kc3-lang/harfbuzz/src/hb-coretext-shape.cc

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• Hash : 38db0f4c
  Author :
  Date : 2025-03-17T08:51:39
  

  [coretext] Always set all variation axes
  

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• src/hb-coretext-shape.cc

• /*
   * Copyright © 2012,2013  Mozilla Foundation.
   * Copyright © 2012,2013  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.
   *
   * Mozilla Author(s): Jonathan Kew
   * Google Author(s): Behdad Esfahbod
   */
  
  #include "hb.hh"
  
  #ifdef HAVE_CORETEXT
  
  #include "hb-shaper-impl.hh"
  
  #include "hb-coretext.hh"
  #include "hb-aat-layout.hh"
  
  hb_coretext_face_data_t *
  _hb_coretext_shaper_face_data_create (hb_face_t *face)
  {
    CGFontRef cg_font = create_cg_font (face);
  
    if (unlikely (!cg_font))
    {
      DEBUG_MSG (CORETEXT, face, "CGFont creation failed..");
      return nullptr;
    }
  
    return (hb_coretext_face_data_t *) cg_font;
  }
  
  void
  _hb_coretext_shaper_face_data_destroy (hb_coretext_face_data_t *data)
  {
    CFRelease ((CGFontRef) data);
  }
  
  
  hb_coretext_font_data_t *
  _hb_coretext_shaper_font_data_create (hb_font_t *font)
  {
    hb_face_t *face = font->face;
    const hb_coretext_face_data_t *face_data = face->data.coretext;
    if (unlikely (!face_data)) return nullptr;
    CGFontRef cg_font = (CGFontRef) (const void *) face->data.coretext;
  
    CGFloat font_size = (CGFloat) (font->ptem > 0.f ? font->ptem : HB_CORETEXT_DEFAULT_FONT_SIZE);
    CTFontRef ct_font = create_ct_font (cg_font, font_size);
  
    if (unlikely (!ct_font))
    {
      DEBUG_MSG (CORETEXT, font, "CGFont creation failed..");
      return nullptr;
    }
  
    {
      CFMutableDictionaryRef variations =
        CFDictionaryCreateMutable (kCFAllocatorDefault,
  				 font->num_coords,
  				 &kCFTypeDictionaryKeyCallBacks,
  				 &kCFTypeDictionaryValueCallBacks);
  
      unsigned num_axes = hb_ot_var_get_axis_count (face);
      unsigned count = hb_max (num_axes, font->num_coords);
      for (unsigned i = 0; i < count; i++)
      {
        hb_ot_var_axis_info_t info;
        unsigned int c = 1;
        hb_ot_var_get_axis_infos (font->face, i, &c, &info);
        float v = i < font->num_coords ?
  		hb_clamp (font->design_coords[i], info.min_value, info.max_value) :
  		info.default_value;
  
        CFNumberRef tag_number = CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &info.tag);
        CFNumberRef value_number = CFNumberCreate (kCFAllocatorDefault, kCFNumberFloatType, &v);
        CFDictionarySetValue (variations, tag_number, value_number);
        CFRelease (tag_number);
        CFRelease (value_number);
      }
  
      CFDictionaryRef attributes =
        CFDictionaryCreate (kCFAllocatorDefault,
  			  (const void **) &kCTFontVariationAttribute,
  			  (const void **) &variations,
  			  1,
  			  &kCFTypeDictionaryKeyCallBacks,
  			  &kCFTypeDictionaryValueCallBacks);
  
      CTFontDescriptorRef varDesc = CTFontDescriptorCreateWithAttributes (attributes);
      CTFontRef new_ct_font = CTFontCreateCopyWithAttributes (ct_font, 0, nullptr, varDesc);
  
      CFRelease (ct_font);
      CFRelease (attributes);
      CFRelease (variations);
      ct_font = new_ct_font;
    }
  
    return (hb_coretext_font_data_t *) ct_font;
  }
  
  void
  _hb_coretext_shaper_font_data_destroy (hb_coretext_font_data_t *data)
  {
    CFRelease ((CTFontRef) data);
  }
  
  /*
   * shaper
   */
  
  struct feature_record_t {
    unsigned int feature;
    unsigned int setting;
  };
  
  struct active_feature_t {
    feature_record_t rec;
    unsigned int order;
  
    HB_INTERNAL static int cmp (const void *pa, const void *pb) {
      const active_feature_t *a = (const active_feature_t *) pa;
      const active_feature_t *b = (const active_feature_t *) pb;
      return a->rec.feature < b->rec.feature ? -1 : a->rec.feature > b->rec.feature ? 1 :
  	   a->order < b->order ? -1 : a->order > b->order ? 1 :
  	   a->rec.setting < b->rec.setting ? -1 : a->rec.setting > b->rec.setting ? 1 :
  	   0;
    }
    bool operator== (const active_feature_t& f) const {
      return cmp (this, &f) == 0;
    }
  };
  
  struct feature_event_t {
    unsigned int index;
    bool start;
    active_feature_t feature;
  
    HB_INTERNAL static int cmp (const void *pa, const void *pb) {
      const feature_event_t *a = (const feature_event_t *) pa;
      const feature_event_t *b = (const feature_event_t *) pb;
      return a->index < b->index ? -1 : a->index > b->index ? 1 :
  	   a->start < b->start ? -1 : a->start > b->start ? 1 :
  	   active_feature_t::cmp (&a->feature, &b->feature);
    }
  };
  
  struct range_record_t {
    CTFontRef font;
    unsigned int index_first; /* == start */
    unsigned int index_last;  /* == end - 1 */
  };
  
  
  hb_bool_t
  _hb_coretext_shape (hb_shape_plan_t    *shape_plan,
  		    hb_font_t          *font,
  		    hb_buffer_t        *buffer,
  		    const hb_feature_t *features,
  		    unsigned int        num_features)
  {
    hb_face_t *face = font->face;
    CGFontRef cg_font = (CGFontRef) (const void *) face->data.coretext;
    CTFontRef ct_font = (CTFontRef) (const void *) font->data.coretext;
  
    CGFloat ct_font_size = CTFontGetSize (ct_font);
    CGFloat x_mult = (CGFloat) font->x_scale / ct_font_size;
    CGFloat y_mult = (CGFloat) font->y_scale / ct_font_size;
  
    /* Attach marks to their bases, to match the 'ot' shaper.
     * Adapted from a very old version of hb-ot-shape:hb_form_clusters().
     * Note that this only makes us be closer to the 'ot' shaper,
     * but by no means the same.  For example, if there's
     * B1 M1 B2 M2, and B1-B2 form a ligature, M2's cluster will
     * continue pointing to B2 even though B2 was merged into B1's
     * cluster... */
    if (HB_BUFFER_CLUSTER_LEVEL_IS_GRAPHEMES (buffer->cluster_level))
    {
      hb_unicode_funcs_t *unicode = buffer->unicode;
      unsigned int count = buffer->len;
      hb_glyph_info_t *info = buffer->info;
      for (unsigned int i = 1; i < count; i++)
        if (HB_UNICODE_GENERAL_CATEGORY_IS_MARK (unicode->general_category (info[i].codepoint)))
  	buffer->merge_clusters (i - 1, i + 1);
    }
  
    hb_vector_t<range_record_t> range_records;
  
    /*
     * Set up features.
     * (copied + modified from code from hb-uniscribe.cc)
     */
    if (num_features)
    {
      /* Sort features by start/end events. */
      hb_vector_t<feature_event_t> feature_events;
      for (unsigned int i = 0; i < num_features; i++)
      {
        active_feature_t feature;
  
  #if MAC_OS_X_VERSION_MIN_REQUIRED < 101000
        const hb_aat_feature_mapping_t * mapping = hb_aat_layout_find_feature_mapping (features[i].tag);
        if (!mapping)
  	continue;
  
        feature.rec.feature = mapping->aatFeatureType;
        feature.rec.setting = features[i].value ? mapping->selectorToEnable : mapping->selectorToDisable;
  #else
        feature.rec.feature = features[i].tag;
        feature.rec.setting = features[i].value;
  #endif
        feature.order = i;
  
        feature_event_t *event;
  
        event = feature_events.push ();
        event->index = features[i].start;
        event->start = true;
        event->feature = feature;
  
        event = feature_events.push ();
        event->index = features[i].end;
        event->start = false;
        event->feature = feature;
      }
      feature_events.qsort ();
      /* Add a strategic final event. */
      {
        active_feature_t feature;
        feature.rec.feature = HB_TAG_NONE;
        feature.rec.setting = 0;
        feature.order = num_features + 1;
  
        feature_event_t *event = feature_events.push ();
        event->index = 0; /* This value does magic. */
        event->start = false;
        event->feature = feature;
      }
  
      /* Scan events and save features for each range. */
      hb_vector_t<active_feature_t> active_features;
      unsigned int last_index = 0;
      for (unsigned int i = 0; i < feature_events.length; i++)
      {
        feature_event_t *event = &feature_events[i];
  
        if (event->index != last_index)
        {
  	/* Save a snapshot of active features and the range. */
  	range_record_t *range = range_records.push ();
  
  	if (active_features.length)
  	{
  	  CFMutableArrayRef features_array = CFArrayCreateMutable(kCFAllocatorDefault, 0, &kCFTypeArrayCallBacks);
  
  	  /* TODO sort and resolve conflicting features? */
  	  /* active_features.qsort (); */
  	  for (unsigned int j = 0; j < active_features.length; j++)
  	  {
  #if MAC_OS_X_VERSION_MIN_REQUIRED < 101000
  	    CFStringRef keys[] = {
  	      kCTFontFeatureTypeIdentifierKey,
  	      kCTFontFeatureSelectorIdentifierKey
  	    };
  	    CFNumberRef values[] = {
  	      CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &active_features[j].rec.feature),
  	      CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &active_features[j].rec.setting)
  	    };
  #else
  	    char tag[5] = {HB_UNTAG (active_features[j].rec.feature)};
  	    CFTypeRef keys[] = {
  	      kCTFontOpenTypeFeatureTag,
  	      kCTFontOpenTypeFeatureValue
  	    };
  	    CFTypeRef values[] = {
  	      CFStringCreateWithCString (kCFAllocatorDefault, tag, kCFStringEncodingASCII),
  	      CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &active_features[j].rec.setting)
  	    };
  #endif
  	    static_assert ((ARRAY_LENGTH_CONST (keys) == ARRAY_LENGTH_CONST (values)), "");
  	    CFDictionaryRef dict = CFDictionaryCreate (kCFAllocatorDefault,
  						       (const void **) keys,
  						       (const void **) values,
  						       ARRAY_LENGTH (keys),
  						       &kCFTypeDictionaryKeyCallBacks,
  						       &kCFTypeDictionaryValueCallBacks);
  	    for (unsigned int i = 0; i < ARRAY_LENGTH (values); i++)
  	      CFRelease (values[i]);
  
  	    CFArrayAppendValue (features_array, dict);
  	    CFRelease (dict);
  
  	  }
  
  	  CFDictionaryRef attributes = CFDictionaryCreate (kCFAllocatorDefault,
  							   (const void **) &kCTFontFeatureSettingsAttribute,
  							   (const void **) &features_array,
  							   1,
  							   &kCFTypeDictionaryKeyCallBacks,
  							   &kCFTypeDictionaryValueCallBacks);
  	  CFRelease (features_array);
  
  	  CTFontDescriptorRef font_desc = CTFontDescriptorCreateWithAttributes (attributes);
  	  CFRelease (attributes);
  
  	  range->font = CTFontCreateCopyWithAttributes (ct_font, 0.0, nullptr, font_desc);
  	  CFRelease (font_desc);
  	}
  	else
  	{
  	  range->font = nullptr;
  	}
  
  	range->index_first = last_index;
  	range->index_last  = event->index - 1;
  
  	last_index = event->index;
        }
  
        if (event->start)
        {
  	active_features.push (event->feature);
        } else {
  	active_feature_t *feature = active_features.lsearch (event->feature);
  	if (feature)
  	  active_features.remove_ordered (feature - active_features.arrayZ);
        }
      }
    }
  
    unsigned int scratch_size;
    hb_buffer_t::scratch_buffer_t *scratch = buffer->get_scratch_buffer (&scratch_size);
  
  #define ALLOCATE_ARRAY(Type, name, len, on_no_room) \
    Type *name = (Type *) scratch; \
    do { \
      unsigned int _consumed = DIV_CEIL ((len) * sizeof (Type), sizeof (*scratch)); \
      if (unlikely (_consumed > scratch_size)) \
      { \
        on_no_room; \
        assert (0); \
      } \
      scratch += _consumed; \
      scratch_size -= _consumed; \
    } while (0)
  
    ALLOCATE_ARRAY (UniChar, pchars, buffer->len * 2, ((void)nullptr) /*nothing*/);
    unsigned int chars_len = 0;
    for (unsigned int i = 0; i < buffer->len; i++) {
      hb_codepoint_t c = buffer->info[i].codepoint;
      if (likely (c <= 0xFFFFu))
        pchars[chars_len++] = c;
      else if (unlikely (c > 0x10FFFFu))
        pchars[chars_len++] = 0xFFFDu;
      else {
        pchars[chars_len++] = 0xD800u + ((c - 0x10000u) >> 10);
        pchars[chars_len++] = 0xDC00u + ((c - 0x10000u) & ((1u << 10) - 1));
      }
    }
  
    ALLOCATE_ARRAY (unsigned int, log_clusters, chars_len, ((void)nullptr) /*nothing*/);
    chars_len = 0;
    for (unsigned int i = 0; i < buffer->len; i++)
    {
      hb_codepoint_t c = buffer->info[i].codepoint;
      unsigned int cluster = buffer->info[i].cluster;
      log_clusters[chars_len++] = cluster;
      if (hb_in_range (c, 0x10000u, 0x10FFFFu))
        log_clusters[chars_len++] = cluster; /* Surrogates. */
    }
  
  #define FAIL(...) \
    HB_STMT_START { \
      DEBUG_MSG (CORETEXT, nullptr, __VA_ARGS__); \
      ret = false; \
      goto fail; \
    } HB_STMT_END
  
    bool ret = true;
    CFStringRef string_ref = nullptr;
    CTLineRef line = nullptr;
  
    if (false)
    {
  resize_and_retry:
      DEBUG_MSG (CORETEXT, buffer, "Buffer resize");
      /* string_ref uses the scratch-buffer for backing store, and line references
       * string_ref (via attr_string).  We must release those before resizing buffer. */
      assert (string_ref);
      assert (line);
      CFRelease (string_ref);
      CFRelease (line);
      string_ref = nullptr;
      line = nullptr;
  
      /* Get previous start-of-scratch-area, that we use later for readjusting
       * our existing scratch arrays. */
      unsigned int old_scratch_used;
      hb_buffer_t::scratch_buffer_t *old_scratch;
      old_scratch = buffer->get_scratch_buffer (&old_scratch_used);
      old_scratch_used = scratch - old_scratch;
  
      if (unlikely (!buffer->ensure (buffer->allocated * 2)))
        FAIL ("Buffer resize failed");
  
      /* Adjust scratch, pchars, and log_cluster arrays.  This is ugly, but really the
       * cleanest way to do without completely restructuring the rest of this shaper. */
      scratch = buffer->get_scratch_buffer (&scratch_size);
      pchars = reinterpret_cast<UniChar *> (((char *) scratch + ((char *) pchars - (char *) old_scratch)));
      log_clusters = reinterpret_cast<unsigned int *> (((char *) scratch + ((char *) log_clusters - (char *) old_scratch)));
      scratch += old_scratch_used;
      scratch_size -= old_scratch_used;
    }
    {
      string_ref = CFStringCreateWithCharactersNoCopy (nullptr,
  						     pchars, chars_len,
  						     kCFAllocatorNull);
      if (unlikely (!string_ref))
        FAIL ("CFStringCreateWithCharactersNoCopy failed");
  
      /* Create an attributed string, populate it, and create a line from it, then release attributed string. */
      {
        CFMutableAttributedStringRef attr_string = CFAttributedStringCreateMutable (kCFAllocatorDefault,
  										  chars_len);
        if (unlikely (!attr_string))
  	FAIL ("CFAttributedStringCreateMutable failed");
        CFAttributedStringReplaceString (attr_string, CFRangeMake (0, 0), string_ref);
        if (HB_DIRECTION_IS_VERTICAL (buffer->props.direction))
        {
  	CFAttributedStringSetAttribute (attr_string, CFRangeMake (0, chars_len),
  					kCTVerticalFormsAttributeName, kCFBooleanTrue);
        }
  
        if (buffer->props.language)
        {
  /* What's the iOS equivalent of this check?
   * The symbols was introduced in iOS 7.0.
   * At any rate, our fallback is safe and works fine. */
  #if !(defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE) && MAC_OS_X_VERSION_MIN_REQUIRED < 1090
  #  define kCTLanguageAttributeName CFSTR ("NSLanguage")
  #endif
  	CFStringRef lang = CFStringCreateWithCStringNoCopy (kCFAllocatorDefault,
  							    hb_language_to_string (buffer->props.language),
  							    kCFStringEncodingUTF8,
  							    kCFAllocatorNull);
  	if (unlikely (!lang))
  	{
  	  CFRelease (attr_string);
  	  FAIL ("CFStringCreateWithCStringNoCopy failed");
  	}
  	CFAttributedStringSetAttribute (attr_string, CFRangeMake (0, chars_len),
  					kCTLanguageAttributeName, lang);
  	CFRelease (lang);
        }
        CFAttributedStringSetAttribute (attr_string, CFRangeMake (0, chars_len),
  				      kCTFontAttributeName, ct_font);
  
        if (num_features && range_records.length)
        {
  	unsigned int start = 0;
  	range_record_t *last_range = &range_records[0];
  	for (unsigned int k = 0; k < chars_len; k++)
  	{
  	  range_record_t *range = last_range;
  	  while (log_clusters[k] < range->index_first)
  	    range--;
  	  while (log_clusters[k] > range->index_last)
  	    range++;
  	  if (range != last_range)
  	  {
  	    if (last_range->font)
  	      CFAttributedStringSetAttribute (attr_string, CFRangeMake (start, k - start),
  					      kCTFontAttributeName, last_range->font);
  
  	    start = k;
  	  }
  
  	  last_range = range;
  	}
  	if (start != chars_len && last_range->font)
  	  CFAttributedStringSetAttribute (attr_string, CFRangeMake (start, chars_len - start),
  					  kCTFontAttributeName, last_range->font);
        }
        /* Enable/disable kern if requested.
         *
         * Note: once kern is disabled, reenabling it doesn't currently seem to work in CoreText.
         */
        if (num_features)
        {
  	unsigned int zeroint = 0;
  	CFNumberRef zero = CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &zeroint);
  	for (unsigned int i = 0; i < num_features; i++)
  	{
  	  const hb_feature_t &feature = features[i];
  	  if (feature.tag == HB_TAG('k','e','r','n') &&
  	      feature.start < chars_len && feature.start < feature.end)
  	  {
  	    CFRange feature_range = CFRangeMake (feature.start,
  						 hb_min (feature.end, chars_len) - feature.start);
  	    if (feature.value)
  	      CFAttributedStringRemoveAttribute (attr_string, feature_range, kCTKernAttributeName);
  	    else
  	      CFAttributedStringSetAttribute (attr_string, feature_range, kCTKernAttributeName, zero);
  	  }
  	}
  	CFRelease (zero);
        }
  
        int level = HB_DIRECTION_IS_FORWARD (buffer->props.direction) ? 0 : 1;
        CFNumberRef level_number = CFNumberCreate (kCFAllocatorDefault, kCFNumberIntType, &level);
  #if !(defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE) && MAC_OS_X_VERSION_MIN_REQUIRED < 1060
        extern const CFStringRef kCTTypesetterOptionForcedEmbeddingLevel;
  #endif
        CFDictionaryRef options = CFDictionaryCreate (kCFAllocatorDefault,
  						    (const void **) &kCTTypesetterOptionForcedEmbeddingLevel,
  						    (const void **) &level_number,
  						    1,
  						    &kCFTypeDictionaryKeyCallBacks,
  						    &kCFTypeDictionaryValueCallBacks);
        CFRelease (level_number);
        if (unlikely (!options))
        {
  	CFRelease (attr_string);
  	FAIL ("CFDictionaryCreate failed");
        }
  
        CTTypesetterRef typesetter = CTTypesetterCreateWithAttributedStringAndOptions (attr_string, options);
        CFRelease (options);
        CFRelease (attr_string);
        if (unlikely (!typesetter))
  	FAIL ("CTTypesetterCreateWithAttributedStringAndOptions failed");
  
        line = CTTypesetterCreateLine (typesetter, CFRangeMake(0, 0));
        CFRelease (typesetter);
        if (unlikely (!line))
  	FAIL ("CTTypesetterCreateLine failed");
      }
  
      CFArrayRef glyph_runs = CTLineGetGlyphRuns (line);
      unsigned int num_runs = CFArrayGetCount (glyph_runs);
      DEBUG_MSG (CORETEXT, nullptr, "Num runs: %d", num_runs);
  
      buffer->len = 0;
      uint32_t status_or = 0;
      CGFloat advances_so_far = 0;
      /* For right-to-left runs, CoreText returns the glyphs positioned such that
       * any trailing whitespace is to the left of (0,0).  Adjust coordinate system
       * to fix for that.  Test with any RTL string with trailing spaces.
       * https://crbug.com/469028
       */
      if (HB_DIRECTION_IS_BACKWARD (buffer->props.direction))
      {
        advances_so_far -= CTLineGetTrailingWhitespaceWidth (line);
        if (HB_DIRECTION_IS_VERTICAL (buffer->props.direction))
  	  advances_so_far = -advances_so_far;
      }
  
      const CFRange range_all = CFRangeMake (0, 0);
  
      for (unsigned int i = 0; i < num_runs; i++)
      {
        CTRunRef run = static_cast<CTRunRef>(CFArrayGetValueAtIndex (glyph_runs, i));
        CTRunStatus run_status = CTRunGetStatus (run);
        status_or  |= run_status;
        DEBUG_MSG (CORETEXT, run, "CTRunStatus: %x", run_status);
        CGFloat run_advance = CTRunGetTypographicBounds (run, range_all, nullptr, nullptr, nullptr);
        if (HB_DIRECTION_IS_VERTICAL (buffer->props.direction))
  	  run_advance = -run_advance;
        DEBUG_MSG (CORETEXT, run, "Run advance: %g", (double) run_advance);
  
        /* CoreText does automatic font fallback (AKA "cascading") for  characters
         * not supported by the requested font, and provides no way to turn it off,
         * so we must detect if the returned run uses a font other than the requested
         * one and fill in the buffer with .notdef glyphs instead of random glyph
         * indices from a different font.
         */
        CFDictionaryRef attributes = CTRunGetAttributes (run);
        CTFontRef run_ct_font = static_cast<CTFontRef>(CFDictionaryGetValue (attributes, kCTFontAttributeName));
        if (!CFEqual (run_ct_font, ct_font))
        {
  	/* The run doesn't use our main font instance.  We have to figure out
  	 * whether font fallback happened, or this is just CoreText giving us
  	 * another CTFont using the same underlying CGFont.  CoreText seems
  	 * to do that in a variety of situations, one of which being vertical
  	 * text, but also perhaps for caching reasons.
  	 *
  	 * First, see if it uses any of our subfonts created to set font features...
  	 *
  	 * Next, compare the CGFont to the one we used to create our fonts.
  	 * Even this doesn't work all the time.
  	 *
  	 * Finally, we compare PS names, which I don't think are unique...
  	 *
  	 * Looks like if we really want to be sure here we have to modify the
  	 * font to change the name table, similar to what we do in the uniscribe
  	 * backend.
  	 *
  	 * However, even that wouldn't work if we were passed in the CGFont to
  	 * construct a hb_face to begin with.
  	 *
  	 * See: https://github.com/harfbuzz/harfbuzz/pull/36
  	 *
  	 * Also see: https://bugs.chromium.org/p/chromium/issues/detail?id=597098
  	 */
  	bool matched = false;
  	for (unsigned int i = 0; i < range_records.length; i++)
  	  if (range_records[i].font && CFEqual (run_ct_font, range_records[i].font))
  	  {
  	    matched = true;
  	    break;
  	  }
  	if (!matched)
  	{
  	  CGFontRef run_cg_font = CTFontCopyGraphicsFont (run_ct_font, nullptr);
  	  if (run_cg_font)
  	  {
  	    matched = CFEqual (run_cg_font, cg_font);
  	    CFRelease (run_cg_font);
  	  }
  	}
  	if (!matched)
  	{
  	  CFStringRef font_ps_name = CTFontCopyName (ct_font, kCTFontPostScriptNameKey);
  	  CFStringRef run_ps_name = CTFontCopyName (run_ct_font, kCTFontPostScriptNameKey);
  	  CFComparisonResult result = CFStringCompare (run_ps_name, font_ps_name, 0);
  	  CFRelease (run_ps_name);
  	  CFRelease (font_ps_name);
  	  if (result == kCFCompareEqualTo)
  	    matched = true;
  	}
  	if (!matched)
  	{
  	  CFRange range = CTRunGetStringRange (run);
  	  DEBUG_MSG (CORETEXT, run, "Run used fallback font: %ld..%ld",
  		     range.location, range.location + range.length);
  	  if (!buffer->ensure_inplace (buffer->len + range.length))
  	    goto resize_and_retry;
  	  hb_glyph_info_t *info = buffer->info + buffer->len;
  
  	  hb_codepoint_t notdef = 0;
  	  hb_direction_t dir = buffer->props.direction;
  	  hb_position_t x_advance, y_advance, x_offset, y_offset;
  	  hb_font_get_glyph_advance_for_direction (font, notdef, dir, &x_advance, &y_advance);
  	  hb_font_get_glyph_origin_for_direction (font, notdef, dir, &x_offset, &y_offset);
  	  hb_position_t advance = x_advance + y_advance;
  	  x_offset = -x_offset;
  	  y_offset = -y_offset;
  
  	  unsigned int old_len = buffer->len;
  	  for (CFIndex j = range.location; j < range.location + range.length; j++)
  	  {
  	      UniChar ch = CFStringGetCharacterAtIndex (string_ref, j);
  	      if (hb_in_range<UniChar> (ch, 0xDC00u, 0xDFFFu) && range.location < j)
  	      {
  		ch = CFStringGetCharacterAtIndex (string_ref, j - 1);
  		if (hb_in_range<UniChar> (ch, 0xD800u, 0xDBFFu))
  		  /* This is the second of a surrogate pair.  Don't need .notdef
  		   * for this one. */
  		  continue;
  	      }
  	      if (buffer->unicode->is_default_ignorable (ch))
  		continue;
  
  	      info->codepoint = notdef;
  	      info->cluster = log_clusters[j];
  
  	      info->mask = advance;
  	      info->var1.i32 = x_offset;
  	      info->var2.i32 = y_offset;
  
  	      info++;
  	      buffer->len++;
  	  }
  	  if (HB_DIRECTION_IS_BACKWARD (buffer->props.direction))
  	    buffer->reverse_range (old_len, buffer->len);
  	  advances_so_far += run_advance;
  	  continue;
  	}
        }
  
        unsigned int num_glyphs = CTRunGetGlyphCount (run);
        if (num_glyphs == 0)
  	continue;
  
        if (!buffer->ensure_inplace (buffer->len + num_glyphs))
  	goto resize_and_retry;
  
        hb_glyph_info_t *run_info = buffer->info + buffer->len;
  
        /* Testing used to indicate that CTRunGetGlyphsPtr, etc (almost?) always
         * succeed, and so copying data to our own buffer will be rare.  Reports
         * have it that this changed in OS X 10.10 Yosemite, and nullptr is returned
         * frequently.  At any rate, we can test that codepath by setting USE_PTR
         * to false. */
  
  #define USE_PTR true
  
  #define SCRATCH_SAVE() \
    unsigned int scratch_size_saved = scratch_size; \
    hb_buffer_t::scratch_buffer_t *scratch_saved = scratch
  
  #define SCRATCH_RESTORE() \
    scratch_size = scratch_size_saved; \
    scratch = scratch_saved
  
        { /* Setup glyphs */
  	SCRATCH_SAVE();
  	const CGGlyph* glyphs = USE_PTR ? CTRunGetGlyphsPtr (run) : nullptr;
  	if (!glyphs) {
  	  ALLOCATE_ARRAY (CGGlyph, glyph_buf, num_glyphs, goto resize_and_retry);
  	  CTRunGetGlyphs (run, range_all, glyph_buf);
  	  glyphs = glyph_buf;
  	}
  	const CFIndex* string_indices = USE_PTR ? CTRunGetStringIndicesPtr (run) : nullptr;
  	if (!string_indices) {
  	  ALLOCATE_ARRAY (CFIndex, index_buf, num_glyphs, goto resize_and_retry);
  	  CTRunGetStringIndices (run, range_all, index_buf);
  	  string_indices = index_buf;
  	}
  	hb_glyph_info_t *info = run_info;
  	for (unsigned int j = 0; j < num_glyphs; j++)
  	{
  	  info->codepoint = glyphs[j];
  	  info->cluster = log_clusters[string_indices[j]];
  	  info++;
  	}
  	SCRATCH_RESTORE();
        }
        {
  	/* Setup positions.
  	 * Note that CoreText does not return advances for glyphs.  As such,
  	 * for all but last glyph, we use the delta position to next glyph as
  	 * advance (in the advance direction only), and for last glyph we set
  	 * whatever is needed to make the whole run's advance add up. */
  	SCRATCH_SAVE();
  	const CGPoint* positions = USE_PTR ? CTRunGetPositionsPtr (run) : nullptr;
  	if (!positions) {
  	  ALLOCATE_ARRAY (CGPoint, position_buf, num_glyphs, goto resize_and_retry);
  	  CTRunGetPositions (run, range_all, position_buf);
  	  positions = position_buf;
  	}
  	hb_glyph_info_t *info = run_info;
  	if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
  	{
  	  hb_position_t x_offset = round ((positions[0].x - advances_so_far) * x_mult);
  	  for (unsigned int j = 0; j < num_glyphs; j++)
  	  {
  	    CGFloat advance;
  	    if (likely (j + 1 < num_glyphs))
  	      advance = positions[j + 1].x - positions[j].x;
  	    else /* last glyph */
  	      advance = run_advance - (positions[j].x - positions[0].x);
  	    /* int cast necessary to pass through negative values. */
  	    info->mask = (int) round (advance * x_mult);
  	    info->var1.i32 = x_offset;
  	    info->var2.i32 = round (positions[j].y * y_mult);
  	    info++;
  	  }
  	}
  	else
  	{
  	  hb_position_t y_offset = round ((positions[0].y - advances_so_far) * y_mult);
  	  for (unsigned int j = 0; j < num_glyphs; j++)
  	  {
  	    CGFloat advance;
  	    if (likely (j + 1 < num_glyphs))
  	      advance = positions[j + 1].y - positions[j].y;
  	    else /* last glyph */
  	      advance = run_advance - (positions[j].y - positions[0].y);
  	    /* int cast necessary to pass through negative values. */
  	    info->mask = (int) round (advance * y_mult);
  	    info->var1.i32 = round (positions[j].x * x_mult);
  	    info->var2.i32 = y_offset;
  	    info++;
  	  }
  	}
  	SCRATCH_RESTORE();
  	advances_so_far += run_advance;
        }
  #undef SCRATCH_RESTORE
  #undef SCRATCH_SAVE
  #undef USE_PTR
  #undef ALLOCATE_ARRAY
  
        buffer->len += num_glyphs;
      }
  
      buffer->clear_positions ();
  
      unsigned int count = buffer->len;
      hb_glyph_info_t *info = buffer->info;
      hb_glyph_position_t *pos = buffer->pos;
      if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
        for (unsigned int i = 0; i < count; i++)
        {
  	pos->x_advance = info->mask;
  	pos->x_offset = info->var1.i32;
  	pos->y_offset = info->var2.i32;
  
  	info++; pos++;
        }
      else
        for (unsigned int i = 0; i < count; i++)
        {
  	pos->y_advance = info->mask;
  	pos->x_offset = info->var1.i32;
  	pos->y_offset = info->var2.i32;
  
  	info++; pos++;
        }
  
      /* Fix up clusters so that we never return out-of-order indices;
       * if core text has reordered glyphs, we'll merge them to the
       * beginning of the reordered cluster.  CoreText is nice enough
       * to tell us whenever it has produced nonmonotonic results...
       * Note that we assume the input clusters were nonmonotonic to
       * begin with.
       *
       * This does *not* mean we'll form the same clusters as Uniscribe
       * or the native OT backend, only that the cluster indices will be
       * monotonic in the output buffer. */
      if (count > 1 && (status_or & kCTRunStatusNonMonotonic) &&
  	HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE (buffer->cluster_level))
      {
        hb_glyph_info_t *info = buffer->info;
        if (HB_DIRECTION_IS_FORWARD (buffer->props.direction))
        {
  	unsigned int cluster = info[count - 1].cluster;
  	for (unsigned int i = count - 1; i > 0; i--)
  	{
  	  cluster = hb_min (cluster, info[i - 1].cluster);
  	  info[i - 1].cluster = cluster;
  	}
        }
        else
        {
  	unsigned int cluster = info[0].cluster;
  	for (unsigned int i = 1; i < count; i++)
  	{
  	  cluster = hb_min (cluster, info[i].cluster);
  	  info[i].cluster = cluster;
  	}
        }
      }
    }
  
    /* TODO: Sometimes the above positioning code generates negative
     * advance values. Fix them up. Example, with NotoNastaliqUrdu
     * font and sequence ابهد. */
  
    buffer->clear_glyph_flags ();
    buffer->unsafe_to_break ();
  
  #undef FAIL
  
  fail:
    if (string_ref)
      CFRelease (string_ref);
    if (line)
      CFRelease (line);
  
    for (unsigned int i = 0; i < range_records.length; i++)
      if (range_records[i].font)
        CFRelease (range_records[i].font);
  
    return ret;
  }
  
  
  #endif
  

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