wayland: Make init and shutdown symmetric

We first initialized the Wayland infrastructure, then the display, but
on shutdown, we first teared down the Wayland infrastructure, then the
display.

Make things a bit more symmetric and tear down the display before
Wayland. This however means we need to tear down some things Wayland a
bit earlier than the rest. For now this is a separate function, but
eventually, it can be replaced with a signal shared by the backend's
'prepare-shutdown' signal.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1863>

src/core/main.c

@@ -308,19 +308,27 @@ meta_finalize (void)
 {
   MetaDisplay *display = meta_get_display ();
   MetaBackend *backend = meta_get_backend ();
+#ifdef HAVE_WAYLAND
+  MetaWaylandCompositor *compositor = meta_wayland_compositor_get_default ();
+#endif
 
   if (backend)
     meta_backend_prepare_shutdown (backend);
 
 #ifdef HAVE_WAYLAND
-  if (meta_is_wayland_compositor ())
+  if (compositor)
-    meta_wayland_finalize ();
+    meta_wayland_compositor_prepare_shutdown (compositor);
 #endif
 
   if (display)
     meta_display_close (display,
                         META_CURRENT_TIME); /* I doubt correct timestamps matter here */
 
+#ifdef HAVE_WAYLAND
+  if (meta_is_wayland_compositor ())
+    meta_wayland_finalize ();
+#endif
+
 #ifdef HAVE_NATIVE_BACKEND
   release_virtual_monitors ();
 #endif

src/wayland/meta-wayland.c

@@ -613,6 +613,15 @@ meta_wayland_get_private_xwayland_display_name (MetaWaylandCompositor *composito
   return compositor->xwayland_manager.private_connection.name;
 }
 
+void
+meta_wayland_compositor_prepare_shutdown (MetaWaylandCompositor *compositor)
+{
+  meta_xwayland_shutdown (&compositor->xwayland_manager);
+
+  if (compositor->wayland_display)
+    wl_display_destroy_clients (compositor->wayland_display);
+}
+
 void
 meta_wayland_finalize (void)
 {
@@ -620,11 +629,6 @@ meta_wayland_finalize (void)
 
   compositor = meta_wayland_compositor_get_default ();
 
-  meta_xwayland_shutdown (&compositor->xwayland_manager);
-
-  if (compositor->wayland_display)
-    wl_display_destroy_clients (compositor->wayland_display);
-
   g_clear_pointer (&compositor->seat, meta_wayland_seat_free);
 
   g_clear_pointer (&compositor->display_name, g_free);

src/wayland/meta-wayland.h

@@ -41,6 +41,8 @@ MetaWaylandCompositor * meta_wayland_compositor_new             (MetaBackend *ba
 
 void                    meta_wayland_compositor_setup           (MetaWaylandCompositor *compositor);
 
+void                    meta_wayland_compositor_prepare_shutdown (MetaWaylandCompositor *compositor);
+
 META_EXPORT_TEST
 MetaWaylandCompositor  *meta_wayland_compositor_get_default     (void);