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

[Peter Constable]

I think the informal-speak "required feature" has long been understood within the OTL community to mean one that a shaping engine for a particular script is required to process for correct handling of that script - i.e., not optional / discretionary, implying not normally* under direct user control. 

*Font development tools would, of course, be an appropriate exception.


Peter

-----Original Message-----
From: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at> On Behalf Of Simon Cozens
Sent: Monday, September 14, 2020 12:33 PM
To: mpeg-otspec at lists.aau.at
Subject: Re: [MPEG-OTSPEC] 'curs' feature: required?

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.
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