What logic should be followed when positioning diacritics such as Low Modifiers, for example Modifier Letter Low Vertical Line (uni02CC) or Modifier Letter Low Macron (uni02CD) and also Combinig Below diacritics, for example Combining Vertical Line Below (uni0329)?
In fact, I note that in some fonts that I am analyzing, they are aligned neither to the same base line at the bottom nor to the same line at the top, but placed at different heights whose logic I do not understand. Thank you!
Comments
A sample (by the way, the up tack is somewhat anemic, I need to fix it) :
2. Overall criterion is to use the same vertical space for diacritics above and below. You will find variations both due to bad design and to optical adjust. I use baselines for diacritics above and below with the same distance from base letters, but sometimes do optical adjusts in diacritics to achieve a consistent view.
An example: in the image below, macron and dot accent would be very low if landed at the same base position of acute or circumflex, so they were raised a bit.
And a sample of diacritics below base letters. Note that y is a special case:
The lines in the example from the 1949 book are not 'long signs'; they're syllabic tone markers. These would be encoded as spacing modifiers, which are different characters from the combining macron mark.