moodle/settings.php

<?php
// This file is part of Book module for Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * Book plugin settings
 *
 * @package    mod
 * @subpackage book
 * @copyright  2004-2010 Petr Skoda  {@link http://skodak.org}
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die;

if ($ADMIN->fulltree) {

    $choices = array('140'=>'140', '160'=>'160', '180'=>'180', '200'=>'200', '220'=>'220', '240'=>'240', '260'=>'260', '280'=>'280', '300'=>'300');
    $settings->add(new admin_setting_configselect('book_tocwidth', get_string('book_tocwidth', 'mod_book'), get_string('tocwidth', 'book'), '180', $choices));

}