Make Emmentaler an OpenType Variation Font
- All current Emmentaler fonts could be replaced with a single font, having an 'optical size' axis. The existing fonts would be represented both with metrics and outlines exactly the same, namely as 'instances' for a given optical size value.
- Both Pango and FreeType support Variation Fonts; this means that the necessary internal infrastructure changes to LilyPond would be rather small. The only technical challenge is to transform the 'LILC' OpenType table into something that responds to the optical size.
- Because of the way the Emmentaler font family is constructed from METAFONT input, it is well suited for such a conversion: regardless of the optical size, the number of outline points doesn't change. There are some exceptions IIRC, however, it should not be too difficult to fix them.
- The biggest problem is that FontForge does not support the creation of Variation Fonts. This means that we would have to use another toolkit, namely either Adobe's Font Developer Kit for OpenType, AFDKO, or FontTools. Given that both tools are written in Python and actively maintained and developed (contrary to FontForge, alas) I wouldn't expect big obstacles in the transition. A possible route could be to replace FontForge with AFDKO/FontTools first. In a second step, the transition to a Variation Font could happen.
I think this would be an excellent GSoC project.
Edited by Werner Lemberg