GNU bug report logs - #1495
emacs -nw inserts unwanted chars if user is impatient

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Paul R <paul.r.ml <at> gmail.com>
To: submit <at> debbugs.gnu.org
Subject: emacs -nw inserts unwanted chars if user is impatient
Date: Thu, 04 Dec 2008 22:46:20 +0100

Hi,

I usually work on X version of emacs 23. However, sometime, I just want
to alter a config file from the terminal. In this case I type 

   emacs -nw conf_file.conf

Very often I know that the line I want to go to is fairly low so before
emacs has finished to load I'm already pressing C-n waiting for the
display to show line and point. I guess a lot of user do the same and
often don't wait for the display to finish before typing what they want.

In this particular case, emacs would insert strange chars at point, for
example : 1;1704;0c

You won't be warned, and it will be saved along with your real
modifications, which is embarassing.

To reproduce, open any multiline file from the terminal, for example
.bash_history, with 'emacs -nw' and immediatly maintain C-n until the
display come up entirely. You should find at point the strange chars.

Tested with emacs23cvs with -Q on Gnu/Linux with xterm and
gnome-terminal.


-- 
  Paul

Message #14 received at 1495 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Chong Yidong <cyd <at> stupidchicken.com>
To: Dan Nicolaescu <dann <at> ics.uci.edu>
Cc: Paul R <paul.r.ml <at> gmail.com>, 1495 <at> debbugs.gnu.org,
        emacs-devel <at> gnu.org
Subject: Re: emacs -nw inserts unwanted chars if user is impatient
Date: Thu, 04 Dec 2008 23:10:35 -0500

Dan Nicolaescu <dann <at> ics.uci.edu> writes:

> I'm fairly confident this is due to the code in xterm.el that deals
> with modifyOtherKeys, the input probably comes while emacs is waiting
> from an answer from xterm.

This indeed seems to be the problem.

Discard pending input before doing the terminal query seems to fix the
bug for me.  I don't know if it's possible for the user's input to come
inat exactly at the correct moment to fool the terminal query; if so, a
more complicated solution might be required.

Thoughts?

*** trunk/lisp/term/xterm.el.~1.59.~	2008-09-30 20:01:30.000000000 -0400
--- trunk/lisp/term/xterm.el	2008-12-04 23:07:47.000000000 -0500
***************
*** 475,480 ****
--- 475,481 ----
  	  (str nil))
        ;; Try to find out the type of terminal by sending a "Secondary
        ;; Device Attributes (DA)" query.
+       (discard-input)
        (send-string-to-terminal "\e[>0c")
  
        ;; The reply should be of the form: \e [ > NUMBER1 ; NUMBER2 ; NUMBER3 c

Message #19 received at 1495 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Chong Yidong <cyd <at> stupidchicken.com>
Cc: Dan Nicolaescu <dann <at> ics.uci.edu>, 1495 <at> debbugs.gnu.org,
        Paul R <paul.r.ml <at> gmail.com>, emacs-devel <at> gnu.org
Subject: Re: emacs -nw inserts unwanted chars if user is impatient
Date: Thu, 11 Dec 2008 11:32:39 -0500

> Discard pending input before doing the terminal query seems to fix the
> bug for me.  I don't know if it's possible for the user's input to come
> inat exactly at the correct moment to fool the terminal query; if so, a
> more complicated solution might be required.

While arguing that there's probably no way to do much better than that,
it occurred to me that "the right way" to do it might be to move the
"check for \e [ > NUMBER1 ; NUMBER2 ; NUMBER3 c and run
xterm-turn-on-modify-other-keys if applicable" into the
input-decode-map.


        Stefan

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