In setting the fractions, I note that generally the fonts have an absolute symmetry in the general dimensions, even at the cost of setting up different kernings. In the image that I attach (this is the Adobe Jenson Pro) it is noted that, for example, the 3.numr and 7.numr have a significantly different distance from the slash.
Now: is it better to aim for a homogeneous kerning or to guarantee the same amplitude for each fraction? And in the latter case, is there a specific technique to gain rigorous results, or simply a shrewd appeal to kerning?
Comments
Certain layouts, such as recipes, require it, where fractions may be stacked.
The numerators and denominators need space—fractions often appear next to whole numbers, so you don’t want to end up with 1¼ being a lot narrower than 5⅝.
In fact, rather than the sample above, it is better to look at fractions alongside whole numbers and alphabetic text, and match the amount of white space.
2. Regarding to space, in practice - again - which setting do you refer to?
And don’t kern them against the <fraction> character.
If you want to introduce kerning, use pre-composed fractions that each have their own Unicode.
If you are intent on proportional fractions, then have separate fractions for tnum and pnum.
If I remember to, I adjust the position of the fraction slash to centre visually between the numerator and denominator. You can see that 7/8 has a lot more space than 1/7 in this font (Verajja, derived from Bitstream Vera).
However, it is not very practical to force the stacking fractions to fit the figure width, or multiples of it. Here:
I just try to make the advance widths uniform for each group.