subclass and override sub edit_text

 sub edit_text
{
        my ($self, $text) = @_;
$self->{password} =  $text;
        $self-> begin_undo_group;
        $self-> push_undo_action( 'edit_text', $self->text);
        $self-> text($text);
        $self-> end_undo_group;
}
[download]

or patch

     $self->{password} =  $cap;
        
        $cap = $self-> {passwordChar} x length $cap if $self-> {writeO
+nly};
        $self-> {wholeLine} = $cap;
[download]