Add Font Face and its tests

phpcs.xml.dist

@@ -259,6 +259,7 @@
 				<element value="WP_Test_Adjacent_Image_Link_TestCase"/>
 				<element value="WP_Tests_Image_Resize_UnitTestCase"/>
 				<element value="WP_Theme_UnitTestCase"/>
+				<element value="WP_Font_Face_UnitTestCase"/>
 
 				<!-- Mock classes. -->
 				<element value="Spy_REST_Server"/>

src/wp-admin/includes/admin-filters.php

@@ -168,3 +168,6 @@
 
 // Append '(Draft)' to draft page titles in the privacy page dropdown.
 add_filter( 'list_pages', '_wp_privacy_settings_filter_draft_page_titles', 10, 2 );
+
+// Font management.
+add_action( 'admin_print_styles', 'wp_print_font_faces', 50 );

src/wp-includes/block-editor.php

@@ -361,6 +361,7 @@ function _wp_get_iframed_editor_assets() {
 
 	ob_start();
 	wp_print_styles();
+	wp_print_font_faces();
 	$styles = ob_get_clean();
 
 	ob_start();

src/wp-includes/default-filters.php

@@ -719,4 +719,7 @@
 // CPT wp_block custom postmeta field.
 add_action( 'init', 'wp_create_initial_post_meta' );
 
+// Font management.
+add_action( 'wp_head', 'wp_print_font_faces', 50 );
+
 unset( $filter, $action );

src/wp-includes/fonts/font-face/class-wp-font-face-resolver.php

@@ -0,0 +1,154 @@
+<?php
+/**
+ * WP_Font_Face_Resolver class.
+ *
+ * @package    WordPress
+ * @subpackage Fonts
+ * @since      6.4.0
+ */
+
+/**
+ * The Font Face Resolver abstracts the processing of different data sources
+ * (such as theme.json) for processing within the Font Face.
+ *
+ * This class is for internal core usage and is not supposed to be used by
+ * extenders (plugins and/or themes).
+ *
+ * @access private
+ */
+class WP_Font_Face_Resolver {
+
+	/**
+	 * Gets fonts defined in theme.json.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @return array Returns the font-families, each with their font-face variations.
+	 */
+	public static function get_fonts_from_theme_json() {
+		$settings = WP_Theme_JSON_Resolver::get_merged_data()->get_settings();
+
+		// Bail out early if there are no font settings.
+		if ( empty( $settings['typography'] ) || empty( $settings['typography']['fontFamilies'] ) ) {
+			return array();
+		}
+
+		return static::parse_settings( $settings );
+	}
+
+	/**
+	 * Parse theme.json settings to extract font definitions with variations grouped by font-family.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param array $settings Font settings to parse.
+	 * @return array Returns an array of fonts, grouped by font-family.
+	 */
+	private static function parse_settings( array $settings ) {
+		$fonts = array();
+
+		foreach ( $settings['typography']['fontFamilies'] as $font_families ) {
+			foreach ( $font_families as $definition ) {
+
+				// Skip if font-family "name" is not defined.
+				if ( empty( $definition['name'] ) ) {
+					continue;
+				}
+
+				// Skip if "fontFace" is not defined, meaning there are no variations.
+				if ( empty( $definition['fontFace'] ) ) {
+					continue;
+				}
+
+				$font_family = $definition['name'];
+
+				// Prepare the fonts array structure for this font-family.
+				if ( ! array_key_exists( $font_family, $fonts ) ) {
+					$fonts[ $font_family ] = array();
+				}
+
+				$fonts[ $font_family ] = static::convert_font_face_properties( $definition['fontFace'], $font_family );
+			}
+		}
+
+		return $fonts;
+	}
+
+	/**
+	 * Converts font-face properties from theme.json format.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param array  $font_face_definition The font-face definitions to convert.
+	 * @param string $font_family_property The value to store in the font-face font-family property.
+	 * @return array Converted font-face properties.
+	 */
+	private static function convert_font_face_properties( array $font_face_definition, $font_family_property ) {
+		$converted_font_faces = array();
+
+		foreach ( $font_face_definition as $font_face ) {
+			// Add the font-family property to the font-face.
+			$font_face['font-family'] = $font_family_property;
+
+			// Converts the "file:./" src placeholder into a theme font file URI.
+			if ( ! empty( $font_face['src'] ) ) {
+				$font_face['src'] = static::to_theme_file_uri( (array) $font_face['src'] );
+			}
+
+			// Convert camelCase properties into kebab-case.
+			$font_face = static::to_kebab_case( $font_face );
+
+			$converted_font_faces[] = $font_face;
+		}
+
+		return $converted_font_faces;
+	}
+
+	/**
+	 * Converts each 'file:./' placeholder into a URI to the font file in the theme.
+	 *
+	 * The 'file:./' is specified in the theme's `theme.json` as a placeholder to be
+	 * replaced with the URI to the font file's location in the theme. When a "src"
+	 * beings with this placeholder, it is replaced, converting the src into a URI.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param array $src An array of font file sources to process.
+	 * @return array An array of font file src URI(s).
+	 */
+	private static function to_theme_file_uri( array $src ) {
+		$placeholder = 'file:./';
+
+		foreach ( $src as $src_key => $src_url ) {
+			// Skip if the src doesn't start with the placeholder, as there's nothing to replace.
+			if ( ! str_starts_with( $src_url, $placeholder ) ) {
+				continue;
+			}
+
+			$src_file        = str_replace( $placeholder, '', $src_url );
+			$src[ $src_key ] = get_theme_file_uri( $src_file );
+		}
+
+		return $src;
+	}
+
+	/**
+	 * Converts all first dimension keys into kebab-case.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param array $data The array to process.
+	 * @return array Data with first dimension keys converted into kebab-case.
+	 */
+	private static function to_kebab_case( array $data ) {
+		foreach ( $data as $key => $value ) {
+			$kebab_case          = _wp_to_kebab_case( $key );
+			$data[ $kebab_case ] = $value;
+			if ( $kebab_case !== $key ) {
+				unset( $data[ $key ] );
+			}
+		}
+
+		return $data;
+	}
+}