From e1cb3b155a219e03fffac1355140a24b6f856cc8 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 4 Feb 2025 17:28:29 +0000
Subject: [PATCH] Revert "[aat] Remove set-digest"

This reverts commit 832f199607292a41b4621b87a646c30cddc00124.
---
 src/hb-aat-layout-common.hh     |  3 ++-
 src/hb-aat-layout-morx-table.hh | 31 +++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/hb-aat-layout-common.hh b/src/hb-aat-layout-common.hh
index 121c25f18..37d919a17 100644
--- a/src/hb-aat-layout-common.hh
+++ b/src/hb-aat-layout-common.hh
@@ -68,6 +68,7 @@ struct hb_aat_apply_context_t :
   hb_set_digest_t buffer_digest = hb_set_digest_t::full ();
   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 ();
   hb_aat_class_cache_t *machine_class_cache = nullptr;
   hb_mask_t subtable_flags = 0;
 
@@ -941,7 +942,7 @@ struct StateTableDriver
   {
     const auto entry = machine.get_entry (StateTableT::STATE_START_OF_TEXT, CLASS_OUT_OF_BOUNDS);
     return !c->is_actionable (ac->buffer, this, entry) &&
-           machine.new_state (entry.newState) == StateTableT::STATE_START_OF_TEXT;
+	    machine.new_state (entry.newState) == StateTableT::STATE_START_OF_TEXT;
   }
 
   template <typename context_t>
diff --git a/src/hb-aat-layout-morx-table.hh b/src/hb-aat-layout-morx-table.hh
index d05737a89..1b836944e 100644
--- a/src/hb-aat-layout-morx-table.hh
+++ b/src/hb-aat-layout-morx-table.hh
@@ -171,6 +171,10 @@ struct RearrangementSubtable
 
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
+    if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
+	!c->buffer_digest.may_have (c->machine_glyph_set))
+      return_trace (false);
+
     driver.drive (&dc, c);
 
     return_trace (dc.ret);
@@ -332,6 +336,10 @@ struct ContextualSubtable
 
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
+    if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
+	!c->buffer_digest.may_have (c->machine_glyph_set))
+      return_trace (false);
+
     driver.drive (&dc, c);
 
     return_trace (dc.ret);
@@ -591,6 +599,10 @@ struct LigatureSubtable
 
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
+    if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
+	!c->buffer_digest.may_have (c->machine_glyph_set))
+      return_trace (false);
+
     driver.drive (&dc, c);
 
     return_trace (dc.ret);
@@ -863,6 +875,10 @@ struct InsertionSubtable
 
     StateTableDriver<Types, EntryData> driver (machine, c->face);
 
+    if (driver.is_idempotent_on_all_out_of_bounds (&dc, c) &&
+	!c->buffer_digest.may_have (c->machine_glyph_set))
+      return_trace (false);
+
     driver.drive (&dc, c);
 
     return_trace (dc.ret);
@@ -919,11 +935,25 @@ struct hb_accelerate_subtables_context_t :
     friend struct hb_aat_layout_lookup_accelerator_t;
 
     public:
+    hb_set_digest_t digest;
     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)
+    )
+
+    template <typename T>
+    void init_ (const T &obj_, unsigned num_glyphs, hb_priority<0>)
+    {
+      digest = digest.full ();
+    }
+
     template <typename T>
     void init (const T &obj_, unsigned num_glyphs)
     {
+      init_ (obj_, num_glyphs, hb_prioritize);
       class_cache.clear ();
     }
 
@@ -1143,6 +1173,7 @@ 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_class_cache = accel ? &accel->subtables[i].class_cache : nullptr;
 
       if (!(subtable->get_coverage() & ChainSubtable<Types>::AllDirections) &&