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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	This set contains the standard properties  associated  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:

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

       o    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

       o    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.

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

       o    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.

       o    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

       o    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.

       o    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.

       o    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	1.6.12			  XLoadFont(3)

NAME | SYNTAX | ARGUMENTS | DESCRIPTION | STRUCTURES | DIAGNOSTICS | SEE ALSO

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