bug#27647: 26.0.50; Line numbers implemented natively disappear momentarily when frame out of focus

[Eli Zaretskii]

> Date: Tue, 17 Oct 2017 10:59:15 +0200
> From: martin rudalics <rudalics@gmx.at>
> CC: 27647@debbugs.gnu.org, Eli Zaretskii <eliz@gnu.org>, 
>  jonaswestlund101@gmail.com, npostavs@users.sourceforge.net, 
>  rom.skiad@gmail.com
> 
>  > ==> https://i.imgur.com/kB6gHDk.gifv <==
> 
> Apparently you move the mouse to some strange glyph on your mode line.
> Which one is that?  Other mode lines elements do not seem to cause it.

Actually, it looks like the numbers disappear when the mouse is on
parts of the mode line devoid of any glyphs.  Kaushal, did you
actually click on those empty parts, or just having the mouse hover
over them causes the numbers to disappear.

And does the problem go away if you disable GTK tooltips in favor of
the native tooltips?