The port maintainer (Antoine Jacoutot) has replied: it seems that this
is an issue with the new Xorg that comes with 4.3. This is what he
said:

> This looks like:
> http://sourceforge.net/tracker/index...&atid =100031
> which is fixed here:
> https://bugs.freedesktop.org/show_bug.cgi?id=13511#c1
> I'll test it and if it fixes it, I'll try to push it in our xenocara.

I willl test the patch myself when I get back home and report my
results here for future reference...

Thanassis.