Shaping: HarfBuzz Manual

Shaping

Shaping — Conversion of text strings into positioned glyphs

Functions

hb_bool_t	hb_feature_from_string ()
void	hb_feature_to_string ()
void	hb_shape ()
hb_bool_t	hb_shape_full ()
const char **	hb_shape_list_shapers ()

Types and Values

hb_feature_t

Object Hierarchy

    GBoxed
    ╰── hb_feature_t

Includes

#include <hb.h>

Description

Shaping is the central operation of HarfBuzz. Shaping operates on buffers, which are sequences of Unicode characters that use the same font and have the same text direction, script and language. After shaping the buffer contains the output glyphs and their positions.

Functions

hb_feature_from_string ()

hb_bool_t
hb_feature_from_string (const char *str,
                        int len,
                        hb_feature_t *feature);

Parses a string into a hb_feature_t.

TODO: document the syntax here.

Parameters

str	a string to parse.	[array length=len][element-type uint8_t]
len	length of `str` , or -1 if string is `NULL` terminated
feature	the hb_feature_t to initialize with the parsed values.	[out]

Returns

true if str is successfully parsed, false otherwise.

Since: 0.9.5

hb_feature_to_string ()

void
hb_feature_to_string (hb_feature_t *feature,
                      char *buf,
                      unsigned int size);

Converts a hb_feature_t into a NULL-terminated string in the format understood by hb_feature_from_string(). The client in responsible for allocating big enough size for buf , 128 bytes is more than enough.

Parameters

feature	an hb_feature_t to convert
buf	output string.	[array length=size][out]
size	the allocated size of `buf`

Since: 0.9.5

hb_shape ()

void
hb_shape (hb_font_t *font,
          hb_buffer_t *buffer,
          const hb_feature_t *features,
          unsigned int num_features);

Shapes buffer using font turning its Unicode characters content to positioned glyphs. If features is not NULL, it will be used to control the features applied during shaping.

Parameters

font	an hb_font_t to use for shaping
buffer	an hb_buffer_t to shape
features	an array of user specified hb_feature_t or `NULL`.	[array length=num_features][allow-none]
num_features	the length of `features` array

Since: 0.9.2

hb_shape_full ()

hb_bool_t
hb_shape_full (hb_font_t *font,
               hb_buffer_t *buffer,
               const hb_feature_t *features,
               unsigned int num_features,
               const char * const *shaper_list);

See hb_shape() for details. If shaper_list is not NULL, the specified shapers will be used in the given order, otherwise the default shapers list will be used.

Parameters

font	an hb_font_t to use for shaping
buffer	an hb_buffer_t to shape
features	an array of user specified hb_feature_t or `NULL`.	[array length=num_features][allow-none]
num_features	the length of `features` array
shaper_list	a `NULL`-terminated array of shapers to use or `NULL`.	[array zero-terminated=1][allow-none]

Returns

false if all shapers failed, true otherwise

Since: 0.9.2

hb_shape_list_shapers ()

const char **
hb_shape_list_shapers (void);

Retrieves the list of shapers supported by HarfBuzz.

Returns

an array of constant strings.

[transfer none][array zero-terminated=1]

Since: 0.9.2

Types and Values

hb_feature_t

typedef struct {
  hb_tag_t      tag;
  uint32_t      value;
  unsigned int  start;
  unsigned int  end;
} hb_feature_t;