Add opentype-best-practices profile & FAIL if dnom/numr features exist

Observed behaviour

In https://typedrawers.com/discussion/comment/45741/#Comment_45741 @tiroj explains

Expected behaviour

This isn’t off-spec - just the opposite - but it is something everyone should know to check, and many don’t, because the OT spec has been undermaintained…

So I propose a new profile like opentype-best-practices and a first check that FAILs if dnom/numr features exist.

he GF profile should include this profile.

[tiroj]

I should also note that while I think the numr and dnom features are unnecessary for implementation of the frac feature, and hence that the features as originally registered by Adobe should have been deprecated, I can’t say for certain if or how the features might be being used today. We, like most other font makers, include them in fonts on the basis that ‘The glyph exists, the features exist, they’re not doing any harm’. Adobe’s typography UI in InDesign provides direct access to the features, and other UIs and markup syntax might do likewise. So it is possible that someone is using them for something that I have not considered.

[tphinney]

I think the desirable check is “if it has numerators and denominators, do fractions work as expected in all environments.” But that is a lot more complex than this request.

Until then…

• ‘numr’ and ‘dnom’ require very little code/space
• they have no known negative effects
• are probably unnecessary (ASSUMING the font is built to use ‘frac’ only)