//.........这里部分代码省略.........
        $forumtracked = forum_tp_is_tracked($forum);
    } else {
        $forumtracked = false;
    }
    if ($forumtracked) {
        $unreads = forum_get_discussions_unread($cm);
    } else {
        $unreads = array();
    }
    if ($displayformat == 'header') {
        echo '<table cellspacing="0" class="forumheaderlist">';
        echo '<thead>';
        echo '<tr>';
        echo '<th class="header topic" scope="col">' . get_string('discussion', 'forum') . '</th>';
        echo '<th class="header author" colspan="2" scope="col">' . get_string('startedby', 'forum') . '</th>';
        if ($groupmode > 0) {
            echo '<th class="header group" scope="col">' . get_string('group') . '</th>';
        }
        if (has_capability('mod/forum:viewdiscussion', $context)) {
            echo '<th class="header replies" scope="col">' . get_string('replies', 'forum') . '</th>';
            // If the forum can be tracked, display the unread column.
            if ($cantrack) {
                echo '<th class="header replies" scope="col">' . get_string('unread', 'forum');
                if ($forumtracked) {
                    echo '<a title="' . get_string('markallread', 'forum') . '" href="' . $CFG->wwwroot . '/mod/forum/markposts.php?f=' . $forum->id . '&amp;mark=read&amp;returnpage=view.php&amp;sesskey=' . sesskey() . '">' . '<img src="' . $OUTPUT->pix_url('t/markasread') . '" class="iconsmall" alt="' . get_string('markallread', 'forum') . '" /></a>';
                }
                echo '</th>';
            }
        }
        echo '<th class="header lastpost" scope="col">' . get_string('lastpost', 'forum') . '</th>';
        if (!is_guest($context, $USER) && isloggedin() && has_capability('mod/forum:viewdiscussion', $context)) {
            if (\mod_forum\subscriptions::is_subscribable($forum)) {
                echo '<th class="header discussionsubscription" scope="col">';
                echo forum_get_discussion_subscription_icon_preloaders();
                echo '</th>';
            }
        }
        echo '</tr>';
        echo '</thead>';
        echo '<tbody>';
    }
    foreach ($discussions as $discussion) {
        if ($forum->type == 'qanda' && !has_capability('mod/forum:viewqandawithoutposting', $context) && !forum_user_has_posted($forum->id, $discussion->discussion, $USER->id)) {
            $canviewparticipants = false;
        }
        if (!empty($replies[$discussion->discussion])) {
            $discussion->replies = $replies[$discussion->discussion]->replies;
            $discussion->lastpostid = $replies[$discussion->discussion]->lastpostid;
        } else {
            $discussion->replies = 0;
        }
        // SPECIAL CASE: The front page can display a news item post to non-logged in users.
        // All posts are read in this case.
        if (!$forumtracked) {
            $discussion->unread = '-';
        } else {
            if (empty($USER)) {
                $discussion->unread = 0;
            } else {
                if (empty($unreads[$discussion->discussion])) {
                    $discussion->unread = 0;
                } else {
                    $discussion->unread = $unreads[$discussion->discussion];
                }
            }
        }

    $node->add(format_string($post->subject), $PAGE->url);
}
$PAGE->set_title("{$course->shortname}: " . format_string($discussion->name));
$PAGE->set_heading($course->fullname);
$PAGE->set_button($searchform);
$renderer = $PAGE->get_renderer('mod_forum');
echo $OUTPUT->header();
echo $OUTPUT->heading(format_string($forum->name), 2);
echo $OUTPUT->heading(format_string($discussion->name), 3, 'discussionname');
// is_guest should be used here as this also checks whether the user is a guest in the current course.
// Guests and visitors cannot subscribe - only enrolled users.
if (!is_guest($modcontext, $USER) && isloggedin() && has_capability('mod/forum:viewdiscussion', $modcontext)) {
    // Discussion subscription.
    if (\mod_forum\subscriptions::is_subscribable($forum)) {
        echo html_writer::div(forum_get_discussion_subscription_icon($forum, $post->discussion, null, true), 'discussionsubscription');
        echo forum_get_discussion_subscription_icon_preloaders();
    }
}
/// Check to see if groups are being used in this forum
/// If so, make sure the current person is allowed to see this discussion
/// Also, if we know they should be able to reply, then explicitly set $canreply for performance reasons
$canreply = forum_user_can_post($forum, $discussion, $USER, $cm, $course, $modcontext);
if (!$canreply and $forum->type !== 'news') {
    if (isguestuser() or !isloggedin()) {
        $canreply = true;
    }
    if (!is_enrolled($modcontext) and !is_viewing($modcontext)) {
        // allow guests and not-logged-in to see the link - they are prompted to log in after clicking the link
        // normal users with temporary guest access see this link too, they are asked to enrol instead
        $canreply = enrol_selfenrol_available($course->id);
    }