Merge pull request #2473 from harfbuzz/gsub-alternate

fixes #673

docs/harfbuzz-sections.txt

@@ -574,6 +574,7 @@ hb_ot_layout_language_get_feature_indexes
 hb_ot_layout_language_get_feature_tags
 hb_ot_layout_language_get_required_feature
 hb_ot_layout_lookup_collect_glyphs
+hb_ot_layout_lookup_get_glyph_alternates
 hb_ot_layout_lookup_substitute_closure
 hb_ot_layout_lookups_substitute_closure
 hb_ot_layout_lookup_would_substitute

src/hb-debug.hh

@@ -373,10 +373,6 @@ struct hb_no_trace_t {
 #define HB_DEBUG_FT (HB_DEBUG+0)
 #endif
 
-#ifndef HB_DEBUG_GET_COVERAGE
-#define HB_DEBUG_GET_COVERAGE (HB_DEBUG+0)
-#endif
-
 #ifndef HB_DEBUG_OBJECT
 #define HB_DEBUG_OBJECT (HB_DEBUG+0)
 #endif

src/hb-dispatch.hh

@@ -35,7 +35,7 @@
  * Dispatch
  */
 
-template <typename Context, typename Return, unsigned int MaxDebugDepth>
+template <typename Context, typename Return=hb_empty_t, unsigned int MaxDebugDepth=0>
 struct hb_dispatch_context_t
 {
   private:
@@ -43,6 +43,8 @@ struct hb_dispatch_context_t
   const Context* thiz () const { return static_cast<const Context *> (this); }
 	Context* thiz ()       { return static_cast<      Context *> (this); }
   public:
+  const char *get_name () { return "UNKNOWN"; }
+  static constexpr unsigned debug_depth = 0;
   static constexpr unsigned max_debug_depth = MaxDebugDepth;
   typedef Return return_t;
   template <typename T, typename F>

src/hb-ot-layout-common.hh

@@ -151,9 +151,8 @@ struct hb_subset_layout_context_t :
 };
 
 struct hb_collect_variation_indices_context_t :
-       hb_dispatch_context_t<hb_collect_variation_indices_context_t, hb_empty_t, 0>
+       hb_dispatch_context_t<hb_collect_variation_indices_context_t>
 {
-  const char *get_name () { return "CLOSURE_LAYOUT_VARIATION_IDXES"; }
   template <typename T>
   return_t dispatch (const T &obj) { obj.collect_variation_indices (this); return hb_empty_t (); }
   static return_t default_return_value () { return hb_empty_t (); }
@@ -161,15 +160,13 @@ struct hb_collect_variation_indices_context_t :
   hb_set_t *layout_variation_indices;
   const hb_set_t *glyph_set;
   const hb_map_t *gpos_lookups;
-  unsigned int debug_depth;
 
   hb_collect_variation_indices_context_t (hb_set_t *layout_variation_indices_,
 					  const hb_set_t *glyph_set_,
 					  const hb_map_t *gpos_lookups_) :
 					layout_variation_indices (layout_variation_indices_),
 					glyph_set (glyph_set_),
-					gpos_lookups (gpos_lookups_),
+					gpos_lookups (gpos_lookups_) {}
-					debug_depth (0) {}
 };
 
 template<typename OutputArray>

src/hb-ot-layout-gsub-table.hh

@@ -556,6 +556,20 @@ struct AlternateSet
     return_trace (true);
   }
 
+  unsigned
+  get_alternates (unsigned        start_offset,
+		  unsigned       *alternate_count  /* IN/OUT.  May be NULL. */,
+		  hb_codepoint_t *alternate_glyphs /* OUT.     May be NULL. */) const
+  {
+    if (alternates.len && alternate_count)
+    {
+      + alternates.sub_array (start_offset, alternate_count)
+      | hb_sink (hb_array (alternate_glyphs, *alternate_count))
+      ;
+    }
+    return alternates.len;
+  }
+
   template <typename Iterator,
 	    hb_requires (hb_is_source_of (Iterator, hb_codepoint_t))>
   bool serialize (hb_serialize_context_t *c,
@@ -628,6 +642,14 @@ struct AlternateSubstFormat1
   bool would_apply (hb_would_apply_context_t *c) const
   { return c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED; }
 
+  unsigned
+  get_glyph_alternates (hb_codepoint_t  gid,
+			unsigned        start_offset,
+			unsigned       *alternate_count  /* IN/OUT.  May be NULL. */,
+			hb_codepoint_t *alternate_glyphs /* OUT.     May be NULL. */) const
+  { return (this+alternateSet[(this+coverage).get_coverage (gid)])
+	   .get_alternates (start_offset, alternate_count, alternate_glyphs); }
+
   bool apply (hb_ot_apply_context_t *c) const
   {
     TRACE_APPLY (this);

src/hb-ot-layout-gsubgpos.hh

@@ -42,26 +42,22 @@ namespace OT {
 
 
 struct hb_intersects_context_t :
-       hb_dispatch_context_t<hb_intersects_context_t, bool, 0>
+       hb_dispatch_context_t<hb_intersects_context_t, bool>
 {
-  const char *get_name () { return "INTERSECTS"; }
   template <typename T>
   return_t dispatch (const T &obj) { return obj.intersects (this->glyphs); }
   static return_t default_return_value () { return false; }
   bool stop_sublookup_iteration (return_t r) const { return r; }
 
   const hb_set_t *glyphs;
-  unsigned int debug_depth;
 
   hb_intersects_context_t (const hb_set_t *glyphs_) :
-			     glyphs (glyphs_),
+			     glyphs (glyphs_) {}
-			     debug_depth (0) {}
 };
 
 struct hb_closure_context_t :
-       hb_dispatch_context_t<hb_closure_context_t, hb_empty_t, 0>
+       hb_dispatch_context_t<hb_closure_context_t>
 {
-  const char *get_name () { return "CLOSURE"; }
   typedef return_t (*recurse_func_t) (hb_closure_context_t *c, unsigned int lookup_index);
   template <typename T>
   return_t dispatch (const T &obj) { obj.closure (this); return hb_empty_t (); }
@@ -102,7 +98,6 @@ struct hb_closure_context_t :
   hb_set_t output[1];
   recurse_func_t recurse_func;
   unsigned int nesting_level_left;
-  unsigned int debug_depth;
 
   hb_closure_context_t (hb_face_t *face_,
 			hb_set_t *glyphs_,
@@ -112,7 +107,6 @@ struct hb_closure_context_t :
 			  glyphs (glyphs_),
 			  recurse_func (nullptr),
 			  nesting_level_left (nesting_level_left_),
-			  debug_depth (0),
 			  done_lookups (done_lookups_),
 			  lookup_count (0)
   {}
@@ -134,9 +128,8 @@ struct hb_closure_context_t :
 };
 
 struct hb_closure_lookups_context_t :
-       hb_dispatch_context_t<hb_closure_lookups_context_t, hb_empty_t, 0>
+       hb_dispatch_context_t<hb_closure_lookups_context_t>
 {
-  const char *get_name () { return "CLOSURE_LOOKUPS"; }
   typedef return_t (*recurse_func_t) (hb_closure_lookups_context_t *c, unsigned lookup_index);
   template <typename T>
   return_t dispatch (const T &obj) { obj.closure_lookups (this); return hb_empty_t (); }
@@ -177,7 +170,6 @@ struct hb_closure_lookups_context_t :
   const hb_set_t *glyphs;
   recurse_func_t recurse_func;
   unsigned int nesting_level_left;
-  unsigned int debug_depth;
 
   hb_closure_lookups_context_t (hb_face_t *face_,
 				const hb_set_t *glyphs_,
@@ -188,7 +180,6 @@ struct hb_closure_lookups_context_t :
 				glyphs (glyphs_),
 				recurse_func (nullptr),
 				nesting_level_left (nesting_level_left_),
-				debug_depth (0),
 				visited_lookups (visited_lookups_),
 				inactive_lookups (inactive_lookups_),
 				lookup_count (0) {}
@@ -202,9 +193,8 @@ struct hb_closure_lookups_context_t :
 };
 
 struct hb_would_apply_context_t :
-       hb_dispatch_context_t<hb_would_apply_context_t, bool, 0>
+       hb_dispatch_context_t<hb_would_apply_context_t, bool>
 {
-  const char *get_name () { return "WOULD_APPLY"; }
   template <typename T>
   return_t dispatch (const T &obj) { return obj.would_apply (this); }
   static return_t default_return_value () { return false; }
@@ -214,7 +204,6 @@ struct hb_would_apply_context_t :
   const hb_codepoint_t *glyphs;
   unsigned int len;
   bool zero_context;
-  unsigned int debug_depth;
 
   hb_would_apply_context_t (hb_face_t *face_,
 			    const hb_codepoint_t *glyphs_,
@@ -223,15 +212,12 @@ struct hb_would_apply_context_t :
 			      face (face_),
 			      glyphs (glyphs_),
 			      len (len_),
-			      zero_context (zero_context_),
+			      zero_context (zero_context_) {}
-			      debug_depth (0) {}
 };
 
-
 struct hb_collect_glyphs_context_t :
-       hb_dispatch_context_t<hb_collect_glyphs_context_t, hb_empty_t, 0>
+       hb_dispatch_context_t<hb_collect_glyphs_context_t>
 {
-  const char *get_name () { return "COLLECT_GLYPHS"; }
   typedef return_t (*recurse_func_t) (hb_collect_glyphs_context_t *c, unsigned int lookup_index);
   template <typename T>
   return_t dispatch (const T &obj) { obj.collect_glyphs (this); return hb_empty_t (); }
@@ -282,7 +268,6 @@ struct hb_collect_glyphs_context_t :
   recurse_func_t recurse_func;
   hb_set_t *recursed_lookups;
   unsigned int nesting_level_left;
-  unsigned int debug_depth;
 
   hb_collect_glyphs_context_t (hb_face_t *face_,
 			       hb_set_t  *glyphs_before, /* OUT.  May be NULL */
@@ -297,8 +282,7 @@ struct hb_collect_glyphs_context_t :
 			      output (glyphs_output ? glyphs_output : hb_set_get_empty ()),
 			      recurse_func (nullptr),
 			      recursed_lookups (hb_set_create ()),
-			      nesting_level_left (nesting_level_left_),
+			      nesting_level_left (nesting_level_left_) {}
-			      debug_depth (0) {}
   ~hb_collect_glyphs_context_t () { hb_set_destroy (recursed_lookups); }
 
   void set_recurse_func (recurse_func_t func) { recurse_func = func; }
@@ -308,10 +292,9 @@ struct hb_collect_glyphs_context_t :
 
 template <typename set_t>
 struct hb_collect_coverage_context_t :
-       hb_dispatch_context_t<hb_collect_coverage_context_t<set_t>, const Coverage &, HB_DEBUG_GET_COVERAGE>
+       hb_dispatch_context_t<hb_collect_coverage_context_t<set_t>, const Coverage &>
 {
-  const char *get_name () { return "GET_COVERAGE"; }
+  typedef const Coverage &return_t; // Stoopid that we have to dupe this here.
-  typedef const Coverage &return_t;
   template <typename T>
   return_t dispatch (const T &obj) { return obj.get_coverage (); }
   static return_t default_return_value () { return Null (Coverage); }
@@ -322,11 +305,9 @@ struct hb_collect_coverage_context_t :
   }
 
   hb_collect_coverage_context_t (set_t *set_) :
-				   set (set_),
+				   set (set_) {}
-				   debug_depth (0) {}
 
   set_t *set;
-  unsigned int debug_depth;
 };
 
 
@@ -701,7 +682,7 @@ struct hb_ot_apply_context_t :
 
 
 struct hb_get_subtables_context_t :
-       hb_dispatch_context_t<hb_get_subtables_context_t, hb_empty_t, HB_DEBUG_APPLY>
+       hb_dispatch_context_t<hb_get_subtables_context_t>
 {
   template <typename Type>
   static inline bool apply_to (const void *obj, OT::hb_ot_apply_context_t *c)
@@ -737,7 +718,6 @@ struct hb_get_subtables_context_t :
   typedef hb_vector_t<hb_applicable_t> array_t;
 
   /* Dispatch interface. */
-  const char *get_name () { return "GET_SUBTABLES"; }
   template <typename T>
   return_t dispatch (const T &obj)
   {

src/hb-ot-layout.cc

@@ -1362,7 +1362,6 @@ hb_ot_layout_lookup_would_substitute (hb_face_t            *face,
   OT::hb_would_apply_context_t c (face, glyphs, glyphs_length, (bool) zero_context);
 
   const OT::SubstLookup& l = face->table.GSUB->table->get_lookup (lookup_index);
-
   return l.would_apply (&c, &face->table.GSUB->accels[lookup_index]);
 }
 
@@ -1969,4 +1968,62 @@ hb_ot_layout_get_baseline (hb_font_t                   *font,
   return result;
 }
 #endif
+
+
+struct hb_get_glyph_alternates_dispatch_t :
+       hb_dispatch_context_t<hb_get_glyph_alternates_dispatch_t, unsigned>
+{
+  static return_t default_return_value () { return 0; }
+  bool stop_sublookup_iteration (return_t r) const { return r; }
+
+  hb_face_t *face;
+
+  hb_get_glyph_alternates_dispatch_t (hb_face_t *face) :
+					face (face) {}
+
+  private:
+  template <typename T, typename ...Ts> auto
+  _dispatch (const T &obj, hb_priority<1>, Ts&&... ds) HB_AUTO_RETURN
+  ( obj.get_glyph_alternates (hb_forward<Ts> (ds)...) )
+  template <typename T, typename ...Ts> auto
+  _dispatch (const T &obj, hb_priority<0>, Ts&&... ds) HB_AUTO_RETURN
+  ( default_return_value () )
+  public:
+  template <typename T, typename ...Ts> auto
+  dispatch (const T &obj, Ts&&... ds) HB_AUTO_RETURN
+  ( _dispatch (obj, hb_prioritize, hb_forward<Ts> (ds)...) )
+};
+
+/**
+ * hb_ot_layout_lookup_get_glyph_alternates:
+ * @face: a face.
+ * @lookup_index: index of the feature lookup to query.
+ * @glyph: a glyph id.
+ * @start_offset: starting offset.
+ * @alternate_count: (inout) (allow-none): Input = the maximum number of alternate glyphs to return;
+ *                   Output = the actual number of alternate glyphs returned (may be zero).
+ * @alternate_glyphs: (out caller-allocates) (array length=alternate_count): A glyphs buffer.
+ *                    Alternate glyphs associated with the glyph id.
+ *
+ * Fetches alternates of a glyph from a given GSUB lookup index.
+ *
+ * Return value: total number of alternates found in the specific lookup index for the given glyph id.
+ *
+ * Since: REPLACEME
+ **/
+HB_EXTERN 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  /* IN/OUT.  May be NULL. */,
+					  hb_codepoint_t *alternate_glyphs /* OUT.     May be NULL. */)
+{
+  hb_get_glyph_alternates_dispatch_t c (face);
+  const OT::SubstLookup &lookup = face->table.GSUB->table->get_lookup (lookup_index);
+  auto ret = lookup.dispatch (&c, glyph, start_offset, alternate_count, alternate_glyphs);
+  if (!ret && alternate_count) *alternate_count = 0;
+  return ret;
+}
+
 #endif

src/hb-ot-layout.h

@@ -323,6 +323,14 @@ hb_ot_layout_feature_with_variations_get_lookups (hb_face_t    *face,
 HB_EXTERN hb_bool_t
 hb_ot_layout_has_substitution (hb_face_t *face);
 
+HB_EXTERN 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 /* IN/OUT */,
+					  hb_codepoint_t *alternate_glyphs /* OUT */);
+
 HB_EXTERN hb_bool_t
 hb_ot_layout_lookup_would_substitute (hb_face_t            *face,
 				      unsigned int          lookup_index,
@@ -449,7 +457,6 @@ hb_ot_layout_get_baseline (hb_font_t                   *font,
 			   hb_tag_t                     language_tag,
 			   hb_position_t               *coord        /* OUT.  May be NULL. */);
 
-
 HB_END_DECLS
 
 #endif /* HB_OT_LAYOUT_H */

test/api/Makefile.am

@@ -40,6 +40,7 @@ TEST_PROGS = \
 	test-font \
 	test-map \
 	test-object \
+	test-ot-alternates \
 	test-ot-color \
 	test-ot-face \
 	test-ot-glyphname \

test/api/meson.build

@@ -16,6 +16,7 @@ tests = [
   'test-font.c',
   'test-map.c',
   'test-object.c',
+  'test-ot-alternates.c',
   'test-ot-color.c',
   'test-ot-face.c',
   'test-ot-glyphname.c',

test/api/test-ot-alternates.c

@@ -0,0 +1,53 @@
+/*
+ * Copyright © 2020  Ebrahim Byagowi
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#include "hb-test.h"
+
+#include <hb.h>
+#include <hb-ot.h>
+
+static void
+test_ot_layout_lookup_get_glyph_alternates (void)
+{
+  hb_face_t *face = hb_test_open_font_file ("fonts/SourceSansPro-Regular.otf");
+
+  hb_codepoint_t alternates[3];
+  unsigned alternates_count = 3;
+  g_assert_cmpuint (7, ==, hb_ot_layout_lookup_get_glyph_alternates (face, 1, 1091, 2, &alternates_count, alternates));
+
+  g_assert_cmpuint (3, ==, alternates_count);
+  g_assert_cmpuint (1606, ==, alternates[0]);
+  g_assert_cmpuint (1578, ==, alternates[1]);
+  g_assert_cmpuint (1592, ==, alternates[2]);
+
+  hb_face_destroy (face);
+}
+
+int
+main (int argc, char **argv)
+{
+  hb_test_init (&argc, &argv);
+  hb_test_add (test_ot_layout_lookup_get_glyph_alternates);
+  return hb_test_run ();
+}