Make Fred play nice w/ Preview

FredPreview.plugin.php

<?php
//** On WebPage Pre-Render **//
$corePath = $modx->getOption('preview.core_path', null, $modx->getOption('core_path') . 'components/preview/');
require_once $corePath . '/model/preview/preview.class.php';
$preview = new Preview($modx);

if(!$modx->user->hasSessionContext('mgr')) return; // currently forcing manager context
if(!$modx->getOption('preview.frontendEnabled')) return; // currently forcing manager context
$qsItem = $modx->getOption('preview.previewKey');
$compareItem = $modx->getOption('preview.compareKey');
$allowedContentTypes = explode(',', $modx->getOption('preview.allowedContentTypes'));
$allowedClassKey = explode(',', $modx->getOption('preview.allowedClassKey'));
$revId = 0;
$parentId = $modx->resource->get('id');
$snip = '';
$ctxId = $preview->findContextContainer($modx->resource->get('context_key'));

$cntType = $modx->getObject('modContentType', $modx->resource->content_type);


if(!in_array($cntType->get('mime_type'), $allowedContentTypes)) {
	return false; // excluded
}

if(!in_array($modx->resource->class_key, $allowedClassKey)) {
	return false; // excluded
}

if(isset($_GET[$qsItem]) && $_GET[$qsItem]) $revId = $_GET[$qsItem];
if(isset($_GET[$compareItem]) && $_GET[$compareItem]) $compareId = $_GET[$compareItem];

$showMenu = true;
$compareMode = false;
$compareModxKey = $modx->getOption('preview.compareMode');
if(isset($_GET[$compareModxKey]) && $_GET[$compareModxKey]) {
	$showMenu = false;
	$compareMode = true;
}

if(!$compareMode && !$modx->getOption('preview.frontendEnabled')) {
	return false;
}

/** Add some preview functionality - Look for the "MODXpreview" QS item */
$prop = $modx->resource->get('properties');
if(isset($prop["preview"]) && isset($prop["preview"]["previewEnabled"]) && $prop["preview"]["previewEnabled"] == false) {
	$showMenu = false;
}

if($showMenu) {
	$_SESSION['fred'] = 5;
}

preview.item.fred.chunk.html

<li>
    <div>
        [[+active:eq=`1`:then=`<span class="extras_extra_preview_status">[[%preview.live? &namespace=`web`]]</span>`]]
        [[+pagetitle]] ([[+id]])
        <span class="extras_extra_preview_desc">
            [[+publishedOn:eq=`0000-00-00 00:00:00`:then=`[[%preview.not.published? &namespace=`web`]]`:else=`[[%preview.Published? &namespace=`web`]] [[+publishedOn:strtotime:date=`%b %e %Y, %l:%M %p`]]`]]
        </span>
        [[+revisionUrl:ne=``:then=`<a class="extras_extra_preview_button extras_extra_preview_button_view" href="[[~[[+id]]]]?fred=[[+editUrl:ne=``:then=`0`:else=`5`]]">[[%preview.view? &namespace=`web`]]</a>`]]
        [[+editUrl:ne=``:then=`<a class="extras_extra_preview_button extras_extra_preview_button_edit" href="[[~[[+id]]]]?fred=1">[[%preview.edit? &namespace=`web`]]</a>`]]
        [[+compareUrl:ne=``:then=`<a class="extras_extra_preview_button extras_extra_preview_button_compare" href="[[+compareUrl]]&fred=0">[[%preview.compare? &namespace=`web`]]</a>`]]
    </div>
</li>

Add the FredPreview plugin to run OnWebPagePreRender prior to Fred. Then adjust the properties of the snippet preview.getRevisions to use the tplRow = preview.item.fred