.ReadAllBytes();
-			output.WriteArray(data);
+			output.Write(data);
 
 			var crc32 = new Crc32();
 			crc32.Update(typeBytes);
@@ -302,7 +324,7 @@ namespace OpenRA.FileFormats
 		{
 			using (var output = new MemoryStream())
 			{
-				output.WriteArray(Signature);
+				output.Write(Signature);
 				using (var header = new MemoryStream())
 				{
 					header.Write(IPAddress.HostToNetworkOrder(Width));
@@ -350,13 +372,14 @@ namespace OpenRA.FileFormats
 
 				using (var data = new MemoryStream())
 				{
-					using (var compressed = new DeflaterOutputStream(data))
+					using (var compressed = new DeflaterOutputStream(data, new Deflater(Deflater.BEST_COMPRESSION)))
 					{
 						var rowStride = Width * PixelStride;
 						for (var y = 0; y < Height; y++)
 						{
-							// Write uncompressed scanlines for simplicity
-							compressed.WriteByte(0);
+							// Assuming no filtering for simplicity
+							const byte FilterType = 0;
+							compressed.WriteByte(FilterType);
 							compressed.Write(Data, y * rowStride, rowStride);
 						}
 
@@ -371,7 +394,7 @@ namespace OpenRA.FileFormats
 				{
 					using (var text = new MemoryStream())
 					{
-						text.WriteArray(Encoding.ASCII.GetBytes(kv.Key + (char)0 + kv.Value));
+						text.Write(Encoding.ASCII.GetBytes(kv.Key + (char)0 + kv.Value));
 						WritePngChunk(output, "tEXt", text);
 					}
 				}

OpenRA.Game/FileFormats/ReplayMetadata.cs

@@ -47,8 +47,8 @@ namespace OpenRA.FileFormats
 				throw new NotSupportedException($"Metadata version {version} is not supported");
 
 			// Read game info (max 100K limit as a safeguard against corrupted files)
-			var data = fs.ReadString(Encoding.UTF8, 1024 * 100);
-			GameInfo = GameInformation.Deserialize(data);
+			var data = fs.ReadLengthPrefixedString(Encoding.UTF8, 1024 * 100);
+			GameInfo = GameInformation.Deserialize(data, path);
 		}
 
 		public void Write(BinaryWriter writer)
@@ -62,7 +62,7 @@ namespace OpenRA.FileFormats
 			{
 				// Write lobby info data
 				writer.Flush();
-				dataLength += writer.BaseStream.WriteString(Encoding.UTF8, GameInfo.Serialize());
+				dataLength += writer.BaseStream.WriteLengthPrefixedString(Encoding.UTF8, GameInfo.Serialize());
 			}
 
 			// Write total length & end marker

OpenRA.Game/FileSystem/FileSystem.cs

@@ -83,14 +83,14 @@ namespace OpenRA.FileSystem
 
 		public void Mount(string name, string explicitName = null)
 		{
-			var optional = name.StartsWith("~", StringComparison.Ordinal);
+			var optional = name.StartsWith('~');
 			if (optional)
 				name = name[1..];
 
 			try
 			{
 				IReadOnlyPackage package;
-				if (name.StartsWith("$", StringComparison.Ordinal))
+				if (name.StartsWith('$'))
 				{
 					name = name[1..];
 
@@ -109,10 +109,8 @@ namespace OpenRA.FileSystem
 
 				Mount(package, explicitName);
 			}
-			catch
+			catch when (optional)
 			{
-				if (!optional)
-					throw;
 			}
 		}
 
@@ -161,9 +159,7 @@ namespace OpenRA.FileSystem
 					explicitMounts.Remove(key);
 
 				// Mod packages aren't owned by us, so we shouldn't dispose them
-				if (modPackages.Contains(package))
-					modPackages.Remove(package);
-				else
+				if (!modPackages.Remove(package))
 					package.Dispose();
 			}
 			else
@@ -190,6 +186,12 @@ namespace OpenRA.FileSystem
 			UnmountAll();
 			foreach (var kv in manifest.Packages)
 				Mount(kv.Key, kv.Value);
+
+			mountedPackages.TrimExcess();
+			explicitMounts.TrimExcess();
+			modPackages.TrimExcess();
+			foreach (var packages in fileIndex.Values)
+				packages.TrimExcess();
 		}
 
 		Stream GetFromCache(string filename)
@@ -226,14 +228,11 @@ namespace OpenRA.FileSystem
 		public bool TryOpen(string filename, out Stream s)
 		{
 			var explicitSplit = filename.IndexOf('|');
-			if (explicitSplit > 0)
+			if (explicitSplit > 0 && explicitMounts.TryGetValue(filename[..explicitSplit], out var explicitPackage))
 			{
-				if (explicitMounts.TryGetValue(filename[..explicitSplit], out var explicitPackage))
-				{
-					s = explicitPackage.GetStream(filename[(explicitSplit + 1)..]);
-					if (s != null)
-						return true;
-				}
+				s = explicitPackage.GetStream(filename[(explicitSplit + 1)..]);
+				if (s != null)
+					return true;
 			}
 
 			s = GetFromCache(filename);
@@ -262,10 +261,10 @@ namespace OpenRA.FileSystem
 		public bool Exists(string filename)
 		{
 			var explicitSplit = filename.IndexOf('|');
-			if (explicitSplit > 0)
-				if (explicitMounts.TryGetValue(filename[..explicitSplit], out var explicitPackage))
-					if (explicitPackage.Contains(filename[(explicitSplit + 1)..]))
-						return true;
+			if (explicitSplit > 0 &&
+				explicitMounts.TryGetValue(filename[..explicitSplit], out var explicitPackage) &&
+				explicitPackage.Contains(filename[(explicitSplit + 1)..]))
+				return true;
 
 			return fileIndex.ContainsKey(filename);
 		}
@@ -295,7 +294,7 @@ namespace OpenRA.FileSystem
 		public static string ResolveAssemblyPath(string path, Manifest manifest, InstalledMods installedMods)
 		{
 			var explicitSplit = path.IndexOf('|');
-			if (explicitSplit > 0 && !path.StartsWith("^"))
+			if (explicitSplit > 0 && !path.StartsWith('^'))
 			{
 				var parent = path[..explicitSplit];
 				var filename = path[(explicitSplit + 1)..];
@@ -304,7 +303,7 @@ namespace OpenRA.FileSystem
 				if (parentPath == null)
 					return null;
 
-				if (parentPath.StartsWith("$", StringComparison.Ordinal))
+				if (parentPath.StartsWith('$'))
 				{
 					if (!installedMods.TryGetValue(parentPath[1..], out var mod))
 						return null;

OpenRA.Game/FileSystem/Folder.cs

@@ -84,7 +84,7 @@ namespace OpenRA.FileSystem
 			// in FileSystem.OpenPackage.  Their internal name therefore contains the
 			// full parent path too.  We need to be careful to not add a second path
 			// prefix to these hacked packages.
-			var filePath = filename.StartsWith(Name) ? filename : Path.Combine(Name, filename);
+			var filePath = filename.StartsWith(Name, StringComparison.Ordinal) ? filename : Path.Combine(Name, filename);
 
 			Directory.CreateDirectory(Path.GetDirectoryName(filePath));
 			using (var s = File.Create(filePath))
@@ -98,7 +98,7 @@ namespace OpenRA.FileSystem
 			// in FileSystem.OpenPackage.  Their internal name therefore contains the
 			// full parent path too.  We need to be careful to not add a second path
 			// prefix to these hacked packages.
-			var filePath = filename.StartsWith(Name) ? filename : Path.Combine(Name, filename);
+			var filePath = filename.StartsWith(Name, StringComparison.Ordinal) ? filename : Path.Combine(Name, filename);
 			if (Directory.Exists(filePath))
 				Directory.Delete(filePath, true);
 			else if (File.Exists(filePath))

OpenRA.Game/FileSystem/ZipFile.cs

@@ -21,7 +21,7 @@ namespace OpenRA.FileSystem
 	{
 		const uint ZipSignature = 0x04034b50;
 
-		class ReadOnlyZipFile : IReadOnlyPackage
+		public class ReadOnlyZipFile : IReadOnlyPackage
 		{
 			public string Name { get; protected set; }
 			protected ZipFile pkg;
@@ -68,6 +68,7 @@ namespace OpenRA.FileSystem
 			public void Dispose()
 			{
 				pkg?.Close();
+				GC.SuppressFinalize(this);
 			}
 
 			public IReadOnlyPackage OpenPackage(string filename, FileSystem context)
@@ -93,7 +94,7 @@ namespace OpenRA.FileSystem
 			}
 		}
 
-		sealed class ReadWriteZipFile : ReadOnlyZipFile, IReadWritePackage
+		public sealed class ReadWriteZipFile : ReadOnlyZipFile, IReadWritePackage
 		{
 			readonly MemoryStream pkgStream = new();
 
@@ -117,10 +118,7 @@ namespace OpenRA.FileSystem
 
 			void Commit()
 			{
-				var pos = pkgStream.Position;
-				pkgStream.Position = 0;
-				File.WriteAllBytes(Name, pkgStream.ReadBytes((int)pkgStream.Length));
-				pkgStream.Position = pos;
+				File.WriteAllBytes(Name, pkgStream.ToArray());
 			}
 
 			public void Update(string filename, byte[] contents)
@@ -147,7 +145,7 @@ namespace OpenRA.FileSystem
 
 			public ZipFolder(ReadOnlyZipFile parent, string path)
 			{
-				if (path.EndsWith("/", StringComparison.Ordinal))
+				if (path.EndsWith('/'))
 					path = path[..^1];
 
 				Name = path;

OpenRA.Game/Game.cs

@@ -180,6 +180,7 @@ namespace OpenRA
 		}
 
 		public static event Action BeforeGameStart = () => { };
+		public static event Action AfterGameStart = () => { };
 		internal static void StartGame(string mapUID, WorldType type)
 		{
 			// Dispose of the old world before creating a new one.
@@ -223,6 +224,12 @@ namespace OpenRA
 			//   Much better to clean up now then to drop frames during gameplay for GC pauses.
 			GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
 			GC.Collect();
+
+			// PostLoadComplete is designed for anything that should trigger at the very end of loading.
+			// e.g. audio notifications that the game is starting.
+			OrderManager.World.PostLoadComplete(worldRenderer);
+
+			AfterGameStart();
 		}
 
 		public static void RestartGame()
@@ -416,7 +423,7 @@ namespace OpenRA
 
 				// Sanitize input from platform-specific launchers
 				// Process.Start requires paths to not be quoted, even if they contain spaces
-				if (launchPath != null && launchPath.First() == '"' && launchPath.Last() == '"')
+				if (launchPath != null && launchPath[0] == '"' && launchPath.Last() == '"')
 					launchPath = launchPath[1..^1];
 
 				// Metadata registration requires an explicit launch path
@@ -524,10 +531,11 @@ namespace OpenRA
 				.Where(m => m.Status == MapStatus.Available && m.Visibility.HasFlag(MapVisibility.Shellmap))
 				.Select(m => m.Uid);
 
-			if (!shellmaps.Any())
+			var shellmap = shellmaps.RandomOrDefault(CosmeticRandom);
+			if (shellmap == null)
 				throw new InvalidDataException("No valid shellmaps available");
 
-			return shellmaps.Random(CosmeticRandom);
+			return shellmap;
 		}
 
 		public static void SwitchToExternalMod(ExternalMod mod, string[] launchArguments = null, Action onFailed = null)
@@ -601,7 +609,10 @@ namespace OpenRA
 
 			if (orderManager.LastTickTime.ShouldAdvance(tick))
 			{
-				using (new PerfSample("tick_time"))
+				if (orderManager.GameStarted && orderManager.LocalFrameNumber == 0)
+					PerfHistory.Reset(); // Remove history that occurred whilst the new game was loading.
+
+				using (var sample = new PerfSample("tick_time"))
 				{
 					orderManager.LastTickTime.AdvanceTickTime(tick);
 
@@ -610,7 +621,11 @@ namespace OpenRA
 					Sync.RunUnsynced(world, orderManager.TickImmediate);
 
 					if (world == null)
+					{
+						if (orderManager.GameStarted)
+							PerfHistory.Reset(); // Remove old history when a new game starts.
 						return;
+					}
 
 					if (orderManager.TryTick())
 					{
@@ -664,7 +679,7 @@ namespace OpenRA
 				// Prepare renderables (i.e. render voxels) before calling BeginFrame
 				using (new PerfSample("render_prepare"))
 				{
-					Renderer.WorldModelRenderer.BeginFrame();
+					worldRenderer?.BeginFrame();
 
 					// World rendering is disabled while the loading screen is displayed
 					if (worldRenderer != null && !worldRenderer.World.IsLoadingGameSave)
@@ -674,7 +689,7 @@ namespace OpenRA
 					}
 
 					Ui.PrepareRenderables();
-					Renderer.WorldModelRenderer.EndFrame();
+					worldRenderer?.EndFrame();
 				}
 
 				// worldRenderer is null during the initial install/download screen
@@ -778,7 +793,7 @@ namespace OpenRA
 				var logicWorld = worldRenderer?.World;
 
 				// ReplayTimestep = 0 means the replay is paused: we need to keep logicInterval as UI.Timestep to avoid breakage
-				if (logicWorld != null && !(logicWorld.IsReplay && logicWorld.ReplayTimestep == 0))
+				if (logicWorld != null && (!logicWorld.IsReplay || logicWorld.ReplayTimestep != 0))
 					logicInterval = logicWorld == OrderManager.World ? OrderManager.SuggestedTimestep : logicWorld.Timestep;
 
 				// Ideal time between screen updates
@@ -913,15 +928,15 @@ namespace OpenRA
 		{
 			var endpoints = new List<IPEndPoint>
 			{
-				new IPEndPoint(IPAddress.IPv6Any, settings.ListenPort),
-				new IPEndPoint(IPAddress.Any, settings.ListenPort)
+				new(IPAddress.IPv6Any, settings.ListenPort),
+				new(IPAddress.Any, settings.ListenPort)
 			};
 			server = new Server.Server(endpoints, settings, ModData, ServerType.Multiplayer);
 
 			return server.GetEndpointForLocalConnection();
 		}
 
-		public static ConnectionTarget CreateLocalServer(string map)
+		public static ConnectionTarget CreateLocalServer(string map, bool isSkirmish = false)
 		{
 			var settings = new ServerSettings()
 			{
@@ -935,9 +950,9 @@ namespace OpenRA
 			// This would break the Restart button, which relies on the PlayerIndex always being the same for local servers
 			var endpoints = new List<IPEndPoint>
 			{
-				new IPEndPoint(IPAddress.Loopback, 0)
+				new(IPAddress.Loopback, 0)
 			};
-			server = new Server.Server(endpoints, settings, ModData, ServerType.Local);
+			server = new Server.Server(endpoints, settings, ModData, isSkirmish ? ServerType.Skirmish : ServerType.Local);
 
 			return server.GetEndpointForLocalConnection();
 		}

OpenRA.Game/GameInformation.cs

@@ -49,13 +49,13 @@ namespace OpenRA
 			playersByRuntime = new Dictionary<OpenRA.Player, Player>();
 		}
 
-		public static GameInformation Deserialize(string data)
+		public static GameInformation Deserialize(string data, string path)
 		{
 			try
 			{
 				var info = new GameInformation();
 
-				var nodes = MiniYaml.FromString(data);
+				var nodes = MiniYaml.FromString(data, path);
 				foreach (var node in nodes)
 				{
 					var keyParts = node.Key.Split('@');
@@ -85,7 +85,7 @@ namespace OpenRA
 		{
 			var nodes = new List<MiniYamlNode>
 			{
-				new MiniYamlNode("Root", FieldSaver.Save(this))
+				new("Root", FieldSaver.Save(this))
 			};
 
 			for (var i = 0; i < Players.Count; i++)

OpenRA.Game/GameRules/ActorInfo.cs

@@ -22,7 +22,7 @@ namespace OpenRA
 	/// </summary>
 	public class ActorInfo
 	{
-		public const string AbstractActorPrefix = "^";
+		public const char AbstractActorPrefix = '^';
 		public const char TraitInstanceSeparator = '@';
 
 		/// <summary>
@@ -130,6 +130,7 @@ namespace OpenRA
 
 			// Continue resolving traits as long as possible.
 			// Each time we resolve some traits, this means dependencies for other traits may then be possible to satisfy in the next pass.
+#pragma warning disable CA1851 // Possible multiple enumerations of 'IEnumerable' collection
 			var readyToResolve = more.ToList();
 			while (readyToResolve.Count != 0)
 			{
@@ -138,6 +139,7 @@ namespace OpenRA
 				readyToResolve.Clear();
 				readyToResolve.AddRange(more);
 			}
+#pragma warning restore CA1851
 
 			if (unresolved.Count != 0)
 			{
@@ -160,7 +162,7 @@ namespace OpenRA
 				throw new YamlException(exceptionString);
 			}
 
-			constructOrderCache = resolved.Select(r => r.Trait).ToList();
+			constructOrderCache = resolved.ConvertAll(r => r.Trait);
 			return constructOrderCache;
 		}
 
@@ -185,7 +187,7 @@ namespace OpenRA
 		public bool HasTraitInfo<T>() where T : ITraitInfoInterface { return traits.Contains<T>(); }
 		public T TraitInfo<T>() where T : ITraitInfoInterface { return traits.Get<T>(); }
 		public T TraitInfoOrDefault<T>() where T : ITraitInfoInterface { return traits.GetOrDefault<T>(); }
-		public IEnumerable<T> TraitInfos<T>() where T : ITraitInfoInterface { return traits.WithInterface<T>(); }
+		public IReadOnlyCollection<T> TraitInfos<T>() where T : ITraitInfoInterface { return traits.WithInterface<T>(); }
 
 		public BitSet<TargetableType> GetAllTargetTypes()
 		{

OpenRA.Game/GameRules/Ruleset.cs

@@ -124,7 +124,7 @@ namespace OpenRA
 			{
 				var actors = MergeOrDefault("Manifest,Rules", fs, m.Rules, null, null,
 					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value),
-					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal));
+					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix));
 
 				var weapons = MergeOrDefault("Manifest,Weapons", fs, m.Weapons, null, null,
 					k => new WeaponInfo(k.Value));
@@ -182,7 +182,7 @@ namespace OpenRA
 			{
 				var actors = MergeOrDefault("Rules", fileSystem, m.Rules, mapRules, dr.Actors,
 					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value),
-					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal));
+					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix));
 
 				var weapons = MergeOrDefault("Weapons", fileSystem, m.Weapons, mapWeapons, dr.Weapons,
 					k => new WeaponInfo(k.Value));
@@ -226,10 +226,10 @@ namespace OpenRA
 
 		static bool AnyCustomYaml(MiniYaml yaml)
 		{
-			return yaml != null && (yaml.Value != null || yaml.Nodes.Count > 0);
+			return yaml != null && (yaml.Value != null || yaml.Nodes.Length > 0);
 		}
 
-		static bool AnyFlaggedTraits(ModData modData, List<MiniYamlNode> actors)
+		static bool AnyFlaggedTraits(ModData modData, IEnumerable<MiniYamlNode> actors)
 		{
 			foreach (var actorNode in actors)
 			{
@@ -260,18 +260,18 @@ namespace OpenRA
 				return true;
 
 			// Any trait overrides that aren't explicitly whitelisted are flagged
-			if (mapRules != null)
-			{
-				if (AnyFlaggedTraits(modData, mapRules.Nodes))
-					return true;
+			if (mapRules == null)
+				return false;
 
-				if (mapRules.Value != null)
-				{
-					var mapFiles = FieldLoader.GetValue<string[]>("value", mapRules.Value);
-					foreach (var f in mapFiles)
-						if (AnyFlaggedTraits(modData, MiniYaml.FromStream(fileSystem.Open(f), f)))
-							return true;
-				}
+			if (AnyFlaggedTraits(modData, mapRules.Nodes))
+				return true;
+
+			if (mapRules.Value != null)
+			{
+				var mapFiles = FieldLoader.GetValue<string[]>("value", mapRules.Value);
+				foreach (var f in mapFiles)
+					if (AnyFlaggedTraits(modData, MiniYaml.FromStream(fileSystem.Open(f), f)))
+						return true;
 			}
 
 			return false;

OpenRA.Game/GameRules/SoundInfo.cs

@@ -40,16 +40,16 @@ namespace OpenRA.GameRules
 		static Dictionary<string, SoundPool> ParseSoundPool(MiniYaml y, string key)
 		{
 			var ret = new Dictionary<string, SoundPool>();
-			var classifiction = y.Nodes.First(x => x.Key == key);
+			var classifiction = y.NodeWithKey(key);
 			foreach (var t in classifiction.Value.Nodes)
 			{
 				var volumeModifier = 1f;
-				var volumeModifierNode = t.Value.Nodes.FirstOrDefault(x => x.Key == nameof(SoundPool.VolumeModifier));
+				var volumeModifierNode = t.Value.NodeWithKeyOrDefault(nameof(SoundPool.VolumeModifier));
 				if (volumeModifierNode != null)
 					volumeModifier = FieldLoader.GetValue<float>(volumeModifierNode.Key, volumeModifierNode.Value.Value);
 
 				var interruptType = SoundPool.DefaultInterruptType;
-				var interruptTypeNode = t.Value.Nodes.FirstOrDefault(x => x.Key == nameof(SoundPool.InterruptType));
+				var interruptTypeNode = t.Value.NodeWithKeyOrDefault(nameof(SoundPool.InterruptType));
 				if (interruptTypeNode != null)
 					interruptType = FieldLoader.GetValue<SoundPool.InterruptType>(interruptTypeNode.Key, interruptTypeNode.Value.Value);
 

OpenRA.Game/GameRules/WeaponInfo.cs

@@ -139,13 +139,14 @@ namespace OpenRA.GameRules
 		{
 			// Resolve any weapon-level yaml inheritance or removals
 			// HACK: The "Defaults" sequence syntax prevents us from doing this generally during yaml parsing
-			content.Nodes = MiniYaml.Merge(new[] { content.Nodes });
+			content = content.WithNodes(MiniYaml.Merge(new IReadOnlyCollection<MiniYamlNode>[] { content.Nodes }));
 			FieldLoader.Load(this, content);
 		}
 
 		static object LoadProjectile(MiniYaml yaml)
 		{
-			if (!yaml.ToDictionary().TryGetValue("Projectile", out var proj))
+			var proj = yaml.NodeWithKeyOrDefault("Projectile")?.Value;
+			if (proj == null)
 				return null;
 
 			var ret = Game.CreateObject<IProjectileInfo>(proj.Value + "Info");
@@ -159,7 +160,7 @@ namespace OpenRA.GameRules
 		static object LoadWarheads(MiniYaml yaml)
 		{
 			var retList = new List<IWarhead>();
-			foreach (var node in yaml.Nodes.Where(n => n.Key.StartsWith("Warhead")))
+			foreach (var node in yaml.Nodes.Where(n => n.Key.StartsWith("Warhead", StringComparison.Ordinal)))
 			{
 				var ret = Game.CreateObject<IWarhead>(node.Value.Value + "Warhead");
 				if (ret == null)

OpenRA.Game/GameSpeed.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -38,7 +37,7 @@ namespace OpenRA
 		static object LoadSpeeds(MiniYaml y)
 		{
 			var ret = new Dictionary<string, GameSpeed>();
-			var speedsNode = y.Nodes.FirstOrDefault(n => n.Key == "Speeds");
+			var speedsNode = y.NodeWithKeyOrDefault("Speeds");
 			if (speedsNode == null)
 				throw new YamlException("Error parsing GameSpeeds: Missing Speeds node!");
 

OpenRA.Game/Graphics/ChromeProvider.cs

@@ -77,11 +77,12 @@ namespace OpenRA.Graphics
 			cachedPanelSprites = new Dictionary<string, Sprite[]>();
 			cachedCollectionSheets = new Dictionary<Collection, (Sheet, int)>();
 
+			var stringPool = new HashSet<string>(); // Reuse common strings in YAML
 			var chrome = MiniYaml.Merge(modData.Manifest.Chrome
-				.Select(s => MiniYaml.FromStream(fileSystem.Open(s), s)));
+				.Select(s => MiniYaml.FromStream(fileSystem.Open(s), s, stringPool: stringPool)));
 
 			foreach (var c in chrome)
-				if (!c.Key.StartsWith("^", StringComparison.Ordinal))
+				if (!c.Key.StartsWith('^'))
 					LoadCollection(c.Key, c.Value);
 		}
 
@@ -234,7 +235,7 @@ namespace OpenRA.Graphics
 			{
 				// PERF: We don't need to search for images if there are no definitions.
 				// PERF: It's more efficient to send an empty array rather than an array of 9 nulls.
-				if (!collection.Regions.Any())
+				if (collection.Regions.Count == 0)
 					return Array.Empty<Sprite>();
 
 				// Support manual definitions for unusual dialog layouts

OpenRA.Game/Graphics/CursorProvider.cs

@@ -24,10 +24,11 @@ namespace OpenRA.Graphics
 		public CursorProvider(ModData modData)
 		{
 			var fileSystem = modData.DefaultFileSystem;
+			var stringPool = new HashSet<string>(); // Reuse common strings in YAML
 			var sequenceYaml = MiniYaml.Merge(modData.Manifest.Cursors.Select(
-				s => MiniYaml.FromStream(fileSystem.Open(s), s)));
+				s => MiniYaml.FromStream(fileSystem.Open(s), s, stringPool: stringPool)));
 
-			var nodesDict = new MiniYaml(null, sequenceYaml).ToDictionary();
+			var cursorsYaml = new MiniYaml(null, sequenceYaml).NodeWithKey("Cursors").Value;
 
 			// Overwrite previous definitions if there are duplicates
 			var pals = new Dictionary<string, IProvidesCursorPaletteInfo>();
@@ -35,14 +36,14 @@ namespace OpenRA.Graphics
 				if (p.Palette != null)
 					pals[p.Palette] = p;
 
-			Palettes = nodesDict["Cursors"].Nodes.Select(n => n.Value.Value)
+			Palettes = cursorsYaml.Nodes.Select(n => n.Value.Value)
 				.Where(p => p != null)
 				.Distinct()
 				.ToDictionary(p => p, p => pals[p].ReadPalette(modData.DefaultFileSystem));
 
 			var frameCache = new FrameCache(fileSystem, modData.SpriteLoaders);
 			var cursors = new Dictionary<string, CursorSequence>();
-			foreach (var s in nodesDict["Cursors"].Nodes)
+			foreach (var s in cursorsYaml.Nodes)
 				foreach (var sequence in s.Value.Nodes)
 					cursors.Add(sequence.Key, new CursorSequence(frameCache, sequence.Key, s.Key, s.Value.Value, sequence.Value));
 

OpenRA.Game/Graphics/CursorSequence.cs

@@ -27,7 +27,7 @@ namespace OpenRA.Graphics
 		{
 			var d = info.ToDictionary();
 
-			Start = Exts.ParseIntegerInvariant(d["Start"].Value);
+			Start = Exts.ParseInt32Invariant(d["Start"].Value);
 			Palette = palette;
 			Name = name;
 
@@ -38,9 +38,9 @@ namespace OpenRA.Graphics
 				(d.TryGetValue("End", out yaml) && yaml.Value == "*"))
 				Length = Frames.Length;
 			else if (d.TryGetValue("Length", out yaml))
-				Length = Exts.ParseIntegerInvariant(yaml.Value);
+				Length = Exts.ParseInt32Invariant(yaml.Value);
 			else if (d.TryGetValue("End", out yaml))
-				Length = Exts.ParseIntegerInvariant(yaml.Value) - Start;
+				Length = Exts.ParseInt32Invariant(yaml.Value) - Start;
 			else
 				Length = 1;
 
@@ -54,13 +54,13 @@ namespace OpenRA.Graphics
 
 			if (d.TryGetValue("X", out yaml))
 			{
-				Exts.TryParseIntegerInvariant(yaml.Value, out var x);
+				Exts.TryParseInt32Invariant(yaml.Value, out var x);
 				Hotspot = Hotspot.WithX(x);
 			}
 
 			if (d.TryGetValue("Y", out yaml))
 			{
-				Exts.TryParseIntegerInvariant(yaml.Value, out var y);
+				Exts.TryParseInt32Invariant(yaml.Value, out var y);
 				Hotspot = Hotspot.WithY(y);
 			}
 		}

OpenRA.Game/Graphics/MarkerTileRenderable.cs

@@ -0,0 +1,56 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Linq;
+using OpenRA.Primitives;
+
+namespace OpenRA.Graphics
+{
+	public class MarkerTileRenderable : IRenderable, IFinalizedRenderable
+	{
+		readonly CPos pos;
+		readonly Color color;
+
+		public MarkerTileRenderable(CPos pos, Color color)
+		{
+			this.pos = pos;
+			this.color = color;
+		}
+
+		public WPos Pos => WPos.Zero;
+		public int ZOffset => 0;
+		public bool IsDecoration => true;
+
+		public IRenderable WithZOffset(int newOffset) { return this; }
+
+		public IRenderable OffsetBy(in WVec vec)
+		{
+			return new MarkerTileRenderable(pos, color);
+		}
+
+		public IRenderable AsDecoration() { return this; }
+
+		public IFinalizedRenderable PrepareRender(WorldRenderer wr) { return this; }
+		public void Render(WorldRenderer wr)
+		{
+			var map = wr.World.Map;
+			var r = map.Grid.Ramps[map.Ramp[pos]];
+			var wpos = map.CenterOfCell(pos) - new WVec(0, 0, r.CenterHeightOffset);
+
+			var corners = r.Corners.Select(corner => wr.Viewport.WorldToViewPx(wr.Screen3DPosition(wpos + corner))).ToList();
+
+			Game.Renderer.RgbaColorRenderer.FillRect(corners[0], corners[1], corners[2], corners[3], color);
+		}
+
+		public void RenderDebugGeometry(WorldRenderer wr) { }
+		public Rectangle ScreenBounds(WorldRenderer wr) { return Rectangle.Empty; }
+	}
+}

OpenRA.Game/Graphics/Model.cs

@@ -10,9 +10,8 @@
 #endregion
 
 using System;
-using System.Collections.Generic;
-using OpenRA.FileSystem;
 using OpenRA.Primitives;
+using OpenRA.Traits;
 
 namespace OpenRA.Graphics
 {
@@ -30,6 +29,14 @@ namespace OpenRA.Graphics
 		Rectangle AggregateBounds { get; }
 	}
 
+	public interface IModelWidget
+	{
+		public string Palette { get; }
+		public float Scale { get; }
+		public void Setup(Func<bool> isVisible, Func<string> getPalette, Func<string> getPlayerPalette,
+			Func<float> getScale, Func<IModel> getVoxel, Func<WRot> getRotation);
+	}
+
 	public readonly struct ModelRenderData
 	{
 		public readonly int Start;
@@ -44,51 +51,13 @@ namespace OpenRA.Graphics
 		}
 	}
 
-	public interface IModelCache : IDisposable
+	public interface IModelCacheInfo : ITraitInfoInterface { }
+
+	public interface IModelCache
 	{
 		IModel GetModel(string model);
 		IModel GetModelSequence(string model, string sequence);
 		bool HasModelSequence(string model, string sequence);
-		IVertexBuffer<Vertex> VertexBuffer { get; }
-	}
-
-	public interface IModelSequenceLoader
-	{
-		Action<string> OnMissingModelError { get; set; }
-		IModelCache CacheModels(IReadOnlyFileSystem fileSystem, ModData modData, IReadOnlyDictionary<string, MiniYamlNode> modelDefinitions);
-	}
-
-	public class PlaceholderModelSequenceLoader : IModelSequenceLoader
-	{
-		public Action<string> OnMissingModelError { get; set; }
-
-		sealed class PlaceholderModelCache : IModelCache
-		{
-			public IVertexBuffer<Vertex> VertexBuffer => throw new NotImplementedException();
-
-			public void Dispose() { }
-
-			public IModel GetModel(string model)
-			{
-				throw new NotImplementedException();
-			}
-
-			public IModel GetModelSequence(string model, string sequence)
-			{
-				throw new NotImplementedException();
-			}
-
-			public bool HasModelSequence(string model, string sequence)
-			{
-				throw new NotImplementedException();
-			}
-		}
-
-		public PlaceholderModelSequenceLoader(ModData modData) { }
-
-		public IModelCache CacheModels(IReadOnlyFileSystem fileSystem, ModData modData, IReadOnlyDictionary<string, MiniYamlNode> modelDefinitions)
-		{
-			return new PlaceholderModelCache();
-		}
+		IVertexBuffer<ModelVertex> VertexBuffer { get; }
 	}
 }

OpenRA.Game/Graphics/ModelVertex.cs

@@ -0,0 +1,53 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Runtime.InteropServices;
+
+namespace OpenRA.Graphics
+{
+	[StructLayout(LayoutKind.Sequential)]
+	public readonly struct ModelVertex
+	{
+		// 3d position
+		public readonly float X, Y, Z;
+
+		// Primary and secondary texture coordinates or RGBA color
+		public readonly float S, T, U, V;
+
+		// Palette and channel flags
+		public readonly float P, C;
+
+		public ModelVertex(in float3 xyz, float s, float t, float u, float v, float p, float c)
+			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, p, c) { }
+
+		public ModelVertex(float x, float y, float z, float s, float t, float u, float v, float p, float c)
+		{
+			X = x; Y = y; Z = z;
+			S = s; T = t;
+			U = u; V = v;
+			P = p; C = c;
+		}
+	}
+
+	public sealed class ModelShaderBindings : ShaderBindings
+	{
+		public ModelShaderBindings()
+			: base("model")
+		{ }
+
+		public override ShaderVertexAttribute[] Attributes { get; } = new[]
+		{
+			new ShaderVertexAttribute("aVertexPosition", ShaderVertexAttributeType.Float, 3, 0),
+			new ShaderVertexAttribute("aVertexTexCoord", ShaderVertexAttributeType.Float, 4, 12),
+			new ShaderVertexAttribute("aVertexTexMetadata", ShaderVertexAttributeType.Float, 2, 28),
+		};
+	}
+}

OpenRA.Game/Graphics/Palette.cs

@@ -30,7 +30,7 @@ namespace OpenRA.Graphics
 
 		public static Color GetColor(this IPalette palette, int index)
 		{
-			return Color.FromArgb((int)palette[index]);
+			return Color.FromArgb(palette[index]);
 		}
 
 		public static IPalette AsReadOnly(this IPalette palette)
@@ -103,7 +103,7 @@ namespace OpenRA.Graphics
 			: this(p)
 		{
 			for (var i = 0; i < Palette.Size; i++)
-				colors[i] = (uint)r.GetRemappedColor(this.GetColor(i), i).ToArgb();
+				colors[i] = r.GetRemappedColor(this.GetColor(i), i).ToArgb();
 		}
 
 		public ImmutablePalette(IPalette p)
@@ -142,7 +142,7 @@ namespace OpenRA.Graphics
 
 		public void SetColor(int index, Color color)
 		{
-			colors[index] = (uint)color.ToArgb();
+			colors[index] = color.ToArgb();
 		}
 
 		public void SetFromPalette(IPalette p)
@@ -153,7 +153,7 @@ namespace OpenRA.Graphics
 		public void ApplyRemap(IPaletteRemap r)
 		{
 			for (var i = 0; i < Palette.Size; i++)
-				colors[i] = (uint)r.GetRemappedColor(this.GetColor(i), i).ToArgb();
+				colors[i] = r.GetRemappedColor(this.GetColor(i), i).ToArgb();
 		}
 	}
 }

OpenRA.Game/Graphics/PaletteReference.cs

@@ -13,19 +13,17 @@ namespace OpenRA.Graphics
 {
 	public sealed class PaletteReference
 	{
-		readonly float index;
 		readonly HardwarePalette hardwarePalette;
 
 		public readonly string Name;
 		public IPalette Palette { get; internal set; }
-		public float TextureIndex => index / hardwarePalette.Height;
-		public float TextureMidIndex => (index + 0.5f) / hardwarePalette.Height;
+		public int TextureIndex { get; }
 
 		public PaletteReference(string name, int index, IPalette palette, HardwarePalette hardwarePalette)
 		{
 			Name = name;
 			Palette = palette;
-			this.index = index;
+			TextureIndex = index;
 			this.hardwarePalette = hardwarePalette;
 		}
 

OpenRA.Game/Graphics/PlatformInterfaces.cs

@@ -20,13 +20,12 @@ namespace OpenRA
 		Automatic,
 		ANGLE,
 		Modern,
-		Embedded,
-		Legacy
+		Embedded
 	}
 
 	public interface IPlatform
 	{
-		IPlatformWindow CreateWindow(Size size, WindowMode windowMode, float scaleModifier, int batchSize, int videoDisplay, GLProfile profile, bool enableLegacyGL);
+		IPlatformWindow CreateWindow(Size size, WindowMode windowMode, float scaleModifier, int vertexBatchSize, int indexBatchSize, int videoDisplay, GLProfile profile);
 		ISoundEngine CreateSound(string device);
 		IFont CreateFont(byte[] data);
 	}
@@ -83,16 +82,18 @@ namespace OpenRA
 
 	public interface IGraphicsContext : IDisposable
 	{
-		IVertexBuffer<Vertex> CreateVertexBuffer(int size);
-		Vertex[] CreateVertices(int size);
+		IVertexBuffer<T> CreateVertexBuffer<T>(int size) where T : struct;
+		T[] CreateVertices<T>(int size) where T : struct;
+		IIndexBuffer CreateIndexBuffer(uint[] indices);
 		ITexture CreateTexture();
 		IFrameBuffer CreateFrameBuffer(Size s);
 		IFrameBuffer CreateFrameBuffer(Size s, Color clearColor);
-		IShader CreateShader(string name);
+		IShader CreateShader(IShaderBindings shaderBindings);
 		void EnableScissor(int x, int y, int width, int height);
 		void DisableScissor();
 		void Present();
 		void DrawPrimitives(PrimitiveType pt, int firstVertex, int numVertices);
+		void DrawElements(int numIndices, int offset);
 		void Clear();
 		void EnableDepthBuffer();
 		void DisableDepthBuffer();
@@ -102,7 +103,14 @@ namespace OpenRA
 		string GLVersion { get; }
 	}
 
-	public interface IVertexBuffer<T> : IDisposable
+	public interface IRenderer
+	{
+		void BeginFrame();
+		void EndFrame();
+		void SetPalette(HardwarePalette palette);
+	}
+
+	public interface IVertexBuffer<T> : IDisposable where T : struct
 	{
 		void Bind();
 		void SetData(T[] vertices, int length);
@@ -114,6 +122,11 @@ namespace OpenRA
 		void SetData(T[] vertices, int offset, int start, int length);
 	}
 
+	public interface IIndexBuffer : IDisposable
+	{
+		void Bind();
+	}
+
 	public interface IShader
 	{
 		void SetBool(string name, bool value);
@@ -124,6 +137,17 @@ namespace OpenRA
 		void SetTexture(string param, ITexture texture);
 		void SetMatrix(string param, float[] mtx);
 		void PrepareRender();
+		void Bind();
+	}
+
+	public interface IShaderBindings
+	{
+		string VertexShaderName { get; }
+		string VertexShaderCode { get; }
+		string FragmentShaderName { get; }
+		string FragmentShaderCode { get; }
+		int Stride { get; }
+		ShaderVertexAttribute[] Attributes { get; }
 	}
 
 	public enum TextureScaleFilter { Nearest, Linear }
@@ -132,6 +156,7 @@ namespace OpenRA
 	{
 		void SetData(byte[] colors, int width, int height);
 		void SetFloatData(float[] data, int width, int height);
+		void SetDataFromReadBuffer(Rectangle rect);
 		byte[] GetData();
 		Size Size { get; }
 		TextureScaleFilter ScaleFilter { get; set; }

OpenRA.Game/Graphics/RenderPostProcessPassVertex.cs

@@ -0,0 +1,64 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Runtime.InteropServices;
+
+namespace OpenRA.Graphics
+{
+	[StructLayout(LayoutKind.Sequential)]
+	public readonly struct RenderPostProcessPassVertex
+	{
+		public readonly float X, Y;
+
+		public RenderPostProcessPassVertex(float x, float y)
+		{
+			X = x; Y = y;
+		}
+	}
+
+	[StructLayout(LayoutKind.Sequential)]
+	public readonly struct RenderPostProcessPassTexturedVertex
+	{
+		// 3d position
+		public readonly float X, Y;
+		public readonly float S, T;
+
+		public RenderPostProcessPassTexturedVertex(float x, float y, float s, float t)
+		{
+			X = x; Y = y;
+			S = s; T = t;
+		}
+	}
+
+	public sealed class RenderPostProcessPassShaderBindings : ShaderBindings
+	{
+		public RenderPostProcessPassShaderBindings(string name)
+			: base("postprocess", "postprocess_" + name) { }
+
+		public override ShaderVertexAttribute[] Attributes { get; } = new[]
+		{
+			new ShaderVertexAttribute("aVertexPosition", ShaderVertexAttributeType.Float, 2, 0)
+		};
+	}
+
+	public sealed class RenderPostProcessPassTexturedShaderBindings : ShaderBindings
+	{
+		public RenderPostProcessPassTexturedShaderBindings(string name)
+			: base("postprocess_textured", "postprocess_textured_" + name)
+		{ }
+
+		public override ShaderVertexAttribute[] Attributes { get; } = new[]
+		{
+			new ShaderVertexAttribute("aVertexPosition", ShaderVertexAttributeType.Float, 2, 0),
+			new ShaderVertexAttribute("aVertexTexCoord", ShaderVertexAttributeType.Float, 2, 8),
+		};
+	}
+}

OpenRA.Game/Graphics/RgbaColorRenderer.cs

@@ -21,7 +21,7 @@ namespace OpenRA.Graphics
 		static readonly float3 Offset = new(0.5f, 0.5f, 0f);
 
 		readonly SpriteRenderer parent;
-		readonly Vertex[] vertices = new Vertex[6];
+		readonly Vertex[] vertices = new Vertex[4];
 
 		public RgbaColorRenderer(SpriteRenderer parent)
 		{
@@ -45,14 +45,12 @@ namespace OpenRA.Graphics
 			var eb = endColor.B / 255.0f;
 			var ea = endColor.A / 255.0f;
 
-			vertices[0] = new Vertex(start - corner + Offset, sr, sg, sb, sa, 0, 0);
-			vertices[1] = new Vertex(start + corner + Offset, sr, sg, sb, sa, 0, 0);
-			vertices[2] = new Vertex(end + corner + Offset, er, eg, eb, ea, 0, 0);
-			vertices[3] = new Vertex(end + corner + Offset, er, eg, eb, ea, 0, 0);
-			vertices[4] = new Vertex(end - corner + Offset, er, eg, eb, ea, 0, 0);
-			vertices[5] = new Vertex(start - corner + Offset, sr, sg, sb, sa, 0, 0);
+			vertices[0] = new Vertex(start - corner + Offset, sr, sg, sb, sa, 0);
+			vertices[1] = new Vertex(start + corner + Offset, sr, sg, sb, sa, 0);
+			vertices[2] = new Vertex(end + corner + Offset, er, eg, eb, ea, 0);
+			vertices[3] = new Vertex(end - corner + Offset, er, eg, eb, ea, 0);
 
-			parent.DrawRGBAVertices(vertices, blendMode);
+			parent.DrawRGBAQuad(vertices, blendMode);
 		}
 
 		public void DrawLine(in float3 start, in float3 end, float width, Color color, BlendMode blendMode = BlendMode.Alpha)
@@ -66,13 +64,11 @@ namespace OpenRA.Graphics
 			var b = color.B / 255.0f;
 			var a = color.A / 255.0f;
 
-			vertices[0] = new Vertex(start - corner + Offset, r, g, b, a, 0, 0);
-			vertices[1] = new Vertex(start + corner + Offset, r, g, b, a, 0, 0);
-			vertices[2] = new Vertex(end + corner + Offset, r, g, b, a, 0, 0);
-			vertices[3] = new Vertex(end + corner + Offset, r, g, b, a, 0, 0);
-			vertices[4] = new Vertex(end - corner + Offset, r, g, b, a, 0, 0);
-			vertices[5] = new Vertex(start - corner + Offset, r, g, b, a, 0, 0);
-			parent.DrawRGBAVertices(vertices, blendMode);
+			vertices[0] = new Vertex(start - corner + Offset, r, g, b, a, 0);
+			vertices[1] = new Vertex(start + corner + Offset, r, g, b, a, 0);
+			vertices[2] = new Vertex(end + corner + Offset, r, g, b, a, 0);
+			vertices[3] = new Vertex(end - corner + Offset, r, g, b, a, 0);
+			parent.DrawRGBAQuad(vertices, blendMode);
 		}
 
 		/// <summary>
@@ -157,13 +153,11 @@ namespace OpenRA.Graphics
 				var cd = closed || i < limit - 1 ? IntersectionOf(end - corner, dir, end - nextCorner, nextDir) : end - corner;
 
 				// Fill segment
-				vertices[0] = new Vertex(ca + Offset, r, g, b, a, 0, 0);
-				vertices[1] = new Vertex(cb + Offset, r, g, b, a, 0, 0);
-				vertices[2] = new Vertex(cc + Offset, r, g, b, a, 0, 0);
-				vertices[3] = new Vertex(cc + Offset, r, g, b, a, 0, 0);
-				vertices[4] = new Vertex(cd + Offset, r, g, b, a, 0, 0);
-				vertices[5] = new Vertex(ca + Offset, r, g, b, a, 0, 0);
-				parent.DrawRGBAVertices(vertices, blendMode);
+				vertices[0] = new Vertex(ca + Offset, r, g, b, a, 0);
+				vertices[1] = new Vertex(cb + Offset, r, g, b, a, 0);
+				vertices[2] = new Vertex(cc + Offset, r, g, b, a, 0);
+				vertices[3] = new Vertex(cd + Offset, r, g, b, a, 0);
+				parent.DrawRGBAQuad(vertices, blendMode);
 
 				// Advance line segment
 				end = next;
@@ -200,20 +194,6 @@ namespace OpenRA.Graphics
 			DrawPolygon(new[] { tl, tr, br, bl }, width, color, blendMode);
 		}
 
-		public void FillTriangle(in float3 a, in float3 b, in float3 c, Color color, BlendMode blendMode = BlendMode.Alpha)
-		{
-			color = Util.PremultiplyAlpha(color);
-			var cr = color.R / 255.0f;
-			var cg = color.G / 255.0f;
-			var cb = color.B / 255.0f;
-			var ca = color.A / 255.0f;
-
-			vertices[0] = new Vertex(a + Offset, cr, cg, cb, ca, 0, 0);
-			vertices[1] = new Vertex(b + Offset, cr, cg, cb, ca, 0, 0);
-			vertices[2] = new Vertex(c + Offset, cr, cg, cb, ca, 0, 0);
-			parent.DrawRGBAVertices(vertices, blendMode);
-		}
-
 		public void FillRect(in float3 tl, in float3 br, Color color, BlendMode blendMode = BlendMode.Alpha)
 		{
 			var tr = new float3(br.X, tl.Y, tl.Z);
@@ -229,13 +209,11 @@ namespace OpenRA.Graphics
 			var cb = color.B / 255.0f;
 			var ca = color.A / 255.0f;
 
-			vertices[0] = new Vertex(a + Offset, cr, cg, cb, ca, 0, 0);
-			vertices[1] = new Vertex(b + Offset, cr, cg, cb, ca, 0, 0);
-			vertices[2] = new Vertex(c + Offset, cr, cg, cb, ca, 0, 0);
-			vertices[3] = new Vertex(c + Offset, cr, cg, cb, ca, 0, 0);
-			vertices[4] = new Vertex(d + Offset, cr, cg, cb, ca, 0, 0);
-			vertices[5] = new Vertex(a + Offset, cr, cg, cb, ca, 0, 0);
-			parent.DrawRGBAVertices(vertices, blendMode);
+			vertices[0] = new Vertex(a + Offset, cr, cg, cb, ca, 0);
+			vertices[1] = new Vertex(b + Offset, cr, cg, cb, ca, 0);
+			vertices[2] = new Vertex(c + Offset, cr, cg, cb, ca, 0);
+			vertices[3] = new Vertex(d + Offset, cr, cg, cb, ca, 0);
+			parent.DrawRGBAQuad(vertices, blendMode);
 		}
 
 		public void FillRect(in float3 a, in float3 b, in float3 c, in float3 d, Color topLeftColor, Color topRightColor, Color bottomRightColor, Color bottomLeftColor, BlendMode blendMode = BlendMode.Alpha)
@@ -243,11 +221,9 @@ namespace OpenRA.Graphics
 			vertices[0] = VertexWithColor(a + Offset, topLeftColor);
 			vertices[1] = VertexWithColor(b + Offset, topRightColor);
 			vertices[2] = VertexWithColor(c + Offset, bottomRightColor);
-			vertices[3] = VertexWithColor(c + Offset, bottomRightColor);
-			vertices[4] = VertexWithColor(d + Offset, bottomLeftColor);
-			vertices[5] = VertexWithColor(a + Offset, topLeftColor);
+			vertices[3] = VertexWithColor(d + Offset, bottomLeftColor);
 
-			parent.DrawRGBAVertices(vertices, blendMode);
+			parent.DrawRGBAQuad(vertices, blendMode);
 		}
 
 		static Vertex VertexWithColor(in float3 xyz, Color color)
@@ -258,7 +234,7 @@ namespace OpenRA.Graphics
 			var cb = color.B / 255.0f;
 			var ca = color.A / 255.0f;
 
-			return new Vertex(xyz, cr, cg, cb, ca, 0, 0);
+			return new Vertex(xyz, cr, cg, cb, ca, 0);
 		}
 
 		public void FillEllipse(in float3 tl, in float3 br, Color color, BlendMode blendMode = BlendMode.Alpha)

OpenRA.Game/Graphics/SequenceSet.cs

@@ -94,7 +94,7 @@ namespace OpenRA.Graphics
 			foreach (var node in nodes)
 			{
 				// Nodes starting with ^ are inheritable but never loaded directly
-				if (node.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal))
+				if (node.Key.StartsWith(ActorInfo.AbstractActorPrefix))
 					continue;
 
 				images[node.Key] = modData.SpriteSequenceLoader.ParseSequences(modData, tileSet, SpriteCache, node);

OpenRA.Game/Graphics/ShaderBindings.cs

@@ -0,0 +1,70 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.IO;
+using System.Linq;
+
+namespace OpenRA.Graphics
+{
+	public enum ShaderVertexAttributeType
+	{
+		// Assign the underlying OpenGL type values
+		// to simplify enum use in the shader
+		Float = 0x1406, // GL_FLOAT
+		Int = 0x1404, // GL_INT
+		UInt = 0x1405 // GL_UNSIGNED_INT
+	}
+
+	public readonly struct ShaderVertexAttribute
+	{
+		public readonly string Name;
+		public readonly ShaderVertexAttributeType Type;
+		public readonly int Components;
+		public readonly int Offset;
+
+		public ShaderVertexAttribute(string name, ShaderVertexAttributeType type, int components, int offset)
+		{
+			Name = name;
+			Type = type;
+			Components = components;
+			Offset = offset;
+		}
+	}
+
+	public abstract class ShaderBindings : IShaderBindings
+	{
+		public string VertexShaderName { get; }
+		public string VertexShaderCode { get; }
+		public string FragmentShaderName { get; }
+		public string FragmentShaderCode { get; }
+		public int Stride { get; }
+
+		public abstract ShaderVertexAttribute[] Attributes { get; }
+
+		protected ShaderBindings(string name)
+			: this(name, name) { }
+
+		protected ShaderBindings(string vertexName, string fragmentName)
+		{
+			Stride = Attributes.Sum(a => a.Components * 4);
+			VertexShaderName = vertexName;
+			VertexShaderCode = GetShaderCode(VertexShaderName + ".vert");
+			FragmentShaderName = fragmentName;
+			FragmentShaderCode = GetShaderCode(FragmentShaderName + ".frag");
+		}
+
+		public static string GetShaderCode(string filename)
+		{
+			var filepath = Path.Combine(Platform.EngineDir, "glsl", filename);
+			return File.ReadAllText(filepath);
+		}
+	}
+}

OpenRA.Game/Graphics/SheetBuilder.cs

@@ -82,16 +82,16 @@ namespace OpenRA.Graphics
 			this.margin = margin;
 		}
 
-		public Sprite Add(ISpriteFrame frame) { return Add(frame.Data, frame.Type, frame.Size, 0, frame.Offset); }
-		public Sprite Add(byte[] src, SpriteFrameType type, Size size) { return Add(src, type, size, 0, float3.Zero); }
-		public Sprite Add(byte[] src, SpriteFrameType type, Size size, float zRamp, in float3 spriteOffset)
+		public Sprite Add(ISpriteFrame frame, bool premultiplied = false) { return Add(frame.Data, frame.Type, frame.Size, 0, frame.Offset, premultiplied); }
+		public Sprite Add(byte[] src, SpriteFrameType type, Size size, bool premultiplied = false) { return Add(src, type, size, 0, float3.Zero, premultiplied); }
+		public Sprite Add(byte[] src, SpriteFrameType type, Size size, float zRamp, in float3 spriteOffset, bool premultiplied = false)
 		{
 			// Don't bother allocating empty sprites
 			if (size.Width == 0 || size.Height == 0)
 				return new Sprite(Current, Rectangle.Empty, 0, spriteOffset, CurrentChannel, BlendMode.Alpha);
 
 			var rect = Allocate(size, zRamp, spriteOffset);
-			Util.FastCopyIntoChannel(rect, src, type);
+			Util.FastCopyIntoChannel(rect, src, type, premultiplied);
 			Current.CommitBufferedData();
 			return rect;
 		}

OpenRA.Game/Graphics/Sprite.cs

@@ -42,11 +42,11 @@ namespace OpenRA.Graphics
 			// in rendering a line of texels that sample outside the sprite rectangle.
 			// Insetting the texture coordinates by a small fraction of a pixel avoids this
 			// with negligible impact on the 1:1 rendering case.
-			var inset = 1 / 128f;
-			Left = (Math.Min(bounds.Left, bounds.Right) + inset) / sheet.Size.Width;
-			Top = (Math.Min(bounds.Top, bounds.Bottom) + inset) / sheet.Size.Height;
-			Right = (Math.Max(bounds.Left, bounds.Right) - inset) / sheet.Size.Width;
-			Bottom = (Math.Max(bounds.Top, bounds.Bottom) - inset) / sheet.Size.Height;
+			const float Inset = 1 / 128f;
+			Left = (Math.Min(bounds.Left, bounds.Right) + Inset) / sheet.Size.Width;
+			Top = (Math.Min(bounds.Top, bounds.Bottom) + Inset) / sheet.Size.Height;
+			Right = (Math.Max(bounds.Left, bounds.Right) - Inset) / sheet.Size.Width;
+			Bottom = (Math.Max(bounds.Top, bounds.Bottom) - Inset) / sheet.Size.Height;
 		}
 	}
 

OpenRA.Game/Graphics/SpriteCache.cs

@@ -24,11 +24,9 @@ namespace OpenRA.Graphics
 		readonly ISpriteLoader[] loaders;
 		readonly IReadOnlyFileSystem fileSystem;
 
-		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location)> spriteReservations = new();
-		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location)> frameReservations = new();
+		readonly Dictionary<int, (int[] Frames, MiniYamlNode.SourceLocation Location, Func<ISpriteFrame, ISpriteFrame> AdjustFrame, bool Premultiplied)> spriteReservations = new();
 		readonly Dictionary<string, List<int>> reservationsByFilename = new();
 
-		readonly Dictionary<int, ISpriteFrame[]> resolvedFrames = new();
 		readonly Dictionary<int, Sprite[]> resolvedSprites = new();
 
 		readonly Dictionary<int, (string Filename, MiniYamlNode.SourceLocation Location)> missingFiles = new();
@@ -47,18 +45,10 @@ namespace OpenRA.Graphics
 			this.loaders = loaders;
 		}
 
-		public int ReserveSprites(string filename, IEnumerable<int> frames, MiniYamlNode.SourceLocation location)
+		public int ReserveSprites(string filename, IEnumerable<int> frames, MiniYamlNode.SourceLocation location, Func<ISpriteFrame, ISpriteFrame> adjustFrame = null, bool premultiplied = false)
 		{
 			var token = nextReservationToken++;
-			spriteReservations[token] = (frames?.ToArray(), location);
-			reservationsByFilename.GetOrAdd(filename, _ => new List<int>()).Add(token);
-			return token;
-		}
-
-		public int ReserveFrames(string filename, IEnumerable<int> frames, MiniYamlNode.SourceLocation location)
-		{
-			var token = nextReservationToken++;
-			frameReservations[token] = (frames?.ToArray(), location);
+			spriteReservations[token] = (frames?.ToArray(), location, adjustFrame, premultiplied);
 			reservationsByFilename.GetOrAdd(filename, _ => new List<int>()).Add(token);
 			return token;
 		}
@@ -84,60 +74,73 @@ namespace OpenRA.Graphics
 			foreach (var sb in SheetBuilders.Values)
 				sb.Current.CreateBuffer();
 
-			var spriteCache = new Dictionary<int, Sprite>();
+			var pendingResolve = new List<(
+				string Filename,
+				int FrameIndex,
+				bool Premultiplied,
+				Func<ISpriteFrame, ISpriteFrame> AdjustFrame,
+				ISpriteFrame Frame,
+				Sprite[] SpritesForToken)>();
 			foreach (var (filename, tokens) in reservationsByFilename)
 			{
 				modData.LoadScreen?.Display();
 				var loadedFrames = GetFrames(fileSystem, filename, loaders, out _);
 				foreach (var token in tokens)
 				{
-					if (frameReservations.TryGetValue(token, out var r))
-					{
-						if (loadedFrames != null)
-						{
-							if (r.Frames != null)
-							{
-								var resolved = new ISpriteFrame[loadedFrames.Length];
-								foreach (var i in r.Frames)
-									resolved[i] = loadedFrames[i];
-								resolvedFrames[token] = resolved;
-							}
-							else
-								resolvedFrames[token] = loadedFrames;
-						}
-						else
-						{
-							resolvedFrames[token] = null;
-							missingFiles[token] = (filename, r.Location);
-						}
-					}
-
-					if (spriteReservations.TryGetValue(token, out r))
+					if (spriteReservations.TryGetValue(token, out var rs))
 					{
 						if (loadedFrames != null)
 						{
 							var resolved = new Sprite[loadedFrames.Length];
-							var frames = r.Frames ?? Enumerable.Range(0, loadedFrames.Length);
-							foreach (var i in frames)
-								resolved[i] = spriteCache.GetOrAdd(i,
-									f => SheetBuilders[SheetBuilder.FrameTypeToSheetType(loadedFrames[f].Type)].Add(loadedFrames[f]));
-
 							resolvedSprites[token] = resolved;
+							var frames = rs.Frames ?? Enumerable.Range(0, loadedFrames.Length);
+
+							foreach (var i in frames)
+							{
+								var frame = loadedFrames[i];
+								if (rs.AdjustFrame != null)
+									frame = rs.AdjustFrame(frame);
+								pendingResolve.Add((filename, i, rs.Premultiplied, rs.AdjustFrame, frame, resolved));
+							}
 						}
 						else
 						{
 							resolvedSprites[token] = null;
-							missingFiles[token] = (filename, r.Location);
+							missingFiles[token] = (filename, rs.Location);
 						}
 					}
 				}
-
-				spriteCache.Clear();
 			}
 
 			spriteReservations.Clear();
-			frameReservations.Clear();
+			spriteReservations.TrimExcess();
 			reservationsByFilename.Clear();
+			reservationsByFilename.TrimExcess();
+
+			// When the sheet builder is adding sprites, it reserves height for the tallest sprite seen along the row.
+			// We can achieve better sheet packing by keeping sprites with similar heights together.
+			var orderedPendingResolve = pendingResolve.OrderBy(x => x.Frame.Size.Height);
+
+			var spriteCache = new Dictionary<(
+				string Filename,
+				int FrameIndex,
+				bool Premultiplied,
+				Func<ISpriteFrame, ISpriteFrame> AdjustFrame),
+				Sprite>(pendingResolve.Count);
+			foreach (var (filename, frameIndex, premultiplied, adjustFrame, frame, spritesForToken) in orderedPendingResolve)
+			{
+				// Premultiplied and non-premultiplied sprites must be cached separately
+				// to cover the case where the same image is requested in both versions.
+				spritesForToken[frameIndex] = spriteCache.GetOrAdd(
+					(filename, frameIndex, premultiplied, adjustFrame),
+					_ =>
+					{
+						var sheetBuilder = SheetBuilders[SheetBuilder.FrameTypeToSheetType(frame.Type)];
+						return sheetBuilder.Add(frame, premultiplied);
+					});
+
+				modData.LoadScreen?.Display();
+			}
 
 			foreach (var sb in SheetBuilders.Values)
 				sb.Current.ReleaseBuffer();
@@ -145,18 +148,11 @@ namespace OpenRA.Graphics
 
 		public Sprite[] ResolveSprites(int token)
 		{
-			var resolved = resolvedSprites[token];
-			resolvedSprites.Remove(token);
-			if (missingFiles.TryGetValue(token, out var r))
-				throw new FileNotFoundException($"{r.Location}: {r.Filename} not found", r.Filename);
+			if (!resolvedSprites.Remove(token, out var resolved))
+				throw new InvalidOperationException($"{nameof(token)} {token} has either already been resolved, or was never reserved via {nameof(ReserveSprites)}");
 
-			return resolved;
-		}
+			resolvedSprites.TrimExcess();
 
-		public ISpriteFrame[] ResolveFrames(int token)
-		{
-			var resolved = resolvedFrames[token];
-			resolvedFrames.Remove(token);
 			if (missingFiles.TryGetValue(token, out var r))
 				throw new FileNotFoundException($"{r.Location}: {r.Filename} not found", r.Filename);
 

OpenRA.Game/Graphics/SpriteLoader.cs

@@ -22,20 +22,30 @@ namespace OpenRA.Graphics
 	/// </summary>
 	public enum SpriteFrameType
 	{
-		// 8 bit index into an external palette
+		/// <summary>
+		/// 8 bit index into an external palette.
+		/// </summary>
 		Indexed8,
 
-		// 32 bit color such as returned by Color.ToArgb() or the bmp file format
-		// (remember that little-endian systems place the little bits in the first byte!)
+		/// <summary>
+		/// 32 bit color such as returned by Color.ToArgb() or the bmp file format
+		/// (remember that little-endian systems place the little bits in the first byte).
+		/// </summary>
 		Bgra32,
 
-		// Like BGRA, but without an alpha channel
+		/// <summary>
+		/// Like BGRA, but without an alpha channel.
+		/// </summary>
 		Bgr24,
 
-		// 32 bit color in big-endian format, like png
+		/// <summary>
+		/// 32 bit color in big-endian format, like png.
+		/// </summary>
 		Rgba32,
 
-		// Like RGBA, but without an alpha channel
+		/// <summary>
+		/// Like RGBA, but without an alpha channel.
+		/// </summary>
 		Rgb24
 	}
 

OpenRA.Game/Graphics/SpriteRenderer.cs

@@ -11,6 +11,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using OpenRA.Primitives;
 
 namespace OpenRA.Graphics
@@ -19,6 +20,7 @@ namespace OpenRA.Graphics
 	{
 		public const int SheetCount = 8;
 		static readonly string[] SheetIndexToTextureName = Exts.MakeArray(SheetCount, i => $"Texture{i}");
+		static readonly int UintSize = Marshal.SizeOf(typeof(uint));
 
 		readonly Renderer renderer;
 		readonly IShader shader;
@@ -27,21 +29,21 @@ namespace OpenRA.Graphics
 		readonly Sheet[] sheets = new Sheet[SheetCount];
 
 		BlendMode currentBlend = BlendMode.Alpha;
-		int nv = 0;
-		int ns = 0;
+		int vertexCount = 0;
+		int sheetCount = 0;
 
 		public SpriteRenderer(Renderer renderer, IShader shader)
 		{
 			this.renderer = renderer;
 			this.shader = shader;
-			vertices = renderer.Context.CreateVertices(renderer.TempBufferSize);
+			vertices = renderer.Context.CreateVertices<Vertex>(renderer.TempVertexBufferSize);
 		}
 
 		public void Flush()
 		{
-			if (nv > 0)
+			if (vertexCount > 0)
 			{
-				for (var i = 0; i < ns; i++)
+				for (var i = 0; i < sheetCount; i++)
 				{
 					shader.SetTexture(SheetIndexToTextureName[i], sheets[i].GetTexture());
 					sheets[i] = null;
@@ -50,12 +52,11 @@ namespace OpenRA.Graphics
 				renderer.Context.SetBlendMode(currentBlend);
 				shader.PrepareRender();
 
-				// PERF: The renderer may choose to replace vertices with a different temporary buffer.
-				renderer.DrawBatch(ref vertices, nv, PrimitiveType.TriangleList);
+				renderer.DrawQuadBatch(ref vertices, shader, vertexCount);
 				renderer.Context.SetBlendMode(BlendMode.None);
 
-				nv = 0;
-				ns = 0;
+				vertexCount = 0;
+				sheetCount = 0;
 			}
 		}
 
@@ -63,7 +64,7 @@ namespace OpenRA.Graphics
 		{
 			renderer.CurrentBatchRenderer = this;
 
-			if (s.BlendMode != currentBlend || nv + 6 > renderer.TempBufferSize)
+			if (s.BlendMode != currentBlend || vertexCount + 4 > renderer.TempVertexBufferSize)
 				Flush();
 
 			currentBlend = s.BlendMode;
@@ -71,7 +72,7 @@ namespace OpenRA.Graphics
 			// Check if the sheet (or secondary data sheet) have already been mapped
 			var sheet = s.Sheet;
 			var sheetIndex = 0;
-			for (; sheetIndex < ns; sheetIndex++)
+			for (; sheetIndex < sheetCount; sheetIndex++)
 				if (sheets[sheetIndex] == sheet)
 					break;
 
@@ -80,7 +81,7 @@ namespace OpenRA.Graphics
 			if (ss != null)
 			{
 				var secondarySheet = ss.SecondarySheet;
-				for (; secondarySheetIndex < ns; secondarySheetIndex++)
+				for (; secondarySheetIndex < sheetCount; secondarySheetIndex++)
 					if (sheets[secondarySheetIndex] == secondarySheet)
 						break;
 
@@ -99,22 +100,22 @@ namespace OpenRA.Graphics
 				secondarySheetIndex = ss != null && ss.SecondarySheet != sheet ? 1 : 0;
 			}
 
-			if (sheetIndex >= ns)
+			if (sheetIndex >= sheetCount)
 			{
 				sheets[sheetIndex] = sheet;
-				ns++;
+				sheetCount++;
 			}
 
-			if (secondarySheetIndex >= ns && ss != null)
+			if (secondarySheetIndex >= sheetCount && ss != null)
 			{
 				sheets[secondarySheetIndex] = ss.SecondarySheet;
-				ns++;
+				sheetCount++;
 			}
 
 			return new int2(sheetIndex, secondarySheetIndex);
 		}
 
-		static float ResolveTextureIndex(Sprite s, PaletteReference pal)
+		static int ResolveTextureIndex(Sprite s, PaletteReference pal)
 		{
 			if (pal == null)
 				return 0;
@@ -128,20 +129,20 @@ namespace OpenRA.Graphics
 			return pal.TextureIndex;
 		}
 
-		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 location, in float3 scale, float rotation = 0f)
+		internal void DrawSprite(Sprite s, int paletteTextureIndex, in float3 location, in float3 scale, float rotation = 0f)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, nv, scale * s.Size, float3.Ones,
+			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, vertexCount, scale * s.Size, float3.Ones,
 								1f, rotation);
-			nv += 6;
+			vertexCount += 4;
 		}
 
-		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 location, float scale, float rotation = 0f)
+		internal void DrawSprite(Sprite s, int paletteTextureIndex, in float3 location, float scale, float rotation = 0f)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, nv, scale * s.Size, float3.Ones,
+			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, vertexCount, scale * s.Size, float3.Ones,
 								1f, rotation);
-			nv += 6;
+			vertexCount += 4;
 		}
 
 		public void DrawSprite(Sprite s, PaletteReference pal, in float3 location, float scale = 1f, float rotation = 0f)
@@ -149,13 +150,13 @@ namespace OpenRA.Graphics
 			DrawSprite(s, ResolveTextureIndex(s, pal), location, scale, rotation);
 		}
 
-		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 location, float scale, in float3 tint, float alpha,
+		internal void DrawSprite(Sprite s, int paletteTextureIndex, in float3 location, float scale, in float3 tint, float alpha,
 			float rotation = 0f)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, nv, scale * s.Size, tint, alpha,
+			Util.FastCreateQuad(vertices, location + scale * s.Offset, s, samplers, paletteTextureIndex, vertexCount, scale * s.Size, tint, alpha,
 								rotation);
-			nv += 6;
+			vertexCount += 4;
 		}
 
 		public void DrawSprite(Sprite s, PaletteReference pal, in float3 location, float scale, in float3 tint, float alpha,
@@ -164,14 +165,14 @@ namespace OpenRA.Graphics
 			DrawSprite(s, ResolveTextureIndex(s, pal), location, scale, tint, alpha, rotation);
 		}
 
-		internal void DrawSprite(Sprite s, float paletteTextureIndex, in float3 a, in float3 b, in float3 c, in float3 d, in float3 tint, float alpha)
+		internal void DrawSprite(Sprite s, int paletteTextureIndex, in float3 a, in float3 b, in float3 c, in float3 d, in float3 tint, float alpha)
 		{
 			var samplers = SetRenderStateForSprite(s);
-			Util.FastCreateQuad(vertices, a, b, c, d, s, samplers, paletteTextureIndex, tint, alpha, nv);
-			nv += 6;
+			Util.FastCreateQuad(vertices, a, b, c, d, s, samplers, paletteTextureIndex, tint, alpha, vertexCount);
+			vertexCount += 4;
 		}
 
-		public void DrawVertexBuffer(IVertexBuffer<Vertex> buffer, int start, int length, PrimitiveType type, IEnumerable<Sheet> sheets, BlendMode blendMode)
+		public void DrawVertexBuffer(IVertexBuffer<Vertex> buffer, IIndexBuffer indices, int start, int length, IEnumerable<Sheet> sheets, BlendMode blendMode)
 		{
 			var i = 0;
 			foreach (var s in sheets)
@@ -185,7 +186,7 @@ namespace OpenRA.Graphics
 
 			renderer.Context.SetBlendMode(blendMode);
 			shader.PrepareRender();
-			renderer.DrawBatch(buffer, start, length, type);
+			renderer.DrawQuadBatch(buffer, indices, shader, length, UintSize * start);
 			renderer.Context.SetBlendMode(BlendMode.None);
 		}
 
@@ -196,29 +197,32 @@ namespace OpenRA.Graphics
 		}
 
 		// For RGBAColorRenderer
-		internal void DrawRGBAVertices(Vertex[] v, BlendMode blendMode)
+		internal void DrawRGBAQuad(Vertex[] v, BlendMode blendMode)
 		{
 			renderer.CurrentBatchRenderer = this;
 
-			if (currentBlend != blendMode || nv + v.Length > renderer.TempBufferSize)
+			if (currentBlend != blendMode || vertexCount + 4 > renderer.TempVertexBufferSize)
 				Flush();
 
 			currentBlend = blendMode;
-			Array.Copy(v, 0, vertices, nv, v.Length);
-			nv += v.Length;
+
+			Array.Copy(v, 0, vertices, vertexCount, v.Length);
+			vertexCount += 4;
 		}
 
-		public void SetPalette(ITexture palette, ITexture colorShifts)
+		public void SetPalette(HardwarePalette palette)
 		{
-			shader.SetTexture("Palette", palette);
-			shader.SetTexture("ColorShifts", colorShifts);
+			shader.SetTexture("Palette", palette.Texture);
+			shader.SetTexture("ColorShifts", palette.ColorShifts);
+			shader.SetVec("PaletteRows", palette.Height);
 		}
 
 		public void SetViewportParams(Size sheetSize, int downscale, float depthMargin, int2 scroll)
 		{
-			// Calculate the scale (r1) and offset (r2) that convert from OpenRA viewport pixels
-			// to OpenGL normalized device coordinates (NDC). OpenGL expects coordinates to vary from [-1, 1],
-			// so we rescale viewport pixels to the range [0, 2] using r1 then subtract 1 using r2.
+			// OpenGL only renders x and y coordinates inside [-1, 1] range. We project world coordinates
+			// using p1 to values [0, 2] and then subtract by 1 using p2, where p stands for projection. It's
+			// standard practice for shaders to use a projection matrix, but as we project orthographically
+			// we are able to send less data to the GPU.
 			var width = 2f / (downscale * sheetSize.Width);
 			var height = 2f / (downscale * sheetSize.Height);
 
@@ -239,8 +243,8 @@ namespace OpenRA.Graphics
 			var depth = depthMargin != 0f ? 2f / (downscale * (sheetSize.Height + depthMargin)) : 0;
 			shader.SetVec("DepthTextureScale", 128 * depth);
 			shader.SetVec("Scroll", scroll.X, scroll.Y, depthMargin != 0f ? scroll.Y : 0);
-			shader.SetVec("r1", width, height, -depth);
-			shader.SetVec("r2", -1, -1, depthMargin != 0f ? 1 : 0);
+			shader.SetVec("p1", width, height, -depth);
+			shader.SetVec("p2", -1, -1, depthMargin != 0f ? 1 : 0);
 		}
 
 		public void SetDepthPreview(bool enabled, float contrast, float offset)

OpenRA.Game/Graphics/TerrainSpriteLayer.cs

@@ -12,12 +12,15 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Runtime.CompilerServices;
 
 namespace OpenRA.Graphics
 {
 	public sealed class TerrainSpriteLayer : IDisposable
 	{
-		static readonly int[] CornerVertexMap = { 0, 1, 2, 2, 3, 0 };
+		// PERF: we can reuse the IndexBuffer as all layers have the same size.
+		static readonly ConditionalWeakTable<World, IndexBufferRc> IndexBuffers = new();
+		readonly IndexBufferRc indexBufferWrapper;
 
 		public readonly BlendMode BlendMode;
 
@@ -28,7 +31,8 @@ namespace OpenRA.Graphics
 		readonly Vertex[] vertices;
 		readonly bool[] ignoreTint;
 		readonly HashSet<int> dirtyRows = new();
-		readonly int rowStride;
+		readonly int indexRowStride;
+		readonly int vertexRowStride;
 		readonly bool restrictToBounds;
 
 		readonly WorldRenderer worldRenderer;
@@ -43,19 +47,25 @@ namespace OpenRA.Graphics
 			this.emptySprite = emptySprite;
 			sheets = new Sheet[SpriteRenderer.SheetCount];
 			BlendMode = blendMode;
-
 			map = world.Map;
-			rowStride = 6 * map.MapSize.X;
 
-			vertices = new Vertex[rowStride * map.MapSize.Y];
+			vertexRowStride = 4 * map.MapSize.X;
+			vertices = new Vertex[vertexRowStride * map.MapSize.Y];
+			vertexBuffer = Game.Renderer.Context.CreateVertexBuffer<Vertex>(vertices.Length);
+
+			indexRowStride = 6 * map.MapSize.X;
+			lock (IndexBuffers)
+			{
+				indexBufferWrapper = IndexBuffers.GetValue(world, world => new IndexBufferRc(world));
+				indexBufferWrapper.AddRef();
+			}
+
 			palettes = new PaletteReference[map.MapSize.X * map.MapSize.Y];
-			vertexBuffer = Game.Renderer.Context.CreateVertexBuffer(vertices.Length);
-
 			wr.PaletteInvalidated += UpdatePaletteIndices;
 
 			if (wr.TerrainLighting != null)
 			{
-				ignoreTint = new bool[rowStride * map.MapSize.Y];
+				ignoreTint = new bool[vertexRowStride * map.MapSize.Y];
 				wr.TerrainLighting.CellChanged += UpdateTint;
 			}
 		}
@@ -65,8 +75,9 @@ namespace OpenRA.Graphics
 			for (var i = 0; i < vertices.Length; i++)
 			{
 				var v = vertices[i];
-				var p = palettes[i / 6]?.TextureIndex ?? 0;
-				vertices[i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, p, v.C, v.R, v.G, v.B, v.A);
+				var p = palettes[i / 4]?.TextureIndex ?? 0;
+				var c = (uint)((p & 0xFFFF) << 16) | (v.C & 0xFFFF);
+				vertices[i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, c, v.R, v.G, v.B, v.A);
 			}
 
 			for (var row = 0; row < map.MapSize.Y; row++)
@@ -97,13 +108,13 @@ namespace OpenRA.Graphics
 
 		void UpdateTint(MPos uv)
 		{
-			var offset = rowStride * uv.V + 6 * uv.U;
+			var offset = vertexRowStride * uv.V + 4 * uv.U;
 			if (ignoreTint[offset])
 			{
-				for (var i = 0; i < 6; i++)
+				for (var i = 0; i < 4; i++)
 				{
 					var v = vertices[offset + i];
-					vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, v.P, v.C, v.A * float3.Ones, v.A);
+					vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, v.C, v.A * float3.Ones, v.A);
 				}
 
 				return;
@@ -125,10 +136,10 @@ namespace OpenRA.Graphics
 
 			// Apply tint directly to the underlying vertices
 			// This saves us from having to re-query the sprite information, which has not changed
-			for (var i = 0; i < 6; i++)
+			for (var i = 0; i < 4; i++)
 			{
 				var v = vertices[offset + i];
-				vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, v.P, v.C, v.A * weights[CornerVertexMap[i]], v.A);
+				vertices[offset + i] = new Vertex(v.X, v.Y, v.Z, v.S, v.T, v.U, v.V, v.C, v.A * weights[i], v.A);
 			}
 
 			dirtyRows.Add(uv.V);
@@ -180,7 +191,7 @@ namespace OpenRA.Graphics
 			if (!map.Tiles.Contains(uv))
 				return;
 
-			var offset = rowStride * uv.V + 6 * uv.U;
+			var offset = vertexRowStride * uv.V + 4 * uv.U;
 			Util.FastCreateQuad(vertices, pos, sprite, samplers, palette?.TextureIndex ?? 0, offset, scale * sprite.Size, alpha * float3.Ones, alpha);
 			palettes[uv.V * map.MapSize.X + uv.U] = palette;
 
@@ -209,13 +220,13 @@ namespace OpenRA.Graphics
 				if (!dirtyRows.Remove(row))
 					continue;
 
-				var rowOffset = rowStride * row;
-				vertexBuffer.SetData(vertices, rowOffset, rowOffset, rowStride);
+				var rowOffset = vertexRowStride * row;
+				vertexBuffer.SetData(vertices, rowOffset, rowOffset, vertexRowStride);
 			}
 
 			Game.Renderer.WorldSpriteRenderer.DrawVertexBuffer(
-				vertexBuffer, rowStride * firstRow, rowStride * (lastRow - firstRow),
-				PrimitiveType.TriangleList, sheets, BlendMode);
+				vertexBuffer, indexBufferWrapper.Buffer, indexRowStride * firstRow,
+				indexRowStride * (lastRow - firstRow), sheets, BlendMode);
 
 			Game.Renderer.Flush();
 		}
@@ -227,6 +238,29 @@ namespace OpenRA.Graphics
 				worldRenderer.TerrainLighting.CellChanged -= UpdateTint;
 
 			vertexBuffer.Dispose();
+
+			lock (IndexBuffers)
+				indexBufferWrapper.Dispose();
+		}
+
+		sealed class IndexBufferRc : IDisposable
+		{
+			public IIndexBuffer Buffer;
+			int count;
+
+			public IndexBufferRc(World world)
+			{
+				Buffer = Game.Renderer.Context.CreateIndexBuffer(Util.CreateQuadIndices(world.Map.MapSize.X * world.Map.MapSize.Y));
+			}
+
+			public void AddRef() { count++; }
+
+			public void Dispose()
+			{
+				count--;
+				if (count == 0)
+					Buffer.Dispose();
+			}
 		}
 	}
 }

OpenRA.Game/Graphics/Util.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System;
+using System.Runtime.InteropServices;
 using OpenRA.FileFormats;
 using OpenRA.Primitives;
 
@@ -20,7 +21,17 @@ namespace OpenRA.Graphics
 		// yes, our channel order is nuts.
 		static readonly int[] ChannelMasks = { 2, 1, 0, 3 };
 
-		public static void FastCreateQuad(Vertex[] vertices, in float3 o, Sprite r, int2 samplers, float paletteTextureIndex, int nv,
+		public static uint[] CreateQuadIndices(int quads)
+		{
+			var indices = new uint[quads * 6];
+			ReadOnlySpan<uint> cornerVertexMap = stackalloc uint[] { 0, 1, 2, 2, 3, 0 };
+			for (var i = 0; i < indices.Length; i++)
+				indices[i] = cornerVertexMap[i % 6] + (uint)(4 * (i / 6));
+
+			return indices;
+		}
+
+		public static void FastCreateQuad(Vertex[] vertices, in float3 o, Sprite r, int2 samplers, int paletteTextureIndex, int nv,
 			in float3 size, in float3 tint, float alpha, float rotation = 0f)
 		{
 			float3 a, b, c, d;
@@ -62,7 +73,7 @@ namespace OpenRA.Graphics
 
 		public static void FastCreateQuad(Vertex[] vertices,
 			in float3 a, in float3 b, in float3 c, in float3 d,
-			Sprite r, int2 samplers, float paletteTextureIndex,
+			Sprite r, int2 samplers, int paletteTextureIndex,
 			in float3 tint, float alpha, int nv)
 		{
 			float sl = 0;
@@ -84,76 +95,33 @@ namespace OpenRA.Graphics
 				attribC |= samplers.Y << 9;
 			}
 
-			var fAttribC = (float)attribC;
-			vertices[nv] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC, tint, alpha);
-			vertices[nv + 1] = new Vertex(b, r.Right, r.Top, sr, st, paletteTextureIndex, fAttribC, tint, alpha);
-			vertices[nv + 2] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC, tint, alpha);
-			vertices[nv + 3] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC, tint, alpha);
-			vertices[nv + 4] = new Vertex(d, r.Left, r.Bottom, sl, sb, paletteTextureIndex, fAttribC, tint, alpha);
-			vertices[nv + 5] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC, tint, alpha);
+			attribC |= (paletteTextureIndex & 0xFFFF) << 16;
+
+			var uAttribC = (uint)attribC;
+			vertices[nv] = new Vertex(a, r.Left, r.Top, sl, st, uAttribC, tint, alpha);
+			vertices[nv + 1] = new Vertex(b, r.Right, r.Top, sr, st, uAttribC, tint, alpha);
+			vertices[nv + 2] = new Vertex(c, r.Right, r.Bottom, sr, sb, uAttribC, tint, alpha);
+			vertices[nv + 3] = new Vertex(d, r.Left, r.Bottom, sl, sb, uAttribC, tint, alpha);
 		}
 
-		public static void FastCopyIntoChannel(Sprite dest, byte[] src, SpriteFrameType srcType)
+		public static void FastCopyIntoChannel(Sprite dest, byte[] src, SpriteFrameType srcType, bool premultiplied = false)
 		{
 			var destData = dest.Sheet.GetData();
+			var stride = dest.Sheet.Size.Width;
+			var x = dest.Bounds.Left;
+			var y = dest.Bounds.Top;
 			var width = dest.Bounds.Width;
 			var height = dest.Bounds.Height;
 
 			if (dest.Channel == TextureChannel.RGBA)
 			{
-				var destStride = dest.Sheet.Size.Width;
-				unsafe
-				{
-					// Cast the data to an int array so we can copy the src data directly
-					fixed (byte* bd = &destData[0])
-					{
-						var data = (int*)bd;
-						var x = dest.Bounds.Left;
-						var y = dest.Bounds.Top;
-
-						var k = 0;
-						for (var j = 0; j < height; j++)
-						{
-							for (var i = 0; i < width; i++)
-							{
-								byte r, g, b, a;
-								switch (srcType)
-								{
-									case SpriteFrameType.Bgra32:
-									case SpriteFrameType.Bgr24:
-									{
-										b = src[k++];
-										g = src[k++];
-										r = src[k++];
-										a = srcType == SpriteFrameType.Bgra32 ? src[k++] : (byte)255;
-										break;
-									}
-
-									case SpriteFrameType.Rgba32:
-									case SpriteFrameType.Rgb24:
-									{
-										r = src[k++];
-										g = src[k++];
-										b = src[k++];
-										a = srcType == SpriteFrameType.Rgba32 ? src[k++] : (byte)255;
-										break;
-									}
-
-									default:
-										throw new InvalidOperationException($"Unknown SpriteFrameType {srcType}");
-								}
-
-								var cc = Color.FromArgb(a, r, g, b);
-								data[(y + j) * destStride + x + i] = PremultiplyAlpha(cc).ToArgb();
-							}
-						}
-					}
-				}
+				CopyIntoRgba(src, srcType, premultiplied, destData, x, y, width, height, stride);
 			}
 			else
 			{
-				var destStride = dest.Sheet.Size.Width * 4;
-				var destOffset = destStride * dest.Bounds.Top + dest.Bounds.Left * 4 + ChannelMasks[(int)dest.Channel];
+				// Copy into single channel of destination.
+				var destStride = stride * 4;
+				var destOffset = destStride * y + x * 4 + ChannelMasks[(int)dest.Channel];
 				var destSkip = destStride - 4 * width;
 
 				var srcOffset = 0;
@@ -170,56 +138,119 @@ namespace OpenRA.Graphics
 			}
 		}
 
+		static void CopyIntoRgba(
+			byte[] src, SpriteFrameType srcType, bool premultiplied, byte[] dest, int x, int y, int width, int height, int stride)
+		{
+			var si = 0;
+			var di = y * stride + x;
+			var d = MemoryMarshal.Cast<byte, uint>(dest);
+
+			// SpriteFrameType.Brga32 is a common source format, and it matches the destination format.
+			// Provide a fast past that just performs memory copies.
+			if (srcType == SpriteFrameType.Bgra32)
+			{
+				var s = MemoryMarshal.Cast<byte, uint>(src);
+				for (var h = 0; h < height; h++)
+				{
+					s[si..(si + width)].CopyTo(d[di..(di + width)]);
+
+					if (!premultiplied)
+					{
+						for (var w = 0; w < width; w++)
+						{
+							d[di] = PremultiplyAlpha(Color.FromArgb(d[di])).ToArgb();
+							di++;
+						}
+
+						di -= width;
+					}
+
+					si += width;
+					di += stride;
+				}
+
+				return;
+			}
+
+			for (var h = 0; h < height; h++)
+			{
+				for (var w = 0; w < width; w++)
+				{
+					byte r, g, b, a;
+					switch (srcType)
+					{
+						case SpriteFrameType.Bgra32:
+						case SpriteFrameType.Bgr24:
+							b = src[si++];
+							g = src[si++];
+							r = src[si++];
+							a = srcType == SpriteFrameType.Bgra32 ? src[si++] : byte.MaxValue;
+							break;
+
+						case SpriteFrameType.Rgba32:
+						case SpriteFrameType.Rgb24:
+							r = src[si++];
+							g = src[si++];
+							b = src[si++];
+							a = srcType == SpriteFrameType.Rgba32 ? src[si++] : byte.MaxValue;
+							break;
+
+						default:
+							throw new InvalidOperationException($"Unknown SpriteFrameType {srcType}");
+					}
+
+					var c = Color.FromArgb(a, r, g, b);
+					if (!premultiplied)
+						c = PremultiplyAlpha(c);
+					d[di++] = c.ToArgb();
+				}
+
+				di += stride - width;
+			}
+		}
+
 		public static void FastCopyIntoSprite(Sprite dest, Png src)
 		{
 			var destData = dest.Sheet.GetData();
-			var destStride = dest.Sheet.Size.Width;
+			var stride = dest.Sheet.Size.Width;
+			var x = dest.Bounds.Left;
+			var y = dest.Bounds.Top;
 			var width = dest.Bounds.Width;
 			var height = dest.Bounds.Height;
 
-			unsafe
+			var si = 0;
+			var di = y * stride + x;
+			var d = MemoryMarshal.Cast<byte, uint>(destData);
+
+			for (var h = 0; h < height; h++)
 			{
-				// Cast the data to an int array so we can copy the src data directly
-				fixed (byte* bd = &destData[0])
+				for (var w = 0; w < width; w++)
 				{
-					var data = (int*)bd;
-					var x = dest.Bounds.Left;
-					var y = dest.Bounds.Top;
-
-					var k = 0;
-					for (var j = 0; j < height; j++)
+					Color c;
+					switch (src.Type)
 					{
-						for (var i = 0; i < width; i++)
-						{
-							Color cc;
-							switch (src.Type)
-							{
-								case SpriteFrameType.Indexed8:
-								{
-									cc = src.Palette[src.Data[k++]];
-									break;
-								}
+						case SpriteFrameType.Indexed8:
+							c = src.Palette[src.Data[si++]];
+							break;
 
-								case SpriteFrameType.Rgba32:
-								case SpriteFrameType.Rgb24:
-								{
-									var r = src.Data[k++];
-									var g = src.Data[k++];
-									var b = src.Data[k++];
-									var a = src.Type == SpriteFrameType.Rgba32 ? src.Data[k++] : (byte)255;
-									cc = Color.FromArgb(a, r, g, b);
-									break;
-								}
+						case SpriteFrameType.Rgba32:
+						case SpriteFrameType.Rgb24:
+							var r = src.Data[si++];
+							var g = src.Data[si++];
+							var b = src.Data[si++];
+							var a = src.Type == SpriteFrameType.Rgba32 ? src.Data[si++] : byte.MaxValue;
+							c = Color.FromArgb(a, r, g, b);
+							break;
 
-								// Pngs don't support BGR[A], so no need to include them here
-								default:
-									throw new InvalidOperationException($"Unknown SpriteFrameType {src.Type}");
-							}
-
-							data[(y + j) * destStride + x + i] = PremultiplyAlpha(cc).ToArgb();
-						}
+						// PNGs don't support BGR[A], so no need to include them here
+						default:
+							throw new InvalidOperationException($"Unknown SpriteFrameType {src.Type}");
 					}
+
+					d[di++] = PremultiplyAlpha(c).ToArgb();
 				}
+
+				di += stride - width;
 			}
 		}
 
@@ -305,239 +336,5 @@ namespace OpenRA.Graphics
 				(int)((byte)(t * a2 * c2.G + 0.5f) + (1 - t) * (byte)(a1 * c1.G + 0.5f)),
 				(int)((byte)(t * a2 * c2.B + 0.5f) + (1 - t) * (byte)(a1 * c1.B + 0.5f))));
 		}
-
-		public static float[] IdentityMatrix()
-		{
-			return Exts.MakeArray(16, j => (j % 5 == 0) ? 1.0f : 0);
-		}
-
-		public static float[] ScaleMatrix(float sx, float sy, float sz)
-		{
-			var mtx = IdentityMatrix();
-			mtx[0] = sx;
-			mtx[5] = sy;
-			mtx[10] = sz;
-			return mtx;
-		}
-
-		public static float[] TranslationMatrix(float x, float y, float z)
-		{
-			var mtx = IdentityMatrix();
-			mtx[12] = x;
-			mtx[13] = y;
-			mtx[14] = z;
-			return mtx;
-		}
-
-		public static float[] MatrixMultiply(float[] lhs, float[] rhs)
-		{
-			var mtx = new float[16];
-			for (var i = 0; i < 4; i++)
-				for (var j = 0; j < 4; j++)
-				{
-					mtx[4 * i + j] = 0;
-					for (var k = 0; k < 4; k++)
-						mtx[4 * i + j] += lhs[4 * k + j] * rhs[4 * i + k];
-				}
-
-			return mtx;
-		}
-
-		public static float[] MatrixVectorMultiply(float[] mtx, float[] vec)
-		{
-			var ret = new float[4];
-			for (var j = 0; j < 4; j++)
-			{
-				ret[j] = 0;
-				for (var k = 0; k < 4; k++)
-					ret[j] += mtx[4 * k + j] * vec[k];
-			}
-
-			return ret;
-		}
-
-		public static float[] MatrixInverse(float[] m)
-		{
-			var mtx = new float[16];
-
-			mtx[0] = m[5] * m[10] * m[15] -
-				m[5] * m[11] * m[14] -
-				m[9] * m[6] * m[15] +
-				m[9] * m[7] * m[14] +
-				m[13] * m[6] * m[11] -
-				m[13] * m[7] * m[10];
-
-			mtx[4] = -m[4] * m[10] * m[15] +
-				m[4] * m[11] * m[14] +
-				m[8] * m[6] * m[15] -
-				m[8] * m[7] * m[14] -
-				m[12] * m[6] * m[11] +
-				m[12] * m[7] * m[10];
-
-			mtx[8] = m[4] * m[9] * m[15] -
-				m[4] * m[11] * m[13] -
-				m[8] * m[5] * m[15] +
-				m[8] * m[7] * m[13] +
-				m[12] * m[5] * m[11] -
-				m[12] * m[7] * m[9];
-
-			mtx[12] = -m[4] * m[9] * m[14] +
-				m[4] * m[10] * m[13] +
-				m[8] * m[5] * m[14] -
-				m[8] * m[6] * m[13] -
-				m[12] * m[5] * m[10] +
-				m[12] * m[6] * m[9];
-
-			mtx[1] = -m[1] * m[10] * m[15] +
-				m[1] * m[11] * m[14] +
-				m[9] * m[2] * m[15] -
-				m[9] * m[3] * m[14] -
-				m[13] * m[2] * m[11] +
-				m[13] * m[3] * m[10];
-
-			mtx[5] = m[0] * m[10] * m[15] -
-				m[0] * m[11] * m[14] -
-				m[8] * m[2] * m[15] +
-				m[8] * m[3] * m[14] +
-				m[12] * m[2] * m[11] -
-				m[12] * m[3] * m[10];
-
-			mtx[9] = -m[0] * m[9] * m[15] +
-				m[0] * m[11] * m[13] +
-				m[8] * m[1] * m[15] -
-				m[8] * m[3] * m[13] -
-				m[12] * m[1] * m[11] +
-				m[12] * m[3] * m[9];
-
-			mtx[13] = m[0] * m[9] * m[14] -
-				m[0] * m[10] * m[13] -
-				m[8] * m[1] * m[14] +
-				m[8] * m[2] * m[13] +
-				m[12] * m[1] * m[10] -
-				m[12] * m[2] * m[9];
-
-			mtx[2] = m[1] * m[6] * m[15] -
-				m[1] * m[7] * m[14] -
-				m[5] * m[2] * m[15] +
-				m[5] * m[3] * m[14] +
-				m[13] * m[2] * m[7] -
-				m[13] * m[3] * m[6];
-
-			mtx[6] = -m[0] * m[6] * m[15] +
-				m[0] * m[7] * m[14] +
-				m[4] * m[2] * m[15] -
-				m[4] * m[3] * m[14] -
-				m[12] * m[2] * m[7] +
-				m[12] * m[3] * m[6];
-
-			mtx[10] = m[0] * m[5] * m[15] -
-				m[0] * m[7] * m[13] -
-				m[4] * m[1] * m[15] +
-				m[4] * m[3] * m[13] +
-				m[12] * m[1] * m[7] -
-				m[12] * m[3] * m[5];
-
-			mtx[14] = -m[0] * m[5] * m[14] +
-				m[0] * m[6] * m[13] +
-				m[4] * m[1] * m[14] -
-				m[4] * m[2] * m[13] -
-				m[12] * m[1] * m[6] +
-				m[12] * m[2] * m[5];
-
-			mtx[3] = -m[1] * m[6] * m[11] +
-				m[1] * m[7] * m[10] +
-				m[5] * m[2] * m[11] -
-				m[5] * m[3] * m[10] -
-				m[9] * m[2] * m[7] +
-				m[9] * m[3] * m[6];
-
-			mtx[7] = m[0] * m[6] * m[11] -
-				m[0] * m[7] * m[10] -
-				m[4] * m[2] * m[11] +
-				m[4] * m[3] * m[10] +
-				m[8] * m[2] * m[7] -
-				m[8] * m[3] * m[6];
-
-			mtx[11] = -m[0] * m[5] * m[11] +
-				m[0] * m[7] * m[9] +
-				m[4] * m[1] * m[11] -
-				m[4] * m[3] * m[9] -
-				m[8] * m[1] * m[7] +
-				m[8] * m[3] * m[5];
-
-			mtx[15] = m[0] * m[5] * m[10] -
-				m[0] * m[6] * m[9] -
-				m[4] * m[1] * m[10] +
-				m[4] * m[2] * m[9] +
-				m[8] * m[1] * m[6] -
-				m[8] * m[2] * m[5];
-
-			var det = m[0] * mtx[0] + m[1] * mtx[4] + m[2] * mtx[8] + m[3] * mtx[12];
-			if (det == 0)
-				return null;
-
-			for (var i = 0; i < 16; i++)
-				mtx[i] *= 1 / det;
-
-			return mtx;
-		}
-
-		public static float[] MakeFloatMatrix(Int32Matrix4x4 imtx)
-		{
-			var multipler = 1f / imtx.M44;
-			return new[]
-			{
-				imtx.M11 * multipler,
-				imtx.M12 * multipler,
-				imtx.M13 * multipler,
-				imtx.M14 * multipler,
-
-				imtx.M21 * multipler,
-				imtx.M22 * multipler,
-				imtx.M23 * multipler,
-				imtx.M24 * multipler,
-
-				imtx.M31 * multipler,
-				imtx.M32 * multipler,
-				imtx.M33 * multipler,
-				imtx.M34 * multipler,
-
-				imtx.M41 * multipler,
-				imtx.M42 * multipler,
-				imtx.M43 * multipler,
-				imtx.M44 * multipler,
-			};
-		}
-
-		public static float[] MatrixAABBMultiply(float[] mtx, float[] bounds)
-		{
-			// Corner offsets
-			var ix = new uint[] { 0, 0, 0, 0, 3, 3, 3, 3 };
-			var iy = new uint[] { 1, 1, 4, 4, 1, 1, 4, 4 };
-			var iz = new uint[] { 2, 5, 2, 5, 2, 5, 2, 5 };
-
-			// Vectors to opposing corner
-			var ret = new[]
-			{
-				float.MaxValue, float.MaxValue, float.MaxValue,
-				float.MinValue, float.MinValue, float.MinValue
-			};
-
-			// Transform vectors and find new bounding box
-			for (var i = 0; i < 8; i++)
-			{
-				var vec = new[] { bounds[ix[i]], bounds[iy[i]], bounds[iz[i]], 1 };
-				var tvec = MatrixVectorMultiply(mtx, vec);
-
-				ret[0] = Math.Min(ret[0], tvec[0] / tvec[3]);
-				ret[1] = Math.Min(ret[1], tvec[1] / tvec[3]);
-				ret[2] = Math.Min(ret[2], tvec[2] / tvec[3]);
-				ret[3] = Math.Max(ret[3], tvec[0] / tvec[3]);
-				ret[4] = Math.Max(ret[4], tvec[1] / tvec[3]);
-				ret[5] = Math.Max(ret[5], tvec[2] / tvec[3]);
-			}
-
-			return ret;
-		}
 	}
 }

OpenRA.Game/Graphics/Vertex.cs

@@ -23,27 +23,42 @@ namespace OpenRA.Graphics
 		public readonly float S, T, U, V;
 
 		// Palette and channel flags
-		public readonly float P, C;
+		public readonly uint C;
 
 		// Color tint
 		public readonly float R, G, B, A;
 
-		public Vertex(in float3 xyz, float s, float t, float u, float v, float p, float c)
-			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, p, c, float3.Ones, 1f) { }
+		public Vertex(in float3 xyz, float s, float t, float u, float v, uint c)
+			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, c, float3.Ones, 1f) { }
 
-		public Vertex(in float3 xyz, float s, float t, float u, float v, float p, float c, in float3 tint, float a)
-			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, p, c, tint.X, tint.Y, tint.Z, a) { }
+		public Vertex(in float3 xyz, float s, float t, float u, float v, uint c, in float3 tint, float a)
+			: this(xyz.X, xyz.Y, xyz.Z, s, t, u, v, c, tint.X, tint.Y, tint.Z, a) { }
 
-		public Vertex(float x, float y, float z, float s, float t, float u, float v, float p, float c, in float3 tint, float a)
-			: this(x, y, z, s, t, u, v, p, c, tint.X, tint.Y, tint.Z, a) { }
+		public Vertex(float x, float y, float z, float s, float t, float u, float v, uint c, in float3 tint, float a)
+			: this(x, y, z, s, t, u, v, c, tint.X, tint.Y, tint.Z, a) { }
 
-		public Vertex(float x, float y, float z, float s, float t, float u, float v, float p, float c, float r, float g, float b, float a)
+		public Vertex(float x, float y, float z, float s, float t, float u, float v, uint c, float r, float g, float b, float a)
 		{
 			X = x; Y = y; Z = z;
 			S = s; T = t;
 			U = u; V = v;
-			P = p; C = c;
+			C = c;
 			R = r; G = g; B = b; A = a;
 		}
 	}
+
+	public sealed class CombinedShaderBindings : ShaderBindings
+	{
+		public CombinedShaderBindings()
+			: base("combined")
+		{ }
+
+		public override ShaderVertexAttribute[] Attributes { get; } = new[]
+		{
+			new ShaderVertexAttribute("aVertexPosition", ShaderVertexAttributeType.Float, 3, 0),
+			new ShaderVertexAttribute("aVertexTexCoord", ShaderVertexAttributeType.Float, 4, 12),
+			new ShaderVertexAttribute("aVertexAttributes", ShaderVertexAttributeType.UInt, 1, 28),
+			new ShaderVertexAttribute("aVertexTint", ShaderVertexAttributeType.Float, 4, 32)
+		};
+	}
 }

OpenRA.Game/Graphics/Viewport.cs

@@ -282,11 +282,23 @@ namespace OpenRA.Graphics
 		IEnumerable<MPos> CandidateMouseoverCells(int2 world)
 		{
 			var map = worldRenderer.World.Map;
+			var tileScale = map.Grid.TileScale / 2;
 			var minPos = worldRenderer.ProjectedPosition(world);
 
-			// Find all the cells that could potentially have been clicked
-			var a = map.CellContaining(minPos - new WVec(1024, 0, 0)).ToMPos(map.Grid.Type);
-			var b = map.CellContaining(minPos + new WVec(512, 512 * map.Grid.MaximumTerrainHeight, 0)).ToMPos(map.Grid.Type);
+			// Find all the cells that could potentially have been clicked.
+			MPos a;
+			MPos b;
+			if (map.Grid.Type == MapGridType.RectangularIsometric)
+			{
+				// TODO: this generates too many cells.
+				a = map.CellContaining(minPos - new WVec(tileScale, 0, 0)).ToMPos(map.Grid.Type);
+				b = map.CellContaining(minPos + new WVec(tileScale, tileScale * map.Grid.MaximumTerrainHeight, 0)).ToMPos(map.Grid.Type);
+			}
+			else
+			{
+				a = map.CellContaining(minPos).ToMPos(map.Grid.Type);
+				b = map.CellContaining(minPos + new WVec(0, tileScale * map.Grid.MaximumTerrainHeight, 0)).ToMPos(map.Grid.Type);
+			}
 
 			for (var v = b.V; v >= a.V; v--)
 				for (var u = b.U; u >= a.U; u--)
@@ -299,10 +311,13 @@ namespace OpenRA.Graphics
 
 		public void Center(IEnumerable<Actor> actors)
 		{
-			if (!actors.Any())
+			var actorsCollection = actors as IReadOnlyCollection<Actor>;
+			actorsCollection ??= actors.ToList();
+
+			if (actorsCollection.Count == 0)
 				return;
 
-			Center(actors.Select(a => a.CenterPosition).Average());
+			Center(actorsCollection.Select(a => a.CenterPosition).Average());
 		}
 
 		public void Center(WPos pos)

OpenRA.Game/Graphics/WorldRenderer.cs

@@ -44,6 +44,8 @@ namespace OpenRA.Graphics
 		readonly List<IFinalizedRenderable> preparedAnnotationRenderables = new();
 
 		readonly List<IRenderable> renderablesBuffer = new();
+		readonly IRenderer[] renderers;
+		readonly IRenderPostProcessPass[] postProcessPasses;
 
 		internal WorldRenderer(ModData modData, World world)
 		{
@@ -66,9 +68,24 @@ namespace OpenRA.Graphics
 			palette.Initialize();
 
 			TerrainLighting = world.WorldActor.TraitOrDefault<ITerrainLighting>();
+			renderers = world.WorldActor.TraitsImplementing<IRenderer>().ToArray();
 			terrainRenderer = world.WorldActor.TraitOrDefault<IRenderTerrain>();
 
 			debugVis = Exts.Lazy(() => world.WorldActor.TraitOrDefault<DebugVisualizations>());
+
+			postProcessPasses = world.WorldActor.TraitsImplementing<IRenderPostProcessPass>().ToArray();
+		}
+
+		public void BeginFrame()
+		{
+			foreach (var r in renderers)
+				r.BeginFrame();
+		}
+
+		public void EndFrame()
+		{
+			foreach (var r in renderers)
+				r.EndFrame();
 		}
 
 		public void UpdatePalettesForPlayer(string internalName, Color color, bool replaceExisting)
@@ -270,6 +287,8 @@ namespace OpenRA.Graphics
 			if (enableDepthBuffer)
 				Game.Renderer.ClearDepthBuffer();
 
+			ApplyPostProcessing(PostProcessPassType.AfterActors);
+
 			World.ApplyToActorsWithTrait<IRenderAboveWorld>((actor, trait) =>
 			{
 				if (actor.IsInWorld && !actor.Disposed)
@@ -279,6 +298,8 @@ namespace OpenRA.Graphics
 			if (enableDepthBuffer)
 				Game.Renderer.ClearDepthBuffer();
 
+			ApplyPostProcessing(PostProcessPassType.AfterWorld);
+
 			World.ApplyToActorsWithTrait<IRenderShroud>((actor, trait) => trait.RenderShroud(this));
 
 			if (enableDepthBuffer)
@@ -292,9 +313,23 @@ namespace OpenRA.Graphics
 				foreach (var r in g)
 					r.Render(this);
 
+			ApplyPostProcessing(PostProcessPassType.AfterShroud);
+
 			Game.Renderer.Flush();
 		}
 
+		void ApplyPostProcessing(PostProcessPassType type)
+		{
+			foreach (var pass in postProcessPasses)
+			{
+				if (pass.Type != type || !pass.Enabled)
+					continue;
+
+				Game.Renderer.Flush();
+				pass.Draw(this);
+			}
+		}
+
 		public void DrawAnnotations()
 		{
 			Game.Renderer.EnableAntialiasingFilter();

OpenRA.Game/HotkeyDefinition.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -31,29 +30,26 @@ namespace OpenRA
 			if (!string.IsNullOrEmpty(node.Value))
 				Default = FieldLoader.GetValue<Hotkey>("value", node.Value);
 
-			var descriptionNode = node.Nodes.FirstOrDefault(n => n.Key == "Description");
-			if (descriptionNode != null)
-				Description = descriptionNode.Value.Value;
+			var nodeDict = node.ToDictionary();
 
-			var typesNode = node.Nodes.FirstOrDefault(n => n.Key == "Types");
-			if (typesNode != null)
-				Types = FieldLoader.GetValue<HashSet<string>>("Types", typesNode.Value.Value);
+			if (nodeDict.TryGetValue("Description", out var descriptionYaml))
+				Description = descriptionYaml.Value;
 
-			var contextsNode = node.Nodes.FirstOrDefault(n => n.Key == "Contexts");
-			if (contextsNode != null)
-				Contexts = FieldLoader.GetValue<HashSet<string>>("Contexts", contextsNode.Value.Value);
+			if (nodeDict.TryGetValue("Types", out var typesYaml))
+				Types = FieldLoader.GetValue<HashSet<string>>("Types", typesYaml.Value);
 
-			var platformNode = node.Nodes.FirstOrDefault(n => n.Key == "Platform");
-			if (platformNode != null)
+			if (nodeDict.TryGetValue("Contexts", out var contextYaml))
+				Contexts = FieldLoader.GetValue<HashSet<string>>("Contexts", contextYaml.Value);
+
+			if (nodeDict.TryGetValue("Platform", out var platformYaml))
 			{
-				var platformOverride = platformNode.Value.Nodes.FirstOrDefault(n => n.Key == Platform.CurrentPlatform.ToString());
+				var platformOverride = platformYaml.NodeWithKeyOrDefault(Platform.CurrentPlatform.ToString());
 				if (platformOverride != null)
 					Default = FieldLoader.GetValue<Hotkey>("value", platformOverride.Value.Value);
 			}
 
-			var readonlyNode = node.Nodes.FirstOrDefault(n => n.Key == "Readonly");
-			if (readonlyNode != null)
-				Readonly = FieldLoader.GetValue<bool>("Readonly", readonlyNode.Value.Value);
+			if (nodeDict.TryGetValue("Readonly", out var readonlyYaml))
+				Readonly = FieldLoader.GetValue<bool>("Readonly", readonlyYaml.Value);
 		}
 	}
 }

OpenRA.Game/LocalPlayerProfile.cs

@@ -84,10 +84,11 @@ namespace OpenRA
 				{
 					var client = HttpClientFactory.Create();
 
-					var httpResponseMessage = await client.GetAsync(playerDatabase.Profile + Fingerprint);
+					var url = playerDatabase.Profile + Fingerprint;
+					var httpResponseMessage = await client.GetAsync(url);
 					var result = await httpResponseMessage.Content.ReadAsStreamAsync();
 
-					var yaml = MiniYaml.FromStream(result).First();
+					var yaml = MiniYaml.FromStream(result, url).First();
 					if (yaml.Key == "Player")
 					{
 						innerData = FieldLoader.Load<PlayerProfile>(yaml.Value);

OpenRA.Game/Manifest.cs

@@ -43,17 +43,6 @@ namespace OpenRA
 		}
 	}
 
-	public sealed class ModelSequenceFormat : IGlobalModData
-	{
-		public readonly string Type;
-		public readonly IReadOnlyDictionary<string, MiniYaml> Metadata;
-		public ModelSequenceFormat(MiniYaml yaml)
-		{
-			Type = yaml.Value;
-			Metadata = new ReadOnlyDictionary<string, MiniYaml>(yaml.ToDictionary());
-		}
-	}
-
 	public class ModMetadata
 	{
 		public string Title;
@@ -105,7 +94,8 @@ namespace OpenRA
 			Id = modId;
 			Package = package;
 
-			var nodes = MiniYaml.FromStream(package.GetStream("mod.yaml"), "mod.yaml");
+			var stringPool = new HashSet<string>(); // Reuse common strings in YAML
+			var nodes = MiniYaml.FromStream(package.GetStream("mod.yaml"), $"{package.Name}:mod.yaml", stringPool: stringPool);
 			for (var i = nodes.Count - 1; i >= 0; i--)
 			{
 				if (nodes[i].Key != "Include")
@@ -118,7 +108,7 @@ namespace OpenRA
 					throw new YamlException($"{nodes[i].Location}: File `{filename}` not found.");
 
 				nodes.RemoveAt(i);
-				nodes.InsertRange(i, MiniYaml.FromStream(contents, filename));
+				nodes.InsertRange(i, MiniYaml.FromStream(contents, $"{package.Name}:{filename}", stringPool: stringPool));
 			}
 
 			// Merge inherited overrides
@@ -211,18 +201,18 @@ namespace OpenRA
 
 		static string[] YamlList(Dictionary<string, MiniYaml> yaml, string key)
 		{
-			if (!yaml.ContainsKey(key))
+			if (!yaml.TryGetValue(key, out var value))
 				return Array.Empty<string>();
 
-			return yaml[key].ToDictionary().Keys.ToArray();
+			return value.Nodes.Select(n => n.Key).ToArray();
 		}
 
 		static IReadOnlyDictionary<string, string> YamlDictionary(Dictionary<string, MiniYaml> yaml, string key)
 		{
-			if (!yaml.ContainsKey(key))
+			if (!yaml.TryGetValue(key, out var value))
 				return new Dictionary<string, string>();
 
-			return yaml[key].ToDictionary(my => my.Value);
+			return value.ToDictionary(my => my.Value);
 		}
 
 		public bool Contains<T>() where T : IGlobalModData

OpenRA.Game/Map/ActorInitializer.cs

@@ -175,8 +175,7 @@ namespace OpenRA
 		protected CompositeActorInit(TraitInfo info)
 			: base(info.InstanceName) { }
 
-		protected CompositeActorInit()
-			: base() { }
+		protected CompositeActorInit() { }
 
 		public virtual void Initialize(MiniYaml yaml)
 		{

OpenRA.Game/Map/ActorReference.cs

@@ -84,7 +84,7 @@ namespace OpenRA
 
 		public MiniYaml Save(Func<ActorInit, bool> initFilter = null)
 		{
-			var ret = new MiniYaml(Type);
+			var nodes = new List<MiniYamlNode>();
 			foreach (var o in initDict.Value)
 			{
 				if (o is not ActorInit init || o is ISuppressInitExport)
@@ -98,10 +98,10 @@ namespace OpenRA
 				if (!string.IsNullOrEmpty(init.InstanceName))
 					initName += ActorInfo.TraitInstanceSeparator + init.InstanceName;
 
-				ret.Nodes.Add(new MiniYamlNode(initName, init.Save()));
+				nodes.Add(new MiniYamlNode(initName, init.Save()));
 			}
 
-			return ret;
+			return new MiniYaml(Type, nodes);
 		}
 
 		public IEnumerator<object> GetEnumerator() { return initDict.Value.GetEnumerator(); }
@@ -139,7 +139,7 @@ namespace OpenRA
 			return removed;
 		}
 
-		public IEnumerable<T> GetAll<T>() where T : ActorInit
+		public IReadOnlyCollection<T> GetAll<T>() where T : ActorInit
 		{
 			return initDict.Value.WithInterface<T>();
 		}
@@ -152,8 +152,9 @@ namespace OpenRA
 			// If a more specific init is not available, fall back to an unnamed init.
 			// If duplicate inits are defined, take the last to match standard yaml override expectations
 			if (info != null && !string.IsNullOrEmpty(info.InstanceName))
-				return inits.LastOrDefault(i => i.InstanceName == info.InstanceName) ??
-				       inits.LastOrDefault(i => string.IsNullOrEmpty(i.InstanceName));
+				return
+					inits.LastOrDefault(i => i.InstanceName == info.InstanceName) ??
+					inits.LastOrDefault(i => string.IsNullOrEmpty(i.InstanceName));
 
 			// Untagged traits will only use untagged inits
 			return inits.LastOrDefault(i => string.IsNullOrEmpty(i.InstanceName));

OpenRA.Game/Map/CellCoordsRegion.cs

@@ -0,0 +1,90 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections;
+using System.Collections.Generic;
+
+namespace OpenRA
+{
+	public readonly struct CellCoordsRegion : IEnumerable<CPos>
+	{
+		public struct CellCoordsEnumerator : IEnumerator<CPos>
+		{
+			readonly CellCoordsRegion r;
+
+			public CellCoordsEnumerator(CellCoordsRegion region)
+				: this()
+			{
+				r = region;
+				Reset();
+			}
+
+			public bool MoveNext()
+			{
+				var x = Current.X + 1;
+				var y = Current.Y;
+
+				// Check for column overflow.
+				if (x > r.BottomRight.X)
+				{
+					y++;
+					x = r.TopLeft.X;
+
+					// Check for row overflow.
+					if (y > r.BottomRight.Y)
+						return false;
+				}
+
+				Current = new CPos(x, y);
+				return true;
+			}
+
+			public void Reset()
+			{
+				Current = new CPos(r.TopLeft.X - 1, r.TopLeft.Y);
+			}
+
+			public CPos Current { get; private set; }
+
+			readonly object IEnumerator.Current => Current;
+			public readonly void Dispose() { }
+		}
+
+		public CellCoordsRegion(CPos topLeft, CPos bottomRight)
+		{
+			TopLeft = topLeft;
+			BottomRight = bottomRight;
+		}
+
+		public override string ToString()
+		{
+			return $"{TopLeft}->{BottomRight}";
+		}
+
+		public CellCoordsEnumerator GetEnumerator()
+		{
+			return new CellCoordsEnumerator(this);
+		}
+
+		IEnumerator<CPos> IEnumerable<CPos>.GetEnumerator()
+		{
+			return GetEnumerator();
+		}
+
+		IEnumerator IEnumerable.GetEnumerator()
+		{
+			return GetEnumerator();
+		}
+
+		public CPos TopLeft { get; }
+		public CPos BottomRight { get; }
+	}
+}

OpenRA.Game/Map/CellRegion.cs

@@ -12,7 +12,6 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -64,9 +63,9 @@ namespace OpenRA
 		}
 
 		/// <summary>Returns the minimal region that covers at least the specified cells.</summary>
-		public static CellRegion BoundingRegion(MapGridType shape, IEnumerable<CPos> cells)
+		public static CellRegion BoundingRegion(MapGridType shape, IReadOnlyCollection<CPos> cells)
 		{
-			if (cells == null || !cells.Any())
+			if (cells == null || cells.Count == 0)
 				throw new ArgumentException("cells must not be null or empty.", nameof(cells));
 
 			var minU = int.MaxValue;
@@ -103,6 +102,7 @@ namespace OpenRA
 		}
 
 		public MapCoordsRegion MapCoords => new(mapTopLeft, mapBottomRight);
+		public CellCoordsRegion CellCoords => new(TopLeft, BottomRight);
 
 		public CellRegionEnumerator GetEnumerator()
 		{
@@ -136,12 +136,12 @@ namespace OpenRA
 
 			public bool MoveNext()
 			{
-				u += 1;
+				u++;
 
 				// Check for column overflow
 				if (u > r.mapBottomRight.U)
 				{
-					v += 1;
+					v++;
 					u = r.mapTopLeft.U;
 
 					// Check for row overflow
@@ -162,8 +162,8 @@ namespace OpenRA
 			}
 
 			public CPos Current { get; private set; }
-			object IEnumerator.Current => Current;
-			public void Dispose() { }
+			readonly object IEnumerator.Current => Current;
+			public readonly void Dispose() { }
 		}
 	}
 }

OpenRA.Game/Map/Map.cs

@@ -11,6 +11,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -90,13 +91,13 @@ namespace OpenRA
 				throw new InvalidOperationException("Map does not have a field/property " + fieldName);
 
 			var t = field != null ? field.FieldType : property.PropertyType;
-			type = t == typeof(List<MiniYamlNode>) ? Type.NodeList :
+			type = t == typeof(IReadOnlyCollection<MiniYamlNode>) ? Type.NodeList :
 				t == typeof(MiniYaml) ? Type.MiniYaml : Type.Normal;
 		}
 
-		public void Deserialize(Map map, List<MiniYamlNode> nodes)
+		public void Deserialize(Map map, MiniYaml yaml)
 		{
-			var node = nodes.FirstOrDefault(n => n.Key == key);
+			var node = yaml.NodeWithKeyOrDefault(key);
 			if (node == null)
 			{
 				if (required)
@@ -130,14 +131,14 @@ namespace OpenRA
 			var value = field != null ? field.GetValue(map) : property.GetValue(map, null);
 			if (type == Type.NodeList)
 			{
-				var listValue = (List<MiniYamlNode>)value;
+				var listValue = (IReadOnlyCollection<MiniYamlNode>)value;
 				if (required || listValue.Count > 0)
 					nodes.Add(new MiniYamlNode(key, null, listValue));
 			}
 			else if (type == Type.MiniYaml)
 			{
 				var yamlValue = (MiniYaml)value;
-				if (required || (yamlValue != null && (yamlValue.Value != null || yamlValue.Nodes.Count > 0)))
+				if (required || (yamlValue != null && (yamlValue.Value != null || yamlValue.Nodes.Length > 0)))
 					nodes.Add(new MiniYamlNode(key, yamlValue));
 			}
 			else
@@ -158,26 +159,26 @@ namespace OpenRA
 		/// <summary>Defines the order of the fields in map.yaml.</summary>
 		static readonly MapField[] YamlFields =
 		{
-			new MapField("MapFormat"),
-			new MapField("RequiresMod"),
-			new MapField("Title"),
-			new MapField("Author"),
-			new MapField("Tileset"),
-			new MapField("MapSize"),
-			new MapField("Bounds"),
-			new MapField("Visibility"),
-			new MapField("Categories"),
-			new MapField("LockPreview", required: false, ignoreIfValue: "False"),
-			new MapField("Players", "PlayerDefinitions"),
-			new MapField("Actors", "ActorDefinitions"),
-			new MapField("Rules", "RuleDefinitions", required: false),
-			new MapField("Translations", "TranslationDefinitions", required: false),
-			new MapField("Sequences", "SequenceDefinitions", required: false),
-			new MapField("ModelSequences", "ModelSequenceDefinitions", required: false),
-			new MapField("Weapons", "WeaponDefinitions", required: false),
-			new MapField("Voices", "VoiceDefinitions", required: false),
-			new MapField("Music", "MusicDefinitions", required: false),
-			new MapField("Notifications", "NotificationDefinitions", required: false),
+			new("MapFormat"),
+			new("RequiresMod"),
+			new("Title"),
+			new("Author"),
+			new("Tileset"),
+			new("MapSize"),
+			new("Bounds"),
+			new("Visibility"),
+			new("Categories"),
+			new("LockPreview", required: false, ignoreIfValue: "False"),
+			new("Players", "PlayerDefinitions"),
+			new("Actors", "ActorDefinitions"),
+			new("Rules", "RuleDefinitions", required: false),
+			new("Translations", "TranslationDefinitions", required: false),
+			new("Sequences", "SequenceDefinitions", required: false),
+			new("ModelSequences", "ModelSequenceDefinitions", required: false),
+			new("Weapons", "WeaponDefinitions", required: false),
+			new("Voices", "VoiceDefinitions", required: false),
+			new("Music", "MusicDefinitions", required: false),
+			new("Notifications", "NotificationDefinitions", required: false),
 		};
 
 		// Format versions
@@ -197,18 +198,18 @@ namespace OpenRA
 		public int2 MapSize { get; private set; }
 
 		// Player and actor yaml. Public for access by the map importers and lint checks.
-		public List<MiniYamlNode> PlayerDefinitions = new();
-		public List<MiniYamlNode> ActorDefinitions = new();
+		public IReadOnlyCollection<MiniYamlNode> PlayerDefinitions = ImmutableArray<MiniYamlNode>.Empty;
+		public IReadOnlyCollection<MiniYamlNode> ActorDefinitions = ImmutableArray<MiniYamlNode>.Empty;
 
 		// Custom map yaml. Public for access by the map importers and lint checks
-		public readonly MiniYaml RuleDefinitions;
-		public readonly MiniYaml TranslationDefinitions;
-		public readonly MiniYaml SequenceDefinitions;
-		public readonly MiniYaml ModelSequenceDefinitions;
-		public readonly MiniYaml WeaponDefinitions;
-		public readonly MiniYaml VoiceDefinitions;
-		public readonly MiniYaml MusicDefinitions;
-		public readonly MiniYaml NotificationDefinitions;
+		public MiniYaml RuleDefinitions;
+		public MiniYaml TranslationDefinitions;
+		public MiniYaml SequenceDefinitions;
+		public MiniYaml ModelSequenceDefinitions;
+		public MiniYaml WeaponDefinitions;
+		public MiniYaml VoiceDefinitions;
+		public MiniYaml MusicDefinitions;
+		public MiniYaml NotificationDefinitions;
 
 		public readonly Dictionary<CPos, TerrainTile> ReplacedInvalidTerrainTiles = new();
 
@@ -274,7 +275,10 @@ namespace OpenRA
 			try
 			{
 				foreach (var filename in contents)
-					if (filename.EndsWith(".yaml") || filename.EndsWith(".bin") || filename.EndsWith(".lua") || (format >= 12 && filename == "map.png"))
+					if (filename.EndsWith(".yaml", StringComparison.Ordinal) ||
+						filename.EndsWith(".bin", StringComparison.Ordinal) ||
+						filename.EndsWith(".lua", StringComparison.Ordinal) ||
+						(format >= 12 && filename == "map.png"))
 						streams.Add(package.GetStream(filename));
 
 				// Take the SHA1
@@ -357,15 +361,15 @@ namespace OpenRA
 			if (!Package.Contains("map.yaml") || !Package.Contains("map.bin"))
 				throw new InvalidDataException($"Not a valid map\n File: {package.Name}");
 
-			var yaml = new MiniYaml(null, MiniYaml.FromStream(Package.GetStream("map.yaml"), package.Name));
+			var yaml = new MiniYaml(null, MiniYaml.FromStream(Package.GetStream("map.yaml"), $"{package.Name}:map.yaml"));
 			foreach (var field in YamlFields)
-				field.Deserialize(this, yaml.Nodes);
+				field.Deserialize(this, yaml);
 
 			if (MapFormat < SupportedMapFormat)
 				throw new InvalidDataException($"Map format {MapFormat} is not supported.\n File: {package.Name}");
 
-			PlayerDefinitions = MiniYaml.NodesOrEmpty(yaml, "Players");
-			ActorDefinitions = MiniYaml.NodesOrEmpty(yaml, "Actors");
+			PlayerDefinitions = yaml.NodeWithKeyOrDefault("Players")?.Value.Nodes ?? ImmutableArray<MiniYamlNode>.Empty;
+			ActorDefinitions = yaml.NodeWithKeyOrDefault("Actors")?.Value.Nodes ?? ImmutableArray<MiniYamlNode>.Empty;
 
 			Grid = modData.Manifest.Get<MapGrid>();
 
@@ -607,7 +611,7 @@ namespace OpenRA
 
 			// Odd-height ramps get bumped up a level to the next even height layer
 			if ((height & 1) == 1 && Ramp[uv] != 0)
-				height += 1;
+				height++;
 
 			var candidates = new List<PPos>();
 
@@ -646,21 +650,24 @@ namespace OpenRA
 				foreach (var file in Package.Contents)
 					toPackage.Update(file, Package.GetStream(file).ReadAllBytes());
 
-			if (!LockPreview)
+			void UpdatePackage(string filename, byte[] data)
 			{
-				var previewData = SavePreview();
-				if (Package != toPackage || !Enumerable.SequenceEqual(previewData, Package.GetStream("map.png").ReadAllBytes()))
-					toPackage.Update("map.png", previewData);
+				if (Package != toPackage)
+					toPackage.Update(filename, data);
+				else
+				{
+					var stream = Package.GetStream(filename);
+					if (stream == null || !Enumerable.SequenceEqual(data, stream.ReadAllBytes()))
+						toPackage.Update(filename, data);
+				}
 			}
 
-			// Update the package with the new map data
-			var textData = Encoding.UTF8.GetBytes(root.WriteToString());
-			if (Package != toPackage || !Enumerable.SequenceEqual(textData, Package.GetStream("map.yaml").ReadAllBytes()))
-				toPackage.Update("map.yaml", textData);
+			if (!LockPreview)
+				UpdatePackage("map.png", SavePreview());
 
-			var binaryData = SaveBinaryData();
-			if (Package != toPackage || !Enumerable.SequenceEqual(binaryData, Package.GetStream("map.bin").ReadAllBytes()))
-				toPackage.Update("map.bin", binaryData);
+			// Update the package with the new map data
+			UpdatePackage("map.yaml", Encoding.UTF8.GetBytes(root.WriteToString()));
+			UpdatePackage("map.bin", SaveBinaryData());
 
 			Package = toPackage;
 
@@ -681,16 +688,16 @@ namespace OpenRA
 				writer.Write((ushort)MapSize.Y);
 
 				// Data offsets
-				var tilesOffset = 17;
+				const int TilesOffset = 17;
 				var heightsOffset = Grid.MaximumTerrainHeight > 0 ? 3 * MapSize.X * MapSize.Y + 17 : 0;
 				var resourcesOffset = (Grid.MaximumTerrainHeight > 0 ? 4 : 3) * MapSize.X * MapSize.Y + 17;
 
-				writer.Write((uint)tilesOffset);
+				writer.Write((uint)TilesOffset);
 				writer.Write((uint)heightsOffset);
 				writer.Write((uint)resourcesOffset);
 
 				// Tile data
-				if (tilesOffset != 0)
+				if (TilesOffset != 0)
 				{
 					for (var i = 0; i < MapSize.X; i++)
 					{
@@ -772,19 +779,10 @@ namespace OpenRA
 
 			if (Grid.MaximumTerrainHeight > 0)
 			{
-				// The minimap is drawn in cell space, so we need to
-				// unproject the PPos bounds to find the MPos boundaries.
-				// This matches the calculation in RadarWidget that is used ingame
-				for (var x = Bounds.Left; x < Bounds.Right; x++)
-				{
-					var allTop = Unproject(new PPos(x, Bounds.Top));
-					var allBottom = Unproject(new PPos(x, Bounds.Bottom));
-					if (allTop.Count > 0)
-						top = Math.Min(top, allTop.MinBy(uv => uv.V).V);
+				(top, bottom) = GetCellSpaceBounds();
 
-					if (allBottom.Count > 0)
-						bottom = Math.Max(bottom, allBottom.MaxBy(uv => uv.V).V);
-				}
+				if (top == int.MaxValue || bottom == int.MinValue)
+					throw new InvalidDataException("The map has invalid boundaries");
 			}
 			else
 			{
@@ -801,7 +799,7 @@ namespace OpenRA
 				bitmapWidth = 2 * bitmapWidth - 1;
 
 			var stride = bitmapWidth * 4;
-			var pxStride = 4;
+			const int PxStride = 4;
 			var minimapData = new byte[stride * height];
 			(Color Left, Color Right) terrainColor = default;
 
@@ -823,10 +821,10 @@ namespace OpenRA
 					{
 						// Odd rows are shifted right by 1px
 						var dx = uv.V & 1;
-						var xOffset = pxStride * (2 * x + dx);
+						var xOffset = PxStride * (2 * x + dx);
 						if (x + dx > 0)
 						{
-							var z = y * stride + xOffset - pxStride;
+							var z = y * stride + xOffset - PxStride;
 							var c = actorColor.A == 0 ? terrainColor.Left : actorColor;
 							minimapData[z++] = c.R;
 							minimapData[z++] = c.G;
@@ -846,7 +844,7 @@ namespace OpenRA
 					}
 					else
 					{
-						var z = y * stride + pxStride * x;
+						var z = y * stride + PxStride * x;
 						var c = actorColor.A == 0 ? terrainColor.Left : actorColor;
 						minimapData[z++] = c.R;
 						minimapData[z++] = c.G;
@@ -860,6 +858,28 @@ namespace OpenRA
 			return png.Save();
 		}
 
+		public (int Top, int Bottom) GetCellSpaceBounds()
+		{
+			var top = int.MaxValue;
+			var bottom = int.MinValue;
+
+			// The minimap is drawn in cell space, so we need to
+			// unproject the PPos bounds to find the MPos boundaries.
+			// This matches the calculation in RadarWidget that is used ingame
+			for (var x = Bounds.Left; x < Bounds.Right; x++)
+			{
+				var allTop = Unproject(new PPos(x, Bounds.Top));
+				var allBottom = Unproject(new PPos(x, Bounds.Bottom));
+				if (allTop.Count > 0)
+					top = Math.Min(top, allTop.MinBy(uv => uv.V).V);
+
+				if (allBottom.Count > 0)
+					bottom = Math.Max(bottom, allBottom.MaxBy(uv => uv.V).V);
+			}
+
+			return (top, bottom);
+		}
+
 		public bool Contains(CPos cell)
 		{
 			if (Grid.Type == MapGridType.RectangularIsometric)
@@ -1180,7 +1200,7 @@ namespace OpenRA
 			// Project this guessed cell and take the first available cell
 			// If it is projected outside the layer, then make another guess.
 			var allProjected = ProjectedCellsCovering(uv);
-			var projected = allProjected.Length > 0 ? allProjected.First()
+			var projected = allProjected.Length > 0 ? allProjected[0]
 				: new PPos(uv.U, uv.V.Clamp(Bounds.Top, Bounds.Bottom));
 
 			// Clamp the projected cell to the map area
@@ -1249,7 +1269,7 @@ namespace OpenRA
 			PPos edge;
 			if (allProjected.Length > 0)
 			{
-				var puv = allProjected.First();
+				var puv = allProjected[0];
 				var horizontalBound = (puv.U - Bounds.Left < Bounds.Width / 2) ? Bounds.Left : Bounds.Right;
 				var verticalBound = (puv.V - Bounds.Top < Bounds.Height / 2) ? Bounds.Top : Bounds.Bottom;
 
@@ -1349,13 +1369,18 @@ namespace OpenRA
 				throw new ArgumentOutOfRangeException(nameof(maxRange),
 					$"The requested range ({maxRange}) cannot exceed the value of MaximumTileSearchRange ({Grid.MaximumTileSearchRange})");
 
-			for (var i = minRange; i <= maxRange; i++)
+			return FindTilesInAnnulus();
+
+			IEnumerable<CPos> FindTilesInAnnulus()
 			{
-				foreach (var offset in Grid.TilesByDistance[i])
+				for (var i = minRange; i <= maxRange; i++)
 				{
-					var t = offset + center;
-					if (allowOutsideBounds ? Tiles.Contains(t) : Contains(t))
-						yield return t;
+					foreach (var offset in Grid.TilesByDistance[i])
+					{
+						var t = offset + center;
+						if (allowOutsideBounds ? Tiles.Contains(t) : Contains(t))
+							yield return t;
+					}
 				}
 			}
 		}

OpenRA.Game/Map/MapCache.cs

@@ -38,7 +38,7 @@ namespace OpenRA
 		readonly object syncRoot = new();
 		readonly Queue<MapPreview> generateMinimap = new();
 
-		public Dictionary<string, string> StringPool { get; } = new Dictionary<string, string>();
+		public HashSet<string> StringPool { get; } = new();
 
 		readonly List<MapDirectoryTracker> mapDirectoryTrackers = new();
 
@@ -97,7 +97,7 @@ namespace OpenRA
 					? MapClassification.Unknown : Enum<MapClassification>.Parse(kv.Value);
 
 				IReadOnlyPackage package;
-				var optional = name.StartsWith("~", StringComparison.Ordinal);
+				var optional = name.StartsWith('~');
 				if (optional)
 					name = name[1..];
 
@@ -106,7 +106,7 @@ namespace OpenRA
 					// HACK: If the path is inside the support directory then we may need to create it
 					// Assume that the path is a directory if there is not an existing file with the same name
 					var resolved = Platform.ResolvePath(name);
-					if (resolved.StartsWith(Platform.SupportDir) && !File.Exists(resolved))
+					if (resolved.StartsWith(Platform.SupportDir, StringComparison.Ordinal) && !File.Exists(resolved))
 						Directory.CreateDirectory(resolved);
 
 					package = modData.ModFiles.OpenPackage(name);
@@ -128,7 +128,10 @@ namespace OpenRA
 			foreach (var kv in MapLocations)
 			{
 				foreach (var map in kv.Key.Contents)
+				{
 					LoadMapInternal(map, kv.Key, kv.Value, mapGrid, null, modDataRules);
+					GC.Collect();
+				}
 			}
 
 			// We only want to track maps in runtime, not at loadtime
@@ -148,11 +151,16 @@ namespace OpenRA
 				using (new PerfTimer(map))
 				{
 					mapPackage = package.OpenPackage(map, modData.ModFiles);
+					Log.Write("debug", $"Loading Map: {map} FROM {mapPackage.Name}");
+					Console.WriteLine($"Loading Map: {map} FROM {mapPackage.Name}");
 					if (mapPackage != null)
 					{
 						var uid = Map.ComputeUID(mapPackage);
 						previews[uid].UpdateFromMap(mapPackage, package, classification, modData.Manifest.MapCompatibility, mapGrid.Type, modDataRules);
 
+						// Freeing the package to save memory if there is a lot of Maps
+						previews[uid].PackageDispose();
+
 						if (oldMap != uid)
 						{
 							LastModifiedMap = uid;
@@ -168,9 +176,13 @@ namespace OpenRA
 				Console.WriteLine($"Failed to load map: {map}");
 				Console.WriteLine("Details:");
 				Console.WriteLine(e);
+				Console.WriteLine("StackTrace:");
+				Console.WriteLine(System.Environment.StackTrace);
 				Log.Write("debug", $"Failed to load map: {map}");
 				Log.Write("debug", "Details:");
 				Log.Write("debug", e);
+				Log.Write("debug", "StackTrace:");
+				Log.Write("debug", System.Environment.StackTrace);
 			}
 		}
 
@@ -190,13 +202,13 @@ namespace OpenRA
 					continue;
 
 				var name = kv.Key;
-				var optional = name.StartsWith("~", StringComparison.Ordinal);
+				var optional = name.StartsWith('~');
 				if (optional)
 					name = name[1..];
 
 				// Don't try to open the map directory in the support directory if it doesn't exist
 				var resolved = Platform.ResolvePath(name);
-				if (resolved.StartsWith(Platform.SupportDir) && (!Directory.Exists(resolved) || !File.Exists(resolved)))
+				if (resolved.StartsWith(Platform.SupportDir, StringComparison.Ordinal) && (!Directory.Exists(resolved) || !File.Exists(resolved)))
 					continue;
 
 				using (var package = (IReadWritePackage)modData.ModFiles.OpenPackage(name))
@@ -233,11 +245,12 @@ namespace OpenRA
 				.ToList();
 
 			foreach (var uid in queryUids)
-				previews[uid].UpdateRemoteSearch(MapStatus.Searching, null);
+				previews[uid].UpdateRemoteSearch(MapStatus.Searching, null, null);
 
 			Task.Run(async () =>
 			{
 				var client = HttpClientFactory.Create();
+				var stringPool = new HashSet<string>(); // Reuse common strings in YAML
 
 				// Limit each query to 50 maps at a time to avoid request size limits
 				for (var i = 0; i < queryUids.Count; i += 50)
@@ -249,15 +262,15 @@ namespace OpenRA
 						var httpResponseMessage = await client.GetAsync(url);
 						var result = await httpResponseMessage.Content.ReadAsStreamAsync();
 
-						var yaml = MiniYaml.FromStream(result);
+						var yaml = MiniYaml.FromStream(result, url, stringPool: stringPool);
 						foreach (var kv in yaml)
-							previews[kv.Key].UpdateRemoteSearch(MapStatus.DownloadAvailable, kv.Value, mapDetailsReceived);
+							previews[kv.Key].UpdateRemoteSearch(MapStatus.DownloadAvailable, kv.Value, modData.Manifest.MapCompatibility, mapDetailsReceived);
 
 						foreach (var uid in batchUids)
 						{
 							var p = previews[uid];
 							if (p.Status != MapStatus.DownloadAvailable)
-								p.UpdateRemoteSearch(MapStatus.Unavailable, null);
+								p.UpdateRemoteSearch(MapStatus.Unavailable, null, null);
 						}
 					}
 					catch (Exception e)
@@ -269,7 +282,7 @@ namespace OpenRA
 						foreach (var uid in batchUids)
 						{
 							var p = previews[uid];
-							p.UpdateRemoteSearch(MapStatus.Unavailable, null);
+							p.UpdateRemoteSearch(MapStatus.Unavailable, null, null);
 							mapQueryFailed?.Invoke(p);
 						}
 					}
@@ -282,11 +295,11 @@ namespace OpenRA
 			Log.Write("debug", "MapCache.LoadAsyncInternal started");
 
 			// Milliseconds to wait on one loop when nothing to do
-			var emptyDelay = 50;
+			const int EmptyDelay = 50;
 
 			// Keep the thread alive for at least 5 seconds after the last minimap generation
-			var maxKeepAlive = 5000 / emptyDelay;
-			var keepAlive = maxKeepAlive;
+			const int MaxKeepAlive = 5000 / EmptyDelay;
+			var keepAlive = MaxKeepAlive;
 
 			while (true)
 			{
@@ -306,11 +319,11 @@ namespace OpenRA
 
 				if (todo.Count == 0)
 				{
-					Thread.Sleep(emptyDelay);
+					Thread.Sleep(EmptyDelay);
 					continue;
 				}
 				else
-					keepAlive = maxKeepAlive;
+					keepAlive = MaxKeepAlive;
 
 				// Render the minimap into the shared sheet
 				foreach (var p in todo)
@@ -348,8 +361,8 @@ namespace OpenRA
 
 			while (this[uid].Status != MapStatus.Available)
 			{
-				if (mapUpdates.ContainsKey(uid))
-					uid = mapUpdates[uid];
+				if (mapUpdates.TryGetValue(uid, out var newUid))
+					uid = newUid;
 				else
 					return null;
 			}
@@ -372,7 +385,6 @@ namespace OpenRA
 				{
 					// Wait for any existing thread to exit before starting a new one.
 					previewLoaderThread?.Join();
-
 					previewLoaderThread = new Thread(LoadAsyncInternal)
 					{
 						Name = "Map Preview Loader",

OpenRA.Game/Map/MapCoordsRegion.cs

@@ -35,7 +35,7 @@ namespace OpenRA
 				// Check for column overflow
 				if (u > r.BottomRight.U)
 				{
-					v += 1;
+					v++;
 					u = r.TopLeft.U;
 
 					// Check for row overflow
@@ -53,8 +53,8 @@ namespace OpenRA
 			}
 
 			public MPos Current { get; private set; }
-			object IEnumerator.Current => Current;
-			public void Dispose() { }
+			readonly object IEnumerator.Current => Current;
+			public readonly void Dispose() { }
 		}
 
 		public MapCoordsRegion(MPos mapTopLeft, MPos mapBottomRight)

OpenRA.Game/Map/MapGrid.cs

@@ -116,12 +116,12 @@ namespace OpenRA
 
 		public readonly WVec[] SubCellOffsets =
 		{
-			new WVec(0, 0, 0),       // full cell - index 0
-			new WVec(-299, -256, 0), // top left - index 1
-			new WVec(256, -256, 0),  // top right - index 2
-			new WVec(0, 0, 0),       // center - index 3
-			new WVec(-299, 256, 0),  // bottom left - index 4
-			new WVec(256, 256, 0),   // bottom right - index 5
+			new(0, 0, 0),       // full cell - index 0
+			new(-299, -256, 0), // top left - index 1
+			new(256, -256, 0),  // top right - index 2
+			new(0, 0, 0),       // center - index 3
+			new(-299, 256, 0),  // bottom left - index 4
+			new(256, 256, 0),   // bottom right - index 5
 		};
 
 		public CellRamp[] Ramps { get; }

OpenRA.Game/Map/MapPreview.cs

@@ -59,6 +59,7 @@ namespace OpenRA
 		public readonly string rules;
 		public readonly string players_block;
 		public readonly int mapformat;
+		public readonly string game_mod;
 	}
 
 	public sealed class MapPreview : IDisposable, IReadOnlyFileSystem
@@ -139,10 +140,11 @@ namespace OpenRA
 							files = files.Append(mapFiles);
 						}
 
+						var stringPool = new HashSet<string>(); // Reuse common strings in YAML
 						var sources =
 							modDataRules.Select(x => x.Where(IsLoadableRuleDefinition).ToList())
-							.Concat(files.Select(s => MiniYaml.FromStream(fileSystem.Open(s), s).Where(IsLoadableRuleDefinition).ToList()));
-						if (RuleDefinitions.Nodes.Count > 0)
+							.Concat(files.Select(s => MiniYaml.FromStream(fileSystem.Open(s), s, stringPool: stringPool).Where(IsLoadableRuleDefinition).ToList()));
+						if (RuleDefinitions.Nodes.Length > 0)
 							sources = sources.Append(RuleDefinitions.Nodes.Where(IsLoadableRuleDefinition).ToList());
 
 						var yamlNodes = MiniYaml.Merge(sources);
@@ -172,7 +174,23 @@ namespace OpenRA
 		readonly ModData modData;
 
 		public readonly string Uid;
-		public IReadOnlyPackage Package { get; private set; }
+		public string PackageName { get; private set; }
+		IReadOnlyPackage pPackage;
+		public IReadOnlyPackage Package
+		{
+			get
+			{
+				if (pPackage == null)
+				{
+					pPackage = parentPackage.OpenPackage(PackageName, modData.ModFiles);
+				}
+
+				return pPackage;
+			}
+
+			private set => pPackage = value;
+		}
+
 		IReadOnlyPackage parentPackage;
 
 		volatile InnerData innerData;
@@ -256,6 +274,7 @@ namespace OpenRA
 		{
 			this.cache = cache;
 			this.modData = modData;
+			this.pPackage = null;
 
 			Uid = uid;
 			innerData = new InnerData
@@ -282,9 +301,10 @@ namespace OpenRA
 		{
 			this.modData = modData;
 			cache = modData.MapCache;
+			this.pPackage = null;
 
 			Uid = map.Uid;
-			Package = map.Package;
+			PackageName = map.Package.Name;
 
 			var mapPlayers = new MapPlayers(map.PlayerDefinitions);
 			var spawns = new List<CPos>();
@@ -333,10 +353,10 @@ namespace OpenRA
 				if (yamlStream == null)
 					throw new FileNotFoundException("Required file map.yaml not present in this map");
 
-				yaml = new MiniYaml(null, MiniYaml.FromStream(yamlStream, "map.yaml", stringPool: cache.StringPool)).ToDictionary();
+				yaml = new MiniYaml(null, MiniYaml.FromStream(yamlStream, $"{p.Name}:map.yaml", stringPool: cache.StringPool)).ToDictionary();
 			}
 
-			Package = p;
+			PackageName = p.Name;
 			parentPackage = parent;
 
 			var newData = innerData.Clone();
@@ -427,7 +447,7 @@ namespace OpenRA
 			innerData = newData;
 		}
 
-		public void UpdateRemoteSearch(MapStatus status, MiniYaml yaml, Action<MapPreview> parseMetadata = null)
+		public void UpdateRemoteSearch(MapStatus status, MiniYaml yaml, string[] mapCompatibility, Action<MapPreview> parseMetadata = null)
 		{
 			var newData = innerData.Clone();
 			newData.Status = status;
@@ -474,11 +494,19 @@ namespace OpenRA
 					}
 
 					var playersString = Encoding.UTF8.GetString(Convert.FromBase64String(r.players_block));
-					newData.Players = new MapPlayers(MiniYaml.FromString(playersString));
+					newData.Players = new MapPlayers(MiniYaml.FromString(playersString,
+						$"{yaml.NodeWithKey(nameof(r.players_block)).Location.Name}:{nameof(r.players_block)}"));
 
 					var rulesString = Encoding.UTF8.GetString(Convert.FromBase64String(r.rules));
-					var rulesYaml = new MiniYaml("", MiniYaml.FromString(rulesString)).ToDictionary();
+					var rulesYaml = new MiniYaml("", MiniYaml.FromString(rulesString,
+						$"{yaml.NodeWithKey(nameof(r.rules)).Location.Name}:{nameof(r.rules)}")).ToDictionary();
 					newData.SetCustomRules(modData, this, rulesYaml, null);
+
+					// Map is for a different mod: update its information so it can be displayed
+					// in the cross-mod server browser UI, but mark it as unavailable so it can't
+					// be selected in a server for the current mod.
+					if (!mapCompatibility.Contains(r.game_mod))
+						newData.Status = MapStatus.Unavailable;
 				}
 				catch (Exception e)
 				{
@@ -577,10 +605,15 @@ namespace OpenRA
 
 		public void Dispose()
 		{
-			if (Package != null)
+			PackageDispose();
+		}
+
+		public void PackageDispose()
+		{
+			if (pPackage != null)
 			{
-				Package.Dispose();
-				Package = null;
+				pPackage.Dispose();
+				pPackage = null;
 			}
 		}
 

OpenRA.Game/Map/ProjectedCellLayer.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using OpenRA.Primitives;
 
 namespace OpenRA
@@ -53,5 +54,15 @@ namespace OpenRA
 		{
 			return Bounds.Contains(uv.U, uv.V);
 		}
+
+		public int IndexOf(T value, int startIndex)
+		{
+			return Array.IndexOf(Entries, value, startIndex);
+		}
+
+		public void SetAll(T value)
+		{
+			Array.Fill(Entries, value);
+		}
 	}
 }

OpenRA.Game/Map/ProjectedCellRegion.cs

@@ -93,12 +93,12 @@ namespace OpenRA
 
 			public bool MoveNext()
 			{
-				u += 1;
+				u++;
 
 				// Check for column overflow
 				if (u > r.BottomRight.U)
 				{
-					v += 1;
+					v++;
 					u = r.TopLeft.U;
 
 					// Check for row overflow
@@ -118,8 +118,8 @@ namespace OpenRA
 			}
 
 			public PPos Current { get; private set; }
-			object IEnumerator.Current => Current;
-			public void Dispose() { }
+			readonly object IEnumerator.Current => Current;
+			public readonly void Dispose() { }
 		}
 	}
 }

OpenRA.Game/MiniYaml.cs

@@ -20,18 +20,36 @@ namespace OpenRA
 {
 	public static class MiniYamlExts
 	{
-		public static void WriteToFile(this List<MiniYamlNode> y, string filename)
+		public static void WriteToFile(this IEnumerable<MiniYamlNode> y, string filename)
 		{
 			File.WriteAllLines(filename, y.ToLines().Select(x => x.TrimEnd()).ToArray());
 		}
 
-		public static string WriteToString(this List<MiniYamlNode> y)
+		public static string WriteToString(this IEnumerable<MiniYamlNode> y)
 		{
 			// Remove all trailing newlines and restore the final EOF newline
 			return y.ToLines().JoinWith("\n").TrimEnd('\n') + "\n";
 		}
 
-		public static IEnumerable<string> ToLines(this List<MiniYamlNode> y)
+		public static IEnumerable<string> ToLines(this IEnumerable<MiniYamlNode> y)
+		{
+			foreach (var kv in y)
+				foreach (var line in kv.Value.ToLines(kv.Key, kv.Comment))
+					yield return line;
+		}
+
+		public static void WriteToFile(this IEnumerable<MiniYamlNodeBuilder> y, string filename)
+		{
+			File.WriteAllLines(filename, y.ToLines().Select(x => x.TrimEnd()).ToArray());
+		}
+
+		public static string WriteToString(this IEnumerable<MiniYamlNodeBuilder> y)
+		{
+			// Remove all trailing newlines and restore the final EOF newline
+			return y.ToLines().JoinWith("\n").TrimEnd('\n') + "\n";
+		}
+
+		public static IEnumerable<string> ToLines(this IEnumerable<MiniYamlNodeBuilder> y)
 		{
 			foreach (var kv in y)
 				foreach (var line in kv.Value.ToLines(kv.Key, kv.Comment))
@@ -43,22 +61,29 @@ namespace OpenRA
 	{
 		public readonly struct SourceLocation
 		{
-			public readonly string Filename;
+			public readonly string Name;
 			public readonly int Line;
 
-			public SourceLocation(string filename, int line)
+			public SourceLocation(string name, int line)
 			{
-				Filename = filename;
+				Name = name;
 				Line = line;
 			}
 
-			public override string ToString() { return $"{Filename}:{Line}"; }
+			public override string ToString() { return $"{Name}:{Line}"; }
 		}
 
-		public SourceLocation Location;
-		public string Key;
-		public MiniYaml Value;
-		public string Comment;
+		public readonly SourceLocation Location;
+		public readonly string Key;
+		public readonly MiniYaml Value;
+		public readonly string Comment;
+
+		public MiniYamlNode WithValue(MiniYaml value)
+		{
+			if (Value == value)
+				return this;
+			return new MiniYamlNode(Key, value, Comment, Location);
+		}
 
 		public MiniYamlNode(string k, MiniYaml v, string c = null)
 		{
@@ -74,26 +99,15 @@ namespace OpenRA
 		}
 
 		public MiniYamlNode(string k, string v, string c = null)
-			: this(k, v, c, null) { }
+			: this(k, new MiniYaml(v, Enumerable.Empty<MiniYamlNode>()), c) { }
 
-		public MiniYamlNode(string k, string v, List<MiniYamlNode> n)
+		public MiniYamlNode(string k, string v, IEnumerable<MiniYamlNode> n)
 			: this(k, new MiniYaml(v, n), null) { }
 
-		public MiniYamlNode(string k, string v, string c, List<MiniYamlNode> n)
-			: this(k, new MiniYaml(v, n), c) { }
-
-		public MiniYamlNode(string k, string v, string c, List<MiniYamlNode> n, SourceLocation loc)
-			: this(k, new MiniYaml(v, n), c, loc) { }
-
 		public override string ToString()
 		{
 			return $"{{YamlNode: {Key} @ {Location}}}";
 		}
-
-		public MiniYamlNode Clone()
-		{
-			return new MiniYamlNode(Key, Value.Clone(), Comment, Location);
-		}
 	}
 
 	public sealed class MiniYaml
@@ -101,15 +115,58 @@ namespace OpenRA
 		const int SpacesPerLevel = 4;
 		static readonly Func<string, string> StringIdentity = s => s;
 		static readonly Func<MiniYaml, MiniYaml> MiniYamlIdentity = my => my;
-		public string Value;
-		public List<MiniYamlNode> Nodes;
 
-		public MiniYaml Clone()
+		public readonly string Value;
+		public readonly ImmutableArray<MiniYamlNode> Nodes;
+
+		public MiniYaml WithValue(string value)
 		{
-			var clonedNodes = new List<MiniYamlNode>(Nodes.Count);
+			if (Value == value)
+				return this;
+			return new MiniYaml(value, Nodes);
+		}
+
+		public MiniYaml WithNodes(IEnumerable<MiniYamlNode> nodes)
+		{
+			if (nodes is ImmutableArray<MiniYamlNode> n && Nodes == n)
+				return this;
+			return new MiniYaml(Value, nodes);
+		}
+
+		public MiniYaml WithNodesAppended(IEnumerable<MiniYamlNode> nodes)
+		{
+			var newNodes = Nodes.AddRange(nodes);
+			if (Nodes == newNodes)
+				return this;
+			return new MiniYaml(Value, newNodes);
+		}
+
+		public MiniYamlNode NodeWithKey(string key)
+		{
+			var result = NodeWithKeyOrDefault(key);
+			if (result == null)
+				throw new InvalidDataException($"No node with key '{key}'");
+			return result;
+		}
+
+		public MiniYamlNode NodeWithKeyOrDefault(string key)
+		{
+			// PERF: Avoid LINQ.
+			var first = true;
+			MiniYamlNode result = null;
 			foreach (var node in Nodes)
-				clonedNodes.Add(node.Clone());
-			return new MiniYaml(Value, clonedNodes);
+			{
+				if (node.Key != key)
+					continue;
+
+				if (!first)
+					throw new InvalidDataException($"Duplicate key '{node.Key}' in {node.Location}");
+
+				first = false;
+				result = node;
+			}
+
+			return result;
 		}
 
 		public Dictionary<string, MiniYaml> ToDictionary()
@@ -125,7 +182,7 @@ namespace OpenRA
 		public Dictionary<TKey, TElement> ToDictionary<TKey, TElement>(
 			Func<string, TKey> keySelector, Func<MiniYaml, TElement> elementSelector)
 		{
-			var ret = new Dictionary<TKey, TElement>(Nodes.Count);
+			var ret = new Dictionary<TKey, TElement>(Nodes.Length);
 			foreach (var y in Nodes)
 			{
 				var key = keySelector(y.Key);
@@ -138,28 +195,27 @@ namespace OpenRA
 		}
 
 		public MiniYaml(string value)
-			: this(value, null) { }
+			: this(value, Enumerable.Empty<MiniYamlNode>()) { }
 
-		public MiniYaml(string value, List<MiniYamlNode> nodes)
+		public MiniYaml(string value, IEnumerable<MiniYamlNode> nodes)
 		{
 			Value = value;
-			Nodes = nodes ?? new List<MiniYamlNode>();
+			Nodes = ImmutableArray.CreateRange(nodes);
 		}
 
-		public static List<MiniYamlNode> NodesOrEmpty(MiniYaml y, string s)
+		static List<MiniYamlNode> FromLines(IEnumerable<ReadOnlyMemory<char>> lines, string name, bool discardCommentsAndWhitespace, HashSet<string> stringPool)
 		{
-			var nd = y.ToDictionary();
-			return nd.TryGetValue(s, out var v) ? v.Nodes : new List<MiniYamlNode>();
-		}
+			// YAML config often contains repeated strings for key, values, comments.
+			// Pool these strings so we only need one copy of each unique string.
+			// This saves on long-term memory usage as parsed values can often live a long time.
+			// A caller can also provide a pool as input, allowing de-duplication across multiple parses.
+			stringPool ??= new HashSet<string>();
 
-		static List<MiniYamlNode> FromLines(IEnumerable<ReadOnlyMemory<char>> lines, string filename, bool discardCommentsAndWhitespace, Dictionary<string, string> stringPool)
-		{
-			stringPool ??= new Dictionary<string, string>();
-
-			var levels = new List<List<MiniYamlNode>>
+			var result = new List<List<MiniYamlNode>>
 			{
-				new List<MiniYamlNode>()
+				new()
 			};
+			var parsedLines = new List<(int Level, string Key, string Value, string Comment, MiniYamlNode.SourceLocation Location)>();
 
 			var lineNo = 0;
 			foreach (var ll in lines)
@@ -175,7 +231,7 @@ namespace OpenRA
 				ReadOnlySpan<char> key = default;
 				ReadOnlySpan<char> value = default;
 				ReadOnlySpan<char> comment = default;
-				var location = new MiniYamlNode.SourceLocation(filename, lineNo);
+				var location = new MiniYamlNode.SourceLocation(name, lineNo);
 
 				if (line.Length > 0)
 				{
@@ -206,15 +262,6 @@ namespace OpenRA
 						}
 					}
 
-					if (levels.Count <= level)
-						throw new YamlException($"Bad indent in miniyaml at {location}");
-
-					while (levels.Count > level + 1)
-					{
-						levels[^1].TrimExcess();
-						levels.RemoveAt(levels.Count - 1);
-					}
-
 					// Extract key, value, comment from line as `<key>: <value>#<comment>`
 					// The # character is allowed in the value if escaped (\#).
 					// Leading and trailing whitespace is always trimmed from keys.
@@ -236,7 +283,7 @@ namespace OpenRA
 						if (commentStart < 0 && line[i] == '#' && (i == 0 || line[i - 1] != '\\'))
 						{
 							commentStart = i + 1;
-							if (commentStart <= keyLength)
+							if (i <= keyStart + keyLength)
 								keyLength = i - keyStart;
 							else
 								valueLength = i - valueStart;
@@ -274,6 +321,12 @@ namespace OpenRA
 
 				if (!key.IsEmpty || !discardCommentsAndWhitespace)
 				{
+					if (parsedLines.Count > 0 && parsedLines[^1].Level < level - 1)
+						throw new YamlException($"Bad indent in miniyaml at {location}");
+
+					while (parsedLines.Count > 0 && parsedLines[^1].Level > level)
+						BuildCompletedSubNode(level);
+
 					var keyString = key.IsEmpty ? null : key.ToString();
 					var valueString = value.IsEmpty ? null : value.ToString();
 
@@ -281,39 +334,68 @@ namespace OpenRA
 					// (i.e. a lone # at the end of a line) can be correctly re-serialized
 					var commentString = comment == default ? null : comment.ToString();
 
-					keyString = keyString == null ? null : stringPool.GetOrAdd(keyString, keyString);
-					valueString = valueString == null ? null : stringPool.GetOrAdd(valueString, valueString);
-					commentString = commentString == null ? null : stringPool.GetOrAdd(commentString, commentString);
+					keyString = keyString == null ? null : stringPool.GetOrAdd(keyString);
+					valueString = valueString == null ? null : stringPool.GetOrAdd(valueString);
+					commentString = commentString == null ? null : stringPool.GetOrAdd(commentString);
 
-					var nodes = new List<MiniYamlNode>();
-					levels[level].Add(new MiniYamlNode(keyString, valueString, commentString, nodes, location));
-
-					levels.Add(nodes);
+					parsedLines.Add((level, keyString, valueString, commentString, location));
 				}
 			}
 
-			foreach (var nodes in levels)
-				nodes.TrimExcess();
+			if (parsedLines.Count > 0)
+				BuildCompletedSubNode(0);
 
-			return levels[0];
+			return result[0];
+
+			void BuildCompletedSubNode(int level)
+			{
+				var lastLevel = parsedLines[^1].Level;
+				while (lastLevel >= result.Count)
+					result.Add(new List<MiniYamlNode>());
+
+				while (parsedLines.Count > 0 && parsedLines[^1].Level >= level)
+				{
+					var parent = parsedLines[^1];
+					var startOfRange = parsedLines.Count - 1;
+					while (startOfRange > 0 && parsedLines[startOfRange - 1].Level == parent.Level)
+						startOfRange--;
+
+					for (var i = startOfRange; i < parsedLines.Count - 1; i++)
+					{
+						var sibling = parsedLines[i];
+						result[parent.Level].Add(
+							new MiniYamlNode(sibling.Key, new MiniYaml(sibling.Value), sibling.Comment, sibling.Location));
+					}
+
+					var childNodes = parent.Level + 1 < result.Count ? result[parent.Level + 1] : null;
+					result[parent.Level].Add(new MiniYamlNode(
+						parent.Key,
+						new MiniYaml(parent.Value, childNodes ?? Enumerable.Empty<MiniYamlNode>()),
+						parent.Comment,
+						parent.Location));
+					childNodes?.Clear();
+
+					parsedLines.RemoveRange(startOfRange, parsedLines.Count - startOfRange);
+				}
+			}
 		}
 
-		public static List<MiniYamlNode> FromFile(string path, bool discardCommentsAndWhitespace = true, Dictionary<string, string> stringPool = null)
+		public static List<MiniYamlNode> FromFile(string path, bool discardCommentsAndWhitespace = true, HashSet<string> stringPool = null)
 		{
 			return FromStream(File.OpenRead(path), path, discardCommentsAndWhitespace, stringPool);
 		}
 
-		public static List<MiniYamlNode> FromStream(Stream s, string fileName = "<no filename available>", bool discardCommentsAndWhitespace = true, Dictionary<string, string> stringPool = null)
+		public static List<MiniYamlNode> FromStream(Stream s, string name, bool discardCommentsAndWhitespace = true, HashSet<string> stringPool = null)
 		{
-			return FromLines(s.ReadAllLinesAsMemory(), fileName, discardCommentsAndWhitespace, stringPool);
+			return FromLines(s.ReadAllLinesAsMemory(), name, discardCommentsAndWhitespace, stringPool);
 		}
 
-		public static List<MiniYamlNode> FromString(string text, string fileName = "<no filename available>", bool discardCommentsAndWhitespace = true, Dictionary<string, string> stringPool = null)
+		public static List<MiniYamlNode> FromString(string text, string name, bool discardCommentsAndWhitespace = true, HashSet<string> stringPool = null)
 		{
-			return FromLines(text.Split(new[] { "\r\n", "\n" }, StringSplitOptions.None).Select(s => s.AsMemory()), fileName, discardCommentsAndWhitespace, stringPool);
+			return FromLines(text.Split(new[] { "\r\n", "\n" }, StringSplitOptions.None).Select(s => s.AsMemory()), name, discardCommentsAndWhitespace, stringPool);
 		}
 
-		public static List<MiniYamlNode> Merge(IEnumerable<List<MiniYamlNode>> sources)
+		public static List<MiniYamlNode> Merge(IEnumerable<IReadOnlyCollection<MiniYamlNode>> sources)
 		{
 			var sourcesList = sources.ToList();
 			if (sourcesList.Count == 0)
@@ -336,7 +418,7 @@ namespace OpenRA
 			}
 
 			// Resolve any top-level removals (e.g. removing whole actor blocks)
-			var nodes = new MiniYaml("", resolved.Select(kv => new MiniYamlNode(kv.Key, kv.Value)).ToList());
+			var nodes = new MiniYaml("", resolved.Select(kv => new MiniYamlNode(kv.Key, kv.Value)));
 			return ResolveInherits(nodes, tree, ImmutableDictionary<string, MiniYamlNode.SourceLocation>.Empty);
 		}
 
@@ -345,19 +427,23 @@ namespace OpenRA
 		{
 			if (existingNodeKeys.Add(overrideNode.Key))
 			{
-				existingNodes.Add(overrideNode.Clone());
+				existingNodes.Add(overrideNode);
 				return;
 			}
 
-			var existingNode = existingNodes.Find(n => n.Key == overrideNode.Key);
-			existingNode.Value = MergePartial(existingNode.Value, overrideNode.Value);
-			existingNode.Value.Nodes = ResolveInherits(existingNode.Value, tree, inherited);
+			var existingNodeIndex = IndexOfKey(existingNodes, overrideNode.Key);
+			var existingNode = existingNodes[existingNodeIndex];
+			var value = MergePartial(existingNode.Value, overrideNode.Value);
+			var nodes = ResolveInherits(value, tree, inherited);
+			if (!value.Nodes.SequenceEqual(nodes))
+				value = value.WithNodes(nodes);
+			existingNodes[existingNodeIndex] = existingNode.WithValue(value);
 		}
 
 		static List<MiniYamlNode> ResolveInherits(MiniYaml node, Dictionary<string, MiniYaml> tree, ImmutableDictionary<string, MiniYamlNode.SourceLocation> inherited)
 		{
-			var resolved = new List<MiniYamlNode>(node.Nodes.Count);
-			var resolvedKeys = new HashSet<string>(node.Nodes.Count);
+			var resolved = new List<MiniYamlNode>(node.Nodes.Length);
+			var resolvedKeys = new HashSet<string>(node.Nodes.Length);
 
 			foreach (var n in node.Nodes)
 			{
@@ -379,7 +465,7 @@ namespace OpenRA
 					foreach (var r in ResolveInherits(parent, tree, inherited))
 						MergeIntoResolved(r, resolved, resolvedKeys, tree, inherited);
 				}
-				else if (n.Key.StartsWith("-", StringComparison.Ordinal))
+				else if (n.Key.StartsWith('-'))
 				{
 					var removed = n.Key[1..];
 					if (resolved.RemoveAll(r => r.Key == removed) == 0)
@@ -390,7 +476,6 @@ namespace OpenRA
 					MergeIntoResolved(n, resolved, resolvedKeys, tree, inherited);
 			}
 
-			resolved.TrimExcess();
 			return resolved;
 		}
 
@@ -398,7 +483,7 @@ namespace OpenRA
 		/// Merges any duplicate keys that are defined within the same set of nodes.
 		/// Does not resolve inheritance or node removals.
 		/// </summary>
-		static List<MiniYamlNode> MergeSelfPartial(List<MiniYamlNode> existingNodes)
+		static IReadOnlyCollection<MiniYamlNode> MergeSelfPartial(IReadOnlyCollection<MiniYamlNode> existingNodes)
 		{
 			var keys = new HashSet<string>(existingNodes.Count);
 			var ret = new List<MiniYamlNode>(existingNodes.Count);
@@ -409,12 +494,12 @@ namespace OpenRA
 				else
 				{
 					// Node with the same key has already been added: merge new node over the existing one
-					var original = ret.First(r => r.Key == n.Key);
-					original.Value = MergePartial(original.Value, n.Value);
+					var originalIndex = IndexOfKey(ret, n.Key);
+					var original = ret[originalIndex];
+					ret[originalIndex] = original.WithValue(MergePartial(original.Value, n.Value));
 				}
 			}
 
-			ret.TrimExcess();
 			return ret;
 		}
 
@@ -432,7 +517,7 @@ namespace OpenRA
 			return new MiniYaml(overrideNodes.Value ?? existingNodes.Value, MergePartial(existingNodes.Nodes, overrideNodes.Nodes));
 		}
 
-		static List<MiniYamlNode> MergePartial(List<MiniYamlNode> existingNodes, List<MiniYamlNode> overrideNodes)
+		static IReadOnlyCollection<MiniYamlNode> MergePartial(IReadOnlyCollection<MiniYamlNode> existingNodes, IReadOnlyCollection<MiniYamlNode> overrideNodes)
 		{
 			if (existingNodes.Count == 0)
 				return overrideNodes;
@@ -452,7 +537,7 @@ namespace OpenRA
 			{
 				// Append Removal nodes to the result.
 				// Therefore: we know the remainder of the method deals with a plain node.
-				if (node.Key.StartsWith("-", StringComparison.Ordinal))
+				if (node.Key.StartsWith('-'))
 				{
 					ret.Add(node);
 					return;
@@ -468,9 +553,8 @@ namespace OpenRA
 				// A Removal node is closer than the previous node.
 				// We should not merge the new node, as the data being merged will jump before the Removal.
 				// Instead, append it so the previous node is applied, then removed, then the new node is applied.
-				var removalKey = $"-{node.Key}";
-				var previousNodeIndex = ret.FindLastIndex(n => n.Key == node.Key);
-				var previousRemovalNodeIndex = ret.FindLastIndex(n => n.Key == removalKey);
+				var previousNodeIndex = LastIndexOfKey(ret, node.Key);
+				var previousRemovalNodeIndex = LastIndexOfKey(ret, $"-{node.Key}");
 				if (previousRemovalNodeIndex != -1 && previousRemovalNodeIndex > previousNodeIndex)
 				{
 					ret.Add(node);
@@ -479,13 +563,30 @@ namespace OpenRA
 
 				// A previous node is present with no intervening Removal.
 				// We should merge the new one into it, in place.
-				ret[previousNodeIndex] = new MiniYamlNode(node.Key, MergePartial(ret[previousNodeIndex].Value, node.Value), node.Comment, node.Location);
+				ret[previousNodeIndex] = node.WithValue(MergePartial(ret[previousNodeIndex].Value, node.Value));
 			}
 
-			ret.TrimExcess();
 			return ret;
 		}
 
+		static int IndexOfKey(List<MiniYamlNode> nodes, string key)
+		{
+			// PERF: Avoid LINQ.
+			for (var i = 0; i < nodes.Count; i++)
+				if (nodes[i].Key == key)
+					return i;
+			return -1;
+		}
+
+		static int LastIndexOfKey(List<MiniYamlNode> nodes, string key)
+		{
+			// PERF: Avoid LINQ.
+			for (var i = nodes.Count - 1; i >= 0; i--)
+				if (nodes[i].Key == key)
+					return i;
+			return -1;
+		}
+
 		public IEnumerable<string> ToLines(string key, string comment = null)
 		{
 			var hasKey = !string.IsNullOrEmpty(key);
@@ -508,14 +609,100 @@ namespace OpenRA
 				files = files.Append(mapFiles);
 			}
 
-			var yaml = files.Select(s => FromStream(fileSystem.Open(s), s));
-			if (mapRules != null && mapRules.Nodes.Count > 0)
+			var stringPool = new HashSet<string>(); // Reuse common strings in YAML
+			IEnumerable<IReadOnlyCollection<MiniYamlNode>> yaml = files.Select(s => FromStream(fileSystem.Open(s), s, stringPool: stringPool));
+			if (mapRules != null && mapRules.Nodes.Length > 0)
 				yaml = yaml.Append(mapRules.Nodes);
 
 			return Merge(yaml);
 		}
 	}
 
+	public sealed class MiniYamlNodeBuilder
+	{
+		public MiniYamlNode.SourceLocation Location;
+		public string Key;
+		public MiniYamlBuilder Value;
+		public string Comment;
+
+		public MiniYamlNodeBuilder(MiniYamlNode node)
+		{
+			Location = node.Location;
+			Key = node.Key;
+			Value = new MiniYamlBuilder(node.Value);
+			Comment = node.Comment;
+		}
+
+		public MiniYamlNodeBuilder(string k, MiniYamlBuilder v, string c = null)
+		{
+			Key = k;
+			Value = v;
+			Comment = c;
+		}
+
+		public MiniYamlNodeBuilder(string k, MiniYamlBuilder v, string c, MiniYamlNode.SourceLocation loc)
+			: this(k, v, c)
+		{
+			Location = loc;
+		}
+
+		public MiniYamlNodeBuilder(string k, string v, string c = null)
+			: this(k, new MiniYamlBuilder(v, null), c) { }
+
+		public MiniYamlNodeBuilder(string k, string v, List<MiniYamlNode> n)
+			: this(k, new MiniYamlBuilder(v, n), null) { }
+
+		public MiniYamlNode Build()
+		{
+			return new MiniYamlNode(Key, Value.Build(), Comment, Location);
+		}
+	}
+
+	public sealed class MiniYamlBuilder
+	{
+		public string Value;
+		public List<MiniYamlNodeBuilder> Nodes;
+
+		public MiniYamlBuilder(MiniYaml yaml)
+		{
+			Value = yaml.Value;
+			Nodes = yaml.Nodes.Select(n => new MiniYamlNodeBuilder(n)).ToList();
+		}
+
+		public MiniYamlBuilder(string value)
+			: this(value, null) { }
+
+		public MiniYamlBuilder(string value, List<MiniYamlNode> nodes)
+		{
+			Value = value;
+			Nodes = nodes == null ? new List<MiniYamlNodeBuilder>() : nodes.ConvertAll(x => new MiniYamlNodeBuilder(x));
+		}
+
+		public MiniYaml Build()
+		{
+			return new MiniYaml(Value, Nodes.Select(n => n.Build()));
+		}
+
+		public IEnumerable<string> ToLines(string key, string comment = null)
+		{
+			var hasKey = !string.IsNullOrEmpty(key);
+			var hasValue = !string.IsNullOrEmpty(Value);
+			var hasComment = comment != null;
+			yield return (hasKey ? key + ":" : "")
+				+ (hasValue ? " " + Value.Replace("#", "\\#") : "")
+				+ (hasComment ? (hasKey || hasValue ? " " : "") + "#" + comment : "");
+
+			if (Nodes != null)
+				foreach (var line in Nodes.ToLines())
+					yield return "\t" + line;
+		}
+
+		public MiniYamlNodeBuilder NodeWithKeyOrDefault(string key)
+		{
+			return Nodes.SingleOrDefault(n => n.Key == key);
+		}
+	}
+
 	[Serializable]
 	public class YamlException : Exception
 	{

OpenRA.Game/ModData.cs

@@ -33,7 +33,6 @@ namespace OpenRA
 		public readonly ISpriteLoader[] SpriteLoaders;
 		public readonly ITerrainLoader TerrainLoader;
 		public readonly ISpriteSequenceLoader SpriteSequenceLoader;
-		public readonly IModelSequenceLoader ModelSequenceLoader;
 		public readonly IVideoLoader[] VideoLoaders;
 		public readonly HotkeyManager Hotkeys;
 		public ILoadScreen LoadScreen { get; }
@@ -90,15 +89,6 @@ namespace OpenRA
 
 			SpriteSequenceLoader = (ISpriteSequenceLoader)sequenceCtor.Invoke(new[] { this });
 
-			var modelFormat = Manifest.Get<ModelSequenceFormat>();
-			var modelLoader = ObjectCreator.FindType(modelFormat.Type + "Loader");
-			var modelCtor = modelLoader?.GetConstructor(new[] { typeof(ModData) });
-			if (modelLoader == null || !modelLoader.GetInterfaces().Contains(typeof(IModelSequenceLoader)) || modelCtor == null)
-				throw new InvalidOperationException($"Unable to find a model loader for type '{modelFormat.Type}'.");
-
-			ModelSequenceLoader = (IModelSequenceLoader)modelCtor.Invoke(new[] { this });
-			ModelSequenceLoader.OnMissingModelError = s => Log.Write("debug", s);
-
 			Hotkeys = new HotkeyManager(ModFiles, Game.Settings.Keys, Manifest);
 
 			defaultRules = Exts.Lazy(() => Ruleset.LoadDefaults(this));
@@ -168,7 +158,8 @@ namespace OpenRA
 
 		public List<MiniYamlNode>[] GetRulesYaml()
 		{
-			return Manifest.Rules.Select(s => MiniYaml.FromStream(DefaultFileSystem.Open(s), s)).ToArray();
+			var stringPool = new HashSet<string>(); // Reuse common strings in YAML
+			return Manifest.Rules.Select(s => MiniYaml.FromStream(DefaultFileSystem.Open(s), s, stringPool: stringPool)).ToArray();
 		}
 
 		public void Dispose()

OpenRA.Game/Network/Connection.cs

@@ -260,15 +260,15 @@ namespace OpenRA.Network
 			try
 			{
 				var ms = new MemoryStream();
-				ms.WriteArray(BitConverter.GetBytes(packet.Length));
-				ms.WriteArray(packet);
+				ms.Write(packet.Length);
+				ms.Write(packet);
 
 				foreach (var s in queuedSyncPackets)
 				{
 					var q = OrderIO.SerializeSync(s);
 
-					ms.WriteArray(BitConverter.GetBytes(q.Length));
-					ms.WriteArray(q);
+					ms.Write(q.Length);
+					ms.Write(q);
 
 					sentSync.Enqueue(s);
 				}

OpenRA.Game/Network/GameSave.cs

@@ -122,10 +122,10 @@ namespace OpenRA.Network
 				LastSyncFrame = rs.ReadInt32();
 				lastSyncPacket = rs.ReadBytes(Order.SyncHashOrderLength);
 
-				var globalSettings = MiniYaml.FromString(rs.ReadString(Encoding.UTF8, Connection.MaxOrderLength));
+				var globalSettings = MiniYaml.FromString(rs.ReadLengthPrefixedString(Encoding.UTF8, Connection.MaxOrderLength), $"{filepath}:globalSettings");
 				GlobalSettings = Session.Global.Deserialize(globalSettings[0].Value);
 
-				var slots = MiniYaml.FromString(rs.ReadString(Encoding.UTF8, Connection.MaxOrderLength));
+				var slots = MiniYaml.FromString(rs.ReadLengthPrefixedString(Encoding.UTF8, Connection.MaxOrderLength), $"{filepath}:slots");
 				Slots = new Dictionary<string, Session.Slot>();
 				foreach (var s in slots)
 				{
@@ -133,7 +133,7 @@ namespace OpenRA.Network
 					Slots.Add(slot.PlayerReference, slot);
 				}
 
-				var slotClients = MiniYaml.FromString(rs.ReadString(Encoding.UTF8, Connection.MaxOrderLength));
+				var slotClients = MiniYaml.FromString(rs.ReadLengthPrefixedString(Encoding.UTF8, Connection.MaxOrderLength), $"{filepath}:slotClients");
 				SlotClients = new Dictionary<string, SlotClient>();
 				foreach (var s in slotClients)
 				{
@@ -144,9 +144,9 @@ namespace OpenRA.Network
 				if (rs.Position != traitDataOffset || rs.ReadInt32() != TraitDataMarker)
 					throw new InvalidDataException("Invalid orasav file");
 
-				var traitData = MiniYaml.FromString(rs.ReadString(Encoding.UTF8, Connection.MaxOrderLength));
+				var traitData = MiniYaml.FromString(rs.ReadLengthPrefixedString(Encoding.UTF8, Connection.MaxOrderLength), $"{filepath}:traitData");
 				foreach (var td in traitData)
-					TraitData.Add(int.Parse(td.Key), td.Value);
+					TraitData.Add(Exts.ParseInt32Invariant(td.Key), td.Value);
 
 				rs.Seek(0, SeekOrigin.Begin);
 				ordersStream.Write(rs.ReadBytes(metadataOffset), 0, metadataOffset);
@@ -226,10 +226,10 @@ namespace OpenRA.Network
 				clientSlot = firstBotSlotIndex;
 			}
 
-			ordersStream.WriteArray(BitConverter.GetBytes(data.Length + 8));
-			ordersStream.WriteArray(BitConverter.GetBytes(frame));
-			ordersStream.WriteArray(BitConverter.GetBytes(clientSlot));
-			ordersStream.WriteArray(data);
+			ordersStream.Write(data.Length + 8);
+			ordersStream.Write(frame);
+			ordersStream.Write(clientSlot);
+			ordersStream.Write(data);
 			LastOrdersFrame = frame;
 		}
 
@@ -238,7 +238,7 @@ namespace OpenRA.Network
 			// Send the trait data first to guarantee that it is available when needed
 			foreach (var kv in TraitData)
 			{
-				var data = new List<MiniYamlNode>() { new MiniYamlNode(kv.Key.ToString(), kv.Value) }.WriteToString();
+				var data = new List<MiniYamlNode>() { new(kv.Key.ToStringInvariant(), kv.Value) }.WriteToString();
 				packetFn(0, 0, Order.FromTargetString("SaveTraitData", data, true).Serialize());
 			}
 
@@ -288,35 +288,35 @@ namespace OpenRA.Network
 			{
 				ordersStream.Seek(0, SeekOrigin.Begin);
 				ordersStream.CopyTo(file);
-				file.Write(BitConverter.GetBytes(MetadataMarker), 0, 4);
-				file.Write(BitConverter.GetBytes(LastOrdersFrame), 0, 4);
-				file.Write(BitConverter.GetBytes(LastSyncFrame), 0, 4);
+				file.Write(MetadataMarker);
+				file.Write(LastOrdersFrame);
+				file.Write(LastSyncFrame);
 				file.Write(lastSyncPacket, 0, Order.SyncHashOrderLength);
 
 				var globalSettingsNodes = new List<MiniYamlNode>() { GlobalSettings.Serialize() };
-				file.WriteString(Encoding.UTF8, globalSettingsNodes.WriteToString());
+				file.WriteLengthPrefixedString(Encoding.UTF8, globalSettingsNodes.WriteToString());
 
 				var slotNodes = Slots
 					.Select(s => s.Value.Serialize())
 					.ToList();
-				file.WriteString(Encoding.UTF8, slotNodes.WriteToString());
+				file.WriteLengthPrefixedString(Encoding.UTF8, slotNodes.WriteToString());
 
 				var slotClientNodes = SlotClients
 					.Select(s => s.Value.Serialize(s.Key))
 					.ToList();
-				file.WriteString(Encoding.UTF8, slotClientNodes.WriteToString());
+				file.WriteLengthPrefixedString(Encoding.UTF8, slotClientNodes.WriteToString());
 
 				var traitDataOffset = file.Length;
-				file.Write(BitConverter.GetBytes(TraitDataMarker), 0, 4);
+				file.Write(TraitDataMarker);
 
 				var traitDataNodes = TraitData
-					.Select(kv => new MiniYamlNode(kv.Key.ToString(), kv.Value))
+					.Select(kv => new MiniYamlNode(kv.Key.ToStringInvariant(), kv.Value))
 					.ToList();
-				file.WriteString(Encoding.UTF8, traitDataNodes.WriteToString());
+				file.WriteLengthPrefixedString(Encoding.UTF8, traitDataNodes.WriteToString());
 
-				file.Write(BitConverter.GetBytes(ordersStream.Length), 0, 4);
-				file.Write(BitConverter.GetBytes(traitDataOffset), 0, 4);
-				file.Write(BitConverter.GetBytes(EOFMarker), 0, 4);
+				file.Write((int)ordersStream.Length);
+				file.Write((int)traitDataOffset);
+				file.Write(EOFMarker);
 			}
 		}
 	}

OpenRA.Game/Network/GameServer.cs

@@ -140,7 +140,7 @@ namespace OpenRA.Network
 		static object LoadClients(MiniYaml yaml)
 		{
 			var clients = new List<GameClient>();
-			var clientsNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Clients");
+			var clientsNode = yaml.NodeWithKeyOrDefault("Clients");
 			if (clientsNode != null)
 			{
 				var regex = new Regex(@"Client@\d+");
@@ -159,7 +159,7 @@ namespace OpenRA.Network
 			// Games advertised using the old API used a single Mods field
 			if (Mod == null || Version == null)
 			{
-				var modsNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Mods");
+				var modsNode = yaml.NodeWithKeyOrDefault("Mods");
 				if (modsNode != null)
 				{
 					var modVersion = modsNode.Value.Value.Split('@');
@@ -169,9 +169,8 @@ namespace OpenRA.Network
 			}
 
 			// Games advertised using the old API calculated the play time locally
-			if (State == 2 && PlayTime < 0)
-				if (DateTime.TryParse(Started, out var startTime))
-					PlayTime = (int)(DateTime.UtcNow - startTime).TotalSeconds;
+			if (State == 2 && PlayTime < 0 && DateTime.TryParse(Started, out var startTime))
+				PlayTime = (int)(DateTime.UtcNow - startTime).TotalSeconds;
 
 			var externalKey = ExternalMod.MakeKey(Mod, Version);
 			if (Game.ExternalMods.TryGetValue(externalKey, out var external) && external.Version == Version)
@@ -217,7 +216,7 @@ namespace OpenRA.Network
 			Name = server.Settings.Name;
 
 			// IP address will be replaced with a real value by the master server / receiving LAN client
-			Address = "0.0.0.0:" + server.Settings.ListenPort.ToString();
+			Address = "0.0.0.0:" + server.Settings.ListenPort.ToStringInvariant();
 			State = (int)server.State;
 			MaxPlayers = server.LobbyInfo.Slots.Count(s => !s.Value.Closed) - server.LobbyInfo.Clients.Count(c1 => c1.Bot != null);
 			Map = server.Map.Uid;
@@ -234,7 +233,7 @@ namespace OpenRA.Network
 
 		public string ToPOSTData(bool lanGame)
 		{
-			var root = new List<MiniYamlNode>() { new MiniYamlNode("Protocol", ProtocolVersion.ToString()) };
+			var root = new List<MiniYamlNode>() { new("Protocol", ProtocolVersion.ToStringInvariant()) };
 			foreach (var field in SerializeFields)
 				root.Add(FieldSaver.SaveField(this, field));
 
@@ -243,18 +242,16 @@ namespace OpenRA.Network
 				// Add fields that are normally generated by the master server
 				// LAN games overload the Id with a GUID string (rather than an ID) to allow deduplication
 				root.Add(new MiniYamlNode("Id", Platform.SessionGUID.ToString()));
-				root.Add(new MiniYamlNode("Players", Clients.Count(c => !c.IsBot && !c.IsSpectator).ToString()));
-				root.Add(new MiniYamlNode("Spectators", Clients.Count(c => c.IsSpectator).ToString()));
-				root.Add(new MiniYamlNode("Bots", Clients.Count(c => c.IsBot).ToString()));
+				root.Add(new MiniYamlNode("Players", Clients.Count(c => !c.IsBot && !c.IsSpectator).ToStringInvariant()));
+				root.Add(new MiniYamlNode("Spectators", Clients.Count(c => c.IsSpectator).ToStringInvariant()));
+				root.Add(new MiniYamlNode("Bots", Clients.Count(c => c.IsBot).ToStringInvariant()));
 
 				// Included for backwards compatibility with older clients that don't support separated Mod/Version.
 				root.Add(new MiniYamlNode("Mods", Mod + "@" + Version));
 			}
 
-			var clientsNode = new MiniYaml("");
-			var i = 0;
-			foreach (var c in Clients)
-				clientsNode.Nodes.Add(new MiniYamlNode("Client@" + i++.ToString(), FieldSaver.Save(c)));
+			var clientsNode = new MiniYaml("", Clients.Select((c, i) =>
+				new MiniYamlNode("Client@" + i, FieldSaver.Save(c))));
 
 			root.Add(new MiniYamlNode("Clients", clientsNode));
 			return new MiniYaml("", root)

OpenRA.Game/Network/Handshake.cs

@@ -20,16 +20,16 @@ namespace OpenRA.Network
 		public string Version;
 		public string AuthToken;
 
-		public static HandshakeRequest Deserialize(string data)
+		public static HandshakeRequest Deserialize(string data, string name)
 		{
 			var handshake = new HandshakeRequest();
-			FieldLoader.Load(handshake, MiniYaml.FromString(data).First().Value);
+			FieldLoader.Load(handshake, MiniYaml.FromString(data, name).First().Value);
 			return handshake;
 		}
 
 		public string Serialize()
 		{
-			var data = new List<MiniYamlNode> { new MiniYamlNode("Handshake", FieldSaver.Save(this)) };
+			var data = new List<MiniYamlNode> { new("Handshake", FieldSaver.Save(this)) };
 			return data.WriteToString();
 		}
 	}
@@ -51,14 +51,14 @@ namespace OpenRA.Network
 		[FieldLoader.Ignore]
 		public Session.Client Client;
 
-		public static HandshakeResponse Deserialize(string data)
+		public static HandshakeResponse Deserialize(string data, string name)
 		{
 			var handshake = new HandshakeResponse
 			{
 				Client = new Session.Client()
 			};
 
-			var ys = MiniYaml.FromString(data);
+			var ys = MiniYaml.FromString(data, name);
 			foreach (var y in ys)
 			{
 				switch (y.Key)
@@ -79,9 +79,9 @@ namespace OpenRA.Network
 		{
 			var data = new List<MiniYamlNode>
 			{
-				new MiniYamlNode("Handshake", null,
+				new("Handshake", null,
 					new[] { "Mod", "Version", "Password", "Fingerprint", "AuthSignature", "OrdersProtocol" }.Select(p => FieldSaver.SaveField(this, p)).ToList()),
-				new MiniYamlNode("Client", FieldSaver.Save(Client))
+				new("Client", FieldSaver.Save(Client))
 			};
 
 			return data.WriteToString();

OpenRA.Game/Network/LocalizedMessage.cs

@@ -9,10 +9,8 @@
  */
 #endregion
 
-using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text.RegularExpressions;
 using Linguini.Shared.Types.Bundle;
 
 namespace OpenRA.Network
@@ -57,61 +55,51 @@ namespace OpenRA.Network
 		public readonly string Key = string.Empty;
 
 		[FieldLoader.LoadUsing(nameof(LoadArguments))]
-		public readonly FluentArgument[] Arguments = Array.Empty<FluentArgument>();
-
-		public string TranslatedText { get; }
+		public readonly Dictionary<string, object> Arguments;
 
 		static object LoadArguments(MiniYaml yaml)
 		{
-			var arguments = new List<FluentArgument>();
-			var argumentsNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Arguments");
+			var arguments = new Dictionary<string, object>();
+			var argumentsNode = yaml.NodeWithKeyOrDefault("Arguments");
 			if (argumentsNode != null)
 			{
-				var regex = new Regex(@"Argument@\d+");
-				foreach (var argument in argumentsNode.Value.Nodes)
-					if (regex.IsMatch(argument.Key))
-						arguments.Add(FieldLoader.Load<FluentArgument>(argument.Value));
+				foreach (var argumentNode in argumentsNode.Value.Nodes)
+				{
+					var argument = FieldLoader.Load<FluentArgument>(argumentNode.Value);
+					if (argument.Type == FluentArgument.FluentArgumentType.Number)
+					{
+						if (!double.TryParse(argument.Value, out var number))
+							Log.Write("debug", $"Failed to parse {argument.Value}");
+
+						arguments.Add(argument.Key, number);
+					}
+					else
+						arguments.Add(argument.Key, argument.Value);
+				}
 			}
 
-			return arguments.ToArray();
+			return arguments;
 		}
 
 		public LocalizedMessage(MiniYaml yaml)
 		{
 			// Let the FieldLoader do the dirty work of loading the public fields.
 			FieldLoader.Load(this, yaml);
-
-			var argumentDictionary = new Dictionary<string, object>();
-			foreach (var argument in Arguments)
-			{
-				if (argument.Type == FluentArgument.FluentArgumentType.Number)
-				{
-					if (!double.TryParse(argument.Value, out var number))
-						Log.Write("debug", $"Failed to parse {argument.Value}");
-
-					argumentDictionary.Add(argument.Key, number);
-				}
-				else
-					argumentDictionary.Add(argument.Key, argument.Value);
-			}
-
-			TranslatedText = TranslationProvider.GetString(Key, argumentDictionary);
 		}
 
 		public static string Serialize(string key, Dictionary<string, object> arguments = null)
 		{
 			var root = new List<MiniYamlNode>
 			{
-				new MiniYamlNode("Protocol", ProtocolVersion.ToString()),
-				new MiniYamlNode("Key", key)
+				new("Protocol", ProtocolVersion.ToStringInvariant()),
+				new("Key", key)
 			};
 
 			if (arguments != null)
 			{
-				var argumentsNode = new MiniYaml("");
-				var i = 0;
-				foreach (var argument in arguments.Select(a => new FluentArgument(a.Key, a.Value)))
-					argumentsNode.Nodes.Add(new MiniYamlNode("Argument@" + i++, FieldSaver.Save(argument)));
+				var argumentsNode = new MiniYaml("", arguments
+					.Select(a => new FluentArgument(a.Key, a.Value))
+					.Select((argument, i) => new MiniYamlNode("Argument@" + i, FieldSaver.Save(argument))));
 
 				root.Add(new MiniYamlNode("Arguments", argumentsNode));
 			}

OpenRA.Game/Network/Order.cs

@@ -156,7 +156,18 @@ namespace OpenRA
 									else
 									{
 										var pos = new WPos(r.ReadInt32(), r.ReadInt32(), r.ReadInt32());
-										target = Target.FromPos(pos);
+
+										var numberOfTerrainPositions = r.ReadInt16();
+										if (numberOfTerrainPositions == -1)
+											target = Target.FromPos(pos);
+										else
+										{
+											var terrainPositions = new WPos[numberOfTerrainPositions];
+											for (var i = 0; i < numberOfTerrainPositions; i++)
+												terrainPositions[i] = new WPos(r.ReadInt32(), r.ReadInt32(), r.ReadInt32());
+
+											target = Target.FromSerializedTerrainPosition(pos, terrainPositions);
+										}
 									}
 
 									break;
@@ -388,6 +399,21 @@ namespace OpenRA
 									w.Write(targetState.Pos.X);
 									w.Write(targetState.Pos.Y);
 									w.Write(targetState.Pos.Z);
+
+									// Don't send extra data over the network that will be restored by the Target ctor
+									var terrainPositions = targetState.TerrainPositions.Length;
+									if (terrainPositions == 1 && targetState.TerrainPositions[0] == targetState.Pos)
+										w.Write((short)-1);
+									else
+									{
+										w.Write((short)terrainPositions);
+										foreach (var position in targetState.TerrainPositions)
+										{
+											w.Write(position.X);
+											w.Write(position.Y);
+											w.Write(position.Z);
+										}
+									}
 								}
 
 								break;

OpenRA.Game/Network/OrderIO.cs

@@ -27,7 +27,7 @@ namespace OpenRA.Network
 			// the Order objects directly on the local client.
 			data = new MemoryStream();
 			foreach (var o in orders)
-				data.WriteArray(o.Serialize());
+				data.Write(o.Serialize());
 		}
 
 		public OrderPacket(MemoryStream data)
@@ -55,7 +55,7 @@ namespace OpenRA.Network
 		public byte[] Serialize(int frame)
 		{
 			var ms = new MemoryStream((int)data.Length + 4);
-			ms.WriteArray(BitConverter.GetBytes(frame));
+			ms.Write(frame);
 
 			data.Position = 0;
 			data.CopyTo(ms);
@@ -83,19 +83,19 @@ namespace OpenRA.Network
 		public static byte[] SerializeSync((int Frame, int SyncHash, ulong DefeatState) data)
 		{
 			var ms = new MemoryStream(4 + Order.SyncHashOrderLength);
-			ms.WriteArray(BitConverter.GetBytes(data.Frame));
+			ms.Write(data.Frame);
 			ms.WriteByte((byte)OrderType.SyncHash);
-			ms.WriteArray(BitConverter.GetBytes(data.SyncHash));
-			ms.WriteArray(BitConverter.GetBytes(data.DefeatState));
+			ms.Write(data.SyncHash);
+			ms.Write(data.DefeatState);
 			return ms.GetBuffer();
 		}
 
 		public static byte[] SerializePingResponse(long timestamp, byte queueLength)
 		{
 			var ms = new MemoryStream(14);
-			ms.WriteArray(BitConverter.GetBytes(0));
+			ms.Write(0);
 			ms.WriteByte((byte)OrderType.Ping);
-			ms.WriteArray(BitConverter.GetBytes(timestamp));
+			ms.Write(timestamp);
 			ms.WriteByte(queueLength);
 			return ms.GetBuffer();
 		}

OpenRA.Game/Network/OrderManager.cs

@@ -22,6 +22,9 @@ namespace OpenRA.Network
 	{
 		const OrderPacket ClientDisconnected = null;
 
+		[TranslationReference("frame")]
+		const string DesyncCompareLogs = "notification-desync-compare-logs";
+
 		readonly SyncReport syncReport;
 		readonly Dictionary<int, Queue<(int Frame, OrderPacket Orders)>> pendingOrders = new();
 		readonly Dictionary<int, (int SyncHash, ulong DefeatState)> syncForFrame = new();
@@ -36,6 +39,9 @@ namespace OpenRA.Network
 		public string ServerError = null;
 		public bool AuthenticationFailed = false;
 
+		// The default null means "no map restriction" while an empty set means "all maps restricted"
+		public HashSet<string> ServerMapPool = null;
+
 		public int NetFrameNumber { get; private set; }
 		public int LocalFrameNumber;
 
@@ -70,7 +76,7 @@ namespace OpenRA.Network
 			public int Client;
 			public Order Order;
 
-			public override string ToString()
+			public override readonly string ToString()
 			{
 				return $"ClientId: {Client} {Order}";
 			}
@@ -85,7 +91,7 @@ namespace OpenRA.Network
 			World.OutOfSync();
 			IsOutOfSync = true;
 
-			TextNotificationsManager.AddSystemLine($"Out of sync in frame {frame}.\nCompare syncreport.log with other players.");
+			TextNotificationsManager.AddSystemLine(DesyncCompareLogs, Translation.Arguments("frame", frame));
 		}
 
 		public void StartGame()

OpenRA.Game/Network/ReplayConnection.cs

@@ -69,7 +69,7 @@ namespace OpenRA.Network
 								if (o.OrderString == "StartGame")
 									IsValid = true;
 								else if (o.OrderString == "SyncInfo" && !IsValid)
-									LobbyInfo = Session.Deserialize(o.TargetString);
+									LobbyInfo = Session.Deserialize(o.TargetString, o.OrderString);
 							}
 						}
 					}

OpenRA.Game/Network/ReplayRecorder.cs

@@ -67,7 +67,7 @@ namespace OpenRA.Network
 				}
 			}
 
-			file.WriteArray(initialContent);
+			file.Write(initialContent);
 			writer = new BinaryWriter(file);
 		}
 
@@ -92,8 +92,8 @@ namespace OpenRA.Network
 		public void ReceiveFrame(int clientID, int frame, byte[] data)
 		{
 			var ms = new MemoryStream(4 + data.Length);
-			ms.WriteArray(BitConverter.GetBytes(frame));
-			ms.WriteArray(data);
+			ms.Write(frame);
+			ms.Write(data);
 			Receive(clientID, ms.GetBuffer());
 		}
 

OpenRA.Game/Network/Session.cs

@@ -41,13 +41,13 @@ namespace OpenRA.Network
 			return null;
 		}
 
-		public static Session Deserialize(string data)
+		public static Session Deserialize(string data, string name)
 		{
 			try
 			{
 				var session = new Session();
 
-				var nodes = MiniYaml.FromString(data);
+				var nodes = MiniYaml.FromString(data, name);
 				foreach (var node in nodes)
 				{
 					var strings = node.Key.Split('@');
@@ -227,7 +227,7 @@ namespace OpenRA.Network
 			{
 				var gs = FieldLoader.Load<Global>(data);
 
-				var optionsNode = data.Nodes.FirstOrDefault(n => n.Key == "Options");
+				var optionsNode = data.NodeWithKeyOrDefault("Options");
 				if (optionsNode != null)
 					foreach (var n in optionsNode.Value.Nodes)
 						gs.LobbyOptions[n.Key] = FieldLoader.Load<LobbyOptionState>(n.Value);
@@ -238,8 +238,9 @@ namespace OpenRA.Network
 			public MiniYamlNode Serialize()
 			{
 				var data = new MiniYamlNode("GlobalSettings", FieldSaver.Save(this));
-				var options = LobbyOptions.Select(kv => new MiniYamlNode(kv.Key, FieldSaver.Save(kv.Value))).ToList();
-				data.Value.Nodes.Add(new MiniYamlNode("Options", new MiniYaml(null, options)));
+				var options = LobbyOptions.Select(kv => new MiniYamlNode(kv.Key, FieldSaver.Save(kv.Value)));
+				data = data.WithValue(data.Value.WithNodesAppended(
+					new[] { new MiniYamlNode("Options", new MiniYaml(null, options)) }));
 				return data;
 			}
 
@@ -264,7 +265,7 @@ namespace OpenRA.Network
 		{
 			var sessionData = new List<MiniYamlNode>()
 			{
-				new MiniYamlNode("DisabledSpawnPoints", FieldSaver.FormatValue(DisabledSpawnPoints))
+				new("DisabledSpawnPoints", FieldSaver.FormatValue(DisabledSpawnPoints))
 			};
 
 			foreach (var client in Clients)

OpenRA.Game/Network/SyncReport.cs

@@ -201,8 +201,12 @@ namespace OpenRA.Network
 			public TypeInfo(Type type)
 			{
 				const BindingFlags Flags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
-				var fields = type.GetFields(Flags).Where(fi => !fi.IsLiteral && !fi.IsStatic && fi.HasAttribute<SyncAttribute>());
-				var properties = type.GetProperties(Flags).Where(pi => pi.HasAttribute<SyncAttribute>());
+				var fields = type.GetFields(Flags)
+					.Where(fi => !fi.IsLiteral && !fi.IsStatic && fi.HasAttribute<SyncAttribute>())
+					.ToList();
+				var properties = type.GetProperties(Flags)
+					.Where(pi => pi.HasAttribute<SyncAttribute>())
+					.ToList();
 
 				foreach (var prop in properties)
 					if (!prop.CanRead || prop.GetIndexParameters().Length > 0)
@@ -300,7 +304,7 @@ namespace OpenRA.Network
 
 			public object this[int index]
 			{
-				get
+				readonly get
 				{
 					if (item2OrSentinel == Sentinel)
 						return ((object[])item1OrArray)[index];

OpenRA.Game/Network/UnitOrders.cs

@@ -20,6 +20,24 @@ namespace OpenRA.Network
 	{
 		public const int ChatMessageMaxLength = 2500;
 
+		[TranslationReference("player")]
+		const string Joined = "notification-joined";
+
+		[TranslationReference("player")]
+		const string Left = "notification-lobby-disconnected";
+
+		[TranslationReference]
+		const string GameStarted = "notification-game-has-started";
+
+		[TranslationReference]
+		const string GameSaved = "notification-game-saved";
+
+		[TranslationReference("player")]
+		const string GamePaused = "notification-game-paused";
+
+		[TranslationReference("player")]
+		const string GameUnpaused = "notification-game-unpaused";
+
 		public static int? KickVoteTarget { get; internal set; }
 
 		static Player FindPlayerByClient(this World world, Session.Client c)
@@ -40,342 +58,350 @@ namespace OpenRA.Network
 
 				// Client side translated server message
 				case "LocalizedMessage":
-					{
-						if (string.IsNullOrEmpty(order.TargetString))
-							break;
-
-						var yaml = MiniYaml.FromString(order.TargetString);
-						foreach (var node in yaml)
-						{
-							var localizedMessage = new LocalizedMessage(node.Value);
-							TextNotificationsManager.AddSystemLine(localizedMessage.TranslatedText);
-						}
-
+				{
+					if (string.IsNullOrEmpty(order.TargetString))
 						break;
+
+					var yaml = MiniYaml.FromString(order.TargetString, order.OrderString);
+					foreach (var node in yaml)
+					{
+						var localizedMessage = new LocalizedMessage(node.Value);
+						if (localizedMessage.Key == Joined)
+							TextNotificationsManager.AddPlayerJoinedLine(localizedMessage.Key, localizedMessage.Arguments);
+						else if (localizedMessage.Key == Left)
+							TextNotificationsManager.AddPlayerLeftLine(localizedMessage.Key, localizedMessage.Arguments);
+						else
+							TextNotificationsManager.AddSystemLine(localizedMessage.Key, localizedMessage.Arguments);
 					}
 
+					break;
+				}
+
 				case "DisableChatEntry":
-					{
-						if (OrderNotFromServerOrWorldIsReplay(clientId, world))
-							break;
-
-						// Server may send MaxValue to indicate that it is disabled until further notice
-						if (order.ExtraData == uint.MaxValue)
-							TextNotificationsManager.ChatDisabledUntil = uint.MaxValue;
-						else
-							TextNotificationsManager.ChatDisabledUntil = Game.RunTime + order.ExtraData;
-
+				{
+					if (OrderNotFromServerOrWorldIsReplay(clientId, world))
 						break;
-					}
+
+					// Server may send MaxValue to indicate that it is disabled until further notice
+					if (order.ExtraData == uint.MaxValue)
+						TextNotificationsManager.ChatDisabledUntil = uint.MaxValue;
+					else
+						TextNotificationsManager.ChatDisabledUntil = Game.RunTime + order.ExtraData;
+
+					break;
+				}
 
 				case "StartKickVote":
-					{
-						if (OrderNotFromServerOrWorldIsReplay(clientId, world))
-							break;
-
-						KickVoteTarget = (int)order.ExtraData;
+				{
+					if (OrderNotFromServerOrWorldIsReplay(clientId, world))
 						break;
-					}
+
+					KickVoteTarget = (int)order.ExtraData;
+					break;
+				}
 
 				case "EndKickVote":
-					{
-						if (OrderNotFromServerOrWorldIsReplay(clientId, world))
-							break;
-
-						if (KickVoteTarget == (int)order.ExtraData)
-							KickVoteTarget = null;
-
+				{
+					if (OrderNotFromServerOrWorldIsReplay(clientId, world))
 						break;
-					}
+
+					if (KickVoteTarget == (int)order.ExtraData)
+						KickVoteTarget = null;
+
+					break;
+				}
 
 				case "Chat":
+				{
+					var client = orderManager.LobbyInfo.ClientWithIndex(clientId);
+					if (client == null)
+						break;
+
+					// Cut chat messages to the hard limit to avoid exploits
+					var message = order.TargetString;
+					if (message.Length > ChatMessageMaxLength)
+						message = order.TargetString[..ChatMessageMaxLength];
+
+					// ExtraData 0 means this is a normal chat order, everything else is team chat
+					if (order.ExtraData == 0)
 					{
-						var client = orderManager.LobbyInfo.ClientWithIndex(clientId);
-						if (client == null)
-							break;
+						var p = world?.FindPlayerByClient(client);
+						var suffix = (p != null && p.WinState == WinState.Lost) ? " (Dead)" : "";
+						suffix = client.IsObserver ? " (Spectator)" : suffix;
 
-						// Cut chat messages to the hard limit to avoid exploits
-						var message = order.TargetString;
-						if (message.Length > ChatMessageMaxLength)
-							message = order.TargetString[..ChatMessageMaxLength];
+						if (orderManager.LocalClient != null && client != orderManager.LocalClient && client.Team > 0 && client.Team == orderManager.LocalClient.Team)
+							suffix += " (Ally)";
 
-						// ExtraData 0 means this is a normal chat order, everything else is team chat
-						if (order.ExtraData == 0)
-						{
-							var p = world?.FindPlayerByClient(client);
-							var suffix = (p != null && p.WinState == WinState.Lost) ? " (Dead)" : "";
-							suffix = client.IsObserver ? " (Spectator)" : suffix;
+						TextNotificationsManager.AddChatLine(clientId, client.Name + suffix, message, client.Color);
+						break;
+					}
 
-							if (orderManager.LocalClient != null && client != orderManager.LocalClient && client.Team > 0 && client.Team == orderManager.LocalClient.Team)
-								suffix += " (Ally)";
-
-							TextNotificationsManager.AddChatLine(clientId, client.Name + suffix, message, client.Color);
-							break;
-						}
-
-						// We are still in the lobby
-						if (world == null)
-						{
-							var prefix = order.ExtraData == uint.MaxValue ? "[Spectators] " : "[Team] ";
-							if (orderManager.LocalClient != null && client.Team == orderManager.LocalClient.Team)
-								TextNotificationsManager.AddChatLine(clientId, prefix + client.Name, message, client.Color);
-
-							break;
-						}
-
-						var player = world.FindPlayerByClient(client);
-						var localClientIsObserver = world.IsReplay || (orderManager.LocalClient != null && orderManager.LocalClient.IsObserver)
-							|| (world.LocalPlayer != null && world.LocalPlayer.WinState != WinState.Undefined);
-
-						// ExtraData gives us the team number, uint.MaxValue means Spectators
-						if (order.ExtraData == uint.MaxValue && localClientIsObserver)
-						{
-							// Validate before adding the line
-							if (client.IsObserver || (player != null && player.WinState != WinState.Undefined))
-								TextNotificationsManager.AddChatLine(clientId, "[Spectators] " + client.Name, message, client.Color);
-
-							break;
-						}
-
-						var valid = client.Team == order.ExtraData && player != null && player.WinState == WinState.Undefined;
-						var isSameTeam = orderManager.LocalClient != null && order.ExtraData == orderManager.LocalClient.Team
-							&& world.LocalPlayer != null && world.LocalPlayer.WinState == WinState.Undefined;
-
-						if (valid && (isSameTeam || world.IsReplay))
-							TextNotificationsManager.AddChatLine(clientId, "[Team" + (world.IsReplay ? " " + order.ExtraData : "") + "] " + client.Name, message, client.Color);
+					// We are still in the lobby
+					if (world == null)
+					{
+						var prefix = order.ExtraData == uint.MaxValue ? "[Spectators] " : "[Team] ";
+						if (orderManager.LocalClient != null && client.Team == orderManager.LocalClient.Team)
+							TextNotificationsManager.AddChatLine(clientId, prefix + client.Name, message, client.Color);
 
 						break;
 					}
 
+					var player = world.FindPlayerByClient(client);
+					var localClientIsObserver = world.IsReplay || (orderManager.LocalClient != null && orderManager.LocalClient.IsObserver)
+						|| (world.LocalPlayer != null && world.LocalPlayer.WinState != WinState.Undefined);
+
+					// ExtraData gives us the team number, uint.MaxValue means Spectators
+					if (order.ExtraData == uint.MaxValue && localClientIsObserver)
+					{
+						// Validate before adding the line
+						if (client.IsObserver || (player != null && player.WinState != WinState.Undefined))
+							TextNotificationsManager.AddChatLine(clientId, "[Spectators] " + client.Name, message, client.Color);
+
+						break;
+					}
+
+					var valid = client.Team == order.ExtraData && player != null && player.WinState == WinState.Undefined;
+					var isSameTeam = orderManager.LocalClient != null && order.ExtraData == orderManager.LocalClient.Team
+						&& world.LocalPlayer != null && world.LocalPlayer.WinState == WinState.Undefined;
+
+					if (valid && (isSameTeam || world.IsReplay))
+						TextNotificationsManager.AddChatLine(clientId, "[Team" + (world.IsReplay ? " " + order.ExtraData : "") + "] " + client.Name, message, client.Color);
+
+					break;
+				}
+
 				case "StartGame":
+				{
+					if (Game.ModData.MapCache[orderManager.LobbyInfo.GlobalSettings.Map].Status != MapStatus.Available)
 					{
-						if (Game.ModData.MapCache[orderManager.LobbyInfo.GlobalSettings.Map].Status != MapStatus.Available)
-						{
-							Game.Disconnect();
-							Game.LoadShellMap();
+						Game.Disconnect();
+						Game.LoadShellMap();
 
-							// TODO: After adding a startup error dialog, notify the replay load failure.
-							break;
-						}
-
-						if (!string.IsNullOrEmpty(order.TargetString))
-						{
-							var data = MiniYaml.FromString(order.TargetString);
-							var saveLastOrdersFrame = data.FirstOrDefault(n => n.Key == "SaveLastOrdersFrame");
-							if (saveLastOrdersFrame != null)
-								orderManager.GameSaveLastFrame =
-									FieldLoader.GetValue<int>("saveLastOrdersFrame", saveLastOrdersFrame.Value.Value);
-
-							var saveSyncFrame = data.FirstOrDefault(n => n.Key == "SaveSyncFrame");
-							if (saveSyncFrame != null)
-								orderManager.GameSaveLastSyncFrame =
-									FieldLoader.GetValue<int>("SaveSyncFrame", saveSyncFrame.Value.Value);
-						}
-						else
-							TextNotificationsManager.AddSystemLine("The game has started.");
-
-						Game.StartGame(orderManager.LobbyInfo.GlobalSettings.Map, WorldType.Regular);
+						// TODO: After adding a startup error dialog, notify the replay load failure.
 						break;
 					}
 
+					if (!string.IsNullOrEmpty(order.TargetString))
+					{
+						var data = MiniYaml.FromString(order.TargetString, order.OrderString);
+						var saveLastOrdersFrame = data.FirstOrDefault(n => n.Key == "SaveLastOrdersFrame");
+						if (saveLastOrdersFrame != null)
+							orderManager.GameSaveLastFrame =
+								FieldLoader.GetValue<int>("saveLastOrdersFrame", saveLastOrdersFrame.Value.Value);
+
+						var saveSyncFrame = data.FirstOrDefault(n => n.Key == "SaveSyncFrame");
+						if (saveSyncFrame != null)
+							orderManager.GameSaveLastSyncFrame =
+								FieldLoader.GetValue<int>("SaveSyncFrame", saveSyncFrame.Value.Value);
+					}
+					else
+						TextNotificationsManager.AddSystemLine(GameStarted);
+
+					Game.StartGame(orderManager.LobbyInfo.GlobalSettings.Map, WorldType.Regular);
+					break;
+				}
+
 				case "SaveTraitData":
-					{
-						var data = MiniYaml.FromString(order.TargetString)[0];
-						var traitIndex = int.Parse(data.Key);
+				{
+					var data = MiniYaml.FromString(order.TargetString, order.OrderString)[0];
+					var traitIndex = Exts.ParseInt32Invariant(data.Key);
 
-						world?.AddGameSaveTraitData(traitIndex, data.Value);
+					world?.AddGameSaveTraitData(traitIndex, data.Value);
 
-						break;
-					}
+					break;
+				}
 
 				case "GameSaved":
 					if (!orderManager.World.IsReplay)
-						TextNotificationsManager.AddSystemLine("Game saved");
+						TextNotificationsManager.AddSystemLine(GameSaved);
 
 					foreach (var nsr in orderManager.World.WorldActor.TraitsImplementing<INotifyGameSaved>())
 						nsr.GameSaved(orderManager.World);
 					break;
 
 				case "PauseGame":
+				{
+					var client = orderManager.LobbyInfo.ClientWithIndex(clientId);
+					if (client != null)
 					{
-						var client = orderManager.LobbyInfo.ClientWithIndex(clientId);
-						if (client != null)
-						{
-							var pause = order.TargetString == "Pause";
+						var pause = order.TargetString == "Pause";
 
-							// Prevent injected unpause orders from restarting a finished game
-							if (orderManager.World.IsGameOver && !pause)
-								break;
+						// Prevent injected unpause orders from restarting a finished game
+						if (orderManager.World.IsGameOver && !pause)
+							break;
 
-							if (orderManager.World.Paused != pause && world != null && world.LobbyInfo.NonBotClients.Count() > 1)
-							{
-								var pausetext = $"The game is {(pause ? "paused" : "un-paused")} by {client.Name}";
-								TextNotificationsManager.AddSystemLine(pausetext);
-							}
+						if (orderManager.World.Paused != pause && world != null && world.LobbyInfo.NonBotClients.Count() > 1)
+							TextNotificationsManager.AddSystemLine(pause ? GamePaused : GameUnpaused, Translation.Arguments("player", client.Name));
 
-							orderManager.World.Paused = pause;
-							orderManager.World.PredictedPaused = pause;
-						}
-
-						break;
+						orderManager.World.Paused = pause;
+						orderManager.World.PredictedPaused = pause;
 					}
 
+					break;
+				}
+
 				case "HandshakeRequest":
+				{
+					// Switch to the server's mod if we need and are able to
+					var mod = Game.ModData.Manifest;
+					var request = HandshakeRequest.Deserialize(order.TargetString, order.OrderString);
+
+					var externalKey = ExternalMod.MakeKey(request.Mod, request.Version);
+					if ((request.Mod != mod.Id || request.Version != mod.Metadata.Version) &&
+						Game.ExternalMods.TryGetValue(externalKey, out var external))
 					{
-						// Switch to the server's mod if we need and are able to
-						var mod = Game.ModData.Manifest;
-						var request = HandshakeRequest.Deserialize(order.TargetString);
-
-						var externalKey = ExternalMod.MakeKey(request.Mod, request.Version);
-						if ((request.Mod != mod.Id || request.Version != mod.Metadata.Version) &&
-							Game.ExternalMods.TryGetValue(externalKey, out var external))
-						{
-							// The ConnectionFailedLogic will prompt the user to switch mods
-							CurrentServerSettings.ServerExternalMod = external;
-							orderManager.Connection.Dispose();
-							break;
-						}
-
-						Game.Settings.Player.Name = Settings.SanitizedPlayerName(Game.Settings.Player.Name);
-						Game.Settings.Save();
-
-						// Otherwise send the handshake with our current settings and let the server reject us
-						var info = new Session.Client()
-						{
-							Name = Game.Settings.Player.Name,
-							PreferredColor = Game.Settings.Player.Color,
-							Color = Game.Settings.Player.Color,
-							Faction = "Random",
-							SpawnPoint = 0,
-							Team = 0,
-							State = Session.ClientState.Invalid
-						};
-
-						var localProfile = Game.LocalPlayerProfile;
-						var response = new HandshakeResponse()
-						{
-							Client = info,
-							Mod = mod.Id,
-							Version = mod.Metadata.Version,
-							Password = CurrentServerSettings.Password,
-							Fingerprint = localProfile.Fingerprint,
-							OrdersProtocol = ProtocolVersion.Orders
-						};
-
-						if (request.AuthToken != null && response.Fingerprint != null)
-							response.AuthSignature = localProfile.Sign(request.AuthToken);
-
-						orderManager.IssueOrder(new Order("HandshakeResponse", null, false)
-						{
-							Type = OrderType.Handshake,
-							IsImmediate = true,
-							TargetString = response.Serialize()
-						});
-
+						// The ConnectionFailedLogic will prompt the user to switch mods
+						CurrentServerSettings.ServerExternalMod = external;
+						orderManager.Connection.Dispose();
 						break;
 					}
 
+					Game.Settings.Player.Name = Settings.SanitizedPlayerName(Game.Settings.Player.Name);
+					Game.Settings.Save();
+
+					// Otherwise send the handshake with our current settings and let the server reject us
+					var info = new Session.Client()
+					{
+						Name = Game.Settings.Player.Name,
+						PreferredColor = Game.Settings.Player.Color,
+						Color = Game.Settings.Player.Color,
+						Faction = "Random",
+						SpawnPoint = 0,
+						Team = 0,
+						State = Session.ClientState.Invalid
+					};
+
+					var localProfile = Game.LocalPlayerProfile;
+					var response = new HandshakeResponse()
+					{
+						Client = info,
+						Mod = mod.Id,
+						Version = mod.Metadata.Version,
+						Password = CurrentServerSettings.Password,
+						Fingerprint = localProfile.Fingerprint,
+						OrdersProtocol = ProtocolVersion.Orders
+					};
+
+					if (request.AuthToken != null && response.Fingerprint != null)
+						response.AuthSignature = localProfile.Sign(request.AuthToken);
+
+					orderManager.IssueOrder(new Order("HandshakeResponse", null, false)
+					{
+						Type = OrderType.Handshake,
+						IsImmediate = true,
+						TargetString = response.Serialize()
+					});
+
+					break;
+				}
+
 				case "ServerError":
-					{
-						orderManager.ServerError = order.TargetString;
-						orderManager.AuthenticationFailed = false;
-						break;
-					}
+				{
+					orderManager.ServerError = order.TargetString;
+					orderManager.AuthenticationFailed = false;
+					break;
+				}
 
 				case "AuthenticationError":
-					{
-						// The ConnectionFailedLogic will prompt the user for the password
-						orderManager.ServerError = order.TargetString;
-						orderManager.AuthenticationFailed = true;
-						break;
-					}
+				{
+					// The ConnectionFailedLogic will prompt the user for the password
+					orderManager.ServerError = order.TargetString;
+					orderManager.AuthenticationFailed = true;
+					break;
+				}
 
 				case "SyncInfo":
-					{
-						orderManager.LobbyInfo = Session.Deserialize(order.TargetString);
-						Game.SyncLobbyInfo();
-						break;
-					}
+				{
+					orderManager.LobbyInfo = Session.Deserialize(order.TargetString, order.OrderString);
+					Game.SyncLobbyInfo();
+					break;
+				}
 
 				case "SyncLobbyClients":
+				{
+					var clients = new List<Session.Client>();
+					var nodes = MiniYaml.FromString(order.TargetString, order.OrderString);
+					foreach (var node in nodes)
 					{
-						var clients = new List<Session.Client>();
-						var nodes = MiniYaml.FromString(order.TargetString);
-						foreach (var node in nodes)
-						{
-							var strings = node.Key.Split('@');
-							if (strings[0] == "Client")
-								clients.Add(Session.Client.Deserialize(node.Value));
-						}
-
-						orderManager.LobbyInfo.Clients = clients;
-						Game.SyncLobbyInfo();
-						break;
+						var strings = node.Key.Split('@');
+						if (strings[0] == "Client")
+							clients.Add(Session.Client.Deserialize(node.Value));
 					}
 
+					orderManager.LobbyInfo.Clients = clients;
+					Game.SyncLobbyInfo();
+					break;
+				}
+
 				case "SyncLobbySlots":
+				{
+					var slots = new Dictionary<string, Session.Slot>();
+					var nodes = MiniYaml.FromString(order.TargetString, order.OrderString);
+					foreach (var node in nodes)
 					{
-						var slots = new Dictionary<string, Session.Slot>();
-						var nodes = MiniYaml.FromString(order.TargetString);
-						foreach (var node in nodes)
+						var strings = node.Key.Split('@');
+						if (strings[0] == "Slot")
 						{
-							var strings = node.Key.Split('@');
-							if (strings[0] == "Slot")
-							{
-								var slot = Session.Slot.Deserialize(node.Value);
-								slots.Add(slot.PlayerReference, slot);
-							}
+							var slot = Session.Slot.Deserialize(node.Value);
+							slots.Add(slot.PlayerReference, slot);
 						}
-
-						orderManager.LobbyInfo.Slots = slots;
-						Game.SyncLobbyInfo();
-						break;
 					}
 
+					orderManager.LobbyInfo.Slots = slots;
+					Game.SyncLobbyInfo();
+					break;
+				}
+
 				case "SyncLobbyGlobalSettings":
+				{
+					var nodes = MiniYaml.FromString(order.TargetString, order.OrderString);
+					foreach (var node in nodes)
 					{
-						var nodes = MiniYaml.FromString(order.TargetString);
-						foreach (var node in nodes)
-						{
-							var strings = node.Key.Split('@');
-							if (strings[0] == "GlobalSettings")
-								orderManager.LobbyInfo.GlobalSettings = Session.Global.Deserialize(node.Value);
-						}
-
-						Game.SyncLobbyInfo();
-						break;
+						var strings = node.Key.Split('@');
+						if (strings[0] == "GlobalSettings")
+							orderManager.LobbyInfo.GlobalSettings = Session.Global.Deserialize(node.Value);
 					}
 
+					Game.SyncLobbyInfo();
+					break;
+				}
+
 				case "SyncConnectionQuality":
+				{
+					var nodes = MiniYaml.FromString(order.TargetString, order.OrderString);
+					foreach (var node in nodes)
 					{
-						var nodes = MiniYaml.FromString(order.TargetString);
-						foreach (var node in nodes)
+						var strings = node.Key.Split('@');
+						if (strings[0] == "ConnectionQuality")
 						{
-							var strings = node.Key.Split('@');
-							if (strings[0] == "ConnectionQuality")
-							{
-								var client = orderManager.LobbyInfo.Clients.FirstOrDefault(c => c.Index == int.Parse(strings[1]));
-								if (client != null)
-									client.ConnectionQuality = FieldLoader.GetValue<Session.ConnectionQuality>("ConnectionQuality", node.Value.Value);
-							}
+							var client = orderManager.LobbyInfo.Clients.FirstOrDefault(c => c.Index == Exts.ParseInt32Invariant(strings[1]));
+							if (client != null)
+								client.ConnectionQuality = FieldLoader.GetValue<Session.ConnectionQuality>("ConnectionQuality", node.Value.Value);
 						}
-
-						break;
 					}
 
+					break;
+				}
+
+				case "SyncMapPool":
+				{
+					orderManager.ServerMapPool = FieldLoader.GetValue<HashSet<string>>("SyncMapPool", order.TargetString);
+					break;
+				}
+
 				default:
-					{
-						if (world == null)
-							break;
-
-						if (order.GroupedActors == null)
-							ResolveOrder(order, world, orderManager, clientId);
-						else
-							foreach (var subject in order.GroupedActors)
-								ResolveOrder(Order.FromGroupedOrder(order, subject), world, orderManager, clientId);
-
+				{
+					if (world == null)
 						break;
-					}
+
+					if (order.GroupedActors == null)
+						ResolveOrder(order, world, orderManager, clientId);
+					else
+						foreach (var subject in order.GroupedActors)
+							ResolveOrder(Order.FromGroupedOrder(order, subject), world, orderManager, clientId);
+
+					break;
+				}
 			}
 		}
 

OpenRA.Game/ObjectCreator.cs

@@ -133,9 +133,9 @@ namespace OpenRA
 
 		public ConstructorInfo GetCtor(Type type)
 		{
-			var flags = BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance;
-			var ctors = type.GetConstructors(flags).Where(x => x.HasAttribute<UseCtorAttribute>());
-			if (ctors.Count() > 1)
+			const BindingFlags Flags = BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance;
+			var ctors = type.GetConstructors(Flags).Where(x => x.HasAttribute<UseCtorAttribute>()).ToList();
+			if (ctors.Count > 1)
 				throw new InvalidOperationException("ObjectCreator: UseCtor on multiple constructors; invalid.");
 			return ctors.FirstOrDefault();
 		}
@@ -152,8 +152,8 @@ namespace OpenRA
 			for (var i = 0; i < p.Length; i++)
 			{
 				var key = p[i].Name;
-				if (!args.ContainsKey(key)) throw new InvalidOperationException($"ObjectCreator: key `{key}' not found");
-				a[i] = args[key];
+				if (!args.TryGetValue(key, out var arg)) throw new InvalidOperationException($"ObjectCreator: key `{key}' not found");
+				a[i] = arg;
 			}
 
 			return ctor.Invoke(a);

OpenRA.Game/OpenRA.Game.csproj

@@ -10,11 +10,10 @@
     <PackageReference Include="System.Collections.Immutable" Version="6.0.0" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Linguini.Bundle" Version="0.5.0" />
+    <PackageReference Include="Linguini.Bundle" Version="0.6.0" />
     <PackageReference Include="OpenRA-Eluant" Version="1.0.22" />
     <PackageReference Include="Mono.NAT" Version="3.0.4" />
     <PackageReference Include="SharpZipLib" Version="1.4.2" />
-    <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="System.Threading.Channels" Version="6.0.0" />
   </ItemGroup>
 </Project>

OpenRA.Game/Platform.cs

@@ -109,14 +109,14 @@ namespace OpenRA
 						var p = Process.Start(psi);
 						string line;
 						while ((line = p.StandardOutput.ReadLine()) != null)
-							if (line.StartsWith("Operating System: "))
+							if (line.StartsWith("Operating System: ", StringComparison.Ordinal))
 								return line[18..] + suffix;
 					}
 					catch { }
 
 					if (File.Exists("/etc/os-release"))
 						foreach (var line in File.ReadLines("/etc/os-release"))
-							if (line.StartsWith("PRETTY_NAME="))
+							if (line.StartsWith("PRETTY_NAME=", StringComparison.Ordinal))
 								return line[13..^1] + suffix;
 				}
 				else if (CurrentPlatform == PlatformType.OSX)
@@ -134,7 +134,7 @@ namespace OpenRA
 						while ((line = p.StandardOutput.ReadLine()) != null)
 						{
 							line = line.Trim();
-							if (line.StartsWith("System Version: "))
+							if (line.StartsWith("System Version: ", StringComparison.Ordinal))
 								return line[16..];
 						}
 					}
@@ -274,7 +274,7 @@ namespace OpenRA
 				throw new DirectoryNotFoundException(path);
 
 			if (!path.EndsWith(Path.DirectorySeparatorChar.ToString(), StringComparison.Ordinal) &&
-			    !path.EndsWith(Path.AltDirectorySeparatorChar.ToString(), StringComparison.Ordinal))
+				!path.EndsWith(Path.AltDirectorySeparatorChar.ToString(), StringComparison.Ordinal))
 				path += Path.DirectorySeparatorChar;
 
 			engineDirAccessed = true;

OpenRA.Game/Player.cs

@@ -133,7 +133,7 @@ namespace OpenRA
 
 		static FactionInfo ResolveDisplayFaction(World world, string factionName)
 		{
-			var factions = world.Map.Rules.Actors[SystemActors.World].TraitInfos<FactionInfo>().ToArray();
+			var factions = world.Map.Rules.Actors[SystemActors.World].TraitInfos<FactionInfo>();
 
 			return factions.FirstOrDefault(f => f.InternalName == factionName) ?? factions.First();
 		}

OpenRA.Game/PlayerDatabase.cs

@@ -9,7 +9,6 @@
  */
 #endregion
 
-using System.Linq;
 using System.Threading.Tasks;
 using OpenRA.FileFormats;
 using OpenRA.Graphics;
@@ -94,10 +93,10 @@ namespace OpenRA
 				});
 			}
 
-			var labelNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Label");
-			var icon24Node = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon24");
-			var icon48Node = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon48");
-			var icon72Node = yaml.Nodes.FirstOrDefault(n => n.Key == "Icon72");
+			var labelNode = yaml.NodeWithKeyOrDefault("Label");
+			var icon24Node = yaml.NodeWithKeyOrDefault("Icon24");
+			var icon48Node = yaml.NodeWithKeyOrDefault("Icon48");
+			var icon72Node = yaml.NodeWithKeyOrDefault("Icon72");
 			if (labelNode == null)
 				return null;
 

OpenRA.Game/PlayerProfile.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -31,7 +30,7 @@ namespace OpenRA
 		{
 			var badges = new List<PlayerBadge>();
 
-			var badgesNode = yaml.Nodes.FirstOrDefault(n => n.Key == "Badges");
+			var badgesNode = yaml.NodeWithKeyOrDefault("Badges");
 			if (badgesNode != null)
 			{
 				var playerDatabase = Game.ModData.Manifest.Get<PlayerDatabase>();

OpenRA.Game/Primitives/BitSet.cs

@@ -86,7 +86,7 @@ namespace OpenRA.Primitives
 
 		public static BitSet<T> FromStringsNoAlloc(string[] values)
 		{
-			return new BitSet<T>(BitSetAllocator<T>.GetBitsNoAlloc(values)) { };
+			return new BitSet<T>(BitSetAllocator<T>.GetBitsNoAlloc(values));
 		}
 
 		public override string ToString()

OpenRA.Game/Primitives/Color.cs

@@ -17,7 +17,7 @@ namespace OpenRA.Primitives
 {
 	public readonly struct Color : IEquatable<Color>, IScriptBindable
 	{
-		readonly long argb;
+		readonly uint argb;
 
 		public static Color FromArgb(int red, int green, int blue)
 		{
@@ -26,7 +26,7 @@ namespace OpenRA.Primitives
 
 		public static Color FromArgb(int alpha, int red, int green, int blue)
 		{
-			return new Color(((byte)alpha << 24) + ((byte)red << 16) + ((byte)green << 8) + (byte)blue);
+			return new Color((uint)(((byte)alpha << 24) + ((byte)red << 16) + ((byte)green << 8) + (byte)blue));
 		}
 
 		public static Color FromAhsl(int alpha, float h, float s, float l)
@@ -55,14 +55,14 @@ namespace OpenRA.Primitives
 			return (A, h, s, v);
 		}
 
-		Color(long argb)
+		Color(uint argb)
 		{
 			this.argb = argb;
 		}
 
-		public int ToArgb()
+		public uint ToArgb()
 		{
-			return (int)argb;
+			return argb;
 		}
 
 		public static Color FromArgb(int alpha, Color baseColor)
@@ -70,14 +70,9 @@ namespace OpenRA.Primitives
 			return FromArgb(alpha, baseColor.R, baseColor.G, baseColor.B);
 		}
 
-		public static Color FromArgb(int argb)
-		{
-			return FromArgb((byte)(argb >> 24), (byte)(argb >> 16), (byte)(argb >> 8), (byte)argb);
-		}
-
 		public static Color FromArgb(uint argb)
 		{
-			return FromArgb((byte)(argb >> 24), (byte)(argb >> 16), (byte)(argb >> 8), (byte)argb);
+			return new Color(argb);
 		}
 
 		static float SrgbToLinear(float c)
@@ -154,7 +149,7 @@ namespace OpenRA.Primitives
 
 			// Wrap negative values into [0-1)
 			if (h < 0)
-				h += 1;
+				h++;
 
 			var s = delta / rgbMax;
 			return (h, s, v);
@@ -169,12 +164,12 @@ namespace OpenRA.Primitives
 
 			byte alpha = 255;
 			if (!byte.TryParse(value.AsSpan(0, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var red)
-			    || !byte.TryParse(value.AsSpan(2, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var green)
-			    || !byte.TryParse(value.AsSpan(4, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var blue))
+				|| !byte.TryParse(value.AsSpan(2, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var green)
+				|| !byte.TryParse(value.AsSpan(4, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var blue))
 				return false;
 
 			if (value.Length == 8
-			    && !byte.TryParse(value.AsSpan(6, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out alpha))
+				&& !byte.TryParse(value.AsSpan(6, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out alpha))
 				return false;
 
 			color = FromArgb(alpha, red, green, blue);
@@ -224,9 +219,9 @@ namespace OpenRA.Primitives
 		public override string ToString()
 		{
 			if (A == 255)
-				return R.ToString("X2") + G.ToString("X2") + B.ToString("X2");
+				return CryptoUtil.ToHex(stackalloc byte[3] { R, G, B });
 
-			return R.ToString("X2") + G.ToString("X2") + B.ToString("X2") + A.ToString("X2");
+			return CryptoUtil.ToHex(stackalloc byte[4] { R, G, B, A });
 		}
 
 		public static Color Transparent => FromArgb(0x00FFFFFF);

OpenRA.Game/Primitives/LongBitSet.cs

@@ -99,7 +99,7 @@ namespace OpenRA.Primitives
 
 		public static LongBitSet<T> FromStringsNoAlloc(string[] values)
 		{
-			return new LongBitSet<T>(LongBitSetAllocator<T>.GetBitsNoAlloc(values)) { };
+			return new LongBitSet<T>(LongBitSetAllocator<T>.GetBitsNoAlloc(values));
 		}
 
 		public static void Reset()

OpenRA.Game/Primitives/Rectangle.cs

@@ -13,13 +13,12 @@ using System;
 
 namespace OpenRA.Primitives
 {
-	public struct Rectangle : IEquatable<Rectangle>
+	public readonly struct Rectangle : IEquatable<Rectangle>
 	{
-		// TODO: Make these readonly: this will require a lot of changes to the UI logic
-		public int X;
-		public int Y;
-		public int Width;
-		public int Height;
+		public readonly int X;
+		public readonly int Y;
+		public readonly int Width;
+		public readonly int Height;
 		public static readonly Rectangle Empty;
 
 		public static Rectangle FromLTRB(int left, int top, int right, int bottom)
@@ -58,35 +57,35 @@ namespace OpenRA.Primitives
 			Height = size.Height;
 		}
 
-		public int Left => X;
-		public int Right => X + Width;
-		public int Top => Y;
-		public int Bottom => Y + Height;
-		public bool IsEmpty => X == 0 && Y == 0 && Width == 0 && Height == 0;
-		public int2 Location => new(X, Y);
-		public Size Size => new(Width, Height);
+		public readonly int Left => X;
+		public readonly int Right => X + Width;
+		public readonly int Top => Y;
+		public readonly int Bottom => Y + Height;
+		public readonly bool IsEmpty => X == 0 && Y == 0 && Width == 0 && Height == 0;
+		public readonly int2 Location => new(X, Y);
+		public readonly Size Size => new(Width, Height);
 
-		public int2 TopLeft => Location;
-		public int2 TopRight => new(X + Width, Y);
-		public int2 BottomLeft => new(X, Y + Height);
-		public int2 BottomRight => new(X + Width, Y + Height);
+		public readonly int2 TopLeft => Location;
+		public readonly int2 TopRight => new(X + Width, Y);
+		public readonly int2 BottomLeft => new(X, Y + Height);
+		public readonly int2 BottomRight => new(X + Width, Y + Height);
 
-		public bool Contains(int x, int y)
+		public readonly bool Contains(int x, int y)
 		{
 			return x >= Left && x < Right && y >= Top && y < Bottom;
 		}
 
-		public bool Contains(int2 pt)
+		public readonly bool Contains(int2 pt)
 		{
 			return Contains(pt.X, pt.Y);
 		}
 
-		public bool Equals(Rectangle other)
+		public readonly bool Equals(Rectangle other)
 		{
 			return this == other;
 		}
 
-		public override bool Equals(object obj)
+		public override readonly bool Equals(object obj)
 		{
 			if (obj is not Rectangle)
 				return false;
@@ -94,17 +93,17 @@ namespace OpenRA.Primitives
 			return this == (Rectangle)obj;
 		}
 
-		public override int GetHashCode()
+		public override readonly int GetHashCode()
 		{
 			return Height + Width ^ X + Y;
 		}
 
-		public bool IntersectsWith(Rectangle rect)
+		public readonly bool IntersectsWith(Rectangle rect)
 		{
 			return Left < rect.Right && Right > rect.Left && Top < rect.Bottom && Bottom > rect.Top;
 		}
 
-		bool IntersectsWithInclusive(Rectangle r)
+		readonly bool IntersectsWithInclusive(Rectangle r)
 		{
 			return Left <= r.Right && Right >= r.Left && Top <= r.Bottom && Bottom >= r.Top;
 		}
@@ -117,14 +116,14 @@ namespace OpenRA.Primitives
 			return FromLTRB(Math.Max(a.Left, b.Left), Math.Max(a.Top, b.Top), Math.Min(a.Right, b.Right), Math.Min(a.Bottom, b.Bottom));
 		}
 
-		public bool Contains(Rectangle rect)
+		public readonly bool Contains(Rectangle rect)
 		{
 			return rect == Intersect(this, rect);
 		}
 
 		public static Rectangle operator *(int a, Rectangle b) { return new Rectangle(a * b.X, a * b.Y, a * b.Width, a * b.Height); }
 
-		public override string ToString()
+		public override readonly string ToString()
 		{
 			return $"{X},{Y},{Width},{Height}";
 		}

OpenRA.Game/Primitives/RingBuffer.cs

@@ -0,0 +1,146 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+
+namespace OpenRA.Primitives
+{
+	/// <summary>Fixed size rorating buffer backed by an array.</summary>
+	public class RingBuffer<T> : ICollection<T>, IEnumerable<T>
+	{
+		readonly IComparer<T> comparer;
+		readonly T[] values;
+		int start;
+
+		public int Capacity => values.Length;
+		public int Count { get; private set; }
+		public bool IsReadOnly => false;
+
+		public RingBuffer(int capacity, IComparer<T> comparer)
+		{
+			this.comparer = comparer;
+			values = new T[capacity];
+			start = 0;
+			Count = 0;
+		}
+
+		public RingBuffer(int capacity)
+			: this(capacity, Comparer<T>.Default) { }
+
+		public void Add(T value)
+		{
+			values[(start + Count) % values.Length] = value;
+			if (Count < values.Length)
+				Count++;
+			else
+				start = (start + 1) % values.Length;
+		}
+
+		public void Clear()
+		{
+			Array.Clear(values, 0, values.Length);
+			start = 0;
+			Count = 0;
+		}
+
+		public bool Contains(T value)
+		{
+			var capacity = values.Length;
+			var end = start + Count;
+			for (var i = start; i < end; ++i)
+				if (comparer.Compare(values[i % capacity], value) == 0)
+					return true;
+
+			return false;
+		}
+
+		public void CopyTo(T[] array, int arrayIndex)
+		{
+			if (array == null)
+				throw new ArgumentNullException(nameof(array));
+
+			if (arrayIndex < 0)
+				throw new ArgumentNullException(nameof(arrayIndex));
+
+			if (arrayIndex + Count >= array.Length)
+				throw new ArgumentException("Invalid array capacity");
+
+			var destinationIndex = arrayIndex;
+			var end = start + Count;
+			var capacity = values.Length;
+			for (var i = start; i < end; ++i)
+				array[destinationIndex++] = values[i % capacity];
+		}
+
+		public bool Remove(T value)
+		{
+			var capacity = values.Length;
+			var end = start + Count;
+			for (var i = start; i < end; ++i)
+			{
+				if (comparer.Compare(values[i % capacity], value) == 0)
+				{
+					end--;
+					for (var j = i; j < end; ++j)
+						values[j % capacity] = values[(j + 1) % capacity];
+
+					Count--;
+					return true;
+				}
+			}
+
+			return false;
+		}
+
+		public T this[int pos]
+		{
+			get => values[(start + pos) % values.Length];
+
+			set
+			{
+				if (pos >= Count)
+					throw new ArgumentException($"Index out of bounds: {pos}");
+
+				values[(start + pos) % values.Length] = value;
+			}
+		}
+
+		public T First()
+		{
+			if (Count == 0)
+				throw new ArgumentException("Empty buffer");
+
+			return values[start];
+		}
+
+		public T Last()
+		{
+			if (Count == 0)
+				throw new ArgumentException("Empty buffer");
+
+			return values[(start + Count - 1) % values.Length];
+		}
+
+		public IEnumerator<T> GetEnumerator()
+		{
+			var initState = start + Count;
+			for (var i = 0; i < Count; i++)
+			{
+				if (start + Count != initState)
+					throw new InvalidOperationException("Collection was modified; enumeration operation may not execute");
+				yield return values[(start + i) % values.Length];
+			}
+		}
+
+		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); }
+	}
+}

OpenRA.Game/Primitives/TypeDictionary.cs

@@ -12,14 +12,20 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA.Primitives
 {
 	public class TypeDictionary : IEnumerable<object>
 	{
-		static readonly Func<Type, List<object>> CreateList = type => new List<object>();
-		readonly Dictionary<Type, List<object>> data = new();
+		static readonly Func<Type, ITypeContainer> CreateTypeContainer = t =>
+			(ITypeContainer)typeof(TypeContainer<>).MakeGenericType(t).GetConstructor(Type.EmptyTypes).Invoke(null);
+
+		readonly Dictionary<Type, ITypeContainer> data = new();
+
+		ITypeContainer InnerGet(Type t)
+		{
+			return data.GetOrAdd(t, CreateTypeContainer);
+		}
 
 		public void Add(object val)
 		{
@@ -33,7 +39,7 @@ namespace OpenRA.Primitives
 
 		void InnerAdd(Type t, object val)
 		{
-			data.GetOrAdd(t, CreateList).Add(val);
+			InnerGet(t).Add(val);
 		}
 
 		public bool Contains<T>()
@@ -48,35 +54,33 @@ namespace OpenRA.Primitives
 
 		public T Get<T>()
 		{
-			return (T)Get(typeof(T), true);
+			return Get<T>(true);
 		}
 
 		public T GetOrDefault<T>()
 		{
-			var result = Get(typeof(T), false);
-			if (result == null)
-				return default;
-			return (T)result;
+			return Get<T>(false);
 		}
 
-		object Get(Type t, bool throwsIfMissing)
+		T Get<T>(bool throwsIfMissing)
 		{
-			if (!data.TryGetValue(t, out var ret))
+			if (!data.TryGetValue(typeof(T), out var container))
 			{
 				if (throwsIfMissing)
-					throw new InvalidOperationException($"TypeDictionary does not contain instance of type `{t}`");
-				return null;
+					throw new InvalidOperationException($"TypeDictionary does not contain instance of type `{typeof(T)}`");
+				return default;
 			}
 
-			if (ret.Count > 1)
-				throw new InvalidOperationException($"TypeDictionary contains multiple instances of type `{t}`");
-			return ret[0];
+			var list = ((TypeContainer<T>)container).Objects;
+			if (list.Count > 1)
+				throw new InvalidOperationException($"TypeDictionary contains multiple instances of type `{typeof(T)}`");
+			return list[0];
 		}
 
-		public IEnumerable<T> WithInterface<T>()
+		public IReadOnlyCollection<T> WithInterface<T>()
 		{
-			if (data.TryGetValue(typeof(T), out var objs))
-				return objs.Cast<T>();
+			if (data.TryGetValue(typeof(T), out var container))
+				return ((TypeContainer<T>)container).Objects;
 			return Array.Empty<T>();
 		}
 
@@ -92,18 +96,19 @@ namespace OpenRA.Primitives
 
 		void InnerRemove(Type t, object val)
 		{
-			if (!data.TryGetValue(t, out var objs))
+			if (!data.TryGetValue(t, out var container))
 				return;
-			objs.Remove(val);
-			if (objs.Count == 0)
+
+			container.Remove(val);
+			if (container.Count == 0)
 				data.Remove(t);
 		}
 
 		public void TrimExcess()
 		{
 			data.TrimExcess();
-			foreach (var objs in data.Values)
-				objs.TrimExcess();
+			foreach (var t in data.Keys)
+				InnerGet(t).TrimExcess();
 		}
 
 		public IEnumerator<object> GetEnumerator()
@@ -115,6 +120,36 @@ namespace OpenRA.Primitives
 		{
 			return GetEnumerator();
 		}
+
+		interface ITypeContainer
+		{
+			int Count { get; }
+			void Add(object value);
+			void Remove(object value);
+			void TrimExcess();
+		}
+
+		sealed class TypeContainer<T> : ITypeContainer
+		{
+			public List<T> Objects { get; } = new List<T>();
+
+			public int Count => Objects.Count;
+
+			public void Add(object value)
+			{
+				Objects.Add((T)value);
+			}
+
+			public void Remove(object value)
+			{
+				Objects.Remove((T)value);
+			}
+
+			public void TrimExcess()
+			{
+				Objects.TrimExcess();
+			}
+		}
 	}
 
 	public static class TypeExts

OpenRA.Game/Renderer.cs

@@ -27,7 +27,7 @@ namespace OpenRA
 		public SpriteRenderer WorldSpriteRenderer { get; }
 		public RgbaSpriteRenderer WorldRgbaSpriteRenderer { get; }
 		public RgbaColorRenderer WorldRgbaColorRenderer { get; }
-		public ModelRenderer WorldModelRenderer { get; }
+		public IRenderer[] WorldRenderers = Array.Empty<IRenderer>();
 		public RgbaColorRenderer RgbaColorRenderer { get; }
 		public SpriteRenderer SpriteRenderer { get; }
 		public RgbaSpriteRenderer RgbaSpriteRenderer { get; }
@@ -41,10 +41,13 @@ namespace OpenRA
 		internal IGraphicsContext Context { get; }
 
 		internal int SheetSize { get; }
-		internal int TempBufferSize { get; }
+		internal int TempVertexBufferSize { get; }
+		internal int TempIndexBufferSize { get; }
 
-		readonly IVertexBuffer<Vertex> tempBuffer;
+		readonly IVertexBuffer<Vertex> tempVertexBuffer;
+		readonly IIndexBuffer quadIndexBuffer;
 		readonly Stack<Rectangle> scissorState = new();
+		readonly ITexture worldBufferSnapshot;
 
 		IFrameBuffer screenBuffer;
 		Sprite screenSprite;
@@ -58,6 +61,15 @@ namespace OpenRA
 		public Size WorldFrameBufferSize => worldSheet.Size;
 		public int WorldDownscaleFactor { get; private set; } = 1;
 
+		/// <summary>
+		/// Copies and returns the currently rendered world state as a temporary texture.
+		/// </summary>
+		public ITexture WorldBufferSnapshot()
+		{
+			worldBufferSnapshot.SetDataFromReadBuffer(new Rectangle(int2.Zero, worldSheet.Size));
+			return worldBufferSnapshot;
+		}
+
 		SheetBuilder fontSheetBuilder;
 		readonly IPlatform platform;
 
@@ -75,24 +87,28 @@ namespace OpenRA
 			this.platform = platform;
 			var resolution = GetResolution(graphicSettings);
 
+			TempVertexBufferSize = graphicSettings.BatchSize - graphicSettings.BatchSize % 4;
+			TempIndexBufferSize = TempVertexBufferSize / 4 * 6;
+
 			Window = platform.CreateWindow(new Size(resolution.Width, resolution.Height),
-				graphicSettings.Mode, graphicSettings.UIScale, graphicSettings.BatchSize,
-				graphicSettings.VideoDisplay, graphicSettings.GLProfile, !graphicSettings.DisableLegacyGL);
+				graphicSettings.Mode, graphicSettings.UIScale, TempVertexBufferSize, TempIndexBufferSize,
+				graphicSettings.VideoDisplay, graphicSettings.GLProfile);
 
 			Context = Window.Context;
 
-			TempBufferSize = graphicSettings.BatchSize;
 			SheetSize = graphicSettings.SheetSize;
 
-			WorldSpriteRenderer = new SpriteRenderer(this, Context.CreateShader("combined"));
+			var combinedBindings = new CombinedShaderBindings();
+			WorldSpriteRenderer = new SpriteRenderer(this, Context.CreateShader(combinedBindings));
 			WorldRgbaSpriteRenderer = new RgbaSpriteRenderer(WorldSpriteRenderer);
 			WorldRgbaColorRenderer = new RgbaColorRenderer(WorldSpriteRenderer);
-			WorldModelRenderer = new ModelRenderer(this, Context.CreateShader("model"));
-			SpriteRenderer = new SpriteRenderer(this, Context.CreateShader("combined"));
+			SpriteRenderer = new SpriteRenderer(this, Context.CreateShader(combinedBindings));
 			RgbaSpriteRenderer = new RgbaSpriteRenderer(SpriteRenderer);
 			RgbaColorRenderer = new RgbaColorRenderer(SpriteRenderer);
 
-			tempBuffer = Context.CreateVertexBuffer(TempBufferSize);
+			tempVertexBuffer = Context.CreateVertexBuffer<Vertex>(TempVertexBufferSize);
+			quadIndexBuffer = Context.CreateIndexBuffer(Util.CreateQuadIndices(TempIndexBufferSize / 6));
+			worldBufferSnapshot = Context.CreateTexture();
 		}
 
 		static Size GetResolution(GraphicSettings graphicsSettings)
@@ -253,8 +269,6 @@ namespace OpenRA
 			if (lastWorldViewport != worldViewport)
 			{
 				WorldSpriteRenderer.SetViewportParams(worldSheet.Size, WorldDownscaleFactor, depthMargin, worldViewport.Location);
-				WorldModelRenderer.SetViewportParams();
-
 				lastWorldViewport = worldViewport;
 			}
 
@@ -300,9 +314,11 @@ namespace OpenRA
 			Flush();
 			currentPaletteTexture = palette.Texture;
 
-			SpriteRenderer.SetPalette(currentPaletteTexture, palette.ColorShifts);
-			WorldSpriteRenderer.SetPalette(currentPaletteTexture, palette.ColorShifts);
-			WorldModelRenderer.SetPalette(currentPaletteTexture);
+			SpriteRenderer.SetPalette(palette);
+			WorldSpriteRenderer.SetPalette(palette);
+
+			foreach (var r in WorldRenderers)
+				r.SetPalette(palette);
 		}
 
 		public void EndFrame(IInputHandler inputHandler)
@@ -326,27 +342,32 @@ namespace OpenRA
 			renderType = RenderType.None;
 		}
 
-		public void DrawBatch(Vertex[] vertices, int numVertices, PrimitiveType type)
-		{
-			tempBuffer.SetData(vertices, numVertices);
-			DrawBatch(tempBuffer, 0, numVertices, type);
-		}
-
-		public void DrawBatch(ref Vertex[] vertices, int numVertices, PrimitiveType type)
-		{
-			tempBuffer.SetData(ref vertices, numVertices);
-			DrawBatch(tempBuffer, 0, numVertices, type);
-		}
-
-		public void DrawBatch<T>(IVertexBuffer<T> vertices,
+		public void DrawBatch<T>(IVertexBuffer<T> vertices, IShader shader,
 			int firstVertex, int numVertices, PrimitiveType type)
 			where T : struct
 		{
 			vertices.Bind();
+			shader.Bind();
 			Context.DrawPrimitives(type, firstVertex, numVertices);
 			PerfHistory.Increment("batches", 1);
 		}
 
+		public void DrawQuadBatch(ref Vertex[] vertices, IShader shader, int numVertices)
+		{
+			tempVertexBuffer.SetData(ref vertices, numVertices);
+			DrawQuadBatch(tempVertexBuffer, quadIndexBuffer, shader, numVertices / 4 * 6, 0);
+		}
+
+		public void DrawQuadBatch<T>(IVertexBuffer<T> vertices, IIndexBuffer indices, IShader shader, int numIndices, int start)
+			where T : struct
+		{
+			vertices.Bind();
+			indices.Bind();
+			shader.Bind();
+			Context.DrawElements(numIndices, start);
+			PerfHistory.Increment("batches", 1);
+		}
+
 		public void Flush()
 		{
 			CurrentBatchRenderer = null;
@@ -374,9 +395,19 @@ namespace OpenRA
 			}
 		}
 
-		public IVertexBuffer<Vertex> CreateVertexBuffer(int length)
+		public IFrameBuffer CreateFrameBuffer(Size s)
 		{
-			return Context.CreateVertexBuffer(length);
+			return Context.CreateFrameBuffer(s);
+		}
+
+		public IShader CreateShader(IShaderBindings bindings)
+		{
+			return Context.CreateShader(bindings);
+		}
+
+		public IVertexBuffer<T> CreateVertexBuffer<T>(int length) where T : struct
+		{
+			return Context.CreateVertexBuffer<T>(length);
 		}
 
 		public void EnableScissor(Rectangle rect)
@@ -503,8 +534,11 @@ namespace OpenRA
 
 		public void Dispose()
 		{
-			WorldModelRenderer.Dispose();
-			tempBuffer.Dispose();
+			worldBuffer?.Dispose();
+			screenBuffer.Dispose();
+			worldBufferSnapshot.Dispose();
+			tempVertexBuffer.Dispose();
+			quadIndexBuffer.Dispose();
 			fontSheetBuilder?.Dispose();
 			if (Fonts != null)
 				foreach (var font in Fonts.Values)

OpenRA.Game/Scripting/ScriptContext.cs

@@ -74,14 +74,17 @@ namespace OpenRA.Scripting
 	/// Provides global bindings in Lua code.
 	/// </summary>
 	/// <remarks>
+	/// <para>
 	/// Instance methods and properties declared in derived classes will be made available in Lua. Use
 	/// <see cref="ScriptGlobalAttribute"/> on your derived class to specify the name exposed in Lua. It is recommended
 	/// to apply <see cref="DescAttribute"/> against each method or property to provide a description of what it does.
-	///
+	/// </para>
+	/// <para>
 	/// Any parameters to your method that are <see cref="LuaValue"/>s will be disposed automatically when your method
 	/// completes. If you need to return any of these values, or need them to live longer than your method, you must
 	/// use <see cref="LuaValue.CopyReference"/> to get your own copy of the value. Any copied values you return will
 	/// be disposed automatically, but you assume responsibility for disposing any other copies.
+	/// </para>
 	/// </remarks>
 	public abstract class ScriptGlobal : ScriptObjectWrapper
 	{
@@ -99,7 +102,7 @@ namespace OpenRA.Scripting
 			if (names.Length != 1)
 				throw new InvalidOperationException($"[ScriptGlobal] attribute not found for global table '{type}'");
 
-			Name = names.First().Name;
+			Name = names[0].Name;
 			Bind(new[] { this });
 		}
 
@@ -111,7 +114,7 @@ namespace OpenRA.Scripting
 				{
 					using (var luaObject = a.ToLuaValue(Context))
 					using (var filterResult = filter.Call(luaObject))
-					using (var result = filterResult.First())
+					using (var result = filterResult[0])
 						return result.ToBoolean();
 				});
 			}
@@ -211,7 +214,7 @@ namespace OpenRA.Scripting
 				var ctor = b.GetConstructors(BindingFlags.Public | BindingFlags.Instance).FirstOrDefault(c =>
 				{
 					var p = c.GetParameters();
-					return p.Length == 1 && p.First().ParameterType == typeof(ScriptContext);
+					return p.Length == 1 && p[0].ParameterType == typeof(ScriptContext);
 				});
 
 				if (ctor == null)

OpenRA.Game/Scripting/ScriptMemberWrapper.cs

@@ -125,8 +125,8 @@ namespace OpenRA.Scripting
 		public static IEnumerable<MemberInfo> WrappableMembers(Type t)
 		{
 			// Only expose defined public non-static methods that were explicitly declared by the author
-			var flags = BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly;
-			foreach (var mi in t.GetMembers(flags))
+			const BindingFlags Flags = BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly;
+			foreach (var mi in t.GetMembers(Flags))
 			{
 				// Properties are always wrappable
 				if (mi is PropertyInfo)
@@ -150,7 +150,7 @@ namespace OpenRA.Scripting
 			// Remove the namespace and the trailing "Info"
 			return types.SelectMany(i => i.GetGenericArguments())
 				.Select(g => g.Name.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries).LastOrDefault())
-				.Select(s => s.EndsWith("Info") ? s.Remove(s.Length - 4, 4) : s)
+				.Select(s => s.EndsWith("Info", StringComparison.Ordinal) ? s.Remove(s.Length - 4, 4) : s)
 				.ToArray();
 		}
 	}

OpenRA.Game/Scripting/ScriptTypes.cs

@@ -40,13 +40,10 @@ namespace OpenRA.Scripting
 				t = nullable;
 
 			// Value wraps a CLR object
-			if (value.TryGetClrObject(out var temp))
+			if (value.TryGetClrObject(out var temp) && temp.GetType() == t)
 			{
-				if (temp.GetType() == t)
-				{
-					clrObject = temp;
-					return true;
-				}
+				clrObject = temp;
+				return true;
 			}
 
 			if (value is LuaNil && !t.IsValueType)

OpenRA.Game/SelectableExts.cs

@@ -62,10 +62,7 @@ namespace OpenRA.Traits
 
 		public static Actor WithHighestSelectionPriority(this IEnumerable<ActorBoundsPair> actors, int2 selectionPixel, Modifiers modifiers)
 		{
-			if (!actors.Any())
-				return null;
-
-			return actors.MaxBy(a => CalculateActorSelectionPriority(a.Actor.Info, a.Bounds, selectionPixel, modifiers)).Actor;
+			return actors.MaxByOrDefault(a => CalculateActorSelectionPriority(a.Actor.Info, a.Bounds, selectionPixel, modifiers)).Actor;
 		}
 
 		public static FrozenActor WithHighestSelectionPriority(this IEnumerable<FrozenActor> actors, int2 selectionPixel, Modifiers modifiers)

OpenRA.Game/Server/Connection.cs

@@ -60,11 +60,11 @@ namespace OpenRA.Server
 		static byte[] CreatePingFrame()
 		{
 			var ms = new MemoryStream(21);
-			ms.WriteArray(BitConverter.GetBytes(13));
-			ms.WriteArray(BitConverter.GetBytes(0));
-			ms.WriteArray(BitConverter.GetBytes(0));
+			ms.Write(13);
+			ms.Write(0);
+			ms.Write(0);
 			ms.WriteByte((byte)OrderType.Ping);
-			ms.WriteArray(BitConverter.GetBytes(Game.RunTime));
+			ms.Write(Game.RunTime);
 			return ms.GetBuffer();
 		}
 
@@ -115,7 +115,7 @@ namespace OpenRA.Server
 									frame = BitConverter.ToInt32(bytes, 4);
 									state = ReceiveState.Data;
 
-									if (expectLength < 0 || (server.Type != ServerType.Local && expectLength > MaxOrderLength))
+									if (expectLength < 0 || (server.IsMultiplayer && expectLength > MaxOrderLength))
 									{
 										Log.Write("server", $"Closing socket connection to {EndPoint} because of excessive order length: {expectLength}");
 										return;
@@ -153,9 +153,8 @@ namespace OpenRA.Server
 						return;
 
 					// Regularly check player ping
-					if (lastPingSent.ElapsedMilliseconds > 1000)
-						if (TrySendData(CreatePingFrame()))
-							lastPingSent.Restart();
+					if (lastPingSent.ElapsedMilliseconds > 1000 && TrySendData(CreatePingFrame()))
+						lastPingSent.Restart();
 
 					// Send all data immediately, we will block again on read
 					while (sendQueue.TryTake(out var data, 0))

OpenRA.Game/Server/OrderBuffer.cs

@@ -68,7 +68,7 @@ namespace OpenRA.Server
 			ticksPerInterval = Interval / timestep;
 
 			this.players = players.ToList();
-			baselinePlayer = this.players.First();
+			baselinePlayer = this.players[0];
 
 			foreach (var player in this.players)
 			{
@@ -128,7 +128,7 @@ namespace OpenRA.Server
 			players.Remove(player);
 			if (player == baselinePlayer && players.Count > 0)
 			{
-				var newBaseline = players.First();
+				var newBaseline = players[0];
 				Interlocked.Exchange(ref baselinePlayer, newBaseline);
 			}
 

OpenRA.Game/Server/ProtocolVersion.cs

@@ -77,6 +77,6 @@ namespace OpenRA.Server
 		// The protocol for server and world orders
 		// This applies after the handshake has completed, and is provided to support
 		// alternative server implementations that wish to support multiple versions in parallel
-		public const int Orders = 20;
+		public const int Orders = 21;
 	}
 }

OpenRA.Game/Server/Server.cs

@@ -40,8 +40,9 @@ namespace OpenRA.Server
 	public enum ServerType
 	{
 		Local = 0,
-		Multiplayer = 1,
-		Dedicated = 2
+		Skirmish = 1,
+		Multiplayer = 2,
+		Dedicated = 3
 	}
 
 	public sealed class Server
@@ -117,6 +118,7 @@ namespace OpenRA.Server
 
 		public readonly MersenneTwister Random = new();
 		public readonly ServerType Type;
+		public bool IsMultiplayer => Type == ServerType.Dedicated || Type == ServerType.Multiplayer;
 
 		public readonly List<Connection> Conns = new();
 
@@ -128,7 +130,8 @@ namespace OpenRA.Server
 		// Managed by LobbyCommands
 		public MapPreview Map;
 		public readonly MapStatusCache MapStatusCache;
-		public GameSave GameSave = null;
+		public GameSave GameSave;
+		public HashSet<string> MapPool;
 
 		// Default to the next frame for ServerType.Local - MP servers take the value from the selected GameSpeed.
 		public int OrderLatency = 1;
@@ -247,12 +250,9 @@ namespace OpenRA.Server
 					{
 						listener.Server.SetSocketOption(SocketOptionLevel.IPv6, SocketOptionName.IPv6Only, 1);
 					}
-					catch (Exception ex)
+					catch (Exception ex) when (ex is SocketException || ex is ArgumentException)
 					{
-						if (ex is SocketException || ex is ArgumentException)
-							Log.Write("server", $"Failed to set socket option on {endpoint}: {ex.Message}");
-						else
-							throw;
+						Log.Write("server", $"Failed to set socket option on {endpoint}: {ex.Message}");
 					}
 
 					listener.Start();
@@ -282,7 +282,8 @@ namespace OpenRA.Server
 								}
 							}
 						}
-					}) { Name = $"Connection listener ({listener.LocalEndpoint})", IsBackground = true }.Start();
+					})
+					{ Name = $"Connection listener ({listener.LocalEndpoint})", IsBackground = true }.Start();
 				}
 				catch (SocketException ex)
 				{
@@ -305,10 +306,10 @@ namespace OpenRA.Server
 
 			randomSeed = (int)DateTime.Now.ToBinary();
 
-			if (type != ServerType.Local && settings.EnableGeoIP)
+			if (IsMultiplayer && settings.EnableGeoIP)
 				GeoIP.Initialize();
 
-			if (type != ServerType.Local)
+			if (IsMultiplayer)
 				Nat.TryForwardPort(Settings.ListenPort, Settings.ListenPort);
 
 			foreach (var trait in modData.Manifest.ServerTraits)
@@ -316,7 +317,6 @@ namespace OpenRA.Server
 
 			serverTraits.TrimExcess();
 
-			Map = ModData.MapCache[settings.Map];
 			MapStatusCache = new MapStatusCache(modData, MapStatusChanged, type == ServerType.Dedicated && settings.EnableLintChecks);
 
 			playerMessageTracker = new PlayerMessageTracker(this, DispatchOrdersToClient, SendLocalizedMessageTo);
@@ -327,8 +327,6 @@ namespace OpenRA.Server
 				GlobalSettings =
 				{
 					RandomSeed = randomSeed,
-					Map = Map.Uid,
-					MapStatus = Session.MapStatus.Unknown,
 					ServerName = settings.Name,
 					EnableSingleplayer = settings.EnableSingleplayer || Type != ServerType.Dedicated,
 					EnableSyncReports = settings.EnableSyncReports,
@@ -348,8 +346,7 @@ namespace OpenRA.Server
 
 			new Thread(_ =>
 			{
-				// Initial status is set off the main thread to avoid triggering a load screen when joining a skirmish game
-				LobbyInfo.GlobalSettings.MapStatus = MapStatusCache[Map];
+				// Note: at least one of these is required to set the initial LobbyInfo.Map and MapStatus
 				foreach (var t in serverTraits.WithInterface<INotifyServerStart>())
 					t.ServerStarted(this);
 
@@ -386,7 +383,7 @@ namespace OpenRA.Server
 					if (State == ServerState.ShuttingDown)
 					{
 						EndGame();
-						if (type != ServerType.Local)
+						if (IsMultiplayer)
 							Nat.TryRemovePortForward();
 						break;
 					}
@@ -439,8 +436,8 @@ namespace OpenRA.Server
 			{
 				// Send handshake and client index.
 				var ms = new MemoryStream(8);
-				ms.WriteArray(BitConverter.GetBytes(ProtocolVersion.Handshake));
-				ms.WriteArray(BitConverter.GetBytes(newConn.PlayerIndex));
+				ms.Write(ProtocolVersion.Handshake);
+				ms.Write(newConn.PlayerIndex);
 				newConn.TrySendData(ms.ToArray());
 
 				// Dispatch a handshake order
@@ -466,7 +463,7 @@ namespace OpenRA.Server
 			Conns.Add(newConn);
 		}
 
-		void ValidateClient(Connection newConn, string data)
+		void ValidateClient(Connection newConn, string data, string name)
 		{
 			try
 			{
@@ -479,7 +476,7 @@ namespace OpenRA.Server
 					return;
 				}
 
-				var handshake = HandshakeResponse.Deserialize(data);
+				var handshake = HandshakeResponse.Deserialize(data, name);
 
 				if (!string.IsNullOrEmpty(Settings.Password) && handshake.Password != Settings.Password)
 				{
@@ -494,7 +491,7 @@ namespace OpenRA.Server
 				{
 					Name = OpenRA.Settings.SanitizedPlayerName(handshake.Client.Name),
 					IPAddress = ipAddress.ToString(),
-					AnonymizedIPAddress = Type != ServerType.Local && Settings.ShareAnonymizedIPs ? Session.AnonymizeIP(ipAddress) : null,
+					AnonymizedIPAddress = IsMultiplayer && Settings.ShareAnonymizedIPs ? Session.AnonymizeIP(ipAddress) : null,
 					Location = GeoIP.LookupCountry(ipAddress),
 					Index = newConn.PlayerIndex,
 					PreferredColor = handshake.Client.PreferredColor,
@@ -583,8 +580,7 @@ namespace OpenRA.Server
 
 						Log.Write("server", $"{client.Name} ({newConn.EndPoint}) has joined the game.");
 
-						if (Type != ServerType.Local)
-							SendLocalizedMessage(Joined, Translation.Arguments("player", client.Name));
+						SendLocalizedMessage(Joined, Translation.Arguments("player", client.Name));
 
 						if (Type == ServerType.Dedicated)
 						{
@@ -607,7 +603,7 @@ namespace OpenRA.Server
 					}
 				}
 
-				if (Type == ServerType.Local)
+				if (!IsMultiplayer)
 				{
 					// Local servers can only be joined by the local client, so we can trust their identity without validation
 					client.Fingerprint = handshake.Fingerprint;
@@ -622,10 +618,11 @@ namespace OpenRA.Server
 						try
 						{
 							var httpClient = HttpClientFactory.Create();
-							var httpResponseMessage = await httpClient.GetAsync(playerDatabase.Profile + handshake.Fingerprint);
+							var url = playerDatabase.Profile + handshake.Fingerprint;
+							var httpResponseMessage = await httpClient.GetAsync(url);
 							var result = await httpResponseMessage.Content.ReadAsStreamAsync();
 
-							var yaml = MiniYaml.FromStream(result).First();
+							var yaml = MiniYaml.FromStream(result, url).First();
 							if (yaml.Key == "Player")
 							{
 								profile = FieldLoader.Load<PlayerProfile>(yaml.Value);
@@ -708,19 +705,19 @@ namespace OpenRA.Server
 		static byte[] CreateFrame(int client, int frame, byte[] data)
 		{
 			var ms = new MemoryStream(data.Length + 12);
-			ms.WriteArray(BitConverter.GetBytes(data.Length + 4));
-			ms.WriteArray(BitConverter.GetBytes(client));
-			ms.WriteArray(BitConverter.GetBytes(frame));
-			ms.WriteArray(data);
+			ms.Write(data.Length + 4);
+			ms.Write(client);
+			ms.Write(frame);
+			ms.Write(data);
 			return ms.GetBuffer();
 		}
 
 		static byte[] CreateAckFrame(int frame, byte count)
 		{
 			var ms = new MemoryStream(14);
-			ms.WriteArray(BitConverter.GetBytes(6));
-			ms.WriteArray(BitConverter.GetBytes(0));
-			ms.WriteArray(BitConverter.GetBytes(frame));
+			ms.Write(6);
+			ms.Write(0);
+			ms.Write(frame);
 			ms.WriteByte((byte)OrderType.Ack);
 			ms.WriteByte(count);
 			return ms.GetBuffer();
@@ -729,9 +726,9 @@ namespace OpenRA.Server
 		static byte[] CreateTickScaleFrame(float scale)
 		{
 			var ms = new MemoryStream(17);
-			ms.WriteArray(BitConverter.GetBytes(9));
-			ms.WriteArray(BitConverter.GetBytes(0));
-			ms.WriteArray(BitConverter.GetBytes(0));
+			ms.Write(9);
+			ms.Write(0);
+			ms.Write(0);
 			ms.WriteByte((byte)OrderType.TickScale);
 			ms.Write(scale);
 			return ms.GetBuffer();
@@ -880,13 +877,13 @@ namespace OpenRA.Server
 
 		public void DispatchServerOrdersToClients(byte[] data, int frame = 0)
 		{
-			var from = 0;
-			var frameData = CreateFrame(from, frame, data);
+			const int From = 0;
+			var frameData = CreateFrame(From, frame, data);
 			foreach (var c in Conns.ToList())
 				if (c.Validated)
-					DispatchFrameToClient(c, from, frameData);
+					DispatchFrameToClient(c, From, frameData);
 
-			RecordOrder(frame, data, from);
+			RecordOrder(frame, data, From);
 		}
 
 		public void ReceiveOrders(Connection conn, int frame, byte[] data)
@@ -972,7 +969,7 @@ namespace OpenRA.Server
 
 		void WriteLineWithTimeStamp(string line)
 		{
-			Console.WriteLine($"[{DateTime.Now.ToString(Settings.TimestampFormat)}] {line}");
+			Console.WriteLine($"[{DateTime.Now.ToString(Settings.TimestampFormat, CultureInfo.CurrentCulture)}] {line}");
 		}
 
 		void InterpretServerOrder(Connection conn, Order o)
@@ -984,7 +981,7 @@ namespace OpenRA.Server
 				if (!conn.Validated)
 				{
 					if (o.OrderString == "HandshakeResponse")
-						ValidateClient(conn, o.TargetString);
+						ValidateClient(conn, o.TargetString, o.OrderString);
 					else
 					{
 						Log.Write("server", $"Rejected connection from {conn.EndPoint}; Order `{o.OrderString}` is not a `HandshakeResponse`.");
@@ -997,70 +994,39 @@ namespace OpenRA.Server
 				switch (o.OrderString)
 				{
 					case "Command":
+					{
+						if (!InterpretCommand(o.TargetString, conn))
 						{
-							var handledBy = serverTraits.WithInterface<IInterpretCommand>()
-								.FirstOrDefault(t => t.InterpretCommand(this, conn, GetClient(conn), o.TargetString));
-
-							if (handledBy == null)
-							{
-								Log.Write("server", $"Unknown server command: {o.TargetString}");
-								SendLocalizedMessageTo(conn, UnknownServerCommand, Translation.Arguments("command", o.TargetString));
-							}
-
-							break;
+							Log.Write("server", $"Unknown server command: {o.TargetString}");
+							SendLocalizedMessageTo(conn, UnknownServerCommand, Translation.Arguments("command", o.TargetString));
 						}
 
+						break;
+					}
+
 					case "Chat":
-						{
-							if (Type == ServerType.Local || !playerMessageTracker.IsPlayerAtFloodLimit(conn))
-								DispatchOrdersToClients(conn, 0, o.Serialize());
+					{
+						if (!IsMultiplayer || !playerMessageTracker.IsPlayerAtFloodLimit(conn))
+							DispatchOrdersToClients(conn, 0, o.Serialize());
 
-							break;
-						}
+						break;
+					}
 
 					case "GameSaveTraitData":
+					{
+						if (GameSave != null)
 						{
-							if (GameSave != null)
-							{
-								var data = MiniYaml.FromString(o.TargetString)[0];
-								GameSave.AddTraitData(int.Parse(data.Key), data.Value);
-							}
-
-							break;
+							var data = MiniYaml.FromString(o.TargetString, o.OrderString)[0];
+							GameSave.AddTraitData(OpenRA.Exts.ParseInt32Invariant(data.Key), data.Value);
 						}
 
+						break;
+					}
+
 					case "CreateGameSave":
+					{
+						if (GameSave != null)
 						{
-							if (GameSave != null)
-							{
-								// Sanitize potentially malicious input
-								var filename = o.TargetString;
-								var invalidIndex = -1;
-								var invalidChars = Path.GetInvalidFileNameChars();
-								while ((invalidIndex = filename.IndexOfAny(invalidChars)) != -1)
-									filename = filename.Remove(invalidIndex, 1);
-
-								var baseSavePath = Path.Combine(
-									Platform.SupportDir,
-									"Saves",
-									ModData.Manifest.Id,
-									ModData.Manifest.Metadata.Version);
-
-								if (!Directory.Exists(baseSavePath))
-									Directory.CreateDirectory(baseSavePath);
-
-								GameSave.Save(Path.Combine(baseSavePath, filename));
-								DispatchServerOrdersToClients(Order.FromTargetString("GameSaved", filename, true));
-							}
-
-							break;
-						}
-
-					case "LoadGameSave":
-						{
-							if (Type == ServerType.Dedicated || State >= ServerState.GameStarted)
-								break;
-
 							// Sanitize potentially malicious input
 							var filename = o.TargetString;
 							var invalidIndex = -1;
@@ -1068,62 +1034,90 @@ namespace OpenRA.Server
 							while ((invalidIndex = filename.IndexOfAny(invalidChars)) != -1)
 								filename = filename.Remove(invalidIndex, 1);
 
-							var savePath = Path.Combine(
+							var baseSavePath = Path.Combine(
 								Platform.SupportDir,
 								"Saves",
 								ModData.Manifest.Id,
-								ModData.Manifest.Metadata.Version,
-								filename);
+								ModData.Manifest.Metadata.Version);
 
-							GameSave = new GameSave(savePath);
-							LobbyInfo.GlobalSettings = GameSave.GlobalSettings;
-							LobbyInfo.Slots = GameSave.Slots;
+							if (!Directory.Exists(baseSavePath))
+								Directory.CreateDirectory(baseSavePath);
 
-							// Reassign clients to slots
-							//  - Bot ordering is preserved
-							//  - Humans are assigned on a first-come-first-serve basis
-							//  - Leftover humans become spectators
-
-							// Start by removing all bots and assigning all players as spectators
-							foreach (var c in LobbyInfo.Clients)
-							{
-								if (c.Bot != null)
-									LobbyInfo.Clients.Remove(c);
-								else
-									c.Slot = null;
-							}
-
-							// Rebuild/remap the saved client state
-							// TODO: Multiplayer saves should leave all humans as spectators so they can manually pick slots
-							var adminClientIndex = LobbyInfo.Clients.First(c => c.IsAdmin).Index;
-							foreach (var kv in GameSave.SlotClients)
-							{
-								if (kv.Value.Bot != null)
-								{
-									var bot = new Session.Client()
-									{
-										Index = ChooseFreePlayerIndex(),
-										State = Session.ClientState.NotReady,
-										BotControllerClientIndex = adminClientIndex
-									};
-
-									kv.Value.ApplyTo(bot);
-									LobbyInfo.Clients.Add(bot);
-								}
-								else
-								{
-									// This will throw if the server doesn't have enough human clients to fill all player slots
-									// See TODO above - this isn't a problem in practice because MP saves won't use this
-									var client = LobbyInfo.Clients.First(c => c.Slot == null);
-									kv.Value.ApplyTo(client);
-								}
-							}
-
-							SyncLobbyInfo();
-							SyncLobbyClients();
-
-							break;
+							GameSave.Save(Path.Combine(baseSavePath, filename));
+							DispatchServerOrdersToClients(Order.FromTargetString("GameSaved", filename, true));
 						}
+
+						break;
+					}
+
+					case "LoadGameSave":
+					{
+						if (Type == ServerType.Dedicated || State >= ServerState.GameStarted)
+							break;
+
+						// Sanitize potentially malicious input
+						var filename = o.TargetString;
+						var invalidIndex = -1;
+						var invalidChars = Path.GetInvalidFileNameChars();
+						while ((invalidIndex = filename.IndexOfAny(invalidChars)) != -1)
+							filename = filename.Remove(invalidIndex, 1);
+
+						var savePath = Path.Combine(
+							Platform.SupportDir,
+							"Saves",
+							ModData.Manifest.Id,
+							ModData.Manifest.Metadata.Version,
+							filename);
+
+						GameSave = new GameSave(savePath);
+						LobbyInfo.GlobalSettings = GameSave.GlobalSettings;
+						LobbyInfo.Slots = GameSave.Slots;
+
+						// Reassign clients to slots
+						//  - Bot ordering is preserved
+						//  - Humans are assigned on a first-come-first-serve basis
+						//  - Leftover humans become spectators
+
+						// Start by removing all bots and assigning all players as spectators
+						foreach (var c in LobbyInfo.Clients)
+						{
+							if (c.Bot != null)
+								LobbyInfo.Clients.Remove(c);
+							else
+								c.Slot = null;
+						}
+
+						// Rebuild/remap the saved client state
+						// TODO: Multiplayer saves should leave all humans as spectators so they can manually pick slots
+						var adminClientIndex = LobbyInfo.Clients.First(c => c.IsAdmin).Index;
+						foreach (var kv in GameSave.SlotClients)
+						{
+							if (kv.Value.Bot != null)
+							{
+								var bot = new Session.Client()
+								{
+									Index = ChooseFreePlayerIndex(),
+									State = Session.ClientState.NotReady,
+									BotControllerClientIndex = adminClientIndex
+								};
+
+								kv.Value.ApplyTo(bot);
+								LobbyInfo.Clients.Add(bot);
+							}
+							else
+							{
+								// This will throw if the server doesn't have enough human clients to fill all player slots
+								// See TODO above - this isn't a problem in practice because MP saves won't use this
+								var client = LobbyInfo.Clients.First(c => c.Slot == null);
+								kv.Value.ApplyTo(client);
+							}
+						}
+
+						SyncLobbyInfo();
+						SyncLobbyClients();
+
+						break;
+					}
 				}
 			}
 		}
@@ -1258,7 +1252,7 @@ namespace OpenRA.Server
 			lock (LobbyInfo)
 			{
 				// TODO: Only need to sync the specific client that has changed to avoid conflicts!
-				var clientData = LobbyInfo.Clients.Select(client => client.Serialize()).ToList();
+				var clientData = LobbyInfo.Clients.ConvertAll(client => client.Serialize());
 
 				DispatchServerOrdersToClients(Order.FromTargetString("SyncLobbyClients", clientData.WriteToString(), true));
 
@@ -1358,7 +1352,7 @@ namespace OpenRA.Server
 
 				State = ServerState.GameStarted;
 
-				if (Type != ServerType.Local)
+				if (IsMultiplayer)
 					OrderLatency = gameSpeed.OrderLatency;
 
 				if (GameSave == null && LobbyInfo.GlobalSettings.GameSavesEnabled)
@@ -1372,8 +1366,8 @@ namespace OpenRA.Server
 					{
 						startGameData = new List<MiniYamlNode>()
 						{
-							new MiniYamlNode("SaveLastOrdersFrame", GameSave.LastOrdersFrame.ToString()),
-							new MiniYamlNode("SaveSyncFrame", GameSave.LastSyncFrame.ToString())
+							new("SaveLastOrdersFrame", GameSave.LastOrdersFrame.ToStringInvariant()),
+							new("SaveSyncFrame", GameSave.LastSyncFrame.ToStringInvariant())
 						}.WriteToString();
 					}
 				}
@@ -1418,6 +1412,15 @@ namespace OpenRA.Server
 			}
 		}
 
+		public bool InterpretCommand(string command, Connection conn)
+		{
+			foreach (var t in serverTraits.WithInterface<IInterpretCommand>())
+				if (t.InterpretCommand(this, conn, GetClient(conn), command))
+					return true;
+
+			return false;
+		}
+
 		public ConnectionTarget GetEndpointForLocalConnection()
 		{
 			var endpoints = new List<DnsEndPoint>();
@@ -1435,6 +1438,27 @@ namespace OpenRA.Server
 			return new ConnectionTarget(endpoints);
 		}
 
+		public bool MapIsUnknown(string uid)
+		{
+			if (string.IsNullOrEmpty(uid))
+				return true;
+
+			var status = ModData.MapCache[uid].Status;
+			return status != MapStatus.Available && status != MapStatus.DownloadAvailable;
+		}
+
+		public bool MapIsKnown(string uid)
+		{
+			if (string.IsNullOrEmpty(uid))
+				return false;
+
+			if (MapPool != null && !MapPool.Contains(uid))
+				return false;
+
+			var status = ModData.MapCache[uid].Status;
+			return status == MapStatus.Available || status == MapStatus.DownloadAvailable;
+		}
+
 		interface IServerEvent { void Invoke(Server server); }
 
 		sealed class ConnectionConnectEvent : IServerEvent
@@ -1490,9 +1514,9 @@ namespace OpenRA.Server
 			readonly int[] pingHistory;
 
 			// TODO: future net code changes
-			#pragma warning disable IDE0052
+#pragma warning disable IDE0052
 			readonly byte queueLength;
-			#pragma warning restore IDE0052
+#pragma warning restore IDE0052
 
 			public ConnectionPingEvent(Connection connection, int[] pingHistory, byte queueLength)
 			{

OpenRA.Game/Settings.cs

@@ -102,6 +102,9 @@ namespace OpenRA
 		[Desc("For dedicated servers only, treat maps that fail the lint checks as invalid.")]
 		public bool EnableLintChecks = true;
 
+		[Desc("For dedicated servers only, a comma separated list of map uids that are allowed to be used.")]
+		public string[] MapPool = Array.Empty<string>();
+
 		[Desc("Delay in milliseconds before newly joined players can send chat messages.")]
 		public int FloodLimitJoinCooldown = 5000;
 
@@ -210,9 +213,6 @@ namespace OpenRA
 		[Desc("Disable operating-system provided cursor rendering.")]
 		public bool DisableHardwareCursors = false;
 
-		[Desc("Disable legacy OpenGL 2.1 support.")]
-		public bool DisableLegacyGL = true;
-
 		[Desc("Display index to use in a multi-monitor fullscreen setup.")]
 		public int VideoDisplay = 0;
 
@@ -370,13 +370,14 @@ namespace OpenRA
 
 		public void Save()
 		{
+			var yamlCacheBuilder = yamlCache.ConvertAll(n => new MiniYamlNodeBuilder(n));
 			foreach (var kv in Sections)
 			{
-				var sectionYaml = yamlCache.FirstOrDefault(x => x.Key == kv.Key);
+				var sectionYaml = yamlCacheBuilder.FirstOrDefault(x => x.Key == kv.Key);
 				if (sectionYaml == null)
 				{
-					sectionYaml = new MiniYamlNode(kv.Key, new MiniYaml(""));
-					yamlCache.Add(sectionYaml);
+					sectionYaml = new MiniYamlNodeBuilder(kv.Key, new MiniYamlBuilder(""));
+					yamlCacheBuilder.Add(sectionYaml);
 				}
 
 				var defaultValues = Activator.CreateInstance(kv.Value.GetType());
@@ -393,27 +394,29 @@ namespace OpenRA
 					else
 					{
 						// Update or add the custom value
-						var fieldYaml = sectionYaml.Value.Nodes.FirstOrDefault(n => n.Key == fli.YamlName);
+						var fieldYaml = sectionYaml.Value.NodeWithKeyOrDefault(fli.YamlName);
 						if (fieldYaml != null)
 							fieldYaml.Value.Value = serialized;
 						else
-							sectionYaml.Value.Nodes.Add(new MiniYamlNode(fli.YamlName, new MiniYaml(serialized)));
+							sectionYaml.Value.Nodes.Add(new MiniYamlNodeBuilder(fli.YamlName, new MiniYamlBuilder(serialized)));
 					}
 				}
 			}
 
-			var keysYaml = yamlCache.FirstOrDefault(x => x.Key == "Keys");
+			var keysYaml = yamlCacheBuilder.FirstOrDefault(x => x.Key == "Keys");
 			if (keysYaml == null)
 			{
-				keysYaml = new MiniYamlNode("Keys", new MiniYaml(""));
-				yamlCache.Add(keysYaml);
+				keysYaml = new MiniYamlNodeBuilder("Keys", new MiniYamlBuilder(""));
+				yamlCacheBuilder.Add(keysYaml);
 			}
 
 			keysYaml.Value.Nodes.Clear();
 			foreach (var kv in Keys)
-				keysYaml.Value.Nodes.Add(new MiniYamlNode(kv.Key, FieldSaver.FormatValue(kv.Value)));
+				keysYaml.Value.Nodes.Add(new MiniYamlNodeBuilder(kv.Key, FieldSaver.FormatValue(kv.Value)));
 
-			yamlCache.WriteToFile(settingsFile);
+			yamlCacheBuilder.WriteToFile(settingsFile);
+			yamlCache.Clear();
+			yamlCache.AddRange(yamlCacheBuilder.Select(n => n.Build()));
 		}
 
 		static string SanitizedName(string dirty)
@@ -424,7 +427,7 @@ namespace OpenRA
 			var clean = dirty;
 
 			// reserved characters for MiniYAML and JSON
-			var disallowedChars = new char[] { '#', '@', ':', '\n', '\t', '[', ']', '{', '}', '"', '`' };
+			var disallowedChars = new char[] { '#', '@', ':', '\n', '\t', '[', ']', '{', '}', '<', '>', '"', '`' };
 			foreach (var disallowedChar in disallowedChars)
 				clean = clean.Replace(disallowedChar.ToString(), string.Empty);