236 lines
5 KiB
Plaintext
236 lines
5 KiB
Plaintext
.TH SUBFONT 2
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.SH NAME
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allocsubfont, freesubfont, installsubfont, lookupsubfont, uninstallsubfont, subfontname, readsubfont, readsubfonti, writesubfont, stringsubfont, strsubfontwidth, mkfont \- subfont manipulation
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.br
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.B #include <draw.h>
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.PP
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.ta \w'\fLSubfont* 'u
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.B
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Subfont* allocsubfont(char *name, int n, int height, int ascent,
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.br
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.B
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Fontchar *info, Image *i)
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.PP
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.B
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void freesubfont(Subfont *f)
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.PP
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.B
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void installsubfont(char *name, Subfont *f)
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.PP
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.B
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Subfont* lookupsubfont(Display *d, char *name)
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.PP
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.B
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void uninstallsubfont(Subfont *f)
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.PP
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.B
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Subfont* readsubfont(Display *d, char *name, int fd, int dolock)
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.PP
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.B
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Subfont* readsubfonti(Display *d, char *name, int fd, Image *im,
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.br
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.B
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int dolock)
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.PP
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.B
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int writesubfont(int fd, Subfont *f)
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.PP
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.B
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Point stringsubfont(Image *dst, Point p, Image *src,
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.br
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.B
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Subfont *f, char *str)
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.PP
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.B
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Point strsubfontwidth(Subfont *f, char *s)
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.PP
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.B
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Font* mkfont(Subfont *f, Rune min)
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.SH DESCRIPTION
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Subfonts are the components of fonts that hold the character images.
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A font comprises an array of subfonts; see
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.IR cachechars (2).
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A new
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.B Subfont
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is allocated and initialized with
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.IR allocsubfont .
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See
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.IR cachechars (2)
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for the meaning of
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.IR n ,
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.IR height ,
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.IR ascent ,
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and
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.IR info ,
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and the arrangement of characters in
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image
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.IR i .
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The
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.I name
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is used to identify the subfont in the subfont cache; see the descriptions
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.I lookupsubfont
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and
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.IR installsubfont
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.RI ( q.v. ).
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The appropriate fields of the returned
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.B Subfont
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structure are set to
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the passed arguments, and the image is registered as a subfont
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with the graphics device
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.IR draw (3).
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.I Allocsubfont
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returns 0 on failure.
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.PP
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.I Freesubfont
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frees a subfont and all its associated structure including the
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associated image.
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Since
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.I freesbufont
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calls
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.I free
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on
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.BR f->info ,
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if
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.B f->info
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was not allocated by
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.IR malloc (2)
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it should be zeroed before calling
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.IR subffree .
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.PP
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A number of subfonts are kept in external files.
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The convention for naming subfont files is:
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.IP
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.B /lib/font/bit/\fIname\fP/\fIclass\fP.\fIsize\fP.\fIdepth
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.PD
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.PP
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where
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.I size
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is approximately the height in pixels of the lower case letters
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(without ascenders or descenders).
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If there is only one version of the subfont, the
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.BI \&. depth
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extension is elided.
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.I Class
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describes the range of runes encoded in the subfont:
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.BR ascii ,
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.BR latin1 ,
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.BR greek ,
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etc.
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.PP
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Subfonts are cached within the program, so a subfont shared between fonts will be loaded only once.
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.I Installsubfont
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stores subfont
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.I f
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under the given
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.IR name ,
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typically the file name from which it was read.
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.I Uninstallsubfont
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removes the subfont from the cache.
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Finally,
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.I lookupsubfont
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searches for a subfont with the given
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.I name
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in the cache and returns it, or nil if no such subfont exists.
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.PP
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.I Subfontname
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is used to locate subfonts given their names within the fonts.
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The default version constructs a name given the
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.IR cfname ,
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its name within the font,
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.IR fname ,
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the name of the font, and the maximum depth suitable for this subfont.
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This interface allows a partially specified name within a font to be resolved
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at run-time to the name of a file holding a suitable subfont.
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Although it is principally a routine internal to the library,
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.I subfontname
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may be substituted by the application to provide a less file-oriented subfont naming scheme.
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.PP
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The format of a subfont file is described in
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.IR font (6).
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Briefly, it contains a image with all the characters in it,
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followed by a subfont header, followed by character information.
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.I Readsubfont
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reads a subfont from the file descriptor
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.IR fd .
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The
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.I name
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is used to identify the font in the cache.
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The
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.I dolock
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argument specifies whether the routine should synchronize
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use of the
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.I Display
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with other processes; for single-threaded applications it may
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always be zero.
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.I Readsubfonti
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does the same for a subfont whose associated image is already in memory; it is passed as the
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argument
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.IR im .
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In other words,
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.I readsubfonti
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reads only the header and character information from the file descriptor.
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.PP
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.I Writesubfont
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writes on
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.I fd
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the part of a subfont file that comes after the image. It should be preceded by
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a call to
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.IR writeimage
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(see
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.IR allocimage (2)).
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.PP
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.I Stringsubfont
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is analogous to
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.B string
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(see
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.IR draw (2))
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for subfonts. Rather than use the underlying font caching primitives,
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it calls
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.B draw
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for each character.
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It is intended for stand-alone environments such as operating system kernels.
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.I Strsubfontwidth
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returns the width of the string
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.I s
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in
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as it would appear if drawn with
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.I stringsubfont
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in
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.B Subfont
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.BR f .
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.PP
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.I Mkfont
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takes as argument a
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.B Subfont
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.I s
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and returns a pointer to a
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.B Font
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that maps the character images in
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.I s
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into the
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.B Runes
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.I min
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to
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.IB min + s ->n-1\f1.
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.SH FILES
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.TF /lib/font/bit
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.TP
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.B /lib/font/bit
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bitmap font file tree
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.SH SOURCE
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.B /sys/src/libdraw
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.SH SEE ALSO
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.IR graphics (2),
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.IR allocimage (2),
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.IR draw (2),
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.IR cachechars (2),
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.IR image (6),
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.IR font (6)
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.SH DIAGNOSTICS
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All of the functions use the graphics error function (see
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.IR graphics (2)).
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