logind: extract has_vts() from can_multi_session()

We currently use seat_can_multi_session() to test for two things:
 * whether the seat can handle session-switching
 * whether the seat has VTs

As both are currently logically equivalent, we didn't care. However, we
want to allow session-switching on seats without VTs, so split this helper
into:
 * seat_can_multi_session(): whether session-switching is supported
 * seat_has_vts(): whether the seat has VTs

Note that only one seat on a system can have VTs. There is only one set of
them. We automatically assign them to seat0 as usual.

With this patch in place, we can easily add new session-switching/tracking
methods without breaking any VT code as it is now protected by has_vts(),
no longer by can_multi_session().

1 files changed, 1 insertions, 0 deletions

diff --git a/src/login/logind-seat.h b/src/login/logind-seat.h
index 47fe89a690..d3438b8495 100644
--- a/src/login/logind-seat.h
+++ b/src/login/logind-seat.h
@@ -60,6 +60,7 @@ int seat_preallocate_vts(Seat *s);
 
 int seat_attach_session(Seat *s, Session *session);
 
+bool seat_has_vts(Seat *s);
 bool seat_is_seat0(Seat *s);
 bool seat_can_multi_session(Seat *s);
 bool seat_can_tty(Seat *s);