The focus signal is used to let the focus switch between elements in a
      way as easy as possible. FIXME: be more verbose here
    
        At the beginning, there is no focus. So, once the focus enters the
	view, it emits the 'focus' signal on the root, FIXME: continue here
      
 
        If there is a focus, we can easily find out which element the focus
	has, the we can move up the canvas tree and find the next item to be
	focused.
      
	  Emit CcItem::focus-next - which actually gets the focus chain, finds
	  out which child currently has he focus and then steps through the
	  list to find the next focus-able child.
	
	  If there is no focus chain, the canvas uses the list of child
	  elements from top to bottom.
	
 
 
        Once there's no item which can take the focus in a cycle, we just
	return FALSE, so the parent's signal handler for the focus event can
	take the focus off us and move it on to the next element.