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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,	char *name);

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

       XFontStruct *XLoadQueryFont(Display *display, 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
       character, and the ``*''	character will match any number	of characters.
       A structured format for font names is specified in the X	Consortium
       standard	X Logical Font Description Conventions.	 If XLoadFont was un-
       successful at loading the specified font, a BadName error results.
       Fonts are not associated	with a particular screen and can be stored as
       a component of any GC.  When the	font is	no longer needed, call XUn-
       loadFont.

       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 as-
       sociated	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 (FontLeftToRight) or a negative (FontRightToLeft)
	    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	1.6.5			  XLoadFont(3)

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

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