[gnome-panel/gnome-3-18] menu-items: fix user switching with gdm

[Alberts Muktupāvels <muktupavels src gnome org>]

commit fccf6f19cb30522a15346717f09e518e539711d7
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Fri Jul 29 03:59:15 2016 +0300

    menu-items: fix user switching with gdm
    
    https://bugzilla.gnome.org/show_bug.cgi?id=769009

 configure.ac                   |    1 +
 gnome-panel/panel-menu-items.c |   35 ++++++++++-------------------------
 2 files changed, 11 insertions(+), 25 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index c0db816..44829b8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -120,6 +120,7 @@ PKG_CHECK_MODULES(PANEL, gmodule-2.0 >= $GLIB_REQUIRED
                         pango >= $PANGO_REQUIRED
                         gtk+-3.0 >= $GTK_REQUIRED
                         cairo-xlib glib-2.0 >= $GLIB_REQUIRED
+                        gdm
                         gmodule-2.0 >= $GLIB_REQUIRED
                         gio-2.0 >= $GLIB_REQUIRED
                         gio-unix-2.0 >= $GLIB_REQUIRED
diff --git a/gnome-panel/panel-menu-items.c b/gnome-panel/panel-menu-items.c
index 4c62b90..2dfec6f 100644
--- a/gnome-panel/panel-menu-items.c
+++ b/gnome-panel/panel-menu-items.c
@@ -46,6 +46,7 @@
 #include <libpanel-util/panel-end-session-dialog.h>
 #include <libpanel-util/panel-session-manager.h>
 #include <libpanel-util/panel-show.h>
+#include <gdm/gdm-user-switching.h>
 
 #include "menu.h"
 #include "panel-action-button.h"
@@ -342,20 +343,20 @@ panel_menu_items_create_action_item (PanelActionButtonType action_type)
                                                         NULL, NULL, FALSE);
 }
 
-#define GDM_FLEXISERVER_COMMAND "gdmflexiserver"
-#define GDM_FLEXISERVER_ARGS    "--startnew"
-
 static void
 panel_menu_item_activate_switch_user (GtkWidget *menuitem,
                                      gpointer   user_data)
 {
+       GError *error;
+
        if (panel_lockdown_get_disable_switch_user_s ())
                return;
 
+       error = 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);
@@ -382,29 +383,13 @@ panel_menu_item_activate_switch_user (GtkWidget *menuitem,
                 if (result)
                         g_variant_unref (result);
         } else {
-               GdkScreen *screen;
-               GAppInfo  *app_info;
-
-               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 (app_info) {
-                       GdkAppLaunchContext *launch_context;
-                       GdkDisplay          *display;
-
-                       display = gdk_screen_get_display (screen);
-                       launch_context = gdk_display_get_app_launch_context (display);
-                       gdk_app_launch_context_set_screen (launch_context, screen);
+               gboolean ret;
 
-                       g_app_info_launch (app_info, NULL,
-                                          G_APP_LAUNCH_CONTEXT (launch_context),
-                                          NULL);
+               ret = gdm_goto_login_session_sync (NULL, &error);
 
-                       g_object_unref (launch_context);
-                       g_object_unref (app_info);
+               if (!ret) {
+                       g_warning ("Failed to switch to greeter: %s", error->message);
+                       g_error_free (error);
                }
        }
 }