rudifa/Electron IPC Pattern #3

## Electron IPC Pattern #3
// 1. Main prepares a Menu that will let the user
//    increment/decrement a counter, whose valu will be displayed
//    in the rendered page
//    On user click, the callback will send a message
//    on the channel (update-counter) with the value to add

// 2. Preload defines the function handleCounter
//    that will let the renderer to specify the callback
//    to be called when a message on the channel (pdate-counter)
//    arrives from the main

// 3. The renderer calls handleCounter to install the callback.
//    The callback will receive the data sent from the main
//    as value and will use it to modify the displayed counter value.

## index.html
<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
    <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self'">
    <title>Menu Counter</title>
  </head>
  <body>
    Current value: <strong id="counter">0</strong>
    <script src="./renderer.js"></script>
  </body>
</html>

## main.js
const {app, BrowserWindow, Menu, ipcMain} = require('electron')
const path = require('path')

function createWindow () {
  const mainWindow = new BrowserWindow({
    webPreferences: {
      preload: path.join(__dirname, 'preload.js')
    }
  })

  // 1. Main prepares a Menu that will let the user
  //    increment/decrement a counter, whose valu will be displayed
  //    in the rendered page
  //    On user click, the callback will send a message
  //    on the channel (update-counter) with the value to add
  const menu = Menu.buildFromTemplate([
    {
      label: app.name,
      submenu: [
      {
        click: () => mainWindow.webContents.send('update-counter', 1),
        label: 'Increment',
      },
      {
        click: () => mainWindow.webContents.send('update-counter', -1),
        label: 'Decrement',
      }
      ]
    }

  ])

  Menu.setApplicationMenu(menu)
  mainWindow.loadFile('index.html')

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

app.whenReady().then(() => {
  ipcMain.on('counter-value', (_event, value) => {
    console.log(value) // will print value to Node console
  })
  createWindow()

  app.on('activate', function () {
    if (BrowserWindow.getAllWindows().length === 0) createWindow()
  })
})

app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') app.quit()
})

## package.json
{
  "name": "several-zoo-diagnose-5ax1c",
  "productName": "several-zoo-diagnose-5ax1c",
  "description": "My Electron application description",
  "keywords": [],
  "main": "./main.js",
  "version": "1.0.0",
  "author": "rudifarkas",
  "scripts": {
    "start": "electron ."
  },
  "dependencies": {},
  "devDependencies": {
    "electron": "21.2.0"
  }
}

## preload.js
const { contextBridge, ipcRenderer } = require('electron')

// 2. Preload defines the function handleCounter
//    that will let the renderer to specify the callback
//    to be called when a message on the channel (pdate-counter)
//    arrives from the main
contextBridge.exposeInMainWorld('electronAPI', {
  handleCounter: (callback) => ipcRenderer.on('update-counter', callback)
})

## renderer.js
const counter = document.getElementById('counter')

// 3. The renderer calls handleCounter to install the callback.
//    The callback will receive the data sent from the main
//    as value and will use it to modify the displayed counter value.
window.electronAPI.handleCounter((event, value) => {
    const oldValue = Number(counter.innerText)
    const newValue = oldValue + value
    counter.innerText = newValue
    event.sender.send('counter-value', newValue)
})

## styles.css
/* styles.css */

/* Add styles here to customize the appearance of your app */
	// 1. Main prepares a Menu that will let the user
	// increment/decrement a counter, whose valu will be displayed
	// in the rendered page
	// On user click, the callback will send a message
	// on the channel (update-counter) with the value to add

	// 2. Preload defines the function handleCounter
	// that will let the renderer to specify the callback
	// to be called when a message on the channel (pdate-counter)
	// arrives from the main

	// 3. The renderer calls handleCounter to install the callback.
	// The callback will receive the data sent from the main
	// as value and will use it to modify the displayed counter value.
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="UTF-8">
	<!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
	<meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self'">
	<title>Menu Counter</title>
	</head>
	<body>
	Current value: <strong id="counter">0</strong>
	<script src="./renderer.js"></script>
	</body>
	</html>
	const {app, BrowserWindow, Menu, ipcMain} = require('electron')
	const path = require('path')

	function createWindow () {
	const mainWindow = new BrowserWindow({
	webPreferences: {
	preload: path.join(__dirname, 'preload.js')
	}
	})

	// 1. Main prepares a Menu that will let the user
	// increment/decrement a counter, whose valu will be displayed
	// in the rendered page
	// On user click, the callback will send a message
	// on the channel (update-counter) with the value to add
	const menu = Menu.buildFromTemplate([
	{
	label: app.name,
	submenu: [
	{
	click: () => mainWindow.webContents.send('update-counter', 1),
	label: 'Increment',
	},
	{
	click: () => mainWindow.webContents.send('update-counter', -1),
	label: 'Decrement',
	}
	]
	}

	])

	Menu.setApplicationMenu(menu)
	mainWindow.loadFile('index.html')

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

	app.whenReady().then(() => {
	ipcMain.on('counter-value', (_event, value) => {
	console.log(value) // will print value to Node console
	})
	createWindow()

	app.on('activate', function () {
	if (BrowserWindow.getAllWindows().length === 0) createWindow()
	})
	})

	app.on('window-all-closed', function () {
	if (process.platform !== 'darwin') app.quit()
	})
	{
	"name": "several-zoo-diagnose-5ax1c",
	"productName": "several-zoo-diagnose-5ax1c",
	"description": "My Electron application description",
	"keywords": [],
	"main": "./main.js",
	"version": "1.0.0",
	"author": "rudifarkas",
	"scripts": {
	"start": "electron ."
	},
	"dependencies": {},
	"devDependencies": {
	"electron": "21.2.0"
	}
	}
	const { contextBridge, ipcRenderer } = require('electron')

	// 2. Preload defines the function handleCounter
	// that will let the renderer to specify the callback
	// to be called when a message on the channel (pdate-counter)
	// arrives from the main
	contextBridge.exposeInMainWorld('electronAPI', {
	handleCounter: (callback) => ipcRenderer.on('update-counter', callback)
	})
	const counter = document.getElementById('counter')

	// 3. The renderer calls handleCounter to install the callback.
	// The callback will receive the data sent from the main
	// as value and will use it to modify the displayed counter value.
	window.electronAPI.handleCounter((event, value) => {
	const oldValue = Number(counter.innerText)
	const newValue = oldValue + value
	counter.innerText = newValue
	event.sender.send('counter-value', newValue)
	})
	/* styles.css */

	/* Add styles here to customize the appearance of your app */