handles key events on canvas

def __onKeyEvent(self, event=None):
        """ handles key events on canvas
        """
        if event is None:
            return
        key = event.guiEvent.GetKeyCode()
        if (key < wx.WXK_SPACE or  key > 255):
            return
        ckey = chr(key)
        mod  = event.guiEvent.ControlDown()
        if self.is_macosx:
            mod = event.guiEvent.MetaDown()
        if mod:
            if ckey == 'C':
                self.canvas.Copy_to_Clipboard(event)
            elif ckey == 'S':
                self.save_figure(event)
            elif ckey == 'K':
                self.configure(event)
            elif ckey == 'Z':
                self.unzoom(event)
            elif ckey == 'P':
                self.canvas.printer.Print(event)