class HexaPDF::Type::AcroForm::SignatureField

See: PDF2.0 s12.7.5.5
width and height; and/or the ‘hidden’ or ‘no_view’ flags of the annotation should be set.
If the signature should not be visible, the associated widget annotation should have zero
digital signature itself.
It serves two purposes: To visually display the signature and to hold the information of the
AcroForm signature fields represent a digital signature.

def field_value

Returns the associated signature dictionary or +nil+ if the signature is not filled in. 
def field_value
  self[:V]
end

def field_value=(sig_dict)

Sets the signature dictionary as value of this signature field. 
def field_value=(sig_dict)
  self[:V] = sig_dict
end

def perform_validation #:nodoc:

:nodoc: 
def perform_validation #:nodoc:
  if field_type != :Sig
    yield("Field /FT of AcroForm signature field has to be :Sig", true)
    self[:FT] = :Sig
  end
  super
end