jinx1281255 · December 31, 2018 14:14
diff --git a/clipboard.html b/clipboard.html

 <!DOCTYPE html>
 <html lang="en">
 <head>
 <title>My App - Clipboard</title>

 <meta charset="utf-8">
 <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' chrome-extension://*;">
 </head>
 <body>

 <--
 This is an example of how to poll the clipboard for changes in an Electron application.

 In this example I'm monitoring the clipboard for the possibility of the user copying a login token -
 identified by a prefix - from an email, and then I notify the rest of the app (not shown in this gist)
 so the token can be pasted automatically into a login form.

 The clipboard.js code creates a hidden Electron window containing this HTML, which is essentially an empty document.
 It also does preload injection with preload_clipboard.js, which is what polls the clipboard every 250 ms.
 The code is run in a separate window like this so it doesn't load the main Electron-Node process.
 However, you could run the polling code anywhere that you can access the require('electron') object.
 -->

 </body>
 </html>

diff --git a/clipboard.js b/clipboard.js

 "use strict";

 // Import dependencies.
 let electron =				require('electron');
 let emitter =				require('events').EventEmitter;
 let path =					require('path');
 let url =					require('url');

 // Constants.
 const LOGIN_TOKEN_PREFIX =				'my-app:login-token#';

 /*================================================================================================*/

 /*································································································*/
 /*
 Constructor to create a clipboard instance and initialise its data.
 */
 function Clipboard()
 	{
 	Object.defineProperty(this, 'window',			{value: null,			writable: true});		// The clipboard window.

 	// Setup event handlers for IPC messages.
 	electron.ipcMain.on('clipboard_message', this.ipc_message_handler.bind(this));

 	// Startup the database window.
 	this.create_window();
 	}

 // Set the inheritance prototype of the constructor and name it.
 Clipboard.prototype = Object.create(emitter.prototype, {constructor: {value: Clipboard}});
 Clipboard.prototype.name = '<Clipboard>';

 /*================================================================================================*/

 /*································································································*/
 /*
 Save any data and close window.
 */
 Clipboard.prototype.shutdown = function shutdown()
 	{
 	// Close the window.
 	this.window.close();
 	}

 /*································································································*/
 /*
 Create the clipboard window.
 */
 Clipboard.prototype.create_window = function create_window()
 	{
 	// Create the browser window.
 	this.window = new electron.BrowserWindow(
 		{
 		width:				0,
 		height:				0,
 		show:				false,
 		webPreferences:
 			{
 			nodeIntegration:	false,
 			preload:			path.join(__dirname, 'preload_injectors', 'preload_clipboard.js'),
 			contextIsolation:	true
 			}
 		}
 	);

 	// Load the base HTML of the application.
 	this.window.loadURL(url.format(
 		{
 		pathname: path.join(__dirname, 'clipboard', 'clipboard.html'),
 		protocol: 'file:',
 		slashes: true
 		}
 	));

 	// Open the Chrome Dev Tools.
 //	this.window.webContents.openDevTools();

 	// Setup window event handlers.
 	this.window.on('closed', this.window_closed.bind(this));
 	}

 /*································································································*/
 /*
 Cleanup after the window is closed.
 */
 Clipboard.prototype.window_closed = function window_closed()
 	{
 	// Dereference the window object.
 	this.window = null;
 	}

 /*································································································*/
 /*
 Handle asynchronous clipboard messages coming in.
 */
 Clipboard.prototype.ipc_message_handler = function ipc_message_handler(event, message)
 	{
 	switch(message.action)
 		{
 		case 'clipboard_changed':
 			if(message.value.indexOf(LOGIN_TOKEN_PREFIX) === 0)
 				{
 				// Notify rest of application that useful clipboard content was found.
 				this.emit('clipboard_login_token', message.value.substr(LOGIN_TOKEN_PREFIX.length));
 				}
 			break;
 		}
 	}

 /*================================================================================================*/

 module.exports = Clipboard;
diff --git a/preload_clipboard.js b/preload_clipboard.js

 "use strict";

 let electron =				require('electron');

 let last_value =			null;

 /*================================================================================================*/

 /*································································································*/
 function post_ipc_message(message)
 	{
 	electron.ipcRenderer.send('clipboard_message', message);
 	}

 /*································································································*/
 /*
 Normally the listener would take the form: function listener(event, message){}.
 However, because our windows are sandboxed the event parameter is dropped and all we get
 is the message parameter, so the listener needs to be: function listener(message){}.
 */
 function add_ipc_message_listener(listener)
 	{
 	electron.ipcRenderer.on('ipc_message', listener);
 	}

 /*································································································*/
 function remove_ipc_message_listener(listener)
 	{
 	electron.ipcRenderer.removeListener('ipc_message', listener);
 	}

 /*================================================================================================*/

 function check_clipboard_for_changes()
 	{
 	let value = electron.clipboard.readText();
 	if(last_value !== value)clipboard_changed(value);
 	}

 function clipboard_changed(value)
 	{
 	last_value = value;
 	post_ipc_message({action: 'clipboard_changed', value: value});
 	}

 // Get the initial value of the clipboard.
 clipboard_changed(electron.clipboard.readText());

 // Check for changes at an interval.
 setInterval(check_clipboard_for_changes, 250);

	<!DOCTYPE html>
	<html lang="en">
	<head>
	<title>My App - Clipboard</title>

	<meta charset="utf-8">
	<meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' chrome-extension://*;">
	</head>
	<body>

	<--
	This is an example of how to poll the clipboard for changes in an Electron application.

	In this example I'm monitoring the clipboard for the possibility of the user copying a login token -
	identified by a prefix - from an email, and then I notify the rest of the app (not shown in this gist)
	so the token can be pasted automatically into a login form.

	The clipboard.js code creates a hidden Electron window containing this HTML, which is essentially an empty document.
	It also does preload injection with preload_clipboard.js, which is what polls the clipboard every 250 ms.
	The code is run in a separate window like this so it doesn't load the main Electron-Node process.
	However, you could run the polling code anywhere that you can access the require('electron') object.
	-->

	</body>
	</html>

	"use strict";

	// Import dependencies.
	let electron = require('electron');
	let emitter = require('events').EventEmitter;
	let path = require('path');
	let url = require('url');

	// Constants.
	const LOGIN_TOKEN_PREFIX = 'my-app:login-token#';

	/================================================================================================/

	/································································································/
	/*
	Constructor to create a clipboard instance and initialise its data.
	*/
	function Clipboard()
	{
	Object.defineProperty(this, 'window', {value: null, writable: true}); // The clipboard window.

	// Setup event handlers for IPC messages.
	electron.ipcMain.on('clipboard_message', this.ipc_message_handler.bind(this));

	// Startup the database window.
	this.create_window();
	}

	// Set the inheritance prototype of the constructor and name it.
	Clipboard.prototype = Object.create(emitter.prototype, {constructor: {value: Clipboard}});
	Clipboard.prototype.name = '<Clipboard>';

	/================================================================================================/

	/································································································/
	/*
	Save any data and close window.
	*/
	Clipboard.prototype.shutdown = function shutdown()
	{
	// Close the window.
	this.window.close();
	}

	/································································································/
	/*
	Create the clipboard window.
	*/
	Clipboard.prototype.create_window = function create_window()
	{
	// Create the browser window.
	this.window = new electron.BrowserWindow(
	{
	width: 0,
	height: 0,
	show: false,
	webPreferences:
	{
	nodeIntegration: false,
	preload: path.join(__dirname, 'preload_injectors', 'preload_clipboard.js'),
	contextIsolation: true
	}
	}
	);

	// Load the base HTML of the application.
	this.window.loadURL(url.format(
	{
	pathname: path.join(__dirname, 'clipboard', 'clipboard.html'),
	protocol: 'file:',
	slashes: true
	}
	));

	// Open the Chrome Dev Tools.
	// this.window.webContents.openDevTools();

	// Setup window event handlers.
	this.window.on('closed', this.window_closed.bind(this));
	}

	/································································································/
	/*
	Cleanup after the window is closed.
	*/
	Clipboard.prototype.window_closed = function window_closed()
	{
	// Dereference the window object.
	this.window = null;
	}

	/································································································/
	/*
	Handle asynchronous clipboard messages coming in.
	*/
	Clipboard.prototype.ipc_message_handler = function ipc_message_handler(event, message)
	{
	switch(message.action)
	{
	case 'clipboard_changed':
	if(message.value.indexOf(LOGIN_TOKEN_PREFIX) === 0)
	{
	// Notify rest of application that useful clipboard content was found.
	this.emit('clipboard_login_token', message.value.substr(LOGIN_TOKEN_PREFIX.length));
	}
	break;
	}
	}

	/================================================================================================/

	module.exports = Clipboard;

	"use strict";

	let electron = require('electron');

	let last_value = null;

	/================================================================================================/

	/································································································/
	function post_ipc_message(message)
	{
	electron.ipcRenderer.send('clipboard_message', message);
	}

	/································································································/
	/*
	Normally the listener would take the form: function listener(event, message){}.
	However, because our windows are sandboxed the event parameter is dropped and all we get
	is the message parameter, so the listener needs to be: function listener(message){}.
	*/
	function add_ipc_message_listener(listener)
	{
	electron.ipcRenderer.on('ipc_message', listener);
	}

	/································································································/
	function remove_ipc_message_listener(listener)
	{
	electron.ipcRenderer.removeListener('ipc_message', listener);
	}

	/================================================================================================/

	function check_clipboard_for_changes()
	{
	let value = electron.clipboard.readText();
	if(last_value !== value)clipboard_changed(value);
	}

	function clipboard_changed(value)
	{
	last_value = value;
	post_ipc_message({action: 'clipboard_changed', value: value});
	}

	// Get the initial value of the clipboard.
	clipboard_changed(electron.clipboard.readText());

	// Check for changes at an interval.
	setInterval(check_clipboard_for_changes, 250);