--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/harfbuzz/src/OT/Layout/GSUB/AlternateSet.hh	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,126 @@
+#ifndef OT_LAYOUT_GSUB_ALTERNATESET_HH
+#define OT_LAYOUT_GSUB_ALTERNATESET_HH
+
+#include "Common.hh"
+
+namespace OT {
+namespace Layout {
+namespace GSUB_impl {
+
+template <typename Types>
+struct AlternateSet
+{
+  protected:
+  Array16Of<typename Types::HBGlyphID>
+                alternates;             /* Array of alternate GlyphIDs--in
+                                         * arbitrary order */
+  public:
+  DEFINE_SIZE_ARRAY (2, alternates);
+
+  bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (alternates.sanitize (c));
+  }
+
+  bool intersects (const hb_set_t *glyphs) const
+  { return hb_any (alternates, glyphs); }
+
+  void closure (hb_closure_context_t *c) const
+  { c->output->add_array (alternates.arrayZ, alternates.len); }
+
+  void collect_glyphs (hb_collect_glyphs_context_t *c) const
+  { c->output->add_array (alternates.arrayZ, alternates.len); }
+
+  bool apply (hb_ot_apply_context_t *c) const
+  {
+    TRACE_APPLY (this);
+    unsigned int count = alternates.len;
+
+    if (unlikely (!count)) return_trace (false);
+
+    hb_mask_t glyph_mask = c->buffer->cur().mask;
+    hb_mask_t lookup_mask = c->lookup_mask;
+
+    /* Note: This breaks badly if two features enabled this lookup together. */
+    unsigned int shift = hb_ctz (lookup_mask);
+    unsigned int alt_index = ((lookup_mask & glyph_mask) >> shift);
+
+    /* If alt_index is MAX_VALUE, randomize feature if it is the rand feature. */
+    if (alt_index == HB_OT_MAP_MAX_VALUE && c->random)
+    {
+      /* Maybe we can do better than unsafe-to-break all; but since we are
+       * changing random state, it would be hard to track that.  Good 'nough. */
+      c->buffer->unsafe_to_break (0, c->buffer->len);
+      alt_index = c->random_number () % count + 1;
+    }
+
+    if (unlikely (alt_index > count || alt_index == 0)) return_trace (false);
+
+    if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())
+    {
+      c->buffer->sync_so_far ();
+      c->buffer->message (c->font,
+			  "replacing glyph at %d (alternate substitution)",
+			  c->buffer->idx);
+    }
+
+    c->replace_glyph (alternates[alt_index - 1]);
+
+    if (HB_BUFFER_MESSAGE_MORE && c->buffer->messaging ())
+    {
+      c->buffer->message (c->font,
+			  "replaced glyph at %d (alternate substitution)",
+			  c->buffer->idx - 1);
+    }
+
+    return_trace (true);
+  }
+
+  unsigned
+  get_alternates (unsigned        start_offset,
+                  unsigned       *alternate_count  /* IN/OUT.  May be NULL. */,
+                  hb_codepoint_t *alternate_glyphs /* OUT.     May be NULL. */) const
+  {
+    if (alternates.len && alternate_count)
+    {
+      + alternates.as_array ().sub_array (start_offset, alternate_count)
+      | hb_sink (hb_array (alternate_glyphs, *alternate_count))
+      ;
+    }
+    return alternates.len;
+  }
+
+  template <typename Iterator,
+            hb_requires (hb_is_source_of (Iterator, hb_codepoint_t))>
+  bool serialize (hb_serialize_context_t *c,
+                  Iterator alts)
+  {
+    TRACE_SERIALIZE (this);
+    return_trace (alternates.serialize (c, alts));
+  }
+
+  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;
+
+    auto it =
+      + hb_iter (alternates)
+      | hb_filter (glyphset)
+      | hb_map (glyph_map)
+      ;
+
+    auto *out = c->serializer->start_embed (*this);
+    return_trace (out->serialize (c->serializer, it) &&
+                  out->alternates);
+  }
+};
+
+}
+}
+}
+
+
+#endif /* OT_LAYOUT_GSUB_ALTERNATESET_HH */