FreeType Fonts

FreeType Fonts — Font support for FreeType

Synopsis




#define             CAIRO_HAS_FT_FONT
cairo_font_face_t*  cairo_ft_font_face_create_for_ft_face
                                                        (FT_Face face,
                                                         int load_flags);
cairo_font_face_t*  cairo_ft_font_face_create_for_pattern
                                                        (FcPattern *pattern);
void                cairo_ft_font_options_substitute    (const cairo_font_options_t *options,
                                                         FcPattern *pattern);
FT_Face             cairo_ft_scaled_font_lock_face      (cairo_scaled_font_t *scaled_font);
void                cairo_ft_scaled_font_unlock_face    (cairo_scaled_font_t *scaled_font);

Description

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

Details

CAIRO_HAS_FT_FONT

#define CAIRO_HAS_FT_FONT 1

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_font_lock_face().

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.

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_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().

pattern :

 A fully resolved fontconfig pattern. A pattern can be resolved, by, among other things, calling FcConfigSubstitute(), FcDefaultSubstitute(), then FcFontMatch(). Cairo will call FcPatternReference() on this pattern, so you should not further modify the pattern, but you can release your reference to the pattern with FcPatternDestroy() if you no longer need to access it.

Returns :

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

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().

options :

 a cairo_font_options_t object

pattern :

 an existing FcPattern

cairo_ft_scaled_font_lock_face ()

FT_Face             cairo_ft_scaled_font_lock_face      (cairo_scaled_font_t *scaled_font);

cairo_ft_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_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_font_lock_face() is called. cairo_ft_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 it's 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).

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_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.

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().

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()).

See Also