The XChangePointerDevice request causes the server to use the
specified device as the X pointer. The device must have been
opened by the client via XOpenDevice or a BadDevice error will
result. The device must support input class Valuators or a
BadMatch error will result. If the implementation does not
support use of the specified device as the X pointer, a
BadDevice error will result.

If the specified device is grabbed by another client,
AlreadyGrabbed is returned. If the specified device is frozen
by a grab on another device, GrabFrozen is returned. If the
request is successful, Success is returned.

If the request succeeds, a ChangeDeviceNotify event is sent to
all clients that have selected that event. A MappingNotify
event with request = MappingPointer is sent to all clients. The
specified device becomes the X pointer, and the old X pointer
becomes accessible through the input extension protocol
requests.

XChangePointerDevice can generate a BadDevice or a BadMatch
error.

BadDevice


       An invalid device was specified. The specified device


       does not exist, has not been opened by this client via


       XOpenInputDevice, or is already one of the core X input


       devices (pointer or keyboard). This error may also occur


       if the server implementation does not support using the


       specified device as the X pointer.

BadMatch


       This error may occur if an XChangePointerDevice request


       was made specifying a device that has less than two


       valuators, or specifying a valuator index beyond the


       range supported by the device.

XChangeKeyboardDevice(3)