diff --git a/src/hb-aat-layout.cc b/src/hb-aat-layout.cc
index fac510e9e..0d667d750 100644
--- a/src/hb-aat-layout.cc
+++ b/src/hb-aat-layout.cc
@@ -79,13 +79,18 @@ AAT::hb_aat_apply_context_t::set_ankr_table (const AAT::ankr *ankr_table_)
  * @short_description: Apple Advanced Typography Layout
  * @include: hb-aat.h
  *
- * Functions for querying OpenType Layout features in the font face.
+ * Functions for querying AAT Layout features in the font face. 
+ *
+ * HarfBuzz supports all of the AAT tables used to implement shaping. Other
+ * AAT tables and their associated features are not supported.
  **/
 
 
 #if !defined(HB_NO_AAT) || defined(HAVE_CORETEXT)
 
-/* Table data courtesy of Apple.  Converted from mnemonics to integers
+/* Mapping from OpenType feature tags to AAT feature names and selectors.
+ *
+ * Table data courtesy of Apple.  Converted from mnemonics to integers
  * when moving to this file. */
 static const hb_aat_feature_mapping_t feature_mappings[] =
 {
@@ -167,6 +172,17 @@ static const hb_aat_feature_mapping_t feature_mappings[] =
   {HB_TAG ('z','e','r','o'), HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS,      HB_AAT_LAYOUT_FEATURE_SELECTOR_SLASHED_ZERO_ON,                HB_AAT_LAYOUT_FEATURE_SELECTOR_SLASHED_ZERO_OFF},
 };
 
+/** 
+ * hb_aat_layout_find_feature_mapping:
+ * @tag: The requested #hb_tag_t feature tag
+ *
+ * Fetches the AAT feature-and-selector combination that corresponds
+ * to a given OpenType feature tag.
+ *  
+ * Return value: the AAT features and selectors corresponding to the
+ * OpenType feature tag queried
+ *
+ **/
 const hb_aat_feature_mapping_t *
 hb_aat_layout_find_feature_mapping (hb_tag_t tag)
 {
@@ -204,9 +220,15 @@ hb_aat_layout_compile_map (const hb_aat_map_builder_t *mapper,
 
 /*
  * hb_aat_layout_has_substitution:
- * @face:
+ * @face: #hb_face_t to work upon
+ *
+ * Tests whether the specified face includes any substitutions in the
+ * `morx` or `mort` tables.
+ *
+ * <note>Note: does not examine the `GSUB` table.</note>
+ *
+ * Return value: true if data found, false otherwise
  *
- * Returns:
  * Since: 2.3.0
  */
 hb_bool_t
@@ -265,9 +287,15 @@ hb_aat_layout_remove_deleted_glyphs (hb_buffer_t *buffer)
 
 /*
  * hb_aat_layout_has_positioning:
- * @face:
+ * @face: #hb_face_t to work upon
+ *
+ * Tests whether the specified face includes any positioning information
+ * in the `kerx` table.
+ *
+ * <note>Note: does not examine the `GPOS` table.</note>
+ *
+ * Return value: true if data found, false otherwise
  *
- * Returns:
  * Since: 2.3.0
  */
 hb_bool_t
@@ -292,9 +320,13 @@ hb_aat_layout_position (const hb_ot_shape_plan_t *plan,
 
 /*
  * hb_aat_layout_has_tracking:
- * @face:
+ * @face:: #hb_face_t to work upon
+ *
+ * Tests whether the specified face includes any tracking information
+ * in the `trak` table.
+ *
+ * Return value: true if data found, false otherwise
  *
- * Returns:
  * Since: 2.3.0
  */
 hb_bool_t
@@ -316,10 +348,13 @@ hb_aat_layout_track (const hb_ot_shape_plan_t *plan,
 
 /**
  * hb_aat_layout_get_feature_types:
- * @face: a face object
- * @start_offset: iteration's start offset
- * @feature_count:(inout) (allow-none): buffer size as input, filled size as output
- * @features: (out caller-allocates) (array length=feature_count): features buffer
+ * @face: #hb_face_t to work upon
+ * @start_offset: offset of the first feature type to retrieve
+ * @feature_count: (inout) (allow-none): Input = the maximum number of feature types to return;
+ *                 Output = the actual number of feature types returned (may be zero)
+ * @features: (out caller-allocates) (array length=feature_count): Array of feature types found
+ *
+ * Fetches a list of the AAT feature types included in the specified face.
  *
  * Return value: Number of all available feature types.
  *
@@ -336,10 +371,12 @@ hb_aat_layout_get_feature_types (hb_face_t                    *face,
 
 /**
  * hb_aat_layout_feature_type_get_name_id:
- * @face: a face object
- * @feature_type: feature id
+ * @face: #hb_face_t to work upon
+ * @feature_type: The #hb_aat_layout_feature_type_t of the requested feature type
  *
- * Return value: Name ID index
+ * Fetches the name ID of the specified feature type in the face's `name` table.
+ *
+ * Return value: Name ID of the requested feature type
  *
  * Since: 2.2.0
  */
@@ -352,18 +389,22 @@ hb_aat_layout_feature_type_get_name_id (hb_face_t                    *face,
 
 /**
  * hb_aat_layout_feature_type_get_selectors:
- * @face:    a face object
- * @feature_type: feature id
- * @start_offset:    iteration's start offset
- * @selector_count: (inout) (allow-none): buffer size as input, filled size as output
- * @selectors: (out caller-allocates) (array length=selector_count): settings buffer
- * @default_index: (out) (allow-none): index of default selector if any
+ * @face: #hb_face_t to work upon
+ * @feature_type: The #hb_aat_layout_feature_type_t of the requested feature type
+ * @start_offset: offset of the first feature type to retrieve
+ * @selector_count: (inout) (allow-none): Input = the maximum number of selectors to return;
+ *                  Output = the actual number of selectors returned (may be zero)
+ * @selectors: (out caller-allocates) (array length=selector_count): A buffer pointer.
+ *             The selectors available for the feature type queries.
+ * @default_index: (out) (allow-none): The index of the feature's default selector, if any
+ *
+ * Fetches a list of the selectors available for the specified feature in the given face.
  *
  * If upon return, @default_index is set to #HB_AAT_LAYOUT_NO_SELECTOR_INDEX, then
  * the feature type is non-exclusive.  Otherwise, @default_index is the index of
  * the selector that is selected by default.
  *
- * Return value: Number of all available feature selectors.
+ * Return value: Number of all available feature selectors
  *
  * Since: 2.2.0
  */
diff --git a/src/hb-aat-layout.h b/src/hb-aat-layout.h
index b617e8b70..89acb3544 100644
--- a/src/hb-aat-layout.h
+++ b/src/hb-aat-layout.h
@@ -37,7 +37,48 @@ HB_BEGIN_DECLS
 
 /**
  * hb_aat_layout_feature_type_t:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_INVALID: Initial, unset feature type
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_ALL_TYPOGRAPHIC:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CURISVE_CONNECTION:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_LETTER_CASE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_SUBSTITUTION:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_LINGUISTIC_REARRANGEMENT:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_SPACING:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_DIACRITICS_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_POSITION:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_FRACTIONS:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_OVERLAPPING_CHARACTERS_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_ALTERNATIVES:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_DESIGN_COMPLEXITY_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_STYLE_OPTIONS:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_CASE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_KANA_SPACING_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_SPACING_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_UNICODE_DECOMPOSITION_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_RUBY_KANA:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CJK_SYMBOL_ALTERNATIVES_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_ALTERNATIVES_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CJK_VERTICAL_ROMAN_PLACEMENT_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_ITALIC_CJK_ROMAN:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CASE_SENSITIVE_LAYOUT:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_ALTERNATE_KANA:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CONTEXTUAL_ALTERNATIVES:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_LOWER_CASE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_UPPER_CASE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_LANGUAGE_TAG_TYPE:
+ * @HB_AAT_LAYOUT_FEATURE_TYPE_CJK_ROMAN_SPACING_TYPE:
  *
+ * The possible feature types defined for AAT shaping.
  *
  * Since: 2.2.0
  */
@@ -85,12 +126,265 @@ typedef enum
   HB_AAT_LAYOUT_FEATURE_TYPE_LANGUAGE_TAG_TYPE			= 39,
   HB_AAT_LAYOUT_FEATURE_TYPE_CJK_ROMAN_SPACING_TYPE		= 103,
 
+  /*< private >*/
   _HB_AAT_LAYOUT_FEATURE_TYPE_MAX_VALUE = HB_TAG_MAX_SIGNED /*< skip >*/
 } hb_aat_layout_feature_type_t;
 
 /**
  * hb_aat_layout_feature_selector_t:
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INVALID: Initial, unset feature selector
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALL_TYPE_FEATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_ALL_TYPOGRAPHIC
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALL_TYPE_FEATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_ALL_TYPOGRAPHIC
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_REQUIRED_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_REQUIRED_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_COMMON_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_COMMON_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_RARE_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_RARE_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LOGOS_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LOGOS_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_REBUS_PICTURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_REBUS_PICTURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DIPHTHONG_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DIPHTHONG_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SQUARED_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SQUARED_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ABBREV_SQUARED_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ABBREV_SQUARED_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SYMBOL_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SYMBOL_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CONTEXTUAL_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CONTEXTUAL_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HISTORICAL_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HISTORICAL_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_UNCONNECTED: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PARTIALLY_CONNECTED: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CURSIVE: for #HB_AAT_LAYOUT_FEATURE_TYPE_LIGATURES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_UPPER_AND_LOWER_CASE: Deprecated
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALL_CAPS: Deprecated
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALL_LOWER_CASE: Deprecated
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SMALL_CAPS: Deprecated
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INITIAL_CAPS: Deprecated
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INITIAL_CAPS_AND_SMALL_CAPS: Deprecated
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SUBSTITUTE_VERTICAL_FORMS_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_SUBSTITUTION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SUBSTITUTE_VERTICAL_FORMS_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_SUBSTITUTION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LINGUISTIC_REARRANGEMENT_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_LINGUISTIC_REARRANGEMENT
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LINGUISTIC_REARRANGEMENT_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_LINGUISTIC_REARRANGEMENT
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_MONOSPACED_NUMBERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PROPORTIONAL_NUMBERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_THIRD_WIDTH_NUMBERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_QUARTER_WIDTH_NUMBERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_WORD_INITIAL_SWASHES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_WORD_INITIAL_SWASHES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_WORD_FINAL_SWASHES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_WORD_FINAL_SWASHES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LINE_INITIAL_SWASHES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LINE_INITIAL_SWASHES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LINE_FINAL_SWASHES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LINE_FINAL_SWASHES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NON_FINAL_SWASHES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NON_FINAL_SWASHES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_SMART_SWASH_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SHOW_DIACRITICS: for #HB_AAT_LAYOUT_FEATURE_TYPE_DIACRITICS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HIDE_DIACRITICS: for #HB_AAT_LAYOUT_FEATURE_TYPE_DIACRITICS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DECOMPOSE_DIACRITICS: for #HB_AAT_LAYOUT_FEATURE_TYPE_DIACRITICS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NORMAL_POSITION: for #HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_POSITION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SUPERIORS: for #HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_POSITION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INFERIORS: for #HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_POSITION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ORDINALS: for #HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_POSITION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SCIENTIFIC_INFERIORS: for #HB_AAT_LAYOUT_FEATURE_TYPE_VERTICAL_POSITION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_FRACTIONS: for #HB_AAT_LAYOUT_FEATURE_TYPE_FRACTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_VERTICAL_FRACTIONS: for #HB_AAT_LAYOUT_FEATURE_TYPE_FRACTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DIAGONAL_FRACTIONS: for #HB_AAT_LAYOUT_FEATURE_TYPE_FRACTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PREVENT_OVERLAP_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_OVERLAPPING_CHARACTERS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PREVENT_OVERLAP_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_OVERLAPPING_CHARACTERS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HYPHENS_TO_EM_DASH_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HYPHENS_TO_EM_DASH_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HYPHEN_TO_EN_DASH_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HYPHEN_TO_EN_DASH_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SLASHED_ZERO_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SLASHED_ZERO_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_FORM_INTERROBANG_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_FORM_INTERROBANG_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SMART_QUOTES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SMART_QUOTES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PERIODS_TO_ELLIPSIS_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PERIODS_TO_ELLIPSIS_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_TYPOGRAPHIC_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HYPHEN_TO_MINUS_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HYPHEN_TO_MINUS_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ASTERISK_TO_MULTIPLY_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ASTERISK_TO_MULTIPLY_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SLASH_TO_DIVIDE_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SLASH_TO_DIVIDE_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INEQUALITY_LIGATURES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INEQUALITY_LIGATURES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_EXPONENTS_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_EXPONENTS_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_MATHEMATICAL_GREEK_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_MATHEMATICAL_GREEK_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_MATHEMATICAL_EXTRAS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_ORNAMENTS: for #HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DINGBATS: for #HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PI_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_FLEURONS: for #HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DECORATIVE_BORDERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INTERNATIONAL_SYMBOLS: for #HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_MATH_SYMBOLS: for #HB_AAT_LAYOUT_FEATURE_TYPE_ORNAMENT_SETS_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_ALTERNATES: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DESIGN_LEVEL1: for #HB_AAT_LAYOUT_FEATURE_TYPE_DESIGN_COMPLEXITY_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DESIGN_LEVEL2: for #HB_AAT_LAYOUT_FEATURE_TYPE_DESIGN_COMPLEXITY_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DESIGN_LEVEL3: for #HB_AAT_LAYOUT_FEATURE_TYPE_DESIGN_COMPLEXITY_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DESIGN_LEVEL4: for #HB_AAT_LAYOUT_FEATURE_TYPE_DESIGN_COMPLEXITY_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DESIGN_LEVEL5: for #HB_AAT_LAYOUT_FEATURE_TYPE_DESIGN_COMPLEXITY_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_STYLE_OPTIONS: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLE_OPTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DISPLAY_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLE_OPTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ENGRAVED_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLE_OPTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ILLUMINATED_CAPS: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLE_OPTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TITLING_CAPS: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLE_OPTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TALL_CAPS: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLE_OPTIONS
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRADITIONAL_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SIMPLIFIED_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_JIS1978_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_JIS1983_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_JIS1990_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRADITIONAL_ALT_ONE: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRADITIONAL_ALT_TWO: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRADITIONAL_ALT_THREE: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRADITIONAL_ALT_FOUR: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRADITIONAL_ALT_FIVE: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_EXPERT_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_JIS2004_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HOJO_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NLCCHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRADITIONAL_NAMES_CHARACTERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_CHARACTER_SHAPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LOWER_CASE_NUMBERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_UPPER_CASE_NUMBERS: for #HB_AAT_LAYOUT_FEATURE_TYPE_NUMBER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PROPORTIONAL_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_MONOSPACED_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HALF_WIDTH_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_THIRD_WIDTH_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_QUARTER_WIDTH_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALT_PROPORTIONAL_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALT_HALF_WIDTH_TEXT: for #HB_AAT_LAYOUT_FEATURE_TYPE_TEXT_SPACING
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_TRANSLITERATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HANJA_TO_HANGUL: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HIRAGANA_TO_KATAKANA: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_KATAKANA_TO_HIRAGANA: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_KANA_TO_ROMANIZATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ROMANIZATION_TO_HIRAGANA: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ROMANIZATION_TO_KATAKANA: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HANJA_TO_HANGUL_ALT_ONE: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HANJA_TO_HANGUL_ALT_TWO: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HANJA_TO_HANGUL_ALT_THREE: for #HB_AAT_LAYOUT_FEATURE_TYPE_TRANSLITERATION
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_BOX_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ROUNDED_BOX_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CIRCLE_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INVERTED_CIRCLE_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PARENTHESIS_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PERIOD_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ROMAN_NUMERAL_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DIAMOND_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INVERTED_BOX_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_INVERTED_ROUNDED_BOX_ANNOTATION: for #HB_AAT_LAYOUT_FEATURE_TYPE_ANNOTATION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_FULL_WIDTH_KANA: for #HB_AAT_LAYOUT_FEATURE_TYPE_KANA_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PROPORTIONAL_KANA: for #HB_AAT_LAYOUT_FEATURE_TYPE_KANA_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_FULL_WIDTH_IDEOGRAPHS: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PROPORTIONAL_IDEOGRAPHS: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HALF_WIDTH_IDEOGRAPHS: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CANONICAL_COMPOSITION_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_UNICODE_DECOMPOSITION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CANONICAL_COMPOSITION_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_UNICODE_DECOMPOSITION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_COMPATIBILITY_COMPOSITION_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_UNICODE_DECOMPOSITION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_COMPATIBILITY_COMPOSITION_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_UNICODE_DECOMPOSITION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRANSCODING_COMPOSITION_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_UNICODE_DECOMPOSITION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_TRANSCODING_COMPOSITION_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_UNICODE_DECOMPOSITION_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_RUBY_KANA: Deprecated; use #HB_AAT_LAYOUT_FEATURE_SELECTOR_RUBY_KANA_OFF instead
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_RUBY_KANA: Deprecated; use #HB_AAT_LAYOUT_FEATURE_SELECTOR_RUBY_KANA_ON instead
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_RUBY_KANA_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_RUBY_KANA
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_RUBY_KANA_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_RUBY_KANA
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_CJK_SYMBOL_ALTERNATIVES: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_SYMBOL_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_SYMBOL_ALT_ONE: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_SYMBOL_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_SYMBOL_ALT_TWO: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_SYMBOL_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_SYMBOL_ALT_THREE: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_SYMBOL_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_SYMBOL_ALT_FOUR: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_SYMBOL_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_SYMBOL_ALT_FIVE: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_SYMBOL_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_IDEOGRAPHIC_ALTERNATIVES: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_IDEOGRAPHIC_ALT_ONE: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_IDEOGRAPHIC_ALT_TWO: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_IDEOGRAPHIC_ALT_THREE: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_IDEOGRAPHIC_ALT_FOUR: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_IDEOGRAPHIC_ALT_FIVE: for #HB_AAT_LAYOUT_FEATURE_TYPE_IDEOGRAPHIC_ALTERNATIVES_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_VERTICAL_ROMAN_CENTERED: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_VERTICAL_ROMAN_PLACEMENT_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_VERTICAL_ROMAN_HBASELINE: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_VERTICAL_ROMAN_PLACEMENT_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_CJK_ITALIC_ROMAN: Deprecated; use #HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_ITALIC_ROMAN_OFF instead
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_ITALIC_ROMAN: Deprecated; use #HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_ITALIC_ROMAN_ON instead
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_ITALIC_ROMAN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_ITALIC_CJK_ROMAN
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CJK_ITALIC_ROMAN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_ITALIC_CJK_ROMAN
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CASE_SENSITIVE_LAYOUT_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_CASE_SENSITIVE_LAYOUT
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CASE_SENSITIVE_LAYOUT_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_CASE_SENSITIVE_LAYOUT
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CASE_SENSITIVE_SPACING_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_CASE_SENSITIVE_LAYOUT
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CASE_SENSITIVE_SPACING_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_CASE_SENSITIVE_LAYOUT
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALTERNATE_HORIZ_KANA_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_ALTERNATE_KANA
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALTERNATE_HORIZ_KANA_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_ALTERNATE_KANA
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALTERNATE_VERT_KANA_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_ALTERNATE_KANA
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_ALTERNATE_VERT_KANA_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_ALTERNATE_KANA
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_NO_STYLISTIC_ALTERNATES: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_ONE_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_ONE_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TWO_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TWO_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_THREE_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_THREE_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FOUR_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FOUR_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FIVE_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FIVE_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SIX_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SIX_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SEVEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SEVEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_EIGHT_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_EIGHT_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_NINE_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_NINE_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_ELEVEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_ELEVEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TWELVE_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TWELVE_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_THIRTEEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_THIRTEEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FOURTEEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FOURTEEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FIFTEEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_FIFTEEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SIXTEEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SIXTEEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SEVENTEEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_SEVENTEEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_EIGHTEEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_EIGHTEEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_NINETEEN_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_NINETEEN_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TWENTY_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_STYLISTIC_ALT_TWENTY_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_STYLISTIC_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CONTEXTUAL_ALTERNATES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_CONTEXTUAL_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CONTEXTUAL_ALTERNATES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_CONTEXTUAL_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SWASH_ALTERNATES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_CONTEXTUAL_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_SWASH_ALTERNATES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_CONTEXTUAL_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CONTEXTUAL_SWASH_ALTERNATES_ON: for #HB_AAT_LAYOUT_FEATURE_TYPE_CONTEXTUAL_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_CONTEXTUAL_SWASH_ALTERNATES_OFF: for #HB_AAT_LAYOUT_FEATURE_TYPE_CONTEXTUAL_ALTERNATIVES
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DEFAULT_LOWER_CASE: for #HB_AAT_LAYOUT_FEATURE_TYPE_LOWER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LOWER_CASE_SMALL_CAPS: for #HB_AAT_LAYOUT_FEATURE_TYPE_LOWER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_LOWER_CASE_PETITE_CAPS: for #HB_AAT_LAYOUT_FEATURE_TYPE_LOWER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DEFAULT_UPPER_CASE: for #HB_AAT_LAYOUT_FEATURE_TYPE_UPPER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_UPPER_CASE_SMALL_CAPS: for #HB_AAT_LAYOUT_FEATURE_TYPE_UPPER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_UPPER_CASE_PETITE_CAPS: for #HB_AAT_LAYOUT_FEATURE_TYPE_UPPER_CASE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_HALF_WIDTH_CJK_ROMAN: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_ROMAN_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_PROPORTIONAL_CJK_ROMAN: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_ROMAN_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_DEFAULT_CJK_ROMAN: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_ROMAN_SPACING_TYPE
+ * @HB_AAT_LAYOUT_FEATURE_SELECTOR_FULL_WIDTH_CJK_ROMAN: for #HB_AAT_LAYOUT_FEATURE_TYPE_CJK_ROMAN_SPACING_TYPE
  *
+ * The selectors defined for specifying AAT feature settings.
  *
  * Since: 2.2.0
  */
@@ -424,6 +718,7 @@ typedef enum
   HB_AAT_LAYOUT_FEATURE_SELECTOR_DEFAULT_CJK_ROMAN		= 2,
   HB_AAT_LAYOUT_FEATURE_SELECTOR_FULL_WIDTH_CJK_ROMAN		= 3,
 
+  /*< private >*/
   _HB_AAT_LAYOUT_FEATURE_SELECTOR_MAX_VALUE = HB_TAG_MAX_SIGNED /*< skip >*/
 } hb_aat_layout_feature_selector_t;
 
@@ -446,6 +741,13 @@ typedef struct hb_aat_layout_feature_selector_info_t
   unsigned int				reserved;
 } hb_aat_layout_feature_selector_info_t;
 
+/**
+ * HB_AAT_LAYOUT_NO_SELECTOR_INDEX
+ *
+ * Used when getting or setting AAT feature selectors. Indicates that
+ * there is no selector index corresponding to the selector of interest.
+ *
+ */
 #define HB_AAT_LAYOUT_NO_SELECTOR_INDEX		0xFFFFu
 
 HB_EXTERN unsigned int