NAME

       Font::TTF::Glyph - Holds a information for a single glyph

DESCRIPTION

       This is a single glyph description as held in a TT font. On creation only its header is
       read. Thus you can get the bounding box of each glyph without having to read all the other
       information.

INSTANCE VARIABLES

       In addition to the named variables in a glyph header ("xMin" etc.), there are also all
       capital instance variables for holding working information, mostly from the location
       table.

   Variables for all glyphs:
       The standard attributes each glyph has are:

       numberOfContours
           For simple glyphs this will be the count of contours. For compound glyphs this will be
           -1.

       xMin
       yMin
       xMax
       yMax
           These identify the bounding box of the glyph.

       There are also other, derived, instance variables for each glyph which are read when the
       whole glyph is read (via "read_dat"):

       instLen
           Number of bytes in the hinting instructions (Warning this variable is deprecated, use
           "length($g-"{'hints'})> instead).

       hints
           The string containing the hinting code for the glyph

   Variables for simple glyphs (numberOfContours >= 0):
       endPoints
           An array of endpoints for each contour in the glyph. There are "numberOfContours"
           contours in a glyph. The number of points in a glyph is equal to the highest endpoint
           of a contour.

       numPoints
           This is a generated value which contains the total number of points for this simple
           glyph.

       There are also a number of arrays indexed by point number:

       flags
           The flags associated with reading this point. The flags for a point are recalculated
           for a point when it is "update"d. Thus the flags are not very useful. The only
           important bit is bit 0 which indicates whether the point is an 'on' curve point, or an
           'off' curve point.

       x   The absolute x co-ordinate of the point.

       y   The absolute y co-ordinate of the point

   Variables for compound glyphs (numberOfContours == -1):
       metric
           This holds the component number (not its glyph number) of the component from which the
           metrics for this glyph should be taken.

       comps
           This is an array of hashes for each component. Each hash has a number of elements:

           glyph
               The glyph number of the glyph which comprises this component of the composite.
               NOTE: In some badly generated fonts, "glyph" may contain a numerical value but
               that glyph might not actually exist in the font file.  This could occur in any
               glyph, but is particularly likely for glyphs that have no strokes, such as SPACE,
               U+00A0 NO-BREAK SPACE, or U+200B ZERO WIDTH SPACE.

           args
               An array of two arguments which may be an x, y co-ordinate or two attachment
               points (one on the base glyph the other on the component). See flags for details.

           flag
               The flag for this component

           scale
               A 4 number array for component scaling. This allows stretching, rotating, etc.
               Note that scaling applies to placement co-ordinates (rather than attachment
               points) before locating rather than after.

       numPoints
           This is a generated value which contains the number of components read in for this
           compound glyph.

   Private instance variables:
       INFILE (P)
           The input file form which to read any information

       LOC (P)
           Location relative to the start of the glyf table in the read file

       BASE (P)
           The location of the glyf table in the read file

       LEN (P)
           This is the number of bytes required by the glyph. It should be kept up to date by
           calling the "update" method whenever any of the glyph content changes.

       OUTLOC (P)
           Location relative to the start of the glyf table. This variable is only active whilst
           the output process is going on. It is used to inform the location table where the
           glyph is located, since the glyf table is output before the loca table due to
           alphabetical ordering.

       OUTLEN (P)
           This indicates the length of the glyph data when it is output. This more accurately
           reflects the internal memory form than the "LEN" variable which only reflects the read
           file length. The "OUTLEN" variable is only set after calling "out" or "out_dat".

   Editing
       If you want to edit a glyph in some way, then you should read_dat the glyph, then make
       your changes and then update the glyph or set the $g->{' isDirty'} variable.  The
       application must ensure that the following instance variables are correct, from which
       update will calculate the rest, including the bounding box information.

           numPoints
           numberOfContours
           endPoints
           x, y, flags         (only flags bit 0)
           instLen
           hints

       For components, the numPoints, x, y, endPoints & flags are not required but the following
       information is required for each component.

           flag                (bits 2, 10, 11, 12)
           glyph
           args
           scale
           metric              (glyph instance variable)

METHODS

Font::TTF::Glyph->new(%parms)

       Creates a new glyph setting various instance variables

   $g->read
       Reads the header component of the glyph (numberOfContours and bounding box) and also the
       glyph content, but into a data field rather than breaking it down into its constituent
       structures. Use read_dat for this.

   $g->read_dat
       Reads the contents of the glyph (components and curves, etc.) from the memory store "DAT"
       into structures within the object.

   $g->out($fh)
       Writes the glyph data to outfile

   $g->out_xml($context, $depth)
       Outputs an XML description of the glyph

   $g->dirty($val)
       This sets the dirty flag to the given value or 1 if no given value. It returns the value
       of the flag

   $g->update
       Generates a "$self-"{'DAT'}> from the internal structures, if the data has been read into
       structures in the first place. If you are building a glyph from scratch you will need to
       set the instance variable ' isDirty'.

   $g->update_bbox
       Updates the bounding box for this glyph according to the points in the glyph

   $g->maxInfo
       Returns lots of information about a glyph so that the "maxp" table can update itself.
       Returns array containing contributions of this glyph to maxPoints, maxContours,
       maxCompositePoints, maxCompositeContours, maxSizeOfInstructions, maxComponentElements, and
       maxComponentDepth.

   $g->empty
       Empties the glyph of all information to the level of not having been read.  Useful for
       saving memory in apps with many glyphs being read

   $g->get_points
       This method creates point information for a compound glyph. The information is stored in
       the same place as if the glyph was not a compound, but since numberOfContours is negative,
       the glyph is still marked as being a compound

   $g->get_refs
       Returns an array of all the glyph ids that are used to make up this glyph. That is all the
       compounds and their references and so on. If this glyph is not a compound, then returns an
       empty array.

       Please note the warning about bad fonts that reference nonexistent glyphs under INSTANCE
       VARIABLES above.  This function will not attempt to filter out nonexistent glyph numbers.

BUGS

       •   The instance variables used here are somewhat clunky and inconsistent with the other
           tables.

       •   "update" doesn't re-calculate the bounding box or "numberOfContours".

AUTHOR

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

LICENSING

       Copyright (c) 1998-2014, 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.