Had to write:

static PangoDirection
get_cursor_direction (GtkLabel *label)
{
  PangoDirection last_direction;
  GSList *lines;
                                                                          
                                          
  g_assert (label->select_info);
                                                                          
                                          
  gtk_label_ensure_layout (label);
                                                                          
                                          
  for (l = pango_layout_get_lines (label->layout);; l; l = l->next)
    {
      PangoLayoutLine *line = l->data;
                                                                          
                                          
      /* If label->select_info->selection_end is at the very end of
       * the line, we don't know if the cursor is on this line or
       * the next without looking ahead at the next line. (End
       * of paragraph is different from line break.) But it's
       * definitely in this paragraph, which is good enough
       * to figure out the resolved direction.
       */
       if (line->start_index + line->length >=
label->select_info->selection_end)
        return line->resolved_dir;
    }
                                                                          
                                          
  return PANGO_DIRECTION_LTR;
}

Should be in Pango.