shimmie2/ext/handle_404/main.php

<?php
/**
 * Name: 404 Detector
 * Author: Shish <webmaster@shishnet.org>
 * Link: http://code.shishnet.org/shimmie2/
 * License: GPLv2
 * Description: Shows an error message when the user views a page with no content
 */

class Handle404 implements Extension {
	public function receive_event(Event $event) {
		if($event instanceof PageRequestEvent) {
			global $page;
			// hax.
			if($page->mode == "page" && (!isset($page->blocks) || $this->count_main($page->blocks) == 0)) {
				$h_pagename = html_escape(implode('/', $event->args));
				header("HTTP/1.0 404 Page Not Found");
				log_info("handle_404", "Hit 404: $h_pagename");
				$page->set_title("404");
				$page->set_heading("404 - No Handler Found");
				$page->add_block(new NavBlock());
				$page->add_block(new Block("Explanation", "No handler could be found for the page '$h_pagename'"));
			}
		}
	}

	private function count_main($blocks) {
		$n = 0;
		foreach($blocks as $block) {
			if($block->section == "main") $n++; // more hax.
		}
		return $n;
	}
}
add_event_listener(new Handle404(), 99); // hax++
?>