protected override void OnSizeChanged( EventArgs e )
{
if ( m_Bitmap != null )
m_Bitmap.Dispose();
m_Bitmap = null;
if ( Width > 0 && Height > 0 )
m_Bitmap = new Bitmap( Width, Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb );
UpdateBitmap();
base.OnSizeChanged( e );
}