Instantiator usWidthClass

We are having an issue with the instantiator regarding usWidthClass. Our Variable font ‘wdth’ axis spans from 50 to 275 (%) but the instantiator tries to map it to 50-200 because of the example of the OpenType specs: https://docs.microsoft.com/en-us/typography/opentype/spec/os2#uswidthclass https://github.com/googlefonts/fontmake/blob/24312140ce114691363f62b9293c46b10f95c0b4/Lib/fontmake/instantiator.py#L633

Why should the ‘wdth’ need to stick to the min=50 max=200 example of the specs? a variable font may as well have very different min-max values and still the named instance would need distinctive usWidthClass values.

In our case the last two wider instances get the same usWidthClass value of 9 (because both are beyond 200) and this is creating the confusion.

width_user_value = min(max(wdth_user_value, 50), 200): wouldn’t it be more correct to replace the arbitrary values of 50 and 200 by the VF wdth max and wdth min then map accordingly the instances values?

[anthrotype]

we could allow it to be greater than 9, but it certainly can’t be less than 0 because it’s an unsigned 16 bit integer in the OS/2 spec…

[fabiocaccamo]

Your suggestion is correct, actually we are using the OS/2 fields for sorting because not all fonts are instantiated from a VF (so they have not instance coordinates).