Many programming-oriented editors allow the user to specify/change the end of line characters, for example in Notepad++:

Edit -> EOL Conversion -> { Windows (CRLF) | Unix (LF) | Macintosh (CR) }

The line endings setting also comes to play when executing COPY, or calling CodeArea::getText.

Several possibilities exist:
1. add the lineEnding property only to CodeArea, use platform default in RTA
2. add *protected* lineEnding property to RTA with the default value of platform default, and make it public in CodeArea. The problem with this particular idea is that a custom StyledTextModel might have its own ideas how to store the newline, or maybe even allow for mixing different styles in one document.
3. add a straightforward property to RTA
4. add property or a field to the StyledTextModel