[SIEM] Attach VisibilitySensor to the TimelineBody instead of window

[patrykkopycinski]

Summary

Currently, VisibilitySensor is attached to the window, so in effect, when we scroll the page, the Timeline table's rows are replaced by placeholders and it causes unnecessary re-renders of the components.
In my opinion, the expected behavior is to render placeholders only when we scroll the table and the row is stop being visible in the context of the table not in the context of the window.

Current:

After the changes:

Checklist

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• This was checked for cross-browser compatibility, including a check against IE11
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[elasticmachine]

Pinging @elastic/siem (Team:SIEM)

[rylnd]

Tried it out locally, and things are working as described! Event rows are rendered as the table's viewport changes (scrolling the table), not as the window's viewport does (scrolling the page).

I agree that this seems like the intended behavior, but I'll defer to someone who was here when this was written :)

[rylnd]

@patrykkopycinski one other thought: we're unmounting these rows as they go out of view and thus throwing away all the work we just did to render it. Is this intentional (so that we always have "fresh" data)? If not, there's another optimization there.

[andrew-goldstein]

@FrankHassanabad @rylnd and I reviewed this PR over a zoom with @patrykkopycinski , and we all agree with and appreciate the perf improvement in this PR. Thanks @patrykkopycinski 🙏
LGT(US)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 51ba25d

History

• 💚 Build #21998 succeeded 58da903

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