Curiosity, albeit marginal, about the Greek, although it could be repeated for other alternative glyphs not necessarily Greek.
In the GaramondPremierePro some variants - such as the letter kappa (uni03BA) and the kappa symbol (uni03F0) reproduced as kappa.alt (always uni03BA) - are present both as Stylistic Alternate ('salt' lookup 26) and in a Style Set (ss02 lookup 31).
What is the use of having this double location? Thank you
Comments
salt: "The 'salt' table maps GIDs for default forms to one or more GIDs for corresponding stylistic alternatives. While many of these substitutions are one-to-one (GSUB lookup type 1), others require a selection from a set (GSUB lookup type 3)."
ssXX: "Glyphs in stylistic sets may be designed to harmonise visually, interract in particular ways, or otherwise work together."
It would certainly make sense for a font with ssXX features to also provide access to the same glyphs via the salt feature.
What's less clear is how applications should handle successive feature selection by the user. E.g., the user applies ss01 across a paragraph. Then in the UI they activate a glyph palette to select a glyph from all alternates for a character (salt). Should the text formatting on that character include both features, ss01 + salt, or only salt? To some extent, it may not matter, depending on how fonts are designed: If both salt and ssXX are supported for glyphs of some character, and if the lookups for salt are ordered to precede the lookups for ssXX, then the scenario would work whether the app applies both features to the given character or turns off ss01 while turning on salt. Note this in the feature description for ssXX:
"font developers are responsible for ordering substitution lookups to obtain desired user experience"
This used to be true, but as of a couple of years ago, both Illustrator and InDesign have support for both Stylistic Alternates (salt) and Stylistic Sets.
Illustrator's Stylistic Alternates button is as useless as ever, only allowing access to the first alternate character if there is more than one. In both apps, you can see all Stylistic Alternates in the Glyph palette using the filter popup menu. Illustrator added a popup menu on its OpenType palette that lets you choose Stylistic Sets.
Photoshop can access Stylistic Sets through its Glyph palette, but not Stylistic Alternates.
OpenType support in all three apps is much better than it used to be.
With current apps and browsers, there is no longer much excuse for this sort of thing.
PS
Consider this, even if rather old, article:
http://www.scholarsfonts.net/Using_OT_in_LibreOffice_1-2.pdf
1.
However, I have not been able to find 'locl' in this window. Which extended entry does it correspond to?
2.
Another strange thing is that if I select <Elzevirian numbers> (those that today, with a less obsolete expression, we call oldstyle) LibreOffice produces the lining figures, but in superscript. I thing there is no error in my lookup, for the same happens with other fonts as GaramondPremierePro
It's a legitimate approach for stylistic set features to have different substitutions for different scripts.
https://bugs.documentfoundation.org/show_bug.cgi?id=132927
Thanx for your suggestion.
el-polyton doesn't work on my system, lang=el-polyton works fine
I don't immediately see a way to have different name table entries for different scripts. Is that possible?
Having said that, the OT spec and implementations of it are about 15 years out of date in that regard: languages can be indicated in name entries only using platform-specific numeric IDs that are totally obsolete. The spec and its implementations could definitely use an update to replace obsolete numeric IDs with a mechanism that leverages BCP 47 tags.
Clarification: A format 1 name table was added in OT 1.6 to incorporate use of BCP 47 tags. In retrospect, it wasn't the best possible design (I think a better design would also do something with OT Layout language systems), and AFAIK no tools or platforms have ever supported it. So, in practice, we're still left with 1990s-era numeric IDs.
This is certainly one of those areas I'd like to see improved in the OT spec.
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Notes:
* If we were talking about strings referenced in a feature parameters table for a feature like ssXX, then the answer is, Yes: OT Layout features are organized in the GSUB and GPOS tables in script/language-system/feature hierarchies. So, suppose a font has OTL data for (say) Latin and Greek; and suppose for both scripts it supports the ss01 feature. The ss01 feature table for Latin and the ss01 feature table for Greek could be one and the same table, but they also could be two different tables:
script: grek / langsys: <dflt> / ss01 feature table @ offsetA
script: latn / langsys: <dflt> /ss01 feature table @offsetB
If those are different feature tables, then they could have independent feature param tables with different name IDs specified. In that way, then, there would be different ss01 name entries for the different scripts.
Where did you find that BCP 47 Language Codes?
Is there a variant for ancient Greek too?
https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry
You should be familiar with the rules for how subtags are combined.
For Ancient Greek, what's relevant is that there is a separate ISO 639 ID, which is reflected in the BCP 47 subtag registry:
And, of course, Ancient Greek ≠ polytonic Greek.