FreeType Fonts

3 CAIRO Library

FreeType Fonts

Font support for FreeType

## Functions

cairo_font_face_t * | cairo_ft_font_face_create_for_ft_face ()
cairo_font_face_t * | cairo_ft_font_face_create_for_pattern ()
void | cairo_ft_font_options_substitute ()
FT_Face | cairo_ft_scaled_font_lock_face ()
void | cairo_ft_scaled_font_unlock_face ()
unsigned int | cairo_ft_font_face_get_synthesize ()
void | cairo_ft_font_face_set_synthesize ()
void | cairo_ft_font_face_unset_synthesize ()

## Types and Values

#define | CAIRO_HAS_FT_FONT
#define | CAIRO_HAS_FC_FONT
enum | cairo_ft_synthesize_t

## Object Hierarchy

## 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`