title: How to detect mouse moving while left button down?
body: <p>I would like to detect mouse moving, while the left button is pressed.</p>
  
  <p>I simply create a drawing application. I can detect the mouse move without any mouse pressed. But I want to detect WITH left mouse pressed.</p>
  
  <p>I think there is not any listener for this. So, what is the idea to do that?</p>