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%%% VFlib 3.5.0 document
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%%% Revised: 1 September 1998
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%%% VFlib 3.5.0 --- a general font library that supports multiple font formats
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%%% by Hirotsugu Kakugawa
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%%% Email: h.kakugawa@computer.org
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%%% FAX: +81-824-24-0757
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%%% Research Institute for Information Science and Education
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%%% Hiroshima University
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%%% 1-7-1 Kagamiyama, Higashi Hiroshima, Hiroshima,
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\documentclass{cah-gut}
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\newcommand{\pkg}[1]{\textsf{#1}}
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\newcommand{\prog}[1]{\texttt{#1}}
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\newcommand{\file}[1]{\texttt{#1}}
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\newcommand{\var}[1]{\textit{#1}}
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\newcommand{\VFlib}{\pkg{VFlib}}
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\newcommand{\freetype}{\pkg{FreeType}}
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\newcommand{\tlib}{\pkg{T1Lib}}
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\newcommand{\vflibcap}{\pkg{vflibcap}}
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\newcommand{\hbfgf}{\prog{hbf2gf}}
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\newcommand{\ttfpk}{\prog{ttf2pk}}
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\selectlanguage{american}
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%%%-----------------------------------------------------------------------
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\title{VFlib 3.5.0 --- a general font library that
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supports multiple font formats\footnote{
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This paper is based on
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``VFlib --- a general font library that
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supports multiple font formats,'' by Hirotsugu Kakugawa,
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Euro\TeX 98, Saint-Malo, France, 1998.}
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\author{Hirotsugu Kakugawa}
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Research Institute for Information Science and Education\\
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Hiroshima University\\
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1-7-1 Kagamiyama, Higashi Hiroshima, Hiroshima,\\
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\authorhead{Hirotsugu Kakugawa}
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\titlehead{A font library VFlib 3.5.0}
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%%%-----------------------------------------------------------------------
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\VFlib\ is a font library written in C providing several functions
71
to obtain bitmaps of characters (i.e., a rasterizer).
72
\VFlib\ hides the font format of font files and provides a unified API
73
for all supported font formats.
74
Thus, programmers of application software need not worry
75
about font file formats and any software using \VFlib\
76
can support various font file formats immediately. In addition to
77
this, when a new font format is supported by \VFlib, application
78
software need not be modified to use such new fonts.
80
\VFlib\ has been developed for not only Latin fonts but also Asian
81
scripts such as Chinese, Japanese, and Korean. Since it is designed
82
as a general font module, it can be used in DVI drivers for \TeX\
83
and \LaTeX. In this paper, we explain the API of \VFlib, a font
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database file called \vflibcap, and the internal structure of \VFlib.
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%%%-----------------------------------------------------------------------
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digital fonts, computer typography, multilingual typography,
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multilingual information processing, \TeX
96
%%%-----------------------------------------------------------------------
98
\section{Introduction}
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\label{SEC:Introduction}
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Commercially and freely available fonts exist in many
102
different font file formats. When we develop software to display or
103
print characters which do not depend on a particular window system
104
and/or an operating system, we must write interface routines for
105
accessing font files for each application program again and again.
106
To do this, programmers must have knowledge of font file formats;
107
it will be a difficult task for programmers if the number of font
108
formats that an application program supports becomes large.
110
\VFlib\ is a font library written in C providing several functions to
111
obtain glyphs (bitmaps). \VFlib\ hides the font format of font
112
files and provides a unified API for all supported font formats so
113
that programmers for application software need not worry about
114
font file formats. Thus, any software using \VFlib\ can support
115
various font file formats immediately without modification even when
116
\VFlib\ is updated to support new font file formats.
117
Furthermore, \VFlib\ is not window- or operating-system dependent.
119
As far as the author knows, there is no general font library other than
120
\VFlib\ that supports multiple font formats in a platform-independent
121
way and that provides a unified API for font access.
122
For example, X~Window servers support multiple font formats.
123
But to use a font service, an X server process is required.
124
Some font libraries have been proposed for general use:
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\freetype\ 1.1 by David Turner, Robert Wilhelm, and Werner Lemberg is a
126
library for accessing TrueType fonts \cite{FreeType}.
127
The \tlib\ by Rainer Menzner is a library to handle
128
Type~1 PostScript fonts \cite{TypeOneLib}.
129
Although both are very useful libraries not dependent on
130
window or operating systems, each of them supports only one
131
font format and has a different API.
133
Conversion of font formats so that application software can use
134
multiple font formats is one possible approach. For example,
135
\ttfpk\ \cite{TTFTOPK} (TrueType fonts to PK fonts)
136
and \hbfgf\ \cite{HBFTOGF} (HBF\footnote{
137
The Hanzi Bitmap Font (HBF) format \cite{HBFspecs}
138
is a binary format for bitmap fonts for
139
Japanese, Chinese, and Korean characters.
142
both written by Werner Lemberg, makes these font formats
143
available to \TeX. This method is useful but one drawback
144
is that we must convert many font files in advance.
146
Currently, \VFlib\ supports the following font file formats:
147
PCF, BDF, HBF, TrueType, Type~1, GF, PK, TFM, VF, Syotai Kurabu
149
PCF (Portable Compiled Font) format is a binary format
150
for bitmap fonts used on X-Window.
151
BDF (Bitmap Distribution Format) \cite{BDFSpec}
152
is an ASCII format for distributing binary fonts.
153
Syotai Kurabu, which means \textit{font club} in English,
154
is a vector font format for Japanese Kanji characters.
155
JG format is another vector font format for
156
Japanese Kanji characters.
158
To search \TeX\ font files (e.g., PK, GF, TFM, VF files)
159
and TrueType font files,
160
\VFlib\ uses the \pkg{kpathsea} library 3.2 by Karl Berry \cite{Kpathsea}.
161
\VFlib\ can be used as a font module for
162
drivers and previewers of DVI files generated by \TeX\ and \LaTeX.
164
This paper describes \VFlib\ version 3.5.0\footnote{
165
\VFlib\ version 3.2 is introduced in \cite{Werner97} and
166
version 3.3 is reported in \cite{Kakugawa98a}.
168
\VFlib\ versions 1 and 2 were designed and implemented
169
for Japanese fonts only; they are widely used
170
in many localized software packages in Japan,
171
e.g. by \pkg{Ghostscript}, \pkg{dvi2ps}, and \pkg{xdvi}
172
for printing Japanese Kanji characters.
173
\VFlib\ version 3 is designed for multilingual
174
document processing in English, French, Chinese, Japanese,
175
Korean, and other languages.
177
This paper is organized as follows. In section \ref{SEC:ConceptsOfVFlib},
178
the basic concepts of \VFlib\ are explained.
179
The API of \VFlib\ is shown in section \ref{SEC:VFlibOfAPI}, and the
180
font database called \vflibcap\ is explained in section
181
\ref{SEC:Vflibcap}. An interesting feature of \VFlib\ is the
182
ability to provide fonts without font files. Section
183
\ref{SEC:ClassesWithoutFontFiles} explains this feature. The author
184
has developed several sample programs using \VFlib, and one of these is
185
introduced briefly in section \ref{SEC:SamplePrograms}.
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Section \ref{SEC:Conclusion} gives concluding remarks.
189
%%%-----------------------------------------------------------------------
191
\section{Basic Concepts}
192
\label{SEC:ConceptsOfVFlib}
194
\subsection{System components}
196
The \VFlib\ system consists of two parts:
199
\item A library (\file{libVFlib.a}) \\
200
It provides several C functions. Any application software using
201
\VFlib\ must link with this library.
202
\item A font database file (\file{vflibcap}) \\
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This file defines fonts and their properties (called {\em capabilities}),
204
such as point size and the font file format. Its syntax is lisp-like
208
When we initialize \VFlib, we can specify a \vflibcap\ file to be used
209
and thus different font sets can be used by different software.
211
\subsection{Font classes and font drivers}
213
\VFlib\ can handle multiple font file formats. Reading a font file
214
according to the font file format is done by an internal module in
215
\VFlib\ corresponding to its font file format. This internal module
216
is called a {\em font driver}. Service units provided by font drivers
217
are called {\em font classes}. From an end-user's point of view,
218
various font formats are distinguished by various names of font
219
classes. Font drivers are internal to \VFlib\ and invisible to
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Some font drivers may not read font files on disk: they may generate
223
glyphs and outlines by internal computation only. In addition, some
224
font drivers may return glyphs which are obtained as glyphs by another
227
\subsection{A view of \VFlib\ font from end-users perspective}
229
Each (virtual) font by \VFlib\ has its inherent information of point
230
size, pixel size, and resolution of the target device. In addition,
231
font metrics are defined for each glyph.
232
Some font file formats may not have such concepts.
233
For instance, TrueType font files are vector font
234
files and do not have information on point size.
235
Syotai Kurabu format fonts do not have font metric information at all.
236
In such case, either (1)~the lacking information
237
is given in \vflibcap\ or (2)~the specific font driver gives such
238
information as default values.
240
\subsection{Font names and font searching mechanism}
242
In \VFlib, a font is specified by a {\em font name} on opening.
243
First, \VFlib\ checks whether the font name is given in \vflibcap\ or
244
not. If the font name is found, \VFlib\ reads the description for the
245
font in \vflibcap. The description contains a font class name; \VFlib\
246
then invokes a font driver corresponding to the font class name.
247
Finally the font driver opens the font file (if necessary).
249
If the font name is not given in a \vflibcap\ file, a font searching
250
mechanism is invoked. Since there are many font files for X~Window
251
and \TeX, this feature is introduced to avoid writing an entry for
252
each font file. Various font drivers will be called to see whether
253
the font can be opened; a list of font drivers for font searching is
254
given in the \vflibcap\ file. If a font driver succeeds in opening the
255
font, font searching finishes and the \VFlib\ font opening function
256
returns successfully. Otherwise, font open fails.
258
Fonts described in a \vflibcap\ file are called {\em explicit fonts} and
259
fonts that are searched for by the font search feature are called {\em
262
\subsection{Two modes of opened fonts}
264
The following two modes are provided to obtain glyphs of fonts.
266
\item High resolution device-oriented mode (mode 1)\\
267
The size of glyphs is specified by the physical size of
268
glyphs and device resolution.
269
\item Low resolution device-oriented mode (mode 2)\\
270
Glyph sizes are specified by pixel size rather than by
273
When the size of a glyph in the
274
source font is different from the target size, \VFlib\ scales the
275
source glyph internally.
276
Thus, users need not know know original size of glyphs in font files.
278
Two modes are provided by the following reason.
279
When we write a application programs that prints documents on printer,
280
it is convenient to specify glyph size by point and device resolution
281
such as glyph of 12 point for a 300 dpi printer.
282
On the other hand, when we write a application programs
283
that displays documents on CRT screen,
284
it is convenient to specify glyph size by pixel.
286
\subsection{Internal Structure}
288
The \VFlib\ library consists of a {\em core} and several {\em font
289
drivers}. The \VFlib\ core provides entry functions of the API,
290
as well as a font driver table, opened font table, \vflibcap\ access module,
291
and other utility modules. The internal structure of \VFlib\ is
292
depicted in Figure \ref{FIG:VFlibInternal}.
296
\mbox{\includegraphics[scale=1.0]{internal.eps}}
298
\caption{Internal structure of \VFlib}
299
\label{FIG:VFlibInternal}
302
Each font driver has corresponding functions for each font operation
303
of \VFlib. Such functions are implemented to provide \VFlib\
304
API-compatible behaviour.
305
The set of capabilities that can be used for each font class
306
in \vflibcap\ file may differ; each font class defines
307
the capabilities it needs.
310
%%%-----------------------------------------------------------------------
313
\label{SEC:VFlibOfAPI}
315
In this section we describe the API of \VFlib. The API that \VFlib\
316
defines is simple. For example, as a contrast, \freetype\ defines
317
a rich set of functions including access to kerning information.
318
The simplicity of \VFlib\ API is a result of the limitation that
319
it must be common to every font format that \VFlib\ supports.
320
\VFlib\ does not have features for typesetting such as obtaining
321
kerning information of fonts. But it is enough strong to print and
322
display typesetted documents such as DVI files.
324
\subsection{Data types}
326
\VFlib\ defines the following three data types for font access: bitmaps
327
and metrics for modes~1 and~2.
330
\item Bitmap object \\
331
A bitmap object is a set of font metrics and bitmap data. The
332
following is the definition of bitmap structure.
336
\setlength{\baselineskip}{1em}
339
int bbx_width, bbx_height; /* in pixels */
340
int off_x, off_y; /* in pixels */
341
int mv_x, mv_y; /* in pixels */
342
unsigned char* bitmap;
349
The members \prog{bbx\_width} and \prog{bbx\_height} are the width
350
and height of the bitmap, respectively. The members \prog{bitmap}
351
and \prog{raster} are pointers to the glyph data and the number of
352
bytes of a raster. The members \prog{off\_x} and \prog{off\_y}
353
form a vector from the reference point to the upper-left corner of a
354
bitmap. The members \prog{mv\_x} and \prog{mv\_y} form a vector to
355
the next reference point. Metric information is given in pixel form.
357
\item Metric object (modes 1 and 2) \\
358
Metric objects for modes~1 (high resolution device-oriented mode)
359
and~2 (low resolution device-oriented mode) are defined similarly
360
as bitmap objects except that they do not have \prog{bitmap} and
361
\prog{raster} members. Member types of mode~1 metric objects
362
are \prog{double}, not \prog{int}; their units are points rather
366
\subsection{Functions}
369
\item \prog{int VF\_Init(char* \var{vflibcap},
370
char* \var{variable\_list})} \\
371
Initialize \VFlib. The first argument \var{vflibcap} is the file name
372
of a \vflibcap\ file. The second argument {\it variable\_list} is a
373
list of parameters passed to \VFlib\ for parameterization of \vflibcap.
374
(See subsection \ref{SUBSEC:VFLIBCAP:PARAM} for details of
377
\item \prog{int VF\_OpenFont1(char* \var{font\_name},
380
double \var{point\_size},
382
double \var{mag\_y})} \\
383
Open a font in mode~1. The font name is given by the first
384
argument. Two arguments \var{mag\_x} and \var{mag\_y} are
385
horizontal and vertical magnification factors. The actual font size
386
is determined by these arguments. This function returns a font
387
identifier (font id) for the opened font. All font operations take
388
this font id to specify a target font.
390
\item \prog{int VF\_OpenFont2(char *\var{font\_name},
391
int \var{pixel\_size},
393
double \var{mag\_y})} \\
394
Open a font in low resolution mode. This function is similar to
395
\prog{VF\_OpenFont1()} except font size is given in pixels.
397
\item \prog{VF\_BITMAP VF\_GetBitmap1(int \var{font\_id},
398
long \var{code\_point},
400
double \var{mag\_y})} \\
401
Obtain a glyph bitmap of a given font id (in mode~1) and code point.
402
The font id \var{font\_id} must be an id returned by
403
\prog{VF\_OpenFont1()}. The size of the bitmap to be obtained can
404
be specified by the \var{mag\_x}, and \var{mag\_y} arguments.
406
\item \prog{VF\_BITMAP VF\_GetBitmap2(int \var{font\_id},
407
long \var{code\_point},
409
double \var{mag\_y})} \\
410
Obtain a glyph bitmap of a given font (in mode~2) and code point.
413
\VFlib\ defines other functions such as \prog{VF\_""METRIC1
414
VF\_""Get""Metric1()} and \prog{VF\_""METRIC2 VF\_""Get""Metric2()}
415
to obtain font metrics of a character of mode~1 and~2 fonts,
416
respectively; \prog{VF\_""OUTLINE VF\_""Get""Outline()} to obtain
417
\VFlib\ format vector data of a character of mode~1 fonts; and
418
\prog{VF\_""BITMAP VF\_""Outline""To""Bitmap()} to convert \VFlib\ format
419
vector data to a bitmap. By calling
420
\prog{VF\_""Install""Font""Driver()}, a font driver is installed.
423
%%%-----------------------------------------------------------------------
425
\section{A Font Database File ``\vflibcap''}
428
A \vflibcap\ file is a database of font definitions for \VFlib. It is
429
read when \VFlib\ is initialized. A simple example of a \vflibcap\ file
434
\setlength{\baselineskip}{1em}
436
(define-default VFlib
437
(uncompression-programs (".Z" "zcat") (".gz" "gzip -cd"))
438
(implicit-font-classes pcf bdf)
439
(extension-hints (".bdf" bdf) (".pcf" pcf)))
442
(filename-extensions ".bdf")
443
(font-directories "/usr/local/share/fonts/X11//")
444
(compression-extensions ".gz" ".Z"))
447
(filename-extensions ".pcf")
448
(font-directories "/usr/X11R6/lib/X11/fonts//"
449
"/usr/openwin/lib/X11/fonts//")
450
(compression-extensions ".gz" ".Z"))
452
(define-font timR24 ; Times Roman 24pt, BDF format
454
(dpi 300) (point-size 24)
455
(font-file "timR24.bdf"))
457
(define-font timR18 ; Times Roman 18pt, PCF format
459
(dpi 300) (point-size 24)
460
(font-file "timR18.pcf"))
465
By a \prog{define-default} construct, a default values of a font class
466
is defined. By a \prog{define-font} construct, a font is defined.
467
Semicolon (\prog{;}) starts a comment.
468
In this example, there are three definitions for font class default
469
(\prog{VFlib}, \prog{BDF}, and \prog{PCF}) and two font definitions
470
(\prog{timR24} and \prog{timR18}). The first three entries are used to
471
give default parameters for \VFlib\ and each font class. We explain
472
these entries later and explain the other two entries first. Although
473
many capabilities are defined, we explain only the fundamental ones.
475
\subsection{Font entries}
477
The entry \prog{timR24} has several capabilities. A capability
478
\prog{font-""class} specifies the font class name. In this example,
479
\prog{timR24} belongs to the \prog{bdf} font class.
480
The capabilities \prog{dpi} and \prog{point-""size} give
481
device resolution and point size of a font.
482
These values are used when this font is opened in mode~1.
483
A capability \prog{pixel-""size} gives the pixel size.
484
This value is used when this font is opened in mode~2.
485
The capabilities \prog{pixel-""size}, \prog{dpi}, and \prog{point-""size}
486
can be omitted since a BDF font file contains their values.
487
A capability \prog{font-""file} gives the file name of the font.
488
Similarly, \prog{timR18} is defined except in cases of PCF fonts.
490
The two font files \prog{timR24.bdf} and \prog{timR18.pcf} are both
491
bitmap fonts used in X~Window. Although pixel size, point size, and
492
target device resolution are together with the bitmap given in the
493
font file, \VFlib\ internally enlarges or shrinks bitmaps to yield the
494
requested size. From a user's point of view, only the font names
495
(\prog{timR24} and \prog{timR18}) are visible; users need not be aware
498
\subsection{Default descriptions}
500
In the example above, there are three default descriptions. The first
501
entry \prog{VFlib} is used to give global parameters of \VFlib. In
502
our example, the relation between the filename extension and an
503
uncompression program is given by the capability
504
\prog{uncompression-""programs}; it specifies that files whose names
505
end in \prog{.Z} and \prog{.gz} are uncompressed by running commands
506
\prog{zcat} and \prog{gzip -cd}, respectively.
507
The capability \prog{implicit-""font-""classes} specifies a
508
list of font classes that search implicit fonts. When a font is
509
opened and a corresponding entry is missing in \vflibcap, font drivers
510
given by this capability are called to search the font in given order.
511
Suppose a font named \prog{timR10.bdf} is requested to open. Since
512
such an entry does not exist in the \vflibcap\ file, the font is
513
searched as an implicit font by calling the PCF font driver first, and
514
then the BDF font driver. A capability \prog{extension-""hints} gives
515
a relation of font name extension and font class. In the example, if
516
an extension of a font name is \prog{.pcf} (\prog{.bdf}), the PCF
517
(BDF) font driver is called for implicit font search. For example, if
518
a font named \prog{timR08.bdf} is requested to open, the BDF font
519
driver is called. This is useful for searching implicit fonts fast.
521
The next definition \prog{BDF} is a default description for the BDF
522
font class. A capability \prog{font-""directories} is a list of font
523
directories in which font files are stored. If the directory name is
524
terminated by \prog{//}, files are searched recursively under the
525
directory. The entry \prog{compression-""extensions} gives a list of
526
file compressions that BDF font class supports.
527
Similarly, default definition for \prog{PCF} font class is given.
529
\subsection{Parameterized \vflibcap}
530
\label{SUBSEC:VFLIBCAP:PARAM}
532
Capability values in \vflibcap\ can be overridden at execution time.
533
By this feature, called {\em parameterization}, several applications
534
can share the same \vflibcap\ file.
535
The next example is a \vflibcap\ for printer driver for \TeX\ DVI file
536
for 300 dpi Canon Laser Shot.
537
Note that all fonts are implicit fonts.
540
\begin{small}\setlength{\baselineskip}{1em}
542
(define-default VFlib
543
(implicit-font-classes pk)
544
(extension-hints ("pk" pk))
545
(variable-values (TeX_USE_KPATHSEA "Yes")
547
(TeX_KPATHSEA_MODE "cx")
548
(TeX_KPATHSEA_PROGRAM "/usr/local/bin/xldvi"))
549
(use-kpathsea $TeX_USE_KPATHSEA)
550
(kpathsea-mode $TeX_KPATHSEA_MODE)
551
(kpathsea-program-name $TeX_KPATHSEA_PROGRAM) )
555
(tfm-directories "TEXMF" "/usr/local/fonts/tfm")
556
(tfm-filename-extensions ".tfm"))
559
(font-directories "TEXMF" "/usr/local/fonts/pk"))
564
In the \prog{VFlib} entry, the capability \prog{variables-""values}
565
gives a list of variable names and their default values. In this
566
example, there are three variables. For instance, the default value of
567
\prog{TeX\_""DPI} is \prog{300}. A capability value can be a value of
568
a variable if a dollar sign (\prog{\$}) followed by a variable name is given.
569
In the \prog{VFlib} entry, initialization parameters for \pkg{kpathsea}
572
In the \prog{TeX} entry, which is used to specify a common
573
default description for \TeX\ related font classes,
574
the value of the capability \prog{dpi}
575
is given as the value of a variable \prog{TeX\_""DPI}, for example.
576
Capabilities \prog{tfm-directories} is a list of TFM files directories,
577
and \prog{tfm-""filename-""extensions} is a extension of a file name
579
The name \prog{"TEXMF"} in \prog{tfm-""directories} is a special name
580
to seach a file using \pkg{kpathsea}.
582
The entry \prog{pk} entry is used to specify default description
583
for font files in PK format.
584
A PK file is search by \pkg{kpathsea} first since the first item
585
of the value of the capability \prog{font-""directories} is \prog{"TEXMF"}.
586
If it is not found, then it is searched in \prog{/usr/""local/""fonts/pk}
589
Default variable values can be overridden by giving a list of pairs of
590
variable names and their values when \VFlib\ is initialized by
591
\prog{VF\_Init()}. If a Unix environment variable
592
\prog{VFLIBCAP\_""PARAM\_\var{var}} (e.g.,
593
\prog{VFLIBCAP\_""PARAM\_TeX\_DPI} is defined, its value becomes the
594
value of the \vflibcap\ variable \prog{TeX\_""DPI}.)
595
The example \vflibcap\ file can be used for 600 dpi HP Laser Jet 4 printers
596
if we override variable values so that
597
\prog{TeX\_""DPI} is \prog{600} and \prog{TeX\_""KPATHSEA\_""MODE} is
598
\prog{ljfour} on execution time without any file modification.
601
%%%-----------------------------------------------------------------------
603
\section{Font Classes without Font Files}
604
\label{SEC:ClassesWithoutFontFiles}
608
\mbox{\includegraphics[scale=0.75]{comic-jp.eps}}
610
\caption{Mixture of {\it gothic} and {\it mincho} fonts in Japanese comics}
614
Fonts provided by font classes need not be associated with font files.
615
As examples of such font classes,
616
the {\em Japanese comic} font class and
617
the {\em try} font class are implemented.
619
\subsection{The Japanese comic font class}
621
In Japanese comics, a gothic font is used for Kanji
622
characters and a {\it mincho} font is used for Kana
623
characters as shown in Figure \ref{FIG:JpComics}.
624
Without creating a new font, we can implement such fonts by
625
the Japanese comic font driver:
626
a font $F$ of the Japanese comic class needs two sub-fonts that are
627
specified in a \vflibcap\ file; fonts for Kanji characters, say $F_1$,
628
and Kana characters, say $F_2$.
629
A glyph for code point $c$ of font $F$ is obtained from $F_1$ if $c$
630
is a Kanji character, and from $F_2$ if $c$ is a Kana character.
631
The font classes of $F_1$ and $F_2$ need not be the same.
634
\subsection{The try font class}
636
The try font class provides a feature to open a font among list of fonts.
637
Each font $f$ of the try font class has a list of fonts, say $g_1, g_2, ...$.
638
When $f$ is requested to open, the font driver tries to open fonts
639
$g_1, g_2, ...$ in this order until one of them,
640
say $g_s$, is opened successfully.
641
Then, any font operation on $f$ is applied on $g_s$ and
642
therefore, $g_s$ is used as a font $f$.
644
This font class is useful when we want to use non-standard
645
(i.e., site dependent) fonts.
646
Suppose that a non-standard font $f_n$ is listed followed by
647
a standard font $f_s$ in a font list of $f$ of try font class.
648
Then, to open $f$ is the same as opening $f_n$ if it is avaiable;
649
otherwise, $f_s$ is used.
650
Since $f_s$ is a standard font, opening $f$ always succeeds.
651
Candidate fonts $g_1, g_2, ...$ can be a fonts of different font classes;
652
for instance, $g_1$ can be a TrueType font and $g_2$ can be a PCF font.
656
%%%-----------------------------------------------------------------------
658
\section{Sample Programs}
659
\label{SEC:SamplePrograms}
661
\VFlib\ is distributed with sample programs.
662
One of them is a previewer for DVI files.
663
In a DVI interpreter, a \TeX\ font is opened
664
by the following sequence.
668
%\mbox{\includegraphics[scale=1.2]{xmdvi-image-rgb.eps}}
669
%\mbox{\includegraphics[scale=1.2]{xmdvi-image-gray.eps}}
670
\mbox{\includegraphics[scale=1.2]{xmdvi-image-bw.eps}}
672
\caption{A DVI file previewer \pkg{xmdvi}}
677
sprintf(f_name, "%s.pk", name);
678
fid = VF_OpenFont1(f_name, h_dpi, v_dpi, -1, mag, mag);
681
The variable \prog{name} is a font name as appearing in a DVI file
682
(e.g., \prog{cmr10}); \prog{h\_dpi} and \prog{v\_dpi} are the
683
horizontal and vertical device resolution of the target device in dpi,
684
respectively. The variable \prog{mag} is a magnification factor. The
685
PK font driver finds an appropriate font file from parameters given in
686
\prog{VF\_OpenFont1()} and the default values given in \prog{TeX}
687
entry in \vflibcap. For instance, if the font
688
name is \prog{cmr10.pk} and \prog{h\_dpi} = \prog{v\_dpi} = 300, and
689
\prog{mag} = 1.2, the PK font driver looks for the font file
690
\prog{cmr10.360pk}. Glyphs are simply obtained by calling the
691
\prog{VF\_GetBitmap1()} function.
693
Figure \ref{FIG:Xmdvi} shows a screen shot of a sample previewer on
694
X~Window using Motif. This previewer supports drawing EPS figures and
698
%%%-----------------------------------------------------------------------
701
\label{SEC:Conclusion}
703
In this paper, we have introduced a font library \VFlib\ which
704
supports multiple font formats with a unified API.
705
It is especially useful for DVI drivers.
707
\VFlib\ has been tested on
708
FreeBSD 2.2.2 and Linux for Pentimun,
709
Solaris 2.5.1 and SunOS 4.1.4 for SPARC, and
711
there is no difficulty to port it to other Unix-like operating systems.
712
The source code and the latest information on \VFlib\
714
|http://|""|www.|""|se.|""|hiroshima-u.|""|ac.|""|jp/|"%
715
"|~kakugawa/|""|VFlib/|.
718
%%%-----------------------------------------------------------------------
719
\section*{Acknowledgements}
720
The author would like to thank Werner Lemberg for helpful comments
721
on specification and implementation of \VFlib.
722
He also thank Ken'ich Handa and Satoru Tomura for
723
valuable discussions.
726
%%%-----------------------------------------------------------------------
728
\bibliographystyle{plain}
729
\bibliography{vflib35}
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%%%-----------------------------------------------------------------------
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doc/Paper1/vflib35.tex
