From 2c0ab34d03477a5ad15bf8cddd4c99e61572efee Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 24 Dec 2022 11:37:59 -0700
Subject: [PATCH] [paint-extents] Lazy-load draw-funcs

---
 src/hb-machinery.hh     | 16 ++++++++++++++++
 src/hb-paint-extents.cc | 39 ++++++++++++++++++++++++++++++---------
 2 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/src/hb-machinery.hh b/src/hb-machinery.hh
index b555739cf..0197f6191 100644
--- a/src/hb-machinery.hh
+++ b/src/hb-machinery.hh
@@ -321,6 +321,22 @@ struct hb_unicode_funcs_lazy_loader_t : hb_lazy_loader_t<hb_unicode_funcs_t, Sub
   static const hb_unicode_funcs_t *get_null ()
   { return hb_unicode_funcs_get_empty (); }
 };
+template <typename Subclass>
+struct hb_draw_funcs_lazy_loader_t : hb_lazy_loader_t<hb_draw_funcs_t, Subclass>
+{
+  static void destroy (hb_draw_funcs_t *p)
+  { hb_draw_funcs_destroy (p); }
+  static const hb_draw_funcs_t *get_null ()
+  { return hb_draw_funcs_get_empty (); }
+};
+template <typename Subclass>
+struct hb_paint_funcs_lazy_loader_t : hb_lazy_loader_t<hb_paint_funcs_t, Subclass>
+{
+  static void destroy (hb_paint_funcs_t *p)
+  { hb_paint_funcs_destroy (p); }
+  static const hb_paint_funcs_t *get_null ()
+  { return hb_paint_funcs_get_empty (); }
+};
 
 
 #endif /* HB_MACHINERY_HH */
diff --git a/src/hb-paint-extents.cc b/src/hb-paint-extents.cc
index a74e50937..a14f756e3 100644
--- a/src/hb-paint-extents.cc
+++ b/src/hb-paint-extents.cc
@@ -25,6 +25,7 @@
 #include "hb.hh"
 #include "hb-paint-extents.hh"
 #include "hb-draw.h"
+#include "hb-machinery.hh"
 
 /*
  * This file implements bounds-extraction as well as boundedness
@@ -114,14 +115,35 @@ hb_draw_extents_cubic_to (hb_draw_funcs_t *dfuncs,
   add_point (extents, to_x, to_y);
 }
 
-static hb_draw_funcs_t *
-hb_draw_extent_get_funcs ()
+static inline void free_static_draw_extents_funcs ();
+
+static struct hb_draw_extents_funcs_lazy_loader_t : hb_draw_funcs_lazy_loader_t<hb_draw_extents_funcs_lazy_loader_t>
 {
-  hb_draw_funcs_t *funcs = hb_draw_funcs_create ();
-  hb_draw_funcs_set_move_to_func (funcs, hb_draw_extents_move_to, nullptr, nullptr);
-  hb_draw_funcs_set_line_to_func (funcs, hb_draw_extents_line_to, nullptr, nullptr);
-  hb_draw_funcs_set_cubic_to_func (funcs, hb_draw_extents_cubic_to, nullptr, nullptr);
-  return funcs;
+  static hb_draw_funcs_t *create ()
+  {
+    hb_draw_funcs_t *funcs = hb_draw_funcs_create ();
+    hb_draw_funcs_set_move_to_func (funcs, hb_draw_extents_move_to, nullptr, nullptr);
+    hb_draw_funcs_set_line_to_func (funcs, hb_draw_extents_line_to, nullptr, nullptr);
+    hb_draw_funcs_set_cubic_to_func (funcs, hb_draw_extents_cubic_to, nullptr, nullptr);
+
+    hb_draw_funcs_make_immutable (funcs);
+
+    hb_atexit (free_static_draw_extents_funcs);
+
+    return funcs;
+  }
+} static_draw_extents_funcs;
+
+static inline
+void free_static_draw_extents_funcs ()
+{
+  static_draw_extents_funcs.free_instance ();
+}
+
+static hb_draw_funcs_t *
+hb_draw_extents_get_funcs ()
+{
+  return static_draw_extents_funcs.get_unconst ();
 }
 
 static void
@@ -134,9 +156,8 @@ hb_paint_extents_push_clip_glyph (hb_paint_funcs_t *funcs HB_UNUSED,
   hb_paint_extents_context_t *c = (hb_paint_extents_context_t *) paint_data;
 
   hb_extents_t extents;
-  hb_draw_funcs_t *draw_extent_funcs = hb_draw_extent_get_funcs ();
+  hb_draw_funcs_t *draw_extent_funcs = hb_draw_extents_get_funcs ();
   hb_font_draw_glyph (font, glyph, draw_extent_funcs, &extents);
-  hb_draw_funcs_destroy (draw_extent_funcs);
   c->push_clip (extents);
 }