ブロックテーマに Google Web Fonts をリンクで追加する

function vkgf_add_font_theme_json_filter( $theme_json ) {
	// theme.json の内容を一旦配列で変数に格納.
	$get_data       = $theme_json->get_data();
	// 追加するフォントの配列
	$add_font_array = array(
		array(
			'fontFamily' => 'Noto Sans JP, sans-serif',
			'name'       => 'Noto Sans JP',
			'slug'       => 'noto-sans-jp',
			'fontFace'   => array(
				array(
					'fontFamily' => 'Noto Sans JP, sans-serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '700',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@700&display=swap' ),
				),
				array(
					'fontFamily' => 'Noto Sans JP, sans-serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '500',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@500&display=swap' ),
				),
				array(
					'fontFamily' => 'Noto Sans JP, sans-serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '400',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@400&display=swap' ),
				),
				array(
					'fontFamily' => 'Noto Sans JP, sans-serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '300',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@300&display=swap' ),
				),
			),
		),
		array(
			'fontFamily' => 'Noto Serif JP, serif',
			'name'       => 'Noto Serif JP',
			'slug'       => 'noto-serif-jp',
			'fontFace'   => array(
				array(
					'fontFamily' => 'Noto Serif JP, serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '700',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Serif+JP:wght@700&display=swap' ),
				),
				array(
					'fontFamily' => 'Noto Serif JP, serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '500',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Serif+JP:wght@500&display=swap' ),
				),
				array(
					'fontFamily' => 'Noto Serif JP, serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '400',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Serif+JP:wght@400&display=swap' ),
				),
				array(
					'fontFamily' => 'Noto Serif JP, serif',
					'fontStyle'  => 'normal',
					'fontWeight' => '300',
					'src'        => array( 'https://fonts.googleapis.com/css2?family=Noto+Serif+JP:wght@300&display=swap' ),
				),
			),
		),
	);
	// フォントをマージ.
	$fontFamilies = array_merge(
		$get_data['settings']['typography']['fontFamilies']['theme'],
		$add_font_array
	);
	$new_data     = array(
		'version'  => 2,
		'settings' => array(
			'typography' => array(
				'fontFamilies' => $fontFamilies,
			),
		),
	);
	// return $theme_json;
	return $theme_json->update_with( $new_data );
}
add_filter( 'wp_theme_json_data_theme', 'vkgf_add_font_theme_json_filter' );

/**
 * Google Web Font を読み込む
 * theme.json の src での指定は 6.3 ではまだ効かないっぽいためここで手動で読み込む
 *
 * @return void
 */
function my_load_web_fonts() {
	// Noto Sans JP 読み込み
	wp_enqueue_style( 'load-font-noto-sans', 'https://fonts.googleapis.com/css2?family=Noto+Sans+JP:wght@300;400;500;700&display=swap', array(), null );
	// Noto Serif JP 読み込み
	wp_enqueue_style( 'load-font-noto-serif', 'https://fonts.googleapis.com/css2?family=Noto+Serif+JP:wght@300;400;500;700&display=swap', array(), null );
}
add_action( 'wp_enqueue_scripts', 'my_load_web_fonts' );
add_action( 'enqueue_block_editor_assets', 'my_load_web_fonts' );