figures that start in background tabs are cut off at bottom

I'm having some trouble with figures getting cut off at the bottom when they're included in tabs other than the first tab. Here's a minimal example. Note that I put the figures in boxes because I have the same problem as #126 if I don't.

%matplotlib widget
import matplotlib.pyplot as plt
plt.ioff()
import ipywidgets as widgets
import numpy as np
fig1,ax1 = plt.subplots()
ax1.scatter(np.arange(10),np.random.random(10))
ax1.set_xlabel('x axis')
ax1.set_ylabel('y axis')
fig2,ax2 = plt.subplots()
ax2.plot(np.arange(10),np.random.random(10))
ax2.set_xlabel('x axis')
ax2.set_ylabel('y axis')
tabs = widgets.Tab(children=[widgets.Box([fig1.canvas]),widgets.Box([fig2.canvas])])
tabs.set_title(0, 'fig1')
tabs.set_title(1, 'fig2')
tabs

The first tab looks like (I clicked on the figure to show the boundaries)

and the second tab looks like:

I just cannot figure out why the bottom of that second figure is getting cut off.

Start by running the minimal notebook example with two ipywidgets tabs and matplotlib figures, then compare the sizing of the initially hidden second figure with the first. Trace how figure dimensions are established when the second tab becomes visible. Done means figures in every tab display their complete plotting area without being cut off.