Am 05.03.2011 00:21, schrieb 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).
Presumably something like "gap is three times the fraction bar width". Not a real problem since very few people use different fraction bars in one document ;-) What is more annyoing in A and C is the inconsistency w.r.t. vertical gaps in display vs. text style: CM uses binomial vgaps that are always larger than the fraction vgap, but in A and C, the binomial vgaps are smaller in text style, but larger in display style! I don't know whether that is a design choice, but I find it a bit annoying. > I'd be interested in knowing what MATH parameters are > involved here to see what need to be fixed; the fonts or luaotfload. Or maybe LuaTeX. Unfortunately I have absolutely no time to investigate right now, only one observation: C has FractionNumeratorDisplayStyleShiftUp = StackTopDisplayStyleShiftUp, but the upper part of the binomial is positioned higher than the numerator in display style. This may be because the StackDisplayStyleGapMin is too large (?).
