[gdm/benzea/wait-seat-graphical: 54/54] local-display-factory: Wait for seats to become graphical

[Benjamin Berg <bberg src gnome org>]

commit 660a3e97d6847dd2801ba0a086852d2835606c12
Author: Benjamin Berg <bberg redhat com>
Date:   Tue Feb 9 15:43:05 2021 +0100

    local-display-factory: Wait for seats to become graphical
    
    It may happen that seats are not graphical initially because the DRM
    device is not ready yet. In that case, ignore the seat and wait for the
    CanGraphical property notification in order to add it at that point.
    
    Fixes: #662

 daemon/gdm-local-display-factory.c | 59 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
---
diff --git a/daemon/gdm-local-display-factory.c b/daemon/gdm-local-display-factory.c
index e7cafeb10..bfb472088 100644
--- a/daemon/gdm-local-display-factory.c
+++ b/daemon/gdm-local-display-factory.c
@@ -62,6 +62,7 @@ struct _GdmLocalDisplayFactory
 
         guint            seat_new_id;
         guint            seat_removed_id;
+        guint            seat_prop_changed_id;
 
 #if defined(ENABLE_USER_DISPLAY_SERVER)
         unsigned int     active_vt;
@@ -610,6 +611,11 @@ on_seat_new (GDBusConnection *connection,
         const char *seat;
 
         g_variant_get (parameters, "(&s&o)", &seat, NULL);
+
+        /* We retry adding it if the CanGraphical value changes. */
+        if (!sd_seat_can_graphical (seat))
+                return;
+
         create_display (GDM_LOCAL_DISPLAY_FACTORY (user_data), seat, NULL, FALSE);
 }
 
@@ -628,6 +634,44 @@ on_seat_removed (GDBusConnection *connection,
         delete_display (GDM_LOCAL_DISPLAY_FACTORY (user_data), seat);
 }
 
+static void
+on_seat_prop_changed (GDBusConnection *connection,
+                      const gchar     *sender_name,
+                      const gchar     *object_path,
+                      const gchar     *interface_name,
+                      const gchar     *signal_name,
+                      GVariant        *parameters,
+                      gpointer         user_data)
+{
+        const gchar *seat = NULL;
+        g_autoptr(GVariant) changed_props = NULL;
+        g_autoptr(GVariant) changed_prop = NULL;
+        g_autofree gchar **invalidated_props = NULL;
+        gboolean changed = FALSE;
+
+        /* Extract seat id, i.e. the last element of the object path. */
+        seat = strrchr (object_path, '/');
+        if (seat == NULL)
+                return;
+        seat += 1;
+
+        g_variant_get (parameters, "(s@a{sv}^a&s)", NULL, &changed_props, &invalidated_props);
+
+        changed_prop = g_variant_lookup_value (changed_props, "CanGraphical", NULL);
+        if (changed_prop)
+                changed = TRUE;
+        if (!changed && g_strv_contains (invalidated_props, "CanGraphical"))
+                changed = TRUE;
+
+        if (!changed)
+                return;
+
+        if (sd_seat_can_graphical (seat))
+                create_display (GDM_LOCAL_DISPLAY_FACTORY (user_data), seat, NULL, FALSE);
+        else
+                delete_display (GDM_LOCAL_DISPLAY_FACTORY (user_data), seat);
+}
+
 static gboolean
 lookup_by_session_id (const char *id,
                       GdmDisplay *display,
@@ -866,6 +910,16 @@ gdm_local_display_factory_start_monitor (GdmLocalDisplayFactory *factory)
                                                                              on_seat_removed,
                                                                              g_object_ref (factory),
                                                                              g_object_unref);
+        factory->seat_prop_changed_id = g_dbus_connection_signal_subscribe (factory->connection,
+                                                                            "org.freedesktop.login1",
+                                                                            
"org.freedesktop.DBus.Properties",
+                                                                            "PropertiesChanged",
+                                                                            NULL,
+                                                                            "org.freedesktop.login1.Seat",
+                                                                            
G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_NAMESPACE,
+                                                                            on_seat_prop_changed,
+                                                                            g_object_ref (factory),
+                                                                            g_object_unref);
 
 #if defined(ENABLE_USER_DISPLAY_SERVER)
         io_channel = g_io_channel_new_file ("/sys/class/tty/tty0/active", "r", NULL);
@@ -894,6 +948,11 @@ gdm_local_display_factory_stop_monitor (GdmLocalDisplayFactory *factory)
                                                       factory->seat_removed_id);
                 factory->seat_removed_id = 0;
         }
+        if (factory->seat_prop_changed_id) {
+                g_dbus_connection_signal_unsubscribe (factory->connection,
+                                                      factory->seat_prop_changed_id);
+                factory->seat_prop_changed_id = 0;
+        }
 #if defined(ENABLE_USER_DISPLAY_SERVER)
         if (factory->active_vt_watch_id) {
                 g_source_remove (factory->active_vt_watch_id);