title: How to update a Tix.ComboBox's text?
body: <p>I have a Tix.ComboBox with an editable text field. How do I force the variable holding the value for the text to update?</p>
  
  <p>Let me give a more concrete explanation. I have a combo box and a button. When I click the button, it pops up a message box with the value of the combo box. Let's say the combo box text field currently has the value "thing1". If I type "new" into the box and then click on the button with my mouse, it will pops up the message "thing1". If I type "new" in the box and then tab focus away from the combo box and then click the button the pop up message says "new".</p>
  
  <p>Ho do I force the combo box to update it's value to new without requiring that I tab away from the combo box?</p>
  
  <p>I have included sample code.</p>
  
  <pre><code>import Tix
  import tkMessageBox
  
  class App(object):
      def __init__(self, window):
          window.winfo_toplevel().wm_title("test")
          self.window = window
  
          self.combo = Tix.ComboBox(window)
          self.combo.insert(Tix.END, 'thing1')
          self.combo.insert(Tix.END, 'thing2')
          self.combo.entry['state'] = "normal"
          self.combo['editable'] = True
          self.combo.pack()
  
          button = Tix.Button(window)
          button['text'] = "Go"
          button['command'] = self.go
          button.pack()
  
      def go(self):
          tkMessageBox.showinfo('info', self.combo['value'])
  
  
  if __name__ == '__main__':
      root = Tix.Tk()
      App(root)
      root.mainloop()
  </code></pre>