[metacity] prefs: use Gtk/DecorationLayout only under GNOME-Flashback

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 27f5c1fd55ac55dd15504705ae6ce0569b0aae61
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Fri Oct 30 20:59:12 2015 +0200

    prefs: use Gtk/DecorationLayout only under GNOME-Flashback
    
    https://bugzilla.gnome.org/show_bug.cgi?id=757044

 src/core/prefs.c |   16 +++++++++++++---
 1 files changed, 13 insertions(+), 3 deletions(-)
---
diff --git a/src/core/prefs.c b/src/core/prefs.c
index 3a4a9e6..6a29fdf 100644
--- a/src/core/prefs.c
+++ b/src/core/prefs.c
@@ -813,8 +813,14 @@ gtk_decoration_layout_changed (GtkSettings *settings,
 static void
 init_gtk_decoration_layout (void)
 {
+  const gchar *current_desktop;
   GtkSettings *settings;
 
+  current_desktop = g_getenv ("XDG_CURRENT_DESKTOP");
+
+  if (!current_desktop || !strstr (current_desktop, "GNOME-Flashback"))
+    return;
+
   settings = gtk_settings_get_default ();
 
   g_signal_connect (settings, "notify::gtk-decoration-layout",
@@ -1376,16 +1382,20 @@ button_layout_handler (GVariant *value,
                        gpointer *result,
                        gpointer  data)
 {
-#if 0
+  const gchar *current_desktop;
   const gchar *string_value;
 
+  *result = NULL; /* ignored */
+  current_desktop = g_getenv ("XDG_CURRENT_DESKTOP");
+
+  if (current_desktop && strstr (current_desktop, "GNOME-Flashback"))
+    return TRUE;
+
   string_value = g_variant_get_string (value, NULL);
 
   if (string_value)
     update_button_layout (string_value);
-#endif
 
-  *result = NULL; /* ignored */
   return TRUE;
 }