wp-includes/class-wp-theme-json.php:3006Given a styles array, it extracts the style properties and adds them to the $declarations array following the format:
$stylesarray$settingsarrayoptionalarray()$propertiesarrayoptionalnull$theme_jsonarrayoptionalnull$selectorstringoptionalnull$use_root_paddingbooleanoptionalnullarray protected static function compute_style_properties( $styles, $settings = array(), $properties = null, $theme_json = null, $selector = null, $use_root_padding = null ) { if ( empty( $styles ) ) { return array(); } if ( null === $properties ) { $properties = static::PROPERTIES_METADATA; } $declarations = array(); $root_variable_duplicates = array(); $root_style_length = strlen( '--wp--style--root--' ); foreach ( $properties as $css_property => $value_path ) { if ( ! is_array( $value_path ) ) { continue; } $is_root_style = str_starts_with( $css_property, '--wp--style--root--' ); if ( $is_root_style && ( static::ROOT_BLOCK_SELECTOR !== $selector || ! $use_root_padding ) ) { continue; } $value = static::get_property_value( $styles, $value_path, $theme_json ); /* * Root-level padding styles don't currently support strings with CSS shorthand values. * This may change: https://github.com/WordPress/gutenberg/issues/40132. */ if ( '--wp--style--root--padding' === $css_property && is_string( $value ) ) { continue; } if ( $is_root_style && $use_root_padding ) { $root_variable_duplicates[] = substr( $css_property, $root_style_length ); } /* * Processes background image styles. * If the value is a URL, it will be converted to a CSS `url()` value. * For uploaded image (images with a database ID), apply size and position defaults, * equal to those applied in block supports in lib/background.php. */ if ( 'background-image' === $css_property ) { $background_image_input = array(); if ( ! empty( $value ) ) { $background_image_input['backgroundImage'] = $value; } $gradient_value = $styles['background']['gradient'] ?? null; if ( ! empty( $gradient_value ) ) { $background_image_input['gradient'] = $gradient_value; } if ( ! empty( $background_image_input ) ) { $background_styles = wp_style_engine_get_styles( array( 'background' => $background_image_input ) ); $value = $background_styles['declarations'][ $css_property ] ?? null; } } if ( empty( $value ) && static::ROOT_BLOCK_SELECTOR !== $selector && ! empty( $styles['background']['backgroundImage']['id'] ) ) { if ( 'background-size' === $css_property ) { $value = 'cover'; } // If the background size is set to `contain` and no position is set, set the position to `center`. if ( 'background-position' === $css_property ) { $background_size = $styles['background']['backgroundSize'] ?? null; $value = 'contain' === $background_size ? '50% 50%' : null; } } // Skip if empty and not "0" or value represents array of longhand values. $has_missing_value = empty( $value ) && ! is_numeric( $value ); if ( $has_missing_value || is_array( $value ) ) { continue; } // Calculates fluid typography rules where available. if ( 'font-size' === $css_property ) { /* * wp_get_typography_font_size_value() will check * if fluid typography has been activated and alsoIntroduced in 5.8.0. Unchanged from 6.7.7 through 7.1.0.
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src/wp-includes/class-wp-theme-json.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.