gdk:device-position-double (device)

device -- a gdk:device pointer device to query status about

screen -- a gdk:screen object the device is on, or nil
x -- a double float with the root window x coordinate of the device, or nil
y -- a double float with the root window y coordinate of the device, or nil

Gets the current location of the device in double precision. As a slave device's coordinates are those of its master pointer, this function may not be called on devices of type :slave, unless there is an ongoing grab on them. See the gdk:device-grab function.