harfbuzz-ng roll

third_party/harfbuzz-ng/src/hb-ot-shape-normalize.cc

 /*
  * 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.
@@ skipping 44 matching lines @@
  *
  *   - 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.
+ *     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 Indic shaper requests decomposed output.  This will handle splitting
- *     matra for the Indic shaper.
+ *   - 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 void
-output_glyph (hb_buffer_t *buffer, hb_codepoint_t glyph)
-{
-  buffer->output_glyph (glyph);
+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 (HB_UNICODE_GENERAL_CATEGORY_IS_MARK (unicode->general_category (a)))
+    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 bool
-decompose (hb_font_t *font, hb_buffer_t *buffer,
-           bool shortest,
-           hb_codepoint_t ab)
-{
-  hb_codepoint_t a, b, glyph;
-
-  if (!hb_unicode_decompose (buffer->unicode, ab, &a, &b) ||
-      (b && !hb_font_get_glyph (font, b, 0, &glyph)))
-    return false;
-
-  bool has_a = hb_font_get_glyph (font, a, 0, &glyph);
+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_glyph (buffer, a);
-    if (b)
-      output_glyph (buffer, b);
-    return true;
-  }
-
-  if (decompose (font, buffer, shortest, a)) {
-    if (b)
-      output_glyph (buffer, b);
-    return true;
+    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_glyph (buffer, a);
-    if (b)
-      output_glyph (buffer, b);
-    return true;
-  }
-
-  return false;
-}
-
-static void
-decompose_current_glyph (hb_font_t *font, hb_buffer_t *buffer,
-                         bool shortest)
-{
-  if (decompose (font, buffer, shortest, buffer->cur().codepoint))
-    buffer->skip_glyph ();
+    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 ();
-}
-
-static void
-decompose_single_char_cluster (hb_font_t *font, hb_buffer_t *buffer,
-                               bool will_recompose)
-{
-  hb_codepoint_t glyph;
-
-  /* If recomposing and font supports this, we're good to go */
-  if (will_recompose && hb_font_get_glyph (font, buffer->cur().codepoint, 0, &glyph)) {
-    buffer->next_glyph ();
-    return;
-  }
-
-  decompose_current_glyph (font, buffer, will_recompose);
-}
-
-static void
-decompose_multi_char_cluster (hb_font_t *font, hb_buffer_t *buffer,
-                              unsigned int end)
+  }
+}
+
+/* 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 (_hb_unicode_is_variation_selector (buffer->info[i].codepoint))) {
-      while (buffer->idx < end)
-        buffer->next_glyph ();
-      return;
+    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_glyph (font, buffer, false);
-}
+    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 short_circuit, unsigned int end)
+{
+  if (likely (buffer->idx + 1 == end))
+    return decompose_current_character (font, buffer, short_circuit);
+  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 has_multichar_clusters = false;
+  bool short_circuit = mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED &&
+                       mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT;
+  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;
 
-    if (buffer->idx + 1 == end)
-      decompose_single_char_cluster (font, buffer, recompose);
-    else {
-      decompose_multi_char_cluster (font, buffer, end);
-      has_multichar_clusters = true;
-    }
+    can_use_recompose = decompose_cluster (font, buffer, short_circuit, end) || can_use_recompose;
   }
   buffer->swap_buffers ();
 
 
-  if (mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_FULL && !has_multichar_clusters)
+  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;
@@ skipping 10 matching lines @@
       i = end;
       continue;
     }
 
     hb_bubble_sort (buffer->info + i, end - i, compare_combining_class);
 
     i = end;
   }
 
 
-  if (!recompose)
+  if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED)
     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. */
-        hb_unicode_compose (buffer->unicode,
-                            buffer->out_info[starter].codepoint,
-                            buffer->cur().codepoint,
-                            &composed) &&
+        compose_func (buffer->unicode,
+                      buffer->out_info[starter].codepoint,
+                      buffer->cur().codepoint,
+                      &composed) &&
         /* And the font has glyph for the composite. */
-        hb_font_get_glyph (font, composed, 0, &glyph))
+        font->get_glyph (composed, 0, &glyph))
     {
-      /* Composes. Modify starter and carry on. */
-      buffer->out_info[starter].codepoint = composed;
-      /* XXX update cluster */
+      /* 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);
 
-      buffer->skip_glyph ();
       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 ();
 
 }