Initial commit.

Backporting block supports filter callback and registrations

src/wp-includes/default-filters.php

@@ -575,6 +575,10 @@
 add_action( 'wp_enqueue_scripts', 'wp_enqueue_global_styles' );
 add_action( 'wp_footer', 'wp_enqueue_global_styles', 1 );
 
+// Block supports, and other styles parsed and stored in the Style Engine.
+add_action( 'wp_enqueue_scripts', 'wp_enqueue_stored_styles' );
+add_action( 'wp_footer', 'wp_enqueue_stored_styles', 1 );
+
 // SVG filters like duotone have to be loaded at the beginning of the body in both admin and the front-end.
 add_action( 'wp_body_open', 'wp_global_styles_render_svg_filters' );
 add_action( 'in_admin_header', 'wp_global_styles_render_svg_filters' );

src/wp-includes/script-loader.php

@@ -2959,6 +2959,64 @@ static function () use ( $style ) {
 	);
 }
 
+/**
+ * Fetches, processes and compiles stored core styles, then combines and renders them to the page.
+ * Styles are stored via the Style Engine API.
+ * See: https://developer.wordpress.org/block-editor/reference-guides/packages/packages-style-engine/
+ *
+ * @since 6.1.0
+ */
+function wp_enqueue_stored_styles() {
+	$is_block_theme   = wp_is_block_theme();
+	$is_classic_theme = ! $is_block_theme;
+
+	/*
+	 * For block themes, this function prints stored styles in the header.
+	 * For classic themes, in the footer.
+	 */
+	if (
+		( $is_block_theme && doing_action( 'wp_footer' ) ) ||
+		( $is_classic_theme && doing_action( 'wp_enqueue_scripts' ) )
+	) {
+		return;
+	}
+
+	$core_styles_keys         = array( 'block-supports' );
+	$compiled_core_stylesheet = '';
+	$style_tag_id             = 'core';
+	foreach ( $core_styles_keys as $style_key ) {
+		// Adds comment to identify core styles sections in debugging.
+		if ( defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ) {
+			$compiled_core_stylesheet .= "/**\n * Core styles: $style_key\n */\n";
+		}
+		// Chains core store ids to signify what the styles contain.
+		$style_tag_id             .= '-' . $style_key;
+		$compiled_core_stylesheet .= wp_style_engine_get_stylesheet_from_context( $style_key );
+	}
+
+	// Combines Core styles.
+	if ( ! empty( $compiled_core_stylesheet ) ) {
+		wp_register_style( $style_tag_id, false, array(), true, true );
+		wp_add_inline_style( $style_tag_id, $compiled_core_stylesheet );
+		wp_enqueue_style( $style_tag_id );
+	}
+
+	// If there are any other stores registered by themes etc, print them out.
+	$additional_stores = WP_Style_Engine_CSS_Rules_Store::get_stores();
+	foreach ( array_keys( $additional_stores ) as $store_name ) {
+		if ( in_array( $store_name, $core_styles_keys, true ) ) {
+			continue;
+		}
+		$styles = wp_style_engine_get_stylesheet_from_context( $store_name );
+		if ( ! empty( $styles ) ) {
+			$key = "wp-style-engine-$store_name";
+			wp_register_style( $key, false, array(), true, true );
+			wp_add_inline_style( $key, $styles );
+			wp_enqueue_style( $key );
+		}
+	}
+}
+
 /**
  * Enqueues a stylesheet for a specific block.
  *

tests/phpunit/tests/script-loader.php

@@ -0,0 +1,8 @@
+<?php
+
+/**
+ * Test functions and classes for widgets and sidebars.
+ *
+ * @group script-loader
+ */
+class Tests_Script_Loader extends WP_UnitTestCase {}