+ $start ||= 1;
+ $start--;
+ s/\A-0*\z// and $_ ||= undef for $end // ();
+
+ $opt{hidemin} = sub {
+ my ($lines) = @_;
+ if ($start < 0) {
+ return max(0, $lines + $start + 2);
+ }
+ return $start;
+ } if $start;
+ $opt{hidemax} = sub {
+ my ($limit, $offset) = @_;
+ if ($end < 0) {
+ return $offset - $end - 1; # count
+ }
+ elsif ($start < 0) {
+ return $limit - $end + 1; # bottom
+ }
+ elsif ($end <= $limit) {
+ return $end - 1; # less
+ }
+ return $limit;
+ } if defined $end;