Module mathparams 

LuaTeX’s math parameters (\Umath…) and how font assignments set them.

LuaTeX takes every font-dependent value of math typesetting from a parameter of the current style. Assigning a TFM font to family 2 or 3 (\textfont2=\tensy, …) sets the parameters of the styles of that size from the font dimensions (LuaTeX manual, “Font-based math parameters”); the assignments obey grouping. Observed details:

• family 2 needs at least 22 font dimensions, family 3 at least 13; other fonts leave the parameters alone;
• \Umathsubshiftdrop and \Umathsupshiftdrop of a style come from the font one size smaller (TeX’s sub_drop(t)), so \scriptfont2 sets them for the display and text styles and \scriptscriptfont2 for the script and scriptscript styles;
• the skewed fraction gaps are set to zero, the radical degree placement to 5/18 and −10/18 quad and 60%;
• \Umathradicalvgap is set when family 3 is assigned (with the x-height of the family-2 font of the same size in display styles);
• \Umathspaceafterscript is set from \scriptspace (globally, for all styles still undefined) when the first formula is typeset, and never again.

A font with OpenType MathConstants sets the parameters of its size from them instead, whatever the family (manual table; \Umathquad is the font size and the limit kerns are zero).

Modules

mp

Math parameter numbers (the chr codes of the \Umath… primitives).