src/hb-ot-shape-normalize.cc - third_party/harfbuzz - Git at Google

 /*
  * Copyright © 2011,2012  Google, Inc.
  *
  *  This is part of HarfBuzz, a text shaping library.
  *
  * Permission is hereby granted, without written agreement and without
  * license or royalty fees, to use, copy, modify, and distribute this
  * software and its documentation for any purpose, provided that the
  * above copyright notice and the following two paragraphs appear in
  * all copies of this software.
  *
  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  * DAMAGE.
  *
  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  *
  * Google Author(s): Behdad Esfahbod
  */

 #include "hb-ot-shape-normalize-private.hh"
 #include "hb-ot-shape-private.hh"


 /*
  * HIGHLEVEL DESIGN:
  *
  * This file exports one main function: _hb_ot_shape_normalize().
  *
  * This function closely reflects the Unicode Normalization Algorithm,
  * yet it's different.
  *
  * Each shaper specifies whether it prefers decomposed (NFD) or composed (NFC).
  * The logic however tries to use whatever the font can support.
  *
  * In general what happens is that: each grapheme is decomposed in a chain
  * of 1:2 decompositions, marks reordered, and then recomposed if desired,
  * so far it's like Unicode Normalization.  However, the decomposition and
  * recomposition only happens if the font supports the resulting characters.
  *
  * The goals are:
  *
  *   - Try to render all canonically equivalent strings similarly.  To really
  *     achieve this we have to always do the full decomposition and then
  *     selectively recompose from there.  It's kinda too expensive though, so
  *     we skip some cases.  For example, if composed is desired, we simply
  *     don't touch 1-character clusters that are supported by the font, even
  *     though their NFC may be different.
  *
  *   - When a font has a precomposed character for a sequence but the 'ccmp'
  *     feature in the font is not adequate, use the precomposed character
  *     which typically has better mark positioning.
  *
  *   - When a font does not support a combining mark, but supports it precomposed
  *     with previous base, use that.  This needs the itemizer to have this
  *     knowledge too.  We need to provide assistance to the itemizer.
  *
  *   - When a font does not support a character but supports its decomposition,
  *     well, use the decomposition (preferring the canonical decomposition, but
  *     falling back to the compatibility decomposition if necessary).  The
  *     compatibility decomposition is really nice to have, for characters like
  *     ellipsis, or various-sized space characters.
  *
  *   - The complex shapers can customize the compose and decompose functions to
  *     offload some of their requirements to the normalizer.  For example, the
  *     Indic shaper may want to disallow recomposing of two matras.
  *
  *   - We try compatibility decomposition if decomposing through canonical
  *     decomposition alone failed to find a sequence that the font supports.
  *     We don't try compatibility decomposition recursively during the canonical
  *     decomposition phase.  This has minimal impact.  There are only a handful
  *     of Greek letter that have canonical decompositions that include characters
  *     with compatibility decomposition.  Those can be found using this command:
  *
  *     egrep  "`echo -n ';('; grep ';<' UnicodeData.txt | cut -d';' -f1 | tr '\n' '|'; echo ') '`" UnicodeData.txt
  */

 static hb_bool_t
 decompose_func (hb_unicode_funcs_t *unicode,
 		hb_codepoint_t  ab,
 		hb_codepoint_t *a,
 		hb_codepoint_t *b)
 {
   /* XXX FIXME, move these to complex shapers and propagage to normalizer.*/
   switch (ab) {
     case 0x0AC9  : return false;

     case 0x0931  : return false;
     case 0x0B94  : return false;

     /* These ones have Unicode decompositions, but we do it
      * this way to be close to what Uniscribe does. */
     case 0x0DDA  : *a = 0x0DD9; *b= 0x0DDA; return true;
     case 0x0DDC  : *a = 0x0DD9; *b= 0x0DDC; return true;
     case 0x0DDD  : *a = 0x0DD9; *b= 0x0DDD; return true;
     case 0x0DDE  : *a = 0x0DD9; *b= 0x0DDE; return true;

     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
     case 0x0B57  : *a = 0xno decomp, -> RIGHT; return true;
     case 0x1C29  : *a = 0xno decomp, -> LEFT; return true;
     case 0xA9C0  : *a = 0xno decomp, -> RIGHT; return true;
     case 0x111BF  : *a = 0xno decomp, -> ABOVE; return true;
 #endif
   }
   return unicode->decompose (ab, a, b);
 }

 static hb_bool_t
 compose_func (hb_unicode_funcs_t *unicode,
 	      hb_codepoint_t  a,
 	      hb_codepoint_t  b,
 	      hb_codepoint_t *ab)
 {
   /* XXX, this belongs to indic normalizer. */
   if ((FLAG (unicode->general_category (a)) &
        (FLAG (HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK) |
 	FLAG (HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) |
 	FLAG (HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK))))
     return false;
   /* XXX, add composition-exclusion exceptions to Indic shaper. */
   if (a == 0x09AF && b == 0x09BC) { *ab = 0x09DF; return true; }

   /* XXX, these belong to the hebew / default shaper. */
   /* Hebrew presentation-form shaping.
    * https://bugzilla.mozilla.org/show_bug.cgi?id=728866 */
   // Hebrew presentation forms with dagesh, for characters 0x05D0..0x05EA;
   // note that some letters do not have a dagesh presForm encoded
   static const hb_codepoint_t sDageshForms[0x05EA - 0x05D0 + 1] = {
     0xFB30, // ALEF
     0xFB31, // BET
     0xFB32, // GIMEL
     0xFB33, // DALET
     0xFB34, // HE
     0xFB35, // VAV
     0xFB36, // ZAYIN
     0, // HET
     0xFB38, // TET
     0xFB39, // YOD
     0xFB3A, // FINAL KAF
     0xFB3B, // KAF
     0xFB3C, // LAMED
     0, // FINAL MEM
     0xFB3E, // MEM
     0, // FINAL NUN
     0xFB40, // NUN
     0xFB41, // SAMEKH
     0, // AYIN
     0xFB43, // FINAL PE
     0xFB44, // PE
     0, // FINAL TSADI
     0xFB46, // TSADI
     0xFB47, // QOF
     0xFB48, // RESH
     0xFB49, // SHIN
     0xFB4A // TAV
   };

   hb_bool_t found = unicode->compose (a, b, ab);

   if (!found && (b & ~0x7F) == 0x0580) {
       // special-case Hebrew presentation forms that are excluded from
       // standard normalization, but wanted for old fonts
       switch (b) {
       case 0x05B4: // HIRIQ
 	  if (a == 0x05D9) { // YOD
 	      *ab = 0xFB1D;
 	      found = true;
 	  }
 	  break;
       case 0x05B7: // patah
 	  if (a == 0x05F2) { // YIDDISH YOD YOD
 	      *ab = 0xFB1F;
 	      found = true;
 	  } else if (a == 0x05D0) { // ALEF
 	      *ab = 0xFB2E;
 	      found = true;
 	  }
 	  break;
       case 0x05B8: // QAMATS
 	  if (a == 0x05D0) { // ALEF
 	      *ab = 0xFB2F;
 	      found = true;
 	  }
 	  break;
       case 0x05B9: // HOLAM
 	  if (a == 0x05D5) { // VAV
 	      *ab = 0xFB4B;
 	      found = true;
 	  }
 	  break;
       case 0x05BC: // DAGESH
 	  if (a >= 0x05D0 && a <= 0x05EA) {
 	      *ab = sDageshForms[a - 0x05D0];
 	      found = (*ab != 0);
 	  } else if (a == 0xFB2A) { // SHIN WITH SHIN DOT
 	      *ab = 0xFB2C;
 	      found = true;
 	  } else if (a == 0xFB2B) { // SHIN WITH SIN DOT
 	      *ab = 0xFB2D;
 	      found = true;
 	  }
 	  break;
       case 0x05BF: // RAFE
 	  switch (a) {
 	  case 0x05D1: // BET
 	      *ab = 0xFB4C;
 	      found = true;
 	      break;
 	  case 0x05DB: // KAF
 	      *ab = 0xFB4D;
 	      found = true;
 	      break;
 	  case 0x05E4: // PE
 	      *ab = 0xFB4E;
 	      found = true;
 	      break;
 	  }
 	  break;
       case 0x05C1: // SHIN DOT
 	  if (a == 0x05E9) { // SHIN
 	      *ab = 0xFB2A;
 	      found = true;
 	  } else if (a == 0xFB49) { // SHIN WITH DAGESH
 	      *ab = 0xFB2C;
 	      found = true;
 	  }
 	  break;
       case 0x05C2: // SIN DOT
 	  if (a == 0x05E9) { // SHIN
 	      *ab = 0xFB2B;
 	      found = true;
 	  } else if (a == 0xFB49) { // SHIN WITH DAGESH
 	      *ab = 0xFB2D;
 	      found = true;
 	  }
 	  break;
       }
   }

   return found;
 }


 static inline void
 set_glyph (hb_glyph_info_t &info, hb_font_t *font)
 {
   font->get_glyph (info.codepoint, 0, &info.glyph_index());
 }

 static inline void
 output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph)
 {
   buffer->cur().glyph_index() = glyph;
   buffer->output_glyph (unichar);
   _hb_glyph_info_set_unicode_props (&buffer->prev(), buffer->unicode);
 }

 static inline void
 next_char (hb_buffer_t *buffer, hb_codepoint_t glyph)
 {
   buffer->cur().glyph_index() = glyph;
   buffer->next_glyph ();
 }

 static inline void
 skip_char (hb_buffer_t *buffer)
 {
   buffer->skip_glyph ();
 }

 /* Returns 0 if didn't decompose, number of resulting characters otherwise. */
 static inline unsigned int
 decompose (hb_font_t *font, hb_buffer_t *buffer, bool shortest, hb_codepoint_t ab)
 {
   hb_codepoint_t a, b, a_glyph, b_glyph;

   if (!decompose_func (buffer->unicode, ab, &a, &b) ||
       (b && !font->get_glyph (b, 0, &b_glyph)))
     return 0;

   bool has_a = font->get_glyph (a, 0, &a_glyph);
   if (shortest && has_a) {
     /* Output a and b */
     output_char (buffer, a, a_glyph);
     if (likely (b)) {
       output_char (buffer, b, b_glyph);
       return 2;
     }
     return 1;
   }

   unsigned int ret;
   if ((ret = decompose (font, buffer, shortest, a))) {
     if (b) {
       output_char (buffer, b, b_glyph);
       return ret + 1;
     }
     return ret;
   }

   if (has_a) {
     output_char (buffer, a, a_glyph);
     if (likely (b)) {
       output_char (buffer, b, b_glyph);
       return 2;
     }
     return 1;
   }

   return 0;
 }

 /* Returns 0 if didn't decompose, number of resulting characters otherwise. */
 static inline bool
 decompose_compatibility (hb_font_t *font, hb_buffer_t *buffer, hb_codepoint_t u)
 {
   unsigned int len, i;
   hb_codepoint_t decomposed[HB_UNICODE_MAX_DECOMPOSITION_LEN];
   hb_codepoint_t glyphs[HB_UNICODE_MAX_DECOMPOSITION_LEN];

   len = buffer->unicode->decompose_compatibility (u, decomposed);
   if (!len)
     return 0;

   for (i = 0; i < len; i++)
     if (!font->get_glyph (decomposed[i], 0, &glyphs[i]))
       return 0;

   for (i = 0; i < len; i++)
     output_char (buffer, decomposed[i], glyphs[i]);

   return len;
 }

 /* Returns true if recomposition may be benefitial. */
 static inline bool
 decompose_current_character (hb_font_t *font, hb_buffer_t *buffer, bool shortest)
 {
   hb_codepoint_t glyph;
   unsigned int len = 1;

   /* Kind of a cute waterfall here... */
   if (shortest && font->get_glyph (buffer->cur().codepoint, 0, &glyph))
     next_char (buffer, glyph);
   else if ((len = decompose (font, buffer, shortest, buffer->cur().codepoint)))
     skip_char (buffer);
   else if (!shortest && font->get_glyph (buffer->cur().codepoint, 0, &glyph))
     next_char (buffer, glyph);
   else if ((len = decompose_compatibility (font, buffer, buffer->cur().codepoint)))
     skip_char (buffer);
   else
     next_char (buffer, glyph); /* glyph is initialized in earlier branches. */

   /*
    * A recomposition would only be useful if we decomposed into at least three
    * characters...
    */
   return len > 2;
 }

 static inline void
 handle_variation_selector_cluster (hb_font_t *font, hb_buffer_t *buffer, unsigned int end)
 {
   for (; buffer->idx < end - 1;) {
     if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) {
       /* The next two lines are some ugly lines... But work. */
       font->get_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index());
       buffer->replace_glyphs (2, 1, &buffer->cur().codepoint);
     } else {
       set_glyph (buffer->cur(), font);
       buffer->next_glyph ();
     }
   }
   if (likely (buffer->idx < end)) {
     set_glyph (buffer->cur(), font);
     buffer->next_glyph ();
   }
 }

 /* Returns true if recomposition may be benefitial. */
 static inline bool
 decompose_multi_char_cluster (hb_font_t *font, hb_buffer_t *buffer, unsigned int end)
 {
   /* TODO Currently if there's a variation-selector we give-up, it's just too hard. */
   for (unsigned int i = buffer->idx; i < end; i++)
     if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) {
       handle_variation_selector_cluster (font, buffer, end);
       return false;
     }

   while (buffer->idx < end)
     decompose_current_character (font, buffer, false);
   /* We can be smarter here and only return true if there are at least two ccc!=0 marks.
    * But does not matter. */
   return true;
 }

 static inline bool
 decompose_cluster (hb_font_t *font, hb_buffer_t *buffer, bool recompose, unsigned int end)
 {
   if (likely (buffer->idx + 1 == end))
     return decompose_current_character (font, buffer, recompose);
   else
     return decompose_multi_char_cluster (font, buffer, end);
 }


 static int
 compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
 {
   unsigned int a = _hb_glyph_info_get_modified_combining_class (pa);
   unsigned int b = _hb_glyph_info_get_modified_combining_class (pb);

   return a < b ? -1 : a == b ? 0 : +1;
 }


 void
 _hb_ot_shape_normalize (hb_font_t *font, hb_buffer_t *buffer,
 			hb_ot_shape_normalization_mode_t mode)
 {
   bool recompose = mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED;
   bool can_use_recompose = false;
   unsigned int count;

   /* We do a fairly straightforward yet custom normalization process in three
    * separate rounds: decompose, reorder, recompose (if desired).  Currently
    * this makes two buffer swaps.  We can make it faster by moving the last
    * two rounds into the inner loop for the first round, but it's more readable
    * this way. */


   /* First round, decompose */

   buffer->clear_output ();
   count = buffer->len;
   for (buffer->idx = 0; buffer->idx < count;)
   {
     unsigned int end;
     for (end = buffer->idx + 1; end < count; end++)
       if (buffer->cur().cluster != buffer->info[end].cluster)
         break;

     can_use_recompose = decompose_cluster (font, buffer, recompose, end) || can_use_recompose;
   }
   buffer->swap_buffers ();


   if (mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_FULL && !can_use_recompose)
     return; /* Done! */


   /* Second round, reorder (inplace) */

   count = buffer->len;
   for (unsigned int i = 0; i < count; i++)
   {
     if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0)
       continue;

     unsigned int end;
     for (end = i + 1; end < count; end++)
       if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0)
         break;

     /* We are going to do a bubble-sort.  Only do this if the
      * sequence is short.  Doing it on long sequences can result
      * in an O(n^2) DoS. */
     if (end - i > 10) {
       i = end;
       continue;
     }

     hb_bubble_sort (buffer->info + i, end - i, compare_combining_class);

     i = end;
   }


   if (!recompose)
     return;

   /* Third round, recompose */

   /* As noted in the comment earlier, we don't try to combine
    * ccc=0 chars with their previous Starter. */

   buffer->clear_output ();
   count = buffer->len;
   unsigned int starter = 0;
   buffer->next_glyph ();
   while (buffer->idx < count)
   {
     hb_codepoint_t composed, glyph;
     if (/* If mode is NOT COMPOSED_FULL (ie. it's COMPOSED_DIACRITICS), we don't try to
 	 * compose a CCC=0 character with it's preceding starter. */
 	(mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_FULL ||
 	 _hb_glyph_info_get_modified_combining_class (&buffer->cur()) != 0) &&
 	/* If there's anything between the starter and this char, they should have CCC
 	 * smaller than this character's. */
 	(starter == buffer->out_len - 1 ||
 	 _hb_glyph_info_get_modified_combining_class (&buffer->prev()) < _hb_glyph_info_get_modified_combining_class (&buffer->cur())) &&
 	/* And compose. */
 	compose_func (buffer->unicode,
 		      buffer->out_info[starter].codepoint,
 		      buffer->cur().codepoint,
 		      &composed) &&
 	/* And the font has glyph for the composite. */
 	font->get_glyph (composed, 0, &glyph))
     {
       /* Composes. */
       buffer->next_glyph (); /* Copy to out-buffer. */
       if (unlikely (buffer->in_error))
         return;
       buffer->merge_out_clusters (starter, buffer->out_len);
       buffer->out_len--; /* Remove the second composable. */
       buffer->out_info[starter].codepoint = composed; /* Modify starter and carry on. */
       set_glyph (buffer->out_info[starter], font);
       _hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer->unicode);

       continue;
     }

     /* Blocked, or doesn't compose. */
     buffer->next_glyph ();

     if (_hb_glyph_info_get_modified_combining_class (&buffer->prev()) == 0)
       starter = buffer->out_len - 1;
   }
   buffer->swap_buffers ();

 }
	/*
	* Copyright © 2011,2012 Google, Inc.
	*
	* This is part of HarfBuzz, a text shaping library.
	*
	* Permission is hereby granted, without written agreement and without
	* license or royalty fees, to use, copy, modify, and distribute this
	* software and its documentation for any purpose, provided that the
	* above copyright notice and the following two paragraphs appear in
	* all copies of this software.
	*
	* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
	* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
	* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
	* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
	* DAMAGE.
	*
	* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
	* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
	* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
	* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
	* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
	*
	* Google Author(s): Behdad Esfahbod
	*/

	#include "hb-ot-shape-normalize-private.hh"
	#include "hb-ot-shape-private.hh"


	/*
	* HIGHLEVEL DESIGN:
	*
	* This file exports one main function: _hb_ot_shape_normalize().
	*
	* This function closely reflects the Unicode Normalization Algorithm,
	* yet it's different.
	*
	* Each shaper specifies whether it prefers decomposed (NFD) or composed (NFC).
	* The logic however tries to use whatever the font can support.
	*
	* In general what happens is that: each grapheme is decomposed in a chain
	* of 1:2 decompositions, marks reordered, and then recomposed if desired,
	* so far it's like Unicode Normalization. However, the decomposition and
	* recomposition only happens if the font supports the resulting characters.
	*
	* The goals are:
	*
	* - Try to render all canonically equivalent strings similarly. To really
	* achieve this we have to always do the full decomposition and then
	* selectively recompose from there. It's kinda too expensive though, so
	* we skip some cases. For example, if composed is desired, we simply
	* don't touch 1-character clusters that are supported by the font, even
	* though their NFC may be different.
	*
	* - When a font has a precomposed character for a sequence but the 'ccmp'
	* feature in the font is not adequate, use the precomposed character
	* which typically has better mark positioning.
	*
	* - When a font does not support a combining mark, but supports it precomposed
	* with previous base, use that. This needs the itemizer to have this
	* knowledge too. We need to provide assistance to the itemizer.
	*
	* - When a font does not support a character but supports its decomposition,
	* well, use the decomposition (preferring the canonical decomposition, but
	* falling back to the compatibility decomposition if necessary). The
	* compatibility decomposition is really nice to have, for characters like
	* ellipsis, or various-sized space characters.
	*
	* - The complex shapers can customize the compose and decompose functions to
	* offload some of their requirements to the normalizer. For example, the
	* Indic shaper may want to disallow recomposing of two matras.
	*
	* - We try compatibility decomposition if decomposing through canonical
	* decomposition alone failed to find a sequence that the font supports.
	* We don't try compatibility decomposition recursively during the canonical
	* decomposition phase. This has minimal impact. There are only a handful
	* of Greek letter that have canonical decompositions that include characters
	* with compatibility decomposition. Those can be found using this command:
	*
	* egrep "`echo -n ';('; grep ';<' UnicodeData.txt \| cut -d';' -f1 \| tr '\n' '\|'; echo ') '`" UnicodeData.txt
	*/

	static hb_bool_t
	decompose_func (hb_unicode_funcs_t *unicode,
	hb_codepoint_t ab,
	hb_codepoint_t *a,
	hb_codepoint_t *b)
	{
	/* XXX FIXME, move these to complex shapers and propagage to normalizer.*/
	switch (ab) {
	case 0x0AC9 : return false;

	case 0x0931 : return false;
	case 0x0B94 : return false;

	/* These ones have Unicode decompositions, but we do it
	* this way to be close to what Uniscribe does. */
	case 0x0DDA : a = 0x0DD9; b= 0x0DDA; return true;
	case 0x0DDC : a = 0x0DD9; b= 0x0DDC; return true;
	case 0x0DDD : a = 0x0DD9; b= 0x0DDD; return true;
	case 0x0DDE : a = 0x0DD9; b= 0x0DDE; return true;

	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
	case 0x0B57 : *a = 0xno decomp, -> RIGHT; return true;
	case 0x1C29 : *a = 0xno decomp, -> LEFT; return true;
	case 0xA9C0 : *a = 0xno decomp, -> RIGHT; return true;
	case 0x111BF : *a = 0xno decomp, -> ABOVE; return true;
	#endif
	}
	return unicode->decompose (ab, a, b);
	}

	static hb_bool_t
	compose_func (hb_unicode_funcs_t *unicode,
	hb_codepoint_t a,
	hb_codepoint_t b,
	hb_codepoint_t *ab)
	{
	/* XXX, this belongs to indic normalizer. */
	if ((FLAG (unicode->general_category (a)) &
	(FLAG (HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK) \|
	FLAG (HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) \|
	FLAG (HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK))))
	return false;
	/* XXX, add composition-exclusion exceptions to Indic shaper. */
	if (a == 0x09AF && b == 0x09BC) { *ab = 0x09DF; return true; }

	/* XXX, these belong to the hebew / default shaper. */
	/* Hebrew presentation-form shaping.
	* https://bugzilla.mozilla.org/show_bug.cgi?id=728866 */
	// Hebrew presentation forms with dagesh, for characters 0x05D0..0x05EA;
	// note that some letters do not have a dagesh presForm encoded
	static const hb_codepoint_t sDageshForms[0x05EA - 0x05D0 + 1] = {
	0xFB30, // ALEF
	0xFB31, // BET
	0xFB32, // GIMEL
	0xFB33, // DALET
	0xFB34, // HE
	0xFB35, // VAV
	0xFB36, // ZAYIN
	0, // HET
	0xFB38, // TET
	0xFB39, // YOD
	0xFB3A, // FINAL KAF
	0xFB3B, // KAF
	0xFB3C, // LAMED
	0, // FINAL MEM
	0xFB3E, // MEM
	0, // FINAL NUN
	0xFB40, // NUN
	0xFB41, // SAMEKH
	0, // AYIN
	0xFB43, // FINAL PE
	0xFB44, // PE
	0, // FINAL TSADI
	0xFB46, // TSADI
	0xFB47, // QOF
	0xFB48, // RESH
	0xFB49, // SHIN
	0xFB4A // TAV
	};

	hb_bool_t found = unicode->compose (a, b, ab);

	if (!found && (b & ~0x7F) == 0x0580) {
	// special-case Hebrew presentation forms that are excluded from
	// standard normalization, but wanted for old fonts
	switch (b) {
	case 0x05B4: // HIRIQ
	if (a == 0x05D9) { // YOD
	*ab = 0xFB1D;
	found = true;
	}
	break;
	case 0x05B7: // patah
	if (a == 0x05F2) { // YIDDISH YOD YOD
	*ab = 0xFB1F;
	found = true;
	} else if (a == 0x05D0) { // ALEF
	*ab = 0xFB2E;
	found = true;
	}
	break;
	case 0x05B8: // QAMATS
	if (a == 0x05D0) { // ALEF
	*ab = 0xFB2F;
	found = true;
	}
	break;
	case 0x05B9: // HOLAM
	if (a == 0x05D5) { // VAV
	*ab = 0xFB4B;
	found = true;
	}
	break;
	case 0x05BC: // DAGESH
	if (a >= 0x05D0 && a <= 0x05EA) {
	*ab = sDageshForms[a - 0x05D0];
	found = (*ab != 0);
	} else if (a == 0xFB2A) { // SHIN WITH SHIN DOT
	*ab = 0xFB2C;
	found = true;
	} else if (a == 0xFB2B) { // SHIN WITH SIN DOT
	*ab = 0xFB2D;
	found = true;
	}
	break;
	case 0x05BF: // RAFE
	switch (a) {
	case 0x05D1: // BET
	*ab = 0xFB4C;
	found = true;
	break;
	case 0x05DB: // KAF
	*ab = 0xFB4D;
	found = true;
	break;
	case 0x05E4: // PE
	*ab = 0xFB4E;
	found = true;
	break;
	}
	break;
	case 0x05C1: // SHIN DOT
	if (a == 0x05E9) { // SHIN
	*ab = 0xFB2A;
	found = true;
	} else if (a == 0xFB49) { // SHIN WITH DAGESH
	*ab = 0xFB2C;
	found = true;
	}
	break;
	case 0x05C2: // SIN DOT
	if (a == 0x05E9) { // SHIN
	*ab = 0xFB2B;
	found = true;
	} else if (a == 0xFB49) { // SHIN WITH DAGESH
	*ab = 0xFB2D;
	found = true;
	}
	break;
	}
	}

	return found;
	}


	static inline void
	set_glyph (hb_glyph_info_t &info, hb_font_t *font)
	{
	font->get_glyph (info.codepoint, 0, &info.glyph_index());
	}

	static inline void
	output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph)
	{
	buffer->cur().glyph_index() = glyph;
	buffer->output_glyph (unichar);
	_hb_glyph_info_set_unicode_props (&buffer->prev(), buffer->unicode);
	}

	static inline void
	next_char (hb_buffer_t *buffer, hb_codepoint_t glyph)
	{
	buffer->cur().glyph_index() = glyph;
	buffer->next_glyph ();
	}

	static inline void
	skip_char (hb_buffer_t *buffer)
	{
	buffer->skip_glyph ();
	}

	/* Returns 0 if didn't decompose, number of resulting characters otherwise. */
	static inline unsigned int
	decompose (hb_font_t font, hb_buffer_t buffer, bool shortest, hb_codepoint_t ab)
	{
	hb_codepoint_t a, b, a_glyph, b_glyph;

	if (!decompose_func (buffer->unicode, ab, &a, &b) \|\|
	(b && !font->get_glyph (b, 0, &b_glyph)))
	return 0;

	bool has_a = font->get_glyph (a, 0, &a_glyph);
	if (shortest && has_a) {
	/* Output a and b */
	output_char (buffer, a, a_glyph);
	if (likely (b)) {
	output_char (buffer, b, b_glyph);
	return 2;
	}
	return 1;
	}

	unsigned int ret;
	if ((ret = decompose (font, buffer, shortest, a))) {
	if (b) {
	output_char (buffer, b, b_glyph);
	return ret + 1;
	}
	return ret;
	}

	if (has_a) {
	output_char (buffer, a, a_glyph);
	if (likely (b)) {
	output_char (buffer, b, b_glyph);
	return 2;
	}
	return 1;
	}

	return 0;
	}

	/* Returns 0 if didn't decompose, number of resulting characters otherwise. */
	static inline bool
	decompose_compatibility (hb_font_t font, hb_buffer_t buffer, hb_codepoint_t u)
	{
	unsigned int len, i;
	hb_codepoint_t decomposed[HB_UNICODE_MAX_DECOMPOSITION_LEN];
	hb_codepoint_t glyphs[HB_UNICODE_MAX_DECOMPOSITION_LEN];

	len = buffer->unicode->decompose_compatibility (u, decomposed);
	if (!len)
	return 0;

	for (i = 0; i < len; i++)
	if (!font->get_glyph (decomposed[i], 0, &glyphs[i]))
	return 0;

	for (i = 0; i < len; i++)
	output_char (buffer, decomposed[i], glyphs[i]);

	return len;
	}

	/* Returns true if recomposition may be benefitial. */
	static inline bool
	decompose_current_character (hb_font_t font, hb_buffer_t buffer, bool shortest)
	{
	hb_codepoint_t glyph;
	unsigned int len = 1;

	/* Kind of a cute waterfall here... */
	if (shortest && font->get_glyph (buffer->cur().codepoint, 0, &glyph))
	next_char (buffer, glyph);
	else if ((len = decompose (font, buffer, shortest, buffer->cur().codepoint)))
	skip_char (buffer);
	else if (!shortest && font->get_glyph (buffer->cur().codepoint, 0, &glyph))
	next_char (buffer, glyph);
	else if ((len = decompose_compatibility (font, buffer, buffer->cur().codepoint)))
	skip_char (buffer);
	else
	next_char (buffer, glyph); /* glyph is initialized in earlier branches. */

	/*
	* A recomposition would only be useful if we decomposed into at least three
	* characters...
	*/
	return len > 2;
	}

	static inline void
	handle_variation_selector_cluster (hb_font_t font, hb_buffer_t buffer, unsigned int end)
	{
	for (; buffer->idx < end - 1;) {
	if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) {
	/* The next two lines are some ugly lines... But work. */
	font->get_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index());
	buffer->replace_glyphs (2, 1, &buffer->cur().codepoint);
	} else {
	set_glyph (buffer->cur(), font);
	buffer->next_glyph ();
	}
	}
	if (likely (buffer->idx < end)) {
	set_glyph (buffer->cur(), font);
	buffer->next_glyph ();
	}
	}

	/* Returns true if recomposition may be benefitial. */
	static inline bool
	decompose_multi_char_cluster (hb_font_t font, hb_buffer_t buffer, unsigned int end)
	{
	/* TODO Currently if there's a variation-selector we give-up, it's just too hard. */
	for (unsigned int i = buffer->idx; i < end; i++)
	if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) {
	handle_variation_selector_cluster (font, buffer, end);
	return false;
	}

	while (buffer->idx < end)
	decompose_current_character (font, buffer, false);
	/* We can be smarter here and only return true if there are at least two ccc!=0 marks.
	* But does not matter. */
	return true;
	}

	static inline bool
	decompose_cluster (hb_font_t font, hb_buffer_t buffer, bool recompose, unsigned int end)
	{
	if (likely (buffer->idx + 1 == end))
	return decompose_current_character (font, buffer, recompose);
	else
	return decompose_multi_char_cluster (font, buffer, end);
	}


	static int
	compare_combining_class (const hb_glyph_info_t pa, const hb_glyph_info_t pb)
	{
	unsigned int a = _hb_glyph_info_get_modified_combining_class (pa);
	unsigned int b = _hb_glyph_info_get_modified_combining_class (pb);

	return a < b ? -1 : a == b ? 0 : +1;
	}


	void
	_hb_ot_shape_normalize (hb_font_t font, hb_buffer_t buffer,
	hb_ot_shape_normalization_mode_t mode)
	{
	bool recompose = mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED;
	bool can_use_recompose = false;
	unsigned int count;

	/* We do a fairly straightforward yet custom normalization process in three
	* separate rounds: decompose, reorder, recompose (if desired). Currently
	* this makes two buffer swaps. We can make it faster by moving the last
	* two rounds into the inner loop for the first round, but it's more readable
	* this way. */


	/* First round, decompose */

	buffer->clear_output ();
	count = buffer->len;
	for (buffer->idx = 0; buffer->idx < count;)
	{
	unsigned int end;
	for (end = buffer->idx + 1; end < count; end++)
	if (buffer->cur().cluster != buffer->info[end].cluster)
	break;

	can_use_recompose = decompose_cluster (font, buffer, recompose, end) \|\| can_use_recompose;
	}
	buffer->swap_buffers ();


	if (mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_FULL && !can_use_recompose)
	return; /* Done! */


	/* Second round, reorder (inplace) */

	count = buffer->len;
	for (unsigned int i = 0; i < count; i++)
	{
	if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0)
	continue;

	unsigned int end;
	for (end = i + 1; end < count; end++)
	if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0)
	break;

	/* We are going to do a bubble-sort. Only do this if the
	* sequence is short. Doing it on long sequences can result
	* in an O(n^2) DoS. */
	if (end - i > 10) {
	i = end;
	continue;
	}

	hb_bubble_sort (buffer->info + i, end - i, compare_combining_class);

	i = end;
	}


	if (!recompose)
	return;

	/* Third round, recompose */

	/* As noted in the comment earlier, we don't try to combine
	* ccc=0 chars with their previous Starter. */

	buffer->clear_output ();
	count = buffer->len;
	unsigned int starter = 0;
	buffer->next_glyph ();
	while (buffer->idx < count)
	{
	hb_codepoint_t composed, glyph;
	if (/* If mode is NOT COMPOSED_FULL (ie. it's COMPOSED_DIACRITICS), we don't try to
	* compose a CCC=0 character with it's preceding starter. */
	(mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_FULL \|\|
	_hb_glyph_info_get_modified_combining_class (&buffer->cur()) != 0) &&
	/* If there's anything between the starter and this char, they should have CCC
	* smaller than this character's. */
	(starter == buffer->out_len - 1 \|\|
	_hb_glyph_info_get_modified_combining_class (&buffer->prev()) < _hb_glyph_info_get_modified_combining_class (&buffer->cur())) &&
	/* And compose. */
	compose_func (buffer->unicode,
	buffer->out_info[starter].codepoint,
	buffer->cur().codepoint,
	&composed) &&
	/* And the font has glyph for the composite. */
	font->get_glyph (composed, 0, &glyph))
	{
	/* Composes. */
	buffer->next_glyph (); /* Copy to out-buffer. */
	if (unlikely (buffer->in_error))
	return;
	buffer->merge_out_clusters (starter, buffer->out_len);
	buffer->out_len--; /* Remove the second composable. */
	buffer->out_info[starter].codepoint = composed; /* Modify starter and carry on. */
	set_glyph (buffer->out_info[starter], font);
	_hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer->unicode);

	continue;
	}

	/* Blocked, or doesn't compose. */
	buffer->next_glyph ();

	if (_hb_glyph_info_get_modified_combining_class (&buffer->prev()) == 0)
	starter = buffer->out_len - 1;
	}
	buffer->swap_buffers ();

	}