Font::TTF::GPOS 0.48

Font::TTF::GPOS is a Perl module to support for Opentype GPOS tables in conjunction with TTOpen.

The GPOS table is one of the most complicated tables in the TTF spec and the corresponding data structure abstraction is also not trivial. While much of the structure of a GPOS is shared with a GSUB table via the Font::TTF::Ttopen

INSTANCE VARIABLES

Here we describe the additions and lookup specific information for GPOS tables. Unfortunately there is no one abstraction which seems to work comfortable for all GPOS tables, so we will also examine how the variables are used for different lookup types.

The following are the values allowed in the ACTION_TYPE and MATCH_TYPE variables:

ACTION_TYPE

 This can take any of the following values

 a

 The ACTION is an array of anchor tables
 o

 Offset. There is no RULE array. The ADJUST variable contains a value record (see later in this description)
 v

 The ACTION is a value record.
 p

 Pair adjustment. The ACTION contains an array of two value records for the matched two glyphs.
 e

 Exit and Entry records. The ACTION contains an array of two anchors corresponding to the exit and entry anchors for the glyph.
 l

 Indicates a lookup based contextual rule as per the GSUB table.

MATCH_TYPE

 This can take any of the following values

 g

 A glyph array
 c

 An array of class values
 o

 An array of coverage tables


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· Perl