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SUBFONT(3)		   Library Functions Manual		    SUBFONT(3)

       allocsubfont, freesubfont, installsubfont, lookupsubfont, uninstallsub-
       font, subfontname, readsubfont, readsubfonti, writesubfont,  stringsub-
       font, strsubfontwidth, mkfont - subfont manipulation

       #include	<u.h>
       #include	<libc.h>
       #include	<draw.h>

       Subfont*	allocsubfont(char *name, int n,	int height, int	ascent,
		Fontchar *info,	Image *i)

       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 dolock)

       int	writesubfont(int fd, Subfont *f)

       Point	stringsubfont(Image *dst, Point	p, Image *src,
		Subfont	*f, char *str)

       Point	strsubfontwidth(Subfont	*f, char *s)

       Font*	mkfont(Subfont *f, Rune	min)

       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 call-
       ing 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 let-
       ters (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.	 Unin-
       stallsubfont  removes  the subfont from the cache.  Finally, lookupsub-
       font searches for  a subfont with the given name	in the cache  and  re-
       turns 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  rou-
       tine internal to	the library, subfontname may be	substituted by the ap-
       plication to provide a less file-oriented subfont naming	scheme.

       The format of a subfont file is described in font(7).  Briefly, it con-
       tains  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 allocim-

       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

       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.

	      bitmap font file tree


       graphics(3), allocimage(3), draw(3), cachechars(3), image(7), font(7)

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



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