[indic] Add back medial-consonant to grammar

Fixes https://github.com/harfbuzz/harfbuzz/issues/1592

src/hb-ot-shape-complex-indic-machine.rl

@@ -52,6 +52,7 @@ DOTTEDCIRCLE = 12;
 RS    = 13;
 Repha = 15;
 Ra    = 16;
+CM    = 17;
 Symbol= 18;
 CS    = 19;
 
@@ -67,10 +68,10 @@ matra_group = z{0,3}.M.N?.(H | forced_rakar)?;
 syllable_tail = (z?.SM.SM?.ZWNJ?)? A{0,3}?;
 halant_group = (z?.H.(ZWJ.N?)?);
 final_halant_group = halant_group | H.ZWNJ;
+medial_group = CM?;
 halant_or_matra_group = (final_halant_group | matra_group{0,4});
 
-complex_syllable_tail = (halant_group.cn){0,4} halant_or_matra_group syllable_tail;
-
+complex_syllable_tail = (halant_group.cn){0,4} medial_group halant_or_matra_group syllable_tail;
 
 consonant_syllable =	(Repha|CS)? cn complex_syllable_tail;
 vowel_syllable =	reph? V.n? (ZWJ | complex_syllable_tail);

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

@@ -720,7 +720,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan,
     indic_position_t last_pos = POS_START;
     for (unsigned int i = start; i < end; i++)
     {
-      if ((FLAG_UNSAFE (info[i].indic_category()) & (JOINER_FLAGS | FLAG (OT_N) | FLAG (OT_RS) | FLAG (OT_H))))
+      if ((FLAG_UNSAFE (info[i].indic_category()) & (JOINER_FLAGS | FLAG (OT_N) | FLAG (OT_RS) | MEDIAL_FLAGS | FLAG (OT_H))))
       {
 	info[i].indic_position() = last_pos;
 	if (unlikely (info[i].indic_category() == OT_H &&

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

@@ -62,17 +62,19 @@ enum indic_category_t {
   OT_Coeng = 14, /* Khmer-style Virama. */
   OT_Repha = 15, /* Atomically-encoded logical or visual repha. */
   OT_Ra = 16,
-  OT_CM = 17,  /* Consonant-Medial; Unused by Indic shaper. */
+  OT_CM = 17,  /* Consonant-Medial. */
   OT_Symbol = 18, /* Avagraha, etc that take marks (SM,A,VD). */
   OT_CS = 19
 };
 
+#define MEDIAL_FLAGS (FLAG (OT_CM))
+
 /* Note:
  *
  * We treat Vowels and placeholders as if they were consonants.  This is safe because Vowels
  * cannot happen in a consonant syllable.  The plus side however is, we can call the
  * consonant syllable logic from the vowel syllable function and get it all right! */
-#define CONSONANT_FLAGS (FLAG (OT_C) | FLAG (OT_CS) | FLAG (OT_Ra) | FLAG (OT_V) | FLAG (OT_PLACEHOLDER) | FLAG (OT_DOTTEDCIRCLE))
+#define CONSONANT_FLAGS (FLAG (OT_C) | FLAG (OT_CS) | FLAG (OT_Ra) | MEDIAL_FLAGS | FLAG (OT_V) | FLAG (OT_PLACEHOLDER) | FLAG (OT_DOTTEDCIRCLE))
 #define JOINER_FLAGS (FLAG (OT_ZWJ) | FLAG (OT_ZWNJ))
 
 

test/shaping/data/in-house/tests/indic-syllable.tests

@@ -6,3 +6,5 @@
 ../fonts/1735326da89f0818cd8c51a0600e9789812c0f94.ttf::U+0A51:[uni25CC=0+1044|udaatguru=0+0]
 ../fonts/1735326da89f0818cd8c51a0600e9789812c0f94.ttf::U+25CC,U+0A51:[uni25CC=0+1044|udaatguru=0+0]
 ../fonts/81c368a33816fb20e9f647e8f24e2180f4720263.ttf:--no-glyph-names:U+0C80,U+0C82:[1=0+502|2=0+502]
+../fonts/f75c4b05a0a4d67c1a808081ae3d74a9c66509e8.ttf::U+0A20,U+0A75,U+0A47:[tthaguru=0+1352|yakashguru=0@-90,0+0|eematraguru=0@-411,0+0]
+../fonts/f75c4b05a0a4d67c1a808081ae3d74a9c66509e8.ttf::U+0A20,U+0A75,U+0A42:[tthaguru=0+1352|yakashuuguru=0+0]