1 .TH FONT 7
2 .SH NAME
3 font, subfont \- external format for fonts and subfonts
4 .SH SYNOPSIS
5 .B #include <draw.h>
6 .SH DESCRIPTION
7 Fonts and subfonts are described in
8 .IR cachechars (3).
9 .PP
10 External fonts are described by a plain text file that can be read using
11 .IR openfont .
12 The format of the file is a header followed by any number of
13 subfont range specifications.
14 The header contains two numbers: the height and the ascent, both in pixels.
15 The height is the inter-line spacing and the ascent is the distance
16 from the top of the line to the baseline.  These numbers are chosen
17 to display consistently all the subfonts of the font.
18 A subfont range specification contains two or three numbers and a file name.
19 The numbers are the inclusive range of characters covered by the subfont,
20 with an optional starting position within the subfont,
21 and the file name names an external file suitable for
22 .I readsubfont
23 (see
24 .IR graphics (3)).
25 The minimum number of a covered range is mapped to the specified starting position
26 (default zero) of the
27 corresponding subfont.
28 If the subfont file name does not begin with a slash, it is taken relative to the
29 directory containing the font file.
30 Each field must be followed by some white space.
31 Each numeric field may be C-format decimal, octal, or hexadecimal.
32 .PP
33 External subfonts are represented in a more rigid format
34 that can be read and written using
35 .I readsubfont
36 and
37 .I writesubfont
38 (see
39 .IR subfont (3)).
40 The format for subfont files is: an image containing character glyphs,
41 followed by a subfont header, followed by character information.
42 The image has the format for external image files described in
43 .IR image (7).
44 The subfont header has 3
45 decimal strings:
46 .BR n ,
47 .BR height ,
48 and
49 .BR ascent .
50 Each number is right-justified and blank padded in 11 characters, followed by a blank.
51 The character
52 .B info
53 consists of
54 .BR n +1
55 6-byte entries, each giving the
56 .B Fontchar
57 .B x
58 (2 bytes, low order byte first),
59 .BR top ,
60 .BR bottom ,
61 .BR left ,
62 and
63 .BR width .
64 The
65 .B x
66 field of the last
67 .B Fontchar
68 is used to calculate the image width
69 of the previous character; the other fields in the last
70 .B Fontchar
71 are irrelevant.
72 .PP
73 Note that the convention of using the character with value zero (NUL) to represent
74 characters of zero width (see
75 .IR draw (3))
76 means that fonts should have, as their zeroth character,
77 one with non-zero width.
78 .SH FILES
79 .TF \*9/font/*
80 .TP
81 .B \*9/font/*
82 font directories
83 .SH "SEE ALSO"
84 .IR graphics (3),
85 .IR draw (3),
86 .IR cachechars (3),
87 .IR subfont (3)