From 2a878b1b7684dac9473f6e64aa01c376d03e7f4f Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 7 Mar 2025 17:23:17 -0700
Subject: [PATCH 01/23] [font-funcs] Add two new API

+ hb_font_set_funcs_using()
+ hb_font_list_funcs()

Part of https://github.com/harfbuzz/harfbuzz/issues/5117
---
 docs/harfbuzz-sections.txt              |   2 +
 perf/benchmark-font.cc                  |  77 ++++-------------
 src/hb-font.cc                          | 107 ++++++++++++++++++++++++
 src/hb-font.h                           |   6 ++
 test/api/test-draw.c                    |  23 +----
 test/api/test-multithread.c             |  15 ++--
 test/api/test-ot-extents-cff.c          |   7 --
 test/api/test-ot-face.c                 |   1 -
 test/api/test-ot-metrics-tt-var.c       |   7 --
 test/fuzzing/hb-shape-fuzzer.cc         |   1 -
 test/shape/data/aots/hb-aots-tester.cpp |   1 -
 test/threads/hb-shape-threads.cc        |  32 ++-----
 util/font-options.hh                    |  70 ++++------------
 13 files changed, 167 insertions(+), 182 deletions(-)

diff --git a/docs/harfbuzz-sections.txt b/docs/harfbuzz-sections.txt
index 74d2e166e..c37138572 100644
--- a/docs/harfbuzz-sections.txt
+++ b/docs/harfbuzz-sections.txt
@@ -458,6 +458,8 @@ hb_font_get_serial
 hb_font_changed
 hb_font_set_funcs
 hb_font_set_funcs_data
+hb_font_set_funcs_using
+hb_font_list_funcs
 hb_font_subtract_glyph_origin_for_direction
 hb_font_funcs_create
 hb_font_funcs_get_empty
diff --git a/perf/benchmark-font.cc b/perf/benchmark-font.cc
index deefecf7a..d513b9fe2 100644
--- a/perf/benchmark-font.cc
+++ b/perf/benchmark-font.cc
@@ -21,8 +21,6 @@ struct test_input_t
 static test_input_t *tests = default_tests;
 static unsigned num_tests = sizeof (default_tests) / sizeof (default_tests[0]);
 
-enum backend_t { HARFBUZZ, FREETYPE, FONTATIONS, CORETEXT };
-
 enum operation_t
 {
   nominal_glyphs,
@@ -81,7 +79,8 @@ _draw_funcs_create (void)
 }
 
 static void BM_Font (benchmark::State &state,
-		     bool is_var, backend_t backend, operation_t operation,
+		     bool is_var, const char * backend,
+		     operation_t operation,
 		     const test_input_t &test_input)
 {
   hb_font_t *font;
@@ -100,29 +99,12 @@ static void BM_Font (benchmark::State &state,
     hb_font_set_variations (font, &wght, 1);
   }
 
-  switch (backend)
+  bool ret = hb_font_set_funcs_using (font, backend);
+  if (!ret)
   {
-    case HARFBUZZ:
-      hb_ot_font_set_funcs (font);
-      break;
-
-    case FREETYPE:
-#ifdef HAVE_FREETYPE
-      hb_ft_font_set_funcs (font);
-#endif
-      break;
-
-    case FONTATIONS:
-#ifdef HAVE_FONTATIONS
-      hb_fontations_font_set_funcs (font);
-#endif
-      break;
-
-    case CORETEXT:
-#ifdef HAVE_CORETEXT
-      hb_coretext_font_set_funcs (font);
-#endif
-      break;
+    state.SkipWithError("Backend failed to initialize for font.");
+    hb_font_destroy (font);
+    return;
   }
 
   switch (operation)
@@ -210,29 +192,12 @@ static void BM_Font (benchmark::State &state,
 	hb_font_t *font = hb_font_create (face);
 	hb_face_destroy (face);
 
-	switch (backend)
+	bool ret = hb_font_set_funcs_using (font, backend);
+	if (!ret)
 	{
-	  case HARFBUZZ:
-	    hb_ot_font_set_funcs (font);
-	    break;
-
-	  case FREETYPE:
-#ifdef HAVE_FREETYPE
-	    hb_ft_font_set_funcs (font);
-#endif
-	    break;
-
-	  case FONTATIONS:
-#ifdef HAVE_FONTATIONS
-	    hb_fontations_font_set_funcs (font);
-#endif
-	    break;
-
-	  case CORETEXT:
-#ifdef HAVE_CORETEXT
-	    hb_coretext_font_set_funcs (font);
-#endif
-	    break;
+	  state.SkipWithError("Backend failed to initialize for font.");
+	  hb_font_destroy (font);
+	  return;
 	}
 
 	hb_buffer_t *buffer = hb_buffer_create ();
@@ -252,8 +217,7 @@ static void BM_Font (benchmark::State &state,
   hb_font_destroy (font);
 }
 
-static void test_backend (backend_t backend,
-			  const char *backend_name,
+static void test_backend (const char *backend,
 			  bool variable,
 			  operation_t op,
 			  const char *op_name,
@@ -267,7 +231,7 @@ static void test_backend (backend_t backend,
   strcat (name, p ? p + 1 : test_input.font_path);
   strcat (name, variable ? "/var" : "");
   strcat (name, "/");
-  strcat (name, backend_name);
+  strcat (name, backend);
 
   benchmark::RegisterBenchmark (name, BM_Font, variable, backend, op, test_input)
    ->Unit(time_unit);
@@ -277,6 +241,7 @@ static void test_operation (operation_t op,
 			    const char *op_name,
 			    benchmark::TimeUnit time_unit)
 {
+  const char **supported_backends = hb_font_list_funcs ();
   for (unsigned i = 0; i < num_tests; i++)
   {
     auto& test_input = tests[i];
@@ -284,16 +249,8 @@ static void test_operation (operation_t op,
     {
       bool is_var = (bool) variable;
 
-      test_backend (HARFBUZZ, "hb", is_var, op, op_name, time_unit, test_input);
-#ifdef HAVE_FREETYPE
-      test_backend (FREETYPE, "ft", is_var, op, op_name, time_unit, test_input);
-#endif
-#ifdef HAVE_FONTATIONS
-      test_backend (FONTATIONS, "fontations", is_var, op, op_name, time_unit, test_input);
-#endif
-#ifdef HAVE_CORETEXT
-      test_backend (CORETEXT, "coretext", is_var, op, op_name, time_unit, test_input);
-#endif
+      for (const char **backend = supported_backends; *backend; backend++)
+	test_backend (*backend, is_var, op, op_name, time_unit, test_input);
     }
   }
 }
diff --git a/src/hb-font.cc b/src/hb-font.cc
index 96b79ecca..8d0ff4c8e 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -38,6 +38,19 @@
 #include "hb-ot-var-avar-table.hh"
 #include "hb-ot-var-fvar-table.hh"
 
+#ifndef HB_NO_OT_FONT
+#include "hb-ot.h"
+#endif
+#ifdef HAVE_FREETYPE
+#include "hb-ft.h"
+#endif
+#ifdef HAVE_FONTATIONS
+#include "hb-fontations.h"
+#endif
+#ifdef HAVE_CORETEXT
+#include "hb-coretext.h"
+#endif
+
 
 /**
  * SECTION:hb-font
@@ -2292,6 +2305,100 @@ hb_font_set_funcs_data (hb_font_t         *font,
   font->destroy = destroy;
 }
 
+static struct supported_font_funcs_t {
+	char name[12];
+	void (*func) (hb_font_t *);
+} supported_font_funcs[] =
+{
+  {"ot",	hb_ot_font_set_funcs},
+#ifdef HAVE_FREETYPE
+  {"ft",	hb_ft_font_set_funcs},
+#endif
+#ifdef HAVE_FONTATIONS
+  {"fontations",hb_fontations_font_set_funcs},
+#endif
+#ifdef HAVE_CORETEXT
+  {"coretext",	hb_coretext_font_set_funcs},
+#endif
+};
+
+/**
+ * hb_font_set_funcs_using:
+ * @font: #hb_font_t to work upon
+ * @name: The name of the font-functions structure to use
+ *
+ * Sets the font-functions structure to use for a font, based on the
+ * specified name.
+ *
+ * If @name is `NULL`, the first functioning font-functions are used.
+ *
+ * Return value: `true` if the font-functions was found and set, `false` otherwise
+ *
+ * XSince: REPLACEME
+ **/
+hb_bool_t
+hb_font_set_funcs_using (hb_font_t  *font,
+			 const char *name)
+{
+  for (unsigned i = 0; i < ARRAY_LENGTH (supported_font_funcs); i++)
+    if (!name || strcmp (supported_font_funcs[i].name, name) == 0)
+    {
+      supported_font_funcs[i].func (font);
+      if (name || font->klass != hb_font_funcs_get_empty ())
+	return true;
+    }
+  return false;
+}
+
+static inline void free_static_font_funcs_list ();
+
+static const char * const nil_font_funcs_list[] = {nullptr};
+
+static struct hb_font_funcs_list_lazy_loader_t : hb_lazy_loader_t<const char *,
+								  hb_font_funcs_list_lazy_loader_t>
+{
+  static const char ** create ()
+  {
+    const char **font_funcs_list = (const char **) hb_calloc (1 + ARRAY_LENGTH (supported_font_funcs), sizeof (const char *));
+    if (unlikely (!font_funcs_list))
+      return nullptr;
+
+    unsigned i;
+    for (i = 0; i < ARRAY_LENGTH (supported_font_funcs); i++)
+      font_funcs_list[i] = supported_font_funcs[i].name;
+    font_funcs_list[i] = nullptr;
+
+    hb_atexit (free_static_font_funcs_list);
+
+    return font_funcs_list;
+  }
+  static void destroy (const char **l)
+  { hb_free (l); }
+  static const char * const * get_null ()
+  { return nil_font_funcs_list; }
+} static_font_funcs_list;
+
+static inline
+void free_static_font_funcs_list ()
+{
+  static_font_funcs_list.free_instance ();
+}
+
+/**
+ * hb_font_list_funcs:
+ *
+ * Retrieves the list of font functions supported by HarfBuzz.
+ *
+ * Return value: (transfer none) (array zero-terminated=1): an array of
+ *    constant strings
+ *
+ * XSince: REPLACEME
+ **/
+const char **
+hb_font_list_funcs ()
+{
+  return static_font_funcs_list.get_unconst ();
+}
 
 /**
  * hb_font_set_scale:
diff --git a/src/hb-font.h b/src/hb-font.h
index 3c2355af2..478c808e1 100644
--- a/src/hb-font.h
+++ b/src/hb-font.h
@@ -1052,6 +1052,12 @@ hb_font_set_funcs_data (hb_font_t         *font,
 			void              *font_data,
 			hb_destroy_func_t  destroy);
 
+HB_EXTERN hb_bool_t
+hb_font_set_funcs_using (hb_font_t  *font,
+			 const char *name);
+
+HB_EXTERN const char **
+hb_font_list_funcs (void);
 
 HB_EXTERN void
 hb_font_set_scale (hb_font_t *font,
diff --git a/test/api/test-draw.c b/test/api/test-draw.c
index c956de398..9b608e1af 100644
--- a/test/api/test-draw.c
+++ b/test/api/test-draw.c
@@ -1077,23 +1077,6 @@ test_hb_draw_immutable (void)
   hb_draw_funcs_destroy (draw_funcs);
 }
 
-static void
-set_font_funcs (hb_font_t *font, const char *font_funcs_name)
-{
-  if (strcmp (font_funcs_name, "ft") == 0)
-#ifdef HAVE_FREETYPE
-    hb_ft_font_set_funcs (font);
-#else
-    g_assert_not_reached ();
-#endif
-  else if (strcmp (font_funcs_name, "fontations") == 0)
-#ifdef HAVE_FONTATIONS
-    hb_fontations_font_set_funcs (font);
-#else
-    g_assert_not_reached ();
-#endif
-}
-
 static void
 test_hb_draw_funcs (const char* font_funcs_name)
 {
@@ -1105,7 +1088,7 @@ test_hb_draw_funcs (const char* font_funcs_name)
   {
     hb_face_t *face = hb_test_open_font_file ("fonts/glyphs.ttf");
     hb_font_t *font = hb_font_create (face);
-    set_font_funcs (font, font_funcs_name);
+    hb_font_set_funcs_using (font, font_funcs_name);
     hb_face_destroy (face);
     {
       draw_data.consumed = 0;
@@ -1124,7 +1107,7 @@ test_hb_draw_funcs (const char* font_funcs_name)
   {
     hb_face_t *face = hb_test_open_font_file ("fonts/cff1_flex.otf");
     hb_font_t *font = hb_font_create (face);
-    set_font_funcs (font, font_funcs_name);
+    hb_font_set_funcs_using (font, font_funcs_name);
     hb_face_destroy (face);
 
     draw_data.consumed = 0;
@@ -1165,7 +1148,7 @@ test_hb_draw_compare_ot_funcs (const char* font_funcs_name)
   hb_font_draw_glyph (font, 1, funcs, &draw_data);
   draw_data.str[draw_data.consumed] = '\0';
 
-  set_font_funcs (font, font_funcs_name);
+  hb_font_set_funcs_using (font, font_funcs_name);
 
   hb_font_draw_glyph (font, 1, funcs, &draw_data2);
   draw_data2.str[draw_data2.consumed] = '\0';
diff --git a/test/api/test-multithread.c b/test/api/test-multithread.c
index f9460497e..f846416cf 100644
--- a/test/api/test-multithread.c
+++ b/test/api/test-multithread.c
@@ -93,8 +93,11 @@ thread_func (void *data)
 }
 
 static void
-test_body (void)
+test_body (const char *backend)
 {
+  if (!hb_font_set_funcs_using (font, backend))
+    return;
+
   int i;
   pthread_t *threads = calloc (num_threads, sizeof (pthread_t));
   hb_buffer_t **buffers = calloc (num_threads, sizeof (hb_buffer_t *));
@@ -145,13 +148,9 @@ main (int argc, char **argv)
   ref_buffer = hb_buffer_create ();
   fill_the_buffer (ref_buffer);
 
-  /* Unnecessary, since version 2 it is ot-font by default */
-  hb_ot_font_set_funcs (font);
-  test_body ();
-
-  /* Test hb-ft in multithread */
-  hb_ft_font_set_funcs (font);
-  test_body ();
+  // TODO Test all backends
+  test_body ("ot");
+  test_body ("ft");
 
   hb_buffer_destroy (ref_buffer);
 
diff --git a/test/api/test-ot-extents-cff.c b/test/api/test-ot-extents-cff.c
index e6aeb0d6e..ecebcf96b 100644
--- a/test/api/test-ot-extents-cff.c
+++ b/test/api/test-ot-extents-cff.c
@@ -37,7 +37,6 @@ test_extents_cff1 (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   hb_bool_t result = hb_font_get_glyph_extents (font, 1, &extents);
@@ -55,7 +54,6 @@ test_extents_cff1 (void)
   hb_font_t *font_j = hb_font_create (face_j);
   hb_face_destroy (face_j);
   g_assert (font_j);
-  hb_ot_font_set_funcs (font_j);
 
   hb_bool_t result_j = hb_font_get_glyph_extents (font_j, 3, &extents);
   g_assert (result_j);
@@ -76,7 +74,6 @@ test_extents_cff1_flex (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   hb_bool_t result = hb_font_get_glyph_extents (font, 1, &extents);
@@ -98,7 +95,6 @@ test_extents_cff1_seac (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   hb_bool_t result = hb_font_get_glyph_extents (font, 3, &extents); /* Agrave */
@@ -128,7 +124,6 @@ test_extents_cff2 (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   hb_bool_t result = hb_font_get_glyph_extents (font, 1, &extents);
@@ -160,7 +155,6 @@ test_extents_cff2_vsindex (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   float coords[2] = { 800.0f, 50.0f };
@@ -192,7 +186,6 @@ test_extents_cff2_vsindex_named_instance (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_font_set_var_named_instance (font, 6); // 6 (BlackMediumContrast): 900, 50
   hb_glyph_extents_t  extents;
diff --git a/test/api/test-ot-face.c b/test/api/test-ot-face.c
index 6360a186e..7e02bd901 100644
--- a/test/api/test-ot-face.c
+++ b/test/api/test-ot-face.c
@@ -45,7 +45,6 @@ test_font (hb_font_t *font, hb_codepoint_t cp)
   char buf[5] = {0};
   unsigned int len = 0;
   hb_glyph_extents_t extents = {0, 0, 0, 0};
-  hb_ot_font_set_funcs (font);
 
   set = hb_set_create ();
   hb_face_collect_unicodes (face, set);
diff --git a/test/api/test-ot-metrics-tt-var.c b/test/api/test-ot-metrics-tt-var.c
index f2587d8a4..43f77a97b 100644
--- a/test/api/test-ot-metrics-tt-var.c
+++ b/test/api/test-ot-metrics-tt-var.c
@@ -37,7 +37,6 @@ test_extents_tt_var (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   hb_bool_t result = hb_font_get_glyph_extents (font, 2, &extents);
@@ -69,7 +68,6 @@ test_advance_tt_var_nohvar (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_position_t x, y;
   hb_font_get_glyph_advance_for_direction(font, 2, HB_DIRECTION_LTR, &x, &y);
@@ -105,7 +103,6 @@ test_advance_tt_var_hvarvvar (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_position_t x, y;
   hb_font_get_glyph_advance_for_direction(font, 1, HB_DIRECTION_LTR, &x, &y);
@@ -141,7 +138,6 @@ test_advance_tt_var_anchor (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   hb_bool_t result = hb_font_get_glyph_extents (font, 2, &extents);
@@ -173,7 +169,6 @@ test_extents_tt_var_comp (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   hb_glyph_extents_t  extents;
   float coords[1] = { 800.0f };
@@ -215,7 +210,6 @@ test_advance_tt_var_comp_v (void)
   hb_font_t *font = hb_font_create (face);
   hb_face_destroy (face);
   g_assert (font);
-  hb_ot_font_set_funcs (font);
 
   float coords[1] = { 800.0f };
   hb_font_set_var_coords_design (font, coords, 1);
@@ -239,7 +233,6 @@ test_advance_tt_var_gvar_infer (void)
 {
   hb_face_t *face = hb_test_open_font_file ("fonts/TestGVAREight.ttf");
   hb_font_t *font = hb_font_create (face);
-  hb_ot_font_set_funcs (font);
   hb_face_destroy (face);
 
   int coords[6] = {100};
diff --git a/test/fuzzing/hb-shape-fuzzer.cc b/test/fuzzing/hb-shape-fuzzer.cc
index f14f6518e..b573b6ae5 100644
--- a/test/fuzzing/hb-shape-fuzzer.cc
+++ b/test/fuzzing/hb-shape-fuzzer.cc
@@ -17,7 +17,6 @@ extern "C" int LLVMFuzzerTestOneInput (const uint8_t *data, size_t size)
 				    HB_MEMORY_MODE_READONLY, nullptr, nullptr);
   hb_face_t *face = hb_face_create (blob, 0);
   hb_font_t *font = hb_font_create (face);
-  hb_ot_font_set_funcs (font);
   hb_font_set_scale (font, 12, 12);
 
   unsigned num_coords = 0;
diff --git a/test/shape/data/aots/hb-aots-tester.cpp b/test/shape/data/aots/hb-aots-tester.cpp
index 51958fc55..cfec17def 100644
--- a/test/shape/data/aots/hb-aots-tester.cpp
+++ b/test/shape/data/aots/hb-aots-tester.cpp
@@ -75,7 +75,6 @@ runTest(const char *testName,
     unsigned int upem = hb_face_get_upem (face);
 
     hb_font_set_scale(font, upem, upem);
-    hb_ot_font_set_funcs (font);
 
     // setup buffer
     hb_buffer_t *buffer = hb_buffer_create();
diff --git a/test/threads/hb-shape-threads.cc b/test/threads/hb-shape-threads.cc
index 93adfc8c8..d72352e8a 100644
--- a/test/threads/hb-shape-threads.cc
+++ b/test/threads/hb-shape-threads.cc
@@ -11,10 +11,6 @@
 #endif
 
 #include "hb.h"
-#include "hb-ot.h"
-#ifdef HAVE_FREETYPE
-#include "hb-ft.h"
-#endif
 
 #define SUBSET_FONT_BASE_PATH "test/subset/data/fonts/"
 
@@ -51,8 +47,6 @@ struct test_input_t
 static test_input_t *tests = default_tests;
 static unsigned num_tests = sizeof (default_tests) / sizeof (default_tests[0]);
 
-enum backend_t { HARFBUZZ, FREETYPE };
-
 // https://en.cppreference.com/w/cpp/thread/condition_variable/wait
 static std::condition_variable cv;
 static std::mutex cv_m;
@@ -105,8 +99,7 @@ static void shape (const test_input_t &input,
   hb_blob_destroy (text_blob);
 }
 
-static void test_backend (backend_t backend,
-			  const char *backend_name,
+static void test_backend (const char *backend,
 			  bool variable,
 			  const test_input_t &test_input)
 {
@@ -120,7 +113,7 @@ static void test_backend (backend_t backend,
   strcat (name, p ? p + 1 : test_input.text_path);
   strcat (name, variable ? "/var" : "");
   strcat (name, "/");
-  strcat (name, backend_name);
+  strcat (name, backend);
 
   printf ("Testing %s\n", name);
 
@@ -140,18 +133,8 @@ static void test_backend (backend_t backend,
     hb_font_set_variations (font, &wght, 1);
   }
 
-  switch (backend)
-  {
-    case HARFBUZZ:
-      hb_ot_font_set_funcs (font);
-      break;
-
-    case FREETYPE:
-#ifdef HAVE_FREETYPE
-      hb_ft_font_set_funcs (font);
-#endif
-      break;
-  }
+  bool ret = hb_font_set_funcs_using (font, backend);
+  assert (ret);
 
   std::vector<std::thread> threads;
   for (unsigned i = 0; i < num_threads; i++)
@@ -200,10 +183,9 @@ int main(int argc, char** argv)
     {
       bool is_var = (bool) variable;
 
-      test_backend (HARFBUZZ, "hb", is_var, test_input);
-#ifdef HAVE_FREETYPE
-      test_backend (FREETYPE, "ft", is_var, test_input);
-#endif
+      // TODO Test all backends.
+      test_backend ("ot", is_var, test_input);
+      test_backend ("ft", is_var, test_input);
     }
   }
 
diff --git a/util/font-options.hh b/util/font-options.hh
index 88b51ec57..095283e52 100644
--- a/util/font-options.hh
+++ b/util/font-options.hh
@@ -29,17 +29,6 @@
 
 #include "face-options.hh"
 
-#include <hb-ot.h>
-#ifdef HAVE_FREETYPE
-#include <hb-ft.h>
-#endif
-#ifdef HAVE_FONTATIONS
-#include <hb-fontations.h>
-#endif
-#ifdef HAVE_CORETEXT
-#include <hb-coretext.h>
-#endif
-
 #define FONT_SIZE_UPEM 0x7FFFFFFF
 #define FONT_SIZE_NONE 0
 
@@ -84,24 +73,6 @@ struct font_options_t : face_options_t
 };
 
 
-static struct supported_font_funcs_t {
-	char name[11];
-	void (*func) (hb_font_t *);
-} supported_font_funcs[] =
-{
-  {"ot",	hb_ot_font_set_funcs},
-#ifdef HAVE_FREETYPE
-  {"ft",	hb_ft_font_set_funcs},
-#endif
-#ifdef HAVE_FONTATIONS
-  {"fontations",hb_fontations_font_set_funcs},
-#endif
-#ifdef HAVE_CORETEXT
-  {"coretext",	hb_coretext_font_set_funcs},
-#endif
-};
-
-
 void
 font_options_t::post_parse (GError **error)
 {
@@ -130,39 +101,35 @@ font_options_t::post_parse (GError **error)
   hb_font_set_variations (font, variations, num_variations);
 #endif
 
-  void (*set_font_funcs) (hb_font_t *) = nullptr;
-  if (!font_funcs)
+  if (font_funcs)
   {
-    set_font_funcs = supported_font_funcs[0].func;
-  }
-  else
-  {
-    for (unsigned int i = 0; i < ARRAY_LENGTH (supported_font_funcs); i++)
-      if (0 == g_ascii_strcasecmp (font_funcs, supported_font_funcs[i].name))
-      {
-	set_font_funcs = supported_font_funcs[i].func;
-	break;
-      }
-    if (!set_font_funcs)
+    if (!hb_font_set_funcs_using (font, font_funcs))
     {
+      const char **supported_font_funcs = hb_font_list_funcs ();
+      if (unlikely (!supported_font_funcs[0]))
+      {
+        g_set_error (error, G_OPTION_ERROR, G_OPTION_ERROR_BAD_VALUE,
+		     "Unknown font function implementation `%s'; no supported values found",
+		     font_funcs);
+	return;
+      }
       GString *s = g_string_new (nullptr);
-      for (unsigned int i = 0; i < ARRAY_LENGTH (supported_font_funcs); i++)
+      for (unsigned i = 0; supported_font_funcs[i]; i++)
       {
 	if (i)
 	  g_string_append_c (s, '/');
-	g_string_append (s, supported_font_funcs[i].name);
+	g_string_append (s, supported_font_funcs[i]);
       }
       char *p = g_string_free (s, FALSE);
       g_set_error (error, G_OPTION_ERROR, G_OPTION_ERROR_BAD_VALUE,
 		   "Unknown font function implementation `%s'; supported values are: %s; default is %s",
 		   font_funcs,
 		   p,
-		   supported_font_funcs[0].name);
+		   supported_font_funcs[0]);
       free (p);
       return;
     }
   }
-  set_font_funcs (font);
 #ifdef HAVE_FREETYPE
   hb_ft_font_set_load_flags (font, ft_load_flags);
 #endif
@@ -309,16 +276,15 @@ font_options_t::add_options (option_parser_t *parser)
 
   char *font_funcs_text = nullptr;
   {
-    static_assert ((ARRAY_LENGTH_CONST (supported_font_funcs) > 0),
-		   "No supported font-funcs found.");
+    const char **supported_font_funcs = hb_font_list_funcs ();
     GString *s = g_string_new (nullptr);
     g_string_printf (s, "Set font functions implementation to use (default: %s)\n    Supported font function implementations are: %s",
-		     supported_font_funcs[0].name,
-		     supported_font_funcs[0].name);
-    for (unsigned int i = 1; i < ARRAY_LENGTH (supported_font_funcs); i++)
+		     supported_font_funcs[0],
+		     supported_font_funcs[0]);
+    for (unsigned i = 1; supported_font_funcs[i]; i++)
     {
       g_string_append_c (s, '/');
-      g_string_append (s, supported_font_funcs[i].name);
+      g_string_append (s, supported_font_funcs[i]);
     }
     font_funcs_text = g_string_free (s, FALSE);
     parser->free_later (font_funcs_text);

From c3eac5c0f345ffd2fa99f6ddbb9bbc49aebe4932 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 11:54:15 -0700
Subject: [PATCH 02/23] [test-threads] Test all font-funcs

Fontations & Coretext are new and seems to pass.
---
 test/api/test-multithread.c      | 5 ++---
 test/threads/hb-shape-threads.cc | 5 ++---
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/test/api/test-multithread.c b/test/api/test-multithread.c
index f846416cf..52f7cefb9 100644
--- a/test/api/test-multithread.c
+++ b/test/api/test-multithread.c
@@ -148,9 +148,8 @@ main (int argc, char **argv)
   ref_buffer = hb_buffer_create ();
   fill_the_buffer (ref_buffer);
 
-  // TODO Test all backends
-  test_body ("ot");
-  test_body ("ft");
+  for (const char **font_funcs = hb_font_list_funcs (); *font_funcs; font_funcs++)
+    test_body (*font_funcs);
 
   hb_buffer_destroy (ref_buffer);
 
diff --git a/test/threads/hb-shape-threads.cc b/test/threads/hb-shape-threads.cc
index d72352e8a..a99f4ab04 100644
--- a/test/threads/hb-shape-threads.cc
+++ b/test/threads/hb-shape-threads.cc
@@ -183,9 +183,8 @@ int main(int argc, char** argv)
     {
       bool is_var = (bool) variable;
 
-      // TODO Test all backends.
-      test_backend ("ot", is_var, test_input);
-      test_backend ("ft", is_var, test_input);
+      for (const char **font_funcs = hb_font_list_funcs (); *font_funcs; font_funcs++)
+	test_backend (*font_funcs, is_var, test_input);
     }
   }
 

From e8ddb4325b856e17aafd7f7d15c5373e00fc812f Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 12:13:31 -0700
Subject: [PATCH 03/23] [fontations] Consolidate args a bit

---
 src/fontations/meson.build | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/src/fontations/meson.build b/src/fontations/meson.build
index d4a9b7ecf..27ed29b42 100644
--- a/src/fontations/meson.build
+++ b/src/fontations/meson.build
@@ -14,7 +14,14 @@ cargo = find_program('cargo')
 rustfmt = find_program('rustfmt')
 
 rust_flags = ''
-cargo_args = []
+cargo_args = [
+  '--package', 'harfbuzz_fontations',
+  '--lib',
+  '--target-dir', meson.current_build_dir(),
+  '--manifest-path', meson.current_source_dir() / 'Cargo.toml',
+  '-Z', 'build-std=std,panic_abort',
+  '-Z', 'build-std-features=panic_immediate_abort',
+]
 
 buildtype = get_option('buildtype')
 if buildtype == 'release' or buildtype == 'debugoptimized'
@@ -24,9 +31,6 @@ endif
 opt_level = get_option('optimization')
 rust_flags += ' -C opt-level=' + opt_level
 
-cargo_args += ['-Z', 'build-std=std,panic_abort',
-               '-Z', 'build-std-features=panic_immediate_abort']
-
 harfbuzz_fontations = custom_target(
   'harfbuzz_fontations',
   input: ['lib.rs', 'Cargo.toml', 'Cargo.lock'],
@@ -38,11 +42,8 @@ harfbuzz_fontations = custom_target(
   command: [
     cargo, 'build',
     ] + cargo_args + [
-    '--lib',
-    '--target-dir', meson.current_build_dir(),
     '-Z', 'unstable-options',
     '--artifact-dir', meson.current_build_dir(),
-    '--manifest-path', meson.current_source_dir() / 'Cargo.toml'
   ],
   install: true,
   install_dir: join_paths(get_option('prefix'), 'lib'),
@@ -57,11 +58,8 @@ clippy_fix = run_target(
   env: ['OUT_DIR=' + meson.current_build_dir()],
   command: [
     cargo, 'clippy',
-    '--allow-dirty', '--fix',
     ] + cargo_args + [
-    '--lib', '-p', 'harfbuzz_fontations',
-    '--target-dir', meson.current_build_dir(),
-    '--manifest-path', meson.current_source_dir() / 'Cargo.toml',
+    '--allow-dirty', '--fix',
   ],
 )
 if get_option('tests').enabled() and cargo.found()
@@ -72,9 +70,6 @@ if get_option('tests').enabled() and cargo.found()
     args: [
       'clippy',
       ] + cargo_args + [
-      '--lib', '-p', 'harfbuzz_fontations',
-      '--target-dir', meson.current_build_dir(),
-      '--manifest-path', meson.current_source_dir() / 'Cargo.toml',
       '--', '-D', 'warnings',
     ],
   )

From fae9d2ab277c6f692bbfe4f13edd7b736ab28e89 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 12:15:25 -0700
Subject: [PATCH 04/23] [fontations] Add dependencies

---
 src/fontations/meson.build | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/fontations/meson.build b/src/fontations/meson.build
index 27ed29b42..d93a5c47d 100644
--- a/src/fontations/meson.build
+++ b/src/fontations/meson.build
@@ -56,6 +56,7 @@ harfbuzz_fontations_dep = declare_dependency(
 clippy_fix = run_target(
   'clippy-fix',
   env: ['OUT_DIR=' + meson.current_build_dir()],
+  depends: [hb_rs, harfbuzz_fontations],
   command: [
     cargo, 'clippy',
     ] + cargo_args + [
@@ -67,6 +68,7 @@ if get_option('tests').enabled() and cargo.found()
     'clippy',
     cargo,
     env: ['OUT_DIR=' + meson.current_build_dir()],
+    depends: [hb_rs, harfbuzz_fontations],
     args: [
       'clippy',
       ] + cargo_args + [
@@ -78,6 +80,7 @@ endif
 rustfmt_fix = run_target(
   'rustfmt-fix',
   env: ['OUT_DIR=' + meson.current_build_dir()],
+  depends: [hb_rs],
   command: [
     rustfmt,
     '--edition', '2021',
@@ -90,6 +93,7 @@ if get_option('tests').enabled() and rustfmt.found()
     'rustfmt',
     rustfmt,
     env: ['OUT_DIR=' + meson.current_build_dir()],
+    depends: [hb_rs],
     args: [
       '--check',
       '--edition', '2021',

From 712a403bec7313436378fed6dc235ffd9609c14a Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 12:23:41 -0700
Subject: [PATCH 05/23] [font-funcs-using] Apply review feedback

---
 src/hb-font.cc              | 6 ++++--
 src/hb-shape.cc             | 4 ++++
 test/api/test-draw.c        | 9 ++++++---
 test/api/test-multithread.c | 4 ++--
 4 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/hb-font.cc b/src/hb-font.cc
index 8d0ff4c8e..dbe915149 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -2389,8 +2389,10 @@ void free_static_font_funcs_list ()
  *
  * Retrieves the list of font functions supported by HarfBuzz.
  *
- * Return value: (transfer none) (array zero-terminated=1): an array of
- *    constant strings
+ * Return value: (transfer none) (array zero-terminated=1): a
+ *    `NULL`-terminated array of supported font functions
+ *    constant string. The returned array is owned by HarfBuzz
+ *    and should not be modified or freed.
  *
  * XSince: REPLACEME
  **/
diff --git a/src/hb-shape.cc b/src/hb-shape.cc
index 844f7b9e8..9aa5f9822 100644
--- a/src/hb-shape.cc
+++ b/src/hb-shape.cc
@@ -93,6 +93,10 @@ void free_static_shaper_list ()
  *
  * Return value: (transfer none) (array zero-terminated=1): an array of
  *    constant strings
+ * Return value: (transfer none) (array zero-terminated=1): a
+ *    `NULL`-terminated array of supported shapers constant string.
+ *    The returned array is owned by HarfBuzz and should not be
+ *    modified or freed.
  *
  * Since: 0.9.2
  **/
diff --git a/test/api/test-draw.c b/test/api/test-draw.c
index 9b608e1af..a068c78f6 100644
--- a/test/api/test-draw.c
+++ b/test/api/test-draw.c
@@ -1088,7 +1088,8 @@ test_hb_draw_funcs (const char* font_funcs_name)
   {
     hb_face_t *face = hb_test_open_font_file ("fonts/glyphs.ttf");
     hb_font_t *font = hb_font_create (face);
-    hb_font_set_funcs_using (font, font_funcs_name);
+    hb_bool_t ret = hb_font_set_funcs_using (font, font_funcs_name);
+    g_assert (ret);
     hb_face_destroy (face);
     {
       draw_data.consumed = 0;
@@ -1107,7 +1108,8 @@ test_hb_draw_funcs (const char* font_funcs_name)
   {
     hb_face_t *face = hb_test_open_font_file ("fonts/cff1_flex.otf");
     hb_font_t *font = hb_font_create (face);
-    hb_font_set_funcs_using (font, font_funcs_name);
+    hb_bool_t ret = hb_font_set_funcs_using (font, font_funcs_name);
+    g_assert (ret);
     hb_face_destroy (face);
 
     draw_data.consumed = 0;
@@ -1148,7 +1150,8 @@ test_hb_draw_compare_ot_funcs (const char* font_funcs_name)
   hb_font_draw_glyph (font, 1, funcs, &draw_data);
   draw_data.str[draw_data.consumed] = '\0';
 
-  hb_font_set_funcs_using (font, font_funcs_name);
+  hb_bool_t ret = hb_font_set_funcs_using (font, font_funcs_name);
+  g_assert (ret);
 
   hb_font_draw_glyph (font, 1, funcs, &draw_data2);
   draw_data2.str[draw_data2.consumed] = '\0';
diff --git a/test/api/test-multithread.c b/test/api/test-multithread.c
index 52f7cefb9..b83ca6693 100644
--- a/test/api/test-multithread.c
+++ b/test/api/test-multithread.c
@@ -95,8 +95,8 @@ thread_func (void *data)
 static void
 test_body (const char *backend)
 {
-  if (!hb_font_set_funcs_using (font, backend))
-    return;
+  bool ret = hb_font_set_funcs_using (font, backend);
+  g_assert (ret);
 
   int i;
   pthread_t *threads = calloc (num_threads, sizeof (pthread_t));

From 5a12bf417b927a511ad864abd6305899a1bd135b Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 12:31:07 -0700
Subject: [PATCH 06/23] [font-funcs-using] Treat empty string like nullptr

---
 src/hb-font.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/hb-font.cc b/src/hb-font.cc
index dbe915149..561f3c06a 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -2330,7 +2330,7 @@ static struct supported_font_funcs_t {
  * Sets the font-functions structure to use for a font, based on the
  * specified name.
  *
- * If @name is `NULL`, the first functioning font-functions are used.
+ * If @name is `NULL` or empty string, the first functioning font-functions are used.
  *
  * Return value: `true` if the font-functions was found and set, `false` otherwise
  *
@@ -2340,6 +2340,8 @@ hb_bool_t
 hb_font_set_funcs_using (hb_font_t  *font,
 			 const char *name)
 {
+  if (name && !*name) name = nullptr;
+
   for (unsigned i = 0; i < ARRAY_LENGTH (supported_font_funcs); i++)
     if (!name || strcmp (supported_font_funcs[i].name, name) == 0)
     {
@@ -2347,6 +2349,7 @@ hb_font_set_funcs_using (hb_font_t  *font,
       if (name || font->klass != hb_font_funcs_get_empty ())
 	return true;
     }
+
   return false;
 }
 

From 68b07475a7515166b308c21807f13a57fb68aedb Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 12:41:50 -0700
Subject: [PATCH 07/23] [font-funcs] Support HB_FONT_FUNCS env var

---
 src/hb-font.cc | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/hb-font.cc b/src/hb-font.cc
index 561f3c06a..6d4032aac 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -1867,10 +1867,19 @@ hb_font_create (hb_face_t *face)
 {
   hb_font_t *font = _hb_font_create (face);
 
-#ifndef HB_NO_OT_FONT
-  /* Install our in-house, very lightweight, funcs. */
-  hb_ot_font_set_funcs (font);
-#endif
+  static hb_atomic_ptr_t<const char> static_funcs_name;
+  const char *funcs_name = static_funcs_name.get_acquire ();
+  if (!funcs_name)
+  {
+    funcs_name = getenv ("HB_FONT_FUNCS");
+    if (!funcs_name)
+      funcs_name = "";
+    if (!static_funcs_name.cmpexch (nullptr, funcs_name))
+      funcs_name = static_funcs_name.get_acquire ();
+  }
+
+  if (unlikely (!hb_font_set_funcs_using (font, funcs_name)))
+    hb_font_set_funcs_using (font, nullptr);
 
 #ifndef HB_NO_VAR
   if (face && face->index >> 16)
@@ -2310,7 +2319,9 @@ static struct supported_font_funcs_t {
 	void (*func) (hb_font_t *);
 } supported_font_funcs[] =
 {
+#ifndef HB_NO_OT_FONT
   {"ot",	hb_ot_font_set_funcs},
+#endif
 #ifdef HAVE_FREETYPE
   {"ft",	hb_ft_font_set_funcs},
 #endif

From 437ce950594241355c577f43a2c65c895daecd7d Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 13:12:15 -0700
Subject: [PATCH 08/23] [util] Add --list-font-funcs

---
 util/font-options.hh | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/util/font-options.hh b/util/font-options.hh
index 095283e52..0b3e098e3 100644
--- a/util/font-options.hh
+++ b/util/font-options.hh
@@ -143,6 +143,18 @@ font_options_t::post_parse (GError **error)
   }
 }
 
+static G_GNUC_NORETURN gboolean
+list_font_funcs (const char *name G_GNUC_UNUSED,
+		 const char *arg G_GNUC_UNUSED,
+		 gpointer    data G_GNUC_UNUSED,
+		 GError    **error G_GNUC_UNUSED)
+{
+  for (const char **funcs = hb_font_list_funcs (); *funcs; funcs++)
+    g_printf ("%s\n", *funcs);
+
+  exit(0);
+}
+
 #ifndef HB_NO_VAR
 static gboolean
 parse_variations (const char *name G_GNUC_UNUSED,
@@ -315,6 +327,8 @@ font_options_t::add_options (option_parser_t *parser)
     {"font-slant",	0, font_size_flags,
 			      G_OPTION_ARG_DOUBLE,	&this->slant,			"Set synthetic slant (default: 0)",		 "slant ratio; eg. 0.2"},
     {"font-funcs",	0, 0, G_OPTION_ARG_STRING,	&this->font_funcs,		font_funcs_text,				"impl"},
+    {"list-font-funcs",	0, G_OPTION_FLAG_NO_ARG,
+			      G_OPTION_ARG_CALLBACK,	(gpointer) &list_font_funcs,	"List available font functions and quit",	nullptr},
     {"sub-font",	0, G_OPTION_FLAG_HIDDEN,
 			      G_OPTION_ARG_NONE,	&this->sub_font,		"Create a sub-font (default: false)",		"boolean"},
     {"ft-load-flags",	0, 0, G_OPTION_ARG_INT,		&this->ft_load_flags,		"Set FreeType load-flags (default: 2)",		"integer"},

From 43ff0f73ccaa41e4dc68ba992506108868b1ac60 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 13:30:10 -0700
Subject: [PATCH 09/23] [fontations] Relax dependency numbers

---
 src/fontations/Cargo.toml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/fontations/Cargo.toml b/src/fontations/Cargo.toml
index 33b6ba40c..0eb031695 100644
--- a/src/fontations/Cargo.toml
+++ b/src/fontations/Cargo.toml
@@ -3,8 +3,8 @@ name = "harfbuzz_fontations"
 edition = "2021"
 
 [dependencies]
-read-fonts = "0.27.2"
-skrifa = "0.28.1"
+read-fonts = "0.27"
+skrifa = "0.28"
 
 [lib]
 name = "harfbuzz_fontations"

From 50ea460b93bd0081c69ccad2ae25fc8392a30bfb Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 8 Mar 2025 16:07:44 -0700
Subject: [PATCH 10/23] Review

---
 src/hb-shape.cc | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/hb-shape.cc b/src/hb-shape.cc
index 9aa5f9822..c62f8c6bc 100644
--- a/src/hb-shape.cc
+++ b/src/hb-shape.cc
@@ -91,8 +91,6 @@ void free_static_shaper_list ()
  *
  * Retrieves the list of shapers supported by HarfBuzz.
  *
- * Return value: (transfer none) (array zero-terminated=1): an array of
- *    constant strings
  * Return value: (transfer none) (array zero-terminated=1): a
  *    `NULL`-terminated array of supported shapers constant string.
  *    The returned array is owned by HarfBuzz and should not be

From 39ade99d4779706169e32d8b63fd734ec16e96a6 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 01:25:52 -0700
Subject: [PATCH 11/23] [face] Two new APIs:

+ hb_face_create_from_file_or_fail_using()
+ hb_face_list_loaders()
---
 src/hb-face.cc       | 105 +++++++++++++++++++++++++++++++++++++++++++
 src/hb-face.h        |   9 ++++
 src/hb-font.cc       |   4 +-
 util/face-options.hh |  91 +++++++++++--------------------------
 util/font-options.hh |  21 ++++++---
 5 files changed, 158 insertions(+), 72 deletions(-)

diff --git a/src/hb-face.cc b/src/hb-face.cc
index 002bb37d4..190a9c52f 100644
--- a/src/hb-face.cc
+++ b/src/hb-face.cc
@@ -34,6 +34,13 @@
 #include "hb-ot-face.hh"
 #include "hb-ot-cmap-table.hh"
 
+#ifdef HAVE_FREETYPE
+#include "hb-ft.h"
+#endif
+#ifdef HAVE_CORETEXT
+#include "hb-coretext.h"
+#endif
+
 
 /**
  * SECTION:hb-face
@@ -320,6 +327,104 @@ hb_face_create_from_file_or_fail (const char   *file_name,
 }
 #endif
 
+static struct supported_face_loaders_t {
+	char name[9];
+	hb_face_t * (*func) (const char *font_file, unsigned face_index);
+} supported_face_loaders[] =
+{
+#ifndef HB_NO_OPEN
+  {"ot",	hb_face_create_from_file_or_fail},
+#endif
+#ifdef HAVE_FREETYPE
+  {"ft",	hb_ft_face_create_from_file_or_fail},
+#endif
+#ifdef HAVE_CORETEXT
+  {"coretext",	hb_coretext_face_create_from_file_or_fail},
+#endif
+};
+
+/**
+ * hb_face_create_from_file_or_fail_using:
+ * @file_name: A font filename
+ * @index: The index of the face within the file
+ * @loader_name: (nullable): The name of the loader to use, or `NULL`
+ *
+ * A thin wrapper around the face loader functions registered with HarfBuzz.
+ * If @loader_name is `NULL`, the first available loader is used.
+ *
+ * Return value: (transfer full): The new face object, or `NULL` if
+ * the file cannot be read or the loader fails to load the face.
+ *
+ * XSince: REPLACEME
+ **/
+hb_face_t *
+hb_face_create_from_file_or_fail_using (const char   *file_name,
+					unsigned int  index,
+					const char   *loader_name)
+{
+  if (loader_name && !*loader_name)
+    loader_name = nullptr;
+  for (unsigned i = 0; i < ARRAY_LENGTH (supported_face_loaders); i++)
+  {
+    if (!loader_name || !strcmp (supported_face_loaders[i].name, loader_name))
+      return supported_face_loaders[i].func (file_name, index);
+  }
+  return nullptr;
+}
+
+static inline void free_static_face_loader_list ();
+
+static const char * const nil_face_loader_list[] = {nullptr};
+
+static struct hb_face_loader_list_lazy_loader_t : hb_lazy_loader_t<const char *,
+								  hb_face_loader_list_lazy_loader_t>
+{
+  static const char ** create ()
+  {
+    const char **face_loader_list = (const char **) hb_calloc (1 + ARRAY_LENGTH (supported_face_loaders), sizeof (const char *));
+    if (unlikely (!face_loader_list))
+      return nullptr;
+
+    unsigned i;
+    for (i = 0; i < ARRAY_LENGTH (supported_face_loaders); i++)
+      face_loader_list[i] = supported_face_loaders[i].name;
+    face_loader_list[i] = nullptr;
+
+    hb_atexit (free_static_face_loader_list);
+
+    return face_loader_list;
+  }
+  static void destroy (const char **l)
+  { hb_free (l); }
+  static const char * const * get_null ()
+  { return nil_face_loader_list; }
+} static_face_loader_list;
+
+static inline
+void free_static_face_loader_list ()
+{
+  static_face_loader_list.free_instance ();
+}
+
+/**
+ * hb_face_list_loaders:
+ *
+ * Retrieves the list of face loaders supported by HarfBuzz.
+ *
+ * Return value: (transfer none) (array zero-terminated=1): a
+ *    `NULL`-terminated array of supported face loaders
+ *    constant strings. The returned array is owned by HarfBuzz
+ *    and should not be modified or freed.
+ *
+ * XSince: REPLACEME
+ **/
+const char **
+hb_face_list_loaders ()
+{
+  return static_face_loader_list.get_unconst ();
+}
+
+
 /**
  * hb_face_get_empty:
  *
diff --git a/src/hb-face.h b/src/hb-face.h
index afc198547..c59ec0c4b 100644
--- a/src/hb-face.h
+++ b/src/hb-face.h
@@ -67,6 +67,15 @@ HB_EXTERN hb_face_t *
 hb_face_create_from_file_or_fail (const char   *file_name,
 				  unsigned int  index);
 
+HB_EXTERN hb_face_t *
+hb_face_create_from_file_or_fail_using (const char   *file_name,
+					unsigned int  index,
+					const char   *loader_name);
+
+HB_EXTERN const char **
+hb_face_list_loaders (void);
+
+
 /**
  * hb_reference_table_func_t:
  * @face: an #hb_face_t to reference table for
diff --git a/src/hb-font.cc b/src/hb-font.cc
index 6d4032aac..5568dd8fc 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -2336,7 +2336,7 @@ static struct supported_font_funcs_t {
 /**
  * hb_font_set_funcs_using:
  * @font: #hb_font_t to work upon
- * @name: The name of the font-functions structure to use
+ * @name: The name of the font-functions structure to use, or `NULL`
  *
  * Sets the font-functions structure to use for a font, based on the
  * specified name.
@@ -2405,7 +2405,7 @@ void free_static_font_funcs_list ()
  *
  * Return value: (transfer none) (array zero-terminated=1): a
  *    `NULL`-terminated array of supported font functions
- *    constant string. The returned array is owned by HarfBuzz
+ *    constant strings. The returned array is owned by HarfBuzz
  *    and should not be modified or freed.
  *
  * XSince: REPLACEME
diff --git a/util/face-options.hh b/util/face-options.hh
index 929ec4c38..5192421f3 100644
--- a/util/face-options.hh
+++ b/util/face-options.hh
@@ -29,13 +29,6 @@
 
 #include "options.hh"
 
-#ifdef HAVE_FREETYPE
-#include <hb-ft.h>
-#endif
-#ifdef HAVE_CORETEXT
-#include <hb-coretext.h>
-#endif
-
 struct face_options_t
 {
   ~face_options_t ()
@@ -74,20 +67,6 @@ struct face_options_t
 
 face_options_t::cache_t face_options_t::cache {};
 
-static struct supported_face_loaders_t {
-	char name[9];
-	hb_face_t * (*func) (const char *font_file, unsigned face_index);
-} supported_face_loaders[] =
-{
-  {"ot",	hb_face_create_from_file_or_fail},
-#ifdef HAVE_FREETYPE
-  {"ft",	hb_ft_face_create_from_file_or_fail},
-#endif
-#ifdef HAVE_CORETEXT
-  {"coretext",	hb_coretext_face_create_from_file_or_fail},
-#endif
-};
-
 void
 face_options_t::post_parse (GError **error)
 {
@@ -112,46 +91,12 @@ face_options_t::post_parse (GError **error)
 #endif
   }
 
-  hb_face_t * (*face_load) (const char *file_name, unsigned face_index) = nullptr;
-  if (!face_loader)
-  {
-    face_load = supported_face_loaders[0].func;
-  }
-  else
-  {
-    for (unsigned int i = 0; i < ARRAY_LENGTH (supported_face_loaders); i++)
-      if (0 == g_ascii_strcasecmp (face_loader, supported_face_loaders[i].name))
-      {
-	face_load = supported_face_loaders[i].func;
-	break;
-      }
-    if (!face_load)
-    {
-      GString *s = g_string_new (nullptr);
-      for (unsigned int i = 0; i < ARRAY_LENGTH (supported_face_loaders); i++)
-      {
-	if (i)
-	  g_string_append_c (s, '/');
-	g_string_append (s, supported_face_loaders[i].name);
-      }
-      g_string_append_c (s, '\n');
-      char *p = g_string_free (s, FALSE);
-      g_set_error (error, G_OPTION_ERROR, G_OPTION_ERROR_BAD_VALUE,
-		   "Unknown face loader `%s'; supported values are: %s; default is %s",
-		   face_loader,
-		   p,
-		   supported_face_loaders[0].name);
-      free (p);
-      return;
-    }
-  }
-
   if (!cache.font_path ||
       0 != strcmp (cache.font_path, font_path) ||
       cache.face_index != face_index)
   {
     hb_face_destroy (cache.face);
-    cache.face = face_load (font_path, face_index);
+    cache.face = hb_face_create_from_file_or_fail_using (font_path, face_index, face_loader);
     cache.face_index = face_index;
 
     free ((char *) cache.font_path);
@@ -168,21 +113,37 @@ face_options_t::post_parse (GError **error)
   face = cache.face;
 }
 
+static G_GNUC_NORETURN gboolean
+list_face_loaders (const char *name G_GNUC_UNUSED,
+		   const char *arg G_GNUC_UNUSED,
+		   gpointer    data G_GNUC_UNUSED,
+		   GError    **error G_GNUC_UNUSED)
+{
+  for (const char **funcs = hb_face_list_loaders (); *funcs; funcs++)
+    g_printf ("%s\n", *funcs);
+
+  exit(0);
+}
+
 void
 face_options_t::add_options (option_parser_t *parser)
 {
   char *face_loaders_text = nullptr;
   {
-    static_assert ((ARRAY_LENGTH_CONST (supported_face_loaders) > 0),
-		   "No supported face-loaders found.");
+    const char **supported_face_loaders = hb_face_list_loaders ();
     GString *s = g_string_new (nullptr);
-    g_string_printf (s, "Set face loader to use (default: %s)\n    Supported face loaders are: %s",
-		     supported_face_loaders[0].name,
-		     supported_face_loaders[0].name);
-    for (unsigned int i = 1; i < ARRAY_LENGTH (supported_face_loaders); i++)
+    if (unlikely (!supported_face_loaders))
+      g_string_printf (s, "Set face loader to use (default: none)\n    No supported face loaders found");
+    else
     {
-      g_string_append_c (s, '/');
-      g_string_append (s, supported_face_loaders[i].name);
+      g_string_printf (s, "Set face loader to use (default: %s)\n    Supported face loaders are: %s",
+		       supported_face_loaders[0],
+		       supported_face_loaders[0]);
+      for (unsigned i = 1; supported_face_loaders[i]; i++)
+      {
+	g_string_append_c (s, '/');
+	g_string_append (s, supported_face_loaders[i]);
+      }
     }
     face_loaders_text = g_string_free (s, FALSE);
     parser->free_later (face_loaders_text);
@@ -193,6 +154,8 @@ face_options_t::add_options (option_parser_t *parser)
     {"font-file",	0, 0, G_OPTION_ARG_STRING,	&this->font_file,		"Set font file-name",				"filename"},
     {"face-index",	'y', 0, G_OPTION_ARG_INT,	&this->face_index,		"Set face index (default: 0)",			"index"},
     {"face-loader",	0, 0, G_OPTION_ARG_STRING,	&this->face_loader,		face_loaders_text,				"loader"},
+    {"list-face-loaders",0, G_OPTION_FLAG_NO_ARG,
+			      G_OPTION_ARG_CALLBACK,	(gpointer) &list_face_loaders,	"List available face loaders and quit",		nullptr},
     {nullptr}
   };
   parser->add_group (entries,
diff --git a/util/font-options.hh b/util/font-options.hh
index 0b3e098e3..bacd7bc9b 100644
--- a/util/font-options.hh
+++ b/util/font-options.hh
@@ -29,6 +29,10 @@
 
 #include "face-options.hh"
 
+#ifdef HAVE_FREETYPE
+#include <hb-ft.h>
+#endif
+
 #define FONT_SIZE_UPEM 0x7FFFFFFF
 #define FONT_SIZE_NONE 0
 
@@ -290,13 +294,18 @@ font_options_t::add_options (option_parser_t *parser)
   {
     const char **supported_font_funcs = hb_font_list_funcs ();
     GString *s = g_string_new (nullptr);
-    g_string_printf (s, "Set font functions implementation to use (default: %s)\n    Supported font function implementations are: %s",
-		     supported_font_funcs[0],
-		     supported_font_funcs[0]);
-    for (unsigned i = 1; supported_font_funcs[i]; i++)
+    if (unlikely (!supported_font_funcs[0]))
+      g_string_printf (s, "Set font functions implementation to use (default: none)\n    No supported font function implementations found");
+    else
     {
-      g_string_append_c (s, '/');
-      g_string_append (s, supported_font_funcs[i]);
+      g_string_printf (s, "Set font functions implementation to use (default: %s)\n    Supported font function implementations are: %s",
+		       supported_font_funcs[0],
+		       supported_font_funcs[0]);
+      for (unsigned i = 1; supported_font_funcs[i]; i++)
+      {
+	g_string_append_c (s, '/');
+	g_string_append (s, supported_font_funcs[i]);
+      }
     }
     font_funcs_text = g_string_free (s, FALSE);
     parser->free_later (font_funcs_text);

From 9d05b03f83ac4064a15cf5e59fd8acfc952867ce Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 01:34:37 -0700
Subject: [PATCH 12/23] [font] Add HB_FONT_FUNCS work into
 hb_font_set_funcs_using()

---
 src/hb-font.cc | 42 ++++++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/src/hb-font.cc b/src/hb-font.cc
index 5568dd8fc..2c79c0d83 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -1867,19 +1867,7 @@ hb_font_create (hb_face_t *face)
 {
   hb_font_t *font = _hb_font_create (face);
 
-  static hb_atomic_ptr_t<const char> static_funcs_name;
-  const char *funcs_name = static_funcs_name.get_acquire ();
-  if (!funcs_name)
-  {
-    funcs_name = getenv ("HB_FONT_FUNCS");
-    if (!funcs_name)
-      funcs_name = "";
-    if (!static_funcs_name.cmpexch (nullptr, funcs_name))
-      funcs_name = static_funcs_name.get_acquire ();
-  }
-
-  if (unlikely (!hb_font_set_funcs_using (font, funcs_name)))
-    hb_font_set_funcs_using (font, nullptr);
+  hb_font_set_funcs_using (font, nullptr);
 
 #ifndef HB_NO_VAR
   if (face && face->index >> 16)
@@ -2341,7 +2329,9 @@ static struct supported_font_funcs_t {
  * Sets the font-functions structure to use for a font, based on the
  * specified name.
  *
- * If @name is `NULL` or empty string, the first functioning font-functions are used.
+ * If @name is `NULL` or empty string, the default (first) functioning font-functions
+ * are used.  This default can be changed by setting the `HB_FONT_FUNCS` environment
+ * variable to the name of the desired font-functions.
  *
  * Return value: `true` if the font-functions was found and set, `false` otherwise
  *
@@ -2351,8 +2341,25 @@ hb_bool_t
 hb_font_set_funcs_using (hb_font_t  *font,
 			 const char *name)
 {
+  bool retry = false;
+
+  if (!name || !*name)
+  {
+    static hb_atomic_ptr_t<const char> static_funcs_name;
+    name = static_funcs_name.get_acquire ();
+    if (!name)
+    {
+      name = getenv ("HB_FONT_FUNCS");
+      if (!name)
+	name = "";
+      if (!static_funcs_name.cmpexch (nullptr, name))
+	name = static_funcs_name.get_acquire ();
+    }
+    retry = true;
+  }
   if (name && !*name) name = nullptr;
 
+retry:
   for (unsigned i = 0; i < ARRAY_LENGTH (supported_font_funcs); i++)
     if (!name || strcmp (supported_font_funcs[i].name, name) == 0)
     {
@@ -2361,6 +2368,13 @@ hb_font_set_funcs_using (hb_font_t  *font,
 	return true;
     }
 
+  if (retry)
+  {
+    retry = false;
+    name = nullptr;
+    goto retry;
+  }
+
   return false;
 }
 

From 6b9d9f7259595f7b6fd98204559224be9e791412 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 01:40:23 -0700
Subject: [PATCH 13/23] [face] Add HB_FACE_LOADER env var

---
 perf/hb-benchmark.hh | 17 +----------------
 src/hb-face.cc       | 37 +++++++++++++++++++++++++++++++++----
 2 files changed, 34 insertions(+), 20 deletions(-)

diff --git a/perf/hb-benchmark.hh b/perf/hb-benchmark.hh
index 28860476d..c976831c0 100644
--- a/perf/hb-benchmark.hh
+++ b/perf/hb-benchmark.hh
@@ -56,22 +56,7 @@ static inline hb_face_t *
 hb_benchmark_face_create_from_file_or_fail (const char *font_path,
 					    unsigned face_index)
 {
-  const char *loader = getenv ("HB_FACE_LOADER");
-  if (loader && !*loader)
-    loader = nullptr;
-
-#ifdef HAVE_FREETYPE
-  if (loader && !strcmp (loader, "ft"))
-    return hb_ft_face_create_from_file_or_fail (font_path, face_index);
-#endif
-#ifdef HAVE_CORETEXT
-  if (loader && !strcmp (loader, "coretext"))
-    return hb_coretext_face_create_from_file_or_fail (font_path, face_index);
-#endif
-  if (!loader || !strcmp (loader, "ot"))
-    return hb_face_create_from_file_or_fail (font_path, face_index);
-
-  assert (false);
+  return hb_face_create_from_file_or_fail_using (font_path, face_index, nullptr);
 }
 
 HB_END_DECLS
diff --git a/src/hb-face.cc b/src/hb-face.cc
index 190a9c52f..a738e9c28 100644
--- a/src/hb-face.cc
+++ b/src/hb-face.cc
@@ -352,6 +352,10 @@ static struct supported_face_loaders_t {
  * A thin wrapper around the face loader functions registered with HarfBuzz.
  * If @loader_name is `NULL`, the first available loader is used.
  *
+ * For example, the FreeType ("ft") loader might be able to load
+ * .woff and .woff2 files if FreeType is built with those features,
+ * whereas the OpenType ("ot") loader will not.
+ *
  * Return value: (transfer full): The new face object, or `NULL` if
  * the file cannot be read or the loader fails to load the face.
  *
@@ -360,15 +364,40 @@ static struct supported_face_loaders_t {
 hb_face_t *
 hb_face_create_from_file_or_fail_using (const char   *file_name,
 					unsigned int  index,
-					const char   *loader_name)
+					const char   *name)
 {
-  if (loader_name && !*loader_name)
-    loader_name = nullptr;
+  bool retry = false;
+
+  if (!name || !*name)
+  {
+    static hb_atomic_ptr_t<const char> static_funcs_name;
+    name = static_funcs_name.get_acquire ();
+    if (!name)
+    {
+      name = getenv ("HB_FACE_LOADER");
+      if (!name)
+	name = "";
+      if (!static_funcs_name.cmpexch (nullptr, name))
+	name = static_funcs_name.get_acquire ();
+    }
+    retry = true;
+  }
+  if (name && !*name) name = nullptr;
+
+retry:
   for (unsigned i = 0; i < ARRAY_LENGTH (supported_face_loaders); i++)
   {
-    if (!loader_name || !strcmp (supported_face_loaders[i].name, loader_name))
+    if (!name || !strcmp (supported_face_loaders[i].name, name))
       return supported_face_loaders[i].func (file_name, index);
   }
+
+  if (retry)
+  {
+    retry = false;
+    name = nullptr;
+    goto retry;
+  }
+
   return nullptr;
 }
 

From 2ecc68c12fb811f696af0de280ec0e96bab4b7d4 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 01:46:07 -0700
Subject: [PATCH 14/23] [face] Fix HB_LEAN build

---
 src/hb-face.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/hb-face.cc b/src/hb-face.cc
index a738e9c28..4a783f74f 100644
--- a/src/hb-face.cc
+++ b/src/hb-face.cc
@@ -325,7 +325,6 @@ hb_face_create_from_file_or_fail (const char   *file_name,
 
   return face;
 }
-#endif
 
 static struct supported_face_loaders_t {
 	char name[9];
@@ -452,6 +451,7 @@ hb_face_list_loaders ()
 {
   return static_face_loader_list.get_unconst ();
 }
+#endif
 
 
 /**

From 5cf1fa3adddfdad74f820867aa11da561fbee117 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 01:47:23 -0700
Subject: [PATCH 15/23] [face] Fix docs

---
 docs/harfbuzz-sections.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/harfbuzz-sections.txt b/docs/harfbuzz-sections.txt
index c37138572..5eb940ee8 100644
--- a/docs/harfbuzz-sections.txt
+++ b/docs/harfbuzz-sections.txt
@@ -365,6 +365,8 @@ hb_face_t
 hb_face_create
 hb_face_create_or_fail
 hb_face_create_from_file_or_fail
+hb_face_create_from_file_or_fail_using
+hb_face_list_loaders
 hb_reference_table_func_t
 hb_face_create_for_tables
 hb_face_get_empty

From 402f89cb79001082534d034e28b8bf4f5a83f170 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 01:52:03 -0700
Subject: [PATCH 16/23] [face] Rename a variable

---
 src/hb-face.cc | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/hb-face.cc b/src/hb-face.cc
index 4a783f74f..a403f086f 100644
--- a/src/hb-face.cc
+++ b/src/hb-face.cc
@@ -363,37 +363,37 @@ static struct supported_face_loaders_t {
 hb_face_t *
 hb_face_create_from_file_or_fail_using (const char   *file_name,
 					unsigned int  index,
-					const char   *name)
+					const char   *loader_name)
 {
   bool retry = false;
 
-  if (!name || !*name)
+  if (!loader_name || !*loader_name)
   {
     static hb_atomic_ptr_t<const char> static_funcs_name;
-    name = static_funcs_name.get_acquire ();
-    if (!name)
+    loader_name = static_funcs_name.get_acquire ();
+    if (!loader_name)
     {
-      name = getenv ("HB_FACE_LOADER");
-      if (!name)
-	name = "";
-      if (!static_funcs_name.cmpexch (nullptr, name))
-	name = static_funcs_name.get_acquire ();
+      loader_name = getenv ("HB_FACE_LOADER");
+      if (!loader_name)
+	loader_name = "";
+      if (!static_funcs_name.cmpexch (nullptr, loader_name))
+	loader_name = static_funcs_name.get_acquire ();
     }
     retry = true;
   }
-  if (name && !*name) name = nullptr;
+  if (loader_name && !*loader_name) loader_name = nullptr;
 
 retry:
   for (unsigned i = 0; i < ARRAY_LENGTH (supported_face_loaders); i++)
   {
-    if (!name || !strcmp (supported_face_loaders[i].name, name))
+    if (!loader_name || !strcmp (supported_face_loaders[i].name, loader_name))
       return supported_face_loaders[i].func (file_name, index);
   }
 
   if (retry)
   {
     retry = false;
-    name = nullptr;
+    loader_name = nullptr;
     goto retry;
   }
 

From a83faa061c6fea251a6878cae0bb02d8d5949d75 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 03:07:45 -0600
Subject: [PATCH 17/23] [ft] Automatically pick up font serial changes

Part of https://github.com/harfbuzz/harfbuzz/issues/5124
---
 src/hb-ft.cc | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index efb4b7d24..786b94b23 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -478,6 +478,8 @@ hb_ft_get_glyph_h_advances (hb_font_t* font, void* font_data,
 			    void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_position_t *orig_first_advance = first_advance;
   hb_lock_t lock (ft_font->lock);
   FT_Face ft_face = ft_font->ft_face;
@@ -561,6 +563,8 @@ hb_ft_get_glyph_v_advance (hb_font_t *font,
 			   void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Fixed v;
   float y_mult;
@@ -614,6 +618,8 @@ hb_ft_get_glyph_v_origin (hb_font_t *font,
 			  void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Face ft_face = ft_font->ft_face;
   float x_mult, y_mult;
@@ -658,6 +664,8 @@ hb_ft_get_glyph_h_kerning (hb_font_t *font,
 			   void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Vector kerningv;
 
@@ -677,6 +685,8 @@ hb_ft_get_glyph_extents (hb_font_t *font,
 			 void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Face ft_face = ft_font->ft_face;
   float x_mult, y_mult;
@@ -749,6 +759,8 @@ hb_ft_get_glyph_contour_point (hb_font_t *font HB_UNUSED,
 			       void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Face ft_face = ft_font->ft_face;
 
@@ -826,6 +838,8 @@ hb_ft_get_font_h_extents (hb_font_t *font HB_UNUSED,
 			  void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Face ft_face = ft_font->ft_face;
   float y_mult;
@@ -916,6 +930,8 @@ hb_ft_draw_glyph (hb_font_t *font,
 		  void *user_data HB_UNUSED)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Face ft_face = ft_font->ft_face;
 
@@ -990,6 +1006,8 @@ hb_ft_paint_glyph (hb_font_t *font,
                    void *user_data)
 {
   const hb_ft_font_t *ft_font = (const hb_ft_font_t *) font_data;
+  _hb_ft_hb_font_check_changed (font, ft_font);
+
   hb_lock_t lock (ft_font->lock);
   FT_Face ft_face = ft_font->ft_face;
 
@@ -1456,6 +1474,10 @@ hb_ft_font_changed (hb_font_t *font)
  * variation-axis settings on the @font.
  * This call is fast if nothing has changed on @font.
  *
+ * Note that as of version REPLACEME, calling this function is not necessary,
+ * as HarfBuzz will automatically detect changes to the font and update
+ * the underlying FT_Face as needed.
+ *
  * Return value: true if changed, false otherwise
  *
  * Since: 4.4.0

From 6ae7ef065978499eb38d2fcfa9e87bb1e512983f Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 03:19:22 -0600
Subject: [PATCH 18/23] [ft] See if I can make tsan happy

---
 src/hb-ft.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index 786b94b23..f5fd7cae0 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -213,9 +213,11 @@ _hb_ft_hb_font_check_changed (hb_font_t *font,
 {
   if (font->serial != ft_font->cached_serial)
   {
+    ft_font->lock.lock ();
     _hb_ft_hb_font_changed (font, ft_font->ft_face);
     ft_font->advance_cache.clear ();
     ft_font->cached_serial = font->serial;
+    ft_font->lock.unlock ();
     return true;
   }
   return false;

From aa268fc8ef84ec353f2ef0c3878d0ba8dcd54303 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 03:31:01 -0600
Subject: [PATCH 19/23] [font/ft] See if tsan is happy with atomic_int_t
 serials

---
 src/hb-atomic.hh |  2 ++
 src/hb-font.cc   | 15 ++++++++++-----
 src/hb-font.hh   |  5 +++--
 src/hb-ft.cc     |  4 ++--
 4 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/hb-atomic.hh b/src/hb-atomic.hh
index 121c463a5..ce6ac38d8 100644
--- a/src/hb-atomic.hh
+++ b/src/hb-atomic.hh
@@ -186,6 +186,8 @@ struct hb_atomic_int_t
 
   hb_atomic_int_t& operator = (int v_) { set_relaxed (v_); return *this; }
   operator int () const { return get_relaxed (); }
+  int operator ++ (int) { return inc (); }
+  int operator -- (int) { return dec (); }
 
   void set_relaxed (int v_) { hb_atomic_int_impl_set_relaxed (&v, v_); }
   void set_release (int v_) { hb_atomic_int_impl_set (&v, v_); }
diff --git a/src/hb-font.cc b/src/hb-font.cc
index 2c79c0d83..526c96bbb 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -2744,7 +2744,8 @@ hb_font_set_variations (hb_font_t            *font,
   if (hb_object_is_immutable (font))
     return;
 
-  font->serial_coords = ++font->serial;
+  font->serial++;
+  font->serial_coords = font->serial;
 
   if (!variations_length && font->instance_index == HB_FONT_NO_VAR_NAMED_INSTANCE)
   {
@@ -2814,7 +2815,8 @@ hb_font_set_variation (hb_font_t *font,
   if (hb_object_is_immutable (font))
     return;
 
-  font->serial_coords = ++font->serial;
+  font->serial++;
+  font->serial_coords = font->serial;
 
   // TODO Share some of this code with set_variations()
 
@@ -2886,7 +2888,8 @@ hb_font_set_var_coords_design (hb_font_t    *font,
   if (hb_object_is_immutable (font))
     return;
 
-  font->serial_coords = ++font->serial;
+  font->serial++;
+  font->serial_coords = font->serial;
 
   int *normalized = coords_length ? (int *) hb_calloc (coords_length, sizeof (int)) : nullptr;
   float *design_coords = coords_length ? (float *) hb_calloc (coords_length, sizeof (float)) : nullptr;
@@ -2924,7 +2927,8 @@ hb_font_set_var_named_instance (hb_font_t *font,
   if (font->instance_index == instance_index)
     return;
 
-  font->serial_coords = ++font->serial;
+  font->serial++;
+  font->serial_coords = font->serial;
 
   font->instance_index = instance_index;
   hb_font_set_variations (font, nullptr, 0);
@@ -2971,7 +2975,8 @@ hb_font_set_var_coords_normalized (hb_font_t    *font,
   if (hb_object_is_immutable (font))
     return;
 
-  font->serial_coords = ++font->serial;
+  font->serial++;
+  font->serial_coords = font->serial;
 
   int *copy = coords_length ? (int *) hb_calloc (coords_length, sizeof (coords[0])) : nullptr;
   int *unmapped = coords_length ? (int *) hb_calloc (coords_length, sizeof (coords[0])) : nullptr;
diff --git a/src/hb-font.hh b/src/hb-font.hh
index 4c8190b0d..a8e6f7b0a 100644
--- a/src/hb-font.hh
+++ b/src/hb-font.hh
@@ -32,6 +32,7 @@
 #include "hb.hh"
 
 #include "hb-face.hh"
+#include "hb-atomic.hh"
 #include "hb-shaper.hh"
 
 
@@ -105,8 +106,8 @@ DECLARE_NULL_INSTANCE (hb_font_funcs_t);
 struct hb_font_t
 {
   hb_object_header_t header;
-  unsigned int serial;
-  unsigned int serial_coords;
+  hb_atomic_int_t serial;
+  hb_atomic_int_t serial_coords;
 
   hb_font_t *parent;
   hb_face_t *face;
diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index f5fd7cae0..fdb021dd8 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -101,7 +101,7 @@ struct hb_ft_font_t
 
   mutable hb_mutex_t lock; /* Protects members below. */
   FT_Face ft_face;
-  mutable unsigned cached_serial;
+  mutable hb_atomic_int_t cached_serial;
   mutable hb_ft_advance_cache_t advance_cache;
 };
 
@@ -118,7 +118,7 @@ _hb_ft_font_create (FT_Face ft_face, bool symbol, bool unref)
 
   ft_font->load_flags = FT_LOAD_DEFAULT | FT_LOAD_NO_HINTING;
 
-  ft_font->cached_serial = (unsigned) -1;
+  ft_font->cached_serial = -1;
   new (&ft_font->advance_cache) hb_ft_advance_cache_t;
 
   return ft_font;

From 7791f50e3ac43df31e210f275f4ee62390a5bdf6 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 03:34:28 -0600
Subject: [PATCH 20/23] [ft] Use a lock-guard

---
 src/hb-ft.cc | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index fdb021dd8..a5a11ce24 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -213,11 +213,10 @@ _hb_ft_hb_font_check_changed (hb_font_t *font,
 {
   if (font->serial != ft_font->cached_serial)
   {
-    ft_font->lock.lock ();
+    hb_lock_t lock (ft_font->lock);
     _hb_ft_hb_font_changed (font, ft_font->ft_face);
     ft_font->advance_cache.clear ();
     ft_font->cached_serial = font->serial;
-    ft_font->lock.unlock ();
     return true;
   }
   return false;

From 1e812e43b3c0a54ffe5f72be66026d6c65eb99c1 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 03:39:52 -0600
Subject: [PATCH 21/23] [ft] Another try at making tsan happy maybe

---
 src/hb-ft.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index a5a11ce24..3159a9ec3 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -216,7 +216,7 @@ _hb_ft_hb_font_check_changed (hb_font_t *font,
     hb_lock_t lock (ft_font->lock);
     _hb_ft_hb_font_changed (font, ft_font->ft_face);
     ft_font->advance_cache.clear ();
-    ft_font->cached_serial = font->serial;
+    ft_font->cached_serial.set_release (font->serial.get_acquire ());
     return true;
   }
   return false;

From 9e639e676a754af87a10430f3f0a948e7de9f110 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 05:10:50 -0600
Subject: [PATCH 22/23] [face] Review

---
 src/hb-face.cc | 3 ++-
 src/hb-font.cc | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/hb-face.cc b/src/hb-face.cc
index a403f086f..e35aa1caf 100644
--- a/src/hb-face.cc
+++ b/src/hb-face.cc
@@ -349,7 +349,8 @@ static struct supported_face_loaders_t {
  * @loader_name: (nullable): The name of the loader to use, or `NULL`
  *
  * A thin wrapper around the face loader functions registered with HarfBuzz.
- * If @loader_name is `NULL`, the first available loader is used.
+ * If @loader_name is `NULL` or the empty string, the first available loader
+ * is used.
  *
  * For example, the FreeType ("ft") loader might be able to load
  * .woff and .woff2 files if FreeType is built with those features,
diff --git a/src/hb-font.cc b/src/hb-font.cc
index 526c96bbb..79655e29a 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -2329,7 +2329,7 @@ static struct supported_font_funcs_t {
  * Sets the font-functions structure to use for a font, based on the
  * specified name.
  *
- * If @name is `NULL` or empty string, the default (first) functioning font-functions
+ * If @name is `NULL` or the empty string, the default (first) functioning font-functions
  * are used.  This default can be changed by setting the `HB_FONT_FUNCS` environment
  * variable to the name of the desired font-functions.
  *

From ec6f99c5eab4e683e24001fdabb34b9410a9d02a Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 9 Mar 2025 05:18:13 -0600
Subject: [PATCH 23/23] [fontations] Give clippy test more time

---
 src/fontations/meson.build | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/fontations/meson.build b/src/fontations/meson.build
index d93a5c47d..d21b9af4c 100644
--- a/src/fontations/meson.build
+++ b/src/fontations/meson.build
@@ -74,6 +74,7 @@ if get_option('tests').enabled() and cargo.found()
       ] + cargo_args + [
       '--', '-D', 'warnings',
     ],
+    timeout: 120,
   )
 endif