Bug 1562761 - Add support for dispatching java runnables to Gecko event targets. r=snorp

Differential Revision: https://phabricator.services.mozilla.com/D52197

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

ipc/glue/GeckoChildProcessHost.cpp

@@ -179,8 +179,6 @@ class BaseProcessLauncher {
     return XRE_ChildProcessTypeToString(mProcessType);
   }
 
-  nsCOMPtr<nsIEventTarget> GetIPCLauncher();
-
   nsCOMPtr<nsISerialEventTarget> mLaunchThread;
   GeckoProcessType mProcessType;
   UniquePtr<base::LaunchOptions> mLaunchOptions;
@@ -840,7 +838,7 @@ IPCLaunchThreadObserver::Observe(nsISupports* aSubject, const char* aTopic,
   return rv;
 }
 
-nsCOMPtr<nsIEventTarget> BaseProcessLauncher::GetIPCLauncher() {
+nsCOMPtr<nsIEventTarget> GetIPCLauncher() {
   StaticMutexAutoLock lock(gIPCLaunchThreadMutex);
   if (!gIPCLaunchThread) {
     nsCOMPtr<nsIThread> thread;
@@ -867,7 +865,7 @@ nsCOMPtr<nsIEventTarget> BaseProcessLauncher::GetIPCLauncher() {
 
 // Other platforms use an on-demand thread pool.
 
-nsCOMPtr<nsIEventTarget> BaseProcessLauncher::GetIPCLauncher() {
+nsCOMPtr<nsIEventTarget> GetIPCLauncher() {
   nsCOMPtr<nsIEventTarget> pool =
       mozilla::SharedThreadPool::Get(NS_LITERAL_CSTRING("IPC Launch"));
   MOZ_DIAGNOSTIC_ASSERT(pool);

ipc/glue/GeckoChildProcessHost.h

@@ -271,6 +271,8 @@ class GeckoChildProcessHost : public ChildProcessHost,
   static StaticMutex sMutex;
 };
 
+nsCOMPtr<nsIEventTarget> GetIPCLauncher();
+
 } /* namespace ipc */
 } /* namespace mozilla */
 

mobile/android/geckoview/src/main/java/org/mozilla/gecko/util/XPCOMEventTarget.java

@@ -0,0 +1,58 @@
+/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.util;
+
+import org.mozilla.gecko.annotation.WrapForJNI;
+import org.mozilla.gecko.mozglue.JNIObject;
+
+/**
+ * Wrapper for nsIEventTarget, enabling seamless dispatch of java runnables to
+ * Gecko event queues.
+ */
+@WrapForJNI
+public final class XPCOMEventTarget extends JNIObject {
+    public void dispatch(final Runnable runnable) {
+        dispatchNative(new JNIRunnable(runnable));
+    }
+
+    public static synchronized XPCOMEventTarget mainThread() {
+        if (mMainThread == null) {
+            mMainThread = createWrapper("main");
+        }
+        return mMainThread;
+    }
+    private static XPCOMEventTarget mMainThread = null;
+
+    public static synchronized XPCOMEventTarget launcherThread() {
+        if (mLauncherThread == null) {
+            mLauncherThread = createWrapper("launcher");
+        }
+        return mLauncherThread;
+    }
+    private static XPCOMEventTarget mLauncherThread = null;
+
+    public native boolean isOnCurrentThread();
+    private native void dispatchNative(JNIRunnable runnable);
+    private static native XPCOMEventTarget createWrapper(String name);
+
+    @Override
+    protected native void disposeNative();
+
+    @WrapForJNI
+    final class JNIRunnable {
+        JNIRunnable(final Runnable inner) {
+            mInner = inner;
+        }
+
+        @WrapForJNI
+        void run() {
+            mInner.run();
+        }
+
+        private Runnable mInner;
+    }
+}
+

widget/android/nsAppShell.cpp

@@ -34,6 +34,7 @@
 #include "mozilla/Hal.h"
 #include "mozilla/dom/BrowserChild.h"
 #include "mozilla/intl/OSPreferences.h"
+#include "mozilla/ipc/GeckoChildProcessHost.h"
 #include "mozilla/widget/ScreenManager.h"
 #include "prenv.h"
 
@@ -350,6 +351,47 @@ class GeckoAppShellSupport final
   }
 };
 
+class XPCOMEventTargetWrapper final
+    : public java::XPCOMEventTarget::Natives<XPCOMEventTargetWrapper> {
+ public:
+  // Wraps a java runnable into an XPCOM runnable and dispatches it to mTarget.
+  void DispatchNative(mozilla::jni::Object::Param aJavaRunnable) {
+    java::XPCOMEventTarget::JNIRunnable::GlobalRef r =
+        java::XPCOMEventTarget::JNIRunnable::Ref::From(aJavaRunnable);
+    mTarget->Dispatch(NS_NewRunnableFunction(
+        "XPCOMEventTargetWrapper::DispatchNative",
+        [runnable = std::move(r)]() { runnable->Run(); }));
+  }
+
+  bool IsOnCurrentThread() { return mTarget->IsOnCurrentThread(); }
+
+  // Instantiates a wrapper. The Java code calls this only once per wrapped
+  // thread, and caches the result.
+  static java::XPCOMEventTarget::LocalRef CreateWrapper(
+      mozilla::jni::String::Param aName) {
+    nsString name(aName->ToString());
+    nsCOMPtr<nsIEventTarget> target;
+    if (name.EqualsLiteral("main")) {
+      target = do_GetMainThread();
+    } else if (name.EqualsLiteral("launcher")) {
+      target = ipc::GetIPCLauncher();
+    } else {
+      MOZ_CRASH("Trying to create JNI wrapper for unknown XPCOM thread");
+    }
+
+    auto java = java::XPCOMEventTarget::New();
+    auto native = MakeUnique<XPCOMEventTargetWrapper>(target.forget());
+    AttachNative(java, std::move(native));
+    return java;
+  }
+
+  explicit XPCOMEventTargetWrapper(already_AddRefed<nsIEventTarget> aTarget)
+      : mTarget(aTarget) {}
+
+ private:
+  nsCOMPtr<nsIEventTarget> mTarget;
+};
+
 nsAppShell::nsAppShell()
     : mSyncRunFinished(*(sAppShellLock = new Mutex("nsAppShell")),
                        "nsAppShell.SyncRun"),
@@ -365,6 +407,7 @@ nsAppShell::nsAppShell()
     if (jni::IsAvailable()) {
       GeckoThreadSupport::Init();
       GeckoAppShellSupport::Init();
+      XPCOMEventTargetWrapper::Init();
       mozilla::GeckoSystemStateListener::Init();
       mozilla::widget::Telemetry::Init();
       mozilla::widget::GeckoTelemetryDelegate::Init();
@@ -383,6 +426,7 @@ nsAppShell::nsAppShell()
     AndroidBridge::ConstructBridge();
     GeckoAppShellSupport::Init();
     GeckoThreadSupport::Init();
+    XPCOMEventTargetWrapper::Init();
     mozilla::GeckoBatteryManager::Init();
     mozilla::GeckoNetworkManager::Init();
     mozilla::GeckoProcessManager::Init();