SUBFONT(3) SUBFONT(3)
NAME
allocsubfont, freesubfont, installsubfont, lookupsubfont,
uninstallsubfont, subfontname, readsubfont, readsubfonti,
writesubfont, stringsubfont, strsubfontwidth, mkfont -
subfont manipulation
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <draw.h>
Subfont* allocsubfont(char *name, int n, int height, int
ascent,
Fontchar *info, Image *i)
void freesubfont(Subfont *f)
void installsubfont(char *name, Subfont *f)
Subfont* lookupsubfont(Subfont *f)
void uninstallsubfont(Subfont *f)
Subfont* readsubfont(Display *d, char *name, int fd, int
dolock)
Subfont* readsubfonti(Display *d, char *name, int fd, Image
*im,
int dolock)
int writesubfont(int fd, Subfont *f)
Point stringsubfont(Image *dst, Point p, Image *src,
Subfont *f, char *str)
Point strsubfontwidth(Subfont *f, char *s)
Font* mkfont(Subfont *f, Rune min)
DESCRIPTION
Subfonts are the components of fonts that hold the character
images. A font comprises an array of subfonts; see
cachechars(3). A new Subfont is allocated and initialized
with allocsubfont. See cachechars(3) for the meaning of n,
height, ascent, and info, and the arrangement of characters
in image i. The name is used to identify the subfont in the
subfont cache; see the descriptions lookupsubfont and
installsubfont (q.v.). The appropriate fields of the
returned Subfont structure are set to the passed arguments,
and the image is registered as a subfont with the graphics
Page 1 Plan 9 (printed 12/22/24)
SUBFONT(3) SUBFONT(3)
device draw(3). Allocsubfont returns 0 on failure.
Freesubfont frees a subfont and all its associated structure
including the associated image. Since freesbufont calls
free on f->info, if f->info was not allocated by malloc(3)
it should be zeroed before calling subffree.
A number of subfonts are kept in external files. The con-
vention for naming subfont files is:
/usr/local/plan9/font/name/class.size.depth
where size is approximately the height in pixels of the
lower case letters (without ascenders or descenders). If
there is only one version of the subfont, the .depth exten-
sion is elided. Class describes the range of runes encoded
in the subfont: ascii, latin1, greek, etc.
Subfonts are cached within the program, so a subfont shared
between fonts will be loaded only once. Installsubfont
stores subfont f under the given name, typically the file
name from which it was read. Uninstallsubfont removes the
subfont from the cache. Finally, lookupsubfont searches for
a subfont with the given name in the cache and returns it,
or nil if no such subfont exists.
Subfontname is used to locate subfonts given their names
within the fonts. The default version constructs a name
given the cfname, its name within the font, fname, the name
of the font, and the maximum depth suitable for this sub-
font. This interface allows a partially specified name
within a font to be resolved at run-time to the name of a
file holding a suitable subfont. Although it is principally
a routine internal to the library, subfontname may be sub-
stituted by the application to provide a less file-oriented
subfont naming scheme.
The format of a subfont file is described in font(7).
Briefly, it contains a image with all the characters in it,
followed by a subfont header, followed by character informa-
tion. Readsubfont reads a subfont from the file descriptor
fd. The name is used to identify the font in the cache. The
dolock argument specifies whether the routine should syn-
chronize use of the Display with other processes; for
single-threaded applications it may always be zero.
Readsubfonti does the same for a subfont whose associated
image is already in memory; it is passed as the argument im.
In other words, readsubfonti reads only the header and char-
acter information from the file descriptor.
Writesubfont writes on fd the part of a subfont file that
comes after the image. It should be preceded by a call to
Page 2 Plan 9 (printed 12/22/24)
SUBFONT(3) SUBFONT(3)
writeimage (see allocimage(3)).
Stringsubfont is analogous to string (see draw(3)) for sub-
fonts. Rather than use the underlying font caching primi-
tives, it calls draw for each character. It is intended for
stand-alone environments such as operating system kernels.
Strsubfontwidth returns the width of the string s in as it
would appear if drawn with stringsubfont in Subfont f.
Mkfont takes as argument a Subfont s and returns a pointer
to a Font that maps the character images in s into the Runes
min to min+s->n-1.
FILES
/usr/local/plan9/font bitmap font file tree
SOURCE
/usr/local/plan9/src/libdraw
SEE ALSO
graphics(3), allocimage(3), draw(3), cachechars(3),
image(7), font(7)
DIAGNOSTICS
All of the functions use the graphics error function (see
graphics(3)).
Page 3 Plan 9 (printed 12/22/24)