bug#7464: 24.0.50; mouse highlighting vanishes upon unsplitting window

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 22 Nov 2010 19:54:21 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 7464@debbugs.gnu.org
> 
> > From: Stephen Berman <stephen.berman@gmx.net>
> > Date: Mon, 22 Nov 2010 15:57:51 +0100
> > Cc: 
> > 
> > 1. emacs -q
> > 2. C-x 2
> > 3. Put the mouse pointer over one of the links in the splash screen, so
> > that the link becomes highlighted.
> > 4. C-x 1
> > => The highlighting from step 3 disappears, although the mouse pointer
> > is still over the link.  If the cursor is moved onto the link, then the
> > character under the cursor shows highlighting again, and moving the
> > cursor within the link extends the highlighting.
> > 
> > This problem is reliably reproducible, also on earlier builds of Emacs
> > 24 I have, but not on Emacs 23.1.91 (I don't have 23.2).
> 
> I can reproduce it on Windows in Emacs 23.2.90 and also in stock Emacs
> 23.2 and Emacs 23.1.  I don't have Emacs 23.1.90 anymore to test.

From tinkering around a bit with GDB, it looks like some code removes
the mouse highlight from the glass without telling the display engine
about that.  That's why redisplay never re-highlights: it thinks the
mouse highlight is already active.