diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/class-wp-block-styles-registry.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-wp-block-styles-registry.php	Tue Dec 15 13:49:49 2020 +0100
@@ -0,0 +1,160 @@
+<?php
+/**
+ * Blocks API: WP_Block_Styles_Registry class
+ *
+ * @package WordPress
+ * @subpackage Blocks
+ * @since 5.3.0
+ */
+
+/**
+ * Class used for interacting with block styles.
+ *
+ * @since 5.3.0
+ */
+final class WP_Block_Styles_Registry {
+	/**
+	 * Registered block styles, as `$block_name => $block_style_name => $block_style_properties` multidimensional arrays.
+	 *
+	 * @since 5.3.0
+	 * @var array
+	 */
+	private $registered_block_styles = array();
+
+	/**
+	 * Container for the main instance of the class.
+	 *
+	 * @since 5.3.0
+	 * @var WP_Block_Styles_Registry|null
+	 */
+	private static $instance = null;
+
+	/**
+	 * Registers a block style.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param string $block_name       Block type name including namespace.
+	 * @param array  $style_properties Array containing the properties of the style name, label,
+	 *                                 style (name of the stylesheet to be enqueued),
+	 *                                 inline_style (string containing the CSS to be added).
+	 * @return boolean True if the block style was registered with success and false otherwise.
+	 */
+	public function register( $block_name, $style_properties ) {
+
+		if ( ! isset( $block_name ) || ! is_string( $block_name ) ) {
+			$message = __( 'Block name must be a string.' );
+			_doing_it_wrong( __METHOD__, $message, '5.3.0' );
+			return false;
+		}
+
+		if ( ! isset( $style_properties['name'] ) || ! is_string( $style_properties['name'] ) ) {
+			$message = __( 'Block style name must be a string.' );
+			_doing_it_wrong( __METHOD__, $message, '5.3.0' );
+			return false;
+		}
+
+		$block_style_name = $style_properties['name'];
+
+		if ( ! isset( $this->registered_block_styles[ $block_name ] ) ) {
+			$this->registered_block_styles[ $block_name ] = array();
+		}
+		$this->registered_block_styles[ $block_name ][ $block_style_name ] = $style_properties;
+
+		return true;
+	}
+
+	/**
+	 * Unregisters a block style.
+	 *
+	 * @param string $block_name       Block type name including namespace.
+	 * @param string $block_style_name Block style name.
+	 * @return boolean True if the block style was unregistered with success and false otherwise.
+	 */
+	public function unregister( $block_name, $block_style_name ) {
+		if ( ! $this->is_registered( $block_name, $block_style_name ) ) {
+			/* translators: 1: Block name, 2: Block style name. */
+			$message = sprintf( __( 'Block "%1$s" does not contain a style named "%2$s".' ), $block_name, $block_style_name );
+			_doing_it_wrong( __METHOD__, $message, '5.3.0' );
+			return false;
+		}
+
+		unset( $this->registered_block_styles[ $block_name ][ $block_style_name ] );
+
+		return true;
+	}
+
+	/**
+	 * Retrieves an array containing the properties of a registered block style.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param string $block_name       Block type name including namespace.
+	 * @param string $block_style_name Block style name.
+	 * @return array Registered block style properties.
+	 */
+	public function get_registered( $block_name, $block_style_name ) {
+		if ( ! $this->is_registered( $block_name, $block_style_name ) ) {
+			return null;
+		}
+
+		return $this->registered_block_styles[ $block_name ][ $block_style_name ];
+	}
+
+	/**
+	 * Retrieves all registered block styles.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @return array Array of arrays containing the registered block styles properties grouped per block,
+	 *               and per style.
+	 */
+	public function get_all_registered() {
+		return $this->registered_block_styles;
+	}
+
+	/**
+	 * Retrieves registered block styles for a specific block.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param string $block_name Block type name including namespace.
+	 * @return array Array whose keys are block style names and whose value are block style properties.
+	 */
+	public function get_registered_styles_for_block( $block_name ) {
+		if ( isset( $this->registered_block_styles[ $block_name ] ) ) {
+			return $this->registered_block_styles[ $block_name ];
+		}
+		return array();
+	}
+
+	/**
+	 * Checks if a block style is registered.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @param string $block_name       Block type name including namespace.
+	 * @param string $block_style_name Block style name.
+	 * @return bool True if the block style is registered, false otherwise.
+	 */
+	public function is_registered( $block_name, $block_style_name ) {
+		return isset( $this->registered_block_styles[ $block_name ][ $block_style_name ] );
+	}
+
+	/**
+	 * Utility method to retrieve the main instance of the class.
+	 *
+	 * The instance will be created if it does not exist yet.
+	 *
+	 * @since 5.3.0
+	 *
+	 * @return WP_Block_Styles_Registry The main instance.
+	 */
+	public static function get_instance() {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+
+		return self::$instance;
+	}
+}