--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/harfbuzz/src/OT/Layout/GSUB/ReverseChainSingleSubstFormat1.hh	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,244 @@
+#ifndef OT_LAYOUT_GSUB_REVERSECHAINSINGLESUBSTFORMAT1_HH
+#define OT_LAYOUT_GSUB_REVERSECHAINSINGLESUBSTFORMAT1_HH
+
+#include "Common.hh"
+
+namespace OT {
+namespace Layout {
+namespace GSUB_impl {
+
+struct ReverseChainSingleSubstFormat1
+{
+  protected:
+  HBUINT16      format;                 /* Format identifier--format = 1 */
+  Offset16To<Coverage>
+                coverage;               /* Offset to Coverage table--from
+                                         * beginning of table */
+  Array16OfOffset16To<Coverage>
+                backtrack;              /* Array of coverage tables
+                                         * in backtracking sequence, in glyph
+                                         * sequence order */
+  Array16OfOffset16To<Coverage>
+                lookaheadX;             /* Array of coverage tables
+                                         * in lookahead sequence, in glyph
+                                         * sequence order */
+  Array16Of<HBGlyphID16>
+                substituteX;            /* Array of substitute
+                                         * GlyphIDs--ordered by Coverage Index */
+  public:
+  DEFINE_SIZE_MIN (10);
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    if (!(coverage.sanitize (c, this) && backtrack.sanitize (c, this)))
+      return_trace (false);
+    const auto &lookahead = StructAfter<decltype (lookaheadX)> (backtrack);
+    if (!lookahead.sanitize (c, this))
+      return_trace (false);
+    const auto &substitute = StructAfter<decltype (substituteX)> (lookahead);
+    return_trace (substitute.sanitize (c));
+  }
+
+  bool intersects (const hb_set_t *glyphs) const
+  {
+    if (!(this+coverage).intersects (glyphs))
+      return false;
+
+    const auto &lookahead = StructAfter<decltype (lookaheadX)> (backtrack);
+
+    unsigned int count;
+
+    count = backtrack.len;
+    for (unsigned int i = 0; i < count; i++)
+      if (!(this+backtrack[i]).intersects (glyphs))
+        return false;
+
+    count = lookahead.len;
+    for (unsigned int i = 0; i < count; i++)
+      if (!(this+lookahead[i]).intersects (glyphs))
+        return false;
+
+    return true;
+  }
+
+  bool may_have_non_1to1 () const
+  { return false; }
+
+  void closure (hb_closure_context_t *c) const
+  {
+    if (!intersects (c->glyphs)) return;
+
+    const auto &lookahead = StructAfter<decltype (lookaheadX)> (backtrack);
+    const auto &substitute = StructAfter<decltype (substituteX)> (lookahead);
+
+    + hb_zip (this+coverage, substitute)
+    | hb_filter (c->parent_active_glyphs (), hb_first)
+    | hb_map (hb_second)
+    | hb_sink (c->output)
+    ;
+  }
+
+  void closure_lookups (hb_closure_lookups_context_t *c) const {}
+
+  void collect_glyphs (hb_collect_glyphs_context_t *c) const
+  {
+    if (unlikely (!(this+coverage).collect_coverage (c->input))) return;
+
+    unsigned int count;
+
+    count = backtrack.len;
+    for (unsigned int i = 0; i < count; i++)
+      if (unlikely (!(this+backtrack[i]).collect_coverage (c->before))) return;
+
+    const auto &lookahead = StructAfter<decltype (lookaheadX)> (backtrack);
+    count = lookahead.len;
+    for (unsigned int i = 0; i < count; i++)
+      if (unlikely (!(this+lookahead[i]).collect_coverage (c->after))) return;
+
+    const auto &substitute = StructAfter<decltype (substituteX)> (lookahead);
+    count = substitute.len;
+    c->output->add_array (substitute.arrayZ, substitute.len);
+  }
+
+  const Coverage &get_coverage () const { return this+coverage; }
+
+  bool would_apply (hb_would_apply_context_t *c) const
+  { return c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED; }
+
+  bool apply (hb_ot_apply_context_t *c) const
+  {
+    TRACE_APPLY (this);
+    if (unlikely (c->nesting_level_left != HB_MAX_NESTING_LEVEL))
+      return_trace (false); /* No chaining to this type */
+
+    unsigned int index = (this+coverage).get_coverage (c->buffer->cur ().codepoint);
+    if (likely (index == NOT_COVERED)) return_trace (false);
+
+    const auto &lookahead = StructAfter<decltype (lookaheadX)> (backtrack);
+    const auto &substitute = StructAfter<decltype (substituteX)> (lookahead);
+
+    if (unlikely (index >= substitute.len)) return_trace (false);
+
+    unsigned int start_index = 0, end_index = 0;
+    if (match_backtrack (c,
+                         backtrack.len, (HBUINT16 *) backtrack.arrayZ,
+                         match_coverage, this,
+                         &start_index) &&
+        match_lookahead (c,
+                         lookahead.len, (HBUINT16 *) lookahead.arrayZ,
+                         match_coverage, this,
+                         c->buffer->idx + 1, &end_index))
+    {
+      c->buffer->unsafe_to_break_from_outbuffer (start_index, end_index);
+
+      if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())
+      {
+	c->buffer->message (c->font,
+			    "replacing glyph at %d (reverse chaining substitution)",
+			    c->buffer->idx);
+      }
+
+      c->replace_glyph_inplace (substitute[index]);
+
+      if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())
+      {
+	c->buffer->message (c->font,
+			    "replaced glyph at %d (reverse chaining substitution)",
+			    c->buffer->idx);
+      }
+
+      /* Note: We DON'T decrease buffer->idx.  The main loop does it
+       * for us.  This is useful for preventing surprises if someone
+       * calls us through a Context lookup. */
+      return_trace (true);
+    }
+    else
+    {
+      c->buffer->unsafe_to_concat_from_outbuffer (start_index, end_index);
+      return_trace (false);
+    }
+  }
+
+  template<typename Iterator,
+           hb_requires (hb_is_iterator (Iterator))>
+  bool serialize_coverage_offset_array (hb_subset_context_t *c, Iterator it) const
+  {
+    TRACE_SERIALIZE (this);
+    auto *out = c->serializer->start_embed<Array16OfOffset16To<Coverage>> ();
+
+    if (unlikely (!c->serializer->allocate_size<HBUINT16> (HBUINT16::static_size)))
+      return_trace (false);
+
+    for (auto& offset : it) {
+      auto *o = out->serialize_append (c->serializer);
+      if (unlikely (!o) || !o->serialize_subset (c, offset, this))
+        return_trace (false);
+    }
+
+    return_trace (true);
+  }
+
+  template<typename Iterator, typename BacktrackIterator, typename LookaheadIterator,
+           hb_requires (hb_is_sorted_source_of (Iterator, hb_codepoint_pair_t)),
+           hb_requires (hb_is_iterator (BacktrackIterator)),
+           hb_requires (hb_is_iterator (LookaheadIterator))>
+  bool serialize (hb_subset_context_t *c,
+                  Iterator coverage_subst_iter,
+                  BacktrackIterator backtrack_iter,
+                  LookaheadIterator lookahead_iter) const
+  {
+    TRACE_SERIALIZE (this);
+
+    auto *out = c->serializer->start_embed (this);
+    if (unlikely (!c->serializer->check_success (out))) return_trace (false);
+    if (unlikely (!c->serializer->embed (this->format))) return_trace (false);
+    if (unlikely (!c->serializer->embed (this->coverage))) return_trace (false);
+
+    if (!serialize_coverage_offset_array (c, backtrack_iter)) return_trace (false);
+    if (!serialize_coverage_offset_array (c, lookahead_iter)) return_trace (false);
+
+    auto *substitute_out = c->serializer->start_embed<Array16Of<HBGlyphID16>> ();
+    auto substitutes =
+    + coverage_subst_iter
+    | hb_map (hb_second)
+    ;
+
+    auto glyphs =
+    + coverage_subst_iter
+    | hb_map_retains_sorting (hb_first)
+    ;
+    if (unlikely (! c->serializer->check_success (substitute_out->serialize (c->serializer, substitutes))))
+        return_trace (false);
+
+    if (unlikely (!out->coverage.serialize_serialize (c->serializer, glyphs)))
+      return_trace (false);
+    return_trace (true);
+  }
+
+  bool subset (hb_subset_context_t *c) const
+  {
+    TRACE_SUBSET (this);
+    const hb_set_t &glyphset = *c->plan->glyphset_gsub ();
+    const hb_map_t &glyph_map = *c->plan->glyph_map;
+
+    const auto &lookahead = StructAfter<decltype (lookaheadX)> (backtrack);
+    const auto &substitute = StructAfter<decltype (substituteX)> (lookahead);
+
+    auto it =
+    + hb_zip (this+coverage, substitute)
+    | hb_filter (glyphset, hb_first)
+    | hb_filter (glyphset, hb_second)
+    | hb_map_retains_sorting ([&] (hb_pair_t<hb_codepoint_t, const HBGlyphID16 &> p) -> hb_codepoint_pair_t
+                              { return hb_pair (glyph_map[p.first], glyph_map[p.second]); })
+    ;
+
+    return_trace (bool (it) && serialize (c, it, backtrack.iter (), lookahead.iter ()));
+  }
+};
+
+}
+}
+}
+
+#endif  /* HB_OT_LAYOUT_GSUB_REVERSECHAINSINGLESUBSTFORMAT1_HH */