A WordPress plugin to build an environment to develop a single stylesheet for the login/reg/pass screen in WP 3.1

future_core_login.php

<?php
/**
 * Plugin Name: 	Future Core Login
 * Plugin URI: 		http://unserkaiser.com
 * Description: 	Replacing the current stylesheets loaded on wp-login.php until this ticket goes into core: <a href="http://core.trac.wordpress.org/ticket/12506">#12506</a>
 * Version: 		0.1
 * Author: 			Franz Josef Kaiser
 * Author URI: 		http://unserkaiser.com
 * License: 		GPL2
 * 
 * This plugin is meant as testing environment for the development of a new stylesheet for the
 * WordPress login/password/register screen. Goal is to remove the admin-colors stylesheet
 * so in the future there would only be one stylesheet.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR 
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, 
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

if ( !class_exists('FutureCoreLogin') ) {
class FutureCoreLogin {
	public function __construct() {
		if ( $this->is_login() ) {
			add_action( 'init', array(&$this, 'deregister') );
			add_action( 'login_head', array( &$this, 'echo_css') );
			# @todo: manipulate (filter?) wp_admin_css to not load login.css and colors-xy.css from /core_root/wp-admin/css/ dir 
		}
	}
	
	/**
	 * Custom "Conditional Tag" to check if we are on the login screen
	 * props	adapted as a plugin function - altered from Ingo Henze & currently in use in my framework
	 * @return  boolean     $is_login
	 * @link	http://schnurpsel.de/suche/is_login/
	 */
		public function is_login() {
			$url_parts 	= parse_url( $_SERVER['REQUEST_URI'] );
			$path_parts = pathinfo( $url_parts['path'] );
			$dir_parts 	= explode( '/', $path_parts['dirname'] );
			$dirname 	= end( $dir_parts );
			$filename 	= $path_parts['basename'];
			
			if ( 'wp-login.php' == $filename ) {
				$is_login = true; 
			} 
			else {
				$is_login = false;
			}
			return $is_login;
		}
		
		// Deregister the current stylesheets for a clean environment
		public function deregister() {
			wp_deregister_style( 'login' );
			wp_deregister_style( 'colors-fresh' );
		}

		// return the file path
		public function locate_file( $filename = 'login.css' ) {
			$plugin_dir = WP_PLUGIN_URL.'/'.str_replace(basename( __FILE__),"",plugin_basename(__FILE__));

			if ( !file_exists( $plugin_dir.'/'.$filename) ) {
				return get_bloginfo('stylesheet_directory').'/'.$filename;
			} 
			else {
				return $plugin_dir.'/'.$filename;
			}
		}

		// Calling the new stylesheet
		public function echo_css() {
			$file = $this->locate_file();
			echo '<link rel="stylesheet" href="'.$file.'" type="text/css" />';
		}

		// Won't work on login_head action hook
		public function enqueue_css() {
			$file = $this->locate_file();
			wp_enqueue_style( 'future-core-login', $file, false, '0.0', 'screen' );
		}
} // END Class FutureCoreLogin


// INIT
new FutureCoreLogin();
} // endif;
?>