bug#34819: 26.1; Blank help-echo tooltips for mode line menus

[Eli Zaretskii]

> From: Phil Sainty <psainty@orcon.net.nz>
> Cc: Daniel Colascione <dancol@dancol.org>
> Date: Thu, 14 Mar 2019 00:52:43 +1300
> 
> > Which probably means the root cause is not double buffering itself,
> > but some other change included in that commit.  I wonder if you can
> > audit the changes and try to identify potential culprits.
> 
> That code is well outside of my areas of expertise, so I'm not confident
> that I'd figure it out very easily.
> 
> I'm CCing this to Daniel Colascione -- I don't imagine anyone else is
> more familiar with that code than he is, so if anyone can intuitively
> narrow down the possible culprits here, it would likely be him.

Btw, I reckon this doesn't happen in the GTK build?  What if you set
x-gtk-use-system-tooltips to a nil value -- does the problem happen in
the GTK build as well then?