RE: font-lock-maximum-decoration should be 2 by default?

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

> > Let say you are defining mode "X". Then `define-derived-mode' and
> > `define-generic-mode' can add X-mode-font-lock-keywords as a
> > (customizable?) variable, which would be a list of keywords or
> > symbols holding keywords.
> 
> That might be a good way to replace the ill-defined notion of 
> levels, yes.

It's not about a "notion".  The name "levels" is a misnomer, but the mechanism
of easily defining different sets/kinds of highlighting for a given mode, and
interactively switching among them, is a plus, not a minus.

Just providing `X-mode-font-lock-keywords' for mode X does not replace such a
mechanism, at all.

Letting users customize multiple such sets of highlighting patterns for a given
mode is a start, but what's also needed is an easy way to interactively switch
among them.

Today's misnamed "levels" are such sets of mode-specific highlighting patterns
(choices).  And you can easily switch among them in a given mode.

We should not be throwing away that possibility just because Emacs Dev has not
kept up with predefining such sets for various modes.  Make it easier for users
do define them and easier for users to switch among them.  _That_ would be an
improvement.