[PoC] Add infrastracture to register icons

docs/reference-guides/core-blocks.md

@@ -431,6 +431,12 @@ Add custom HTML code and preview it as you edit. ([Source](https://github.com/Wo
 -	**Supports:** interactivity (clientNavigation), ~~className~~, ~~customClassName~~, ~~html~~
 -	**Attributes:** content
 
+## Icon
+
+undefined ([Source](https://github.com/WordPress/gutenberg/tree/trunk/packages/block-library/src/icon))
+
+-	**Name:** core/icon
+
 ## Image
 
 Insert an image to make a visual statement. ([Source](https://github.com/WordPress/gutenberg/tree/trunk/packages/block-library/src/image))

lib/experimental/class-wp-icons-registry.php

@@ -0,0 +1,204 @@
+<?php
+/**
+ * Icons API: WP_Icons_Registry class
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Class used for interacting with icons.
+ */
+if ( ! class_exists( 'WP_Icons_Registry' ) ) {
+	class WP_Icons_Registry {
+		/**
+		 * Registered icons array.
+		 *
+		 * @var array[]
+		 */
+		private $registered_icons = array();
+
+
+		/**
+		 * Container for the main instance of the class.
+		 *
+		 * @var WP_Icons_Registry|null
+		 */
+		private static $instance = null;
+
+		/**
+		 * Registers an icon.
+		 *
+		 *
+		 * @param string $icon_name       Icon name including namespace.
+		 * @param array  $icon_properties {
+		 *     List of properties for the icon.
+		 *
+		 *     @type string $title    Required. A human-readable title for the icon.
+		 *     @type string $content  Optional. SVG markup for the icon.
+		 *                            If not provided, the content will be retrieved from the `filePath` if set.
+		 *                            If both `content` and `filePath` are not set, the icon will not be registered.
+		 *     @type string $filePath Optional. The full path to the file containing the icon content.
+		 * }
+		 * @return bool True if the icon was registered with success and false otherwise.
+		 */
+		public function register( $icon_name, $icon_properties ) {
+			if ( ! isset( $icon_name ) || ! is_string( $icon_name ) ) {
+				_doing_it_wrong(
+					__METHOD__,
+					__( 'Icon name must be a string.', 'gutenberg' ),
+					''
+				);
+				return false;
+			}
+
+			if ( ! isset( $icon_properties['title'] ) || ! is_string( $icon_properties['title'] ) ) {
+				_doing_it_wrong(
+					__METHOD__,
+					__( 'Icon title must be a string.', 'gutenberg' ),
+					''
+				);
+				return false;
+			}
+
+			if ( ! isset( $icon_properties['filePath'] ) ) {
+				if ( ! isset( $icon_properties['content'] ) || ! is_string( $icon_properties['content'] ) ) {
+					_doing_it_wrong(
+						__METHOD__,
+						__( 'Icon content must be a string.', 'gutenberg' ),
+						''
+					);
+					return false;
+				}
+			}
+
+			$icon = array_merge(
+				$icon_properties,
+				array( 'name' => $icon_name )
+			);
+
+			$this->registered_icons[ $icon_name ] = $icon;
+
+			return true;
+		}
+
+		/**
+		 * Unregisters an icon.
+		 *
+		 *
+		 * @param string $icon_name Icon name including namespace.
+		 * @return bool True if the icon was unregistered with success and false otherwise.
+		 */
+		public function unregister( $icon_name ) {
+			if ( ! $this->is_registered( $icon_name ) ) {
+				_doing_it_wrong(
+					__METHOD__,
+					/* translators: %s: Icon name. */
+					sprintf( __( 'Icon "%s" not found.', 'gutenberg' ), $icon_name ),
+					''
+				);
+				return false;
+			}
+
+			unset( $this->registered_icons[ $icon_name ] );
+
+			return true;
+		}
+
+		/**
+		 * Retrieves the content of a registered icon.
+		 *
+		 * @param string $icon_name Icon name including namespace.
+		 * @return string The content of the icon.
+		 * @since 6.9.0
+		 */
+		private function get_content( $icon_name ) {
+			if ( ! isset( $this->registered_icons[ $icon_name ]['content'] ) && isset( $this->registered_icons[ $icon_name ]['filePath'] ) ) {
+				ob_start();
+				include $this->registered_icons[ $icon_name ]['filePath'];
+				$this->registered_icons[ $icon_name ]['content'] = ob_get_clean();
+				unset( $this->registered_icons[ $icon_name ]['filePath'] );
+			}
+			return $this->registered_icons[ $icon_name ]['content'];
+		}
+
+		/**
+		 * Retrieves an array containing the properties of a registered icon.
+		 *
+		 *
+		 * @param string $icon_name Icon name including namespace.
+		 * @return array|null Registered icon properties or `null` if the icon is not registered.
+		 */
+		public function get_registered( $icon_name ) {
+			if ( ! $this->is_registered( $icon_name ) ) {
+				return null;
+			}
+
+			$icon            = $this->registered_icons[ $icon_name ];
+			$content         = $this->get_content( $icon_name );
+			$icon['content'] = $content;
+
+			return $icon;
+		}
+
+		/**
+		 * Retrieves all registered icons.
+		 *
+		 * @return array[] Array of arrays containing the registered icon properties.
+		 */
+		public function get_all_registered() {
+			$icons = $this->registered_icons;
+
+			foreach ( $icons as $index => $icon ) {
+				$content                    = $this->get_content( $icon['name'] );
+				$icons[ $index ]['content'] = $content;
+			}
+
+			return array_values( $icons );
+		}
+
+		/**
+		 * Checks if an icon is registered.
+		 *
+		 *
+		 * @param string $icon_name Icon name including namespace.
+		 * @return bool True if the icon is registered, false otherwise.
+		 */
+		public function is_registered( $icon_name ) {
+			return isset( $this->registered_icons[ $icon_name ] );
+		}
+
+		/**
+		 * Magic method for object serialization.
+		 *
+		 */
+		public function __wakeup() {
+			if ( ! $this->registered_icons ) {
+				return;
+			}
+			if ( ! is_array( $this->registered_icons ) ) {
+				throw new UnexpectedValueException();
+			}
+			foreach ( $this->registered_icons as $value ) {
+				if ( ! is_array( $value ) ) {
+					throw new UnexpectedValueException();
+				}
+			}
+		}
+
+		/**
+		 * Utility method to retrieve the main instance of the class.
+		 *
+		 * The instance will be created if it does not exist yet.
+		 *
+		 *
+		 * @return WP_Icons_Registry The main instance.
+		 */
+		public static function get_instance() {
+			if ( null === self::$instance ) {
+				self::$instance = new self();
+			}
+
+			return self::$instance;
+		}
+	}
+}