Font::TTF::GSUB

lib::Font::TTF::GSUB(3User Contributed Perl Documentatilib::Font::TTF::GSUB(3)



NAME
       Font::TTF::GSUB - Module support for the GSUB table in conjunction with
       TTOpen

DESCRIPTION
       Handles the GSUB subtables in relation to Ttopen tables. Due to the
       variety of different lookup types, the data structures are not all that
       straightforward, although I have tried to make life easy for myself
       when using this!

INSTANCE VARIABLES
       The structure of a GSUB table is the same as that given in the
       Font::TTF::Ttopen manpage.  Here we give some of the semantics specific
       to GSUB lookups.

       ACTION_TYPE
           This is a string taking one of 4 values indicating the nature of
           the information in the ACTION array of the rule:

       g           The action contains a string of glyphs to replace the match
                   string by

       l           The action array contains a list of lookups and offsets to
                   run, in order, on the matched string

       a           The action array is an unordered set of optional
                   replacements for the matched glyph. The application should
                   make the selection somehow.

       o           The action array is empty (in fact there is no rule array
                   for this type of rule) and the ADJUST value should be added
                   to the glyph id to find the replacement glyph id value

       MATCH_TYPE
           This indicates which type of information the various MATCH arrays
           (MATCH, PRE, POST) hold in the rule:

       g           The array holds a string of glyph ids which should match
                   exactly

       c           The array holds a sequence of class definitions which each
                   glyph should correspondingly match to

       o           The array holds offsets to coverage tables

CORRESPONDANCE TO LAYOUT TYPES
       The following table gives the values for ACTION_TYPE and MATCH_TYPE for
       each of the 11 different lookup types found in the GSUB table
       definition I have:

                       1.1 1.2 2   3   4   5.1 5.2 5.3 6.1 6.2 6.3
         ACTION_TYPE    o   g  g   a   g    l   l   l   l   l   l
         MATCH_TYPE                    g    g   c   o   g   c   o

       Hopefully, the rest of the uses of the variables should make sense from
       this table.

METHODS
       $t->read_sub($fh, $lookup, $index)

       Asked by the superclass to read in from the given file the indexth
       subtable from lookup number lookup. The file is positioned ready for
       the read.

       $t->out_sub($fh, $lookup, $index)

       Passed the filehandle to output to, suitably positioned, the lookup and
       subtable index, this function outputs the subtable to $fh at that
       point.

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






















3rd Berkeley Distribution    perl 5.005, patch 03      lib::Font::TTF::GSUB(3)