[mpeg-OTspec] Re: [OpenType] RE: Proposal: deprecate ReqFeatureIndex

John Hudson john at tiro.ca
Wed Aug 22 20:20:51 CEST 2012

On 22/08/12 11:02 AM, Behdad Esfahbod wrote:

> Wrong.  ReqFeatureIndex does not have to point to an existing feature.  In
> fact, a font editor can give you an option to mark certain lookups as
> mandatory, and the font builder can put all those mandatory lookups in the
> required feature.  You are confusing font format with what font editor UIs
> provide.  What's missing is UI and support in font builders for what you want.

Ah. So I could create a feature tag, <fuba>, associate with it whatever 
lookups I wished to be required, and reference this in the 
ReqFeatureIndex? Actually, the first two parts of this are adequately 
supported in VOLT and, I believe, AFDKO-based font tools. It is possible 
to create custom feature tags and to associate lookups to them. The 
tricky part, which probably requires use of a table editor, will be 
setting the value for the ReqFeatureIndex itself.

What seems unclear in this model, though, is how a set of lookups mapped 
to ReqFeatureIndex in this way should be presumed to interact with other 
layout features. Can we rely on lookup ordering in this respect, or must 
we presume that for some scripts at least precedence will be given to 
certain registered features that will be processed in blocks?



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