From e0a5231657a6f09ca4afc93e1b2224eba7a0b544 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 16 Jun 2022 13:24:02 -0600
Subject: [PATCH] [draw] Lazy-allocate user-data/destroy callback vector

---
 src/hb-draw.cc | 53 ++++++++++++++++++++++++++++++++++++--------------
 src/hb-draw.hh | 14 ++++++-------
 2 files changed, 45 insertions(+), 22 deletions(-)

diff --git a/src/hb-draw.cc b/src/hb-draw.cc
index 29ac6a66e..b2d280b91 100644
--- a/src/hb-draw.cc
+++ b/src/hb-draw.cc
@@ -89,18 +89,39 @@ hb_draw_funcs_set_##name##_func (hb_draw_funcs_t	 *dfuncs,		\
   if (hb_object_is_immutable (dfuncs))						\
     return;									\
 										\
-  if (dfuncs->destroy.name)							\
-    dfuncs->destroy.name (dfuncs->user_data.name);				\
-										\
-  if (func) {									\
-    dfuncs->func.name = func;							\
-    dfuncs->user_data.name = user_data;						\
-    dfuncs->destroy.name = destroy;						\
-  } else {									\
-    dfuncs->func.name = hb_draw_##name##_nil;					\
-    dfuncs->user_data.name = nullptr;						\
-    dfuncs->destroy.name = nullptr;						\
-  }										\
+  if (dfuncs->destroy && dfuncs->destroy->name)					\
+    dfuncs->destroy->name (!dfuncs->user_data ? nullptr : dfuncs->user_data->name); \
+									 \
+  if (user_data && !dfuncs->user_data)                                   \
+  {                                                                      \
+    dfuncs->user_data = (decltype (dfuncs->user_data)) hb_calloc (1, sizeof (*dfuncs->user_data)); \
+    if (unlikely (!dfuncs->user_data))                                   \
+      goto fail;                                                         \
+  }                                                                      \
+  if (destroy && !dfuncs->destroy)                                       \
+  {                                                                      \
+    dfuncs->destroy = (decltype (dfuncs->destroy)) hb_calloc (1, sizeof (*dfuncs->destroy)); \
+    if (unlikely (!dfuncs->destroy))                                     \
+      goto fail;                                                         \
+  }                                                                      \
+									\
+  if (func) {								\
+    dfuncs->func.name = func;						\
+    if (dfuncs->user_data)						\
+      dfuncs->user_data->name = user_data;				\
+    if (dfuncs->destroy)						\
+      dfuncs->destroy->name = destroy;					\
+  } else {								\
+    dfuncs->func.name = hb_draw_##name##_nil;				\
+    if (dfuncs->user_data)						\
+      dfuncs->user_data->name = nullptr;				\
+    if (dfuncs->destroy)						\
+      dfuncs->destroy->name = nullptr;					\
+  }									\
+                                                                         \
+fail:                                                                    \
+  if (destroy)                                                           \
+    destroy (user_data);                                                 \
 }
 
 HB_DRAW_FUNCS_IMPLEMENT_CALLBACKS
@@ -177,11 +198,13 @@ hb_draw_funcs_destroy (hb_draw_funcs_t *dfuncs)
 {
   if (!hb_object_destroy (dfuncs)) return;
 
+  if (dfuncs->destroy)
+  {
 #define HB_DRAW_FUNC_IMPLEMENT(name) \
-  if (dfuncs->destroy.name) dfuncs->destroy.name (dfuncs->user_data.name);
-    HB_DRAW_FUNCS_IMPLEMENT_CALLBACKS
+    if (dfuncs->destroy->name) dfuncs->destroy->name (!dfuncs->user_data ? nullptr : dfuncs->user_data->name);
+      HB_DRAW_FUNCS_IMPLEMENT_CALLBACKS
 #undef HB_DRAW_FUNC_IMPLEMENT
-
+  }
 
   hb_free (dfuncs);
 }
diff --git a/src/hb-draw.hh b/src/hb-draw.hh
index 28bc9218e..768f51a87 100644
--- a/src/hb-draw.hh
+++ b/src/hb-draw.hh
@@ -54,31 +54,31 @@ struct hb_draw_funcs_t
 #define HB_DRAW_FUNC_IMPLEMENT(name) void *name;
     HB_DRAW_FUNCS_IMPLEMENT_CALLBACKS
 #undef HB_DRAW_FUNC_IMPLEMENT
-  } user_data;
+  } *user_data;
 
   struct {
 #define HB_DRAW_FUNC_IMPLEMENT(name) hb_destroy_func_t name;
     HB_DRAW_FUNCS_IMPLEMENT_CALLBACKS
 #undef HB_DRAW_FUNC_IMPLEMENT
-  } destroy;
+  } *destroy;
 
   void emit_move_to (void *draw_data, hb_draw_state_t &st,
 		     float to_x, float to_y)
   { func.move_to (this, draw_data, &st,
 		  to_x, to_y,
-		  user_data.move_to); }
+		  !user_data ? nullptr : user_data->move_to); }
   void emit_line_to (void *draw_data, hb_draw_state_t &st,
 		     float to_x, float to_y)
   { func.line_to (this, draw_data, &st,
 		  to_x, to_y,
-		  user_data.line_to); }
+		  !user_data ? nullptr : user_data->line_to); }
   void emit_quadratic_to (void *draw_data, hb_draw_state_t &st,
 			  float control_x, float control_y,
 			  float to_x, float to_y)
   { func.quadratic_to (this, draw_data, &st,
 		       control_x, control_y,
 		       to_x, to_y,
-		       user_data.quadratic_to); }
+		       !user_data ? nullptr : user_data->quadratic_to); }
   void emit_cubic_to (void *draw_data, hb_draw_state_t &st,
 		      float control1_x, float control1_y,
 		      float control2_x, float control2_y,
@@ -87,10 +87,10 @@ struct hb_draw_funcs_t
 		   control1_x, control1_y,
 		   control2_x, control2_y,
 		   to_x, to_y,
-		   user_data.cubic_to); }
+		   !user_data ? nullptr : user_data->cubic_to); }
   void emit_close_path (void *draw_data, hb_draw_state_t &st)
   { func.close_path (this, draw_data, &st,
-		     user_data.close_path); }
+		     !user_data ? nullptr : user_data->close_path); }
 
 
   void move_to (void *draw_data, hb_draw_state_t &st,