'Grow the window, if necessary'

def _grow(self):

    N = self._chart.num_leaves()
    width = max(int(self._chart_canvas['width']), ((N * self._unitsize) + (ChartView._MARGIN * 2)))
    self._chart_canvas.configure(width=width)
    self._chart_canvas.configure(height=self._chart_canvas['height'])
    self._unitsize = ((width - (2 * ChartView._MARGIN)) / N)
    if (self._sentence_canvas is not None):
        self._sentence_canvas['height'] = self._sentence_height
