title: Font width returns incorrect values
body: <p>The following code should return the width in pixels of the character 'a' in the default font; it doesn't:  </p>
  
  <pre><code>import pygtk
  gtk.require20()
  import gtk
  
  t = gtk.TextView()
  print t.get_style().get_font().width("w") # Always returns -6
  </code></pre>