void signup_PreviewTouchUp(object sender, TouchEventArgs e)
{
signup.Background = Brushes.White;
log.WriteInteractionLog(5, "", e.TouchDevice);
window_manager.open_signup_window(last_pos_x, signup.PointToScreen(new Point(0, 0)).Y);
last_pos_x = last_pos_x + pos_x_increment;
if (last_pos_x > max_pos_x) last_pos_x = init_pos_x;
}