Opening a pop up window in a Vaadin Portlet

Vaadin 6 / 7 / 8 Framework UI
1

I followed
this tutorial
 that shows how to pop up a print window.

But, as I’m using portlets, I must get the right windows URL. I figured out how to get the portlet URL (from the response object).

But, the problem is still the same : How can I get/create the Window’s URL ?

Thank you.