Header part not reflecting Jupyter Notebook Top Area default setting

[yumyumqing]

Describe the bug
In settings editor, Jupyter Notebook Top Area is only reflecting changes from User Preferences but not Settings Overrides.

When I start the jupyter notebook with default settings overrides, the menu does pick up the visible: false setting, but the notebook is still showing header part.
If I toggle the setting manually by clicking the box, the change does reflect in the notebook header part.
But then if I click Restore to Defaults, the notebook header is not picking up the change again.

To Reproduce
Steps to reproduce the behavior:

1. Set up dev environment as https://github.com/jupyter/notebook/blob/main/CONTRIBUTING.md#setting-up-a-development-environment
2. Create a overrides.json file in settings dir in JupyterLab Application Directory.
   If using mamba as step 1, the dir should look something like $HOME/mambaforge/envs/notebook/share/jupyter/lab/settings.

{
  "@jupyter-notebook/application-extension:top": {
    "visible": false
  }
}

3. Build and launch jupyter notebook in dev mode
4. Go to the browser page opened by jupyter notebook
5. Click Settings - Settings Editor - Jupyter Notebook Top Area
6. See the box is not checked
7. In a new tab, open a notebook in notebook mode, and the header is still showing
8. Back to the setting page and check the box and uncheck again
9. Refresh the notebook page, see the header is not showing now
10. Back to the setting page and check the box and then click Restore to Defaults
11. Refresh the notebook page, see the header is still showing

Expected behavior
In my opinion, I think the header part should reflect the default settings (if there is no User Preference) for 2 reasons:

1. The user might get confused when a unchecked box can lead to 2 different behaviors
2. For tools like jupyterlite, that uses this plugin but does not support User Preference override, it would be hard for the users to hide the header part by default.
   (I think jupyterlite uses browser cache for User Preference settings and does not allow overrides at build time. Please correct me if I am wrong on this.)

Screenshots

Desktop (please complete the following information):

• OS: MacOS Ventura 13.2.1
• Browser: chrome
• Version: tip of main branch

Additional context
I think the reason for the bug might come from these 2 places:

1. updateSettings is only changing top visibility when there is User Preference set up. This should probably be outside of the user setting check.
   

   notebook/packages/application-extension/src/index.ts

   Lines 497 to 499 in 1512c82

   	if (settings.user.visible !== undefined) {
   	settingsOverride = true;
   	top.setHidden(!visible);

2. Whenever refreshing a page, if the User Preference isn't set up, the plugin will adjust the header showing based on screen size only.
   

   notebook/packages/application-extension/src/index.ts

   Lines 519 to 528 in 1512c82

   	const onChanged = (): void => {
   	if (settingsOverride) {
   	return;
   	}
   	if (app.format === 'desktop') {
   	notebookShell.expandTop();
   	} else {
   	notebookShell.collapseTop();
   	}
   	};

If we fix the bug as in Expected behavior, this neat feature of adjusting based on screen size might go away.
If we still want to keep the adjustment, maybe we can have another variable to flag whether we would like to do adjustment like adjustToScreen: true which could overrides the header settings.

Thanks for taking a look!

[jtpio]

Thanks @yumyumqing for opening this issue and providing all the details 👍

In my opinion, I think the header part should reflect the default settings (if there is no User Preference) for 2 reasons:

Would you like to open a draft PR so we can see how that would work?

1. updateSettings is only changing top visibility when there is User Preference set up.

I don't recall exactly why it is like this. But this git history seems to be pointing to this commit: 6c96c80

[yumyumqing]

Thanks @jtpio for your help!

I opened this PR draft and listed a couple different expected behavior cases. #6836
All the checks passed except for the Enforce PR label. Can you please help take a look? Thanks a lot!

[yumyumqing]

Fixed with PR #6836