title: How do I set the minimum size of a Gtk ButtonBox child?
body: <p><img src="https://i.imgur.com/IkN6R8F.png" alt="pic"></p>
  
  <p>I'm trying to set the minimum size of the buttons in this GtkButtonBox.  Currently they seem to be fixed - approx 85 pixels I think.</p>
  
  <p>Is this possible?  </p>
  
  <p>If not, is there another way in Gtk to get two small sized buttons to snuggle together like in the above picture rather than having them appear to be two separate buttons? For example GtkStackSwitcher may be something I could use but there doesn't appear to be a way to respond to click events for a button.</p>
  
  <p>I've used this test program to create the above (Ubuntu 14.04, Gtk+3.10 and Python3):</p>
  
  <pre><code>from gi.repository import Gtk
  import sys
  
  
  class MyWindow(Gtk.ApplicationWindow):
  
      def __init__(self, app):
          Gtk.Window.__init__(self, title="example", application=app)
          self.set_default_size(350, 200)
          self.set_border_width(10)
  
          hbox = Gtk.ButtonBox.new(Gtk.Orientation.HORIZONTAL)
          hbox.set_layout(Gtk.ButtonBoxStyle.EXPAND)
          button = Gtk.Button(label="a")
          hbox.add(button)
          button2 = Gtk.Button(label="b")
          hbox.add(button2)
  
          self.add(hbox)
  
  class MyApplication(Gtk.Application):
  
      def __init__(self):
          Gtk.Application.__init__(self)
  
      def do_activate(self):
          win = MyWindow(self)
          win.show_all()
  
      def do_startup(self):
          Gtk.Application.do_startup(self)
  
  app = MyApplication()
  exit_status = app.run(sys.argv)
  sys.exit(exit_status)
  </code></pre>
  
  <hr>
  
  <p>With regards to a question about the desktop environment I'm using.</p>
  
  <p>I've tried Mate, Unity and Gnome-Shell.  All work the same way.  I've removed the title and those controls.  Still the same thing happens. To me this looks more like a GTK issue.</p>