[gnome-screensaver] Make sure it cannot be running twice

[William Jon McCann <mccann src gnome org>]

commit 85d22a5d784b2b8201054257f8696138de1e1b70
Author: Marc Deslauriers <marc deslauriers ubuntu com>
Date:   Wed Feb 16 08:40:15 2011 -0500

    Make sure it cannot be running twice
    
    It is currently possible to start gnome-screensaver twice because
    of a race condition. This change makes sure that we bail out if
    we cannot become the primary owner of the bus name.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=642462

 src/gs-listener-dbus.c |   19 ++++++++++++++-----
 1 files changed, 14 insertions(+), 5 deletions(-)
---
diff --git a/src/gs-listener-dbus.c b/src/gs-listener-dbus.c
index 6d0d4e5..e11c7fc 100644
--- a/src/gs-listener-dbus.c
+++ b/src/gs-listener-dbus.c
@@ -1169,7 +1169,7 @@ gboolean
 gs_listener_acquire (GSListener *listener,
                      GError    **error)
 {
-        gboolean  acquired;
+        int       res;
         DBusError buserror;
         gboolean  is_connected;
 
@@ -1213,9 +1213,10 @@ gs_listener_acquire (GSListener *listener,
                 return FALSE;
         }
 
-        acquired = dbus_bus_request_name (listener->priv->connection,
-                                          GS_LISTENER_SERVICE,
-                                          0, &buserror) != -1;
+        res = dbus_bus_request_name (listener->priv->connection,
+                                     GS_LISTENER_SERVICE,
+                                     DBUS_NAME_FLAG_DO_NOT_QUEUE,
+                                     &buserror);
         if (dbus_error_is_set (&buserror)) {
                 g_set_error (error,
                              GS_LISTENER_ERROR,
@@ -1223,6 +1224,14 @@ gs_listener_acquire (GSListener *listener,
                              "%s",
                              buserror.message);
         }
+        if (res == DBUS_REQUEST_NAME_REPLY_EXISTS) {
+                g_set_error (error,
+                             GS_LISTENER_ERROR,
+                             GS_LISTENER_ERROR_ACQUISITION_FAILURE,
+                             "%s",
+                             _("screensaver already running in this session"));
+                return FALSE;
+        }
 
         dbus_error_free (&buserror);
 
@@ -1263,7 +1272,7 @@ gs_listener_acquire (GSListener *listener,
                                     NULL);
         }
 
-        return acquired;
+        return (res != -1);
 }
 
 static char *