//click arrow
 public void HandleArrowButtonClick(object sender, System.EventArgs e)
 {
     _model.ClickArrow();
     _buttonEllipse.Enabled   = true;
     _buttonLine.Enabled      = true;
     _buttonRectangle.Enabled = true;
     _buttonArrow.Enabled     = false;
     _buttonSelect.Enabled    = true;
 }