getscreenmedia/getscreenmedia.js

// getScreenMedia helper by @HenrikJoreteg
var getUserMedia = require('getusermedia');

// cache for constraints and callback
var cache = {};

module.exports = function (constraints, cb) {
    var hasConstraints = arguments.length === 2;
    var callback = hasConstraints ? cb : constraints;
    var error;

    if (typeof window === 'undefined' || window.location.protocol === 'http:') {
        error = new Error('NavigatorUserMediaError');
        error.name = 'HTTPS_REQUIRED';
        return callback(error);
    }

    if (window.navigator.userAgent.match('Chrome')) { 
        var chromever = parseInt(window.navigator.userAgent.match(/Chrome\/(.*) /)[1], 10);
        var maxver = 33;
        // "known" crash in chrome 34 and 35 on linux
        if (window.navigator.userAgent.match('Linux')) maxver = 35;
        if (chromever >= 26 && chromever <= maxver) {
            // chrome 26 - chrome 33 way to do it -- requires bad chrome://flags
            // note: this is basically in maintenance mode and will go away soon
            constraints = (hasConstraints && constraints) || { 
                video: {
                    mandatory: {
                        googLeakyBucket: true,
                        maxWidth: window.screen.width,
                        maxHeight: window.screen.height,
                        maxFrameRate: 3,
                        chromeMediaSource: 'screen'
                    }
                }
            };
            getUserMedia(constraints, callback);
        } else {
            // chrome 34+ way requiring an extension
            var pending = window.setTimeout(function () {
                error = new Error('NavigatorUserMediaError');
                error.name = 'EXTENSION_UNAVAILABLE';
                return callback(error);
            }, 1000);
            cache[pending] = [callback, hasConstraints ? constraint : null];
            window.postMessage({ type: 'getScreen', id: pending }, '*');
        }
    } else if (window.navigator.userAgent.match('Firefox')) {
        var ffver = parseInt(window.navigator.userAgent.match(/Firefox\/(.*)/)[1], 10);
        if (ffver >= 33) {
            constraints = (hasConstraints && constraints) || {
                video: {
                    mozMediaSource: 'window',
                    mediaSource: 'window'
                }
            }
            getUserMedia(constraints, function (err, stream) {
                callback(err, stream);
                // workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1045810
                if (!err) {
                    var lastTime = stream.currentTime;
                    var polly = window.setInterval(function () {
                        if (!stream) window.clearInterval(polly);
                        if (stream.currentTime == lastTime) {
                            window.clearInterval(polly);
                            if (stream.onended) {
                                stream.onended();
                            }
                        }
                        lastTime = stream.currentTime;
                    }, 500);
                }
            });
        } else {
            error = new Error('NavigatorUserMediaError');
            error.name = 'EXTENSION_UNAVAILABLE'; // does not make much sense but...
        }
    }
};

window.addEventListener('message', function (event) { 
    if (event.origin != window.location.origin) {
        return;
    }
    if (event.data.type == 'gotScreen' && cache[event.data.id]) {
        var data = cache[event.data.id];
        var constraints = data[1];
        var callback = data[0];
        delete cache[event.data.id];

        if (event.data.sourceId === '') { // user canceled
            var error = new Error('NavigatorUserMediaError');
            error.name = 'PERMISSION_DENIED';
            callback(error);
        } else {
            constraints = constraints || {audio: false, video: {
                mandatory: {
                    chromeMediaSource: 'desktop',
                    maxWidth: window.screen.width,
                    maxHeight: window.screen.height,
                    maxFrameRate: 3
                },
                optional: [
                    {googLeakyBucket: true},
                    {googTemporalLayeredScreencast: true}
                ]
            }};
            constraints.video.mandatory.chromeMediaSourceId = event.data.sourceId;
            getUserMedia(constraints, callback);
        }
    } else if (event.data.type == 'getScreenPending') {
        window.clearTimeout(event.data.id);
    }
});