title: D3 put arc labels in a Pie Chart if there is enough space
body: <p>I will put a text element in every arc of my Pie Chart (center) - as shown in this example:
  <a href="http://bl.ocks.org/mbostock/3887235">http://bl.ocks.org/mbostock/3887235</a></p>
  
  <p>But I will only put the text element if the room is sufficient for the whole text, so im must compare the size of my text element with the "available" space in every arc. </p>
  
  <p>I think I can do this with getBBox() to get the text dimensions... but how can I get (and compare) the dimension of the available space in every arc.</p>
  
  <p>thx...!</p>