erickzhao/index.html

## index.html
<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Hello World!</title>
    <link rel="stylesheet" type="text/css" href="./styles.css">
  </head>
  <body>
    <h1>Hello World!</h1>
    <p>Current theme source: <strong id="theme-source">System</strong></p>

    <button id="toggle-dark-mode">Toggle Dark Mode</button>
    <button id="reset-to-system">Reset to System Theme</button>

    <script>
      // You can also require other files to run in this process
      require('./renderer.js')
    </script>
  </body>
</html>

## main.js
// Modules to control application life and create native browser window
const {app, BrowserWindow, ipcMain, nativeTheme} = require('electron')

function createWindow () {
  // Create the browser window.
  const mainWindow = new BrowserWindow({
    width: 800,
    height: 600,
    webPreferences: {
      nodeIntegration: true
    }
  })

  // and load the index.html of the app.
  mainWindow.loadFile('index.html')

  ipcMain.handle('dark-mode:toggle', () => {
    if (nativeTheme.shouldUseDarkColors) {
      nativeTheme.themeSource = 'light';
    } else {
      nativeTheme.themeSource = 'dark';
    }
    return nativeTheme.shouldUseDarkColors;
  });

  ipcMain.handle('dark-mode:system', () => {
    nativeTheme.themeSouce = 'system';
  });

  // Open the DevTools.
  // mainWindow.webContents.openDevTools()
}

// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.whenReady().then(createWindow)

// Quit when all windows are closed, except on macOS. There, it's common
// for applications and their menu bar to stay active until the user quits
// explicitly with Cmd + Q.
app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') {
    app.quit()
  }
})

app.on('activate', function () {
  // On OS X it's common to re-create a window in the app when the
  // dock icon is clicked and there are no other windows open.
  if (BrowserWindow.getAllWindows().length === 0) {
    createWindow()
  }
})

// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.

## preload.js
// Empty

## renderer.js
// This file is required by the index.html file and will
// be executed in the renderer process for that window.
// All of the Node.js APIs are available in this process.

const {ipcRenderer} = require('electron');

document.getElementById('toggle-dark-mode').addEventListener('click', async () => {
  const isDarkMode = await ipcRenderer.invoke('dark-mode:toggle');
  document.getElementById('theme-source').innerHTML = isDarkMode ? 'Dark' : 'Light';

});

document.getElementById('reset-to-system').addEventListener('click', async () => {
  await ipcRenderer.invoke('dark-mode:system');
  document.getElementById('theme-source').innerHTML = 'System';

});

## styles.css
@media (prefers-color-scheme: dark) {
  body  { background:  #333; color: white; }
}

@media (prefers-color-scheme: light) {
  body  { background:  #ddd; color: black; }
}
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="UTF-8">
	<title>Hello World!</title>
	<link rel="stylesheet" type="text/css" href="./styles.css">
	</head>
	<body>
	<h1>Hello World!</h1>
	<p>Current theme source: <strong id="theme-source">System</strong></p>

	<button id="toggle-dark-mode">Toggle Dark Mode</button>
	<button id="reset-to-system">Reset to System Theme</button>

	<script>
	// You can also require other files to run in this process
	require('./renderer.js')
	</script>
	</body>
	</html>
	// Modules to control application life and create native browser window
	const {app, BrowserWindow, ipcMain, nativeTheme} = require('electron')

	function createWindow () {
	// Create the browser window.
	const mainWindow = new BrowserWindow({
	width: 800,
	height: 600,
	webPreferences: {
	nodeIntegration: true
	}
	})

	// and load the index.html of the app.
	mainWindow.loadFile('index.html')

	ipcMain.handle('dark-mode:toggle', () => {
	if (nativeTheme.shouldUseDarkColors) {
	nativeTheme.themeSource = 'light';
	} else {
	nativeTheme.themeSource = 'dark';
	}
	return nativeTheme.shouldUseDarkColors;
	});

	ipcMain.handle('dark-mode:system', () => {
	nativeTheme.themeSouce = 'system';
	});

	// Open the DevTools.
	// mainWindow.webContents.openDevTools()
	}

	// This method will be called when Electron has finished
	// initialization and is ready to create browser windows.
	// Some APIs can only be used after this event occurs.
	app.whenReady().then(createWindow)

	// Quit when all windows are closed, except on macOS. There, it's common
	// for applications and their menu bar to stay active until the user quits
	// explicitly with Cmd + Q.
	app.on('window-all-closed', function () {
	if (process.platform !== 'darwin') {
	app.quit()
	}
	})

	app.on('activate', function () {
	// On OS X it's common to re-create a window in the app when the
	// dock icon is clicked and there are no other windows open.
	if (BrowserWindow.getAllWindows().length === 0) {
	createWindow()
	}
	})

	// In this file you can include the rest of your app's specific main process
	// code. You can also put them in separate files and require them here.
	// This file is required by the index.html file and will
	// be executed in the renderer process for that window.
	// All of the Node.js APIs are available in this process.

	const {ipcRenderer} = require('electron');

	document.getElementById('toggle-dark-mode').addEventListener('click', async () => {
	const isDarkMode = await ipcRenderer.invoke('dark-mode:toggle');
	document.getElementById('theme-source').innerHTML = isDarkMode ? 'Dark' : 'Light';

	});

	document.getElementById('reset-to-system').addEventListener('click', async () => {
	await ipcRenderer.invoke('dark-mode:system');
	document.getElementById('theme-source').innerHTML = 'System';

	});
	@media (prefers-color-scheme: dark) {
	body { background: #333; color: white; }
	}

	@media (prefers-color-scheme: light) {
	body { background: #ddd; color: black; }
	}