Re: setnu-mode and Emacs 21.

[Miles Bader]

Juanma Barranquero <address@hidden> writes:
> > I think it's much better to think about how such
> > designs can be avoided (for instance, in the line-numbering case, using
> > jit-lock to add overlays only to displayed lines).
> 
> Yes, I agree, but if it is so frequent a problem, perhaps we need a
> more generic answer (for font-locking, setnu.el, and other new ideas
> that will eventually pop) that jit-lock, which, AFAICS, is just for
> font-locking.

Stefan says he's used jit-lock to do something besides font-locking
(`glasses-mode'), so it may be more generally useful.

I do agree that it would be nice if overlays were faster, BTW, but I
think that's just a general improvement, not a solution to problems
like setnu-mode.

> > what I think is _bad_ is a design that requires _every_ line of
> > the file to have an overlay (even if never display or modified), rather
> > than somehow adding overlays on a more `as needed' basis.
> 
> What if you just add them as each fragment of the buffer is being
> displayed, but you don't want to delete them afterwards (perhaps they
> store relevant information)?

Actually, that's the way jit-lock works now.  I was suggesting `lazy
deletion' as an extension (to save resources), but it would obviously
be optional.

-Miles
-- 
Fast, small, soon; pick any 2.