logind: mute/restore VT on behalf of session controllers

If a session process calls TakeControl(), we now put the VT into
KD_GRAPHICS+K_OFF mode. This way, the new session controller can solely
rely on the logind-dbus API to manage the session.

Once the controller exits or calls ReleaseControl(), we restore the VT. We
also restore it, if we lost a controller during crash/restart (but only if
there really *was* a controller previously).

Note that we also must put the VT into VT_PROCESS mode. We want VT_AUTO
semantics, but VT_AUTO+KD_GRAPHICS actually disables *all* VT switches
(who came up with that great idea?). Hence, we set VT_PROCESS for logind
but acknowledge *all* requests immediately.

If a compositor wants custom VT setups, they can still get this by *first*
calling TakeControl() and afterwards setting up the VT. logind doesn't
touch the VT during controller runtime, only during setup/teardown. This
is actually what weston already does.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/login/logind-session.h b/src/login/logind-session.h
index f7a9dbc24..aab39b72e 100644
--- a/src/login/logind-session.h
+++ b/src/login/logind-session.h
@@ -89,8 +89,10 @@ struct Session {
         char *scope;
         char *scope_job;
 
-        int vtnr;
         Seat *seat;
+        int vtnr;
+        int vtfd;
+        sd_event_source *vt_source;
 
         pid_t leader;
         uint32_t audit_id;
@@ -162,6 +164,9 @@ SessionClass session_class_from_string(const char *s) _pure_;
 const char *kill_who_to_string(KillWho k) _const_;
 KillWho kill_who_from_string(const char *s) _pure_;
 
+void session_mute_vt(Session *s);
+void session_restore_vt(Session *s);
+
 bool session_is_controller(Session *s, const char *sender);
 int session_set_controller(Session *s, const char *sender, bool force);
 void session_drop_controller(Session *s);