bug#29416: 26.0.90: display glitch

[Noam Postavsky]

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Thu, 23 Nov 2017 21:07:18 +0100
>> From: charles@aurox.ch (Charles A. Roelli)
>> 
>> Using Ubuntu GNU/Linux and launching emacs -q on the pretest:
>> 
>> M-x find-function RET format-message RET
>> M-x load-theme RET wombat RET
>> C-5 C-v C-5 C-v
>> 
>> There are a few horizontal blue lines visible on the last line of:
>> 
>> > {
>> >    return styled_format (nargs, args, true);
>> > }
>> 
>> so that it looks a little like this instead:
>> 
>> > }                                        ___   _    ____ __
>
> I don't see this on my system (which is not GNU/Linux).

I don't see it on my Debian GNU/Linux box either (tried with both lucid
and gtk builds).  Does disabling double buffering have any effect?
Perhaps installed fonts could also be significant?