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Fonts

Fonts — Loading and manipulating fonts

Types and Values

  GdkFont
enum GdkFontType
typedef GdkWChar

Includes

#include <gdk/gdk.h>

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:

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

The fields in the XLFD are:

Foundry the company or organization where the font originated.
Family the font family (a group of related font designs).
Weight A name for the font's typographic weight For example, 'bold' or 'medium').
Slant The slant of the font. Common values are 'R' for Roman, 'I' for italoc, and 'O' for oblique.
Set Width A name for the width of the font. For example, 'normal' or 'condensed'.
Add Style Additional information to distinguish a font from other fonts of the same family.
Pixel Size The body size of the font in pixels.
Point Size The body size of the font in 10ths of a point. (A point is 1/72.27 inch)
Resolution X The horizontal resolution that the font was designed for.
Resolution Y The vertical resolution that the font was designed for .
Spacing The type of spacing for the font - can be 'p' for proportional, 'm' for monospaced or 'c' for charcell.
Average Width The average width of a glyph in the font. For monospaced and charcell fonts, all glyphs in the font have this width
Charset Registry The registration authority that owns the encoding for the font. Together with the Charset Encoding field, this defines the character set for the font.
Charset Encoding An 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

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"-*-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.

Functions

gdk_font_load ()

GdkFont *
gdk_font_load (const gchar *font_name);

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.

Parameters

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);

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.

Parameters

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);

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.

Parameters

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);

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.

Parameters

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);

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.

Parameters

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);

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.

Parameters

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);

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

Returns the GdkDisplay for font .

Parameters

font

the GdkFont.

 

Returns

the corresponding GdkDisplay.

Since: 2.2


gdk_font_ref ()

GdkFont *
gdk_font_ref (GdkFont *font);

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

Increases the reference count of a font by one.

Parameters

font

a GdkFont

 

Returns

font


gdk_font_unref ()

void
gdk_font_unref (GdkFont *font);

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.

Parameters

font

a GdkFont

 

gdk_font_id ()

gint
gdk_font_id (const GdkFont *font);

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

Returns the X Font ID for the given font.

Parameters

font

a GdkFont.

 

Returns

the numeric X Font ID


gdk_font_equal ()

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

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.

Parameters

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);

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

Gets the metrics of a nul-terminated string.

Parameters

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);

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

Gets the metrics of a string.

Parameters

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);

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

Gets the metrics of a string of wide characters.

Parameters

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);

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)

Parameters

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);

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

Determines the width of a given string.

Parameters

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);

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

Determines the width of a given wide-character string.

Parameters

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);

gdk_char_width has been deprecated since version 2.2 and should not be used in newly-written code.

Use gdk_text_extents() instead.

Determines the width of a given character.

Parameters

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);

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).

Parameters

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);

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().

Parameters

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);

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().

Parameters

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);

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.

Parameters

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);

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().

Parameters

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);

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().

Parameters

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);

gdk_char_height has been deprecated since version 2.2 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().

Parameters

font

a GdkFont

 

character

the character to measure.

 

Returns

the height of the character in pixels.


gdk_wcstombs ()

gchar *
gdk_wcstombs (const GdkWChar *src);

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').

Parameters

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);

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').

Parameters

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.

Types and Values

GdkFont

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

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()

Members

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

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

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

Members

GDK_FONT_FONT

the font is a single font.

 

GDK_FONT_FONTSET

the font is a fontset.

 

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.

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