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NAME
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allocsubfont, freesubfont, installsubfont, lookupsubfont, uninstallsubfont,
subfontname, readsubfont, readsubfonti, writesubfont, stringsubfont,
strsubfontwidth, mkfont – subfont manipulation
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SYNOPSIS
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#include <u.h>
#include <libc.h>
#include <draw.h>
Subfont* allocsubfont(char *name, int n, int height, int ascent,
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Fontchar *info, Image *i)
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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 writesubfont(int fd, Subfont *f)
Point stringsubfont(Image *dst, Point p, Image *src,
Point strsubfontwidth(Subfont *f, char *s)
Font* mkfont(Subfont *f, Rune min)
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DESCRIPTION
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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 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 convention
for naming subfont files is:
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 extension 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 subfont. 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 substituted 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 information. 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 synchronize 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 character 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 writeimage
(see allocimage(3)).
Stringsubfont is analogous to string (see draw(3)) for subfonts.
Rather than use the underlying font caching primitives, 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.
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FILES
SOURCE
SEE ALSO
DIAGNOSTICS
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All of the functions use the graphics error function (see graphics(3)).
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