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<head>
<title>UK TeX FAQ -- question label virtualfonts</title>
</head><body>
<h3>Virtual fonts</h3>
<p>Virtual fonts for TeX were first implemented by David Fuchs in the
early days of TeX, but for most people they date from when Knuth
redefined the format, and wrote some support software, in 1989 (he
published an article in <i>TUGboat</i> at the time, and a copy is
available on CTAN).
Virtual fonts provide a way of telling TeX about something more
complicated than just a one-to-one character mapping. The entities you
define in a virtual font look like characters to TeX (they appear
with their sizes in a font metric file), but the DVI processor may
expand them to something quite different. You can use this facility
just to remap characters, to make a composite font with glyphs drawn
from several sources, or to build up an effect in arbitrarily
complicated ways - a virtual font may contain anything which is
legal in a DVI file. A "how to", describing how to generate
virtual fonts from scratch, is available.
<p>In practice, however, the most common use of virtual fonts is to remap
PostScript fonts (see <a href="FAQ-metrics.html">font metrics</a>). Other
interesting uses have been to build 'fake' maths fonts (by bundling
glyphs from several fonts together), and (utilising the facility to
use bits of DVI) to build useful subsets of the T1 fonts
using nothing but the PostScript Type 1 versions of Knuth's Computer Modern fonts.
<p>It is important to realise that TeX itself does <em>not</em> see
virtual fonts; for every virtual font read by the DVI driver there
is a corresponding TFM file read by TeX. Virtual fonts are normally
created in a single ASCII <code>vpl</code> (Virtual Property List)
file, which
includes both sets of information. The <i>vptovf</i> program is
then used to the create the binary TFM and VF files. The
commonest way (nowadays) of generating <code>vpl</code> files is to use the
<i>fontinst</i> package, which is described in detail
together with the discussion of
<a href="FAQ-metrics.html">PostScript font metrics</a>.
<i>qdtexvpl</i> is another utility for creating ad-hoc virtual
fonts.
<dl>
<dt><tt><i>fontinst</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/fonts/utilities/fontinst.zip">fonts/utilities/fontinst</a> (<a href="ftp://cam.ctan.org/tex-archive/fonts/utilities/fontinst.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/fonts/utilities/fontinst/">browse</a>)
<dt><tt><i>Knuth on virtual fonts</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/info/virtual-fonts.knuth">info/virtual-fonts.knuth</a>
<dt><tt><i>Virtual fonts "how to"</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/info/virtualfontshowto/virtualfontshowto.txt">info/virtualfontshowto/virtualfontshowto.txt</a>
<dt><tt><i>qdtexvpl</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/fonts/utilities/qdtexvpl.zip">fonts/utilities/qdtexvpl</a> (<a href="ftp://cam.ctan.org/tex-archive/fonts/utilities/qdtexvpl.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/fonts/utilities/qdtexvpl/">browse</a>)
</dl>
<p><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=virtualfonts">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=virtualfonts</a>
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