[MPEG-OTSPEC] Feature name parameters in multi-script and multi-language fonts

[Behdad Esfahbod]

Hi John,

What you want is fully doable already. I wrote about it in the older
OpenType list one.

The point is that the different language systems can point to different
Feature table for the same tag. And it's the Feature table that carries the
extra metadata (name-table entry etc).

Hope that helps,

behdad
behdad
http://behdad.org/


On Sun, Oct 15, 2023 at 10:07 AM John Hudson <john at tiro.ca> wrote:

> I posted this query on the MS typography-issues board back in March, but
> received no replies.
> https://github.com/MicrosoftDocs/typography-issues/issues/1015
>
> My understanding from reading the specification for GSUB feature
> parameters for Stylistic Sets and Character Variant features is that a
> single feature parameter can be applied to a feature tag, regardless of
> how that tag is used in terms of lookup contents for different script or
> language system tags. Is that understanding correct?
>
> This seems to me to be contrary to the overall OTL model of script and
> langsys structures that are specifically designed to enable different
> writing systems to have different layout behaviours. So, for example,
> when making a font supporting Latin, Cyrillic and Greek script, it is
> perfectly feasible for a stylistic set feature such as ss01 to have
> entirely different behaviour appropriate to each script, and given the
> limited number of 20 registered stylistic set features this is a more
> efficient use of the features; also, it is more intuitive for the user
> of a particular script for accessible stylistic sets in the UI to begin
> as ss01, ss02, etc. rather than these be reserved to some other, unused
> writing system.
>
> There are also cases where behaviour of stylistic set features might
> differ within a script, at the langsys level. I am currently looking at
> implementing a stylistic set within the Latin script that is specific to
> traditional Irish orthography (langsys IRT). Since it is the only
> stylistic set that would be meaningful within that langsys, my
> inclination would be to use ss01, but that feature has different
> behaviour for other Latin script languages, and different behaviour
> again for other scripts.
>
> Can anyone see a route out of this, in terms of being able to link
> feature parameters to specific script/langsys combinations?
>
> JH
>
>
> --
>
> John Hudson
> Tiro Typeworks Ltd    www.tiro.com
>
> Tiro Typeworks is physically located on islands
> in the Salish Sea, on the traditional territory
> of the Snuneymuxw and Penelakut First Nations.
>
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