Bug report

Bug summary

When trying the Lasso selector example in a Jupyter notebook, the lasso does not show.
It does however show correctly in the Qt window, if I try the same code example in a classic ipython terminal shell.

I also tried with a simpler example:

import matplotlib.pyplot as plt
from matplotlib.widgets import LassoSelector

fig, ax = plt.subplots()

def onSelect(x):
    print(x)

lineprops = {'color': 'red', 'linewidth': 4, 'alpha': 0.8}
lsso = LassoSelector(ax=ax, onselect=onSelect, lineprops=lineprops)

plt.show()

but the same happens:

Jupyter:

Qt window:

Matplotlib version

• Operating system: Ubuntu 18.04
• Matplotlib version: 3.1.1
• Matplotlib backend (print(matplotlib.get_backend())): Qt5Agg + nbAgg
• Python version: 3.7.3
• Jupyter version (if applicable): 1.0.0 notebook: 6.0.2
• Other libraries:

Matplotlib installed from conda