Style engine: enqueue block supports styles in Gutenberg

lib/compat/wordpress-6.1/script-loader.php

@@ -36,6 +36,61 @@ 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: packages/style-engine/README.md
+ */
+function gutenberg_enqueue_stored_styles() {
+	$is_block_theme   = wp_is_block_theme();
+	$is_classic_theme = ! $is_block_theme;
+
+	/*
+	 * For block themes, print 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 ) {
+		// Add comment to identify core styles sections in debugging.
+		if ( defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ) {
+			$compiled_core_stylesheet .= "/**\n * Core styles: $style_key\n */\n";
+		}
+		// Chain core store ids to signify what the styles contain.
+		$style_tag_id             .= '-' . $style_key;
+		$compiled_core_stylesheet .= gutenberg_style_engine_get_stylesheet_from_store( $style_key );
+	}
+
+	// Combine 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_Gutenberg::get_stores();
+	foreach ( array_keys( $additional_stores ) as $store_name ) {
+		if ( in_array( $store_name, $core_styles_keys, true ) ) {
+			continue;
+		}
+		$styles = gutenberg_style_engine_get_stylesheet_from_store( $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 );
+		}
+	}
+}
+
 /**
  * This applies a filter to the list of style nodes that comes from `get_style_nodes` in WP_Theme_JSON.
  * This particular filter removes all of the blocks from the array.
@@ -109,5 +164,8 @@ function gutenberg_enqueue_global_styles() {
 remove_action( 'wp_enqueue_scripts', 'gutenberg_enqueue_global_styles_assets' );
 remove_action( 'wp_footer', 'gutenberg_enqueue_global_styles_assets' );
 
+// Enqueue global styles, and then block supports styles.
 add_action( 'wp_enqueue_scripts', 'gutenberg_enqueue_global_styles' );
 add_action( 'wp_footer', 'gutenberg_enqueue_global_styles', 1 );
+add_action( 'wp_enqueue_scripts', 'gutenberg_enqueue_stored_styles' );
+add_action( 'wp_footer', 'gutenberg_enqueue_stored_styles', 1 );

packages/style-engine/README.md

@@ -2,6 +2,158 @@
 
 The Style Engine powering global styles and block customizations.
 
+## Backend API
+
+### wp_style_engine_get_styles()
+
+Global public function to generate styles from a single style object, e.g., the value of
+a [block's attributes.style object](https://developer.wordpress.org/block-editor/reference-guides/theme-json-reference/theme-json-living/#styles)
+or
+the [top level styles in theme.json](https://developer.wordpress.org/block-editor/reference-guides/block-api/block-supports/)
+.
+
+_Parameters_
+
+-   _$block_styles_ `array` A block's `attributes.style` object or the top level styles in theme.json
+-   _$options_ `array<string|boolean>` An array of options to determine the output.
+    -   _context_ `string` An identifier describing the origin of the style object, e.g., 'block-supports' or '
+        global-styles'. Default is 'block-supports'.
+    -   _enqueue_ `boolean` When `true` will attempt to store and enqueue for rendering in a `style` tag on the site frontend.
+    -   _convert_vars_to_classnames_ `boolean` Whether to skip converting CSS var:? values to var( --wp--preset--\* )
+        values. Default is `false`.
+    -   _selector_ `string` When a selector is passed, `generate()` will return a full CSS rule `$selector { ...rules }`,
+        otherwise a concatenated string of properties and values.
+
+_Returns_
+`array<string|array>|null`
+
+```php
+array(
+    'css'           => (string) A CSS ruleset or declarations block formatted to be placed in an HTML `style` attribute or tag.
+    'declarations'  => (array) An array of property/value pairs representing parsed CSS declarations.
+    'classnames'    => (string) Classnames separated by a space.
+);
+```
+
+It will return compiled CSS declarations for inline styles, or, where a selector is provided, a complete CSS rule.
+
+To enqueue a style for rendering in the site's frontend, the `$options` array requires the following:
+
+1.  **selector (string)** - this is the CSS selector for your block style CSS declarations.
+2.  **context (string)** - this tells the style engine where to store the styles. Styles in the same context will be
+    batched together and printed in the same HTML style tag. The default is `'block-supports'`.
+3.  **enqueue (boolean)** - tells the style engine to store the styles.
+
+`wp_style_engine_get_styles` will return the compiled CSS and CSS declarations array.
+
+#### Usage
+
+```php
+$block_styles =  array(
+     'spacing' => array( 'padding' => '100px' )
+);
+$styles = wp_style_engine_get_styles(
+    $block_styles,
+    array(
+        'selector' => '.a-selector',
+        'context'  => 'block-supports',
+        'enqueue'  => true,
+    )
+);
+print_r( $styles );
+
+/*
+array(
+    'css'                 => '.a-selector{padding:10px}'
+    'declarations'  => array( 'padding' => '100px' )
+)
+*/
+```
+
+### wp_style_engine_get_stylesheet_from_css_rules()
+
+Use this function to compile and return a stylesheet for any CSS rules. The style engine will automatically merge declarations and combine selectors.
+
+This function acts as a CSS compiler, but will also enqueue styles for rendering where `enqueue` and `context` strings are passed in the options.
+
+_Parameters_
+
+-   _$css_rules_ `array<array>`
+-   _$options_ `array<string|boolean>` An array of options to determine the output.
+    -   _context_ `string` An identifier describing the origin of the style object, e.g., 'block-supports' or '
+        global-styles'. Default is 'block-supports'.
+    -   _enqueue_ `boolean` When `true` will store using the `context` value as a key.
+
+_Returns_
+`string` A compiled CSS string based on `$css_rules`.
+
+#### Usage
+
+```php
+$styles = array(
+    array(
+        'selector'.       => '.wp-pumpkin',
+        'declarations' => array( 'color' => 'orange' )
+    ),
+    array(
+        'selector'.       => '.wp-tomato',
+        'declarations' => array( 'color' => 'red' )
+    ),
+    array(
+        'selector'.       => '.wp-tomato',
+        'declarations' => array( 'padding' => '100px' )
+    ),
+    array(
+        'selector'.       => '.wp-kumquat',
+        'declarations' => array( 'color' => 'orange' )
+    ),
+);
+
+$stylesheet = wp_style_engine_get_stylesheet_from_css_rules(
+    $styles,
+    array(
+        'context'  => 'block-supports', // Indicates that these styles should be stored with block supports CSS.
+        'enqueue'  => true, // Render the styles for output.
+    )
+);
+print_r( $stylesheet ); // .wp-pumpkin, .wp-kumquat {color:orange}.wp-tomato{color:red;padding:100px}
+```
+
+### wp_style_engine_get_stylesheet_from_store()
+
+Returns compiled CSS from a store, if found.
+
+_Parameters_
+
+-   _$store_key_ `string` An identifier describing the origin of the style object, e.g., 'block-supports' or ' global-styles'. Default is 'block-supports'.
+
+_Returns_
+`string` A compiled CSS string from the stored CSS rules.
+
+#### Usage
+
+```php
+// First register some styles.
+$styles = array(
+    array(
+        'selector'.       => '.wp-apple',
+        'declarations' => array( 'color' => 'green' )
+    ),
+);
+
+$stylesheet = wp_style_engine_get_stylesheet_from_css_rules(
+    $styles,
+    array(
+        'context'  => 'fruit-styles',
+        'enqueue'  => true,
+    )
+);
+
+// Later, fetch compiled rules from store.
+$stylesheet = gutenberg_style_engine_get_stylesheet_from_store( 'fruit-styles' );
+print_r( $stylesheet ); // .wp-apple{color:green;}
+```
+
 ## Installation (JS only)
 
 Install the module
@@ -10,13 +162,18 @@ Install the module
 npm install @wordpress/style-engine --save
 ```
 
-_This package assumes that your code will run in an **ES2015+** environment. If you're using an environment that has limited or no support for such language features and APIs, you should include [the polyfill shipped in `@wordpress/babel-preset-default`](https://github.com/WordPress/gutenberg/tree/HEAD/packages/babel-preset-default#polyfill) in your code._
+_This package assumes that your code will run in an **ES2015+** environment. If you're using an environment that has
+limited or no support for such language features and APIs, you should
+include [the polyfill shipped in `@wordpress/babel-preset-default`](https://github.com/WordPress/gutenberg/tree/HEAD/packages/babel-preset-default#polyfill)
+in your code._
 
 ## Important
 
-This Package is considered experimental at the moment. The idea is to have a package used to generate styles based on a style object that is consistent between: backend, frontend, block style object and theme.json.
+This Package is considered experimental at the moment. The idea is to have a package used to generate styles based on a
+style object that is consistent between: backend, frontend, block style object and theme.json.
 
-Because this package is experimental and still in development it does not yet generate a `wp.styleEngine` global. To get there, the following tasks need to be completed:
+Because this package is experimental and still in development it does not yet generate a `wp.styleEngine` global. To get
+there, the following tasks need to be completed:
 
 **TODO List:**
 
@@ -26,7 +183,8 @@ Because this package is experimental and still in development it does not yet ge
 -   Support generating styles in the backend (block supports and theme.json stylesheet). (Ongoing)
 -   Refactor all block styles to use the style engine server side. (Ongoing)
 -   Consolidate global and block style rendering and enqueuing
--   Refactor all blocks to consistently use the "style" attribute for all customizations (get rid of the preset specific attributes).
+-   Refactor all blocks to consistently use the "style" attribute for all customizations (get rid of the preset specific
+    attributes).
 
 See [Tracking: Add a Style Engine to manage rendering block styles #38167](https://github.com/WordPress/gutenberg/issues/38167)
 

packages/style-engine/class-wp-style-engine-processor.php

@@ -128,7 +128,8 @@ private function combine_rules_selectors() {
 				unset( $this->css_rules[ $key ] );
 			}
 			// Create a new rule with the combined selectors.
-			$this->css_rules[ implode( ',', $duplicates ) ] = new WP_Style_Engine_CSS_Rule( implode( ',', $duplicates ), $declarations );
+			$duplicate_selectors                     = implode( ',', $duplicates );
+			$this->css_rules[ $duplicate_selectors ] = new WP_Style_Engine_CSS_Rule( $duplicate_selectors, $declarations );
 		}
 	}
 }