205 lines
7.4 KiB
Markdown
205 lines
7.4 KiB
Markdown
# Dark Mode
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## Overview
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### Automatically update the native interfaces
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"Native interfaces" include the file picker, window border, dialogs, context
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menus, and more - anything where the UI comes from your operating system and
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not from your app. The default behavior is to opt into this automatic theming
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from the OS.
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### Automatically update your own interfaces
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If your app has its own dark mode, you should toggle it on and off in sync with
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the system's dark mode setting. You can do this by using the
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[prefers-color-scheme][] CSS media query.
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### Manually update your own interfaces
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If you want to manually switch between light/dark modes, you can do this by
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setting the desired mode in the
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[themeSource](../api/native-theme.md#nativethemethemesource)
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property of the `nativeTheme` module. This property's value will be propagated
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to your Renderer process. Any CSS rules related to `prefers-color-scheme` will
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be updated accordingly.
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## macOS settings
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In macOS 10.14 Mojave, Apple introduced a new [system-wide dark mode][system-wide-dark-mode]
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for all macOS computers. If your Electron app has a dark mode, you can make it
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follow the system-wide dark mode setting using
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[the `nativeTheme` api](../api/native-theme.md).
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In macOS 10.15 Catalina, Apple introduced a new "automatic" dark mode option
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for all macOS computers. In order for the `nativeTheme.shouldUseDarkColors` and
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`Tray` APIs to work correctly in this mode on Catalina, you need to use Electron
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`>=7.0.0`, or set `NSRequiresAquaSystemAppearance` to `false` in your
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`Info.plist` file for older versions. Both [Electron Packager][electron-packager]
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and [Electron Forge][electron-forge] have a
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[`darwinDarkModeSupport` option][packager-darwindarkmode-api]
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to automate the `Info.plist` changes during app build time.
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If you wish to opt-out while using Electron > 8.0.0, you must
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set the `NSRequiresAquaSystemAppearance` key in the `Info.plist` file to
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`true`. Please note that Electron 8.0.0 and above will not let you opt-out
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of this theming, due to the use of the macOS 10.14 SDK.
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## Example
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This example demonstrates an Electron application that derives its theme colors from the
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`nativeTheme`. Additionally, it provides theme toggle and reset controls using IPC channels.
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```javascript fiddle='docs/fiddles/features/dark-mode'
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```
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### How does this work?
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Starting with the `index.html` file:
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```html title='index.html'
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="UTF-8">
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<title>Hello World!</title>
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<meta http-equiv="Content-Security-Policy" content="script-src 'self' 'unsafe-inline';" />
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<link rel="stylesheet" type="text/css" href="./styles.css">
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</head>
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<body>
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<h1>Hello World!</h1>
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<p>Current theme source: <strong id="theme-source">System</strong></p>
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<button id="toggle-dark-mode">Toggle Dark Mode</button>
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<button id="reset-to-system">Reset to System Theme</button>
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<script src="renderer.js"></script>
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</body>
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</body>
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</html>
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```
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And the `styles.css` file:
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```css title='styles.css'
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@media (prefers-color-scheme: dark) {
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body { background: #333; color: white; }
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}
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@media (prefers-color-scheme: light) {
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body { background: #ddd; color: black; }
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}
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```
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The example renders an HTML page with a couple elements. The `<strong id="theme-source">`
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element shows which theme is currently selected, and the two `<button>` elements are the
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controls. The CSS file uses the [`prefers-color-scheme`][prefers-color-scheme] media query
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to set the `<body>` element background and text colors.
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The `preload.js` script adds a new API to the `window` object called `darkMode`. This API
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exposes two IPC channels to the renderer process, `'dark-mode:toggle'` and `'dark-mode:system'`.
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It also assigns two methods, `toggle` and `system`, which pass messages from the renderer to the
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main process.
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```js title='preload.js'
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const { contextBridge, ipcRenderer } = require('electron')
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contextBridge.exposeInMainWorld('darkMode', {
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toggle: () => ipcRenderer.invoke('dark-mode:toggle'),
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system: () => ipcRenderer.invoke('dark-mode:system')
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})
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```
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Now the renderer process can communicate with the main process securely and perform the necessary
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mutations to the `nativeTheme` object.
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The `renderer.js` file is responsible for controlling the `<button>` functionality.
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```js title='renderer.js' @ts-expect-error=[2,7]
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document.getElementById('toggle-dark-mode').addEventListener('click', async () => {
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const isDarkMode = await window.darkMode.toggle()
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document.getElementById('theme-source').innerHTML = isDarkMode ? 'Dark' : 'Light'
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})
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document.getElementById('reset-to-system').addEventListener('click', async () => {
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await window.darkMode.system()
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document.getElementById('theme-source').innerHTML = 'System'
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})
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```
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Using `addEventListener`, the `renderer.js` file adds `'click'` [event listeners][event-listeners]
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to each button element. Each event listener handler makes calls to the respective `window.darkMode`
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API methods.
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Finally, the `main.js` file represents the main process and contains the actual `nativeTheme` API.
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```js
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const { app, BrowserWindow, ipcMain, nativeTheme } = require('electron')
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const path = require('node:path')
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const createWindow = () => {
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const win = new BrowserWindow({
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width: 800,
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height: 600,
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webPreferences: {
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preload: path.join(__dirname, 'preload.js')
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}
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})
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win.loadFile('index.html')
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ipcMain.handle('dark-mode:toggle', () => {
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if (nativeTheme.shouldUseDarkColors) {
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nativeTheme.themeSource = 'light'
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} else {
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nativeTheme.themeSource = 'dark'
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}
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return nativeTheme.shouldUseDarkColors
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})
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ipcMain.handle('dark-mode:system', () => {
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nativeTheme.themeSource = 'system'
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})
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}
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app.whenReady().then(() => {
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createWindow()
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app.on('activate', () => {
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if (BrowserWindow.getAllWindows().length === 0) {
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createWindow()
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}
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})
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})
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app.on('window-all-closed', () => {
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if (process.platform !== 'darwin') {
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app.quit()
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}
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})
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```
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The `ipcMain.handle` methods are how the main process responds to the click events from the buttons
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on the HTML page.
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The `'dark-mode:toggle'` IPC channel handler method checks the `shouldUseDarkColors` boolean property,
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sets the corresponding `themeSource`, and then returns the current `shouldUseDarkColors` property.
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Looking back on the renderer process event listener for this IPC channel, the return value from this
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handler is utilized to assign the correct text to the `<strong id='theme-source'>` element.
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The `'dark-mode:system'` IPC channel handler method assigns the string `'system'` to the `themeSource`
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and returns nothing. This also corresponds with the relative renderer process event listener as the
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method is awaited with no return value expected.
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Run the example using Electron Fiddle and then click the "Toggle Dark Mode" button; the app should
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start alternating between a light and dark background color.
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[system-wide-dark-mode]: https://developer.apple.com/design/human-interface-guidelines/macos/visual-design/dark-mode/
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[electron-forge]: https://www.electronforge.io/
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[electron-packager]: https://github.com/electron/electron-packager
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[packager-darwindarkmode-api]: https://electron.github.io/electron-packager/main/interfaces/electronpackager.options.html#darwindarkmodesupport
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[prefers-color-scheme]: https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme
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[event-listeners]: https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener
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