Variable font creates strange forms when testing in Adobe Illustrator (Bug report)

Hello!

This is something that happens to me every time I try to test my variable font in Adobe Illustrator. In the example I use letter E but it also happens with other letters. I have 8 masters (thin, black, thin italic, black italic, thin expanded, black expanded, thin italic expanded, black italic expanded).

Have anyone struggled with this issue before? How did you solve it?

Glyphs bug.zip (1.6 MB)

Have you tried in other apps (browsers, FontGoggles)?

Hello Georg! Yes, I’ve just tried it in fontgaunlet and it works perfectly well.

Glyphs FontGaunlet.zip (2.8 MB)

Then it is a bug in Illustrator.

And do you know what may cause this bug in Illustrator?

Can you show a screenshot of the strange forms in AI?

That is weird. Can you send me the font (or a subset) to check? I can see what’s going on and file bugs where needed.

It looks like Illustrator has still problems with inferred deltas.

I tried to make a test that looks like the same construction as here (E only), but it still works fine so I can’t tell where it’s going wrong.
@GeorgSeifert What kind of inflected deltas? Do you have another example that doesn’t work in Illustrator?

I meant “inferred” (I have fixed the spelling).
You can disable this optimization with this custom parameter in the font: Variable Font Optimize Deltas.

That is the only problem I found in my Illustrator (B and E when being expanded and italic at the same time).

I tried my font in another Illustrator, in another computer and works perfectly well.

It’s just a problem with my version of Illustrator.

I didn’t find that custom parameter? Is it in font info?

Actually, I think I found it. This is what I did and now works well in my Illustrator!

Have you tried adding the Variable Font Optimize Deltas parameter to the font (in the original setup?

Yes Georg! It’s now working. Thank very much!

That means my hunch was correct. But it is not really a solution if you need the font on the web as the file size will increase.

Which version of Illustrator has the issue?

@GeorgSeifert is there anywhere we can learn more about what it does (and when it may fail)?

What do you mean?