ahglyph.c

a very goog book

          point->oy = point->y = FT_MulFix( vec->y, y_scale );

          point->flags = 0;
        }
      }

      /* compute Bezier flags */
      {
        char*  tag = source->tags;


        for ( point = points; point < point_limit; point++, tag++ )
        {
          switch ( FT_CURVE_TAG( *tag ) )
          {
          case FT_Curve_Tag_Conic:
            point->flags = ah_flag_conic; break;
          case FT_Curve_Tag_Cubic:
            point->flags = ah_flag_cubic; break;
          default:
            ;
          }
        }
      }

      /* compute `next' and `prev' */
      {
        FT_Int     contour_index;
        AH_Point*  prev;
        AH_Point*  first;
        AH_Point*  end;


        contour_index = 0;

        first = points;
        end   = points + source->contours[0];
        prev  = end;

        for ( point = points; point < point_limit; point++ )
        {
          point->prev = prev;
          if ( point < end )
          {
            point->next = point + 1;
            prev        = point;
          }
          else
          {
            point->next = first;
            contour_index++;
            if ( point + 1 < point_limit )
            {
              end   = points + source->contours[contour_index];
              first = point + 1;
              prev  = end;
            }
          }
        }
      }

      /* set-up the contours array */
      {
        AH_Point**  contour       = outline->contours;
        AH_Point**  contour_limit = contour + outline->num_contours;
        short*      end           = source->contours;
        short       idx           = 0;


        for ( ; contour < contour_limit; contour++, end++ )
        {
          contour[0] = points + idx;
          idx        = (short)( end[0] + 1 );
        }
      }

      /* compute directions of in & out vectors */
      {
        for ( point = points; point < point_limit; point++ )
        {
          AH_Point*  prev;
          AH_Point*  next;
          FT_Vector  ivec, ovec;


          prev   = point->prev;
          ivec.x = point->fx - prev->fx;
          ivec.y = point->fy - prev->fy;

          point->in_dir = ah_compute_direction( ivec.x, ivec.y );

          next   = point->next;
          ovec.x = next->fx - point->fx;
          ovec.y = next->fy - point->fy;

          point->out_dir = ah_compute_direction( ovec.x, ovec.y );

#ifndef AH_OPTION_NO_WEAK_INTERPOLATION
          if ( point->flags & (ah_flag_conic | ah_flag_cubic) )
          {
          Is_Weak_Point:
            point->flags |= ah_flag_weak_interpolation;
          }
          else if ( point->out_dir == point->in_dir )
          {
            AH_Angle  angle_in, angle_out, delta;


            if ( point->out_dir != ah_dir_none )
              goto Is_Weak_Point;

            angle_in  = ah_angle( &ivec );
            angle_out = ah_angle( &ovec );
            delta     = angle_in - angle_out;

            if ( delta > AH_PI )
              delta = AH_2PI - delta;

            if ( delta < 0 )
              delta = -delta;

            if ( delta < 2 )
              goto Is_Weak_Point;
          }
          else if ( point->in_dir == -point->out_dir )
            goto Is_Weak_Point;
#endif
        }
      }
    }

  Exit:
    return error;
  }


  FT_LOCAL_DEF( void )
  ah_setup_uv( AH_Outline*  outline,
               AH_UV        source )
  {
    AH_Point*  point       = outline->points;
    AH_Point*  point_limit = point + outline->num_points;


    for ( ; point < point_limit; point++ )
    {
      FT_Pos  u, v;


      switch ( source )
      {
      case ah_uv_fxy:
        u = point->fx;
        v = point->fy;
        break;
      case ah_uv_fyx:
        u = point->fy;
        v = point->fx;
        break;
      case ah_uv_oxy:
        u = point->ox;
        v = point->oy;
        break;
      case ah_uv_oyx:
        u = point->oy;
        v = point->ox;
        break;
      case ah_uv_yx:
        u = point->y;
        v = point->x;
        break;
      case ah_uv_ox:
        u = point->x;
        v = point->ox;
        break;
      case ah_uv_oy:
        u = point->y;
        v = point->oy;
        break;
      default:
        u = point->x;
        v = point->y;
        break;
      }
      point->u = u;
      point->v = v;
    }
  }


  FT_LOCAL_DEF( void )
  ah_outline_compute_segments( AH_Outline*  outline )
  {
    int           dimension;
    AH_Segment*   segments;
    FT_Int*       p_num_segments;
    AH_Direction  segment_dir;
    AH_Direction  major_dir;


    segments       = outline->horz_segments;
    p_num_segments = &outline->num_hsegments;
    major_dir      = ah_dir_right;      /* This value must be positive! */
    segment_dir    = major_dir;

    /* set up (u,v) in each point */
    ah_setup_uv( outline, ah_uv_fyx );

    for ( dimension = 1; dimension >= 0; dimension-- )
    {
      AH_Point**   contour       =  outline->contours;
      AH_Point**   contour_limit =  contour + outline->num_contours;
      AH_Segment*  segment       =  segments;
      FT_Int       num_segments  =  0;

#ifdef AH_HINT_METRICS
      AH_Point*    min_point     =  0;
      AH_Point*    max_point     =  0;
      FT_Pos       min_coord     =  32000;
      FT_Pos       max_coord     = -32000;
#endif


      /* do each contour separately */
      for ( ; contour < contour_limit; contour++ )
      {
        AH_Point*  point   = contour[0];
        AH_Point*  last    = point->prev;
        int        on_edge = 0;
        FT_Pos     min_pos = +32000;  /* minimum segment pos != min_coord */
        FT_Pos     max_pos = -32000;  /* maximum segment pos != max_coord */
        FT_Bool    passed;


#ifdef AH_HINT_METRICS
        if ( point->u < min_coord )
        {
          min_coord = point->u;
          min_point = point;
        }
        if ( point->u > max_coord )
        {
          max_coord = point->u;
          max_point = point;
        }
#endif

        if ( point == last )  /* skip singletons -- just in case? */
          continue;

        if ( ABS( last->out_dir )  == major_dir &&
             ABS( point->out_dir ) == major_dir )
        {
          /* we are already on an edge, try to locate its start */
          last = point;

          for (;;)
          {
            point = point->prev;
            if ( ABS( point->out_dir ) != major_dir )
            {
              point = point->next;
              break;
            }
            if ( point == last )
              break;
          }
        }

        last   = point;
        passed = 0;

        for (;;)
        {
          FT_Pos  u, v;


          if ( on_edge )
          {
            u = point->u;
            if ( u < min_pos )
              min_pos = u;
            if ( u > max_pos )
              max_pos = u;

            if ( point->out_dir != segment_dir || point == last )
            {
              /* we are just leaving an edge; record a new segment! */
              segment->last = point;
              segment->pos  = ( min_pos + max_pos ) >> 1;

              /* a segment is round if either its first or last point */
              /* is a control point                                   */
              if ( ( segment->first->flags | point->flags ) &
                     ah_flag_control                        )
                segment->flags |= ah_edge_round;

              /* compute segment size */
              min_pos = max_pos = point->v;

              v = segment->first->v;
              if ( v < min_pos )
                min_pos = v;
              if ( v > max_pos )
                max_pos = v;

              segment->min_coord = min_pos;
              segment->max_coord = max_pos;

              on_edge = 0;
              num_segments++;
              segment++;
              /* fallthrough */
            }
          }

          /* now exit if we are at the start/end point */
          if ( point == last )
          {
            if ( passed )
              break;
            passed = 1;
          }

          if ( !on_edge && ABS( point->out_dir ) == major_dir )
          {
            /* this is the start of a new segment! */
            segment_dir = point->out_dir;

            /* clear all segment fields */
            FT_MEM_SET( segment, 0, sizeof ( *segment ) );

            segment->dir      = segment_dir;
            segment->flags    = ah_edge_normal;
            min_pos = max_pos = point->u;
            segment->first    = point;
            segment->last     = point;
            segment->contour  = contour;
            on_edge           = 1;

#ifdef AH_HINT_METRICS
            if ( point == max_point )
              max_point = 0;

            if ( point == min_point )
              min_point = 0;
#endif
          }

          point = point->next;
        }

      } /* contours */

#ifdef AH_HINT_METRICS
      /* we need to ensure that there are edges on the left-most and  */
      /* right-most points of the glyph in order to hint the metrics; */
      /* we do this by inserting fake segments when needed            */
      if ( dimension == 0 )
      {
        AH_Point*  point       =  outline->points;
        AH_Point*  point_limit =  point + outline->num_points;

        FT_Pos     min_pos     =  32000;
        FT_Pos     max_pos     = -32000;


        min_point = 0;
        max_point = 0;

        /* compute minimum and maximum points */
        for ( ; point < point_limit; point++ )
        {
          FT_Pos  x = point->fx;


          if ( x < min_pos )
          {
            min_pos   = x;
            min_point = point;
          }
          if ( x > max_pos )
          {
            max_pos   = x;
            max_point = point;
          }
        }

        /* insert minimum segment */
        if ( min_point )
        {
          /* clear all segment fields */
          FT_MEM_SET( segment, 0, sizeof ( *segment ) );

          segment->dir   = segment_dir;
          segment->flags = ah_edge_normal;
          segment->first = min_point;
          segment->last  = min_point;
          segment->pos   = min_pos;

          num_segments++;
          segment++;
        }

        /* insert maximum segment */
        if ( max_point )
        {
          /* clear all segment fields */
          FT_MEM_SET( segment, 0, sizeof ( *segment ) );

          segment->dir   = segment_dir;
          segment->flags = ah_edge_normal;
          segment->first = max_point;
          segment->last  = max_point;
          segment->pos   = max_pos;

          num_segments++;
          segment++;
        }
      }
#endif /* AH_HINT_METRICS */

      *p_num_segments = num_segments;

      segments       = outline->vert_segments;
      major_dir      = ah_dir_up;
      p_num_segments = &outline->num_vsegments;
      ah_setup_uv( outline, ah_uv_fxy );
    }
  }


  FT_LOCAL_DEF( void )
  ah_outline_link_segments( AH_Outline*  outline )
  {
    AH_Segment*  segments;
    AH_Segment*  segment_limit;
    int          dimension;


    ah_setup_uv( outline, ah_uv_fyx );

    segments      = outline->horz_segments;
    segment_limit = segments + outline->num_hsegments;

    for ( dimension = 1; dimension >= 0; dimension-- )
    {
      AH_Segment*  seg1;
      AH_Segment*  seg2;

      /* now compare each segment to the others */
      for ( seg1 = segments; seg1 < segment_limit; seg1++ )
      {
        FT_Pos       best_score;
        AH_Segment*  best_segment;

        /* the fake segments are introduced to hint the metrics -- */
        /* we must never link them to anything                     */
        if ( seg1->first == seg1->last )
          continue;

        best_segment = seg1->link;
        if ( best_segment )
          best_score = seg1->score;
        else
          best_score = 32000;

        for ( seg2 = segments; seg2 < segment_limit; seg2++ )
          if ( seg1 != seg2 && seg1->dir + seg2->dir == 0 )
          {
            FT_Pos   pos1 = seg1->pos;
            FT_Pos   pos2 = seg2->pos;
            FT_Bool  is_dir;
            FT_Bool  is_pos;


            /* check that the segments are correctly oriented and */
            /* positioned to form a black distance                */

            is_dir = (FT_Bool)( seg1->dir == outline->horz_major_dir ||
                                seg1->dir == outline->vert_major_dir );
            is_pos = (FT_Bool)( pos1 > pos2 );

            if ( pos1 == pos2 || !(is_dir ^ is_pos) )
              continue;

            {