WP_Theme_JSON::get_block_classes() WordPress Method

	protected function get_block_classes( $style_nodes ) {
		$block_rules = '';

		foreach ( $style_nodes as $metadata ) {
			if ( null === $metadata['selector'] ) {
				continue;
			}

			$node         = _wp_array_get( $this->theme_json, $metadata['path'], array() );
			$selector     = $metadata['selector'];
			$settings     = _wp_array_get( $this->theme_json, array( '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.
			$declarations_duotone = array();
			foreach ( $declarations as $index => $declaration ) {
				if ( 'filter' === $declaration['name'] ) {
					unset( $declarations[ $index ] );
					$declarations_duotone[] = $declaration;
				}
			}

			/*
			 * Reset default browser margin on the root body element.
			 * This is set on the root selector **before** generating the ruleset
			 * from the `theme.json`. This is to ensure that if the `theme.json` declares
			 * `margin` in its `spacing` declaration for the `body` element then these
			 * user-generated values take precedence in the CSS cascade.
			 * @link https://github.com/WordPress/gutenberg/issues/36147.
			 */
			if ( static::ROOT_BLOCK_SELECTOR === $selector ) {
				$block_rules .= 'body { margin: 0; }';
			}

			// 2. Generate the rules that use the general selector.
			$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 = static::scope_selector( $metadata['selector'], $metadata['duotone'] );
				$block_rules     .= static::to_ruleset( $selector_duotone, $declarations_duotone );
			}

			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; }';

				$has_block_gap_support = _wp_array_get( $this->theme_json, array( 'settings', 'spacing', 'blockGap' ) ) !== null;
				if ( $has_block_gap_support ) {
					$block_rules .= '.wp-site-blocks > * { margin-block-start: 0; margin-block-end: 0; }';
					$block_rules .= '.wp-site-blocks > * + * { margin-block-start: var( --wp--style--block-gap ); }';
				}
			}
		}

		return $block_rules;
	}