Overflow error when exporting variable font

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rohh
Posts: 2
Joined: 24 Apr 2021

Overflow error when exporting variable font

Post by rohh »

Hello Tim,

I am working on 1-axis variable typeface, having 4 weight masters. After applying Kern On to the project, there is a problem with exporting the font, I get a message:

Problem compiling “GPOS” tableSubtable Overflow in lookup: 1 type: PairAdjustment

The problem disappears when deleting the kerning. I tried to export 64kB kerning, 36kB as well - the problem persists.

Another thing - the typeface contains 740 glyphs, Kern On produces over 16000 kerning pairs. Is this behaviour normal?

Thanks!
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SCarewe
Posts: 71
Joined: 23 Apr 2021

Re: Overflow error when exporting variable font

Post by SCarewe »

This happens when the kerning size is too big. You can adjust the kB size or add the custom parameter Use Extension Kerning to your Font Info.

The number of pairs is (somewhat directly) related to the kB size, 17k for 64kB doesn't seem to outlandish.
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Tim Ahrens
Site Admin
Posts: 264
Joined: 11 Jul 2019

Re: Overflow error when exporting variable font

Post by Tim Ahrens »

If you select 64kB or less then you should not get the error, so something is going wrong somewhere.

Which version of Glyphs are you using? Is it the same error in Glyphs 2 and Glyphs 3?

Would you mind sending me the .glyphs file? Thanks!
rohh
Posts: 2
Joined: 24 Apr 2021

Re: Overflow error when exporting variable font

Post by rohh »

Thanks for your answers! I use Glyphs 3 for this project, I do not know how it behaves in Glyphs 2. However, adding the "Use Extension Kerning" parameter solved the problem and variable font exports without any problems now! Thank you!
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SCarewe
Posts: 71
Joined: 23 Apr 2021

Re: Overflow error when exporting variable font

Post by SCarewe »

Tim Ahrens wrote:
> If you select 64kB or less then you should not get the error, so something
> is going wrong somewhere.

Hmm, I get this error all the time, even using 36kB. I suspected this kB limit would be per master, so each exported instance essentially cannot have a kerning table larger than 36kB. Is this assumption false?
I have no idea about the technicalities and how kerning values are stored in a variable font (one origin table and the rest as deltas, so to speak?), but in any case, I found the kB limit needed to be adjusted to be lower and lower the more masters I have in my font, in order for it to work in a variable font export.
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