diff --git a/src/wp-includes/class-wp-theme-json-resolver.php b/src/wp-includes/class-wp-theme-json-resolver.php
index 38df6cebf1e82..56d398aacbfe1 100644
--- a/src/wp-includes/class-wp-theme-json-resolver.php
+++ b/src/wp-includes/class-wp-theme-json-resolver.php
@@ -25,7 +25,7 @@ class WP_Theme_JSON_Resolver {
 	 * @since 5.8.0
 	 * @var WP_Theme_JSON
 	 */
-	private static $core = null;
+	protected static $core = null;
 
 	/**
 	 * Container for data coming from the theme.
@@ -33,7 +33,7 @@ class WP_Theme_JSON_Resolver {
 	 * @since 5.8.0
 	 * @var WP_Theme_JSON
 	 */
-	private static $theme = null;
+	protected static $theme = null;
 
 	/**
 	 * Whether or not the theme supports theme.json.
@@ -41,7 +41,7 @@ class WP_Theme_JSON_Resolver {
 	 * @since 5.8.0
 	 * @var bool
 	 */
-	private static $theme_has_support = null;
+	protected static $theme_has_support = null;
 
 	/**
 	 * Container for data coming from the user.
@@ -49,7 +49,7 @@ class WP_Theme_JSON_Resolver {
 	 * @since 5.9.0
 	 * @var WP_Theme_JSON
 	 */
-	private static $user = null;
+	protected static $user = null;
 
 	/**
 	 * Stores the ID of the custom post type
@@ -58,7 +58,7 @@ class WP_Theme_JSON_Resolver {
 	 * @since 5.9.0
 	 * @var int
 	 */
-	private static $user_custom_post_type_id = null;
+	protected static $user_custom_post_type_id = null;
 
 	/**
 	 * Container to keep loaded i18n schema for `theme.json`.
@@ -67,7 +67,7 @@ class WP_Theme_JSON_Resolver {
 	 * @since 5.9.0 Renamed from `$theme_json_i18n` to `$i18n_schema`.
 	 * @var array
 	 */
-	private static $i18n_schema = null;
+	protected static $i18n_schema = null;
 
 	/**
 	 * Processes a file that adheres to the theme.json schema
@@ -78,7 +78,7 @@ class WP_Theme_JSON_Resolver {
 	 * @param string $file_path Path to file. Empty if no file.
 	 * @return array Contents that adhere to the theme.json schema.
 	 */
-	private static function read_json_file( $file_path ) {
+	protected static function read_json_file( $file_path ) {
 		$config = array();
 		if ( $file_path ) {
 			$decoded_file = wp_json_file_decode( $file_path, array( 'associative' => true ) );
@@ -113,13 +113,13 @@ public static function get_fields_to_translate() {
 	 *                           Default 'default'.
 	 * @return array Returns the modified $theme_json_structure.
 	 */
-	private static function translate( $theme_json, $domain = 'default' ) {
-		if ( null === self::$i18n_schema ) {
-			$i18n_schema       = wp_json_file_decode( __DIR__ . '/theme-i18n.json' );
-			self::$i18n_schema = null === $i18n_schema ? array() : $i18n_schema;
+	protected static function translate( $theme_json, $domain = 'default' ) {
+		if ( null === static::$i18n_schema ) {
+			$i18n_schema         = wp_json_file_decode( __DIR__ . '/theme-i18n.json' );
+			static::$i18n_schema = null === $i18n_schema ? array() : $i18n_schema;
 		}
 
-		return translate_settings_using_i18n_schema( self::$i18n_schema, $theme_json, $domain );
+		return translate_settings_using_i18n_schema( static::$i18n_schema, $theme_json, $domain );
 	}
 
 	/**
@@ -130,15 +130,15 @@ private static function translate( $theme_json, $domain = 'default' ) {
 	 * @return WP_Theme_JSON Entity that holds core data.
 	 */
 	public static function get_core_data() {
-		if ( null !== self::$core ) {
-			return self::$core;
+		if ( null !== static::$core ) {
+			return static::$core;
 		}
 
-		$config     = self::read_json_file( __DIR__ . '/theme.json' );
-		$config     = self::translate( $config );
-		self::$core = new WP_Theme_JSON( $config, 'default' );
+		$config       = static::read_json_file( __DIR__ . '/theme.json' );
+		$config       = static::translate( $config );
+		static::$core = new WP_Theme_JSON( $config, 'default' );
 
-		return self::$core;
+		return static::$core;
 	}
 
 	/**
@@ -159,21 +159,21 @@ public static function get_theme_data( $deprecated = array() ) {
 		if ( ! empty( $deprecated ) ) {
 			_deprecated_argument( __METHOD__, '5.9.0' );
 		}
-		if ( null === self::$theme ) {
-			$theme_json_data = self::read_json_file( self::get_file_path_from_theme( 'theme.json' ) );
-			$theme_json_data = self::translate( $theme_json_data, wp_get_theme()->get( 'TextDomain' ) );
-			self::$theme     = new WP_Theme_JSON( $theme_json_data );
+		if ( null === static::$theme ) {
+			$theme_json_data = static::read_json_file( static::get_file_path_from_theme( 'theme.json' ) );
+			$theme_json_data = static::translate( $theme_json_data, wp_get_theme()->get( 'TextDomain' ) );
+			static::$theme   = new WP_Theme_JSON( $theme_json_data );
 
 			if ( wp_get_theme()->parent() ) {
 				// Get parent theme.json.
-				$parent_theme_json_data = self::read_json_file( self::get_file_path_from_theme( 'theme.json', true ) );
-				$parent_theme_json_data = self::translate( $parent_theme_json_data, wp_get_theme()->parent()->get( 'TextDomain' ) );
+				$parent_theme_json_data = static::read_json_file( static::get_file_path_from_theme( 'theme.json', true ) );
+				$parent_theme_json_data = static::translate( $parent_theme_json_data, wp_get_theme()->parent()->get( 'TextDomain' ) );
 				$parent_theme           = new WP_Theme_JSON( $parent_theme_json_data );
 
 				// Merge the child theme.json into the parent theme.json.
 				// The child theme takes precedence over the parent.
-				$parent_theme->merge( self::$theme );
-				self::$theme = $parent_theme;
+				$parent_theme->merge( static::$theme );
+				static::$theme = $parent_theme;
 			}
 		}
 
@@ -181,10 +181,10 @@ public static function get_theme_data( $deprecated = array() ) {
 		 * We want the presets and settings declared in theme.json
 		 * to override the ones declared via theme supports.
 		 * So we take theme supports, transform it to theme.json shape
-		 * and merge the self::$theme upon that.
+		 * and merge the static::$theme upon that.
 		 */
 		$theme_support_data = WP_Theme_JSON::get_from_editor_settings( get_default_block_editor_settings() );
-		if ( ! self::theme_has_support() ) {
+		if ( ! static::theme_has_support() ) {
 			if ( ! isset( $theme_support_data['settings']['color'] ) ) {
 				$theme_support_data['settings']['color'] = array();
 			}
@@ -210,7 +210,7 @@ public static function get_theme_data( $deprecated = array() ) {
 			$theme_support_data['settings']['color']['defaultGradients'] = $default_gradients;
 		}
 		$with_theme_supports = new WP_Theme_JSON( $theme_support_data );
-		$with_theme_supports->merge( self::$theme );
+		$with_theme_supports->merge( static::$theme );
 
 		return $with_theme_supports;
 	}
@@ -299,12 +299,12 @@ public static function get_user_data_from_wp_global_styles( $theme, $create_post
 	 * @return WP_Theme_JSON Entity that holds styles for user data.
 	 */
 	public static function get_user_data() {
-		if ( null !== self::$user ) {
-			return self::$user;
+		if ( null !== static::$user ) {
+			return static::$user;
 		}
 
 		$config   = array();
-		$user_cpt = self::get_user_data_from_wp_global_styles( wp_get_theme() );
+		$user_cpt = static::get_user_data_from_wp_global_styles( wp_get_theme() );
 
 		if ( array_key_exists( 'post_content', $user_cpt ) ) {
 			$decoded_data = json_decode( $user_cpt['post_content'], true );
@@ -326,9 +326,9 @@ public static function get_user_data() {
 				$config = $decoded_data;
 			}
 		}
-		self::$user = new WP_Theme_JSON( $config, 'custom' );
+		static::$user = new WP_Theme_JSON( $config, 'custom' );
 
-		return self::$user;
+		return static::$user;
 	}
 
 	/**
@@ -363,11 +363,11 @@ public static function get_merged_data( $origin = 'custom' ) {
 		}
 
 		$result = new WP_Theme_JSON();
-		$result->merge( self::get_core_data() );
-		$result->merge( self::get_theme_data() );
+		$result->merge( static::get_core_data() );
+		$result->merge( static::get_theme_data() );
 
 		if ( 'custom' === $origin ) {
-			$result->merge( self::get_user_data() );
+			$result->merge( static::get_user_data() );
 		}
 
 		return $result;
@@ -382,17 +382,17 @@ public static function get_merged_data( $origin = 'custom' ) {
 	 * @return integer|null
 	 */
 	public static function get_user_global_styles_post_id() {
-		if ( null !== self::$user_custom_post_type_id ) {
-			return self::$user_custom_post_type_id;
+		if ( null !== static::$user_custom_post_type_id ) {
+			return static::$user_custom_post_type_id;
 		}
 
-		$user_cpt = self::get_user_data_from_wp_global_styles( wp_get_theme(), true );
+		$user_cpt = static::get_user_data_from_wp_global_styles( wp_get_theme(), true );
 
 		if ( array_key_exists( 'ID', $user_cpt ) ) {
-			self::$user_custom_post_type_id = $user_cpt['ID'];
+			static::$user_custom_post_type_id = $user_cpt['ID'];
 		}
 
-		return self::$user_custom_post_type_id;
+		return static::$user_custom_post_type_id;
 	}
 
 	/**
@@ -404,14 +404,14 @@ public static function get_user_global_styles_post_id() {
 	 * @return bool
 	 */
 	public static function theme_has_support() {
-		if ( ! isset( self::$theme_has_support ) ) {
-			self::$theme_has_support = (
-				is_readable( self::get_file_path_from_theme( 'theme.json' ) ) ||
-				is_readable( self::get_file_path_from_theme( 'theme.json', true ) )
+		if ( ! isset( static::$theme_has_support ) ) {
+			static::$theme_has_support = (
+				is_readable( static::get_file_path_from_theme( 'theme.json' ) ) ||
+				is_readable( static::get_file_path_from_theme( 'theme.json', true ) )
 			);
 		}
 
-		return self::$theme_has_support;
+		return static::$theme_has_support;
 	}
 
 	/**
@@ -426,7 +426,7 @@ public static function theme_has_support() {
 	 * @param bool   $template  Optional. Use template theme directory. Default false.
 	 * @return string The whole file path or empty if the file doesn't exist.
 	 */
-	private static function get_file_path_from_theme( $file_name, $template = false ) {
+	protected static function get_file_path_from_theme( $file_name, $template = false ) {
 		$path      = $template ? get_template_directory() : get_stylesheet_directory();
 		$candidate = $path . '/' . $file_name;
 
@@ -441,12 +441,12 @@ private static function get_file_path_from_theme( $file_name, $template = false
 	 *              and `$i18n_schema` variables to reset.
 	 */
 	public static function clean_cached_data() {
-		self::$core                     = null;
-		self::$theme                    = null;
-		self::$user                     = null;
-		self::$user_custom_post_type_id = null;
-		self::$theme_has_support        = null;
-		self::$i18n_schema              = null;
+		static::$core                     = null;
+		static::$theme                    = null;
+		static::$user                     = null;
+		static::$user_custom_post_type_id = null;
+		static::$theme_has_support        = null;
+		static::$i18n_schema              = null;
 	}
 
 }
diff --git a/src/wp-includes/class-wp-theme-json.php b/src/wp-includes/class-wp-theme-json.php
index 5c643cf138a67..7aa653948fa98 100644
--- a/src/wp-includes/class-wp-theme-json.php
+++ b/src/wp-includes/class-wp-theme-json.php
@@ -24,7 +24,7 @@ class WP_Theme_JSON {
 	 * @since 5.8.0
 	 * @var array
 	 */
-	private $theme_json = null;
+	protected $theme_json = null;
 
 	/**
 	 * Holds block metadata extracted from block.json
@@ -34,7 +34,7 @@ class WP_Theme_JSON {
 	 * @since 5.8.0
 	 * @var array
 	 */
-	private static $blocks_metadata = null;
+	protected static $blocks_metadata = null;
 
 	/**
 	 * The CSS selector for the top-level styles.
@@ -366,20 +366,20 @@ class WP_Theme_JSON {
 	 *                           One of 'default', 'theme', or 'custom'. Default 'theme'.
 	 */
 	public function __construct( $theme_json = array(), $origin = 'theme' ) {
-		if ( ! in_array( $origin, self::VALID_ORIGINS, true ) ) {
+		if ( ! in_array( $origin, static::VALID_ORIGINS, true ) ) {
 			$origin = 'theme';
 		}
 
 		$this->theme_json    = WP_Theme_JSON_Schema::migrate( $theme_json );
-		$valid_block_names   = array_keys( self::get_blocks_metadata() );
-		$valid_element_names = array_keys( self::ELEMENTS );
-		$theme_json          = self::sanitize( $this->theme_json, $valid_block_names, $valid_element_names );
-		$this->theme_json    = self::maybe_opt_in_into_settings( $theme_json );
+		$valid_block_names   = array_keys( static::get_blocks_metadata() );
+		$valid_element_names = array_keys( static::ELEMENTS );
+		$theme_json          = static::sanitize( $this->theme_json, $valid_block_names, $valid_element_names );
+		$this->theme_json    = static::maybe_opt_in_into_settings( $theme_json );
 
 		// Internally, presets are keyed by origin.
-		$nodes = self::get_setting_nodes( $this->theme_json );
+		$nodes = static::get_setting_nodes( $this->theme_json );
 		foreach ( $nodes as $node ) {
-			foreach ( self::PRESETS_METADATA as $preset_metadata ) {
+			foreach ( static::PRESETS_METADATA as $preset_metadata ) {
 				$path   = array_merge( $node['path'], $preset_metadata['path'] );
 				$preset = _wp_array_get( $this->theme_json, $path, null );
 				if ( null !== $preset ) {
@@ -400,20 +400,20 @@ public function __construct( $theme_json = array(), $origin = 'theme' ) {
 	 * @param array $theme_json A theme.json structure to modify.
 	 * @return array The modified theme.json structure.
 	 */
-	private static function maybe_opt_in_into_settings( $theme_json ) {
+	protected static function maybe_opt_in_into_settings( $theme_json ) {
 		$new_theme_json = $theme_json;
 
 		if (
 			isset( $new_theme_json['settings']['appearanceTools'] ) &&
 			true === $new_theme_json['settings']['appearanceTools']
 		) {
-			self::do_opt_in_into_settings( $new_theme_json['settings'] );
+			static::do_opt_in_into_settings( $new_theme_json['settings'] );
 		}
 
 		if ( isset( $new_theme_json['settings']['blocks'] ) && is_array( $new_theme_json['settings']['blocks'] ) ) {
 			foreach ( $new_theme_json['settings']['blocks'] as &$block ) {
 				if ( isset( $block['appearanceTools'] ) && ( true === $block['appearanceTools'] ) ) {
-					self::do_opt_in_into_settings( $block );
+					static::do_opt_in_into_settings( $block );
 				}
 			}
 		}
@@ -428,7 +428,7 @@ private static function maybe_opt_in_into_settings( $theme_json ) {
 	 *
 	 * @param array $context The context to which the settings belong.
 	 */
-	private static function do_opt_in_into_settings( &$context ) {
+	protected static function do_opt_in_into_settings( &$context ) {
 		$to_opt_in = array(
 			array( 'border', 'color' ),
 			array( 'border', 'radius' ),
@@ -463,18 +463,18 @@ private static function do_opt_in_into_settings( &$context ) {
 	 * @param array $valid_element_names List of valid element names.
 	 * @return array The sanitized output.
 	 */
-	private static function sanitize( $input, $valid_block_names, $valid_element_names ) {
+	protected static function sanitize( $input, $valid_block_names, $valid_element_names ) {
 		$output = array();
 
 		if ( ! is_array( $input ) ) {
 			return $output;
 		}
 
-		$output = array_intersect_key( $input, array_flip( self::VALID_TOP_LEVEL_KEYS ) );
+		$output = array_intersect_key( $input, array_flip( static::VALID_TOP_LEVEL_KEYS ) );
 
 		// Some styles are only meant to be available at the top-level (e.g.: blockGap),
 		// hence, the schema for blocks & elements should not have them.
-		$styles_non_top_level = self::VALID_STYLES;
+		$styles_non_top_level = static::VALID_STYLES;
 		foreach ( array_keys( $styles_non_top_level ) as $section ) {
 			foreach ( array_keys( $styles_non_top_level[ $section ] ) as $prop ) {
 				if ( 'top' === $styles_non_top_level[ $section ][ $prop ] ) {
@@ -492,14 +492,14 @@ private static function sanitize( $input, $valid_block_names, $valid_element_nam
 		$schema_styles_blocks   = array();
 		$schema_settings_blocks = array();
 		foreach ( $valid_block_names as $block ) {
-			$schema_settings_blocks[ $block ]           = self::VALID_SETTINGS;
+			$schema_settings_blocks[ $block ]           = static::VALID_SETTINGS;
 			$schema_styles_blocks[ $block ]             = $styles_non_top_level;
 			$schema_styles_blocks[ $block ]['elements'] = $schema_styles_elements;
 		}
-		$schema['styles']             = self::VALID_STYLES;
+		$schema['styles']             = static::VALID_STYLES;
 		$schema['styles']['blocks']   = $schema_styles_blocks;
 		$schema['styles']['elements'] = $schema_styles_elements;
-		$schema['settings']           = self::VALID_SETTINGS;
+		$schema['settings']           = static::VALID_SETTINGS;
 		$schema['settings']['blocks'] = $schema_settings_blocks;
 
 		// Remove anything that's not present in the schema.
@@ -513,7 +513,7 @@ private static function sanitize( $input, $valid_block_names, $valid_element_nam
 				continue;
 			}
 
-			$result = self::remove_keys_not_in_schema( $input[ $subtree ], $schema[ $subtree ] );
+			$result = static::remove_keys_not_in_schema( $input[ $subtree ], $schema[ $subtree ] );
 
 			if ( empty( $result ) ) {
 				unset( $output[ $subtree ] );
@@ -554,12 +554,12 @@ private static function sanitize( $input, $valid_block_names, $valid_element_nam
 	 *
 	 * @return array Block metadata.
 	 */
-	private static function get_blocks_metadata() {
-		if ( null !== self::$blocks_metadata ) {
-			return self::$blocks_metadata;
+	protected static function get_blocks_metadata() {
+		if ( null !== static::$blocks_metadata ) {
+			return static::$blocks_metadata;
 		}
 
-		self::$blocks_metadata = array();
+		static::$blocks_metadata = array();
 
 		$registry = WP_Block_Type_Registry::get_instance();
 		$blocks   = $registry->get_all_registered();
@@ -568,32 +568,32 @@ private static function get_blocks_metadata() {
 				isset( $block_type->supports['__experimentalSelector'] ) &&
 				is_string( $block_type->supports['__experimentalSelector'] )
 			) {
-				self::$blocks_metadata[ $block_name ]['selector'] = $block_type->supports['__experimentalSelector'];
+				static::$blocks_metadata[ $block_name ]['selector'] = $block_type->supports['__experimentalSelector'];
 			} else {
-				self::$blocks_metadata[ $block_name ]['selector'] = '.wp-block-' . str_replace( '/', '-', str_replace( 'core/', '', $block_name ) );
+				static::$blocks_metadata[ $block_name ]['selector'] = '.wp-block-' . str_replace( '/', '-', str_replace( 'core/', '', $block_name ) );
 			}
 
 			if (
 				isset( $block_type->supports['color']['__experimentalDuotone'] ) &&
 				is_string( $block_type->supports['color']['__experimentalDuotone'] )
 			) {
-				self::$blocks_metadata[ $block_name ]['duotone'] = $block_type->supports['color']['__experimentalDuotone'];
+				static::$blocks_metadata[ $block_name ]['duotone'] = $block_type->supports['color']['__experimentalDuotone'];
 			}
 
 			// Assign defaults, then overwrite those that the block sets by itself.
 			// If the block selector is compounded, will append the element to each
 			// individual block selector.
-			$block_selectors = explode( ',', self::$blocks_metadata[ $block_name ]['selector'] );
-			foreach ( self::ELEMENTS as $el_name => $el_selector ) {
+			$block_selectors = explode( ',', static::$blocks_metadata[ $block_name ]['selector'] );
+			foreach ( static::ELEMENTS as $el_name => $el_selector ) {
 				$element_selector = array();
 				foreach ( $block_selectors as $selector ) {
 					$element_selector[] = $selector . ' ' . $el_selector;
 				}
-				self::$blocks_metadata[ $block_name ]['elements'][ $el_name ] = implode( ',', $element_selector );
+				static::$blocks_metadata[ $block_name ]['elements'][ $el_name ] = implode( ',', $element_selector );
 			}
 		}
 
-		return self::$blocks_metadata;
+		return static::$blocks_metadata;
 	}
 
 	/**
@@ -607,7 +607,7 @@ private static function get_blocks_metadata() {
 	 * @param array $schema Schema to adhere to.
 	 * @return array Returns the modified $tree.
 	 */
-	private static function remove_keys_not_in_schema( $tree, $schema ) {
+	protected static function remove_keys_not_in_schema( $tree, $schema ) {
 		$tree = array_intersect_key( $tree, $schema );
 
 		foreach ( $schema as $key => $data ) {
@@ -616,7 +616,7 @@ private static function remove_keys_not_in_schema( $tree, $schema ) {
 			}
 
 			if ( is_array( $schema[ $key ] ) && is_array( $tree[ $key ] ) ) {
-				$tree[ $key ] = self::remove_keys_not_in_schema( $tree[ $key ], $schema[ $key ] );
+				$tree[ $key ] = static::remove_keys_not_in_schema( $tree[ $key ], $schema[ $key ] );
 
 				if ( empty( $tree[ $key ] ) ) {
 					unset( $tree[ $key ] );
@@ -670,10 +670,14 @@ public function get_settings() {
 	 *                       - `variables`: only the CSS Custom Properties for presets & custom ones.
 	 *                       - `styles`: only the styles section in theme.json.
 	 *                       - `presets`: only the classes for the presets.
-	 * @param array $origins A list of origins to include. By default it includes `self::VALID_ORIGINS`.
+	 * @param array $origins A list of origins to include. By default it includes VALID_ORIGINS.
 	 * @return string Stylesheet.
 	 */
-	public function get_stylesheet( $types = array( 'variables', 'styles', 'presets' ), $origins = self::VALID_ORIGINS ) {
+	public function get_stylesheet( $types = array( 'variables', 'styles', 'presets' ), $origins = null ) {
+		if ( null === $origins ) {
+			$origins = static::VALID_ORIGINS;
+		}
+
 		if ( is_string( $types ) ) {
 			// Dispatch error and map old arguments to new ones.
 			_deprecated_argument( __FUNCTION__, '5.9.0' );
@@ -686,9 +690,9 @@ public function get_stylesheet( $types = array( 'variables', 'styles', 'presets'
 			}
 		}
 
-		$blocks_metadata = self::get_blocks_metadata();
-		$style_nodes     = self::get_style_nodes( $this->theme_json, $blocks_metadata );
-		$setting_nodes   = self::get_setting_nodes( $this->theme_json, $blocks_metadata );
+		$blocks_metadata = static::get_blocks_metadata();
+		$style_nodes     = static::get_style_nodes( $this->theme_json, $blocks_metadata );
+		$setting_nodes   = static::get_setting_nodes( $this->theme_json, $blocks_metadata );
 
 		$stylesheet = '';
 
@@ -775,7 +779,7 @@ public function get_template_parts() {
 	 * @param array $style_nodes Nodes with styles.
 	 * @return string The new stylesheet.
 	 */
-	private function get_block_classes( $style_nodes ) {
+	protected function get_block_classes( $style_nodes ) {
 		$block_rules = '';
 
 		foreach ( $style_nodes as $metadata ) {
@@ -786,7 +790,7 @@ private function get_block_classes( $style_nodes ) {
 			$node         = _wp_array_get( $this->theme_json, $metadata['path'], array() );
 			$selector     = $metadata['selector'];
 			$settings     = _wp_array_get( $this->theme_json, array( 'settings' ) );
-			$declarations = self::compute_style_properties( $node, $settings );
+			$declarations = static::compute_style_properties( $node, $settings );
 
 			// 1. Separate the ones who use the general selector
 			// and the ones who use the duotone selector.
@@ -806,20 +810,20 @@ private function get_block_classes( $style_nodes ) {
 			 * user-generated values take precedence in the CSS cascade.
 			 * @link https://github.com/WordPress/gutenberg/issues/36147.
 			 */
-			if ( self::ROOT_BLOCK_SELECTOR === $selector ) {
+			if ( static::ROOT_BLOCK_SELECTOR === $selector ) {
 				$block_rules .= 'body { margin: 0; }';
 			}
 
 			// 2. Generate the rules that use the general selector.
-			$block_rules .= self::to_ruleset( $selector, $declarations );
+			$block_rules .= static::to_ruleset( $selector, $declarations );
 
 			// 3. Generate the rules that use the duotone selector.
 			if ( isset( $metadata['duotone'] ) && ! empty( $declarations_duotone ) ) {
-				$selector_duotone = self::scope_selector( $metadata['selector'], $metadata['duotone'] );
-				$block_rules     .= self::to_ruleset( $selector_duotone, $declarations_duotone );
+				$selector_duotone = static::scope_selector( $metadata['selector'], $metadata['duotone'] );
+				$block_rules     .= static::to_ruleset( $selector_duotone, $declarations_duotone );
 			}
 
-			if ( self::ROOT_BLOCK_SELECTOR === $selector ) {
+			if ( static::ROOT_BLOCK_SELECTOR === $selector ) {
 				$block_rules .= '.wp-site-blocks > .alignleft { float: left; margin-right: 2em; }';
 				$block_rules .= '.wp-site-blocks > .alignright { float: right; margin-left: 2em; }';
 				$block_rules .= '.wp-site-blocks > .aligncenter { justify-content: center; margin-left: auto; margin-right: auto; }';
@@ -864,7 +868,7 @@ private function get_block_classes( $style_nodes ) {
 	 * @param array $origins       List of origins to process presets from.
 	 * @return string The new stylesheet.
 	 */
-	private function get_preset_classes( $setting_nodes, $origins ) {
+	protected function get_preset_classes( $setting_nodes, $origins ) {
 		$preset_rules = '';
 
 		foreach ( $setting_nodes as $metadata ) {
@@ -874,7 +878,7 @@ private function get_preset_classes( $setting_nodes, $origins ) {
 
 			$selector      = $metadata['selector'];
 			$node          = _wp_array_get( $this->theme_json, $metadata['path'], array() );
-			$preset_rules .= self::compute_preset_classes( $node, $selector, $origins );
+			$preset_rules .= static::compute_preset_classes( $node, $selector, $origins );
 		}
 
 		return $preset_rules;
@@ -901,7 +905,7 @@ private function get_preset_classes( $setting_nodes, $origins ) {
 	 * @param array $origins List of origins to process.
 	 * @return string The new stylesheet.
 	 */
-	private function get_css_variables( $nodes, $origins ) {
+	protected function get_css_variables( $nodes, $origins ) {
 		$stylesheet = '';
 		foreach ( $nodes as $metadata ) {
 			if ( null === $metadata['selector'] ) {
@@ -911,9 +915,9 @@ private function get_css_variables( $nodes, $origins ) {
 			$selector = $metadata['selector'];
 
 			$node         = _wp_array_get( $this->theme_json, $metadata['path'], array() );
-			$declarations = array_merge( self::compute_preset_vars( $node, $origins ), self::compute_theme_vars( $node ) );
+			$declarations = array_merge( static::compute_preset_vars( $node, $origins ), static::compute_theme_vars( $node ) );
 
-			$stylesheet .= self::to_ruleset( $selector, $declarations );
+			$stylesheet .= static::to_ruleset( $selector, $declarations );
 		}
 
 		return $stylesheet;
@@ -929,7 +933,7 @@ private function get_css_variables( $nodes, $origins ) {
 	 * @param array  $declarations List of declarations.
 	 * @return string CSS ruleset.
 	 */
-	private static function to_ruleset( $selector, $declarations ) {
+	protected static function to_ruleset( $selector, $declarations ) {
 		if ( empty( $declarations ) ) {
 			return '';
 		}
@@ -957,7 +961,7 @@ static function ( $carry, $element ) {
 	 * @param string $to_append Selector to append.
 	 * @return string
 	 */
-	private static function append_to_selector( $selector, $to_append ) {
+	protected static function append_to_selector( $selector, $to_append ) {
 		$new_selectors = array();
 		$selectors     = explode( ',', $selector );
 		foreach ( $selectors as $sel ) {
@@ -979,22 +983,22 @@ private static function append_to_selector( $selector, $to_append ) {
 	 * @param array  $origins  List of origins to process.
 	 * @return string The result of processing the presets.
 	 */
-	private static function compute_preset_classes( $settings, $selector, $origins ) {
-		if ( self::ROOT_BLOCK_SELECTOR === $selector ) {
+	protected static function compute_preset_classes( $settings, $selector, $origins ) {
+		if ( static::ROOT_BLOCK_SELECTOR === $selector ) {
 			// Classes at the global level do not need any CSS prefixed,
 			// and we don't want to increase its specificity.
 			$selector = '';
 		}
 
 		$stylesheet = '';
-		foreach ( self::PRESETS_METADATA as $preset_metadata ) {
-			$slugs = self::get_settings_slugs( $settings, $preset_metadata, $origins );
+		foreach ( static::PRESETS_METADATA as $preset_metadata ) {
+			$slugs = static::get_settings_slugs( $settings, $preset_metadata, $origins );
 			foreach ( $preset_metadata['classes'] as $class => $property ) {
 				foreach ( $slugs as $slug ) {
-					$css_var     = self::replace_slug_in_string( $preset_metadata['css_vars'], $slug );
-					$class_name  = self::replace_slug_in_string( $class, $slug );
-					$stylesheet .= self::to_ruleset(
-						self::append_to_selector( $selector, $class_name ),
+					$css_var     = static::replace_slug_in_string( $preset_metadata['css_vars'], $slug );
+					$class_name  = static::replace_slug_in_string( $class, $slug );
+					$stylesheet .= static::to_ruleset(
+						static::append_to_selector( $selector, $class_name ),
 						array(
 							array(
 								'name'  => $property,
@@ -1026,7 +1030,7 @@ private static function compute_preset_classes( $settings, $selector, $origins )
 	 * @param string $selector Original selector.
 	 * @return string Scoped selector.
 	 */
-	private static function scope_selector( $scope, $selector ) {
+	protected static function scope_selector( $scope, $selector ) {
 		$scopes    = explode( ',', $scope );
 		$selectors = explode( ',', $selector );
 
@@ -1076,7 +1080,7 @@ private static function scope_selector( $scope, $selector ) {
 	 * @param array $origins         List of origins to process.
 	 * @return array Array of presets where each key is a slug and each value is the preset value.
 	 */
-	private static function get_settings_values_by_slug( $settings, $preset_metadata, $origins ) {
+	protected static function get_settings_values_by_slug( $settings, $preset_metadata, $origins ) {
 		$preset_per_origin = _wp_array_get( $settings, $preset_metadata['path'], array() );
 
 		$result = array();
@@ -1118,7 +1122,11 @@ private static function get_settings_values_by_slug( $settings, $preset_metadata
 	 * @param array $origins         List of origins to process.
 	 * @return array Array of presets where the key and value are both the slug.
 	 */
-	private static function get_settings_slugs( $settings, $preset_metadata, $origins = self::VALID_ORIGINS ) {
+	protected static function get_settings_slugs( $settings, $preset_metadata, $origins = null ) {
+		if ( null === $origins ) {
+			$origins = static::VALID_ORIGINS;
+		}
+
 		$preset_per_origin = _wp_array_get( $settings, $preset_metadata['path'], array() );
 
 		$result = array();
@@ -1145,7 +1153,7 @@ private static function get_settings_slugs( $settings, $preset_metadata, $origin
 	 * @param string $slug  The slug value to use to generate the custom property.
 	 * @return string The CSS Custom Property. Something along the lines of `--wp--preset--color--black`.
 	 */
-	private static function replace_slug_in_string( $input, $slug ) {
+	protected static function replace_slug_in_string( $input, $slug ) {
 		return strtr( $input, array( '$slug' => $slug ) );
 	}
 
@@ -1166,13 +1174,13 @@ private static function replace_slug_in_string( $input, $slug ) {
 	 * @param array $origins  List of origins to process.
 	 * @return array Returns the modified $declarations.
 	 */
-	private static function compute_preset_vars( $settings, $origins ) {
+	protected static function compute_preset_vars( $settings, $origins ) {
 		$declarations = array();
-		foreach ( self::PRESETS_METADATA as $preset_metadata ) {
-			$values_by_slug = self::get_settings_values_by_slug( $settings, $preset_metadata, $origins );
+		foreach ( static::PRESETS_METADATA as $preset_metadata ) {
+			$values_by_slug = static::get_settings_values_by_slug( $settings, $preset_metadata, $origins );
 			foreach ( $values_by_slug as $slug => $value ) {
 				$declarations[] = array(
-					'name'  => self::replace_slug_in_string( $preset_metadata['css_vars'], $slug ),
+					'name'  => static::replace_slug_in_string( $preset_metadata['css_vars'], $slug ),
 					'value' => $value,
 				);
 			}
@@ -1196,10 +1204,10 @@ private static function compute_preset_vars( $settings, $origins ) {
 	 * @param array $settings Settings to process.
 	 * @return array Returns the modified $declarations.
 	 */
-	private static function compute_theme_vars( $settings ) {
+	protected static function compute_theme_vars( $settings ) {
 		$declarations  = array();
 		$custom_values = _wp_array_get( $settings, array( 'custom' ), array() );
-		$css_vars      = self::flatten_tree( $custom_values );
+		$css_vars      = static::flatten_tree( $custom_values );
 		foreach ( $css_vars as $key => $value ) {
 			$declarations[] = array(
 				'name'  => '--wp--custom--' . $key,
@@ -1247,7 +1255,7 @@ private static function compute_theme_vars( $settings ) {
 	 * @param string $token  Optional. Token to use between levels. Default '--'.
 	 * @return array The flattened tree.
 	 */
-	private static function flatten_tree( $tree, $prefix = '', $token = '--' ) {
+	protected static function flatten_tree( $tree, $prefix = '', $token = '--' ) {
 		$result = array();
 		foreach ( $tree as $property => $value ) {
 			$new_key = $prefix . str_replace(
@@ -1260,7 +1268,7 @@ private static function flatten_tree( $tree, $prefix = '', $token = '--' ) {
 				$new_prefix = $new_key . $token;
 				$result     = array_merge(
 					$result,
-					self::flatten_tree( $value, $new_prefix, $token )
+					static::flatten_tree( $value, $new_prefix, $token )
 				);
 			} else {
 				$result[ $new_key ] = $value;
@@ -1286,22 +1294,26 @@ private static function flatten_tree( $tree, $prefix = '', $token = '--' ) {
 	 * @param array $properties Properties metadata.
 	 * @return array Returns the modified $declarations.
 	 */
-	private static function compute_style_properties( $styles, $settings = array(), $properties = self::PROPERTIES_METADATA ) {
+	protected static function compute_style_properties( $styles, $settings = array(), $properties = null ) {
+		if ( null === $properties ) {
+			$properties = static::PROPERTIES_METADATA;
+		}
+
 		$declarations = array();
 		if ( empty( $styles ) ) {
 			return $declarations;
 		}
 
 		foreach ( $properties as $css_property => $value_path ) {
-			$value = self::get_property_value( $styles, $value_path );
+			$value = static::get_property_value( $styles, $value_path );
 
 			// Look up protected properties, keyed by value path.
 			// Skip protected properties that are explicitly set to `null`.
 			if ( is_array( $value_path ) ) {
 				$path_string = implode( '.', $value_path );
 				if (
-					array_key_exists( $path_string, self::PROTECTED_PROPERTIES ) &&
-					_wp_array_get( $settings, self::PROTECTED_PROPERTIES[ $path_string ], null ) === null
+					array_key_exists( $path_string, static::PROTECTED_PROPERTIES ) &&
+					_wp_array_get( $settings, static::PROTECTED_PROPERTIES[ $path_string ], null ) === null
 				) {
 					continue;
 				}
@@ -1336,7 +1348,7 @@ private static function compute_style_properties( $styles, $settings = array(),
 	 * @param array $path   Which property to process.
 	 * @return string|array Style property value.
 	 */
-	private static function get_property_value( $styles, $path ) {
+	protected static function get_property_value( $styles, $path ) {
 		$value = _wp_array_get( $styles, $path, '' );
 
 		if ( '' === $value || is_array( $value ) ) {
@@ -1379,7 +1391,7 @@ private static function get_property_value( $styles, $path ) {
 	 * @param array $selectors  List of selectors per block.
 	 * @return array
 	 */
-	private static function get_setting_nodes( $theme_json, $selectors = array() ) {
+	protected static function get_setting_nodes( $theme_json, $selectors = array() ) {
 		$nodes = array();
 		if ( ! isset( $theme_json['settings'] ) ) {
 			return $nodes;
@@ -1388,7 +1400,7 @@ private static function get_setting_nodes( $theme_json, $selectors = array() ) {
 		// Top-level.
 		$nodes[] = array(
 			'path'     => array( 'settings' ),
-			'selector' => self::ROOT_BLOCK_SELECTOR,
+			'selector' => static::ROOT_BLOCK_SELECTOR,
 		);
 
 		// Calculate paths for blocks.
@@ -1433,7 +1445,7 @@ private static function get_setting_nodes( $theme_json, $selectors = array() ) {
 	 * @param array $selectors  List of selectors per block.
 	 * @return array
 	 */
-	private static function get_style_nodes( $theme_json, $selectors = array() ) {
+	protected static function get_style_nodes( $theme_json, $selectors = array() ) {
 		$nodes = array();
 		if ( ! isset( $theme_json['styles'] ) ) {
 			return $nodes;
@@ -1442,14 +1454,14 @@ private static function get_style_nodes( $theme_json, $selectors = array() ) {
 		// Top-level.
 		$nodes[] = array(
 			'path'     => array( 'styles' ),
-			'selector' => self::ROOT_BLOCK_SELECTOR,
+			'selector' => static::ROOT_BLOCK_SELECTOR,
 		);
 
 		if ( isset( $theme_json['styles']['elements'] ) ) {
 			foreach ( $theme_json['styles']['elements'] as $element => $node ) {
 				$nodes[] = array(
 					'path'     => array( 'styles', 'elements', $element ),
-					'selector' => self::ELEMENTS[ $element ],
+					'selector' => static::ELEMENTS[ $element ],
 				);
 			}
 		}
@@ -1523,10 +1535,10 @@ public function merge( $incoming ) {
 		 * with the equivalent dfefault presets: if a slug is present as a default
 		 * we remove it from the theme presets.
 		 */
-		$nodes        = self::get_setting_nodes( $incoming_data );
-		$slugs_global = self::get_default_slugs( $this->theme_json, array( 'settings' ) );
+		$nodes        = static::get_setting_nodes( $incoming_data );
+		$slugs_global = static::get_default_slugs( $this->theme_json, array( 'settings' ) );
 		foreach ( $nodes as $node ) {
-			$slugs_node = self::get_default_slugs( $this->theme_json, $node['path'] );
+			$slugs_node = static::get_default_slugs( $this->theme_json, $node['path'] );
 			$slugs      = array_merge_recursive( $slugs_global, $slugs_node );
 
 			// Replace the spacing.units.
@@ -1537,10 +1549,10 @@ public function merge( $incoming ) {
 			}
 
 			// Replace the presets.
-			foreach ( self::PRESETS_METADATA as $preset ) {
-				$override_preset = self::should_override_preset( $this->theme_json, $node['path'], $preset['override'] );
+			foreach ( static::PRESETS_METADATA as $preset ) {
+				$override_preset = static::should_override_preset( $this->theme_json, $node['path'], $preset['override'] );
 
-				foreach ( self::VALID_ORIGINS as $origin ) {
+				foreach ( static::VALID_ORIGINS as $origin ) {
 					$base_path = array_merge( $node['path'], $preset['path'] );
 					$path      = array_merge( $base_path, array( $origin ) );
 					$content   = _wp_array_get( $incoming_data, $path, null );
@@ -1551,7 +1563,7 @@ public function merge( $incoming ) {
 					if ( 'theme' === $origin && $preset['use_default_names'] ) {
 						foreach ( $content as &$item ) {
 							if ( ! array_key_exists( 'name', $item ) ) {
-								$name = self::get_name_from_defaults( $item['slug'], $base_path );
+								$name = static::get_name_from_defaults( $item['slug'], $base_path );
 								if ( null !== $name ) {
 									$item['name'] = $name;
 								}
@@ -1566,7 +1578,7 @@ public function merge( $incoming ) {
 						_wp_array_set( $this->theme_json, $path, $content );
 					} else {
 						$slugs_for_preset = _wp_array_get( $slugs, $preset['path'], array() );
-						$content          = self::filter_slugs( $content, $slugs_for_preset );
+						$content          = static::filter_slugs( $content, $slugs_for_preset );
 						_wp_array_set( $this->theme_json, $path, $content );
 					}
 				}
@@ -1584,7 +1596,7 @@ public function merge( $incoming ) {
 	 * @param bool|array $override Data to compute whether to override the preset.
 	 * @return boolean
 	 */
-	private static function should_override_preset( $theme_json, $path, $override ) {
+	protected static function should_override_preset( $theme_json, $path, $override ) {
 		if ( is_bool( $override ) ) {
 			return $override;
 		}
@@ -1636,10 +1648,10 @@ private static function should_override_preset( $theme_json, $path, $override )
 	 * @param array $node_path The path to inspect. It's 'settings' by default.
 	 * @return array
 	 */
-	private static function get_default_slugs( $data, $node_path ) {
+	protected static function get_default_slugs( $data, $node_path ) {
 		$slugs = array();
 
-		foreach ( self::PRESETS_METADATA as $metadata ) {
+		foreach ( static::PRESETS_METADATA as $metadata ) {
 			$path   = array_merge( $node_path, $metadata['path'], array( 'default' ) );
 			$preset = _wp_array_get( $data, $path, null );
 			if ( ! isset( $preset ) ) {
@@ -1668,7 +1680,7 @@ static function( $value ) {
 	 * @param array  $base_path The path to inspect. It's 'settings' by default.
 	 * @return string|null
 	 */
-	private function get_name_from_defaults( $slug, $base_path ) {
+	protected function get_name_from_defaults( $slug, $base_path ) {
 		$path            = array_merge( $base_path, array( 'default' ) );
 		$default_content = _wp_array_get( $this->theme_json, $path, null );
 		if ( ! $default_content ) {
@@ -1691,7 +1703,7 @@ private function get_name_from_defaults( $slug, $base_path ) {
 	 * @param array $slugs The slugs that should not be overriden.
 	 * @return array The new node.
 	 */
-	private static function filter_slugs( $node, $slugs ) {
+	protected static function filter_slugs( $node, $slugs ) {
 		if ( empty( $slugs ) ) {
 			return $node;
 		}
@@ -1719,32 +1731,32 @@ public static function remove_insecure_properties( $theme_json ) {
 
 		$theme_json = WP_Theme_JSON_Schema::migrate( $theme_json );
 
-		$valid_block_names   = array_keys( self::get_blocks_metadata() );
-		$valid_element_names = array_keys( self::ELEMENTS );
-		$theme_json          = self::sanitize( $theme_json, $valid_block_names, $valid_element_names );
+		$valid_block_names   = array_keys( static::get_blocks_metadata() );
+		$valid_element_names = array_keys( static::ELEMENTS );
+		$theme_json          = static::sanitize( $theme_json, $valid_block_names, $valid_element_names );
 
-		$blocks_metadata = self::get_blocks_metadata();
-		$style_nodes     = self::get_style_nodes( $theme_json, $blocks_metadata );
+		$blocks_metadata = static::get_blocks_metadata();
+		$style_nodes     = static::get_style_nodes( $theme_json, $blocks_metadata );
 		foreach ( $style_nodes as $metadata ) {
 			$input = _wp_array_get( $theme_json, $metadata['path'], array() );
 			if ( empty( $input ) ) {
 				continue;
 			}
 
-			$output = self::remove_insecure_styles( $input );
+			$output = static::remove_insecure_styles( $input );
 			if ( ! empty( $output ) ) {
 				_wp_array_set( $sanitized, $metadata['path'], $output );
 			}
 		}
 
-		$setting_nodes = self::get_setting_nodes( $theme_json );
+		$setting_nodes = static::get_setting_nodes( $theme_json );
 		foreach ( $setting_nodes as $metadata ) {
 			$input = _wp_array_get( $theme_json, $metadata['path'], array() );
 			if ( empty( $input ) ) {
 				continue;
 			}
 
-			$output = self::remove_insecure_settings( $input );
+			$output = static::remove_insecure_settings( $input );
 			if ( ! empty( $output ) ) {
 				_wp_array_set( $sanitized, $metadata['path'], $output );
 			}
@@ -1774,10 +1786,10 @@ public static function remove_insecure_properties( $theme_json ) {
 	 * @param array $input Node to process.
 	 * @return array
 	 */
-	private static function remove_insecure_settings( $input ) {
+	protected static function remove_insecure_settings( $input ) {
 		$output = array();
-		foreach ( self::PRESETS_METADATA as $preset_metadata ) {
-			foreach ( self::VALID_ORIGINS as $origin ) {
+		foreach ( static::PRESETS_METADATA as $preset_metadata ) {
+			foreach ( static::VALID_ORIGINS as $origin ) {
 				$path_with_origin = array_merge( $preset_metadata['path'], array( $origin ) );
 				$presets          = _wp_array_get( $input, $path_with_origin, null );
 				if ( null === $presets ) {
@@ -1802,7 +1814,7 @@ private static function remove_insecure_settings( $input ) {
 
 						$preset_is_valid = true;
 						foreach ( $preset_metadata['properties'] as $property ) {
-							if ( ! self::is_safe_css_declaration( $property, $value ) ) {
+							if ( ! static::is_safe_css_declaration( $property, $value ) ) {
 								$preset_is_valid = false;
 								break;
 							}
@@ -1831,13 +1843,13 @@ private static function remove_insecure_settings( $input ) {
 	 * @param array $input Node to process.
 	 * @return array
 	 */
-	private static function remove_insecure_styles( $input ) {
+	protected static function remove_insecure_styles( $input ) {
 		$output       = array();
-		$declarations = self::compute_style_properties( $input );
+		$declarations = static::compute_style_properties( $input );
 
 		foreach ( $declarations as $declaration ) {
-			if ( self::is_safe_css_declaration( $declaration['name'], $declaration['value'] ) ) {
-				$path = self::PROPERTIES_METADATA[ $declaration['name'] ];
+			if ( static::is_safe_css_declaration( $declaration['name'], $declaration['value'] ) ) {
+				$path = static::PROPERTIES_METADATA[ $declaration['name'] ];
 
 				// Check the value isn't an array before adding so as to not
 				// double up shorthand and longhand styles.
@@ -1859,7 +1871,7 @@ private static function remove_insecure_styles( $input ) {
 	 * @param string $property_value Value in a CSS declaration, i.e. the `red` in `color: red`.
 	 * @return bool
 	 */
-	private static function is_safe_css_declaration( $property_name, $property_value ) {
+	protected static function is_safe_css_declaration( $property_name, $property_value ) {
 		$style_to_validate = $property_name . ': ' . $property_value;
 		$filtered          = esc_html( safecss_filter_attr( $style_to_validate ) );
 		return ! empty( trim( $filtered ) );
@@ -1887,7 +1899,7 @@ public function get_raw_data() {
 	 */
 	public static function get_from_editor_settings( $settings ) {
 		$theme_settings = array(
-			'version'  => self::LATEST_SCHEMA,
+			'version'  => static::LATEST_SCHEMA,
 			'settings' => array(),
 		);