Ubuntu Manpage: XCreateFontSet, XFreeFontSet - create and free an international text drawing font set

NAME

       XCreateFontSet, XFreeFontSet - create and free an international text drawing font set

SYNTAX

       XFontSet   XCreateFontSet(Display   *display,   _Xconst  char  *base_font_name_list,  char
              ***missing_charset_list_return,     int     *missing_charset_count_return,     char
              **def_string_return);

       void XFreeFontSet(Display *display, XFontSet font_set);

ARGUMENTS

       display   Specifies the connection to the X server.

       base_font_name_list
                 Specifies the base font names.

       def_string_return
                 Returns the string drawn for missing charsets.

       font_set  Specifies the font set.

       missing_charset_count_return
                 Returns the number of missing charsets.

       missing_charset_list_return
                 Returns the missing charsets.

DESCRIPTION

The XCreateFontSet function creates a font set for the specified display. The font set is
bound to the current locale when XCreateFontSet is called. The font set may be used in
subsequent calls to obtain font and character information and to image text in the locale
of the font set.

The base_font_name_list argument is a list of base font names that Xlib uses to load the
fonts needed for the locale. The base font names are a comma-separated list. The string
is null-terminated and is assumed to be in the Host Portable Character Encoding;
otherwise, the result is implementation-dependent. White space immediately on either side
of a separating comma is ignored.

Use of XLFD font names permits Xlib to obtain the fonts needed for a variety of locales
from a single locale-independent base font name. The single base font name should name a
family of fonts whose members are encoded in the various charsets needed by the locales of
interest.

An XLFD base font name can explicitly name a charset needed for the locale. This allows
the user to specify an exact font for use with a charset required by a locale, fully
controlling the font selection.

If a base font name is not an XLFD name, Xlib will attempt to obtain an XLFD name from the
font properties for the font. If this action is successful in obtaining an XLFD name, the
XBaseFontNameListOfFontSet function will return this XLFD name instead of the client-
supplied name.

Xlib uses the following algorithm to select the fonts that will be used to display text
with the XFontSet.

For each font charset required by the locale, the base font name list is searched for the
first appearance of one of the following cases that names a set of fonts that exist at the
server:

• The first XLFD-conforming base font name that specifies the required charset or a
superset of the required charset in its CharSetRegistry and CharSetEncoding fields.
The implementation may use a base font name whose specified charset is a superset of
the required charset, for example, an ISO8859-1 font for an ASCII charset.

• The first set of one or more XLFD-conforming base font names that specify one or more
charsets that can be remapped to support the required charset. The Xlib
implementation may recognize various mappings from a required charset to one or more
other charsets and use the fonts for those charsets. For example, JIS Roman is ASCII
with tilde and backslash replaced by yen and overbar; Xlib may load an ISO8859-1 font
to support this character set if a JIS Roman font is not available.

• The first XLFD-conforming font name or the first non-XLFD font name for which an XLFD
font name can be obtained, combined with the required charset (replacing the
CharSetRegistry and CharSetEncoding fields in the XLFD font name). As in case 1, the
implementation may use a charset that is a superset of the required charset.

• The first font name that can be mapped in some implementation-dependent manner to one
or more fonts that support imaging text in the charset.

For example, assume that a locale required the charsets:

ISO8859-1
JISX0208.1983
JISX0201.1976
GB2312-1980.0

The user could supply a base_font_name_list that explicitly specifies the charsets,
ensuring that specific fonts are used if they exist. For example:

"-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-240-JISX0208.1983-0,\
-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-120-JISX0201.1976-0,\
-GB-Fixed-Medium-R-Normal--26-180-100-100-C-240-GB2312-1980.0,\
-Adobe-Courier-Bold-R-Normal--25-180-75-75-M-150-ISO8859-1"

Alternatively, the user could supply a base_font_name_list that omits the charsets,
letting Xlib select font charsets required for the locale. For example:

"-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-240,\
-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-120,\
-GB-Fixed-Medium-R-Normal--26-180-100-100-C-240,\
-Adobe-Courier-Bold-R-Normal--25-180-100-100-M-150"

Alternatively, the user could simply supply a single base font name that allows Xlib to
select from all available fonts that meet certain minimum XLFD property requirements. For
example:

"-*-*-*-R-Normal--*-180-100-100-*-*"

If XCreateFontSet is unable to create the font set, either because there is insufficient
memory or because the current locale is not supported, XCreateFontSet returns NULL,
missing_charset_list_return is set to NULL, and missing_charset_count_return is set to
zero. If fonts exist for all of the charsets required by the current locale,
XCreateFontSet returns a valid XFontSet, missing_charset_list_return is set to NULL, and
missing_charset_count_return is set to zero.

If no font exists for one or more of the required charsets, XCreateFontSet sets
missing_charset_list_return to a list of one or more null-terminated charset names for
which no font exists and sets missing_charset_count_return to the number of missing fonts.
The charsets are from the list of the required charsets for the encoding of the locale and
do not include any charsets to which Xlib may be able to remap a required charset.

If no font exists for any of the required charsets or if the locale definition in Xlib
requires that a font exist for a particular charset and a font is not found for that
charset, XCreateFontSet returns NULL. Otherwise, XCreateFontSet returns a valid XFontSet
to font_set.

When an Xmb/wc drawing or measuring function is called with an XFontSet that has missing
charsets, some characters in the locale will not be drawable. If def_string_return is
non-NULL, XCreateFontSet returns a pointer to a string that represents the glyphs that are
drawn with this XFontSet when the charsets of the available fonts do not include all font
glyphs required to draw a codepoint. The string does not necessarily consist of valid
characters in the current locale and is not necessarily drawn with the fonts loaded for
the font set, but the client can draw and measure the default glyphs by including this
string in a string being drawn or measured with the XFontSet.

If the string returned to def_string_return is the empty string (""), no glyphs are drawn,
and the escapement is zero. The returned string is null-terminated. It is owned by Xlib
and should not be modified or freed by the client. It will be freed by a call to
XFreeFontSet with the associated XFontSet. Until freed, its contents will not be modified
by Xlib.

The client is responsible for constructing an error message from the missing charset and
default string information and may choose to continue operation in the case that some
fonts did not exist.

The returned XFontSet and missing charset list should be freed with XFreeFontSet and
XFreeStringList, respectively. The client-supplied base_font_name_list may be freed by
the client after calling XCreateFontSet.

The XFreeFontSet function frees the specified font set. The associated base font name
list, font name list, XFontStruct list, and XFontSetExtents, if any, are freed.

NAME

SYNTAX

ARGUMENTS

DESCRIPTION

SEE ALSO