# Font::TTF::Kern - phpMan

## NAME
    [Font::TTF::Kern] - Kerning tables

## DESCRIPTION
    Kerning tables are held as an ordered collection of subtables each
    giving incremental information regarding the kerning of various pairs of
    glyphs.

    The basic structure of the kerning data structure is:

        $kern = $f->{'kern'}{'tables'}[$tnum]{'kerns'}{$leftnum}{$rightnum};

    Due to the possible complexity of some kerning tables the above
    information is insufficient. Reference also needs to be made to the type
    of the table and the coverage field.

## INSTANCE VARIABLES
    The instance variables for a kerning table are relatively
    straightforward.

    Version
        Version number of the kerning table

    Num Number of subtables in the kerning table

    tables
        Array of subtables in the kerning table

        Each subtable has a number of instance variables.

        kern
            A two level hash array containing kerning values. The indexing
            is left is via left class and right class. It may seem using
            hashes is strange, but most tables are not type 2 and this
            method saves empty array values.

        type
            Stores the table type. Only type 0 and type 2 tables are
            specified for TrueType so far.

        coverage
            A bit field of coverage information regarding the kerning value.
            See the TrueType specification for details.

        Version
            Contains the version number of the table.

        Num Number of kerning pairs in this type 0 table.

        left
            An array indexed by glyph - left_first which returns a class
            number for the glyph in type 2 tables.

        right
            An array indexed by glyph - right_first which returns a class
            number for the glyph in type 2 tables.

        left_first
            the glyph number of the first element in the left array for type
            2 tables.

        right_first
            the glyph number of the first element in the right array for
            type 2 tables.

        num_left
            Number of left classes

        num_right
            Number of right classes

## METHODS
  $t->read
    Reads the whole kerning table into structures

  $t->out($fh)
    Outputs the kerning tables to the given file

  $t->XML_element($context, $depth, $key, $value)
    Handles outputting the kern hash into XML a little more tidily

  $t->minsize()
    Returns the minimum size this table can be. If it is smaller than this,
    then the table must be bad and should be deleted or whatever.

## BUGS
    *   Only supports kerning table types 0 & 2.

    *   No real support functions to *do* anything with the kerning tables
        yet.

## AUTHOR
    Martin Hosken <<http://scripts.sil.org/FontUtils>>.

## 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.