This method tells if all set's #GdaHolder objects are valid, and if
they represent a valid combination of values, as defined by rules
external to Libgda: the "validate-set" signal is emitted and if none of the signal handlers return an
error, then the returned value is TRUE, otherwise the return value is FALSE as soon as a signal handler
returns an error.
This method tells if all set's #GdaHolder objects are valid, and if they represent a valid combination of values, as defined by rules external to Libgda: the "validate-set" signal is emitted and if none of the signal handlers return an error, then the returned value is TRUE, otherwise the return value is FALSE as soon as a signal handler returns an error.