special-background.php

<?php
/**
 * Special Background Wordpress Plugin
 * 
 * @-wp-header Plugin Name: Special Background
 * @-wp-header Plugin URI: http://wordpress.stackexchange.com/questions/972/
 * @-wp-header Description: Example to show how to add a special background using exiting background admin page in core.
 * @-wp-header Version: 0.2
 * @-wp-header Author: Mike Schinkel, hakre
 * @-wp-header Author URI: http://mikeschinkel.com/custom-wordpress-plugins/
 */

return SpecialBackgroundPlugin::bootstrap();

class SpecialBackgroundPlugin {
	private $title        = 'Special Background';
	private $slug         = 'special-background';
	private $accessLevel  = 'manage_options';
	private $parentPage   = 'themes.php'; 
	private $optionPrefix = 'mods_';
	/** Theme Modification
	 * @var SpecialBackgroundMod 
	 */
	private $mod;
	/** Option Swapper
	 * @var SpecialBackgroundOptionSwapper
	 */
	private $swapper;
	static $instance;
	public function isAdminPage() {
		return $this->parentPage === $GLOBALS['pagenow'] 
				&& isset($_GET['page'])
				&& $this->slug === $_GET['page'];
	}
	/**
	 * Plugin Bootstrap
	 * 
	 * @return SpecialBackgroundPlugin
	 */
	public static function bootstrap() {
		(self::$instance === null) && 
			(self::$instance = new self());
		return self::$instance;
	}
	/**
	 * Plugin Constructor
	 */
	public function __construct() {
		$this->title = __($this->title);
		add_filter('admin_menu', array($this, 'admin_menu'));
		add_filter('admin_init', array($this, 'admin_init'));
		$optionName = $this->optionPrefix . get_current_theme();
		$this->swapper = new SpecialBackgroundOptionSwapper($optionName, $this);
	}
	public function admin_init() {
		if ($this->isAdminPage()) {
			$optionName = $this->optionPrefix . get_current_theme();
			'mods_' . get_current_theme();
			$this->mod  = new SpecialBackgroundMod($optionName);
			wp_enqueue_script('custom-background');
			wp_enqueue_style ('farbtastic');
		}
		$hook = sprintf('load-appearance_page_%s', $this->slug);
		foreach(array(
			'admin_load'    => 10,
			'take_action'   => 49,
			'handle_upload' => 49,
		) as $func => $priority) 
			add_action($hook, array($GLOBALS['custom_background'], $func), $priority);
	}
	public function admin_menu() {
		$title = $this->title;
		$slug  = $this->slug;
		add_theme_page($title, $title,'edit_theme_options', $slug, array($this, 'admin_page'));
	}
	public function admin_page() {
		if (!$this->isAdminPage())
			return;
		if (!current_user_can($this->accessLevel)) 
			return;
			
		$title = $this->title;
		
		$GLOBALS['parent_file']  = $this->parentPage;
		$GLOBALS['submenu_file'] = $this->parentPage.'?page=special-background';
		$GLOBALS['title']        = $title; // FIXME goes nowhere so far, check and/or remove
		require_once(ABSPATH . 'wp-admin/admin-header.php');
		ob_start();
		$GLOBALS['custom_background']->admin_page();
		echo preg_replace('#<h2>([^<]+)</h2>#', "<h2>{$title}</h2>", ob_get_clean());
	}
} // class



/**
 * SpecialBackground Theme Modification Class
 */
class SpecialBackgroundMod {
	/**
	 * Theme Mod Properties Prefix
	 * 
	 * @var string
	 */
	private $prefix     = 'background_';
	/**
	 * Theme Mod Properties 
	 * @var array
	 */
	private $properties = array(
		'image', 
		'image_thumb', 
		'repeat', 
		'position_x', 
		'attachment', 
		'color',
	);
	private $wpFilterPrefix = 'theme_mod_';
	private $funcPrefix     = 'background_';
	private $optionName;
	public function __construct($optionName) {
		$this->optionName = $optionName;
		$this->AddFilter();
	}
	/**
	 * AddFilter - Register all theme modification properties
	 */
	public function AddFilter() {
		$wp_prefix = $this->wpFilterPrefix . $this->prefix;
		$my_prefix = $this->funcPrefix;
		foreach($this->properties as $property)
			add_filter($wp_prefix.$property, array($this, $my_prefix.$property));
	}
	/**
	 * undefined function "hook"
	 * 
	 * @param string $name
	 * @param array  $arguments 
	 */
	public function __call($name , $arguments) {
		$funcPrefix = $this->funcPrefix;
		$properties = $this->properties;
		if (
			substr($name,0,strlen($funcPrefix))!==$funcPrefix
			|| !in_array(($attr = substr($name, strlen($funcPrefix))), $properties)
		) throw new BadMethodCallException(sprintf('Invalid Method: %s::%s.', __CLASS__, $name));
		
		// get theme property value from option store
		$defaults = $arguments[0];
		$mods     = get_option($this->optionName);
		$key      = 'special_background_'.$attr;
		$defaults = !empty($mods[$key]) ? $mods[$key] : '';
		
		return $defaults;
	}
} // class

/**
 * OptionSwapper Class
 *
 * Transparently hook into Backgrouind Picture 
 * Form Option processing Stream.
 */
class SpecialBackgroundOptionSwapper {
	private $option;
	/** 
	 * @var SpecialBackgroundPlugin */
	private $plugin;
	public function __construct($option, SpecialBackgroundPlugin $plugin) {
		$this->option = $option;
		$this->plugin = $plugin;
		add_filter('pre_update_option_'. $option,  array($this, 'pre_update_option'), 10, 2);
	}
	public function pre_update_option($vnew, $vold) {
		static $times = 0;
		if (!empty($_POST) && $this->plugin->isAdminPage()) {
			$key = null;
			if (  (isset($_POST['action']) && 'save' === $_POST['action'])
				 ||isset($_POST['reset-background']) 
				 ||isset($_POST['remove-background'])) {
				 $values = array(
				 	'image', 
				 	'image_thumb',
				 );
				 !empty($values[$times]) && ($key = $values[$times]);
			} else {
				$values = array(
					array('background-repeat', 'repeat'),
					array('background-position-x','position_x'),
					array('background-attachment','attachment'),
					array('background-color','color'),
				);
				!empty($values[$times]) && ($value = $values[$times]) 
				&& isset($_POST[$value[0]]) && ($key = $value[1]); 
			}
			if (null !== $key) {
				$vnew["special_background_{$key}"] = $vnew["background_{$key}"];
				$vnew["background_{$key}"]         = $vold["background_{$key}"];
			}
		}
		$times++;
		return $vnew;
	}
} //class
#EOF;