  tt_size_reset( TT_Size  size,
                 FT_Bool  only_height )
  {
    TT_Face           face;
     FT_Size_Metrics*  metrics;
 
 
    size->ttmetrics.valid = FALSE;
     face = (TT_Face)size->root.face;
 
     metrics = &size->metrics;
 
     /* copy the result from base layer */

    /* This bit flag, if set, indicates that the ppems must be       */
    /* rounded to integers.  Nearly all TrueType fonts have this bit */
    /* set, as hinting won't work really well otherwise.             */
    /*                                                               */
    if ( face->header.Flags & 8 )
    {
      metrics->ascender =
        FT_PIX_ROUND( FT_MulFix( face->root.ascender, metrics->y_scale ) );
      metrics->descender =
        FT_PIX_ROUND( FT_MulFix( face->root.descender, metrics->y_scale ) );
      metrics->height =
        FT_PIX_ROUND( FT_MulFix( face->root.height, metrics->y_scale ) );
    }

    size->ttmetrics.valid = TRUE;

    if ( only_height )
      return FT_Err_Ok;

    if ( face->header.Flags & 8 )
    {
      metrics->x_scale = FT_DivFix( metrics->x_ppem << 6,
                                    face->root.units_per_EM );
      metrics->y_scale = FT_DivFix( metrics->y_ppem << 6,
                                    face->root.units_per_EM );

      metrics->max_advance =
        FT_PIX_ROUND( FT_MulFix( face->root.max_advance_width,
                                 metrics->x_scale ) );
    }

    /* compute new transformation */
    if ( metrics->x_ppem >= metrics->y_ppem )
    {
      size->ttmetrics.scale   = metrics->x_scale;
      size->ttmetrics.ppem    = metrics->x_ppem;
      size->ttmetrics.x_ratio = 0x10000L;
      size->ttmetrics.y_ratio = FT_DivFix( metrics->y_ppem,
                                           metrics->x_ppem );
    }
    else
    {
      size->ttmetrics.scale   = metrics->y_scale;
      size->ttmetrics.ppem    = metrics->y_ppem;
      size->ttmetrics.x_ratio = FT_DivFix( metrics->x_ppem,
                                           metrics->y_ppem );
      size->ttmetrics.y_ratio = 0x10000L;
    }

#ifdef TT_USE_BYTECODE_INTERPRETER
    size->cvt_ready = -1;
#endif /* TT_USE_BYTECODE_INTERPRETER */

    return FT_Err_Ok;
  }

The product writes data past the end, or before the beginning, of the intended buffer.