Use mathfontdimen font feature in LuaTeX

[zauguin]

Status

READY

Description

unicode-math sets \fontdimens to emulate either traditional TeX or XeTeX fonts. Since this functionality is usefful n a more general context than just with unicode-math, it has been added to luaotfload directly. This changes unicode-math to make use of this new luaotfload functionality and therefore makes font loading faster, avoids caching issues, does not require to load fonts with weird scaling factors and simplifies the code.

The current code still loads the family 2/3 funts scaled by 0.9999/1.001 to avoid small changes to existing documents and keep compatibility with XeTeX.

Todo

• [ ] Tests added to cover new/fixed functionality
• [ ] Documentation added if necessary
• [x] Code follows expl3 style guidelines

Minimal example demonstrating the new/fixed functionality

n/a (Only refactors existing functionality)

[wspr]

Excellent -- thanks very much for implementing this.