[oXygen-user] invert selection

[Syd Bauman]

I am off once again teaching an XML class using oXygen. When we do
this, we often project an XML document up on the screen and select an
area (typically an element with some children) as being that to which
we want the students to pay attention.

But as soon as we've selected it in order to highlight it, the
background becomes distinctive (gray in my case, but can be changed
in the preferences), and color syntaxing is lost.

I'd like to somehow have the reverse visual effect. I'd like
everything else to be gray and dull w/o syntax highlighting, and the
selected text to be bright and with syntax highlighting. 

Of course, I don't want the whole file to be w/o syntax highlighting
until I select something. I want the act of selection to make
everything else look dull, leaving the selection bright and cheery. 

One way to achieve this would be to have a "inverse selection"
command. I realize that doing so would mean that there would be two
discontiguous chunks of selection, and I'm not sure that's easy to
do, or a good idea. 

But *some* way to achieve this marvelous pedagogical goal would be
appreciated.