show_info() not working when running napari from a Jupyter notebook

[LucaMarconato]

🐛 Bug Report

show_info() doesn't work when I run napari from a Jupyter notebook. Everything is fine when I run napari from a script. Below is code to reproduce this.

💡 Steps to Reproduce

Run this code in a Jupyter notebook and the click anywhere on the image.

from napari.utils.notifications import show_info
import napari
from skimage import data

viewer = napari.Viewer()
layer = viewer.add_image(data.astronaut(), name='astro')

@layer.mouse_drag_callbacks.append
def update_tooltip(layer, event):
    show_info(f'{event.position}')
napari.run()

💡 Expected Behavior

On click, it should show the notification on the bottom like in the screenshot

🌎 Environment

napari: 0.4.16
Platform: macOS-13.4.1-arm64-arm-64bit
System: MacOS 13.4.1
Python: 3.9.18 | packaged by conda-forge | (main, Aug 30 2023, 03:53:08) [Clang 15.0.7 ]
Qt: 5.15.8
PyQt5: 5.15.9
NumPy: 1.24.4
SciPy: 1.9.1
Dask: 2023.10.1
VisPy: 0.10.0

OpenGL:

• GL version: 2.1 Metal - 83.1
• MAX_TEXTURE_SIZE: 16384

Screens:

• screen 1: resolution 2056x1329, scale 2.0

Plugins:

• napari-console: 0.0.9
• napari-matplotlib: 1.2.1.dev2+g7b6a4a4
• napari-spatialdata: 0.1.0
• napari-svg: 0.1.10
• scikit-image: 0.4.16

💡 Additional Context

No response

[Czaki]

Explanation:

Because jupyter starts ow qt event loop the get_app() called from napari.run() function does not connect NapariQtNotification dispatchers to notification_manager signals.

napari/napari/_qt/qt_event_loop.py

Lines 191 to 197 in 8ed7f4c

	if not _ipython_has_eventloop():
	notification_manager.notification_ready.connect(
	NapariQtNotification.show_notification
	)
	notification_manager.notification_ready.connect(
	show_console_notification
	)

In meantime, we update the guard in NapariQtNotification.show_notification to not trigger a notification if there is no main window in #4839

napari/napari/_qt/dialogs/qt_notification.py

Lines 380 to 396 in 8ed7f4c

	@classmethod
	@ensure_main_thread
	def show_notification(cls, notification: Notification):
	from napari._qt.qt_main_window import _QtMainWindow
	from napari.settings import get_settings
	settings = get_settings()
	# after https://github.com/napari/napari/issues/2370,
	# the os.getenv can be removed (and NAPARI_CATCH_ERRORS retired)
	if (
	notification.severity
	>= settings.application.gui_notification_level
	and _QtMainWindow.current()
	):
	canvas = _QtMainWindow.current()._qt_viewer._welcome_widget
	cls.from_notification(notification, canvas).show()

So we may should revisit our design decision.

[psobolewskiPhD]

I ran into this today. Pretty important use-case, particularly for keybindings, because printing prints to the Jupyter so it's not readily visible in napari if you are working on a smaller screen. Definitely should aim to fix this (lack of) interaction.

Edit: because it's not immediately apparent from the post above, it works from iPython because we specifically make the connections--I think. So we should aim to do the same for Jupyter.

OK, LOL, so it works from iPython but shouldn't.
Here's the _ipython_has_eventloop():

napari/napari/_qt/qt_event_loop.py

Lines 308 to 324 in 8ed7f4c

	def _ipython_has_eventloop() -> bool:
	"""Return True if IPython %gui qt is active.
	Using this is better than checking ``QApp.thread().loopLevel() > 0``,
	because IPython starts and stops the event loop continuously to accept code
	at the prompt. So it will likely "appear" like there is no event loop
	running, but we still don't need to start one.
	"""
	ipy_module = sys.modules.get("IPython")
	if not ipy_module:
	return False
	shell: InteractiveShell = ipy_module.get_ipython() # type: ignore
	if not shell:
	return False
	return shell.active_eventloop == 'qt'

in iPython I get:

In [9]: sys.modules.get("IPython").get_ipython().active_eventloop
Out[9]: 'qt5'

But the check, uses just 'qt'

napari/napari/_qt/qt_event_loop.py

Line 324 in 8ed7f4c

return shell.active_eventloop == 'qt'

so it returns False. So then we have if not False and the connections are made, just like if shell was False

@Czaki Is there any workaround that could be used in the meanwhile?

[Czaki]

OK, LOL, so it works from iPython but shouldn't.
Here's the _ipython_has_eventloop():

Did you run ipython with qtbackend?

@Czaki Is there any workaround that could be used in the meanwhile?

Manually perform this steep?

     notification_manager.notification_ready.connect( 
         NapariQtNotification.show_notification 
     ) 

And we should check if we could perform bind always. if was introduced in #2633

[psobolewskiPhD]

I just typed ipython in my terminal in an env with just napari and jupyterlab. So I'm not sure what backend, but it returned qt5 so safe to assume qt. i didn't run any magics.

[Czaki]

Ok. I see.
We should dig now if the if guard is still needed.

[psobolewskiPhD]

What I don't get is why jupyter gets caught by that if
From jupyter, all that code works and shell.active_eventloop returns None, so the logic should fire, because shell.active_eventloop == 'qt' returns False

[psobolewskiPhD]

Dropping the if seems to work fine with jupyter and ipython, but I'm not sure how to test this better:
https://github.com/psobolewskiPhD/napari/tree/fix_notif_jupyter

[Czaki]

I think that you should make a PR with remove of this if. Then it will be present on main and maybe someone will report some problem if any exists.

[LucaMarconato]

I have tried #6882 and the problem is solved! Thanks a lot!