Re: locked narrowing in ELisp

[Eli Zaretskii]

> Date: Wed, 17 Aug 2022 03:05:05 +0300
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> If the user-level narrow/widen commands didn't use _actual_ narrowing, 
> but display engine tricks or whatever (example: 
> https://github.com/Malabarba/fancy-narrow/), "other parts of the major 
> mode" wouldn't have to do the usual (save-restriction (widen) ...) 
> dance, which a lot of code is littered with.

I don't think this is reliable solution for a general problem such as
this one.  What that package does is prevent _some_ commands and APIs
from escaping the "narrowing".  But in the general case, once you get
low enough into our infrastructure code, there's no way of knowing
what is TRT wrt this "narrowing", because the intent of the caller is
unknown, and quite a few places in our code will happily ignore it.

So I think it is eventually unavoidable to have to define some
property of the narrowing that every piece of Emacs will test in order
to understand whether it should or shouldn't move outside of the
narrowed region.