[Sensors] Decouple sensor readings update from rAF

third_party/WebKit/Source/modules/sensor/SensorProxy.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/sensor/SensorProxy.h"
 
-#include "core/dom/Document.h"
+#include "core/dom/TaskRunnerHelper.h"
 #include "core/frame/LocalFrame.h"
 #include "modules/sensor/SensorProviderProxy.h"
-#include "modules/sensor/SensorReadingUpdater.h"
 #include "platform/mojo/MojoHelper.h"
 #include "public/platform/Platform.h"
 
 using namespace device::mojom::blink;
 
 namespace blink {
 
 SensorProxy::SensorProxy(SensorType sensor_type,
                          SensorProviderProxy* provider,
                          Page* page)
     : PageVisibilityObserver(page),
       type_(sensor_type),
       mode_(ReportingMode::CONTINUOUS),
       provider_(provider),
       client_binding_(this),
       state_(SensorProxy::kUninitialized),
-      suspended_(false) {}
+      suspended_(false),
+      polling_timer_(TaskRunnerHelper::Get(TaskType::kSensor,
+                                           provider->GetSupplementable()),
+                     this,
+                     &SensorProxy::OnPollingTimer) {}
 
 SensorProxy::~SensorProxy() {}
 
 void SensorProxy::Dispose() {
   client_binding_.Close();
 }
 
 DEFINE_TRACE(SensorProxy) {
-  visitor->Trace(reading_updater_);
   visitor->Trace(observers_);
   visitor->Trace(provider_);
   PageVisibilityObserver::Trace(visitor);
 }
 
 void SensorProxy::AddObserver(Observer* observer) {
   if (!observers_.Contains(observer))
     observers_.insert(observer);
 }
 
@@ skipping 10 matching lines @@
     return;
   }
 
   state_ = kInitializing;
   auto callback = ConvertToBaseCallback(
       WTF::Bind(&SensorProxy::OnSensorCreated, WrapWeakPersistent(this)));
   provider_->GetSensorProvider()->GetSensor(type_, mojo::MakeRequest(&sensor_),
                                             callback);
 }
 
-bool SensorProxy::IsActive() const {
-  return IsInitialized() && !suspended_ && !frequencies_used_.IsEmpty();
-}
-
 void SensorProxy::AddConfiguration(
     SensorConfigurationPtr configuration,
     std::unique_ptr<Function<void(bool)>> callback) {
   DCHECK(IsInitialized());
   auto wrapper = WTF::Bind(&SensorProxy::OnAddConfigurationCompleted,
                            WrapWeakPersistent(this), configuration->frequency,
                            WTF::Passed(std::move(callback)));
   sensor_->AddConfiguration(std::move(configuration),
                             ConvertToBaseCallback(std::move(wrapper)));
 }
 
 void SensorProxy::RemoveConfiguration(SensorConfigurationPtr configuration) {
   DCHECK(IsInitialized());
   auto callback = WTF::Bind(&SensorProxy::OnRemoveConfigurationCompleted,
                             WrapWeakPersistent(this), configuration->frequency);
   sensor_->RemoveConfiguration(std::move(configuration),
                                ConvertToBaseCallback(std::move(callback)));
 }
 
 void SensorProxy::Suspend() {
   DCHECK(IsInitialized());
   if (suspended_)
     return;
 
   sensor_->Suspend();
   suspended_ = true;
+  UpdatePollingStatus();
 }
 
 void SensorProxy::Resume() {
   DCHECK(IsInitialized());
   if (!suspended_)
     return;
 
   sensor_->Resume();
   suspended_ = false;
-
-  if (IsActive())
-    reading_updater_->Start();
+  UpdatePollingStatus();
 }
 
 const SensorConfiguration* SensorProxy::DefaultConfig() const {
   DCHECK(IsInitialized());
   return default_config_.get();
 }
 
-Document* SensorProxy::GetDocument() const {
-  return provider_->GetSupplementable()->GetDocument();
-}
-
 void SensorProxy::UpdateSensorReading() {
   DCHECK(IsInitialized());
   int read_attempts = 0;
   const int kMaxReadAttemptsCount = 10;
   device::SensorReading reading_data;
   while (!TryReadFromBuffer(reading_data)) {
     if (++read_attempts == kMaxReadAttemptsCount) {
       HandleSensorError();
       return;
     }
   }
 
   if (reading_.timestamp != reading_data.timestamp) {
     reading_ = reading_data;
+    auto now = WTF::MonotonicallyIncreasingTime();

[Reilly Grant (use Gerrit), 2017/05/11 18:28:12]

nit: use double here as the type of the return value is not clear from the
function name.

[Mikhail, 2017/05/12 08:42:13]

Done.

     for (Observer* observer : observers_)
-      observer->OnSensorReadingChanged();
+      observer->OnSensorReadingChanged(now);
   }
 }
 
-void SensorProxy::NotifySensorChanged(double timestamp) {
-  // This notification leads to sync 'onchange' event sending, so
-  // we must cache m_observers as it can be modified within event handlers.
-  auto copy = observers_;
-  for (Observer* observer : copy)
-    observer->NotifySensorChanged(timestamp);
-}
-
 void SensorProxy::RaiseError() {
   HandleSensorError();
 }
 
 void SensorProxy::SensorReadingChanged() {
   DCHECK_EQ(ReportingMode::ON_CHANGE, mode_);
-  if (IsActive())
-    reading_updater_->Start();
+  UpdateSensorReading();
 }
 
 void SensorProxy::PageVisibilityChanged() {
   if (!IsInitialized())
     return;
 
   if (GetPage()->VisibilityState() != kPageVisibilityStateVisible) {
     Suspend();
   } else {
     Resume();
   }
 }
 
 void SensorProxy::HandleSensorError() {
   state_ = kUninitialized;
   frequencies_used_.clear();
   reading_ = device::SensorReading();
+  UpdatePollingStatus();
 
   // The m_sensor.reset() will release all callbacks and its bound parameters,
   // therefore, handleSensorError accepts messages by value.
   sensor_.reset();
   shared_buffer_.reset();
   shared_buffer_handle_.reset();
   default_config_.reset();
   client_binding_.Close();
 
   auto copy = observers_;
@@ skipping 40 matching lines @@
   DCHECK_GE(frequency_limits_.second, frequency_limits_.first);
   constexpr double kMaxAllowedFrequency =
       SensorConfiguration::kMaxAllowedFrequency;
   DCHECK_GE(kMaxAllowedFrequency, frequency_limits_.second);
 
   auto error_callback =
       WTF::Bind(&SensorProxy::HandleSensorError, WrapWeakPersistent(this));
   sensor_.set_connection_error_handler(
       ConvertToBaseCallback(std::move(error_callback)));
 
-  reading_updater_ = SensorReadingUpdater::Create(this, mode_);
-
   state_ = kInitialized;
 
   for (Observer* observer : observers_)
     observer->OnSensorInitialized();
 }
 
 void SensorProxy::OnAddConfigurationCompleted(
     double frequency,
     std::unique_ptr<Function<void(bool)>> callback,
     bool result) {
   if (result) {
     frequencies_used_.push_back(frequency);
     std::sort(frequencies_used_.begin(), frequencies_used_.end());
-    if (IsActive())
-      reading_updater_->Start();
+    UpdatePollingStatus();
   }
 
   (*callback)(result);
 }
 
 void SensorProxy::OnRemoveConfigurationCompleted(double frequency,
                                                  bool result) {
   if (!result)
     DVLOG(1) << "Failure at sensor configuration removal";
 
@@ skipping 12 matching lines @@
       static_cast<const ReadingBuffer*>(shared_buffer_.get());
   const device::OneWriterSeqLock& seqlock = buffer->seqlock.value();
   auto version = seqlock.ReadBegin();
   auto reading_data = buffer->reading;
   if (seqlock.ReadRetry(version))
     return false;
   result = reading_data;
   return true;
 }
 
+void SensorProxy::OnPollingTimer(TimerBase*) {
+  UpdateSensorReading();
+}
+
+void SensorProxy::UpdatePollingStatus() {
+  bool start_polling = (mode_ == ReportingMode::CONTINUOUS) &&
+                       IsInitialized() && !suspended_ &&
+                       !frequencies_used_.IsEmpty();
+  if (start_polling) {
+    // TODO(Mikhail) : We need to find out an algorithm for resulting
+    // polling frequency.

[Reilly Grant (use Gerrit), 2017/05/10 14:53:28]

Please create an issue for this.

[Mikhail, 2017/05/11 10:46:20]

Done https://bugs.chromium.org/p/chromium/issues/detail?id=721297

[Reilly Grant (use Gerrit), 2017/05/11 18:28:12]

Please update the comment with the issue number. That is preferable to putting
people's names in the code.

[Mikhail, 2017/05/12 08:42:13]

Done.

+    polling_timer_.StartRepeating(1 / frequencies_used_.back(),
+                                  BLINK_FROM_HERE);
+  } else {
+    polling_timer_.Stop();
+  }
+}
+
 }  // namespace blink