From e0c6872cf40896c7be36b11dcc744620f10adf1d Mon Sep 17 00:00:00 2001
From: Norbert Preining <norbert@preining.info>
Date: Mon, 2 Sep 2019 13:46:59 +0900
Subject: Initial commit

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+\title{Further thoughts on virtual fonts \ldots}
+\author[Yannis Haralambous]{Yannis Haralambous\\
+\texttt{Yannis.Haralambous@univ-lille1.fr}}
+\begin{Article}
+
+In a paper I published in 1993 (``Virtual fonts: great fun, not for
+grand wizards only!'') I have already
+addressed many of Berthold Horn's arguments; nevertheless I would
+like to take the opportunity to respond a little further.
+
+The basic argument of Horn is that PostScript drivers can reencode
+fonts, so that virtual fonts are unnecessary for plain reencoding.
+This is certainly true, but unfortunately \emph{only in a very limited
+scope}.
+
+% Fonts originally created to be used with \TeX\ (both CM, DC
+%and most of the other fonts) use the first~32 positions of the
+%table to represent glyphs, while PostScript and TrueType need part
+%of (or all of) these positions as control codes.  A reencoded
+%PostScript (or TrueType) font is still a PostScript (or
+%TrueType) font, and hence it \emph{cannot} use some (or all) of
+%these~32 positions. Blue Sky Research has found a way out of this
+%problem by re-encoding (internally) CM fonts so that the first~32
+%positions are translated to the upper part of the 8-bit table.
+%This works fine for~128-character fonts (CMR, CMMI, MSAM, Euler
+%etc.) but \emph{not} for DC fonts, since these occupy
+%\emph{already} all~256 positions.
+
+%It follows that one will never be able to reencode a PostScript
+%font so as to obtain a complete DC font. People will argue that
+%many east-European characters are not available anyway in the
+%fonts we might want to reencode. Nevertheless, virtual font
+%techniques (such as those used by Alan Jeffrey in
+%\texttt{fontinst.tex}, allow the creation of accented
+%east-European characters, but composition of glyphs (glyphs for
+%Eastern diacritics, like the h\'a\v cek or the ogonek, \emph{are}
+%included in every font, one just has to use them to produce the
+%characters, a thing plain reencoding cannot do)\footnote{Horn
+% mentions utilities which can create \emph{new} PostScript fonts
+% with new composed characters.  Alan Jeffrey uses \TeX\ to do
+% this work, a much natural process than any utility. Furthemore,
+% the copyright situation of such ``mutant'' PostScript fonts is
+% unclear.}.
+ To produce accented letters, many PostScript fonts contain
+ ``composite character data'': these are just translation
+ coordinates for character parts, which will be composed to
+ produce the result. PostScript interpreters know about these
+ characters and can automatically take care of characters defined
+ in that way in the font. But these accented characters cover
+ only the West European range (excluding of course Welsh and
+ Maltese); a PostScript interpreter is not clever enough to
+ define a new composite character, for example, a \.z as needed
+ in Polish, or a \^w as needed in Welsh. Alan Jeffrey's utility
+ can do this very easily; this is far more than just plain
+ reencoding, but is everyday practice for virtual
+ fonts.
+
+ The reader may have little interest in exotic languages (like the
+ Polish or Welsh in the previous paragraph); but DC fonts have
+ additional features which are implemented in virtual Cork-like
+ PostScript fonts by Alan Jeffrey's virtual font creation tool:
+   \begin{itemize}
+   \item certain characters may need special kerning (such as the
+ little zero for the perthousand sign, the German single and
+ double opening quotes etc.);
+   \item some symbols (such as \verb*= =,\S,\pounds) may be
+ missing; these can be taken from other fonts;
+   \item the glyph `-' is used twice: once for the text dash, and
+ once for the hyphenation dash (cf.~\cite{Ha1} why these are
+ separate characters); I doubt that reencoding can assign the
+ same glyph to two different positions (?);
+   \item the uppercase version of \ss\ is made out of two `S'
+ letters; this is too much to ask for a poor PostScript
+ interpreter\ldots
+   \item PostScript fonts can contain ligatures, but not
+ \emph{smart} ligatures: if you want your Dutch `\"e' to
+ become an `e' at the end of a line, you need a
+ begin-of-word ligature, something trivial for \TeX.
+   \end{itemize}
+
+ Virtual fonts are one of the most important aspects of
+ the \TeX\ system.  This is not just the case for exotic
+ situations; I voluntarily do not speak of Arabic and other
+ extremely important uses of virtual fonts in oriental
+ languages; virtual fonts are important for all of us
+ Occidental language writers.  A PostScript font has poor
+ typographical properties (no smart ligatures, restricted
+ character composition, since you have to remain in the same
+ font and the same size, etc.); by the use of virtual fonts,
+ \TeX's typographical possibilities can be added to the font:
+ a virtual font structure makes a PostScript font richer.
+
+\begin{quote}\emph{\ldots It is not necessary to use virtual fonts to reencode a
+font\ldots}\end{quote}
+
+  True. But we want more than just re-encoding: word processors like
+  Word or WordPerfect simply reencode fonts; \TeX\ can do more out of
+  a PostScript font, and the proof can be found in the virtual fonts
+  made by Alan Jeffrey's utility.
+
+% \begin{quote}\emph{\ldots Users of Y\&Y software use scalable outline fonts
+% without VF}\end{quote}
+% 
+%  Rephrased: users of etc. etc. can use neither VF nor DC fonts (since
+%   these are not yet scalable). Fortunately there are public domain
+%   implementations of \TeX\ which give users these possibilities.
+%   Anyway, I wouldn't like to make out of these notes the critique of
+%   any software.
+% 
+Horn states that virtual fonts cannot make unencoded
+characters accessible.  This is certainly true, and---as he
+says---this issue is solely solved by reencoding of fonts. But it
+is not an argument against the use of virtual fonts: one can
+always reencode a font into some universal encoding, for example
+\texttt{ISOLatin1}. The latter might be universal, but is still
+not Cork. Some extra work must be done to make a Cork-like font
+out of it, and this is best handled by a virtual font.
+
+I agree that reencoding is the only way to make characters such as
+the Thorn or Eth appear; but it should be only one step of the
+printing progress, between others.
+
+\begin{quote}\emph{\ldots Making a fake smallcaps font\ldots
+A smallcaps font should have properly designed small caps
+letters\ldots}\end{quote}
+
+  Horn is \emph{absolutely} right when he says that one should rather
+  adopt an `Expert' font than faking small caps by scaling regular
+  caps. Now, suppose you buy that Expert font.  What's the next step?
+  You will discover that Expert fonts do not contain uppercase letters
+  (cf.~\cite{Post}, page~602).  Is there a possibility of merging the
+  regular and expert fonts into what we expect to be small-caps font,
+  using plain reencoding? I'm afraid not, since reencoding means
+  ``assigning glyphs to positions, \emph{inside} a font'' and not
+  ``\emph{between} fonts''; you will have to use virtual fonts. Alan
+  Jeffrey's utility automatically finds out if there is an expert font
+  and what characters it contains. It then either creates fake small
+  caps, or takes (just) the real small caps from the expert font.
+  Furthermore, there cannot possibly be any kerning pairs between small
+  caps and uppercase letters in the PostScript fonts since these are
+  not contained in the same 256-characters table. But the \TeX\ 
+  virtual font can contain such kerning pairs (some of them, like
+  \textsc{Ta} or \textsc{Va} being quite important); after a little
+  experimenting the quality-conscious user will easily add the most
+  important kerning pairs to the VPL file.
+
+\begin{quote}\emph{\ldots Only \TeX\ knows anything about virtual fonts\ldots}
+\end{quote}
+
+Actually Horn is not saying ``do not use virtual fonts'', but ``do not
+use PK fonts'', since ``they will never be able to enter into
+illustrations''. He continues:
+
+\begin{quote}\emph{\ldots Well, in the \TeX\ world we tend to be somewhat myopic.
+    \ldots} \ldots \emph{\ldots Hence PK bitmapped fonts are not
+    useful, one needs to use fonts in some established industry
+    standard form such as Type~1 or TrueType\ldots}\end{quote}
+
+  To my (myopic?) eyes the PostScript world seems much more myopic.
+  For many years poor PostScript fonts have been designed; in the
+  meantime the \TeX\ community kept saying ``fonts without metaness
+  are anti-typographic'' but (apart from a few exceptions, like Jacques
+  Andr\'e's papers on pointsize dependent PostScript font code,
+  cf.~\cite{andre} and~\cite{andre-vatton}) metaness seemed to be
+  tabou outside the \TeX\ world; suddenly two years ago the goddess
+  Adobe declared that fonts without metaness are no good, and
+  introduced a new object of veneration: Multiple Master fonts.
+  These are extremely complex and memory consuming, but still much
+  poorer than \MF\ created fonts; nevertheless (myopic) PostScript
+  font users consider them as the \emph{non plus ultra}.
+
+  \MF\ can do things PostScript cannot even dream of. Try to adjust
+  gray density of Hindi, Arabic and Latin text on the same page with
+  PostScript fonts. Horn says that \emph{scaled small caps are fake
+    small caps}. I say: scaled fonts are always faked: \emph{all
+    PostScript fonts are faked when used in a size different that
+    their design size} (and most of the time we don't even know what
+  that design size is; these are things the customer had better not find
+  out\ldots).
+
+  Erik-Jan Vens has developed a tool to convert PostScript fonts to
+  \MF. This opens new horizons to digital typography, since we can
+  manipulate these fonts using \MF\ tools. DVI drivers which do not
+  read PK files will never take advantage of these methods
+  (cf.~\cite{HarDar}).
+
+\begin{quote}\emph{\ldots (note that virtually 
+    all fonts commonly used with \TeX\ are now available in Type1 format,
+    including CM, AMS etc.\ldots}\end{quote}
+
+  But I would add the word `obsolete' after `CM': IMHO, CM fonts are
+  \emph{just good enough to write English}. It is quite an irony that
+  the text you are reading this very moment is written in
+  English\footnote{Bien que j'aurais pu changer de langue \`a tout
+    instant~; si j'\'ecris en anglais ce n'est pas pour la gloire de
+    la langue mais pour faciliter la lecture au lecteur britannique.
+    Passons\ldots }, but here in Europe hundreds of millions of people
+  communicate through other languages, which cannot be hyphenated with
+  CM fonts (cf.~\cite{HaTTN}).  Of course, nobody will ever force the
+  only-English-writing-\TeX-user to use DC fonts, but can progress be
+  stopped?
+
+  Finally, Horn omits a very important issue: there is a tool called
+  DVICopy (written by Peter Breitenlohner). Using DVICopy one can
+  \emph{de-virtualize} a document, that is \emph{replace characters
+    from a virtual font by the real character(s) they represent}.
+  This eliminates all communication problems: suppose I have created a
+  document using a PostScript font, which itself is encoded in some
+  standard encoding.  For this I have used a virtual font, which my
+  correspondant might not necessarily have
+%  \begin{tiny}(in fact, if he/she uses certain software, he/she won't
+%even able to use virtual fonts anyway, but that's another
+%issue)\end{tiny}. 
+By devirtualizing my DVI file, I obtain a new
+DVI file which uses precisely and exclusively the real font on
+which my virtual font was based. In the case of PostScript fonts,
+this means that if my virtual fonts were constructed upon Adobe
+Standard encoded PostScript fonts (that's the usual encoding for
+PostScript fonts) a de-virtualized DVI file will contain
+references to these original PostScript fonts only, which makes it
+as portable as a DVI file can be.
+
+I would like to close this paper by some general remarks on the
+``\TeX\ world'', as I see it: I don't believe \TeX\ users are myopic
+or isolated from the rest of the world. On the contrary, they see
+problems that commercial programs can barely handle, and solve them
+through \TeX\ without even making much noise about it. In the last few
+years it has happened that there has been much more development in
+public domain \TeX ware, than in commercial software around \TeX.
+Important innovations have always appeared first in public domain
+software\footnote{With a single exception: the user interface. Public
+  domain software is never as user-friendly as commercial ones.}.
+Many times commercial software has adopted those innovations; but
+there are also many \TeX\ features yet undiscovered by the commercial
+world---and many commercial products still at the stone age of \TeX.
+This is a sad consequence of the fact that \TeX\ is a public domain
+program, whose ``official'' development has stopped, and has been
+unofficially taken over by mostly unorganized volunteers: this makes
+both the charm and the pain of \TeX\ history. Virtual fonts may be one
+of the innovations that all commercial products haven't adopted
+yet---or maybe not; but we should think twice before giving away
+virtual fonts in exchange for something poorer (PostScript font
+reencoding), when we can equally well use both at the same time, and
+produce even better results.
+
+\begin{thebibliography}{666}
+\bibitem{Post} Adobe Systems International, PostScript Language
+Reference Manual, second edition, Addison Wesley, 1990.
+\bibitem{andre} Jacques Andr\'e, `Adapting Character Shape to Point
+Size', \emph{PostScript Review}, April 1991.  \bibitem{andre-vatton} Jacques
+Andr\'e and Ir\`ene Vatton, `Contextual Typesetting of Mathematical
+Symbols---Taking Care of Optical Scaling', submitted to \emph{Electronic
+Publishing}, 1993.  \bibitem{HaTTN} Yannis Haralambous, `\TeX\ 
+conventions concerning languages', \emph{\TeX\ and TUG News}, Volume
+1, Number 4, 1992.  \bibitem{Ha1} Yannis Haralambous, `Virtual Fonts:
+Great Fun, not for Wizards Only', \emph{Minutes and APendiceS} 93.1,
+Nederlandstalige \TeX\ Gebruikersgroep, 1993.  \bibitem{HarDar} Yannis
+Haralambous, `Parameterization of PostScript fonts through \MF\ --- an
+alternative to Adobe's multiple-master fonts', to appear in \emph{Proceedings
+of Raster Imaging and Digital Typography}, Darmstadt 1994.
+\end{thebibliography}
+\end{Article}
+\endinput
+
-- 
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