Tearing on interactive ROI

还没有人认领这个 Issue。

## Describe the issue

The plots tear heavily when using interactive rois after creating a new environment (`conda create --name testplot ipympl matplotlib jupyterlab`).

First noticed in hyperspy/hyperspy#2706, it appears to be a problem with both mpl 3.3/3.4 and ipympl 0.6/0.7.

[This matplotlib interactive example](https://matplotlib.org/stable/gallery/widgets/rectangle_selector.html#sphx-glr-gallery-widgets-rectangle-selector-py) results in the following output, both with `useblit=True` and `=False`.


## Versions

```
3.9.2 | packaged by conda-forge | (default, Feb 21 2021, 04:59:43) [MSC v.1916 64 bit (AMD64)]
ipympl version: 0.7.0
jupyter core : 4.7.1
jupyter-notebook : 6.3.0
qtconsole : not installed
ipython : 7.22.0
ipykernel : 5.5.3
jupyter client : 6.1.12
jupyter lab : 3.0.14
nbconvert : 6.0.7
ipywidgets : 7.6.3
nbformat : 5.1.3
traitlets : 5.0.5
Known nbextensions:
config dir: C:\Users\thomasaar\Miniconda3\envs\testplot\etc\jupyter\nbconfig
notebook section
jupyter-matplotlib/extension enabled
- Validating: ok
jupyter-js-widgets/extension enabled
- Validating: ok
JupyterLab v3.0.14
C:\Users\thomasaar\Miniconda3\envs\testplot\share\jupyter\labextensions
jupyter-matplotlib v0.9.0 enabled ok
@jupyter-widgets/jupyterlab-manager v3.0.0 enabled ok (python, jupyterlab_widgets)
```

使用提供的 conda 环境、ipympl 0.7.0、JupyterLab 3.0.14 以及链接的 Matplotlib RectangleSelector 示例复现 tearing，同时测试 useblit=True 和 useblit=False。跟踪问题究竟出在交互式 ROI 渲染还是 Jupyter 小部件集成；在所报告的设置下绘图不再出现 tearing 即表示完成。

由索引模型根据 Issue 内容生成。