Yes, thank you, Victor. I had just now figured out that the OpenType feature IDs can be directly substituted for our existing Graphite IDs. This was my original question: whether different coding (beyond the CSS file) is needed for Graphite vs OT.
I was going to ask whether it is possible to specify both sets at the same time in the CSS, because in my test Andika New Basic does not seem to recognize the OT IDs. However, the Features documentation for Andika New Basic says it contains both OT and Graphite
It sounds as if you are saying that OT works in both the v5 and v6 SIL fonts, so changing the CSS to use the OT IDs should work with Andika New Basic and other v5 fonts as well as with the new v6 SIL fonts. But in my Bloom test the OT features I’ve specified in customCollectionStyles.css are not visible when I change the font to Andika New Basic, which is the default font in Bloom (at least with English system), I believe. If ANB recognized the OT IDs it would be simpler to use Bloom as shipped and also retain the ability to switch fonts without losing alternate glyphs.
It might be worth reminding Bloom users that Andika New Basic was created to provide “real” italic and bold glyphs for Latin-based orthographies, during the development phase of the full Andika and other SIL fonts. Bloom and other PDF-generating routines (including Bloom and Paratext’s Save as PDF) ignore the “fake” bold and italic forms generated for on-screen viewing when a font contains only a single “normal” variety. This is one good reason to use quality fonts when producing printed or digital reading materials, rather than using a free font that may “look very cool”.
(Sorry for not using proper terminology! I’m extremely grateful to the font developers for your “wizardry” in fonts and scripts, as well as to the language program developers for knowing how to use it.)