This
page describes various font file formats and how to manipulate them.
Font File Formats - .bdf and .snf
Font files contained in the MIT X distribution are in .bdf format
(Bitmap Distribution Format, a generic, human-readable format). Other
systems, such as DECwindows or Open Look, provide fonts in other
formats, such as .dwf (DEC Windows Format) which are pre-compiled for
the particular machine architecture they use. These fonts must be
recompiled into a special .snf format (Server Natural Format)
specifically for the HDS ViewStation (or the .snf format for the machine
they are running on). Each server type has different .snf format
requirements, based on its memory configuration and processor type, bit
and byte order, etc. Other servers will use different .snf files, and
you must create specific ones for the HDS View Station, as shown below.
The first step is to create a special directory for these font
files. Then the .bdf fonts you need should be copied into the directory
and converted to the .snf format for the ViewStation.
Handling
.bdf Fonts and Fonts in other Formats
There are large directories of .bdf font files supplied with the
standard MIT X distribution. You may not want to use all of these fonts
or create .snf files for all of them. This choice depends on the X
clients and applications you want to use.
All of these fonts
must be compiled into .snf format to be used on the ViewStation (or use
the pre-compiled HDS .snf fonts from the HDSware tape).
Font Sizes
Other important font considerations include choosing the correct
75dpi (dpi = dots per inch) or 100dpi files for your HDS ViewStation.
These sets of files are provided for monitors with different screen
resolutions. ViewStation Monitors gives you
information about the screen resolutions of particular monitors.
The appearance of a font on the screen is best when the dots per inch
resolution on the screen is as closely matched as possible to the
number of dots provided for each character in the font file. (This can
become a rather complicated question for users concerned about exact
character size. For instance, a 24 point font from the 75dpi directory
displayed on a monitor whose resolution is actually 85 dpi will be
slightly smaller than 24 points. [The calculation goes like this: Since
a point is about 1/72nd of an inch, a 24 point character from the 75dpi
directory is about 24 dots high. This means that 24 dots displayed on
85 dpi results in a smaller character - 24/85ths compared with 24/75ths
of an inch.] On the other hand, the same 24 point font from the 100dpi
directory will be larger than 24 points when displayed on the same
monitor [24/85ths compared to 24/100ths of an inch].
Since
most applications where this is important, such as WYSIWYG publishing
programs, take these factors into consideration with internal
mechanisms for their screen displays and printing, most users won't
need to be concerned about it. If this is an important consideration,
put the preferred font directory, 75dpi or 100dpi, first in your search
path. This will insure that when a particular font is requested [if it
is available in both directories] it will be loaded from that
directory.)
The HDS ViewStation uses either 75dpi or 100dpi font files,
depending on the monitor used. Some application programs specify
specific dpi values in their font requests and may require loading both
100dpi and 75dpi font directories. The correct font size is calculated
by measuring the horizontal display width in inches, then dividing it
into the horizontal resolution of the screen to give pixels/inch. Then
choose the font resolution closest to that value, 75 or 100 dpi.
This information is also provided by the X command xdpyinfo. If your
.bdf fonts appear as files with a .Z extension, they are compressed
files (all files from the MIT distribution are compressed). You can
convert these files easily with the uncompress command:
uncompress filename.bdf.Z
Or, using a wildcard character: uncompress
*.bdf.Z
The new files appear with the .bdf extension only. They then
may be compiled into .snf font files.
Other systems, such as OPEN LOOK (usually .ff or .f3b font
format), Hewlett Packard (in .scf format), or DECwindows (in .dwf
format), have their own sets of precompiled fonts and font directories
necessary for their operation. Some of these fonts may be in a scalable
format (which means that they are general formulas for fonts and
individual font files, in the desired sizes, must be created before
they can be used); scalable fonts often have the .f3b extension on their
file name, and their extended font name has 0-0's in the size and
spacing fields.
Other common font formats include .afb and
.afm, which are Adobe formats, bitmap and metric. On SUN systems,
scalable fonts are converted to various size font files with the makeafb
utility program, and these .afb files are converted to .bdf files with
the convertfont utility. Other systems may use different formats
and/or different utility conversion programs.
All of these font format types may be converted to HDS .snf
format by using the HDS font utility programs, specifically, the
hdsfc960 font compiler. This compiler takes font files of any format
(even if they can be read only by the particular server they belong
to), reads them with general X routines, and creates HDS format .snf
files.
Return to Section Heading Page
Return to the Home Page
If you need more information than is available here, you can reach
HDS via email at info@hds.com, or
call us at 1.800.HDS.1551 in the USA, or at +610.277.8300 from outside
the US. For questions or problems regarding the HDS WWW page, contact
webmaster@hds.com.
© 1996 by HDS Network Systems
Inc.