docs: 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)