content: """
  Example on how to add widgets the toolbar of a Matplotlib figure using the
  QT backend.
  
  No QT application is created, only the toolbar of the native MPL figure is
  modified.
  """
  
  
  from PySide import QtGui, QtCore
  import matplotlib
  
  
  def test():
      plot([1,2,3], lw=2)
      q = qt4_interface(gcf())
      return q   # WARNING: it's paramount to return the object otherwise, with 
                 # no references, python deletes it and the GUI doesn't respond!
      
  class qt4_interface:
      def __init__(self,fig):
          self.fig = fig
          toolbar = fig.canvas.toolbar
          
          self.line_edit = QtGui.QLineEdit()
          toolbar.addWidget(self.line_edit)
          self.line_edit.editingFinished.connect(self.do_something)
  
          self.spinbox = QtGui.QDoubleSpinBox()
          toolbar.addWidget(self.spinbox)
          self.spinbox.valueChanged.connect(self.do_something2)
  
      def do_something(self, *args):
          self.fig.axes[0].set_title(self.line_edit.text())
          self.fig.canvas.draw()
          #f = open('l','a'); f.write('yes\n'); f.flush(); f.close()    
      
      def do_something2(self, *args):
          self.fig.axes[0].set_xlim(0, self.spinbox.value())
          self.fig.canvas.draw()
          #f = open('l','a'); f.write('yes\n'); f.flush(); f.close()
  