[mpeg-OTspec] Final draft - AHG input contribution - REVIEW NEEDED (was: Clarification of some aspect of opentype SVG spec)

[John Hudson]

On 16/02/16 17:08, Bob Hallissy bobh528 at yahoo.com [mpeg-OTspec] wrote:
> In the "Application interface" paragraph for the revised 
> init/fina/medi/isol descriptions, the wording is revised from what 
> John originally wrote, and I'm not sure the revision is correct. For 
> example, the "Application interface" paragraph for "fina" ends by saying:
>
>> For GIDs with single-joining final forms found in the ‘fina’ coverage 
>> table, the application passes a GID to the feature and gets back a 
>> new GID.
>>
>
> The problem with this wording is that single-joining final forms won't 
> be /found in the 'fina' //coverage /table. Rather, for those isolates 
> that have final forms it is the /isolate form glyphs/ that will be in 
> the coverage table and it is the purpose of the 'fina' feature to 
> replace the isolate with the final form.

[That portion of the proposed revision is actually exactly as I wrote it 
in my original proposal. The part that was revised is the Example section.]


I'm happy to have the wording of the Application Interface section 
revised if you think it is misleading, but the same complaint probably 
applies to most of the registered layout feature descriptions. This 
section tends to be pretty opaque, e.g. <calt>:

     The application passes sequences of GIDs to the feature table, and 
gets back new GIDs. Note that full sequences must be passed.

The impression I get is that, early on, this standard format for feature 
descriptions was devised, and everyone has felt obliged to follow it 
ever since, including this Application Interface section without good 
understanding of what it is supposed to be for or how it is supposed to 
be useful.


For now, I propose this as a revision for the proposed joining form 
feature revisions, using <fina>, again, as the archetype:

     For GIDs found in the 'fina' coverage table, the application passes 
a GID to the feature and gets back a new GID.


JH


-- 

John Hudson
Tiro Typeworks Ltd    www.tiro.com
Salish Sea, BC        tiro at tiro.com

Getting Spiekermann to not like Helvetica is like training
a cat to stay out of water. But I'm impressed that people
know who to ask when they want to ask someone to not like
Helvetica. That's progress. -- David Berlow