[mutter] screen: Make sure to initialize NUMBER_OF_DESKTOPS

[Florian Müllner <fmuellner src gnome org>]

commit 98d77d37d061a4da7653bb30a11b4f326b3d2a18
Author: Florian Müllner <fmuellner gnome org>
Date:   Sat Sep 30 00:38:37 2017 +0200

    screen: Make sure to initialize NUMBER_OF_DESKTOPS
    
    update_num_workspaces() is a no-op when the number of workspaces
    did not actually change. That is fine, except that we still want
    to initialize the _NET_NUMBER_OF_DESKTOPS hint on startup to not
    break components like nautilus-desktop that rely on it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=760651

 src/core/screen.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/src/core/screen.c b/src/core/screen.c
index c96aefd..abc133d 100644
--- a/src/core/screen.c
+++ b/src/core/screen.c
@@ -1215,7 +1215,11 @@ update_num_workspaces (MetaScreen *screen,
   g_assert (new_num > 0);
 
   if (g_list_length (screen->workspaces) == (guint) new_num)
-    return;
+    {
+      if (screen->display->display_opening)
+        set_number_of_spaces_hint (screen, new_num);
+      return;
+    }
 
   last_remaining = NULL;
   extras = NULL;