XLoadFont(3X11) X11R5 XLoadFont(3X11)NAME
XLoadFont, XQueryFont, XLoadQueryFont, XFreeFont, XGetFontProperty,
XUnloadFont, XCharStruct, XFontProp, XChar2b, XFontStruct - load or
unload fonts and font metric structures
SYNTAX
Font XLoadFont(display, name)
Display *display;
char *name;
XFontStruct *XQueryFont(display, font_ID)
Display *display;
XID font_ID;
XFontStruct *XLoadQueryFont(display, name)
Display *display;
char *name;
XFreeFont(display, font_struct)
Display *display;
XFontStruct *font_struct;
Bool XGetFontProperty(font_struct, atom, value_return)
XFontStruct *font_struct;
Atom atom;
unsigned long *value_return;
XUnloadFont(display, font)
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 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 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 standard X Logical Font Description Conventions. If was
unsuccessful at loading the specified font, a error results. Fonts are
not associated with a particular screen and can be stored as a compo‐
nent of any GC. When the font is no longer needed, call
can generate and errors.
The function returns a pointer to the structure, which contains infor‐
mation associated with the font. You can query a font or the font
stored in a GC. The font ID stored in the structure will be the ID,
and you need to be careful when using this ID in other functions (see
If the font does not exist, returns NULL. To free this data, use
can generate a error.
The function provides the most common way for accessing a font. both
opens (loads) the specified font and returns a pointer to the appropri‐
ate structure. If the font name is not in the Host Portable Character
Encoding the result is implementation dependent. If the font does not
exist, returns NULL.
The function deletes the association between the font resource ID and
the specified font and frees the structure. The font itself will be
freed when no other resource references it. The data and the font
should not be referenced again.
can generate a error.
Given the atom for that property, the function returns the value of the
specified font property. also returns if the property was not defined
or if it was defined. A set of predefined atoms exists for font prop‐
erties, 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 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.
can generate a error.
STRUCTURES
The 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
structures for the characters contained in the font. The and struc‐
tures 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 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 information in the
min and max bounds are used.
The members of the have the following semantics:
· The direction member can be either or It is just a hint as to
whether most elements have a positive or a negative 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 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
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 performed for an undefined or nonexis‐
tent character.
· The min_bounds and max_bounds members contain the most extreme
values of each individual 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
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.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 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 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
defines the extent of the top edge of the character ink from the ori‐
gin. 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
The server failed to allocate the requested resource or server memory.
A value for a Font or GContext argument does not name a defined Font.
A font or color of the specified name does not exist.
SEE ALSOXCreateGC(3X11), XListFonts(3X11), XSetFontPath(3X11)
Xlib - C Language X Interface
XLoadFont(3X11)