PushButton clicked event is not triggered

[hanjinliu]

Describe the bug

In ipynb backend, clicking a PushButton does not trigger changed event. Callback functions are correctly triggered if the signal is programmatically emitted.

1.mp4

To Reproduce
Steps to reproduce the behavior:

Run following code in jupyter notebook or jupyter lab, and click the button.

from magicgui import magicgui, use_app
from magicgui.widgets import PushButton, Container, LineEdit

use_app("ipynb")

btn = PushButton(text="click")
line = LineEdit()

@btn.clicked.connect
def f():
    line.value = "a"

c = Container(widgets=[btn, line])
c.show(True)

Expected behavior
Event should be triggered.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS: Windows 11
• backend: ipywidgets=8.0.2
• magicgui version 0.6.0rc0