From: Stefan Monnier <monnier@iro.umontreal.ca>
To: emacs-devel@gnu.org
Subject: Re: How can I undo a change from a modification-hook?
Date: Wed, 26 Apr 2017 08:26:13 -0400 [thread overview]
Message-ID: <jwvshkvcqik.fsf-monnier+gmane.emacs.devel@gnu.org> (raw)
In-Reply-To: 2448005f-9fc4-78b2-3203-9fc8204f6f5b@mit.edu
> (by raising an error), and to allow changes when in a comment. I can't
> find a good way to allow whitespace edits at the end of a line, though.
> I can detect such changes from the second call to the modification hook
> (during which it's easy to know whether the change is only adding or
> removing space at the end of a line), but I can't easily undo the changes
> and error out if they involve more than whitespace, can I?
Technically you can, but it's a bit messy and will likely not be
100% reliable. Personally, in your case, I wouldn't bother doing it,
but here's how I'd do it otherwise:
- in the before-hook stash the value of buffer-undo-list somewhere.
[ While you're at it, stash the beg/end there as well. ]
- in the after-hook check the change (using beg/end/len) [ and while
you're there, check that the beg/end/len is within the announces
beg/end stashed earlier, and if it's not just don't do anything
since it means the stash buffer-undo-list is likely unrelated. ]
and if it doesn't fit your criteria, call undo until you reach the
previously stashed value of buffer-undo-list, and then signal the error.
-- Stefan
next prev parent reply other threads:[~2017-04-26 12:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-26 7:02 How can I undo a change from a modification-hook? Clément Pit--Claudel
2017-04-26 12:26 ` Stefan Monnier [this message]
2017-04-26 13:45 ` Clément Pit-Claudel
2017-04-26 13:52 ` Stefan Monnier
2017-04-26 14:23 ` Clément Pit-Claudel
2017-04-26 14:51 ` Stefan Monnier
2017-04-26 16:38 ` Clément Pit-Claudel
2017-04-26 18:43 ` Stefan Monnier
2017-04-26 19:02 ` Clément Pit-Claudel
2017-04-27 12:48 ` Stefan Monnier
2017-04-27 12:58 ` Clément Pit-Claudel
2017-04-27 17:36 ` Stefan Monnier
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=jwvshkvcqik.fsf-monnier+gmane.emacs.devel@gnu.org \
--to=monnier@iro.umontreal.ca \
--cc=emacs-devel@gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.