CSS node tests: Add a way to test rtl vs ltr

CSS nodes have a linear sibling relationship; this is supposed
to correspond to left-to-right placement in horizontal arrangements.
This commit explicitly sets the text direction to rtl if the
filename ends in .rtl.ui, so we can test differences in node
tree layout between text directions.

testsuite/css/nodes/test-css-nodes.c

@@ -104,6 +104,11 @@ load_ui_file (GFile *file, gboolean generate)
 
   ui_file = g_file_get_path (file);
 
+  if (g_str_has_suffix (ui_file, ".rtl.ui"))
+    gtk_widget_set_default_direction (GTK_TEXT_DIR_RTL);
+  else
+    gtk_widget_set_default_direction (GTK_TEXT_DIR_LTR);
+
   builder = gtk_builder_new_from_file (ui_file);
   window = GTK_WIDGET (gtk_builder_get_object (builder, "window1"));