If this isn't in the fonts information on the web site, it really should
be. We can't use X for all font information because X sucks--it doesn't
leak enough information so that we can create printable documents.
We can't get the raw Type1 fonts to embed in PostScript output through
X, we can only get character metrics and pre-rendered bitmaps. To
get the Type1 information, we need a copy of the fonts locally.
GhostScript uses fonts this way, mapped through its Fontmap. X loads
fonts through fonts.dir, and so people (and us, programmatically)
don't have to maintain two seperate font lists, we parse the same fonts.dir
to find our Type1 fonts.
X has no concept of "printing"--it's just a window display system,
and even scalable Type1 fonts are a relatively new thing to X
(as of X11R5). Before that you had fixed resolution bitmap
fonts which would be unreadable at 10 pixels high on a 600 DPI laser
printer, but horribly aliased at 600 pixels high.
We use Type1 fonts because they're portable (ASCII and binary formats
easily converted using free tools), scalable (not resolution-dependent
bitmaps), and there is a set of printables with GhostScript that
look very nice on paper. They could use a few more hints for display,
though, but zooming in on a document will give them a bit more space
to smooth out.
-- Shaw Terwilliger