Notebook scrolling out of sync

[jrieken]

related #148164

• have my-endgame-GHINB
• run all cell, scroll to the bottom, and run touch <path>
• scroll upwards
• 🧀 notice an occasional layout shift, the alignment of code and MD cells is getting out of sync

Recording of the recording

Screen.Recording.2022-06-29.at.17.40.30.mov

Recording of the scroll

Screen.Recording.2022-06-29.at.17.37.18.mov

[jrieken]

There will still be some layout shifts. I spent awhile trying to eliminate the scroll shift that you will see when you run touch. That turns out to be essentially impossible.

From #148164 (comment) - Unsure if this case is meant by that but if it is too hard did you consider some creative workaround, like animating the scrolling (positioning of markdown) might make it look less chunky and more "fluent"

[jrieken]

(what the heck... it seems GH confuses the default commenting command and I keep closing/re-opening issues)

[roblourens]

The first one shows an editor adding and removing the horizontal scroll bar, I have no idea why that would happen and can't repro it, any idea @rebornix?

The second is editors getting their scrollbars, we don't know whether they will overflow until they are rendered. I'm not sure whether that would be fixed by keeping view state across the model reload, like the other issue.

I'm not that motivated to work more on these specific cases because a model reload is probably not actually that common. The most common case would probably be doing a git pull with changes in that file.

[jrieken]

I'm not that motivated to work more on these specific cases because a model reload is probably not actually that common. The most common case would probably be doing a git pull with changes in that file.

Can you explain to me why the handling of reload is different from clear all output (or an API notebook edit)?

[roblourens]

You are replacing all cells with a totally different set of cells, vs editing an existing cell. Or inserting some cells with a notebook edit that are probably actually new.

[roblourens]

Looking at that first gif again, clearly there is something messed up with the editor.

Regarding the editors resizing when scrolled into view, this can show up in other cases and I'd like to do something about it. We could do a better at guessing whether the editor will get a scrollbar (early on tried to do an accurate estimate of text width in the editor, turns out to be complex) or we can render editors ahead of the viewport, like we already do for outputs. I guess we only aren't doing that currently for the expense. I guess I should say that a model reset is an easy way to repro the issue, but this will show up in other more common scenarios too and we should definitely keep trying to improve.

@rebornix was also continuing a leftover investigation item this week from #148164, which would improve the case of a model reset while scrolled near the bottom of the list.

[rebornix]

In the first gif, the editor of the first visible code cell is always in the viewport, meaning there is no re-render while slightly scrolling up and down. However the horizontal bar hides sometimes, it feels wrong to me.

[connor4312]

When I follow the directions and run touch .vscode/notebooks/my-endgame.github-issues, I see the content jump and all outputs get cleared, which prevents verifying with the original steps. Is this a different bug or are there different steps now?

[roblourens]

The outputs are going to be cleared because they aren't saved. But when you scroll up after this model reload, there should be less jumping with the markdown cells

Edit - oh, this was an old one...