Stateful dark mode

app.vue

@@ -8,9 +8,6 @@
 import EventBus from '@/layouts/AppEventBus';
 
 export default {
-    themeChangeListener: null,
-    newsActivate: null,
-    newsService: null,
     watch: {
         $route: {
             handler(to) {
@@ -20,16 +17,29 @@ export default {
             }
         }
     },
-    mounted() {
-        this.themeChangeListener = (event) => {
-            if (!document.startViewTransition) {
-                this.applyTheme(event);
-
-                return;
+    created() {
+        useServerHead({
+            link: [
+                {
+                    id: 'theme-link',
+                    rel: 'stylesheet',
+                    href: '/themes/lara-light-green/theme.css'
+                },
+                {
+                    id: 'home-table-link',
+                    rel: 'stylesheet',
+                    href: '/styles/landing/themes/lara-light-green/theme.css'
                 }
+            ]
+        });
+    },
+    mounted() {
+        const preferredColorScheme = localStorage.getItem(this.$appState.colorSchemeKey);
+        const prefersDarkColorScheme = window.matchMedia('(prefers-color-scheme: dark)').matches;
 
-            document.startViewTransition(() => this.applyTheme(event));
-        };
+        if ((preferredColorScheme === null && prefersDarkColorScheme) || preferredColorScheme === 'dark') {
+            this.applyTheme({ theme: 'lara-dark-green', dark: true });
+        }
 
         EventBus.on('theme-change', this.themeChangeListener);
     },
@@ -37,10 +47,20 @@ export default {
         EventBus.off('theme-change', this.themeChangeListener);
     },
     methods: {
+        themeChangeListener(event) {
+            if (!document.startViewTransition) {
+                this.applyTheme(event);
+
+                return;
+            }
+
+            document.startViewTransition(() => this.applyTheme(event));
+        },
         applyTheme(event) {
             this.$primevue.changeTheme(this.$appState.theme, event.theme, 'theme-link', () => {
                 this.$appState.theme = event.theme;
                 this.$appState.darkTheme = event.dark;
+
                 EventBus.emit('theme-change-complete', { theme: event.theme, dark: event.dark });
             });
         }

layouts/default.vue

@@ -92,9 +92,12 @@ export default {
 
             if (this.$appState.darkTheme) {
                 newTheme = currentTheme.replace('dark', 'light');
+                localStorage.setItem(this.$appState.colorSchemeKey, 'light');
             } else {
                 if (currentTheme.includes('light') && currentTheme !== 'fluent-light') newTheme = currentTheme.replace('light', 'dark');
                 else newTheme = 'lara-dark-green'; //fallback
+
+                localStorage.setItem(this.$appState.colorSchemeKey, 'dark');
             }
 
             EventBus.emit('theme-change', { theme: newTheme, dark: !this.$appState.darkTheme });

nuxt.config.js

@@ -52,19 +52,7 @@ export default defineNuxtConfig({
                 { property: 'og:image', content: 'https://www.primefaces.org/static/social/primevue-preview.jpg' },
                 { property: 'og:ttl', content: '604800' }
             ],
-            link: [
-                {
-                    id: 'home-table-link',
-                    rel: 'stylesheet',
-                    href: baseUrl + 'styles/landing/themes/lara-light-green/theme.css'
-                },
-                {
-                    id: 'theme-link',
-                    rel: 'stylesheet',
-                    href: baseUrl + 'themes/lara-light-green/theme.css'
-                },
-                { rel: 'icon', href: baseUrl + 'favicon.ico' }
-            ],
+            link: [{ rel: 'icon', href: baseUrl + 'favicon.ico' }],
             script: [
                 {
                     src: baseUrl + 'scripts/prism.js',

pages/index.vue

@@ -53,13 +53,21 @@ export default {
             document.cookie = 'primeaffiliateid=' + afId + ';expires=' + expire.toUTCString() + ';path=/; domain:primefaces.org';
         }
 
-        this.replaceTableTheme(this.$appState.darkTheme ? 'lara-dark-green' : 'lara-light-green');
+        const preferredColorScheme = localStorage.getItem(this.$appState.colorSchemeKey);
+        const prefersDarkColorScheme = window.matchMedia('(prefers-color-scheme: dark)').matches;
+
+        if ((preferredColorScheme === null && prefersDarkColorScheme) || preferredColorScheme === 'dark') {
+            this.replaceTableTheme('lara-dark-green');
+        } else {
+            this.replaceTableTheme('lara-light-green');
+        }
     },
     methods: {
         onDarkModeToggle() {
             const newTheme = this.$appState.darkTheme ? 'lara-light-green' : 'lara-dark-green';
             const newTableTheme = this.$appState.darkTheme ? this.tableTheme.replace('dark', 'light') : this.tableTheme.replace('light', 'dark');
 
+            localStorage.setItem(this.$appState.colorSchemeKey, this.$appState.darkTheme ? 'light' : 'dark');
             EventBus.emit('theme-change', { theme: newTheme, dark: !this.$appState.darkTheme });
             this.replaceTableTheme(newTableTheme);
         },

plugins/app-state.js

@@ -1,6 +1,15 @@
 const $appState = {
     install: (Vue, options) => {
-        Vue.config.globalProperties.$appState = reactive({ theme: 'lara-light-green', darkTheme: false, codeSandbox: false, sourceType: 'options-api', newsActive: false, announcement: null, storageKey: 'primevue' });
+        Vue.config.globalProperties.$appState = reactive({
+            theme: 'lara-light-green',
+            darkTheme: false,
+            codeSandbox: false,
+            sourceType: 'options-api',
+            newsActive: false,
+            announcement: null,
+            storageKey: 'primevue',
+            colorSchemeKey: 'primevue-color-scheme'
+        });
     }
 };