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: Mon, 11 May 2015 12:46:38 +0100 [thread overview]
Message-ID: <87617zl4kh.fsf@newcastle.ac.uk> (raw)
In-Reply-To: <jwvfv733nlw.fsf-monnier+emacs@gnu.org> (Stefan Monnier's message of "Sun, 10 May 2015 21:42:51 -0400")
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> I am wondering why the "nil" undo-boundaries get inserted when I change
>> *a different* buffer. This does not really make sense to me, and is
>> causing breakage in my package.
>
> The 3 separate undo entries you're seeing are actually the "normal"
> outcome (one undo-boundary per buffer-modifying command).
>
> self-insert-command has special ad-hoc code to try and merge sequences
> of single-char insertions by removing the previous undo-boundary.
> Which is why you normally only see a single undo entry.
>
> In your second case, I suspect that this ad-hoc code doesn't get to do
> what it's intended to do, because it does not recognize the
> undo-boundary that is candidate for removal as being "an undo-boundary
> we've auto-inserted". So, self-insert-command thinks that this
> undo-boundary may have been inserted by an explicit call to
> `undo-boundary' at the end of the previous command, in which case it
> should not be removed.
>
> The relevant code is in the remove_excessive_undo_boundaries function,
> in src/cmds.c.
Unfortunately, this is a general problem. Try enabling the a-c-f I sent
previously, and then run "fill-paragraph" on an overly long line.
With after-change-hook disabled....
Now is the winter of our discontent made glorious summer by the sun over york, whether it is
M-q
Now is the winter of our discontent made glorious summer by the sun over york,
whether it is
C-/
Now is the winter of our discontent made glorious summer by the sun over york, whether it is
With after-change-hook enabled...
Now is the winter of our discontent made glorious summer by the sun over york, whether it is
M-q
Now is the winter of our discontent made glorious summer by the sun over york,
whether it is
C-/
Now is the winter of our discontent made glorious summer by the sun over york,
whether it is
C-/
Now is the winter of our discontent made glorious summer by the sun over york,
whether it is
So, I have to do two undo's rather than one.
The problem seems to come from here in record_point, in undo.c
if ((current_buffer != last_undo_buffer)
/* Don't call Fundo_boundary for the first change. Otherwise we
risk overwriting last_boundary_position in Fundo_boundary with
PT of the current buffer and as a consequence not insert an
undo boundary because last_boundary_position will equal pt in
the test at the end of the present function (Bug#731). */
&& (MODIFF > SAVE_MODIFF))
Fundo_boundary ();
last_undo_buffer = current_buffer;
The a-c-f call causes an undo-able in scratch which means that
"current-buffer != last_undo_buffer" succeeds, which forces an
Fundo_boundary call on the NEXT call to record_point which is why I
cannot see this boundary on a-c-f.
The best thing that I can think of at the moment is to use
post-command-hook to clean up the excessive undo-boundaries, but I am
not sure how I am going to work out which ones are "real" and which ones
not. The obvious solution (delete all those adding since the last
command) will fail for both self-insert-command's logic and anywhere
else that undo-boundary has been explicitly called.
Better ideas welcome.
Phil
next prev parent reply other threads:[~2015-05-11 11:46 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 [this message]
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
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
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