ftstroke.c

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      else /* this is a bevel (intersection) */
      {
        FT_Fixed   length;
        FT_Vector  delta;


        length = FT_DivFix( stroker->radius, thcos );

        FT_Vector_From_Polar( &delta, length, phi );
        delta.x += stroker->center.x;
        delta.y += stroker->center.y;

        error = ft_stroke_border_lineto( border, &delta, 0 );
        if (error) goto Exit;

        /* now add end point */
        FT_Vector_From_Polar( &delta, stroker->radius,
                              stroker->angle_out + rotate );
        delta.x += stroker->center.x;
        delta.y += stroker->center.y;

        error = ft_stroke_border_lineto( border, &delta, 1 );
      }
    }

  Exit:
    return error;
  }


  static FT_Error
  ft_stroker_process_corner( FT_Stroker  stroker )
  {
    FT_Error  error = 0;
    FT_Angle  turn;
    FT_Int    inside_side;


    turn = FT_Angle_Diff( stroker->angle_in, stroker->angle_out );

    /* no specific corner processing is required if the turn is 0 */
    if ( turn == 0 )
      goto Exit;

    /* when we turn to the right, the inside side is 0 */
    inside_side = 0;

    /* otherwise, the inside side is 1 */
    if ( turn < 0 )
      inside_side = 1;

    /* process the inside side */
    error = ft_stroker_inside( stroker, inside_side );
    if ( error )
      goto Exit;

    /* process the outside side */
    error = ft_stroker_outside( stroker, 1 - inside_side );

  Exit:
    return error;
  }


  /* add two points to the left and right borders corresponding to the */
  /* start of the subpath..                                            */
  static FT_Error
  ft_stroker_subpath_start( FT_Stroker  stroker,
                            FT_Angle    start_angle )
  {
    FT_Vector        delta;
    FT_Vector        point;
    FT_Error         error;
    FT_StrokeBorder  border;


    FT_Vector_From_Polar( &delta, stroker->radius,
                          start_angle + FT_ANGLE_PI2 );

    point.x = stroker->center.x + delta.x;
    point.y = stroker->center.y + delta.y;

    border = stroker->borders;
    error = ft_stroke_border_moveto( border, &point );
    if ( error )
      goto Exit;

    point.x = stroker->center.x - delta.x;
    point.y = stroker->center.y - delta.y;

    border++;
    error = ft_stroke_border_moveto( border, &point );

    /* save angle for last cap */
    stroker->subpath_angle = start_angle;
    stroker->first_point   = 0;

  Exit:
    return error;
  }


  /* documentation is in ftstroke.h */

  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_LineTo( FT_Stroker  stroker,
                     FT_Vector*  to )
  {
    FT_Error         error = 0;
    FT_StrokeBorder  border;
    FT_Vector        delta;
    FT_Angle         angle;
    FT_Int           side;

    delta.x = to->x - stroker->center.x;
    delta.y = to->y - stroker->center.y;

    angle = FT_Atan2( delta.x, delta.y );
    FT_Vector_From_Polar( &delta, stroker->radius, angle + FT_ANGLE_PI2 );

    /* process corner if necessary */
    if ( stroker->first_point )
    {
      /* This is the first segment of a subpath.  We need to     */
      /* add a point to each border at their respective starting */
      /* point locations.                                        */
      error = ft_stroker_subpath_start( stroker, angle );
      if ( error )
        goto Exit;
    }
    else
    {
      /* process the current corner */
      stroker->angle_out = angle;
      error = ft_stroker_process_corner( stroker );
      if ( error )
        goto Exit;
    }

    /* now add a line segment to both the "inside" and "outside" paths */

    for ( border = stroker->borders, side = 1; side >= 0; side--, border++ )
    {
      FT_Vector  point;


      point.x = to->x + delta.x;
      point.y = to->y + delta.y;

      error = ft_stroke_border_lineto( border, &point, 1 );
      if ( error )
        goto Exit;

      delta.x = -delta.x;
      delta.y = -delta.y;
    }

    stroker->angle_in = angle;
    stroker->center   = *to;

  Exit:
    return error;
  }


  /* documentation is in ftstroke.h */

  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_ConicTo( FT_Stroker  stroker,
                      FT_Vector*  control,
                      FT_Vector*  to )
  {
    FT_Error    error = 0;
    FT_Vector   bez_stack[34];
    FT_Vector*  arc;
    FT_Vector*  limit = bez_stack + 30;
    FT_Angle    start_angle;
    FT_Bool     first_arc = 1;


    arc    = bez_stack;
    arc[0] = *to;
    arc[1] = *control;
    arc[2] = stroker->center;

    while ( arc >= bez_stack )
    {
      FT_Angle  angle_in, angle_out;


      angle_in = angle_out = 0;  /* remove compiler warnings */

      if ( arc < limit                                             &&
           !ft_conic_is_small_enough( arc, &angle_in, &angle_out ) )
      {
        ft_conic_split( arc );
        arc += 2;
        continue;
      }

      if ( first_arc )
      {
        first_arc = 0;

        start_angle = angle_in;

        /* process corner if necessary */
        if ( stroker->first_point )
          error = ft_stroker_subpath_start( stroker, start_angle );
        else
        {
          stroker->angle_out = start_angle;
          error = ft_stroker_process_corner( stroker );
        }
      }

      /* the arc's angle is small enough; we can add it directly to each */
      /* border                                                          */
      {
        FT_Vector  ctrl, end;
        FT_Angle   theta, phi, rotate;
        FT_Fixed   length;
        FT_Int     side;


        theta  = FT_Angle_Diff( angle_in, angle_out ) / 2;
        phi    = angle_in + theta;
        length = FT_DivFix( stroker->radius, FT_Cos( theta ) );

        for ( side = 0; side <= 1; side++ )
        {
          rotate = FT_SIDE_TO_ROTATE( side );

          /* compute control point */
          FT_Vector_From_Polar( &ctrl, length, phi + rotate );
          ctrl.x += arc[1].x;
          ctrl.y += arc[1].y;

          /* compute end point */
          FT_Vector_From_Polar( &end, stroker->radius, angle_out + rotate );
          end.x += arc[0].x;
          end.y += arc[0].y;

          error = ft_stroke_border_conicto( stroker->borders + side,
                                            &ctrl, &end );
          if ( error )
            goto Exit;
        }
      }

      arc -= 2;

      if ( arc < bez_stack )
        stroker->angle_in = angle_out;
    }

    stroker->center = *to;

  Exit:
    return error;
  }


  /* documentation is in ftstroke.h */

  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_CubicTo( FT_Stroker  stroker,
                      FT_Vector*  control1,
                      FT_Vector*  control2,
                      FT_Vector*  to )
  {
    FT_Error    error = 0;
    FT_Vector   bez_stack[37];
    FT_Vector*  arc;
    FT_Vector*  limit = bez_stack + 32;
    FT_Angle    start_angle;
    FT_Bool     first_arc = 1;


    arc    = bez_stack;
    arc[0] = *to;
    arc[1] = *control2;
    arc[2] = *control1;
    arc[3] = stroker->center;

    while ( arc >= bez_stack )
    {
      FT_Angle  angle_in, angle_mid, angle_out;


      /* remove compiler warnings */
      angle_in = angle_out = angle_mid = 0;

      if ( arc < limit                                         &&
           !ft_cubic_is_small_enough( arc, &angle_in,
                                      &angle_mid, &angle_out ) )
      {
        ft_cubic_split( arc );
        arc += 3;
        continue;
      }

      if ( first_arc )
      {
        first_arc = 0;

        /* process corner if necessary */
        start_angle = angle_in;

        if ( stroker->first_point )
          error = ft_stroker_subpath_start( stroker, start_angle );
        else
        {
          stroker->angle_out = start_angle;
          error = ft_stroker_process_corner( stroker );
        }
        if ( error )
          goto Exit;
      }

      /* the arc's angle is small enough; we can add it directly to each */
      /* border                                                          */
      {
        FT_Vector  ctrl1, ctrl2, end;
        FT_Angle   theta1, phi1, theta2, phi2, rotate;
        FT_Fixed   length1, length2;
        FT_Int     side;


        theta1  = ft_pos_abs( angle_mid - angle_in ) / 2;
        theta2  = ft_pos_abs( angle_out - angle_mid ) / 2;
        phi1    = (angle_mid + angle_in ) / 2;
        phi2    = (angle_mid + angle_out ) / 2;
        length1 = FT_DivFix( stroker->radius, FT_Cos( theta1 ) );
        length2 = FT_DivFix( stroker->radius, FT_Cos(theta2) );

        for ( side = 0; side <= 1; side++ )
        {
          rotate = FT_SIDE_TO_ROTATE( side );

          /* compute control points */
          FT_Vector_From_Polar( &ctrl1, length1, phi1 + rotate );
          ctrl1.x += arc[2].x;
          ctrl1.y += arc[2].y;

          FT_Vector_From_Polar( &ctrl2, length2, phi2 + rotate );
          ctrl2.x += arc[1].x;
          ctrl2.y += arc[1].y;

          /* compute end point */
          FT_Vector_From_Polar( &end, stroker->radius, angle_out + rotate );
          end.x += arc[0].x;
          end.y += arc[0].y;

          error = ft_stroke_border_cubicto( stroker->borders + side,
                                            &ctrl1, &ctrl2, &end );
          if ( error )
            goto Exit;
        }
      }

      arc -= 3;
      if ( arc < bez_stack )
        stroker->angle_in = angle_out;
    }

    stroker->center = *to;

  Exit:
    return error;
  }


  /* documentation is in ftstroke.h */

  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_BeginSubPath( FT_Stroker  stroker,
                           FT_Vector*  to,
                           FT_Bool     open )
  {
    /* We cannot process the first point, because there is not enough      */
    /* information regarding its corner/cap.  The latter will be processed */
    /* in the "end_subpath" routine.                                       */
    /*                                                                     */
    stroker->first_point   = 1;
    stroker->center        = *to;
    stroker->subpath_open  = open;

    /* record the subpath start point index for each border */
    stroker->subpath_start = *to;
    return 0;
  }


  static FT_Error
  ft_stroker_add_reverse_left( FT_Stroker  stroker,
                               FT_Bool     open )
  {
    FT_StrokeBorder  right  = stroker->borders + 0;
    FT_StrokeBorder  left   = stroker->borders + 1;
    FT_Int           new_points;
    FT_Error         error  = 0;


    FT_ASSERT( left->start >= 0 );

    new_points = left->num_points - left->start;
    if ( new_points > 0 )
    {
      error = ft_stroke_border_grow( right, (FT_UInt)new_points );
      if ( error )
        goto Exit;

      {
        FT_Vector*  dst_point = right->points + right->num_points;
        FT_Byte*    dst_tag   = right->tags   + right->num_points;
        FT_Vector*  src_point = left->points  + left->num_points - 1;
        FT_Byte*    src_tag   = left->tags    + left->num_points - 1;

        while ( src_point >= left->points + left->start )
        {
          *dst_point = *src_point;
          *dst_tag   = *src_tag;

          if ( open )
            dst_tag[0] &= ~FT_STROKE_TAG_BEGIN_END;
          else
          {
            FT_Byte  ttag = (FT_Byte)( dst_tag[0] & FT_STROKE_TAG_BEGIN_END );


            /* switch begin/end tags if necessary */
            if ( ttag == FT_STROKE_TAG_BEGIN ||
                 ttag == FT_STROKE_TAG_END   )
              dst_tag[0] ^= FT_STROKE_TAG_BEGIN_END;

          }

          src_point--;
          src_tag--;
          dst_point++;
          dst_tag++;
        }
      }

      left->num_points   = left->start;
      right->num_points += new_points;

      right->movable = 0;
      left->movable  = 0;
    }

  Exit:
    return error;
  }


  /* documentation is in ftstroke.h */

  /* there's a lot of magic in this function! */
  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_EndSubPath( FT_Stroker  stroker )
  {
    FT_Error  error  = 0;

    if ( stroker->subpath_open )
    {
      FT_StrokeBorder  right = stroker->borders;

      /* All right, this is an opened path, we need to add a cap between */
      /* right & left, add the reverse of left, then add a final cap     */
      /* between left & right.                                           */
      error = ft_stroker_cap( stroker, stroker->angle_in, 0 );
      if ( error )
        goto Exit;

      /* add reversed points from "left" to "right" */
      error = ft_stroker_add_reverse_left( stroker, 1 );
      if ( error )
        goto Exit;

      /* now add the final cap */
      stroker->center = stroker->subpath_start;
      error = ft_stroker_cap( stroker,
                              stroker->subpath_angle + FT_ANGLE_PI, 0 );
      if ( error )
        goto Exit;

      /* Now end the right subpath accordingly.  The left one is */
      /* rewind and doesn't need further processing.             */
      ft_stroke_border_close( right, 0 );
    }
    else
    {
      FT_Angle  turn;
      FT_Int    inside_side;

      /* close the path if needed */
      if ( stroker->center.x != stroker->subpath_start.x ||
           stroker->center.y != stroker->subpath_start.y )
      {
        error = FT_Stroker_LineTo( stroker, &stroker->subpath_start );
        if ( error )