.\" Contributed to 386bsd 0.1 and later versions
.\"
.\"	Copyright 1992 by Holger Veit
.\"	May be freely used with Bill Jolitz's port of 
.\"	386bsd and may be included in a 386bsd collection
.\"	as long as binary and source are available and reproduce the above
.\"	copyright.
.\"	 
.\"	You may freely modify this code and contribute improvements based
.\"	on this code as long as you don't claim to be the original author.
.\"	Commercial use of this source requires permittance of the copyright 
.\"	holder. A general license for 386bsd will override this restriction.
.\"
.\"	Use at your own risk. The copyright holder or any person who makes
.\"	this code available for the public (administrators of public archives
.\"	for instance) are not responsible for any harm to hardware or software
.\"	that might happen due to wrong application or program faults.
.\"
.\"	You must have the codriver driver in the same package generated
.\"	into the 386bsd kernel, otherwise this program does not work.
.\"
.\"     @(#)vgafont.5	1.0 (contributed to 386bsd) 10/25/92
.\"
.Dd October 25, 1992
.Dt CONSOLE 5
.Os
.Sh NAME
.Nm vgafont
.Nd setfont bdf font format
.Sh DESCRIPTION
This document describes the differences between the font format loadable by 
the
.Xr setfont 3
routine and the original bdf (bitmap distribution format) as used by
the X11 Windows System Release 5.
.Pp
In general, 
.Fn setfont
understands all keywords of the bdf file, but only uses a subset of them.
.Pp
The main restriction for usability of fonts is that the console is 
operated in text mode whereas the X11 Windows system uses 
graphics to display a character. Thus, a usable
font underlies the following limits:
.Pp
.Bl -enum -compact
.It
The bitmap of a character must be smaller than 8x16. Note that this fits for
a 3x5 font for instance; it is, however, not recommended to load such small
fonts, because this font is displayed in a 8x16 pixel map anyway, and thus
might look quite funny.
.It
The font should have fixed width, however, proportional fonts may be
loaded into the fixed grid, but look quite ugly then.
.It
A character set may contain a maximum of 256 entries. Together with the
facility of the console driver to load two fonts, there may be 512 different
characters displayed simultaneously. This is sufficient for most 
latin character sets (if you want to do word processing or TeX, use a
graphical video system).
.It
X11 uses a 16 bit encoding scheme similiar to the ISO 10646-1 Draft standard
to express a character code. 386bsd is currently based on a 8 bit scheme.
To allow more than 256 character codes and retaining 8 bit compatibility,
the console driver uses a pair of special codes to switch between fonts.
The code 
.Em 0x0e (SO)
enables the second font, the code
.Em 0x0f (SI)
switches back to the first (default) font. If no second font is loaded,
SI and SO are ignored.
.Pp
This handling of fonts and encoding is experimental, and may be modified
in the future, if a better scheme (UniCode, or ISO-DIS 10646 1.2) is 
available and standardized.
.Pp
.Sh EXAMPLE
The following is a sample bdf font skeleton which is accepted by 
.Fn setfont .
It should not be misunderstood as an official description of the bdf font 
format.
.Pp
.Bd -literal
COMMENT	This is a comment and may occur anywhere
STARTFONT 2.1	ignored
FONT vga	ignored
SIZE 16 75 75	first number used as box length
FONTBOUNDINGBOX 8 16 0 -4	first two numbers used as box size
STARTPROPERTIES 3	ignored
FONT_DESCENT 4	ignored
FONT_ASCENT 12	ignored
DEFAULT_CHAR 0	used to fill empty slots
ENDPROPERTIES	used
CHARS 256	used
STARTCHAR C0000	ignored
ENCODING 0	used
SWIDTH 666 0	ignored
DWIDTH 8 0	ignored
BBX 8 16 0 -4	used
BITMAP		used
00		bitmap must fit length and width
00
00
7c
c6
c6
de
de
de
dc
c0
7c
00
00
00
00
ENDCHAR		used
... Startchar-Endchar repeated
ENDFONT		used
.Ed
.Pp
.Sh Files
.Bl -tag -width *.bdf -compact
.It Pa *.bdf
bdf font file
.El
.Sh SEE ALSO
.Xr co 4 ,
.Xr keycap 5
.Sh HISTORY
The bdf font format is part of the MIT X11 distribution.
.Sh BUGS
The problem of languages writing right-to-left is not yet handled. Currently,
words in such a language must be prepared as an inverse character string.