Fonts may be added to this postscript system by placing a piece of
PostScript source in the directory $POSTSCRIPTLIB/font.  This is where
postscript looks when findfont is called. File names in this directory
may be mapped from font names by placing entries of the form:
	FontMap /postscript-name /base-file-name. put
in the font-map file in $POSTSCRIPTLIB.

If postscript-name is not found there, an identity mapping is assumed.

The existing fonts are similarly structured, so most of the work is
done by executing a common proforma file in that directory. This sets
up the appropriate font information.  A version of BuildChar is
installed which will read in the bulk of the font infromation when it
is first executed. It will then replace itself with the normal
BuildChar.

NOTE the metrics are currently loaded with the rest of the font
information on demand, so programs which attempt to read metric
infromation before using a font will fail. This is a bug, but can be
fixed in PostScript.

There is a parallel cache directory, $POSTSCRIPTLIB/cache. This
contains a directory corresponding to each file in $POSTSCRIPT/font,
into which cached versions of fonts may be placed. The operator
savecurrentfont may be called after imaging some characters from a
font, whereupon a diskcache will be made of the characters imaged so
far. Caches loaded may be subsequently modified and saved, thus built
incrementally.  There should be an operator to save all modified caches
into the disk cache. This could be built into PostScript, but might
cause problems.  There is a program called buildcache in the demos
directory which will build a cache of the standard fonts in a variety
of useful sizes.

PostScript searches the disk cache automatically, and will not call BuildChar if it find a cache.
This version of the cache stores metrics for the font.