Re: read a reply from the terminal

[Dan Nicolaescu <dann@ics.uci.edu>]

Eli Zaretskii <eliz@gnu.org> writes:

  > > From: Dan Nicolaescu <dann@ics.uci.edu>
  > > Date: Sun, 15 Jul 2007 08:30:00 -0700
  > > Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
  > > 
  > > Andreas Schwab <schwab@suse.de> writes:
  > > 
  > >   > Dan Nicolaescu <dann@ics.uci.edu> writes:
  > >   > 
  > >   > > !       ;; Try to find out the type of terminal by sending a "Secondary
  > >   > > !       ;; Device Attributes (DA)" query.
  > >   > > !       (send-string-to-terminal "\e[>0c")
  > >   > > ! 
  > >   > > !       ;; The reply should be of the form: \e [ > NUMBER1 ; NUMBER2 ; NUMBER3 c
  > >   > > !       (when (equal (read-event) ?\e)
  > >   > 
  > >   > > ! 	(when (equal (read-event) 91)
  > >   > > ! 	  (while (not (equal (setq chr (read-event)) ?c))
  > >   > > ! 	    (setq str (concat str (string chr))))
  > >   > 
  > >   > What if the terminal is ignoring the query, or there is some other
  > >   > communication problem, wouldn't that mean that read-event would hang
  > >   > here?  IMHO the calls should use the timeout feature.
  > > 
  > > Good point.
  > 
  > I thought about the same problem as Andreas, but didn't ask the
  > question since you told that you've tested the code on many terminals,
  > and I assumed those terminals included at least one that didn't
  > support this command.  If that's not so, I suggest to test the new
  > code (with timeout) on such a terminal, as well as on those which do
  > support the command.

I have now tested the code using a timeout of 0.1 on xterm, rxvt,
gnome-terminal, konsole, putty, and a very old xterm (from an old
Solaris). It works fine for all of them. All these terminals support
the "\e[>0c" query. 
I also tested it on a Linux console, that does not support the query.

It works fine everywhere.