SUBFALLOC(2G) SUBFALLOC(2G)
NAME
subfalloc, subffree, rdsubfontfile, wrsubfontfile, mkfont -
subfont manipulation
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <libg.h>
Subfont* subfalloc(int n, int height, int ascent,
Fontchar *info, Bitmap *b, ulong q0, ulong q1)
void subffree(Subfont *f)
Subfont* rdsubfontfile(int fd, Bitmap *b)
void wrsubfontfile(int fd, Subfont *f)
Font* mkfont(Subfont *f);
DESCRIPTION
Subfonts are the components of fonts that hold the character
images. A font is composed from an array of subfonts; see
cachechars(2). A new Subfont is allocated and initialized
with subfalloc. See cachechars(2) for the meaning of n,
height, ascent, and info, and the arrangement of characters
in bitmap b. The fields of the returned Subfont structure
are set to the passed arguments, and the id field is set to
the identifying number used by /dev/bitblt (see bit(3)).
After a successful subfalloc, b is attached to the subfont
and is unavailable to the application; it should not be
used. Subfalloc returns 0 on failure.
The q0 and q1 arguments are used as tags in a cache of sub-
fonts (see below). If all ones, they disable caching.
Subffree frees a subfont and all its associated structure
including the associated bitmap. Since subffree calls free
on f->info, if f->info was not allocated by malloc(2) it
should be zeroed before calling subffree.
A number of subfonts are kept in external files. The con-
vention for naming subfont files is:
/lib/font/bit/name/class.size.ldepth
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 .ldepth exten-
sion is elided. Class describes the range of runes encoded
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SUBFALLOC(2G) SUBFALLOC(2G)
in the subfont: ascii, latin1, greek, etc.
The format of a subfont file is described in font(6)).
Briefly, it contains a bitmap with all the characters in it,
followed by a subfont header, followed by character informa-
tion. Rdsubfontfile reads a subfont from the file descrip-
tor fd. If b is zero, rdsubfontfile reads the bitmap as well
as the character information from the file and allows the
resulting subfont and bitmap to be cached in the server for
sharing with other applications. The first thing such an
rdsubfontfile call does is check to see if the subfont can
be recovered directly from the server: if the qid (see
intro(5)) of the file pointed to by fd matches q0 and q1 of
a cache entry, the subfont is read from the server instead
of from fd. This is the normal use of rdsubfontfile.
Unusual applications such as font editors may choose to have
uncached (hence unshared) subfonts or to associate arbitrary
bitmaps with the character data. If the b argument to
rdsubfontfile is non-null, rdsubfontfile reads only the
character information from fd (which must be positioned
after the bitmap in the file) and the resulting subfont is
uncached. Nonetheless, rdsubfontfile calls subfalloc with b
and hence b is unusable afterwards; make a copy first if
necessary. Rdsubfontfile returns 0 on error.
Wrsubfontfile writes on fd the part of a subfont file that
comes after the bitmap. Because the bitmap of a cached sub-
font is unavailable to the application, without extraordi-
nary measures only uncached subfonts may be written whole to
files.
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
/lib/font/bit bitmap font file tree
SEE ALSO
graphics(2), balloc(2), bitblt(2), cachechars(2), bitmap(6),
font(6)
DIAGNOSTICS
All of the functions use the graphics error function (see
graphics(2)).
BUGS
Subfonts can contain no more than about 1300 characters.
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