Bug 1511063 - Only send GeckoView history messages when there are listeners r=lina,geckoview-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D13432

--HG--
extra : moz-landing-system : lando

mobile/android/components/geckoview/GeckoViewHistory.cpp

@@ -26,6 +26,9 @@ using namespace mozilla::dom;
 using namespace mozilla::ipc;
 using namespace mozilla::widget;
 
+static const char16_t kOnVisitedMessage[] = u"GeckoView:OnVisited";
+static const char16_t kGetVisitedMessage[] = u"GeckoView:GetVisited";
+
 // Keep in sync with `GeckoSession.HistoryDelegate.VisitFlags`.
 enum class GeckoViewVisitFlags : int32_t {
   VISIT_TOP_LEVEL = 1 << 0,
@@ -386,6 +389,11 @@ GeckoViewHistory::VisitURI(nsIWidget* aWidget, nsIURI* aURI,
     return NS_OK;
   }
 
+  // If nobody is listening for this, we can stop now.
+  if (!dispatcher->HasListener(kOnVisitedMessage)) {
+    return NS_OK;
+  }
+
   AutoTArray<jni::String::LocalRef, 3> keys;
   AutoTArray<jni::Object::LocalRef, 3> values;
 
@@ -444,8 +452,8 @@ GeckoViewHistory::VisitURI(nsIWidget* aWidget, nsIURI* aURI,
   nsCOMPtr<nsIAndroidEventCallback> callback =
       new OnVisitedCallback(this, dispatcher->GetGlobalObject(), aURI);
 
-  Unused << NS_WARN_IF(NS_FAILED(
-      dispatcher->Dispatch(u"GeckoView:OnVisited", bundle, callback)));
+  Unused << NS_WARN_IF(
+      NS_FAILED(dispatcher->Dispatch(kOnVisitedMessage, bundle, callback)));
 
   return NS_OK;
 }
@@ -590,6 +598,11 @@ void GeckoViewHistory::QueryVisitedState(
     return;
   }
 
+  // If nobody is listening for this we can stop now
+  if (!dispatcher->HasListener(kGetVisitedMessage)) {
+    return;
+  }
+
   // Assemble a bundle like `{ urls: ["http://example.com/1", ...] }`.
   auto uris = jni::ObjectArray::New<jni::String>(aURIs.Length());
   for (size_t i = 0; i < aURIs.Length(); ++i) {
@@ -614,8 +627,8 @@ void GeckoViewHistory::QueryVisitedState(
   nsCOMPtr<nsIAndroidEventCallback> callback =
       new GetVisitedCallback(this, dispatcher->GetGlobalObject(), aURIs);
 
-  Unused << NS_WARN_IF(NS_FAILED(
-      dispatcher->Dispatch(u"GeckoView:GetVisited", bundle, callback)));
+  Unused << NS_WARN_IF(
+      NS_FAILED(dispatcher->Dispatch(kGetVisitedMessage, bundle, callback)));
 }
 
 /**

mobile/android/geckoview/src/main/java/org/mozilla/gecko/EventDispatcher.java

@@ -325,6 +325,21 @@ public final class EventDispatcher extends JNIObject {
         return false;
     }
 
+    @WrapForJNI
+    public boolean hasListener(final String event) {
+        for (final Map<String, ?> listenersMap : Arrays.asList(mGeckoThreadListeners,
+                mUiThreadListeners,
+                mBackgroundThreadListeners)) {
+            synchronized (listenersMap) {
+                if (listenersMap.get(event) != null) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
     private boolean dispatchToThread(final String type,
                                      final GeckoBundle message,
                                      final EventCallback callback,

widget/android/EventDispatcher.cpp

@@ -760,6 +760,16 @@ EventDispatcher::WrapCallback(nsIAndroidEventCallback* aCallback,
   return callback;
 }
 
+bool EventDispatcher::HasListener(const char16_t* aEvent) {
+  java::EventDispatcher::LocalRef dispatcher(mDispatcher);
+  if (!dispatcher) {
+    return false;
+  }
+
+  nsDependentString event(aEvent);
+  return dispatcher->HasListener(event);
+}
+
 NS_IMETHODIMP
 EventDispatcher::Dispatch(JS::HandleValue aEvent, JS::HandleValue aData,
                           nsIAndroidEventCallback* aCallback,

widget/android/EventDispatcher.h

@@ -44,6 +44,7 @@ class EventDispatcher final
                     java::GeckoBundle::Param aData = nullptr,
                     nsIAndroidEventCallback* aCallback = nullptr);
 
+  bool HasListener(const char16_t* aEvent);
   bool HasGeckoListener(jni::String::Param aEvent);
   void DispatchToGecko(jni::String::Param aEvent, jni::Object::Param aData,
                        jni::Object::Param aCallback);