terminal: signal object removal during sysview_context_stop()

Now that we no longer propagate callback return values, we can safely call
into user-callbacks during sysview_context_stop(). This way, users can
rely on all objects to be removed via callbacks (except if they failed
during object creation). This avoids duplicating any object hashtables on
the users' side and reduces memory consumption.

src/libsystemd-terminal/evcat.c

@@ -330,7 +330,8 @@ static int evcat_sysview_fn(sysview_context *c, void *userdata, sysview_event *e
         case SYSVIEW_EVENT_SESSION_REMOVE:
                 idev_session_disable(e->idev_session);
                 e->idev_session = idev_session_free(e->idev_session);
-                sd_event_exit(e->event, 0);
+                if (sd_event_get_exit_code(e->event, &r) == -ENODATA)
+                        sd_event_exit(e->event, 0);
                 break;
         case SYSVIEW_EVENT_SESSION_ATTACH:
                 d = ev->session_attach.device;

src/libsystemd-terminal/modeset.c

@@ -332,7 +332,8 @@ static int modeset_sysview_fn(sysview_context *c, void *userdata, sysview_event
                 grdev_session_restore(m->grdev_session);
                 grdev_session_disable(m->grdev_session);
                 m->grdev_session = grdev_session_free(m->grdev_session);
-                sd_event_exit(m->event, 0);
+                if (sd_event_get_exit_code(m->event, &r) == -ENODATA)
+                        sd_event_exit(m->event, 0);
                 break;
         case SYSVIEW_EVENT_SESSION_ATTACH:
                 d = ev->session_attach.device;

src/libsystemd-terminal/sysview.c

@@ -1437,20 +1437,6 @@ void sysview_context_stop(sysview_context *c) {
 
         log_debug("sysview: stop");
 
-        c->running = false;
-        c->scanned = false;
-        c->event_fn = NULL;
-        c->userdata = NULL;
-        c->scan_src = sd_event_source_unref(c->scan_src);
-        context_ud_stop(c);
-        context_ld_stop(c);
-
-        /*
-         * Event-callbacks are already cleared, hence we can safely ignore
-         * return codes of the context_remove_*() helpers. They cannot be
-         * originated from user-callbacks, so we already handled them.
-         */
-
         while ((device = hashmap_first(c->device_map)))
                 context_remove_device(c, device);
 
@@ -1459,6 +1445,14 @@ void sysview_context_stop(sysview_context *c) {
 
         while ((seat = hashmap_first(c->seat_map)))
                 context_remove_seat(c, seat);
+
+        c->running = false;
+        c->scanned = false;
+        c->event_fn = NULL;
+        c->userdata = NULL;
+        c->scan_src = sd_event_source_unref(c->scan_src);
+        context_ud_stop(c);
+        context_ld_stop(c);
 }
 
 static int context_scan_fn(sd_event_source *s, void *userdata) {