# [Dev-luatex] How to use an OpenType font.

Javier Múgica javier at digi21.eu
Wed Oct 1 11:38:41 CEST 2008

I am trying to use an open type font. In the manual I can see a piece of Lua
code for loading such a font. I "suppose" that I have to enclose it within
\direclua0{}, so I wrote

local metrics = nil
local font = fontforge.open(filename)
if font then
metrics = fontforge.to_table(font)
fontforge.close(font)
end
return metrics
end
}

but it still does not solve the problem. I have no idea of how to make the
font known for TeX.

This is command is expandable. As an example, the following input:
$\pi = \directlua0{tex.print(math.pi)}$

will result in p = 3.1415926535898

But this leaves me none the wiser about fonts. The problem is: which is the
equivalent of

\font\tenrm=cmr10

for OpenType (or TrueType) fonts?

This problem is present to some extent all troughout the manual. It seems as
if you were taking always something for granted about the
interaction between Lua and TeX that is not explained anywhere. You may find
it obvious, but keep in mind that manuals are intended for people who
still don't know.
For somebody like me who comes from TeX, the impression got when reading
the manual (or at least the impression I had) is as having all the pieces
from a conglomerate rock but not having the cement. And the lack of examples
is exasperating. This I understand given the development state of the
program, but men, since one of the main features of LuaTeX is accesing and
modifing the TeX parameters and state with Lua code, some exemples of this,
even if kept to a minimum, would be very helpful.
I wouldn't have any problem in taking the time to write them myself... if
knew it, but the LuaTeX manual is still very far from serving to the
learning of LuaTeX in the same way as the TeXBook serves for the learnig TeX
or "the red book" serves for the learning of the postscript language.

Continuing with my problem with using an otf font, I found some pages below
in the manual an example intended for a diferent purpose but that looked
usefull for solving my problem even if not the way it should be done. So
below the avobe mentioned lua code I boldly wrote

\directlua0 {
callback.register('define_font', function (name,size)
if name == 'LMRoman12-Regular' then
f = twelverm
else
end
return f
end
)
}
\font\twelverm= LMRoman12-Regular
it does not work, but it exhibits a bug in LuaTeX: I get a warning at \dump
time:

luaTeX warning: lua-loaded font [1] (<NULL>) has no character table!

but right afterwards the program dies and is closed by Windows.

--Javier A.
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