If the input in valueFrom is valid, the content should be
copied in valueTo, otherwise valueTo should be cleared.
But if I insert a valid value eg. "12" and press return, the
not copied! I must mistake the value eg. "12xy" and press
return (the valueTo field is cleared) and
only the next time if I insert a valid value eg. "12" and
return, the value is copied. And this continues so on .... I must
mistake the value and only the next time it is accepted.
It's very possible I haven't understood how to use
NumberValidator or I haven't use it correctly. Please, tell me.