[NTG-context] Kerning and ligatures in math roman font

[Ulrike Fischer]

In this example there is no kerning and no ligatures in the math:

\starttext
 WAiff $\mfunction{WAiff}$
\stoptext

This is a different behaviour than with legacy math fonts. 

A question about this has been asked some month ago on tex.sx
(http://tex.stackexchange.com/questions/252493/ligatures-are-not-used-in-opentype-maths-families).
The problem (or feature) exist also with xetex. 

With luatex one can avoid to loose the kerning by loading as math
roman font a font in mode base
(http://tex.stackexchange.com/questions/277362/lualatex-no-kerning-within-operatorname-when-not-loading-lmodern-package/277395#277395,
I have no idea how to do this in context).

Is this a luatex/xetex bug? Or a feature? How could one enable
kerning and/or ligatures without going back to base mode? 


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/