I know when I used to use gnu Emacs, there was an option that you can
turn on so that if the matching paren is out of your screen but
exists, the who region between the parentheses is highlit. (normally,
I only highlight the parentheses themselves)
Mic-paren has something similar, except it quotes the text where the
matching parentheses is found, but it would be nice if the region was
highlit as well, but only of course if the matching parenthesis is out
of the view area.
Has this been implemented in XEmacs?