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// 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 "third_party/blink/renderer/modules/sensor/ambient_light_sensor.h"
#include "third_party/blink/public/mojom/feature_policy/feature_policy_feature.mojom-blink.h"
#include "third_party/blink/renderer/bindings/core/v8/script_promise.h"
#include "third_party/blink/renderer/bindings/core/v8/script_promise_resolver.h"
using device::mojom::blink::SensorType;
namespace blink {
namespace {
// Even though the underlying value has changed, for ALS we provide readouts to
// JS to the nearest 50 Lux.
constexpr int kAlsRoundingThreshold = 50;
// Decrease precision of ALS readouts.
// Round off to the nearest kAlsRoundingThreshold.
double RoundIlluminance(double value) {
return kAlsRoundingThreshold * std::round(value / kAlsRoundingThreshold);
}
// Value will have to vary by at least half the rounding threshold before it has
// an effect on the output.
bool IsSignificantlyDifferent(double als_old, double als_new) {
return std::fabs(als_old - als_new) >= kAlsRoundingThreshold / 2;
}
} // namespace
// static
AmbientLightSensor* AmbientLightSensor::Create(
ExecutionContext* execution_context,
const SensorOptions* options,
ExceptionState& exception_state) {
return MakeGarbageCollected<AmbientLightSensor>(execution_context, options,
exception_state);
}
// static
AmbientLightSensor* AmbientLightSensor::Create(
ExecutionContext* execution_context,
ExceptionState& exception_state) {
return Create(execution_context, SensorOptions::Create(), exception_state);
}
AmbientLightSensor::AmbientLightSensor(ExecutionContext* execution_context,
const SensorOptions* options,
ExceptionState& exception_state)
: Sensor(execution_context,
options,
exception_state,
SensorType::AMBIENT_LIGHT,
{mojom::blink::FeaturePolicyFeature::kAmbientLightSensor}) {}
base::Optional<double> AmbientLightSensor::illuminance() const {
if (hasReading()) {
DCHECK(latest_reading_.has_value());
return RoundIlluminance(latest_reading_.value());
}
return base::nullopt;
}
double AmbientLightSensor::illuminance(bool& is_null) const {
INIT_IS_NULL_AND_RETURN(is_null, 0.0);
DCHECK(latest_reading_.has_value());
return RoundIlluminance(*latest_reading_);
}
// When the reading we get does not differ significantly from our current
// value, we discard this reading and do not emit any events. This is a privacy
// measure to avoid giving readings that are too specific.
void AmbientLightSensor::OnSensorReadingChanged() {
// The platform sensor may start sending readings before the sensor is fully
// activated on the Blink side. In this case, bail out early, otherwise we
// will set |latest_reading_| and not send a "reading" event.
if (!IsActivated())
return;
const double new_reading = GetReading().als.value;
if (latest_reading_.has_value() &&
!IsSignificantlyDifferent(*latest_reading_, new_reading)) {
return;
}
latest_reading_ = new_reading;
Sensor::OnSensorReadingChanged();
}
} // namespace blink
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