A space separated list with 2 items:

   1. the proportional font family used by pfm;

   2. the proportional font size used by pfm.

If the size is preceded by a '-' sign, the size is in pixels, else,
the size is in points (= 1/72 inch).

The default is: helvetica -12

If the name of the font family consists of more than 1 word, enclose
it in curly braces { and }, as in

{luxi sans} -12

