where n is a decimal integer giving the position of the character in the font, and c1, c2,... are the groff names of the character. If a character has no groff names but exists in the tfm file, then it will be put in the groff font file as an unnamed character. font is the name of the groff font file. The groff font file is written to font.
The -s option should be given if the font is special (a font is special if troff should search it whenever a character is not found in the current font.) If the font is special, it should be listed in the fonts command in the DESC file; if it is not special, there is no need to list it, since troff can automatically mount it when it's first used.
To do a good job of math typesetting, groff requires font metric information not present in the tfm file. The reason for this is that TeX has separate math italic fonts whereas groff uses normal italic fonts for math. The additional information required by groff is given by the two arguments to the math_fit macro in the Metafont programs for the Computer Modern fonts. In a text font (a font for which math_fitting is false), Metafont normally ignores these two arguments. Metafont can be made to put this information in the gf file by loading the following definition after cmbase when creating cm.base:
def ignore_math_fit(expr left_adjustment,right_adjustment) = special "adjustment"; numspecial left_adjustment*16/designsize; numspecial right_adjustment*16/designsize; enddef;
For the EC font family, load the following definition after exbase (it is probably easiest to patch exbase.mf locally):
def ignore_math_fit(expr left_adjustment,right_adjustment) = ori_special "adjustment"; ori_numspecial left_adjustment*16/designsize; ori_numspecial right_adjustment*16/designsize; enddef;