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Fonts

Fonts — Loading and manipulating fonts

Synopsis


#include <gdk/gdk.h>


            GdkFont;
enum        GdkFontType;
GdkFont*    gdk_font_load                   (const gchar *font_name);
GdkFont*    gdk_font_load_for_display       (GdkDisplay *display,
                                             const gchar *font_name);
GdkFont*    gdk_fontset_load                (const gchar *fontset_name);
GdkFont*    gdk_fontset_load_for_display    (GdkDisplay *display,
                                             const gchar *fontset_name);
GdkFont*    gdk_font_from_description       (PangoFontDescription *font_desc);
GdkFont*    gdk_font_from_description_for_display
                                            (GdkDisplay *display,
                                             PangoFontDescription *font_desc);
GdkDisplay* gdk_font_get_display            (GdkFont *font);
GdkFont*    gdk_font_ref                    (GdkFont *font);
void        gdk_font_unref                  (GdkFont *font);
gint        gdk_font_id                     (const GdkFont *font);
gboolean    gdk_font_equal                  (const GdkFont *fonta,
                                             const GdkFont *fontb);

void        gdk_string_extents              (GdkFont *font,
                                             const gchar *string,
                                             gint *lbearing,
                                             gint *rbearing,
                                             gint *width,
                                             gint *ascent,
                                             gint *descent);
void        gdk_text_extents                (GdkFont *font,
                                             const gchar *text,
                                             gint text_length,
                                             gint *lbearing,
                                             gint *rbearing,
                                             gint *width,
                                             gint *ascent,
                                             gint *descent);
void        gdk_text_extents_wc             (GdkFont *font,
                                             const GdkWChar *text,
                                             gint text_length,
                                             gint *lbearing,
                                             gint *rbearing,
                                             gint *width,
                                             gint *ascent,
                                             gint *descent);
gint        gdk_string_width                (GdkFont *font,
                                             const gchar *string);
gint        gdk_text_width                  (GdkFont *font,
                                             const gchar *text,
                                             gint text_length);
gint        gdk_text_width_wc               (GdkFont *font,
                                             const GdkWChar *text,
                                             gint text_length);
gint        gdk_char_width                  (GdkFont *font,
                                             gchar character);
gint        gdk_char_width_wc               (GdkFont *font,
                                             GdkWChar character);
gint        gdk_string_measure              (GdkFont *font,
                                             const gchar *string);
gint        gdk_text_measure                (GdkFont *font,
                                             const gchar *text,
                                             gint text_length);
gint        gdk_char_measure                (GdkFont *font,
                                             gchar character);
gint        gdk_string_height               (GdkFont *font,
                                             const gchar *string);
gint        gdk_text_height                 (GdkFont *font,
                                             const gchar *text,
                                             gint text_length);
gint        gdk_char_height                 (GdkFont *font,
                                             gchar character);

typedef     GdkWChar;
gchar*      gdk_wcstombs                    (const GdkWChar *src);
gint        gdk_mbstowcs                    (GdkWChar *dest,
                                             const gchar *src,
                                             gint dest_max);


Description

The GdkFont data type represents a font for drawing on the screen. These functions provide support for loading fonts, and also for determining the dimensions of characters and strings when drawn with a particular font.

Fonts in X are specified by a X Logical Font Description. The following description is considerably simplified. For definitive information about XLFD's see the X reference documentation. A X Logical Font Description (XLFD) consists of a sequence of fields separated (and surrounded by) '-' characters. For example, Adobe Helvetica Bold 12 pt, has the full description:

"-adobe-helvetica-bold-r-normal--12-120-75-75-p-70-iso8859-1"

The fields in the XLFD are:

Foundrythe company or organization where the font originated.
Familythe font family (a group of related font designs).
WeightA name for the font's typographic weight For example, 'bold' or 'medium').
SlantThe slant of the font. Common values are 'R' for Roman, 'I' for italoc, and 'O' for oblique.
Set WidthA name for the width of the font. For example, 'normal' or 'condensed'.
Add StyleAdditional information to distinguish a font from other fonts of the same family.
Pixel SizeThe body size of the font in pixels.
Point SizeThe body size of the font in 10ths of a point. (A point is 1/72.27 inch)
Resolution XThe horizontal resolution that the font was designed for.
Resolution YThe vertical resolution that the font was designed for .
SpacingThe type of spacing for the font - can be 'p' for proportional, 'm' for monospaced or 'c' for charcell.
Average WidthThe average width of a glyph in the font. For monospaced and charcell fonts, all glyphs in the font have this width
Charset RegistryThe registration authority that owns the encoding for the font. Together with the Charset Encoding field, this defines the character set for the font.
Charset EncodingAn identifier for the particular character set encoding.

When specifying a font via a X logical Font Description, '*' can be used as a wildcard to match any portion of the XLFD. For instance, the above example could also be specified as

"-*-helvetica-bold-r-normal--*-120-*-*-*-*-iso8859-1"

It is generally a good idea to use wildcards for any portion of the XLFD that your program does not care about specifically, since that will improve the chances of finding a matching font.

A fontset is a list of fonts that is used for drawing international text that may contain characters from a number of different character sets. It is represented by a list of XLFD's.

The font for a given character set is determined by going through the list of XLFD's in order. For each one, if the registry and and encoding fields match the desired character set, then that font is used, otherwise if the XLFD contains wild-cards for the registry and encoding fields, the registry and encoding for the desired character set are substituted in and a lookup is done. If a match is found that font is used. Otherwise, processing continues on to the next font in the list.

The functions for determining the metrics of a string come in several varieties that can take a number of forms of string input:

8-bit string

When using functions like gdk_string_width() that take a gchar *, if the font is of type GDK_FONT_FONT and is an 8-bit font, then each gchar indexes the glyphs in the font directly.

16-bit string

For functions taking a gchar *, if the font is of type GDK_FONT_FONT, and is a 16-bit font, then the gchar * argument is interpreted as a guint16 * cast to a gchar * and each guint16 indexes the glyphs in the font directly.

Multibyte string

For functions taking a gchar *, if the font is of type GDK_FONT_FONTSET, then the input string is interpreted as a multibyte encoded according to the current locale. (A multibyte string is one in which each character may consist of one or more bytes, with different lengths for different characters in the string). They can be converted to and from wide character strings (see below) using gdk_wcstombs() and gdk_mbstowcs().) The string will be rendered using one or more different fonts from the fontset.

Wide character string

For a number of the text-measuring functions, GDK provides a variant (such as gdk_text_width_wc()) which takes a GdkWChar * instead of a gchar *. The input is then taken to be a wide character string in the encoding of the current locale. (A wide character string is a string in which each character consists of several bytes, and the width of each character in the string is constant.)

GDK provides functions to determine a number of different measurements (metrics) for a given string. (Need diagram here).

ascent

The vertical distance from the origin of the drawing opereration to the top of the drawn character.

descent

The vertical distance from the origin of the drawing opereration to the bottom of the drawn character.

left bearing

The horizontal distance from the origin of the drawing operation to the left-most part of the drawn character.

right bearing

The horizontal distance from the origin of the drawing operation to the right-most part of the drawn character.

width bearing

The horizontal distance from the origin of the drawing operation to the correct origin for drawing another string to follow the current one. Depending on the font, this could be greater than or less than the right bearing.

Details

GdkFont

typedef struct {
  GdkFontType type;
  gint ascent;
  gint descent;
} GdkFont;

Warning

GdkFont is deprecated and should not be used in newly-written code.

The GdkFont structure represents a font or fontset. It contains the following public fields. A new GdkFont structure is returned by gdk_font_load() or gdk_fontset_load(), and is reference counted with gdk_font_ref() and gdk_font_unref()

GdkFontType type;a value of type GdkFontType which indicates whether this font is a single font or a fontset.
gint ascent;the maximum distance that the font, when drawn, ascends above the baseline.
gint descent;the maximum distance that the font, when drawn, descends below the baseline.

enum GdkFontType

typedef enum
{
  GDK_FONT_FONT,
  GDK_FONT_FONTSET
} GdkFontType;

Warning

GdkFontType is deprecated and should not be used in newly-written code.

Indicates the type of a font. The possible values are currently:

GDK_FONT_FONTthe font is a single font.
GDK_FONT_FONTSETthe font is a fontset.

gdk_font_load ()

GdkFont*    gdk_font_load                   (const gchar *font_name);

Warning

gdk_font_load is deprecated and should not be used in newly-written code.

Loads a font.

The font may be newly loaded or looked up the font in a cache. You should make no assumptions about the initial reference count.

font_name : a XLFD describing the font to load.
Returns : a GdkFont, or NULL if the font could not be loaded.

gdk_font_load_for_display ()

GdkFont*    gdk_font_load_for_display       (GdkDisplay *display,
                                             const gchar *font_name);

Warning

gdk_font_load_for_display is deprecated and should not be used in newly-written code.

Loads a font for use on display.

The font may be newly loaded or looked up the font in a cache. You should make no assumptions about the initial reference count.

display : a GdkDisplay
font_name : a XLFD describing the font to load.
Returns : a GdkFont, or NULL if the font could not be loaded.

Since 2.2


gdk_fontset_load ()

GdkFont*    gdk_fontset_load                (const gchar *fontset_name);

Warning

gdk_fontset_load is deprecated and should not be used in newly-written code.

Loads a fontset.

The fontset may be newly loaded or looked up in a cache. You should make no assumptions about the initial reference count.

fontset_name : a comma-separated list of XLFDs describing the component fonts of the fontset to load.
Returns : a GdkFont, or NULL if the fontset could not be loaded.

gdk_fontset_load_for_display ()

GdkFont*    gdk_fontset_load_for_display    (GdkDisplay *display,
                                             const gchar *fontset_name);

Warning

gdk_fontset_load_for_display is deprecated and should not be used in newly-written code.

Loads a fontset for use on display.

The fontset may be newly loaded or looked up in a cache. You should make no assumptions about the initial reference count.

display : a GdkDisplay
fontset_name : a comma-separated list of XLFDs describing the component fonts of the fontset to load.
Returns : a GdkFont, or NULL if the fontset could not be loaded.

Since 2.2


gdk_font_from_description ()

GdkFont*    gdk_font_from_description       (PangoFontDescription *font_desc);

Warning

gdk_font_from_description is deprecated and should not be used in newly-written code.

Load a GdkFont based on a Pango font description. This font will only be an approximation of the Pango font, and internationalization will not be handled correctly. This function should only be used for legacy code that cannot be easily converted to use Pango. Using Pango directly will produce better results.

font_desc : a PangoFontDescription.
Returns : the newly loaded font, or NULL if the font cannot be loaded.

gdk_font_from_description_for_display ()

GdkFont*    gdk_font_from_description_for_display
                                            (GdkDisplay *display,
                                             PangoFontDescription *font_desc);

Warning

gdk_font_from_description_for_display is deprecated and should not be used in newly-written code.

Loads a GdkFont based on a Pango font description for use on display. This font will only be an approximation of the Pango font, and internationalization will not be handled correctly. This function should only be used for legacy code that cannot be easily converted to use Pango. Using Pango directly will produce better results.

display : a GdkDisplay
font_desc : a PangoFontDescription.
Returns : the newly loaded font, or NULL if the font cannot be loaded.

Since 2.2


gdk_font_get_display ()

GdkDisplay* gdk_font_get_display            (GdkFont *font);

Warning

gdk_font_get_display is deprecated and should not be used in newly-written code.

Returns the GdkDisplay for font.

font : the GdkFont.
Returns : the corresponding GdkDisplay.

Since 2.2


gdk_font_ref ()

GdkFont*    gdk_font_ref                    (GdkFont *font);

Warning

gdk_font_ref is deprecated and should not be used in newly-written code.

Increases the reference count of a font by one.

font : a GdkFont
Returns : font

gdk_font_unref ()

void        gdk_font_unref                  (GdkFont *font);

Warning

gdk_font_unref is deprecated and should not be used in newly-written code.

Decreases the reference count of a font by one. If the result is zero, destroys the font.

font : a GdkFont

gdk_font_id ()

gint        gdk_font_id                     (const GdkFont *font);

Warning

gdk_font_id is deprecated and should not be used in newly-written code.

Returns the X Font ID for the given font.

font : a GdkFont.
Returns : the numeric X Font ID

gdk_font_equal ()

gboolean    gdk_font_equal                  (const GdkFont *fonta,
                                             const GdkFont *fontb);

Warning

gdk_font_equal is deprecated and should not be used in newly-written code.

Compares two fonts for equality. Single fonts compare equal if they have the same X font ID. This operation does not currently work correctly for fontsets.

fonta : a GdkFont.
fontb : another GdkFont.
Returns : TRUE if the fonts are equal.

gdk_string_extents ()

void        gdk_string_extents              (GdkFont *font,
                                             const gchar *string,
                                             gint *lbearing,
                                             gint *rbearing,
                                             gint *width,
                                             gint *ascent,
                                             gint *descent);

Warning

gdk_string_extents is deprecated and should not be used in newly-written code.

Gets the metrics of a nul-terminated string.

font : a GdkFont.
string : the nul-terminated string to measure.
lbearing : the left bearing of the string.
rbearing : the right bearing of the string.
width : the width of the string.
ascent : the ascent of the string.
descent : the descent of the string.

gdk_text_extents ()

void        gdk_text_extents                (GdkFont *font,
                                             const gchar *text,
                                             gint text_length,
                                             gint *lbearing,
                                             gint *rbearing,
                                             gint *width,
                                             gint *ascent,
                                             gint *descent);

Warning

gdk_text_extents is deprecated and should not be used in newly-written code.

Gets the metrics of a string.

font : a GdkFont
text : the text to measure
text_length : the length of the text in bytes. (If the font is a 16-bit font, this is twice the length of the text in characters.)
lbearing : the left bearing of the string.
rbearing : the right bearing of the string.
width : the width of the string.
ascent : the ascent of the string.
descent : the descent of the string.

gdk_text_extents_wc ()

void        gdk_text_extents_wc             (GdkFont *font,
                                             const GdkWChar *text,
                                             gint text_length,
                                             gint *lbearing,
                                             gint *rbearing,
                                             gint *width,
                                             gint *ascent,
                                             gint *descent);

Warning

gdk_text_extents_wc is deprecated and should not be used in newly-written code.

Gets the metrics of a string of wide characters.

font : a GdkFont
text : the text to measure.
text_length : the length of the text in character.
lbearing : the left bearing of the string.
rbearing : the right bearing of the string.
width : the width of the string.
ascent : the ascent of the string.
descent : the descent of the string.

gdk_string_width ()

gint        gdk_string_width                (GdkFont *font,
                                             const gchar *string);

Warning

gdk_string_width is deprecated and should not be used in newly-written code.

Determines the width of a nul-terminated string. (The distance from the origin of the string to the point where the next string in a sequence of strings should be drawn)

font : a GdkFont
string : the nul-terminated string to measure
Returns : the width of the string in pixels.

gdk_text_width ()

gint        gdk_text_width                  (GdkFont *font,
                                             const gchar *text,
                                             gint text_length);

Warning

gdk_text_width is deprecated and should not be used in newly-written code.

Determines the width of a given string.

font : a GdkFont
text : the text to measure.
text_length : the length of the text in bytes.
Returns : the width of the string in pixels.

gdk_text_width_wc ()

gint        gdk_text_width_wc               (GdkFont *font,
                                             const GdkWChar *text,
                                             gint text_length);

Warning

gdk_text_width_wc is deprecated and should not be used in newly-written code.

Determines the width of a given wide-character string.

font : a GdkFont
text : the text to measure.
text_length : the length of the text in characters.
Returns : the width of the string in pixels.

gdk_char_width ()

gint        gdk_char_width                  (GdkFont *font,
                                             gchar character);

Warning

gdk_char_width is deprecated and should not be used in newly-written code. Use gdk_text_extents() instead.

Determines the width of a given character.

font : a GdkFont
character : the character to measure.
Returns : the width of the character in pixels.

gdk_char_width_wc ()

gint        gdk_char_width_wc               (GdkFont *font,
                                             GdkWChar character);

Warning

gdk_char_width_wc is deprecated and should not be used in newly-written code.

Determines the width of a given wide character. (Encoded in the wide-character encoding of the current locale).

font : a GdkFont
character : the character to measure.
Returns : the width of the character in pixels.

gdk_string_measure ()

gint        gdk_string_measure              (GdkFont *font,
                                             const gchar *string);

Warning

gdk_string_measure is deprecated and should not be used in newly-written code.

Determines the distance from the origin to the rightmost portion of a nul-terminated string when drawn. This is not the correct value for determining the origin of the next portion when drawing text in multiple pieces. See gdk_string_width().

font : a GdkFont
string : the nul-terminated string to measure.
Returns : the right bearing of the string in pixels.

gdk_text_measure ()

gint        gdk_text_measure                (GdkFont *font,
                                             const gchar *text,
                                             gint text_length);

Warning

gdk_text_measure is deprecated and should not be used in newly-written code.

Determines the distance from the origin to the rightmost portion of a string when drawn. This is not the correct value for determining the origin of the next portion when drawing text in multiple pieces. See gdk_text_width().

font : a GdkFont
text : the text to measure.
text_length : the length of the text in bytes.
Returns : the right bearing of the string in pixels.

gdk_char_measure ()

gint        gdk_char_measure                (GdkFont *font,
                                             gchar character);

Warning

gdk_char_measure is deprecated and should not be used in newly-written code.

Determines the distance from the origin to the rightmost portion of a character when drawn. This is not the correct value for determining the origin of the next portion when drawing text in multiple pieces.

font : a GdkFont
character : the character to measure.
Returns : the right bearing of the character in pixels.

gdk_string_height ()

gint        gdk_string_height               (GdkFont *font,
                                             const gchar *string);

Warning

gdk_string_height is deprecated and should not be used in newly-written code.

Determines the total height of a given nul-terminated string. This value is not generally useful, because you cannot determine how this total height will be drawn in relation to the baseline. See gdk_string_extents().

font : a GdkFont
string : the nul-terminated string to measure.
Returns : the height of the string in pixels.

gdk_text_height ()

gint        gdk_text_height                 (GdkFont *font,
                                             const gchar *text,
                                             gint text_length);

Warning

gdk_text_height is deprecated and should not be used in newly-written code.

Determines the total height of a given string. This value is not generally useful, because you cannot determine how this total height will be drawn in relation to the baseline. See gdk_text_extents().

font : a GdkFont
text : the text to measure.
text_length : the length of the text in bytes.
Returns : the height of the string in pixels.

gdk_char_height ()

gint        gdk_char_height                 (GdkFont *font,
                                             gchar character);

Warning

gdk_char_height is deprecated and should not be used in newly-written code. Use gdk_text_extents() instead.

Determines the total height of a given character. This value is not generally useful, because you cannot determine how this total height will be drawn in relation to the baseline. See gdk_text_extents().

font : a GdkFont
character : the character to measure.
Returns : the height of the character in pixels.

GdkWChar

typedef guint32			    GdkWChar;

Specifies a wide character type, used to represent character codes. This is needed since some native languages have character sets which have more than 256 characters (Japanese and Chinese, for example).

Wide character values between 0 and 127 are always identical in meaning to the ASCII character codes. The wide character value 0 is often used to terminate strings of wide characters in a similar way to normal strings using the char type.

An alternative to wide characters is multi-byte characters, which extend normal char strings to cope with larger character sets. As the name suggests, multi-byte characters use a different number of bytes to store different character codes. For example codes 0-127 (i.e. the ASCII codes) often use just one byte of memory, while other codes may use 2, 3 or even 4 bytes. Multi-byte characters have the advantage that they can often be used in an application with little change, since strings are still represented as arrays of char values. However multi-byte strings are much easier to manipulate since the character are all of the same size.

Applications typically use wide characters to represent character codes internally, and multi-byte strings when saving the characters to a file. The gdk_wcstombs() and gdk_mbstowcs() functions can be used to convert from one representation to the other.

See the 'Extended Characters' section of the GNU C Library Reference Manual for more detailed information on wide and multi-byte characters.


gdk_wcstombs ()

gchar*      gdk_wcstombs                    (const GdkWChar *src);

Warning

gdk_wcstombs is deprecated and should not be used in newly-written code.

Converts a wide character string to a multi-byte string. (The function name comes from an acronym of 'Wide Character String TO Multi-Byte String').

src : a wide character string.
Returns : the multi-byte string corresponding to src, or NULL if the conversion failed. The returned string should be freed with g_free() when no longer needed.

gdk_mbstowcs ()

gint        gdk_mbstowcs                    (GdkWChar *dest,
                                             const gchar *src,
                                             gint dest_max);

Warning

gdk_mbstowcs is deprecated and should not be used in newly-written code.

Converts a multi-byte string to a wide character string. (The function name comes from an acronym of 'Multi-Byte String TO Wide Character String').

dest : the space to place the converted wide character string into.
src : the multi-byte string to convert, which must be nul-terminated.
dest_max : the maximum number of wide characters to place in dest.
Returns : the number of wide characters written into dest, or -1 if the conversion failed.