[subset] Add memoization of GSUB lookup closures.

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

@@ -1156,10 +1156,13 @@ struct SubstLookup : Lookup
     return_trace (dispatch (c));
   }
 
-  inline hb_closure_context_t::return_t closure (hb_closure_context_t *c) const
+  inline hb_closure_context_t::return_t closure (hb_closure_context_t *c, unsigned int this_index) const
   {
     TRACE_CLOSURE (this);
-    c->set_recurse_func (dispatch_recurse_func<hb_closure_context_t>);
+    if (!c->start_lookup (this_index))
+      return_trace (HB_VOID);
+
+    c->set_recurse_func (dispatch_closure_recurse_func);
     return_trace (dispatch (c));
   }
 
@@ -1258,6 +1261,14 @@ struct SubstLookup : Lookup
   template <typename context_t>
   static inline typename context_t::return_t dispatch_recurse_func (context_t *c, unsigned int lookup_index);
 
+  static inline hb_closure_context_t::return_t dispatch_closure_recurse_func
+  (hb_closure_context_t *c, unsigned int lookup_index)
+  {
+    if (!c->start_lookup (lookup_index))
+      return HB_VOID;
+    return dispatch_recurse_func (c, lookup_index);
+  }
+
   template <typename context_t>
   inline typename context_t::return_t dispatch (context_t *c) const
   { return Lookup::dispatch<SubstLookupSubTable> (c); }

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

@@ -32,6 +32,7 @@
 #include "hb-private.hh"
 #include "hb-debug.hh"
 #include "hb-buffer-private.hh"
+#include "hb-map-private.hh"
 #include "hb-ot-layout-gdef-table.hh"
 #include "hb-set-private.hh"
 
@@ -59,6 +60,20 @@ struct hb_closure_context_t :
     return HB_VOID;
   }
 
+  bool start_lookup (unsigned int lookup_index)
+  {
+    if (is_lookup_done (lookup_index))
+      return false;
+    done_lookups->set (lookup_index, glyphs->get_population ());
+    return true;
+  }
+
+  bool is_lookup_done (unsigned int lookup_index)
+  {
+    // Have we visited this lookup with the current set of glyphs?
+    return done_lookups->get (lookup_index) == glyphs->get_population ();
+  }
+
   hb_face_t *face;
   hb_set_t *glyphs;
   recurse_func_t recurse_func;
@@ -67,14 +82,19 @@ struct hb_closure_context_t :
 
   hb_closure_context_t (hb_face_t *face_,
 			hb_set_t *glyphs_,
+                        hb_map_t *done_lookups_,
 		        unsigned int nesting_level_left_ = HB_MAX_NESTING_LEVEL) :
 			  face (face_),
 			  glyphs (glyphs_),
+                          done_lookups (done_lookups_),
 			  recurse_func (nullptr),
 			  nesting_level_left (nesting_level_left_),
 			  debug_depth (0) {}
 
   void set_recurse_func (recurse_func_t func) { recurse_func = func; }
+
+  private:
+  hb_map_t *done_lookups;
 };
 
 

src/hb-ot-layout.cc

@@ -44,6 +44,7 @@
 #include "hb-ot-color-sbix-table.hh"
 #include "hb-ot-color-svg-table.hh"
 #include "hb-ot-name-table.hh"
+#include "hb-map-private.hh"
 
 
 hb_ot_layout_t *
@@ -943,11 +944,12 @@ hb_ot_layout_lookup_substitute_closure (hb_face_t    *face,
 				        unsigned int  lookup_index,
 				        hb_set_t     *glyphs)
 {
-  OT::hb_closure_context_t c (face, glyphs);
+  hb_auto_t<hb_map_t> done_lookups;
+  OT::hb_closure_context_t c (face, glyphs, &done_lookups);
 
   const OT::SubstLookup& l = _get_gsub (face).get_lookup (lookup_index);
 
-  l.closure (&c);
+  l.closure (&c, lookup_index);
 }
 
 /*