Read dark/light mode from system, automatically listen for changes, and add button for toggling the mode to the status bar

electron/main/index.ts

@@ -54,7 +54,7 @@ async function createWindow() {
             // Consider using contextBridge.exposeInMainWorld
             // Read more on https://www.electronjs.org/docs/latest/tutorial/context-isolation
             nodeIntegration: true,
-            contextIsolation: false,
+            contextIsolation: true,
         },
     })
 
@@ -121,3 +121,10 @@ ipcMain.handle('open-win', (_, arg) => {
         childWindow.loadFile(indexHtml, { hash: arg })
     }    
 })
+
+
+ipcMain.handle('dark-mode:set', (event, mode) => {
+    nativeTheme.themeSource = mode
+})
+
+ipcMain.handle('dark-mode:get', () => nativeTheme.themeSource)

electron/preload/index.ts

@@ -1,3 +1,32 @@
+const { contextBridge, ipcRenderer } = require('electron')
+
+const getComputedTheme = () => window.matchMedia('(prefers-color-scheme: dark)').matches ? "dark" : "light"
+const mediaMatch = window.matchMedia('(prefers-color-scheme: dark)')
+let darkModeChangeListener = null
+
+contextBridge.exposeInMainWorld('darkMode', {
+    set: (mode) => ipcRenderer.invoke('dark-mode:set', mode),
+    get: async () => {
+        const mode = await ipcRenderer.invoke('dark-mode:get')
+        return {
+            theme: mode,
+            computed: getComputedTheme(),
+        }
+    },
+    onChange: (callback) => {
+        darkModeChangeListener = (event) => {
+            callback(event.matches ? "dark" : "light")
+        }
+        mediaMatch.addEventListener('change', darkModeChangeListener)
+        return mediaMatch
+    },
+    removeListener() {
+        mediaMatch.removeEventListener('change', darkModeChangeListener)
+    },
+    initial: getComputedTheme(),
+})
+
+
 function domReady(condition: DocumentReadyState[] = ['complete', 'interactive']) {
   return new Promise((resolve) => {
     if (condition.includes(document.readyState)) {

src/App.vue

@@ -3,7 +3,6 @@
     import StatusBar from './components/StatusBar.vue'
     import Editor from './components/Editor.vue'
     
-    console.log("[App.vue]", `Hello world from Electron ${process.versions.electron}!`)
 
     export default {
         components: {
@@ -18,11 +17,39 @@
                 column: 1,
                 language: "plaintext",
                 languageAuto: true,
-                theme: "dark",
+                theme: window.darkMode.initial,
+                initialTheme: window.darkMode.initial,
+                systemTheme: 'system',
             }
         },
 
+        mounted() {
+            window.darkMode.get().then((mode) => {
+                this.theme = mode.computed
+                this.systemTheme = mode.theme
+            })
+            window.darkMode.onChange((theme) => {
+                this.theme = theme
+            })
+        },
+
+        beforeUnmount() {
+            window.darkMode.removeListener()
+        },
+
         methods: {
+            toggleTheme() {
+                let newTheme
+                // when the "system" theme is used, make sure that the first click always results in amn actual theme change
+                if (this.initialTheme === "light") {
+                    newTheme = this.systemTheme === "system" ? "dark" : (this.systemTheme === "dark" ? "light" : "system")
+                } else {
+                    newTheme = this.systemTheme === "system" ? "light" : (this.systemTheme === "light" ? "dark" : "system")
+                }
+                window.darkMode.set(newTheme)
+                this.systemTheme = newTheme
+            },
+
             onCursorChange(e) {
                 //console.log("onCursorChange:", e)
                 this.line = e.cursorLine.line
@@ -47,7 +74,8 @@
         :language="language" 
         :languageAuto="languageAuto"
         :theme="theme"
-        @toggleTheme="theme = theme === 'dark' ? 'light' : 'dark'"
+        :systemTheme="systemTheme"
+        @toggleTheme="toggleTheme"
         class="status" 
     />
 </template>

src/components/StatusBar.vue

@@ -19,6 +19,7 @@
             "language", 
             "languageAuto",
             "theme",
+            "systemTheme",
         ],
 
         mounted() {
@@ -44,11 +45,13 @@
             Col <span class="num">{{ column }}</span>
         </div>
         <div class="spacer"></div>
-        <div class="status-block theme clickable" @click="$emit('toggleTheme')">{{ theme }}</div>
         <div class="status-block lang clickable">
             {{ languageName }} 
             <span v-if="languageAuto" class="auto">(auto)</span>
         </div>
+        <div class="status-block theme clickable" @click="$emit('toggleTheme')">
+            <span :class="'icon ' + systemTheme"></span>
+        </div>
     </div>
 </template>
 
@@ -76,23 +79,45 @@
                     color: rgba(255, 255, 255, 0.75)
             .status-block.lang .auto
                 color: rgba(255, 255, 255, 0.55)
+            .theme .icon
+                opacity: 0.9
 
         .spacer
             flex-grow: 1
         
         .status-block
-            padding: 2px 12px
+            padding: 2px 10px
             cursor: default
+            &:first-child
+                padding-left: 12px
+            &:last-child
+                padding-right: 12px
             &.clickable
                 cursor: pointer
                 &:hover
-                    background: rgba(255,255,255, 0.1)
-            &.line-number
+                    background-color: rgba(255,255,255, 0.1)
+        .line-number
             color: rgba(255, 255, 255, 0.7)
             .num
                 color: rgba(255, 255, 255, 1.0)
-            &.lang
+        .lang
             .auto
                 color: rgba(255, 255, 255, 0.7)
+        .theme
+            padding-top: 0
+            padding-bottom: 0
+            .icon
+                display: block
+                width: 14px
+                height: 22px
+                background-size: 14px
+                background-repeat: no-repeat
+                background-position: center center
+                &.dark
+                    background-image: url("/icons/dark-mode.png")
+                &.light
+                    background-image: url("/icons/light-mode.png")
+                &.system
+                    background-image: url("/icons/both-mode.png")
 
 </style>

src/editor/editor.js

@@ -24,7 +24,7 @@ export class HeynoteEditor {
                 //minimalSetup,
                 customSetup, 
                 
-                this.theme.of("dark" ? heynoteDark : heynoteLight),
+                this.theme.of(theme === "dark" ? heynoteDark : heynoteLight),
                 heynoteBase,
                 indentUnit.of("    "),
                 EditorView.scrollMargins.of(f => {