No. The spec says literally the opposite. How would using the ital axis prevent the user from choosing their slant angle, more than other axes?
Users cannot specify their desired angle on an ital axis because the range is required to be from 0 to 1. A type designer could probably build a font with an ital axis from 0 to -12 to allow users to specify their desired angle, and it might work in some software, but it would be an invalid font.
I’m surprised that your interpretation of the spec is so different from mine. Now I’m doubting myself, since I’m certain that you are far more familiar with the spec than I am.
The clearest part of the spec that implies ital is meant to be used for true italics that don’t interpolate and slnt is meant to be used for oblique italics that do interpolate, is simply the numerical ranges described for those axes. ital must be from 0 to 1. I would call it a “pseudo-binary” axis, because the spec does allow for fractional values, but it states, “this is not expected to be common”. Therefore, I would say the ital axis is meant to be used for non-interpolating italics, aka “true” italics.
The range of slnt must be within -90 to 90 and is said to represent the angle of the slant, which clearly points to interpolating italics, aka “oblique” italics.
The standard practises followed at Google Fonts seem to agree with my conclusions, as they put non-interpolating italics on a binary ital axis with two separate font files set to ital=0 and ital=1, and families with interpolable italics use a slnt axis.
References:
It literally says:
The Italic axis can be used as a variation axis within a variable font, though this is not expected to be common.
(Emphasis mine)
I’m not even interpreting anything. This is literally quoted from the spec, from one of the bits you posted.
Hello,
I have been advised to contribute to this discussion with my case which is explained here with more details:
So in the end Sebastian advice is:
I advise you to use only the “Slant” axis. Don’t forget to add the Axis Locations and the STAT table.
Do you have any advise how to keep ital for Microsoft? Searching all the day, but couldn’t find any information.