cachechars(3) - Plan 9 from User Space

From adc93f6097615f16d57e8a24a256302f2144ec4e Mon Sep 17 00:00:00 2001 From: rsc Date: Fri, 14 Jan 2005 17:37:50 +0000 Subject: cut out the html - they're going to cause diffing problems. --- man/man3/cachechars.html | 292 ----------------------------------------------- 1 file changed, 292 deletions(-) delete mode 100644 man/man3/cachechars.html (limited to 'man/man3/cachechars.html') diff --git a/man/man3/cachechars.html b/man/man3/cachechars.html deleted file mode 100644 index 382b5e7e..00000000 --- a/man/man3/cachechars.html +++ /dev/null @@ -1,292 +0,0 @@ - -cachechars(3) - Plan 9 from User Space - - - - -

CACHECHARS(3) CACHECHARS(3) -

-
-

NAME
- -
- - cachechars, agefont, loadchar, Subfont, Fontchar, Font – font utilities
- -
-

SYNOPSIS
- -
- - #include <u.h> - #include <libc.h> - #include <draw.h> - - - -
- - int cachechars(Font *f, char **s, Rune **r, ushort *c, int max, - - - - -
- - -
- - int *widp, char **sfname) - - - -
- -
- int loadchar(Font *f, Rune r, Cacheinfo *c, int h, - - - -
- - -
- - int noclr, char **sfname) - - - -
- -
- void agefont(Font *f) - -
-

DESCRIPTION
- -
- - A Font may contain too many characters to hold in memory simultaneously. - The graphics library and draw device (see draw(3)) cooperate to - solve this problem by maintaining a cache of recently used character - images. The details of this cooperation need not be known by most - programs: initdraw and its associated - font variable, openfont, stringwidth, string, and freefont are - sufficient for most purposes. The routines described below are - used internally by the graphics library to maintain the font cache. - -
- - A Subfont is a set of images for a contiguous range of characters, - stored as a single image with the characters placed side-by-side - on a common baseline. It is described by the following data structures.
- -
- - typedef - struct Fontchar { - - - - int x; /* left edge of bits */ - uchar top; /* first non−zero scan−line */ - uchar bottom; /* last non−zero scan−line */ - char left; /* offset of baseline */ - uchar width; /* width of baseline */ - - - } Fontchar; - typedef - struct Subfont { - - - - char *name; - short n; /* number of chars in subfont */ - uchar height; /* height of image */ - char ascent; /* top of image to baseline */ - Fontchar *info; /* n+1 Fontchars */ - Image *bits; /* of font */ - - - } Subfont; - - - - -
- The image fills the rectangle (0, 0, w, height), where w is the - sum of the horizontal extents (of non-zero pixels) for all characters. - The pixels to be displayed for character c are in the rectangle - (i−>x, i−>top, (i+1)−>x, i−>bottom) where i is &subfont−>info[c]. When - a character is displayed - at Point p in an image, the character rectangle is placed at (p.x+i−>left, - p.y) and the next character of the string is displayed at (p.x+i−>width, - p.y). The baseline of the characters is ascent rows down from - the top of the subfont image. The info array has n+1 elements, - one each for characters 0 - to n−1 plus an additional entry so the size of the last character - can be calculated. Thus the width, w, of the Image associated - with a Subfont s is s−>info[s−>n].x. -
- - A Font consists of an overall height and ascent and a collection - of subfonts together with the ranges of runes (see utf(7)) they - represent. Fonts are described by the following structures.
- -
- - typedef - struct Cachefont { - - - - Rune min; /* value of 0th char in subfont */ - Rune max; /* value+1 of last char in subfont */ - int offset; /* posn in subfont of char at min */ - char *name; /* stored in font */ - char *subfontname;/* to access subfont */ - - - } Cachefont; - typedef - struct Cacheinfo { - - - - ushort x; /* left edge of bits */ - uchar width; /* width of baseline */ - schar left; /* offset of baseline */ - Rune value; /* of char at this slot in cache */ - ushort age; - - - } Cacheinfo; - typedef - struct Cachesubf { - - - - ulong age; /* for replacement */ - Cachefont *cf; /* font info that owns us */ - Subfont *f; /* attached subfont */ - - - } Cachesubf; - typedef - struct Font { - - - - char *name; - Display *display; - short height; /* max ht of image;interline space*/ - short ascent; /* top of image to baseline */ - short width; /* widest so far; used in caching */ - short nsub; /* number of subfonts */ - ulong age; /* increasing counter; for LRU */ - int ncache; /* size of cache */ - int nsubf; /* size of subfont list */ - Cacheinfo *cache; - Cachesubf *subf; - Cachefont **sub; /* as read from file */ - Image *cacheimage; - - - } Font; - - - - -
- The height and ascent fields of Font are described in graphics(3). - Sub contains nsub pointers to Cachefonts. A Cachefont connects - runes min through max, inclusive, to the subfont with file name - name; it corresponds to a line of the file describing the font. - -
- - The characters are taken from the subfont starting at character - number offset (usually zero) in the subfont, permitting selection - of parts of subfonts. Thus the image for rune r is found in position - r−min+offset of the subfont. -
- - For each font, the library, with support from the graphics server, - maintains a cache of subfonts and a cache of recently used character - images. The subf and cache fields are used by the library to maintain - these caches. The width of a font is the maximum of the horizontal - extents of the characters in the cache. - String draws a string by loading the cache and emitting a sequence - of cache indices to draw. Cachechars guarantees the images for - the characters pointed to by *s or *r (one of these must be nil - in each call) are in the cache of f. It calls loadchar to put - missing characters into the cache. Cachechars translates the - character string into a set of cache indices which it loads into - the array c, up to a maximum of n indices or the length of the - string. Cachechars returns in c the number of cache indices emitted, - updates *s to point to the next character to be processed, and - sets *widp to the total width of the characters processed. - Cachechars may return before the end of the string if it cannot - proceed without destroying active data in the caches. If it needs - to load a new subfont, it will fill *sfname with the name of the - subfont it needs and return –1. It can return zero if it is unable - to make progress because it cannot resize the caches. -
- - Loadchar loads a character image into the character cache. Then - it tells the graphics server to copy the character into position - h in the character cache. If the current font width is smaller - than the horizontal extent of the character being loaded, loadfont - clears the cache and resets it to accept characters with the - bigger width, unless noclr is set, in which case it just returns - –1. If the character does not exist in the font at all, loadfont - returns 0; if it is unable to load the character without destroying - cached information, it returns –1, updating *sfname as described - above. It returns 1 to indicate success. -
- - The age fields record when subfonts and characters have been used. - The font age is increased every time the font is used (agefont - does this). A character or subfont age is set to the font age - at each use. Thus, characters or subfonts with small ages are - the best candidates for replacement when the cache is full. - -
-

SOURCE
- -
- - /usr/local/plan9/src/libdraw - -
-

SEE ALSO
- -
- - graphics(3), allocimage(3), draw(3), subfont(3), image(7), font(7)
- -
-

DIAGNOSTICS
- -
- - All of the functions use the graphics error function (see graphics(3)).
- -
- -

- - -

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