Add basic versioning check to Chromoting's plugin/JS code.

remoting/client/appengine/static_files/chromoting_session.js

 // Copyright (c) 2011 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.
 
 // Maximum numer of lines to record in the debug log.
 // Only the most recent <n> lines are displayed.
 var MAX_DEBUG_LOG_SIZE = 1000;
 
+// Chromoting session API version (for this javascript).
+// This is compared with the plugin API version to verify that they are
+// compatible.
+chromoting.apiVersion = 42;

[Jamie, 2011/05/25 00:29:34]

Apart from the HHGTTG reference, why 42? Left-over debugging?

[garykac, 2011/05/25 16:39:44]

Indeed. leftover debugging. I fixed up the webapp version, but missed this.
grr...

+
+// The oldest API version that we support.
+// This will differ from the |apiVersion| if we decide to maintain backward
+// compatibility with older API versions.
+chromoting.apiMinVersion = 1;
+
 // Message id so that we can identify (and ignore) message fade operations for
 // old messages.  This starts at 1 and is incremented for each new message.
 chromoting.messageId = 1;
 
 chromoting.scaleToFit = false;
 
 // Default to trying to sandboxed connections.
 chromoting.connectMethod = 'sandboxed';
 
 // This executes a poll loop on the server for more Iq packets, and feeds them
@@ skipping 68 matching lines @@
   var xhr = new XMLHttpRequest();
   xhr.open("POST", chromoting.httpXmppProxy + '/sendIq', true);
   xhr.withCredentials = true;
   xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
   xhr.send("to=" + encodeURIComponent(to) +
            "&payload_xml=" + encodeURIComponent(payload_xml) +
            "&id=" + id + "&type=" + type +
            "&host_jid=" + encodeURIComponent(chromoting.hostjid));
 }
 
+function checkVersion(plugin) {
+  return chromoting.apiVersion >= plugin.apiMinVersion &&
+      plugin.apiVersion >= chromoting.apiMinVersion;
+}
+
 function init() {
   // Kick off the connection.
   var plugin = document.getElementById('chromoting');
 
   chromoting.plugin = plugin;
   chromoting.username = document.username;
   chromoting.hostname = document.hostname;
   chromoting.hostjid = document.hostjid;
   chromoting.talkToken = document.talkToken;
   chromoting.connectMethod = document.connectMethod;
@@ skipping 10 matching lines @@
   chromoting.httpXmppProxy = document.httpXmppProxy;
 
   // Setup the callback that the plugin will call when the connection status
   // has changes and the UI needs to be updated. It needs to be an object with
   // a 'callback' property that contains the callback function.
   plugin.connectionInfoUpdate = connectionInfoUpdateCallback;
   plugin.debugInfo = debugInfoCallback;
   plugin.desktopSizeUpdate = desktopSizeChanged;
   plugin.loginChallenge = loginChallengeCallback;
 
+  if (!checkVersion(plugin)) {
+    // TODO(garykac): We need better messaging here. Perhaps an install link.
+    setClientStateMessage("Out of date. Please re-install.");
+    return;
+  }
+
   addToDebugLog('Connect to ' + chromoting.hostname + ' as user ' +
                 chromoting.username);
 
   // TODO(garykac): Clean exit if |connect| isn't a function.
   if (typeof plugin.connect === 'function') {
     if (chromoting.connectMethod == "sandboxed") {
       registerConnection();
     } else {
       // TODO:(jamiewalch): Pass in the correct nonce.
       plugin.connect(chromoting.username, chromoting.hostjid,
@@ skipping 204 matching lines @@
   setClientStateMessage(
       "Video stats: bandwidth: " + videoBandwidth.toFixed(2) + "Kbps" +
       ", Latency: capture: " + videoCaptureLatency.toFixed(2) + "ms" +
       ", encode: " + videoEncodeLatency.toFixed(2) + "ms" +
       ", decode: " + videoDecodeLatency.toFixed(2) + "ms" +
       ", render: " + videoRenderLatency.toFixed(2) + "ms");
 
   // Update the stats once per second.
   window.setTimeout("updateStatusBarStats()", 1000);
 }