diff -r be944660c56a -r 3d72ae0968f4 wp/wp-includes/block-supports/dimensions.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/block-supports/dimensions.php	Tue Sep 27 16:37:53 2022 +0200
@@ -0,0 +1,73 @@
+<?php
+/**
+ * Dimensions block support flag.
+ *
+ * This does not include the `spacing` block support even though that visually
+ * appears under the "Dimensions" panel in the editor. It remains in its
+ * original `spacing.php` file for compatibility with core.
+ *
+ * @package WordPress
+ * @since 5.9.0
+ */
+
+/**
+ * Registers the style block attribute for block types that support it.
+ *
+ * @since 5.9.0
+ * @access private
+ *
+ * @param WP_Block_Type $block_type Block Type.
+ */
+function wp_register_dimensions_support( $block_type ) {
+	// Setup attributes and styles within that if needed.
+	if ( ! $block_type->attributes ) {
+		$block_type->attributes = array();
+	}
+
+	// Check for existing style attribute definition e.g. from block.json.
+	if ( array_key_exists( 'style', $block_type->attributes ) ) {
+		return;
+	}
+
+	$has_dimensions_support = block_has_support( $block_type, array( '__experimentalDimensions' ), false );
+	// Future block supports such as height & width will be added here.
+
+	if ( $has_dimensions_support ) {
+		$block_type->attributes['style'] = array(
+			'type' => 'object',
+		);
+	}
+}
+
+/**
+ * Adds CSS classes for block dimensions to the incoming attributes array.
+ * This will be applied to the block markup in the front-end.
+ *
+ * @since 5.9.0
+ * @access private
+ *
+ * @param WP_Block_Type $block_type       Block Type.
+ * @param array         $block_attributes Block attributes.
+ * @return array Block dimensions CSS classes and inline styles.
+ */
+function wp_apply_dimensions_support( $block_type, $block_attributes ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+	if ( wp_should_skip_block_supports_serialization( $block_type, '__experimentalDimensions' ) ) {
+		return array();
+	}
+
+	$styles = array();
+
+	// Height support to be added in near future.
+	// Width support to be added in near future.
+
+	return empty( $styles ) ? array() : array( 'style' => implode( ' ', $styles ) );
+}
+
+// Register the block support.
+WP_Block_Supports::get_instance()->register(
+	'dimensions',
+	array(
+		'register_attribute' => 'wp_register_dimensions_support',
+		'apply'              => 'wp_apply_dimensions_support',
+	)
+);