Improve scrolling to heading

[fcollonval]

References

Fixes #15228
Fixes #15215 (@krassowski - would you mind confirm this I'm unsure)
Fixes #14684
Fixes #14591

Code changes

• Emit onActiveHeadingChanged in toc model even when the value is not changing
• Add a new attribute scrollToTop to the notebook ToC factory that is true by default but allows to configure the heading navigation scroll behavior
• Switch to command mode when in edit mode and jumping to a heading in a md cell

User-facing changes

By default, jumping to a heading from the toc will not make the markdown cell turn in edit mode and will scroll it to the top of the view port.

Backwards-incompatible changes

None

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[krassowski]

I guess this could be backported to 4.0.x but without the new setting?

[fcollonval]

I guess this could be backported to 4.0.x but without the new setting?

I was thinking of backported it with the setting but changing the default value as lots of user consider scroll to top a better behavior.

[krassowski]

Not sure if this fixes #15215 because that is not trivial to reproduce, but I did find a way to break this PR:

[krassowski]

Sorry accidentally clicked submit too early, here is the traceback:

DOMException: Failed to execute 'removeChild' on 'Node': The node to be removed is not a child of this node.
    at NotebookWindowedLayout.detachWidget (http://127.0.0.1:8889/static/lab/packages_notebook_lib_index_js.a0899e5b2c84c0887c94.js:9919:38)
    at NotebookWindowedLayout.removeWidget (http://127.0.0.1:8889/static/lab/packages_notebook_lib_index_js.a0899e5b2c84c0887c94.js:9806:18)
    at NotebookWindowedLayout.onChildRemoved (http://127.0.0.1:8889/static/lab/jlab_core.ac50a29a806e5e41bc1f.js:13723:14)
    at NotebookWindowedLayout.onChildRemoved (http://127.0.0.1:8889/static/lab/packages_notebook_lib_index_js.a0899e5b2c84c0887c94.js:9997:15)
    at NotebookWindowedLayout.processParentMessage (http://127.0.0.1:8889/static/lab/jlab_core.ac50a29a806e5e41bc1f.js:13522:22)
    at Notebook.notifyLayout (http://127.0.0.1:8889/static/lab/jlab_core.ac50a29a806e5e41bc1f.js:12938:26)
    at Notebook.processMessage (http://127.0.0.1:8889/static/lab/jlab_core.ac50a29a806e5e41bc1f.js:12918:22)
    at invokeHandler (http://127.0.0.1:8889/static/lab/jlab_core.ac50a29a806e5e41bc1f.js:9381:21)
    at Object.sendMessage (http://127.0.0.1:8889/static/lab/jlab_core.ac50a29a806e5e41bc1f.js:9135:13)
    at set parent [as parent] (http://127.0.0.1:8889/static/lab/jlab_core.ac50a29a806e5e41bc1f.js:12581:72)
exceptionHandler @ index.es6.js:377

followed by:

windowedlist.ts:1126 Uncaught Error: Inconsistent dataset index
    at Notebook._update (windowedlist.ts:1126:15)
    at windowedlist.ts:1005:16

[krassowski]

The error above is unrelated (it also happens in 4.0.8 and 4.1.0a3), I tracked it down to "Revert" breaking windowed notebooks, here is the issue: #15415.

[krassowski]

The failing test appears to reflect change in the behaviour and likely needs to be updated (or change in test settings):

Expected	Actual

[fcollonval]

bot please update the galata snapshots

[krassowski]

bot please update galata snapshots

[github-actions]

Galata snapshots updated.

[krassowski]

Thank you @fcollonval!

[krassowski]

@meeseeksdev please backport to 4.0.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 4.0.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 98d1e06796906ce622559146ed127075a7a46f71

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #15386: Improve scrolling to heading'

4. Push to a named branch:

git push YOURFORK 4.0.x:auto-backport-of-pr-15386-on-4.0.x

5. Create a PR against branch 4.0.x, I would have named this PR:

"Backport PR #15386 on branch 4.0.x (Improve scrolling to heading)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.