Re: Emacs's handling of line numbers [from bug#5042]

[Juanma Barranquero <lekktu@gmail.com>]

On Sun, Apr 18, 2010 at 19:29, Eli Zaretskii <eliz@gnu.org> wrote:

> If that's the problem, we could disable narrowing/widening in Info
> mode.

Surely there are legitimate reasons why a user would want to use
narrowing to show just part of an Info node.

> (I'm not saying we should, but if we decided to do so, it would
> be IMO a better solution than a whole new infrastructure with two
> kinds of restrictions.)

OK, don't think of it as two kinds of restrictions, but the current
restriction user interface, and an additional elisp API to treat parts
of a buffer as a "virtual buffer" or some such.

> Actually, it happens to be a feature (more accurately, a basis for a
> feature), both in Info and in Rmail.

It is that feature inequivocally linked to being implemented via narrowing?

> But you will never be able to disallow widening completely, because
> the primitives are not going to go away, and there's nothing to
> prevent a motivated individual from invoking them, even if they are
> non-interactive.

Of course. You can always shoot your own foot. That's no reason not to
provide adequate abstractions.

> IOW, I don't see how the suggested duplicity will solve enough of the
> problem to justify the added complexity.

I'm not sure, either. It's hard to say beforehand whether adding that
would be a waste of resources (sort of like frame-local variables), or
an enabling technology for some kind of problems... A priori, it seems
like Info and rmail and some other packages could benefit from it.

    Juanma