This specification defines a means to receive events that correspond to a proximity sensor detecting the presence of a physical object.

The functionality described in this specification was initially specified as part of the Sensor API but has been extracted in order to be more straightforward to implement, and in order to produce a specification that could be implemented on its own merits without interference with other features.

Introduction

The DeviceProximityEvent interface provides web developers information about the distance between the hosting device and a nearby object.

The UserProximityEvent interface provides web developers a user-agent- and platform-specific approximation that the hosting device has sensed a nearby object.

This is achieved by interrogating a proximity sensor of a device, which is a sensor that can detect the presence of a physical object without physical contact. Not all devices contain a proximity sensor, and when there is no proximity sensor, this API is still exposed to the scripting environment but it does nothing.

Because most proximity sensors detect electromagnetic radiation (e.g., an infrared light or a magnetic field), certain material properties can interfere with the sensor's ability to sense the presence of a physical object. Things that can interfere with a sensor include, but are not limited to, the material's translucency, reflectiveness, color, temperature, chemical composition, and even the angle at which the object is reflecting the radiation back at the sensor. As such, proximity sensors should not be relied on as a means to measure distance: the only thing that can be deduced from a proximity sensor is that an object is somewhere in the distance between the minimum sensing distance and the maximum sensing distance with some degree of certainty.

This specification defines conformance criteria that apply to a single product: the user agent that implements the interfaces that it contains.

Terminology

The EventHandler interface represents a callback used for event handlers as defined in [[!HTML5]].

The concepts queue a task, fires a simple event, and browsing context are defined in [[!HTML5]].

The terms event handlers and event handler event types are defined in [[!HTML5]].

The concepts create an event and fire an event are defined in [[!DOM4]].

The current device proximity is a value that represents the proximity of the hosting device to a physical object (i.e., some value between the maximum sensing distance and the minimum sensing distance), in centimeters.

The minimum sensing distance at which the sensor can detect a physical object, in centimeters.

The maximum sensing distance at which the sensor can detect a physical object, in centimeters.

The current user proximity state, a boolean state, is a user-agent- and platform-specific approximation of the closeness of a physical object with the hosting device.

Security and privacy considerations

Device proximity

The HTML5 specification [[!HTML5]] defines a Window interface, which this specification extends:

attribute EventHandler ondeviceproximity

The ondeviceproximity event handler and its corresponding event handler event type deviceproximity MUST be supported as an IDL attribute by all objects implementing the Window interface.

DeviceProximityEvent Interface

readonly attribute double value
The current device proximity.
readonly attribute double min
The minimum sensing distance.
readonly attribute double max
The maximum sensing distance.
double value
double min
double max

The value attribute of the DeviceProximityEvent interface MUST return the value it was initialized to. When the object is created, this attribute MUST be initialized to positive Infinity. It represents the current device proximity.

The min attribute of the DeviceProximityEvent interface MUST return the value it was initialized to. When the object is created, this attribute MUST be initialized to negative Infinity. It represents the minimum sensing distance.

The max attribute of the DeviceProximityEvent interface MUST return the value it was initialized to. When the object is created, this attribute MUST be initialized to positive Infinity. It represents the maximum sensing distance.

When a user agent is required to fire a device proximity event, the user agent MUST run the following steps:

  1. Create an event that uses the DeviceProximityEvent interface, with the name deviceproximity, which bubbles, is not cancelable, and has no default action, that also meets the following conditions:
    1. If the implementation is unable to report the current device proximity, initialize the value attribute to positive Infinity, otherwise initialize the attribute to the current device proximity.
    2. If the implementation is unable to report the minimum sensing distance, initialize the min attribute to negative Infinity, otherwise initialize the attribute to the minimum sensing distance.
    3. If the implementation is unable to report the maximum sensing distance, initialize the max attribute to positive Infinity, otherwise initialize the attribute to the maximum sensing distance.

When the current device proximity changes, the user agent MUST queue a task to fire a device proximity event at each browsing context's Window object.

The definition of granularity i.e. how often the event is fired is left to the implementation. Implementations can fire the event if they have reason to believe that the page does not have sufficiently fresh data. Different devices can also support different minimum and maximum sensing distances as well as different resolution, thus authors are strongly advised to use the UserProximityEvent interface if they are only interested in finding out if the user is near or far.

Event handlers

The following are the event handlers (and their corresponding event handler event types) that MUST be supported as attributes by the Window object:

event handler event handler event type
ondeviceproximity deviceproximity

User proximity

The HTML5 specification [[!HTML5]] defines a Window interface, which this specification extends:

attribute EventHandler onuserproximity

The onuserproximity event handler and its corresponding event handler event type userproximity MUST be supported as an IDL attribute by all objects implementing the Window interface.

UserProximityEvent Interface

readonly attribute boolean near
The current user proximity state.
boolean near

The near attribute of the UserProximityEvent interface MUST return the value it was initialized to. When the object is created, this attribute MUST be initialized to false. It represents the current user proximity state.

When a user agent is required to fire a user proximity event, the user agent MUST run the following steps:

  1. Create an event that uses the UserProximityEvent interface, with the name userproximity, which bubbles, is not cancelable, and has no default action, that also meets the following conditions:
    1. If the implementation is unable to report the current user proximity state, initialize the near attribute to false, otherwise initialize the attribute to the current user proximity state.

When the current user proximity state changes, the user agent MUST queue a task to fire a user proximity event at each browsing context's Window object.

Event handlers

The following are the event handlers (and their corresponding event handler event types) that MUST be supported as attributes by the Window object:

event handler event handler event type
onuserproximity userproximity

Acknowledgements

Doug Turner for the initial prototype. All Device APIs working group participants who have sent helpful feedback. Marcos Caceres for his excellent work on the test suite.