Contextual alternative end of word syntax

Glyphs
1

Hey,
I am pretty new to Glyphs and I’m trying my first steps in alternatives. I want to make a style set with longs and since there are some conventions about its use, I made some substitutions (f.e. that only the first of two s is a longs).

They also work fine, except I don’t know what to do with the end of words.
I made a class with all characters that indicate ends of words, most importantly space.
But since it’s a very display-ish font I know that it’s mostly going to be used for headlines, which mostly don’t use any punctuation and cut the last space.
How is the syntax for the last character in a given text (in my case that s)?

2

This isn’t accurate, double long s also occurs. It’s at the end of words that only the first s is long.

There is no syntax for “last character of word”, sadly. You could (but shouldn’t) hijack the fina feature, which is intended for Arabic.

3

The fina feature is only supposed to be use with Arabic. But this Features, part 4: positional alternates | Glyphs explains a workaround (using ignore sub).

4

Not the job of an OT feature. Perhaps that of a layout engine.