toytoolkit assumes wl_seat-s are announced after the wl_data_device_manager

registry_handle_global() handles wl_seats and the wl_data_device_manager like this:

} else if (strcmp(interface, "wl_seat") == 0) {
	display_add_input(d, id, version);
} else /*...*/ if (strcmp(interface, "wl_data_device_manager") == 0) {
	d->data_device_manager_version = MIN(version, 3);
	d->data_device_manager =
		wl_registry_bind(registry, id,
				 &wl_data_device_manager_interface,
				 d->data_device_manager_version);
}

while display_add_input() does this:

if (d->data_device_manager) {
	input->data_device =
		wl_data_device_manager_get_data_device(d->data_device_manager,
						       input->seat);
	wl_data_device_add_listener(input->data_device,
				    &data_device_listener,
				    input);
}

So, in case the registry happens to announce wl_data_device_manager after a wl_seat, that seat ends up unable to copy/paste/drag-n-drop.

Weston does this:

$ weston-info | egrep 'data|seat'
interface: 'wl_data_device_manager', version: 3, name: 8
interface: 'wl_seat', version: 5, name: 10

and Mutter this:

$ weston-info | egrep 'data|seat'
interface: 'wl_data_device_manager', version: 3, name: 7
interface: 'wl_seat', version: 5, name: 16
	name: seat0

which is probably why this bug has gone unnoticed 😃