bug#20677: tooltips generate garbage

[Eli Zaretskii]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Cc: 20677@debbugs.gnu.org,  Angelo Graziosi <angelo.graziosi@alice.it>
> Date: Tue, 02 Jun 2015 17:54:27 +0200
> 
> Michael Heerdegen <michael_heerdegen@web.de> writes:
> 
> > Mmh, wait, I tested too superficially.  Reverting this change and "make"
> > doesn't make a difference.  Will try again with "make bootstrap"...
> 
> ... no, reverting that change _doesn't_ make a difference here.

Does it even compile?  I think it shouldn't compile.  Or maybe I'm
missing something.

> BTW, in dired, I can always reproduce the problem by hovering with the
> mouse.  Where text is displayed, the artifact is not visible, only on
> regions where the buffer is empty.

So this probably means we don't clear the area that was obscured by
the tip, we only redisplay the text in the obscured region.  Does this
match what you see?

Can you see whether Emacs gets an expose event when the tip pops down?