dvips: Encoding file format
6.3.1.5 Encoding file format
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Afm2tfm's encoding files have the same format as an encoding vector in a
PostScript font. Here is a skeletal example:
% Comments are ignored, unless the first word after the percent sign
% is 'LIGKERN'; see below.
/MyEncoding [ % exactly 256 entries follow, each with a leading '/'
/Alpha /Beta /Gamma /Delta ...
/A /B ... /Z
... /.notdef /xfooaccent /yfooaccent /zfooaccent
] def
These encoding files are downloaded as part of changing the encoding
at the PostScript level (see the previous section).
Comments, which start with a percent sign and continue until the end
of the line, are ignored unless they start with 'LIGKERN' (see below).
The first non-comment word of the file must start with a forward
slash '/' (i.e., a PostScript literal name) and defines the name of the
encoding. The next word must be an left bracket '['. Following that
must be precisely 256 character names; use '/.notdef' for any that you
want to leave undefined. Then there must be a matching right bracket
']'. A final 'def' token is optional. All names are case-sensitive.
Any ligature or kern information is given as a comment. If the first
word after the '%' is 'LIGKERN', then the entire rest of the line is
parsed for ligature and kern information. This ligature and kern
information is given in groups of words: each group is terminated by a
space and a semicolon and (unless the semicolon is at the end of a line)
another space.
In these 'LIGKERN' statements, three types of information may be
specified. These three types are ligature pairs, kerns to ignore, and
the character value of this font's boundary character.
Throughout a 'LIGKERN' statement, the boundary character is specified
as '||'. To set the font's boundary character value for TeX:
% LIGKERN || = 39 ;
To indicate a kern to remove, give the names of the two characters
(without the leading slash) separated by '{}', as in 'one {} one ;'.
This is intended to be reminiscent of the way you might use '{}' in a
TeX file to turn off ligatures or kerns at a particular location.
Either or both of the character names can be given as '*', which is a
wild card matching any character; thus, all kerns can be removed with '*
{} * ;'.
To specify a ligature, specify the names of the pair of characters,
followed by the ligature operation (as in Metafont), followed by the
replacing character name. Either (but not both) of the first two
characters can be '||' to indicate a word boundary.
The most common operation is '=:' meaning that both characters are
removed and replaced by the third character, but by adding the '|'
character on either side of the '=:', you can retain either or both of
the two leading characters. In addition, by suffixing the ligature
operation with one or two '>' signs, you can make the ligature scanning
operation skip that many resulting characters before proceeding. This
works just like in Metafont. For example, the 'fi' ligature is
specified with 'f i =: fi ;'. A more convoluted ligature is 'one one
|=:|>> exclam ;' which separates a pair of adjacent '1''s with an
exclamation point, and then skips over two of the resulting characters
before continuing searching for ligatures and kerns. You cannot give
more >'s than |'s in an ligature operation, so there are a total of
eight possibilities:
=: |=: |=:> =:| =:|> |=:| |=:|> |=:|>>
The default set of ligatures and kerns built in to Afm2tfm is:
% LIGKERN question quoteleft =: questiondown ;
% LIGKERN exclam quoteleft =: exclamdown ;
% LIGKERN hyphen hyphen =: endash ; endash hyphen =: emdash ;
% LIGKERN quoteleft quoteleft =: quotedblleft ;
% LIGKERN quoteright quoteright =: quotedblright ;
% LIGKERN space {} * ; * {} space ; 0 {} * ; * {} 0 ;
% LIGKERN 1 {} * ; * {} 1 ; 2 {} * ; * {} 2 ; 3 {} * ; * {} 3 ;
% LIGKERN 4 {} * ; * {} 4 ; 5 {} * ; * {} 5 ; 6 {} * ; * {} 6 ;
% LIGKERN 7 {} * ; * {} 7 ; 8 {} * ; * {} 8 ; 9 {} * ; * {} 9 ;
Info Catalog
dvips: Reencoding with Afm2tfm
dvips: Changing font encodings