GNU bug report logs - #13882
24.2; saveplace.el limit drop least recently used

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Karl Fogel <kfogel <at> red-bean.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#13882: closed (24.2; saveplace.el limit drop least recently used)
Date: Wed, 13 Mar 2013 19:01:01 +0000

[Message part 1 (text/plain, inline)]

Your message dated Wed, 13 Mar 2013 13:59:12 -0500
with message-id <87vc8vktxb.fsf <at> kwarm.red-bean.com>
and subject line Re: bug#13882: 24.2; saveplace.el limit drop least recently used
has caused the debbugs.gnu.org bug report #13882,
regarding 24.2; saveplace.el limit drop least recently used
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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13882: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13882
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[Message part 2 (message/rfc822, inline)]

From: Kevin Ryde <user42 <at> zip.com.au>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.2; saveplace.el limit drop least recently used
Date: Wed, 06 Mar 2013 07:49:14 +1100

[Message part 3 (text/plain, inline)]

When saveplace.el reaches save-place-limit, the file positions retained
via ~/.emacs-places are the first limit-many in alphabetical order.
I hoped instead it would be the first limit-many most recently used.
Ie. drop the least recently visited files in order to enforce the limit.

I struck this when I reached my save-place-limit with lots of files I
had visited long ago but which happened to be alphabetically before ones
I was visiting now.  The save-place feature no longer saved places
across sessions for files I now visited.

The effect can be seen by setting a small limit per init.el below.  Then
foo.el to visit three files successively

    HOME=`pwd` emacs -Q -l ./init.el -l ./foo.el

This leaves .emacs-places (in the current directory due to faked $HOME)
containing

    (("/tmp/aa" . 4)
     ("/tmp/bb" . 4)
     ("/tmp/cc" . 4))

Notice /tmp/cc was the most recently visited file but it's at the end of
the list and will be truncated when load-save-place-alist-from-file
enforces save-place-limit of 2.

    HOME=`pwd` emacs -Q -l ./init.el /tmp/cc
    =>
    point is at start of buffer /tmp/cc
    I hoped it would be at the end from the last visit

Note that you must exit and restart emacs to see the effect, because
save-place-limit is only enforced by load-save-place-alist-from-file.
Within a session there's no limit, only in reading the .emacs-places
file on restarting emacs.

I get some joy from not sorting save-place-alist when saving per change
below.

I believe save-place-to-alist keeps save-place-alist in "most recent
first" order (by delq and re-push to move an existing entry to the
start), and that that order should be preserved when saving.

2013-03-04  Kevin Ryde  <user42 <at> zip.com.au>

	* saveplace.el (save-place-alist-to-file): Don't `sort'
	save-place-alist alphabetically, keep it in "most recent first" order.
	This ensures save-place-limit drops the least recently visited files,
	not the alphabetically last files.  Dropping alphabetically last files
	had meant save-place stopped working across sessions after
	.emacs-places filled with alphabetically early names.

[init.el (application/emacs-lisp, attachment)]

[foo.el (application/emacs-lisp, attachment)]

[saveplace.el.nosort.diff (text/x-diff, attachment)]

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In GNU Emacs 24.2.1 (i486-pc-linux-gnu, GTK+ Version 2.24.10)
 of 2012-09-10 on biber, modified by Debian
Configured using:
 `configure '--build' 'i486-linux-gnu' '--build' 'i486-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 '--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.2/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/i386-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars'
 'build_alias=i486-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall'
 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU
  value of $XMODIFIERS: nil
  locale-coding-system: iso-latin-1-unix
  default enable-multibyte-characters: t

[Message part 8 (message/rfc822, inline)]

From: Karl Fogel <kfogel <at> red-bean.com>
To: Kevin Ryde <user42 <at> zip.com.au>
Cc: Ian Dalton <iain.dalton <at> gmail.com>, 13882-done <at> debbugs.gnu.org,
	Dmitry Gutov <dgutov <at> yandex.ru>
Subject: Re: bug#13882: 24.2; saveplace.el limit drop least recently used
Date: Wed, 13 Mar 2013 13:59:12 -0500

Kevin Ryde <user42 <at> zip.com.au> writes:
>Ian Dalton <iain.dalton <at> gmail.com> writes:
>> I no longer use this setup, so I don't know how useful a change it was. I
>> think that the Unison UI had some kind of option to do guided file merges,
>> but it only worked for the usual simple line-oriented diff.
>
>Hmm.  Making the file line-wise probably helped, but I imagine there's
>no file format which could give the perfect result from the usual
>diff/patch contextual merges.
>
>How about keeping the line-by-line pretty print for everyone's
>readability, but drop the sort since it's actively harmful, and leave
>anything more for future thought.

Done; see revision below.  Thanks, Dmitry, Kevin, and Ian, for your
thorough & patient explanations.

  ------------------------------------------------------------
  revno: 112040
  revision-id: kfogel <at> red-bean.com-20130313185405-ibq2um8vj55d4x0a
  parent: eggert <at> cs.ucla.edu-20130313184222-yq69wjnyhzd6o40d
  committer: Karl Fogel <kfogel <at> red-bean.com>
  branch nick: trunk
  timestamp: Wed 2013-03-13 13:54:05 -0500
  message:
    * saveplace.el (save-place-alist-to-file): Don't sort
    `save-place-alist', just pretty-print it (bug#13882).
  modified:
    lisp/ChangeLog      changelog-20091113204419-o5vbwnq5f7feedwu-1432
    lisp/saveplace.el   saveplace.el-20091113204419-o5vbwnq5f7feedwu-622
  ------------------------------------------------------------

-Karl

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