Add initial version of the style engine

docs/manifest.json

@@ -1745,6 +1745,12 @@
 		"markdown_source": "../packages/shortcode/README.md",
 		"parent": "packages"
 	},
+	{
+		"title": "@wordpress/style-engine",
+		"slug": "packages-style-engine",
+		"markdown_source": "../packages/style-engine/README.md",
+		"parent": "packages"
+	},
 	{
 		"title": "@wordpress/stylelint-config",
 		"slug": "packages-stylelint-config",

package.json

@@ -76,6 +76,7 @@
 		"@wordpress/rich-text": "file:packages/rich-text",
 		"@wordpress/server-side-render": "file:packages/server-side-render",
 		"@wordpress/shortcode": "file:packages/shortcode",
+		"@wordpress/style-engine": "file:packages/style-engine",
 		"@wordpress/token-list": "file:packages/token-list",
 		"@wordpress/url": "file:packages/url",
 		"@wordpress/viewport": "file:packages/viewport",

packages/block-editor/package.json

@@ -53,6 +53,7 @@
 		"@wordpress/notices": "file:../notices",
 		"@wordpress/rich-text": "file:../rich-text",
 		"@wordpress/shortcode": "file:../shortcode",
+		"@wordpress/style-engine": "file:../style-engine",
 		"@wordpress/token-list": "file:../token-list",
 		"@wordpress/url": "file:../url",
 		"@wordpress/warning": "file:../warning",

packages/block-editor/src/hooks/style.js

@@ -27,6 +27,7 @@ import {
 	__EXPERIMENTAL_ELEMENTS as ELEMENTS,
 } from '@wordpress/blocks';
 import { createHigherOrderComponent, useInstanceId } from '@wordpress/compose';
+import { getCSSRules } from '@wordpress/style-engine';
 
 /**
  * Internal dependencies
@@ -85,21 +86,35 @@ export function getInlineStyles( styles = {} ) {
 			// option and backwards compatibility for border radius support.
 			const styleValue = get( styles, path );
 
-			if ( !! subPaths && ! isString( styleValue ) ) {
-				Object.entries( subPaths ).forEach( ( entry ) => {
-					const [ name, subPath ] = entry;
-					const value = get( styleValue, [ subPath ] );
-
-					if ( value ) {
-						output[ name ] = compileStyleValue( value );
-					}
-				} );
-			} else if ( ! ignoredStyles.includes( path.join( '.' ) ) ) {
-				output[ propKey ] = compileStyleValue( get( styles, path ) );
+			if ( ! STYLE_PROPERTY[ propKey ].useEngine ) {
+				if ( !! subPaths && ! isString( styleValue ) ) {
+					Object.entries( subPaths ).forEach( ( entry ) => {
+						const [ name, subPath ] = entry;
+						const value = get( styleValue, [ subPath ] );
+
+						if ( value ) {
+							output[ name ] = compileStyleValue( value );
+						}
+					} );
+				} else if ( ! ignoredStyles.includes( path.join( '.' ) ) ) {
+					output[ propKey ] = compileStyleValue(
+						get( styles, path )
+					);
+				}
 			}
 		}
 	} );
 
+	// The goal is to move everything to server side generated engine styles
+	// This is temporary as we absorb more and more styles into the engine.
+	const extraRules = getCSSRules( styles, { selector: 'self' } );
+	extraRules.forEach( ( rule ) => {
+		if ( rule.selector !== 'self' ) {
+			throw "This style can't be added as inline style";
+		}
+		output[ rule.key ] = rule.value;
+	} );
+
 	return output;
 }
 

packages/blocks/src/api/constants.js

@@ -99,6 +99,7 @@ export const __EXPERIMENTAL_STYLE_PROPERTY = {
 			paddingBottom: 'bottom',
 			paddingLeft: 'left',
 		},
+		useEngine: true,
 	},
 	textDecoration: {
 		value: [ 'typography', 'textDecoration' ],

packages/dependency-extraction-webpack-plugin/lib/util.js

@@ -1,5 +1,9 @@
 const WORDPRESS_NAMESPACE = '@wordpress/';
-const BUNDLED_PACKAGES = [ '@wordpress/icons', '@wordpress/interface' ];
+const BUNDLED_PACKAGES = [
+	'@wordpress/icons',
+	'@wordpress/interface',
+	'@wordpress/style-engine',
+];
 
 /**
  * Default request to global transformation

packages/edit-site/package.json

@@ -50,6 +50,7 @@
 		"@wordpress/notices": "file:../notices",
 		"@wordpress/plugins": "file:../plugins",
 		"@wordpress/reusable-blocks": "file:../reusable-blocks",
+		"@wordpress/style-engine": "file:../style-engine",
 		"@wordpress/url": "file:../url",
 		"@wordpress/viewport": "file:../viewport",
 		"classnames": "^2.3.1",

packages/edit-site/src/components/global-styles/use-global-styles-output.js

@@ -23,6 +23,7 @@ import {
 	getBlockTypes,
 } from '@wordpress/blocks';
 import { useEffect, useState, useContext } from '@wordpress/element';
+import { getCSSRules } from '@wordpress/style-engine';
 
 /**
  * Internal dependencies
@@ -146,11 +147,11 @@ function flattenTree( input = {}, prefix, token ) {
  * @return {Array} An array of style declarations.
  */
 function getStylesDeclarations( blockStyles = {} ) {
-	return reduce(
+	const output = reduce(
 		STYLE_PROPERTY,
-		( declarations, { value, properties }, key ) => {
+		( declarations, { value, properties, useEngine }, key ) => {
 			const pathToValue = value;
-			if ( first( pathToValue ) === 'elements' ) {
+			if ( first( pathToValue ) === 'elements' || useEngine ) {
 				return declarations;
 			}
 
@@ -188,6 +189,21 @@ function getStylesDeclarations( blockStyles = {} ) {
 		},
 		[]
 	);
+
+	// The goal is to move everything to server side generated engine styles
+	// This is temporary as we absorb more and more styles into the engine.
+	const extraRules = getCSSRules( blockStyles, { selector: 'self' } );
+	extraRules.forEach( ( rule ) => {
+		if ( rule.selector !== 'self' ) {
+			throw "This style can't be added as inline style";
+		}
+		const cssProperty = rule.key.startsWith( '--' )
+			? rule.key
+			: kebabCase( rule.key );
+		output.push( `${ cssProperty }: ${ compileStyleValue( rule.value ) }` );
+	} );
+
+	return output;
 }
 
 export const getNodesWithStyles = ( tree, blockSelectors ) => {

packages/style-engine/.npmrc

@@ -0,0 +1 @@
+package-lock=false

packages/style-engine/CHANGELOG.md

@@ -0,0 +1,7 @@
+<!-- Learn how to maintain this file at https://github.com/WordPress/gutenberg/tree/HEAD/packages#maintaining-changelogs. -->
+
+## Unreleased
+
+### New Feature
+
+-   Added initial version of the style engine ([#37978](https://github.com/WordPress/gutenberg/pull/37978)).

packages/style-engine/README.md

@@ -0,0 +1,62 @@
+# Style Engine
+
+The Style Engine powering global styles and block customizations.
+
+## Installation
+
+Install the module
+
+```bash
+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._
+
+## 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.
+
+Currently it's not a package that generates a wp.styleEngine global because it's not ready yet, it's still a bundled package but ultimately, we want it to be so, once the roadmap is finished:
+
+**TODO List:**
+
+-   Add style definitions for all the currently supported styles in blocks and theme.json.
+-   the CSS variable shortcuts for values (for presets...)
+-   Support generating styles in the frontend.
+-   Support generating styles in the backend (block supports and theme.json stylesheet).
+-   Refactor all block styles to use the style engine server side.
+-   Refactor all blocks to consistently use the "style" attribute for all customizations (get rid of the preset specific attributes).
+
+## Usage
+
+<!-- START TOKEN(Autogenerated API docs) -->
+
+### generate
+
+Generates a stylesheet for a given style object and selector.
+
+_Parameters_
+
+-   _style_ `Style`: Style object.
+-   _options_ `StyleOptions`: Options object with settings to adjust how the styles are generated.
+
+_Returns_
+
+-   `string`: generated stylesheet.
+
+### getCSSRules
+
+Returns a JSON representation of the generated CSS rules.
+
+_Parameters_
+
+-   _style_ `Style`: Style object.
+-   _options_ `StyleOptions`: Options object with settings to adjust how the styles are generated.
+
+_Returns_
+
+-   `GeneratedCSSRule[]`: generated styles.
+
+<!-- END TOKEN(Autogenerated API docs) -->
+
+<br/><br/><p align="center"><img src="https://s.w.org/style/images/codeispoetry.png?1" alt="Code is Poetry." /></p>

packages/style-engine/package.json

@@ -0,0 +1,37 @@
+{
+	"name": "@wordpress/style-engine",
+	"version": "0.1.0",
+	"description": "WordPress Style engine.",
+	"author": "The WordPress Contributors",
+	"license": "GPL-2.0-or-later",
+	"keywords": [
+		"wordpress",
+		"gutenberg",
+		"styles",
+		"global styles"
+	],
+	"homepage": "https://github.com/WordPress/gutenberg/tree/HEAD/packages/style-engine/README.md",
+	"repository": {
+		"type": "git",
+		"url": "https://github.com/WordPress/gutenberg.git",
+		"directory": "packages/style-engine"
+	},
+	"bugs": {
+		"url": "https://github.com/WordPress/gutenberg/issues"
+	},
+	"engines": {
+		"node": ">=12"
+	},
+	"main": "build/index.js",
+	"module": "build-module/index.js",
+	"react-native": "src/index",
+	"types": "build-types",
+	"sideEffects": false,
+	"dependencies": {
+		"@babel/runtime": "^7.16.0",
+		"lodash": "^4.17.21"
+	},
+	"publishConfig": {
+		"access": "public"
+	}
+}

packages/style-engine/src/index.ts

@@ -0,0 +1,64 @@
+/**
+ * External dependencies
+ */
+import { groupBy, kebabCase } from 'lodash';
+
+/**
+ * Internal dependencies
+ */
+import type {
+	Style,
+	StyleOptions,
+	GeneratedCSSRule,
+	StyleDefinition,
+} from './types';
+import { styleDefinitions } from './styles';
+
+/**
+ * Generates a stylesheet for a given style object and selector.
+ *
+ * @param  style   Style object.
+ * @param  options Options object with settings to adjust how the styles are generated.
+ *
+ * @return generated stylesheet.
+ */
+export function generate( style: Style, options: StyleOptions ): string {
+	const rules = getCSSRules( style, options );
+	const groupedRules = groupBy( rules, 'selector' );
+	const selectorRules = Object.keys( groupedRules ).reduce(
+		( acc: string[], subSelector: string ) => {
+			acc.push(
+				`${ subSelector } { ${ groupedRules[ subSelector ]
+					.map(
+						( rule: GeneratedCSSRule ) =>
+							`${ kebabCase( rule.key ) }: ${ rule.value };`
+					)
+					.join( ' ' ) } }`
+			);
+			return acc;
+		},
+		[]
+	);
+
+	return selectorRules.join( '\n' );
+}
+
+/**
+ * Returns a JSON representation of the generated CSS rules.
+ *
+ * @param  style   Style object.
+ * @param  options Options object with settings to adjust how the styles are generated.
+ *
+ * @return generated styles.
+ */
+export function getCSSRules(
+	style: Style,
+	options: StyleOptions
+): GeneratedCSSRule[] {
+	const rules: GeneratedCSSRule[] = [];
+	styleDefinitions.forEach( ( definition: StyleDefinition ) => {
+		rules.push( ...definition.generate( style, options ) );
+	} );
+
+	return rules;
+}

packages/style-engine/src/styles/index.ts

@@ -0,0 +1,6 @@
+/**
+ * Internal dependencies
+ */
+import padding from './padding';
+
+export const styleDefinitions = [ padding ];

packages/style-engine/src/styles/padding.ts

@@ -0,0 +1,19 @@
+/**
+ * Internal dependencies
+ */
+import type { Style, StyleOptions } from '../types';
+import { generateBoxRules } from './utils';
+
+const padding = {
+	name: 'padding',
+	generate: ( style: Style, options: StyleOptions ) => {
+		return generateBoxRules(
+			style,
+			options,
+			[ 'spacing', 'padding' ],
+			'padding'
+		);
+	},
+};
+
+export default padding;