[lltx] $n\choose k$-issue with OpenType math fonts

[Khaled Hosny]

On Fri, Mar 04, 2011 at 11:29:13PM +0100, Philipp Stephani wrote:
> @Andreas: please use only the ZIP archive format since it's the only one
> everybody can read.
> 
> Am 04.03.2011 22:50, schrieb Khaled Hosny:
> > On Fri, Mar 04, 2011 at 09:53:10PM +0100, Andreas Harder wrote:
> >> Hi all,
> >>
> >> I was asked to post this also on the LuaLaTeX-list, so here it is.
> >>
> >> I'm tying to draw some attention to the $n\choose k$-issue with OpenType math
> >> fonts. 
> >>
> >> I've made some test files:
> >> http://dl.dropbox.com/u/151837/OpenType-Math.7z 
> >>
> >> The best output is generated by LuaLaTeX (at least for Asana and Cambria). 
> > 
> > So you are getting the best output which, IMHO, is a good thing, what is
> > the problem then? :)
> 
> "Best" here unfortunately means "not very good, but not as bad as the
> others."
> 
> For the following discussion, I use the notation LN, where X is the
> letter A, C, or X, depending on the font, and N is a number representing
> the N-th symbol from the left. I'm only looking at the document ending
> in lualatex.pdf.
> A1, A2, A3, A5, A6, A7, A8, A9, A11, C1, C2, C3, C5, C6, C7, C8, C9,
> C10, C11, X5, X9, X10, X11 look good.
> A4, C4, X4: upper and lower part are too far away from each other; as
> there is no fraction bar, they should be closer to each other than the
> numerator/denominator in ACX5.
> A10: numerator and denominator are too far away from the fraction bar.
> X1, X3, X6, X7, X8: lower part is too far to the bottom.
> X2: parentheses are too high.
> 
> The issues that occur with Computer Modern are: 4, 10, i.e. those that
> also appear with A and C; these are more-or-less design problems;
> someone should check if they also occur in Word. X has more issues;
> LuaLaTeX + A/C can be declared okay-ish, but not perfect IMO.
> 
> It would be interesting to know whether there are established
> conventions regarding the vertical gaps in fractions vs. binomials.
> Personally I'd prefer a smaller gap for the latter since the bar is absent.

Thanks Philipp, that was very helpful.

Comparing to CM I think Cambria's is OK, so 10 might be related to
actual TeX math algorithms (someone have to check Appendix G rules
regarding this). I'd be interested in knowing what MATH parameters are
involved here to see what need to be fixed; the fonts or luaotfload.

Regards,
 Khaled

-- 
 Khaled Hosny
 Egyptian
 Arab