public void DrawString(GLBitmap glBmp, GLRenderVxFormattedString renderVx, double x, double y)
 {
     _pcx.FontFillColor = _painter.FontFillColor;
     //for sharp edge glyph
     _pcx.DrawGlyphImageWithSubPixelRenderingTechnique4_FromVBO(
         glBmp,
         renderVx.GetVbo(),
         renderVx.IndexArrayCount,
         (float)Math.Round(x),
         (float)Math.Floor(y));
 }