[plt-scheme] Text% getting and setting text, images, etc.

I need to re-implement all insert/copy/paste/undo/redo operations in a 
text% subclass. However, I haven't yet figured out how to get and 
insert editor data that may contain more than just text. Does 
"flattened text" include subeditors and images? How would I insert 
"flattened text" into the editor again?

I shouldn't really use on-copy and on-paste, because I also need to 
save ranges of editor data for my own custom undo scheme. So what I'd 
need is something like:

(get-rich-text start-position end-position) ==> rich text data or 
whatever
(insert-rich-text text-data position)

How to?

Best regards,

Erich