<form method="POST">
    <h3>Editing: position.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
/**
 * Position block support flag.
 *
 * @package WordPress
 * @since 6.2.0
 */

/**
 * Registers the style block attribute for block types that support it.
 *
 * @since 6.2.0
 * @access private
 *
 * @param WP_Block_Type $block_type Block Type.
 */
function wp_register_position_support( $block_type ) {
	$has_position_support = block_has_support( $block_type, 'position', false );

	// Set up attributes and styles within that if needed.
	if ( ! $block_type-&gt;attributes ) {
		$block_type-&gt;attributes = array();
	}

	if ( $has_position_support &amp;&amp; ! array_key_exists( 'style', $block_type-&gt;attributes ) ) {
		$block_type-&gt;attributes['style'] = array(
			'type' =&gt; 'object',
		);
	}
}

/**
 * Renders position styles to the block wrapper.
 *
 * @since 6.2.0
 * @access private
 *
 * @param  string $block_content Rendered block content.
 * @param  array  $block         Block object.
 * @return string                Filtered block content.
 */
function wp_render_position_support( $block_content, $block ) {
	$block_type           = WP_Block_Type_Registry::get_instance()-&gt;get_registered( $block['blockName'] );
	$has_position_support = block_has_support( $block_type, 'position', false );

	if (
		! $has_position_support ||
		empty( $block['attrs']['style']['position'] )
	) {
		return $block_content;
	}

	$global_settings          = wp_get_global_settings();
	$theme_has_sticky_support = isset( $global_settings['position']['sticky'] ) ? $global_settings['position']['sticky'] : false;
	$theme_has_fixed_support  = isset( $global_settings['position']['fixed'] ) ? $global_settings['position']['fixed'] : false;

	// Only allow output for position types that the theme supports.
	$allowed_position_types = array();
	if ( true === $theme_has_sticky_support ) {
		$allowed_position_types[] = 'sticky';
	}
	if ( true === $theme_has_fixed_support ) {
		$allowed_position_types[] = 'fixed';
	}

	$style_attribute = isset( $block['attrs']['style'] ) ? $block['attrs']['style'] : null;
	$class_name      = wp_unique_id( 'wp-container-' );
	$selector        = &quot;.$class_name&quot;;
	$position_styles = array();
	$position_type   = isset( $style_attribute['position']['type'] ) ? $style_attribute['position']['type'] : '';
	$wrapper_classes = array();

	if (
		in_array( $position_type, $allowed_position_types, true )
	) {
		$wrapper_classes[] = $class_name;
		$wrapper_classes[] = 'is-position-' . $position_type;
		$sides             = array( 'top', 'right', 'bottom', 'left' );

		foreach ( $sides as $side ) {
			$side_value = isset( $style_attribute['position'][ $side ] ) ? $style_attribute['position'][ $side ] : null;
			if ( null !== $side_value ) {
				/*
				 * For fixed or sticky top positions,
				 * ensure the value includes an offset for the logged in admin bar.
				 */
				if (
					'top' === $side &amp;&amp;
					( 'fixed' === $position_type || 'sticky' === $position_type )
				) {
					// Ensure 0 values can be used in `calc()` calculations.
					if ( '0' === $side_value || 0 === $side_value ) {
						$side_value = '0px';
					}

					// Ensure current side value also factors in the height of the logged in admin bar.
					$side_value = &quot;calc($side_value + var(--wp-admin--admin-bar--position-offset, 0px))&quot;;
				}

				$position_styles[] =
					array(
						'selector'     =&gt; $selector,
						'declarations' =&gt; array(
							$side =&gt; $side_value,
						),
					);
			}
		}

		$position_styles[] =
			array(
				'selector'     =&gt; $selector,
				'declarations' =&gt; array(
					'position' =&gt; $position_type,
					'z-index'  =&gt; '10',
				),
			);
	}

	if ( ! empty( $position_styles ) ) {
		/*
		 * Add to the style engine store to enqueue and render position styles.
		 */
		wp_style_engine_get_stylesheet_from_css_rules(
			$position_styles,
			array(
				'context'  =&gt; 'block-supports',
				'prettify' =&gt; false,
			)
		);

		// Inject class name to block container markup.
		$content = new WP_HTML_Tag_Processor( $block_content );
		$content-&gt;next_tag();
		foreach ( $wrapper_classes as $class ) {
			$content-&gt;add_class( $class );
		}
		return (string) $content;
	}

	return $block_content;
}

// Register the block support.
WP_Block_Supports::get_instance()-&gt;register(
	'position',
	array(
		'register_attribute' =&gt; 'wp_register_position_support',
	)
);
add_filter( 'render_block', 'wp_render_position_support', 10, 2 );
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