[GSUB] Allow non-zero-context matching in would_apply()

To be used in the next patch.

src/hb-ot-layout-gsubgpos-private.hh

@@ -76,17 +76,20 @@ struct hb_would_apply_context_t
   hb_face_t *face;
   const hb_codepoint_t *glyphs;
   unsigned int len;
+  bool zero_context;
   const hb_set_digest_t digest;
   unsigned int debug_depth;
 
   hb_would_apply_context_t (hb_face_t *face_,
 			    const hb_codepoint_t *glyphs_,
 			    unsigned int len_,
+			    bool zero_context_,
 			    const hb_set_digest_t *digest_
 			    ) :
 			      face (face_),
 			      glyphs (glyphs_),
 			      len (len_),
+			      zero_context (zero_context_),
 			      digest (*digest_),
 			      debug_depth (0) {};
 };
@@ -1066,8 +1069,7 @@ static inline bool chain_context_would_apply_lookup (hb_would_apply_context_t *c
 						     const LookupRecord lookupRecord[],
 						     ChainContextApplyLookupContext &lookup_context)
 {
-  return !backtrackCount
+  return (c->zero_context ? !backtrackCount && !lookaheadCount : true)
-      && !lookaheadCount
       && would_match_input (c,
 			    inputCount, input,
 			    lookup_context.funcs.match, lookup_context.match_data[1]);

src/hb-ot-layout-private.hh

@@ -139,9 +139,10 @@ static inline uint8_t allocate_lig_id (hb_buffer_t *buffer) {
 
 HB_INTERNAL hb_bool_t
 hb_ot_layout_would_substitute_lookup_fast (hb_face_t            *face,
+					   unsigned int          lookup_index,
 					   const hb_codepoint_t *glyphs,
 					   unsigned int          glyphs_length,
-					   unsigned int          lookup_index);
+					   hb_bool_t             zero_context);
 
 
 /* Should be called before all the substitute_lookup's are done. */

src/hb-ot-layout.cc

@@ -401,22 +401,24 @@ hb_ot_layout_has_substitution (hb_face_t *face)
 
 hb_bool_t
 hb_ot_layout_would_substitute_lookup (hb_face_t            *face,
+				      unsigned int          lookup_index,
 				      const hb_codepoint_t *glyphs,
 				      unsigned int          glyphs_length,
-				      unsigned int          lookup_index)
+				      hb_bool_t             zero_context)
 {
   if (unlikely (!hb_ot_shaper_face_data_ensure (face))) return false;
-  return hb_ot_layout_would_substitute_lookup_fast (face, glyphs, glyphs_length, lookup_index);
+  return hb_ot_layout_would_substitute_lookup_fast (face, lookup_index, glyphs, glyphs_length, zero_context);
 }
 
 hb_bool_t
 hb_ot_layout_would_substitute_lookup_fast (hb_face_t            *face,
+					   unsigned int          lookup_index,
 					   const hb_codepoint_t *glyphs,
 					   unsigned int          glyphs_length,
-					   unsigned int          lookup_index)
+					   hb_bool_t             zero_context)
 {
   if (unlikely (lookup_index >= hb_ot_layout_from_face (face)->gsub_lookup_count)) return false;
-  hb_would_apply_context_t c (face, glyphs, glyphs_length, &hb_ot_layout_from_face (face)->gsub_digests[lookup_index]);
+  hb_would_apply_context_t c (face, glyphs, glyphs_length, zero_context, &hb_ot_layout_from_face (face)->gsub_digests[lookup_index]);
   return hb_ot_layout_from_face (face)->gsub->would_substitute_lookup (&c, lookup_index);
 }
 
@@ -445,8 +447,8 @@ hb_ot_layout_substitute_finish (hb_font_t *font, hb_buffer_t *buffer)
 
 void
 hb_ot_layout_substitute_closure_lookup (hb_face_t    *face,
-				        hb_set_t     *glyphs,
+				        unsigned int  lookup_index,
-				        unsigned int  lookup_index)
+				        hb_set_t     *glyphs)
 {
   hb_closure_context_t c (face, glyphs);
   _get_gsub (face).closure_lookup (&c, lookup_index);

src/hb-ot-layout.h

@@ -171,14 +171,15 @@ hb_ot_layout_has_substitution (hb_face_t *face);
 
 hb_bool_t
 hb_ot_layout_would_substitute_lookup (hb_face_t            *face,
+				      unsigned int          lookup_index,
 				      const hb_codepoint_t *glyphs,
 				      unsigned int          glyphs_length,
-				      unsigned int          lookup_index);
+				      hb_bool_t             zero_context);
 
 void
 hb_ot_layout_substitute_closure_lookup (hb_face_t    *face,
-				        hb_set_t     *glyphs,
+				        unsigned int  lookup_index,
-				        unsigned int  lookup_index);
+				        hb_set_t     *glyphs);
 
 /*
  * GPOS

src/hb-ot-map.cc

@@ -116,16 +116,8 @@ void hb_ot_map_t::position (const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_
 void hb_ot_map_t::substitute_closure (const hb_ot_shape_plan_t *plan, hb_face_t *face, hb_set_t *glyphs) const
 {
   unsigned int table_index = 0;
-  unsigned int i = 0;
+  for (unsigned int i = 0; i < lookups[table_index].len; i++)
-
+    hb_ot_layout_substitute_closure_lookup (face, lookups[table_index][i].index, glyphs);
-  for (unsigned int pause_index = 0; pause_index < pauses[table_index].len; pause_index++) {
-    const pause_map_t *pause = &pauses[table_index][pause_index];
-    for (; i < pause->num_lookups; i++)
-      hb_ot_layout_substitute_closure_lookup (face, glyphs, lookups[table_index][i].index);
-  }
-
-  for (; i < lookups[table_index].len; i++)
-    hb_ot_layout_substitute_closure_lookup (face, glyphs, lookups[table_index][i].index);
 }
 
 void hb_ot_map_builder_t::add_pause (unsigned int table_index, hb_ot_map_t::pause_func_t pause_func)

src/hb-ot-shape-complex-indic.cc

@@ -257,7 +257,7 @@ struct would_substitute_feature_t
 				hb_face_t         *face) const
   {
     for (unsigned int i = 0; i < count; i++)
-      if (hb_ot_layout_would_substitute_lookup_fast (face, glyphs, glyphs_count, lookups[i].index))
+      if (hb_ot_layout_would_substitute_lookup_fast (face, lookups[i].index, glyphs, glyphs_count, true))
 	return true;
     return false;
   }

src/test-would-substitute.cc

@@ -99,5 +99,5 @@ main (int argc, char **argv)
       (argc > 4 &&
        !hb_font_glyph_from_string (font, argv[4], -1, &glyphs[1])))
     return 2;
-  return !hb_ot_layout_would_substitute_lookup (face, glyphs, len, strtol (argv[2], NULL, 0));
+  return !hb_ot_layout_would_substitute_lookup (face, strtol (argv[2], NULL, 0), glyphs, len, false);
 }