Add Gerrit.on('history', f) to JS plugin API

The history event is fired when the browser displays a new screen.  It
replaces the older gerrit_addHistoryHook(f) function.  To give plugins
and site owners time to migrate the UI will continue supporting the
old function.

Change-Id: I3fdaa326b50cae1daa24564c4f1b3349fdc765fe

Documentation/config-themes.txt

@@ -104,12 +104,13 @@ To connect Gerrit to Google Analytics add the following to your
       var pageTracker = _gat._getTracker("UA-nnnnnnn-n");
       pageTracker._trackPageview();
     </script>
-  <!-- /standard analytics code -->
+  be <!-- /standard analytics code -->
 
   <script type="text/javascript">
     window.onload = function() {
-      gerrit_addHistoryHook(function (s) {
-        pageTracker._trackPageview(s.replace(/#/, '/'))
+      var p = window.location.pathname;
+      Gerrit.on('history', function (s) {
+        pageTracker._trackPageview(p + '/' + s)
       });
     };
   </script>
@@ -124,19 +125,22 @@ If your footer is otherwise empty, wrap all of the script tags into
 a single `<div>` tag (like above) to ensure it is a well-formed
 XHTML document file.
 
-The global function `gerrit_addHistoryHook` accepts functions that
+The global function `Gerrit.on("history")` accepts functions that
 accept a string parameter.  These functions are put into a list and
 invoked any time Gerrit shifts URLs.  You'll see page names like
-`/#change,123` be passed to these functions, which in turn
-are handed off to Google Analytics for tracking.  Our example hook
-above replaces '#' with '/' because Analytics won't track anchors.
+`/c/123` be passed to these functions, which in turn are handed off
+to Google Analytics for tracking.  Our example hook above uses '/'
+instead of '#' because Analytics won't track anchors.
 
 The `window.onload` callback is necessary to ensure that the
-`gerrit_addHistoryHook` function has actually been defined by the
+`Gerrit.on()` function has actually been defined by the
 page.  Because GWT loads the module asynchronously any `<script>`
 block in the header or footer will execute before Gerrit has defined
 the function and is ready to register the hook callback.
 
+The function `gerrit_addHistoryHook` is deprecated and may be
+removed in a future release.
+
 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]

Documentation/js-api.txt

@@ -148,6 +148,11 @@ Gerrit.on(event, callback);
 
 Supported events:
 
+* `history`: Invoked when the view is changed to a new page within the
+  Gerrit web application.  The token after "#" is passed as the
+  argument to the callback function, for example "/c/42/" while
+  showing change 42.
+
 * `showchange`: Invoked when a change is made visible. A
   link:rest-api-changes.html#change-info[ChangeInfo] and
   link:rest-api-changes.html#revision-info[RevisionInfo]

gerrit-gwtui/src/main/java/com/google/gerrit/client/Gerrit.java

@@ -92,7 +92,6 @@ import com.google.gwtjsonrpc.client.impl.ResultDeserializer;
 import com.google.gwtjsonrpc.common.AsyncCallback;
 import com.google.gwtorm.client.KeyUtil;
 
-import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -446,38 +445,13 @@ public class Gerrit implements EntryPoint {
     }
   }
 
-  private static ArrayList<JavaScriptObject> historyHooks;
   private static Anchor signInAnchor;
 
-  private static native void initHistoryHooks()
-  /*-{ $wnd['gerrit_addHistoryHook'] = function(h) { @com.google.gerrit.client.Gerrit::addHistoryHook(Lcom/google/gwt/core/client/JavaScriptObject;)(h); }; }-*/;
-
-  static void addHistoryHook(final JavaScriptObject hook) {
-    if (historyHooks == null) {
-      historyHooks = new ArrayList<JavaScriptObject>();
-      History.addValueChangeHandler(new ValueChangeHandler<String>() {
-        @Override
-        public void onValueChange(ValueChangeEvent<String> event) {
-          dispatchHistoryHooks(event.getValue());
-        }
-      });
-    }
-    historyHooks.add(hook);
-  }
-
-  private static native void callHistoryHook(JavaScriptObject hook, String url)
-  /*-{ hook(url); }-*/;
-
-  private static void dispatchHistoryHooks(final String historyToken) {
+  private static void dispatchHistoryHooks(String token) {
     if (signInAnchor != null) {
-      signInAnchor.setHref(loginRedirect(historyToken));
-    }
-    if (historyHooks != null) {
-      final String url = Location.getPath() + "#" + historyToken;
-      for (final JavaScriptObject hook : historyHooks) {
-        callHistoryHook(hook, url);
-      }
+      signInAnchor.setHref(loginRedirect(token));
     }
+    ApiGlue.fireEvent("history", token);
   }
 
   private static void populateBottomMenu(RootPanel btmmenu, HostPageData hpd) {
@@ -572,15 +546,15 @@ public class Gerrit implements EntryPoint {
     gStarting.getElement().getParentElement().removeChild(
         gStarting.getElement());
     RootPanel.detachNow(gStarting);
+    ApiGlue.init();
 
     applyUserPreferences();
-    initHistoryHooks();
     populateBottomMenu(bottomMenu, hpd);
     refreshMenuBar();
 
     History.addValueChangeHandler(new ValueChangeHandler<String>() {
       @Override
-      public void onValueChange(final ValueChangeEvent<String> event) {
+      public void onValueChange(ValueChangeEvent<String> event) {
         display(event.getValue());
       }
     });
@@ -607,7 +581,6 @@ public class Gerrit implements EntryPoint {
   }
 
   private void loadPlugins(HostPageData hpd, final String token) {
-    ApiGlue.init();
     if (hpd.plugins != null && !hpd.plugins.isEmpty()) {
       for (final String url : hpd.plugins) {
         ScriptInjector.fromUrl(url)

gerrit-gwtui/src/main/java/com/google/gerrit/client/api/ApiGlue.java

@@ -26,6 +26,7 @@ public class ApiGlue {
   public static void init() {
     init0();
     ActionContext.init();
+    addHistoryHook();
   }
 
   private static native void init0() /*-{
@@ -110,6 +111,14 @@ public class ApiGlue {
     $wnd.Gerrit = Gerrit;
   }-*/;
 
+  /** Install deprecated {@code gerrit_addHistoryHook()} function. */
+  private static native void addHistoryHook() /*-{
+    $wnd.gerrit_addHistoryHook = function(h) {
+      var p = @com.google.gwt.user.client.Window.Location::getPath()();
+      $wnd.Gerrit.on('history', function(t) { h(p + "#" + t) })
+     };
+  }-*/;
+
   private static void install(JavaScriptObject cb, JavaScriptObject p) {
     try {
       pluginName = PluginName.get();
@@ -142,6 +151,13 @@ public class ApiGlue {
   static final native void invoke(JavaScriptObject f, JavaScriptObject a, JavaScriptObject b) /*-{ f(a,b) }-*/;
   static final native void invoke(JavaScriptObject f, String a) /*-{ f(a); }-*/;
 
+  public static final void fireEvent(String event, String a) {
+    JsArray<JavaScriptObject> h = getEventHandlers(event);
+    for (int i = 0; i < h.length(); i++) {
+      invoke(h.get(i), a);
+    }
+  }
+
   static final void fireEvent(String event, JavaScriptObject a, JavaScriptObject b) {
     JsArray<JavaScriptObject> h = getEventHandlers(event);
     for (int i = 0; i < h.length(); i++) {