GNU bug report logs - #22303
24.5; toggle-truncate-lines not mentioned in docstring for truncate-lines nor in elisp manual

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: phs <phs <at> lsv.fr>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.5; toggle-truncate-lines not mentioned in docstring for
 truncate-lines nor in elisp manual
Date: Mon, 4 Jan 2016 10:30:17 +0100

In general, changing the value of `truncate-lines' should be done via 
`toggle-truncate-lines' not by `(setq truncate-lines ..)'

However the documentation string for `truncate-lines' does not mention 
the existence of `toggle-truncate-lines', nor is it mentioned in the
elisp manual (section "37.3 Truncation").

It seems that modifying `truncate-lines' with just `(setq ..)' may 
suffer from redisplay problems, see 
http://emacs.stackexchange.com/questions/19228 for a way to trip the 
problem from emacs -Q.

--phs

In GNU Emacs 24.5.1 (x86_64-apple-darwin13.4.0, NS apple-appkit-1265.21)
 of 2015-04-10 on builder10-9.porkrind.org
Windowing system distributor `Apple', version 10.3.1404
Configured using:
 `configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application 
Support/Emacs/site-lisp''

Important settings:
  value of $LC_ALL: en_US
  value of $LANG: en_US
  locale-coding-system: utf-8-unix

-- 
Philippe SCHNOEBELEN,       	                  www.lsv.ens-cachan.fr/~phs
LSV, CNRS UMR 8643 & ENS de Cachan   		  Tel: (+33/0) 147 407 530
"Algebraic symbols are used when you do not know what you are talking about"

Message #10 received at 22303-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: phs <at> lsv.fr
Cc: 22303-done <at> debbugs.gnu.org
Subject: Re: bug#22303: 24.5;
 toggle-truncate-lines not mentioned in docstring for truncate-lines
 nor in elisp manual
Date: Mon, 04 Jan 2016 19:11:31 +0200

> From: phs <phs <at> lsv.fr>
> Date: Mon, 4 Jan 2016 10:30:17 +0100
> 
> In general, changing the value of `truncate-lines' should be done via 
> `toggle-truncate-lines' not by `(setq truncate-lines ..)'
> 
> However the documentation string for `truncate-lines' does not mention 
> the existence of `toggle-truncate-lines', nor is it mentioned in the
> elisp manual (section "37.3 Truncation").
> 
> It seems that modifying `truncate-lines' with just `(setq ..)' may 
> suffer from redisplay problems, see 
> http://emacs.stackexchange.com/questions/19228 for a way to trip the 
> problem from emacs -Q.

Thanks for pointing this out.

The answers on stackexchange are incorrect: there's nothing wrong with
setting 'truncate-lines' directly.  The situation described there
revealed a bug, which I just fixed for the next release.

I see no need to change the documentation in this regard.

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