


XLoadFont(3X11)						      XLoadFont(3X11)
X11R5									X11R5



NAME
  XLoadFont, XQueryFont, XLoadQueryFont, XFreeFont, XGetFontProperty, XUn-
  loadFont, XCharStruct, XFontProp, XChar2b, XFontStruct - load	or unload
  fonts	and font metric	structures

SYNTAX
  Font XLoadFont(_d_i_s_p_l_a_y, _n_a_m_e)
	Display	*_d_i_s_p_l_a_y;
	char *_n_a_m_e;

  XFontStruct *XQueryFont(_d_i_s_p_l_a_y, _f_o_n_t__I_D)
	Display	*_d_i_s_p_l_a_y;
	XID _f_o_n_t__I_D;

  XFontStruct *XLoadQueryFont(_d_i_s_p_l_a_y, _n_a_m_e)
	Display	*_d_i_s_p_l_a_y;
	char *_n_a_m_e;

  XFreeFont(_d_i_s_p_l_a_y, _f_o_n_t__s_t_r_u_c_t)
	Display	*_d_i_s_p_l_a_y;
	XFontStruct *_f_o_n_t__s_t_r_u_c_t;

  Bool XGetFontProperty(_f_o_n_t__s_t_r_u_c_t, _a_t_o_m, _v_a_l_u_e__r_e_t_u_r_n)
	XFontStruct *_f_o_n_t__s_t_r_u_c_t;
	Atom _a_t_o_m;
	unsigned long *_v_a_l_u_e__r_e_t_u_r_n;

  XUnloadFont(_d_i_s_p_l_a_y, _f_o_n_t)
	Display	*_d_i_s_p_l_a_y;
	Font _f_o_n_t;

ARGUMENTS

  _a_t_o_m	    Specifies the atom for the property	name you want returned.

  _d_i_s_p_l_a_y   Specifies the connection to	the X server.

  _f_o_n_t	    Specifies the font.

  _f_o_n_t__I_D   Specifies the font ID or the _G_C_o_n_t_e_x_t ID.

  _f_o_n_t__s_t_r_u_c_t
	    Specifies the storage associated with the font.

  _g_c	    Specifies the GC.

  _n_a_m_e	    Specifies the name of the font, which is a null-terminated
	    string.

  _v_a_l_u_e__r_e_t_u_r_n
	    Returns the	value of the font property.

DESCRIPTION
  The _X_L_o_a_d_F_o_n_t	function loads the specified font and returns its associated
  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.  The interpretation of characters	``?'' and ``*''	in the name
  is not defined by the	core protocol but is reserved for future definition.
  A structured format for font names is	specified in the X Consortium stan-
  dard _X _L_o_g_i_c_a_l _F_o_n_t _D_e_s_c_r_i_p_t_i_o_n _C_o_n_v_e_n_t_i_o_n_s.	If _X_L_o_a_d_F_o_n_t was unsuccessful
  at loading the specified font, a _B_a_d_N_a_m_e 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 _X_U_n_l_o_a_d_F_o_n_t.

  _X_L_o_a_d_F_o_n_t can	generate _B_a_d_A_l_l_o_c and _B_a_d_N_a_m_e errors.

  The _X_Q_u_e_r_y_F_o_n_t function returns a pointer to the _X_F_o_n_t_S_t_r_u_c_t 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 _X_F_o_n_t_S_t_r_u_c_t struc-
  ture will be the _G_C_o_n_t_e_x_t ID,	and you	need to	be careful when	using this ID
  in other functions (see _X_G_C_o_n_t_e_x_t_F_r_o_m_G_C).  If	the font does not exist,
  _X_Q_u_e_r_y_F_o_n_t returns NULL.  To free this data, use _X_F_r_e_e_F_o_n_t_I_n_f_o.

  _X_L_o_a_d_Q_u_e_r_y_F_o_n_t can generate a	_B_a_d_A_l_l_o_c error.

  The _X_L_o_a_d_Q_u_e_r_y_F_o_n_t function provides the most	common way for accessing a
  font.	 _X_L_o_a_d_Q_u_e_r_y_F_o_n_t	both opens (loads) the specified font and returns a
  pointer to the appropriate _X_F_o_n_t_S_t_r_u_c_t structure.  If	the font name is not
  in the Host Portable Character Encoding the result is	implementation depen-
  dent.	 If the	font does not exist, _X_L_o_a_d_Q_u_e_r_y_F_o_n_t returns NULL.

  The _X_F_r_e_e_F_o_n_t	function deletes the association between the font resource ID
  and the specified font and frees the _X_F_o_n_t_S_t_r_u_c_t structure.  The font
  itself will be freed when no other resource references it.  The data and
  the font should not be referenced again.

  _X_F_r_e_e_F_o_n_t can	generate a _B_a_d_F_o_n_t error.

  Given	the atom for that property, the	_X_G_e_t_F_o_n_t_P_r_o_p_e_r_t_y function returns the
  value	of the specified font property.	_X_G_e_t_F_o_n_t_P_r_o_p_e_r_t_y also returns _F_a_l_s_e
  if the property was not defined or _T_r_u_e if it	was defined.  A	set of prede-
  fined	atoms exists for font properties, which	can be found in
  <_X_1_1/_X_a_t_o_m._h>.  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 _X_U_n_l_o_a_d_F_o_n_t function deletes the association between the font resource
  ID and the specified font.  The font itself will be freed when no other
  resource references it.  The font should not be referenced again.

  _X_U_n_l_o_a_d_F_o_n_t can generate a _B_a_d_F_o_n_t error.

STRUCTURES
  The _X_F_o_n_t_S_t_r_u_c_t 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 _X_C_h_a_r_S_t_r_u_c_t structures for	the characters contained in the	font.  The
  _X_F_o_n_t_S_t_r_u_c_t, _X_F_o_n_t_P_r_o_p, and _X_C_h_a_r_S_t_r_u_c_t 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 characters: 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 _X_C_h_a_r_S_t_r_u_c_t	of that	char-
  acter.  When characters are absent from a font, the default_char is used.
  When fonts have all characters of the	same size, only	the information	in
  the _X_F_o_n_t_S_t_r_u_c_t min and max bounds are used.

  The members of the _X_F_o_n_t_S_t_r_u_c_t have the following semantics:

  oo++    The direction member can	be either _F_o_n_t_L_e_f_t_T_o_R_i_g_h_t or _F_o_n_t_R_i_g_h_t_T_o_L_e_f_t.
       It is just a hint as to whether most _X_C_h_a_r_S_t_r_u_c_t	elements have a	posi-
       tive (_F_o_n_t_L_e_f_t_T_o_R_i_g_h_t) or a negative (_F_o_n_t_R_i_g_h_t_T_o_L_e_f_t) character	width
       metric.	The core protocol defines no support for vertical text.

  oo++    If the min_byte1	and max_byte1 members are both zero,
       min_char_or_byte2 specifies the linear character	index corresponding
       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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o++    If all_chars_exist is _T_r_u_e, all characters in the per_char array	have
       nonzero bounding	boxes.

  oo++    The default_char	member specifies the character that will be used when
       an undefined or nonexistent character is	printed. The default_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 per-
       formed for an undefined or nonexistent character.

  oo++    The min_bounds and max_bounds members contain the most extreme values
       of each individual _X_C_h_a_r_S_t_r_u_c_t component	over all elements of this
       array (and ignore nonexistent characters).  The bounding	box of the
       font (the smallest rectangle enclosing the shape	obtained by superim-
       posing 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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o++    The descent member is the logical extent	of the font at or below	the
       baseline	that is	used for determining line spacing.  Specific charac-
       ters may	extend beyond this.

  oo++    If the baseline is at Y-coordinate y, the logical extent	of the font
       is inclusive between the	Y-coordinate values (y - font.ascent) and (y
       + font.descent -	1).  Typically,	the minimum interline 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) described	in
  terms	of _X_C_h_a_r_S_t_r_u_c_t components is a rectangle with its upper-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 character
  ink from the origin.	The rbearing member defines the	extent of the right
  edge of the character	ink from the origin.  The ascent member	defines	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 character	ink from the
  origin.  The width member defines the	logical	width of the character.

DIAGNOSTICS

  _B_a_d_A_l_l_o_c  The	server failed to allocate the requested	resource or server
	    memory.

  _B_a_d_F_o_n_t   A value for	a Font or GContext argument does not name a defined
	    Font.

  _B_a_d_N_a_m_e   A font or color of the specified name does not exist.

SEE ALSO
  XCreateGC(3X11), XListFonts(3X11), XSetFontPath(3X11)
  _X_l_i_b - _C _L_a_n_g_u_a_g_e _X _I_n_t_e_r_f_a_c_e














































