title: JavaFX extract calendar-popup from DatePicker / only show popup
body: <p>I'm trying to build an CalendarView for an JavaFX application, to only display dates(no selecting required). Since the <code>DatePicker</code> class has a nice calendar popup I thought I might try to extract it so that I already have all the style-questions covered.</p>
  
  <p>So is there an easy way to extract the DatePicker calendar popup and insert it into a new CalendarView?</p>
  
  <p>I already looked at the <code>show()</code> method from the <code>ComboBoxBase</code> class to see what exactly happens when the popup is triggered but I have to admit I couldn't really get my head around it.</p>
  
  <p>Alternatively I could think about simply edit the DatePicker in a way that only the popup shows all the time with the editor-TextField and button component always hiding, but again I couldn't quite figure out how to do that without hiding the popup as well. Also I would propably need to get the bounds of the popup to approptiately manage height and width in this alternativw, which again seems to be not that easy.</p>