[ft] Fontconfig Gotcha

[Lawrence D'Oliveiro]

Fontconfig is a wonderful API for doing flexible font-matching. Given a
pattern which can contain any of a whole range of different criteria
(e.g. family name, slant, weight, decorative style), it will find the
most suitable font from those installed on the system.

Having found a FreeType font, Fontconfig provides the call
FcFreeTypeQueryFace, which will construct a very elaborate pattern that,
I assumed, would match exactly that font again.

However, it never seemed to work: trying to use that pattern to search
for fonts would always fail with no matches.

Today, I figured out that the problem seems to come from the inclusion
of the “lang” and “charset” criteria in the returned pattern: the
values for these tend to consist of long lists of items separated by “|”
characters. But remove them, and the resulting pattern will correctly
find the font again.