Kerning pair shown as exception on both sides but actually changes group kerning

Glyphs
1

3.2 (3225)

I have a pair /jcircumflex.ss03/imacron which has unlocked kening for both sides, but when I change the kerning, the kerning for /jcircumflex.ss03/igrave and /jcircumflex.ss03/idotless also changes, even though /jcircumflex.ss03/idotless actually also has a kerning exception, very concerning:

Download video

2

Can you check the kerning list. It might be that you have an exception and class kerning in various combinations. If you can’t figure this out, can you send me the file?

3

Sorry I can’t figure it out, the kerning is generated by iKern and it’s an absolute mess. I’ll email you the file.

4

So the problem is:
there is a pair

jcircumflex.ss03 > @i

and one

@i igrave

That means from both sides, it looks like it has an exception. But when setting the value, it has to decide which of the two it will use.
To avoid this, you might like to split the groups. In a font like this, you could stick the “i” into a class with the “l”, the idotless into “n”/“u” and all the “i” with accents that stick out in its own class.

1 Like
5

I understand now, I notice in MetricsMachine, when making an exception it detects when there are clashes and it asks if I would like to override them.