From: phillip.lord@newcastle.ac.uk (Phillip Lord)
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: Emacs-Devel devel <emacs-devel@gnu.org>
Subject: Re: disabling undo boundaries
Date: Sat, 16 May 2015 14:31:49 +0100 [thread overview]
Message-ID: <87iobsr6m2.fsf@newcastle.ac.uk> (raw)
In-Reply-To: <jwvd221s8yz.fsf-monnier+emacs@gnu.org> (Stefan Monnier's message of "Fri, 15 May 2015 19:45:58 -0400")
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> Yes, I can see that. Although iff this is the reason for the
>> undo-boundary, it would still make more sense to me to have the process
>> code insert this. Aside from being a more discrete effect, it would also
>> avoid the current "do nothing now, but insert an undo-boundary before
>> the next change where ever that is" semantics.
>
> I don't claim it's the best solution, indeed. It's just that if we
> remove it, we'll have to replace it with other mechanisms.
> So we need a clear description of the current cases that are considered
> misbehaviors and those that are considered good (tho not necessarily
> perfect).
I entirely agree with this, of course. This is why I am trying to find
positive behaviour.
So, I have tested this, and indeed commenting out that code does affect
undo behaviour. To test this, I wrote a "countdown" script which, well,
counts down, and then ran this in *shell*. Then I typed into *scratch*
at defined points. With the undo-boundary code, indeed, the typing in
*scratch* does add boundaries -- so that a countdown from 100 say, gets
split up into multiple undos. Without this code, the countdown gets
undone in one go.
So, while it clearly has an effect, I am not sure why this is better.
For example, if I launch two shell buffers, then run "countdown 20" in
both at the same time, then both buffers now undo in 20 steps, one
second at a time, because their output interleaves. Again, the "add an
undo boundary because of a change in another buffer" semantics does not
seem intuitive to me.
>> I don't understand how that would that work. undo-boundaries are nil, so
>> surely they are all the same object?
>
> No, we'd record put the cons cell in which the nil is placed.
Oh, yes, of course. That does assume, though, that any operations on
buffer-undo-list are destructive. For instance, if I filter the
buffer-undo-list with seq.el or dash, do I not get all new cons cells?
Still, most of the undo.c code seems to change in place, so I guess it
would work in most cases.
Phil
next prev parent reply other threads:[~2015-05-16 13:31 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-10 21:43 disabling undo boundaries Phillip Lord
2015-05-11 1:42 ` Stefan Monnier
2015-05-11 11:46 ` Phillip Lord
2015-05-11 14:45 ` Stefan Monnier
2015-05-11 16:31 ` Phillip Lord
2015-05-11 19:30 ` Stefan Monnier
2015-05-11 20:42 ` Phillip Lord
2015-05-11 22:23 ` Stefan Monnier
2015-05-12 11:52 ` Phillip Lord
2015-05-12 20:15 ` Stefan Monnier
2015-05-12 20:59 ` Phillip Lord
2015-05-13 12:32 ` Stefan Monnier
2015-05-13 15:40 ` Phillip Lord
2015-05-14 15:28 ` Stefan Monnier
2015-05-15 12:27 ` Phillip Lord
2015-05-15 18:08 ` Stefan Monnier
2015-05-15 19:49 ` Phillip Lord
2015-05-15 23:45 ` Stefan Monnier
2015-05-16 13:31 ` Phillip Lord [this message]
2015-05-19 11:59 ` Phillip Lord
2015-05-19 19:42 ` Stefan Monnier
2015-05-19 21:48 ` Phillip Lord
2015-05-20 2:00 ` Stefan Monnier
2015-05-20 7:45 ` Phillip Lord
2015-05-20 12:53 ` Stefan Monnier
2015-05-21 11:15 ` Phillip Lord
2015-05-21 15:44 ` Stefan Monnier
2015-05-21 17:03 ` Phillip Lord
2015-05-27 11:46 ` Phillip Lord
2015-06-29 0:46 ` Stefan Monnier
2015-08-04 14:18 ` Phillip Lord
2015-08-06 21:02 ` Phillip Lord
2015-08-06 22:20 ` Stefan Monnier
2015-08-07 13:40 ` Phillip Lord
2015-08-07 13:59 ` David Kastrup
2015-08-07 21:10 ` Phillip Lord
2015-08-08 5:39 ` David Kastrup
2015-08-08 9:58 ` Phillip Lord
2015-08-07 17:10 ` Stefan Monnier
2015-08-08 21:28 ` Stefan Monnier
2015-08-09 15:39 ` Phillip Lord
2015-08-09 16:30 ` Stefan Monnier
2015-08-09 16:50 ` Phillip Lord
2015-08-09 17:40 ` Stefan Monnier
2015-08-10 9:27 ` Phillip Lord
2015-08-10 21:21 ` Phillip Lord
2015-08-12 21:15 ` Stefan Monnier
2015-08-12 22:34 ` Phillip Lord
2015-08-13 2:23 ` Stefan Monnier
2015-08-21 9:40 ` Phillip Lord
2015-08-07 23:49 ` Davis Herring
2015-08-08 10:01 ` Phillip Lord
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=87iobsr6m2.fsf@newcastle.ac.uk \
--to=phillip.lord@newcastle.ac.uk \
--cc=emacs-devel@gnu.org \
--cc=monnier@iro.umontreal.ca \
/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.