Remote assistance on Chrome OS Part VI - Enable It2me on ChromeOS in the webapp

remoting/webapp/crd/js/remoting.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 'use strict';
 
 /** @suppress {duplicate} */
 var remoting = remoting || {};
 
 /** @type {remoting.HostSession} */ remoting.hostSession = null;
@@ skipping 99 matching lines @@
   remoting.showOrHideIT2MeUi();
   remoting.showOrHideMe2MeUi();
 
   // The plugin's onFocus handler sends a paste command to |window|, because
   // it can't send one to the plugin element itself.
   window.addEventListener('paste', pluginGotPaste_, false);
   window.addEventListener('copy', pluginGotCopy_, false);
 
   remoting.initModalDialogs();
 
-  if (isHostModeSupported_()) {
-    var noShare = document.getElementById('chrome-os-no-share');
-    noShare.parentNode.removeChild(noShare);
-  } else {
-    var button = document.getElementById('share-button');
-    button.disabled = true;
-  }
+  isHostModeSupported_().then(
+    /** @param {Boolean} supported */
+    function(supported){
+      if (supported) {

[Jamie, 2014/11/03 19:41:34]

Part of the responsibility of the init method is to replace the "Loading..." UI
with the real UI once everything is ready. By making this asynchronous, is there
a risk of incomplete UI flashing briefly? You could move the call to setMode
into the promise resolution, but that might make the flow harder to understand.

[Jamie, 2014/11/03 23:15:11]

Given the difficulty in fixing this, the relative unlikliness of the problem
having a significant impact, and the fact that we should be able to remove this
code once all ChromeOS releases support sharing, I withdraw my objection. Please
add a TODO for that work.

+        var noShare = document.getElementById('chrome-os-no-share');
+        noShare.parentNode.removeChild(noShare);
+      } else {
+        var button = document.getElementById('share-button');
+        button.disabled = true;
+      }
+    });
 
   /**
    * @return {Promise} A promise that resolves to the id of the current
    * containing tab/window.
    */
   var getCurrentId = function () {
     if (base.isAppsV2()) {
       return Promise.resolve(chrome.app.window.current().id);
     }
 
@@ skipping 60 matching lines @@
   /** @enum {string} */
   remoting.testEvents.Names = {
     uiModeChanged: 'uiModeChanged'
   };
   remoting.testEvents.defineEvents(base.values(remoting.testEvents.Names));
 
   remoting.ClientPlugin.factory.preloadPlugin();
 };
 
 /**
- * Returns whether or not IT2Me is supported via the host NPAPI plugin.
- *
- * @return {boolean}
- */
-function isIT2MeSupported_() {
-  // Currently, IT2Me on Chromebooks is not supported.
-  return !remoting.runningOnChromeOS();
-}
-
-/**
  * Returns true if the current platform is fully supported. It's only used when
  * we detect that host native messaging components are not installed. In that
  * case the result of this function determines if the webapp should show the
  * controls that allow to install and enable Me2Me host.
  *
  * @return {boolean}
  */
 remoting.isMe2MeInstallable = function() {
   // The chromoting host is currently not installable on ChromeOS.
   // For Linux, we have a install package for Ubuntu but not other distros.
@@ skipping 15 matching lines @@
   document.getElementById('get-started-it2me').disabled = false;
   document.getElementById('get-started-me2me').disabled = false;
 };
 
 /**
  * initHomeScreenUi is called if the app is not starting up in session mode,
  * and also if the user cancels pin entry or the connection in session mode.
  */
 remoting.initHomeScreenUi = function() {
   remoting.hostController = new remoting.HostController();
-  document.getElementById('share-button').disabled = !isIT2MeSupported_();
   remoting.setMode(remoting.AppMode.HOME);
   remoting.hostSetupDialog =
       new remoting.HostSetupDialog(remoting.hostController);
   var dialog = document.getElementById('paired-clients-list');
   var message = document.getElementById('paired-client-manager-message');
   var deleteAll = document.getElementById('delete-all-paired-clients');
   var close = document.getElementById('close-paired-client-manager-dialog');
   var working = document.getElementById('paired-client-manager-dialog-working');
   var error = document.getElementById('paired-client-manager-dialog-error');
   var noPairedClients = document.getElementById('no-paired-clients');
@@ skipping 131 matching lines @@
   var event = /** @type {remoting.ClipboardEvent} */ eventUncast;
   if (event && event.clipboardData) {
     if (remoting.clipboard.toOs(event.clipboardData)) {
       // The default action may overwrite items that we added to clipboardData.
       event.preventDefault();
     }
   }
 }
 
 /**
- * Returns whether Host mode is supported on this platform.
+ * Returns whether Host mode is supported on this platform for It2me.
  *
- * @return {boolean} True if Host mode is supported.
+ * @return {Promise} Resolves to true if Host mode is supported.
  */
 function isHostModeSupported_() {
-  // Currently, sharing on Chromebooks is not supported.
-  return !remoting.runningOnChromeOS();
+  if (!remoting.platformIsChromeOS()) {
+    return Promise.resolve(true);
+  }
+  // Sharing on Chrome OS is currently behind a flag.
+  // isInstalled() will return false if the flag is disabled.
+  var hostInstaller = new remoting.HostInstaller();
+  return hostInstaller.isInstalled();
 }
 
 /**
  * @return {Object.<string, string>} The URL parameters.
  */
 function getUrlParameters_() {
   var result = {};
   var parts = window.location.search.substring(1).split('&');
   for (var i = 0; i < parts.length; i++) {
     var pair = parts[i].split('=');
@@ skipping 124 matching lines @@
 }
 
 /**
  * Tests whether we are running on ChromeOS.
  *
  * @return {boolean} True if the platform is ChromeOS.
  */
 remoting.platformIsChromeOS = function() {
   return navigator.userAgent.match(/\bCrOS\b/) != null;
 }