wp_get_global_styles: allow transforming the CSS Custom Properties into the values they represent.

Props samnajian, ramonopoly, isabel_brison.
Fixes #58588.

Built from https://develop.svn.wordpress.org/trunk@55986


git-svn-id: http://core.svn.wordpress.org/trunk@55498 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-theme-json.php

@@ -3529,4 +3529,77 @@ class WP_Theme_JSON {
 		return $tree;
 	}
 
+	/**
+	 * Replaces CSS variables with their values in place.
+	 *
+	 * @since 6.3.0
+	 * @param array $styles CSS declarations to convert.
+	 * @param array $values key => value pairs to use for replacement.
+	 * @return array
+	 */
+	private static function convert_variables_to_value( $styles, $values ) {
+		foreach ( $styles as $key => $style ) {
+			if ( is_array( $style ) ) {
+				$styles[ $key ] = self::convert_variables_to_value( $style, $values );
+				continue;
+			}
+
+			if ( 0 <= strpos( $style, 'var(' ) ) {
+				// find all the variables in the string in the form of var(--variable-name, fallback), with fallback in the second capture group.
+
+				$has_matches = preg_match_all( '/var\(([^),]+)?,?\s?(\S+)?\)/', $style, $var_parts );
+
+				if ( $has_matches ) {
+					$resolved_style = $styles[ $key ];
+					foreach ( $var_parts[1] as $index => $var_part ) {
+						$key_in_values   = 'var(' . $var_part . ')';
+						$rule_to_replace = $var_parts[0][ $index ]; // the css rule to replace e.g. var(--wp--preset--color--vivid-green-cyan).
+						$fallback        = $var_parts[2][ $index ]; // the fallback value.
+						$resolved_style  = str_replace(
+							array(
+								$rule_to_replace,
+								$fallback,
+							),
+							array(
+								isset( $values[ $key_in_values ] ) ? $values[ $key_in_values ] : $rule_to_replace,
+								isset( $values[ $fallback ] ) ? $values[ $fallback ] : $fallback,
+							),
+							$resolved_style
+						);
+					}
+					$styles[ $key ] = $resolved_style;
+				}
+			}
+		}
+
+		return $styles;
+	}
+
+	/**
+	 * Resolves the values of CSS variables in the given styles.
+	 *
+	 * @since 6.3.0
+	 * @param WP_Theme_JSON $theme_json The theme json resolver.
+	 *
+	 * @return WP_Theme_JSON The $theme_json with resolved variables.
+	 */
+	public static function resolve_variables( $theme_json ) {
+		$settings    = $theme_json->get_settings();
+		$styles      = $theme_json->get_raw_data()['styles'];
+		$preset_vars = static::compute_preset_vars( $settings, static::VALID_ORIGINS );
+		$theme_vars  = static::compute_theme_vars( $settings );
+		$vars        = array_reduce(
+			array_merge( $preset_vars, $theme_vars ),
+			function( $carry, $item ) {
+				$name                    = $item['name'];
+				$carry[ "var({$name})" ] = $item['value'];
+				return $carry;
+			},
+			array()
+		);
+
+		$theme_json->theme_json['styles'] = self::convert_variables_to_value( $styles, $vars );
+		return $theme_json;
+	}
+
 }