bug#29416: 26.0.90: display glitch

[Charles A. Roelli]

> From: Noam Postavsky <npostavs@users.sourceforge.net>
> Date: Thu, 23 Nov 2017 19:02:52 -0500
> 
> 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?

Yes, inhibiting double buffering fixes it.