712 lines
21 KiB
Perl
712 lines
21 KiB
Perl
package Font::TTF::GPOS;
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=head1 NAME
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Font::TTF::GPOS - Support for Opentype GPOS tables in conjunction with TTOpen
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=head1 DESCRIPTION
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The GPOS table is one of the most complicated tables in the TTF spec and the
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corresponding data structure abstraction is also not trivial. While much of the
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structure of a GPOS is shared with a GSUB table via the L<Font::TTF::Ttopen>
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=head1 INSTANCE VARIABLES
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Here we describe the additions and lookup specific information for GPOS tables.
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Unfortunately there is no one abstraction which seems to work comfortable for
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all GPOS tables, so we will also examine how the variables are used for different
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lookup types.
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The following are the values allowed in the ACTION_TYPE and MATCH_TYPE variables:
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=over 4
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=item ACTION_TYPE
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This can take any of the following values
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=over 8
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=item a
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The ACTION is an array of anchor tables
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=item o
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Offset. There is no RULE array. The ADJUST variable contains a value record (see
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later in this description)
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=item v
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The ACTION is a value record.
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=item p
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Pair adjustment. The ACTION contains an array of two value records for the matched
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two glyphs.
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=item e
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Exit and Entry records. The ACTION contains an array of two anchors corresponding
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to the exit and entry anchors for the glyph.
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=item l
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Indicates a lookup based contextual rule as per the GSUB table.
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=back
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=item MATCH_TYPE
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This can take any of the following values
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=over 8
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=item g
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A glyph array
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=item c
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An array of class values
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=item o
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An array of coverage tables
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=back
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=back
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The following variables are added for Attachment Positioning Subtables:
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=over 4
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=item MATCH
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This contains an array of glyphs to match against for all RULES. It is much like
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having the same MATCH string in all RULES. In the cases it is used so far, it only
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ever contains one element.
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=item MARKS
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This contains a Mark array consisting of each element being a subarray of two
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elements:
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=over 8
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=item CLASS
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The class that this mark uses on its base
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=item ANCHOR
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The anchor with which to attach this mark glyph
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=back
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The base table for mark to base, ligature or mark attachment positioning is
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structured with the ACTION containing an array of anchors corresponding to each
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attachment class. For ligatures, there is more than one RULE in the RULE array
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corresponding to each glyph in the coverage table.
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=back
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Other variables which are provided for informational purposes are:
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=over 4
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=item VFMT
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Value format for the adjustment of the glyph matched by the coverage table.
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=item VFMT2
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Value format used in pair adjustment for the second glyph in the pair
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=back
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=head2 Value Records
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There is a subtype used in GPOS tables called a value record. It is used to adjust
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the position of a glyph from its default position. The value record is variable
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length with a bitfield at the beginning to indicate which of the following
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entries are included. The bitfield is not stored since it is recalculated at
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write time.
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=over 4
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=item XPlacement
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Horizontal adjustment for placement (not affecting other unattached glyphs)
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=item YPlacement
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Vertical adjustment for placement (not affecting other unattached glyphs)
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=item XAdvance
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Adjust the advance width glyph (used only in horizontal writing systems)
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=item YAdvance
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Adjust the vertical advance (used only in vertical writing systems)
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=item XPlaDevice
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Device table for device specific adjustment of horizontal placement
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=item YPlaDevice
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Device table for device specific adjustment of vertical placement
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=item XAdvDevice
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Device table for device specific adjustment of horizontal advance
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=item YAdDevice
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Device table for device specific adjustment of vertical advance
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=item XIdPlacement
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Horizontal placement metric id (for Multiple Master fonts - but that is all I know!)
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=item YIdPlacement
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Vertical placement metric id
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=item XIdAdvance
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Horizontal advance metric id
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=item YIdAdvance
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Vertical advance metric id
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=back
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=head1 CORRESPONDANCE TO LAYOUT TYPES
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Here is what is stored in the ACTION_TYPE and MATCH_TYPE for each of the known
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GPOS subtable types:
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1.1 1.2 2.1 2.2 3 4 5 6 7.1 7.2 7.3 8.1 8.2 8.3
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ACTION_TYPE o v p p e a a a l l l l l l
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MATCH_TYPE g c g c o g c o
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=head1 METHODS
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=cut
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use strict;
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use Font::TTF::Ttopen;
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use Font::TTF::Delta;
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use Font::TTF::Anchor;
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use Font::TTF::Utils;
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use vars qw(@ISA);
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@ISA = qw(Font::TTF::Ttopen);
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=head2 read_sub
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Reads the subtable into the data structures
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=cut
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sub read_sub
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{
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my ($self, $fh, $main_lookup, $sindex) = @_;
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my ($type) = $main_lookup->{'TYPE'};
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my ($loc) = $fh->tell();
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my ($lookup) = $main_lookup->{'SUB'}[$sindex];
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my ($dat, $mcount, $scount, $i, $j, $count, $fmt, $fmt2, $cover, $srec, $subst);
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my ($c1, $c2, $s, $moff, $boff);
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if ($type == 8)
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{
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$fh->read($dat, 4);
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($fmt, $cover) = TTF_Unpack('S2', $dat);
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if ($fmt < 3)
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{
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$fh->read($dat, 2);
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$count = TTF_Unpack('S', $dat);
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}
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} else
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{
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$fh->read($dat, 6);
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($fmt, $cover, $count) = TTF_Unpack("S3", $dat);
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}
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unless ($fmt == 3 && ($type == 7 || $type == 8))
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{ $lookup->{'COVERAGE'} = $self->read_cover($cover, $loc, $lookup, $fh, 1); }
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$lookup->{'FORMAT'} = $fmt;
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if ($type == 1 && $fmt == 1)
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{
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$lookup->{'VFMT'} = $count;
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$lookup->{'ADJUST'} = $self->read_value($count, $loc, $lookup, $fh);
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$lookup->{'ACTION_TYPE'} = 'o';
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} elsif ($type == 1 && $fmt == 2)
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{
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$lookup->{'VFMT'} = $count;
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$fh->read($dat, 2);
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$mcount = unpack('n', $dat);
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for ($i = 0; $i < $mcount; $i++)
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{ push (@{$lookup->{'RULES'}}, [{'ACTION' =>
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[$self->read_value($count, $loc, $lookup, $fh)]}]); }
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$lookup->{'ACTION_TYPE'} = 'v';
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} elsif ($type == 2 && $fmt == 1)
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{
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$lookup->{'VFMT'} = $count;
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$fh->read($dat, 4);
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($fmt2, $mcount) = unpack('n2', $dat);
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$lookup->{'VFMT2'} = $fmt2;
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$fh->read($dat, $mcount << 1);
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foreach $s (unpack('n*', $dat))
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{
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$fh->seek($loc + $s, 0);
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$fh->read($dat, 2);
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$scount = TTF_Unpack('S', $dat);
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$subst = [];
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for ($i = 0; $i < $scount; $i++)
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{
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$srec = {};
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$fh->read($dat, 2);
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$srec->{'MATCH'} = [TTF_Unpack('S', $dat)];
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$srec->{'ACTION'} = [$self->read_value($count, $loc, $lookup, $fh),
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$self->read_value($fmt2, $loc, $lookup, $fh)];
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push (@$subst, $srec);
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}
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push (@{$lookup->{'RULES'}}, $subst);
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}
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$lookup->{'ACTION_TYPE'} = 'p';
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$lookup->{'MATCH_TYPE'} = 'g';
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} elsif ($type == 2 && $fmt == 2)
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{
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$fh->read($dat, 10);
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($lookup->{'VFMT2'}, $c1, $c2, $mcount, $scount) = TTF_Unpack('S*', $dat);
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$lookup->{'CLASS'} = $self->read_cover($c1, $loc, $lookup, $fh, 0);
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$lookup->{'MATCH'} = [$self->read_cover($c2, $loc, $lookup, $fh, 0)];
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$lookup->{'VFMT'} = $count;
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for ($i = 0; $i < $mcount; $i++)
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{
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$subst = [];
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for ($j = 0; $j < $scount; $j++)
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{
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$srec = {};
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$srec->{'ACTION'} = [$self->read_value($lookup->{'VFMT'}, $loc, $lookup, $fh),
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$self->read_value($lookup->{'VFMT2'}, $loc, $lookup, $fh)];
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push (@$subst, $srec);
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}
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push (@{$lookup->{'RULES'}}, $subst);
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}
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$lookup->{'ACTION_TYPE'} = 'p';
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$lookup->{'MATCH_TYPE'} = 'c';
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} elsif ($type == 3 && $fmt == 1)
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{
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$fh->read($dat, $count << 2);
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for ($i = 0; $i < $count; $i++)
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{ push (@{$lookup->{'RULES'}}, [{'ACTION' =>
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[$self->read_anchor(TTF_Unpack('S', substr($dat, $i << 2, 2)),
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$loc, $lookup, $fh),
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$self->read_anchor(TTF_Unpack('S', substr($dat, ($i << 2) + 2, 2)),
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$loc, $lookup, $fh)]}]); }
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$lookup->{'ACTION_TYPE'} = 'e';
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} elsif ($type == 4 || $type == 5 || $type == 6)
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{
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my (@offs, $mloc, $thisloc, $ncomp, $k);
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$lookup->{'MATCH'} = [$lookup->{'COVERAGE'}]; # Attaching mark
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$lookup->{'COVERAGE'} = $self->read_cover($count, $loc, $lookup, $fh, 1); # base/lig/mark being attached to
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$fh->read($dat, 6);
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($mcount, $moff, $boff) = TTF_Unpack('S*', $dat);
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# Read MarkArray
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$fh->seek($loc + $moff, 0);
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$fh->read($dat, 2);
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$count = TTF_Unpack('S', $dat);
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for ($i = 0; $i < $count; $i++)
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{
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$fh->read($dat, 4);
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push (@{$lookup->{'MARKS'}}, [TTF_Unpack('S', $dat),
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$self->read_anchor(TTF_Unpack('S', substr($dat, 2, 2)) + $moff,
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$loc, $lookup, $fh)]);
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}
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# Read BaseArray/LigatureArray/Mark2Array
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$fh->seek($loc + $boff, 0);
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$fh->read($dat, 2);
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$count = TTF_Unpack('S', $dat);
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$mloc = $fh->tell() - 2;
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$thisloc = $mloc;
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if ($type == 5)
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{
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$fh->read($dat, $count << 1);
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@offs = TTF_Unpack('S*', $dat);
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}
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for ($i = 0; $i < $count; $i++)
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{
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if ($type == 5)
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{
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$thisloc = $mloc + $offs[$i];
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$fh->seek($thisloc, 0);
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$fh->read($dat, 2);
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$ncomp = TTF_Unpack('S', $dat);
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} else
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{ $ncomp = 1; }
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for ($j = 0; $j < $ncomp; $j++)
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{
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$subst = [];
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$fh->read($dat, $mcount << 1);
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for ($k = 0; $k < $mcount; $k++)
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{ push (@$subst, $self->read_anchor(TTF_Unpack('S', substr($dat, $k << 1, 2)),
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$thisloc, $lookup, $fh)); }
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push (@{$lookup->{'RULES'}[$i]}, {'ACTION' => $subst});
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}
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}
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$lookup->{'ACTION_TYPE'} = 'a';
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} elsif ($type == 7 || $type == 8)
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{ $self->read_context($lookup, $fh, $type - 2, $fmt, $cover, $count, $loc); }
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$lookup;
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}
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=head2 $t->extension
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Returns the table type number for the extension table
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=cut
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sub extension
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{ return 9; }
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=head2 $t->out_sub
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Outputs the subtable to the given filehandle
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=cut
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sub out_sub
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{
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my ($self, $fh, $main_lookup, $index, $ctables, $base) = @_;
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my ($type) = $main_lookup->{'TYPE'};
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my ($lookup) = $main_lookup->{'SUB'}[$index];
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my ($fmt) = $lookup->{'FORMAT'};
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my ($out, $r, $s, $t, $i, $j, $vfmt, $vfmt2, $loc1);
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my ($num) = $#{$lookup->{'RULES'}} + 1;
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my ($mtables) = {};
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my (@reftables);
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if ($type == 1 && $fmt == 1)
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{
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$out = pack('n2', $fmt, Font::TTF::Ttopen::ref_cache($lookup->{'COVERAGE'}, $ctables, 2 + $base));
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$vfmt = $self->fmt_value($lookup->{'ADJUST'});
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$out .= pack('n', $vfmt) . $self->out_value($lookup->{'ADJUST'}, $vfmt, $ctables, 6 + $base);
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} elsif ($type == 1 && $fmt == 2)
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{
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$vfmt = 0;
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foreach $r (@{$lookup->{'RULES'}})
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{ $vfmt |= $self->fmt_value($r->[0]{'ACTION'}[0]); }
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$out = pack('n4', $fmt, Font::TTF::Ttopen::ref_cache($lookup->{'COVERAGE'}, $ctables, 2 + $base),
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$vfmt, $#{$lookup->{'RULES'}} + 1);
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foreach $r (@{$lookup->{'RULES'}})
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{ $out .= $self->out_value($r->[0]{'ACTION'}[0], $vfmt, $ctables, length($out) + $base); }
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} elsif ($type == 2 && $fmt < 3)
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{
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$vfmt = 0;
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$vfmt2 = 0;
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foreach $r (@{$lookup->{'RULES'}})
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{
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foreach $t (@$r)
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{
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$vfmt |= $self->fmt_value($t->{'ACTION'}[0]);
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$vfmt2 |= $self->fmt_value($t->{'ACTION'}[1]);
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}
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}
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if ($fmt == 1)
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{
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# start PairPosFormat1 subtable
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$out = pack('n5',
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$fmt,
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Font::TTF::Ttopen::ref_cache($lookup->{'COVERAGE'}, $ctables, 2 + $base),
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$vfmt,
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$vfmt2,
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$#{$lookup->{'RULES'}} + 1); # PairSetCount
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my $off = 0;
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$off += length($out);
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$off += 2 * ($#{$lookup->{'RULES'}} + 1); # there will be PairSetCount offsets here
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my $pairsets = '';
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my (%cache);
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foreach $r (@{$lookup->{'RULES'}}) # foreach PairSet table
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{
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# write offset to this PairSet at end of PairPosFormat1 table
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if (defined $cache{"$r"})
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{ $out .= pack('n', $cache{"$r"}); }
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else
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{
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$out .= pack('n', $off);
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$cache{"$r"} = $off;
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# generate PairSet itself (using $off as eventual offset within PairPos subtable)
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my $pairset = pack('n', $#{$r} + 1); # PairValueCount
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foreach $t (@$r) # foreach PairValueRecord
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{
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$pairset .= pack('n', $t->{'MATCH'}[0]); # SecondGlyph - MATCH has only one entry
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$pairset .=
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$self->out_value($t->{'ACTION'}[0], $vfmt, $ctables, $off + length($pairset) + $base);
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$pairset .=
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$self->out_value($t->{'ACTION'}[1], $vfmt2, $ctables, $off + length($pairset) + $base);
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}
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$off += length($pairset);
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$pairsets .= $pairset;
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}
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}
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$out .= $pairsets;
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die "internal error: PairPos size not as calculated" if (length($out) != $off);
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} else
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{
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$out = pack('n8', $fmt, Font::TTF::Ttopen::ref_cache($lookup->{'COVERAGE'}, $ctables, 2 + $base),
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$vfmt, $vfmt2,
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Font::TTF::Ttopen::ref_cache($lookup->{'CLASS'}, $ctables, 8 + $base),
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Font::TTF::Ttopen::ref_cache($lookup->{'MATCH'}[0], $ctables, 10 + $base),
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$lookup->{'CLASS'}{'max'} + 1, $lookup->{'MATCH'}[0]{'max'} + 1);
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for ($i = 0; $i <= $lookup->{'CLASS'}{'max'}; $i++)
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{
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for ($j = 0; $j <= $lookup->{'MATCH'}[0]{'max'}; $j++)
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{
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$out .= $self->out_value($lookup->{'RULES'}[$i][$j]{'ACTION'}[0], $vfmt, $ctables, length($out) + $base);
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$out .= $self->out_value($lookup->{'RULES'}[$i][$j]{'ACTION'}[1], $vfmt2, $ctables, length($out) + $base);
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}
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}
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}
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} elsif ($type == 3 && $fmt == 1)
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{
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$out = pack('n3', $fmt, Font::TTF::Ttopen::ref_cache($lookup->{'COVERAGE'}, $ctables, 2 + $base),
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$#{$lookup->{'RULES'}} + 1);
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foreach $r (@{$lookup->{'RULES'}})
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{
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$out .= pack('n2', Font::TTF::Ttopen::ref_cache($r->[0]{'ACTION'}[0], $ctables, length($out) + $base),
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Font::TTF::Ttopen::ref_cache($r->[0]{'ACTION'}[1], $ctables, length($out) + 2 + $base));
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}
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} elsif ($type == 4 || $type == 5 || $type == 6)
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{
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my ($loc_off, $loc_t, $ltables);
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$out = pack('n7', $fmt, Font::TTF::Ttopen::ref_cache($lookup->{'MATCH'}[0], $ctables, 2 + $base),
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Font::TTF::Ttopen::ref_cache($lookup->{'COVERAGE'}, $ctables, 4 + $base),
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$#{$lookup->{'RULES'}[0][0]{'ACTION'}} + 1, 12, ($#{$lookup->{'MARKS'}} + 4) << 2,
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$#{$lookup->{'MARKS'}} + 1);
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foreach $r (@{$lookup->{'MARKS'}})
|
|
{ $out .= pack('n2', $r->[0], Font::TTF::Ttopen::ref_cache($r->[1], $mtables, length($out) + 2)); }
|
|
push (@reftables, [$mtables, 12]);
|
|
|
|
$loc_t = length($out);
|
|
substr($out, 10, 2) = pack('n', $loc_t);
|
|
$out .= pack('n', $#{$lookup->{'RULES'}} + 1);
|
|
if ($type == 5)
|
|
{
|
|
$loc1 = length($out);
|
|
$out .= pack('n*', (0) x ($#{$lookup->{'RULES'}} + 1));
|
|
}
|
|
$ltables = {};
|
|
for ($i = 0; $i <= $#{$lookup->{'RULES'}}; $i++)
|
|
{
|
|
if ($type == 5)
|
|
{
|
|
$ltables = {};
|
|
$loc_t = length($out);
|
|
substr($out, $loc1 + ($i << 1), 2) = TTF_Pack('S', $loc_t - $loc1 + 2);
|
|
}
|
|
|
|
$r = $lookup->{'RULES'}[$i];
|
|
$out .= pack('n', $#{$r} + 1) if ($type == 5);
|
|
foreach $t (@$r)
|
|
{
|
|
foreach $s (@{$t->{'ACTION'}})
|
|
{ $out .= pack('n', Font::TTF::Ttopen::ref_cache($s, $ltables, length($out))); }
|
|
}
|
|
push (@reftables, [$ltables, $loc_t]) if ($type == 5);
|
|
}
|
|
push (@reftables, [$ltables, $loc_t]) unless ($type == 5);
|
|
$out = Font::TTF::Ttopen::out_final($fh, $out, \@reftables, 1);
|
|
} elsif ($type == 7 || $type == 8)
|
|
{ $out = $self->out_context($lookup, $fh, $type - 2, $fmt, $ctables, $out, $num, $base); }
|
|
# push (@reftables, [$ctables, 0]);
|
|
$out;
|
|
}
|
|
|
|
|
|
=head2 $t->read_value($format, $base, $lookup, $fh)
|
|
|
|
Reads a value record from the current location in the file, according to the
|
|
format given.
|
|
|
|
=cut
|
|
|
|
sub read_value
|
|
{
|
|
my ($self, $fmt, $base, $lookup, $fh) = @_;
|
|
my ($flag) = 1;
|
|
my ($res) = {};
|
|
my ($s, $i, $dat);
|
|
|
|
$s = 0;
|
|
for ($i = 0; $i < 12; $i++)
|
|
{
|
|
$s++ if ($flag & $fmt);
|
|
$flag <<= 1;
|
|
}
|
|
|
|
$fh->read($dat, $s << 1);
|
|
$flag = 1; $i = 0;
|
|
foreach $s (qw(XPlacement YPlacement XAdvance YAdvance))
|
|
{
|
|
$res->{$s} = TTF_Unpack('s', substr($dat, $i++ << 1, 2)) if ($fmt & $flag);
|
|
$flag <<= 1;
|
|
}
|
|
|
|
foreach $s (qw(XPlaDevice YPlaDevice XAdvDevice YAdvDevice))
|
|
{
|
|
if ($fmt & $flag)
|
|
{ $res->{$s} = $self->read_delta(TTF_Unpack('S', substr($dat, $i++ << 1, 2)),
|
|
$base, $lookup, $fh); }
|
|
$flag <<= 1;
|
|
}
|
|
|
|
foreach $s (qw(XIdPlacement YIdPlacement XIdAdvance YIdAdvance))
|
|
{
|
|
$res->{$s} = TTF_Unpack('S', substr($dat, $i++ << 1, 2)) if ($fmt & $flag);
|
|
$flag <<= 1;
|
|
}
|
|
$res;
|
|
}
|
|
|
|
|
|
=head2 $t->read_delta($offset, $base, $lookup, $fh)
|
|
|
|
Reads a delta (device table) at the given offset if it hasn not already been read.
|
|
Store the offset and item in the lookup cache ($lookup->{' CACHE'})
|
|
|
|
=cut
|
|
|
|
sub read_delta
|
|
{
|
|
my ($self, $offset, $base, $lookup, $fh) = @_;
|
|
my ($loc) = $fh->tell();
|
|
my ($res, $str);
|
|
|
|
return undef unless $offset;
|
|
$str = sprintf("%X", $base + $offset);
|
|
return $lookup->{' CACHE'}{$str} if defined $lookup->{' CACHE'}{$str};
|
|
$fh->seek($base + $offset, 0);
|
|
$res = Font::TTF::Delta->new->read($fh);
|
|
$fh->seek($loc, 0);
|
|
$lookup->{' CACHE'}{$str} = $res;
|
|
return $res;
|
|
}
|
|
|
|
|
|
=head2 $t->read_anchor($offset, $base, $lookup, $fh)
|
|
|
|
Reads an Anchor table at the given offset if it has not already been read.
|
|
|
|
=cut
|
|
|
|
sub read_anchor
|
|
{
|
|
my ($self, $offset, $base, $lookup, $fh) = @_;
|
|
my ($loc) = $fh->tell();
|
|
my ($res, $str);
|
|
|
|
return undef unless $offset;
|
|
$str = sprintf("%X", $base + $offset);
|
|
return $lookup->{' CACHE'}{$str} if defined $lookup->{' CACHE'}{$str};
|
|
$fh->seek($base + $offset, 0);
|
|
$res = Font::TTF::Anchor->new->read($fh);
|
|
$fh->seek($loc, 0);
|
|
$lookup->{' CACHE'}{$str} = $res;
|
|
return $res;
|
|
}
|
|
|
|
|
|
=head2 $t->fmt_value
|
|
|
|
Returns the value format for a given value record
|
|
|
|
=cut
|
|
|
|
sub fmt_value
|
|
{
|
|
my ($self, $value) = @_;
|
|
my ($fmt) = 0;
|
|
my ($n);
|
|
|
|
foreach $n (reverse qw(XPlacement YPlacement XAdvance YAdvance XPlaDevice YPlaDevice
|
|
XAdvDevice YAdvDevice XIdPlacement YIdPlacement XIdAdvance
|
|
YIdAdvance))
|
|
{
|
|
$fmt <<= 1;
|
|
$fmt |= 1 if (defined $value->{$n} && (ref $value->{$n} || $value->{$n}));
|
|
}
|
|
$fmt;
|
|
}
|
|
|
|
|
|
=head2 $t->out_value
|
|
|
|
Returns the output string for the outputting of the value for a given format. Also
|
|
updates the offset cache for any device tables referenced.
|
|
|
|
=cut
|
|
|
|
sub out_value
|
|
{
|
|
my ($self, $value, $fmt, $tables, $offset) = @_;
|
|
my ($n, $flag, $out);
|
|
|
|
$flag = 1;
|
|
foreach $n (qw(XPlacement YPlacement XAdvance YAdvance))
|
|
{
|
|
$out .= pack('n', $value->{$n}) if ($flag & $fmt);
|
|
$flag <<= 1;
|
|
}
|
|
foreach $n (qw(XPlaDevice YPlaDevice XAdvDevice YAdvDevice))
|
|
{
|
|
if ($flag & $fmt)
|
|
{
|
|
$out .= pack('n', Font::TTF::Ttopen::ref_cache(
|
|
$value->{$n}, $tables, $offset + length($out)));
|
|
}
|
|
$flag <<= 1;
|
|
}
|
|
foreach $n (qw(XIdPlacement YIdPlacement XIdAdvance YIdAdvance))
|
|
{
|
|
$out .= pack('n', $value->{$n}) if ($flag & $fmt);
|
|
$flag <<= 1;
|
|
}
|
|
$out;
|
|
}
|
|
|
|
1;
|
|
|
|
=head1 AUTHOR
|
|
|
|
Martin Hosken L<http://scripts.sil.org/FontUtils>.
|
|
|
|
|
|
=head1 LICENSING
|
|
|
|
Copyright (c) 1998-2016, SIL International (http://www.sil.org)
|
|
|
|
This module is released under the terms of the Artistic License 2.0.
|
|
For details, see the full text of the license in the file LICENSE.
|
|
|
|
|
|
|
|
=cut
|
|
|