Read-only value that can be used to determine if the XR device is active.
When true, Unity is accepting input from the device and attempting to render to the device's display(s). Note that this will return true even if the device is not currently rendering due to lack of user presence (see XRDevice.userPresence). This can become false if a device is disconnected, a device could not be intialized (see XRSettings.LoadDeviceByName), or XRSettings.enabled is set to false.
XR output is automatically mirrored to the main display (if applicable). This can be controlled with XRSettings.showDeviceView.
The main window is still controlled by Screen and related APIs.