About boundary characters

Didier Verna didier at didierverna.net
Tue Sep 17 17:47:04 CEST 2019


I have several questions about boundary characters in the TFM format.

1. if there is a "right boundary character" in a font, it has a code
   (maybe outside [bc,ec]). So far so good. However, the description of
   this format only mentions /a/ left boundary character, and apparently
   no code for it. I don't really understand why. Is it the same as the
   right one (in which case I guess we'd have [word1 B word2] and not
   [word1 R L word2] as I first imagined.

2. I found many fonts in which the right boundary character actually
   exists, and has non zero metrics. On the other hand, the TFM
   description claims that these characters do not appear in the output.
   So why having existing characters as boundary ones?

3. Finally, the right boundary character is specified by a special
   /first/ lig/kern instruction, and the left by a special /last/
   lig/kern instruction. However, nothing is said about the case where
   the lig/kern table is of length 1 (meaning first = last). TFTOPL
   doesn't seem to care. So I wonder if that situation makes any sense
   (I haven't checked for fonts like this yet).


Resistance is futile. You will be jazzimilated.

Lisp, Jazz, Aïkido: http://www.didierverna.info

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