bug#28591: 27.0.50; xterm-set-window-title

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 29 Sep 2017 07:57:00 -0400
> From: Mark Oteiza <mvoteiza@udel.edu>
> Cc: yamaoka@jpl.org, 28591@debbugs.gnu.org
> 
> Everything except foregrounding a client works (I did not test this),
> where the following occurs:
> 
>   Error in post-command-hook (xterm-set-window-title): (error "Terminal
>   is currently suspended")

This error comes from here:

  DEFUN ("send-string-to-terminal", Fsend_string_to_terminal,
	 Ssend_string_to_terminal, 1, 2, 0,
	 doc: /* Send STRING to the terminal without alteration.
  Control characters in STRING will have terminal-dependent effects.

  Optional parameter TERMINAL specifies the tty terminal device to use.
  It may be a terminal object, a frame, or nil for the terminal used by
  the currently selected frame.  In batch mode, STRING is sent to stdout
  when TERMINAL is nil.  */)
    (Lisp_Object string, Lisp_Object terminal)
  {

    ...
	if (! tty->output)
	  error ("Terminal is currently suspended");

So one way of fixing it would be to have a suspend-hook set some flag
which your post-command-hook would check, and avoid calling
send-string-to-terminal when the terminal is suspended.

Another possibility would be to add a utility function, called
'tty-suspended-p', which you could then test in your
post-command-hook.  Its implementation should test the tty->output
value.

Would any of this make sense?