display: include wayland clients in the tab list

Make sure that meta_display_list_windows() returns wayland windows
too, by keeping a separate hash for wayland clients.
This fixes a crash in the alt-tab code of gnome-shell.

Reviewed by drago01 in IRC.

src/core/display.c

@@ -607,6 +607,7 @@ meta_display_open (void)
   
   the_display->xids = g_hash_table_new (meta_unsigned_long_hash,
                                         meta_unsigned_long_equal);
+  the_display->wayland_windows = g_hash_table_new (NULL, NULL);
 
   i = 0;
   while (i < N_IGNORED_CROSSING_SERIALS)
@@ -1048,6 +1049,19 @@ meta_display_list_windows (MetaDisplay          *display,
         winlist = g_slist_prepend (winlist, window);
     }
 
+  g_hash_table_iter_init (&iter, display->wayland_windows);
+  while (g_hash_table_iter_next (&iter, &key, &value))
+    {
+      MetaWindow *window = value;
+
+      if (!META_IS_WINDOW (window))
+        continue;
+
+      if (!window->override_redirect ||
+          (flags & META_LIST_INCLUDE_OVERRIDE_REDIRECT) != 0)
+        winlist = g_slist_prepend (winlist, window);
+    }
+
   /* Uniquify the list, since both frame windows and plain
    * windows are in the hash
    */
@@ -3864,6 +3878,20 @@ meta_display_unregister_x_window (MetaDisplay *display,
   remove_pending_pings_for_window (display, xwindow);
 }
 
+void
+meta_display_register_wayland_window (MetaDisplay *display,
+                                      MetaWindow  *window)
+{
+  g_hash_table_add (display->wayland_windows, window);
+}
+
+void
+meta_display_unregister_wayland_window (MetaDisplay *display,
+                                        MetaWindow  *window)
+{
+  g_hash_table_remove (display->wayland_windows, window);
+}
+
 #ifdef HAVE_XSYNC
 /* We store sync alarms in the window ID hash table, because they are
  * just more types of XIDs in the same global space, but we have