hb-ot-layout: HarfBuzz Manual

hb-ot-layout

hb-ot-layout — OpenType Layout

Functions

hb_language_t	hb_ot_tag_to_language ()
hb_script_t	hb_ot_tag_to_script ()
void	hb_ot_tags_from_script_and_language ()
void	hb_ot_tags_to_script_and_language ()
void	hb_ot_layout_collect_lookups ()
void	hb_ot_layout_collect_features ()
void	hb_ot_layout_collect_features_map ()
unsigned int	hb_ot_layout_feature_get_characters ()
unsigned int	hb_ot_layout_feature_get_lookups ()
hb_bool_t	hb_ot_layout_feature_get_name_ids ()
unsigned int	hb_ot_layout_feature_with_variations_get_lookups ()
unsigned int	hb_ot_layout_get_attach_points ()
hb_bool_t	hb_ot_layout_get_font_extents ()
hb_bool_t	hb_ot_layout_get_font_extents2 ()
hb_ot_layout_baseline_tag_t	hb_ot_layout_get_horizontal_baseline_tag_for_script ()
hb_bool_t	hb_ot_layout_get_baseline ()
hb_bool_t	hb_ot_layout_get_baseline2 ()
void	hb_ot_layout_get_baseline_with_fallback ()
void	hb_ot_layout_get_baseline_with_fallback2 ()
hb_ot_layout_glyph_class_t	hb_ot_layout_get_glyph_class ()
void	hb_ot_layout_get_glyphs_in_class ()
unsigned int	hb_ot_layout_get_ligature_carets ()
hb_bool_t	hb_ot_layout_get_size_params ()
hb_bool_t	hb_ot_layout_has_glyph_classes ()
hb_bool_t	hb_ot_layout_has_positioning ()
hb_bool_t	hb_ot_layout_has_substitution ()
hb_bool_t	hb_ot_layout_language_find_feature ()
unsigned int	hb_ot_layout_language_get_feature_indexes ()
unsigned int	hb_ot_layout_language_get_feature_tags ()
hb_bool_t	hb_ot_layout_language_get_required_feature ()
void	hb_ot_layout_lookup_collect_glyphs ()
unsigned	hb_ot_layout_lookup_get_glyph_alternates ()
hb_position_t	hb_ot_layout_lookup_get_optical_bound ()
void	hb_ot_layout_lookup_substitute_closure ()
void	hb_ot_layout_lookups_substitute_closure ()
hb_bool_t	hb_ot_layout_lookup_would_substitute ()
hb_bool_t	hb_ot_layout_script_find_language ()
unsigned int	hb_ot_layout_script_get_language_tags ()
hb_bool_t	hb_ot_layout_script_select_language ()
hb_bool_t	hb_ot_layout_script_select_language2 ()
hb_bool_t	hb_ot_layout_table_find_feature_variations ()
unsigned int	hb_ot_layout_table_get_feature_tags ()
unsigned int	hb_ot_layout_table_get_script_tags ()
unsigned int	hb_ot_layout_table_get_lookup_count ()
hb_bool_t	hb_ot_layout_table_select_script ()
void	hb_ot_shape_plan_collect_lookups ()
hb_bool_t	hb_ot_layout_language_get_required_feature_index ()

Types and Values

#define	HB_OT_MAX_TAGS_PER_LANGUAGE
#define	HB_OT_MAX_TAGS_PER_SCRIPT
#define	HB_OT_TAG_DEFAULT_LANGUAGE
#define	HB_OT_TAG_DEFAULT_SCRIPT
#define	HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX
#define	HB_OT_LAYOUT_NO_FEATURE_INDEX
#define	HB_OT_LAYOUT_NO_SCRIPT_INDEX
#define	HB_OT_LAYOUT_NO_VARIATIONS_INDEX
#define	HB_OT_TAG_BASE
#define	HB_OT_TAG_GDEF
#define	HB_OT_TAG_GPOS
#define	HB_OT_TAG_GSUB
#define	HB_OT_TAG_JSTF
enum	hb_ot_layout_baseline_tag_t
enum	hb_ot_layout_glyph_class_t

Includes

#include <hb-ot.h>

Description

Functions for querying OpenType Layout features in the font face. See the OpenType specification for details.

Functions

hb_ot_tag_to_language ()

hb_language_t
hb_ot_tag_to_language (hb_tag_t tag);

Converts a language tag to an hb_language_t.

Parameters

tag

an language tag

Returns

The hb_language_t corresponding to tag .

[transfer none][nullable]

Since: 0.9.2

hb_ot_tag_to_script ()

hb_script_t
hb_ot_tag_to_script (hb_tag_t tag);

Converts a script tag to an hb_script_t.

Parameters

tag

a script tag

Returns

The hb_script_t corresponding to tag .

hb_ot_tags_from_script_and_language ()

void
hb_ot_tags_from_script_and_language (hb_script_t script,
                                     hb_language_t language,
                                     unsigned int *script_count,
                                     hb_tag_t *script_tags,
                                     unsigned int *language_count,
                                     hb_tag_t *language_tags);

Converts an hb_script_t and an hb_language_t to script and language tags.

Parameters

script	an hb_script_t to convert.
language	an hb_language_t to convert.	[nullable]
script_count	maximum number of script tags to retrieve (IN) and actual number of script tags retrieved (OUT).	[inout][optional]
script_tags	array of size at least `script_count` to store the script tag results.	[out][optional]
language_count	maximum number of language tags to retrieve (IN) and actual number of language tags retrieved (OUT).	[inout][optional]
language_tags	array of size at least `language_count` to store the language tag results.	[out][optional]

Since: 2.0.0

hb_ot_tags_to_script_and_language ()

void
hb_ot_tags_to_script_and_language (hb_tag_t script_tag,
                                   hb_tag_t language_tag,
                                   hb_script_t *script,
                                   hb_language_t *language);

Converts a script tag and a language tag to an hb_script_t and an hb_language_t.

Parameters

script_tag	a script tag
language_tag	a language tag
script	the hb_script_t corresponding to `script_tag` .	[out][optional]
language	the hb_language_t corresponding to `script_tag` and `language_tag` .	[out][optional]

Since: 2.0.0

hb_ot_layout_collect_lookups ()

void
hb_ot_layout_collect_lookups (hb_face_t *face,
                              hb_tag_t table_tag,
                              const hb_tag_t *scripts,
                              const hb_tag_t *languages,
                              const hb_tag_t *features,
                              hb_set_t *lookup_indexes);

Fetches a list of all feature-lookup indexes in the specified face's GSUB table or GPOS table, underneath the specified scripts, languages, and features. If no list of scripts is provided, all scripts will be queried. If no list of languages is provided, all languages will be queried. If no list of features is provided, all features will be queried.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
scripts	The array of scripts to collect lookups for, terminated by `HB_TAG_NONE`.	[nullable][array zero-terminated=1]
languages	The array of languages to collect lookups for, terminated by `HB_TAG_NONE`.	[nullable][array zero-terminated=1]
features	The array of features to collect lookups for, terminated by `HB_TAG_NONE`.	[nullable][array zero-terminated=1]
lookup_indexes	The array of lookup indexes found for the query.	[out]

Since: 0.9.8

hb_ot_layout_collect_features ()

void
hb_ot_layout_collect_features (hb_face_t *face,
                               hb_tag_t table_tag,
                               const hb_tag_t *scripts,
                               const hb_tag_t *languages,
                               const hb_tag_t *features,
                               hb_set_t *feature_indexes);

Fetches a list of all feature indexes in the specified face's GSUB table or GPOS table, underneath the specified scripts, languages, and features. If no list of scripts is provided, all scripts will be queried. If no list of languages is provided, all languages will be queried. If no list of features is provided, all features will be queried.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
scripts	The array of scripts to collect features for, terminated by `HB_TAG_NONE`.	[nullable][array zero-terminated=1]
languages	The array of languages to collect features for, terminated by `HB_TAG_NONE`.	[nullable][array zero-terminated=1]
features	The array of features to collect, terminated by `HB_TAG_NONE`.	[nullable][array zero-terminated=1]
feature_indexes	The set of feature indexes found for the query.	[out]

Since: 1.8.5

hb_ot_layout_collect_features_map ()

void
hb_ot_layout_collect_features_map (hb_face_t *face,
                                   hb_tag_t table_tag,
                                   unsigned  script_index,
                                   unsigned  language_index,
                                   hb_map_t *feature_map);

Fetches the mapping from feature tags to feature indexes for the specified script and language.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_index	The index of the requested language tag
feature_map	The map of feature tag to feature index.	[out]

Since: 8.1.0

hb_ot_layout_feature_get_characters ()

unsigned int
hb_ot_layout_feature_get_characters (hb_face_t *face,
                                     hb_tag_t table_tag,
                                     unsigned int feature_index,
                                     unsigned int start_offset,
                                     unsigned int *char_count,
                                     hb_codepoint_t *characters);

Fetches a list of the characters defined as having a variant under the specified "Character Variant" ("cvXX") feature tag.

Parameters

face	hb_face_t to work upon
table_tag	table tag to query, "GSUB" or "GPOS".
feature_index	index of feature to query.
start_offset	offset of the first character to retrieve
char_count	Input = the maximum number of characters to return; Output = the actual number of characters returned (may be zero).	[inout][optional]
characters	A buffer pointer. The Unicode codepoints of the characters for which this feature provides glyph variants.	[out caller-allocates][array length=char_count]

Returns

Number of total sample characters in the cvXX feature.

Since: 2.0.0

hb_ot_layout_feature_get_lookups ()

unsigned int
hb_ot_layout_feature_get_lookups (hb_face_t *face,
                                  hb_tag_t table_tag,
                                  unsigned int feature_index,
                                  unsigned int start_offset,
                                  unsigned int *lookup_count,
                                  unsigned int *lookup_indexes);

Fetches a list of all lookups enumerated for the specified feature, in the specified face's GSUB table or GPOS table. The list returned will begin at the offset provided.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
feature_index	The index of the requested feature
start_offset	offset of the first lookup to retrieve
lookup_count	Input = the maximum number of lookups to return; Output = the actual number of lookups returned (may be zero).	[inout][optional]
lookup_indexes	The array of lookup indexes found for the query.	[out][array length=lookup_count]

Returns

Total number of lookups.

Since: 0.9.7

hb_ot_layout_feature_get_name_ids ()

hb_bool_t
hb_ot_layout_feature_get_name_ids (hb_face_t *face,
                                   hb_tag_t table_tag,
                                   unsigned int feature_index,
                                   hb_ot_name_id_t *label_id,
                                   hb_ot_name_id_t *tooltip_id,
                                   hb_ot_name_id_t *sample_id,
                                   unsigned int *num_named_parameters,
                                   hb_ot_name_id_t *first_param_id);

Fetches name indices from feature parameters for "Stylistic Set" ('ssXX') or "Character Variant" ('cvXX') features.

Parameters

face	hb_face_t to work upon
table_tag	table tag to query, "GSUB" or "GPOS".
feature_index	index of feature to query.
label_id	The ‘name’ table name ID that specifies a string for a user-interface label for this feature. (May be NULL.).	[out][optional]
tooltip_id	The ‘name’ table name ID that specifies a string that an application can use for tooltip text for this feature. (May be NULL.).	[out][optional]
sample_id	The ‘name’ table name ID that specifies sample text that illustrates the effect of this feature. (May be NULL.).	[out][optional]
num_named_parameters	Number of named parameters. (May be zero.).	[out][optional]
first_param_id	The first ‘name’ table name ID used to specify strings for user-interface labels for the feature parameters. (Must be zero if numParameters is zero.).	[out][optional]

Returns

true if data found, false otherwise

Since: 2.0.0

hb_ot_layout_feature_with_variations_get_lookups ()

unsigned int
hb_ot_layout_feature_with_variations_get_lookups
                               (hb_face_t *face,
                                hb_tag_t table_tag,
                                unsigned int feature_index,
                                unsigned int variations_index,
                                unsigned int start_offset,
                                unsigned int *lookup_count,
                                unsigned int *lookup_indexes);

Fetches a list of all lookups enumerated for the specified feature, in the specified face's GSUB table or GPOS table, enabled at the specified variations index. The list returned will begin at the offset provided.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
feature_index	The index of the feature to query
variations_index	The index of the feature variation to query
start_offset	offset of the first lookup to retrieve
lookup_count	Input = the maximum number of lookups to return; Output = the actual number of lookups returned (may be zero).	[inout][optional]
lookup_indexes	The array of lookups found for the query.	[out][array length=lookup_count]

Returns

Total number of lookups.

Since: 1.4.0

hb_ot_layout_get_attach_points ()

unsigned int
hb_ot_layout_get_attach_points (hb_face_t *face,
                                hb_codepoint_t glyph,
                                unsigned int start_offset,
                                unsigned int *point_count,
                                unsigned int *point_array);

Fetches a list of all attachment points for the specified glyph in the GDEF table of the face. The list returned will begin at the offset provided.

Useful if the client program wishes to cache the list.

Parameters

face	The hb_face_t to work on
glyph	The hb_codepoint_t code point to query
start_offset	offset of the first attachment point to retrieve
point_count	Input = the maximum number of attachment points to return; Output = the actual number of attachment points returned (may be zero).	[inout][optional]
point_array	The array of attachment points found for the query.	[out][array length=point_count]

Returns

Total number of attachment points for glyph .

hb_ot_layout_get_font_extents ()

hb_bool_t
hb_ot_layout_get_font_extents (hb_font_t *font,
                               hb_direction_t direction,
                               hb_tag_t script_tag,
                               hb_tag_t language_tag,
                               hb_font_extents_t *extents);

Fetches script/language-specific font extents. These values are looked up in the BASE table's MinMax records.

If no such extents are found, the default extents for the font are fetched. As such, the return value of this function can for the most part be ignored. Note that the per-script/language extents do not have a line-gap value, and the line-gap is set to zero in that case.

Parameters

font	a font
direction	text direction.
script_tag	script tag.
language_tag	language tag.
extents	font extents if found.	[out][nullable]

Returns

true if found script/language-specific font extents.

Since: 8.0.0

hb_ot_layout_get_font_extents2 ()

hb_bool_t
hb_ot_layout_get_font_extents2 (hb_font_t *font,
                                hb_direction_t direction,
                                hb_script_t script,
                                hb_language_t language,
                                hb_font_extents_t *extents);

Fetches script/language-specific font extents. These values are looked up in the BASE table's MinMax records.

This function is like hb_ot_layout_get_font_extents() but takes hb_script_t and hb_language_t instead of OpenType hb_tag_t.

Parameters

font	a font
direction	text direction.
script	script.
language	language.	[nullable]
extents	font extents if found.	[out][nullable]

Returns

true if found script/language-specific font extents.

Since: 8.0.0

hb_ot_layout_get_horizontal_baseline_tag_for_script ()

hb_ot_layout_baseline_tag_t
hb_ot_layout_get_horizontal_baseline_tag_for_script
                               (hb_script_t script);

Fetches the dominant horizontal baseline tag used by script .

Parameters

script

a script tag.

Returns

dominant baseline tag for the script .

Since: 4.0.0

hb_ot_layout_get_baseline ()

hb_bool_t
hb_ot_layout_get_baseline (hb_font_t *font,
                           hb_ot_layout_baseline_tag_t baseline_tag,
                           hb_direction_t direction,
                           hb_tag_t script_tag,
                           hb_tag_t language_tag,
                           hb_position_t *coord);

Fetches a baseline value from the face.

Parameters

font	a font
baseline_tag	a baseline tag
direction	text direction.
script_tag	script tag.
language_tag	language tag, currently unused.
coord	baseline value if found.	[out][nullable]

Returns

true if found baseline value in the font.

Since: 2.6.0

hb_ot_layout_get_baseline2 ()

hb_bool_t
hb_ot_layout_get_baseline2 (hb_font_t *font,
                            hb_ot_layout_baseline_tag_t baseline_tag,
                            hb_direction_t direction,
                            hb_script_t script,
                            hb_language_t language,
                            hb_position_t *coord);

Fetches a baseline value from the face.

This function is like hb_ot_layout_get_baseline() but takes hb_script_t and hb_language_t instead of OpenType hb_tag_t.

Parameters

font	a font
baseline_tag	a baseline tag
direction	text direction.
script	script.
language	language, currently unused.	[nullable]
coord	baseline value if found.	[out][nullable]

Returns

true if found baseline value in the font.

Since: 8.0.0

hb_ot_layout_get_baseline_with_fallback ()

void
hb_ot_layout_get_baseline_with_fallback
                               (hb_font_t *font,
                                hb_ot_layout_baseline_tag_t baseline_tag,
                                hb_direction_t direction,
                                hb_tag_t script_tag,
                                hb_tag_t language_tag,
                                hb_position_t *coord);

Fetches a baseline value from the face, and synthesizes it if the font does not have it.

Parameters

font	a font
baseline_tag	a baseline tag
direction	text direction.
script_tag	script tag.
language_tag	language tag, currently unused.
coord	baseline value if found.	[out]

Since: 4.0.0

hb_ot_layout_get_baseline_with_fallback2 ()

void
hb_ot_layout_get_baseline_with_fallback2
                               (hb_font_t *font,
                                hb_ot_layout_baseline_tag_t baseline_tag,
                                hb_direction_t direction,
                                hb_script_t script,
                                hb_language_t language,
                                hb_position_t *coord);

Fetches a baseline value from the face, and synthesizes it if the font does not have it.

This function is like hb_ot_layout_get_baseline_with_fallback() but takes hb_script_t and hb_language_t instead of OpenType hb_tag_t.

Parameters

font	a font
baseline_tag	a baseline tag
direction	text direction.
script	script.
language	language, currently unused.	[nullable]
coord	baseline value if found.	[out]

Since: 8.0.0

hb_ot_layout_get_glyph_class ()

hb_ot_layout_glyph_class_t
hb_ot_layout_get_glyph_class (hb_face_t *face,
                              hb_codepoint_t glyph);

Fetches the GDEF class of the requested glyph in the specified face.

Parameters

face	The hb_face_t to work on
glyph	The hb_codepoint_t code point to query

Returns

The hb_ot_layout_glyph_class_t glyph class of the given code point in the GDEF table of the face.

Since: 0.9.7

hb_ot_layout_get_glyphs_in_class ()

void
hb_ot_layout_get_glyphs_in_class (hb_face_t *face,
                                  hb_ot_layout_glyph_class_t klass,
                                  hb_set_t *glyphs);

Retrieves the set of all glyphs from the face that belong to the requested glyph class in the face's GDEF table.

Parameters

face	The hb_face_t to work on
klass	The hb_ot_layout_glyph_class_t GDEF class to retrieve
glyphs	The hb_set_t set of all glyphs belonging to the requested class.	[out]

Since: 0.9.7

hb_ot_layout_get_ligature_carets ()

unsigned int
hb_ot_layout_get_ligature_carets (hb_font_t *font,
                                  hb_direction_t direction,
                                  hb_codepoint_t glyph,
                                  unsigned int start_offset,
                                  unsigned int *caret_count,
                                  hb_position_t *caret_array);

Fetches a list of the caret positions defined for a ligature glyph in the GDEF table of the font. The list returned will begin at the offset provided.

Note that a ligature that is formed from n characters will have n-1 caret positions. The first character is not represented in the array, since its caret position is the glyph position.

The positions returned by this function are 'unshaped', and will have to be fixed up for kerning that may be applied to the ligature glyph.

Parameters

font	The hb_font_t to work on
direction	The hb_direction_t text direction to use
glyph	The hb_codepoint_t code point to query
start_offset	offset of the first caret position to retrieve
caret_count	Input = the maximum number of caret positions to return; Output = the actual number of caret positions returned (may be zero).	[inout][optional]
caret_array	The array of caret positions found for the query.	[out][array length=caret_count]

Returns

Total number of ligature caret positions for glyph .

hb_ot_layout_get_size_params ()

hb_bool_t
hb_ot_layout_get_size_params (hb_face_t *face,
                              unsigned int *design_size,
                              unsigned int *subfamily_id,
                              hb_ot_name_id_t *subfamily_name_id,
                              unsigned int *range_start,
                              unsigned int *range_end);

Fetches optical-size feature data (i.e., the size feature from GPOS). Note that the subfamily_id and the subfamily name string (accessible via the subfamily_name_id) as used here are defined as pertaining only to fonts within a font family that differ specifically in their respective size ranges; other ways to differentiate fonts within a subfamily are not covered by the size feature.

For more information on this distinction, see the size feature documentation.

Parameters

face	hb_face_t to work upon
design_size	The design size of the face.	[out]
subfamily_id	The identifier of the face within the font subfamily.	[out]
subfamily_name_id	The ‘name’ table name ID of the face within the font subfamily.	[out]
range_start	The minimum size of the recommended size range for the face.	[out]
range_end	The maximum size of the recommended size range for the face.	[out]

Returns

true if data found, false otherwise

Since: 0.9.10

hb_ot_layout_has_glyph_classes ()

hb_bool_t
hb_ot_layout_has_glyph_classes (hb_face_t *face);

Tests whether a face has any glyph classes defined in its GDEF table.

Parameters

face

hb_face_t to work upon

Returns

true if data found, false otherwise

hb_ot_layout_has_positioning ()

hb_bool_t
hb_ot_layout_has_positioning (hb_face_t *face);

Tests whether the specified face includes any GPOS positioning.

Parameters

face

hb_face_t to work upon

Returns

true if the face has GPOS data, false otherwise

hb_ot_layout_has_substitution ()

hb_bool_t
hb_ot_layout_has_substitution (hb_face_t *face);

Tests whether the specified face includes any GSUB substitutions.

Parameters

face

hb_face_t to work upon

Returns

true if data found, false otherwise

Since: 0.6.0

hb_ot_layout_language_find_feature ()

hb_bool_t
hb_ot_layout_language_find_feature (hb_face_t *face,
                                    hb_tag_t table_tag,
                                    unsigned int script_index,
                                    unsigned int language_index,
                                    hb_tag_t feature_tag,
                                    unsigned int *feature_index);

Fetches the index of a given feature tag in the specified face's GSUB table or GPOS table, underneath the specified script and language.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_index	The index of the requested language tag
feature_tag	hb_tag_t of the feature tag requested
feature_index	The index of the requested feature.	[out]

Returns

true if the feature is found, false otherwise

Since: 0.6.0

hb_ot_layout_language_get_feature_indexes ()

unsigned int
hb_ot_layout_language_get_feature_indexes
                               (hb_face_t *face,
                                hb_tag_t table_tag,
                                unsigned int script_index,
                                unsigned int language_index,
                                unsigned int start_offset,
                                unsigned int *feature_count,
                                unsigned int *feature_indexes);

Fetches a list of all features in the specified face's GSUB table or GPOS table, underneath the specified script and language. The list returned will begin at the offset provided.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_index	The index of the requested language tag
start_offset	offset of the first feature tag to retrieve
feature_count	Input = the maximum number of feature tags to return; Output: the actual number of feature tags returned (may be zero).	[inout][optional]
feature_indexes	The array of feature indexes found for the query.	[out][array length=feature_count]

Returns

Total number of features.

Since: 0.6.0

hb_ot_layout_language_get_feature_tags ()

unsigned int
hb_ot_layout_language_get_feature_tags
                               (hb_face_t *face,
                                hb_tag_t table_tag,
                                unsigned int script_index,
                                unsigned int language_index,
                                unsigned int start_offset,
                                unsigned int *feature_count,
                                hb_tag_t *feature_tags);

Fetches a list of all features in the specified face's GSUB table or GPOS table, underneath the specified script and language. The list returned will begin at the offset provided.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_index	The index of the requested language tag
start_offset	offset of the first feature tag to retrieve
feature_count	Input = the maximum number of feature tags to return; Output = the actual number of feature tags returned (may be zero).	[inout][optional]
feature_tags	The array of hb_tag_t feature tags found for the query.	[out][array length=feature_count]

Returns

Total number of feature tags.

Since: 0.6.0

hb_ot_layout_language_get_required_feature ()

hb_bool_t
hb_ot_layout_language_get_required_feature
                               (hb_face_t *face,
                                hb_tag_t table_tag,
                                unsigned int script_index,
                                unsigned int language_index,
                                unsigned int *feature_index,
                                hb_tag_t *feature_tag);

Fetches the tag of a requested feature index in the given face's GSUB or GPOS table, underneath the specified script and language.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_index	The index of the requested language tag
feature_index	The index of the requested feature.	[out]
feature_tag	The hb_tag_t of the requested feature.	[out]

Returns

true if the feature is found, false otherwise

Since: 0.9.30

hb_ot_layout_lookup_collect_glyphs ()

void
hb_ot_layout_lookup_collect_glyphs (hb_face_t *face,
                                    hb_tag_t table_tag,
                                    unsigned int lookup_index,
                                    hb_set_t *glyphs_before,
                                    hb_set_t *glyphs_input,
                                    hb_set_t *glyphs_after,
                                    hb_set_t *glyphs_output);

Fetches a list of all glyphs affected by the specified lookup in the specified face's GSUB table or GPOS table.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
lookup_index	The index of the feature lookup to query
glyphs_before	Array of glyphs preceding the substitution range.	[out]
glyphs_input	Array of input glyphs that would be substituted by the lookup.	[out]
glyphs_after	Array of glyphs following the substitution range.	[out]
glyphs_output	Array of glyphs that would be the substituted output of the lookup.	[out]

Since: 0.9.7

hb_ot_layout_lookup_get_glyph_alternates ()

unsigned
hb_ot_layout_lookup_get_glyph_alternates
                               (hb_face_t *face,
                                unsigned  lookup_index,
                                hb_codepoint_t glyph,
                                unsigned  start_offset,
                                unsigned *alternate_count,
                                hb_codepoint_t *alternate_glyphs);

Fetches alternates of a glyph from a given GSUB lookup index.

Parameters

face	a face.
lookup_index	index of the feature lookup to query.
glyph	a glyph id.
start_offset	starting offset.
alternate_count	Input = the maximum number of alternate glyphs to return; Output = the actual number of alternate glyphs returned (may be zero).	[inout][optional]
alternate_glyphs	A glyphs buffer. Alternate glyphs associated with the glyph id.	[out caller-allocates][array length=alternate_count]

Returns

Total number of alternates found in the specific lookup index for the given glyph id.

Since: 2.6.8

hb_ot_layout_lookup_get_optical_bound ()

hb_position_t
hb_ot_layout_lookup_get_optical_bound (hb_font_t *font,
                                       unsigned  lookup_index,
                                       hb_direction_t direction,
                                       hb_codepoint_t glyph);

Fetches the optical bound of a glyph positioned at the margin of text. The direction identifies which edge of the glyph to query.

Parameters

font	a font.
lookup_index	index of the feature lookup to query.
direction	edge of the glyph to query.
glyph	a glyph id.

Returns

Adjustment value. Negative values mean the glyph will stick out of the margin.

Since: 5.3.0

hb_ot_layout_lookup_substitute_closure ()

void
hb_ot_layout_lookup_substitute_closure
                               (hb_face_t *face,
                                unsigned int lookup_index,
                                hb_set_t *glyphs);

Compute the transitive closure of glyphs needed for a specified lookup.

Parameters

face	hb_face_t to work upon
lookup_index	index of the feature lookup to query
glyphs	Array of glyphs comprising the transitive closure of the lookup.	[out]

Since: 0.9.7

hb_ot_layout_lookups_substitute_closure ()

void
hb_ot_layout_lookups_substitute_closure
                               (hb_face_t *face,
                                const hb_set_t *lookups,
                                hb_set_t *glyphs);

Compute the transitive closure of glyphs needed for all of the provided lookups.

Parameters

face	hb_face_t to work upon
lookups	The set of lookups to query
glyphs	Array of glyphs comprising the transitive closure of the lookups.	[out]

Since: 1.8.1

hb_ot_layout_lookup_would_substitute ()

hb_bool_t
hb_ot_layout_lookup_would_substitute (hb_face_t *face,
                                      unsigned int lookup_index,
                                      const hb_codepoint_t *glyphs,
                                      unsigned int glyphs_length,
                                      hb_bool_t zero_context);

Tests whether a specified lookup in the specified face would trigger a substitution on the given glyph sequence.

Parameters

face	hb_face_t to work upon
lookup_index	The index of the lookup to query
glyphs	The sequence of glyphs to query for substitution
glyphs_length	The length of the glyph sequence
zero_context	hb_bool_t indicating whether pre-/post-context are disallowed in substitutions

Returns

true if a substitution would be triggered, false otherwise

Since: 0.9.7

hb_ot_layout_script_find_language ()

hb_bool_t
hb_ot_layout_script_find_language (hb_face_t *face,
                                   hb_tag_t table_tag,
                                   unsigned int script_index,
                                   hb_tag_t language_tag,
                                   unsigned int *language_index);

hb_ot_layout_script_find_language has been deprecated since version 2.0.0 and should not be used in newly-written code.

Fetches the index of a given language tag in the specified face's GSUB table or GPOS table, underneath the specified script tag.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_tag	The hb_tag_t of the requested language
language_index	The index of the requested language

Returns

true if the language tag is found, false otherwise

Since: 0.6.0

hb_ot_layout_script_get_language_tags ()

unsigned int
hb_ot_layout_script_get_language_tags (hb_face_t *face,
                                       hb_tag_t table_tag,
                                       unsigned int script_index,
                                       unsigned int start_offset,
                                       unsigned int *language_count,
                                       hb_tag_t *language_tags);

Fetches a list of language tags in the given face's GSUB or GPOS table, underneath the specified script index. The list returned will begin at the offset provided.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
start_offset	offset of the first language tag to retrieve
language_count	Input = the maximum number of language tags to return; Output = the actual number of language tags returned (may be zero).	[inout][optional]
language_tags	Array of language tags found in the table.	[out][array length=language_count]

Returns

Total number of language tags.

Since: 0.6.0

hb_ot_layout_script_select_language ()

hb_bool_t
hb_ot_layout_script_select_language (hb_face_t *face,
                                     hb_tag_t table_tag,
                                     unsigned int script_index,
                                     unsigned int language_count,
                                     const hb_tag_t *language_tags,
                                     unsigned int *language_index);

Fetches the index of the first language tag fom language_tags that is present in the specified face's GSUB or GPOS table, underneath the specified script index.

If none of the given language tags is found, false is returned and language_index is set to the default language index.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_count	The number of languages in the specified script
language_tags	The array of language tags
language_index	The index of the requested language.	[out]

Returns

true if one of the given language tags is found, false otherwise

Since: 2.0.0

hb_ot_layout_script_select_language2 ()

hb_bool_t
hb_ot_layout_script_select_language2 (hb_face_t *face,
                                      hb_tag_t table_tag,
                                      unsigned int script_index,
                                      unsigned int language_count,
                                      const hb_tag_t *language_tags,
                                      unsigned int *language_index,
                                      hb_tag_t *chosen_language);

Fetches the index of the first language tag fom language_tags that is present in the specified face's GSUB or GPOS table, underneath the specified script index.

If none of the given language tags is found, false is returned and language_index is set to HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX and chosen_language is set to HB_TAG_NONE.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_count	The number of languages in the specified script
language_tags	The array of language tags
language_index	The index of the chosen language.	[out]
chosen_language	hb_tag_t of the chosen language.	[out]

Returns

true if one of the given language tags is found, false otherwise

Since: 7.0.0

hb_ot_layout_table_find_feature_variations ()

hb_bool_t
hb_ot_layout_table_find_feature_variations
                               (hb_face_t *face,
                                hb_tag_t table_tag,
                                const int *coords,
                                unsigned int num_coords,
                                unsigned int *variations_index);

Fetches a list of feature variations in the specified face's GSUB table or GPOS table, at the specified variation coordinates.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
coords	The variation coordinates to query
num_coords	The number of variation coordinates
variations_index	The array of feature variations found for the query.	[out]

Returns

true if feature variations were found, false otherwise.

Since: 1.4.0

hb_ot_layout_table_get_feature_tags ()

unsigned int
hb_ot_layout_table_get_feature_tags (hb_face_t *face,
                                     hb_tag_t table_tag,
                                     unsigned int start_offset,
                                     unsigned int *feature_count,
                                     hb_tag_t *feature_tags);

Fetches a list of all feature tags in the given face's GSUB or GPOS table. Note that there might be duplicate feature tags, belonging to different script/language-system pairs of the table.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
start_offset	offset of the first feature tag to retrieve
feature_count	Input = the maximum number of feature tags to return; Output = the actual number of feature tags returned (may be zero).	[inout][optional]
feature_tags	Array of feature tags found in the table.	[out][array length=feature_count]

Returns

Total number of feature tags.

Since: 0.6.0

hb_ot_layout_table_get_script_tags ()

unsigned int
hb_ot_layout_table_get_script_tags (hb_face_t *face,
                                    hb_tag_t table_tag,
                                    unsigned int start_offset,
                                    unsigned int *script_count,
                                    hb_tag_t *script_tags);

Fetches a list of all scripts enumerated in the specified face's GSUB table or GPOS table. The list returned will begin at the offset provided.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
start_offset	offset of the first script tag to retrieve
script_count	Input = the maximum number of script tags to return; Output = the actual number of script tags returned (may be zero).	[inout][optional]
script_tags	The array of hb_tag_t script tags found for the query.	[out][array length=script_count]

Returns

Total number of script tags.

hb_ot_layout_table_get_lookup_count ()

unsigned int
hb_ot_layout_table_get_lookup_count (hb_face_t *face,
                                     hb_tag_t table_tag);

Fetches the total number of lookups enumerated in the specified face's GSUB table or GPOS table.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS

Returns

Total number of lookups.

Since: 0.9.22

hb_ot_layout_table_select_script ()

hb_bool_t
hb_ot_layout_table_select_script (hb_face_t *face,
                                  hb_tag_t table_tag,
                                  unsigned int script_count,
                                  const hb_tag_t *script_tags,
                                  unsigned int *script_index,
                                  hb_tag_t *chosen_script);

Selects an OpenType script for table_tag from the script_tags array.

If the table does not have any of the requested scripts, then DFLT, dflt, and latn tags are tried in that order. If the table still does not have any of these scripts, script_index is set to HB_OT_LAYOUT_NO_SCRIPT_INDEX and chosen_script is set to HB_TAG_NONE.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_count	Number of script tags in the array
script_tags	Array of hb_tag_t script tags
script_index	The index of the requested script.	[out][optional]
chosen_script	hb_tag_t of the requested script.	[out][optional]

Returns

true if one of the requested scripts is selected, false if a fallback script is selected or if no scripts are selected.

Since: 2.0.0

hb_ot_shape_plan_collect_lookups ()

void
hb_ot_shape_plan_collect_lookups (hb_shape_plan_t *shape_plan,
                                  hb_tag_t table_tag,
                                  hb_set_t *lookup_indexes);

Computes the complete set of GSUB or GPOS lookups that are applicable under a given shape_plan .

Parameters

shape_plan	hb_shape_plan_t to query
table_tag	GSUB or GPOS
lookup_indexes	The hb_set_t set of lookups returned.	[out]

Since: 0.9.7

hb_ot_layout_language_get_required_feature_index ()

hb_bool_t
hb_ot_layout_language_get_required_feature_index
                               (hb_face_t *face,
                                hb_tag_t table_tag,
                                unsigned int script_index,
                                unsigned int language_index,
                                unsigned int *feature_index);

Fetches the index of a requested feature in the given face's GSUB or GPOS table, underneath the specified script and language.

Parameters

face	hb_face_t to work upon
table_tag	HB_OT_TAG_GSUB or HB_OT_TAG_GPOS
script_index	The index of the requested script tag
language_index	The index of the requested language tag
feature_index	The index of the requested feature.	[out]

Returns

true if the feature is found, false otherwise

Since: 0.6.0

Types and Values

HB_OT_MAX_TAGS_PER_LANGUAGE

#define HB_OT_MAX_TAGS_PER_LANGUAGE 3u

Maximum number of OpenType tags that can correspond to a give hb_language_t.

Since: 2.0.0

HB_OT_MAX_TAGS_PER_SCRIPT

#define HB_OT_MAX_TAGS_PER_SCRIPT 3u

Maximum number of OpenType tags that can correspond to a give hb_script_t.

Since: 2.0.0

HB_OT_TAG_DEFAULT_LANGUAGE

#define HB_OT_TAG_DEFAULT_LANGUAGE HB_TAG ('d', 'f', 'l', 't')

OpenType language tag, dflt. Not a valid language tag, but some fonts mistakenly use it.

HB_OT_TAG_DEFAULT_SCRIPT

#define HB_OT_TAG_DEFAULT_SCRIPT HB_TAG ('D', 'F', 'L', 'T')

OpenType script tag, DFLT, for features that are not script-specific.

HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX

#define HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX 0xFFFFu

Special value for language index indicating default or unsupported language.

HB_OT_LAYOUT_NO_FEATURE_INDEX

#define HB_OT_LAYOUT_NO_FEATURE_INDEX		0xFFFFu

Special value for feature index indicating unsupported feature.

HB_OT_LAYOUT_NO_SCRIPT_INDEX

#define HB_OT_LAYOUT_NO_SCRIPT_INDEX		0xFFFFu

Special value for script index indicating unsupported script.

HB_OT_LAYOUT_NO_VARIATIONS_INDEX

#define HB_OT_LAYOUT_NO_VARIATIONS_INDEX 0xFFFFFFFFu

Special value for variations index indicating unsupported variation.

HB_OT_TAG_BASE

#define HB_OT_TAG_BASE HB_TAG('B','A','S','E')

OpenType Baseline Table.

HB_OT_TAG_GDEF

#define HB_OT_TAG_GDEF HB_TAG('G','D','E','F')

OpenType Glyph Definition Table.

HB_OT_TAG_GPOS

#define HB_OT_TAG_GPOS HB_TAG('G','P','O','S')

OpenType Glyph Positioning Table.

HB_OT_TAG_GSUB

#define HB_OT_TAG_GSUB HB_TAG('G','S','U','B')

OpenType Glyph Substitution Table.

HB_OT_TAG_JSTF

#define HB_OT_TAG_JSTF HB_TAG('J','S','T','F')

OpenType Justification Table.

enum hb_ot_layout_baseline_tag_t

Baseline tags from Baseline Tags registry.

Members

HB_OT_LAYOUT_BASELINE_TAG_ROMAN	The baseline used by alphabetic scripts such as Latin, Cyrillic and Greek. In vertical writing mode, the alphabetic baseline for characters rotated 90 degrees clockwise. (This would not apply to alphabetic characters that remain upright in vertical writing mode, since these characters are not rotated.)
HB_OT_LAYOUT_BASELINE_TAG_HANGING	The hanging baseline. In horizontal direction, this is the horizontal line from which syllables seem, to hang in Tibetan and other similar scripts. In vertical writing mode, for Tibetan (or some other similar script) characters rotated 90 degrees clockwise.
HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_BOTTOM_OR_LEFT	Ideographic character face bottom or left edge, if the direction is horizontal or vertical, respectively.
HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT	Ideographic character face top or right edge, if the direction is horizontal or vertical, respectively.
HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_CENTRAL	The center of the ideographic character face. Since: 4.0.0
HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT	Ideographic em-box bottom or left edge, if the direction is horizontal or vertical, respectively.
HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT	Ideographic em-box top or right edge baseline,
HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_CENTRAL	The center of the ideographic em-box. Since: 4.0.0 if the direction is horizontal or vertical, respectively.
HB_OT_LAYOUT_BASELINE_TAG_MATH	The baseline about which mathematical characters are centered. In vertical writing mode when mathematical characters rotated 90 degrees clockwise, are centered.

Since: 2.6.0

enum hb_ot_layout_glyph_class_t

The GDEF classes defined for glyphs.

Members

HB_OT_LAYOUT_GLYPH_CLASS_UNCLASSIFIED	Glyphs not matching the other classifications
HB_OT_LAYOUT_GLYPH_CLASS_BASE_GLYPH	Spacing, single characters, capable of accepting marks
HB_OT_LAYOUT_GLYPH_CLASS_LIGATURE	Glyphs that represent ligation of multiple characters
HB_OT_LAYOUT_GLYPH_CLASS_MARK	Non-spacing, combining glyphs that represent marks
HB_OT_LAYOUT_GLYPH_CLASS_COMPONENT	Spacing glyphs that represent part of a single character