[sensors] [mac] Implement ambient light sensor for macOS

device/generic_sensor/platform_sensor_ambient_light_mac.cc

+// 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 "device/generic_sensor/platform_sensor_ambient_light_mac.h"
+
+#include "base/bind.h"
+#include "device/generic_sensor/ambient_light_mac.h"
+#include "device/generic_sensor/platform_sensor_provider_mac.h"
+#include "device/generic_sensor/platform_sensor_util_mac.h"
+#include "device/generic_sensor/shared_memory_seqlock_buffer.h"
+
+namespace device {
+
+struct DeviceLightData {

[Mikhail, 2016/09/16 16:23:54]

why is that needed?

+  DeviceLightData() : illuminance(0) {}
+  double illuminance;
+};
+
+typedef SharedMemorySeqLockBuffer<DeviceLightData> DeviceLightHardwareBuffer;

[Mikhail, 2016/09/16 16:23:54]

nit: using DeviceLightHardwareBuffer = ..

+
+PlatformSensorAmbientLightMac::PlatformSensorAmbientLightMac(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    uint64_t buffer_size,
+    PlatformSensorProvider* provider,
+    const scoped_refptr<base::SingleThreadTaskRunner>&
+        polling_thread_task_runner)
+    : PlatformSensorMac(type,
+                        std::move(mapping),
+                        provider,
+                        polling_thread_task_runner),
+      current_lux(0) {
+  platformSensor_ = AmbientLightSensor::Create();
+}
+
+mojom::ReportingMode PlatformSensorAmbientLightMac::GetReportingMode() {
+  return mojom::ReportingMode::ON_CHANGE;
+}
+
+bool PlatformSensorAmbientLightMac::CheckSensorConfiguration(
+    const PlatformSensorConfiguration& configuration) {
+  return configuration.frequency() > 0 && configuration.frequency() <= 60;

[Mikhail, 2016/09/16 16:23:54]

PlatformSensorConfiguration::kMaxAllowedFrequency instead of 60.0

+}
+
+PlatformSensorConfiguration
+PlatformSensorAmbientLightMac::GetDefaultConfiguration() {
+  PlatformSensorConfiguration default_configuration;
+  // Default configuration inherited from content/browser/device_sensors.
+  default_configuration.set_frequency(5);
+  return default_configuration;
+}
+
+void PlatformSensorAmbientLightMac::UpdateReading() {
+  uint64_t lux_value[2];
+  platformSensor_->ReadSensorValue(lux_value);
+  uint64_t mean = (lux_value[0] + lux_value[1]) / 2;
+  double lux = device::LMUvalueToLux(mean);
+  if (lux == current_lux)
+    return;
+  current_lux = lux;
+  DeviceLightHardwareBuffer* light_buffer =
+      static_cast<DeviceLightHardwareBuffer*>(shared_buffer_mapping_.get());
+  light_buffer->seqlock.WriteBegin();
+  light_buffer->data.illuminance = lux;
+  light_buffer->seqlock.WriteEnd();
+  ui_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&PlatformSensorAmbientLightMac::NotifySensorReadingChanged,
+                 base::Unretained(this)));
+}
+
+}  // namespace device