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bug#35536: 27.0.50; Expose buffer's marker list to Elisp
From: |
Basil L. Contovounesios |
Subject: |
bug#35536: 27.0.50; Expose buffer's marker list to Elisp |
Date: |
Fri, 03 May 2019 16:50:56 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> I attach a patch implementing this based on BUF_MARKERS, as per Martin's
>> suggestion. Any reasons not to expose such a function?
>
> AFAIK the main reason for such a function is so that you can implement
> "replace" functions which preserves markers better than "insert+delete"
> does, right?
AIUI, yes.
> Random thoughts:
> - I wouldn't expose a `(marker-list)` function but rather `(markers-in
> BEG END)` so you're not bothered by unrelated markers outside of
> the region of interest.
The patch in the OP accepts optional BEG and END arguments for the
caller's typing convenience.
> - The main problem I see is that some of the markers in BUF_MARKERS are
> "proper" markers, while others are just the markers that we happen to
> use in the current internal representation of overlays.
> If you can get your hands on those markers, you might end up breaking
> some invariants on which the C code relies (e.g. place the
> overlay-start after the overlay-end, or in a different buffer).
> - I think the serious risks (e.g. crashes) are solvable. E.g. there's
> room for an additional boolean field `lisp_marker` which could be used
> to distinguish those markers which can be safely returned (because
> they're normal Lisp-level markers already accessible from Lisp anyway)
> from the internal ones (such as those from overlays).
> - Then we'd probably want to discussion whether markers used within
> `save-excursion` and friends should be marked as `lisp_marker` or not.
>
> This said, as you say later:
>> I have yet to see a use-case for marker-list which can't be engineered
>> in a different way
>
> So, whether it's worth the trouble: I don't know.
Given a sufficiently sufficient save+restore primitive as per Eli's
suggestion, it's not looking worth the trouble.
Thanks,
--
Basil
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, (continued)
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Drew Adams, 2019/05/03
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Stefan Monnier, 2019/05/03
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Drew Adams, 2019/05/03
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Stefan Monnier, 2019/05/03
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Drew Adams, 2019/05/03
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Richard Stallman, 2019/05/04
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Mauro Aranda, 2019/05/03
- bug#35536: 27.0.50; Expose buffer's marker list to Elisp, martin rudalics, 2019/05/04
bug#35536: 27.0.50; Expose buffer's marker list to Elisp, Stefan Monnier, 2019/05/02