docs: def on_press(self, event):
          'on but-ton press we will see if the mouse is over us and store data'
          if event.inaxes != self.ax:
              return
          # contains, attrd = self.rect.contains(event)
          # if not contains: return
          # print('event contains', self.rect.xy)
          # x0, y0 = self.rect.xy
          self.press = [event.xdata], [event.ydata], event.button