Font::TTF::Hmtx - Horizontal Metrics

Font-TTF documentation Contained in the Font-TTF distribution.

Index

Code Index:

NAME

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Font::TTF::Hmtx - Horizontal Metrics

DESCRIPTION

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Contains the advance width and left side bearing for each glyph. Given the compressability of the data onto disk, this table uses information from other tables, and thus must do part of its output during the output of other tables

INSTANCE VARIABLES

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The horizontal metrics are kept in two arrays by glyph id. The variable names do not start with a space

advance

An array containing the advance width for each glyph

lsb

An array containing the left side bearing for each glyph

METHODS

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$t->read

Reads the horizontal metrics from the TTF file into memory

$t->numMetrics

Calculates again the number of long metrics required to store the information here. Returns undef if the table has not been read.

$t->out($fh)

Writes the metrics to a TTF file. Assumes that the hhea has updated the numHMetrics from here

$t->update

Updates the lsb values from the xMin from the each glyph

$t->out_xml($context, $depth)

Outputs the table in XML

BUGS

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None known

AUTHOR

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Martin Hosken Martin_Hosken@sil.org. See Font::TTF::Font for copyright and licensing.

Font-TTF documentation Contained in the Font-TTF distribution. 
package Font::TTF::Hmtx;


use strict;
use vars qw(@ISA);
require Font::TTF::Table;

@ISA = qw(Font::TTF::Table);



sub read
{
    my ($self) = @_;
    my ($numh, $numg);

    $numh = $self->{' PARENT'}{'hhea'}->read->{'numberOfHMetrics'};
    $numg = $self->{' PARENT'}{'maxp'}{'numGlyphs'};
    $self->_read($numg, $numh, "advance", "lsb");
}

sub _read
{
    my ($self, $numg, $numh, $tAdv, $tLsb) = @_;
    my ($fh) = $self->{' INFILE'};
    my ($i, $dat);
    
    $self->SUPER::read or return $self;

    for ($i = 0; $i < $numh; $i++)
    {
        $fh->read($dat, 4);
        ($self->{$tAdv}[$i], $self->{$tLsb}[$i]) = unpack("nn", $dat);
        $self->{$tLsb}[$i] -= 65536 if ($self->{$tLsb}[$i] >= 32768);
    }
    
    $i--;
    while (++$i < $numg)
    {
        $fh->read($dat, 2);
        $self->{$tAdv}[$i] = $self->{$tAdv}[$numh - 1];
        $self->{$tLsb}[$i] = unpack("n", $dat);
        $self->{$tLsb}[$i] -= 65536 if ($self->{$tLsb}[$i] >= 32768);
    }
    $self;
}
    

sub numMetrics
{
    my ($self) = @_;
    my ($numg) = $self->{' PARENT'}{'maxp'}{'numGlyphs'};
    my ($i);

    return undef unless $self->{' read'};

    for ($i = $numg - 2; $i >= 0; $i--)
    { last if ($self->{'advance'}[$i] != $self->{'advance'}[$i + 1]); }

    return $i + 2;
}



sub out
{
    my ($self, $fh) = @_;
    my ($numg) = $self->{' PARENT'}{'maxp'}{'numGlyphs'};
    my ($numh) = $self->{' PARENT'}{'hhea'}->read->{'numberOfHMetrics'};
    $self->_out($fh, $numg, $numh, "advance", "lsb");
}

sub _out
{
    my ($self, $fh, $numg, $numh, $tAdv, $tLsb) = @_;
    my ($i, $lsb);

    return $self->SUPER::out($fh) unless ($self->{' read'});

    for ($i = 0; $i < $numg; $i++)
    {
        $lsb = $self->{$tLsb}[$i];
        $lsb += 65536 if $lsb < 0;
        if ($i >= $numh)
        { $fh->print(pack("n", $lsb)); }
        else
        { $fh->print(pack("n2", $self->{$tAdv}[$i], $lsb)); }
    }
    $self;
}



sub update
{
    my ($self) = @_;
    my ($numg) = $self->{' PARENT'}{'maxp'}{'numGlyphs'};
    my ($i);

    return undef unless ($self->SUPER::update);
# lsb & xMin must always be the same, regardless of any flags!
#    return $self unless ($self->{' PARENT'}{'head'}{'flags'} & 2);        # lsb & xMin the same

    $self->{' PARENT'}{'loca'}->update;
    for ($i = 0; $i < $numg; $i++)
    {
        my ($g) = $self->{' PARENT'}{'loca'}{'glyphs'}[$i];
        if ($g)
        { $self->{'lsb'}[$i] = $g->read->update_bbox->{'xMin'}; }
        else
        { $self->{'lsb'}[$i] = 0; }
    }
    $self->{' PARENT'}{'head'}{'flags'} |= 2;
    $self;
}
    


sub out_xml
{
    my ($self, $context, $depth) = @_;
    my ($fh) = $context->{'fh'};
    my ($numg) = $self->{' PARENT'}{'maxp'}{'numGlyphs'};
    my ($addr) = ($self =~ m/\((.+)\)$/o);
    my ($i);

    if ($context->{'addresses'}{$addr})
    {
        $fh->printf("%s<%s id_ref='%s'/>\n", $depth, $context->{'name'}, $addr);
        return $self;
    }
    else
    { $fh->printf("%s<%s id='%s'>\n", $depth, $context->{'name'}, $addr); }

    $self->read;

    for ($i = 0; $i < $numg; $i++)
    { $fh->print("$depth$context->{'indent'}<width adv='$self->{'advance'}[$i]' lsb='$self->{'lsb'}[$i]'/>\n"); }

    $fh->print("$depth</$context->{'name'}>\n");
    $self;
}

1;