title: (py)cairo - fill
body: <p>is there a way to fill everything outside of a closed path (polygon)?</p>
  
  <p>Background: I'd like to render some maps with coastlines - so sometimes I need to fill the sea with blue color, so I thought it would be the easiest and in my situation the most efficient to fill everything outside of this coastline polygon with blue color.</p>
  
  <p>Thanks in advance!</p>