feat(theme): allow defining dark as the default theme (#1498)

innocenzi · brc-dd · web-flow · commit d404753005bf · 2022-10-18T22:27:26.000+05:30
Co-authored-by: Divyansh Singh &lt;40380293+brc-dd@users.noreply.github.com&gt;
diff --git a/docs/config/app-configs.md b/docs/config/app-configs.md
@@ -14,10 +14,14 @@ export default {
 
 ## appearance
 
-- Type: `boolean`
+- Type: `boolean | 'dark'`
 - Default: `true`
 
-Whether to enable "Dark Mode" or not. If the option is set to `true`, it adds `.dark` class to the `<html>` tag depending on the users preference.
+Whether to enable dark mode or not.
+
+- If the option is set to `true`, the default theme will be determined by the user's preferred color scheme.
+- If the option is set to `dark`, the theme will be dark by default, unless the user manually toggles it.
+- If the option is set to `false`, users will not be able to toggle the theme.
 
 It also injects inline script that tries to read users settings from local storage by `vitepress-theme-appearance` key and restores users preferred color mode.
 
@@ -199,7 +203,7 @@ export default {
 - Type: `string`
 - Default: `.`
 
-The directory where your markdown pages are stored, relative to project root. 
+The directory where your markdown pages are stored, relative to project root.
 
 ```ts
 export default {
diff --git a/src/client/theme-default/components/VPSwitchAppearance.vue b/src/client/theme-default/components/VPSwitchAppearance.vue
@@ -1,10 +1,12 @@
 <script lang="ts" setup>
 import { ref, onMounted } from 'vue'
+import { useData } from 'vitepress'
 import { APPEARANCE_KEY } from '../../shared.js'
 import VPSwitch from './VPSwitch.vue'
 import VPIconSun from './icons/VPIconSun.vue'
 import VPIconMoon from './icons/VPIconMoon.vue'
 
+const { site } = useData()
 const checked = ref(false)
 const toggle = typeof localStorage !== 'undefined' ? useAppearance() : () => {}
 
@@ -16,11 +18,13 @@ function useAppearance() {
   const query = window.matchMedia('(prefers-color-scheme: dark)')
   const classList = document.documentElement.classList
 
-  let userPreference = localStorage.getItem(APPEARANCE_KEY) || 'auto'
+  let userPreference =
+    localStorage.getItem(APPEARANCE_KEY) || site.value.appearance !== true
+      ? site.value.appearance
+      : 'auto'
 
-  let isDark = userPreference === 'auto'
-    ? query.matches
-    : userPreference === 'dark'
+  let isDark =
+    userPreference === 'auto' ? query.matches : userPreference === 'dark'
 
   query.onchange = (e) => {
     if (userPreference === 'auto') {
diff --git a/src/node/config.ts b/src/node/config.ts
@@ -36,7 +36,7 @@ export interface UserConfig<ThemeConfig = any> {
   titleTemplate?: string | boolean
   description?: string
   head?: HeadConfig[]
-  appearance?: boolean
+  appearance?: boolean | 'dark'
   themeConfig?: ThemeConfig
   locales?: Record<string, LocaleConfig>
   markdown?: MarkdownOptions
@@ -332,16 +332,21 @@ function resolveSiteDataHead(userConfig?: UserConfig): HeadConfig[] {
   const head = userConfig?.head ?? []
 
   // add inline script to apply dark mode, if user enables the feature.
-  // this is required to prevent "flush" on initial page load.
+  // this is required to prevent "flash" on initial page load.
   if (userConfig?.appearance ?? true) {
+    // if appearance mode set to light or dark, default to the defined mode
+    // in case the user didn't specify a preference - otherwise, default to auto
+    const fallbackPreference =
+      userConfig?.appearance !== true ? userConfig?.appearance ?? '' : 'auto'
+
     head.push([
       'script',
       { id: 'check-dark-light' },
       `
         ;(() => {
-          const saved = localStorage.getItem('${APPEARANCE_KEY}')
-          const prefereDark = window.matchMedia('(prefers-color-scheme: dark)').matches
-          if (!saved || saved === 'auto' ? prefereDark : saved === 'dark') {
+          const preference = localStorage.getItem('${APPEARANCE_KEY}') || '${fallbackPreference}'
+          const prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches
+          if (!preference || preference === 'auto' ? prefersDark : preference === 'dark') {
             document.documentElement.classList.add('dark')
           }
         })()
diff --git a/types/shared.d.ts b/types/shared.d.ts
@@ -62,7 +62,7 @@ export interface SiteData<ThemeConfig = any> {
   titleTemplate?: string | boolean
   description: string
   head: HeadConfig[]
-  appearance: boolean
+  appearance: boolean | 'dark'
   themeConfig: ThemeConfig
   scrollOffset: number | string
   locales: Record<string, LocaleConfig>
