[luatex] babel, fontspec und lualatex

[Philipp Gesang]

···<date: 2013-07-26, Friday>···<from: Khaled Hosny>···

> On Fri, Jul 26, 2013 at 12:59:55PM +0200, Philipp Gesang wrote:
> > ···<Datum: Friday, 26. July 2013>···<Von: Ulrike Fischer>···
> > 
> > > Am Fri, 26 Jul 2013 12:19:23 +0200 schrieb Javier Bezos:
> > > 
> > > > Ulrike,
> > > > 
> > > >> The new babel redefines the \TeX command and surrounds it by
> > > >> \textlatin and this reveals a bug:
> > > > 
> > > > Do you know if it works with the old (3.8) babel? (I've not tried
> > > > it out yet -- just back from holidays). I have not changed this part
> > > > (afaik :-)) because I'm still investigating how to fix the whole
> > > > \text<script> stuff in a backward compatible way.
> > > 
> > > miktex still has Babel <v3.8m>, so I could test: There is the same
> > > problem, the fontdimen is 0 and there is to much space between X and
> > > n. 
> > > 
> > > Imho the correct solution would be that luatex/luaotfload sets
> > > \fontdimen1 for italic fonts to a sensible positiv value. 
> > 
> > What’s “a sensible value” if italic correction is done on node
> > level?
> 
> Note that \fontdimen1 is *not* italic correction, but the italic angle
> of the font i.e. its slant amount.
> 
> > Someone knowledgeable about font parameters and how they translate to
> > the original values would have to supply the code, though,
> 
> ConTeXt code in luaotfload already does that, at least I see that
> copytotfm() sets parameters.slant for italic fonts, so someone needs to
> check why this is not working as expected.
> 
> > especially when it comes to the more delicate parts described in
> > appendix G.
> 
> You don’t need to worry about math font dimentions, the OpenType math
> machinary does not need them (they might even confuse LuaTeX to thing it
> is dealing with an old font) and old math fonts should have them in the
> loaded TFM files already.


This line:

  http://repo.or.cz/w/context.git/blob/refs/heads/origin:/tex/context/base/font-otf.lua#l1954

rounds the value of parameters.slant to -0. If I scale it to the
point size:

  parameters.slant=- math.round(math.tan(italicangle*math.pi/180) * 2^16)

I get the same output visually with babel as with polyglossia in
Herbert’s original example.

I’ll put Hans in the CC since he know’s best.

Best,
Philipp

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