PangoOTTag

typedef guint32 PangoOTTag;

The PangoOTTag typedef is used to represent TrueType and OpenType four letter tags inside Pango. Use PANGO_OT_TAG_MAKE() or PANGO_OT_TAG_MAKE_FROM_STRING() macros to create PangoOTTags manually.

PangoOTInfo

typedef struct _PangoOTInfo PangoOTInfo;

The PangoOTInfo struct contains the various tables associated with an OpenType font. It contains only private fields and should only be accessed via the pango_ot_info_* functions which are documented below. To obtain a PangoOTInfo, use pango_ot_info_new().

PangoOTBuffer

typedef struct _PangoOTBuffer PangoOTBuffer;

The PangoOTBuffer structure is used to store strings of glyphs associated with a PangoFcFont, suitable for OpenType layout processing. It contains only private fields and should only be accessed via the pango_ot_buffer_* functions which are documented below. To obtain a PangoOTBuffer, use pango_ot_buffer_new().

struct PangoOTGlyph

struct PangoOTGlyph {
  guint32  glyph;
  guint    properties;
  guint    cluster;
  gushort  component;
  gushort  ligID;

  guint    internal;
};

The PangoOTGlyph structure represents a single glyph together with information used for OpenType layout processing of the glyph. It contains the following fields.

PangoOTRuleset

typedef struct _PangoOTRuleset PangoOTRuleset;

The PangoOTRuleset structure holds a set of features selected from the tables in an OpenType font. (A feature is an operation such as adjusting glyph positioning that should be applied to a text feature such as a certain type of accent.) A PangoOTRuleset is created with pango_ot_ruleset_new(), features are added to it with pango_ot_ruleset_add_feature(), then it is applied to a PangoGlyphString with pango_ot_ruleset_shape().

struct PangoOTRulesetDescription

struct PangoOTRulesetDescription {
  PangoScript               script;
  PangoLanguage            *language;
  const PangoOTFeatureMap  *static_gsub_features;
  guint                   n_static_gsub_features;
  const PangoOTFeatureMap  *static_gpos_features;
  guint                   n_static_gpos_features;
  const PangoOTFeatureMap  *other_features;
  guint                   n_other_features;
};

The PangoOTRuleset structure holds all the information needed to build a complete PangoOTRuleset from an OpenType font. The main use of this struct is to act as the key for a per-font hash of rulesets. The user populates a ruleset description and gets the ruleset using pango_ot_ruleset_get_for_description() or create a new one using pango_ot_ruleset_new_from_description().

Since 1.18

enum PangoOTTableType

typedef enum
{
  PANGO_OT_TABLE_GSUB,
  PANGO_OT_TABLE_GPOS
} PangoOTTableType;

The PangoOTTableType enumeration values are used to identify the various OpenType tables in the pango_ot_info_* functions.

struct PangoOTFeatureMap

struct PangoOTFeatureMap {
  char     feature_name[5];
  gulong   property_bit;
};

The PangoOTFeatureMap typedef is used to represent an OpenType feature with the property bit associated with it. The feature tag is represented as a char array instead of a PangoOTTag for convenience.

Since 1.18

PANGO_OT_TAG_MAKE()

#define PANGO_OT_TAG_MAKE(c1,c2,c3,c4)		((PangoOTTag) FT_MAKE_TAG (c1, c2, c3, c4))

Creates a PangoOTTag from four characters. This is similar and compatible with the FT_MAKE_TAG() macro from FreeType.

PANGO_OT_TAG_MAKE_FROM_STRING()

#define             PANGO_OT_TAG_MAKE_FROM_STRING(s)

Creates a PangoOTTag from a string. The string should be at least four characters long (pad with space characters if needed), and need not be nul-terminated. This is a convenience wrapper around PANGO_OT_TAG_MAKE(), but cannot be used in certain situations, for example, as a switch expression, as it dereferences pointers.

PANGO_OT_ALL_GLYPHS

#define PANGO_OT_ALL_GLYPHS			((guint) 0xFFFF)

This is used as the property bit in pango_ot_ruleset_add_feature() when a feature should be applied to all glyphs.

Since 1.16

PANGO_OT_NO_FEATURE

#define PANGO_OT_NO_FEATURE			((guint) 0xFFFF)

This is used as a feature index that represent no feature, that is, should be skipped. It may be returned as feature index by pango_ot_info_find_feature() if the feature is not found, and pango_ot_rulset_add_feature() function automatically skips this value, so no special handling is required by the user.

Since 1.18

PANGO_OT_NO_SCRIPT

#define PANGO_OT_NO_SCRIPT			((guint) 0xFFFF)

This is used as a script index that represent no script, that is, when the requested script was not found, and a default ('DFLT') script was not found either. It may be returned as script index by pango_ot_info_find_script() if the script or a default script are not found, all other functions taking a script index essentially return if the input script index is this value, so no special handling is required by the user.

Since 1.18

PANGO_OT_DEFAULT_LANGUAGE

#define PANGO_OT_DEFAULT_LANGUAGE		((guint) 0xFFFF)

This is used as the language index in pango_ot_info_find_feature() when the default language system of the script is desired. It is also returned by pango_ot_info_find_language() if the requested language is not found, or the requested language tag was PANGO_OT_TAG_DEFAULT_LANGUAGE. The end result is that one can always call pango_ot_tag_from_language() followed by pango_ot_info_find_language() and pass the result to pango_ot_info_find_feature() without having to worry about falling back to default language system explicitly.

Since 1.16

PANGO_OT_TAG_DEFAULT_LANGUAGE

#define PANGO_OT_TAG_DEFAULT_LANGUAGE		PANGO_OT_TAG_MAKE ('d', 'f', 'l', 't')

This is a PangoOTTag representing a special language tag 'dflt'. It is returned as language tag by pango_ot_tag_from_language() if the requested language is not found. It is safe to pass this value to pango_ot_info_find_language() as that function falls back to returning default language-system if the requested language tag is not found.

Since 1.18

PANGO_OT_TAG_DEFAULT_SCRIPT

#define PANGO_OT_TAG_DEFAULT_SCRIPT		PANGO_OT_TAG_MAKE ('D', 'F', 'L', 'T')

This is a PangoOTTag representing the special script tag 'DFLT'. It is returned as script tag by pango_ot_tag_from_script() if the requested script is not found.

Since 1.18

pango_ot_info_get ()

PangoOTInfo *       pango_ot_info_get                   (FT_Face face);

Returns the PangoOTInfo structure for the given FreeType font face.

Since 1.2

pango_ot_info_find_script ()

gboolean            pango_ot_info_find_script           (PangoOTInfo *info,
                                                         PangoOTTableType table_type,
                                                         PangoOTTag script_tag,
                                                         guint *script_index);

Finds the index of a script. If not found, tries to find the 'DFLT' and then 'dflt' scripts and return the index of that in script_index. If none of those is found either, PANGO_OT_NO_SCRIPT is placed in script_index.

All other functions taking an input script_index parameter know how to handle PANGO_OT_NO_SCRIPT, so one can ignore the return value of this function completely and proceed, to enjoy the automatic fallback to the 'DFLT'/'dflt' script.

pango_ot_info_find_language ()

gboolean            pango_ot_info_find_language         (PangoOTInfo *info,
                                                         PangoOTTableType table_type,
                                                         guint script_index,
                                                         PangoOTTag language_tag,
                                                         guint *language_index,
                                                         guint *required_feature_index);

Finds the index of a language and its required feature index. If the language is not found, sets language_index to PANGO_OT_DEFAULT_LANGUAGE and the required feature of the default language system is returned in required_feature_index. For best compatibility with some fonts, also searches the language system tag 'dflt' before falling back to the default language system, but that is transparent to the user. The user can simply ignore the return value of this function to automatically fall back to the default language system.

pango_ot_info_find_feature ()

gboolean            pango_ot_info_find_feature          (PangoOTInfo *info,
                                                         PangoOTTableType table_type,
                                                         PangoOTTag feature_tag,
                                                         guint script_index,
                                                         guint language_index,
                                                         guint *feature_index);

Finds the index of a feature. If the feature is not found, sets feature_index to PANGO_OT_NO_FEATURE, which is safe to pass to pango_ot_ruleset_add_feature() and similar functions.

In the future, this may set feature_index to an special value that if used in pango_ot_ruleset_add_feature() will ask Pango to synthesize the requested feature based on Unicode properties and data. However, this function will still return FALSE in those cases. So, users may want to ignore the return value of this function in certain cases.

pango_ot_info_list_scripts ()

PangoOTTag *        pango_ot_info_list_scripts          (PangoOTInfo *info,
                                                         PangoOTTableType table_type);

Obtains the list of available scripts.

pango_ot_info_list_languages ()

PangoOTTag *        pango_ot_info_list_languages        (PangoOTInfo *info,
                                                         PangoOTTableType table_type,
                                                         guint script_index,
                                                         PangoOTTag language_tag);

Obtains the list of available languages for a given script.

pango_ot_info_list_features ()

PangoOTTag *        pango_ot_info_list_features         (PangoOTInfo *info,
                                                         PangoOTTableType table_type,
                                                         PangoOTTag tag,
                                                         guint script_index,
                                                         guint language_index);

Obtains the list of features for the given language of the given script.

pango_ot_buffer_new ()

PangoOTBuffer *     pango_ot_buffer_new                 (PangoFcFont *font);

Creates a new PangoOTBuffer for the given OpenType font.

Since 1.4

pango_ot_buffer_destroy ()

void                pango_ot_buffer_destroy             (PangoOTBuffer *buffer);

Destroys a PangoOTBuffer and free all associated memory.

Since 1.4

pango_ot_buffer_clear ()

void                pango_ot_buffer_clear               (PangoOTBuffer *buffer);

Empties a PangoOTBuffer, make it ready to add glyphs to.

Since 1.4

pango_ot_buffer_add_glyph ()

void                pango_ot_buffer_add_glyph           (PangoOTBuffer *buffer,
                                                         guint glyph,
                                                         guint properties,
                                                         guint cluster);

Appends a glyph to a PangoOTBuffer, with properties identifying which features should be applied on this glyph. See pango_ruleset_add_feature().

Since 1.4

pango_ot_buffer_set_rtl ()

void                pango_ot_buffer_set_rtl             (PangoOTBuffer *buffer,
                                                         gboolean rtl);

Sets whether glyphs will be rendered right-to-left. This setting is needed for proper horizontal positioning of right-to-left scripts.

Since 1.4

pango_ot_buffer_set_zero_width_marks ()

void                pango_ot_buffer_set_zero_width_marks
                                                        (PangoOTBuffer *buffer,
                                                         gboolean zero_width_marks);

Sets whether characters with a mark class should be forced to zero width. This setting is needed for proper positioning of Arabic accents, but will produce incorrect results with standard OpenType Indic fonts.

Since 1.6

pango_ot_buffer_get_glyphs ()

void                pango_ot_buffer_get_glyphs          (const PangoOTBuffer *buffer,
                                                         PangoOTGlyph **glyphs,
                                                         int *n_glyphs);

Gets the glyph array contained in a PangoOTBuffer. The glyphs are owned by the buffer and should not be freed, and are only valid as long as buffer is not modified.

Since 1.4

pango_ot_buffer_output ()

void                pango_ot_buffer_output              (const PangoOTBuffer *buffer,
                                                         PangoGlyphString *glyphs);

Exports the glyphs in a PangoOTBuffer into a PangoGlyphString. This is typically used after the OpenType layout processing is over, to convert the resulting glyphs into a generic Pango glyph string.

Since 1.4

pango_ot_ruleset_get_for_description ()

const PangoOTRuleset * pango_ot_ruleset_get_for_description
                                                        (PangoOTInfo *info,
                                                         const PangoOTRulesetDescription *desc);

Returns a ruleset for the given OpenType info and ruleset description. Rulesets are created on demand using pango_ot_ruleset_new_from_description(). The returned ruleset should not be modified or destroyed.

The static feature map members of desc should be alive as long as info is.

Since 1.18

pango_ot_ruleset_new ()

PangoOTRuleset *    pango_ot_ruleset_new                (PangoOTInfo *info);

Creates a new PangoOTRuleset for the given OpenType info.

pango_ot_ruleset_new_for ()

PangoOTRuleset *    pango_ot_ruleset_new_for            (PangoOTInfo *info,
                                                         PangoScript script,
                                                         PangoLanguage *language);

Creates a new PangoOTRuleset for the given OpenType info, script, and language.

This function is part of a convenience scheme that highly simplifies using a PangoOTRuleset to represent features for a specific pair of script and language. So one can use this function passing in the script and language of interest, and later try to add features to the ruleset by just specifying the feature name or tag, without having to deal with finding script, language, or feature indices manually.

In excess to what pango_ot_ruleset_new() does, this function will:

Because of the way return values of pango_ot_info_find_script() and pango_ot_info_find_language() are ignored, this function automatically finds and uses the 'DFLT' script and the default language-system.

Since 1.18

pango_ot_ruleset_new_from_description ()

PangoOTRuleset *    pango_ot_ruleset_new_from_description
                                                        (PangoOTInfo *info,
                                                         const PangoOTRulesetDescription *desc);

Creates a new PangoOTRuleset for the given OpenType infor and matching the given ruleset description.

This is a convenience function that calls pango_ot_ruleset_new_for() and adds the static GSUB/GPOS features to the resulting ruleset, followed by adding other features to both GSUB and GPOS.

The static feature map members of desc should be alive as long as info is.

Since 1.18

pango_ot_ruleset_add_feature ()

void                pango_ot_ruleset_add_feature        (PangoOTRuleset *ruleset,
                                                         PangoOTTableType table_type,
                                                         guint feature_index,
                                                         gulong property_bit);

Adds a feature to the ruleset.

pango_ot_ruleset_maybe_add_feature ()

gboolean            pango_ot_ruleset_maybe_add_feature  (PangoOTRuleset *ruleset,
                                                         PangoOTTableType table_type,
                                                         PangoOTTag feature_tag,
                                                         gulong property_bit);

This is a convenience function that first tries to find the feature using pango_ot_info_find_feature() and the ruleset script and language passed to pango_ot_ruleset_new_for(), and if the feature is found, adds it to the ruleset.

If ruleset was not created using pango_ot_ruleset_new_for(), this function does nothing.

Since 1.18

pango_ot_ruleset_maybe_add_features ()

guint               pango_ot_ruleset_maybe_add_features (PangoOTRuleset *ruleset,
                                                         PangoOTTableType table_type,
                                                         const PangoOTFeatureMap *features,
                                                         guint n_features);

This is a convenience function that for each feature in the feature map array features converts the feature name to a PangoOTTag feature tag using PANGO_OT_TAG_MAKE() and calls pango_ot_ruleset_maybe_add_feature() on it.

Since 1.18

pango_ot_ruleset_get_feature_count ()

guint               pango_ot_ruleset_get_feature_count  (const PangoOTRuleset *ruleset,
                                                         guint *n_gsub_features,
                                                         guint *n_gpos_features);

Gets the number of GSUB and GPOS features in the ruleset.

Since 1.18

pango_ot_ruleset_substitute ()

void                pango_ot_ruleset_substitute         (const PangoOTRuleset *ruleset,
                                                         PangoOTBuffer *buffer);

Performs the OpenType GSUB substitution on buffer using the features in ruleset

Since 1.4

pango_ot_ruleset_position ()

void                pango_ot_ruleset_position           (const PangoOTRuleset *ruleset,
                                                         PangoOTBuffer *buffer);

Performs the OpenType GPOS positioning on buffer using the features in ruleset

Since 1.4

pango_ot_ruleset_description_copy ()

PangoOTRulesetDescription * pango_ot_ruleset_description_copy
                                                        (const PangoOTRulesetDescription *desc);

Creates a copy of desc, which should be freed with pango_ot_ruleset_description_free(). Primarily used internally by pango_ot_ruleset_get_for_description() to cache rulesets for ruleset descriptions.

Since 1.18

pango_ot_ruleset_description_equal ()

gboolean            pango_ot_ruleset_description_equal  (const PangoOTRulesetDescription *desc1,
                                                         const PangoOTRulesetDescription *desc2);

Compares two ruleset descriptions for equality. Two ruleset descriptions are considered equal if the rulesets they describe are provably identical. This means that their script, language, and all feature sets should be equal. For static feature sets, the array addresses are compared directly, while for other features, the list of features is compared one by one. (Two ruleset descriptions may result in identical rulesets being created, but still compare FALSE.)

Since 1.18

pango_ot_ruleset_description_free ()

void                pango_ot_ruleset_description_free   (PangoOTRulesetDescription *desc);

Frees a ruleset description allocated by pango_ot_ruleset_description_copy().

Since 1.18

pango_ot_ruleset_description_hash ()

guint               pango_ot_ruleset_description_hash   (const PangoOTRulesetDescription *desc);

Computes a hash of a PangoOTRulesetDescription structure suitable to be used, for example, as an argument to g_hash_table_new().

Since 1.18

pango_ot_tag_from_language ()

PangoOTTag          pango_ot_tag_from_language          (PangoLanguage *language);

Finds the OpenType language-system tag best describing language.

Since 1.18

pango_ot_tag_from_script ()

PangoOTTag          pango_ot_tag_from_script            (PangoScript script);

Finds the OpenType script tag corresponding to script.

The PANGO_SCRIPT_COMMON, PANGO_SCRIPT_INHERITED, and PANGO_SCRIPT_UNKNOWN scripts are mapped to the OpenType 'DFLT' script tag that is also defined as PANGO_OT_TAG_DEFAULT_SCRIPT.

Note that multiple PangoScript values may map to the same OpenType script tag. In particular, PANGO_SCRIPT_HIRAGANA and PANGO_SCRIPT_KATAKANA both map to the OT tag 'kana'.

Since 1.18

pango_ot_tag_to_language ()

PangoLanguage *     pango_ot_tag_to_language            (PangoOTTag language_tag);

Finds a PangoLanguage corresponding to language_tag.

Since 1.18

pango_ot_tag_to_script ()

PangoScript         pango_ot_tag_to_script              (PangoOTTag script_tag);

Finds the PangoScript corresponding to script_tag.

The 'DFLT' script tag is mapped to PANGO_SCRIPT_COMMON.

Note that an OpenType script tag may correspond to multiple PangoScript values. In such cases, the PangoScript value with the smallest value is returned. In particular, PANGO_SCRIPT_HIRAGANA and PANGO_SCRIPT_KATAKANA both map to the OT tag 'kana'. This function will return PANGO_SCRIPT_HIRAGANA for 'kana'.

Since 1.18