Re: [9fans] [RFC] fonts and unicode/utf [TeX]

["Joel C. Salomon" <joelcsalomon@gmail.com>]

On Thu, Jun 16, 2011 at 8:17 AM,  <tlaronde@polynum.com> wrote:
> Second question: I'm trying to find if, in western languages, including
> ligatures for ae and oe would be good since it is generally needed (one
> can forbid ligatures by inserting "{}" between the letters), or if it's
> not correct to set this by default for fonts (having the glyphes) since
> some western languages use generally the ae or oe combinations without
> knowing or expecting the substitution.

Unicode has part of the answer:  Some ligatures (e.g., U+FB03 “ffi”) are
“Presentation Forms”, i.e., not “real” characters but alternate visual
presentations of the the comprising characters.  Those are (usually)
OK to generate automatically.  But “ae”≠“æ” and “oe”≠“œ”, &c.—please
don’t make these substitutions

Unicode doesn’t have many of these Presentation Forms, and only
includes them for round-trip compatibility with other code sets that
have them.  New ligatures of this sort are *very* unlikely to be
added.

Better solution, as Russ suggested, is OpenType.  In that format, the
font designer can include common (e.g., “ff”), historical (e.g., “st”
& “ſs”), and even ad-hoc ligatures.  (There are “fun” fonts with “LOL”
ligatures, for example.)  Different sets of ligatures can be
enabled/disabled by selecting combinations of OTF features.

At which point you’ve reinvented XɘTeX.

—Joel