feat: add 'disableDesktopSharing' option (#548)

* feat: add 'disableDesktopSharing' option

* ref(ScreenObtainer): simplify init

doc/API.md

@@ -38,24 +38,25 @@ You can access the following methods and objects trough ```JitsiMeetJS``` object
 
 *  ```JitsiMeetJS.init(options)``` - this method initialized Jitsi Meet API.
 The ```options``` parameter is JS object with the following properties:
-    1. useIPv6 - boolean property
-    2. desktopSharingChromeExtId - The ID of the jidesha extension for Chrome. Example: 'mbocklcggfhnbahlnepmldehdhpjfcjp'
-    3. desktopSharingChromeDisabled - Boolean. Whether desktop sharing should be disabled on Chrome. Example: false.
-    4. desktopSharingChromeSources - Array of strings with the media sources to use when using screen sharing with the Chrome extension. Example: ['screen', 'window']
-    5. desktopSharingChromeMinExtVersion - Required version of Chrome extension. Example: '0.1'
-    6. desktopSharingFirefoxExtId - The ID of the jidesha extension for Firefox. If null, we assume that no extension is required.
-    7. desktopSharingFirefoxDisabled - Boolean. Whether desktop sharing should be disabled on Firefox. Example: false.
-    8. desktopSharingFirefoxMaxVersionExtRequired - The maximum version of Firefox which requires a jidesha extension. Example: if set to 41, we will require the extension for Firefox versions up to and including 41. On Firefox 42 and higher, we will run without the extension. If set to -1, an extension will be required for all versions of Firefox.
-    9. desktopSharingFirefoxExtensionURL - The URL to the Firefox extension for desktop sharing. "null" if no extension is required.
-    10. disableAudioLevels - boolean property. Enables/disables audio levels.
-    11. disableSimulcast - boolean property. Enables/disables simulcast.
-    12. enableWindowOnErrorHandler - boolean property (default false). Enables/disables attaching global onerror handler (window.onerror).
-    13. disableThirdPartyRequests - if true - callstats will be disabled and the callstats API won't be included.
-    14. enableAnalyticsLogging - boolean property (default false). Enables/disables analytics logging.
-    15. callStatsCustomScriptUrl - (optional) custom url to access callstats client script
-    16. callStatsConfIDNamespace - (optional) a namespace to prepend the callstats conference ID with. Defaults to the window.location.hostname
-    17. disableRtx - (optional) boolean property (default to false).  Enables/disable the use of RTX.
-    18. preferH264 - (optional) boolean property (default to false).  Enables/disable preferring the first instance of an h264 codec in an offer by moving it to the front of the codec list.
+    - `useIPv6` - boolean property
+    - `disableDesktopSharing` - Boolean. When set to true disables desktop sharing on all browsers. 
+    - `desktopSharingChromeExtId` - The ID of the jidesha extension for Chrome. Example: 'mbocklcggfhnbahlnepmldehdhpjfcjp'
+    - `desktopSharingChromeDisabled` - Boolean. Whether desktop sharing should be disabled on Chrome. Example: false.
+    - `desktopSharingChromeSources` - Array of strings with the media sources to use when using screen sharing with the Chrome extension. Example: ['screen', 'window']
+    - `desktopSharingChromeMinExtVersion` - Required version of Chrome extension. Example: '0.1'
+    - `desktopSharingFirefoxExtId` - The ID of the jidesha extension for Firefox. If null, we assume that no extension is required.
+    - `desktopSharingFirefoxDisabled` - Boolean. Whether desktop sharing should be disabled on Firefox. Example: false.
+    - `desktopSharingFirefoxMaxVersionExtRequired` - The maximum version of Firefox which requires a jidesha extension. Example: if set to 41, we will require the extension for Firefox versions up to and including 41. On Firefox 42 and higher, we will run without the extension. If set to -1, an extension will be required for all versions of Firefox.
+    - `desktopSharingFirefoxExtensionURL` - The URL to the Firefox extension for desktop sharing. "null" if no extension is required.
+    - `disableAudioLevels` - boolean property. Enables/disables audio levels.
+    - `disableSimulcast` - boolean property. Enables/disables simulcast.
+    - `enableWindowOnErrorHandler` - boolean property (default false). Enables/disables attaching global onerror handler (window.onerror).
+    - `disableThirdPartyRequests` - if true - callstats will be disabled and the callstats API won't be included.
+    - `enableAnalyticsLogging` - boolean property (default false). Enables/disables analytics logging.
+    - `callStatsCustomScriptUrl` - (optional) custom url to access callstats client script
+    - `callStatsConfIDNamespace` - (optional) a namespace to prepend the callstats conference ID with. Defaults to the window.location.hostname
+    - `disableRtx` - (optional) boolean property (default to false).  Enables/disable the use of RTX.
+    - `preferH264` - (optional) boolean property (default to false).  Enables/disable preferring the first instance of an h264 codec in an offer by moving it to the front of the codec list.
 
 * ```JitsiMeetJS.JitsiConnection``` - the ```JitsiConnection``` constructor. You can use that to create new server connection.
 

modules/RTC/ScreenObtainer.js

@@ -66,29 +66,53 @@ const ScreenObtainer = {
      * Initializes the function used to obtain a screen capture
      * (this.obtainStream).
      *
-     * @param options {object}
-     * @param gum {Function} GUM method
+     * @param {object} options
+     * @param {boolean} [options.disableDesktopSharing]
+     * @param {boolean} [options.desktopSharingChromeDisabled]
+     * @param {boolean} [options.desktopSharingChromeExtId]
+     * @param {boolean} [options.desktopSharingFirefoxDisabled]
+     * @param {boolean} [options.desktopSharingFirefoxExtId] (deprecated)
+     * @param {Function} gum GUM method
      */
-    init(options, gum) {
-        let obtainDesktopStream = null;
-
+    init(options = {
+        disableDesktopSharing: false,
+        desktopSharingChromeDisabled: false,
+        desktopSharingChromeExtId: null,
+        desktopSharingFirefoxDisabled: false,
+        desktopSharingFirefoxExtId: null
+    }, gum) {
         // eslint-disable-next-line no-param-reassign
         this.options = options = options || {};
         gumFunction = gum;
 
-        if (RTCBrowserType.isFirefox()) {
-            initFirefoxExtensionDetection(options);
+        this.obtainStream
+            = this.options.disableDesktopSharing
+                ? null : this._createObtainStreamMethod(options);
+
+        if (!this.obtainStream) {
+            logger.info('Desktop sharing disabled');
         }
+    },
 
+    /**
+     * Returns a method which will be used to obtain the screen sharing stream
+     * (based on the browser type).
+     *
+     * @param {object} options passed from {@link init} - check description
+     * there
+     * @returns {Function}
+     * @private
+     */
+    _createObtainStreamMethod(options) {
         if (RTCBrowserType.isNWJS()) {
-            obtainDesktopStream = (_, onSuccess, onFailure) => {
+            return (_, onSuccess, onFailure) => {
                 window.JitsiMeetNW.obtainDesktopStream(
                     onSuccess,
                     (error, constraints) => {
                         let jitsiError;
 
                         // FIXME:
-                        // This is very very durty fix for recognising that the
+                        // This is very very dirty fix for recognising that the
                         // user have clicked the cancel button from the Desktop
                         // sharing pick window. The proper solution would be to
                         // detect this in the NWJS application by checking the
@@ -116,57 +140,67 @@ const ScreenObtainer = {
                     });
             };
         } else if (RTCBrowserType.isElectron()) {
-            obtainDesktopStream = this.obtainScreenOnElectron;
+            return this.obtainScreenOnElectron;
         } else if (RTCBrowserType.isTemasysPluginUsed()) {
             // XXX Don't require Temasys unless it's to be used because it
             // doesn't run on React Native, for example.
             const plugin
                 = require('./adapter.screenshare').WebRTCPlugin.plugin;
 
-            if (plugin.HasScreensharingFeature) {
-                if (plugin.isScreensharingAvailable) {
-                    obtainDesktopStream = obtainWebRTCScreen;
-                    logger.info('Using Temasys plugin for desktop sharing');
-                } else {
-                    logger.info(
-                        'Screensharing not available with Temasys plugin on'
-                            + ' this site');
-                }
-            } else {
-                logger.info(
+            if (!plugin.HasScreensharingFeature) {
+                logger.warn(
                     'Screensharing not supported by this plugin version');
+
+                return null;
+            } else if (!plugin.isScreensharingAvailable) {
+                logger.warn(
+                    'Screensharing not available with Temasys plugin on'
+                        + ' this site');
+
+                return null;
             }
+
+            logger.info('Using Temasys plugin for desktop sharing');
+
+            return obtainWebRTCScreen;
         } else if (RTCBrowserType.isChrome()) {
-            if (options.desktopSharingChromeDisabled
+            if (RTCBrowserType.getChromeVersion() < 34) {
+                logger.info('Chrome extension not supported until ver 34');
+
+                return null;
+            } else if (options.desktopSharingChromeDisabled
                 || options.desktopSharingChromeMethod === false
                 || !options.desktopSharingChromeExtId) {
+
                 // TODO: desktopSharingChromeMethod is deprecated, remove.
-                obtainDesktopStream = null;
-            } else if (RTCBrowserType.getChromeVersion() >= 34) {
-                obtainDesktopStream
-                    = this.obtainScreenFromExtension;
-                logger.info('Using Chrome extension for desktop sharing');
-                initChromeExtension(options);
-            } else {
-                logger.info('Chrome extension not supported until ver 34');
+                return null;
             }
+
+            logger.info('Using Chrome extension for desktop sharing');
+            initChromeExtension(options);
+
+            return this.obtainScreenFromExtension;
         } else if (RTCBrowserType.isFirefox()) {
             if (options.desktopSharingFirefoxDisabled) {
-                obtainDesktopStream = null;
+                return null;
             } else if (window.location.protocol === 'http:') {
                 logger.log('Screen sharing is not supported over HTTP. '
                     + 'Use of HTTPS is required.');
-                obtainDesktopStream = null;
-            } else {
-                obtainDesktopStream = this.obtainScreenOnFirefox;
+
+                return null;
             }
-        }
 
-        if (!obtainDesktopStream) {
-            logger.info('Desktop sharing disabled');
+            initFirefoxExtensionDetection(options);
+
+            return this.obtainScreenOnFirefox;
         }
 
-        this.obtainStream = obtainDesktopStream;
+        logger.warn(
+            'Screen sharing not supported by the current browser: ',
+            RTCBrowserType.getBrowserType(),
+            RTCBrowserType.getBrowserName());
+
+        return null;
     },
 
     /**