diff --git a/OpenRA.Game/OpenRA.Game.csproj b/OpenRA.Game/OpenRA.Game.csproj
index dd5530d090..5c2fc91229 100644
--- a/OpenRA.Game/OpenRA.Game.csproj
+++ b/OpenRA.Game/OpenRA.Game.csproj
@@ -297,6 +297,7 @@
     <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
new file mode 100644
index 0000000000..40a235634c
--- /dev/null
+++ b/OpenRA.Game/Support/Evaluator.cs
@@ -0,0 +1,109 @@
+#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 1a20c6fe06..41a099a9ea 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 IntegerExpression X;
-		public IntegerExpression Y;
-		public IntegerExpression Width;
-		public IntegerExpression Height;
+		public string X = "0";
+		public string Y = "0";
+		public string Width = "0";
+		public string Height = "0";
 		public string[] Logic = { };
 		public ChromeLogic[] LogicObjects { get; private set; }
 		public bool Visible = true;
@@ -275,17 +275,16 @@ namespace OpenRA.Widgets
 			substitutions.Add("PARENT_LEFT", parentBounds.Left);
 			substitutions.Add("PARENT_TOP", parentBounds.Top);
 			substitutions.Add("PARENT_BOTTOM", parentBounds.Height);
-
-			var readOnlySubstitutions = new ReadOnlyDictionary<string, int>(substitutions);
-			var width = Width != null ? Width.Evaluate(readOnlySubstitutions) : 0;
-			var height = Height != null ? Height.Evaluate(readOnlySubstitutions) : 0;
+			var width = Evaluator.Evaluate(Width, substitutions);
+			var height = Evaluator.Evaluate(Height, substitutions);
 
 			substitutions.Add("WIDTH", width);
 			substitutions.Add("HEIGHT", height);
 
-			var x = X != null ? X.Evaluate(readOnlySubstitutions) : 0;
-			var y = Y != null ? Y.Evaluate(readOnlySubstitutions) : 0;
-			Bounds = new Rectangle(x, y, width, height);
+			Bounds = new Rectangle(Evaluator.Evaluate(X, substitutions),
+								   Evaluator.Evaluate(Y, substitutions),
+								   width,
+								   height);
 		}
 
 		public void PostInit(WidgetArgs args)