The history of luaTEX 2006–2009 / v 0.50 - Pragma ADE

OPENTYPE 144 17.571.732
ENC 268 782.680
MAP 406 6.098.982 110 129.135
OFM 39 10.309.792
OVF 39 413.352
OVP 22 2.698.027
SOURCE 4.736 25.932.413
We omitted the more obscure le types. The last two columns show the numbers for one
of my local font trees.
In due time we will see a shift from Type1 to OpenType and TrueType les and because
these fonts are more complete, they may take some more space. More important is that
the TEX specic font metric les will phase out and the less Type1 fonts we have, the less
afm companions we need (afm les are not compressed and therefore relatively large).
Mapping and encoding les can also go away.
In LuaTEX we can do with less les, but the number of bytes may grow a bit depending
on how much is catched (especially fonts). Anyhow, we can safely assume that a LuaTEX
based distributions will carry less les and less bytes around.
fallbacks
Do we need virtual fonts? Currently in ConTEXt, when a font encoding is chosen, a fallback
mechanism steps in as soon as a character is not in the encoding. So far, so good. But
occasionally we run into a font that does not (completely) ts an encoding and we end
up with dening a non standard one. In traditional TEX a side effects of font encodings is
that they relate to hyphenation. ConTEXt can deal with that comfortably and multiple instances
of the same set of hyphenation patterns can be loaded, but for custom encodings
this is kind of cumbersome.
In LuaTEX we have just one font encoding: Unicode. When OpenType fonts are used, we
don't expect many problems related to missing glyphs, but you can bet on it that they will
occur. This is where in ConTEXt MkIV fallbacks will be used and this will be implemented
using vitual fonts. The advantage of using virtual fonts is that we still deal with proper
characters and hyphenation will take place as expected. And since virtual fonts can be
dened on the y, we can be exible in our implementation. We can think of generic
fallbacks, not much different than macro based representations, or font specic ones,
where we even may rely on MetaPost for generating the glyph data.
How do we dene a fall back character. When building this mechanism I used the ‘¢’ as
an example. A cent symbol is roughly dened as follows:
42 A fresh look at fonts