[gnome-panel] Add support for user switch with LightDM

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 140a7393cc74fd773db865223eff5e8ae7f003d2
Author: Balló György <ballogyor gmail com>
Date:   Fri Oct 17 19:06:53 2014 +0200

    Add support for user switch with LightDM

 gnome-panel/panel-menu-items.c |   69 +++++++++++++++++++++++++++++-----------
 1 files changed, 50 insertions(+), 19 deletions(-)
---
diff --git a/gnome-panel/panel-menu-items.c b/gnome-panel/panel-menu-items.c
index 6340a87..1421c29 100644
--- a/gnome-panel/panel-menu-items.c
+++ b/gnome-panel/panel-menu-items.c
@@ -441,32 +441,63 @@ static void
 panel_menu_item_activate_switch_user (GtkWidget *menuitem,
                                      gpointer   user_data)
 {
-       GdkScreen *screen;
-       GAppInfo  *app_info;
-
        if (panel_lockdown_get_disable_switch_user_s ())
                return;
 
-       screen = gtk_widget_get_screen (GTK_WIDGET (menuitem));
-       app_info = g_app_info_create_from_commandline (GDM_FLEXISERVER_COMMAND " " GDM_FLEXISERVER_ARGS,
-                                                      GDM_FLEXISERVER_COMMAND,
-                                                      G_APP_INFO_CREATE_NONE,
-                                                      NULL);
+       /* If running under LightDM switch to the greeter using dbus */
+       if (g_getenv("XDG_SEAT_PATH")) {
+               GDBusConnection *bus;
+               GError  *error = NULL;
+               GVariant *result = NULL;
+
+               bus = g_bus_get_sync (G_BUS_TYPE_SYSTEM, NULL, &error);
+               if (error)
+                       g_warning ("Failed to get system bus: %s", error->message);
+               g_clear_error (&error);
+
+               if (bus)
+                       result = g_dbus_connection_call_sync (bus,
+                                                             "org.freedesktop.DisplayManager",
+                                                             g_getenv ("XDG_SEAT_PATH"),
+                                                             "org.freedesktop.DisplayManager.Seat",
+                                                             "SwitchToGreeter",
+                                                             g_variant_new ("()"),
+                                                             G_VARIANT_TYPE ("()"),
+                                                             G_DBUS_CALL_FLAGS_NONE,
+                                                             -1,
+                                                             NULL,
+                                                             &error);
+                if (error)
+                        g_warning ("Failed to switch to greeter: %s", error->message);
+                g_clear_error (&error);
+
+                if (result)
+                        g_variant_unref (result);
+        } else {
+               GdkScreen *screen;
+               GAppInfo  *app_info;
 
-       if (app_info) {
-               GdkAppLaunchContext *launch_context;
-               GdkDisplay          *display;
+               screen = gtk_widget_get_screen (GTK_WIDGET (menuitem));
+               app_info = g_app_info_create_from_commandline (GDM_FLEXISERVER_COMMAND " " 
GDM_FLEXISERVER_ARGS,
+                                                              GDM_FLEXISERVER_COMMAND,
+                                                              G_APP_INFO_CREATE_NONE,
+                                                              NULL);
 
-               display = gdk_screen_get_display (screen);
-               launch_context = gdk_display_get_app_launch_context (display);
-               gdk_app_launch_context_set_screen (launch_context, screen);
+               if (app_info) {
+                       GdkAppLaunchContext *launch_context;
+                       GdkDisplay          *display;
 
-               g_app_info_launch (app_info, NULL,
-                                  G_APP_LAUNCH_CONTEXT (launch_context),
-                                  NULL);
+                       display = gdk_screen_get_display (screen);
+                       launch_context = gdk_display_get_app_launch_context (display);
+                       gdk_app_launch_context_set_screen (launch_context, screen);
 
-               g_object_unref (launch_context);
-               g_object_unref (app_info);
+                       g_app_info_launch (app_info, NULL,
+                                          G_APP_LAUNCH_CONTEXT (launch_context),
+                                          NULL);
+
+                       g_object_unref (launch_context);
+                       g_object_unref (app_info);
+               }
        }
 }