Editor: Introduce the Font Library post types and low level APIs.

This is the first step towards adding the font library to WordPress.
This commit includes the font library and font face CPTs.
It also adds the necessary APIs and classes to register and manipulate font collections.

This PR backports the font library post types and low level APIs to Core. This is the first step to include the font library entirely into Core. Once this merged, we'll open a PR with the necessary REST API controllers.

Props youknowriad, get_dave, grantmkin, swissspidy, hellofromtonya, mukesh27, mcsf.
See #59166.

git-svn-id: https://develop.svn.wordpress.org/trunk@57539 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/default-filters.php

@@ -748,5 +748,7 @@
 
 // Font management.
 add_action( 'wp_head', 'wp_print_font_faces', 50 );
+add_action( 'deleted_post', '_wp_after_delete_font_family', 10, 2 );
+add_action( 'before_delete_post', '_wp_before_delete_font_face', 10, 2 );
 
 unset( $filter, $action );

src/wp-includes/fonts.php

@@ -51,3 +51,140 @@ function wp_print_font_faces( $fonts = array() ) {
 	$wp_font_face = new WP_Font_Face();
 	$wp_font_face->generate_and_print( $fonts );
 }
+
+/**
+ * Registers a new Font Collection in the Font Library.
+ *
+ * @since 6.5.0
+ *
+ * @param string       $slug Font collection slug. May only contain alphanumeric characters, dashes,
+ *                     and underscores. See sanitize_title().
+ * @param array|string $data_or_file {
+ *     Font collection data array or a path/URL to a JSON file containing the font collection.
+ *
+ *     @link https://schemas.wp.org/trunk/font-collection.json
+ *
+ *     @type string $name           Required. Name of the font collection shown in the Font Library.
+ *     @type string $description    Optional. A short descriptive summary of the font collection. Default empty.
+ *     @type array  $font_families  Required. Array of font family definitions that are in the collection.
+ *     @type array  $categories     Optional. Array of categories, each with a name and slug, that are used by the
+ *                                  fonts in the collection. Default empty.
+ * }
+ * @return WP_Font_Collection|WP_Error A font collection if it was registered
+ *                                     successfully, or WP_Error object on failure.
+ */
+function wp_register_font_collection( $slug, $data_or_file ) {
+	return WP_Font_Library::get_instance()->register_font_collection( $slug, $data_or_file );
+}
+
+/**
+ * Unregisters a font collection from the Font Library.
+ *
+ * @since 6.5.0
+ *
+ * @param string $slug Font collection slug.
+ * @return bool True if the font collection was unregistered successfully, else false.
+ */
+function wp_unregister_font_collection( $slug ) {
+	return WP_Font_Library::get_instance()->unregister_font_collection( $slug );
+}
+
+/**
+ * Returns an array containing the current fonts upload directory's path and URL.
+ *
+ * @since 6.5.0
+ *
+ * @param array $defaults {
+ *     Array of information about the upload directory.
+ *
+ *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
+ *     @type string       $url     Base URL and subdirectory or absolute URL to the fonts upload directory.
+ *     @type string       $subdir  Subdirectory
+ *     @type string       $basedir Path without subdir.
+ *     @type string       $baseurl URL path without subdir.
+ *     @type string|false $error   False or error message.
+ * }
+ * @return array $defaults {
+ *     Array of information about the upload directory.
+ *
+ *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
+ *     @type string       $url     Base URL and subdirectory or absolute URL to the fonts upload directory.
+ *     @type string       $subdir  Subdirectory
+ *     @type string       $basedir Path without subdir.
+ *     @type string       $baseurl URL path without subdir.
+ *     @type string|false $error   False or error message.
+ * }
+ */
+function wp_get_font_dir( $defaults = array() ) {
+	$site_path = '';
+	if ( is_multisite() && ! ( is_main_network() && is_main_site() ) ) {
+		$site_path = '/sites/' . get_current_blog_id();
+	}
+
+	// Sets the defaults.
+	$defaults['path']    = path_join( WP_CONTENT_DIR, 'fonts' ) . $site_path;
+	$defaults['url']     = untrailingslashit( content_url( 'fonts' ) ) . $site_path;
+	$defaults['subdir']  = '';
+	$defaults['basedir'] = path_join( WP_CONTENT_DIR, 'fonts' ) . $site_path;
+	$defaults['baseurl'] = untrailingslashit( content_url( 'fonts' ) ) . $site_path;
+	$defaults['error']   = false;
+
+	/**
+	 * Filters the fonts directory data.
+	 *
+	 * This filter allows developers to modify the fonts directory data.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param array $defaults The original fonts directory data.
+	 */
+	return apply_filters( 'font_dir', $defaults );
+}
+
+/**
+ * Deletes child font faces when a font family is deleted.
+ *
+ * @access private
+ * @since 6.5.0
+ *
+ * @param int     $post_id Post ID.
+ * @param WP_Post $post    Post object.
+ */
+function _wp_after_delete_font_family( $post_id, $post ) {
+	if ( 'wp_font_family' !== $post->post_type ) {
+		return;
+	}
+
+	$font_faces = get_children(
+		array(
+			'post_parent' => $post_id,
+			'post_type'   => 'wp_font_face',
+		)
+	);
+
+	foreach ( $font_faces as $font_face ) {
+		wp_delete_post( $font_face->ID, true );
+	}
+}
+
+/**
+ * Deletes associated font files when a font face is deleted.
+ *
+ * @access private
+ * @since 6.5.0
+ *
+ * @param int     $post_id Post ID.
+ * @param WP_Post $post    Post object.
+ */
+function _wp_before_delete_font_face( $post_id, $post ) {
+	if ( 'wp_font_face' !== $post->post_type ) {
+		return;
+	}
+
+	$font_files = get_post_meta( $post_id, '_wp_font_face_file', false );
+	$font_dir   = wp_get_font_dir()['path'];
+
+	foreach ( $font_files as $font_file ) {
+		wp_delete_file( $font_dir . '/' . $font_file );
+	}
+}