1 files changed, 373 insertions, 0 deletions
diff --git a/widget/android/AndroidUiThread.cpp b/widget/android/AndroidUiThread.cpp
new file mode 100644
index 0000000000..97a5105787
--- /dev/null
+++ b/widget/android/AndroidUiThread.cpp
@@ -0,0 +1,373 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "base/message_loop.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/EventQueue.h"
+#include "mozilla/java/GeckoThreadWrappers.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Monitor.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/ThreadEventQueue.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/UniquePtr.h"
+#include "GeckoProfiler.h"
+#include "nsThread.h"
+#include "nsThreadManager.h"
+#include "nsThreadUtils.h"
+
+#include <android/api-level.h>
+#include <pthread.h>
+
+using namespace mozilla;
+
+namespace {
+
+class AndroidUiThread;
+class AndroidUiTask;
+
+StaticAutoPtr<LinkedList<AndroidUiTask> > sTaskQueue;
+StaticAutoPtr<mozilla::Mutex> sTaskQueueLock;
+StaticRefPtr<AndroidUiThread> sThread;
+static bool sThreadDestroyed;
+static MessageLoop* sMessageLoop;
+static Atomic<Monitor*> sMessageLoopAccessMonitor;
+
+void EnqueueTask(already_AddRefed<nsIRunnable> aTask, int aDelayMs);
+
+/*
+ * The AndroidUiThread is derived from nsThread so that nsIRunnable objects that
+ * get dispatched may be intercepted. Only nsIRunnable objects that need to be
+ * synchronously executed are passed into the nsThread to be queued. All other
+ * nsIRunnable object are immediately dispatched to the Android UI thread.
+ * AndroidUiThread is derived from nsThread instead of being an nsIEventTarget
+ * wrapper that contains an nsThread object because if nsIRunnable objects with
+ * a delay were dispatch directly to an nsThread object, such as obtained from
+ * nsThreadManager::GetCurrentThread(), the nsIRunnable could get stuck in the
+ * nsThread nsIRunnable queue. This is due to the fact that Android controls the
+ * event loop in the Android UI thread and has no knowledge of when the nsThread
+ * needs to be drained.
+ */
+
+class AndroidUiThread : public nsThread {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_INHERITED(AndroidUiThread, nsThread)
+  AndroidUiThread()
+      : nsThread(
+            MakeNotNull<ThreadEventQueue*>(MakeUnique<mozilla::EventQueue>()),
+            nsThread::NOT_MAIN_THREAD, {.stackSize = 0}) {}
+
+  nsresult Dispatch(already_AddRefed<nsIRunnable> aEvent,
+                    uint32_t aFlags) override;
+  nsresult DelayedDispatch(already_AddRefed<nsIRunnable> aEvent,
+                           uint32_t aDelayMs) override;
+
+ private:
+  ~AndroidUiThread() {}
+};
+
+NS_IMETHODIMP
+AndroidUiThread::Dispatch(already_AddRefed<nsIRunnable> aEvent,
+                          uint32_t aFlags) {
+  EnqueueTask(std::move(aEvent), 0);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+AndroidUiThread::DelayedDispatch(already_AddRefed<nsIRunnable> aEvent,
+                                 uint32_t aDelayMs) {
+  EnqueueTask(std::move(aEvent), aDelayMs);
+  return NS_OK;
+}
+
+static void PumpEvents() { NS_ProcessPendingEvents(sThread.get()); }
+
+class ThreadObserver : public nsIThreadObserver {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSITHREADOBSERVER
+
+  ThreadObserver() {}
+
+ private:
+  virtual ~ThreadObserver() {}
+};
+
+NS_IMPL_ISUPPORTS(ThreadObserver, nsIThreadObserver)
+
+NS_IMETHODIMP
+ThreadObserver::OnDispatchedEvent() {
+  EnqueueTask(NS_NewRunnableFunction("PumpEvents", &PumpEvents), 0);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ThreadObserver::OnProcessNextEvent(nsIThreadInternal* thread, bool mayWait) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ThreadObserver::AfterProcessNextEvent(nsIThreadInternal* thread,
+                                      bool eventWasProcessed) {
+  return NS_OK;
+}
+
+class AndroidUiTask : public LinkedListElement<AndroidUiTask> {
+  using TimeStamp = mozilla::TimeStamp;
+  using TimeDuration = mozilla::TimeDuration;
+
+ public:
+  explicit AndroidUiTask(already_AddRefed<nsIRunnable> aTask)
+      : mTask(aTask),
+        mRunTime()  // Null timestamp representing no delay.
+  {}
+
+  AndroidUiTask(already_AddRefed<nsIRunnable> aTask, int aDelayMs)
+      : mTask(aTask),
+        mRunTime(TimeStamp::Now() + TimeDuration::FromMilliseconds(aDelayMs)) {}
+
+  bool IsEarlierThan(const AndroidUiTask& aOther) const {
+    if (mRunTime) {
+      return aOther.mRunTime ? mRunTime < aOther.mRunTime : false;
+    }
+    // In the case of no delay, we're earlier if aOther has a delay.
+    // Otherwise, we're not earlier, to maintain task order.
+    return !!aOther.mRunTime;
+  }
+
+  int64_t MillisecondsToRunTime() const {
+    if (mRunTime) {
+      return int64_t((mRunTime - TimeStamp::Now()).ToMilliseconds());
+    }
+    return 0;
+  }
+
+  already_AddRefed<nsIRunnable> TakeTask() { return mTask.forget(); }
+
+ private:
+  nsCOMPtr<nsIRunnable> mTask;
+  const TimeStamp mRunTime;
+};
+
+class CreateOnUiThread : public Runnable {
+ public:
+  CreateOnUiThread() : Runnable("CreateOnUiThread") {}
+
+  NS_IMETHOD Run() override {
+    MOZ_ASSERT(!sThreadDestroyed);
+    MOZ_ASSERT(sMessageLoopAccessMonitor);
+    MonitorAutoLock lock(*sMessageLoopAccessMonitor);
+    sThread = new AndroidUiThread();
+    sThread->InitCurrentThread();
+    sThread->SetObserver(new ThreadObserver());
+    RegisterThreadWithProfiler();
+    sMessageLoop =
+        new MessageLoop(MessageLoop::TYPE_MOZILLA_ANDROID_UI, sThread.get());
+    lock.NotifyAll();
+    return NS_OK;
+  }
+
+ private:
+  static void RegisterThreadWithProfiler() {
+#if defined(MOZ_GECKO_PROFILER)
+    // We don't use the PROFILER_REGISTER_THREAD macro here because by this
+    // point the Android UI thread is already quite a ways into its stack;
+    // the profiler's sampler thread will ignore a lot of frames if we do not
+    // provide a better value for the stack top. We'll manually obtain that
+    // info via pthreads.
+
+    // Fallback address if any pthread calls fail
+    char fallback;
+    char* stackTop = &fallback;
+
+    auto regOnExit = MakeScopeExit(
+        [&stackTop]() { profiler_register_thread("AndroidUI", stackTop); });
+
+    pthread_attr_t attrs;
+    if (pthread_getattr_np(pthread_self(), &attrs)) {
+      return;
+    }
+
+    void* stackBase;
+    size_t stackSize;
+    if (pthread_attr_getstack(&attrs, &stackBase, &stackSize)) {
+      return;
+    }
+
+    stackTop = static_cast<char*>(stackBase) + stackSize - 1;
+#endif  // defined(MOZ_GECKO_PROFILER)
+  }
+};
+
+class DestroyOnUiThread : public Runnable {
+ public:
+  DestroyOnUiThread() : Runnable("DestroyOnUiThread"), mDestroyed(false) {}
+
+  NS_IMETHOD Run() override {
+    MOZ_ASSERT(!sThreadDestroyed);
+    MOZ_ASSERT(sMessageLoopAccessMonitor);
+    MOZ_ASSERT(sTaskQueue);
+    MonitorAutoLock lock(*sMessageLoopAccessMonitor);
+    sThreadDestroyed = true;
+
+    {
+      // Flush the queue
+      MutexAutoLock lock(*sTaskQueueLock);
+      while (AndroidUiTask* task = sTaskQueue->getFirst()) {
+        delete task;
+      }
+    }
+
+    delete sMessageLoop;
+    sMessageLoop = nullptr;
+    MOZ_ASSERT(sThread);
+    PROFILER_UNREGISTER_THREAD();
+    nsThreadManager::get().UnregisterCurrentThread(*sThread);
+    sThread = nullptr;
+    mDestroyed = true;
+    lock.NotifyAll();
+    return NS_OK;
+  }
+
+  void WaitForDestruction() {
+    MOZ_ASSERT(sMessageLoopAccessMonitor);
+    MonitorAutoLock lock(*sMessageLoopAccessMonitor);
+    while (!mDestroyed) {
+      lock.Wait();
+    }
+  }
+
+ private:
+  bool mDestroyed;
+};
+
+void EnqueueTask(already_AddRefed<nsIRunnable> aTask, int aDelayMs) {
+  if (sThreadDestroyed) {
+    return;
+  }
+
+  // add the new task into the sTaskQueue, sorted with
+  // the earliest task first in the queue
+  AndroidUiTask* newTask =
+      (aDelayMs ? new AndroidUiTask(std::move(aTask), aDelayMs)
+                : new AndroidUiTask(std::move(aTask)));
+
+  bool headOfList = false;
+  {
+    MOZ_ASSERT(sTaskQueue);
+    MOZ_ASSERT(sTaskQueueLock);
+    MutexAutoLock lock(*sTaskQueueLock);
+
+    AndroidUiTask* task = sTaskQueue->getFirst();
+
+    while (task) {
+      if (newTask->IsEarlierThan(*task)) {
+        task->setPrevious(newTask);
+        break;
+      }
+      task = task->getNext();
+    }
+
+    if (!newTask->isInList()) {
+      sTaskQueue->insertBack(newTask);
+    }
+    headOfList = !newTask->getPrevious();
+  }
+
+  if (headOfList) {
+    // if we're inserting it at the head of the queue, notify Java because
+    // we need to get a callback at an earlier time than the last scheduled
+    // callback
+    java::GeckoThread::RequestUiThreadCallback(int64_t(aDelayMs));
+  }
+}
+
+}  // namespace
+
+namespace mozilla {
+
+void CreateAndroidUiThread() {
+  MOZ_ASSERT(!sThread);
+  MOZ_ASSERT(!sMessageLoopAccessMonitor);
+  sTaskQueue = new LinkedList<AndroidUiTask>();
+  sTaskQueueLock = new Mutex("AndroidUiThreadTaskQueueLock");
+  sMessageLoopAccessMonitor =
+      new Monitor("AndroidUiThreadMessageLoopAccessMonitor");
+  sThreadDestroyed = false;
+  RefPtr<CreateOnUiThread> runnable = new CreateOnUiThread;
+  EnqueueTask(do_AddRef(runnable), 0);
+}
+
+void DestroyAndroidUiThread() {
+  MOZ_ASSERT(sThread);
+  RefPtr<DestroyOnUiThread> runnable = new DestroyOnUiThread;
+  EnqueueTask(do_AddRef(runnable), 0);
+  runnable->WaitForDestruction();
+  delete sMessageLoopAccessMonitor;
+  sMessageLoopAccessMonitor = nullptr;
+}
+
+MessageLoop* GetAndroidUiThreadMessageLoop() {
+  if (!sMessageLoopAccessMonitor) {
+    return nullptr;
+  }
+
+  MonitorAutoLock lock(*sMessageLoopAccessMonitor);
+  while (!sMessageLoop) {
+    lock.Wait();
+  }
+
+  return sMessageLoop;
+}
+
+RefPtr<nsThread> GetAndroidUiThread() {
+  if (!sMessageLoopAccessMonitor) {
+    return nullptr;
+  }
+
+  MonitorAutoLock lock(*sMessageLoopAccessMonitor);
+  while (!sThread) {
+    lock.Wait();
+  }
+
+  return sThread;
+}
+
+int64_t RunAndroidUiTasks() {
+  MutexAutoLock lock(*sTaskQueueLock);
+
+  if (sThreadDestroyed) {
+    return -1;
+  }
+
+  while (!sTaskQueue->isEmpty()) {
+    AndroidUiTask* task = sTaskQueue->getFirst();
+    const int64_t timeLeft = task->MillisecondsToRunTime();
+    if (timeLeft > 0) {
+      // this task (and therefore all remaining tasks)
+      // have not yet reached their runtime. return the
+      // time left until we should be called again
+      return timeLeft;
+    }
+
+    // Retrieve task before unlocking/running.
+    nsCOMPtr<nsIRunnable> runnable(task->TakeTask());
+    // LinkedListElements auto remove from list upon destruction
+    delete task;
+
+    // Unlock to allow posting new tasks reentrantly.
+    MutexAutoUnlock unlock(*sTaskQueueLock);
+    runnable->Run();
+    if (sThreadDestroyed) {
+      return -1;
+    }
+  }
+  return -1;
+}
+
+}  // namespace mozilla