Instances do not get referenced spacing right

I have a 4 masters file: compressed light, xbold & regular light & xbold. I am doing the spacing of some glyphs using “referenced spacing”, for example ‘F’ right sidebearing is =E-15 in the light compressed; =E-8 in the xbold compressed; =E-10 in the light; and =E-5 in the xbold. All the values are updated, no red figures.

However when I “generate instances”, all the glyphs using referenced values suddenly get a warning sign and all this sidebearing are red and need to be updated. If I generate the OTFs referenced metrics are also wrong.

Is this a bug or maybe the app does not support different referenced spacing values?

The metrics keys are not interpolated so it will get the value that is assigned to the glyph instead of the layer value. And there might be some rounding errors.

wow, that sounds to me like something quite huge, don t you think? I wouldn t call it “rounding errors”, in some cases is a big difference!

Metrics keys are not supposed to work in this way. Fix all metrics before you interpolate. Or what do you plan to do with the instances?

I don t think I explained myself correctly because all my metrics are fixed, let me upload a few screenshots.

This is the MM, here you can see the metrics of my cap F in each master

The when I generate for example the condensed bold this is what happens

Right sidebearing needs to be updated, otherwise is wrong. If I generate the OTF, the file gets exported with incorrect values as well. If individual instances need to be updated before being generated, all the coolness of the production workflow in glyphs suddenly blows up, don t you think?

Can you send us the file to support at this website without www?

The interpolated spacing is correct. The metrics key is wrong.
E.g., If you interpolate in the first two masters. The light has a metrics key of =E-15 and the bold =E-8. The interpolated instance will have the value from either of the two but would need =E-11 or =E-12.

You only need to update the metics if you changed the spacing of the base glyph.