X-Git-Url: https://scripts.mit.edu/gitweb/autoinstalls/wordpress.git/blobdiff_plain/596d585e1dc1eb25bccd3781e37210a4e2504179..refs/tags/wordpress-4.3:/wp-includes/theme.php

diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index f449ae50..823d2ca4 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -14,6 +14,9 @@
  *
  * @since 3.4.0
  *
+ * @global array $wp_theme_directories
+ * @staticvar array $_themes
+ *
  * @param array $args The search arguments. Optional.
  * - errors      mixed  True to return themes with errors, false to return themes without errors, null
  *                      to return all themes. Defaults to false.
@@ -22,7 +25,7 @@
  *                      to return only network-allowed themes. Null to return all themes. Defaults to null.
  * - blog_id     int    (Multisite) The blog ID used to calculate which themes are allowed. Defaults to 0,
  *                      synonymous for the current blog.
- * @return Array of WP_Theme objects.
+ * @return array Array of WP_Theme objects.
  */
 function wp_get_themes( $args = array() ) {
 	global $wp_theme_directories;
@@ -84,9 +87,11 @@ function wp_get_themes( $args = array() ) {
  *
  * @since 3.4.0
  *
+ * @global array $wp_theme_directories
+ *
  * @param string $stylesheet Directory name for the theme. Optional. Defaults to current theme.
  * @param string $theme_root Absolute path of the theme root to look in. Optional. If not specified, get_raw_theme_root()
- * 	is used to calculate the theme root for the $stylesheet provided (or current theme).
+ * 	                         is used to calculate the theme root for the $stylesheet provided (or current theme).
  * @return WP_Theme Theme object. Be sure to check the object's exists() method if you need to confirm the theme's existence.
  */
 function wp_get_theme( $stylesheet = null, $theme_root = null ) {
@@ -106,6 +111,20 @@ function wp_get_theme( $stylesheet = null, $theme_root = null ) {
 	return new WP_Theme( $stylesheet, $theme_root );
 }
 
+/**
+ * Clears the cache held by get_theme_roots() and WP_Theme.
+ *
+ * @since 3.5.0
+ * @param bool $clear_update_cache Whether to clear the Theme updates cache
+ */
+function wp_clean_themes_cache( $clear_update_cache = true ) {
+	if ( $clear_update_cache )
+		delete_site_transient( 'update_themes' );
+	search_theme_directories( true );
+	foreach ( wp_get_themes( array( 'errors' => null ) ) as $theme )
+		$theme->cache_delete();
+}
+
 /**
  * Whether a child theme is in use.
  *
@@ -123,23 +142,28 @@ function is_child_theme() {
  * The theme name that the administrator has currently set the front end theme
  * as.
  *
- * For all extensive purposes, the template name and the stylesheet name are
+ * For all intents and purposes, the template name and the stylesheet name are
  * going to be the same for most cases.
  *
  * @since 1.5.0
- * @uses apply_filters() Calls 'stylesheet' filter on stylesheet name.
  *
  * @return string Stylesheet name.
  */
 function get_stylesheet() {
-	return apply_filters('stylesheet', get_option('stylesheet'));
+	/**
+	 * Filter the name of current stylesheet.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $stylesheet Name of the current stylesheet.
+	 */
+	return apply_filters( 'stylesheet', get_option( 'stylesheet' ) );
 }
 
 /**
  * Retrieve stylesheet directory path for current theme.
  *
  * @since 1.5.0
- * @uses apply_filters() Calls 'stylesheet_directory' filter on stylesheet directory and theme name.
  *
  * @return string Path to current theme directory.
  */
@@ -148,6 +172,15 @@ function get_stylesheet_directory() {
 	$theme_root = get_theme_root( $stylesheet );
 	$stylesheet_dir = "$theme_root/$stylesheet";
 
+	/**
+	 * Filter the stylesheet directory path for current theme.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $stylesheet_dir Absolute path to the current them.
+	 * @param string $stylesheet     Directory name of the current theme.
+	 * @param string $theme_root     Absolute path to themes directory.
+	 */
 	return apply_filters( 'stylesheet_directory', $stylesheet_dir, $stylesheet, $theme_root );
 }
 
@@ -159,10 +192,19 @@ function get_stylesheet_directory() {
  * @return string
  */
 function get_stylesheet_directory_uri() {
-	$stylesheet = get_stylesheet();
+	$stylesheet = str_replace( '%2F', '/', rawurlencode( get_stylesheet() ) );
 	$theme_root_uri = get_theme_root_uri( $stylesheet );
 	$stylesheet_dir_uri = "$theme_root_uri/$stylesheet";
 
+	/**
+	 * Filter the stylesheet directory URI.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $stylesheet_dir_uri Stylesheet directory URI.
+	 * @param string $stylesheet         Name of the activated theme's directory.
+	 * @param string $theme_root_uri     Themes root URI.
+	 */
 	return apply_filters( 'stylesheet_directory_uri', $stylesheet_dir_uri, $stylesheet, $theme_root_uri );
 }
 
@@ -173,14 +215,21 @@ function get_stylesheet_directory_uri() {
  * get_stylesheet_directory_uri() stylesheet directory URI} path.
  *
  * @since 1.5.0
- * @uses apply_filters() Calls 'stylesheet_uri' filter on stylesheet URI path and stylesheet directory URI.
  *
  * @return string
  */
 function get_stylesheet_uri() {
 	$stylesheet_dir_uri = get_stylesheet_directory_uri();
 	$stylesheet_uri = $stylesheet_dir_uri . '/style.css';
-	return apply_filters('stylesheet_uri', $stylesheet_uri, $stylesheet_dir_uri);
+	/**
+	 * Filter the URI of the current theme stylesheet.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $stylesheet_uri     Stylesheet URI for the current theme/child theme.
+	 * @param string $stylesheet_dir_uri Stylesheet directory URI for the current theme/child theme.
+	 */
+	return apply_filters( 'stylesheet_uri', $stylesheet_uri, $stylesheet_dir_uri );
 }
 
 /**
@@ -198,7 +247,8 @@ function get_stylesheet_uri() {
  * separate folder, then change the latter.
  *
  * @since 2.1.0
- * @uses apply_filters() Calls 'locale_stylesheet_uri' filter on stylesheet URI path and stylesheet directory URI.
+ *
+ * @global WP_Locale $wp_locale
  *
  * @return string
  */
@@ -213,26 +263,39 @@ function get_locale_stylesheet_uri() {
 		$stylesheet_uri = "$stylesheet_dir_uri/{$wp_locale->text_direction}.css";
 	else
 		$stylesheet_uri = '';
-	return apply_filters('locale_stylesheet_uri', $stylesheet_uri, $stylesheet_dir_uri);
+	/**
+	 * Filter the localized stylesheet URI.
+	 *
+	 * @since 2.1.0
+	 *
+	 * @param string $stylesheet_uri     Localized stylesheet URI.
+	 * @param string $stylesheet_dir_uri Stylesheet directory URI.
+	 */
+	return apply_filters( 'locale_stylesheet_uri', $stylesheet_uri, $stylesheet_dir_uri );
 }
 
 /**
  * Retrieve name of the current theme.
  *
  * @since 1.5.0
- * @uses apply_filters() Calls 'template' filter on template option.
  *
  * @return string Template name.
  */
 function get_template() {
-	return apply_filters('template', get_option('template'));
+	/**
+	 * Filter the name of the current theme.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $template Current theme's directory name.
+	 */
+	return apply_filters( 'template', get_option( 'template' ) );
 }
 
 /**
  * Retrieve current theme directory.
  *
  * @since 1.5.0
- * @uses apply_filters() Calls 'template_directory' filter on template directory path and template name.
  *
  * @return string Template directory path.
  */
@@ -241,6 +304,15 @@ function get_template_directory() {
 	$theme_root = get_theme_root( $template );
 	$template_dir = "$theme_root/$template";
 
+	/**
+	 * Filter the current theme directory path.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $template_dir The URI of the current theme directory.
+	 * @param string $template     Directory name of the current theme.
+	 * @param string $theme_root   Absolute path to the themes directory.
+	 */
 	return apply_filters( 'template_directory', $template_dir, $template, $theme_root );
 }
 
@@ -248,15 +320,23 @@ function get_template_directory() {
  * Retrieve theme directory URI.
  *
  * @since 1.5.0
- * @uses apply_filters() Calls 'template_directory_uri' filter on template directory URI path and template name.
  *
  * @return string Template directory URI.
  */
 function get_template_directory_uri() {
-	$template = get_template();
+	$template = str_replace( '%2F', '/', rawurlencode( get_template() ) );
 	$theme_root_uri = get_theme_root_uri( $template );
 	$template_dir_uri = "$theme_root_uri/$template";
 
+	/**
+	 * Filter the current theme directory URI.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $template_dir_uri The URI of the current theme directory.
+	 * @param string $template         Directory name of the current theme.
+	 * @param string $theme_root_uri   The themes root URI.
+	 */
 	return apply_filters( 'template_directory_uri', $template_dir_uri, $template, $theme_root_uri );
 }
 
@@ -265,6 +345,8 @@ function get_template_directory_uri() {
  *
  * @since 2.9.0
  *
+ * @global array $wp_theme_directories
+ *
  * @return array|string An array of theme roots keyed by template/stylesheet or a single theme root if all themes have the same root.
  */
 function get_theme_roots() {
@@ -286,6 +368,8 @@ function get_theme_roots() {
  *
  * @since 2.9.0
  *
+ * @global array $wp_theme_directories
+ *
  * @param string $directory Either the full filesystem path to a theme folder or a folder within WP_CONTENT_DIR
  * @return bool
  */
@@ -296,11 +380,19 @@ function register_theme_directory( $directory ) {
 		// Try prepending as the theme directory could be relative to the content directory
 		$directory = WP_CONTENT_DIR . '/' . $directory;
 		// If this directory does not exist, return and do not register
-		if ( ! file_exists( $directory ) )
+		if ( ! file_exists( $directory ) ) {
 			return false;
+		}
 	}
 
-	$wp_theme_directories[] = $directory;
+	if ( ! is_array( $wp_theme_directories ) ) {
+		$wp_theme_directories = array();
+	}
+
+	$untrailed = untrailingslashit( $directory );
+	if ( ! empty( $untrailed ) && ! in_array( $untrailed, $wp_theme_directories ) ) {
+		$wp_theme_directories[] = $untrailed;
+	}
 
 	return true;
 }
@@ -310,25 +402,30 @@ function register_theme_directory( $directory ) {
  *
  * @since 2.9.0
  *
+ * @global array $wp_theme_directories
+ * @staticvar array $found_themes
+ *
  * @param bool $force Optional. Whether to force a new directory scan. Defaults to false.
- * @return array Valid themes found
+ * @return array|false Valid themes found
  */
 function search_theme_directories( $force = false ) {
 	global $wp_theme_directories;
+	static $found_themes = null;
+
 	if ( empty( $wp_theme_directories ) )
 		return false;
 
-	static $found_themes;
 	if ( ! $force && isset( $found_themes ) )
 		return $found_themes;
 
 	$found_themes = array();
 
 	$wp_theme_directories = (array) $wp_theme_directories;
+	$relative_theme_roots = array();
 
 	// Set up maybe-relative, maybe-absolute array of theme directories.
 	// We always want to return absolute, but we need to cache relative
-	// use in for get_theme_root().
+	// to use in get_theme_root().
 	foreach ( $wp_theme_directories as $theme_root ) {
 		if ( 0 === strpos( $theme_root, WP_CONTENT_DIR ) )
 			$relative_theme_roots[ str_replace( WP_CONTENT_DIR, '', $theme_root ) ] = $theme_root;
@@ -336,6 +433,14 @@ function search_theme_directories( $force = false ) {
 			$relative_theme_roots[ $theme_root ] = $theme_root;
 	}
 
+	/**
+	 * Filter whether to get the cache of the registered theme directories.
+	 *
+	 * @since 3.4.0
+	 *
+	 * @param bool   $cache_expiration Whether to get the cache of the theme directories. Default false.
+	 * @param string $cache_directory  Directory to be searched for the cache.
+	 */
 	if ( $cache_expiration = apply_filters( 'wp_cache_themes_persistently', false, 'search_theme_directories' ) ) {
 		$cached_roots = get_site_transient( 'theme_roots' );
 		if ( is_array( $cached_roots ) ) {
@@ -361,8 +466,10 @@ function search_theme_directories( $force = false ) {
 
 		// Start with directories in the root of the current theme directory.
 		$dirs = @ scandir( $theme_root );
-		if ( ! $dirs )
-			return false;
+		if ( ! $dirs ) {
+			trigger_error( "$theme_root is not readable", E_USER_NOTICE );
+			continue;
+		}
 		foreach ( $dirs as $dir ) {
 			if ( ! is_dir( $theme_root . '/' . $dir ) || $dir[0] == '.' || $dir == 'CVS' )
 				continue;
@@ -378,8 +485,10 @@ function search_theme_directories( $force = false ) {
 				// wp-content/themes/a-folder-of-themes/*
 				// wp-content/themes is $theme_root, a-folder-of-themes is $dir, then themes are $sub_dirs
 				$sub_dirs = @ scandir( $theme_root . '/' . $dir );
-				if ( ! $sub_dirs )
-					return false;
+				if ( ! $sub_dirs ) {
+					trigger_error( "$theme_root/$dir is not readable", E_USER_NOTICE );
+					continue;
+				}
 				foreach ( $sub_dirs as $sub_dir ) {
 					if ( ! is_dir( $theme_root . '/' . $dir . '/' . $sub_dir ) || $dir[0] == '.' || $dir == 'CVS' )
 						continue;
@@ -423,7 +532,8 @@ function search_theme_directories( $force = false ) {
  * Does not have trailing slash.
  *
  * @since 1.5.0
- * @uses apply_filters() Calls 'theme_root' filter on path.
+ *
+ * @global array $wp_theme_directories
  *
  * @param string $stylesheet_or_template The stylesheet or template name of the theme
  * @return string Theme path.
@@ -440,6 +550,13 @@ function get_theme_root( $stylesheet_or_template = false ) {
 		$theme_root = WP_CONTENT_DIR . '/themes';
 	}
 
+	/**
+	 * Filter the absolute path to the themes directory.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $theme_root Absolute path to themes directory.
+	 */
 	return apply_filters( 'theme_root', $theme_root );
 }
 
@@ -450,10 +567,12 @@ function get_theme_root( $stylesheet_or_template = false ) {
  *
  * @since 1.5.0
  *
+ * @global array $wp_theme_directories
+ *
  * @param string $stylesheet_or_template Optional. The stylesheet or template name of the theme.
- * 	Default is to leverage the main theme root.
- * @param string $theme_root Optional. The theme root for which calculations will be based, preventing
- * 	the need for a get_raw_theme_root() call.
+ * 	                                     Default is to leverage the main theme root.
+ * @param string $theme_root             Optional. The theme root for which calculations will be based, preventing
+ * 	                                     the need for a get_raw_theme_root() call.
  * @return string Themes URI.
  */
 function get_theme_root_uri( $stylesheet_or_template = false, $theme_root = false ) {
@@ -480,7 +599,16 @@ function get_theme_root_uri( $stylesheet_or_template = false, $theme_root = fals
 		$theme_root_uri = content_url( 'themes' );
 	}
 
-	return apply_filters( 'theme_root_uri', $theme_root_uri, get_option('siteurl'), $stylesheet_or_template );
+	/**
+	 * Filter the URI for themes directory.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string $theme_root_uri         The URI for themes directory.
+	 * @param string $siteurl                WordPress web address which is set in General Options.
+	 * @param string $stylesheet_or_template Stylesheet or template name of the theme.
+	 */
+	return apply_filters( 'theme_root_uri', $theme_root_uri, get_option( 'siteurl' ), $stylesheet_or_template );
 }
 
 /**
@@ -488,8 +616,11 @@ function get_theme_root_uri( $stylesheet_or_template = false, $theme_root = fals
  *
  * @since 3.1.0
  *
+ * @global array $wp_theme_directories
+ *
  * @param string $stylesheet_or_template The stylesheet or template name of the theme
- * @param bool $skip_cache Optional. Whether to skip the cache. Defaults to false, meaning the cache is used.
+ * @param bool   $skip_cache             Optional. Whether to skip the cache.
+ *                                       Defaults to false, meaning the cache is used.
  * @return string Theme root
  */
 function get_raw_theme_root( $stylesheet_or_template, $skip_cache = false ) {
@@ -530,131 +661,42 @@ function locale_stylesheet() {
 }
 
 /**
- * Start preview theme output buffer.
- *
- * Will only preform task if the user has permissions and template and preview
- * query variables exist.
- *
- * @since 2.6.0
- */
-function preview_theme() {
-	if ( ! (isset($_GET['template']) && isset($_GET['preview'])) )
-		return;
-
-	if ( !current_user_can( 'switch_themes' ) )
-		return;
-
-	// Admin Thickbox requests
-	if ( isset( $_GET['preview_iframe'] ) )
-		show_admin_bar( false );
-
-	$_GET['template'] = preg_replace('|[^a-z0-9_./-]|i', '', $_GET['template']);
-
-	if ( validate_file($_GET['template']) )
-		return;
-
-	add_filter( 'template', '_preview_theme_template_filter' );
-
-	if ( isset($_GET['stylesheet']) ) {
-		$_GET['stylesheet'] = preg_replace('|[^a-z0-9_./-]|i', '', $_GET['stylesheet']);
-		if ( validate_file($_GET['stylesheet']) )
-			return;
-		add_filter( 'stylesheet', '_preview_theme_stylesheet_filter' );
-	}
-
-	// Prevent theme mods to current theme being used on theme being previewed
-	add_filter( 'pre_option_theme_mods_' . get_option( 'stylesheet' ), '__return_empty_array' );
-
-	ob_start( 'preview_theme_ob_filter' );
-}
-add_action('setup_theme', 'preview_theme');
-
-/**
- * Private function to modify the current template when previewing a theme
+ * Switches the theme.
  *
- * @since 2.9.0
- * @access private
- *
- * @return string
- */
-function _preview_theme_template_filter() {
-	return isset($_GET['template']) ? $_GET['template'] : '';
-}
-
-/**
- * Private function to modify the current stylesheet when previewing a theme
- *
- * @since 2.9.0
- * @access private
- *
- * @return string
- */
-function _preview_theme_stylesheet_filter() {
-	return isset($_GET['stylesheet']) ? $_GET['stylesheet'] : '';
-}
-
-/**
- * Callback function for ob_start() to capture all links in the theme.
- *
- * @since 2.6.0
- * @access private
- *
- * @param string $content
- * @return string
- */
-function preview_theme_ob_filter( $content ) {
-	return preg_replace_callback( "|(<a.*?href=([\"']))(.*?)([\"'].*?>)|", 'preview_theme_ob_filter_callback', $content );
-}
-
-/**
- * Manipulates preview theme links in order to control and maintain location.
- *
- * Callback function for preg_replace_callback() to accept and filter matches.
- *
- * @since 2.6.0
- * @access private
- *
- * @param array $matches
- * @return string
- */
-function preview_theme_ob_filter_callback( $matches ) {
-	if ( strpos($matches[4], 'onclick') !== false )
-		$matches[4] = preg_replace('#onclick=([\'"]).*?(?<!\\\)\\1#i', '', $matches[4]); //Strip out any onclicks from rest of <a>. (?<!\\\) means to ignore the '" if its escaped by \  to prevent breaking mid-attribute.
-	if (
-		( false !== strpos($matches[3], '/wp-admin/') )
-	||
-		( false !== strpos( $matches[3], '://' ) && 0 !== strpos( $matches[3], home_url() ) )
-	||
-		( false !== strpos($matches[3], '/feed/') )
-	||
-		( false !== strpos($matches[3], '/trackback/') )
-	)
-		return $matches[1] . "#$matches[2] onclick=$matches[2]return false;" . $matches[4];
-
-	$link = add_query_arg( array( 'preview' => 1, 'template' => $_GET['template'], 'stylesheet' => @$_GET['stylesheet'], 'preview_iframe' => 1 ), $matches[3] );
-	if ( 0 === strpos($link, 'preview=1') )
-		$link = "?$link";
-	return $matches[1] . esc_attr( $link ) . $matches[4];
-}
-
-/**
- * Switches current theme to new template and stylesheet names.
+ * Accepts one argument: $stylesheet of the theme. It also accepts an additional function signature
+ * of two arguments: $template then $stylesheet. This is for backwards compatibility.
  *
  * @since 2.5.0
- * @uses do_action() Calls 'switch_theme' action, passing the new theme.
  *
- * @param string $template Template name
- * @param string $stylesheet Stylesheet name.
+ * @global array                $wp_theme_directories
+ * @global WP_Customize_Manager $wp_customize
+ * @global array                $sidebars_widgets
+ *
+ * @param string $stylesheet Stylesheet name
  */
-function switch_theme( $template, $stylesheet ) {
-	global $wp_theme_directories, $sidebars_widgets;
+function switch_theme( $stylesheet ) {
+	global $wp_theme_directories, $wp_customize, $sidebars_widgets;
+
+	$_sidebars_widgets = null;
+	if ( 'wp_ajax_customize_save' === current_action() ) {
+		$_sidebars_widgets = $wp_customize->post_value( $wp_customize->get_setting( 'old_sidebars_widgets_data' ) );
+	} elseif ( is_array( $sidebars_widgets ) ) {
+		$_sidebars_widgets = $sidebars_widgets;
+	}
 
-	if ( is_array( $sidebars_widgets ) )
-		set_theme_mod( 'sidebars_widgets', array( 'time' => time(), 'data' => $sidebars_widgets ) );
+	if ( is_array( $_sidebars_widgets ) ) {
+		set_theme_mod( 'sidebars_widgets', array( 'time' => time(), 'data' => $_sidebars_widgets ) );
+	}
 
 	$old_theme  = wp_get_theme();
 	$new_theme = wp_get_theme( $stylesheet );
-	$new_name  = $new_theme->get('Name');
+
+	if ( func_num_args() > 1 ) {
+		$template = $stylesheet;
+		$stylesheet = func_get_arg( 1 );
+	} else {
+		$template = $new_theme->get_template();
+	}
 
 	update_option( 'template', $template );
 	update_option( 'stylesheet', $stylesheet );
@@ -662,16 +704,39 @@ function switch_theme( $template, $stylesheet ) {
 	if ( count( $wp_theme_directories ) > 1 ) {
 		update_option( 'template_root', get_raw_theme_root( $template, true ) );
 		update_option( 'stylesheet_root', get_raw_theme_root( $stylesheet, true ) );
+	} else {
+		delete_option( 'template_root' );
+		delete_option( 'stylesheet_root' );
 	}
 
+	$new_name  = $new_theme->get('Name');
+
 	update_option( 'current_theme', $new_name );
 
+	// Migrate from the old mods_{name} option to theme_mods_{slug}.
 	if ( is_admin() && false === get_option( 'theme_mods_' . $stylesheet ) ) {
 		$default_theme_mods = (array) get_option( 'mods_' . $new_name );
 		add_option( "theme_mods_$stylesheet", $default_theme_mods );
+	} else {
+		/*
+		 * Since retrieve_widgets() is called when initializing a theme in the Customizer,
+		 * we need to to remove the theme mods to avoid overwriting changes made via
+		 * the Customizer when accessing wp-admin/widgets.php.
+		 */
+		if ( 'wp_ajax_customize_save' === current_action() ) {
+			remove_theme_mod( 'sidebars_widgets' );
+		}
 	}
 
 	update_option( 'theme_switched', $old_theme->get_stylesheet() );
+	/**
+	 * Fires after the theme is switched.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string   $new_name  Name of the new theme.
+	 * @param WP_Theme $new_theme WP_Theme instance of the new theme.
+	 */
 	do_action( 'switch_theme', $new_name, $new_theme );
 }
 
@@ -689,22 +754,28 @@ function switch_theme( $template, $stylesheet ) {
  * @return bool
  */
 function validate_current_theme() {
-	// Don't validate during an install/upgrade.
-	if ( defined('WP_INSTALLING') || !apply_filters( 'validate_current_theme', true ) )
+	/**
+	 * Filter whether to validate the current theme.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param bool true Validation flag to check the current theme.
+	 */
+	if ( defined('WP_INSTALLING') || ! apply_filters( 'validate_current_theme', true ) )
 		return true;
 
 	if ( get_template() != WP_DEFAULT_THEME && !file_exists(get_template_directory() . '/index.php') ) {
-		switch_theme( WP_DEFAULT_THEME, WP_DEFAULT_THEME );
+		switch_theme( WP_DEFAULT_THEME );
 		return false;
 	}
 
 	if ( get_stylesheet() != WP_DEFAULT_THEME && !file_exists(get_template_directory() . '/style.css') ) {
-		switch_theme( WP_DEFAULT_THEME, WP_DEFAULT_THEME );
+		switch_theme( WP_DEFAULT_THEME );
 		return false;
 	}
 
 	if ( is_child_theme() && ! file_exists( get_stylesheet_directory() . '/style.css' ) ) {
-		switch_theme( WP_DEFAULT_THEME, WP_DEFAULT_THEME );
+		switch_theme( WP_DEFAULT_THEME );
 		return false;
 	}
 
@@ -716,11 +787,12 @@ function validate_current_theme() {
  *
  * @since 3.1.0
  *
- * @return array Theme modifications.
+ * @return array|void Theme modifications.
  */
 function get_theme_mods() {
 	$theme_slug = get_option( 'stylesheet' );
-	if ( false === ( $mods = get_option( "theme_mods_$theme_slug" ) ) ) {
+	$mods = get_option( "theme_mods_$theme_slug" );
+	if ( false === $mods ) {
 		$theme_name = get_option( 'current_theme' );
 		if ( false === $theme_name )
 			$theme_name = wp_get_theme()->get('Name');
@@ -742,22 +814,35 @@ function get_theme_mods() {
  * directory URI.
  *
  * @since 2.1.0
- * @uses apply_filters() Calls 'theme_mod_$name' filter on the value.
  *
- * @param string $name Theme modification name.
+ * @param string      $name    Theme modification name.
  * @param bool|string $default
  * @return string
  */
 function get_theme_mod( $name, $default = false ) {
 	$mods = get_theme_mods();
 
-	if ( isset( $mods[ $name ] ) )
-		return apply_filters( "theme_mod_$name", $mods[ $name ] );
+	if ( isset( $mods[$name] ) ) {
+		/**
+		 * Filter the theme modification, or 'theme_mod', value.
+		 *
+		 * The dynamic portion of the hook name, `$name`, refers to
+		 * the key name of the modification array. For example,
+		 * 'header_textcolor', 'header_image', and so on depending
+		 * on the theme options.
+		 *
+		 * @since 2.2.0
+		 *
+		 * @param string $current_mod The value of the current theme modification.
+		 */
+		return apply_filters( "theme_mod_{$name}", $mods[$name] );
+	}
 
 	if ( is_string( $default ) )
 		$default = sprintf( $default, get_template_directory_uri(), get_stylesheet_directory_uri() );
 
-	return apply_filters( "theme_mod_$name", $default );
+	/** This filter is documented in wp-includes/theme.php */
+	return apply_filters( "theme_mod_{$name}", $default );
 }
 
 /**
@@ -765,13 +850,26 @@ function get_theme_mod( $name, $default = false ) {
  *
  * @since 2.1.0
  *
- * @param string $name Theme modification name.
- * @param string $value theme modification value.
+ * @param string $name  Theme modification name.
+ * @param mixed  $value Theme modification value.
  */
 function set_theme_mod( $name, $value ) {
 	$mods = get_theme_mods();
-
-	$mods[ $name ] = $value;
+	$old_value = isset( $mods[ $name ] ) ? $mods[ $name ] : false;
+
+	/**
+	 * Filter the theme mod value on save.
+	 *
+	 * The dynamic portion of the hook name, `$name`, refers to the key name of
+	 * the modification array. For example, 'header_textcolor', 'header_image',
+	 * and so on depending on the theme options.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $value     The new value of the theme mod.
+	 * @param string $old_value The current value of the theme mod.
+	 */
+	$mods[ $name ] = apply_filters( "pre_set_theme_mod_$name", $value, $old_value );
 
 	$theme = get_option( 'stylesheet' );
 	update_option( "theme_mods_$theme", $mods );
@@ -786,7 +884,6 @@ function set_theme_mod( $name, $value ) {
  * @since 2.1.0
  *
  * @param string $name Theme modification name.
- * @return null
  */
 function remove_theme_mod( $name ) {
 	$mods = get_theme_mods();
@@ -796,9 +893,10 @@ function remove_theme_mod( $name ) {
 
 	unset( $mods[ $name ] );
 
-	if ( empty( $mods ) )
-		return remove_theme_mods();
-
+	if ( empty( $mods ) ) {
+		remove_theme_mods();
+		return;
+	}
 	$theme = get_option( 'stylesheet' );
 	update_option( "theme_mods_$theme", $mods );
 }
@@ -850,7 +948,20 @@ function display_header_text() {
 		return false;
 
 	$text_color = get_theme_mod( 'header_textcolor', get_theme_support( 'custom-header', 'default-text-color' ) );
-	return 'blank' != $text_color;
+	return 'blank' !== $text_color;
+}
+
+/**
+ * Check whether a header image is set or not.
+ *
+ * @since 4.2.0
+ *
+ * @see get_header_image()
+ *
+ * @return bool Whether a header image is set or not.
+ */
+function has_header_image() {
+	return (bool) get_header_image();
 }
 
 /**
@@ -858,7 +969,7 @@ function display_header_text() {
  *
  * @since 2.1.0
  *
- * @return string
+ * @return string|false
  */
 function get_header_image() {
 	$url = get_theme_mod( 'header_image', get_theme_support( 'custom-header', 'default-image' ) );
@@ -869,12 +980,7 @@ function get_header_image() {
 	if ( is_random_header_image() )
 		$url = get_random_header_image();
 
-	if ( is_ssl() )
-		$url = str_replace( 'http://', 'https://', $url );
-	else
-		$url = str_replace( 'https://', 'http://', $url );
-
-	return esc_url_raw( $url );
+	return esc_url_raw( set_url_scheme( $url ) );
 }
 
 /**
@@ -884,11 +990,13 @@ function get_header_image() {
  *
  * @access private
  *
- * @return string Path to header image
+ * @global array  $_wp_default_headers
+ * @staticvar object $_wp_random_header
+ *
+ * @return object
  */
-
 function _get_random_header_data() {
-	static $_wp_random_header;
+	static $_wp_random_header = null;
 
 	if ( empty( $_wp_random_header ) ) {
 		global $_wp_default_headers;
@@ -924,7 +1032,6 @@ function _get_random_header_data() {
  *
  * @return string Path to header image
  */
-
 function get_random_header_image() {
 	$random_image = _get_random_header_data();
 	if ( empty( $random_image->url ) )
@@ -942,7 +1049,7 @@ function get_random_header_image() {
  * @since 3.2.0
  *
  * @param string $type The random pool to use. any|default|uploaded
- * @return boolean
+ * @return bool
  */
 function is_random_header_image( $type = 'any' ) {
 	$header_image_mod = get_theme_mod( 'header_image', get_theme_support( 'custom-header', 'default-image' ) );
@@ -961,12 +1068,15 @@ function is_random_header_image( $type = 'any' ) {
 }
 
 /**
- * Display header image path.
+ * Display header image URL.
  *
  * @since 2.1.0
  */
 function header_image() {
-	echo get_header_image();
+	$image = get_header_image();
+	if ( $image ) {
+		echo esc_url( $image );
+	}
 }
 
 /**
@@ -986,15 +1096,20 @@ function get_uploaded_header_images() {
 		return array();
 
 	foreach ( (array) $headers as $header ) {
-		$url = esc_url_raw( $header->guid );
+		$url = esc_url_raw( wp_get_attachment_url( $header->ID ) );
 		$header_data = wp_get_attachment_metadata( $header->ID );
 		$header_index = basename($url);
+
 		$header_images[$header_index] = array();
-		$header_images[$header_index]['attachment_id'] =  $header->ID;
+		$header_images[$header_index]['attachment_id'] = $header->ID;
 		$header_images[$header_index]['url'] =  $url;
-		$header_images[$header_index]['thumbnail_url'] =  $url;
-		$header_images[$header_index]['width'] = $header_data['width'];
-		$header_images[$header_index]['height'] = $header_data['height'];
+		$header_images[$header_index]['thumbnail_url'] = $url;
+		$header_images[$header_index]['alt_text'] = get_post_meta( $header->ID, '_wp_attachment_image_alt', true );
+
+		if ( isset( $header_data['width'] ) )
+			$header_images[$header_index]['width'] = $header_data['width'];
+		if ( isset( $header_data['height'] ) )
+			$header_images[$header_index]['height'] = $header_data['height'];
 	}
 
 	return $header_images;
@@ -1005,10 +1120,35 @@ function get_uploaded_header_images() {
  *
  * @since 3.4.0
  *
+ * @global array $_wp_default_headers
+ *
  * @return object
  */
 function get_custom_header() {
-	$data = is_random_header_image()? _get_random_header_data() : get_theme_mod( 'header_image_data' );
+	global $_wp_default_headers;
+
+	if ( is_random_header_image() ) {
+		$data = _get_random_header_data();
+	} else {
+		$data = get_theme_mod( 'header_image_data' );
+		if ( ! $data && current_theme_supports( 'custom-header', 'default-image' ) ) {
+			$directory_args = array( get_template_directory_uri(), get_stylesheet_directory_uri() );
+			$data = array();
+			$data['url'] = $data['thumbnail_url'] = vsprintf( get_theme_support( 'custom-header', 'default-image' ), $directory_args );
+			if ( ! empty( $_wp_default_headers ) ) {
+				foreach ( (array) $_wp_default_headers as $default_header ) {
+					$url = vsprintf( $default_header['url'], $directory_args );
+					if ( $data['url'] == $url ) {
+						$data = $default_header;
+						$data['url'] = $url;
+						$data['thumbnail_url'] = vsprintf( $data['thumbnail_url'], $directory_args );
+						break;
+					}
+				}
+			}
+		}
+	}
+
 	$default = array(
 		'url'           => '',
 		'thumbnail_url' => '',
@@ -1023,6 +1163,8 @@ function get_custom_header() {
  *
  * @since 3.0.0
  *
+ * @global array $_wp_default_headers
+ *
  * @param array $headers Array of headers keyed by a string id. The ids point to arrays containing 'url', 'thumbnail_url', and 'description' keys.
  */
 function register_default_headers( $headers ) {
@@ -1040,8 +1182,11 @@ function register_default_headers( $headers ) {
  * @see register_default_headers()
  * @since 3.0.0
  *
+ * @global array $_wp_default_headers
+ *
  * @param string|array $header The header string id (key of array) to remove, or an array thereof.
- * @return True on success, false on failure.
+ * @return bool|void A single header returns true on success, false on failure.
+ *                   There is currently no return value for multiple headers.
  */
 function unregister_default_headers( $header ) {
 	global $_wp_default_headers;
@@ -1103,11 +1248,15 @@ function background_color() {
  */
 function _custom_background_cb() {
 	// $background is the saved custom image, or the default image.
-	$background = get_background_image();
+	$background = set_url_scheme( get_background_image() );
 
 	// $color is the saved custom color.
 	// A default has to be specified in style.css. It will not be printed here.
-	$color = get_theme_mod( 'background_color' );
+	$color = get_background_color();
+
+	if ( $color === get_theme_support( 'custom-background', 'default-color' ) ) {
+		$color = false;
+	}
 
 	if ( ! $background && ! $color )
 		return;
@@ -1117,17 +1266,17 @@ function _custom_background_cb() {
 	if ( $background ) {
 		$image = " background-image: url('$background');";
 
-		$repeat = get_theme_mod( 'background_repeat', 'repeat' );
+		$repeat = get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'default-repeat' ) );
 		if ( ! in_array( $repeat, array( 'no-repeat', 'repeat-x', 'repeat-y', 'repeat' ) ) )
 			$repeat = 'repeat';
 		$repeat = " background-repeat: $repeat;";
 
-		$position = get_theme_mod( 'background_position_x', 'left' );
+		$position = get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'default-position-x' ) );
 		if ( ! in_array( $position, array( 'center', 'right', 'left' ) ) )
 			$position = 'left';
 		$position = " background-position: top $position;";
 
-		$attachment = get_theme_mod( 'background_attachment', 'scroll' );
+		$attachment = get_theme_mod( 'background_attachment', get_theme_support( 'custom-background', 'default-attachment' ) );
 		if ( ! in_array( $attachment, array( 'fixed', 'scroll' ) ) )
 			$attachment = 'scroll';
 		$attachment = " background-attachment: $attachment;";
@@ -1158,11 +1307,12 @@ body.custom-background { <?php echo trim( $style ); ?> }
  *
  * @since 3.0.0
  *
- * @param mixed $stylesheet Optional. Stylesheet name or array thereof, relative to theme root.
- * 	Defaults to 'editor-style.css'
+ * @global array $editor_styles
+ *
+ * @param array|string $stylesheet Optional. Stylesheet name or array thereof, relative to theme root.
+ * 	                               Defaults to 'editor-style.css'
  */
 function add_editor_style( $stylesheet = 'editor-style.css' ) {
-
 	add_theme_support( 'editor-style' );
 
 	if ( ! is_admin() )
@@ -1184,6 +1334,8 @@ function add_editor_style( $stylesheet = 'editor-style.css' ) {
  *
  * @since 3.1.0
  *
+ * @global array $editor_styles
+ *
  * @return bool True on success, false if there were no stylesheets to remove.
  */
 function remove_editor_styles() {
@@ -1195,6 +1347,62 @@ function remove_editor_styles() {
 	return true;
 }
 
+/**
+ * Retrieve any registered editor stylesheets
+ *
+ * @since 4.0.0
+ *
+ * @global array $editor_styles Registered editor stylesheets
+ *
+ * @return array If registered, a list of editor stylesheet URLs.
+ */
+function get_editor_stylesheets() {
+	$stylesheets = array();
+	// load editor_style.css if the current theme supports it
+	if ( ! empty( $GLOBALS['editor_styles'] ) && is_array( $GLOBALS['editor_styles'] ) ) {
+		$editor_styles = $GLOBALS['editor_styles'];
+
+		$editor_styles = array_unique( array_filter( $editor_styles ) );
+		$style_uri = get_stylesheet_directory_uri();
+		$style_dir = get_stylesheet_directory();
+
+		// Support externally referenced styles (like, say, fonts).
+		foreach ( $editor_styles as $key => $file ) {
+			if ( preg_match( '~^(https?:)?//~', $file ) ) {
+				$stylesheets[] = esc_url_raw( $file );
+				unset( $editor_styles[ $key ] );
+			}
+		}
+
+		// Look in a parent theme first, that way child theme CSS overrides.
+		if ( is_child_theme() ) {
+			$template_uri = get_template_directory_uri();
+			$template_dir = get_template_directory();
+
+			foreach ( $editor_styles as $key => $file ) {
+				if ( $file && file_exists( "$template_dir/$file" ) ) {
+					$stylesheets[] = "$template_uri/$file";
+				}
+			}
+		}
+
+		foreach ( $editor_styles as $file ) {
+			if ( $file && file_exists( "$style_dir/$file" ) ) {
+				$stylesheets[] = "$style_uri/$file";
+			}
+		}
+	}
+
+	/**
+	 * Filter the array of stylesheets applied to the editor.
+	 *
+	 * @since 4.3.0
+	 *
+	 * @param array $stylesheets Array of stylesheets to be applied to the editor.
+	 */
+	return apply_filters( 'editor_stylesheets', $stylesheets );
+}
+
 /**
  * Allows a theme to register its support of a certain feature
  *
@@ -1203,7 +1411,11 @@ function remove_editor_styles() {
  * The init hook may be too late for some features.
  *
  * @since 2.9.0
- * @param string $feature the feature being added
+ *
+ * @global array $_wp_theme_features
+ *
+ * @param string $feature The feature being added.
+ * @return void|bool False on failure, void otherwise.
  */
 function add_theme_support( $feature ) {
 	global $_wp_theme_features;
@@ -1215,13 +1427,31 @@ function add_theme_support( $feature ) {
 
 	switch ( $feature ) {
 		case 'post-formats' :
-			if ( is_array( $args[0] ) )
-				$args[0] = array_intersect( $args[0], array_keys( get_post_format_slugs() ) );
+			if ( is_array( $args[0] ) ) {
+				$post_formats = get_post_format_slugs();
+				unset( $post_formats['standard'] );
+
+				$args[0] = array_intersect( $args[0], array_keys( $post_formats ) );
+			}
+			break;
+
+		case 'html5' :
+			// You can't just pass 'html5', you need to pass an array of types.
+			if ( empty( $args[0] ) ) {
+				// Build an array of types for back-compat.
+				$args = array( 0 => array( 'comment-list', 'comment-form', 'search-form' ) );
+			} elseif ( ! is_array( $args[0] ) ) {
+				_doing_it_wrong( "add_theme_support( 'html5' )", __( 'You need to pass an array of types.' ), '3.6.1' );
+				return false;
+			}
+
+			// Calling 'html5' again merges, rather than overwrites.
+			if ( isset( $_wp_theme_features['html5'] ) )
+				$args[0] = array_merge( $_wp_theme_features['html5'][0], $args[0] );
 			break;
 
 		case 'custom-header-uploads' :
 			return add_theme_support( 'custom-header', array( 'uploads' => true ) );
-			break;
 
 		case 'custom-header' :
 			if ( ! is_array( $args ) )
@@ -1305,10 +1535,13 @@ function add_theme_support( $feature ) {
 				$args = array( 0 => array() );
 
 			$defaults = array(
-				'default-image' => '',
-				'default-color' => '',
-				'wp-head-callback' => '_custom_background_cb',
-				'admin-head-callback' => '',
+				'default-image'          => '',
+				'default-repeat'         => 'repeat',
+				'default-position-x'     => 'left',
+				'default-attachment'     => 'scroll',
+				'default-color'          => '',
+				'wp-head-callback'       => '_custom_background_cb',
+				'admin-head-callback'    => '',
 				'admin-preview-callback' => '',
 			);
 
@@ -1333,6 +1566,17 @@ function add_theme_support( $feature ) {
 				define( 'BACKGROUND_IMAGE', $args[0]['default-image'] );
 
 			break;
+
+		// Ensure that 'title-tag' is accessible in the admin.
+		case 'title-tag' :
+			// Can be called in functions.php but must happen before wp_loaded, i.e. not in header.php.
+			if ( did_action( 'wp_loaded' ) ) {
+				/* translators: 1: Theme support 2: hook name */
+				_doing_it_wrong( "add_theme_support( 'title-tag' )", sprintf( __( 'Theme support for %1$s should be registered before the %2$s hook.' ),
+					'<code>title-tag</code>', '<code>wp_loaded</code>' ), '4.1' );
+
+				return false;
+			}
 	}
 
 	$_wp_theme_features[ $feature ] = $args;
@@ -1343,6 +1587,9 @@ function add_theme_support( $feature ) {
  *
  * @since 3.4.0
  * @access private
+ *
+ * @global Custom_Image_Header $custom_image_header
+ * @global Custom_Background   $custom_background
  */
 function _custom_header_background_just_in_time() {
 	global $custom_image_header, $custom_background;
@@ -1374,14 +1621,16 @@ function _custom_header_background_just_in_time() {
 		}
 	}
 }
-add_action( 'wp_loaded', '_custom_header_background_just_in_time' );
 
 /**
  * Gets the theme support arguments passed when registering that support
  *
- * @since 3.1
+ * @since 3.1.0
+ *
+ * @global array $_wp_theme_features
+ *
  * @param string $feature the feature to check
- * @return array The array of extra arguments
+ * @return mixed The array of extra arguments or the value for the registered feature.
  */
 function get_theme_support( $feature ) {
 	global $_wp_theme_features;
@@ -1398,10 +1647,9 @@ function get_theme_support( $feature ) {
 			if ( isset( $_wp_theme_features[ $feature ][0][ $args[0] ] ) )
 				return $_wp_theme_features[ $feature ][0][ $args[0] ];
 			return false;
-			break;
+
 		default :
 			return $_wp_theme_features[ $feature ];
-			break;
 	}
 }
 
@@ -1414,7 +1662,7 @@ function get_theme_support( $feature ) {
  * @since 3.0.0
  * @see add_theme_support()
  * @param string $feature the feature being added
- * @return bool Whether feature was removed.
+ * @return bool|void Whether feature was removed.
  */
 function remove_theme_support( $feature ) {
 	// Blacklist: for internal registrations not used directly by themes.
@@ -1429,6 +1677,12 @@ function remove_theme_support( $feature ) {
  *
  * @access private
  * @since 3.1.0
+ *
+ * @global array               $_wp_theme_features
+ * @global Custom_Image_Header $custom_image_header
+ * @global Custom_Background   $custom_background
+ *
+ * @param string $feature
  */
 function _remove_theme_support( $feature ) {
 	global $_wp_theme_features;
@@ -1446,6 +1700,8 @@ function _remove_theme_support( $feature ) {
 
 	switch ( $feature ) {
 		case 'custom-header' :
+			if ( ! did_action( 'wp_loaded' ) )
+				break;
 			$support = get_theme_support( 'custom-header' );
 			if ( $support[0]['wp-head-callback'] )
 				remove_action( 'wp_head', $support[0]['wp-head-callback'] );
@@ -1454,6 +1710,8 @@ function _remove_theme_support( $feature ) {
 			break;
 
 		case 'custom-background' :
+			if ( ! did_action( 'wp_loaded' ) )
+				break;
 			$support = get_theme_support( 'custom-background' );
 			remove_action( 'wp_head', $support[0]['wp-head-callback'] );
 			remove_action( 'admin_menu', array( $GLOBALS['custom_background'], 'init' ) );
@@ -1469,8 +1727,11 @@ function _remove_theme_support( $feature ) {
  * Checks a theme's support for a given feature
  *
  * @since 2.9.0
+ *
+ * @global array $_wp_theme_features
+ *
  * @param string $feature the feature being checked
- * @return boolean
+ * @return bool
  */
 function current_theme_supports( $feature ) {
 	global $_wp_theme_features;
@@ -1481,6 +1742,14 @@ function current_theme_supports( $feature ) {
 	if ( !isset( $_wp_theme_features[$feature] ) )
 		return false;
 
+	if ( 'title-tag' == $feature ) {
+		// Don't confirm support unless called internally.
+		$trace = debug_backtrace();
+		if ( ! in_array( $trace[1]['function'], array( '_wp_render_title_tag', 'wp_title' ) ) ) {
+			return false;
+		}
+	}
+
 	// If no args passed then no extra checks need be performed
 	if ( func_num_args() <= 1 )
 		return true;
@@ -1496,14 +1765,16 @@ function current_theme_supports( $feature ) {
 				return true;
 			$content_type = $args[0];
 			return in_array( $content_type, $_wp_theme_features[$feature][0] );
-			break;
 
+		case 'html5':
 		case 'post-formats':
 			// specific post formats can be registered by passing an array of types to
 			// add_theme_support()
-			$post_format = $args[0];
-			return in_array( $post_format, $_wp_theme_features[$feature][0] );
-			break;
+
+			// Specific areas of HTML5 support *must* be passed via an array to add_theme_support()
+
+			$type = $args[0];
+			return in_array( $type, $_wp_theme_features[$feature][0] );
 
 		case 'custom-header':
 		case 'custom-background' :
@@ -1511,48 +1782,68 @@ function current_theme_supports( $feature ) {
 			// an array to add_theme_support()
 			$header_support = $args[0];
 			return ( isset( $_wp_theme_features[$feature][0][$header_support] ) && $_wp_theme_features[$feature][0][$header_support] );
-			break;
 	}
 
-	return apply_filters('current_theme_supports-' . $feature, true, $args, $_wp_theme_features[$feature]);
+	/**
+	 * Filter whether the current theme supports a specific feature.
+	 *
+	 * The dynamic portion of the hook name, `$feature`, refers to the specific theme
+	 * feature. Possible values include 'post-formats', 'post-thumbnails', 'custom-background',
+	 * 'custom-header', 'menus', 'automatic-feed-links', and 'html5'.
+	 *
+	 * @since 3.4.0
+	 *
+	 * @param bool   true     Whether the current theme supports the given feature. Default true.
+	 * @param array  $args    Array of arguments for the feature.
+	 * @param string $feature The theme feature.
+	 */
+	return apply_filters( "current_theme_supports-{$feature}", true, $args, $_wp_theme_features[$feature] );
 }
 
 /**
  * Checks a theme's support for a given feature before loading the functions which implement it.
  *
  * @since 2.9.0
- * @param string $feature the feature being checked
- * @param string $include the file containing the functions that implement the feature
+ *
+ * @param string $feature The feature being checked.
+ * @param string $include Path to the file.
+ * @return bool True if the current theme supports the supplied feature, false otherwise.
  */
-function require_if_theme_supports( $feature, $include) {
-	if ( current_theme_supports( $feature ) )
+function require_if_theme_supports( $feature, $include ) {
+	if ( current_theme_supports( $feature ) ) {
 		require ( $include );
+		return true;
+	}
+	return false;
 }
 
 /**
  * Checks an attachment being deleted to see if it's a header or background image.
  *
  * If true it removes the theme modification which would be pointing at the deleted
- * attachment
+ * attachment.
  *
  * @access private
  * @since 3.0.0
- * @param int $id the attachment id
+ * @since 4.3.0 Also removes `header_image_data`.
+ *
+ * @param int $id The attachment id.
  */
 function _delete_attachment_theme_mod( $id ) {
 	$attachment_image = wp_get_attachment_url( $id );
-	$header_image = get_header_image();
+	$header_image     = get_header_image();
 	$background_image = get_background_image();
 
-	if ( $header_image && $header_image == $attachment_image )
+	if ( $header_image && $header_image == $attachment_image ) {
 		remove_theme_mod( 'header_image' );
+		remove_theme_mod( 'header_image_data' );
+	}
 
-	if ( $background_image && $background_image == $attachment_image )
+	if ( $background_image && $background_image == $attachment_image ) {
 		remove_theme_mod( 'background_image' );
+	}
 }
 
-add_action( 'delete_attachment', '_delete_attachment_theme_mod' );
-
 /**
  * Checks if a theme has been changed and runs 'after_switch_theme' hook on the next WP load
  *
@@ -1562,10 +1853,31 @@ function check_theme_switched() {
 	if ( $stylesheet = get_option( 'theme_switched' ) ) {
 		$old_theme = wp_get_theme( $stylesheet );
 
-		if ( $old_theme->exists() )
-			do_action( 'after_switch_theme', $old_theme->get('Name'), $old_theme );
-		else
+		// Prevent retrieve_widgets() from running since Customizer already called it up front
+		if ( get_option( 'theme_switched_via_customizer' ) ) {
+			remove_action( 'after_switch_theme', '_wp_sidebars_changed' );
+			update_option( 'theme_switched_via_customizer', false );
+		}
+
+		if ( $old_theme->exists() ) {
+			/**
+			 * Fires on the first WP load after a theme switch if the old theme still exists.
+			 *
+			 * This action fires multiple times and the parameters differs
+			 * according to the context, if the old theme exists or not.
+			 * If the old theme is missing, the parameter will be the slug
+			 * of the old theme.
+			 *
+			 * @since 3.3.0
+			 *
+			 * @param string   $old_name  Old theme name.
+			 * @param WP_Theme $old_theme WP_Theme instance of the old theme.
+			 */
+			do_action( 'after_switch_theme', $old_theme->get( 'Name' ), $old_theme );
+		} else {
+			/** This action is documented in wp-includes/theme.php */
 			do_action( 'after_switch_theme', $stylesheet );
+		}
 
 		update_option( 'theme_switched', false );
 	}
@@ -1577,6 +1889,8 @@ function check_theme_switched() {
  * Fires when ?wp_customize=on or on wp-admin/customize.php.
  *
  * @since 3.4.0
+ *
+ * @global WP_Customize_Manager $wp_customize
  */
 function _wp_customize_include() {
 	if ( ! ( ( isset( $_REQUEST['wp_customize'] ) && 'on' == $_REQUEST['wp_customize'] )
@@ -1584,11 +1898,9 @@ function _wp_customize_include() {
 	) )
 		return;
 
-	require( ABSPATH . WPINC . '/class-wp-customize-manager.php' );
-	// Init Customize class
-	$GLOBALS['wp_customize'] = new WP_Customize_Manager;
+	require_once ABSPATH . WPINC . '/class-wp-customize-manager.php';
+	$GLOBALS['wp_customize'] = new WP_Customize_Manager();
 }
-add_action( 'plugins_loaded', '_wp_customize_include' );
 
 /**
  * Adds settings for the customize-loader script.
@@ -1596,8 +1908,6 @@ add_action( 'plugins_loaded', '_wp_customize_include' );
  * @since 3.4.0
  */
 function _wp_customize_loader_settings() {
-	global $wp_scripts;
-
 	$admin_origin = parse_url( admin_url() );
 	$home_origin  = parse_url( home_url() );
 	$cross_domain = ( strtolower( $admin_origin[ 'host' ] ) != strtolower( $home_origin[ 'host' ] ) );
@@ -1611,25 +1921,30 @@ function _wp_customize_loader_settings() {
 		'url'           => esc_url( admin_url( 'customize.php' ) ),
 		'isCrossDomain' => $cross_domain,
 		'browser'       => $browser,
+		'l10n'          => array(
+			'saveAlert'       => __( 'The changes you made will be lost if you navigate away from this page.' ),
+			'mainIframeTitle' => __( 'Customizer' ),
+		),
 	);
 
-	$script = 'var _wpCustomizeLoaderSettings = ' . json_encode( $settings ) . ';';
+	$script = 'var _wpCustomizeLoaderSettings = ' . wp_json_encode( $settings ) . ';';
 
+	$wp_scripts = wp_scripts();
 	$data = $wp_scripts->get_data( 'customize-loader', 'data' );
 	if ( $data )
 		$script = "$data\n$script";
 
 	$wp_scripts->add_data( 'customize-loader', 'data', $script );
 }
-add_action( 'admin_enqueue_scripts', '_wp_customize_loader_settings' );
 
 /**
- * Returns a URL to load the theme customizer.
+ * Returns a URL to load the Customizer.
  *
  * @since 3.4.0
  *
  * @param string $stylesheet Optional. Theme to customize. Defaults to current theme.
- * 	The theme's stylesheet will be urlencoded if necessary.
+ * 	                         The theme's stylesheet will be urlencoded if necessary.
+ * @return string
  */
 function wp_customize_url( $stylesheet = null ) {
 	$url = admin_url( 'customize.php' );
@@ -1639,7 +1954,7 @@ function wp_customize_url( $stylesheet = null ) {
 }
 
 /**
- * Prints a script to check whether or not the customizer is supported,
+ * Prints a script to check whether or not the Customizer is supported,
  * and apply either the no-customize-support or customize-support class
  * to the body.
  *
@@ -1669,9 +1984,24 @@ function wp_customize_support_script() {
 			request = true;
 <?php		endif; ?>
 
-			b[c] = b[c].replace( rcs, '' );
+			b[c] = b[c].replace( rcs, ' ' );
 			b[c] += ( window.postMessage && request ? ' ' : ' no-' ) + cs;
 		}());
 	</script>
 	<?php
-}
\ No newline at end of file
+}
+
+/**
+ * Whether the site is being previewed in the Customizer.
+ *
+ * @since 4.0.0
+ *
+ * @global WP_Customize_Manager $wp_customize Customizer instance.
+ *
+ * @return bool True if the site is being previewed in the Customizer, false otherwise.
+ */
+function is_customize_preview() {
+	global $wp_customize;
+
+	return ( $wp_customize instanceof WP_Customize_Manager ) && $wp_customize->is_preview();
+}