Adding new glyphs to pair adjustments

[tjdickinson]

I'm working with two existing fonts (Alegreya Regular and Alegreya Sans Regular), and I've added phonetic glyphs to each font. I want to improve the kerning, but this aspect of font creation is new to me and I'm not really sure the best way to go about it.

The upshot is that IPA symbols only go with lowercase letters, and most of the consonants and some of the vowels are already 'normal' characters (like b, p, t, a, e, ...). I've added 19 new glyphs, most of which resemble other glyphs in the font:
ɑ ɒ ɛ ɜ ǝ ɪ ʌ ɔ ʊ ɡ ʒ ʤ ʃ ʧ ʔ ː 〈 〉

Since the font already exists, there are already a lot of classes and kerning pairs set up. Is it best to just add the new glyphs to existing classes? Which classes should I add them to to make sure they are paired with all the other necessary glyphs? Some of them are easy to match, for example:

• ɑ is copied from Greek lower case alpha, so it can go in classes a1 and c
• ɒ is the alpha upside down, so it can go in class b1
• ǝ already exists at another code point, so I can add it to classes a and b1
• ɔ is similar to o, so it can go in classes b1 and c
• ʤ starts with a d, so it can go in class d
• ʧ starts with a t, so it can go in class t
• ː is just a colon with triangles, so it can go in the class with : and ;

But the rest are trickier. Some of them only exist in Cyrillic, and the classes that contain the original glyphs only have other Cyrillic letters (so they won't be paired with Latin letters). Others have features that don't exist in other letters, like the serifs on the ɪ (in the sans font), the hooks on the ʃ, the style of descender on the ɡ...and the glottal stop ʔ is something altogether different.

So then I wonder if I should just make new classes for each of these glyphs and create a new subtable specifically for IPA, but that seems inefficient and redundant. On the one hand, I'm looking for whatever is quickest and easiest, but on the other hand, I'm also trying to think ahead to when I may add other phonetic glyphs to the font, so maybe it's worth the effort now?

Thanks in advance for any advice or tips.

[Bhikkhu Pesala]

I would not add them to existing classes, nor even create new classes. Just add new pairs wherever they are needed. IPA glyphs only pair with each other.

[tjdickinson]

I would not add them to existing classes, nor even create new classes. Just add new pairs wherever they are needed. IPA glyphs only pair with each other.

Thanks for the reply, Bhikkhu. (I watched your instructional video on YouTube before having a start at this, too--very helpful.)

The only thing is that IPA glyphs don't just pair with each other. For English, there are 26 other glyphs (32 if you include punctuation) besides the 19 I created, which are already in the font and (in most cases) kerned:
a æ e i o u b d f h j k l m n p r s t v w x z ð θ ŋ . ˈ ˌ / [ ]

For example: /taɪˈpɒɡrǝfi/ 〈typography〉 uses a combination of Latin letters with IPA symbols, and the 〈angle brackets〉 can be next to any letter of the alphabet, including lowercase letters not used in English IPA (ex. q y g c) and capital letters.

If I kern the new glyphs in individual pairs with each other and with the existing classes, I'd have to make over 800 pairings.

Does your advice still stand, or would you recommend a different approach in this case?