pagelib.php

<?php
// This file is part of 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/>.

/**
 * This file contains the moodle_page class. There is normally a single instance
 * of this class in the $PAGE global variable. This class is a central repository
 * of information about the page we are building up to send back to the user.
 *
 * @package core
 * @category page
 * @copyright  1999 onwards Martin Dougiamas  {@link http://moodle.com}
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();

/**
 * $PAGE is a central store of information about the current page we are
 * generating in response to the user's request.
 *
 * It does not do very much itself
 * except keep track of information, however, it serves as the access point to
 * some more significant components like $PAGE->theme, $PAGE->requires,
 * $PAGE->blocks, etc.
 *
 * @copyright 2009 Tim Hunt
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @since Moodle 2.0
 * @package core
 * @category page
 *
 * The following properties are alphabetical. Please keep it that way so that its
 * easy to maintain.
 *
 * @property-read string $activityname The type of activity we are in, for example 'forum' or 'quiz'.
 *      Will be null if this page is not within a module.
 * @property-read stdClass $activityrecord The row from the activities own database table (for example
 *      the forum or quiz table) that this page belongs to. Will be null
 *      if this page is not within a module.
 * @property-read array $alternativeversions Mime type => object with ->url and ->title.
 * @property-read block_manager $blocks The blocks manager object for this page.
 * @property-read array $blockmanipulations
 * @property-read string $bodyclasses A string to use within the class attribute on the body tag.
 * @property-read string $bodyid A string to use as the id of the body tag.
 * @property-read string $button The HTML to go where the Turn editing on button normally goes.
 * @property-read bool $cacheable Defaults to true. Set to false to stop the page being cached at all.
 * @property-read array $categories An array of all the categories the page course belongs to,
 *      starting with the immediately containing category, and working out to
 *      the top-level category. This may be the empty array if we are in the
 *      front page course.
 * @property-read mixed $category The category that the page course belongs to.
 * @property-read cm_info $cm The course_module that this page belongs to. Will be null
 *      if this page is not within a module. This is a full cm object, as loaded
 *      by get_coursemodule_from_id or get_coursemodule_from_instance,
 *      so the extra modname and name fields are present.
 * @property-read context $context The main context to which this page belongs.
 * @property-read stdClass $course The current course that we are inside - a row from the
 *      course table. (Also available as $COURSE global.) If we are not inside
 *      an actual course, this will be the site course.
 * @property-read string $devicetypeinuse The name of the device type in use
 * @property-read string $docspath The path to the Moodle docs for this page.
 * @property-read string $focuscontrol The id of the HTML element to be focused when the page has loaded.
 * @property-read bool $headerprinted True if the page header has already been printed.
 * @property-read string $heading The main heading that should be displayed at the top of the <body>.
 * @property-read string $headingmenu The menu (or actions) to display in the heading
 * @property-read array $layout_options An arrays with options for the layout file.
 * @property-read array $legacythemeinuse True if the legacy browser theme is in use.
 * @property-read navbar $navbar The navbar object used to display the navbar
 * @property-read global_navigation $navigation The navigation structure for this page.
 * @property-read xhtml_container_stack $opencontainers Tracks XHTML tags on this page that have been opened but not closed.
 *      mainly for internal use by the rendering code.
 * @property-read string $pagelayout The general type of page this is. For example 'normal', 'popup', 'home'.
 *      Allows the theme to display things differently, if it wishes to.
 * @property-read string $pagetype The page type string, should be used as the id for the body tag in the theme.
 * @property-read int $periodicrefreshdelay The periodic refresh delay to use with meta refresh
 * @property-read page_requirements_manager $requires Tracks the JavaScript, CSS files, etc. required by this page.
 * @property-read string $requestip The IP address of the current request, null if unknown.
 * @property-read string $requestorigin The type of request 'web', 'ws', 'cli', 'restore', etc.
 * @property-read settings_navigation $settingsnav The settings navigation
 * @property-read int $state One of the STATE_... constants
 * @property-read string $subpage The subpage identifier, if any.
 * @property-read theme_config $theme The theme for this page.
 * @property-read string $title The title that should go in the <head> section of the HTML of this page.
 * @property-read moodle_url $url The moodle url object for this page.
 */
class moodle_page {

    /** The state of the page before it has printed the header **/
    const STATE_BEFORE_HEADER = 0;

    /** The state the page is in temporarily while the header is being printed **/
    const STATE_PRINTING_HEADER = 1;

    /** The state the page is in while content is presumably being printed **/
    const STATE_IN_BODY = 2;

    /**
     * The state the page is when the footer has been printed and its function is
     * complete.
     */
    const STATE_DONE = 3;

    /**
     * @var int The current state of the page. The state a page is within
     * determines what actions are possible for it.
     */
    protected $_state = self::STATE_BEFORE_HEADER;

    /**
     * @var stdClass The course currently associated with this page.
     * If not has been provided the front page course is used.
     */
    protected $_course = null;

    /**
     * @var cm_info If this page belongs to a module, this is the cm_info module
     * description object.
     */
    protected $_cm = null;

    /**
     * @var stdClass If $_cm is not null, then this will hold the corresponding
     * row from the modname table. For example, if $_cm->modname is 'quiz', this
     * will be a row from the quiz table.
     */
    protected $_module = null;

    /**
     * @var context The context that this page belongs to.
     */
    protected $_context = null;

    /**
     * @var array This holds any categories that $_course belongs to, starting with the
     * particular category it belongs to, and working out through any parent
     * categories to the top level. These are loaded progressively, if needed.
     * There are three states. $_categories = null initially when nothing is
     * loaded; $_categories = array($id => $cat, $parentid => null) when we have
     * loaded $_course->category, but not any parents; and a complete array once
     * everything is loaded.
     */
    protected $_categories = null;

    /**
     * @var array An array of CSS classes that should be added to the body tag in HTML.
     */
    protected $_bodyclasses = array();

    /**
     * @var string The title for the page. Used within the title tag in the HTML head.
     */
    protected $_title = '';

    /**
     * @var string The string to use as the heading of the page. Shown near the top of the
     * page within most themes.
     */
    protected $_heading = '';

    /**
     * @var string The pagetype is used to describe the page and defaults to a representation
     * of the physical path to the page e.g. my-index, mod-quiz-attempt
     */
    protected $_pagetype = null;

    /**
     * @var string The pagelayout to use when displaying this page. The
     * pagelayout needs to have been defined by the theme in use, or one of its
     * parents. By default base is used however standard is the more common layout.
     * Note that this gets automatically set by core during operations like
     * require_login.
     */
    protected $_pagelayout = 'base';

    /**
     * @var array List of theme layout options, these are ignored by core.
     * To be used in individual theme layout files only.
     */
    protected $_layout_options = null;

    /**
     * @var string An optional arbitrary parameter that can be set on pages where the context
     * and pagetype is not enough to identify the page.
     */
    protected $_subpage = '';

    /**
     * @var string Set a different path to use for the 'Moodle docs for this page' link.
     * By default, it uses the path of the file for instance mod/quiz/attempt.
     */
    protected $_docspath = null;

    /**
     * @var string A legacy class that will be added to the body tag
     */
    protected $_legacyclass = null;

    /**
     * @var moodle_url The URL for this page. This is mandatory and must be set
     * before output is started.
     */
    protected $_url = null;

    /**
     * @var array An array of links to alternative versions of this page.
     * Primarily used for RSS versions of the current page.
     */
    protected $_alternateversions = array();

    /**
     * @var block_manager The blocks manager for this page. It is responsible for
     * the blocks and there content on this page.
     */
    protected $_blocks = null;

    /**
     * @var page_requirements_manager Page requirements manager. It is responsible
     * for all JavaScript and CSS resources required by this page.
     */
    protected $_requires = null;

    /**
     * @var string The capability required by the user in order to edit blocks
     * and block settings on this page.
     */
    protected $_blockseditingcap = 'moodle/site:manageblocks';

    /**
     * @var bool An internal flag to record when block actions have been processed.
     * Remember block actions occur on the current URL and it is important that
     * even they are never executed more than once.
     */
    protected $_block_actions_done = false;

    /**
     * @var array An array of any other capabilities the current user must have
     * in order to editing the page and/or its content (not just blocks).
     */
    protected $_othereditingcaps = array();

    /**
     * @var bool Sets whether this page should be cached by the browser or not.
     * If it is set to true (default) the page is served with caching headers.
     */
    protected $_cacheable = true;

    /**
     * @var string Can be set to the ID of an element on the page, if done that
     * element receives focus when the page loads.
     */
    protected $_focuscontrol = '';

    /**
     * @var string HTML to go where the turn on editing button is located. This
     * is nearly a legacy item and not used very often any more.
     */
    protected $_button = '';

    /**
     * @var theme_config The theme to use with this page. This has to be properly
     * initialised via {@link moodle_page::initialise_theme_and_output()} which
     * happens magically before any operation that requires it.
     */
    protected $_theme = null;

    /**
     * @var global_navigation Contains the global navigation structure.
     */
    protected $_navigation = null;

    /**
     * @var settings_navigation Contains the settings navigation structure.
     */
    protected $_settingsnav = null;

    /**
     * @var navbar Contains the navbar structure.
     */
    protected $_navbar = null;

    /**
     * @var string The menu (or actions) to display in the heading.
     */
    protected $_headingmenu = null;

    /**
     * @var array stack trace. Then the theme is initialised, we save the stack
     * trace, for use in error messages.
     */
    protected $_wherethemewasinitialised = null;

    /**
     * @var xhtml_container_stack Tracks XHTML tags on this page that have been
     * opened but not closed.
     */
    protected $_opencontainers;

    /**
     * @var int Sets the page to refresh after a given delay (in seconds) using
     * meta refresh in {@link standard_head_html()} in outputlib.php
     * If set to null(default) the page is not refreshed
     */
    protected $_periodicrefreshdelay = null;

    /**
     * @var array Associative array of browser shortnames (as used by check_browser_version)
     * and their minimum required versions
     */
    protected $_legacybrowsers = array('MSIE' => 6.0);

    /**
     * @var string Is set to the name of the device type in use.
     * This will we worked out when it is first used.
     */
    protected $_devicetypeinuse = null;

    /**
     * @var bool Used to determine if HTTPS should be required for login.
     */
    protected $_https_login_required = false;

    /**
     * @var bool Determines if popup notifications allowed on this page.
     * Code such as the quiz module disables popup notifications in situations
     * such as upgrading or completing a quiz.
     */
    protected $_popup_notification_allowed = true;

    // Magic getter methods =============================================================
    // Due to the __get magic below, you normally do not call these as $PAGE->magic_get_x
    // methods, but instead use the $PAGE->x syntax.

    /**
     * Please do not call this method directly, use the ->state syntax. {@link moodle_page::__get()}.
     * @return integer one of the STATE_XXX constants. You should not normally need
     * to use this in your code. It is intended for internal use by this class
     * and its friends like print_header, to check that everything is working as
     * expected. Also accessible as $PAGE->state.
     */
    protected function magic_get_state() {
        return $this->_state;
    }

    /**
     * Please do not call this method directly, use the ->headerprinted syntax. {@link moodle_page::__get()}.
     * @return bool has the header already been printed?
     */
    protected function magic_get_headerprinted() {
        return $this->_state >= self::STATE_IN_BODY;
    }

    /**
     * Please do not call this method directly, use the ->course syntax. {@link moodle_page::__get()}.
     * @return stdClass the current course that we are inside - a row from the
     * course table. (Also available as $COURSE global.) If we are not inside
     * an actual course, this will be the site course.
     */
    protected function magic_get_course() {
        global $SITE;
        if (is_null($this->_course)) {
            return $SITE;
        }
        return $this->_course;
    }

    /**
     * Please do not call this method directly, use the ->cm syntax. {@link moodle_page::__get()}.
     * @return cm_info the course_module that this page belongs to. Will be null
     * if this page is not within a module. This is a full cm object, as loaded
     * by get_coursemodule_from_id or get_coursemodule_from_instance,
     * so the extra modname and name fields are present.
     */
    protected function magic_get_cm() {
        return $this->_cm;
    }

    /**
     * Please do not call this method directly, use the ->activityrecord syntax. {@link moodle_page::__get()}.
     * @return stdClass the row from the activities own database table (for example
     * the forum or quiz table) that this page belongs to. Will be null
     * if this page is not within a module.
     */
    protected function magic_get_activityrecord() {
        if (is_null($this->_module) && !is_null($this->_cm)) {
            $this->load_activity_record();
        }
        return $this->_module;
    }

    /**
     * Please do not call this method directly, use the ->activityname syntax. {@link moodle_page::__get()}.
     * @return string the The type of activity we are in, for example 'forum' or 'quiz'.
     * Will be null if this page is not within a module.
     */
    protected function magic_get_activityname() {
        if (is_null($this->_cm)) {
            return null;
        }
        return $this->_cm->modname;
    }

    /**
     * Please do not call this method directly, use the ->category syntax. {@link moodle_page::__get()}.
     * @return stdClass the category that the page course belongs to. If there isn't one
     * (that is, if this is the front page course) returns null.
     */
    protected function magic_get_category() {
        $this->ensure_category_loaded();
        if (!empty($this->_categories)) {
            return reset($this->_categories);
        } else {
            return null;
        }
    }

    /**
     * Please do not call this method directly, use the ->categories syntax. {@link moodle_page::__get()}.
     * @return array an array of all the categories the page course belongs to,
     * starting with the immediately containing category, and working out to
     * the top-level category. This may be the empty array if we are in the
     * front page course.
     */
    protected function magic_get_categories() {
        $this->ensure_categories_loaded();
        return $this->_categories;
    }

    /**
     * Please do not call this method directly, use the ->context syntax. {@link moodle_page::__get()}.
     * @return context the main context to which this page belongs.
     */
    protected function magic_get_context() {
        if (is_null($this->_context)) {
            if (CLI_SCRIPT or NO_MOODLE_COOKIES) {
                // Cli scripts work in system context, do not annoy devs with debug info.
                // Very few scripts do not use cookies, we can safely use system as default context there.
            } else {
                debugging('Coding problem: $PAGE->context was not set. You may have forgotten '
                    .'to call require_login() or $PAGE->set_context(). The page may not display '
                    .'correctly as a result');
            }
            $this->_context = context_system::instance();
        }
        return $this->_context;
    }

    /**
     * Please do not call this method directly, use the ->pagetype syntax. {@link moodle_page::__get()}.
     * @return string e.g. 'my-index' or 'mod-quiz-attempt'.
     */
    protected function magic_get_pagetype() {
        global $CFG;
        if (is_null($this->_pagetype) || isset($CFG->pagepath)) {
            $this->initialise_default_pagetype();
        }
        return $this->_pagetype;
    }

    /**
     * Please do not call this method directly, use the ->pagetype syntax. {@link moodle_page::__get()}.
     * @return string The id to use on the body tag, uses {@link magic_get_pagetype()}.
     */
    protected function magic_get_bodyid() {
        return 'page-'.$this->pagetype;
    }

    /**
     * Please do not call this method directly, use the ->pagelayout syntax. {@link moodle_page::__get()}.
     * @return string the general type of page this is. For example 'standard', 'popup', 'home'.
     *      Allows the theme to display things differently, if it wishes to.
     */
    protected function magic_get_pagelayout() {
        return $this->_pagelayout;
    }

    /**
     * Please do not call this method directly, use the ->layout_options syntax. {@link moodle_page::__get()}.
     * @return array returns arrays with options for layout file
     */
    protected function magic_get_layout_options() {
        if (!is_array($this->_layout_options)) {
            $this->_layout_options = $this->_theme->pagelayout_options($this->pagelayout);
        }
        return $this->_layout_options;
    }

    /**
     * Please do not call this method directly, use the ->subpage syntax. {@link moodle_page::__get()}.
     * @return string The subpage identifier, if any.
     */
    protected function magic_get_subpage() {
        return $this->_subpage;
    }

    /**
     * Please do not call this method directly, use the ->bodyclasses syntax. {@link moodle_page::__get()}.
     * @return string the class names to put on the body element in the HTML.
     */
    protected function magic_get_bodyclasses() {
        return implode(' ', array_keys($this->_bodyclasses));
    }

    /**
     * Please do not call this method directly, use the ->title syntax. {@link moodle_page::__get()}.
     * @return string the title that should go in the <head> section of the HTML of this page.
     */
    protected function magic_get_title() {
        return $this->_title;
    }

    /**
     * Please do not call this method directly, use the ->heading syntax. {@link moodle_page::__get()}.
     * @return string the main heading that should be displayed at the top of the <body>.
     */
    protected function magic_get_heading() {
        return $this->_heading;
    }

    /**
     * Please do not call this method directly, use the ->heading syntax. {@link moodle_page::__get()}.
     * @return string The menu (or actions) to display in the heading
     */
    protected function magic_get_headingmenu() {
        return $this->_headingmenu;
    }

    /**
     * Please do not call this method directly, use the ->docspath syntax. {@link moodle_page::__get()}.
     * @return string the path to the Moodle docs for this page.
     */
    protected function magic_get_docspath() {
        if (is_string($this->_docspath)) {
            return $this->_docspath;
        } else {
            return str_replace('-', '/', $this->pagetype);
        }
    }

    /**
     * Please do not call this method directly, use the ->url syntax. {@link moodle_page::__get()}.
     * @return moodle_url the clean URL required to load the current page. (You
     * should normally use this in preference to $ME or $FULLME.)
     */
    protected function magic_get_url() {
        global $FULLME;
        if (is_null($this->_url)) {
            debugging('This page did not call $PAGE->set_url(...). Using '.s($FULLME), DEBUG_DEVELOPER);
            $this->_url = new moodle_url($FULLME);
            // Make sure the guessed URL cannot lead to dangerous redirects.
            $this->_url->remove_params('sesskey');
        }
        return new moodle_url($this->_url); // Return a clone for safety.
    }

    /**
     * The list of alternate versions of this page.
     * @return array mime type => object with ->url and ->title.
     */
    protected function magic_get_alternateversions() {
        return $this->_alternateversions;
    }

    /**
     * Please do not call this method directly, use the ->blocks syntax. {@link moodle_page::__get()}.
     * @return block_manager the blocks manager object for this page.
     */
    protected function magic_get_blocks() {
        global $CFG;
        if (is_null($this->_blocks)) {
            if (!empty($CFG->blockmanagerclass)) {
                if (!empty($CFG->blockmanagerclassfile)) {
                    require_once($CFG->blockmanagerclassfile);
                }
                $classname = $CFG->blockmanagerclass;
            } else {
                $classname = 'block_manager';
            }
            $this->_blocks = new $classname($this);
        }
        return $this->_blocks;
    }

    /**
     * Please do not call this method directly, use the ->requires syntax. {@link moodle_page::__get()}.
     * @return page_requirements_manager tracks the JavaScript, CSS files, etc. required by this page.
     */
    protected function magic_get_requires() {
        if (is_null($this->_requires)) {
            $this->_requires = new page_requirements_manager();
        }
        return $this->_requires;
    }

    /**
     * Please do not call this method directly, use the ->cacheable syntax. {@link moodle_page::__get()}.
     * @return bool can this page be cached by the user's browser.
     */
    protected function magic_get_cacheable() {
        return $this->_cacheable;
    }

    /**
     * Please do not call this method directly, use the ->focuscontrol syntax. {@link moodle_page::__get()}.
     * @return string the id of the HTML element to be focused when the page has loaded.
     */
    protected function magic_get_focuscontrol() {
        return $this->_focuscontrol;
    }

    /**
     * Please do not call this method directly, use the ->button syntax. {@link moodle_page::__get()}.
     * @return string the HTML to go where the Turn editing on button normally goes.
     */
    protected function magic_get_button() {
        return $this->_button;
    }

    /**
     * Please do not call this method directly, use the ->theme syntax. {@link moodle_page::__get()}.
     * @return theme_config the initialised theme for this page.
     */
    protected function magic_get_theme() {
        if (is_null($this->_theme)) {
            $this->initialise_theme_and_output();
        }
        return $this->_theme;
    }

    /**
     * Returns an array of minipulations or false if there are none to make.
     *
     * @since Moodle 2.5.1 2.6
     * @return bool|array
     */
    protected function magic_get_blockmanipulations() {
        if (!right_to_left()) {
            return false;
        }
        if (is_null($this->_theme)) {
            $this->initialise_theme_and_output();
        }
        return $this->_theme->blockrtlmanipulations;
    }

    /**
     * Please do not call this method directly, use the ->devicetypeinuse syntax. {@link moodle_page::__get()}.
     * @return string The device type being used.
     */
    protected function magic_get_devicetypeinuse() {
        if (empty($this->_devicetypeinuse)) {
            $this->_devicetypeinuse = core_useragent::get_user_device_type();
        }
        return $this->_devicetypeinuse;
    }

    /**
     * Please do not call this method directly use the ->periodicrefreshdelay syntax
     * {@link moodle_page::__get()}
     * @return int The periodic refresh delay to use with meta refresh
     */
    protected function magic_get_periodicrefreshdelay() {
        return $this->_periodicrefreshdelay;
    }

    /**
     * Please do not call this method directly use the ->opencontainers syntax. {@link moodle_page::__get()}
     * @return xhtml_container_stack tracks XHTML tags on this page that have been opened but not closed.
     *      mainly for internal use by the rendering code.
     */
    protected function magic_get_opencontainers() {
        if (is_null($this->_opencontainers)) {
            $this->_opencontainers = new xhtml_container_stack();
        }
        return $this->_opencontainers;
    }

    /**
     * Return the navigation object
     * @return global_navigation
     */
    protected function magic_get_navigation() {
        if ($this->_navigation === null) {
            $this->_navigation = new global_navigation($this);
        }
        return $this->_navigation;
    }

    /**
     * Return a navbar object
     * @return navbar
     */
    protected function magic_get_navbar() {
        if ($this->_navbar === null) {
            $this->_navbar = new navbar($this);
        }
        return $this->_navbar;
    }

    /**
     * Returns the settings navigation object
     * @return settings_navigation
     */
    protected function magic_get_settingsnav() {
        if ($this->_settingsnav === null) {
            $this->_settingsnav = new settings_navigation($this);
            $this->_settingsnav->initialise();
        }
        return $this->_settingsnav;
    }

    /**
     * Returns request IP address.
     *
     * @return string IP address or null if unknown
     */
    protected function magic_get_requestip() {
        return getremoteaddr(null);
    }

    /**
     * Returns the origin of current request.
     *
     * Note: constants are not required because we need to use these values in logging and reports.
     *
     * @return string 'web', 'ws', 'cli', 'restore', etc.
     */
    protected function magic_get_requestorigin() {
        if (class_exists('restore_controller', false) && restore_controller::is_executing()) {
            return 'restore';
        }

        if (WS_SERVER) {
            return 'ws';
        }

        if (CLI_SCRIPT) {
            return 'cli';
        }

        return 'web';
    }

    /**
     * PHP overloading magic to make the $PAGE->course syntax work by redirecting
     * it to the corresponding $PAGE->magic_get_course() method if there is one, and
     * throwing an exception if not.
     *
     * @param string $name property name
     * @return mixed
     * @throws coding_exception
     */
    public function __get($name) {
        $getmethod = 'magic_get_' . $name;
        if (method_exists($this, $getmethod)) {
            return $this->$getmethod();
        } else {
            throw new coding_exception('Unknown property ' . $name . ' of $PAGE.');
        }
    }

    /**
     * PHP overloading magic to catch obvious coding errors.
     *
     * This method has been created to catch obvious coding errors where the
     * developer has tried to set a page property using $PAGE->key = $value.
     * In the moodle_page class all properties must be set using the appropriate
     * $PAGE->set_something($value) method.
     *
     * @param string $name property name
     * @param mixed $value Value
     * @return void Throws exception if field not defined in page class
     * @throws coding_exception
     */
    public function __set($name, $value) {
        if (method_exists($this, 'set_' . $name)) {
            throw new coding_exception('Invalid attempt to modify page object', "Use \$PAGE->set_$name() instead.");
        } else {
            throw new coding_exception('Invalid attempt to modify page object', "Unknown property $name");
        }
    }

    // Other information getting methods ==========================================.

    /**
     * Returns instance of page renderer
     *
     * @param string $component name such as 'core', 'mod_forum' or 'qtype_multichoice'.
     * @param string $subtype optional subtype such as 'news' resulting to 'mod_forum_news'
     * @param string $target one of rendering target constants
     * @return renderer_base
     */
    public function get_renderer($component, $subtype = null, $target = null) {
        if ($this->pagelayout === 'maintenance') {
            // If the page is using the maintenance layout then we're going to force target to maintenance.
            // This leads to a special core renderer that is designed to block access to API's that are likely unavailable for this
            // page layout.
            $target = RENDERER_TARGET_MAINTENANCE;
        }
        return $this->magic_get_theme()->get_renderer($this, $component, $subtype, $target);
    }

    /**
     * Checks to see if there are any items on the navbar object
     *
     * @return bool true if there are, false if not
     */
    public function has_navbar() {
        if ($this->_navbar === null) {
            $this->_navbar = new navbar($this);
        }
        return $this->_navbar->has_items();
    }

    /**
     * Changes the requirements manager over to receive fragments.
     */
    public function set_requirements_for_fragments() {
        $this->_requires = new fragment_requirements_manager();
    }

    /**
     * Should the current user see this page in editing mode.
     * That is, are they allowed to edit this page, and are they currently in
     * editing mode.
     * @return bool
     */
    public function user_is_editing() {
        global $USER;
        return !empty($USER->editing) && $this->user_allowed_editing();
    }

    /**
     * Does the user have permission to edit blocks on this page.
     * @return bool
     */
    public function user_can_edit_blocks() {
        return has_capability($this->_blockseditingcap, $this->_context);
    }

    /**
     * Does the user have permission to see this page in editing mode.
     * @return bool
     */
    public function user_allowed_editing() {
        return has_any_capability($this->all_editing_caps(), $this->_context);
    }

    /**
     * Get a description of this page. Normally displayed in the footer in developer debug mode.
     * @return string
     */
    public function debug_summary() {
        $summary = '';
        $summary .= 'General type: ' . $this->pagelayout . '. ';
        if (!during_initial_install()) {
            $summary .= 'Context ' . $this->context->get_context_name() . ' (context id ' . $this->_context->id . '). ';
        }
        $summary .= 'Page type ' . $this->pagetype .  '. ';
        if ($this->subpage) {
            $summary .= 'Sub-page ' . $this->subpage .  '. ';