Adding your own highlighting scheme can be done, but it takes a little work. I need to write up some documentation on how to do this, as well as make the process itself a little easier. It's been on my to-do list for ages, but I haven't gotten around to it yet.
If you're really motivated, grab the source for RSyntaxTextArea, either at its SourceForge page
or get the bleeding edge from the Subversion repository
. The look at the file RSyntaxTextArea/src/org/fife/ui/rsyntaxtextarea/modes/JavaTokenMaker.flex. This file generates the class that does Java syntax highlighting by using JFlex
. There is a comment at the top of the file that describes some special steps you'll need to take to massage the JFlex output to work with RSyntaxTextArea. Look through this as a first step.
I can probably look up a NetRexx grammar online and add this syntax myself if you're okay with that.
I would like to create a grammar designer program that would generate a highlighter for arbitrary languages usable by RSyntaxTextArea. That would be a fun project, and would be useful as well, but again; it's more of a time issue.