From 8b2a2111235af22ca969898737835e904badf92f Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 16 Nov 2022 16:57:44 -0700
Subject: [PATCH] [layout] Keep digest updated in the context

Don't recompute digest after every (applied) GSUB lookup.
---
 src/hb-ot-layout-gsubgpos.hh | 16 ++++++++++------
 src/hb-ot-layout.cc          | 19 +++++++++----------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index 019e65265..fe8e7105d 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -686,6 +686,7 @@ struct hb_ot_apply_context_t :
   bool random = false;
   uint32_t random_state = 1;
   unsigned new_syllables = (unsigned) -1;
+  hb_set_digest_t digest;
 
   hb_ot_apply_context_t (unsigned int table_index_,
 			 hb_font_t *font_,
@@ -708,7 +709,8 @@ struct hb_ot_apply_context_t :
 #endif
 					),
 			direction (buffer_->props.direction),
-			has_glyph_classes (gdef.has_glyph_classes ())
+			has_glyph_classes (gdef.has_glyph_classes ()),
+			digest (buffer_->digest ())
   { init_iters (); }
 
   ~hb_ot_apply_context_t ()
@@ -781,8 +783,10 @@ struct hb_ot_apply_context_t :
   void _set_glyph_class (hb_codepoint_t glyph_index,
 			  unsigned int class_guess = 0,
 			  bool ligature = false,
-			  bool component = false) const
+			  bool component = false)
   {
+    digest.add (glyph_index);
+
     if (new_syllables != (unsigned) -1)
       buffer->cur().syllable() = new_syllables;
 
@@ -815,24 +819,24 @@ struct hb_ot_apply_context_t :
       _hb_glyph_info_set_glyph_props (&buffer->cur(), props);
   }
 
-  void replace_glyph (hb_codepoint_t glyph_index) const
+  void replace_glyph (hb_codepoint_t glyph_index)
   {
     _set_glyph_class (glyph_index);
     (void) buffer->replace_glyph (glyph_index);
   }
-  void replace_glyph_inplace (hb_codepoint_t glyph_index) const
+  void replace_glyph_inplace (hb_codepoint_t glyph_index)
   {
     _set_glyph_class (glyph_index);
     buffer->cur().codepoint = glyph_index;
   }
   void replace_glyph_with_ligature (hb_codepoint_t glyph_index,
-				    unsigned int class_guess) const
+				    unsigned int class_guess)
   {
     _set_glyph_class (glyph_index, class_guess, true);
     (void) buffer->replace_glyph (glyph_index);
   }
   void output_glyph_for_component (hb_codepoint_t glyph_index,
-				   unsigned int class_guess) const
+				   unsigned int class_guess)
   {
     _set_glyph_class (glyph_index, class_guess, false, true);
     (void) buffer->output_glyph (glyph_index);
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index b09d203c5..69d81672e 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1955,8 +1955,6 @@ inline void hb_ot_map_t::apply (const Proxy &proxy,
   OT::hb_ot_apply_context_t c (table_index, font, buffer);
   c.set_recurse_func (Proxy::Lookup::template dispatch_recurse_func<OT::hb_ot_apply_context_t>);
 
-  hb_set_digest_t digest = buffer->digest ();
-
   for (unsigned int stage_index = 0; stage_index < stages[table_index].length; stage_index++)
   {
     const stage_map_t *stage = &stages[table_index][stage_index];
@@ -1967,7 +1965,7 @@ inline void hb_ot_map_t::apply (const Proxy &proxy,
       unsigned int lookup_index = lookup.index;
       if (!buffer->message (font, "start lookup %d", lookup_index)) continue;
 
-      if (proxy.accels[lookup_index].digest.may_have (digest))
+      if (proxy.accels[lookup_index].digest.may_have (c.digest))
       {
 	c.set_lookup_index (lookup_index);
 	c.set_lookup_mask (lookup.mask);
@@ -1976,13 +1974,9 @@ inline void hb_ot_map_t::apply (const Proxy &proxy,
 	c.set_random (lookup.random);
 	c.set_per_syllable (lookup.per_syllable);
 
-	if (apply_string<Proxy> (&c,
-				 proxy.table.get_lookup (lookup_index),
-				 proxy.accels[lookup_index]) &&
-	    table_index == 0)
-	{
-	  digest = buffer->digest ();
-	}
+	apply_string<Proxy> (&c,
+			     proxy.table.get_lookup (lookup_index),
+			     proxy.accels[lookup_index]);
       }
       else
 	(void) buffer->message (font, "skipped lookup %d because no glyph matches", lookup_index);
@@ -1991,7 +1985,12 @@ inline void hb_ot_map_t::apply (const Proxy &proxy,
     }
 
     if (stage->pause_func)
+    {
       stage->pause_func (plan, font, buffer);
+      /* Refresh working buffer digest since buffer content
+       * might have changed. */
+      c.digest = buffer->digest ();
+    }
   }
 }