[Sensors] Align sensor reading updates and 'onchange' notification with 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/frame/LocalFrame.h"
 #include "modules/sensor/SensorProviderProxy.h"
 #include "modules/sensor/SensorReading.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 sensorType,
                          SensorProviderProxy* provider,
-                         Page* page,
+                         Document* document,
                          std::unique_ptr<SensorReadingFactory> readingFactory)
-    : PageVisibilityObserver(page),
+    : PageVisibilityObserver(document->page()),
       m_type(sensorType),
       m_mode(ReportingMode::CONTINUOUS),
       m_provider(provider),
       m_clientBinding(this),
       m_state(SensorProxy::Uninitialized),
       m_suspended(false),
+      m_document(document),
       m_readingFactory(std::move(readingFactory)),
-      m_maximumFrequency(0.0),
-      m_timer(this, &SensorProxy::onTimerFired) {}
+      m_maximumFrequency(0.0) {}
 
 SensorProxy::~SensorProxy() {}
 
 void SensorProxy::dispose() {
   m_clientBinding.Close();
 }
 
 DEFINE_TRACE(SensorProxy) {
+  visitor->trace(m_document);
+  visitor->trace(m_readingUpdater);
   visitor->trace(m_reading);
   visitor->trace(m_observers);
   visitor->trace(m_provider);
   PageVisibilityObserver::trace(visitor);
 }
 
 void SensorProxy::addObserver(Observer* observer) {
   if (!m_observers.contains(observer))
     m_observers.add(observer);
 }
@@ skipping 11 matching lines @@
     return;
   }
 
   m_state = Initializing;
   auto callback = convertToBaseCallback(
       WTF::bind(&SensorProxy::onSensorCreated, wrapWeakPersistent(this)));
   m_provider->getSensorProvider()->GetSensor(m_type, mojo::GetProxy(&m_sensor),
                                              callback);
 }
 
+bool SensorProxy::isActive() const {
+  return isInitialized() && !m_suspended && !m_frequenciesUsed.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,
                            passed(std::move(callback)));
   m_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);
   m_sensor->RemoveConfiguration(std::move(configuration),
                                 convertToBaseCallback(std::move(callback)));
 }
 
 void SensorProxy::suspend() {
   DCHECK(isInitialized());
   if (m_suspended)
     return;
 
   m_sensor->Suspend();
   m_suspended = true;
 
-  if (usesPollingTimer())
-    updatePollingStatus();
-
-  for (Observer* observer : m_observers)
-    observer->onSuspended();
+  m_readingUpdater->stop();
 }
 
 void SensorProxy::resume() {
   DCHECK(isInitialized());
   if (!m_suspended)
     return;
 
   m_sensor->Resume();
   m_suspended = false;
 
-  if (usesPollingTimer())
-    updatePollingStatus();
+  if (isActive())
+    m_readingUpdater->start();
 }
 
 const SensorConfiguration* SensorProxy::defaultConfig() const {
   DCHECK(isInitialized());
   return m_defaultConfig.get();
 }
 
-bool SensorProxy::usesPollingTimer() const {
-  return isInitialized() && (m_mode == ReportingMode::CONTINUOUS);
-}
-
 void SensorProxy::updateSensorReading() {
   DCHECK(isInitialized());
   DCHECK(m_readingFactory);
   int readAttempts = 0;
   const int kMaxReadAttemptsCount = 10;
   device::SensorReading readingData;
   while (!tryReadFromBuffer(readingData)) {
     if (++readAttempts == kMaxReadAttemptsCount) {
       handleSensorError();
       return;
     }
   }
 
   m_reading = m_readingFactory->createSensorReading(readingData);
+}
 
-  for (Observer* observer : m_observers)
-    observer->onSensorReadingChanged();
+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 = m_observers;
+  for (Observer* observer : copy)
+    observer->onSensorReadingChanged(timestamp);
 }
 
 void SensorProxy::RaiseError() {
   handleSensorError();
 }
 
 void SensorProxy::SensorReadingChanged() {
   DCHECK_EQ(ReportingMode::ON_CHANGE, m_mode);
-  updateSensorReading();
+  if (isActive())
+    m_readingUpdater->start();
 }
 
 void SensorProxy::pageVisibilityChanged() {
   if (!isInitialized())
     return;
 
   if (page()->visibilityState() != PageVisibilityStateVisible) {
     suspend();
   } else {
     resume();
   }
 }
 
 void SensorProxy::handleSensorError(ExceptionCode code,
                                     String sanitizedMessage,
                                     String unsanitizedMessage) {
   if (!Platform::current()) {
     // TODO(rockot): Remove this hack once renderer shutdown sequence is fixed.
     return;
   }
 
-  if (usesPollingTimer()) {  // Stop polling.
-    m_frequenciesUsed.clear();
-    updatePollingStatus();
-  }
+  m_state = Uninitialized;
+  m_frequenciesUsed.clear();
+  if (m_readingUpdater)
+    m_readingUpdater->stop();
 
-  m_state = Uninitialized;
   // The m_sensor.reset() will release all callbacks and its bound parameters,
   // therefore, handleSensorError accepts messages by value.
   m_sensor.reset();
   m_sharedBuffer.reset();
   m_sharedBufferHandle.reset();
   m_defaultConfig.reset();
   m_clientBinding.Close();
   m_reading = nullptr;
 
   for (Observer* observer : m_observers)
@@ skipping 33 matching lines @@
 
   m_maximumFrequency = params->maximum_frequency;
   DCHECK(m_maximumFrequency <= SensorConfiguration::kMaxAllowedFrequency);
 
   auto errorCallback =
       WTF::bind(&SensorProxy::handleSensorError, wrapWeakPersistent(this),
                 UnknownError, String("Internal error"), String());
   m_sensor.set_connection_error_handler(
       convertToBaseCallback(std::move(errorCallback)));
 
+  m_readingUpdater = SensorReadingUpdater::create(this, m_mode);
+
   m_state = Initialized;
+
   for (Observer* observer : m_observers)
     observer->onSensorInitialized();
 }
 
 void SensorProxy::onAddConfigurationCompleted(
     double frequency,
     std::unique_ptr<Function<void(bool)>> callback,
     bool result) {
-  if (usesPollingTimer() && result) {
+  if (result) {
     m_frequenciesUsed.append(frequency);
-    updatePollingStatus();
+    std::sort(m_frequenciesUsed.begin(), m_frequenciesUsed.end());
+    if (isActive())
+      m_readingUpdater->start();
   }
 
   (*callback)(result);
 }
 
 void SensorProxy::onRemoveConfigurationCompleted(double frequency,
                                                  bool result) {
   if (!result)
     DVLOG(1) << "Failure at sensor configuration removal";
 
-  if (!usesPollingTimer())
-    return;
-
   size_t index = m_frequenciesUsed.find(frequency);
   if (index == kNotFound) {
     // Could happen e.g. if 'handleSensorError' was called before.
     return;
   }
 
   m_frequenciesUsed.remove(index);
-  updatePollingStatus();
+
+  if (m_frequenciesUsed.isEmpty())
+    m_readingUpdater->stop();
 }
 
 bool SensorProxy::tryReadFromBuffer(device::SensorReading& result) {
   DCHECK(isInitialized());
   const ReadingBuffer* buffer =
       static_cast<const ReadingBuffer*>(m_sharedBuffer.get());
   const device::OneWriterSeqLock& seqlock = buffer->seqlock.value();
   auto version = seqlock.ReadBegin();
   auto readingData = buffer->reading;
   if (seqlock.ReadRetry(version))
     return false;
   result = readingData;
   return true;
 }
 
-void SensorProxy::updatePollingStatus() {
-  DCHECK(usesPollingTimer());
-
-  if (m_suspended || m_frequenciesUsed.isEmpty()) {
-    m_timer.stop();
-    return;
-  }
-  // TODO(Mikhail): Consider using sorted queue instead of searching
-  // max element each time.
-  auto it =
-      std::max_element(m_frequenciesUsed.begin(), m_frequenciesUsed.end());
-  DCHECK_GT(*it, 0.0);
-
-  double repeatInterval = 1 / *it;
-  if (!m_timer.isActive() || m_timer.repeatInterval() != repeatInterval) {
-    updateSensorReading();
-    m_timer.startRepeating(repeatInterval, BLINK_FROM_HERE);
-  }
-}
-
-void SensorProxy::onTimerFired(TimerBase*) {
-  updateSensorReading();
-}
-
 }  // namespace blink