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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 () |
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.
1 2 3 4 5 6 7 8 9 10 |
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 |
|
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 |
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 |
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()
.
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 and applies OpenType
font variations if applicable. 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 |
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 |
Since: 1.0
cairo_ft_font_face_get_synthesize ()
unsigned int
cairo_ft_font_face_get_synthesize (cairo_font_face_t *font_face
);
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.
Since: 1.12