FreeType Fonts

FreeType Fonts — Font support for FreeType

Functions

Types and Values

Description

The FreeType font backend is primarily used to render text on GNU/Linux systems, but can be used on other platforms too.

Functions

cairo_ft_font_face_create_for_ft_face ()

cairo_font_face_t *
cairo_ft_font_face_create_for_ft_face (FT_Face face,
                                       int load_flags);

Creates a new font face for the FreeType font backend from a pre-opened FreeType face. This font can then be used with cairo_set_font_face() or cairo_scaled_font_create(). The cairo_scaled_font_t returned from cairo_scaled_font_create() is also for the FreeType backend and can be used with functions such as cairo_ft_scaled_font_lock_face(). Note that Cairo may keep a reference to the FT_Face alive in a font-cache and the exact lifetime of the reference depends highly upon the exact usage pattern and is subject to external factors. You must not call FT_Done_Face() before the last reference to the cairo_font_face_t has been dropped.

As an example, below is how one might correctly couple the lifetime of the FreeType face object to the cairo_font_face_t.

static const cairo_user_data_key_t key;

font_face = cairo_ft_font_face_create_for_ft_face (ft_face, 0);
status = cairo_font_face_set_user_data (font_face, &key,
                               ft_face, (cairo_destroy_func_t) FT_Done_Face);
if (status) {
   cairo_font_face_destroy (font_face);
   FT_Done_Face (ft_face);
   return ERROR;
}

Parameters

face

A FreeType face object, already opened. This must be kept around until the face's ref_count drops to zero and it is freed. Since the face may be referenced internally to Cairo, the best way to determine when it is safe to free the face is to pass a cairo_destroy_func_t to cairo_font_face_set_user_data()

 

load_flags

flags to pass to FT_Load_Glyph when loading glyphs from the font. These flags are OR'ed together with the flags derived from the cairo_font_options_t passed to cairo_scaled_font_create(), so only a few values such as FT_LOAD_VERTICAL_LAYOUT, and FT_LOAD_FORCE_AUTOHINT are useful. You should not pass any of the flags affecting the load target, such as FT_LOAD_TARGET_LIGHT.

 

Returns

a newly created cairo_font_face_t. Free with cairo_font_face_destroy() when you are done using it.

Since: 1.0


cairo_ft_font_face_create_for_pattern ()

cairo_font_face_t *
cairo_ft_font_face_create_for_pattern (FcPattern *pattern);

Creates a new font face for the FreeType font backend based on a fontconfig pattern. This font can then be used with cairo_set_font_face() or cairo_scaled_font_create(). The cairo_scaled_font_t returned from cairo_scaled_font_create() is also for the FreeType backend and can be used with functions such as cairo_ft_scaled_font_lock_face().

Font rendering options are represented both here and when you call cairo_scaled_font_create(). Font options that have a representation in a FcPattern must be passed in here; to modify FcPattern appropriately to reflect the options in a cairo_font_options_t, call cairo_ft_font_options_substitute().

The pattern's FC_FT_FACE element is inspected first and if that is set, that will be the FreeType font face associated with the returned cairo font face. Otherwise the FC_FILE element is checked. If it's set, that and the value of the FC_INDEX element (defaults to zero) of pattern are used to load a font face from file.

If both steps from the previous paragraph fails, pattern will be passed to FcConfigSubstitute, FcDefaultSubstitute, and finally FcFontMatch, and the resulting font pattern is used.

If the FC_FT_FACE element of pattern is set, the user is responsible for making sure that the referenced FT_Face remains valid for the life time of the returned cairo_font_face_t. See cairo_ft_font_face_create_for_ft_face() for an example of how to couple the life time of the FT_Face to that of the cairo font-face.

Parameters

pattern

A fontconfig pattern. Cairo makes a copy of the pattern if it needs to. You are free to modify or free pattern after this call.

 

Returns

a newly created cairo_font_face_t. Free with cairo_font_face_destroy() when you are done using it.

Since: 1.0


cairo_ft_font_options_substitute ()

void
cairo_ft_font_options_substitute (const cairo_font_options_t *options,
                                  FcPattern *pattern);

Add options to a FcPattern based on a cairo_font_options_t font options object. Options that are already in the pattern, are not overridden, so you should call this function after calling FcConfigSubstitute() (the user's settings should override options based on the surface type), but before calling FcDefaultSubstitute().

Parameters

options

a cairo_font_options_t object

 

pattern

an existing FcPattern

 

Since: 1.0


cairo_ft_scaled_font_lock_face ()

FT_Face
cairo_ft_scaled_font_lock_face (cairo_scaled_font_t *scaled_font);

cairo_ft_scaled_font_lock_face() gets the FT_Face object from a FreeType backend font and scales it appropriately for the font. You must release the face with cairo_ft_scaled_font_unlock_face() when you are done using it. Since the FT_Face object can be shared between multiple cairo_scaled_font_t objects, you must not lock any other font objects until you unlock this one. A count is kept of the number of times cairo_ft_scaled_font_lock_face() is called. cairo_ft_scaled_font_unlock_face() must be called the same number of times.

You must be careful when using this function in a library or in a threaded application, because freetype's design makes it unsafe to call freetype functions simultaneously from multiple threads, (even if using distinct FT_Face objects). Because of this, application code that acquires an FT_Face object with this call must add its own locking to protect any use of that object, (and which also must protect any other calls into cairo as almost any cairo function might result in a call into the freetype library).

Parameters

scaled_font

A cairo_scaled_font_t from the FreeType font backend. Such an object can be created by calling cairo_scaled_font_create() on a FreeType backend font face (see cairo_ft_font_face_create_for_pattern(), cairo_ft_font_face_create_for_ft_face()).

 

Returns

The FT_Face object for font , scaled appropriately, or NULL if scaled_font is in an error state (see cairo_scaled_font_status()) or there is insufficient memory.

Since: 1.0


cairo_ft_scaled_font_unlock_face ()

void
cairo_ft_scaled_font_unlock_face (cairo_scaled_font_t *scaled_font);

Releases a face obtained with cairo_ft_scaled_font_lock_face().

Parameters

scaled_font

A cairo_scaled_font_t from the FreeType font backend. Such an object can be created by calling cairo_scaled_font_create() on a FreeType backend font face (see cairo_ft_font_face_create_for_pattern(), cairo_ft_font_face_create_for_ft_face()).

 

Since: 1.0


cairo_ft_font_face_get_synthesize ()

unsigned int
cairo_ft_font_face_get_synthesize (cairo_font_face_t *font_face);

See cairo_ft_synthesize_t.

Parameters

font_face

The cairo_ft_font_face_t object to query

 

Returns

the current set of synthesis options.

Since: 1.12


cairo_ft_font_face_set_synthesize ()

void
cairo_ft_font_face_set_synthesize (cairo_font_face_t *font_face,
                                   unsigned int synth_flags);

FreeType provides the ability to synthesize different glyphs from a base font, which is useful if you lack those glyphs from a true bold or oblique font. See also cairo_ft_synthesize_t.

Parameters

font_face

The cairo_ft_font_face_t object to modify

 

synth_flags

the set of synthesis options to enable

 

Since: 1.12


cairo_ft_font_face_unset_synthesize ()

void
cairo_ft_font_face_unset_synthesize (cairo_font_face_t *font_face,
                                     unsigned int synth_flags);

See cairo_ft_font_face_set_synthesize().

Parameters

font_face

The cairo_ft_font_face_t object to modify

 

synth_flags

the set of synthesis options to disable

 

Since: 1.12

Types and Values

CAIRO_HAS_FT_FONT

#define CAIRO_HAS_FT_FONT 1

Defined if the FreeType font backend is available. This macro can be used to conditionally compile backend-specific code.

Since: 1.0


CAIRO_HAS_FC_FONT

#define CAIRO_HAS_FC_FONT 1

Defined if the Fontconfig-specific functions of the FreeType font backend are available. This macro can be used to conditionally compile backend-specific code.

Since: 1.10


enum cairo_ft_synthesize_t

A set of synthesis options to control how FreeType renders the glyphs for a particular font face.

Individual synthesis features of a cairo_ft_font_face_t can be set using cairo_ft_font_face_set_synthesize(), or disabled using cairo_ft_font_face_unset_synthesize(). The currently enabled set of synthesis options can be queried with cairo_ft_font_face_get_synthesize().

Note: that when synthesizing glyphs, the font metrics returned will only be estimates.

Members

CAIRO_FT_SYNTHESIZE_BOLD

Embolden the glyphs (redraw with a pixel offset)

 

CAIRO_FT_SYNTHESIZE_OBLIQUE

Slant the glyph outline by 12 degrees to the right.

 

Since: 1.12

See Also

cairo_font_face_t