Fabric: Cross-platform implementation of SynchronousEventBeat and AsynchronousEventBeat

Summary:
`SynchronousEventBeat` and `AsynchronousEventBeat` are a cross-platform re-implementation of run loop related parts of `MainRunLoopEventBeat` and `RuntimeEventBeat` (iOS specific classes for now). In the future, they will replace iOS- and Android-specifc event beat classes.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: sammy-SC

Differential Revision: D21341996

fbshipit-source-id: 8eda9a5df537cd666b7728e32212a8bb5ddb3ab7

ReactCommon/fabric/scheduler/AsynchronousEventBeat.cpp

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "AsynchronousEventBeat.h"
+
+namespace facebook {
+namespace react {
+
+AsynchronousEventBeat::AsynchronousEventBeat(
+    RunLoopObserver::Unique uiRunLoopObserver,
+    RuntimeExecutor runtimeExecutor)
+    : EventBeat({}),
+      uiRunLoopObserver_(std::move(uiRunLoopObserver)),
+      runtimeExecutor_(std::move(runtimeExecutor)) {
+  uiRunLoopObserver_->setDelegate(this);
+  uiRunLoopObserver_->enable();
+}
+
+void AsynchronousEventBeat::activityDidChange(
+    RunLoopObserver::Delegate const *delegate,
+    RunLoopObserver::Activity activity) const noexcept {
+  assert(delegate == this);
+  induce();
+}
+
+void AsynchronousEventBeat::induce() const {
+  if (!isRequested_) {
+    return;
+  }
+
+  // Here we know that `this` object exists because the caller has a strong
+  // pointer to `owner`. To ensure the object will exist inside
+  // `runtimeExecutor_` callback, we need to copy the  pointer there.
+  auto weakOwner = uiRunLoopObserver_->getOwner();
+
+  runtimeExecutor_([this, weakOwner](jsi::Runtime &runtime) mutable {
+    auto owner = weakOwner.lock();
+    if (!owner) {
+      return;
+    }
+
+    if (!isRequested_) {
+      return;
+    }
+
+    this->beat(runtime);
+  });
+}
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/scheduler/AsynchronousEventBeat.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <ReactCommon/RuntimeExecutor.h>
+#include <react/core/EventBeat.h>
+#include <react/utils/RunLoopObserver.h>
+
+namespace facebook {
+namespace react {
+
+/*
+ * Event beat associated with JavaScript runtime.
+ * The beat is called on `RuntimeExecutor`'s thread induced by the UI thread
+ * event loop.
+ */
+class AsynchronousEventBeat : public EventBeat,
+                              public RunLoopObserver::Delegate {
+ public:
+  AsynchronousEventBeat(
+      RunLoopObserver::Unique uiRunLoopObserver,
+      RuntimeExecutor runtimeExecutor);
+
+  void induce() const override;
+
+#pragma mark - RunLoopObserver::Delegate
+
+  void activityDidChange(
+      RunLoopObserver::Delegate const *delegate,
+      RunLoopObserver::Activity activity) const noexcept override;
+
+ private:
+  RunLoopObserver::Unique uiRunLoopObserver_;
+  RuntimeExecutor runtimeExecutor_;
+};
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/scheduler/SynchronousEventBeat.cpp

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import "SynchronousEventBeat.h"
+
+namespace facebook {
+namespace react {
+
+SynchronousEventBeat::SynchronousEventBeat(
+    RunLoopObserver::Unique uiRunLoopObserver,
+    RuntimeExecutor runtimeExecutor)
+    : EventBeat({}),
+      uiRunLoopObserver_(std::move(uiRunLoopObserver)),
+      runtimeExecutor_(std::move(runtimeExecutor)) {
+  uiRunLoopObserver_->setDelegate(this);
+  uiRunLoopObserver_->enable();
+}
+
+void SynchronousEventBeat::activityDidChange(
+    RunLoopObserver::Delegate const *delegate,
+    RunLoopObserver::Activity activity) const noexcept {
+  assert(delegate == this);
+  lockExecutorAndBeat();
+}
+
+void SynchronousEventBeat::induce() const {
+  if (!this->isRequested_) {
+    return;
+  }
+
+  if (uiRunLoopObserver_->isOnRunLoopThread()) {
+    this->lockExecutorAndBeat();
+  }
+}
+
+void SynchronousEventBeat::lockExecutorAndBeat() const {
+  if (!this->isRequested_) {
+    return;
+  }
+
+  executeSynchronouslyOnSameThread_CAN_DEADLOCK(
+      runtimeExecutor_, [this](jsi::Runtime &runtime) { beat(runtime); });
+}
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/scheduler/SynchronousEventBeat.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <ReactCommon/RuntimeExecutor.h>
+#include <react/core/EventBeat.h>
+#include <react/utils/RunLoopObserver.h>
+
+namespace facebook {
+namespace react {
+
+/*
+ * Event beat associated with main run loop.
+ * The callback is always called on the main thread.
+ */
+class SynchronousEventBeat final : public EventBeat,
+                                   public RunLoopObserver::Delegate {
+ public:
+  SynchronousEventBeat(
+      RunLoopObserver::Unique uiRunLoopObserver,
+      RuntimeExecutor runtimeExecutor);
+
+  void induce() const override;
+
+#pragma mark - RunLoopObserver::Delegate
+
+  void activityDidChange(
+      RunLoopObserver::Delegate const *delegate,
+      RunLoopObserver::Activity activity) const noexcept override;
+
+ private:
+  void lockExecutorAndBeat() const;
+
+  RunLoopObserver::Unique uiRunLoopObserver_;
+  RuntimeExecutor runtimeExecutor_;
+};
+
+} // namespace react
+} // namespace facebook