Add block support to apply block style variation element and inner bl…

…ock styles

lib/block-supports/variations.php

@@ -0,0 +1,118 @@
+<?php
+/**
+ * Block support to enable per-section styling of block types via
+ * block style variations.
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Get the class name for this application of this blocks variation styles.
+ *
+ * @param array  $block     Block object.
+ * @param string $variation Slug for the variation..
+ *
+ * @return string The unique class name.
+ */
+function gutenberg_get_variation_class_name( $block, $variation ) {
+	return 'is-style-' . $variation . '-' . md5( serialize( $block ) );
+}
+
+/**
+ * Update the block content with the variation's class name.
+ *
+ * @param string $block_content Rendered block content.
+ * @param array  $block         Block object.
+ *
+ * @return string Filtered block content.
+ */
+function gutenberg_render_variation_support( $block_content, $block ) {
+	if ( ! $block_content || empty( $block['attrs'] ) ) {
+		return $block_content;
+	}
+
+	// Apply the variation's classname. Like the layout hook, this assumes the
+	// hook only applies to blocks with a single wrapper.
+	$tags = new WP_HTML_Tag_Processor( $block_content );
+
+	if ( $tags->next_tag() ) {
+		preg_match( '/\bis-style-(\S+)\b/', $tags->get_attribute( 'class' ), $matches );
+		$variation = $matches[1] ?? null;
+
+		if ( $variation ) {
+			$tree       = WP_Theme_JSON_Resolver_Gutenberg::get_merged_data();
+			$theme_json = $tree->get_raw_data();
+
+			if ( ! empty( $theme_json['styles']['blocks'][ $block['blockName'] ]['variations'][ $variation ] ) ) {
+				$tags->add_class( gutenberg_get_variation_class_name( $block, $variation ) );
+			}
+		}
+	}
+
+	return $tags->get_updated_html();
+}
+
+/**
+ * Render the block style variation's styles.
+ *
+ * In the case of nested blocks with variations applies, we want the parent
+ * variation's styles to be rendered before their descendants. This solves the
+ * issue of a block type being styled in both the parent and descendant: we want
+ * the descendant style to take priority, and this is done by loading it after,
+ * in the DOM order. This is why the variation stylesheet generation is in a
+ * different filter.
+ *
+ * @param string|null $pre_render The pre-rendered content. Default null.
+ * @param array       $block      The block being rendered.
+ *
+ * @return null
+ */
+function gutenberg_render_variation_support_styles( $pre_render, $block ) {
+	$variation = $block['attrs']['style']['variation'] ?? null;
+
+	if ( ! $variation ) {
+		return null;
+	}
+
+	$tree           = WP_Theme_JSON_Resolver_Gutenberg::get_merged_data();
+	$theme_json     = $tree->get_raw_data();
+	$variation_data = $theme_json['styles']['blocks'][ $block['blockName'] ]['variations'][ $variation ] ?? array();
+
+	if ( empty( $variation_data['elements'] ) && empty( $variation_data['blocks'] ) ) {
+		return null;
+	}
+
+	$config = array(
+		'version' => 2,
+		'styles'  => $variation_data,
+	);
+
+	$class_name = gutenberg_get_variation_class_name( $block, $variation );
+	$class_name = ".$class_name";
+
+	$variation_theme_json = new WP_Theme_JSON_Gutenberg( $config, 'blocks' );
+	$variation_styles     = $variation_theme_json->get_stylesheet(
+		array( 'styles' ),
+		array( 'custom' ),
+		array(
+			'root_selector'           => $class_name,
+			'skip_root_layout_styles' => true,
+			'scope'                   => $class_name,
+		)
+	);
+
+	if ( empty( $variation_styles ) ) {
+		return null;
+	}
+
+	wp_register_style( 'variation-styles', false );
+	wp_add_inline_style( 'variation-styles', $variation_styles );
+	wp_enqueue_style( 'variation-styles' );
+}
+
+
+// Register the block support.
+WP_Block_Supports::get_instance()->register( 'variation', array() );
+
+add_filter( 'pre_render_block', 'gutenberg_render_variation_support_styles', 10, 2 );
+add_filter( 'render_block', 'gutenberg_render_variation_support', 10, 2 );

lib/class-wp-theme-json-gutenberg.php

@@ -1267,7 +1267,7 @@ public function get_stylesheet( $types = array( 'variables', 'styles', 'presets'
 		}
 
 		if ( in_array( 'styles', $types, true ) ) {
-			if ( false !== $root_style_key ) {
+			if ( false !== $root_style_key && empty( $options['skip_root_layout_styles'] ) ) {
 				$stylesheet .= $this->get_root_layout_rules( $style_nodes[ $root_style_key ]['selector'], $style_nodes[ $root_style_key ] );
 			}
 			$stylesheet .= $this->get_block_classes( $style_nodes );

lib/load.php

@@ -216,6 +216,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 require __DIR__ . '/block-supports/duotone.php';
 require __DIR__ . '/block-supports/shadow.php';
 require __DIR__ . '/block-supports/background.php';
+require __DIR__ . '/block-supports/variations.php';
 
 // Data views.
 require_once __DIR__ . '/experimental/data-views.php';