Ambient Light Sensor

1. Introduction

The Ambient Light Sensor extends the Generic Sensor API [GENERIC-SENSOR] to provide information about ambient light levels, as detected by the device’s main light detector, in terms of lux units.

The light-level media feature [MEDIAQUERIES-4] provides less granular information about the ambient light level.

Note: it might be worthwhile to provide a high-level Light Level Sensor which would mirror the light-level media feature, but in JavaScript. This sensor would _not require additional user permission to be activated_ in user agents that exposed the light-level media feature.

2. Examples

let sensor = new AmbientLightSensor();
sensor.start();
    
sensor.onchange = function(event) {
    console.log(event.reading.illuminance);
};

sensor.onerror = function(event) {
    console.log(event.error.name, event.error.message);
};

3. Security and Privacy Considerations

There are no specific security and privacy considerations beyond those described in the Generic Sensor API [GENERIC-SENSOR].

4. Model

The Ambient Light Sensor’s associated Sensor subclass is the AmbientLightSensor class.

The Ambient Light Sensor’s associated SensorReading subclass is the AmbientLightSensorReading class.

The Ambient Light Sensor has a default sensor, which is the device’s main light detector.

The Ambient Light Sensor has a single supported reporting mode which is "auto".

The Ambient Light Sensor’s permission name is "ambient-light". It has no associated PermissionDescriptor.

The Ambient Light Sensor has an associated abstract operation to retrieve the sensor permission which must simply return a permission whose name is "ambient-light".

The Ambient Light Sensor has an associated abstract operation to construct a SensorReading object which creates a new AmbientLightSensorReading object and sets its illuminance attribute to the current light level.

The current light level#current-light-levelReferenced in:4. Model5.2.2. The illuminance attribute or illuminance is a value that represents the ambient light levels around the hosting device. Its unit is the lux (lx) [SI].

Note: The precise lux value reported by different devices in the same light can be different, due to differences in detection method, sensor construction, etc.

5. API

5.1. The AmbientLightSensor Interface

[Constructor(optional SensorOptions sensorOptions)]
interface AmbientLightSensor#ambientlightsensorReferenced in:4. Model : Sensor {
  readonly attribute AmbientLightSensorReading? reading;
};

To Construct an AmbientLightSensor Object the user agent must invoke the construct a Sensor object abstract operation.

5.2. The AmbientLightSensorReading Interface

[Constructor(AmbientLightSensorReadingInit ambientLightSensorReadingInit)]
interface AmbientLightSensorReading#ambientlightsensorreadingReferenced in:4. Model (2)5.1. The AmbientLightSensor Interface5.2.2. The illuminance attribute : SensorReading {
    readonly attribute unrestricted double illuminance#dom-ambientlightsensorreading-illuminanceReferenced in:4. Model5.2.2. The illuminance attribute;
};
  
dictionary AmbientLightSensorReadingInit#dictdef-ambientlightsensorreadinginitReferenced in:5.2. The AmbientLightSensorReading Interface {
  unrestricted double illuminance;
};

5.2.1. The AmbientLightSensorReading constructor

5.2.2. The illuminance attribute

The illuminance attribute of the AmbientLightSensorReading interface represents the current light level.

6. Acknowledgements

Doug Turner for the initial prototype and Marcos Caceres for the test suite.

Paul Bakaus for the LightLevelSensor idea.