C API: add OpenType script selection and feature queries

harfrust_capi/README.md

@@ -101,7 +101,10 @@ along with the tags, directions, scripts, languages, features and variations
 they need. OpenType `BASE` baseline queries are available through
 `hr_ot_layout_get_baseline` and its related functions. OpenType `MATH` queries
 are available through `hr_ot_math_*` functions. Layout lookup queries support
-glyph participation checks. The complete HarfBuzz set and map APIs are available
+glyph participation checks. Script selection and language-specific feature lookup
+are available with `hr_ot_layout_table_select_script` and
+`hr_ot_layout_language_find_feature`; `hr_ot_layout_table_get_feature_tags`
+enumerates all feature records, including duplicate tags. The complete HarfBuzz set and map APIs are available
 as `hr_set_*` and `hr_map_*`, including inverted sets, ranges, set algebra, and
 iteration. OpenType script and language tags can be converted with
 `hr_ot_tag_to_language` and `hr_ot_tags_from_script_and_language`.

harfrust_capi/include/hr-hb-ot.h

@@ -14,8 +14,11 @@
 #define hb_ot_layout_get_horizontal_baseline_tag_for_script hr_ot_layout_get_horizontal_baseline_tag_for_script
 #define hb_ot_layout_has_positioning                     hr_ot_layout_has_positioning
 #define hb_ot_layout_has_substitution                    hr_ot_layout_has_substitution
+#define hb_ot_layout_language_find_feature               hr_ot_layout_language_find_feature
 #define hb_ot_layout_lookup_collect_glyphs               hr_ot_layout_lookup_collect_glyphs
+#define hb_ot_layout_table_get_feature_tags              hr_ot_layout_table_get_feature_tags
 #define hb_ot_layout_table_get_lookup_count              hr_ot_layout_table_get_lookup_count
+#define hb_ot_layout_table_select_script                 hr_ot_layout_table_select_script
 #define hb_ot_math_constant_t                            hr_ot_math_constant_t
 #define hb_ot_math_get_constant                          hr_ot_math_get_constant
 #define hb_ot_math_get_glyph_assembly                    hr_ot_math_get_glyph_assembly
@@ -46,6 +49,9 @@
 #define HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT HR_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT
 #define HB_OT_LAYOUT_BASELINE_TAG_MATH                HR_OT_LAYOUT_BASELINE_TAG_MATH
 #define HB_OT_LAYOUT_BASELINE_TAG_ROMAN               HR_OT_LAYOUT_BASELINE_TAG_ROMAN
+#define HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX           HR_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX
+#define HB_OT_LAYOUT_NO_FEATURE_INDEX                 HR_OT_LAYOUT_NO_FEATURE_INDEX
+#define HB_OT_LAYOUT_NO_SCRIPT_INDEX                  HR_OT_LAYOUT_NO_SCRIPT_INDEX
 #define HB_OT_MATH_CONSTANT_ACCENT_BASE_HEIGHT        HR_OT_MATH_CONSTANT_ACCENT_BASE_HEIGHT
 #define HB_OT_MATH_CONSTANT_AXIS_HEIGHT               HR_OT_MATH_CONSTANT_AXIS_HEIGHT
 #define HB_OT_MATH_CONSTANT_DELIMITED_SUB_FORMULA_MIN_HEIGHT HR_OT_MATH_CONSTANT_DELIMITED_SUB_FORMULA_MIN_HEIGHT
@@ -107,6 +113,10 @@
 #define HB_OT_MATH_KERN_BOTTOM_RIGHT                  HR_OT_MATH_KERN_BOTTOM_RIGHT
 #define HB_OT_MATH_KERN_TOP_LEFT                      HR_OT_MATH_KERN_TOP_LEFT
 #define HB_OT_MATH_KERN_TOP_RIGHT                     HR_OT_MATH_KERN_TOP_RIGHT
+#define HB_OT_TAG_DEFAULT_LANGUAGE                    HR_OT_TAG_DEFAULT_LANGUAGE
+#define HB_OT_TAG_DEFAULT_SCRIPT                      HR_OT_TAG_DEFAULT_SCRIPT
+#define HB_OT_TAG_GPOS                                HR_OT_TAG_GPOS
+#define HB_OT_TAG_GSUB                                HR_OT_TAG_GSUB
 #define HB_OT_TAG_MATH                                HR_OT_TAG_MATH
 #define HB_OT_TAG_MATH_SCRIPT                         HR_OT_TAG_MATH_SCRIPT
 

harfrust_capi/include/hr-hb.h

@@ -16,7 +16,7 @@
  * macros below would rewrite HarfBuzz's own declarations. Include one or the
  * other.
  *
- * Shaping, BASE baseline, MATH, layout lookup, set, map, and OpenType tag
+ * Shaping, BASE baseline, MATH, layout script/feature/lookup, set, map, and OpenType tag
  * conversion APIs are covered.
  * Anything else HarfBuzz offers -- drawing and painting callbacks,
  * subsetting, other layout table introspection, custom Unicode
@@ -378,6 +378,7 @@
 #define HB_GLYPH_FLAG_UNSAFE_TO_CONCAT                HR_GLYPH_FLAG_UNSAFE_TO_CONCAT
 #define HB_LANGUAGE_INVALID                           HR_LANGUAGE_INVALID
 #define HB_MAP_VALUE_INVALID                          HR_MAP_VALUE_INVALID
+#define HB_MATH_GLYPH_PART_FLAG_EXTENDER              HR_MATH_GLYPH_PART_FLAG_EXTENDER
 #define HB_MEMORY_MODE_DUPLICATE                      HR_MEMORY_MODE_DUPLICATE
 #define HB_MEMORY_MODE_READONLY                       HR_MEMORY_MODE_READONLY
 #define HB_MEMORY_MODE_READONLY_MAY_MAKE_WRITABLE     HR_MEMORY_MODE_READONLY_MAY_MAKE_WRITABLE

harfrust_capi/include/hr.h

@@ -36,6 +36,21 @@
  */
 #define HR_FEATURE_GLOBAL_END 4294967295
 
+/**
+ * No script was selected.
+ */
+#define HR_OT_LAYOUT_NO_SCRIPT_INDEX 65535
+
+/**
+ * No feature was found.
+ */
+#define HR_OT_LAYOUT_NO_FEATURE_INDEX 65535
+
+/**
+ * Selects a script's default language system.
+ */
+#define HR_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX 65535
+
 /**
  * The major version of this library.
  *
@@ -1662,6 +1677,26 @@ typedef struct hr_ot_math_glyph_part_t {
  */
 #define HR_MAP_VALUE_INVALID HR_CODEPOINT_INVALID
 
+/**
+ * The OpenType substitution table tag.
+ */
+#define HR_OT_TAG_GSUB 1196643650
+
+/**
+ * The OpenType positioning table tag.
+ */
+#define HR_OT_TAG_GPOS 1196445523
+
+/**
+ * The default OpenType script tag, `DFLT`.
+ */
+#define HR_OT_TAG_DEFAULT_SCRIPT 1145457748
+
+/**
+ * The default OpenType language tag, `dflt`.
+ */
+#define HR_OT_TAG_DEFAULT_LANGUAGE 1684434036
+
 #define HR_OT_LAYOUT_BASELINE_TAG_ROMAN 1919905134
 
 #define HR_OT_LAYOUT_BASELINE_TAG_HANGING 1751215719
@@ -1802,6 +1837,11 @@ typedef struct hr_ot_math_glyph_part_t {
 
 #define HR_OT_MATH_GLYPH_PART_FLAG_EXTENDER 1
 
+/**
+ * Deprecated HarfBuzz spelling of `HR_OT_MATH_GLYPH_PART_FLAG_EXTENDER`.
+ */
+#define HR_MATH_GLYPH_PART_FLAG_EXTENDER HR_OT_MATH_GLYPH_PART_FLAG_EXTENDER
+
 #define HR_OT_TAG_MATH 1296127048
 
 #define HR_OT_TAG_MATH_SCRIPT 1835103336
@@ -3911,6 +3951,58 @@ void hr_map_keys(const struct hr_map_t *map, struct hr_set_t *keys);
  */
 void hr_map_values(const struct hr_map_t *map, struct hr_set_t *values);
 
+/**
+ * Selects the first available requested script in GSUB or GPOS.
+ *
+ * If none matches, tries `DFLT`, `dflt`, then `latn`. Returns true only for
+ * a requested script, even when a fallback was selected. With no match,
+ * writes `HR_OT_LAYOUT_NO_SCRIPT_INDEX` and a zero tag to the outputs.
+ *
+ * # Safety
+ * `face` must be null or live; `script_tags` must hold `script_count` tags
+ * when non-null. Both output pointers must be null or writable.
+ */
+hr_bool_t hr_ot_layout_table_select_script(struct hr_face_t *face,
+                                           hr_tag_t table_tag,
+                                           unsigned int script_count,
+                                           const hr_tag_t *script_tags,
+                                           unsigned int *script_index,
+                                           hr_tag_t *chosen_script);
+
+/**
+ * Returns the total number of feature records in GSUB or GPOS.
+ *
+ * Copies tags starting at `start_offset`, including duplicates. When both
+ * array and count are non-null, the count gives capacity on entry and the
+ * number written on return. A null array leaves the count unchanged.
+ *
+ * # Safety
+ * `face` must be null or live; `feature_count` must be null or writable;
+ * `feature_tags` must hold the input capacity when non-null.
+ */
+unsigned int hr_ot_layout_table_get_feature_tags(struct hr_face_t *face,
+                                                 hr_tag_t table_tag,
+                                                 unsigned int start_offset,
+                                                 unsigned int *feature_count,
+                                                 hr_tag_t *feature_tags);
+
+/**
+ * Finds an optional feature in a script's language system in GSUB or GPOS.
+ *
+ * Use `HR_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX` for the default language system.
+ * A required feature is not included in this search. Writes the feature's
+ * table-wide index, or `HR_OT_LAYOUT_NO_FEATURE_INDEX` on failure.
+ *
+ * # Safety
+ * `face` must be null or live; `feature_index` must be null or writable.
+ */
+hr_bool_t hr_ot_layout_language_find_feature(struct hr_face_t *face,
+                                             hr_tag_t table_tag,
+                                             unsigned int script_index,
+                                             unsigned int language_index,
+                                             hr_tag_t feature_tag,
+                                             unsigned int *feature_index);
+
 /**
  * Returns whether the face has a readable GSUB table.
  *

harfrust_capi/src/lib.rs

@@ -10,7 +10,7 @@ as HarfBuzz itself without collisions.
 # Scope
 
 This covers shaping: blobs, faces, fonts, buffers and `hr_shape`, plus OpenType
-`BASE` baseline and `MATH` queries. It also provides layout lookup queries,
+`BASE` baseline and `MATH` queries. It also provides layout script/feature and lookup queries,
 OpenType script and language tag conversion, and the complete set and map
 container APIs. Drawing and painting callbacks and subsetting are outside this API.
 
@@ -84,3 +84,11 @@ mod skia_batch_tests;
 #[cfg(test)]
 #[path = "../tests/skia_version.rs"]
 mod skia_version_tests;
+
+#[cfg(test)]
+#[path = "../tests/tables.rs"]
+mod table_tests;
+
+#[cfg(test)]
+#[path = "../tests/ot_queries.rs"]
+mod ot_query_tests;