#!/usr/bin/perl

use strict;
use Font::TTF::Font;
use Getopt::Std;
use Pod::Usage;

our $VERSION = 0.1;     #   MH      2011-02-28  Original

our $CHAIN_CALL;
our %opts;
our $f;

unless($CHAIN_CALL)
{
    getopts('a:d:hl:', \%opts);

    pod2usage( -verbose => 2, -noperldoc => 1) if $opts{'h'};

    pod2usage(-verbose => 1) unless defined $ARGV[0];

    $f = Font::TTF::Font->open($ARGV[0]) || die "Can't open file $ARGV[0]";
}

my $h = $f->{'hhea'}->read;
my $o = $f->{'OS/2'}->read;
if ($opts{'a'})
{
    $h->{'Ascender'} = $opts{'a'};
    $o->{'sTypoAscender'} = $opts{'a'};
    $o->{'usWinAscent'} = $opts{'a'};
}

if ($opts{'d'})
{
    $h->{'Descender'} = -$opts{'d'};
    $o->{'sTypoDescender'} = -$opts{'d'};
    $o->{'usWinDescent'} = $opts{'d'};
}

if ($opts{'l'})
{
    $o->{'sTypoLineGap'} = $opts{'l'};
}

$f->out($ARGV[1]) if (defined $ARGV[1]);

__END__

=head1 TITLE

ttfascent - sets ascent and descent of a TrueType font

=head1 SYNOPSIS

ttfascent [-a num] [-d num] [-l num] infile [outfile]

Opens infile (a .ttf file) changes the ascent and descent values in the Hhea and
OS/2 table and then writes the resulting file to outfile if specified.

=head1 OPTIONS

  -a num    Sets the ascent value to this number of em units
  -d num    Sets the descent value to this number of em units. This value is
            usually positive.
  -l num    Sets the typographical line gap in the OS/2 table.

=head1 DESCRIPTION

Setting the ascent and descent values of a font is a fiddly business. This program
sets the values in their default relationship.

=cut