Adding theme directories via XDG_DATA_DIRS in control-panel 2.10?

[Albert Chin <gnomecc-list mlists thewrittenword com>]

We have GTK+ 2.6.8 installed to /opt/libgtk+26 and GNOME 2.10 to
/opt/gnome210. I'd like control-center's gnome-theme-manager to pick
up /opt/libgtk+26/share/themes and /opt/gnome210/share/themes. So, I
made the change below to pick up the theme directories from
XDG_DATA_DIRS. However, while the themes from multiple directories
_are_ displayed, selecting them does nothing. If I set
GTK_DATA_PREFIX=/opt/gnome210, then the GNOME themes are displayed and
selecting them changes to the theme. Why doesn't the code below work?

-- 
albert chin (china thewrittenword com)

-- snip snip
--- capplets/common/gnome-theme-info.c.orig	2005-10-05 08:17:34.000000000 -0500
+++ capplets/common/gnome-theme-info.c	2005-10-07 15:44:37.000000000 -0500
@@ -1591,6 +1591,8 @@
   static gboolean initted = FALSE;
   GnomeVFSResult result;
   const gchar *gtk_data_dir;
+  const gchar * const *xdg_data_dirs;
+  int i;
   if (initted)
     return;
 
@@ -1604,14 +1606,26 @@
   theme_hash_by_name = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
 
 
-  /* Add all the toplevel theme dirs. */
-  /* $datadir/themes */
+  /* Add the default GTK+ theme dirs. */
+  /* $gtk_data_dir/themes */
   top_theme_dir_string = gtk_rc_get_theme_dir ();
   top_theme_dir_uri = gnome_vfs_uri_new (top_theme_dir_string);
   result = add_top_theme_dir_monitor (top_theme_dir_uri, &real_monitor_not_added, 1, NULL);
   g_free (top_theme_dir_string);
   gnome_vfs_uri_unref (top_theme_dir_uri);
 
+  /* Add the themes under XDG_DATA_DIRS */
+  xdg_data_dirs = g_get_system_data_dirs ();
+  for (i = 0; xdg_data_dirs[i]; i++)
+    {
+      top_theme_dir_string = g_build_filename (xdg_data_dirs[i], "themes", NULL);
+      top_theme_dir_uri = gnome_vfs_uri_new (top_theme_dir_string);
+      if (gnome_vfs_uri_exists (top_theme_dir_uri))
+        result = add_top_theme_dir_monitor (top_theme_dir_uri, &real_monitor_not_added, 1, NULL);
+      gnome_vfs_uri_unref (top_theme_dir_uri);
+      g_free (top_theme_dir_string);
+    }
+
   /* ~/.themes */
   top_theme_dir_string  = g_build_filename (g_get_home_dir (), ".themes", NULL);
   top_theme_dir_uri = gnome_vfs_uri_new (top_theme_dir_string);
@@ -1646,6 +1660,16 @@
   result = add_top_icon_theme_dir_monitor (top_theme_dir_uri, &real_monitor_not_added, 1, NULL);
   gnome_vfs_uri_unref (top_theme_dir_uri);
 
+  for (i = 0; xdg_data_dirs[i]; i++)
+    {
+      top_theme_dir_string = g_build_filename (xdg_data_dirs[i], "icons", NULL);
+      top_theme_dir_uri = gnome_vfs_uri_new (top_theme_dir_string);
+      g_free (top_theme_dir_string);
+      if (gnome_vfs_uri_exists (top_theme_dir_uri))
+        result = add_top_icon_theme_dir_monitor (top_theme_dir_uri, &real_monitor_not_added, 2, NULL);
+      gnome_vfs_uri_unref (top_theme_dir_uri);
+    }
+
   /* ~/.icons */
   top_theme_dir_string  = g_build_filename (g_get_home_dir (), ".icons", NULL);
   top_theme_dir_uri = gnome_vfs_uri_new (top_theme_dir_string);