Composited locate mouse effect

[Carlos Garnacho <carlosg gnome org>]

Hi!,

Now that metacity has a composite manager, I thought it'd be nice to
have a "locate mouse" effect that's more appealing than the current
one :), so here's my try!

http://www.gnome.org/~carlosg/stuff/locate-pointer-composited.gif

You can see the code at:

http://www.gnome.org/~carlosg/stuff/random/locate-mouse.tar.bz2

At the moment it's separated from the g-s-d source, but it won't be hard
to replace, it's still missing code to do the old animation if there's
no composite available, though.

Another pending issue is that it uses a GtkInvisible to get events from,
but GtkInvisible currently isn't able to receive style-set signals, so
changing theme ends doesn't update the effect color. While that gets
fixed, it should either use a hardcoded color or find another way to get
an updated GtkStyle.

To see the effect, just click on the window in the test app, would it be
possible to get it in for 2.22? I'd consider this just an UI change :)

Regards,
   Carlos