[Dev-luatex] HarfBuzz [slightly off-topic]

[Hans Hagen]

On 1-2-2011 8:54, Paul Isambert wrote:

> With LuaTeX (which I don't pretend to understand exactly either), when
> it comes to such matters, you're alone: you're the one in charge of
> "text shaping", even for ligatures from pairs of glyphs (e.g. "ff"),
> since you're supposed to have created them when loading the font. So I
> don't think integrating HarfBuzz would be in line with LuaTeX's
> philosophy, otherwise it would be no different from XeTeX in that
> respect. On the other hand, nothing prevents you (the user) from calling
> HarfBuzz (or doing whatever you're supposed to do with it) from LuaTeX,
> I guess.
>
> As for the sentence "LuaTeX should be made to do the same thing", if
> "should" means "it'd be good", I suppose the author hasn't really
> understood LuaTeX; if "should" means "it is going to happen, normally",
> then /I/ haven't really understood LuaTeX. What the last sentence means
> is obscure to me.
>
> Again, I don't know much about HarfBuzz, and I can't obviously make any
> authorized statement on LuaTeX, but that's how I see things.

LuaTeX is and will remain a TeX engine, an opened up one. One of the 
principles is that we won't hard code solutions other than the one 
provided by (traditional) TeX (although unicode is the coding and wide 
tfm fonts are corner stones). There is the default (relatively 
lightweight) font loader based on fontforge. There is no universal 
solution and hardcoding or binding to some other library is no option, 
if only because they come and go, and fashion can change. The idea is to 
have a stable engine (as stable as traditional tex itself) that can act 
as basis.

However, as one can load Lua libraries, any library that has a Lua 
interface can in principle be plugged in. So if someone wants another 
renderer, he/she can plug in something and as long as what gets returned 
suits tex's inner model (node lists) it's ok. In that respect luatex is 
indifferent to how/what/where it happens. Using some renderer is not so 
much different from using libraries to access databases or filesystems 
or ...

So, to answer your question: no extrnal rendering libraries will be 
linked in by default and none will be provided by the luatex team, but 
one can imagine external libraries to be used that get fed data from 
luatex and give something back that gets fed back into the machinery.

Of course, when a macro package depends on such libraries, it adds 
another depedency which can be a long term maintainance problem.

Hans

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