_wp_add_block_level_presets_class

_wp_add_block_level_presets_class()： 这个函数在WordPress编辑器中根据预设的设置给一个块元素添加一个自定义的CSS类。

function _wp_add_block_level_presets_class( $block_content, $block ) {
	if ( ! $block_content ) {
		return $block_content;
	}

	// return early if the block doesn't have support for settings.
	$block_type = WP_Block_Type_Registry::get_instance()->get_registered( $block['blockName'] );
	if ( ! block_has_support( $block_type, array( '__experimentalSettings' ), false ) ) {
		return $block_content;
	}

	// return early if no settings are found on the block attributes.
	$block_settings = _wp_array_get( $block, array( 'attrs', 'settings' ), null );
	if ( empty( $block_settings ) ) {
		return $block_content;
	}

	// Like the layout hook this assumes the hook only applies to blocks with a single wrapper.
	// Add the class name to the first element, presuming it's the wrapper, if it exists.
	$tags = new WP_HTML_Tag_Processor( $block_content );
	if ( $tags->next_tag() ) {
		$tags->add_class( _wp_get_presets_class_name( $block ) );
	}

	return $tags->get_updated_html();
}