Is there a way to find out what pairs of contextual alternatives of characters of an OpenType font through luatex (and possibly other packages such as luaotfload and fontspec)?
The question is a little vague. For example, the contextual alternative feature
calt will cause a variant glyph being used, but only in a certain context. I am wondering if it is possible to programmatically find all such "context", or at least character pairs that will cause one of them to use an alternative glyph.
This is not a question about how to get a list of features. It is more of how to inspect the substitution table of a specific table such as