From 474bef1cfd8f8c839cfe7e6d1333bbf93057dde4 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 4 Feb 2025 19:17:13 +0000
Subject: [PATCH] [aat] Use exact set for buffer intersection versus subchains

---
 src/hb-aat-layout-common.hh     |  4 ++--
 src/hb-aat-layout-morx-table.hh | 24 +++++++++++++-----------
 src/hb-buffer.hh                |  8 +++++++-
 3 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/src/hb-aat-layout-common.hh b/src/hb-aat-layout-common.hh
index 5db0d1212..4213ee280 100644
--- a/src/hb-aat-layout-common.hh
+++ b/src/hb-aat-layout-common.hh
@@ -63,10 +63,10 @@ struct hb_aat_apply_context_t :
   const ankr *ankr_table;
   const OT::GDEF *gdef_table;
   const hb_sorted_vector_t<hb_aat_map_t::range_flags_t> *range_flags = nullptr;
-  hb_set_digest_t buffer_digest = hb_set_digest_t::full ();
+  hb_set_t buffer_digest;
   const hb_set_t *left_set = nullptr;
   const hb_set_t *right_set = nullptr;
-  hb_set_digest_t machine_glyph_set = hb_set_digest_t::full ();
+  const hb_set_t *machine_glyph_set = nullptr;
   hb_aat_class_cache_t *machine_class_cache = nullptr;
   hb_mask_t subtable_flags = 0;
 
diff --git a/src/hb-aat-layout-morx-table.hh b/src/hb-aat-layout-morx-table.hh
index f5c986349..b2fd47d1f 100644
--- a/src/hb-aat-layout-morx-table.hh
+++ b/src/hb-aat-layout-morx-table.hh
@@ -172,7 +172,7 @@ struct RearrangementSubtable
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
     if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
-	!c->buffer_digest.intersects (c->machine_glyph_set))
+	!c->buffer_digest.intersects (*c->machine_glyph_set))
     {
       (void) c->buffer->message (c->font, "skipped chainsubtable because no glyph matches");
       return_trace (false);
@@ -340,7 +340,7 @@ struct ContextualSubtable
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
     if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
-	!c->buffer_digest.intersects (c->machine_glyph_set))
+	!c->buffer_digest.intersects (*c->machine_glyph_set))
     {
       (void) c->buffer->message (c->font, "skipped chainsubtable because no glyph matches");
       return_trace (false);
@@ -606,7 +606,7 @@ struct LigatureSubtable
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
     if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
-	!c->buffer_digest.intersects (c->machine_glyph_set))
+	!c->buffer_digest.intersects (*c->machine_glyph_set))
     {
       (void) c->buffer->message (c->font, "skipped chainsubtable because no glyph matches");
       return_trace (false);
@@ -885,7 +885,7 @@ struct InsertionSubtable
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
     if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
-	!c->buffer_digest.intersects (c->machine_glyph_set))
+	!c->buffer_digest.intersects (*c->machine_glyph_set))
     {
       (void) c->buffer->message (c->font, "skipped chainsubtable because no glyph matches");
       return_trace (false);
@@ -947,19 +947,21 @@ struct hb_accelerate_subtables_context_t :
     friend struct hb_aat_layout_lookup_accelerator_t;
 
     public:
-    hb_set_digest_t digest;
+    hb_set_t glyph_set;
     mutable hb_aat_class_cache_t class_cache;
 
     template <typename T>
     auto init_ (const T &obj_, unsigned num_glyphs, hb_priority<1>) HB_AUTO_RETURN
-    (
-      obj_.machine.collect_glyphs (this->digest, num_glyphs)
-    )
+    ((
+      glyph_set.init (),
+      obj_.machine.collect_glyphs (glyph_set, num_glyphs)
+    ))
 
     template <typename T>
     void init_ (const T &obj_, unsigned num_glyphs, hb_priority<0>)
     {
-      digest = digest.full ();
+      glyph_set.init ();
+      glyph_set.invert ();
     }
 
     template <typename T>
@@ -1185,7 +1187,7 @@ struct Chain
 		   hb_map ([subtable_flags] (const hb_aat_map_t::range_flags_t _) -> bool { return subtable_flags & (_.flags); })))
 	goto skip;
       c->subtable_flags = subtable_flags;
-      c->machine_glyph_set = accel ? accel->subtables[i].digest : hb_set_digest_t::full ();
+      c->machine_glyph_set = accel ? &accel->subtables[i].glyph_set : nullptr;
       c->machine_class_cache = accel ? &accel->subtables[i].class_cache : nullptr;
 
       if (!(subtable->get_coverage() & ChainSubtable<Types>::AllDirections) &&
@@ -1416,7 +1418,7 @@ struct mortmorx
 
     c->buffer->unsafe_to_concat ();
 
-    c->buffer_digest = c->buffer->digest ();
+    c->buffer_digest = c->buffer->set ();
 
     c->set_lookup_index (0);
     const Chain<Types> *chain = &firstChain;
diff --git a/src/hb-buffer.hh b/src/hb-buffer.hh
index 2a6ad6128..4a4a9631a 100644
--- a/src/hb-buffer.hh
+++ b/src/hb-buffer.hh
@@ -32,6 +32,7 @@
 
 #include "hb.hh"
 #include "hb-unicode.hh"
+#include "hb-set.hh"
 #include "hb-set-digest.hh"
 
 
@@ -194,7 +195,12 @@ struct hb_buffer_t
   hb_set_digest_t digest () const
   {
     hb_set_digest_t d;
-    d.init ();
+    d.add_array (&info[0].codepoint, len, sizeof (info[0]));
+    return d;
+  }
+  hb_set_t set () const
+  {
+    hb_set_t d;
     d.add_array (&info[0].codepoint, len, sizeof (info[0]));
     return d;
   }