<?php
/**
* Custom CSS block support.
*
* @package WordPress
*/
/**
* Render the custom CSS stylesheet and add class name to block as required.
*
* @since 7.0.0
*
* @param array $parsed_block The parsed block.
* @return array The same parsed block with custom CSS class name added if appropriate.
*
* @phpstan-param array{
* blockName: string|null,
* attrs: array{
* className?: string,
* style?: array{
* css?: string,
* ...
* },
* ...
* },
* ...
* } $parsed_block
* @phpstan-return array{
* blockName: string|null,
* attrs: array{
* className?: string,
* style?: array{
* css?: string,
* ...
* },
* ...
* },
* ...
* }
*/
function wp_render_custom_css_support_styles( $parsed_block ) {
$custom_css = $parsed_block['attrs']['style']['css'] ?? null;
if ( ! is_string( $custom_css ) || '' === trim( $custom_css ) ) {
return $parsed_block;
}
$block_type = WP_Block_Type_Registry::get_instance()->get_registered( $parsed_block['blockName'] );
if ( ! block_has_support( $block_type, 'customCSS', true ) ) {
return $parsed_block;
}
// Validate CSS doesn't contain HTML markup (same validation as global styles REST API).
if ( preg_match( '#</?\w+#', $custom_css ) ) {
return $parsed_block;
}
// Generate a unique class name for this block instance.
$class_name = wp_unique_id_from_values( $parsed_block, 'wp-custom-css-' );
$existing_class_name = $parsed_block['attrs']['className'] ?? null;
$updated_class_name = is_string( $existing_class_name )
? "$existing_class_name $class_name"
: $class_name;
$parsed_block['attrs']['className'] = $updated_class_name;
// Process the custom CSS using the same method as global styles.
$selector = '.' . $class_name;
$processed_css = WP_Theme_JSON::process_blocks_custom_css( $custom_css, $selector );
if ( ! empty( $processed_css ) ) {
/**
* Reuse one handle so identical custom CSS is enqueued only once via
* {@see wp_unique_id_from_values()}. Explicitly declare the `wp-block-library`
* dependency so `global-styles` is guaranteed to print after it, preventing
* block default styles from unintentionally overriding global styles.
*/
$handle = 'wp-block-custom-css';
if ( ! wp_style_is( $handle, 'registered' ) ) {
wp_register_style( $handle, false, array( 'wp-block-library', 'global-styles' ) );
}
$after_styles = wp_styles()->get_data( $handle, 'after' );
if ( ! is_array( $after_styles ) ) {
$after_styles = array();
}
if ( ! in_array( $processed_css, $after_styles, true ) ) {
wp_add_inline_style( $handle, $processed_css );
}
}
return $parsed_block;
}
/**
* Enqueues the block custom CSS styles.
*
* @since 7.0.0
*/
function wp_enqueue_block_custom_css() {
wp_enqueue_style( 'wp-block-custom-css' );
}
/**
* Applies the custom CSS class name to the block's rendered HTML.
*
* The class name is generated in {@see wp_render_custom_css_support_styles()}
* and stored in block attributes. This filter adds it to the actual markup.
*
* @since 7.0.0
*
* @param string $block_content Rendered block content.
* @param array $block Block object.
* @return string Filtered block content.
*
* @phpstan-param array{
* attrs: array{
* className?: string,
* ...
* },
* ...
* } $block
*/
function wp_render_custom_css_class_name( $block_content, $block ) {
$class_name_attr = $block['attrs']['className'] ?? null;
$class_name_prefix = 'wp-custom-css-';
if ( ! is_string( $class_name_attr ) || ! str_contains( $class_name_attr, $class_name_prefix ) ) {
return $block_content;
}
// Parse out the 'wp-custom-css-*' class name added by wp_render_custom_css_support_styles().
$matched_class_name = null;
$token_delimiter = " \t\f\r\n";
$class_token = strtok( $class_name_attr, $token_delimiter );
while ( false !== $class_token ) {
if ( str_starts_with( $class_token, $class_name_prefix ) ) {
$matched_class_name = $class_token;
break;
}
$class_token = strtok( $token_delimiter );
}
if ( null === $matched_class_name ) {
return $block_content;
}
$tags = new WP_HTML_Tag_Processor( $block_content );
if ( $tags->next_tag() ) {
$tags->add_class( 'has-custom-css' );
$tags->add_class( $matched_class_name );
}
return $tags->get_updated_html();
}
add_filter( 'render_block', 'wp_render_custom_css_class_name', 10, 2 );
add_filter( 'render_block_data', 'wp_render_custom_css_support_styles', 10, 1 );
add_action( 'wp_enqueue_scripts', 'wp_enqueue_block_custom_css', 1 );
/**
* Registers the style block attribute for block types that support it.
*
* @param WP_Block_Type $block_type Block Type.
*/
function wp_register_custom_css_support( $block_type ) {
// Setup attributes and styles within that if needed.
if ( ! $block_type->attributes ) {
$block_type->attributes = array();
}
// Check for existing style attribute definition e.g. from block.json.
if ( array_key_exists( 'style', $block_type->attributes ) ) {
return;
}
$has_custom_css_support = block_has_support( $block_type, array( 'customCSS' ), true );
if ( $has_custom_css_support ) {
$block_type->attributes['style'] = array(
'type' => 'object',
);
}
}
/**
* Strips custom CSS (`style.css` in attributes) from all blocks in post content.
*
* Uses {@see WP_Block_Parser::next_token()} to scan block tokens and surgically
* replace only the attribute JSON that changed — no parse_blocks() +
* serialize_blocks() round-trip needed.
*
* @since 7.0.0
* @access private
*
* @param string $content Post content to filter, expected to be escaped with slashes.
* @return string Filtered post content with block custom CSS removed.
*/
function wp_strip_custom_css_from_blocks( $content ) {
if ( ! has_blocks( $content ) ) {
return $content;
}
$unslashed = stripslashes( $content );
$parser = new WP_Block_Parser();
$parser->document = $unslashed;
$parser->offset = 0;
$end = strlen( $unslashed );
$replacements = array();
while ( $parser->offset < $end ) {
$next_token = $parser->next_token();
if ( 'no-more-tokens' === $next_token[0] ) {
break;
}
list( $token_type, , $attrs, $start_offset, $token_length ) = $next_token;
$parser->offset = $start_offset + $token_length;
if ( 'block-opener' !== $token_type && 'void-block' !== $token_type ) {
continue;
}
if ( ! isset( $attrs['style']['css'] ) ) {
continue;
}
// Remove css and clean up empty style.
unset( $attrs['style']['css'] );
if ( empty( $attrs['style'] ) ) {
unset( $attrs['style'] );
}
// Locate the JSON portion within the token.
$token_string = substr( $unslashed, $start_offset, $token_length );
$json_rel_start = strcspn( $token_string, '{' );
$json_rel_end = strrpos( $token_string, '}' );
$json_start = $start_offset + $json_rel_start;
$json_length = $json_rel_end - $json_rel_start + 1;
// Re-encode attributes. If attrs is now empty, remove JSON and trailing space.
if ( empty( $attrs ) ) {
// Remove the trailing space after JSON.
$replacements[] = array( $json_start, $json_length + 1, '' );
} else {
$replacements[] = array( $json_start, $json_length, serialize_block_attributes( $attrs ) );
}
}
if ( empty( $replacements ) ) {
return $content;
}
// Build the result by splicing replacements into the original string.
$result = '';
$was_at = 0;
foreach ( $replacements as $replacement ) {
list( $offset, $length, $new_json ) = $replacement;
$result .= substr( $unslashed, $was_at, $offset - $was_at ) . $new_json;
$was_at = $offset + $length;
}
if ( $was_at < $end ) {
$result .= substr( $unslashed, $was_at );
}
return addslashes( $result );
}
/**
* Adds the filters to strip custom CSS from block content on save.
* Priority of 8 to run before wp_filter_global_styles_post (priority 9) and wp_filter_post_kses (priority 10).
*
* @since 7.0.0
* @access private
*/
function wp_custom_css_kses_init_filters() {
add_filter( 'content_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
add_filter( 'content_filtered_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
}
/**
* Removes the filters that strip custom CSS from block content on save.
* Priority of 8 to run before wp_filter_global_styles_post (priority 9) and wp_filter_post_kses (priority 10).
*
* @since 7.0.0
* @access private
*/
function wp_custom_css_remove_filters() {
remove_filter( 'content_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
remove_filter( 'content_filtered_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
}
/**
* Registers the custom CSS content filters if the user does not have the edit_css capability.
*
* @since 7.0.0
* @access private
*/
function wp_custom_css_kses_init() {
wp_custom_css_remove_filters();
if ( ! current_user_can( 'edit_css' ) ) {
wp_custom_css_kses_init_filters();
}
}
/**
* Initializes custom CSS content filters when imported data should be filtered.
*
* Runs at priority 999 on {@see 'force_filtered_html_on_import'} to ensure it
* fires after general KSES initialization, independently of user capabilities.
* If the input of the filter is true it means we are in an import situation and should
* enable the custom CSS filters, independently of the user capabilities.
*
* @since 7.0.0
* @access private
*
* @param mixed $arg Input argument of the filter.
* @return mixed Input argument of the filter.
*/
function wp_custom_css_force_filtered_html_on_import_filter( $arg ) {
if ( $arg ) {
wp_custom_css_kses_init_filters();
}
return $arg;
}
// Run before wp_filter_global_styles_post (priority 9) and wp_filter_post_kses (priority 10).
add_action( 'init', 'wp_custom_css_kses_init', 20 );
add_action( 'set_current_user', 'wp_custom_css_kses_init' );
add_filter( 'force_filtered_html_on_import', 'wp_custom_css_force_filtered_html_on_import_filter', 999 );
// Register the block support.
WP_Block_Supports::get_instance()->register(
'custom-css',
array(
'register_attribute' => 'wp_register_custom_css_support',
)
);