[luatex] Poor Spacing in the \frac Environment

Dan Luecking dluecking at sbcglobal.net
Mon Jan 19 22:51:15 CET 2015

On 2013-01-18 at 21:59:19 CET, Reinhard Kotucha wrote

>On 2015-01-18 at 23:52:39 -0500, Emil E wrote:
>  > I've also noted that LuaLaTeX is making the correct adjustments for
>  > superscripted denominators (ex. a denominator of \delta^{2}), but
>  > this _only_ occurs on the LuaLaTeX engine with OTF TeX Gyre Pagella
>  > fonts (it does not happen on LuaLaTeX Computer Modern defaults, or
>  > in PDFLaTeX).
>  > This can be seen in the top right section of the linked image,
>  > on the third and fourth fractions from the right.
>I don't think that LuaLaTeX does any correction here.  I suppose that
>the position of the superscript is a little bit too heigh in TG
>Pagella so that TeX has to lower the complete denominator accordingly.
>The same happens if you insert the line
>   \frac{\Big|\delta}{\Big|\gamma} \;

I agree. In fact, I think this is, in fact, a problem with the
combination of LuaLaTeX with OTF TeX Gyre Pagella and unicode-math.

The various font parameters in cmr, it seems to me, are designed so
that when "normal" symbols are used with "normal" 'scripts there is no
shift in the numerators or denominators. This allows the baselines
and math-axes of numerators and denominators of adjacent fractions
to be aligned most of the time. That is, the \gamma's in
   $$\frac{\gamma}{\delta} \frac{\gamma_1}{\delta^2}$$
line up and the \delta's should also. That is, I think, the ideal
that Knuth was trying for.


Daniel H. Luecking
Department of Mathematical Sciences
Fayetteville, Arkansas

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