[gdm] daemon: check for Xwayland availability

[Frédéric Crozat <fcrozat src gnome org>]

commit 9ab95809ddd201c2c8b030a814287c3be73d03be
Author: Frederic Crozat <fcrozat suse com>
Date:   Mon Sep 18 15:53:36 2017 +0200

    daemon: check for Xwayland availability
    
    prevent gnome-shell crash when testing Wayland session
    if Xwayland isn't installed.
    
    https://bugzilla.gnome.org/show_bug.cgi?787837

 daemon/gdm-local-display-factory.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/daemon/gdm-local-display-factory.c b/daemon/gdm-local-display-factory.c
index 7a4643d..95bdc59 100644
--- a/daemon/gdm-local-display-factory.c
+++ b/daemon/gdm-local-display-factory.c
@@ -450,7 +450,7 @@ gdm_local_display_factory_sync_seats (GdmLocalDisplayFactory *factory)
 #ifdef ENABLE_WAYLAND_SUPPORT
                         gboolean wayland_enabled = FALSE;
                         if (gdm_settings_direct_get_boolean (GDM_KEY_WAYLAND_ENABLE, &wayland_enabled)) {
-                                if (wayland_enabled) {
+                                if (wayland_enabled && g_file_test ("/usr/bin/Xwayland", 
G_FILE_TEST_IS_EXECUTABLE) ) {
                                         session_type = "wayland";
                                 }
                         }