Fevol/index.html

## 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'; style-src 'self' 'unsafe-inline'">
    <link href="./styles.css" rel="stylesheet">
    <title>Hello World!</title>
  </head>
  <body>
    <h1>Hello World!</h1>

    <!-- You can also require other files to run in this process -->
    <script src="./renderer.js"></script>
  </body>
</html>

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

function createWindow () {
  session.defaultSession.setSpellCheckerLanguages(['en-US'])

  ipcMain.on('update-spellchecker-languages', (event, languages) => {
    session.defaultSession.setSpellCheckerLanguages(languages)
    console.log("Updated spellchecker languages: ", session.defaultSession.getSpellCheckerLanguages())
  });

  // Create the browser window.
  const mainWindow = new BrowserWindow({
    width: 450,
    height: 600,
    webPreferences: {
      preload: path.join(__dirname, 'preload.js'),
      spellcheck: true,
    }
  })

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

  // 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()

  app.on('activate', function () {
    // On macOS 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()
  })
})

// 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()
})

// 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
// All of the Node.js APIs are available in the preload process.
// It has the same sandbox as a Chrome extension.
const { contextBridge, ipcRenderer, webFrame, ipcMain } = require('electron');

// Test helpers
const test = {
  assert: (ok, ...logs) => {
    if (!ok) test.fail(...logs)
  },
  fail: (...logs) => test.done(false, ...logs),
  done: (success = true, ...logs) => {
    if (!success) logs.unshift(new Error('test failed'))
    ipcRenderer.send('test-done', success, ...logs)
  },
  isWordMisspelled: (str) => webFrame.isWordMisspelled(str),
  getSpellCheckerSuggestions: (str) => webFrame.getWordSuggestions(str),
  setSpellCheckerLanguages: (languages) => ipcRenderer.send('update-spellchecker-languages', languages),
};

contextBridge.exposeInMainWorld('test', test);


window.addEventListener('DOMContentLoaded', () => {
  const platform_information = document.createElement('div');
  platform_information.style.marginTop = '20px';
  document.body.appendChild(platform_information);

  platform_information.innerText = `platform: ${process.platform} ${process.arch}\nelectron: ${process.versions.electron}\nnode: ${process.versions.node}\nchrome: ${process.versions.chrome}`;
})

## renderer.js
/**
 * This file is loaded via the <script> tag in the index.html file and will
 * be executed in the renderer process for that window. No Node.js APIs are
 * available in this process because `nodeIntegration` is turned off and
 * `contextIsolation` is turned on. Use the contextBridge API in `preload.js`
 * to expose Node.js functionality from the main process.
 */

let element = document.createElement('textarea');
element.spellcheck = true;
element.value = 'ths is an incorrctly spelld englsh sentense\ndt is een fuot gesplde nederlands zin\nund ein faelsch geschrjebener deutschez Satz';
element.style = "min-width: 400px; min-height: 100px; margin-bottom: 10px;";

document.body.appendChild(element);
element.focus();

let selected_text = '';

let text_selection = document.createElement('div');
document.body.appendChild(text_selection);
text_selection.innerText = "selection: ";

let selection_is_misspelled = document.createElement('div');
document.body.appendChild(selection_is_misspelled);
selection_is_misspelled.innerText = "misspelled: ";

let spellchecker_suggestions = document.createElement('div');
document.body.appendChild(spellchecker_suggestions);
spellchecker_suggestions.innerText = "suggestions: ";

function update_spellchecker() {
    text_selection.innerText = "selection: " + selected_text;
    selection_is_misspelled.innerText = "misspelled: " + window.test.isWordMisspelled(selected_text);
    spellchecker_suggestions.innerText = "suggestions: " + window.test.getSpellCheckerSuggestions(selected_text) || 'no suggestions';
}

element.onmouseup = function() {
    selected_text = element.value.substring(element.selectionStart, element.selectionEnd);
    update_spellchecker();
}


let spellchecker_languages = ['en-US'];

let current_spellchecker_languages = document.createElement('div');
current_spellchecker_languages.style.marginTop = '20px';


// Spellchecker languages: currently selected and selectable

document.body.appendChild(current_spellchecker_languages);
current_spellchecker_languages.innerText = "current spellchecker languages: ";
update_languages();
available_spellchecker_languages = document.createElement('select');

let option = document.createElement('option');
option.innerText = "add language";
option.value = "";
available_spellchecker_languages.appendChild(option);

document.body.appendChild(available_spellchecker_languages);
const all_spellchecker_languages = ['af', 'pt', 'nl', 'en-US', 'en-GB', 'fr', 'de', 'es', 'it'];
for (let i = 0; i < all_spellchecker_languages.length; i++) {
    let option = document.createElement('option');
    available_spellchecker_languages.appendChild(option);
    option.value = all_spellchecker_languages[i];
    option.innerText = all_spellchecker_languages[i];
}
available_spellchecker_languages.onchange = function() {
    if (!spellchecker_languages.includes(available_spellchecker_languages.value)) {
        spellchecker_languages.push(available_spellchecker_languages.value);
        window.test.setSpellCheckerLanguages(spellchecker_languages);
        update_languages();
        // Wait 0.3 ms for spellchecker to update
        setTimeout(function() { update_spellchecker() }, 300);
    }
    available_spellchecker_languages.value = "";
}

function update_languages() {
    current_spellchecker_languages.innerHTML = "current spellchecker languages: ";

    for (let i = 0; i < spellchecker_languages.length; i++) {
        let language = document.createElement('span');
        language.innerText = spellchecker_languages[i];
        language.style = "margin-right: 10px; cursor: pointer; text-decoration: underline;";
        language.onclick = function() {
            spellchecker_languages.splice(i, 1);
            window.test.setSpellCheckerLanguages(spellchecker_languages);
            update_languages();
            // Wait 0.3 ms for spellchecker to update
            setTimeout(function() { update_spellchecker() }, 300);
        }
        current_spellchecker_languages.appendChild(language);
    }
}
	<!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'; style-src 'self' 'unsafe-inline'">
	<link href="./styles.css" rel="stylesheet">
	<title>Hello World!</title>
	</head>
	<body>
	<h1>Hello World!</h1>

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

	function createWindow () {
	session.defaultSession.setSpellCheckerLanguages(['en-US'])

	ipcMain.on('update-spellchecker-languages', (event, languages) => {
	session.defaultSession.setSpellCheckerLanguages(languages)
	console.log("Updated spellchecker languages: ", session.defaultSession.getSpellCheckerLanguages())
	});

	// Create the browser window.
	const mainWindow = new BrowserWindow({
	width: 450,
	height: 600,
	webPreferences: {
	preload: path.join(__dirname, 'preload.js'),
	spellcheck: true,
	}
	})

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

	// 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()

	app.on('activate', function () {
	// On macOS 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()
	})
	})

	// 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()
	})

	// 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.
	// All of the Node.js APIs are available in the preload process.
	// It has the same sandbox as a Chrome extension.
	const { contextBridge, ipcRenderer, webFrame, ipcMain } = require('electron');

	// Test helpers
	const test = {
	assert: (ok, ...logs) => {
	if (!ok) test.fail(...logs)
	},
	fail: (...logs) => test.done(false, ...logs),
	done: (success = true, ...logs) => {
	if (!success) logs.unshift(new Error('test failed'))
	ipcRenderer.send('test-done', success, ...logs)
	},
	isWordMisspelled: (str) => webFrame.isWordMisspelled(str),
	getSpellCheckerSuggestions: (str) => webFrame.getWordSuggestions(str),
	setSpellCheckerLanguages: (languages) => ipcRenderer.send('update-spellchecker-languages', languages),
	};

	contextBridge.exposeInMainWorld('test', test);


	window.addEventListener('DOMContentLoaded', () => {
	const platform_information = document.createElement('div');
	platform_information.style.marginTop = '20px';
	document.body.appendChild(platform_information);

	platform_information.innerText = `platform: ${process.platform} ${process.arch}\nelectron: ${process.versions.electron}\nnode: ${process.versions.node}\nchrome: ${process.versions.chrome}`;
	})
	/**
	* This file is loaded via the <script> tag in the index.html file and will
	* be executed in the renderer process for that window. No Node.js APIs are
	* available in this process because `nodeIntegration` is turned off and
	* `contextIsolation` is turned on. Use the contextBridge API in `preload.js`
	* to expose Node.js functionality from the main process.
	*/

	let element = document.createElement('textarea');
	element.spellcheck = true;
	element.value = 'ths is an incorrctly spelld englsh sentense\ndt is een fuot gesplde nederlands zin\nund ein faelsch geschrjebener deutschez Satz';
	element.style = "min-width: 400px; min-height: 100px; margin-bottom: 10px;";

	document.body.appendChild(element);
	element.focus();

	let selected_text = '';

	let text_selection = document.createElement('div');
	document.body.appendChild(text_selection);
	text_selection.innerText = "selection: ";

	let selection_is_misspelled = document.createElement('div');
	document.body.appendChild(selection_is_misspelled);
	selection_is_misspelled.innerText = "misspelled: ";

	let spellchecker_suggestions = document.createElement('div');
	document.body.appendChild(spellchecker_suggestions);
	spellchecker_suggestions.innerText = "suggestions: ";

	function update_spellchecker() {
	text_selection.innerText = "selection: " + selected_text;
	selection_is_misspelled.innerText = "misspelled: " + window.test.isWordMisspelled(selected_text);
	spellchecker_suggestions.innerText = "suggestions: " + window.test.getSpellCheckerSuggestions(selected_text) \|\| 'no suggestions';
	}

	element.onmouseup = function() {
	selected_text = element.value.substring(element.selectionStart, element.selectionEnd);
	update_spellchecker();
	}


	let spellchecker_languages = ['en-US'];

	let current_spellchecker_languages = document.createElement('div');
	current_spellchecker_languages.style.marginTop = '20px';



	// Spellchecker languages: currently selected and selectable

	document.body.appendChild(current_spellchecker_languages);
	current_spellchecker_languages.innerText = "current spellchecker languages: ";
	update_languages();
	available_spellchecker_languages = document.createElement('select');

	let option = document.createElement('option');
	option.innerText = "add language";
	option.value = "";
	available_spellchecker_languages.appendChild(option);

	document.body.appendChild(available_spellchecker_languages);
	const all_spellchecker_languages = ['af', 'pt', 'nl', 'en-US', 'en-GB', 'fr', 'de', 'es', 'it'];
	for (let i = 0; i < all_spellchecker_languages.length; i++) {
	let option = document.createElement('option');
	available_spellchecker_languages.appendChild(option);
	option.value = all_spellchecker_languages[i];
	option.innerText = all_spellchecker_languages[i];
	}
	available_spellchecker_languages.onchange = function() {
	if (!spellchecker_languages.includes(available_spellchecker_languages.value)) {
	spellchecker_languages.push(available_spellchecker_languages.value);
	window.test.setSpellCheckerLanguages(spellchecker_languages);
	update_languages();
	// Wait 0.3 ms for spellchecker to update
	setTimeout(function() { update_spellchecker() }, 300);
	}
	available_spellchecker_languages.value = "";
	}

	function update_languages() {
	current_spellchecker_languages.innerHTML = "current spellchecker languages: ";

	for (let i = 0; i < spellchecker_languages.length; i++) {
	let language = document.createElement('span');
	language.innerText = spellchecker_languages[i];
	language.style = "margin-right: 10px; cursor: pointer; text-decoration: underline;";
	language.onclick = function() {
	spellchecker_languages.splice(i, 1);
	window.test.setSpellCheckerLanguages(spellchecker_languages);
	update_languages();
	// Wait 0.3 ms for spellchecker to update
	setTimeout(function() { update_spellchecker() }, 300);
	}
	current_spellchecker_languages.appendChild(language);
	}
	}