Merge function for proplists

planet/System.ocg/Proplists.c

@@ -2,9 +2,54 @@
 	Proplists.c
 	General helper functions that create or work with proplists.
 		
-	@author Guenther, Maikel
+	@author Guenther, Maikel, Marky
 */
 
+/*
+ Adds the contents of one proplist to the other.
+ Usually you can do this by using a prototype, but 
+ this is not possible when you receive a second proplist
+ from another function.
+ 
+ @par original This proplist will be expanded.
+ @par additional These are the additional contents.
+ @par no_overwrite By default the function overwrites
+      existing properties in the original proplist,
+      as it would happen if you derive from a prototype.
+      If this parameter is 'true' the function will report
+      an error instead of overwriting a parameter.
+ 
+ @return proplist The original proplist. This is in fact the same
+         proplist that was passed as an argument, the functions just
+         returns it for convenience.
+ */
+global func AddProperties(proplist original, proplist additional, bool no_overwrite)
+{
+	if (original == nil)
+	{
+		FatalError("Cannot add properties to 'nil'");
+	}
+	if (additional == nil)
+	{
+		FatalError("Adding proplist 'nil' to another proplist makes no sense.");
+	}
+	
+	for (var property in GetProperties(additional))
+	{
+		if (no_overwrite && (original[property] != nil)) // about to overwrite?
+		{
+			FatalError(Format("Cancelling overwrite of property '%s', original value %v, with new value %v", property, original[property], additional[property]));
+		}
+		else
+		{
+			original[property] = additional[property];
+		}
+	}
+	
+	return original;
+}
+
+
 // Turns a property into a writable one. This for example useful if an object
 // inherits a property from a definition which should not stay read-only.
 global func MakePropertyWritable(name, obj)