[Indic] Implement per-script matra positioning

Following what the spec says.

Brings down Telugu failures from 40% to 3.75%, and Kannada failures from
44% to 10%.  Does NOT affect other scripts' test results.

src/hb-ot-shape-complex-indic-private.hh

@@ -39,7 +39,7 @@
 
 
 
-#define IN_HALF_BLOCK(u, Base) ((u) & ~0x7F == (Base))
+#define IN_HALF_BLOCK(u, Base) (((u) & ~0x7F) == (Base))
 
 #define IS_DEVA(u) (IN_HALF_BLOCK (u, 0x900))
 #define IS_BENG(u) (IN_HALF_BLOCK (u, 0x980))

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

@@ -105,9 +105,43 @@ consonant_position (hb_codepoint_t u)
 }
 
 #define MATRA_POS_LEFT(u)	POS_PRE_M
-#define MATRA_POS_RIGHT(u)	POS_AFTER_POST
-#define MATRA_POS_TOP(u)	POS_BEFORE_POST
-#define MATRA_POS_BOTTOM(u)	POS_BEFORE_POST
+#define MATRA_POS_RIGHT(u)	( \
+				  IS_DEVA(u) ? POS_AFTER_SUB   : \
+				  IS_BENG(u) ? POS_AFTER_POST  : \
+				  IS_GURM(u) ? POS_AFTER_POST  : \
+				  IS_GUJA(u) ? POS_AFTER_POST  : \
+				  IS_ORYA(u) ? POS_AFTER_POST  : \
+				  IS_TAML(u) ? POS_AFTER_POST  : \
+				  IS_TELU(u) ? (u <= 0x0C42 ? POS_BEFORE_SUB : POS_AFTER_SUB)  : \
+				  IS_KNDA(u) ? POS_BEFORE_SUB  : \
+				  IS_MLYM(u) ? POS_AFTER_POST  : \
+				  IS_SINH(u) ? POS_AFTER_SUB   : \
+				  /*default*/  POS_AFTER_SUB     \
+				)
+#define MATRA_POS_TOP(u)	( /* BENG and MLYM don't have top matras. */ \
+				  IS_DEVA(u) ? POS_AFTER_SUB  : \
+				  IS_GURM(u) ? POS_AFTER_SUB  : \
+				  IS_GUJA(u) ? POS_AFTER_SUB  : \
+				  IS_ORYA(u) ? POS_AFTER_MAIN : \
+				  IS_TAML(u) ? POS_AFTER_SUB  : \
+				  IS_TELU(u) ? POS_BEFORE_SUB : \
+				  IS_KNDA(u) ? POS_BEFORE_SUB : \
+				  IS_SINH(u) ? POS_AFTER_SUB  : \
+				  /*default*/  POS_AFTER_SUB    \
+				)
+#define MATRA_POS_BOTTOM(u)	( \
+				  IS_DEVA(u) ? POS_AFTER_SUB  : \
+				  IS_BENG(u) ? POS_AFTER_SUB  : \
+				  IS_GURM(u) ? POS_AFTER_POST : \
+				  IS_GUJA(u) ? POS_AFTER_POST : \
+				  IS_ORYA(u) ? POS_AFTER_SUB  : \
+				  IS_TAML(u) ? POS_AFTER_POST : \
+				  IS_TELU(u) ? POS_BEFORE_SUB : \
+				  IS_KNDA(u) ? POS_BEFORE_SUB : \
+				  IS_MLYM(u) ? POS_AFTER_POST : \
+				  IS_SINH(u) ? POS_AFTER_SUB  : \
+				  /*default*/  POS_AFTER_SUB    \
+				)
 
 
 static indic_position_t

src/hb-unicode.cc

@@ -272,7 +272,7 @@ hb_unicode_decompose (hb_unicode_funcs_t *ufuncs,
     case 0x0AC9  : *a = 0x0AC5; *b= 0x0ABE; return true;
 
     case 0x0931  : return false;
-    case 0x0B92  : return false;
+    case 0x0B94  : return false;
 
     /* These ones have Unicode decompositions, but we do it
      * this way to be close to what Uniscribe does. */