diff --git a/OpenRA.Game/OpenRA.Game.csproj b/OpenRA.Game/OpenRA.Game.csproj
index a6ab5f21dd..518f35eb45 100644
--- a/OpenRA.Game/OpenRA.Game.csproj
+++ b/OpenRA.Game/OpenRA.Game.csproj
@@ -316,7 +316,6 @@
     <Compile Include="Primitives\TypeDictionary.cs" />
     <Compile Include="Map\ActorInitializer.cs" />
     <Compile Include="Map\ActorReference.cs" />
-    <Compile Include="Support\Evaluator.cs" />
     <Compile Include="Settings.cs" />
     <Compile Include="Graphics\PlayerColorRemap.cs" />
     <Compile Include="Graphics\Palette.cs" />
diff --git a/OpenRA.Game/Support/Evaluator.cs b/OpenRA.Game/Support/Evaluator.cs
deleted file mode 100644
index 40a235634c..0000000000
--- a/OpenRA.Game/Support/Evaluator.cs
+++ /dev/null
@@ -1,109 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2017 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation, 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;
-using System.Linq;
-
-namespace OpenRA.Support
-{
-	public static class Evaluator
-	{
-		public static int Evaluate(string expr)
-		{
-			return Evaluate(expr, new Dictionary<string, int>());
-		}
-
-		public static int Evaluate(string expr, Dictionary<string, int> syms)
-		{
-			var toks = Tokens(expr, "+-*/()");
-			var postfix = ToPostfix(toks, syms);
-
-			var s = new Stack<int>();
-
-			foreach (var t in postfix)
-			{
-				switch (t[0])
-				{
-					case '+': ApplyBinop(s, (x, y) => y + x); break;
-					case '-': ApplyBinop(s, (x, y) => y - x); break;
-					case '*': ApplyBinop(s, (x, y) => y * x); break;
-					case '/': ApplyBinop(s, (x, y) => y / x); break;
-					default: s.Push(Exts.ParseIntegerInvariant(t)); break;
-				}
-			}
-
-			return s.Pop();
-		}
-
-		static void ApplyBinop(Stack<int> s, Func<int, int, int> f)
-		{
-			var x = s.Pop();
-			var y = s.Pop();
-			s.Push(f(x, y));
-		}
-
-		static IEnumerable<string> ToPostfix(IEnumerable<string> toks, Dictionary<string, int> syms)
-		{
-			var s = new Stack<string>();
-			foreach (var t in toks)
-			{
-				if (t[0] == '(') s.Push(t);
-				else if (t[0] == ')')
-				{
-					var temp = "";
-					while ((temp = s.Pop()) != "(") yield return temp;
-				}
-				else if (char.IsNumber(t[0])) yield return t;
-				else if (char.IsLetter(t[0]))
-				{
-					if (!syms.ContainsKey(t))
-						throw new InvalidOperationException("Substitution `{0}` undefined".F(t));
-
-					yield return syms[t].ToString();
-				}
-				else
-				{
-					while (s.Count > 0 && Prec[t] <= Prec[s.Peek()]) yield return s.Pop();
-					s.Push(t);
-				}
-			}
-
-			while (s.Count > 0) yield return s.Pop();
-		}
-
-		static readonly Dictionary<string, int> Prec
-			= new Dictionary<string, int> { { "+", 0 }, { "-", 0 }, { "*", 1 }, { "/", 1 }, { "(", -1 } };
-
-		static IEnumerable<string> Tokens(string expr, string ops)
-		{
-			var s = "";
-			foreach (var c in expr)
-			{
-				if (char.IsWhiteSpace(c))
-				{
-					if (s != "") yield return s;
-					s = "";
-				}
-				else if (ops.Contains(c))
-				{
-					if (s != "") yield return s;
-					s = "";
-					yield return "" + c;
-				}
-				else
-					s += c;
-			}
-
-			if (s != "") yield return s;
-		}
-	}
-}
diff --git a/OpenRA.Game/Widgets/Widget.cs b/OpenRA.Game/Widgets/Widget.cs
index ca7e85bb7b..34911a4e4a 100644
--- a/OpenRA.Game/Widgets/Widget.cs
+++ b/OpenRA.Game/Widgets/Widget.cs
@@ -196,10 +196,10 @@ namespace OpenRA.Widgets
 
 		// Info defined in YAML
 		public string Id = null;
-		public string X = "0";
-		public string Y = "0";
-		public string Width = "0";
-		public string Height = "0";
+		public IntegerExpression X;
+		public IntegerExpression Y;
+		public IntegerExpression Width;
+		public IntegerExpression Height;
 		public string[] Logic = { };
 		public ChromeLogic[] LogicObjects { get; private set; }
 		public bool Visible = true;
@@ -275,16 +275,17 @@ namespace OpenRA.Widgets
 			substitutions.Add("PARENT_LEFT", parentBounds.Left);
 			substitutions.Add("PARENT_TOP", parentBounds.Top);
 			substitutions.Add("PARENT_BOTTOM", parentBounds.Height);
-			var width = Evaluator.Evaluate(Width, substitutions);
-			var height = Evaluator.Evaluate(Height, substitutions);
+
+			var readOnlySubstitutions = new ReadOnlyDictionary<string, int>(substitutions);
+			var width = Width != null ? Width.Evaluate(readOnlySubstitutions) : 0;
+			var height = Height != null ? Height.Evaluate(readOnlySubstitutions) : 0;
 
 			substitutions.Add("WIDTH", width);
 			substitutions.Add("HEIGHT", height);
 
-			Bounds = new Rectangle(Evaluator.Evaluate(X, substitutions),
-								   Evaluator.Evaluate(Y, substitutions),
-								   width,
-								   height);
+			var x = X != null ? X.Evaluate(readOnlySubstitutions) : 0;
+			var y = Y != null ? Y.Evaluate(readOnlySubstitutions) : 0;
+			Bounds = new Rectangle(x, y, width, height);
 		}
 
 		public void PostInit(WidgetArgs args)