private void Keyboard_KeyDown(object sender, OpenTK.Input.KeyboardKeyEventArgs e)
{
if (_allowAltF4 && e.Key == OpenTK.Input.Key.F4 && keys.Contains(Keys.LeftAlt))
{
window.Close();
return;
}
Keys xnaKey = KeyboardUtil.ToXna(e.Key);
if (!keys.Contains(xnaKey)) keys.Add(xnaKey);
}