From: phillip.lord@russet.org.uk (Phillip Lord)
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: [Emacs-diffs] fix/no-undo-boundary-on-secondary-buffer-change e5ff575 2/2: Add a timer to ensure undo-boundaries in buffers.
Date: Tue, 01 Sep 2015 13:24:26 +0100 [thread overview]
Message-ID: <87d1y272f9.fsf@russet.org.uk> (raw)
In-Reply-To: <jwvio7xsbga.fsf-monnier+emacsdiffs@gnu.org> (Stefan Monnier's message of "Sat, 29 Aug 2015 23:30:13 -0400")
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> +(defun undo-ensure-boundary ()
>> + "Add an `undo-boundary' if `buffer-undo-list' is long.
>> +
>> +Return t if an undo boundary has been added.
>> +
>> +Normally, Emacs will only garbage collect data from
>> +`buffer-undo-list' when this list is longer than `undo-limit'. It
>> +then collects data from after the first `undo-boundary' after
>> +`undo-limit'. If there are no boundaries in the list,
>> +`buffer-undo-list' will grow until it reaches
>> +`undo-outer-limit' (by default a much larger value than
>> +`undo-limit'), when it will discard the data anyway. In this
>> +case, however, it is treated as an exceptional case, and the a
>> +warning is signalled.
>> +
>> +This function add an `undo-boundary' to `buffer-undo-list' if
>> +there is no other `undo-boundary', and `buffer-undo-list' is
>> +longer than `undo-limit'. It provides a useful default mechanism
>> +for adding an `undo-boundary' which retains data where possible,
>> +without signalling warnings to the user."
>
> I think this makes sense, but we should do it in the GC code, then.
It's possible, but it then negates the utility of the
`under-outer-limit' functionality. The point is that after
undo-outer-limit GC ditches the undo data anyway in the absence of any
boundaries, but does so noisily. But, if we run undo-ensure-boundary
before compaction, the boundary will mean the undo-list is always
GC'able with noise.
Phil
next prev parent reply other threads:[~2015-09-01 12:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20150821093606.11577.60349@vcs.savannah.gnu.org>
[not found] ` <E1ZSik4-000326-4S@vcs.savannah.gnu.org>
2015-08-30 3:30 ` [Emacs-diffs] fix/no-undo-boundary-on-secondary-buffer-change e5ff575 2/2: Add a timer to ensure undo-boundaries in buffers Stefan Monnier
2015-09-01 12:24 ` Phillip Lord [this message]
2015-09-01 16:16 ` Stefan Monnier
2015-09-01 17:19 ` Phillip Lord
2015-09-06 23:03 ` Stefan Monnier
2015-09-14 14:41 ` RFM: How to make a buffer-local var in C layer Phillip Lord
2015-09-15 1:48 ` Stefan Monnier
2015-09-15 12:08 ` Phillip Lord
2015-09-15 14:18 ` Stefan Monnier
2015-09-15 14:20 ` Stefan Monnier
2015-09-15 15:27 ` Phillip Lord
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