7 files changed, 38 insertions, 26 deletions
diff --git a/thirdparty/harfbuzz/src/hb-aat-layout-morx-table.hh b/thirdparty/harfbuzz/src/hb-aat-layout-morx-table.hh
index 2f99510925..b77c1f4d44 100644
--- a/thirdparty/harfbuzz/src/hb-aat-layout-morx-table.hh
+++ b/thirdparty/harfbuzz/src/hb-aat-layout-morx-table.hh
@@ -1038,12 +1038,12 @@ struct Chain
 	goto skip;
 
       if (reverse)
-	_hb_ot_layout_reverse_graphemes (c->buffer);
+	c->buffer->reverse ();
 
       subtable->apply (c);
 
       if (reverse)
-	_hb_ot_layout_reverse_graphemes (c->buffer);
+	c->buffer->reverse ();
 
       (void) c->buffer->message (c->font, "end chainsubtable %d", c->lookup_index);
 
diff --git a/thirdparty/harfbuzz/src/hb-blob.cc b/thirdparty/harfbuzz/src/hb-blob.cc
index f120002d17..65e44c7f6a 100644
--- a/thirdparty/harfbuzz/src/hb-blob.cc
+++ b/thirdparty/harfbuzz/src/hb-blob.cc
@@ -631,7 +631,7 @@ hb_blob_create_from_file_or_fail (const char *file_name)
      Allison Lortie permission but changed a lot to suit our need. */
 #if defined(HAVE_MMAP) && !defined(HB_NO_MMAP)
   hb_mapped_file_t *file = (hb_mapped_file_t *) hb_calloc (1, sizeof (hb_mapped_file_t));
-  if (unlikely (!file)) return hb_blob_get_empty ();
+  if (unlikely (!file)) return nullptr;
 
   int fd = open (file_name, O_RDONLY | O_BINARY, 0);
   if (unlikely (fd == -1)) goto fail_without_close;
@@ -671,7 +671,7 @@ fail_without_close:
 
 #elif defined(_WIN32) && !defined(HB_NO_MMAP)
   hb_mapped_file_t *file = (hb_mapped_file_t *) hb_calloc (1, sizeof (hb_mapped_file_t));
-  if (unlikely (!file)) return hb_blob_get_empty ();
+  if (unlikely (!file)) return nullptr;
 
   HANDLE fd;
   unsigned int size = strlen (file_name) + 1;
diff --git a/thirdparty/harfbuzz/src/hb-ot-layout-gsubgpos.hh b/thirdparty/harfbuzz/src/hb-ot-layout-gsubgpos.hh
index 3faa1e53d5..56e8c5b006 100644
--- a/thirdparty/harfbuzz/src/hb-ot-layout-gsubgpos.hh
+++ b/thirdparty/harfbuzz/src/hb-ot-layout-gsubgpos.hh
@@ -1415,11 +1415,6 @@ static inline void apply_lookup (hb_ot_apply_context_t *c,
     if (idx >= count)
       continue;
 
-    /* Don't recurse to ourself at same position.
-     * Note that this test is too naive, it doesn't catch longer loops. */
-    if (unlikely (idx == 0 && lookupRecord[i].lookupListIndex == c->lookup_index))
-      continue;
-
     unsigned int orig_len = buffer->backtrack_len () + buffer->lookahead_len ();
 
     /* This can happen if earlier recursed lookups deleted many entries. */
@@ -1457,11 +1452,10 @@ static inline void apply_lookup (hb_ot_apply_context_t *c,
      *     NOT the one after it.
      *
      *   - If buffer length was decreased by n, it does not necessarily
-     *     mean that n match positions where removed, as there might
-     *     have been marks and default-ignorables in the sequence.  We
-     *     should instead drop match positions between current-position
-     *     and current-position + n instead. Though, am not sure which
-     *     one is better. Both cases have valid uses. Sigh.
+     *     mean that n match positions where removed, as there recursed-to
+     *     lookup might had a different LookupFlag.  Here's a constructed
+     *     case of that:
+     *     https://github.com/harfbuzz/harfbuzz/discussions/3538
      *
      * It should be possible to construct tests for both of these cases.
      */
diff --git a/thirdparty/harfbuzz/src/hb-ot-shape-complex-khmer.cc b/thirdparty/harfbuzz/src/hb-ot-shape-complex-khmer.cc
index d7ec1632ea..a7d5bf574b 100644
--- a/thirdparty/harfbuzz/src/hb-ot-shape-complex-khmer.cc
+++ b/thirdparty/harfbuzz/src/hb-ot-shape-complex-khmer.cc
@@ -110,7 +110,14 @@ collect_features_khmer (hb_ot_shape_planner_t *plan)
   map->enable_feature (HB_TAG('l','o','c','l'), F_PER_SYLLABLE);
   map->enable_feature (HB_TAG('c','c','m','p'), F_PER_SYLLABLE);
 
-  for (unsigned i = 0; i < KHMER_NUM_FEATURES; i++)
+  unsigned int i = 0;
+  for (; i < KHMER_BASIC_FEATURES; i++)
+    map->add_feature (khmer_features[i]);
+
+  /* https://github.com/harfbuzz/harfbuzz/issues/3531 */
+  map->add_gsub_pause (nullptr);
+
+  for (; i < KHMER_NUM_FEATURES; i++)
     map->add_feature (khmer_features[i]);
 }
 
diff --git a/thirdparty/harfbuzz/src/hb-ot-shape-complex-myanmar.cc b/thirdparty/harfbuzz/src/hb-ot-shape-complex-myanmar.cc
index c7aa80a79a..13beaf4d4c 100644
--- a/thirdparty/harfbuzz/src/hb-ot-shape-complex-myanmar.cc
+++ b/thirdparty/harfbuzz/src/hb-ot-shape-complex-myanmar.cc
@@ -105,8 +105,7 @@ setup_masks_myanmar (const hb_ot_shape_plan_t *plan HB_UNUSED,
   HB_BUFFER_ALLOCATE_VAR (buffer, myanmar_category);
   HB_BUFFER_ALLOCATE_VAR (buffer, myanmar_position);
 
-  /* We cannot setup masks here.  We save information about characters
-   * and setup masks later on in a pause-callback. */
+  /* No masks, we just save information about characters. */
 
   unsigned int count = buffer->len;
   hb_glyph_info_t *info = buffer->info;
diff --git a/thirdparty/harfbuzz/src/hb-ot-shape.cc b/thirdparty/harfbuzz/src/hb-ot-shape.cc
index 298cf47786..99aadab3f0 100644
--- a/thirdparty/harfbuzz/src/hb-ot-shape.cc
+++ b/thirdparty/harfbuzz/src/hb-ot-shape.cc
@@ -47,6 +47,9 @@
 
 #include "hb-aat-layout.hh"
 
+static inline bool
+_hb_codepoint_is_regional_indicator (hb_codepoint_t u)
+{ return hb_in_range<hb_codepoint_t> (u, 0x1F1E6u, 0x1F1FFu); }
 
 #ifndef HB_NO_AAT_SHAPE
 static inline bool
@@ -504,9 +507,9 @@ hb_set_unicode_props (hb_buffer_t *buffer)
     }
     /* Regional_Indicators are hairy as hell...
      * https://github.com/harfbuzz/harfbuzz/issues/2265 */
-    else if (unlikely (i && hb_in_range<hb_codepoint_t> (info[i].codepoint, 0x1F1E6u, 0x1F1FFu)))
+    else if (unlikely (i && _hb_codepoint_is_regional_indicator (info[i].codepoint)))
     {
-      if (hb_in_range<hb_codepoint_t> (info[i - 1].codepoint, 0x1F1E6u, 0x1F1FFu) &&
+      if (_hb_codepoint_is_regional_indicator (info[i - 1].codepoint) &&
 	  !_hb_glyph_info_is_continuation (&info[i - 1]))
 	_hb_glyph_info_set_continuation (&info[i]);
     }
@@ -598,24 +601,33 @@ hb_ensure_native_direction (hb_buffer_t *buffer)
    * direction, so that features like ligatures will work as intended.
    *
    * https://github.com/harfbuzz/harfbuzz/issues/501
+   *
+   * Similar thing about Regional_Indicators; They are bidi=L, but Script=Common.
+   * If they are present in a run of natively-RTL text, they get assigned a script
+   * with natively RTL direction, which would result in wrong shaping if we
+   * assign such native RTL direction to them then. Detect that as well.
+   *
+   * https://github.com/harfbuzz/harfbuzz/issues/3314
    */
   if (unlikely (horiz_dir == HB_DIRECTION_RTL && direction == HB_DIRECTION_LTR))
   {
-    bool found_number = false, found_letter = false;
+    bool found_number = false, found_letter = false, found_ri = false;
     const auto* info = buffer->info;
     const auto count = buffer->len;
     for (unsigned i = 0; i < count; i++)
     {
       auto gc = _hb_glyph_info_get_general_category (&info[i]);
       if (gc == HB_UNICODE_GENERAL_CATEGORY_DECIMAL_NUMBER)
-        found_number = true;
+	found_number = true;
       else if (HB_UNICODE_GENERAL_CATEGORY_IS_LETTER (gc))
       {
-        found_letter = true;
-        break;
+	found_letter = true;
+	break;
       }
+      else if (_hb_codepoint_is_regional_indicator (info[i].codepoint))
+	found_ri = true;
     }
-    if (found_number && !found_letter)
+    if ((found_number || found_ri) && !found_letter)
       horiz_dir = HB_DIRECTION_LTR;
   }
 
diff --git a/thirdparty/harfbuzz/src/hb-version.h b/thirdparty/harfbuzz/src/hb-version.h
index 39fbde45c1..94c73e15bf 100644
--- a/thirdparty/harfbuzz/src/hb-version.h
+++ b/thirdparty/harfbuzz/src/hb-version.h
@@ -53,14 +53,14 @@ HB_BEGIN_DECLS
  *
  * The micro component of the library version available at compile-time.
  */
-#define HB_VERSION_MICRO 0
+#define HB_VERSION_MICRO 1
 
 /**
  * HB_VERSION_STRING:
  *
  * A string literal containing the library version available at compile-time.
  */
-#define HB_VERSION_STRING "4.2.0"
+#define HB_VERSION_STRING "4.2.1"
 
 /**
  * HB_VERSION_ATLEAST: