[XeTeX] \ifFontExists

[Benct Philip Jonsson]

Mike Maxwell wrote:
> Apostolos Syropoulos wrote:
>>> But how would we define "matches closely"? How do you measure the  
>>> "closeness" of fonts...
>> This is an excellent topic for someone willing to apply fuzzy set theory to
>> typography. The basic idea is to define an ideal font (i.e., a font where
>> glyphs have the most standard form) and then to define similarity
>> degrees, etc. 
> 
> Wasn't Donald Knuth's original concept of 'metafont' something along 
> these lines?  And of course Douglas Hofstadter has worked on analogy, 
> testing his ideas on fonts (his "letter spirit" project).  In both 
> cases, though, I believe the idea is to *generate* fonts, not recognize 
> similarities among existing fonts.

Mathematical/geometrical similarity is indeed one way of 
doing it.  Another is by such parameters as serif style,
general font style (uncial/gothic/antiqua, 
medieval/transitional/modern/sans), relative thickness of
thick/thin strokes (where verticals and leftwards-leaning 
strokes are canonically thick, horizontals and leftward-
leaners canonically thin), tilt of bowls, ratio of ascender 
height to x-height and cap height to x-height etc.

The latter scheme is admittedly coarser, but has the merit
that anybody can relatively quickly grasp these parameters,
form an idea where their ideal font stands in terms of it
and write a CSS-like description of it.  While there are
font managers and font generation software based on such
parameters I haven't yet seen a CSS-like font feature
description system which could be used to choose between
available fonts when displaying a document.  Such a system
could be useful with HTML, (Xe)TeX and other WYGIWYM
plaintext-cum-markup document preparation systems.

/BP 8^)>
-- 
Benct Philip Jonsson -- melroch atte melroch dotte se
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  "C'est en vain que nos Josués littéraires crient
  à la langue de s'arrêter; les langues ni le soleil
  ne s'arrêtent plus. Le jour où elles se *fixent*,
  c'est qu'elles meurent."           (Victor Hugo)