DeviceOrientation API on ChromeOS

content/public/browser/sensor_manager.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.

[timvolodine, 2014/11/06 02:53:47]

can you call this file sensor_manager_chromeos.cc? this would be in line with
how other platforms are implemented.

[timvolodine, 2014/11/06 02:53:47]

also I don't understand why this needs to be in content/public/...
can this file simply live in content/browser/device_sensors/?
Looks like there is some analogy with mac implementation where a
sudden_motion_sensor_mac.cc is used from a third_party/.

[jonross, 2014/11/06 18:18:52]

This file is also called from the ash library. So I placed it in content/public/
so that it is exposed.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/public/browser/sensor_manager.h"
+
+#include "base/logging.h"
+#include "base/memory/singleton.h"
+
+namespace {
+// Conversion ratio from radians to degrees.
+const double kRad2deg = 180.0 / M_PI;
+}
+
+namespace content {
+
+SensorManager* SensorManager::GetInstance() {
+  return Singleton<SensorManager, LeakySingletonTraits<SensorManager>>::get();
+}
+
+void SensorManager::OnAccelerationIncludingGravity(double x,
+                                                   double y,
+                                                   double z) {

[timvolodine, 2014/11/06 02:53:47]

on which thread is this method called?
do you need an autolock(orientation_buffer_lock_) here?

[jonross, 2014/11/06 18:18:52]

This will be called from the UI thread. I'm adding the lock for
safety/consistency.

+  if (!orientation_buffer_)
+    return;
+
+  // Create a unit vector to remove gravity.
+  // TODO(jonross): Stop reversing signs for vector components once
+  // accelerometer values have been reversed.
+  gfx::Vector3dF data(x, y ? -y : 0.0f, z ? -z : 0.0f);
+  data.Scale(1.0f / data.Length());
+
+  // Transform accelerometer to W3C angles, using the Z-X-Y Eulerangles matrix.
+  // x = sin(gamma)
+  // y = -cos(gamma) * sin(beta)
+  // z = cos(beta) * cos(gamma)
+  // With only accelerometer alpha cannot be provided.
+  double beta = kRad2deg * atan2(data.y(), data.z());
+  double gamma = kRad2deg * asin(data.x());
+
+  // Have the interval boundaries comply with the specification. Beta is
+  // [-180,180) and gamma is [-90, 90).
+  if (beta >= 180.0f)
+    beta = -180.0f;
+  if (gamma >= 90.0f)
+    gamma = -90.0f;
+
+  orientation_buffer_->seqlock.WriteBegin();
+  orientation_buffer_->data.beta = beta;
+  orientation_buffer_->data.hasBeta = true;
+  orientation_buffer_->data.gamma = gamma;
+  orientation_buffer_->data.hasGamma = true;
+  orientation_buffer_->data.allAvailableSensorsAreActive = true;
+  orientation_buffer_->seqlock.WriteEnd();
+}
+
+void SensorManager::StartFetchingDeviceOrientationData(
+    DeviceOrientationHardwareBuffer* buffer) {
+  DCHECK(buffer);
+  base::AutoLock autolock(orientation_buffer_lock_);
+  orientation_buffer_ = buffer;
+
+  // No compass information, so we cannot provide absolute orientation.
+  orientation_buffer_->seqlock.WriteBegin();
+  orientation_buffer_->data.absolute = false;
+  orientation_buffer_->data.hasAbsolute = true;
+  orientation_buffer_->seqlock.WriteEnd();
+}
+
+void SensorManager::StopFetchingDeviceOrientationData() {
+  base::AutoLock autolock(orientation_buffer_lock_);
+  if (!orientation_buffer_)
+    return;
+  // Null message to signify that sensora are no longer available.

[timvolodine, 2014/11/06 02:53:47]

sensora -> sensors

[jonross, 2014/11/06 18:18:52]

Done.

+  orientation_buffer_->seqlock.WriteBegin();
+  orientation_buffer_->data.allAvailableSensorsAreActive = false;
+  orientation_buffer_->seqlock.WriteEnd();
+  orientation_buffer_ = nullptr;
+}
+
+SensorManager::SensorManager() : orientation_buffer_(nullptr) {
+}
+
+SensorManager::~SensorManager() {
+}
+
+}  // namespace content