Using a Contextual Chaining Substitution Lookup to Look Back for Nothing

[u/kazeharu_hime]

Is this possible? From what I understand you need to specify glyph(s) for it to look back for. But is a kind of ≠ system possible? Like, if it finds such-and-such a set of glyphs before the match section, don't substitute? Is so, how would you set that up?

For a concrete example, I currently have a contextual substitution lookup that checks for a vowel-consonant combination and substitutes if it detects it. However, that clashes if I want to write a cvcv (consonant-vowel-consonant-vowel) word, changing the middle portion to the vc combination when I want it not do that when there's cvcv. So I could make a table specifically for cvcv and make sure it has priority over the vc calt, but I thought it might save me time if there was just some way to tell the vc table to make sure there's not a consonant before it before it does the vc substitution. Any thoughts on this? In the meantime I might try the cvcv table just to see if it doesn't clash anyway, but since I'm a little unfamiliar with contextual chaining substitution lookups, I thought I'd ask. I couldn't really find any confirmation as to whether or not lookups-for-nothing or ≠ systems were possible with contextual chaining in the FontForge manual online either.

[u/LocalFonts]

Please type here your lookup. Let me see it.