chrome.js

var detect = require('rtc-core/detect');
var extend = require('cog/extend');
var OPT_DEFAULTS = {
  target: 'rtc.io screenshare'
};
var REQUEST_OPTS = {
  targets: ['screen', 'window']
};
var CHROME_VERSION = getChromeVersion();

// Chrome >= 50 allows for greater sharing options
if (CHROME_VERSION >= 50) {
  REQUEST_OPTS.targets.push('tab');

  REQUEST_OPTS.targets.push('audio');
}

/**
  Returns true if we should use Chrome screensharing
 **/
exports.supported = function() {
  return detect.browser === 'chrome';
}

/**
  Creates the share context.
 **/
exports.share = function(opts) {

  // if disableAudio, then hide the checkbox in the popup
  if (!(opts || {}).disableAudio) {
    var index = REQUEST_OPTS.targets.indexOf('audio');
    if (index !== -1) REQUEST_OPTS.targets.splice(index, 1);
  }

  var extension = require('chromex/client')(extend({}, OPT_DEFAULTS, opts, {
    target: (opts || {}).chromeExtension
  }));

  extension.type = 'google/chrome';

  extension.available = function(callback) {
    return extension.satisfies((opts || {}).version, callback);
  };

  // patch in our capture function
  extension.request = function(callback) {
    var requestOptions = extend({}, REQUEST_OPTS, (opts || {}).requests || {});
    extension.sendCommand('share', requestOptions, function(err, sourceId) {
      if (err) {
        return callback(err);
      }

      if (! sourceId) {
        return callback(new Error('user rejected screen share request'));
      }

      var audioConstraints = false;
      // Support audio on Chrome 50+
      if (CHROME_VERSION >= 50 && !(opts || {}).disableAudio) {
        audioConstraints = {
          mandatory: {
            chromeMediaSource: 'desktop',
            chromeMediaSourceId: sourceId
          }
        };
      }

      // pass the constraints through
      return callback(null, extend({
        audio: audioConstraints,
        video: {
          mandatory: {
            chromeMediaSource: 'desktop',
            chromeMediaSourceId: sourceId,
            maxWidth: screen.width,
            maxHeight: screen.height,
            minFrameRate: 1,
            maxFrameRate: 5
          },
          optional: []
        }
      }, opts.constraints));
    });
  };

  extension.cancel = function() {
    extension.sendCommand('cancel', function(err) {
    });
  };

  return extension;
};

function getChromeVersion() {
  var raw = navigator.userAgent.match(/Chrom(e|ium)\/([0-9]+)\./);
  return raw ? parseInt(raw[2], 10) : -1;
}