Use appEvents for page tracking so widgets can listen to it easily

app/assets/javascripts/discourse/initializers/page-tracking.js.es6

@@ -1,9 +1,10 @@
 import { cleanDOM } from 'discourse/lib/clean-dom';
-import { startPageTracking, onPageChange } from 'discourse/lib/page-tracker';
+import { startPageTracking } from 'discourse/lib/page-tracker';
 import { viewTrackingRequired } from 'discourse/lib/ajax';
 
 export default {
   name: "page-tracking",
+  after: 'inject-objects',
 
   initialize(container) {
 
@@ -12,33 +13,34 @@ export default {
     router.on('willTransition', viewTrackingRequired);
     router.on('didTransition', cleanDOM);
 
-    startPageTracking(router);
+    let appEvents = container.lookup('app-events:main');
+    startPageTracking(router, appEvents);
 
     // Out of the box, Discourse tries to track google analytics
     // if it is present
     if (typeof window._gaq !== 'undefined') {
-      onPageChange((url, title) => {
-        window._gaq.push(["_set", "title", title]);
-        window._gaq.push(['_trackPageview', url]);
+      appEvents.on('page:changed', data => {
+        window._gaq.push(["_set", "title", data.title]);
+        window._gaq.push(['_trackPageview', data.url]);
       });
       return;
     }
 
     // Also use Universal Analytics if it is present
     if (typeof window.ga !== 'undefined') {
-      onPageChange((url, title) => {
-        window.ga('send', 'pageview', {page: url, title: title});
+      appEvents.on('page:changed', data => {
+        window.ga('send', 'pageview', {page: data.url, title: data.title});
       });
     }
 
     // And Google Tag Manager too
     if (typeof window.dataLayer !== 'undefined') {
-      onPageChange((url, title) => {
+      appEvents.on('page:changed', data => {
         window.dataLayer.push({
           'event': 'virtualPageView',
           'page': {
-            'title': title,
-            'url': url
+            'title': data.title,
+            'url': data.url
           }
         });
       });

app/assets/javascripts/discourse/initializers/subscribe-user-notifications.js.es6

@@ -13,6 +13,7 @@ export default {
     const user = container.lookup('current-user:main');
     const keyValueStore = container.lookup('key-value-store:main');
     const bus = container.lookup('message-bus:main');
+    const appEvents = container.lookup('app-events:main');
 
     // clear old cached notifications, we used to store in local storage
     // TODO 2017 delete this line
@@ -33,7 +34,6 @@ export default {
 
       bus.subscribe(`/notification/${user.get('id')}`, data => {
         const store = container.lookup('store:main');
-        const appEvents = container.lookup('app-events:main');
 
         const oldUnread = user.get('unread_notifications');
         const oldPM = user.get('unread_private_messages');
@@ -102,7 +102,7 @@ export default {
       if (!Ember.testing) {
         if (!site.mobileView) {
           bus.subscribe(alertChannel(user), data => onNotification(data, user));
-          initDesktopNotifications(bus);
+          initDesktopNotifications(bus, appEvents);
         }
       }
     }

app/assets/javascripts/discourse/lib/desktop-notifications.js.es6

@@ -1,6 +1,5 @@
 import DiscourseURL from 'discourse/lib/url';
 import KeyValueStore from 'discourse/lib/key-value-store';
-import { onPageChange } from 'discourse/lib/page-tracker';
 
 let primaryTab = false;
 let liveEnabled = false;
@@ -15,7 +14,7 @@ const context = "discourse_desktop_notifications_";
 const keyValueStore = new KeyValueStore(context);
 
 // Called from an initializer
-function init(messageBus) {
+function init(messageBus, appEvents) {
   liveEnabled = false;
   mbClientId = messageBus.clientId;
 
@@ -49,14 +48,14 @@ function init(messageBus) {
   liveEnabled = true;
   try {
     // Preliminary checks passed, continue with setup
-    setupNotifications();
+    setupNotifications(appEvents);
   } catch (e) {
     Em.Logger.error(e);
   }
 }
 
 // This function is only called if permission was granted
-function setupNotifications() {
+function setupNotifications(appEvents) {
 
   window.addEventListener("storage", function(e) {
     // note: This event only fires when other tabs setItem()
@@ -85,7 +84,7 @@ function setupNotifications() {
     document.addEventListener("scroll", resetIdle);
   }
 
-  onPageChange(resetIdle);
+  appEvents.on('page:changed', resetIdle);
 }
 
 function resetIdle() {

app/assets/javascripts/discourse/lib/page-tracker.js.es6

@@ -1,8 +1,3 @@
-import deprecated from 'discourse-common/lib/deprecated';
-
-const PageTracker = Ember.Object.extend(Ember.Evented);
-let _pageTracker = PageTracker.create();
-
 let _started = false;
 
 const cache = {};
@@ -16,7 +11,7 @@ export function getTransient(key) {
   return cache[key];
 }
 
-export function startPageTracking(router) {
+export function startPageTracking(router, appEvents) {
   if (_started) { return; }
 
   router.on('didTransition', function() {
@@ -25,7 +20,10 @@ export function startPageTracking(router) {
 
     // Refreshing the title is debounced, so we need to trigger this in the
     // next runloop to have the correct title.
-    Em.run.next(() => _pageTracker.trigger('change', url, Discourse.get('_docTitle')));
+    Ember.run.next(() => {
+      let title = Discourse.get('_docTitle');
+      appEvents.trigger('page:changed', { url, title });
+    });
 
     transitionCount++;
     _.each(cache, (v,k) => {
@@ -36,18 +34,3 @@ export function startPageTracking(router) {
   });
   _started = true;
 }
-
-export function onPageChange(fn) {
-  _pageTracker.on('change', fn);
-}
-
-// backwards compatibility
-const BackwardsCompat = {
-  current() {
-    deprecated(`Using PageTracker.current() is deprecated. Your plugin should use the PluginAPI`);
-    return _pageTracker;
-  }
-};
-
-Discourse.PageTracker = BackwardsCompat;
-export default BackwardsCompat;

app/assets/javascripts/discourse/lib/plugin-api.js.es6

@@ -6,7 +6,6 @@ import { includeAttributes } from 'discourse/lib/transform-post';
 import { addToolbarCallback } from 'discourse/components/d-editor';
 import { addWidgetCleanCallback } from 'discourse/components/mount-widget';
 import { createWidget, reopenWidget, decorateWidget, changeSetting } from 'discourse/widgets/widget';
-import { onPageChange } from 'discourse/lib/page-tracker';
 import { preventCloak } from 'discourse/widgets/post-stream';
 import { h } from 'virtual-dom';
 import { addFlagProperty } from 'discourse/components/site-header';
@@ -350,7 +349,8 @@ class PluginApi {
     ```
   **/
   onPageChange(fn) {
-    onPageChange(fn);
+    let appEvents = this.container.lookup('app-events:main');
+    appEvents.on('page:changed', data => fn(data.url, data.title));
   }
 
   /**