code: def on_resize(self, event):
          
          if self._aspect is None:
              return
          w, h = self._canvas.size
          aspect = self._aspect / (w / h)
          self.scale = (self.scale[0], self.scale[0] / aspect)
          self.shader_map()
docs: Resize handler
  
          Parameters
          ----------
          event : instance of Event
              The event.