deleteoncloseis that you could then end up with python objects not backed by a c++ object
currently this "works"
fig = plt.figure() plt.close('all') fig.canvas.manager.window.show() fig.subplots()
gc.collectbut we had users report major performance issues if they had lots of non-Matplotlib objects in their code
destroy()(the C-level object)
destroyon the widgets on manager destruction