feat(react): add Theme component, useTheme hook

packages/carbon-react/src/components/Theme/Theme-story.scss

@@ -0,0 +1,16 @@
+//
+// Copyright IBM Corp. 2018, 2018
+//
+// This source code is licensed under the Apache-2.0 license found in the
+// LICENSE file in the root directory of this source tree.
+//
+
+@use '@carbon/styles/scss/themes';
+@use '@carbon/styles/scss/theme';
+@use '@carbon/styles/scss/zone';
+
+.theme-section {
+  padding: 1rem;
+  background: theme.$background;
+  color: theme.$text-primary;
+}

packages/carbon-react/src/components/Theme/Theme.mdx

@@ -0,0 +1,85 @@
+import { Story, Props, Source, Preview } from '@storybook/addon-docs/blocks';
+
+# Theme
+
+[Source code](https://github.com/carbon-design-system/carbon/tree/main/packages/carbon-react/src/components/Theme)
+
+<!-- prettier-ignore-start -->
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+## Table of Contents
+
+- [Overview](#overview)
+  - [`useTheme`](#usetheme)
+- [Component API](#component-api)
+  - [Theme as](#theme-as)
+- [Feedback](#feedback)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+<!-- prettier-ignore-end -->
+
+## Overview
+
+The `Theme` component allows you to specify the theme for a page, or a portion
+of a page. It is most often used to implement inline theming in order to specify
+what theme a section of the page should render with.
+
+The `Theme` component accepts a `theme` prop which allows you to specify the
+theme. This value is propagated to the entire sub-tree of components and can be
+accessed by any child component using the `useTheme` hook.
+
+```jsx
+<Theme theme="g100">
+  <ChildComponent />
+</Theme>
+```
+
+The `Theme` component will render a wrapper element on which all of the values
+of the given theme will be applied as CSS Custom Properties. These CSS Custom
+Properties can be accessed directly, or you can use the Sass Variables provided
+in the styles from the Carbon Design System to refer to these properties in your
+styles.
+
+### `useTheme`
+
+The `useTheme` hook allows you to access the current theme in a component. This
+can be useful if you need to conditionally render something based on the theme.
+For example, if you have an illustration that needs to be rendered differently
+in a light or dark theme.
+
+You can use this hook in any component by calling `useTheme`:
+
+```jsx
+function ExampleComponent() {
+  const { theme } = useTheme();
+
+  if (theme === 'g100') {
+    // ...
+  }
+}
+```
+
+## Component API
+
+<Props />
+
+### Theme as
+
+You can configure the base element rendered by `Theme` using the `as` prop. For
+example, if you would like the `Theme` component to render as a `section` you
+could write the following:
+
+```jsx
+<Theme as="section" theme="g100">
+  <ChildComponent />
+</Theme>
+```
+
+Similarly, you can provide any custom component to the `as` prop which the
+`Theme` component will use.
+
+## Feedback
+
+Help us improve this component by providing feedback, asking questions on Slack,
+or updating this file on
+[GitHub](https://github.com/carbon-design-system/carbon/edit/main/packages/carbon-react/src/components/Theme/Theme.mdx).

packages/carbon-react/src/components/Theme/Theme.stories.js

@@ -0,0 +1,96 @@
+/**
+ * Copyright IBM Corp. 2016, 2018
+ *
+ * This source code is licensed under the Apache-2.0 license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import './Theme-story.scss';
+import React from 'react';
+import { Theme, useTheme } from '../Theme';
+import mdx from './Theme.mdx';
+
+export default {
+  title: 'Components/Theme',
+  component: Theme,
+  parameters: {
+    controls: {
+      hideNoControlsWarning: true,
+    },
+    docs: {
+      page: mdx,
+    },
+  },
+  argTypes: {
+    as: {
+      table: {
+        disable: true,
+      },
+    },
+    children: {
+      table: {
+        disable: true,
+      },
+    },
+    theme: {
+      defaultValue: 'g10',
+    },
+  },
+};
+
+export const Default = () => {
+  return (
+    <>
+      <Theme theme="g100">
+        <section className="theme-section">
+          <p>g100 theme</p>
+        </section>
+      </Theme>
+      <Theme theme="g90">
+        <section className="theme-section">
+          <p>g90 theme</p>
+        </section>
+      </Theme>
+      <Theme theme="g10">
+        <section className="theme-section">
+          <p>g10 theme</p>
+        </section>
+      </Theme>
+      <Theme theme="white">
+        <section className="theme-section">
+          <p>white theme</p>
+        </section>
+      </Theme>
+    </>
+  );
+};
+
+export const UseTheme = () => {
+  function Example() {
+    const { theme } = useTheme();
+    return <div className="theme-section">The current theme is: {theme}</div>;
+  }
+
+  return (
+    <div>
+      <Example />
+      <Theme theme="g100">
+        <Example />
+      </Theme>
+    </div>
+  );
+};
+
+UseTheme.storyName = 'useTheme';
+
+const PlaygroundStory = (args) => {
+  return (
+    <Theme {...args}>
+      <section className="theme-section">
+        <p>{args.theme} theme</p>
+      </section>
+    </Theme>
+  );
+};
+
+export const Playground = PlaygroundStory.bind({});

packages/carbon-react/src/components/Theme/__tests__/Theme-test.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright IBM Corp. 2016, 2018
+ *
+ * This source code is licensed under the Apache-2.0 license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import React from 'react';
+import { Theme, useTheme } from '../../Theme';
+import { screen, render } from '@testing-library/react';
+
+describe('Theme', () => {
+  it('should render the children passed in as a prop', () => {
+    render(
+      <Theme>
+        <span data-testid="test">test</span>
+      </Theme>
+    );
+
+    expect(screen.getByTestId('test')).toBeInTheDocument();
+  });
+
+  it('should set the theme in context', () => {
+    function TestComponent({ id }) {
+      const { theme } = useTheme();
+      return <span data-testid={id}>{theme}</span>;
+    }
+    render(
+      <Theme theme="white">
+        <TestComponent id="default" />
+        <Theme theme="g100">
+          <TestComponent id="nested" />
+        </Theme>
+      </Theme>
+    );
+
+    expect(screen.getByTestId('default')).toHaveTextContent('white');
+    expect(screen.getByTestId('nested')).toHaveTextContent('g100');
+  });
+});

packages/carbon-react/src/components/Theme/index.js

@@ -0,0 +1,80 @@
+/**
+ * Copyright IBM Corp. 2016, 2018
+ *
+ * This source code is licensed under the Apache-2.0 license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import React from 'react';
+import PropTypes from 'prop-types';
+import cx from 'classnames';
+
+const ThemeContext = React.createContext({
+  theme: 'white',
+});
+
+/**
+ * Specify the theme to be applied to a page, or a region in a page
+ */
+export function Theme({
+  as: BaseComponent = 'div',
+  children,
+  className: customClassName,
+  theme,
+  ...rest
+}) {
+  const className = cx(customClassName, {
+    'bx--white': theme === 'white',
+    'bx--g10': theme === 'g10',
+    'bx--g90': theme === 'g90',
+    'bx--g100': theme === 'g100',
+  });
+  const value = React.useMemo(() => {
+    return {
+      theme,
+    };
+  }, [theme]);
+
+  return (
+    <ThemeContext.Provider value={value}>
+      <BaseComponent {...rest} className={className}>
+        {children}
+      </BaseComponent>
+    </ThemeContext.Provider>
+  );
+}
+
+Theme.propTypes = {
+  /**
+   * Specify a custom component or element to be rendered as the top-level
+   * element in the component
+   */
+  as: PropTypes.oneOfType([
+    PropTypes.func,
+    PropTypes.string,
+    PropTypes.elementType,
+  ]),
+
+  /**
+   * Provide child elements to be rendered inside of `Theme`
+   */
+  children: PropTypes.node,
+
+  /**
+   * Provide a custom class name to be used on the outermost element rendered by
+   * the component
+   */
+  className: PropTypes.string,
+
+  /**
+   * Specify the theme
+   */
+  theme: PropTypes.oneOf(['white', 'g10', 'g90', 'g100']),
+};
+
+/**
+ * Get access to the current theme
+ */
+export function useTheme() {
+  return React.useContext(ThemeContext);
+}

packages/carbon-react/src/index.js

@@ -204,3 +204,5 @@ export {
   Grid,
   Column,
 } from './components/Grid';
+
+export { Theme, useTheme } from './components/Theme';

packages/styles/scss/_zone.scss

@@ -0,0 +1,33 @@
+//
+// Copyright IBM Corp. 2018, 2018
+//
+// This source code is licensed under the Apache-2.0 license found in the
+// LICENSE file in the root directory of this source tree.
+//
+
+@use 'sass:map';
+@use 'sass:meta';
+@use './config';
+@use './themes';
+@use './theme';
+@use './utilities/custom-property';
+
+/// Specify a Map of zones where the key will be used as part of the selector
+/// and the value will be a map used to emit CSS Custom Properties for all color
+/// values
+$zones: (
+  white: themes.$white,
+  g10: themes.$g10,
+  g90: themes.$g90,
+  g100: themes.$g100,
+) !default;
+
+@each $name, $theme in $zones {
+  .#{config.$prefix}--#{'' + $name} {
+    @each $key, $value in $theme {
+      @if type-of($value) == color {
+        @include custom-property.declaration($key, $value);
+      }
+    }
+  }
+}