code: def on_resize(self, event):
          
          self._update_transforms()
          
          if self._central_widget is not None:
              self._central_widget.size = self.size
              
          if len(self._vp_stack) == 0:
              self.context.set_viewport(0, 0, *self.physical_size)
docs: Resize handler
  
          Parameters
          ----------
          event : instance of Event
              The resize event.