custom-properties: extend ThemeProvider to insert CSS Custom Props

packages/custom-properties/README.md

@@ -1,40 +1,126 @@
 # @theme-ui/custom-properties
 
-Generate CSS custom properties for use with Theme UI.
+Extend [ThemeUI](https://theme-ui.com)'s core functionality with CSS Custom Properties.
 
-https://theme-ui.com
 
 ## Installation
 
 ```
 yarn add @theme-ui/custom-properties
 ```
 
+## API
 
-## Usage
+### toCustomProperties
 
-Transform your Theme UI compliant theme config with the library:
+Transform your Theme UI compliant theme to an object of CSS Custom Properties. 
 
-```js
-const toCustomProperties = require('@theme-ui/custom-properties')
-const theme = require('../theme');
+**Type**: `Function`
 
-module.exports = () => {
-  const customProperties = toCustomProperties(theme, '🍭');
+**Parameters**:
+1. theme - The theme ui specification object
+2. prefix - An optional string prefix for the css custom property (_optional_)
 
-  return customProperties;
+**Returns**: `Object`
+```js
+// Example response
+{
+  '--color-primary': '#2980b9',
+  '--color-secondary': '#f7df1e',
+  '--fontSize-0': 12,
+  ' -fontSize-1': 14,
+  '--fontSize-2': 16,
+  '--fontSize-3': 24,
+  '--fontSize-4': 32,
+  '--fontSize-5': 48,
+  '--fontSize-6': 64
 }
 ```
 
+**Example**:
+```js
+import toCustomProperties from '@theme-ui/custom-properties';
+import theme from '../theme';
 
-## Parameters
+const customProperties = toCustomProperties(theme, '🍭');
+console.log(customProperties);
+```
 
-The @theme-ui/custom-properties function takes two parameters:
+### withCustomProperties
+Extend the base `ThemeProvider` to allow native styling by using CSS Custom Properties.
 
-```js
-toCustomProperties( $theme, $prefix );
+**Type**: `Function`
+
+**Parameters**:
+1. prefix - An optional string prefix for the css custom property (_optional_)
+2. className - An optional class name to add onto the wrapper. All CSS Custom Properties will be defined on this element.
+
+**Returns** a React Component which extends the default `ThemeProvider` by adding CSS Custom Properties to the wrapper element.
+
+For example: 
+
+```jsx
+const ExtendedThemeProvider = withCustomProperties('app-name', 'extended-theme-provider');
+
+ReactDOM.render(
+    <ExtendedThemeProvider theme={theme}>
+      <p> Hello world! </p>
+    </ExtendedThemeProvider>,
+    root
+  );
 ```
 
-1. theme - The theme ui specification object
-1. prefix - An optional prefix for the css custom property _optional_
+will render:
+
+```jsx
+  <div class="extended-theme-provider">
+    <p> Hello world! </p>
+  </div>
+```
+
+Then in CSS we can do something like:
+
+```css
+p {
+  color: var(--app-name-color-primary);
+  background: var(--app-name-color-secondary);
+}
+```
 
+These CSS Custom Properties are in total sync with the theme. Also, sub-theming works as expected.
+
+```jsx
+const theme = {
+  colors: {
+    primary: 'red',
+    secondary: 'blue'
+  }
+};
+
+const subTheme = {
+  colors: {
+    primary: 'orange'
+  }
+};
+
+const ExtendedThemeProvider = withCustomProperties('app-name');
+
+ReactDOM.render(
+  <ExtendedThemeProvider theme={theme}>
+    <p> Hello world! </p> // red on a blue background 
+
+    <ExtendedThemeProvider theme={subTheme}>
+      <p> Hello Aliens! </p> // orange on a blue background
+    </ExtendedThemeProvider>
+
+  </ExtendedThemeProvider>,
+  root
+);
+```
+
+```css
+p {
+  color: var(--app-name-color-primary);
+  background: var(--app-name-color-secondary);
+}
+```

packages/custom-properties/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@theme-ui/custom-properties",
   "description": "Generate CSS custom properties for use with Theme UI",
-  "version": "0.4.0-alpha.3",
+  "version": "0.5.0-alpha.1",
   "source": "src/index.ts",
   "main": "dist/index.js",
   "module": "dist/index.esm.js",
@@ -16,7 +16,11 @@
     "access": "public"
   },
   "dependencies": {
-    "pluralize": "^8.0.0"
+    "pluralize": "^8.0.0",
+    "@theme-ui/core": "^0.4.0-alpha.3"
+  },
+  "peerDependencies": {
+    "react": "^16.11.0"
   },
   "devDependencies": {
     "@theme-ui/css": "^0.4.0-alpha.3",

packages/custom-properties/src/index.ts

@@ -1,11 +1,13 @@
+import React, { useEffect, useRef } from 'react'
 import pluralize from 'pluralize'
 import { Theme } from '@theme-ui/css'
+import { ThemeProviderProps, useThemeUI, ThemeProvider } from '@theme-ui/core'
 
 interface CustomProperties {
   [key: string]: string | number
 }
 
-export default (theme: Theme, prefix?: string) => {
+export default function toCustomProperties(theme: Theme, prefix?: string) {
   const customProperties: CustomProperties = {}
 
   const generateProperties = (object: object, previousKey?: string) => {
@@ -36,3 +38,37 @@ export default (theme: Theme, prefix?: string) => {
 
   return customProperties
 }
+
+export function withCustomProperties(
+  prefix?: string,
+  className: string = 'theme-ui-provider'
+) {
+  return function customThemeProvider(props: ThemeProviderProps) {
+    const ref = useRef<HTMLDivElement>(null)
+    const outerTheme = useThemeUI().theme
+
+    useEffect(() => {
+      if (!ref.current) {
+        return
+      }
+
+      const theme = typeof props.theme === 'function'
+          ? props.theme(outerTheme)
+          : props.theme
+      const cssProperties = toCustomProperties(theme, prefix)
+
+      Object.entries(cssProperties).forEach(([key, value]) => {
+        ref.current!.style.setProperty(key, value.toString())
+      })
+    })
+
+    return React.createElement(
+      'div',
+      {
+        ref,
+        className,
+      },
+      React.createElement(ThemeProvider, props)
+    )
+  }
+}

packages/custom-properties/test/__snapshots__/test.js.snap

@@ -1,5 +1,25 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`adds a specific className on the wrapping element of ThemeProvider 1`] = `
+<div
+  className="🍧"
+>
+  <p>
+     Hello world! 
+  </p>
+</div>
+`;
+
+exports[`adds the default className on the wrapping element of ThemeProvider 1`] = `
+<div
+  className="theme-ui-provider"
+>
+  <p>
+     Hello world! 
+  </p>
+</div>
+`;
+
 exports[`transforms a theme config to CSS custom properties 1`] = `
 Object {
   "--color-accent": "#609",

packages/custom-properties/test/test.js

@@ -1,4 +1,6 @@
-import toCustomProperties from '../src'
+import React from 'react'
+import renderer from 'react-test-renderer'
+import toCustomProperties, { withCustomProperties } from '../src'
 
 const theme = {
   colors: {
@@ -45,3 +47,27 @@ it('transforms a theme config to CSS custom properties with prefix', () => {
 
   expect(result).toMatchSnapshot()
 })
+
+it('adds the default className on the wrapping element of ThemeProvider', () => {
+  const ExtendedThemeProvider = withCustomProperties('🍭')
+  const themeProvider = renderer.create(
+    <ExtendedThemeProvider theme={theme}>
+      <p> Hello world! </p>
+    </ExtendedThemeProvider>
+  )
+
+  let tree = themeProvider.toJSON()
+  expect(tree).toMatchSnapshot()
+})
+
+it('adds a specific className on the wrapping element of ThemeProvider', () => {
+  const ExtendedThemeProvider = withCustomProperties('🍭', '🍧')
+  const themeProvider = renderer.create(
+    <ExtendedThemeProvider theme={theme}>
+      <p> Hello world! </p>
+    </ExtendedThemeProvider>
+  )
+
+  let tree = themeProvider.toJSON()
+  expect(tree).toMatchSnapshot()
+})