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Font::TTF::Font.3pm

NAME

Font::TTF::Font - Memory representation of a font

SYNOPSIS

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.

     $f = Font::TTF::Font->open($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!
 
 

DESCRIPTION

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 "table" is used, which defaults to Font::TTF::Table. The current tables which are supported are:

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

Links are:

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

INSTANCE VARIABLES

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.

noharmony

If set, do not harmonize the script and lang trees of GPOS and GSUB tables. See Font::TTF::Ttopen for more info.

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.

METHODS

Font::TTF::Font->AddTable($tablename, $class)

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

Font::TTF::Font->Init

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 Font::TTF::Font::read before using a table.

Font::TTF::Font->new(%props)

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.

Font::TTF::Font->open($fname)

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

$f->read

Reads a Truetype font directory starting from the current location in the file. This has been separated from the "open" function to allow support for embedded TTFs for example in TTCs. Also reads the "head" and "maxp" tables immediately.

$f->out($fname [, @tablelist])

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 @tablelist, in which case the subroutine will output all the defined tables in the font in alphabetical order.

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

All output files must include the "head" table.

$f->out_xml($filename [, @tables])

Outputs the font in XML format

$f->XML_start($context, $tag, %attrs)

Handles start messages from the XML parser. Of particular interest to us are <font> and <table>.

$f->update

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).

$f->dirty

Dirties all the tables in the font

$f->tables_do(&func [, tables])

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);
 
 

May optionally take a list of table names in which case func is called for each of them in the given order.

$f->release

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 "Font::TTF::Font" object.

NOTE, that it is important that you call this method on any "Font::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 '"release()"' 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 "Font::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 "Font::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

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 Font::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.

AUTHOR

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.

Licensing

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