Re: [Emacs-diffs] scratch/widen-less a4ba846: Replace prog-widen with consolidating widen calls

[Vitalie Spinu <spinuvit@gmail.com>]

Please correct me if I am wrong but the current patch requires all modes to use
`prog-widen` and reserve `widen` to the interactive use, right? If so, this is
the opposite of the older idea of adding `hard-limits` for widening which only
multi-modes should use.

I have proposed a patch for `set-widen-limits` 1.5 years ago which still lives
in scratch/hard-narrow branch. It turned to be a pretty straightforward feat and
worked without requiring any changes of the excising elisp code.

The lengthy discussion started here:

  https://lists.gnu.org/archive/html/emacs-devel/2016-04/msg00629.html

Somewhere along the way we decided in favor of adding an extra `hard` argument
to `narrow` instead of having a new `set-widen-limits` function. That turned to
be impossible as it required backward-incompatible changes to the byte-code. I
run out of steam by then and the whole idea died :(

If adding a new function is back on the table then I think `set-widen-limits` is
a better approach than `prog-widen`. It doesn't impose new restrictions on the
existing code and it avoids introducing new types of narrowing or widening.

Unless something changed in the meanwhile, the changes to the C code to make
that work were minimal. If there is interest I can get it another shot.

  Vitalie