ref: 3cc97ac108a3a2889efedfccef6a904baf8ed4e0
dir: /sys/man/2/subfont/
.TH SUBFONT 2 .SH NAME allocsubfont, freesubfont, installsubfont, lookupsubfont, uninstallsubfont, subfontname, readsubfont, readsubfonti, writesubfont, stringsubfont, strsubfontwidth, mkfont \- subfont manipulation .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .br .B #include <draw.h> .PP .ta \w'\fLSubfont* 'u .B Subfont* allocsubfont(char *name, int n, int height, int ascent, .br .B Fontchar *info, Image *i) .PP .B void freesubfont(Subfont *f) .PP .B void installsubfont(char *name, Subfont *f) .PP .B Subfont* lookupsubfont(Display *d, char *name) .PP .B void uninstallsubfont(Subfont *f) .PP .B Subfont* readsubfont(Display *d, char *name, int fd, int dolock) .PP .B Subfont* readsubfonti(Display *d, char *name, int fd, Image *im, .br .B int dolock) .PP .B int writesubfont(int fd, Subfont *f) .PP .B Point stringsubfont(Image *dst, Point p, Image *src, .br .B Subfont *f, char *str) .PP .B Point strsubfontwidth(Subfont *f, char *s) .PP .B Font* mkfont(Subfont *f, Rune min) .SH DESCRIPTION Subfonts are the components of fonts that hold the character images. A font comprises an array of subfonts; see .IR cachechars (2). A new .B Subfont is allocated and initialized with .IR allocsubfont . See .IR cachechars (2) for the meaning of .IR n , .IR height , .IR ascent , and .IR info , and the arrangement of characters in image .IR i . The .I name is used to identify the subfont in the subfont cache; see the descriptions .I lookupsubfont and .IR installsubfont .RI ( q.v. ). The appropriate fields of the returned .B Subfont structure are set to the passed arguments, and the image is registered as a subfont with the graphics device .IR draw (3). .I Allocsubfont returns 0 on failure. .PP .I Freesubfont frees a subfont and all its associated structure including the associated image. Since .I freesbufont calls .I free on .BR f->info , if .B f->info was not allocated by .IR malloc (2) it should be zeroed before calling .IR subffree . .PP A number of subfonts are kept in external files. The convention for naming subfont files is: .IP .B /lib/font/bit/\fIname\fP/\fIclass\fP.\fIsize\fP.\fIdepth .PD .PP where .I 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 .BI \&. depth extension is elided. .I Class describes the range of runes encoded in the subfont: .BR ascii , .BR latin1 , .BR greek , etc. .PP Subfonts are cached within the program, so a subfont shared between fonts will be loaded only once. .I Installsubfont stores subfont .I f under the given .IR name , typically the file name from which it was read. .I Uninstallsubfont removes the subfont from the cache. Finally, .I lookupsubfont searches for a subfont with the given .I name in the cache and returns it, or nil if no such subfont exists. .PP .I Subfontname is used to locate subfonts given their names within the fonts. The default version constructs a name given the .IR cfname , its name within the font, .IR 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, .I subfontname may be substituted by the application to provide a less file-oriented subfont naming scheme. .PP The format of a subfont file is described in .IR font (6). Briefly, it contains a image with all the characters in it, followed by a subfont header, followed by character information. .I Readsubfont reads a subfont from the file descriptor .IR fd . The .I name is used to identify the font in the cache. The .I dolock argument specifies whether the routine should synchronize use of the .I Display with other processes; for single-threaded applications it may always be zero. .I Readsubfonti does the same for a subfont whose associated image is already in memory; it is passed as the argument .IR im . In other words, .I readsubfonti reads only the header and character information from the file descriptor. .PP .I Writesubfont writes on .I fd the part of a subfont file that comes after the image. It should be preceded by a call to .IR writeimage (see .IR allocimage (2)). .PP .I Stringsubfont is analogous to .B string (see .IR draw (2)) for subfonts. Rather than use the underlying font caching primitives, it calls .B draw for each character. It is intended for stand-alone environments such as operating system kernels. .I Strsubfontwidth returns the width of the string .I s in as it would appear if drawn with .I stringsubfont in .B Subfont .BR f . .PP .I Mkfont takes as argument a .B Subfont .I s and returns a pointer to a .B Font that maps the character images in .I s into the .B Runes .I min to .IB min + s ->n-1\f1. .SH FILES .TF /lib/font/bit .TP .B /lib/font/bit bitmap font file tree .SH SOURCE .B /sys/src/libdraw .SH SEE ALSO .IR graphics (2), .IR allocimage (2), .IR draw (2), .IR cachechars (2), .IR image (6), .IR font (6) .SH DIAGNOSTICS All of the functions use the graphics error function (see .IR graphics (2)).