bug#15899: 24.3.50; regression: `region' overlay is lower priority than default

[Drew Adams <drew.adams@oracle.com>]

> > I don't think so. The region overlay priority won't change, even
> > if people decide to shoot themselves in the foot and raise
> > priorities of overlays inappropriately.
> 
> That's not the race I had in mind.  What I had in mind was users
> complaining about their favorite overlay-based features being
> obscured by the region, lobbying the maintainers to increase the
> priorities of those overlays above the region (and possibly also
> above the easy-mark overlay), or increase the priority of the region
> overlay; then other users complaining about the effects of that,
> and so on and so forth ad nauseam.  How can you even assume that
> the "region overlay priority won't change", given the possibility
> and enough pressure from users?

User complaint escalation is the escalation you fear?  That's a new
one.  Emacs Dev has never had much trouble resisting user complaints
to change defaults.  And foreclosing such debate is never the
solution anyway.

Just set the default priority for the region overlay to a value close
to but lower than the isearch overlays.  If there are future
suggestions to tweak default priorities then that will be discussed
concretely when it comes up.  If users - or you - have good reasons
to change default priorities, then those can be adjusted.

> Once out of the bottle, this genie cannot be easily put back.

Once face `region' is used for an overlay and not a text property,
the overlay genie is out of the bottle, yes.  New possibilities
arrive, and some old possibilities leave.