Imported Upstream version 0.9.12upstream/0.9.12

1 files changed, 333 insertions, 60 deletions

diff --git a/src/hb-ot-shape-complex-indic.cc b/src/hb-ot-shape-complex-indic.cc
index 6fbd5c8..5afede0 100644
--- a/src/hb-ot-shape-complex-indic.cc
+++ b/src/hb-ot-shape-complex-indic.cc
@@ -123,6 +123,8 @@ static const indic_config_t indic_configs[] =
   {HB_SCRIPT_MALAYALAM,	true, 0x0D4D,BASE_POS_LAST, REPH_POS_AFTER_MAIN, REPH_MODE_LOG_REPHA},
   {HB_SCRIPT_SINHALA,	false,0x0DCA,BASE_POS_FIRST,REPH_POS_AFTER_MAIN, REPH_MODE_EXPLICIT},
   {HB_SCRIPT_KHMER,	false,0x17D2,BASE_POS_FIRST,REPH_POS_DEFAULT,    REPH_MODE_VIS_REPHA},
+  /* Myanmar does not have the "old_indic" behavior, even though it has a "new" tag. */
+  {HB_SCRIPT_MYANMAR,	false,0x1039,BASE_POS_LAST, REPH_POS_DEFAULT,    REPH_MODE_EXPLICIT},
 };
 
 
@@ -203,6 +205,10 @@ enum {
 };
 
 static void
+setup_syllables (const hb_ot_shape_plan_t *plan,
+		 hb_font_t *font,
+		 hb_buffer_t *buffer);
+static void
 initial_reordering (const hb_ot_shape_plan_t *plan,
 		    hb_font_t *font,
 		    hb_buffer_t *buffer);
@@ -216,6 +222,9 @@ collect_features_indic (hb_ot_shape_planner_t *plan)
 {
   hb_ot_map_builder_t *map = &plan->map;
 
+  /* Do this before any lookups have been applied. */
+  map->add_gsub_pause (setup_syllables);
+
   map->add_bool_feature (HB_TAG('l','o','c','l'));
   /* The Indic specs do not require ccmp, but we apply it here since if
    * there is a use of it, it's typically at the beginning. */
@@ -240,6 +249,8 @@ override_features_indic (hb_ot_shape_planner_t *plan)
   /* Uniscribe does not apply 'kern'. */
   if (indic_options ().uniscribe_bug_compatible)
     plan->map.add_feature (HB_TAG('k','e','r','n'), 0, true);
+
+  plan->map.add_feature (HB_TAG('l','i','g','a'), 0, true);
 }
 
 
@@ -254,10 +265,11 @@ struct would_substitute_feature_t
 
   inline bool would_substitute (hb_codepoint_t    *glyphs,
 				unsigned int       glyphs_count,
+				bool               zero_context,
 				hb_face_t         *face) const
   {
     for (unsigned int i = 0; i < count; i++)
-      if (hb_ot_layout_would_substitute_lookup_fast (face, glyphs, glyphs_count, lookups[i].index))
+      if (hb_ot_layout_lookup_would_substitute_fast (face, lookups[i].index, glyphs, glyphs_count, zero_context))
 	return true;
     return false;
   }
@@ -295,6 +307,7 @@ struct indic_shape_plan_t
   bool is_old_spec;
   hb_codepoint_t virama_glyph;
 
+  would_substitute_feature_t rphf;
   would_substitute_feature_t pref;
   would_substitute_feature_t blwf;
   would_substitute_feature_t pstf;
@@ -316,9 +329,10 @@ data_create_indic (const hb_ot_shape_plan_t *plan)
       break;
     }
 
-  indic_plan->is_old_spec = indic_plan->config->has_old_spec && ((plan->map.get_chosen_script (0) & 0x000000FF) != '2');
+  indic_plan->is_old_spec = indic_plan->config->has_old_spec && ((plan->map.chosen_script[0] & 0x000000FF) != '2');
   indic_plan->virama_glyph = (hb_codepoint_t) -1;
 
+  indic_plan->rphf.init (&plan->map, HB_TAG('r','p','h','f'));
   indic_plan->pref.init (&plan->map, HB_TAG('p','r','e','f'));
   indic_plan->blwf.init (&plan->map, HB_TAG('b','l','w','f'));
   indic_plan->pstf.init (&plan->map, HB_TAG('p','s','t','f'));
@@ -340,13 +354,25 @@ consonant_position_from_face (const indic_shape_plan_t *indic_plan,
 			      hb_codepoint_t *glyphs, unsigned int glyphs_len,
 			      hb_face_t      *face)
 {
-  if (indic_plan->pref.would_substitute (glyphs, glyphs_len, face)) return POS_BELOW_C;
-  if (indic_plan->blwf.would_substitute (glyphs, glyphs_len, face)) return POS_BELOW_C;
-  if (indic_plan->pstf.would_substitute (glyphs, glyphs_len, face)) return POS_POST_C;
+  bool zero_context = indic_plan->is_old_spec ? false : true;
+  if (indic_plan->pref.would_substitute (glyphs, glyphs_len, zero_context, face)) return POS_BELOW_C;
+  if (indic_plan->blwf.would_substitute (glyphs, glyphs_len, zero_context, face)) return POS_BELOW_C;
+  if (indic_plan->pstf.would_substitute (glyphs, glyphs_len, zero_context, face)) return POS_POST_C;
   return POS_BASE_C;
 }
 
 
+enum syllable_type_t {
+  consonant_syllable,
+  vowel_syllable,
+  standalone_cluster,
+  broken_cluster,
+  non_indic_cluster,
+};
+
+#include "hb-ot-shape-complex-indic-machine.hh"
+
+
 static void
 setup_masks_indic (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		   hb_buffer_t              *buffer,
@@ -363,6 +389,14 @@ setup_masks_indic (const hb_ot_shape_plan_t *plan HB_UNUSED,
     set_indic_properties (buffer->info[i]);
 }
 
+static void
+setup_syllables (const hb_ot_shape_plan_t *plan HB_UNUSED,
+		 hb_font_t *font HB_UNUSED,
+		 hb_buffer_t *buffer)
+{
+  find_syllables (buffer);
+}
+
 static int
 compare_indic_order (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
 {
@@ -400,7 +434,9 @@ update_consonant_positions (const hb_ot_shape_plan_t *plan,
  * https://www.microsoft.com/typography/otfntdev/devanot/shaping.aspx */
 
 static void
-initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer_t *buffer,
+initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan,
+				       hb_face_t *face,
+				       hb_buffer_t *buffer,
 				       unsigned int start, unsigned int end)
 {
   const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) plan->data;
@@ -431,22 +467,36 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
     unsigned int limit = start;
     if (indic_plan->mask_array[RPHF] &&
 	start + 3 <= end &&
-	info[start].indic_category() == OT_Ra &&
-	info[start + 1].indic_category() == OT_H &&
-	(/* TODO Handle other Reph modes. */
+	(
 	 (indic_plan->config->reph_mode == REPH_MODE_IMPLICIT && !is_joiner (info[start + 2])) ||
 	 (indic_plan->config->reph_mode == REPH_MODE_EXPLICIT && info[start + 2].indic_category() == OT_ZWJ)
 	))
     {
-      limit += 2;
-      while (limit < end && is_joiner (info[limit]))
-        limit++;
-      base = start;
-      has_reph = true;
-    };
-
-    switch (indic_plan->config->base_pos == BASE_POS_LAST)
+      /* See if it matches the 'rphf' feature. */
+      hb_codepoint_t glyphs[2] = {info[start].codepoint, info[start + 1].codepoint};
+      if (indic_plan->rphf.would_substitute (glyphs, ARRAY_LENGTH (glyphs), true, face))
+      {
+	limit += 2;
+	while (limit < end && is_joiner (info[limit]))
+	  limit++;
+	base = start;
+	has_reph = true;
+      }
+    } else if (indic_plan->config->reph_mode == REPH_MODE_LOG_REPHA && info[start].indic_category() == OT_Repha)
+    {
+	limit += 1;
+	while (limit < end && is_joiner (info[limit]))
+	  limit++;
+	base = start;
+	has_reph = true;
+    }
+
+    switch (indic_plan->config->base_pos)
     {
+      default:
+        assert (false);
+	/* fallthrough */
+
       case BASE_POS_LAST:
       {
 	/* -> starting from the end of the syllable, move backwards */
@@ -486,7 +536,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
 	     * half form.
 	     * A ZWJ before a Halant, requests a subjoined form instead, and hence
 	     * search continues.  This is particularly important for Bengali
-	     * sequence Ra,H,Ya that shouls form Ya-Phalaa by subjoining Ya. */
+	     * sequence Ra,H,Ya that should form Ya-Phalaa by subjoining Ya. */
 	    if (start < i &&
 		info[i].indic_category() == OT_ZWJ &&
 		info[i - 1].indic_category() == OT_H)
@@ -520,9 +570,6 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
 	    info[i].indic_position() = POS_BELOW_C;
       }
       break;
-
-      default:
-      abort ();
     }
 
     /* -> If the syllable starts with Ra + Halant (in a script that has Reph)
@@ -530,7 +577,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
      *    base consonants.
      *
      *  Only do this for unforced Reph. (ie. not for Ra,H,ZWJ. */
-    if (has_reph && base == start && start + 2 == limit) {
+    if (has_reph && base == start && start - limit <= 2) {
       /* Have no other consonant, so Reph is not formed and Ra becomes base. */
       has_reph = false;
     }
@@ -597,15 +644,16 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
     info[start].indic_position() = POS_RA_TO_BECOME_REPH;
 
   /* For old-style Indic script tags, move the first post-base Halant after
-   * last consonant. */
+   * last consonant.  Only do this if there is *not* a Halant after last
+   * consonant.  Otherwise it becomes messy. */
   if (indic_plan->is_old_spec) {
     for (unsigned int i = base + 1; i < end; i++)
       if (info[i].indic_category() == OT_H) {
         unsigned int j;
         for (j = end - 1; j > i; j--)
-	  if (is_consonant (info[j]))
+	  if (is_consonant (info[j]) || info[j].indic_category() == OT_H)
 	    break;
-	if (j > i) {
+	if (info[j].indic_category() != OT_H && j > i) {
 	  /* Move Halant to after last consonant. */
 	  hb_glyph_info_t t = info[i];
 	  memmove (&info[i], &info[i + 1], (j - i) * sizeof (info[0]));
@@ -623,13 +671,17 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
       if ((FLAG (info[i].indic_category()) & (JOINER_FLAGS | FLAG (OT_N) | FLAG (OT_RS) | HALANT_OR_COENG_FLAGS)))
       {
 	info[i].indic_position() = last_pos;
-	if (unlikely (indic_options ().uniscribe_bug_compatible &&
-		      info[i].indic_category() == OT_H &&
+	if (unlikely (info[i].indic_category() == OT_H &&
 		      info[i].indic_position() == POS_PRE_M))
 	{
 	  /*
 	   * Uniscribe doesn't move the Halant with Left Matra.
 	   * TEST: U+092B,U+093F,U+094DE
+	   * We follow.  This is important for the Sinhala
+	   * U+0DDA split matra since it decomposes to U+0DD9,U+0DCA
+	   * where U+0DD9 is a left matra and U+0DCA is the virama.
+	   * We don't want to move the virama with the left matra.
+	   * TEST: U+0D9A,U+0DDA
 	   */
 	  for (unsigned int j = i; j > start; j--)
 	    if (info[j - 1].indic_position() != POS_PRE_M) {
@@ -694,13 +746,12 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
       info[i].mask  |= mask;
   }
 
-  /* XXX This will not match for old-Indic spec since the Halant-Ra order is reversed already. */
   if (indic_plan->mask_array[PREF] && base + 2 < end)
   {
     /* Find a Halant,Ra sequence and mark it for pre-base reordering processing. */
-    for (unsigned int i = base + 1; i + 1 < end; i++)
-      if (is_halant_or_coeng (info[i]) &&
-	  info[i + 1].indic_category() == OT_Ra)
+    for (unsigned int i = base + 1; i + 1 < end; i++) {
+      hb_codepoint_t glyphs[2] = {info[i].codepoint, info[i + 1].codepoint};
+      if (indic_plan->pref.would_substitute (glyphs, ARRAY_LENGTH (glyphs), true, face))
       {
 	info[i++].mask |= indic_plan->mask_array[PREF];
 	info[i++].mask |= indic_plan->mask_array[PREF];
@@ -716,6 +767,7 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
 
 	break;
       }
+    }
   }
 
   /* Apply ZWJ/ZWNJ effects */
@@ -741,15 +793,17 @@ initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan, hb_buffer
 
 static void
 initial_reordering_vowel_syllable (const hb_ot_shape_plan_t *plan,
+				   hb_face_t *face,
 				   hb_buffer_t *buffer,
 				   unsigned int start, unsigned int end)
 {
   /* We made the vowels look like consonants.  So let's call the consonant logic! */
-  initial_reordering_consonant_syllable (plan, buffer, start, end);
+  initial_reordering_consonant_syllable (plan, face, buffer, start, end);
 }
 
 static void
 initial_reordering_standalone_cluster (const hb_ot_shape_plan_t *plan,
+				       hb_face_t *face,
 				       hb_buffer_t *buffer,
 				       unsigned int start, unsigned int end)
 {
@@ -765,19 +819,103 @@ initial_reordering_standalone_cluster (const hb_ot_shape_plan_t *plan,
       return;
   }
 
-  initial_reordering_consonant_syllable (plan, buffer, start, end);
+  initial_reordering_consonant_syllable (plan, face, buffer, start, end);
 }
 
 static void
-initial_reordering_non_indic (const hb_ot_shape_plan_t *plan HB_UNUSED,
-			      hb_buffer_t *buffer HB_UNUSED,
-			      unsigned int start HB_UNUSED, unsigned int end HB_UNUSED)
+initial_reordering_broken_cluster (const hb_ot_shape_plan_t *plan,
+				   hb_face_t *face,
+				   hb_buffer_t *buffer,
+				   unsigned int start, unsigned int end)
+{
+  /* We already inserted dotted-circles, so just call the standalone_cluster. */
+  initial_reordering_standalone_cluster (plan, face, buffer, start, end);
+}
+
+static void
+initial_reordering_non_indic_cluster (const hb_ot_shape_plan_t *plan HB_UNUSED,
+				      hb_face_t *face HB_UNUSED,
+				      hb_buffer_t *buffer HB_UNUSED,
+				      unsigned int start HB_UNUSED, unsigned int end HB_UNUSED)
 {
   /* Nothing to do right now.  If we ever switch to using the output
    * buffer in the reordering process, we'd need to next_glyph() here. */
 }
 
-#include "hb-ot-shape-complex-indic-machine.hh"
+
+static void
+initial_reordering_syllable (const hb_ot_shape_plan_t *plan,
+			     hb_face_t *face,
+			     hb_buffer_t *buffer,
+			     unsigned int start, unsigned int end)
+{
+  syllable_type_t syllable_type = (syllable_type_t) (buffer->info[start].syllable() & 0x0F);
+  switch (syllable_type) {
+  case consonant_syllable:	initial_reordering_consonant_syllable (plan, face, buffer, start, end); return;
+  case vowel_syllable:		initial_reordering_vowel_syllable     (plan, face, buffer, start, end); return;
+  case standalone_cluster:	initial_reordering_standalone_cluster (plan, face, buffer, start, end); return;
+  case broken_cluster:		initial_reordering_broken_cluster     (plan, face, buffer, start, end); return;
+  case non_indic_cluster:	initial_reordering_non_indic_cluster  (plan, face, buffer, start, end); return;
+  }
+}
+
+static inline void
+insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
+		       hb_font_t *font,
+		       hb_buffer_t *buffer)
+{
+  /* Note: This loop is extra overhead, but should not be measurable. */
+  bool has_broken_syllables = false;
+  unsigned int count = buffer->len;
+  for (unsigned int i = 0; i < count; i++)
+    if ((buffer->info[i].syllable() & 0x0F) == broken_cluster) {
+      has_broken_syllables = true;
+      break;
+    }
+  if (likely (!has_broken_syllables))
+    return;
+
+
+  hb_codepoint_t dottedcircle_glyph;
+  if (!font->get_glyph (0x25CC, 0, &dottedcircle_glyph))
+    return;
+
+  hb_glyph_info_t dottedcircle = {0};
+  dottedcircle.codepoint = 0x25CC;
+  set_indic_properties (dottedcircle);
+  dottedcircle.codepoint = dottedcircle_glyph;
+
+  buffer->clear_output ();
+
+  buffer->idx = 0;
+  unsigned int last_syllable = 0;
+  while (buffer->idx < buffer->len)
+  {
+    unsigned int syllable = buffer->cur().syllable();
+    syllable_type_t syllable_type = (syllable_type_t) (syllable & 0x0F);
+    if (unlikely (last_syllable != syllable && syllable_type == broken_cluster))
+    {
+      last_syllable = syllable;
+
+      hb_glyph_info_t info = dottedcircle;
+      info.cluster = buffer->cur().cluster;
+      info.mask = buffer->cur().mask;
+      info.syllable() = buffer->cur().syllable();
+
+      /* Insert dottedcircle after possible Repha. */
+      while (buffer->idx < buffer->len &&
+	     last_syllable == buffer->cur().syllable() &&
+	     buffer->cur().indic_category() == OT_Repha)
+        buffer->next_glyph ();
+
+      buffer->output_info (info);
+    }
+    else
+      buffer->next_glyph ();
+  }
+
+  buffer->swap_buffers ();
+}
 
 static void
 initial_reordering (const hb_ot_shape_plan_t *plan,
@@ -785,7 +923,20 @@ initial_reordering (const hb_ot_shape_plan_t *plan,
 		    hb_buffer_t *buffer)
 {
   update_consonant_positions (plan, font, buffer);
-  find_syllables (plan, buffer);
+  insert_dotted_circles (plan, font, buffer);
+
+  hb_glyph_info_t *info = buffer->info;
+  unsigned int count = buffer->len;
+  if (unlikely (!count)) return;
+  unsigned int last = 0;
+  unsigned int last_syllable = info[0].syllable();
+  for (unsigned int i = 1; i < count; i++)
+    if (last_syllable != info[i].syllable()) {
+      initial_reordering_syllable (plan, font->face, buffer, last, i);
+      last = i;
+      last_syllable = info[last].syllable();
+    }
+  initial_reordering_syllable (plan, font->face, buffer, last, count);
 }
 
 static void
@@ -829,11 +980,11 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
     /* If we lost track of base, alas, position before last thingy. */
     unsigned int new_pos = base == end ? base - 2 : base - 1;
 
-    /* Malayalam does not have "half" forms or explicit virama forms.
-     * The glyphs formed by 'half' are Chillus.  We want to position
-     * matra after them all.
+    /* Malayalam / Tamil do not have "half" forms or explicit virama forms.
+     * The glyphs formed by 'half' are Chillus or ligated explicit viramas.
+     * We want to position matra after them.
      */
-    if (buffer->props.script != HB_SCRIPT_MALAYALAM)
+    if (buffer->props.script != HB_SCRIPT_MALAYALAM && buffer->props.script != HB_SCRIPT_TAMIL)
     {
       while (new_pos > start &&
 	     !(is_one_of (info[new_pos], (FLAG (OT_M) | FLAG (OT_H) | FLAG (OT_Coeng)))))
@@ -853,7 +1004,7 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
         new_pos = start; /* No move. */
     }
 
-    if (start < new_pos)
+    if (start < new_pos && info[new_pos].indic_position () != POS_PRE_M)
     {
       /* Now go see if there's actually any matras... */
       for (unsigned int i = new_pos; i > start; i--)
@@ -1045,21 +1196,28 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
 	   */
 
 	  unsigned int new_pos = base;
-	  while (new_pos > start &&
-		 !(is_one_of (info[new_pos - 1], FLAG(OT_M) | HALANT_OR_COENG_FLAGS)))
-	    new_pos--;
-
-	  /* In Khmer coeng model, a V,Ra can go *after* matras.  If it goes after a
-	   * split matra, it should be reordered to *before* the left part of such matra. */
-	  if (new_pos > start && info[new_pos - 1].indic_category() == OT_M)
+	  /* Malayalam / Tamil do not have "half" forms or explicit virama forms.
+	   * The glyphs formed by 'half' are Chillus or ligated explicit viramas.
+	   * We want to position matra after them.
+	   */
+	  if (buffer->props.script != HB_SCRIPT_MALAYALAM && buffer->props.script != HB_SCRIPT_TAMIL)
 	  {
-	    unsigned int old_pos = i;
-	    for (unsigned int i = base + 1; i < old_pos; i++)
-	      if (info[i].indic_category() == OT_M)
-	      {
-		new_pos--;
-		break;
-	      }
+	    while (new_pos > start &&
+		   !(is_one_of (info[new_pos - 1], FLAG(OT_M) | HALANT_OR_COENG_FLAGS)))
+	      new_pos--;
+
+	    /* In Khmer coeng model, a V,Ra can go *after* matras.  If it goes after a
+	     * split matra, it should be reordered to *before* the left part of such matra. */
+	    if (new_pos > start && info[new_pos - 1].indic_category() == OT_M)
+	    {
+	      unsigned int old_pos = i;
+	      for (unsigned int i = base + 1; i < old_pos; i++)
+		if (info[i].indic_category() == OT_M)
+		{
+		  new_pos--;
+		  break;
+		}
+	    }
 	  }
 
 	  if (new_pos > start && is_halant_or_coeng (info[new_pos - 1]))
@@ -1105,11 +1263,11 @@ final_reordering_syllable (const hb_ot_shape_plan_t *plan,
 
 static void
 final_reordering (const hb_ot_shape_plan_t *plan,
-		  hb_font_t *font,
+		  hb_font_t *font HB_UNUSED,
 		  hb_buffer_t *buffer)
 {
   unsigned int count = buffer->len;
-  if (!count) return;
+  if (unlikely (!count)) return;
 
   hb_glyph_info_t *info = buffer->info;
   unsigned int last = 0;
@@ -1122,11 +1280,123 @@ final_reordering (const hb_ot_shape_plan_t *plan,
     }
   final_reordering_syllable (plan, buffer, last, count);
 
+  /* Zero syllables now... */
+  for (unsigned int i = 0; i < count; i++)
+    info[i].syllable() = 0;
+
   HB_BUFFER_DEALLOCATE_VAR (buffer, indic_category);
   HB_BUFFER_DEALLOCATE_VAR (buffer, indic_position);
 }
 
 
+static hb_ot_shape_normalization_mode_t
+normalization_preference_indic (const hb_segment_properties_t *props HB_UNUSED)
+{
+  return HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT;
+}
+
+static bool
+decompose_indic (const hb_ot_shape_normalize_context_t *c,
+		 hb_codepoint_t  ab,
+		 hb_codepoint_t *a,
+		 hb_codepoint_t *b)
+{
+  switch (ab)
+  {
+    /* Don't decompose these. */
+    case 0x0931  : return false;
+    case 0x0B94  : return false;
+
+
+    /*
+     * Decompose split matras that don't have Unicode decompositions.
+     */
+
+    case 0x0F77  : *a = 0x0FB2; *b= 0x0F81; return true;
+    case 0x0F79  : *a = 0x0FB3; *b= 0x0F81; return true;
+    case 0x17BE  : *a = 0x17C1; *b= 0x17BE; return true;
+    case 0x17BF  : *a = 0x17C1; *b= 0x17BF; return true;
+    case 0x17C0  : *a = 0x17C1; *b= 0x17C0; return true;
+    case 0x17C4  : *a = 0x17C1; *b= 0x17C4; return true;
+    case 0x17C5  : *a = 0x17C1; *b= 0x17C5; return true;
+    case 0x1925  : *a = 0x1920; *b= 0x1923; return true;
+    case 0x1926  : *a = 0x1920; *b= 0x1924; return true;
+    case 0x1B3C  : *a = 0x1B42; *b= 0x1B3C; return true;
+    case 0x1112E  : *a = 0x11127; *b= 0x11131; return true;
+    case 0x1112F  : *a = 0x11127; *b= 0x11132; return true;
+#if 0
+    /* This one has no decomposition in Unicode, but needs no decomposition either. */
+    /* case 0x0AC9  : return false; */
+    case 0x0B57  : *a = no decomp, -> RIGHT; return true;
+    case 0x1C29  : *a = no decomp, -> LEFT; return true;
+    case 0xA9C0  : *a = no decomp, -> RIGHT; return true;
+    case 0x111BF  : *a = no decomp, -> ABOVE; return true;
+#endif
+  }
+
+  if ((ab == 0x0DDA || hb_in_range<hb_codepoint_t> (ab, 0x0DDC, 0x0DDE)))
+  {
+    /*
+     * Sinhala split matras...  Let the fun begin.
+     *
+     * These four characters have Unicode decompositions.  However, Uniscribe
+     * decomposes them "Khmer-style", that is, it uses the character itself to
+     * get the second half.  The first half of all four decompositions is always
+     * U+0DD9.
+     *
+     * Now, there are buggy fonts, namely, the widely used lklug.ttf, that are
+     * broken with Uniscribe.  But we need to support them.  As such, we only
+     * do the Uniscribe-style decomposition if the character is transformed into
+     * its "sec.half" form by the 'pstf' feature.  Otherwise, we fall back to
+     * Unicode decomposition.
+     *
+     * Note that we can't unconditionally use Unicode decomposition.  That would
+     * break some other fonts, that are designed to work with Uniscribe, and
+     * don't have positioning features for the Unicode-style decomposition.
+     *
+     * Argh...
+     *
+     * The Uniscribe behavior is now documented in the newly published Sinhala
+     * spec in 2012:
+     *
+     *   http://www.microsoft.com/typography/OpenTypeDev/sinhala/intro.htm#shaping
+     */
+
+    const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) c->plan->data;
+
+    hb_codepoint_t glyph;
+
+    if (indic_options ().uniscribe_bug_compatible ||
+	(c->font->get_glyph (ab, 0, &glyph) &&
+	 indic_plan->pstf.would_substitute (&glyph, 1, true, c->font->face)))
+    {
+      /* Ok, safe to use Uniscribe-style decomposition. */
+      *a = 0x0DD9;
+      *b = ab;
+      return true;
+    }
+  }
+
+  return c->unicode->decompose (ab, a, b);
+}
+
+static bool
+compose_indic (const hb_ot_shape_normalize_context_t *c,
+	       hb_codepoint_t  a,
+	       hb_codepoint_t  b,
+	       hb_codepoint_t *ab)
+{
+  /* Avoid recomposing split matras. */
+  if (HB_UNICODE_GENERAL_CATEGORY_IS_MARK (c->unicode->general_category (a)))
+    return false;
+
+  /* Composition-exclusion exceptions that we want to recompose. */
+  if (a == 0x09AF && b == 0x09BC) { *ab = 0x09DF; return true; }
+
+  return c->unicode->compose (a, b, ab);
+}
+
+
 const hb_ot_complex_shaper_t _hb_ot_complex_shaper_indic =
 {
   "indic",
@@ -1135,7 +1405,10 @@ const hb_ot_complex_shaper_t _hb_ot_complex_shaper_indic =
   data_create_indic,
   data_destroy_indic,
   NULL, /* preprocess_text */
-  NULL, /* normalization_preference */
+  normalization_preference_indic,
+  decompose_indic,
+  compose_indic,
   setup_masks_indic,
   false, /* zero_width_attached_marks */
+  false, /* fallback_position */
 };