Read-only value that can be used to determine if the VR device is active.
When true, Unity is accepting input from the HMD and rendering to the HMD's display(s). This can become false if a device is disconnected, a device could not be intialized (see VRSettings.LoadDeviceByName), or VRSettings.enabled is set to false.
VR output is automatically mirrored to the main display (if applicable). This can be controlled with VRSettings.showDeviceView.
主窗口仍然由 Screen 和相关 API 控制。