Created attachment 6725 GTK3.20 GDKSeat Conditional Functionality gdk_display_get_device_manager() and gdk_device_manager_get_client_pointer() are deprecated in GTK3.20 in favour of gdk_display_get_default_seat() and gdk_seat_get_pointer(). Attached is a patch that checks for GTK3.20 and if found, uses the new GdkSeat functionality.
Thanks, I've been meaning to fix that myself :) Pushed to master: http://git.xfce.org/apps/xfce4-notifyd/commit/?id=a27dd0f021698d2313593adc2a6406294cf01cb8