[normalizer] Add c.override_decompose_and_compose

src/hb-ot-shape-normalize.cc

@@ -290,15 +290,14 @@ _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
       mode = HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS;
   }
 
-  const hb_ot_shape_normalize_context_t c = {
+  hb_ot_shape_normalize_context_t c = {
     plan,
     buffer,
     font,
     buffer->unicode,
     buffer->not_found,
-    plan->shaper->decompose ? plan->shaper->decompose : hb_ot_shape_normalize_context_t::decompose_unicode,
-    plan->shaper->compose   ? plan->shaper->compose   : hb_ot_shape_normalize_context_t::compose_unicode
   };
+  c.override_decompose_and_compose (plan->shaper->decompose, plan->shaper->compose);
 
   bool always_short_circuit = mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE;
   bool might_short_circuit = always_short_circuit ||

src/hb-ot-shape-normalize.hh

@@ -71,6 +71,20 @@ struct hb_ot_shape_normalize_context_t
     return (bool) c->unicode->compose (a, b, ab);
   }
 
+  void
+  override_decompose_and_compose (bool (*decompose) (const hb_ot_shape_normalize_context_t *c,
+						      hb_codepoint_t  ab,
+						      hb_codepoint_t *a,
+						      hb_codepoint_t *b),
+				  bool (*compose) (const hb_ot_shape_normalize_context_t *c,
+						   hb_codepoint_t  a,
+						   hb_codepoint_t  b,
+						   hb_codepoint_t *ab))
+  {
+    this->decompose = decompose ? decompose : decompose_unicode;
+    this->compose = compose ? compose : compose_unicode;
+  }
+
   const hb_ot_shape_plan_t *plan;
   hb_buffer_t *buffer;
   hb_font_t *font;