PDF::API2::Basic::TTF::Font - Memory representation of a font

Here is the regression test (you provide your own font). Run it once and then again on the output of the first run. There should be no differences between the outputs of the two runs.

    $f = PDF::API2::Basic::TTF::Font->open($ARGV[0]);

    # force a read of all the tables
    $f->tables_do(sub { $_[0]->read; });

    # force read of all glyphs (use read_dat to use lots of memory!)
    # $f->{'loca'}->glyphs_do(sub { $_[0]->read; });
    $f->{'loca'}->glyphs_do(sub { $_[0]->read_dat; });
    # NB. no need to $g->update since $f->{'glyf'}->out will do it for us

    $f->out($ARGV[1]);
    $f->release;            # clear up memory forcefully!

A Truetype font consists of a header containing a directory of tables which constitute the rest of the file. This class holds that header and directory and also creates objects of the appropriate type for each table within the font. Note that it does not read each table into memory, but creates a short reference which can be read using the form:

    $f->{$tablename}->read;

Classes are included that support many of the different TrueType tables. For those for which no special code exists, the table type CWtable is used, which defaults to PDF::API2::Basic::TTF::Table. The current tables which are supported are:

    table       PDF::API2::Basic::TTF::Table      - for unknown tables
    GDEF        PDF::API2::Basic::TTF::GDEF
    GPOS        PDF::API2::Basic::TTF::GPOS
    GSUB        PDF::API2::Basic::TTF::GSUB
    LTSH        PDF::API2::Basic::TTF::LTSH
    OS/2        PDF::API2::Basic::TTF::OS_2
    PCLT        PDF::API2::Basic::TTF::PCLT
    bsln        PDF::API2::Basic::TTF::Bsln
    cmap        PDF::API2::Basic::TTF::Cmap       - see also PDF::API2::Basic::TTF::OldCmap
    cvt         PDF::API2::Basic::TTF::Cvt_
    fdsc        PDF::API2::Basic::TTF::Fdsc
    feat        PDF::API2::Basic::TTF::Feat
    fmtx        PDF::API2::Basic::TTF::Fmtx
    fpgm        PDF::API2::Basic::TTF::Fpgm
    glyf        PDF::API2::Basic::TTF::Glyf       - see also PDF::API2::Basic::TTF::Glyph
    hdmx        PDF::API2::Basic::TTF::Hdmx
    head        PDF::API2::Basic::TTF::Head
    hhea        PDF::API2::Basic::TTF::Hhea
    hmtx        PDF::API2::Basic::TTF::Hmtx
    kern        PDF::API2::Basic::TTF::Kern       - see alternative PDF::API2::Basic::TTF::AATKern
    loca        PDF::API2::Basic::TTF::Loca
    maxp        PDF::API2::Basic::TTF::Maxp
    mort        PDF::API2::Basic::TTF::Mort       - see also PDF::API2::Basic::TTF::OldMort
    name        PDF::API2::Basic::TTF::Name
    post        PDF::API2::Basic::TTF::Post
    prep        PDF::API2::Basic::TTF::Prep
    prop        PDF::API2::Basic::TTF::Prop
    vhea        PDF::API2::Basic::TTF::Vhea
    vmtx        PDF::API2::Basic::TTF::Vmtx

Links are:

PDF::API2::Basic::TTF::Table PDF::API2::Basic::TTF::GDEF PDF::API2::Basic::TTF::GPOS PDF::API2::Basic::TTF::GSUB PDF::API2::Basic::TTF::LTSH PDF::API2::Basic::TTF::OS_2 PDF::API2::Basic::TTF::PCLT PDF::API2::Basic::TTF::Bsln PDF::API2::Basic::TTF::Cmap PDF::API2::Basic::TTF::Cvt_ PDF::API2::Basic::TTF::Fdsc PDF::API2::Basic::TTF::Feat PDF::API2::Basic::TTF::Fmtx PDF::API2::Basic::TTF::Fpgm PDF::API2::Basic::TTF::Glyf PDF::API2::Basic::TTF::Hdmx PDF::API2::Basic::TTF::Head PDF::API2::Basic::TTF::Hhea PDF::API2::Basic::TTF::Hmtx PDF::API2::Basic::TTF::Kern PDF::API2::Basic::TTF::Loca PDF::API2::Basic::TTF::Maxp PDF::API2::Basic::TTF::Mort PDF::API2::Basic::TTF::Name PDF::API2::Basic::TTF::Post PDF::API2::Basic::TTF::Prep PDF::API2::Basic::TTF::Prop PDF::API2::Basic::TTF::Vhea PDF::API2::Basic::TTF::Vmtx PDF::API2::Basic::TTF::OldCmap PDF::API2::Basic::TTF::Glyph PDF::API2::Basic::TTF::AATKern PDF::API2::Basic::TTF::OldMort

Instance variables begin with a space (and have lengths greater than the 4 characters which make up table names).

nocsum

This is used during output to disable the creation of the file checksum in the head table. For example, during DSIG table creation, this flag will be set to ensure that the file checksum is left at zero.

fname (R)

Contains the filename of the font which this object was read from.

INFILE (P)

The file handle which reflects the source file for this font.

OFFSET (P)

Contains the offset from the beginning of the read file of this particular font directory, thus providing support for TrueType Collections.

Adds the given class to be used when representing the given table name. It also 'requires' the class for you.

For those people who like making fonts without reading them. This subroutine will require all the table code for the various table types for you. Not needed if using PDF::API2::Basic::TTF::Font::read before using a table.

Creates a new font object and initialises with the given properties. This is primarily for use when a TTF is embedded somewhere. Notice that the properties are automatically preceded by a space when inserted into the object. This is in order that fields do not clash with tables.

Reads the header and directory for the given font file and creates appropriate objects for each table in the font.

Reads a Truetype font directory starting from the current location in the file. This has been separated from the CWopen function to allow support for embedded TTFs for example in TTCs. Also reads the CWhead and CWmaxp tables immediately. Writes a TTF file consisting of the tables in tablelist. The list is checked to ensure that only tables that exist are output. (This means that you can't have non table information stored in the font object with key length of exactly 4)

In many cases the user simply wants to output all the tables in alphabetical order. This can be done by not including a CW@tablelist, in which case the subroutine will output all the defined tables in the font in alphabetical order.

Returns CW$f on success and undef on failure, including warnings.

All output files must include the CWhead table. Outputs the font in XML format Handles start messages from the XML parser. Of particular interest to us are <font> and <table>.

Sends update to all the tables in the font and then resets all the isDirty flags on each table. The data structure in now consistent as a font (we hope).

Dirties all the tables in the font

Calls &func for each table in the font. Calls the table in alphabetical sort order as per the order in the directory:

    &func($table, $name);

Releases ALL of the memory used by the TTF font and all of its component objects. After calling this method, do NOT expect to have anything left in the CWPDF::API2::Basic::TTF::Font object.

NOTE, that it is important that you call this method on any CWPDF::API2::Basic::TTF::Font object when you wish to destruct it and free up its memory. Internally, we track things in a structure that can result in circular references, and without calling 'CWrelease()' these will not properly get cleaned up by Perl. Once you've called this method, though, don't expect to be able to do anything else with the CWPDF::API2::Basic::TTF::Font object; it'll have no internal state whatsoever.

Developer note: As part of the brute-force cleanup done here, this method will throw a warning message whenever unexpected key values are found within the CWPDF::API2::Basic::TTF::Font object. This is done to help ensure that any unexpected and unfreed values are brought to your attention so that you can bug us to keep the module updated properly; otherwise the potential for memory leaks due to dangling circular references will exist.

Bugs abound aplenty I am sure. There is a lot of code here and plenty of scope. The parts of the code which haven't been implemented yet are:

Post

Version 4 format types are not supported yet.

Cmap

Format type 2 (MBCS) has not been implemented yet and therefore may cause somewhat spurious results for this table type.

Kern

Only type 0 & type 2 tables are supported (type 1 & type 3 yet to come).

TTC

The current PDF::API2::Basic::TTF::Font::out method does not support the writing of TrueType Collections.

In addition there are weaknesses or features of this module library

•

There is very little (or no) error reporting. This means that if you have garbled data or garbled data structures, then you are liable to generate duff fonts.

•

The exposing of the internal data structures everywhere means that doing radical re-structuring is almost impossible. But it stop the code from becoming ridiculously large.

Apart from these, I try to keep the code in a state of no known bugs, which given the amount of testing this code has had, is not a guarantee of high quality, yet.

For more details see the appropriate class files.

Martin Hosken Martin_Hosken@sil.org

Copyright Martin Hosken 1998.

No warranty or expression of effectiveness, least of all regarding anyone's safety, is implied in this software or documentation.

The Perl TTF module is licensed under the Perl Artistic License.