Xboard uses libcanberra for sound effects but since it's still based on GTK+ 2 and I have USE="gtk3 -gtk" for media-libs/libcanberra, I get the following warning:
> Gtk-Message: 10:21:29.616: Failed to load module "canberra-gtk-module"
I suggest maybe having a "sound" USE flag and something like this in the ebuild's RDEPEND:
"sound? ( media-libs/libcanberra[gtk] )"
Or maybe a hard dep with no USE flag at all...