[EuiProvider] Detect OS/system light vs darkmode as a default

packages/eui/.storybook/decorator.tsx

@@ -103,7 +103,9 @@ const storybookToolbarWritingModes: Array<
 export const euiProviderDecoratorGlobals: Preview['globalTypes'] = {
   colorMode: {
     description: 'Color mode for EuiProvider theme',
-    defaultValue: 'light',
+    defaultValue: window?.matchMedia?.('(prefers-color-scheme: dark)').matches
+      ? 'dark'
+      : 'light',
     toolbar: {
       title: 'Color mode',
       items: storybookToolbarColorModes,

packages/eui/changelogs/upcoming/8026.md

@@ -0,0 +1 @@
+- Updated `EuiProvider` to inherit from the user's OS/system light/dark mode setting if a `colorMode` prop has not been passed

packages/eui/src-docs/src/components/guide_theme_selector/guide_theme_selector.tsx

@@ -3,6 +3,7 @@ import React, { useState } from 'react';
 
 import {
   EuiThemeProvider,
+  useEuiTheme,
   useIsWithinBreakpoints,
 } from '../../../../src/services';
 import { EUI_THEME, EUI_THEMES } from '../../../../src/themes';
@@ -34,8 +35,6 @@ export const GuideThemeSelector: React.FunctionComponent<
   );
 };
 
-const STORAGE_KEY = 'legacy_theme_notification';
-
 const GuideThemeSelectorComponent: React.FunctionComponent<
   GuideThemeSelectorProps
 > = ({ context, onToggleLocale, selectedLocale }) => {
@@ -44,15 +43,17 @@ const GuideThemeSelectorComponent: React.FunctionComponent<
 
   const onButtonClick = () => {
     setPopover(!isPopoverOpen);
-    localStorage.setItem(STORAGE_KEY, 'dismissed');
   };
 
   const closePopover = () => {
     setPopover(false);
   };
 
+  const systemColorMode = useEuiTheme().colorMode.toLowerCase();
   const currentTheme: EUI_THEME =
-    EUI_THEMES.find((theme) => theme.value === context.theme) || EUI_THEMES[0];
+    EUI_THEMES.find(
+      (theme) => theme.value === (context.theme ?? systemColorMode)
+    ) || EUI_THEMES[0];
 
   const getIconType = (value: EUI_THEME['value']) => {
     return value === currentTheme.value ? 'check' : 'empty';

packages/eui/src-docs/src/components/with_theme/theme_context.tsx

@@ -28,30 +28,27 @@ export const theme_languages: THEME_LANGUAGES[] = [
 const THEME_NAMES = EUI_THEMES.map(({ value }) => value);
 const THEME_LANGS = theme_languages.map(({ id }) => id);
 
-const defaultState = {
-  themeLanguage: THEME_LANGS[0],
-  // eslint-disable-next-line @typescript-eslint/no-unused-vars
-  changeThemeLanguage: (language: THEME_LANGUAGES['id']) => {},
-  theme: THEME_NAMES[0],
-  changeTheme: (themeValue: EUI_THEME['value']) => {
-    applyTheme(themeValue);
-  },
-};
-
-interface State {
-  theme: EUI_THEME['value'];
+type ThemeContextType = {
+  theme?: EUI_THEME['value'];
+  changeTheme: (themeValue: EUI_THEME['value']) => void;
   themeLanguage: THEME_LANGUAGES['id'];
-}
+  changeThemeLanguage: (language: THEME_LANGUAGES['id']) => void;
+};
+export const ThemeContext = React.createContext<ThemeContextType>({
+  theme: undefined,
+  changeTheme: () => {},
+  themeLanguage: THEME_LANGS[0],
+  changeThemeLanguage: () => {},
+});
 
-export const ThemeContext = React.createContext(defaultState);
+type State = Pick<ThemeContextType, 'theme' | 'themeLanguage'>;
 
 export class ThemeProvider extends React.Component<PropsWithChildren, State> {
   constructor(props: object) {
     super(props);
 
-    let theme = localStorage.getItem('theme');
-    if (!theme || !THEME_NAMES.includes(theme)) theme = defaultState.theme;
-    applyTheme(theme);
+    const theme = localStorage.getItem('theme') || undefined;
+    applyTheme(theme && THEME_NAMES.includes(theme) ? theme : THEME_NAMES[0]);
 
     const themeLanguage = this.getThemeLanguage();
 
@@ -83,7 +80,7 @@ export class ThemeProvider extends React.Component<PropsWithChildren, State> {
 
     // If not set by either param or storage, or an invalid value, use the default
     if (!themeLanguage || !THEME_LANGS.includes(themeLanguage))
-      themeLanguage = defaultState.themeLanguage;
+      themeLanguage = THEME_LANGS[0];
 
     return themeLanguage;
   };

packages/eui/src-docs/src/index.js

@@ -97,15 +97,10 @@ root.render(
                                 isDeprecated,
                               }}
                             >
-                              {({ theme }) => (
-                                <>
-                                  {meta}
-                                  {createElement(component, {
-                                    selectedTheme: theme,
-                                    title: name,
-                                  })}
-                                </>
-                              )}
+                              {meta}
+                              {createElement(component, {
+                                title: name,
+                              })}
                             </AppView>
                           );
                         }

packages/eui/src-docs/src/views/app_context.js

@@ -56,7 +56,9 @@ export const AppContext = ({ children }) => {
         utility: utilityCache,
       }}
       theme={EUI_THEMES.find((t) => t.value === theme)?.provider}
-      colorMode={theme.includes('light') ? 'light' : 'dark'}
+      colorMode={
+        theme ? (theme.includes('light') ? 'light' : 'dark') : undefined
+      }
     >
       <Helmet>
         <link

packages/eui/src-docs/src/views/app_view.js

@@ -1,8 +1,8 @@
-import React, { useContext } from 'react';
+import React from 'react';
 import { useDispatch, useSelector } from 'react-redux';
 import { useLocation } from 'react-router-dom';
 import { toggleLocale as _toggleLocale } from '../actions';
-import { GuidePageChrome, ThemeContext, GuidePageHeader } from '../components';
+import { GuidePageChrome, GuidePageHeader } from '../components';
 import { getLocale, getRoutes } from '../store';
 import {
   useScrollToHash,
@@ -21,7 +21,6 @@ export const AppView = ({ children, currentRoute = {} }) => {
   const toggleLocale = (locale) => dispatch(_toggleLocale(locale));
   const locale = useSelector((state) => getLocale(state));
   const routes = useSelector((state) => getRoutes(state));
-  const { theme } = useContext(ThemeContext);
 
   const portalledHeadingAnchorLinks = useHeadingAnchorLinks();
 
@@ -59,7 +58,7 @@ export const AppView = ({ children, currentRoute = {} }) => {
           />
         </EuiPageTemplate.Sidebar>
 
-        {children({ theme })}
+        {children}
       </EuiPageTemplate>
     </LinkWrapper>
   );

packages/eui/src-docs/src/views/avatar/avatar_icon.js

@@ -1,15 +1,8 @@
-import React, { useContext } from 'react';
-import { ThemeContext } from '../../components';
-
-import { EuiAvatar, EuiSpacer, EuiTitle } from '../../../../src/components';
+import React from 'react';
+import { EuiAvatar, EuiSpacer, EuiTitle, useEuiTheme } from '../../../../src';
 
 export default () => {
-  const themeContext = useContext(ThemeContext);
-
-  /**
-   * Setup theme based on current light/dark theme
-   */
-  const isDarkTheme = themeContext.theme.includes('dark');
+  const isDarkTheme = useEuiTheme().colorMode === 'DARK';
 
   return (
     <div>

packages/eui/src-docs/src/views/empty_prompt/_types_of_empty_states.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useEffect, useContext } from 'react';
+import React, { useState, useEffect } from 'react';
 import reactElementToJSXString from 'react-element-to-jsx-string';
 import classNames from 'classnames';
 import {
@@ -20,8 +20,8 @@ import {
   EuiDescriptionListDescription,
   EuiLoadingSpinner,
   useIsWithinBreakpoints,
+  useEuiTheme,
 } from '../../../../src';
-import { ThemeContext } from '../../components/with_theme';
 import { typesOfPanelColors } from './_types_of_panel_colors';
 // @ts-ignore Importing from JS file
 import { typesOfUseCases } from './_types_of_use_cases';
@@ -43,12 +43,7 @@ import singleSvg from '../../images/single.svg';
 import contentCenterSvg from '../../images/content_center.svg';
 
 export default () => {
-  const themeContext = useContext(ThemeContext);
-
-  /**
-   * Setup theme based on current light/dark theme
-   */
-  const isDarkTheme = themeContext.theme.includes('dark');
+  const isDarkTheme = useEuiTheme().colorMode === 'DARK';
 
   const useCasesOptions: EuiRadioGroupOption[] = Object.values(
     typesOfUseCases

packages/eui/src-docs/src/views/empty_prompt/prompt_types/no_permission.tsx

@@ -1,17 +1,16 @@
-import React, { useContext } from 'react';
+import React from 'react';
 import {
   EuiEmptyPrompt,
   EuiImage,
   EuiButton,
   EuiButtonEmpty,
-} from '../../../../../src/components';
-import { ThemeContext } from '../../../components/with_theme';
+  useEuiTheme,
+} from '../../../../../src';
 import pageNotFoundLight from '../../../images/empty-prompt/accessDenied--light.png';
 import pageNotFoundDark from '../../../images/empty-prompt/accessDenied--dark.png';
 
 export default () => {
-  const themeContext = useContext(ThemeContext);
-  const isDarkTheme = themeContext.theme.includes('dark');
+  const isDarkTheme = useEuiTheme().colorMode === 'DARK';
 
   const iconImg: string = isDarkTheme ? pageNotFoundDark : pageNotFoundLight;
 

packages/eui/src-docs/src/views/empty_prompt/prompt_types/page_not_found.tsx

@@ -1,20 +1,19 @@
-import React, { useContext } from 'react';
+import React from 'react';
 import {
   EuiEmptyPrompt,
   EuiImage,
   EuiButton,
   EuiButtonEmpty,
-} from '../../../../../src/components';
-import { ThemeContext } from '../../../components/with_theme';
+  useEuiTheme,
+} from '../../../../../src';
 
 import pageNotFoundDark from '../../../images/empty-prompt/pageNotFound--dark.png';
 import pageNotFoundLight from '../../../images/empty-prompt/pageNotFound--light.png';
 import pageNotFoundDark2x from '../../../images/empty-prompt/[email protected]';
 import pageNotFoundLight2x from '../../../images/empty-prompt/[email protected]';
 
 export default () => {
-  const themeContext = useContext(ThemeContext);
-  const isDarkTheme = themeContext.theme.includes('dark');
+  const isDarkTheme = useEuiTheme().colorMode === 'DARK';
 
   const pageNotFound = isDarkTheme ? pageNotFoundDark : pageNotFoundLight;
   const pageNotFound2x = isDarkTheme ? pageNotFoundDark2x : pageNotFoundLight2x;

packages/eui/src-docs/src/views/home/home_illustration.tsx

@@ -1,17 +1,17 @@
-import React, { useContext } from 'react';
-import { ThemeContext } from '../../components/with_theme';
+import React from 'react';
 import illustrationDarkMode from '../../images/illustration-eui-hero-500-darkmode-shadow.svg';
 import illustrationLightMode from '../../images/illustration-eui-hero-500-shadow.svg';
-import { EuiImage } from '../../../../src/components/image';
+import { EuiImage, useEuiTheme } from '../../../../src';
 
 function Icon() {
-  const themeContext: any = useContext(ThemeContext);
+  const { colorMode } = useEuiTheme();
 
-  const illustration = themeContext.theme.includes('dark') ? (
-    <EuiImage alt="Elastic UI" url={illustrationDarkMode} />
-  ) : (
-    <EuiImage alt="Elastic UI" url={illustrationLightMode} />
-  );
+  const illustration =
+    colorMode === 'DARK' ? (
+      <EuiImage alt="Elastic UI" url={illustrationDarkMode} />
+    ) : (
+      <EuiImage alt="Elastic UI" url={illustrationLightMode} />
+    );
 
   return (
     <div className="guideHomePage__illustration">

packages/eui/src-docs/src/views/text/text_example.js

@@ -1,5 +1,4 @@
-import React, { useContext } from 'react';
-import { ThemeContext } from '../../components/with_theme';
+import React from 'react';
 
 import { GuideSectionTypes } from '../../components';
 
@@ -45,22 +44,6 @@ const textAlignSnippet = [
 `,
 ];
 
-const LineHeightText = () => {
-  const themeContext = useContext(ThemeContext);
-  let text;
-  switch (themeContext.theme) {
-    default:
-      text = (
-        <>
-          The goal is that the every line-height lands on the{' '}
-          <EuiCode>4px</EuiCode> baseline grid.
-        </>
-      );
-  }
-
-  return text;
-};
-
 export const TextExample = {
   title: 'Text',
   sections: [
@@ -130,7 +113,8 @@ export const TextExample = {
         <p>
           Using the <EuiCode>size</EuiCode> prop on <strong>EuiText</strong> you
           can get smaller sizes of text than the default. This demo compares the
-          scaling for all sizes. <LineHeightText />
+          scaling for all sizes. The goal is that the every line-height lands on
+          the <EuiCode>4px</EuiCode> baseline grid.
         </p>
       ),
       snippet: textScalingSnippet,

packages/eui/src-docs/src/views/text/text_scaling.js

@@ -1,5 +1,4 @@
-import React, { useState, useContext } from 'react';
-import { ThemeContext } from '../../components/with_theme';
+import React, { useState } from 'react';
 
 import {
   EuiText,
@@ -84,7 +83,6 @@ const text = [
 ];
 
 export default () => {
-  const themeContext = useContext(ThemeContext);
   const textSizeArray = ['xs', 's', 'm'];
   const textSizeNamesArray = ['Extra small', 'Small', 'Medium'];
 
@@ -132,10 +130,7 @@ export default () => {
             options={firstOptions}
           />
           <EuiHorizontalRule />
-          <EuiText
-            className={`guideDemo__textLines guideDemo__textLines--${themeContext.theme}`}
-            size={firstSize}
-          >
+          <EuiText className="guideDemo__textLines" size={firstSize}>
             {text}
           </EuiText>
         </EuiFlexItem>
@@ -154,10 +149,7 @@ export default () => {
             options={secondOptions}
           />
           <EuiHorizontalRule />
-          <EuiText
-            className={`guideDemo__textLines guideDemo__textLines--${themeContext.theme}`}
-            size={secondSize}
-          >
+          <EuiText className="guideDemo__textLines" size={secondSize}>
             {text}
           </EuiText>
         </EuiFlexItem>