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.

首先运行包含两个 ipywidgets 选项卡和 matplotlib 图形的最小 notebook 示例，然后比较最初隐藏的第二个图形与第一个图形的大小。跟踪第二个选项卡变为可见时图形尺寸是如何确定的。完成标准是每个选项卡中的图形都能显示完整的绘图区，且不会被截断。