Make it possible to determine if the final input of a QWidget was not accepted by a validator

It would be nice if the existing QWidget subclasses supporting the usage of a QValidator (such as QLineEdit) would make it possible to determine when the final input was not accepted. For instance, QLineEdit has a editingFinished() signal, but this one is not emitted if the input was not valid, it could be useful to have a signal emitted when the input is not accepted as well in case one wants to show a dialog when this happens.