text: /*
   * 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-fallback.hh"
  #include "hb-kern.hh"
  
  static unsigned int
  recategorize_combining_class (hb_codepoint_t u,
                                unsigned int klass)
  {
    if (klass >= 200)
      return klass;
  
    /* Thai / Lao need some per-character work. */
    if ((u & ~0xFF) == 0x0E00u)
    {
      if (unlikely (klass == 0))
      {
        switch (u)
        {
          case 0x0E31u:
          case 0x0E34u:
          case 0x0E35u:
          case 0x0E36u:
          case 0x0E37u:
          case 0x0E47u:
          case 0x0E4Cu:
          case 0x0E4Du:
          case 0x0E4Eu:
            klass = HB_UNICODE_COMBINING_CLASS_ABOVE_RIGHT;
            break;
  
          case 0x0EB1u:
          case 0x0EB4u:
          case 0x0EB5u:
          case 0x0EB6u:
          case 0x0EB7u:
          case 0x0EBBu:
          case 0x0ECCu:
          case 0x0ECDu:
            klass = HB_UNICODE_COMBINING_CLASS_ABOVE;
            break;
  
          case 0x0EBCu:
            klass = HB_UNICODE_COMBINING_CLASS_BELOW;
            break;
        }
      } else {
        /* Thai virama is below-right */
        if (u == 0x0E3Au)
          klass = HB_UNICODE_COMBINING_CLASS_BELOW_RIGHT;
      }
    }
  
    switch (klass)
    {
  
      /* Hebrew */
  
      case HB_MODIFIED_COMBINING_CLASS_CCC10: /* sheva */
      case HB_MODIFIED_COMBINING_CLASS_CCC11: /* hataf segol */
      case HB_MODIFIED_COMBINING_CLASS_CCC12: /* hataf patah */
      case HB_MODIFIED_COMBINING_CLASS_CCC13: /* hataf qamats */
      case HB_MODIFIED_COMBINING_CLASS_CCC14: /* hiriq */
      case HB_MODIFIED_COMBINING_CLASS_CCC15: /* tsere */
      case HB_MODIFIED_COMBINING_CLASS_CCC16: /* segol */
      case HB_MODIFIED_COMBINING_CLASS_CCC17: /* patah */
      case HB_MODIFIED_COMBINING_CLASS_CCC18: /* qamats */
      case HB_MODIFIED_COMBINING_CLASS_CCC20: /* qubuts */
      case HB_MODIFIED_COMBINING_CLASS_CCC22: /* meteg */
        return HB_UNICODE_COMBINING_CLASS_BELOW;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC23: /* rafe */
        return HB_UNICODE_COMBINING_CLASS_ATTACHED_ABOVE;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC24: /* shin dot */
        return HB_UNICODE_COMBINING_CLASS_ABOVE_RIGHT;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC25: /* sin dot */
      case HB_MODIFIED_COMBINING_CLASS_CCC19: /* holam */
        return HB_UNICODE_COMBINING_CLASS_ABOVE_LEFT;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC26: /* point varika */
        return HB_UNICODE_COMBINING_CLASS_ABOVE;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC21: /* dagesh */
        break;
  
  
      /* Arabic and Syriac */
  
      case HB_MODIFIED_COMBINING_CLASS_CCC27: /* fathatan */
      case HB_MODIFIED_COMBINING_CLASS_CCC28: /* dammatan */
      case HB_MODIFIED_COMBINING_CLASS_CCC30: /* fatha */
      case HB_MODIFIED_COMBINING_CLASS_CCC31: /* damma */
      case HB_MODIFIED_COMBINING_CLASS_CCC33: /* shadda */
      case HB_MODIFIED_COMBINING_CLASS_CCC34: /* sukun */
      case HB_MODIFIED_COMBINING_CLASS_CCC35: /* superscript alef */
      case HB_MODIFIED_COMBINING_CLASS_CCC36: /* superscript alaph */
        return HB_UNICODE_COMBINING_CLASS_ABOVE;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC29: /* kasratan */
      case HB_MODIFIED_COMBINING_CLASS_CCC32: /* kasra */
        return HB_UNICODE_COMBINING_CLASS_BELOW;
  
  
      /* Thai */
  
      case HB_MODIFIED_COMBINING_CLASS_CCC103: /* sara u / sara uu */
        return HB_UNICODE_COMBINING_CLASS_BELOW_RIGHT;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC107: /* mai */
        return HB_UNICODE_COMBINING_CLASS_ABOVE_RIGHT;
  
  
      /* Lao */
  
      case HB_MODIFIED_COMBINING_CLASS_CCC118: /* sign u / sign uu */
        return HB_UNICODE_COMBINING_CLASS_BELOW;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC122: /* mai */
        return HB_UNICODE_COMBINING_CLASS_ABOVE;
  
  
      /* Tibetan */
  
      case HB_MODIFIED_COMBINING_CLASS_CCC129: /* sign aa */
        return HB_UNICODE_COMBINING_CLASS_BELOW;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC130: /* sign i*/
        return HB_UNICODE_COMBINING_CLASS_ABOVE;
  
      case HB_MODIFIED_COMBINING_CLASS_CCC132: /* sign u */
        return HB_UNICODE_COMBINING_CLASS_BELOW;
  
    }
  
    return klass;
  }
  
  void
  _hb_ot_shape_fallback_mark_position_recategorize_marks (const hb_ot_shape_plan_t *plan HB_UNUSED,
                                                          hb_font_t *font HB_UNUSED,
                                                          hb_buffer_t  *buffer)
  {
    unsigned int count = buffer->len;
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = 0; i < count; i++)
      if (_hb_glyph_info_get_general_category (&info[i]) == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) {
        unsigned int combining_class = _hb_glyph_info_get_modified_combining_class (&info[i]);
        combining_class = recategorize_combining_class (info[i].codepoint, combining_class);
        _hb_glyph_info_set_modified_combining_class (&info[i], combining_class);
      }
  }
  
  
  static void
  zero_mark_advances (hb_buffer_t *buffer,
                      unsigned int start,
                      unsigned int end,
                      bool adjust_offsets_when_zeroing)
  {
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = start; i < end; i++)
      if (_hb_glyph_info_get_general_category (&info[i]) == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)
      {
        if (adjust_offsets_when_zeroing)
        {
          buffer->pos[i].x_offset -= buffer->pos[i].x_advance;
          buffer->pos[i].y_offset -= buffer->pos[i].y_advance;
        }
        buffer->pos[i].x_advance = 0;
        buffer->pos[i].y_advance = 0;
      }
  }
  
  static inline void
  position_mark (const hb_ot_shape_plan_t *plan HB_UNUSED,
                 hb_font_t *font,
                 hb_buffer_t  *buffer,
                 hb_glyph_extents_t &base_extents,
                 unsigned int i,
                 unsigned int combining_class)
  {
    hb_glyph_extents_t mark_extents;
    if (!font->get_glyph_extents (buffer->info[i].codepoint, &mark_extents))
      return;
  
    hb_position_t y_gap = font->y_scale / 16;
  
    hb_glyph_position_t &pos = buffer->pos[i];
    pos.x_offset = pos.y_offset = 0;
  
  
    /* We don't position LEFT and RIGHT marks. */
  
    /* X positioning */
    switch (combining_class)
    {
      case HB_UNICODE_COMBINING_CLASS_DOUBLE_BELOW:
      case HB_UNICODE_COMBINING_CLASS_DOUBLE_ABOVE:
        if (buffer->props.direction == HB_DIRECTION_LTR) {
          pos.x_offset += base_extents.x_bearing + base_extents.width - mark_extents.width / 2 - mark_extents.x_bearing;
          break;
        } else if (buffer->props.direction == HB_DIRECTION_RTL) {
          pos.x_offset += base_extents.x_bearing - mark_extents.width / 2 - mark_extents.x_bearing;
          break;
        }
        HB_FALLTHROUGH;
  
      default:
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_BELOW:
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_ABOVE:
      case HB_UNICODE_COMBINING_CLASS_BELOW:
      case HB_UNICODE_COMBINING_CLASS_ABOVE:
        /* Center align. */
        pos.x_offset += base_extents.x_bearing + (base_extents.width - mark_extents.width) / 2 - mark_extents.x_bearing;
        break;
  
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_BELOW_LEFT:
      case HB_UNICODE_COMBINING_CLASS_BELOW_LEFT:
      case HB_UNICODE_COMBINING_CLASS_ABOVE_LEFT:
        /* Left align. */
        pos.x_offset += base_extents.x_bearing - mark_extents.x_bearing;
        break;
  
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_ABOVE_RIGHT:
      case HB_UNICODE_COMBINING_CLASS_BELOW_RIGHT:
      case HB_UNICODE_COMBINING_CLASS_ABOVE_RIGHT:
        /* Right align. */
        pos.x_offset += base_extents.x_bearing + base_extents.width - mark_extents.width - mark_extents.x_bearing;
        break;
    }
  
    /* Y positioning */
    switch (combining_class)
    {
      case HB_UNICODE_COMBINING_CLASS_DOUBLE_BELOW:
      case HB_UNICODE_COMBINING_CLASS_BELOW_LEFT:
      case HB_UNICODE_COMBINING_CLASS_BELOW:
      case HB_UNICODE_COMBINING_CLASS_BELOW_RIGHT:
        /* Add gap, fall-through. */
        base_extents.height -= y_gap;
        HB_FALLTHROUGH;
  
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_BELOW_LEFT:
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_BELOW:
        pos.y_offset = base_extents.y_bearing + base_extents.height - mark_extents.y_bearing;
        /* Never shift up "below" marks. */
        if ((y_gap > 0) == (pos.y_offset > 0))
        {
          base_extents.height -= pos.y_offset;
          pos.y_offset = 0;
        }
        base_extents.height += mark_extents.height;
        break;
  
      case HB_UNICODE_COMBINING_CLASS_DOUBLE_ABOVE:
      case HB_UNICODE_COMBINING_CLASS_ABOVE_LEFT:
      case HB_UNICODE_COMBINING_CLASS_ABOVE:
      case HB_UNICODE_COMBINING_CLASS_ABOVE_RIGHT:
        /* Add gap, fall-through. */
        base_extents.y_bearing += y_gap;
        base_extents.height -= y_gap;
        HB_FALLTHROUGH;
  
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_ABOVE:
      case HB_UNICODE_COMBINING_CLASS_ATTACHED_ABOVE_RIGHT:
        pos.y_offset = base_extents.y_bearing - (mark_extents.y_bearing + mark_extents.height);
        /* Don't shift down "above" marks too much. */
        if ((y_gap > 0) != (pos.y_offset > 0))
        {
          unsigned int correction = -pos.y_offset / 2;
          base_extents.y_bearing += correction;
          base_extents.height -= correction;
          pos.y_offset += correction;
        }
        base_extents.y_bearing -= mark_extents.height;
        base_extents.height += mark_extents.height;
        break;
    }
  }
  
  static inline void
  position_around_base (const hb_ot_shape_plan_t *plan,
                        hb_font_t *font,
                        hb_buffer_t  *buffer,
                        unsigned int base,
                        unsigned int end,
                        bool adjust_offsets_when_zeroing)
  {
    hb_direction_t horiz_dir = HB_DIRECTION_INVALID;
  
    buffer->unsafe_to_break (base, end);
  
    hb_glyph_extents_t base_extents;
    if (!font->get_glyph_extents (buffer->info[base].codepoint,
                                  &base_extents))
    {
      /* If extents don't work, zero marks and go home. */
      zero_mark_advances (buffer, base + 1, end, adjust_offsets_when_zeroing);
      return;
    }
    base_extents.y_bearing += buffer->pos[base].y_offset;
    /* Use horizontal advance for horizontal positioning.
     * Generally a better idea.  Also works for zero-ink glyphs.  See:
     * https://github.com/harfbuzz/harfbuzz/issues/1532 */
    base_extents.x_bearing = 0;
    base_extents.width = font->get_glyph_h_advance (buffer->info[base].codepoint);
  
    unsigned int lig_id = _hb_glyph_info_get_lig_id (&buffer->info[base]);
    /* Use integer for num_lig_components such that it doesn't convert to unsigned
     * when we divide or multiply by it. */
    int num_lig_components = _hb_glyph_info_get_lig_num_comps (&buffer->info[base]);
  
    hb_position_t x_offset = 0, y_offset = 0;
    if (HB_DIRECTION_IS_FORWARD (buffer->props.direction)) {
      x_offset -= buffer->pos[base].x_advance;
      y_offset -= buffer->pos[base].y_advance;
    }
  
    hb_glyph_extents_t component_extents = base_extents;
    int last_lig_component = -1;
    unsigned int last_combining_class = 255;
    hb_glyph_extents_t cluster_extents = base_extents; /* Initialization is just to shut gcc up. */
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = base + 1; i < end; i++)
      if (_hb_glyph_info_get_modified_combining_class (&info[i]))
      {
        if (num_lig_components > 1) {
          unsigned int this_lig_id = _hb_glyph_info_get_lig_id (&info[i]);
          int this_lig_component = _hb_glyph_info_get_lig_comp (&info[i]) - 1;
          /* Conditions for attaching to the last component. */
          if (!lig_id || lig_id != this_lig_id || this_lig_component >= num_lig_components)
            this_lig_component = num_lig_components - 1;
          if (last_lig_component != this_lig_component)
          {
            last_lig_component = this_lig_component;
            last_combining_class = 255;
            component_extents = base_extents;
            if (unlikely (horiz_dir == HB_DIRECTION_INVALID)) {
              if (HB_DIRECTION_IS_HORIZONTAL (plan->props.direction))
                horiz_dir = plan->props.direction;
              else
                horiz_dir = hb_script_get_horizontal_direction (plan->props.script);
            }
            if (horiz_dir == HB_DIRECTION_LTR)
              component_extents.x_bearing += (this_lig_component * component_extents.width) / num_lig_components;
            else
              component_extents.x_bearing += ((num_lig_components - 1 - this_lig_component) * component_extents.width) / num_lig_components;
            component_extents.width /= num_lig_components;
          }
        }
  
        unsigned int this_combining_class = _hb_glyph_info_get_modified_combining_class (&info[i]);
        if (last_combining_class != this_combining_class)
        {
          last_combining_class = this_combining_class;
          cluster_extents = component_extents;
        }
  
        position_mark (plan, font, buffer, cluster_extents, i, this_combining_class);
  
        buffer->pos[i].x_advance = 0;
        buffer->pos[i].y_advance = 0;
        buffer->pos[i].x_offset += x_offset;
        buffer->pos[i].y_offset += y_offset;
  
      } else {
        if (HB_DIRECTION_IS_FORWARD (buffer->props.direction)) {
          x_offset -= buffer->pos[i].x_advance;
          y_offset -= buffer->pos[i].y_advance;
        } else {
          x_offset += buffer->pos[i].x_advance;
          y_offset += buffer->pos[i].y_advance;
        }
      }
  }
  
  static inline void
  position_cluster (const hb_ot_shape_plan_t *plan,
                    hb_font_t *font,
                    hb_buffer_t  *buffer,
                    unsigned int start,
                    unsigned int end,
                    bool adjust_offsets_when_zeroing)
  {
    if (end - start < 2)
      return;
  
    /* Find the base glyph */
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = start; i < end; i++)
      if (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&info[i])))
      {
        /* Find mark glyphs */
        unsigned int j;
        for (j = i + 1; j < end; j++)
          if (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&info[j])))
            break;
  
        position_around_base (plan, font, buffer, i, j, adjust_offsets_when_zeroing);
  
        i = j - 1;
      }
  }
  
  void
  _hb_ot_shape_fallback_mark_position (const hb_ot_shape_plan_t *plan,
                                       hb_font_t *font,
                                       hb_buffer_t  *buffer,
                                       bool adjust_offsets_when_zeroing)
  {
    _hb_buffer_assert_gsubgpos_vars (buffer);
  
    unsigned int start = 0;
    unsigned int count = buffer->len;
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = 1; i < count; i++)
      if (likely (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&info[i])))) {
        position_cluster (plan, font, buffer, start, i, adjust_offsets_when_zeroing);
        start = i;
      }
    position_cluster (plan, font, buffer, start, count, adjust_offsets_when_zeroing);
  }
  
  
  struct hb_ot_shape_fallback_kern_driver_t
  {
    hb_ot_shape_fallback_kern_driver_t (hb_font_t   *font_,
                                        hb_buffer_t *buffer) :
      font (font_), direction (buffer->props.direction) {}
  
    hb_position_t get_kerning (hb_codepoint_t first, hb_codepoint_t second) const
    {
      hb_position_t kern = 0;
      font->get_glyph_kerning_for_direction (first, second,
                                             direction,
                                             &kern, &kern);
      return kern;
    }
  
    hb_font_t *font;
    hb_direction_t direction;
  };
  
  /* Performs font-assisted kerning. */
  void
  _hb_ot_shape_fallback_kern (const hb_ot_shape_plan_t *plan,
                              hb_font_t *font,
                              hb_buffer_t *buffer)
  {
    if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction) ?
        !font->has_glyph_h_kerning_func () :
        !font->has_glyph_v_kerning_func ())
      return;
  
    bool reverse = HB_DIRECTION_IS_BACKWARD (buffer->props.direction);
  
    if (reverse)
      buffer->reverse ();
  
    hb_ot_shape_fallback_kern_driver_t driver (font, buffer);
    OT::hb_kern_machine_t<hb_ot_shape_fallback_kern_driver_t> machine (driver);
    machine.kern (font, buffer, plan->kern_mask, false);
  
    if (reverse)
      buffer->reverse ();
  }
  
  
  /* Adjusts width of various spaces. */
  void
  _hb_ot_shape_fallback_spaces (const hb_ot_shape_plan_t *plan HB_UNUSED,
                                hb_font_t *font,
                                hb_buffer_t  *buffer)
  {
    hb_glyph_info_t *info = buffer->info;
    hb_glyph_position_t *pos = buffer->pos;
    bool horizontal = HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction);
    unsigned int count = buffer->len;
    for (unsigned int i = 0; i < count; i++)
      if (_hb_glyph_info_is_unicode_space (&info[i]) && !_hb_glyph_info_ligated (&info[i]))
      {
        hb_unicode_funcs_t::space_t space_type = _hb_glyph_info_get_unicode_space_fallback_type (&info[i]);
        hb_codepoint_t glyph;
        typedef hb_unicode_funcs_t t;
        switch (space_type)
        {
          case t::NOT_SPACE: /* Shouldn't happen. */
          case t::SPACE:
            break;
  
          case t::SPACE_EM:
          case t::SPACE_EM_2:
          case t::SPACE_EM_3:
          case t::SPACE_EM_4:
          case t::SPACE_EM_5:
          case t::SPACE_EM_6:
          case t::SPACE_EM_16:
            if (horizontal)
              pos[i].x_advance = +(font->x_scale + ((int) space_type)/2) / (int) space_type;
            else
              pos[i].y_advance = -(font->y_scale + ((int) space_type)/2) / (int) space_type;
            break;
  
          case t::SPACE_4_EM_18:
            if (horizontal)
              pos[i].x_advance = (int64_t) +font->x_scale * 4 / 18;
            else
              pos[i].y_advance = (int64_t) -font->y_scale * 4 / 18;
            break;
  
          case t::SPACE_FIGURE:
            for (char u = '0'; u <= '9'; u++)
              if (font->get_nominal_glyph (u, &glyph))
              {
                if (horizontal)
                  pos[i].x_advance = font->get_glyph_h_advance (glyph);
                else
                  pos[i].y_advance = font->get_glyph_v_advance (glyph);
                break;
              }
            break;
  
          case t::SPACE_PUNCTUATION:
            if (font->get_nominal_glyph ('.', &glyph) ||
                font->get_nominal_glyph (',', &glyph))
            {
              if (horizontal)
                pos[i].x_advance = font->get_glyph_h_advance (glyph);
              else
                pos[i].y_advance = font->get_glyph_v_advance (glyph);
            }
            break;
  
          case t::SPACE_NARROW:
            /* Half-space?
             * Unicode doc https://unicode.org/charts/PDF/U2000.pdf says ~1/4 or 1/5 of EM.
             * However, in my testing, many fonts have their regular space being about that
             * size.  To me, a percentage of the space width makes more sense.  Half is as
             * good as any. */
            if (horizontal)
              pos[i].x_advance /= 2;
            else
              pos[i].y_advance /= 2;
            break;
        }
      }
  }
  