Load assets using absolute paths. Fixes #6717.

OpenRA.Game/Platform.cs

@@ -93,6 +93,40 @@ namespace OpenRA
 			}
 		}
 
+		public static string GameDir { get { return AppDomain.CurrentDomain.BaseDirectory; } }
+
+		/// <summary>Replace special character prefixes with full paths</summary>
+		public static string ResolvePath(string path)
+		{
+			// paths starting with ^ are relative to the support dir
+			if (path.StartsWith("^"))
+				path = SupportDir + path.Substring(1);
+
+			// paths starting with . are relative to the game dir
+			if (path.StartsWith("./") || path.StartsWith(".\\"))
+				path = GameDir + path.Substring(2);
+
+			return path;
+		}
+
+		/// <summary>Replace special character prefixes with full paths</summary>
+		public static string ResolvePath(params string[] path)
+		{
+			return ResolvePath(path.Aggregate(Path.Combine));
+		}
+
+		/// <summary>Replace the full path prefix with the special notation characters ^ or .</summary>
+		public static string UnresolvePath(string path)
+		{
+			if (path.StartsWith(SupportDir))
+				path = "^" + path.Substring(SupportDir.Length);
+
+			if (path.StartsWith(GameDir))
+				path = "." + path.Substring(GameDir.Length);
+
+			return path;
+		}
+
 		public static void ShowFatalErrorDialog()
 		{
 			var process = "OpenRA.CrashDialog.exe";