diff --git a/src/hb-ot-layout-gpos-table.hh b/src/hb-ot-layout-gpos-table.hh
index c8020d87ca77da66b94ca3032a1fb0c9e5dbff81..fa229348a9c25948be101afaee864a0eff3f4416 100644
--- a/src/hb-ot-layout-gpos-table.hh
+++ b/src/hb-ot-layout-gpos-table.hh
@@ -1268,7 +1268,7 @@ struct ChainContextPos : ChainContext
 };
 
 
-struct ExtensionPos : Extension
+struct ExtensionPos : Extension<struct GPOS>
 {
   friend struct PosLookupSubTable;
 
@@ -1382,8 +1382,10 @@ struct PosLookupSubTable
 
 struct PosLookup : Lookup
 {
-  inline const PosLookupSubTable& get_subtable (unsigned int i) const
-  { return this+CastR<OffsetArrayOf<PosLookupSubTable> > (subTable)[i]; }
+  typedef struct PosLookupSubTable SubTable;
+
+  inline const SubTable& get_subtable (unsigned int i) const
+  { return this+CastR<OffsetArrayOf<SubTable> > (subTable)[i]; }
 
   inline bool apply_once (hb_apply_context_t *c) const
   {
@@ -1424,7 +1426,7 @@ struct PosLookup : Lookup
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     if (unlikely (!Lookup::sanitize (c))) return TRACE_RETURN (false);
-    OffsetArrayOf<PosLookupSubTable> &list = CastR<OffsetArrayOf<PosLookupSubTable> > (subTable);
+    OffsetArrayOf<SubTable> &list = CastR<OffsetArrayOf<SubTable> > (subTable);
     return TRACE_RETURN (list.sanitize (c, this, get_type ()));
   }
 };
@@ -1437,6 +1439,8 @@ typedef OffsetListOf<PosLookup> PosLookupList;
 
 struct GPOS : GSUBGPOS
 {
+  typedef struct PosLookup Lookup;
+
   static const hb_tag_t Tag	= HB_OT_TAG_GPOS;
 
   inline const PosLookup& get_lookup (unsigned int i) const
@@ -1545,10 +1549,10 @@ inline bool ExtensionPos::apply (hb_apply_context_t *c) const
 inline bool ExtensionPos::sanitize (hb_sanitize_context_t *c)
 {
   TRACE_SANITIZE ();
-  if (unlikely (!Extension::sanitize (c))) return TRACE_RETURN (false);
+  if (unlikely (!Extension<GPOS>::sanitize (c))) return TRACE_RETURN (false);
   unsigned int offset = get_offset ();
   if (unlikely (!offset)) return TRACE_RETURN (true);
-  return TRACE_RETURN (StructAtOffset<PosLookupSubTable> (this, offset).sanitize (c, get_type ()));
+  return TRACE_RETURN (StructAtOffset<PosLookup::SubTable> (this, offset).sanitize (c, get_type ()));
 }
 
 static inline bool position_lookup (hb_apply_context_t *c, unsigned int lookup_index)
diff --git a/src/hb-ot-layout-gsub-table.hh b/src/hb-ot-layout-gsub-table.hh
index f5f38cc41de0e842666885e5ef5cdb03cb333a07..06a84889771c4a9487e4460b393304f08b70e117 100644
--- a/src/hb-ot-layout-gsub-table.hh
+++ b/src/hb-ot-layout-gsub-table.hh
@@ -750,7 +750,7 @@ struct ChainContextSubst : ChainContext
 };
 
 
-struct ExtensionSubst : Extension
+struct ExtensionSubst : Extension<struct GSUB>
 {
   friend struct SubstLookupSubTable;
   friend struct SubstLookup;
@@ -1037,16 +1037,18 @@ struct SubstLookupSubTable
 
 struct SubstLookup : Lookup
 {
-  inline const SubstLookupSubTable& get_subtable (unsigned int i) const
-  { return this+CastR<OffsetArrayOf<SubstLookupSubTable> > (subTable)[i]; }
+  typedef struct SubstLookupSubTable SubTable;
+
+  inline const SubTable& get_subtable (unsigned int i) const
+  { return this+CastR<OffsetArrayOf<SubTable> > (subTable)[i]; }
 
   inline static bool lookup_type_is_reverse (unsigned int lookup_type)
-  { return lookup_type == SubstLookupSubTable::ReverseChainSingle; }
+  { return lookup_type == SubTable::ReverseChainSingle; }
 
   inline bool is_reverse (void) const
   {
     unsigned int type = get_type ();
-    if (unlikely (type == SubstLookupSubTable::Extension))
+    if (unlikely (type == SubTable::Extension))
       return CastR<ExtensionSubst> (get_subtable(0)).is_reverse ();
     return lookup_type_is_reverse (type);
   }
@@ -1087,7 +1089,7 @@ struct SubstLookup : Lookup
 
     /* TODO: For the most common case this can move out of the main
      * loop, but it's not a big deal for now. */
-    if (unlikely (lookup_type == SubstLookupSubTable::Extension))
+    if (unlikely (lookup_type == SubTable::Extension))
     {
       /* The spec says all subtables should have the same type.
        * This is specially important if one has a reverse type!
@@ -1155,7 +1157,7 @@ struct SubstLookup : Lookup
   inline bool sanitize (hb_sanitize_context_t *c) {
     TRACE_SANITIZE ();
     if (unlikely (!Lookup::sanitize (c))) return TRACE_RETURN (false);
-    OffsetArrayOf<SubstLookupSubTable> &list = CastR<OffsetArrayOf<SubstLookupSubTable> > (subTable);
+    OffsetArrayOf<SubTable> &list = CastR<OffsetArrayOf<SubTable> > (subTable);
     return TRACE_RETURN (list.sanitize (c, this, get_type ()));
   }
 };
@@ -1168,6 +1170,8 @@ typedef OffsetListOf<SubstLookup> SubstLookupList;
 
 struct GSUB : GSUBGPOS
 {
+  typedef struct SubstLookup Lookup;
+
   static const hb_tag_t Tag	= HB_OT_TAG_GSUB;
 
   inline const SubstLookup& get_lookup (unsigned int i) const
@@ -1238,16 +1242,16 @@ inline bool ExtensionSubst::apply (hb_apply_context_t *c) const
 inline bool ExtensionSubst::sanitize (hb_sanitize_context_t *c)
 {
   TRACE_SANITIZE ();
-  if (unlikely (!Extension::sanitize (c))) return TRACE_RETURN (false);
+  if (unlikely (!Extension<GSUB>::sanitize (c))) return TRACE_RETURN (false);
   unsigned int offset = get_offset ();
   if (unlikely (!offset)) return TRACE_RETURN (true);
-  return TRACE_RETURN (StructAtOffset<SubstLookupSubTable> (this, offset).sanitize (c, get_type ()));
+  return TRACE_RETURN (StructAtOffset<GSUB::Lookup::SubTable> (this, offset).sanitize (c, get_type ()));
 }
 
 inline bool ExtensionSubst::is_reverse (void) const
 {
   unsigned int type = get_type ();
-  if (unlikely (type == SubstLookupSubTable::Extension))
+  if (unlikely (type == SubstLookup::SubTable::Extension))
     return CastR<ExtensionSubst> (get_subtable()).is_reverse ();
   return SubstLookup::lookup_type_is_reverse (type);
 }
diff --git a/src/hb-ot-layout-gsubgpos-private.hh b/src/hb-ot-layout-gsubgpos-private.hh
index 98d4e0a494c5b71cb41dbc7b4e7087cad4656da1..0e9d08a0c435681ebc9c981fe30e70047e50403a 100644
--- a/src/hb-ot-layout-gsubgpos-private.hh
+++ b/src/hb-ot-layout-gsubgpos-private.hh
@@ -298,6 +298,27 @@ static inline bool intersects_array (hb_closure_context_t *c,
 }
 
 
+struct match_glyph_t {
+  inline bool operator() (hb_codepoint_t glyph_id, const USHORT &value, const void *data)
+  {
+    return glyph_id == value;
+  }
+};
+struct match_class_t {
+  inline bool operator() (hb_codepoint_t glyph_id, const USHORT &value, const void *data)
+  {
+    const ClassDef &class_def = *reinterpret_cast<const ClassDef *>(data);
+    return class_def.get_class (glyph_id) == value;
+  }
+};
+struct match_coverage_t {
+  inline bool operator() (hb_codepoint_t glyph_id, const USHORT &value, const void *data)
+  {
+    const OffsetTo<Coverage> &coverage = (const OffsetTo<Coverage>&)value;
+    return (data+coverage).get_coverage (glyph_id) != NOT_COVERED;
+  }
+};
+
 static inline bool match_glyph (hb_codepoint_t glyph_id, const USHORT &value, const void *data HB_UNUSED)
 {
   return glyph_id == value;
@@ -314,6 +335,7 @@ static inline bool match_coverage (hb_codepoint_t glyph_id, const USHORT &value,
 }
 
 
+template <typename match_func_t>
 static inline bool match_input (hb_apply_context_t *c,
 				unsigned int count, /* Including the first glyph (not matched) */
 				const USHORT input[], /* Array of input values--start with second glyph */
@@ -340,6 +362,7 @@ static inline bool match_input (hb_apply_context_t *c,
   return true;
 }
 
+template <typename match_func_t>
 static inline bool match_backtrack (hb_apply_context_t *c,
 				    unsigned int count,
 				    const USHORT backtrack[],
@@ -362,6 +385,7 @@ static inline bool match_backtrack (hb_apply_context_t *c,
   return true;
 }
 
+template <typename match_func_t>
 static inline bool match_lookahead (hb_apply_context_t *c,
 				    unsigned int count,
 				    const USHORT lookahead[],
@@ -1262,9 +1286,12 @@ struct ChainContext
 };
 
 
+template <typename Table> struct Extension;
+
+template <typename Table>
 struct ExtensionFormat1
 {
-  friend struct Extension;
+  friend struct Extension<Table>;
 
   protected:
   inline unsigned int get_type (void) const { return extensionLookupType; }
@@ -1286,6 +1313,7 @@ struct ExtensionFormat1
   DEFINE_SIZE_STATIC (8);
 };
 
+template <typename Table>
 struct Extension
 {
   inline unsigned int get_type (void) const
@@ -1315,7 +1343,8 @@ struct Extension
   private:
   union {
   USHORT		format;		/* Format identifier */
-  ExtensionFormat1	format1;
+  ExtensionFormat1<Table>
+			format1;
   } u;
 };