[mpeg-OTspec] Re: [OpenType] More than 20 Stylistic Sets!

[John Hudson]

On 20032019 12:40 pm, Ken Lunde lunde at adobe.com [mpeg-OTspec] wrote:
> At this point, based on the discussions thus far, I doubt that anyone 
> can provide a convincing argument against registering 'ss21' through 
> 'ss99' as additional Stylistic Set features. 


Well...

The original intention of the Stylistic Set features was to provide 
access for coordinated sets of design variants of complete or 
significant portions of a character subset, e.g. all lowercase letters, 
grouped by shared style. The initial use case was the OpenType-ification 
of the Poetica and Zapfino families, in which the stylistic sets had 
been shipped as separate fonts in their pre-OT incarnations. The 
decision to limit the number of Stylistic Set features to twenty was 
influenced by a couple of factors: one was that the number of stylistic 
sets in Poetica and Zapfino was four, so twenty seemed like quite a lot, 
and the other was that a smaller number was more likely to get buy-in 
from applications needing to give some kind of UI real-estate to the 
features, possibly à la InDesign with a menu listing (I'll leave aside 
the whole other topic of poor UI design for OpenType Layout).

What began to happen fairly soon after the Stylistic Set features were 
registered and began to show up in applications is that font makers 
began using them to provide access to variants of individual characters 
instead of sets of characters, e.g. multiple variants of an ampersand, 
each mapped to a different Stylistic Set feature. And used in this way 
the features very quickly get used up and people start asking why there 
aren't more.

Meanwhile, SIL registered the 0–99 Character Variant features, which not 
only, by design, provide access to variants of individual glyphs, but 
also recommend doing so using GSUB one-to-one-of-many lookups, rather 
than one variant per feature. [It is technically possible, of course, to 
build Stylistic Set feature using such lookups, but application UI for 
these features tends only to expose the first enumerated variant.]

The Character Variant features — including enumerated variants — are 
supported in CSS, but not in common desktop applications, and so font 
makers have continued to use Stylistic Set features to access individual 
character variants, and continued to complain that twenty isn't enough 
to accommodate this use.

I don't know if this is a 'convincing argument', but it seems to me that 
if one is going to have to ask application makers to add support for 80 
new Stylistic Set features, why not ask them to support the existing 100 
Character Variant features instead?

JH


-- 

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

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