Create NWjs kiosk that spans multiple displays in OSX

init.js

/**
 * There may be a better way to do this and I'd love to hear of them. This technique revolves around 2 specifics:
 * 1. In OSX Mavericks+ you need to set the displays to not have their own "space"; I have bruted this by adding a cmd 
 *    to actually write this preference on each app start. Needless to say this should NOT be done to an unsuspecting user...
 * 2. Kiosk mode should be set BEFORE setting the width and height of your window. Below I include a function that will calculate 
 *    all available space and position the window relatively to the "main" screen.
 */
 
// require the GUI object so that we can access Window and Screen
var gui = require("nw.gui");
// Shelljs is a package that runs bash commands from node
var shell = require('shelljs');
// Execute a cmd line to set Mission Control displays to be treated as single space
shell.exec("defaults write com.apple.spaces spans-displays -bool true", function (code, output) {
    // ... Run code upon completion here ...
});

var win = gui.Window.get();
win.height = 1080;
win.width = 1920;

// init must be called once during startup, before any function to gui.Screen can be called
gui.Screen.Init();


var screens = gui.Screen.screens;
var len = screens.length;
var height = 0;
var width = 0;
var screenOffsetX = 0;
var screenOffsetY = 0;

/**
 * Function to calculate available screens and offsets and automatically
 * resize and place the kiosk window
 * @return {void}
 */
function calculateScreens() {
    var i = 0;

    // store all the screen information into string
    for (; i < len; i++) {
        var bounds = screens[i].bounds;

        // Always treats the 'main' screen as first in array, which has x and y of 0
        if (bounds.x !== 0) {
            if (bounds.x < 0) {
                screenOffsetX = Math.min(screenOffsetX, bounds.x);
            }
        }

        if (bounds.y !== 0) {
            if (bounds.y < 0) {
                screenOffsetY = Math.min(screenOffsetY, bounds.y);
            }
        }

        width += bounds.width;
        height += bounds.height;

        // Here enter kioskMode before setting the window width, height and offsets
        win.enterKioskMode();
        win.width = width;
        win.height = height;
        win.moveTo(screenOffsetX, screenOffsetY);
    }
}

/**
 * Utitlity function to allow toggling kioskMode - connect to some trigger like keypress
 * @return {void}
 */
function toggleKiosk() {
    alert("kiosk")
    win.toggleKioskMode();
}

/**
 * Utitlity function to allow close kiosk - connect to some trigger like keypress
 * @return {void}
 */
function closeWindow() {
    alert("close")
    win.close();
}

// EVENTS
win.on("loaded", function (){
    calculateScreens();
});

win.on("close", function () {
    // Pretend to be closed already
    this.hide();
    this.close(true);
});