feat(external_api) facilitate gDM Electron

In order to use gDM in Electron the flow is somewhat reversed. It starts
from the Electron main process, so we need an API in the external_api
that can trigger the builtin picker. The picker is still necessary.

modules/API/API.js

@@ -75,6 +75,7 @@ import {
     toggleChat
 } from '../../react/features/chat/actions';
 import { openChat } from '../../react/features/chat/actions.web';
+import { showDesktopPicker } from '../../react/features/desktop-picker/actions';
 import {
     processExternalDeviceRequest
 } from '../../react/features/device-selection/functions';
@@ -1048,6 +1049,23 @@ function initCommands() {
         }
         case '_new_electron_screensharing_supported': {
             callback(true);
+
+            break;
+        }
+        case 'open-desktop-picker': {
+            const { desktopSharingSources } = APP.store.getState()['features/base/config'];
+            const options = {
+                desktopSharingSources: desktopSharingSources ?? [ 'screen', 'window' ]
+            };
+            const onSourceChoose = (_streamId, _type, screenShareAudio, source) => {
+                callback({
+                    screenShareAudio,
+                    source
+                });
+            };
+
+            dispatch(showDesktopPicker(options, onSourceChoose));
+
             break;
         }
         default:

modules/API/external/external_api.js

@@ -1243,7 +1243,7 @@ export default class JitsiMeetExternalAPI extends EventEmitter {
      * @returns {Promise}
      *
      * TODO: should be removed after we make sure that all Electron clients use only versions
-     * after with the legacy SS suport was removed from the electron SDK. If we remove it now the SS for Electron
+     * after with the legacy SS support was removed from the electron SDK. If we remove it now the SS for Electron
      * clients with older versions wont work.
      */
     _isNewElectronScreensharingSupported() {
@@ -1455,4 +1455,15 @@ export default class JitsiMeetExternalAPI extends EventEmitter {
     setVirtualBackground(enabled, backgroundImage) {
         this.executeCommand('setVirtualBackground', enabled, backgroundImage);
     }
+
+    /**
+     * Opens the desktop picker. This is invoked by the Electron SDK when gDM is used.
+     *
+     * @returns {Promise}
+     */
+    _openDesktopPicker() {
+        return this._transport.sendRequest({
+            name: 'open-desktop-picker'
+        });
+    }
 }