title: How to reset or change behaviour of mouse cursor in impoly/imroi
body: <p>I have question concerning reset of interactive behavior of mouse.
  When I click on button and activate  mouse to create a ROI on the image
  But user did it by mistake and want to select different option and click on listbox and then on button ROI. 
  How can I reset ( option impoly with cross like this; +)?</p>
  
  <p>I would appreciate any help or advice.</p>