88 lines
2.5 KiB
Plaintext
88 lines
2.5 KiB
Plaintext
|
.TH FONT 6
|
||
|
|
.SH NAME
|
||
|
|
font, subfont \- external format for fonts and subfonts
|
||
|
|
.SH SYNOPSIS
|
||
|
|
.B #include <draw.h>
|
||
|
|
.SH DESCRIPTION
|
||
|
|
Fonts and subfonts are described in
|
||
|
|
.IR cachechars (2).
|
||
|
|
.PP
|
||
|
|
External fonts are described by a plain text file that can be read using
|
||
|
|
.IR openfont .
|
||
|
|
The format of the file is a header followed by any number of
|
||
|
|
subfont range specifications.
|
||
|
|
The header contains two numbers: the height and the ascent, both in pixels.
|
||
|
|
The height is the inter-line spacing and the ascent is the distance
|
||
|
|
from the top of the line to the baseline. These numbers are chosen
|
||
|
|
to display consistently all the subfonts of the font.
|
||
|
|
A subfont range specification contains two or three numbers and a file name.
|
||
|
|
The numbers are the inclusive range of characters covered by the subfont,
|
||
|
|
with an optional starting position within the subfont,
|
||
|
|
and the file name names an external file suitable for
|
||
|
|
.I readsubfont
|
||
|
|
(see
|
||
|
|
.IR graphics (2)).
|
||
|
|
The minimum number of a covered range is mapped to the specified starting position
|
||
|
|
(default zero) of the
|
||
|
|
corresponding subfont.
|
||
|
|
If the subfont file name does not begin with a slash, it is taken relative to the
|
||
|
|
directory containing the font file.
|
||
|
|
Each field must be followed by some white space.
|
||
|
|
Each numeric field may be C-format decimal, octal, or hexadecimal.
|
||
|
|
.PP
|
||
|
|
External subfonts are represented in a more rigid format
|
||
|
|
that can be read and written using
|
||
|
|
.I readsubfont
|
||
|
|
and
|
||
|
|
.I writesubfont
|
||
|
|
(see
|
||
|
|
.IR subfont (2)).
|
||
|
|
The format for subfont files is: an image containing character glyphs,
|
||
|
|
followed by a subfont header, followed by character information.
|
||
|
|
The image has the format for external image files described in
|
||
|
|
.IR image (6).
|
||
|
|
The subfont header has 3
|
||
|
|
decimal strings:
|
||
|
|
.BR n ,
|
||
|
|
.BR height ,
|
||
|
|
and
|
||
|
|
.BR ascent .
|
||
|
|
Each number is right-justified and blank padded in 11 characters, followed by a blank.
|
||
|
|
The character
|
||
|
|
.B info
|
||
|
|
consists of
|
||
|
|
.BR n +1
|
||
|
|
6-byte entries, each giving the
|
||
|
|
.B Fontchar
|
||
|
|
.B x
|
||
|
|
(2 bytes, low order byte first),
|
||
|
|
.BR top ,
|
||
|
|
.BR bottom ,
|
||
|
|
.BR left ,
|
||
|
|
and
|
||
|
|
.BR width .
|
||
|
|
The
|
||
|
|
.B x
|
||
|
|
field of the last
|
||
|
|
.B Fontchar
|
||
|
|
is used to calculate the image width
|
||
|
|
of the previous character; the other fields in the last
|
||
|
|
.B Fontchar
|
||
|
|
are irrelevant.
|
||
|
|
.PP
|
||
|
|
Note that the convention of using the character with value zero (NUL) to represent
|
||
|
|
characters of zero width (see
|
||
|
|
.IR draw (2))
|
||
|
|
means that fonts should have, as their zeroth character,
|
||
|
|
one with non-zero width.
|
||
|
|
.SH FILES
|
||
|
|
.TF /lib/font/bit/*
|
||
|
|
.TP
|
||
|
|
.B /lib/font/bit/*
|
||
|
|
font directories
|
||
|
|
.SH "SEE ALSO"
|
||
|
|
.IR graphics (2),
|
||
|
|
.IR draw (2),
|
||
|
|
.IR cachechars (2),
|
||
|
|
.IR subfont (2)
|