/**
  * Defines the form fields.
  */
 public function definition()
 {
     global $USER, $CFG, $DB;
     $mform = $this->_form;
     $course = $this->_customdata['course'];
     // Overall criteria aggregation.
     $context = context_course::instance($course->id);
     $roles = array();
     $assumedrole = -1;
     if (is_role_switched($course->id)) {
         $roles[0] = get_string('switchrolereturn');
         $assumedrole = $USER->access['rsw'][$context->path];
     }
     $availableroles = get_switchable_roles($context);
     if (is_array($availableroles)) {
         foreach ($availableroles as $key => $role) {
             if ($assumedrole == (int) $key) {
                 continue;
             }
             $roles[$key] = $role;
         }
     }
     $mform->addElement('select', 'switchrole', get_string('role'), $roles);
     // Add common action buttons.
     $this->add_action_buttons();
     // Add hidden fields.
     $mform->addElement('hidden', 'id', $course->id);
     $mform->setType('id', PARAM_INT);
 }

//.........这里部分代码省略.........
                     if (has_capability('gradereport/' . $plugin . ':view', $coursecontext)) {
                         //stop when the first visible plugin is found
                         $reportavailable = true;
                         break;
                     }
                 }
             }
         }
     }
     if ($reportavailable) {
         $url = new moodle_url('/grade/report/index.php', array('id' => $course->id));
         $gradenode = $coursenode->add(get_string('grades'), $url, self::TYPE_SETTING, null, 'grades', new pix_icon('i/grades', ''));
     }
     //  Add outcome if permitted
     if (!empty($CFG->enableoutcomes) && has_capability('moodle/course:update', $coursecontext)) {
         $url = new moodle_url('/grade/edit/outcome/course.php', array('id' => $course->id));
         $coursenode->add(get_string('outcomes', 'grades'), $url, self::TYPE_SETTING, null, 'outcomes', new pix_icon('i/outcomes', ''));
     }
     // Backup this course
     if (has_capability('moodle/backup:backupcourse', $coursecontext)) {
         $url = new moodle_url('/backup/backup.php', array('id' => $course->id));
         $coursenode->add(get_string('backup'), $url, self::TYPE_SETTING, null, 'backup', new pix_icon('i/backup', ''));
     }
     // Restore to this course
     if (has_capability('moodle/restore:restorecourse', $coursecontext)) {
         $url = new moodle_url('/backup/restorefile.php', array('contextid' => $coursecontext->id));
         $coursenode->add(get_string('restore'), $url, self::TYPE_SETTING, null, 'restore', new pix_icon('i/restore', ''));
     }
     // Import data from other courses
     if (has_capability('moodle/restore:restoretargetimport', $coursecontext)) {
         $url = new moodle_url('/backup/import.php', array('id' => $course->id));
         $coursenode->add(get_string('import'), $url, self::TYPE_SETTING, null, 'import', new pix_icon('i/restore', ''));
     }
     // Publish course on a hub
     if (has_capability('moodle/course:publish', $coursecontext)) {
         $url = new moodle_url('/course/publish/index.php', array('id' => $course->id));
         $coursenode->add(get_string('publish'), $url, self::TYPE_SETTING, null, 'publish', new pix_icon('i/publish', ''));
     }
     // Reset this course
     if (has_capability('moodle/course:reset', $coursecontext)) {
         $url = new moodle_url('/course/reset.php', array('id' => $course->id));
         $coursenode->add(get_string('reset'), $url, self::TYPE_SETTING, null, null, new pix_icon('i/return', ''));
     }
     // Questions
     require_once $CFG->libdir . '/questionlib.php';
     question_extend_settings_navigation($coursenode, $coursecontext)->trim_if_empty();
     if (has_capability('moodle/course:update', $coursecontext)) {
         // Repository Instances
         if (!$this->cache->cached('contexthasrepos' . $coursecontext->id)) {
             require_once $CFG->dirroot . '/repository/lib.php';
             $editabletypes = repository::get_editable_types($coursecontext);
             $haseditabletypes = !empty($editabletypes);
             unset($editabletypes);
             $this->cache->set('contexthasrepos' . $coursecontext->id, $haseditabletypes);
         } else {
             $haseditabletypes = $this->cache->{'contexthasrepos' . $coursecontext->id};
         }
         if ($haseditabletypes) {
             $url = new moodle_url('/repository/manage_instances.php', array('contextid' => $coursecontext->id));
             $coursenode->add(get_string('repositories'), $url, self::TYPE_SETTING, null, null, new pix_icon('i/repository', ''));
         }
     }
     // Manage files
     if ($course->legacyfiles == 2 and has_capability('moodle/course:managefiles', $coursecontext)) {
         // hidden in new courses and courses where legacy files were turned off
         $url = new moodle_url('/files/index.php', array('contextid' => $coursecontext->id));
         $coursenode->add(get_string('courselegacyfiles'), $url, self::TYPE_SETTING, null, 'coursefiles', new pix_icon('i/files', ''));
     }
     // Switch roles
     $roles = array();
     $assumedrole = $this->in_alternative_role();
     if ($assumedrole !== false) {
         $roles[0] = get_string('switchrolereturn');
     }
     if (has_capability('moodle/role:switchroles', $coursecontext)) {
         $availableroles = get_switchable_roles($coursecontext);
         if (is_array($availableroles)) {
             foreach ($availableroles as $key => $role) {
                 if ($assumedrole == (int) $key) {
                     continue;
                 }
                 $roles[$key] = $role;
             }
         }
     }
     if (is_array($roles) && count($roles) > 0) {
         $switchroles = $this->add(get_string('switchroleto'));
         if (count($roles) == 1 && array_key_exists(0, $roles) || $assumedrole !== false) {
             $switchroles->force_open();
         }
         $returnurl = $this->page->url;
         $returnurl->param('sesskey', sesskey());
         foreach ($roles as $key => $name) {
             $url = new moodle_url('/course/switchrole.php', array('id' => $course->id, 'sesskey' => sesskey(), 'switchrole' => $key, 'returnurl' => $returnurl->out(false)));
             $switchroles->add($name, $url, self::TYPE_SETTING, null, $key, new pix_icon('i/roles', ''));
         }
     }
     // Return we are done
     return $coursenode;
 }

// Defined here to avoid notices on errors etc
// Prevent caching of this page to stop confusion when changing page after making AJAX changes
$PAGE->set_cacheable(false);
preload_course_contexts($course->id);
$context = context_course::instance($course->id, MUST_EXIST);
// Remove any switched roles before checking login
if ($switchrole == 0 && confirm_sesskey()) {
    role_switch($switchrole, $context);
}
require_login($course);
// Switchrole - sanity check in cost-order...
$reset_user_allowed_editing = false;
if ($switchrole > 0 && confirm_sesskey() && has_capability('moodle/role:switchroles', $context)) {
    // is this role assignable in this context?
    // inquiring minds want to know...
    $aroles = get_switchable_roles($context);
    if (is_array($aroles) && isset($aroles[$switchrole])) {
        role_switch($switchrole, $context);
        // Double check that this role is allowed here
        require_login($course);
    }
    // reset course page state - this prevents some weird problems ;-)
    $USER->activitycopy = false;
    $USER->activitycopycourse = NULL;
    unset($USER->activitycopyname);
    unset($SESSION->modform);
    $USER->editing = 0;
    $reset_user_allowed_editing = true;
}
//If course is hosted on an external server, redirect to corresponding
//url with appropriate authentication attached as parameter

//.........这里部分代码省略.........
     if (!empty($CFG->enableoutcomes) && has_capability('moodle/course:update', $coursecontext)) {
         $url = new moodle_url('/grade/edit/outcome/course.php', array('id' => $course->id));
         $coursenode->add(get_string('outcomes', 'grades'), $url, self::TYPE_SETTING, null, 'outcomes', new pix_icon('i/outcomes', ''));
     }
     //Add badges navigation
     if (!empty($CFG->enablebadges)) {
         require_once $CFG->libdir . '/badgeslib.php';
         badges_add_course_navigation($coursenode, $course);
     }
     // Backup this course
     if (has_capability('moodle/backup:backupcourse', $coursecontext)) {
         $url = new moodle_url('/backup/backup.php', array('id' => $course->id));
         $coursenode->add(get_string('backup'), $url, self::TYPE_SETTING, null, 'backup', new pix_icon('i/backup', ''));
     }
     // Restore to this course
     if (has_capability('moodle/restore:restorecourse', $coursecontext)) {
         $url = new moodle_url('/backup/restorefile.php', array('contextid' => $coursecontext->id));
         $coursenode->add(get_string('restore'), $url, self::TYPE_SETTING, null, 'restore', new pix_icon('i/restore', ''));
     }
     // Import data from other courses
     if (has_capability('moodle/restore:restoretargetimport', $coursecontext)) {
         $url = new moodle_url('/backup/import.php', array('id' => $course->id));
         $coursenode->add(get_string('import'), $url, self::TYPE_SETTING, null, 'import', new pix_icon('i/import', ''));
     }
     // Publish course on a hub
     if (has_capability('moodle/course:publish', $coursecontext)) {
         $url = new moodle_url('/course/publish/index.php', array('id' => $course->id));
         $coursenode->add(get_string('publish'), $url, self::TYPE_SETTING, null, 'publish', new pix_icon('i/publish', ''));
     }
     // Reset this course
     if (has_capability('moodle/course:reset', $coursecontext)) {
         $url = new moodle_url('/course/reset.php', array('id' => $course->id));
         $coursenode->add(get_string('reset'), $url, self::TYPE_SETTING, null, 'reset', new pix_icon('i/return', ''));
     }
     // Questions
     require_once $CFG->libdir . '/questionlib.php';
     question_extend_settings_navigation($coursenode, $coursecontext)->trim_if_empty();
     if (has_capability('moodle/course:update', $coursecontext)) {
         // Repository Instances
         if (!$this->cache->cached('contexthasrepos' . $coursecontext->id)) {
             require_once $CFG->dirroot . '/repository/lib.php';
             $editabletypes = repository::get_editable_types($coursecontext);
             $haseditabletypes = !empty($editabletypes);
             unset($editabletypes);
             $this->cache->set('contexthasrepos' . $coursecontext->id, $haseditabletypes);
         } else {
             $haseditabletypes = $this->cache->{'contexthasrepos' . $coursecontext->id};
         }
         if ($haseditabletypes) {
             $url = new moodle_url('/repository/manage_instances.php', array('contextid' => $coursecontext->id));
             $coursenode->add(get_string('repositories'), $url, self::TYPE_SETTING, null, null, new pix_icon('i/repository', ''));
         }
     }
     // Manage files
     if ($course->legacyfiles == 2 and has_capability('moodle/course:managefiles', $coursecontext)) {
         // hidden in new courses and courses where legacy files were turned off
         $url = new moodle_url('/files/index.php', array('contextid' => $coursecontext->id));
         $coursenode->add(get_string('courselegacyfiles'), $url, self::TYPE_SETTING, null, 'coursefiles', new pix_icon('i/folder', ''));
     }
     // Switch roles
     $roles = array();
     $assumedrole = $this->in_alternative_role();
     if ($assumedrole !== false) {
         $roles[0] = get_string('switchrolereturn');
     }
     if (has_capability('moodle/role:switchroles', $coursecontext)) {
         $availableroles = get_switchable_roles($coursecontext);
         if (is_array($availableroles)) {
             foreach ($availableroles as $key => $role) {
                 if ($assumedrole == (int) $key) {
                     continue;
                 }
                 $roles[$key] = $role;
             }
         }
     }
     if (is_array($roles) && count($roles) > 0) {
         $switchroles = $this->add(get_string('switchroleto'), null, self::TYPE_CONTAINER, null, 'switchroleto');
         if (count($roles) == 1 && array_key_exists(0, $roles) || $assumedrole !== false) {
             $switchroles->force_open();
         }
         foreach ($roles as $key => $name) {
             $url = new moodle_url('/course/switchrole.php', array('id' => $course->id, 'sesskey' => sesskey(), 'switchrole' => $key, 'returnurl' => $this->page->url->out_as_local_url(false)));
             $switchroles->add($name, $url, self::TYPE_SETTING, null, $key, new pix_icon('i/switchrole', ''));
         }
     }
     // Let plugins hook into course navigation.
     $pluginsfunction = get_plugins_with_function('extend_navigation_course', 'lib.php');
     foreach ($pluginsfunction as $plugintype => $plugins) {
         // Ignore the report plugin as it was already loaded above.
         if ($plugintype == 'report') {
             continue;
         }
         foreach ($plugins as $pluginfunction) {
             $pluginfunction($coursenode, $course, $coursecontext);
         }
     }
     // Return we are done
     return $coursenode;
 }

 function test_get_switchable_roles()
 {
     global $USER;
     $tablenames = array('role', 'role_capabilities', 'role_assignments', 'role_allow_switch', 'capabilities', 'context', 'role_names');
     $this->create_test_tables($tablenames, 'lib');
     $this->switch_to_test_db();
     $this->switch_to_test_cfg();
     // Ensure SYSCONTEXTID is set.
     get_context_instance(CONTEXT_SYSTEM);
     $contexts = $this->load_test_data('context', array('contextlevel', 'instanceid', 'path', 'depth'), array('sys' => array(CONTEXT_SYSTEM, 0, '/' . SYSCONTEXTID, 1), 'cat' => array(CONTEXT_COURSECAT, 66, '/' . SYSCONTEXTID . '/' . (SYSCONTEXTID + 1), 2), 'cou' => array(CONTEXT_COURSE, 666, '/' . SYSCONTEXTID . '/' . (SYSCONTEXTID + 1) . '/' . (SYSCONTEXTID + 2), 3), 'fp' => array(CONTEXT_COURSE, SITEID, '/' . SYSCONTEXTID . '/' . SITEID, 2)));
     $this->testdb->set_field('context', 'id', SYSCONTEXTID, array('id' => $contexts['sys']->id));
     $this->testdb->set_field('context', 'id', SYSCONTEXTID + 1, array('id' => $contexts['cat']->id));
     $this->testdb->set_field('context', 'id', SYSCONTEXTID + 2, array('id' => $contexts['cou']->id));
     $syscontext = $contexts['sys'];
     $syscontext->id = SYSCONTEXTID;
     $context = $contexts['cou'];
     $context->id = SYSCONTEXTID + 2;
     $roles = $this->load_test_data('role', array('name', 'shortname', 'description', 'sortorder'), array('r1' => array('r1', 'r1', 'not null', 2), 'r2' => array('r2', 'r2', 'not null', 3), 'funny' => array('funny', 'funny', 'not null', 4)));
     $r1id = $roles['r1']->id;
     $r2id = $roles['r2']->id;
     $funnyid = $roles['funny']->id;
     // strange role
     // Note that get_switchable_roles requires at least one capability for
     // each role. I am not really clear why it was implemented that way
     // but this makes the test work.
     $roles = $this->load_test_data('role_capabilities', array('roleid', 'capability'), array(array($r1id, 'moodle/say:hello'), array($r2id, 'moodle/say:hello'), array($funnyid, 'moodle/say:hello')));
     $this->load_test_data('role_assignments', array('userid', 'contextid', 'roleid'), array(array(2, SYSCONTEXTID + 1, $r1id), array(3, SYSCONTEXTID + 2, $r2id)));
     $this->load_test_data('role_allow_switch', array('roleid', 'allowswitch'), array(array($r1id, $r2id), array($r2id, $r1id), array($r2id, $r2id), array($r2id, $funnyid)));
     // r1 should be able to switch to r2, but this user only has r1 in $context, not $syscontext.
     $this->switch_global_user_id(2);
     accesslib_clear_all_caches_for_unit_testing();
     $this->assert(new ArraysHaveSameValuesExpectation(array()), array_keys(get_switchable_roles($syscontext)));
     $this->assert(new ArraysHaveSameValuesExpectation(array($r2id)), array_keys(get_switchable_roles($context)));
     $this->revert_global_user_id();
     // The table says r2 should be able to switch to all of r1, r2 and funny;
     // this used to be restricted further beyond the switch table (for example
     // to prevent you switching to roles with doanything) but is not any more
     // (for example because doanything does not exist).
     $this->switch_global_user_id(3);
     accesslib_clear_all_caches_for_unit_testing();
     $this->assert(new ArraysHaveSameValuesExpectation(array()), array_keys(get_switchable_roles($syscontext)));
     $this->assert(new ArraysHaveSameValuesExpectation(array($r2id, $r1id, $funnyid)), array_keys(get_switchable_roles($context)));
 }

 /**
  * Test getting of all switchable roles.
  */
 public function test_get_switchable_roles()
 {
     global $DB;
     $this->resetAfterTest();
     $course = $this->getDataGenerator()->create_course();
     $coursecontext = context_course::instance($course->id);
     $teacherrole = $DB->get_record('role', array('shortname' => 'editingteacher'), '*', MUST_EXIST);
     $teacher = $this->getDataGenerator()->create_user();
     role_assign($teacherrole->id, $teacher->id, $coursecontext);
     $teacherename = (object) array('roleid' => $teacherrole->id, 'name' => 'Učitel', 'contextid' => $coursecontext->id);
     $DB->insert_record('role_names', $teacherename);
     $contexts = $DB->get_records('context');
     $users = $DB->get_records('user');
     $allroles = $DB->get_records('role');
     // Evaluate all results for all users in all contexts.
     foreach ($users as $user) {
         $this->setUser($user);
         foreach ($contexts as $contextid => $unused) {
             $context = context_helper::instance_by_id($contextid);
             $roles = get_switchable_roles($context);
             foreach ($allroles as $roleid => $role) {
                 if (is_siteadmin()) {
                     $this->assertTrue(isset($roles[$roleid]));
                 } else {
                     $parents = $context->get_parent_context_ids(true);
                     $pcontexts = implode(',', $parents);
                     $allowed = $DB->record_exists_sql("SELECT r.id\n                               FROM {role} r\n                               JOIN {role_allow_switch} ras ON ras.allowswitch = r.id\n                               JOIN {role_assignments} ra ON ra.roleid = ras.roleid\n                              WHERE ra.userid = :userid AND ra.contextid IN ({$pcontexts}) AND r.id = :roleid\n                            ", array('userid' => $user->id, 'roleid' => $roleid));
                     if (isset($roles[$roleid])) {
                         $this->assertTrue($allowed);
                     } else {
                         $this->assertFalse($allowed);
                     }
                 }
                 if (isset($roles[$roleid])) {
                     $coursecontext = $context->get_course_context(false);
                     $this->assertSame(role_get_name($role, $coursecontext), $roles[$roleid]);
                 }
             }
         }
     }
 }

/**
 * Returns a little popup menu for switching roles
 *
 * @uses $CFG
 * @uses $USER
 * @param int $courseid The course  to update by id as found in 'course' table
 * @return string
 */
function switchroles_form($courseid)
{
    global $CFG, $USER;
    if (!($context = get_context_instance(CONTEXT_COURSE, $courseid))) {
        return '';
    }
    if (!empty($USER->access['rsw'][$context->path])) {
        // Just a button to return to normal
        $options = array();
        $options['id'] = $courseid;
        $options['sesskey'] = sesskey();
        $options['switchrole'] = 0;
        return print_single_button($CFG->wwwroot . '/course/view.php', $options, get_string('switchrolereturn'), 'post', '_self', true);
    }
    if (has_capability('moodle/role:switchroles', $context)) {
        if (!($roles = get_switchable_roles($context))) {
            return '';
            // Nothing to show!
        }
        // unset default user role - it would not work
        unset($roles[$CFG->guestroleid]);
        return popup_form($CFG->wwwroot . '/course/view.php?id=' . $courseid . '&sesskey=' . sesskey() . '&switchrole=', $roles, 'switchrole', '', get_string('switchroleto'), 'switchrole', get_string('switchroleto'), true);
    }
    return '';
}

 function test_get_switchable_roles()
 {
     global $USER;
     $tablenames = array('role', 'role_capabilities', 'role_assignments', 'role_allow_switch', 'capabilities', 'context', 'role_names');
     $this->create_test_tables($tablenames, 'lib');
     $this->switch_to_test_db();
     // Ensure SYSCONTEXTID is set.
     get_context_instance(CONTEXT_SYSTEM);
     $contexts = $this->load_test_data('context', array('contextlevel', 'instanceid', 'path', 'depth'), array('sys' => array(CONTEXT_SYSTEM, 0, '/' . SYSCONTEXTID, 1), 'cat' => array(CONTEXT_COURSECAT, 66, '/' . SYSCONTEXTID . '/' . (SYSCONTEXTID + 1), 2), 'cou' => array(CONTEXT_COURSE, 666, '/' . SYSCONTEXTID . '/' . (SYSCONTEXTID + 1) . '/' . (SYSCONTEXTID + 2), 3), 'fp' => array(CONTEXT_COURSE, SITEID, '/' . SYSCONTEXTID . '/' . SITEID, 2)));
     $this->testdb->set_field('context', 'id', SYSCONTEXTID, array('id' => $contexts['sys']->id));
     $this->testdb->set_field('context', 'id', SYSCONTEXTID + 1, array('id' => $contexts['cat']->id));
     $this->testdb->set_field('context', 'id', SYSCONTEXTID + 2, array('id' => $contexts['cou']->id));
     $syscontext = $contexts['sys'];
     $syscontext->id = SYSCONTEXTID;
     $context = $contexts['cou'];
     $context->id = SYSCONTEXTID + 2;
     $this->load_test_data('capabilities', array('name'), array(array('moodle/site:doanything'), array('moodle/course:view')));
     $roles = $this->load_test_data('role', array('name', 'shortname', 'description', 'sortorder'), array('admin' => array('admin', 'admin', 'not null', 1), 'r1' => array('r1', 'r1', 'not null', 2), 'r2' => array('r2', 'r2', 'not null', 3), 'funny' => array('funny', 'funny', 'not null', 4)));
     $adminid = $roles['admin']->id;
     $r1id = $roles['r1']->id;
     $r2id = $roles['r2']->id;
     $funnyid = $roles['funny']->id;
     // strange role to test that roles with 'moodle/site:doanything' and 'moodle/course:view' are not returned.
     $this->load_test_data('role_capabilities', array('roleid', 'capability', 'contextid', 'permission'), array(array($adminid, 'moodle/site:doanything', SYSCONTEXTID, CAP_ALLOW), array($r1id, 'moodle/course:view', SYSCONTEXTID + 1, CAP_ALLOW), array($r2id, 'moodle/course:view', SYSCONTEXTID, CAP_ALLOW), array($funnyid, 'moodle/site:doanything', SYSCONTEXTID, CAP_ALLOW), array($funnyid, 'moodle/course:view', SYSCONTEXTID, CAP_ALLOW)));
     $this->load_test_data('role_assignments', array('userid', 'contextid', 'roleid'), array(array(1, SYSCONTEXTID, $adminid), array(2, SYSCONTEXTID + 1, $r1id), array(3, SYSCONTEXTID + 2, $r2id)));
     $this->load_test_data('role_allow_switch', array('roleid', 'allowswitch'), array(array($r1id, $r2id), array($r2id, $r1id), array($r2id, $r2id), array($r2id, $funnyid)));
     // Admin should be able to switch to any role with 'moodle/course:view' in any context.
     $this->switch_global_user_id(1);
     accesslib_clear_all_caches_for_unit_testing();
     $this->assert(new ArraysHaveSameValuesExpectation(array($r2id)), array_keys(get_switchable_roles($syscontext)));
     $this->assert(new ArraysHaveSameValuesExpectation(array($r2id)), array_keys(get_switchable_roles($context)));
     $this->revert_global_user_id();
     // r1 should be able to switch to r2, but this user only has r1 in $context, not $syscontext.
     $this->switch_global_user_id(2);
     accesslib_clear_all_caches_for_unit_testing();
     $this->assert(new ArraysHaveSameValuesExpectation(array()), array_keys(get_switchable_roles($syscontext)));
     $this->assert(new ArraysHaveSameValuesExpectation(array($r2id)), array_keys(get_switchable_roles($context)));
     $this->revert_global_user_id();
     // The table says r2 should be able to switch to all of r1, r2 and funny, however, only r2 passes the tests on which roles can be returnd..
     $this->switch_global_user_id(3);
     accesslib_clear_all_caches_for_unit_testing();
     $this->assert(new ArraysHaveSameValuesExpectation(array()), array_keys(get_switchable_roles($syscontext)));
     $this->assert(new ArraysHaveSameValuesExpectation(array($r2id)), array_keys(get_switchable_roles($context)));
 }

/**
 * Returns a little popup menu for switching roles
 *
 * @global object
 * @global object
 * @uses CONTEXT_COURSE
 * @param int $courseid The course  to update by id as found in 'course' table
 * @return string
 */
function switchroles_form($courseid)
{
    global $CFG, $USER, $OUTPUT;
    if (!($context = get_context_instance(CONTEXT_COURSE, $courseid))) {
        return '';
    }
    if (!empty($USER->access['rsw'][$context->path])) {
        // Just a button to return to normal
        $options = array();
        $options['id'] = $courseid;
        $options['sesskey'] = sesskey();
        $options['switchrole'] = 0;
        return $OUTPUT->button(html_form::make_button($CFG->wwwroot . '/course/view.php', $options, get_string('switchrolereturn')));
    }
    if (has_capability('moodle/role:switchroles', $context)) {
        if (!($roles = get_switchable_roles($context))) {
            return '';
            // Nothing to show!
        }
        // unset default user role - it would not work
        unset($roles[$CFG->guestroleid]);
        $popupurl = $CFG->wwwroot . '/course/view.php?id=' . $courseid . '&sesskey=' . sesskey();
        $select = html_select::make_popup_form($popupurl, 'switchrole', $roles, 'switchrole', '');
        $select->nothinglabel = get_string('switchroleto');
        $select->set_help_icon('switchrole', get_string('switchroleto'));
        return $OUTPUT->select($select);
    }
    return '';
}

//.........这里部分代码省略.........
    $myhome->title = get_string('mymoodle', 'admin');
    $myhome->titleidentifier = 'mymoodle,admin';
    $myhome->pix = "i/course";
    $returnobject->navitems[] = $myhome;

    // Links: My Profile.
    $myprofile = new stdClass();
    $myprofile->itemtype = 'link';
    $myprofile->url = new moodle_url('/user/profile.php', array('id' => $user->id));
    $myprofile->title = get_string('profile');
    $myprofile->titleidentifier = 'profile,moodle';
    $myprofile->pix = "i/user";
    $returnobject->navitems[] = $myprofile;

    $returnobject->metadata['asotherrole'] = false;

    // Before we add the last items (usually a logout + switch role link), add any
    // custom-defined items.
    $customitems = user_convert_text_to_menu_items($CFG->customusermenuitems, $page);
    foreach ($customitems as $item) {
        $returnobject->navitems[] = $item;
    }


    if ($returnobject->metadata['asotheruser'] = \core\session\manager::is_loggedinas()) {
        $realuser = \core\session\manager::get_realuser();

        // Save values for the real user, as $user will be full of data for the
        // user the user is disguised as.
        $returnobject->metadata['realuserid'] = $realuser->id;
        $returnobject->metadata['realuserfullname'] = fullname($realuser, true);
        $returnobject->metadata['realuserprofileurl'] = new moodle_url('/user/profile.php', array(
            'id' => $realuser->id
        ));
        $returnobject->metadata['realuseravatar'] = $OUTPUT->user_picture($realuser, $avataroptions);

        // Build a user-revert link.
        $userrevert = new stdClass();
        $userrevert->itemtype = 'link';
        $userrevert->url = new moodle_url('/course/loginas.php', array(
            'id' => $course->id,
            'sesskey' => sesskey()
        ));
        $userrevert->pix = "a/logout";
        $userrevert->title = get_string('logout');
        $userrevert->titleidentifier = 'logout,moodle';
        $returnobject->navitems[] = $userrevert;

    } else {

        // Build a logout link.
        $logout = new stdClass();
        $logout->itemtype = 'link';
        $logout->url = new moodle_url('/login/logout.php', array('sesskey' => sesskey()));
        $logout->pix = "a/logout";
        $logout->title = get_string('logout');
        $logout->titleidentifier = 'logout,moodle';
        $returnobject->navitems[] = $logout;
    }

    if (is_role_switched($course->id)) {
        if ($role = $DB->get_record('role', array('id' => $user->access['rsw'][$context->path]))) {
            // Build role-return link instead of logout link.
            $rolereturn = new stdClass();
            $rolereturn->itemtype = 'link';
            $rolereturn->url = new moodle_url('/course/switchrole.php', array(
                'id' => $course->id,
                'sesskey' => sesskey(),
                'switchrole' => 0,
                'returnurl' => $page->url->out_as_local_url(false)
            ));
            $rolereturn->pix = "a/logout";
            $rolereturn->title = get_string('switchrolereturn');
            $rolereturn->titleidentifier = 'switchrolereturn,moodle';
            $returnobject->navitems[] = $rolereturn;

            $returnobject->metadata['asotherrole'] = true;
            $returnobject->metadata['rolename'] = role_get_name($role, $context);

        }
    } else {
        // Build switch role link.
        $roles = get_switchable_roles($context);
        if (is_array($roles) && (count($roles) > 0)) {
            $switchrole = new stdClass();
            $switchrole->itemtype = 'link';
            $switchrole->url = new moodle_url('/course/switchrole.php', array(
                'id' => $course->id,
                'switchrole' => -1,
                'returnurl' => $page->url->out_as_local_url(false)
            ));
            $switchrole->pix = "i/switchrole";
            $switchrole->title = get_string('switchroleto');
            $switchrole->titleidentifier = 'switchroleto,moodle';
            $returnobject->navitems[] = $switchrole;
        }
    }

    return $returnobject;
}

    }
} else {
    if ($switchrole < 0) {
        $PAGE->set_title(get_string('switchroleto'));
        $PAGE->set_heading($course->fullname);
        $PAGE->set_pagelayout('incourse');
        echo $OUTPUT->header();
        echo $OUTPUT->heading(get_string('switchroleto'));
        // Overall criteria aggregation.
        $roles = array();
        $assumedrole = -1;
        if (is_role_switched($course->id)) {
            $roles[0] = get_string('switchrolereturn');
            $assumedrole = $USER->access['rsw'][$context->path];
        }
        $availableroles = get_switchable_roles($context);
        if (is_array($availableroles)) {
            foreach ($availableroles as $key => $role) {
                if ($assumedrole == (int) $key) {
                    continue;
                }
                $roles[$key] = $role;
            }
        }
        echo $OUTPUT->box(markdown_to_html(get_string('switchroleto_help')));
        foreach ($roles as $key => $role) {
            $url = new moodle_url('/course/switchrole.php', array('id' => $id, 'switchrole' => $key, 'returnurl' => $returnurl));
            echo $OUTPUT->container($OUTPUT->single_button($url, $role), 'm-x-3 m-b-1');
        }
        $url = new moodle_url($returnurl);
        echo $OUTPUT->container($OUTPUT->action_link($url, get_string('cancel')), 'm-x-3 m-b-1');