The WebXR Device API's XRSessionEvent interface describes an event which indicates the change of the state of an XRSession. These events occur, for example, when the session ends or the visibility of its context changes.

XRSessionEvent()

Creates and returns a new XRSessionEvent object.

In addition to properties inherited from its parent interface, Event, XRSessionEvent provides the following:

session Read only

The XRSession to which the event refers.

While XRSessionEvent defines no methods, it inherits methods from its parent interface, Event.

The following events are represented using the XRSessionEvent interface, and are permitted values for its type property.

end

Fired at the session when it has ended, after being terminated by the application or the user agent.

visibilitychange

Fired at the session whenever its visibility state changes.

This example creates a listener that watches for the visibility state of the session to change. It reacts by calling a function mySessionVisible() with a Boolean indicating whether or not the session is visible; this function might, for instance, spin up or reconfigure a worker that handles rendering the scene.

xrSession.addEventListener("visibilitystate", (e) => {
  switch (e.session.visibilitystate) {
    case "visible":
    case "visible-blurred":
      mySessionVisible(true);
      break;
    case "hidden":
      mySessionVisible(false);
      break;
  }
});