Use Coverage digests in would_apply

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

@@ -1170,6 +1170,7 @@ struct SubstLookup : Lookup
 
   inline bool would_apply (hb_would_apply_context_t *c) const
   {
+    if (!c->digest.may_have (c->first)) return false;
     unsigned int lookup_type = get_type ();
     unsigned int count = get_subtable_count ();
     for (unsigned int i = 0; i < count; i++)

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

@@ -77,14 +77,18 @@ struct hb_would_apply_context_t
   hb_face_t *face;
   hb_codepoint_t first;
   hb_codepoint_t second;
+  const hb_set_digest_t digest;
   unsigned int len;
   unsigned int debug_depth;
 
   hb_would_apply_context_t (hb_face_t *face_,
 			    hb_codepoint_t first_,
-			    hb_codepoint_t second_ = -1) :
+			    hb_codepoint_t second_,
+			    const hb_set_digest_t *digest_
+			    ) :
 			      face (face_),
 			      first (first_), second (second_), len (second == (hb_codepoint_t) -1 ? 1 : 2),
+			      digest (*digest_),
 			      debug_depth (0) {};
 };
 

src/hb-ot-layout.cc

@@ -406,7 +406,7 @@ hb_ot_layout_would_substitute_lookup (hb_face_t            *face,
 				      unsigned int          lookup_index)
 {
   if (unlikely (glyphs_length < 1 || glyphs_length > 2)) return false;
-  hb_would_apply_context_t c (face, glyphs[0], glyphs_length == 2 ? glyphs[1] : -1);
+  hb_would_apply_context_t c (face, glyphs[0], glyphs_length == 2 ? glyphs[1] : -1, NULL);
   return _get_gsub (face).would_substitute_lookup (&c, lookup_index);
 }
 
@@ -417,7 +417,7 @@ hb_ot_layout_would_substitute_lookup_fast (hb_face_t            *face,
 					   unsigned int          lookup_index)
 {
   if (unlikely (glyphs_length < 1 || glyphs_length > 2)) return false;
-  hb_would_apply_context_t c (face, glyphs[0], glyphs_length == 2 ? glyphs[1] : -1);
+  hb_would_apply_context_t c (face, glyphs[0], glyphs_length == 2 ? glyphs[1] : -1, &hb_ot_layout_from_face (face)->gsub_digests[lookup_index]);
   return hb_ot_layout_from_face (face)->gsub->would_substitute_lookup (&c, lookup_index);
 }