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

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 30 Mar 2012 09:43:52 +0200
> From: "Jan D." <jan.h.d@swipnet.se>
> CC: Stephen Berman <stephen.berman@gmx.net>, cyd@gnu.org, 
>  7464@debbugs.gnu.org
> 
> It probably has something to do with the fact that Gtk+ scrollbars 
> aren't handeled by the display engine and we therefore have to force a 
> redraw of the scroll bars at certain points so the scrollbars look ok. 
> Presumably one of these redraws does something that triggers a redraw of 
> mouse highlight?  It might be that a redraw of the scroll bar generates 
> some X expose/configuration event that in turn invokes the display 
> engine.  I'm just speculating.

I think your speculation is exactly right.  Perhaps Stephen or someone
else who has access to a GTK build could confirm that an extra
redraw of mouse highlight is triggered at some point in this scenario.

Anyway, I think it is not important (however interesting and exciting)
to determine the exact reason which causes the bug not to appear in
the GTK build.  It suffices to say that any non-GTK build suffers from
this bug, and suffered in the past (Emacs 23 at least) as well.  I
think this information, and the patch that cures the bug I posted
earlier, is enough for Chong and Stefan to make the decision whether
to install the change now or defer it until after v24.1.