When we last built this font, glyphsLib did not support removing open corners, such as this one found in the bold master of f.sups in the Italic:
It now does try to remove them, but it doesn't do so in an interpolatable way. The Regular master does not have an open corner, so it is not removed, and the two paths end up having different numbers of points. (Glyphs.app actually has the same problem and now refuses to build the italic as a variable font.)
The problem is the curve construction here, which probably needs to be fixed so that it is interpolatable. An alternative is to fix the gftools-builder such that it can turn off the default filters. I can do the second, but it's better to do the first as well.
When we last built this font, glyphsLib did not support removing open corners, such as this one found in the bold master of
f.supsin the Italic:It now does try to remove them, but it doesn't do so in an interpolatable way. The Regular master does not have an open corner, so it is not removed, and the two paths end up having different numbers of points. (Glyphs.app actually has the same problem and now refuses to build the italic as a variable font.)
The problem is the curve construction here, which probably needs to be fixed so that it is interpolatable. An alternative is to fix the gftools-builder such that it can turn off the default filters. I can do the second, but it's better to do the first as well.