I have two glyph classes — r_lc and r_lc_top. Apart from the accents above the glyphs, they are identical in terms of bearings and advance width, so why are the kerning values returned by Autokern so different?
racute hyphen is exactly the same value for me (-53 x-advance) in your font project.
But unless there is a reason not to, I would combine both of these classes anyway.
Thanks for looking. I adjusted the values manually after taking the screen shot, but the calculated XAdvance value for r_lc_top is -8, as shown in my screen shot.
Yes, there is a reason for separating the “r”s into two classes. I use the naming convention “@class_name_top” for those glyphs that are likely to clash with the top of capital T, V, W, Y, etc.
I am still refining the kerning classes to have as few classes as necessary, while avoiding overlaps. The method of “@class_name_first” and “@class_name_second” works better in some cases. I have attached an updated project file to this post and removed the older version from the previous post.
Talapanna Regular.fcp (596 KB)
I’ve just run Autokern (right-click the lookup) with glyph spacing factor 27, and both get 61.
I tried with spacing value of 27 and got positive kerning values of 39 and 77.
With my spacing value of 23, I still get -53 and -8.
I noted that c_lc hyphen and c hyphen give the same results (-104), but z_lc hyphen (-88) and z_lc_top hyphen (-83) do not.
I’m puzzled.
I’ve reduced the pairs to:
lookup PairAdjustmentLatin {
subtable Subtable_0 {
pos @r_lc @hyphen <61> <0>;
pos @r_lc_top @hyphen <61> <0>;
}
}
And right-click the lookup to Autokern keeps them the same.
Me too. I tried with just those two pairs and still get the same results as before:
53, -8 @ 23 space factor
39, 77 @ 27 space factor
So, at least it’s consistently wrong! 
We’re both using the same project file, and the same build 10.1.0.2257 so what else could be different? Is it the rendering dll again?
I was testing with a more recent version; not released yet. Somehow that version works fine, so I might have accidentally fixed the problem.
The latest update (FC 10.1 build 2272) has fixed this bug.