bug#6915: Please consider making left-margin-width etc buffer local instead of major mode local

[Juanma Barranquero <lekktu@gmail.com>]

On Thu, Aug 26, 2010 at 14:40, Lennart Borgman
<lennart.borgman@gmail.com> wrote:

> If there is only one major mode in the buffer this is perhaps the case, yes.

This is what happens now, and in the foreseeable future, in the vast
majority of buffers. Or do you anticipate the need to use mumamo in
all kinds of buffers?

> Emacs was not very good prepared for several major modes in a buffer.

Agreed.

> I suppose this will change in the future, but we are not there yet.

Why?

>  - Emulator mode buffer local variable.
>  - Modified state buffer local variables.

I lack context (or knowledge) to understand what you mean here.

> I try to move this a bit forward by pointing to cases where a major
> mode local variable probably is seen by users more like something
> belonging to the buffer contents.

Yes, I understand, but I think here is where I disagree. A priori, I
don't know why margins would be related more to buffer contents than
to buffer mode.

> Yes, of course mumamo can take care of these cases, but it comes at a cost.

Making variables permanent buffer-local also has a cost. Surprise and
bugs, if the user or other modes weren't expecting it, for example.

> (And it definitively can not be taken care of the way that was
> suggested in the answer you are commenting on.)

I trust you on this. But perhaps what is lacking is something at the
Emacs API level.

What I mean is that making permanent buffer-local every variable that
mumamo needs so isn't necessarily the best answer.

    Juanma