func deviceGetID(d *C.cairo_device_t) id {
p := C.cairo_device_get_user_data(d, idkey)
if p == nil {
panic("device does not have ID - created outside of cairo binding and not registered")
}
return id(ctoint(p))
}
func deviceSetID(d *C.cairo_device_t) {
if C.cairo_device_get_user_data(d, idkey) != nil {
return
}
C.cairo_device_set_user_data(d, idkey, generateID(), free)
}