title: Filling the action area of a gtk.Dialog window with its buttons - instead of having them aligned to the right
body: <p>Using PyGTK, I create a bunch of buttons in the action area of a <code>gtk.Dialog</code> using the <code>add_button()</code> method, as below:</p>
  
  <pre><code>self.replace_all_button = self.add_button(_("Replace All"), 
              gtk.RESPONSE_ACCEPT)
  </code></pre>
  
  <p>The resulting dialog has all the buttons aligned to the right, as seen in the following image:</p>
  
  <p><img src="https://i.stack.imgur.com/9PLof.png" alt="gtk.Dialog with action buttons aligned to the right"></p>
  
  <p>However, I want to fill the action area with the buttons, just like in this image:</p>
  
  <p><img src="https://i.stack.imgur.com/sw1sI.png" alt="enter image description here"></p>
  
  <p>I have tried some curious strategies, such as to redefine the packing parameters of all widgets from the action area, as seen in the code below, but it did not work.</p>
  
  <pre><code>def redefine_packing(widget):
      _, _, padding, _ = self.action_area.query_child_packing(widget)
      self.action_area.set_child_packing(widget, True, True, padding, _)
  
  self.action_area.foreach(redefine_packing)
  </code></pre>
  
  <p>How could I do it? (A solution does not need to be written in Python if I can intuitively translate it from the original language, which I usually can do)</p>