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XLoadFont(3)			XLIB FUNCTIONS			  XLoadFont(3)

NAME
       XLoadFont,  XQueryFont,	XLoadQueryFont,	 XFreeFont,  XGetFontProperty,
       XUnloadFont, XCharStruct, XFontProp, XChar2b, XFontStruct - load	or un-
       load fonts and font metric structures

SYNTAX

       Font XLoadFont(Display *display,	_Xconst	char *name);

       XFontStruct *XQueryFont(Display *display, XID font_ID);

       XFontStruct *XLoadQueryFont(Display *display, _Xconst char *name);

       int XFreeFont(Display *display, XFontStruct *font_struct);

       Bool XGetFontProperty(XFontStruct  *font_struct,	 Atom  atom,  unsigned
	      long *value_return);

       int XUnloadFont(Display *display, Font font);

ARGUMENTS
       atom	 Specifies the atom for	the property name you want returned.

       display	 Specifies the connection to the X server.

       font	 Specifies the font.

       font_ID	 Specifies the font ID or the GContext ID.

       font_struct
		 Specifies the storage associated with the font.

       gc	 Specifies the GC.

       name	 Specifies  the	 name  of the font, which is a null-terminated
		 string.

       value_return
		 Returns the value of the font property.

DESCRIPTION
       The XLoadFont function loads the	specified font and returns its associ-
       ated font ID.  If the font name is not in the Host  Portable  Character
       Encoding,  the result is	implementation-dependent.  Use of uppercase or
       lowercase does not matter.  When	the characters "?" and "" are used  in
       a  font	name,  a  pattern  match is performed and any matching font is
       used.  In the pattern, the "?" character	will match any single  charac-
       ter,  and  the  "*"  character  will match any number of	characters.  A
       structured format for font names	is specified in	the X Consortium stan-
       dard X Logical Font Description Conventions.  If	XLoadFont  was	unsuc-
       cessful	at loading the specified font, a BadName error results.	 Fonts
       are not associated with a particular screen and can be stored as	a com-
       ponent of any GC.  When the font	is no longer needed, call XUnloadFont.

       XLoadFont can generate BadAlloc and BadName errors.

       The XQueryFont function returns a pointer to the	XFontStruct structure,
       which contains information associated with the font.  You can  query  a
       font or the font	stored in a GC.	 The font ID stored in the XFontStruct
       structure  will be the GContext ID, and you need	to be careful when us-
       ing this	ID in other functions (see XGContextFromGC).  If the font does
       not exist, XQueryFont returns NULL.  To	free  this  data,  use	XFree-
       FontInfo.

       XLoadQueryFont can generate a BadAlloc error.

       The  XLoadQueryFont function provides the most common way for accessing
       a font.	XLoadQueryFont both opens (loads) the specified	font  and  re-
       turns  a	pointer	to the appropriate XFontStruct structure.  If the font
       name is not in the Host Portable	Character Encoding, the	result is  im-
       plementation-dependent.	If the font does not exist, XLoadQueryFont re-
       turns NULL.

       The  XFreeFont  function	 deletes  the association between the font re-
       source ID and the specified font	and frees the  XFontStruct  structure.
       The  font  itself  will	be freed when no other resource	references it.
       The data	and the	font should not	be referenced again.

       XFreeFont can generate a	BadFont	error.

       Given the atom for that property, the XGetFontProperty function returns
       the value of the	specified font property.   XGetFontProperty  also  re-
       turns  False if the property was	not defined or True if it was defined.
       A set of	predefined atoms exists	for  font  properties,	which  can  be
       found  in X11/Xatom.h.  This set	contains the standard properties asso-
       ciated with a font.  Although it	is not guaranteed, it is  likely  that
       the predefined font properties will be present.

       The  XUnloadFont	 function deletes the association between the font re-
       source ID and the specified font.  The font itself will be  freed  when
       no  other  resource  references	it.  The font should not be referenced
       again.

       XUnloadFont can generate	a BadFont error.

STRUCTURES
       The XFontStruct structure contains all of the information for the  font
       and  consists  of the font-specific information as well as a pointer to
       an array	of XCharStruct structures for the characters contained in  the
       font.  The XFontStruct, XFontProp, and XCharStruct structures contain:

       typedef struct {
	    short lbearing;	/* origin to left edge of raster */
	    short rbearing;	/* origin to right edge	of raster */
	    short width;   /* advance to next char's origin */
	    short ascent;  /* baseline to top edge of raster */
	    short descent; /* baseline to bottom edge of raster	*/
	    unsigned short attributes;	  /* per char flags (not predefined) */
       } XCharStruct;

       typedef struct {
	    Atom name;
	    unsigned long card32;
       } XFontProp;

       typedef struct {	   /* normal 16	bit characters are two bytes */
	   unsigned char byte1;
	   unsigned char byte2;
       } XChar2b;

       typedef struct {
	    XExtData *ext_data;	/* hook	for extension to hang data */
	    Font fid; /* Font id for this font */
	    unsigned direction;	/* hint	about the direction font is painted */
	    unsigned min_char_or_byte2;	  /* first character */
	    unsigned max_char_or_byte2;	  /* last character */
	    unsigned min_byte1;	/* first row that exists */
	    unsigned max_byte1;	/* last	row that exists	*/
	    Bool all_chars_exist;    /*	flag if	all characters have nonzero size */
	    unsigned default_char;   /*	char to	print for undefined character */
	    int	n_properties;	/* how many properties there are */
	    XFontProp *properties;   /*	pointer	to array of additional properties */
	    XCharStruct	min_bounds;  /*	minimum	bounds over all	existing char */
	    XCharStruct	max_bounds;  /*	maximum	bounds over all	existing char */
	    XCharStruct	*per_char;   /*	first_char to last_char	information */
	    int	ascent;	   /* logical extent above baseline for	spacing	*/
	    int	descent;   /* logical decent below baseline for	spacing	*/
       } XFontStruct;

       X  supports  single  byte/character,  two  bytes/character  matrix, and
       16-bit character	text operations.  Note that any	of these forms can  be
       used  with  a  font,  but a single byte/character text request can only
       specify a single	byte (that is, the first row of	a 2-byte  font).   You
       should view 2-byte fonts	as a two-dimensional matrix of defined charac-
       ters:  byte1  specifies the range of defined rows and byte2 defines the
       range of	defined	columns	of the font.  Single byte/character fonts have
       one row defined,	and the	byte2 range specified in the structure defines
       a range of characters.

       The bounding box	of a character is defined by the XCharStruct  of  that
       character.  When	characters are absent from a font, the default_char is
       used.  When fonts have all characters of	the same size, only the	infor-
       mation in the XFontStruct min and max bounds are	used.

       The members of the XFontStruct have the following semantics:

           The	 direction  member can be either FontLeftToRight or FontRight-
	    ToLeft.  It	is just	a hint as to whether most XCharStruct elements
	    have a positive (FontLeftToRight) or a negative  (FontRightToLeft)
	    character  width metric.  The core protocol	defines	no support for
	    vertical text.

           If	the  min_byte1	and   max_byte1	  members   are	  both	 zero,
	    min_char_or_byte2 specifies	the linear character index correspond-
	    ing	  to   the   first   element   of   the	 per_char  array,  and
	    max_char_or_byte2 specifies	the linear character index of the last
	    element.

	    If	 either	  min_byte1   or   max_byte1   are    nonzero,	  both
	    min_char_or_byte2 and max_char_or_byte2 are	less than 256, and the
	    2-byte  character index values corresponding to the	per_char array
	    element N (counting	from 0)	are:

		 byte1 = N/D + min_byte1
		 byte2 = N\D + min_char_or_byte2
	    where:
		    D =	max_char_or_byte2 - min_char_or_byte2 +	1
		    / =	integer	division
		    \\ = integer modulus

           If the per_char pointer is NULL, all glyphs	between	the first  and
	    last  character  indexes  inclusive	 have the same information, as
	    given by both min_bounds and max_bounds.

           If all_chars_exist is True,	all characters in the  per_char	 array
	    have nonzero bounding boxes.

           The	 default_char member specifies the character that will be used
	    when an undefined or nonexistent character is  printed.   The  de-
	    fault_char	is a 16-bit character (not a 2-byte character).	 For a
	    font using 2-byte matrix format, the default_char has byte1	in the
	    most-significant byte and byte2 in the least significant byte.  If
	    the	default_char itself  specifies	an  undefined  or  nonexistent
	    character,	no  printing is	performed for an undefined or nonexis-
	    tent character.

           The	min_bounds and max_bounds members  contain  the	 most  extreme
	    values  of each individual XCharStruct component over all elements
	    of this array (and ignore nonexistent characters).	 The  bounding
	    box	 of  the  font (the smallest rectangle enclosing the shape ob-
	    tained by superimposing all	of the characters at the  same	origin
	    [x,y]) has its upper-left coordinate at:
		 [x + min_bounds.lbearing, y - max_bounds.ascent]

	    Its	width is:
		 max_bounds.rbearing - min_bounds.lbearing

	    Its	height is:
		 max_bounds.ascent + max_bounds.descent

           The	 ascent	 member	 is  the  logical extent of the	font above the
	    baseline that is used  for	determining  line  spacing.   Specific
	    characters may extend beyond this.

           The	 descent  member is the	logical	extent of the font at or below
	    the	baseline that is used for determining line spacing.   Specific
	    characters may extend beyond this.

           If	the  baseline  is at Y-coordinate y, the logical extent	of the
	    font is inclusive between the Y-coordinate values  (y  -  font.as-
	    cent)  and	(y + font.descent - 1).	 Typically, the	minimum	inter-
	    line spacing between rows of text is given by ascent + descent.

       For a character origin at [x,y],	the bounding box of a character	 (that
       is,  the	 smallest  rectangle  that encloses the	character's shape) de-
       scribed in terms	of XCharStruct components is a rectangle with its  up-
       per-left	corner at:

       [x + lbearing, y	- ascent]

       Its width is:

       rbearing	- lbearing

       Its height is:

       ascent +	descent

       The origin for the next character is defined to be:

       [x + width, y]

       The  lbearing member defines the	extent of the left edge	of the charac-
       ter ink from the	origin.	 The rbearing member defines the extent	of the
       right edge of the character ink from the	origin.	 The ascent member de-
       fines the extent	of the top edge	of the character ink from the  origin.
       The descent member defines the extent of	the bottom edge	of the charac-
       ter ink from the	origin.	 The width member defines the logical width of
       the character.

DIAGNOSTICS
       BadAlloc	 The  server  failed  to  allocate  the	 requested resource or
		 server	memory.

       BadFont	 A value for a Font or GContext	argument does not name	a  de-
		 fined Font.

       BadName	 A font	or color of the	specified name does not	exist.

SEE ALSO
       XCreateGC(3), XListFonts(3), XSetFontPath(3)
       Xlib - C	Language X Interface

X Version 11			 libX11	1.8.12			  XLoadFont(3)

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