bug#23819: 25.0.95; display botched badly in xterm window

[Eli Zaretskii <eliz@gnu.org>]

> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Wed, 22 Jun 2016 04:01:34 +0200
> 
> This appears to be a relatively recent regression in the emacs-25 
> branch.

How recent?  Can you estimate when this started to happen to you?  The
relevant file (xterm.el) hasn't been touched in months, except by you,
for the paste feature.

> I just now tried a similar recipe (without the '_'), and this time Emacs 
> contained the following text at the start of the (now-modified) 
> conf_post.h buffer:
> 
> 1;3201;0chas/* conf_post.h --- configure.ac includes this via AH_BOTTOM
> 
> and view-lossage showed the following:
>   C-s C-s C-s [isearch-forward]
>   ESC [ > [nil]
>   1 [self-insert-command]
>   ; [c-electric-semi&comma]
>   3 [self-insert-command]
>   2 [self-insert-command]
>   0 [self-insert-command]
>   1 [self-insert-command]
>   ; [c-electric-semi&comma]
>   0 [self-insert-command]
>   c [self-insert-command]
>   h [self-insert-command]
>   a [self-insert-command]
>   s [self-insert-command]
>   ESC x [execute-extended-command]
>   v [self-insert-command]
>   i [self-insert-command]
>   e [self-insert-command]
>   w [self-insert-command]
>   - [self-insert-command]
>   l [self-insert-command]

The "ESC [ > 1;3201;0c" thingy is the response to query by
xterm--query, see xterm--version-handler.  Is it true that all these
problems happen right in the beginning of a session?  What happens if
you wait at least 2 sec after starting a session, without typing any
commands -- do these problems still happen?

> My guess is that there is something wrong with the initial handshake 
> with the terminal, to find out its characteristics; if memory serves 
> this is something we've fiddled with in emacs-25 reasonably recently.

Your guess is probably right, except that I don't see any fiddling in
the Git log, certainly not recently.  So if this indeed started
happening recently, there must be some other factor at work here.