[MPEG-OTSPEC] 'curs' feature: required?

[Simon Cozens]

On 14/09/2020 19:29, Peter Constable wrote:
> Is the ‘curs’ feature considered a required feature for Arabic or other 
> cursively-connecting scripts?

I'm not sure what is really meant by "required feature" - required to be 
processed or required to be present?

It's certainly not required to be present, as Arabic fonts (particularly 
Naskh style) *may* be designed to connect "on the flat" just by placing 
the entry and exit strokes at consistent Y positions.

As to whether it is required to be processed, there's no good reason why 
it should be optional from the user's perspective - while it *may* still 
render correctly (in cases of a font designed "on the flat"), nothing 
good is going to come from turning it off.