[config] Add HB_NO_UNISCRIBE_BUG_COMPATIBLE

Part of https://github.com/harfbuzz/harfbuzz/issues/1652

src/hb-config.hh

@@ -82,6 +82,10 @@
 #define HB_NO_SUBSET_CFF
 #endif
 
+#ifdef HB_NO_GETENV
+#define HB_NO_UNISCRIBE_BUG_COMPATIBLE
+#endif
+
 #ifdef HB_NO_LEGACY
 #define HB_NO_OT_LAYOUT_BLACKLIST
 #define HB_NO_OT_SHAPE_FALLBACK

src/hb-ot-shape-complex-indic.cc

@@ -274,7 +274,9 @@ struct indic_shape_plan_t
   const indic_config_t *config;
 
   bool is_old_spec;
+#ifndef HB_NO_UNISCRIBE_BUG_COMPATIBLE
   bool uniscribe_bug_compatible;
+#endif
   mutable hb_atomic_int_t virama_glyph;
 
   would_substitute_feature_t rphf;
@@ -300,7 +302,9 @@ data_create_indic (const hb_ot_shape_plan_t *plan)
     }
 
   indic_plan->is_old_spec = indic_plan->config->has_old_spec && ((plan->map.chosen_script[0] & 0x000000FFu) != '2');
+#ifndef HB_NO_UNISCRIBE_BUG_COMPATIBLE
   indic_plan->uniscribe_bug_compatible = hb_options ().uniscribe_bug_compatible;
+#endif
   indic_plan->virama_glyph.set_relaxed (-1);
 
   /* Use zero-context would_substitute() matching for new-spec of the main
@@ -918,11 +922,11 @@ initial_reordering_standalone_cluster (const hb_ot_shape_plan_t *plan,
 				       hb_buffer_t *buffer,
 				       unsigned int start, unsigned int end)
 {
-  const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) plan->data;
-
   /* We treat placeholder/dotted-circle as if they are consonants, so we
    * should just chain.  Only if not in compatibility mode that is... */
 
+#ifndef HB_NO_UNISCRIBE_BUG_COMPATIBLE
+  const HB_UNUSED indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) plan->data;
   if (indic_plan->uniscribe_bug_compatible)
   {
     /* For dotted-circle, this is what Uniscribe does:
@@ -931,6 +935,7 @@ initial_reordering_standalone_cluster (const hb_ot_shape_plan_t *plan,
     if (buffer->info[end - 1].indic_category() == OT_DOTTEDCIRCLE)
       return;
   }
+#endif
 
   initial_reordering_consonant_syllable (plan, face, buffer, start, end);
 }
@@ -1370,14 +1375,18 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
        * Uniscribe doesn't do this.
        * TEST: U+0930,U+094D,U+0915,U+094B,U+094D
        */
+#ifndef HB_NO_UNISCRIBE_BUG_COMPATIBLE
       if (!indic_plan->uniscribe_bug_compatible &&
-	  unlikely (is_halant (info[new_reph_pos]))) {
+	  unlikely (is_halant (info[new_reph_pos])))
+      {
 	for (unsigned int i = base + 1; i < new_reph_pos; i++)
 	  if (info[i].indic_category() == OT_M) {
 	    /* Ok, got it. */
 	    new_reph_pos--;
 	  }
       }
+#endif
+
       goto reph_move;
     }
 
@@ -1476,6 +1485,7 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
   /*
    * Finish off the clusters and go home!
    */
+#ifndef HB_NO_UNISCRIBE_BUG_COMPATIBLE
   if (indic_plan->uniscribe_bug_compatible)
   {
     switch ((hb_tag_t) plan->props.script)
@@ -1493,6 +1503,7 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
 	break;
     }
   }
+#endif
 }
 
 
@@ -1590,11 +1601,11 @@ decompose_indic (const hb_ot_shape_normalize_context_t *c,
      *   https://docs.microsoft.com/en-us/typography/script-development/sinhala#shaping
      */
 
+
+#ifndef HB_NO_UNISCRIBE_BUG_COMPATIBLE
     const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) c->plan->data;
-
     hb_codepoint_t glyph;
-
+    if (indic_plan->uniscribe_bug_compatible ||
-    if (hb_options ().uniscribe_bug_compatible ||
 	(c->font->get_nominal_glyph (ab, &glyph) &&
 	 indic_plan->pstf.would_substitute (&glyph, 1, c->font->face)))
     {
@@ -1603,6 +1614,7 @@ decompose_indic (const hb_ot_shape_normalize_context_t *c,
       *b = ab;
       return true;
     }
+#endif
   }
 
   return (bool) c->unicode->decompose (ab, a, b);