bug#6758: 23.2; xterm.el: please provide an option to not discard input in terminal-init-xterm

[Jim Paris]

This bug report will be sent to the Free Software Foundation,
not to your local site managers!
Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the bug-gnu-emacs@gnu.org mailing list,
and to the gnu.emacs.bug news group.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug.  If you can, give
a recipe starting from `emacs -Q':


Since upgrading to emacs-23, the terminal-init-xterm function in term/xterm.el
performs a "discard-input" followed by a couple of xterm queries.  You
can see the effect of this in the "recent input" line below -- all I did
was start emacs and do M-x report-bug, the preceding input was generated
by the xterm in response to terminal-init-xterm's queries.

This causes several problems when I start emacs in a terminal:

- Everything that I type while emacs is still loading gets discarded.
  This problem is more common than you might initially think, because
  I very frequently load emacs and immediately hit C-s to search for
  something.  Now, the C-s gets lost and my search terms go into the
  buffer instead.  To reproduce this, just start emacs (preferably on
  a slow machine, or one with delays in ~/.emacs, for example)
  and start typing before emacs has finished loading.  Everything typed
  is lost.

- There are race conditions here.  If I'm typing when this
  query-response happens, my typing is discarded by terminal-init-xterm,
  and the actual xterm response gets inserted directly into my buffer as if
  I had typed it.  Since I type quickly, I see this quite frequently:
  I load emacs, start typing, and the buffer ends up with "0;251;0c" 
  rather than what I had typed.  This one is harder to reproduce, but
  it is not difficult for me if I just run "emacs -nw" from the
  commandline and quickly hit "asdfasdf" while it's loading.

I understand that the modify-other-keys feature is useful, but this
makes emacs-23 difficult to use.  Can an option be provided to disable
these probes?  Maybe we can just skip the discard-input and
query/response if the user provides, say, predetermined "xterm-version"
and "xterm-background-color" variables in their ~/.emacs?
That seems to be the quickest and easiest approach, although it requires
user intervention to work around the issue.

I can also imagine a more complete fix that would involve not flushing
the input buffer, and interpreting the Xterm responses in a more
asynchronous fashion:
- Don't discard input
- Send the \e[>0c probe
- Allow input into the buffer as usual, but for the next few seconds,
  interpret \e[>0;251;0c responses and perform
  (xterm-turn-on-modify-other-keys) etc. as necessary.

-jim


If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
For information about debugging Emacs, please read the file
/usr/share/emacs/23.2/etc/DEBUG.


In GNU Emacs 23.2.1 (x86_64-pc-linux-gnu, GTK+ Version 2.20.1)
 of 2010-05-16 on barber, modified by Debian
configured using `configure  '--build' 'x86_64-linux-gnu' '--build' 
'x86_64-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/emacs23:/etc/emacs:/usr/local/share/emacs/23.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.2/leim'
 '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 
'build_alias=x86_64-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 
'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: en_US.UTF-8
  value of $LC_MESSAGES: en_US
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: POSIX
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Text

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
ESC [ > 0 ; 2 5 1 ; 0 c ESC ] 1 1 ; r g b : 0 0 0 0 
/ 0 0 0 0 / 0 0 0 0 ESC \ ESC x r e p o r t TAB RE
T

Recent messages:
Loading /etc/emacs/site-start.d/50namazu2.el (source)...done
Loading /etc/emacs/site-start.d/50php-elisp.el (source)...done
Loading /etc/emacs/site-start.d/50psvn.el (source)...done
Loading /etc/emacs/site-start.d/51debian-el.el (source)...done
Loading /etc/emacs/site-start.d/70jim.el (source)...
Toggling menu-bar-mode off; better pass an explicit argument.
Ready.
Loading /etc/emacs/site-start.d/70jim.el (source)...done
Loading quail/latin-ltx...done
Ready.

Load-path shadows:
/usr/share/emacs/23.2/site-lisp/debian-startup hides 
/usr/share/emacs/site-lisp/debian-startup
/usr/share/emacs23/site-lisp/easypg/epg hides /usr/share/emacs/23.2/lisp/epg
/usr/share/emacs23/site-lisp/easypg/epa-mail hides 
/usr/share/emacs/23.2/lisp/epa-mail
/usr/share/emacs23/site-lisp/easypg/epa-dired hides 
/usr/share/emacs/23.2/lisp/epa-dired
/usr/share/emacs23/site-lisp/flim/sha1 hides /usr/share/emacs/23.2/lisp/sha1
/usr/share/emacs23/site-lisp/easypg/epa-file hides 
/usr/share/emacs/23.2/lisp/epa-file
/usr/share/emacs23/site-lisp/emacs-goodies-el/ido hides 
/usr/share/emacs/23.2/lisp/ido
/usr/share/emacs23/site-lisp/flim/md4 hides /usr/share/emacs/23.2/lisp/md4
/usr/share/emacs23/site-lisp/emacs-goodies-el/ibuffer hides 
/usr/share/emacs/23.2/lisp/ibuffer
/usr/share/emacs23/site-lisp/emacs-goodies-el/wdired hides 
/usr/share/emacs/23.2/lisp/wdired
/usr/share/emacs23/site-lisp/flim/hex-util hides 
/usr/share/emacs/23.2/lisp/hex-util
/usr/share/emacs23/site-lisp/easypg/epg-config hides 
/usr/share/emacs/23.2/lisp/epg-config
/usr/share/emacs23/site-lisp/easypg/epa hides /usr/share/emacs/23.2/lisp/epa
/usr/share/emacs23/site-lisp/dictionaries-common/ispell hides 
/usr/share/emacs/23.2/lisp/textmodes/ispell
/usr/share/emacs23/site-lisp/emacs-goodies-el/table hides 
/usr/share/emacs/23.2/lisp/textmodes/table
/usr/share/emacs23/site-lisp/dictionaries-common/flyspell hides 
/usr/share/emacs/23.2/lisp/textmodes/flyspell
/usr/share/emacs23/site-lisp/emacs-goodies-el/cfengine hides 
/usr/share/emacs/23.2/lisp/progmodes/cfengine
/usr/share/emacs23/site-lisp/flim/ntlm hides /usr/share/emacs/23.2/lisp/net/ntlm
/usr/share/emacs23/site-lisp/flim/hmac-def hides 
/usr/share/emacs/23.2/lisp/net/hmac-def
/usr/share/emacs23/site-lisp/flim/sasl hides /usr/share/emacs/23.2/lisp/net/sasl
/usr/share/emacs23/site-lisp/emacs-goodies-el/newsticker hides 
/usr/share/emacs/23.2/lisp/net/newsticker
/usr/share/emacs23/site-lisp/flim/sasl-digest hides 
/usr/share/emacs/23.2/lisp/net/sasl-digest
/usr/share/emacs23/site-lisp/flim/hmac-md5 hides 
/usr/share/emacs/23.2/lisp/net/hmac-md5
/usr/share/emacs23/site-lisp/flim/sasl-ntlm hides 
/usr/share/emacs/23.2/lisp/net/sasl-ntlm
/usr/share/emacs23/site-lisp/flim/sasl-cram hides 
/usr/share/emacs/23.2/lisp/net/sasl-cram
/usr/share/emacs23/site-lisp/latex-cjk-thai/thai-word hides 
/usr/share/emacs/23.2/lisp/language/thai-word

Features:
(shadow sort mail-extr message sendmail regexp-opt ecomplete rfc822 mml
mml-sec password-cache mm-decode mm-bodies mm-encode mailcap mail-parse
rfc2231 rfc2047 rfc2045 qp ietf-drums mailabbrev nnheader gnus-util
netrc time-date mm-util mail-prsvr gmm-utils wid-edit mailheader canlock
sha1 sha1-el hex-util hashcash mail-utils warnings emacsbug quail
help-mode easymenu view debian-el debian-el-loaddefs path-util byte-opt
bytecomp byte-compile advice help-fns advice-preload poe pym static
apel-ver product emacs-goodies-el emacs-goodies-custom
emacs-goodies-loaddefs epa-setup epa-file epa derived epg epg-config
epg-package-info dpkg-dev-el dpkg-dev-el-loaddefs tooltip ediff-hook
vc-hooks lisp-float-type mwheel x-win x-dnd font-setting tool-bar dnd
fontset image fringe lisp-mode register page menu-bar rfn-eshadow timer
select scroll-bar mldrag mouse jit-lock font-lock syntax facemenu
font-core frame cham georgian utf-8-lang misc-lang vietnamese tibetan
thai tai-viet lao korean japanese hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese case-table epa-hook
jka-cmpr-hook help simple abbrev loaddefs button minibuffer faces
cus-face files text-properties overlay md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote
make-network-process dbusbind system-font-setting font-render-setting
gtk x-toolkit x multi-tty emacs)